Ammunition Reliability Against the Harsh Environments During the Launch of an Electromagnetic Gun: A Review
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paper_title: A long-range naval railgun

paper_content:

The U.S. Navy is considering developing an electromagnetic railgun for use on future ships for long-range shore bombardment missions. The goals are to provide support for ground forces in a timely fashion, increase the ship-to-shore standoff distance, and improve ship survivability in combat situations. This paper describes the parameters of a notional railgun design that may be capable of supporting the Navy's needs. The Naval Surface Fire Support mission requires a railgun capable of firing high-energy projectiles for ranges of 300-500 km with a firing rate of up to 12 rounds per minute. The notional system described here is intended to meet these requirements while providing the ability to take advantage of the integrated electric drive architecture to be used on the next generation destroyer. Several important technology issues will need to be addressed before the feasibility of such a system can be demonstrated. These issues are identified and discussed.
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paper_title: Review of Inductive Pulsed Power Generators for Railguns

paper_content:

This paper addresses inductive pulsed power generators and their major components. Different inductive storage designs, such as solenoids, toroids, and force-balanced coils, are briefly presented and their advantages and disadvantages are mentioned. Special emphasis is given to inductive circuit topologies, which have been investigated in railgun research, such as the XRAM, meat grinder, or pulse transformer topologies. One section deals with opening switches as they are indispensable for inductive storages and another one deals briefly with superconducting magnetic energy storage for pulsed power applications. Finally, the most relevant inductor systems, which have been realized with respect to railgun research, are summarized in Table I , together with their main characteristics.
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paper_title: Development of the high-velocity gas-dynamics gun

paper_content:

Abstract The subjects of this paper are the historical overview and development of the high-velocity gas-dynamics gun. These are guns that derive their energy from a reservoir of compressed gas. Other 3uns derive their energy from electricity or from high explosive. Their historical overviews and developments are covered in papers by Mr. William Weldon and Mr. Alex Wenzel. The gas dynamics gun is viewed first from the standpoint of modern technology. An idealized configuration, the “Reference Gun”, is analysed in order to quantify the effects of gun diameter and length, projectile mass, and propellant gas pressure and composition. The analysis assumes that the propellant is an ideal gas, and formulae are derived for the base pressure and velocity of the projectile as functions of the size and loading parameters of the gun. The analysis demonstrates that the prime requirements for high velocity are a high gas pressure, a low molecular weight gas, a light projectile, and a long gun. The history of guns is reviewed briefly from 14th century black-powder muzzle-loaders to 20th century, nitrocellulose -propellant, breech-loaded guns. The velocity limit of the modern gun is shown to be around 3 km/s, if the gun is loaded with nitrocellulose propellant and is very long (200 calibers). However, if the gun is loaded with hydrogen and the length doubled, it is shown that the velocity limit can be increased to 7 km/s, thus approaching current needs. The problem of using hydrogen has been solved by the invention of the piston-compression light-gas gun (PCLGG). However, the limited strength of the fragile, sabot-model projectiles of experimental research has capped the maximum acceleration and has placed a demand on the gun's operating cycle to generate a constant pressure at the base of the projectile for the launching run. This second problem has been partially solved by the invention of a modification to the PCLGG known as the piston-compression, accelerated-reservoir, light-gas gun (PCARLGG). Both the PCLGG and the PCARLGG are described. The performance of the PCARLGG has been analyzed by a hydrocode developed for this purpose, and the results of the calculations are presented and compared with experiment. The concept of a frictionless, adiabatic “Ideal Gun” is introduced in order to simplify the analysis of performance. It is shown that the performance of any ideal gun is given by a simple equation involving two dimensionless parameters that relate the projectile's velocity to its mass, its average base pressure, and the diameter and length of the gun. Based on the ideal gun equation, the maximum operating velocity of the gas-dynamics gun is estimated to be about 12 km/s.
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paper_title: Naval Railguns

paper_content:

Compared with propellant guns, railguns can fire at higher velocities and do not require gun propellant but use ships' fuel. These features lead to important advantages, including shorter time of flight (important for ship defense), higher lethality on target (important for direct fire), and very extensive range capability (important for support of troops on shore). Such extended range capability also supports the sea-basing concept in which a forward-deployed battle group is able to operate far enough off shore to be safe while providing a long reach for distant targets. In this paper, the characteristics of the railgun systems needed for these applications are identified and discussed, leading to a definition of the most important science and technology objectives for near-term research programs
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paper_title: Miniature mechanical safety and arming device with runaway escapement arming delay mechanism for artillery fuze

paper_content:

Abstract In this research, a miniature mechanical SAD (Safety and Arming Device) with arming delay was developed for actual munitions application. Reliable arming delay performance was achieved by applying a runaway escapement system that operates by a rack-and-pinion motion. The miniature mechanical SAD was fabricated using a stainless steel wet etching process that provided not only miniaturization but also a high processing yield. The miniature mechanical SAD performed successfully under the desired safety and arming conditions in lab tests and showed fine agreement with the finite element method simulation results. Field tests were performed with a grenade launcher to validate its performance under the actual firing conditions. One hundred samples that were shot 23.6 m (safety distance) and 200 m (arming distance), and every specific test criterion was met successfully. The new SAD was also found to be appropriate for safe use in artillery fuzes by conducting environmental tests under a variety of temperature, vibration, and impact conditions.
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paper_title: Measure variation of magnetic field waveforms above the rails of rail-gun during the launching period

paper_content:

The rail-gun has two rails with an armature sliding along the rails, and the armature is accelerated by the transient current. In order to analysis variation of magnetic field waveforms above rails of the rail-gun during the launching period for EMI designs, the magnetic fields are measured by loop probes, and current waveforms are measured by calibrated probes. The magnetic fields waveform besides static rails has the same raise time and width time as the main current. According to the armature movement states and measurement positions, magnetic waveforms are distinguished with each other. The experiment results show that magnetic field waveforms above the rails change for the different positions. There are narrower raise time and last time with higher velocities. The truncated waveforms introduce new spectrum signals around the rails. The waveforms at different positions are compared with each other, which can inflect the magnetic field distribution along the rails during the armature is launching. The results are useful to analysis the interference of the transient environment for the rail launcher and it is also useful for the EMI design of rail-gun systems.
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paper_title: The 100-kJ Modular Pulsed Power Units for Railgun

paper_content:

A 3.2-MJ pulsed power supply system for railgun has been built. The power supply system consists of 32 pulse forming units (PFUs) of 100 kJ each. Each PUF can be triggered and controlled independently by the center computer by fiber optic transmitters. The maximum total current of the 3.2-MJ supply system reaches 500 kA. The new PFU is smaller than the former one. The PFU is composed of two capacitors, a set of semiconducting switches (thyristor and crowbar diode), an inductor, a safety device, a local controller and data acquisition circuit, a current coil, and coaxial cables. The modular PFU is designed for a maximum charging voltage of 10 kV and the peak current up to 50 kA/module. In order to reduce the influence of the electromagnetic interference and the electromagnetic force and to provide the high flexibility reliability, the arrangement of components and the configuration of the pulsed power module have been improved. A local data acquisition circuit in each PFU can record and save the discharging current and the voltage of the capacitor itself and upload test data to the computer by fiber optics. This paper describes the stack configuration, the test facility, and the prototype arrangement of 32 modular pulsed power units.
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paper_title: A Four-Stage XRAM Generator as Inductive Pulsed Power Supply for a Small-Caliber Railgun

paper_content:

A four-stage XRAM generator is built and then applied to a railgun having a caliber of 15 × 15 mm. The XRAM generator is based on 1-mH Brooks coils and on standard high-power thyristors which are employed as opening switches according to the ICCOS countercurrent commutation principle. The coils of the generator are charged with a current of 10 kA, which corresponds to an energy of 200 kJ. The current is successfully commutated and a pulse with a maximum current of 40 kA is applied to the railgun. Consequently, a projectile with a total weight of 33 g is accelerated to 157 m/s within the railgun length of 2.1 m. The semiconductor switches are exposed to a steep voltage rise due to the muzzle flash when the projectile leaves the railgun without their critical limit being exceeded. Thus, the successful operation of the XRAM generator using semiconductor switches during railgun experiments is demonstrated. Furthermore, we are able to show in a further experiment that the muzzle flash of the railgun can be significantly reduced by switching the XRAM back into charging mode when the projectile leaves the bore. This method also allows the conservation of the energy that remains in the coils after the exit of the projectile from the railgun.
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paper_title: History and the Status of Electric Ship Propulsion, Integrated Power Systems, and Future Trends in the U.S. Navy

paper_content:

