Rubin M B, Bodner S R, Binur N S
Faculty of Mechanical Engineering, Technion-Israel Institute of Technology, Haifa, Israel.
J Biomech Eng. 1998 Oct;120(5):686-9. doi: 10.1115/1.2834762.
Unified constitutive equations for elastic-viscoplastic materials were modified and used to model the highly nonlinear elastic and rate-dependent inelastic response exhibited in recent experiments on excised facial tissues. These included the skin and the underlying supportive tissue SMAS (the Superficial Musculoaponeurotic System). This study indicates a number of relevant results: The skin is more strain rate dependent than the SMAS; the nonlinearity of the elasticity of the skin is greater than that of the SMAS; both tissues exhibit a hardening effect indicated by increased resistance to inelastic deformation due to stress acting over a time period; the hardening effect leads to a decrease in time dependence and an increased elastic range, which is more pronounced for SMAS. Consequently, the SMAS can be viewed as the firmer elastic foundation of the more viscous skin. Moreover, the relaxation time for the skin is fairly short so the skin would be expected to conform to the deformation of the SMAS if it remained attached to the SMAS during stretching. This is relevant when it is undesirable to separate the skin from the SMAS for physiological reasons.
对弹黏塑性材料的统一本构方程进行了修正，并用于模拟近期对切除的面部组织（包括皮肤和其下方的支持组织SMAS，即浅表肌肉腱膜系统）进行的实验中所呈现的高度非线性弹性和应变率相关的非弹性响应。该研究表明了一些相关结果：皮肤比SMAS更依赖应变率；皮肤弹性的非线性程度大于SMAS；两种组织均表现出一种硬化效应，即由于应力在一段时间内作用，对非弹性变形的抵抗力增加；硬化效应导致时间依赖性降低和弹性范围增加，这在SMAS中更为明显。因此，SMAS可被视为黏性更强的皮肤的更坚实弹性基础。此外，皮肤的松弛时间相当短，所以如果在拉伸过程中皮肤仍与SMAS相连，预计皮肤会顺应SMAS的变形。当出于生理原因不宜将皮肤与SMAS分离时，这一点很重要。
