Viscoelastic constitutive model for uniaxial time-dependent ratcheting of polyetherimide polymer

What is it about?

Based on the experimental observations, a cyclic nonlinear viscoelastic constitutive model was proposed to describe the uniaxial time-dependent ratcheting of polyetherimide (PEI) under tension–compression and tension–tension cyclic loading. The model was constructed by extending the nonlinear viscoelastic Schapery model. The extension emphasized the changes of parameter functions used in the original model.

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Why is it important?

Time-dependent ratcheting of polymer materials is of great importance in the safety design and life assessment of polymer structure components. However all the previous models did not predict the time-dependent ratcheting of polymers very well. The model proposed in this work was capable to describe the ratcheting of polymer material successfully.