While electric propulsion for warships has existed for nearly a century, it has only been since the end of the Cold War that modern integrated power systems have been developed and implemented on U.S. Navy warships. The principal enablers have been the products of research and development for rotating machines (generators and propulsion motors), power electronics (power conversion and motor drives), energy storage, and controls. The U.S. Navy has implemented this advanced technology incrementally. Notably, DDG 1000 with its integrated propulsion system and CVN 78 with its electromagnetic aircraft launch system will soon join the fleet and mark another important advance to the electric warship. In the future, the integration of electric weapons such as railguns, high power radars, and lasers will result in the final achievement of the electric warship.
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paper_title: The image processing and target identification of laser imaging fuze

paper_content:

Imaging detection can get the geometric shape and exterior features of target in very close distance, and supply the information for target recognition. But because of the large amount of the information and the real-time requirement, the image of target is always distorted and incomplete.To solve this probolem,the image proecessing and target identification method of laser imaging fuze are introduced. Firstly,a thinning algorithm for binary image is proposed to get the target skeleton. Secondly, the feature of the target is extracted, this kind of feature is very helpful on the hardware design of system. Finally ,the FMW (Feature Mapping Wave) network is developed from M-P network and ART theory to recognitize target status. This kind of image processing system including plane target identification and the engagement of missile and plane identification. The validity of the system has been validated.
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paper_title: Design and fabrication of large- and small-bore railguns

paper_content:

A joint program between the Lawrence Livermore National Laboratory and the Los Alamos National Laboratory was conducted to establish whether railguns could be operated at megampere currents, to set operating limits, and to provide data to validate the modeling of railgun technology. This paper discusses the 12.7- and 50.0-mm-bore railguns designed and fabricated for this program. The design criteria, the materials and fabrication methods, and the success of the designs are discussed in detail.
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paper_title: Thermal Analysis of High-Energy Railgun Tests

paper_content:

This paper describes temperature measurements made on the high-energy medium-caliber launcher at the Institute for Advanced Technology. Simulations performed in Maxwell 3-D and E-Physics showed that Joule heating from current diffusing into the rails accounts for most of the temperature rise in the conductors. Temporal skin effects increase thermal dissipation significantly over what would be expected by the ohmic losses under fully diffused conditions. Based on this analysis, Joule heating is the overwhelmingly dominant source of heating in low-speed tests. As the velocity of the armature increases, Joule heating remains the dominant source of heat; however, additional mechanisms-which may include frictional heating, arcing energy, aluminum deposition, and temperature-dependent properties-are required to more satisfactorily explain the temperature profile obtained.
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paper_title: Electromagnetic launch: a review of the U.S. National Program

paper_content:

The United States Program to use electric energy rather than chemical energy to propel materials to high velocity is now focused almost entirely on fundamental research efforts to provide an understanding of the critical research issues for selected military applications, specifically on applications of direct interest to the U.S. Army. Almost all of the applications envisioned since the inception of the program in the late 1970's still appear to be viable. But, the military interest to propel projectiles to higher and higher velocities for direct and indirect fire applications dominates the funding for research and consequently determines the current directions of the science and technology.
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paper_title: A 10 MJ cryogenic inductor

paper_content:

A high current, high efficiency inductor for a 10 MJ pulsed power supply for powering experimental electromagnetic launcher systems has been designed and is in fabrication. This inductor employs liquid nitrogen cooled copper windings which are compensated for transient effects and high strength aluminum structure to react magnetic forces. A toroidal geometry minimizes external fields, and is capable of being connected in either a 20 µH or 5 µH configuration with peak currents of 1 and 2 MA, respectively. The details of the concept selection and design are presented.
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paper_title: Early electric gun research

paper_content:

There have been sporadic efforts to use electricity to power guns and launch projectiles at high velocity for more than a century. Each generation seems to have "reinvented" the idea and has built upon prior efforts, leading to successively greater progress. With the present interest in electric guns for military, and other, applications, it is instructive to review previous developments and examine their relevance to present research. Although there are isolated reports of early efforts in the 19th century, the major developments have been in the 20th century. They include efforts in Norway in 1901, French developments in World War I and research in Germany and Japan during World War II. The primary focus of this paper is to review the work of Andre Louis Octave Fauchon-Villeplee in France and Joachim Hansler in Germany, although the early Japanese and Russian interests are also mentioned. The various novel ideas suggested are highlighted, especially where they are relevant to ideas that are being studied or considered today.
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paper_title: The ISL Rapid Fire Railgun Project RAFIRA Part I: Technical Aspects and Design Considerations

paper_content:

This paper reports on the progress made within the rapid fire railgun (RAFIRA) project recently launched at the ISL. The goal of this project is to investigate the multishot capacity of the armature technology developed at ISL. This technology is characterized by the use of multiple metal fiber brush armatures. The project bases on results mainly obtained with the railgun EMA3 at ISL (muzzle velocity v0 les 2 km/s, applied energy per shot Eprim < 1MJ, 1 = 3 m, regular cal. = 15 mm x 30 mm). These results are characterized by good contact performance with respect to friction, rail erosion and contact transition in the range up to 2 km/s. The paper summarizes the main results in single shot mode and introduces preliminary experiments with respect to multishot applications. Subsequently technical aspects about loading and switching technologies for a multishot system are discussed and last but not least concrete design considerations for the medium caliber system RAFIRA are presented.
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paper_title: Magnetic Diffusion Inside the Rails of an Electromagnetic Launcher: Experimental and Numerical Studies

paper_content:

The topic of this paper is the distribution of magnetic fields inside the rails of the electromagnetic railgun RAFIRA located at the ISL. The magnetic field pulse characteristics are measured using colossal magnetoresistance-B-scalar sensors placed at different depths inside the rails of the accelerator. During launch the muzzle velocity reached up to 1.4 km/s, the electrical shot energy is about 1.2 MJ and the projectile mass was 140 g. The obtained results are analyzed using two models based on analytic solutions of Maxwell's equations. The first model considers the 1-D magnetic field diffusion in the direction perpendicular to the rails. The second model includes convection and simulates the 2-D behavior of the magnetic field distribution in three regions: the armature, the contact zone between rail and armature and the rail behind the armature. Additionally, 2-D and 3-D quasistationary finite element models are developed using Comsol Multiphysics. Excellent agreement is found between the 3-D simulation results and the measurements of magnetic diffusion.
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paper_title: Thermal and electromagnetic analysis of an electromagnetic launcher

paper_content:

An advanced high-power electromagnetic launcher (EML) improves performance by as much as 30% over conventional launchers. Electrical energy is the main driving source for the electromagnetic launcher. In the new EML, thermal energy, generated by the extraordinarily high current that goes through the rail and the armature, changes the electrical, thermal, and mechanical specifications of the structure. This paper reports on a study of the thermal and magnetic induction distribution in the rail and the armature at different locations. In our formulation of governing nonlinear differential equations, because of the electrical conductivity and ohmic heating of the rail and the armature, Maxwell equations are coupled with energy equations. The friction force that causes heat between the armature and the rail is considered in the equations, as is the melting latent heat effect. To solve the nonlinear governing differential equations, we utilize an unstructured, moving-mesh-generation, control-volume-based finite-difference code for the rail and the armature. In this method of solution, unlike most others, the rail stays stationary and the armature moves in the forward direction. Results obtained for the rail and the armature show that the maximum temperature occurs at the trailing edge of the armature. In this region, the temperature reaches about 600 K. However, the temperature of 1 m of rail stays around 360 K.
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paper_title: Pulsed magnetic field measurement system based on colossal magnetoresistance-B-scalar sensors for railgun investigation

paper_content:

A high pulsed magnetic field measurement system based on the use of CMR-B-scalar sensors was developed for the investigations of the electrodynamic processes in electromagnetic launchers. The system consists of four independent modules (channels) which are controlled by a personal computer. Each channel is equipped with a CMR-B-scalar sensor connected to the measurement device—B-scalar meter. The system is able to measure the magnitude of pulsed magnetic fields from 0.3 T to 20 T in the range from DC up to 20 kHz independently of the magnetic field direction. The measurement equipment circuit is electrically separated from the ground and shielded against low and high frequency electromagnetic noise. The B-scalar meters can be operated in the presence of ambient pulsed magnetic fields with amplitudes up to 0.2 T and frequencies higher than 1 kHz. The recorded signals can be transmitted to a personal computer in a distance of 25 m by means of a fiber optic link. The system was tested using the electromagnet...
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paper_title: Measurement of Solid Armature’s In-Bore Velocity Using B-Dot Probes in a Series-Augmented Railguns

paper_content:

