Conversion of engineering stresses to Cauchy stresses in tensile and compression tests of thermoplastic polymers

Current Directions in Biomedical Engineering

Röhr Udo¹  Grabow Niels¹  Schmitz Klaus-Peter¹  Schümann Kerstin² 

[1] Institute for Biomedical Engineering, Rostock University Medical Center and Institute for ImplantTechnology and Biomaterials, Rostock, Germany;Institute for Biomedical Engineering, Rostock University Medical Center, Rostock, Germany;

关键词: Cauchy stress;    compression test;    non-isochoric;    tensile test;    thermoplastic polymers;   

DOI  :  10.1515/cdbme-2016-0142

来源: DOAJ

【 摘 要 】

Thermoplastic polymers exhibit non-isochoric behaviour during tensile and compression testing as well as particular deformations like local necking (tension) or buckling (compression). A method for the determination of Cauchy stresses from tensile and compression tests is presented, that considers the actual deformations of the test specimens. The exact geometry of the specimens in the respective present configuration is determined in photographs, which are taken continuously throughout the test. The engineering stresses at several time points are converted into Cauchy stresses using newly developed formulas in consideration of the actual specimen geometry. For validation finite element analyses of the tensile and compression tests are performed using the identified stress-strain curves. The numerical results show good agreement with the experiments for the tested polymers. Thus a method for conversion of engineering to Cauchy stresses in tensile and compression tests could be established considering the non-isochoric deformation in plasticity. With this method “true” stress-strain curves as input for finite element material models can be identified for arbitrary materials.

【 授权许可】

Unknown