Thermomechanical Analysis and Thermodilatometry

Thermomechanical Analysis (TMA) can be defined as the measurement of a specimen s dimensions (length or volume) as a function of temperature whilst it is subjected to a constant mechanical stress. In this way thermal expansion coefficients can be determined and changes in this property with temperature (and/or time) monitored. Many materials will deform under the applied stress at a particular temperature which is often connected with the material melting or undergoing a glass-rubber transition. Alternatively, the specimen may possess residual stresses which have 

Stress (c) is defined as the ratio of the mechanical force applied (F) divided by the area over which it acts A)  

If the applied stress is negligible then the technique becomes that of thermodilatometry. This technique is used to determine the coefficient of thermal expansion of the specimen from the relationship  

---