The waveform of solid armature displacement and velocity can be obtained by arranging B-dot probe arrays along the barrel of a series augmented railgun. The moment of armature arrival can be detected by an evident change in the differential signal from the B-dot probe while armature passes by. However, it is difficult or even impossible in a railgun to directly pick up the arrival moment, because both armature movement and rail current are responsible for the change of differential signal, especially in the series-augmented railgun where currents in both outer rails and connecting conductors are probably sensed by the B-dot probe. A ratio function (RF) has been introduced to eliminate the influence of current change, which is the ratio of the integral of differential signal to the current. The RF of the armature probe aimed at the armature current will reach a maximum at the moment of armature arrival, while the one at the rail current will reach the median. Three shots with identical initial conditions were conducted in a series-augmented railgun, each of which had adopted the armature probe, rail probe, and Velocity Interferometer System for Any Reflector, respectively. The good agreement between the displacement and velocity waveforms derived from B-dot probes indicated that the method and measurement were valid. The accuracy of the B-dot method is mainly affected by probe dimension and position, railgun current distribution, and electromagnetic noise.
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paper_title: Application of W-band, Doppler Radar to Railgun Velocity Measurements

paper_content:

Abstract This paper describes a W-Band Doppler radar system in use at the electromagnetic launch facility at the Naval Surface Warfare Center in Dahgren, VA. Experimental results for a medium caliber railgun launch at 2000 m/s are presented. A discussion of the radar signal characteristics is given and the Doppler velocity profile during launch is computed. The in-bore time history of the launch package derived from the radar system is found to have good agreement with that derived from traditional magnetic field flux sensors (B-dot sensors). Given the increased temporal resolution of the radar system over B-dot measurements, time resolved friction coefficients can be estimated based on launch parameters. Due to the capabilities of the Dahlgren test range, the radar is able to track the projectile for a portion of flight just after the projectile exits the launcher. Drag coefficients for the projectile in hypervelocity free-flight are also presented.
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paper_title: Thermal and electromagnetic analysis of an electromagnetic launcher

paper_content:

An advanced high-power electromagnetic launcher (EML) improves performance by as much as 30% over conventional launchers. Electrical energy is the main driving source for the electromagnetic launcher. In the new EML, thermal energy, generated by the extraordinarily high current that goes through the rail and the armature, changes the electrical, thermal, and mechanical specifications of the structure. This paper reports on a study of the thermal and magnetic induction distribution in the rail and the armature at different locations. In our formulation of governing nonlinear differential equations, because of the electrical conductivity and ohmic heating of the rail and the armature, Maxwell equations are coupled with energy equations. The friction force that causes heat between the armature and the rail is considered in the equations, as is the melting latent heat effect. To solve the nonlinear governing differential equations, we utilize an unstructured, moving-mesh-generation, control-volume-based finite-difference code for the rail and the armature. In this method of solution, unlike most others, the rail stays stationary and the armature moves in the forward direction. Results obtained for the rail and the armature show that the maximum temperature occurs at the trailing edge of the armature. In this region, the temperature reaches about 600 K. However, the temperature of 1 m of rail stays around 360 K.
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paper_title: Measurement of Solid Armature’s In-Bore Velocity Using B-Dot Probes in a Series-Augmented Railguns

paper_content:

The waveform of solid armature displacement and velocity can be obtained by arranging B-dot probe arrays along the barrel of a series augmented railgun. The moment of armature arrival can be detected by an evident change in the differential signal from the B-dot probe while armature passes by. However, it is difficult or even impossible in a railgun to directly pick up the arrival moment, because both armature movement and rail current are responsible for the change of differential signal, especially in the series-augmented railgun where currents in both outer rails and connecting conductors are probably sensed by the B-dot probe. A ratio function (RF) has been introduced to eliminate the influence of current change, which is the ratio of the integral of differential signal to the current. The RF of the armature probe aimed at the armature current will reach a maximum at the moment of armature arrival, while the one at the rail current will reach the median. Three shots with identical initial conditions were conducted in a series-augmented railgun, each of which had adopted the armature probe, rail probe, and Velocity Interferometer System for Any Reflector, respectively. The good agreement between the displacement and velocity waveforms derived from B-dot probes indicated that the method and measurement were valid. The accuracy of the B-dot method is mainly affected by probe dimension and position, railgun current distribution, and electromagnetic noise.
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paper_title: Application of W-band, Doppler Radar to Railgun Velocity Measurements

paper_content:

Abstract This paper describes a W-Band Doppler radar system in use at the electromagnetic launch facility at the Naval Surface Warfare Center in Dahgren, VA. Experimental results for a medium caliber railgun launch at 2000 m/s are presented. A discussion of the radar signal characteristics is given and the Doppler velocity profile during launch is computed. The in-bore time history of the launch package derived from the radar system is found to have good agreement with that derived from traditional magnetic field flux sensors (B-dot sensors). Given the increased temporal resolution of the radar system over B-dot measurements, time resolved friction coefficients can be estimated based on launch parameters. Due to the capabilities of the Dahlgren test range, the radar is able to track the projectile for a portion of flight just after the projectile exits the launcher. Drag coefficients for the projectile in hypervelocity free-flight are also presented.
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paper_title: Thermal and electromagnetic analysis of an electromagnetic launcher

paper_content:

An advanced high-power electromagnetic launcher (EML) improves performance by as much as 30% over conventional launchers. Electrical energy is the main driving source for the electromagnetic launcher. In the new EML, thermal energy, generated by the extraordinarily high current that goes through the rail and the armature, changes the electrical, thermal, and mechanical specifications of the structure. This paper reports on a study of the thermal and magnetic induction distribution in the rail and the armature at different locations. In our formulation of governing nonlinear differential equations, because of the electrical conductivity and ohmic heating of the rail and the armature, Maxwell equations are coupled with energy equations. The friction force that causes heat between the armature and the rail is considered in the equations, as is the melting latent heat effect. To solve the nonlinear governing differential equations, we utilize an unstructured, moving-mesh-generation, control-volume-based finite-difference code for the rail and the armature. In this method of solution, unlike most others, the rail stays stationary and the armature moves in the forward direction. Results obtained for the rail and the armature show that the maximum temperature occurs at the trailing edge of the armature. In this region, the temperature reaches about 600 K. However, the temperature of 1 m of rail stays around 360 K.
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paper_title: Thermal Analysis of High-Energy Railgun Tests

paper_content:

This paper describes temperature measurements made on the high-energy medium-caliber launcher at the Institute for Advanced Technology. Simulations performed in Maxwell 3-D and E-Physics showed that Joule heating from current diffusing into the rails accounts for most of the temperature rise in the conductors. Temporal skin effects increase thermal dissipation significantly over what would be expected by the ohmic losses under fully diffused conditions. Based on this analysis, Joule heating is the overwhelmingly dominant source of heating in low-speed tests. As the velocity of the armature increases, Joule heating remains the dominant source of heat; however, additional mechanisms-which may include frictional heating, arcing energy, aluminum deposition, and temperature-dependent properties-are required to more satisfactorily explain the temperature profile obtained.
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paper_title: Numerical simulation of interior ballistic process of railgun based on the multi-field coupled model

paper_content:

Railgun launcher design relies on appropriate models. A multi-field coupled model of railgun launcher was presented in this paper. The 3D transient multi-field was composed of electromagnetic field, thermal field and structural field. The magnetic diffusion equations were solved by a finite-element boundary-element coupling method. The thermal diffusion equations and structural equations were solved by a finite element method. A coupled calculation was achieved by the transfer data from the electromagnetic field to the thermal and structural fields. Some characteristics of railgun shot, such as velocity skin effect, melt-wave erosion and magnetic sawing, which are generated under the condition of large-current and high-speed sliding electrical contact, were demonstrated by numerical simulation.
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paper_title: Thermal Analysis of High-Energy Railgun Tests

paper_content:

This paper describes temperature measurements made on the high-energy medium-caliber launcher at the Institute for Advanced Technology. Simulations performed in Maxwell 3-D and E-Physics showed that Joule heating from current diffusing into the rails accounts for most of the temperature rise in the conductors. Temporal skin effects increase thermal dissipation significantly over what would be expected by the ohmic losses under fully diffused conditions. Based on this analysis, Joule heating is the overwhelmingly dominant source of heating in low-speed tests. As the velocity of the armature increases, Joule heating remains the dominant source of heat; however, additional mechanisms-which may include frictional heating, arcing energy, aluminum deposition, and temperature-dependent properties-are required to more satisfactorily explain the temperature profile obtained.
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paper_title: Thermal runaway mechanism of lithium ion battery for electric vehicles: A review

paper_content:

