高分子溶融体に対する微分型・積分型粘弾性モデルのパラメーターの最適化とモデルの検討―第1報:緩和スペクトルの自動最適化とせん断流動特性からの非線形パラメーターの決定―
Optimum Determination of Parameters in Differential and Integral Viscoelastic Models and Study on Reliability of the Models for Polymer Melts−1. Automatic Optimization of a Relaxation Spectrum and Determination of Nonlinear Parameters from Rheological Shear Data−
梶原稔尚・富山秀樹・金丸英樹・山村方人・足立毅太郎
Kajiwara, Toshihisa / Tomiyama, Hideki / Kanamaru, Hideki / Yamamura, Masato / Adachi, Kitaro
We have developed a full nonlinear regression program to determine the relaxation spectrum and the nonlinear parameters for differential and integral viscoelastic models that will give the best fit to experimental rheological data. The least-squares procedure is based on the Levenberg-Marquardt method. The program for determining the optimum relaxation spectrum from dynamic linear viscoelastic data includes a function to automatically reset the initial guesses in the computation. The program was tested against experimental data for several polymer melts and a good fit was obtained. This new program was confirmed not only to be reliable but also to reduce the labor of manually resetting the initial guesses. The program for determining the nonlinear parameters was developed for the Phan Thien-Tanner (PTT), Larson, Giesekus and K-BKZ models and the determination from the experimental data of simple shear flow (shear viscosity and first normal stress difference) was performed for several polymer melts. The best-fit curves for all models were in good agreement with the experimental data within the range of experimental shear rate.
Key words: Material constant / Nonlinear regression / Relaxation spectrum / Rheological property / Viscoelastic model