Rammin presentation


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"Axial stress"
name : DM rammin
Ahsanulah university of science and technology
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Rammin presentation

  3. 3. ON A SERIOUS NOTE STRESS IN MECHANICS IS  a physical quantity that expresses the internal forces that neighboring particles of a continuous material exert on each other.  For example, when a solid vertical bar is supporting a weight, each particle in the bar pulls on the particles immediately above and below it.
  4. 4. When some external system of forces or loads act on a body ,the internal forces ( equal and opposite) are set up at various sections of the body, which resists the external forces .  This internal force per unit area at any section of the body is known as unit stress or simply stress.   Where, F = FORCE or LOAD acting on the body, and A = Cross-sectional area of the body. 0
  5. 5.  The force applied tends to deflect the body .Due to cohesion between the molecules, the body resists deformation.  Simple Stresses are mainly of 4 types: 1.Axial or Normal Stress 2. Shear Stress 3.Bearing Stress 4.Thin-walled Pressure Vessel  So, some sort of force is required in a direction to calculate the stress
  6. 6. LET US NOW SEE WHAT DOES AXIAL FORCE REFERS TO: An axial force is any force that directly acts through or parallel to the major axis of an object.  These forces are typically stretching force or compression force, depending on direction.  In addition, when the force load is even across the form’s geometric center, it is concentric, and when it is uneven, it is eccentric. Unlike many acting forces, an axial force is often its own counter; an object pulled or pushed evenly in opposing directions doesn’t move. Sheer force occupies a similar position to axial force, but operates perpendicular to the center axis of the object. 
  7. 7.  One of the most important parts of examining axial forces is the idea of a geometric center.  This is a point within the boundaries of a solid object that is the perfect center of the entire mass.  In a simple object, such as a cylinder, it is easy to find the exact middle of the object by simply measuring the sides. In a complex object, such as a bicycle, the process is much more complicated.
  8. 8. AXIAL MEMBERS which support load only along their primary axis, are the most basic of structural members. Equilibrium requires that forces in Axial Members are always Equal, Opposite, and Co-Linear. In most cases, axial members have pinned ends.  Some examples of axial members include: 1.Bars; 2.Truss Members; 3.Ropes and Cables. etc 
  9. 9. THEREFORE AXIAL STRESS IS, defined as the force perpendicular to the cross sectional area of the member divided by the cross sectional area. If a cut is taken perpendicular to a bar's axis, exposing an internal cross-section of area A, the force per unit area on the face of this cut is termed AXIAL STRESS.  The symbol used for axial stress in most engineering texts is (sigma).  Stress is positive in tension (P>0) and negative in compression (P<0); English units: psi (pounds per square inch), or ksi (kilopounds per square inch); 
  10. 10. Stress caused in axial direction due to axial force.  Generally two types of axial stress are there :  1.compressive axial stress 2.tensile axial stress
  11. 11.  Compressive stress is axial stress that tends to cause a body to become shorter along the direction of applied force.  Tensile stress is axial stress that tends to cause a body to become longer along the direction of applied force.
  12. 12. EXAMPLES OF TENSILE AXIAL STRESS INCLUDE  a chain carrying a load and tension cables on a bridge.
  13. 13. EXAMPLES OF COMPRESSIVE AXIAL STRESS INCLUDE  decorative columns in architecture and the steel structure of a high rise building.
  14. 14. SOME ASSUMPTIONS REGARDING AXIAL STRESS Loads pass through the centroid of the section  Member should be straight  Load less than buckling load  stress,  Stress is positive in tension (P>0) and negative in compression (P<0). 
  15. 15. EXAMPLE Example 1 :A hollow steel tube with an inside diameter of 100 mm must carry a tensile load of 400 kN. Determine the outside diameter of the tube if the stress is limited to 120 MN/m2. Solution : Where: Thus,
  16. 16. Question