Abstract The safety concern is the main obstacle that hinders the large-scale applications of lithium ion batteries in electric vehicles. With continuous improvement of lithium ion batteries in energy density, enhancing their safety is becoming increasingly urgent for the electric vehicle development. Thermal runaway is the key scientific problem in battery safety research. Therefore, this paper provides a comprehensive review on the thermal runaway mechanism of the commercial lithium ion battery for electric vehicles. Learning from typical accidents, the abuse conditions that may lead to thermal runaway have been summarized. The abuse conditions include mechanical abuse, electrical abuse, and thermal abuse. Internal short circuit is the most common feature for all the abuse conditions. The thermal runaway follows a mechanism of chain reactions, during which the decomposition reaction of the battery component materials occurs one after another. A novel energy release diagram, which can quantify the reaction kinetics for all the battery component materials, is proposed to interpret the mechanisms of the chain reactions during thermal runaway. The relationship between the internal short circuit and the thermal runaway is further clarified using the energy release diagram with two cases. Finally, a three-level protection concept is proposed to help reduce the thermal runaway hazard. The three-level protection can be fulfilled by providing passive defense and early warning before the occurrence of thermal runaway, by enhancing the intrinsic thermal stability of the materials, and by reducing the secondary hazard like thermal runaway propagation.
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paper_title: Synergy of Melt-Wave and Electromagnetic Force on the Transition Mechanism in Electromagnetic Launch

paper_content:

Synergy of melting wave and electromagnetic force on the transition mechanism is studied in this paper. The 3-D electromagnetic field, temperature field, and structure field coupling model are established to simulate the velocity skin effect and melting wave phenomenon. It is found that the melting wave and electromagnetic force together lead to the occurrence of transition. And the two are inextricably linked. The melting wave will enlarge the separating electromagnetic force on the armature trailing arm. The separating electromagnetic force may result in the reduction of contact area, which would accelerate the melting wave. It is getting worse and worse, eventually lead to the transition. And the analytical results are consistent with the experimental phenomena. The transition prediction method will be more accurate when combining the melt-wave and the electromagnetic force.
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paper_title: 3D numerical simulation and analysis of railgun gouging mechanism

paper_content:

A gouging phenomenon with a hypervelocity sliding electrical contact in railgun not only shortens the rail lifetime but also affects the interior ballistic performance. In this paper, a 3-D numerical model was introduced to simulate and analyze the generation mechanism and evolution of the rail gouging phenomenon. The results show that a rail surface bulge is an important factor to induce gouging. High density and high pressure material flow on the contact surface, obliquely extruded into the rail when accelerating the armature to a high velocity, can produce gouging. Both controlling the bulge size to a certain range and selecting suitable materials for rail surface coating will suppress the formation of gouging. The numerical simulation had a good agreement with experiments, which validated the computing model and methodology are reliable.
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paper_title: Experiments with the Green Farm electric gun facility

paper_content:

The design and construction of a major electric gun facility at Green Farm in San Diego is described. The facility is driven by an 11 kV 32 MJ capacitor bank, arranged in 4 MJ modules that can be independently triggered to provide a choice of pulse shapes. The bank has powered a variety of EM and ET guns, including an 8-meter Single Shot Rail gun and a modified 5-inch Naval gun. World record high energy and high velocity shots have been achieved. The highest rail gun muzzle energy was 8.6 MJ and the highest muzzle velocity was 4.3 km/s with a plasma driven projectile of 0.64 kg, corresponding to a muzzle energy of 6 MJ. Intact projectile launch and flight was confirmed by high speed (8000 frames/sec.) photography and flash X-rays. >
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paper_title: Analysis of in-bore magnetic field in C-shaped armature railguns

paper_content:

Abstract In order to analysis the distribution characteristics of in-bore magnetic field for C-shaped armature electromagnetic railgun, a computational model considering dynamic contact pressure is established. By solving the dynamic equation, the in-bore motion characteristics of the armature are obtained. The distribution of current in the rail and armature is analyzed based on the magnetic diffusion equation and Ampere's law. On this basis, three simulation models are proposed, which correspond to static state, motion state and motion state considering the velocity skin effect. The magnetic field of the investigated points along the central axes of the armature front end are obtained. The results show that, in static state, the peak magnetic flux density of each investigated point is greater than the other two states. Velocity skin effect leads to a decrease in peak magnetic flux density. The change of motion state has little influence on the peak magnetic flux density of the investigated point that far away from the armature. The calculated results can be used in the electromagnetic shielding design of intelligent ammunition.
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paper_title: Research on Thermal Stress by Current Skin Effect in a Railgun

paper_content:

In this paper, a research on the damages of material caused by thermal stress in electromagnetic launch is presented. 3-D finite-element program is established to calculate the transient electromagnetic fields and temperature fields including a moving armature. The focus is mainly on the high temperature and large thermal stress damages to the rail. Thermal stress is produced by the current density concentration and defined as the skin effect. There are two main reasons for the current skin effect. One is due to the rapid changes of the current wave. The other is due to the moving conductors known as the velocity skin effect. The simulation results illustrate that with the influence of the current skin effect, the thermal stress will concentrate at a small area. This area may cause the grooving damage at startup, besides, the gouging damage at high velocity. Finally, the results are in agreement with the experiments.
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paper_title: Numerical simulation of interior ballistic process of railgun based on the multi-field coupled model

paper_content:

Railgun launcher design relies on appropriate models. A multi-field coupled model of railgun launcher was presented in this paper. The 3D transient multi-field was composed of electromagnetic field, thermal field and structural field. The magnetic diffusion equations were solved by a finite-element boundary-element coupling method. The thermal diffusion equations and structural equations were solved by a finite element method. A coupled calculation was achieved by the transfer data from the electromagnetic field to the thermal and structural fields. Some characteristics of railgun shot, such as velocity skin effect, melt-wave erosion and magnetic sawing, which are generated under the condition of large-current and high-speed sliding electrical contact, were demonstrated by numerical simulation.
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paper_title: Magnetic Diffusion Inside the Rails of an Electromagnetic Launcher: Experimental and Numerical Studies

paper_content:

The topic of this paper is the distribution of magnetic fields inside the rails of the electromagnetic railgun RAFIRA located at the ISL. The magnetic field pulse characteristics are measured using colossal magnetoresistance-B-scalar sensors placed at different depths inside the rails of the accelerator. During launch the muzzle velocity reached up to 1.4 km/s, the electrical shot energy is about 1.2 MJ and the projectile mass was 140 g. The obtained results are analyzed using two models based on analytic solutions of Maxwell's equations. The first model considers the 1-D magnetic field diffusion in the direction perpendicular to the rails. The second model includes convection and simulates the 2-D behavior of the magnetic field distribution in three regions: the armature, the contact zone between rail and armature and the rail behind the armature. Additionally, 2-D and 3-D quasistationary finite element models are developed using Comsol Multiphysics. Excellent agreement is found between the 3-D simulation results and the measurements of magnetic diffusion.
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paper_title: The Use of Electronic Components in Railgun Projectiles

paper_content:

This paper deals with experiments and calculations performed in order to investigate the influence of the electromagnetic hardening of payloads in a railgun. This is a complex task: besides the large amplitudes of the in-bore magnetic fields due to the pulsed current, the exit of the projectile from the muzzle and the consequences of plasma arcs have to be considered. At the muzzle the magnetic induction can drop from several Teslas to zero within some microseconds, leading to very high induced voltages and electric fields in the metallic parts of the projectile. On the other hand, the electric contact established by solid armatures tends to develop into electric arcs at high velocities during the launch. These plasma arcs as well as the closing switch transients of the railgun circuit are a source of electromagnetic radiation in a broad spectral range. Some electronic devices were selected and tested with static setups corresponding to the previous conditions. In a first phase a series of static railgun experiments (no projectile movement) was performed. In a second phase, static experiments simulating the muzzle exit conditions were carried out. Finally, the influence of electromagnetic waves emitted during railgun experiments on electronic devices was investigated, using a static setup with a conventional spark gap.
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paper_title: The Use of Electronic Components in Railgun Projectiles

paper_content:

This paper deals with experiments and calculations performed in order to investigate the influence of the electromagnetic hardening of payloads in a railgun. This is a complex task: besides the large amplitudes of the in-bore magnetic fields due to the pulsed current, the exit of the projectile from the muzzle and the consequences of plasma arcs have to be considered. At the muzzle the magnetic induction can drop from several Teslas to zero within some microseconds, leading to very high induced voltages and electric fields in the metallic parts of the projectile. On the other hand, the electric contact established by solid armatures tends to develop into electric arcs at high velocities during the launch. These plasma arcs as well as the closing switch transients of the railgun circuit are a source of electromagnetic radiation in a broad spectral range. Some electronic devices were selected and tested with static setups corresponding to the previous conditions. In a first phase a series of static railgun experiments (no projectile movement) was performed. In a second phase, static experiments simulating the muzzle exit conditions were carried out. Finally, the influence of electromagnetic waves emitted during railgun experiments on electronic devices was investigated, using a static setup with a conventional spark gap.
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paper_title: The Use of Electronic Components in Railgun Projectiles

paper_content:

