Host: The Japan Society of Mechanical Engineers
Name : [in Japanese]
Date : November 02, 2019 - November 04, 2019
Creep recovery testing is widely used to evaluate nonlinear viscoelasticity for polymer material. In the creep recovery testing, it is necessary to separate viscoelastic strain and viscoplastic strain from the measured strain. Thus, the conventional evaluation method uses the postulate in which the residual strain at the end of the testing is viscoplastic strain. The present study investigates the validity of this postulate through the creep recovery testing and finite element analysis for polybutylene terephthalate (PBT). The creep recovery testing reveals that the behavior of PBT is nonlinear viscoelasticity because the creep strain is larger than that predicted by linear viscoelastic analysis of finite element method. The residual strain at the end of the testing is significantly larger than that predicted by linear viscoelastic-viscoplastic analysis of finite element method. Therefore, it is thought that the viscoplastic strain is overestimated in the conventional evaluation method. The stress dependency of the nonlinear viscoelastic parameters is not affected the estimated viscoplastic strain but the accurate evaluation of the nonlinear viscoelastic parameters requires exact estimation of the viscoplastic strain.
