Bougherara Habiba, Rahim Ehsan, Shah Suraj, Dubov Anton, Schemitsch Emil H, Zdero Rad
Department of Mechanical and Industrial Engineering, Ryerson University, Toronto, ON, M5B-2K3, Canada.
J Biomech Eng. 2011 Jul;133(7):074503. doi: 10.1115/1.4004414.
With the resurgence of composite materials in orthopaedic applications, a rigorous assessment of stress is needed to predict any failure of bone-implant systems. For current biomechanics research, strain gage measurements are employed to experimentally validate finite element models, which then characterize stress in the bone and implant. Our preliminary study experimentally validates a relatively new nondestructive testing technique for orthopaedic implants. Lock-in infrared (IR) thermography validated with strain gage measurements was used to investigate the stress and strain patterns in a novel composite hip implant made of carbon fiber reinforced polyamide 12 (CF/PA12). The hip implant was instrumented with strain gages and mechanically tested using average axial cyclic forces of 840 N, 1500 N, and 2100 N with the implant at an adduction angle of 15 deg to simulate the single-legged stance phase of walking gait. Three-dimensional surface stress maps were also obtained using an IR thermography camera. Results showed almost perfect agreement of IR thermography versus strain gage data with a Pearson correlation of R(2) = 0.96 and a slope = 1.01 for the line of best fit. IR thermography detected hip implant peak stresses on the inferior-medial side just distal to the neck region of 31.14 MPa (at 840 N), 72.16 MPa (at 1500 N), and 119.86 MPa (at 2100 N). There was strong correlation between IR thermography-measured stresses and force application level at key locations on the implant along the medial (R(2) = 0.99) and lateral (R(2) = 0.83 to 0.99) surface, as well as at the peak stress point (R(2) = 0.81 to 0.97). This is the first study to experimentally validate and demonstrate the use of lock-in IR thermography to obtain three-dimensional stress fields of an orthopaedic device manufactured from a composite material.
随着复合材料在骨科应用中的再度兴起，需要对应力进行严格评估，以预测骨植入系统的任何失效情况。对于当前的生物力学研究，采用应变片测量来通过实验验证有限元模型，进而表征骨骼和植入物中的应力。我们的初步研究通过实验验证了一种用于骨科植入物的相对较新的无损检测技术。用应变片测量验证的锁定红外（IR）热成像技术，被用于研究一种由碳纤维增强聚酰胺12（CF/PA12）制成的新型复合髋关节植入物中的应力和应变模式。该髋关节植入物安装了应变片，并使用840 N、1500 N和2100 N的平均轴向循环力进行力学测试，植入物处于15度内收角，以模拟步行步态的单腿站立阶段。还使用红外热成像相机获得了三维表面应力图。结果显示，红外热成像与应变片数据几乎完全吻合，最佳拟合线的皮尔逊相关系数R(2) = 0.96，斜率 = 1.01。红外热成像检测到髋关节植入物在颈部区域远端下方内侧的峰值应力分别为31.14 MPa（840 N时）、72.16 MPa（1500 N时）和119.86 MPa（2100 N时）。沿着植入物内侧（R(2) = 0.99）和外侧（R(2) = 0.83至0.99）表面以及峰值应力点（R(2) = 0.81至0.97），红外热成像测量的应力与力施加水平之间存在很强的相关性。这是第一项通过实验验证并展示使用锁定红外热成像来获取由复合材料制造的骨科装置三维应力场的研究。
