**Appendix (Identification of the generalized Maxwell model and development of a curve fit program)**

When the generalized Maxwell model for time domain is identified based on the master curve in frequency domain using Eq. (25), the following three points should be noted.

## **Ee, En, τn of positive definite**

Since the generalized Maxwell model is regarded as a mechanical model, it is preferable that all the values of these coefficients are always positive. However, the input rule for them is different among general purpose FEMs. For example, some codes allow negative value input, while others strictly prohibit negative value input. Hence, there is no unified rule among all the codes. Since it is empirically observed that master curves may oscillate due to the affect of terms with negative values, it is considered reasonable to control the input data to make them positive definite.
