A computer program for interconversion between creep compliance and stress relaxation

Numerical interconversion of linear viscoelastic functions is an important problem in rheology. This work focuses on interconversion between creep compliance ( J) and relaxation modulus ( G) via the convolution relation. A discrete spectrum or Prony series is used to describe both the source ( G or J) and the target ( J or G) of the interconversion. A previously developed numerical template [Loy et al., J. Rheol. 59(5), 1261 (2015)] is modified to bypass singularities. It is released as an open-source computer program called PSI (Prony series interconversion). PSI is tested on a variety of materials including viscoelastic solids and liquids and used for both G ? J and J ? G interconversions. It is fast and numerically stable for input data that span over 20 decades in time. It fills a gap in the existing software landscape for conversion of linear viscoelastic functions.