小腿残肢与接受腔界面的摩擦行为分析及测试

利用断层扫描数据,图像处理和反求技术建立了骨骼、软组织以及假肢接受腔的三维有限元模型,分别施加Heel Strike、Foot Flat、Mid-Stance、Heel Off和Toe Off五个典型步态时相的载荷,计算残肢皮肤在一个步态周期内的应力、滑移量变化,确定最大临界参数;借助UMT-II多功能摩擦磨损试验机模拟残肢皮肤和接受腔摩擦界面,研究皮肤在步态周期临界参数下的摩擦行为变化.有限元结果表明:一个步态周期内五个典型时相,软组织表面最大正应力和剪切力均发生在髌韧带处,在Heel off步态时相,最大临界正应力为384.3 k Pa,剪应力为102.1 k Pa;随着正压力的减小,摩擦力减小,摩擦系数增大;当正应力下降到39.5 k Pa临界值时,接触面发生相对滑动,摩擦系数达到最大值.摩擦学试验结果表明:法向载荷分别为17 N和7 N时,残肢皮肤均处于黏着状态;皮肤弹性变形越大,黏着程度越大.

Analysis and Test of Tribological Behavior at Interface between Lower Residual Limb and Prosthetic Socket

The 3D models of the bones, soft tissue and prosthetic socket were reconstructed by using CT scanning, image processing and reverse engineering techniques. The stress and slippage of the residual limb skin in a gait cycle were calculated by applying the load of five typical phases, i.e. Heel Strike,Foot Flat, Mid-Stance, Heel Off and Toe Off, respectively. Consequently, the maximum critical parameters were determined on the basis of the above results. By using a UMT-II tribometer to simulate lower residual limb/prosthetic socket interface, the tribological behavior of residual limb skin was investigated in vivo under the critical parameters in a gait cycle. The finite element results show that the maximum normal stress and shear stress in the five typical phases occurred all at the position of patellar tendon. In the phase of Heel off, the maximum normal stress was 384.3 kPa and shear stress was 102.1 kPa. With decreasing normal force, the friction force reduced while the friction coefficient increased. When the normal stress was lower than the critical value of 39.5 kPa, the relative sliding occurred on the contact interface and the friction coefficient reached the maximum value. Frictional experiment results show that the residual limb skin was in a frictional state of adhesion when the normal loads were 17 N and 7 N. The adhesion degree increased with the skin elastic deformation increasing.