This paper deals with experiments and calculations performed in order to investigate the influence of the electromagnetic hardening of payloads in a railgun. This is a complex task: besides the large amplitudes of the in-bore magnetic fields due to the pulsed current, the exit of the projectile from the muzzle and the consequences of plasma arcs have to be considered. At the muzzle the magnetic induction can drop from several Teslas to zero within some microseconds, leading to very high induced voltages and electric fields in the metallic parts of the projectile. On the other hand, the electric contact established by solid armatures tends to develop into electric arcs at high velocities during the launch. These plasma arcs as well as the closing switch transients of the railgun circuit are a source of electromagnetic radiation in a broad spectral range. Some electronic devices were selected and tested with static setups corresponding to the previous conditions. In a first phase a series of static railgun experiments (no projectile movement) was performed. In a second phase, static experiments simulating the muzzle exit conditions were carried out. Finally, the influence of electromagnetic waves emitted during railgun experiments on electronic devices was investigated, using a static setup with a conventional spark gap.
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paper_title: Microstructure, electromagnetic shielding effectiveness and mechanical properties of Mg–Zn–Y–Zr alloys

paper_content:

Abstract The microstructure, electromagnetic interference (EMI) shielding effectiveness (SE) and mechanical properties of Mg–Zn–Y–Zr alloys with 0–3.91 wt.% Y were investigated systematically in this work. The results indicated that addition of Y brought about the formation of I-phase (Mg 3 Zn 6 Y) and W-phase (Mg 3 Zn 3 Y 2 ) and refined grains in as-cast state. After hot extrusion, there was more and more broken particles dispersing in matrix when Y content ranged from 0 to 3.19 wt.%. With increasing Y content, EMI SE was enhanced significantly in extruded state. The alloy with 1.9 wt.% Y exhibited the optimal EMI shielding capacity with the SE value of 79–118 dB. It was found that good mechanical properties could be achieved by adding very low Y content. The extruded alloy with 0.5 wt.% Y presented higher yield strength (268 MPa), ultimate tensile strength (334 MPa) and good elongation ( δ = 12.3%) compared with other extruded alloys. A subsequent aging treatment on the extruded alloy with 1.29 wt.% Y exhibiting outstanding comprehensive EMI SE and mechanical properties resulted in precipitation of W, β 1 ′ and β 2 ′ phases, which led to further improvement in EMI SE. The peak-aged sample showed the superior mechanical properties. Based on the microstructure observation, the changes of EMI shielding capacity and mechanical properties have been discussed.
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paper_title: Microstructure, electromagnetic shielding effectiveness and mechanical properties of Mg–Zn–Y–Zr alloys

paper_content:

Abstract The microstructure, electromagnetic interference (EMI) shielding effectiveness (SE) and mechanical properties of Mg–Zn–Y–Zr alloys with 0–3.91 wt.% Y were investigated systematically in this work. The results indicated that addition of Y brought about the formation of I-phase (Mg 3 Zn 6 Y) and W-phase (Mg 3 Zn 3 Y 2 ) and refined grains in as-cast state. After hot extrusion, there was more and more broken particles dispersing in matrix when Y content ranged from 0 to 3.19 wt.%. With increasing Y content, EMI SE was enhanced significantly in extruded state. The alloy with 1.9 wt.% Y exhibited the optimal EMI shielding capacity with the SE value of 79–118 dB. It was found that good mechanical properties could be achieved by adding very low Y content. The extruded alloy with 0.5 wt.% Y presented higher yield strength (268 MPa), ultimate tensile strength (334 MPa) and good elongation ( δ = 12.3%) compared with other extruded alloys. A subsequent aging treatment on the extruded alloy with 1.29 wt.% Y exhibiting outstanding comprehensive EMI SE and mechanical properties resulted in precipitation of W, β 1 ′ and β 2 ′ phases, which led to further improvement in EMI SE. The peak-aged sample showed the superior mechanical properties. Based on the microstructure observation, the changes of EMI shielding capacity and mechanical properties have been discussed.
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paper_title: Microstructure, electromagnetic shielding effectiveness and mechanical properties of Mg–Zn–Cu–Zr alloys

paper_content:

Abstract The microstructure, electromagnetic interference (EMI) shielding effectiveness (SE) and mechanical properties of Mg–Zn– x Cu–Zr alloys ( x = 0–2.32 wt.%) were investigated in this study. The results indicated that the addition of Cu led to the formation of MgZnCu phase with a face-center cubic structure, and resulted in grain refinement. EMI SE increased significantly with increasing Cu content in extruded state. The alloy with 2.32 wt.% Cu exhibited optimal EMI shielding capacity with SE value of 84–117 dB. Meanwhile, it was found that good mechanical properties could be achieved by adding low Cu content. The extruded alloy with 0.37 wt.% Cu presented higher yield strength (276 MPa), ultimate tensile strength (346 MPa) and elongation ( δ = 11.4%) compared with other extruded alloys. However, a higher Cu content would substantially deteriorate tensile properties of the alloys. Based on microstructure observation, the variation of EMI shielding capacity and mechanical properties have been discussed.
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paper_title: Electromagnetic shielding properties of soft magnetic powder–polymer composite films for the application to suppress noise in the radio frequency range

paper_content:

Abstract Electromagnetic absorption characteristics in the near- and the far-field regime were evaluated from measurements of power loss by the coaxial transmission and reflection method and the microstrip line method, respectively, for high-density soft magnetic Fe–Al–Si alloy–polymer composite films that were highly effective in the radio frequency (RF) range. The electromagnetic absorption in the near- and the far-field regime for the soft magnetic metal–polymer composite films was greatly dependent on the film density. The electromagnetic absorption in the RF range significantly increased with increasing film density, which was caused by the increase of the magnetic permeability and the electrical conductivity. As a result, the high-density soft magnetic film showed excellent electromagnetic absorption for the near- and the far-field electromagnetic shielding and was applicable as an electromagnetic absorber for high-frequency devices operated over 0.1 GHz.
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paper_title: Electromagnetic shielding mechanisms using soft magnetic stainless steel fiber enabled polyester textiles

paper_content:

Abstract This work studied the effects of conductivity, magnetic loss, and complex permittivity when using blended textiles (SSF/PET) of polyester fibers (PET) with stainless steel fibers (SSF) on electromagnetic wave shielding mechanisms at electromagnetic wave frequencies ranging from 30 MHz to 1500 MHz. The 316L stainless steel fiber used in this study had 38 vol% γ austenite and 62 vol% α′ martensite crystalline phases, which was characterized by an x-ray diffractometer. Due to the magnetic and dielectric loss of soft metallic magnetic stainless steel fiber enabled polyester textiles, the relationship between the reflection/absorption/transmission behaviors of the electromagnetic wave and the electrical/magnetic/dielectric properties of the SSF and SSF/PET fabrics was analyzed. Our results showed that the electromagnetic interference shielding of the SSF/PET textiles show an absorption-dominant mechanism, which attributed to the dielectric loss and the magnetic loss at a lower frequency and attributed to the magnetic loss at a higher frequency, respectively.
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paper_title: Magnetic and conductive graphene papers toward thin layers of effective electromagnetic shielding

paper_content:

Graphene-based hybrids, specifically free-standing graphene-based hybrid papers, have recently attracted increasing attention in many communities for their great potential applications. As the most commonly used precursors for the preparation of graphene-based hybrids, electrically-insulating graphene oxides (GO) generally must be further chemically reduced or thermally annealed back to reduced GO (RGO) if high electrical conductivity is needed. However, various concerns are generated if the hybrid structures are sensitive to the treatments used to produce RGO. In this work, we develop a highly facile strategy to fabricate free-standing magnetic and conductive graphene-based hybrid papers. Electrically conductive graphene nanosheets (GNs) are used directly to grow Fe3O4 magnetic nanoparticles without additional chemical reduction or thermal annealing, thus completely avoiding the concerns in the utilisation of GO. The free-standing Fe3O4/GN papers are magnetic, electrically conductive and present sufficient magnetic shielding (>20 dB), making them promising for applications in the conductive magnetically-controlled switches. The shielding results suggest that the Fe3O4/GN papers of very small thickness (<0.3 mm) and light weight (∼0.78 g cm−3) exhibit comparable shielding effectiveness to polymeric graphene-based composites of much larger thickness. Fundamental mechanisms for shielding performance and associated opportunities are discussed.
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paper_title: Electromagnetic shielding effectiveness of aluminum alloy-fly ash composites

paper_content:

