A nonlinear viscoelastic model for the lung is implemented and evaluated for high-rate loading. Principal features of the model include a closed-cell approximation of the bulk compressibility accounting for air inside the lung and a damage-injury component by which local trauma is induced by cumulative normalized internal energy and amplified by gradients of energy density. The latter feature is adapted for use in standard numerical (i.e., explicit finite element) simulations in terms of the local rate of strain energy density and the longitudinal wave speed. Injury predictions for direct loading of a block of extracted lung material, rather than the entire thorax, via pressure pulses are in reasonably close agreement with experimental observations for an extracted rabbit lung: a threshold applied pressure exists above which edema is observed experimentally, correlating with low but non-negligible damage in the numerical results. Responses to impact by cylindrical and spherical projectiles are also interrogated. Penetration depths are comparable to those observed experimentally, as is drastically increasing damage with increasing impact velocity. Damage initiates and propagates from the impact surface, with local severity of injury decreasing with distance from the impact zone, in agreement with some empirical evidence. The model predicts more severe local injury, relative to the aforementioned surface pressure loading, than what is observed experimentally. Possible reasons for the discrepancy are analyzed, and adjustments to the model, with caveats, are suggested accordingly.

实施和评估肺的非线性粘弹性模型以用于高速率加载。该模型的主要特征包括考虑肺内空气的体积压缩率的闭孔近似值和损伤-损伤分量，通过该分量，局部创伤由累积归一化内部能量引起并被能量密度梯度放大。后一特征适用于在应变能量密度的局部速率和纵波速度方面的标准数值（即，显式有限元）模拟中使用。通过压力脉冲直接加载一块提取的肺物质而不是整个胸部的损伤预测与提取的兔肺的实验观察结果非常接近：存在阈值施加压力，高于该阈值可通过实验观察到水肿，与数值结果中的低但不可忽略的损伤相关。圆柱形和球形弹丸对撞击的响应也被询问。穿透深度与实验观察到的深度相当，随着冲击速度的增加，损伤也会急剧增加。损伤从撞击表面开始并传播，局部损伤的严重程度随着与撞击区域的距离而降低，这与一些经验证据一致。相对于上述表面压力载荷，该模型预测比实验观察到的更严重的局部损伤。分析了差异的可能原因，并相应地建议对模型进行调整，并提出警告。与数值结果中的低但不可忽略的损伤相关。圆柱形和球形弹丸对撞击的响应也被询问。穿透深度与实验观察到的深度相当，随着冲击速度的增加，损伤也会急剧增加。损伤从撞击表面开始并传播，局部损伤的严重程度随着与撞击区域的距离而降低，这与一些经验证据一致。相对于上述表面压力载荷，该模型预测比实验观察到的更严重的局部损伤。分析了差异的可能原因，并相应地建议对模型进行调整，并提出警告。与数值结果中的低但不可忽略的损伤相关。圆柱形和球形弹丸对撞击的响应也被询问。穿透深度与实验观察到的深度相当，随着冲击速度的增加，损伤也会急剧增加。损伤从撞击表面开始并传播，局部损伤的严重程度随着与撞击区域的距离而降低，这与一些经验证据一致。相对于上述表面压力载荷，该模型预测比实验观察到的更严重的局部损伤。分析了差异的可能原因，并相应地建议对模型进行调整，并提出警告。穿透深度与实验观察到的深度相当，随着冲击速度的增加，损伤也会急剧增加。损伤从撞击表面开始并传播，局部损伤的严重程度随着与撞击区域的距离而降低，这与一些经验证据一致。相对于上述表面压力载荷，该模型预测比实验观察到的更严重的局部损伤。分析了差异的可能原因，并相应地建议对模型进行调整，并提出警告。穿透深度与实验观察到的深度相当，随着冲击速度的增加，损伤也会急剧增加。损伤从撞击表面开始并传播，局部损伤的严重程度随着与撞击区域的距离而降低，这与一些经验证据一致。相对于上述表面压力载荷，该模型预测比实验观察到的更严重的局部损伤。分析了差异的可能原因，并相应地建议对模型进行调整，并提出警告。与一些经验证据一致。相对于上述表面压力载荷，该模型预测比实验观察到的更严重的局部损伤。分析了差异的可能原因，并相应地建议对模型进行调整，并提出警告。与一些经验证据一致。相对于上述表面压力载荷，该模型预测比实验观察到的更严重的局部损伤。分析了差异的可能原因，并相应地建议对模型进行调整，并提出警告。