Effect of interspecies differences on the mechanical behavior of liver and a strain-rate dependent visco-hyperelastic...

The limited availability of human liver tissue necessitates the use of animal surrogates in biomechanical studies, yet interspecies differences in mechanical behavior remain poorly quantified, especially under high-strain-rate conditions relevant to impact scenarios. This study investigated the mechanical behaviors of porcine, bovine, and monkey livers under uniaxial compression, spanning quasi-static (0.001, 0.01, 0.1 s^-1) to high strain rates (2000, 3000, 4000 s^-1). Mechanical testing was complemented by microstructural analysis using Masson's trichrome staining to quantify collagen content and organization. Results demonstrated that all livers exhibited significant strain-rate sensitivity, with bovine liver showing the strongest strain-rate sensitivity and porcine liver the weakest. Microstructural analysis indicated that collagen fiber content and alignment are primary contributors to the observed macroscopic mechanical differences. Furthermore, a novel visco-hyperelastic constitutive model was developed to characterize the nonlinear response under high-strain-rate loading, with a mean relative fitting error below 11.32 %. This study provides a theoretical foundation for high-precision numerical simulations of liver injury and offers experimental support for selecting appropriate surrogate animal models.