Optimum recovery time for cyclic compression tests on bovine brain tissue

Abstract

In conducting mechanical tests on the brain tissue, it is preferred to perform multiple tests on the same sample. In this study we investigated the behavior of the bovine brain tissue in repeated compression tests with six recovery periods (10, 60, 120, 180, 240 and 300 s). Compression tests were performed on cylindrical samples with an average diameter and height of 18.0 mm and 15.0 mm respectively. Two testing protocols were employed: first protocol comprised of experiments with 5, 25 and 125 mm/min loading speed up to 33% strain and the second protocol consisted of tests with 25 and 125 mm/min loading speed up to 17% strain. Each experiment was conducted in two cycles separated by a specific recovery period. Stress-strain data from the first and second cycles were compared using three criteria, namely Normalized root-mean-square error (NRMSE), coefficient of variation (R2) and effective height ratio (EHR). The analysis suggests that the optimum recovery period for the first and second protocols are 120 s and 180 s respectively. Moreover, differences between the first and second cycles of medium and high speed tests were found to be smaller compared to the low-speed experiments.