Abstract The cenosphere and precipitator fly ash particulates were used to produce two kinds of aluminum matrix composites with the density of 1.4–1.6 g cm −3 and 2.2–2.4 g cm −3 separately. The electromagnetic interference shielding effectiveness (EMSE) properties of the composites were measured in the frequency range of 30.0 kHz–1.5 GHz. The results indicated the EMSE properties of the two types of composites were nearly the same. By using the fly ash particles, the shielding effectiveness properties of the matrix aluminum have been improved in the frequency ranges 30.0 kHz–600.0 MHz and the increment varied with increasing frequency. The EMSE properties of 2024Al are in the range −36.1 ± 0.2 to −46.3 ± 0.3 dB while the composites are in the range −40.0 ± 0.8 to −102.5 ± 0.1 dB in the frequency range 1.0–600.0 MHz. At higher frequency, the EMSE properties of the composites are similar to that of the matrix. The tensile strength of the matrix aluminum has been decreased by addition of the fly ash particulate and the tensile strength of the composites were 110.2 MPa and 180.6 MPa separately. The fractography showed that one composite fractured brittly and the other fractured in a microductile manner.
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paper_title: A novel structure of Ferro-Aluminum based sandwich composite for magnetic and electromagnetic interference shielding

paper_content:

Abstract A novel Ferro-Aluminum based sandwich composite for magnetic and electromagnetic interference shielding was designed and fabricated by hot pressing and subsequent diffusion treatment. The microstructure evolution of sandwich composite was characterized. Magnetic and electromagnetic interference shielding properties and mechanisms of the composites were also investigated. Sandwich composite is obtained with pure iron/Fe–Al alloy layer/pure iron structure and the Fe–Al/Fe interface shows good bonding. Al elemental content in reaction layer presents gradient distribution and the Al-riched brittle phase turns into ductile phase with diffusion time increasing. The electromagnetic shielding effectiveness of sandwich composite is higher than that of pure iron plate and increases with diffusion time extension, reaching 70 – 80 dB at the frequency of 30 KHz – 1.5 GHz. The multiple reflection loss in Fe–Al gradient layer is the primary contribution to the shielding effectiveness improvement of sandwich composite. The magnetic shielding effectiveness of sandwich composite can amount to 10 dB, about 2.5 times of that of pure iron plate. Fe–Al intermetallic layer, as non-magnetic spacer, is added between two iron plates and the permeable layer in sandwich composite can shunt magnetic field twice to improve shielding effectiveness.
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paper_title: Modeling and reliability characterization of area-array electronics subjected to high-g mechanical shock up to 50,000g

paper_content:

Electronics in aerospace applications may be subjected to very high g-loads during normal operation. A novel micro-coil array interconnect has been studied for increased reliability during extended duration aerospace missions in presence of high-g loads. Ceramic area-array components have been populated with micro-coil interconnects. The micro-coil spring (MCS) is fabricated using a beryllium copper wire post plated with 100 μin of Sn63Pb37, 50 mils in height with a diameter of 20 mils. Board assemblies have been subjected to high g-loads in the 0°, horizontal orientation. The board assemblies are daisy chained. Damage initiation and progression in interconnects has been measured using in-situ monitoring with high speed data-acquisition systems. Transient deformation of the board assemblies has been measured using high-speed cameras with digital image correlation. Multiple board assemblies have been subjected to shock tests till failure. Peak shock pulse magnitude ranges from 1,500g typical of JEDEC standard, to very high g-levels of 50,000g. The MCS interconnects are daisy chained and failures are measured using electrical continuity. A finite element model using explicit global to local models has been used to study interconnect reliability under shock loads. Models have been correlated with experimental data. The reliability performance of micro-coil interconnects has been compared to column interconnects. Results have shown that the micro-coil spring array has a higher reliability than the ceramic column grid array (CCGA). Failure modes have been determined.
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paper_title: Experimental study on the package of high-g accelerometer

paper_content:

Abstract In this paper, the effect of the package die adhesive and package shell on the performances of silicon based MEMS high-g accelerometers was reported. Using Raman spectroscopy, the residual stress caused by different package die adhesive thickness and different package shell material was characterized. It can be concluded from the testing results that: with thicker die adhesive, the residual stress increment was much smaller; the piezoresistance variation caused by this residual stress was much smaller; and the temperature shift of the output voltage was much smaller. Comparing with the ceramic package, the stainless steel package has bigger sensitivity and bigger anti-overload ability.
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paper_title: Out-of-plane micro triple-hot-wire anemometer based on Pyrex bubble for airflow sensing

paper_content:

The paper reports novel design and fabrication of out-of-plane micro airflow sensors based on the hot-wire sensing principle, i.e. gas cooling of electrically-heated wires. Three micro Ti/Au/Cu hot-wire resistors have been fabricated on an out-of-plane Pyrex bubble with height of 300 μm. They are arranged 120 degrees apart on the sidewall of a bubble at height of 100 μm for airflow velocity and direction detection. Air velocity around the out-of-plane bubble structure has been investigated for square and circular package designs. The sensor with axisymmetric circular package has demonstrated the ability to detect velocity (<;10 m/s) and to determine flow direction with an error less than ±8° when the velocity is 10m/s. The sensitivity could be further improved in a new design with increased bubble height (1 mm) and elevated hot-wire resistor position (500 μm), according to the modeling results.
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paper_title: Carbon-MEMS-Based Alternating Stacked MoS2 @rGO-CNT Micro-Supercapacitor with High Capacitance and Energy Density

paper_content:

A novel process to fabricate a carbon-microelectromechanical-system-based alternating stacked MoS2@rGO–carbon-nanotube (CNT) micro-supercapacitor (MSC) is reported. The MSC is fabricated by successively repeated spin-coating of MoS2@rGO/photoresist and CNT/photoresist composites twice, followed by photoetching, developing, and pyrolysis. MoS2@rGO and CNTs are embedded in the carbon microelectrodes, which cooperatively enhance the performance of the MSC. The fabricated MSC exhibits a high areal capacitance of 13.7 mF cm−2 and an energy density of 1.9 µWh cm−2 (5.6 mWh cm−3), which exceed many reported carbon- and MoS2-based MSCs. The MSC also retains 68% of capacitance at a current density of 2 mA cm−2 (5.9 A cm−3) and an outstanding cycling performance (96.6% after 10 000 cycles, at a scan rate of 1 V s−1). Compared with other MSCs, the MSC in this study is fabricated by a low-cost and facile process, and it achieves an excellent and stable electrochemical performance. This approach could be highly promising for applications in integration of micro/nanostructures into microdevices/systems.
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paper_title: Fabrication of a symmetric micro supercapacitor based on tubular ruthenium oxide on silicon 3D microstructures

paper_content:

Abstract A micro-supercapacitor with a three-dimensional configuration has been fabricated using an ICP etching technique. Hydrous ruthenium oxide with a tubular morphology is successfully synthesized using a cathodic deposition technique with a Si micro prominence as a template. The desired tubular RuO 2 · x H 2 O architecture facilitates electrolyte penetration and proton exchange/diffusion. A single MEMS electrode is studied using cyclic voltammetry, and a specific capacitance of 99.3 mF cm −2 and 70 F g −1 is presented at 5 mV s −1 in neutral Na 2 SO 4 solution. The accelerated cycle life is tested at 80 mV s −1 , and satisfactory cyclability is observed. When placed on a chip, the symmetric cell exhibits good supercapacitor properties, and a specific capacitance as high as 23 mF cm −2 is achieved at 10 mA cm −2 . Therefore, 3D MEMS microelectrode arrays with electrochemically deposited ruthenium oxide films are promising candidates for on-chip electrochemical micro-capacitor applications.
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paper_title: Impact experiment analysis of MEMS ultra-high G piezoresistive shock accelerometer

paper_content:

A novel ultra-high g shock micro accelerometer with four self-supporting piezoresistive micro beams was proposed to simultaneously enhance the sensor performance of sensitivity and frequency response. The finite element method (FEM) simulations indicated that the pure axial deformations could occur on self-supporting piezoresistive micro beams via optimizing structure dimensions. And the average stress distribution in piezoresistive beams was 81.5 MPa, the natural frequency of sensor was about 505.00 kHz. To verify the sensitivity and natural frequency of fabricated shock accelerometer, impact tests were carried out using Hopkinson pressure bar under impact loads of 100,000 g. The results were obtained in the form of response curves of a shock signal. Then, the average sensitivity was calculated as 1.586 μV/g/3V, and the natural frequency was obtained as 445 kHz by fast Fourier transform. The experimental results agreed well with the FEM simulations except for a slight mismatch in natural frequency which was probably resulted from the errors of device fabrication and package processes. The experiment results reliably demonstrate that the proposed shock accelerometer, with high natural frequency and high sensitivity, is capable of measuring ultra-high g loading shock.
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paper_title: Silicon micromachined high-shock accelerometers with a curved-surface-application structure for over-range stop protection and free-mode-resonance depression

paper_content:

