I am new to the characterization tests for materials like Thermoplastic Polyurethane (TPU). I made specimens following the ASTM D638 and carried out the relaxation tests. However, some works indicate relaxation tests using compression specimens (fabricated based on ISO 3386-1:2010).
I would like to know which test is preferred to get the stress relaxation data, tension or compression?
My actual application is to compress cylindrical shells made of TPU. Will there be any difference in the stress relaxation data taken from tension and compression experiments?
Thanks and regards