Caractérisation thermomécanique et endommagement de membranes sous pression de gaz.

Numerical calculations become a more and more efficient way to estimate the lifetime of structures under thermomechanical loading. But these life estimations cannot be reliable if the needed parameters have not been correctly identified and measured and if not all the damage causes have been considered. The disk testing under gas pressure is an experimental technique used for the mechanical characterization of thin sheets with various conditions: monotonous loading (biaxial rupture tests at strain rates from 10-6 to 10° s-1), constant loading under high stresses (sustained load) at elevated temperature (creep tests), cyclic loading (mechanical fatigue tests); the temperature may be chosen between 20 and 900 °C. The disk testing quickly reveals the damage when crossing cracks through the membrane create leakages detected by a mass spectrometer. Besides, we have developed a calculation method in order to measure the true mechanical properties of the pressurized disk. We evidence the quality of the results obtained with this method in the thermomechanical characterization of thin sheets and its sensitivity to secondary parameters. The analytical method of calculation will be optimized in order to obtain the best modelling of thermomechanical behaviour of materials loaded at temperature and strain rates within very large ranges and subject to different environments as gaseous hydrogen. [ABSTRACT FROM AUTHOR]