In this paper we present a high-shock accelerometer that is in high demand in many engineering applications. The device, formed by using advanced silicon bulk micromachining technology, including deep-reactive ionic etching, uses a single-chip structure that facilitates packaging and contributes to low-cost mass-production. A novel curved-surface-application stop structure is designed and micromachining formed for the improved protection of over-range shock and the depression of free-mode resonance. By using a dropping-hammer testing system, characterizations of the sensors show a sensitivity of 3 μV g−1 for a 13 700g shock-range and satisfied wave fidelity of response to shock.
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paper_title: Simulation, fabrication and characterization of an all-metal contact-enhanced triaxial inertial microswitch with low axial disturbance

paper_content:

Abstract An all-metal inertial microswitch that is sensitive to three axial accelerations (+ x , + y and + z ) is fabricated by low-temperature photoresist modeled metal-electroplating technology. The inertial switch consists of four main parts: a quartz wafer with anti-stiction strips as the substrate; a proof mass suspended by conjoined serpentine springs as the movable electrode; two L -shaped flexible cantilevers and a multi-hole crossbeam as horizontal and vertical fixed electrodes, respectively; two anchors located in the middle of proof mass as limit blocks. ANSYS software is used to simulate the dynamic contact process in the microswitch, and the simulation results reveal that the flexible fixed electrode can prolong the contact time and eliminate the rebound during the contact process. The axial disturbance among different sensitive directions has been discussed by dynamic simulation. The modal analysis, crosstalk between horizontal and vertical directions, cross-axis sensitivity, and the disturbance under overload shock along the reverse sensitive direction are also simulated and discussed. The suspension and gap in the device structure can be precisely controlled utilizing the photoresist modeled metal-electroplating technology to reduce the axial disturbance effectively. Finally, the prototype is fabricated successfully and tested by dropping hammer system. It is shown that the test threshold acceleration is 255–260 g in horizontal directions (+ x and + y ), ∼75 g in vertical direction. The contact time of the switch with elastic contact point is ∼60 μs in horizontal direction and ∼80 μs in vertical direction. The crosstalk between horizontal and vertical direction, cross-axis and overload disturbance have been also demonstrated by test results, which indicate the axial disturbance is low in the present inertial switch.
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paper_title: Symmetric redox supercapacitor based on micro-fabrication with three-dimensional polypyrrole electrodes

paper_content:

Abstract To achieve higher energy density and power density, we have designed and fabricated a symmetric redox supercapacitor based on microelectromechanical system (MEMS) technologies. The supercapacitor consists of a three-dimensional (3D) microstructure on silicon substrate micromachined by high-aspect-ratio deep reactive ion etching (DRIE) method, two sputtered Ti current collectors and two electrochemical polymerized polypyrrole (PPy) films as electrodes. Electrochemical tests, including cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatical charge/discharge methods have been carried out on the single PPy electrodes and the symmetric supercapacitor in different electrolytes. The specific capacitance (capacitance per unit footprint area) and specific power (power per unit footprint area) of the PPy electrodes and symmetric supercapacitor can be calculated from the electrochemical test data. It is found that NaCl solution is a good electrolyte for the polymerized PPy electrodes. In NaCl electrolyte, single PPy electrodes exhibit 0.128 F cm −2 specific capacitance and 1.28 mW cm −2 specific power at 20 mV s −1 scan rate. The symmetric supercapacitor presents 0.056 F cm −2 specific capacitance and 0.56 mW cm −2 specific power at 20 mV s −1 scan rate.
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paper_title: Trends and challenges in modern MEMS sensor packages

paper_content:

Modern MEMS sensors for automotive as well as consumer electronics face a continuous pressure for size reduction. This can be met not only by a consistent shrink of sensing elements and ASICs resulting in a smaller package but also through the integration of several sensors into one system. The trends and challenges of this steady shrink will be explained and several examples of current automotive and consumer MEMS sensors will be shown.
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paper_title: Flexible transparent tribotronic transistor for active modulation of conventional electronics

paper_content:

Abstract Flexible and transparent electronics have attracted wide attention for electronic skin, wearable sensors and man-machine interactive interfacing. In this paper, a novel flexible transparent tribotronic transistor (FTT) is developed by coupling an organic thin film transistor (OTFT) and a triboelectric nanogenerator (TENG) in free-standing sliding mode. The carrier transport between drain and source can be modulated by the sliding-induced electrostatic potential of the TENG instead of the conventional gate voltage. With the sliding distance increases from 0 to 7 mm, the reverse drain current is almost linearly increased from 2 to 22 μA. The FTT has excellent performances in stability and durability in different bending modes and radius. The optical transmittance of the device is about 71.6% in the visible wavelength range from 400 to 800 nm. Moreover, the FTT is used for active modulation of conventional electronics, in which the luminance, magnetism, sound and micro-motion can be modulated by sliding a finger. This work has provided a new way to actively modulate conventional electronics, and demonstrated the practicability of tribotronics for human-machine interaction.
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paper_title: Discharge voltage behavior of electric double-layer capacitors during high-g impact and their application to autonomously sensing high-g accelerometers

paper_content:

In this study, the discharge voltage behavior of electric double-layer capacitors (EDLCs) during high-g impact is studied both theoretically and experimentally. A micro-scale dynamic mechanism is proposed to describe the physical basis of the increase in the discharge voltage during a high-g impact. Based on this dynamic mechanism, a multi-field model is established, and the simulation and experimental studies of the discharge voltage increase phenomenon are conducted. From the simulation and experimental data, the relationship between the increased voltage and the high-g acceleration is revealed. An acceleration detection range of up to 10,000g is verified. The design of the device is optimized by studying the influences of the parameters, such as the electrode thickness and discharge current, on the outputs. This work opens up new avenues for the development of autonomous sensor systems based on energy storage devices and is significant for many practical applications such as in collision testing and automobile safety.
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paper_title: Triboelectric nanogenerators as self-powered acceleration sensor under high-g impact

paper_content:

Abstract In the field of automobiles and many other industries, there is an urgent demand for the sensing of high-g acceleration. In this paper, a self-powered high-g acceleration sensor based on a triboelectric nanogenerator is proposed for the first time. It is micro-fabricated with a total volume of 14 × 14 × 8 mm 3 , and its sensing ability is confirmed via a Machete hammer experiment, with a measurement range of up to 1.8 × 10 4 g , a sensitivity of 1.8 mV/g, and a Pearson correlation coefficient of 0.99959. In addition, the output signal of this novel acceleration sensor has few clutters, which is beneficial for recognition and subsequent signal processing. The effects of the aluminum-electrode thickness on the sensitivity and linearity of the sensor are investigated via modeling, theoretical analysis, and experiment, providing a reliable basis for the parameter optimization of the structural design. Experiment results indicate that this novel acceleration sensor covers a wide measurement range and meets the urgent needs of monitoring various high-g impacts for military equipment and automobiles.
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paper_title: Pressure Sensitivity Enhancement of Porous Carbon Electrode and Its Application in Self-Powered Mechanical Sensors

paper_content:

Microsystems with limited power supplies, such as electronic skin and smart fuzes, have a strong demand for self-powered pressure and impact sensors. In recent years, new self-powered mechanical sensors based on the piezoresistive characteristics of porous electrodes have been rapidly developed, and have unique advantages compared to conventional piezoelectric sensors. In this paper, in order to optimize the mechanical sensitivity of porous electrodes, a material preparation process that can enhance the piezoresistive characteristics is proposed. A flexible porous electrode with superior piezoresistive characteristics and elasticity was prepared by modifying the microstructure of the porous electrode material and adding an elastic rubber component. Furthermore, based on the porous electrode, a self-powered pressure sensor and an impact sensor were fabricated. Through experimental results, the response signals of the sensors present a voltage peak under such mechanical effects and the sensitive signal has less clutter, making it easy to identify the features of the mechanical effects.
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paper_title: Self-Powered Magnetic Sensor Based on a Triboelectric Nanogenerator

paper_content:

MagneticsensorsareusuallybasedontheHalleffect or a magnetoresistive sensing mechanism. Here we demonstrate that a nanogenerator can serve as a sensor for detecting the variation of the time-dependent magnetic field. The output voltage of the sensor was found to exponentially increase with increasing magnetic field. The detection sensitivities for the change and the changingrateofmagnetic fieldareabout0.0363(0.0004ln(mV)/G and 0.0497 ( 0.0006 ln(mV)/(G/s), respectively. The response time and reset time of the sensor are about 0.13 and 0.34 s, respectively. The fabricated sensor has a detection resolution of about 3 G and can work under low frequencies (<0.4 Hz).
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paper_title: Detection and measurement of impacts in composite structures using a self-powered triboelectric sensor

paper_content:

