# Evaluation of the mechanical properties of porcine kidney

## TL;DR

This study measures how porcine kidney tissue responds to mechanical stress, revealing how strain rate affects its strength and elasticity.

## Contribution

The first presentation of stress-strain relations for porcine kidney cortex under different strain rates and a damage-dependent viscoelastic model for the data.

## Key findings

- Higher strain rates increase ultimate strength and initial Young's modulus but decrease rupture strain in porcine kidney cortex.
- A damage-dependent viscoelastic model accurately captures tension and relaxation data, showing damage's influence on mechanical behavior.
- Compressive strength and rupture strain are higher in compression than in tension for the kidney cortex.

## Abstract

With the development of medical diagnosis and treatment, knowing the mechanical properties of living tissues becomes critical. The aim of this study was to investigation material properties of the fresh porcine kidney and the parametric characterization of its viscoelastic material behavior. The material investigation included uniaxial tension tests in different strain rates, relaxation tests, as well as hydrostatic compression tests on the samples extracted from the fresh porcine kidney cortex. Tension tests and relaxation tests were performed by a planar dog-bone specimen with a micron loading testing machine. Hydrostatic compression tests were performed on the kidney cylinder sample which was placed in a compression chamber. Furthermore, a nonlinear viscoelastic model recently proposed by us was employed to characterize the tension data at different strain rates and relaxation test data. The the experimental and numerical results show that the stress-strain relations of the porcine kidney cortex at different strain rates in tension are presented for the first time and a higher strain rate results in higher ultimate strength and initial Young modulus but a lower rupture strain. A damage-dependent visco-elastic model is employed to model the tension data at different strain rates and relaxation data and exhibits a good agreement with the experimental data, which also demonstrates that the damage has an obvious influence on the stress-strain relation. Through comparison with the existing reference covering the uniaxial compression data, it seems that the mechanical behavior of the porcine kidney cortex manifests a stress state-dependent mechanical behavior. The ultimate strength and rupture strain are larger in compression than that in tension.