模拟颅脑受撞击致伤时颅内应力的光弹性法测定

Measurement of shear stress in simulated human head by photoelastic method

目的 采用模拟人体颅脑和光弹性法 ,观察颅脑受撞击时颅内在不同位置 (额、顶、枕和颞部 )的剪应力变化。方法 采用光弹性材料制做矢状面、冠状面两种颅脑光弹性模型 ,两种模型均包含颅骨和脑体两种结构 ,脑体由对应于人体脑解剖分叶的几部分组成。在模型的不同位置分别施加相同的撞击载荷 ,用动态光弹性仪记录模型每次受载后 0～ 12 0 0 μs之间的 3 2幅等差线照片。根据瞬时等差线照片计算最大剪应力。结果 在模拟人脑的颅骨中 ,以矢状面受顶载、冠状面受顶载、颞载时的应力为最大 ;在光弹材料模拟的脑体中 ,以矢状面受顶载、冠状面受顶载时的应力为最大。结论 应力最大部位 (应力集中点 )在闭合性颅脑损伤中是发生骨折、脑挫伤、撕裂损伤的常见部位 ,说明剪切应力是造成上述损伤的主要原因。

Objective With simulated a human head and photoelastic method, observe the changes of shear stress at different sites of head subjected to different orientation impacts. Methods Two kinds of models simulating the sagittal and coronary section of human head were made with photoelastic materials. Both the models were composed of cranial bone and encephalic parts. The encephalic part was separated into different sections according to the anatomy structure. The models were impacted in different positions with the same load capacity, and during the period (0 to 1 200 μs) of impact 32 sheets photos of arithmetical stripes presented on the models were taken using a dynamic photoelastic device. According to the photos of arithmetical stripes the maximal shear stress was calculated. Results The maximal shear stress appeared in the cranial bone of model when the sagittal head model was impacted in a parietal direction and coronary head model was impacted in a parietal and temporal direction; however, the maximal shear stress showed in the encephalon when the sagittal model was impacted in a parietal direction and coronary model was impacted in a temporal directions. Conclusion Positions undergoing the maximal shear stress corresponded to those at which most fracture, contusion and laceration occurs clinically, suggesting that the shear stress played an important role in the damages.