Abstract Composite structures as e.g. aircrafts, wind turbines or racing cars are frequently subjected to numerous impacts. For example, aircrafts may collide with birds during take-off and landing or get damaged due to the impact of hailstones. These impacts harm the integrity of the composite laminates used in their structures which results in delamination and other failures which are usually very difficult to detect by visual inspections. Hence, the detection and quantification of impacts is of vital importance for monitoring the health state of composite structures. Recently, triboelectric sensors have been demonstrated to detect touches, pressures, vibrations and other mechanical motions with the advantages of being self-powered, maintenance-free and easy to fabricate. However, there is no research focusing on the potential of triboelectric sensors to detect impacts in a wide energy range. In this paper, a self-powered triboelectric sensor is developed to measure impacts at high energy in structures made of composite materials. This could be particularly beneficial for the detection of bird strikes, hailstones and other high energy impacts in aircraft composite structures. For that purpose, composite plates are subjected to various energy impacts using a drop weight impact machine and the electric responses provided by the developed triboelectric sensor are measured in terms of voltage and current. The idea is to evaluate the sensitivity of the electrical signals provided by the sensor to changes in the impact energy. The results prove that the generated electric responses are affected by the energy of the impact and their amplitude increases linearly with the impact energy. The voltage and current sensor responses demonstrate a very good impact sensitivity of 160 mV/J and a strong linear relationship to the impact energy (R = 0.999) in a wide energy range from 2 to 30 J. This work suggests a novel approach to measure the magnitude of the impacts in composite structures using the newly developed triboelectric sensor. The findings of this work demonstrate that the developed triboelectric sensor meets the urgent needs for monitoring high energy impacts for aeronautic and civil composite structures.
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paper_title: A 137 dB Dynamic Range and 0.32 V Self-Powered CMOS Imager With Energy Harvesting Pixels

paper_content:

This work presents an 0.32 V self-powered high dynamic range (DR) CMOS imager in standard $0.18~\mu \text {m}$ CMOS technology with dual-mode operation: imaging (IMG) and optical energy harvesting (OEH) modes. In IMG mode, a dual-exposure extended-counting (DEEC) scheme is proposed and implemented with a 5-bit programmable current-controlled threshold (PCCT) generator. By combining the DR of a short-exposure (88 dB) and an extended long-exposure (49 dB) conversions, the DEEC achieves a high DR of 137 dB. The chip consumes $10.6~\mu \text {W}$ at 6.5 fps with 0.32 V operation and $32.1~\mu \text {W}$ at 16.5 fps with 0.4 V operation, which results in an iFoM of 8.1 f and 9.8 fJ/pixel $\cdot $ code. In OEH mode, the sensing pixels turns into energy harvesting pixels with an additional global micro solar cell and corresponding mode control circuit, which generates 455 mV and $14~\mu \text {W}$ at 60 klux (sunny day) and supports a self-powered imaging operation at 4.1 fps.
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paper_title: Theoretical study and applications of self-sensing supercapacitors under extreme mechanical effects

paper_content:

Abstract Supercapacitors exhibit a self-sensing phenomenon with voltage sensitivity under mechanical effects. This paper proposes a dynamic model that reveals the mechanism of this sensitivity phenomenon. During a mechanical process such as an extreme impact or a finger press, transient changes of the coupled micro-deformation, porosity and output voltage of the supercapacitors are simulated, and the relationship between change in voltage and strength of the mechanical impacts is obtained. In particular, the experimental phenomenon that the output signal of the supercapacitors under extreme effects exhibits few clutters is theoretically explained and simulated. Finally, for the application of electronic skin and wearable electronics, the self-sensing characteristics of the supercapacitors under finger pressing are experimentally studied, and the ability to perceive the magnitude and duration of pressing is verified. This work provides a strong theoretical foundation for designing self-sensing supercapacitors with superior performance and expands their applications under various mechanical effects, from electronic skin to car crash protection.
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paper_title: Flexible transparent tribotronic transistor for active modulation of conventional electronics

paper_content:

Abstract Flexible and transparent electronics have attracted wide attention for electronic skin, wearable sensors and man-machine interactive interfacing. In this paper, a novel flexible transparent tribotronic transistor (FTT) is developed by coupling an organic thin film transistor (OTFT) and a triboelectric nanogenerator (TENG) in free-standing sliding mode. The carrier transport between drain and source can be modulated by the sliding-induced electrostatic potential of the TENG instead of the conventional gate voltage. With the sliding distance increases from 0 to 7 mm, the reverse drain current is almost linearly increased from 2 to 22 μA. The FTT has excellent performances in stability and durability in different bending modes and radius. The optical transmittance of the device is about 71.6% in the visible wavelength range from 400 to 800 nm. Moreover, the FTT is used for active modulation of conventional electronics, in which the luminance, magnetism, sound and micro-motion can be modulated by sliding a finger. This work has provided a new way to actively modulate conventional electronics, and demonstrated the practicability of tribotronics for human-machine interaction.
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paper_title: Self-Powered Magnetic Sensor Based on a Triboelectric Nanogenerator

paper_content:

MagneticsensorsareusuallybasedontheHalleffect or a magnetoresistive sensing mechanism. Here we demonstrate that a nanogenerator can serve as a sensor for detecting the variation of the time-dependent magnetic field. The output voltage of the sensor was found to exponentially increase with increasing magnetic field. The detection sensitivities for the change and the changingrateofmagnetic fieldareabout0.0363(0.0004ln(mV)/G and 0.0497 ( 0.0006 ln(mV)/(G/s), respectively. The response time and reset time of the sensor are about 0.13 and 0.34 s, respectively. The fabricated sensor has a detection resolution of about 3 G and can work under low frequencies (<0.4 Hz).
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paper_title: A 137 dB Dynamic Range and 0.32 V Self-Powered CMOS Imager With Energy Harvesting Pixels

paper_content:

This work presents an 0.32 V self-powered high dynamic range (DR) CMOS imager in standard $0.18~\mu \text {m}$ CMOS technology with dual-mode operation: imaging (IMG) and optical energy harvesting (OEH) modes. In IMG mode, a dual-exposure extended-counting (DEEC) scheme is proposed and implemented with a 5-bit programmable current-controlled threshold (PCCT) generator. By combining the DR of a short-exposure (88 dB) and an extended long-exposure (49 dB) conversions, the DEEC achieves a high DR of 137 dB. The chip consumes $10.6~\mu \text {W}$ at 6.5 fps with 0.32 V operation and $32.1~\mu \text {W}$ at 16.5 fps with 0.4 V operation, which results in an iFoM of 8.1 f and 9.8 fJ/pixel $\cdot $ code. In OEH mode, the sensing pixels turns into energy harvesting pixels with an additional global micro solar cell and corresponding mode control circuit, which generates 455 mV and $14~\mu \text {W}$ at 60 klux (sunny day) and supports a self-powered imaging operation at 4.1 fps.
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Title: Ammunition Reliability Against the Harsh Environments During the Launch of an Electromagnetic Gun: A Review

Section 1: INTRODUCTION
Description 1: Describe the background, importance, and advancements in electromagnetic launch technology, including key historical milestones and research objectives.

Section 2: HARSH ENVIRONMENT IN THE LAUNCH PROCESS
Description 2: Discuss the extreme conditions experienced during the electromagnetic railgun launch process, including magnetic fields, high-g impacts, and high temperatures, and the need for quantitative research.

Section 3: STRONG MAGNETIC FIELD
Description 3: Present experimental results and simulations on the strong and varying magnetic fields during the launch process, including challenges in measurement and modeling techniques.

Section 4: HIGH-G IMPACT
Description 4: Explain the extreme acceleration and its effects during the launch, presenting experimental results and adequacy of existing models and simulations to predict high-g impacts.

Section 5: HIGH TEMPERATURE
Description 5: Analyze the generation of high temperatures due to friction and Joule heating, discussing experimental measurements and modeling approaches to understand temperature distributions and effects.

Section 6: LIMITATIONS OF MODELING ON SINGLE FIELD
Description 6: Critique the limitations of modeling individual extreme factors and the necessity to consider multiphysics coupling for accurate simulations.

Section 7: THE 'CHAIN REACTION': THE DECISIVE ROLE OF MULTIPHYSICS COUPLING ON EXTREME ENVIRONMENTS
Description 7: Examine the interdependent and exacerbatory effects of multiphysics coupling on the harsh environments, highlighting the importance of integrated modeling approaches.

Section 8: PROTECTION OF THE KEY COMPONENTS OF FUZES IN HARSH ENVIRONMENTS
Description 8: Discuss the potential failure mechanisms of fuze components under extreme conditions and propose protective measures including electromagnetic shielding and anti-high-g impact technologies.

Section 9: CONCLUSION
Description 9: Summarize the key findings regarding extreme environments during electromagnetic railgun launches, emphasize the importance of advanced protection methods for fuzes, and suggest future research directions.