Department of Materials Science and Engineering, K. N. Toosi University of Technology, Tehran, Iran.
Department of Materials Science and Engineering, K. N. Toosi University of Technology, Tehran, Iran.
J Mech Behav Biomed Mater. 2018 Mar;79:104-113. doi: 10.1016/j.jmbbm.2017.12.019. Epub 2017 Dec 23.
In this research, the exponential stretched based hyperelastic strain energy was generalized to the hyper-viscoelastic model using the heredity integral of deformation history to take into account the strain rate effects on the mechanical behavior of materials. The heredity integral was approximated by the approach of Goh et al. to determine the model parameters and the same estimation was used for constitutive modeling. To present the ability of the proposed hyper-viscoelastic model, the stress-strain response of the thermoplastic elastomer gel tissue at different strain rates from 0.001 to 100/s was studied. In addition to better agreement between the current model and experimental data in comparison to the extended Mooney-Rivlin hyper-viscoelastic model, a stable material behavior was predicted for pure shear and balance biaxial deformation modes. To present the engineering application of current model, the Kolsky bars impact test of gel tissue was simulated and the effects of specimen size and inertia on the uniform deformation were investigated. As the mechanical response of polyurea was provided over wide strain rates of 0.0016-6500/s, the current model was applied to fit the experimental data. The results were shown more accuracy could be expected from the current research than the extended Ogden hyper-viscoelastic model. In the final verification example, the pig skin experimental data was used to determine parameters of the hyper-viscoelastic model. Subsequently, a specimen of pig skin at different strain rates was loaded to a fixed strain and the change of stress with time (stress relaxation) was obtained. The stress relaxation results were revealed the peak stress increases by applied strain rate until the saturated loading rate and the equilibrium stress with magnitude of 0.281MPa could be reached.
在这项研究中，指数拉伸的超弹性应变能通过变形历史的遗传积分被推广到超粘弹性模型中，以考虑应变率对材料力学行为的影响。遗传积分通过 Goh 等人的方法进行逼近，以确定模型参数，并对本构模型进行相同的估计。为了展示所提出的超粘弹性模型的能力，研究了不同应变速率（0.001 至 100/s）下热塑性弹性体凝胶组织的应力-应变响应。与扩展的 Mooney-Rivlin 超粘弹性模型相比，当前模型与实验数据的吻合度更好，并且预测了纯剪切和平衡双轴变形模式下的稳定材料行为。为了展示当前模型的工程应用，模拟了凝胶组织的 Kolsky 杆冲击试验，并研究了试样尺寸和惯性对均匀变形的影响。由于聚脲的力学响应在 0.0016-6500/s 的宽应变率范围内提供，因此应用当前模型来拟合实验数据。结果表明，与扩展的 Ogden 超粘弹性模型相比，当前研究可以预期更高的准确性。在最后一个验证示例中，使用猪皮实验数据来确定超粘弹性模型的参数。随后，在不同应变速率下对猪皮试样进行加载，达到固定应变，并获得随时间变化的应力（应力松弛）。应力松弛结果表明，施加的应变速率会增加峰值应力，直到达到饱和加载速率，并达到 0.281MPa 的平衡应力。
