 This use of the term dynamic is distinct from the situation where the force is periodically changed with time, typically following a sine relationship, where the term modulated is recommended.Most thermomechanical instruments are force controlled, that is they apply a force, then measure a resulting change in a dimension of the test specimen.Usually a constant strain rate is used for stress–strain measurements, but in the case of df-TM the stress will be applied at a chosen rate.