离体心肌被动力学属性超声印压检测方法

为了探讨介入超声印压系统检测心肌被动力学属性可行性,为活体检测提供基础.采用循环印压犬离体心室肌,获得印压力和心肌形变实验数据.以准线性粘弹性理论(QLV)模型处理所获得的应力、形变数据,得出左心室心肌被动力学属性参数,活性组为A 1.02±0.45,B 16.54±5.21,C -169.42±51.23,D 1 876.52±428.67,E 4 307.37±1 100.81,无活性组为A 2.47±1.29,B 27.78±9.59,C -298.67±85.36,D 2 947.89±691.52,E 8 561.26±2 234.19,两者相应参数比较差异有统计学意义(p＜0.05).结果表明,采用介入超声印压系统检测心肌被动力学属性是可行的.可望在活体检测不同状态下舒张期心肌被动力学属性,从生物力学层面加深对舒张性心力衰竭的认识.     

基于动态微印压方法的前臂皮肤粘弹性属性测量*

对前臂皮肤粘弹性属性的了解有助于临床康复产品设计。基于动态微印压方法,对6位男性志愿者前臂皮肤进行了测量,最大压入位移为 ,频率范围为 。前臂皮肤的平均接触刚度和平均接触阻尼系数分别为 、 ,平均储能模量为 ,平均损耗模量为 ,平均复模量值为 。结果表明前臂皮肤层的粘弹性属性采用Kelvin线性粘弹性模型描述具有一定合理性。     

Influence of Residual Stress on the Elastic-plastic Response to Indentation

The indentation method is useful in determining the residual stress according to the elastic-plastic properties of materials. So the effect of the residual stress on the elastic-plastic indentation properties of materials was studied by using the finite element method to find better indentation parameters which are strongly induced by the residual stress. The results show that load-depth curve, plastic pile-up, indentation shape, indentation contact stress and indentation residual stress are affected by different residual stress, and these parameters can be used to deduce the residual stress. Also, a special indentation equipment was developed to analyze the elastic-plastic properties of materials with different residual stress, and the experimental results show a good agreement with the FEM results. For practical application, the elastic-plastic indentation properties of materials with unknown residual stress could be obtained by the developed equipment to deduce the residual stress comprehensively.     

对称楔形压头作用下玻璃裂纹的产生及扩展规律

玻璃在各个尖端科技中的应用越来越广泛,对其加工精度的要求也愈来愈高,玻璃切削因能高效、低成本获得各种形状的精密玻璃零件而日益受到重视,为了获得高精度的加工表面,便于刀具设计和切削参数选择,本文中研究了玻璃在对称楔形压头作用下的裂纹产生和扩展规律．研究结果表明,采用楔角在30^。～120^。之间的对称楔印压玻璃时,玻璃裂纹的产生和扩展规律是相同的;采用楔角等于或大于150^。的对称楔印压玻璃时,裂纹的产生及扩展规律具有特殊性．文中还研究了采用楔角在30^。～120^。之间的对称楔印压玻璃时,中位裂纹长度与载荷的关系．     

石墨边位印压裂纹的产生和扩展规律

为揭示石墨切削材料的去除过程和已加工表面的形成机理,研究了石墨边位印压时裂纹的产生和扩展规律.结果表明:当印压载荷增加到某一临界值时,裂纹突然产生并迅速扩展;初始裂纹朝试件内部扩展,然后逐渐向印压表面扩展,最后到达印压表面,裂纹扩展路径呈圆弧形;随着压头楔角和印压厚度的增加,裂纹愈朝试件内部扩展,在试件表面留下的凹坑深度和宽度愈大.切削实验结果表明,边位印压裂纹的产生和扩展规律能很好地解释石墨切削时切屑的去除过程和已加工表面的形成原因.