星型负泊松比蜂窝夹层板的低速冲击动态响应分析
Dynamic response analysis of star shaped honeycomb sandwich panel with negative Poisson’s ratio under low velocity impact
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摘要: 从结构响应信号中挖掘敏感损伤特征是基于模式分类的损伤识别方法的关键。为此,将深度信念网络和长短期记忆网络进行混合组网,通过混合学习机制有机结合了两种网络在高阶抽象特征提取和考虑数据序列相关性上的优点。将响应信号传递比值输入深度信念网络,实现初步数据压缩和特征提取,以减少响应中的冗余信息;将特征序列依次输入长短期记忆网络,以考虑响应间的相关性并获取敏感损伤特征;利用 Softmax 分类层对长短期记忆网络输出的特征进行分类,实现对不同结构损伤模式的识别。三维试验钢框架的损伤识别结果表明:混合学习机制能更好地训练网络参数,整体微调后更有利于后续的损伤特征分类;混合组网方式在包含数值或实测噪声的情况下仍可以有效进行数据压缩、特征提取和分类,准确识别了试验框架的多种损伤工况。Abstract: The star-shaped negative Poisson’s ratio structure is used as the core of sandwich panels. The dynamic model of a sandwich plate is established, and the equivalent elastic parameters of sandwich layer are derived. The equations of motion of sandwich plates are derived based on Hertz theory, first order shear deformation theory and Hamilton principle. Then, the equations of motion are solved by navier method. The contact force of the impact model is obtained through the spring-mass model with two degrees of freedom, and the lateral displacement of the sandwich plate after impact is calculated by Duhamel integral. The predicted results of plate contact force and lateral displacement are compared with the published papers to verify the accuracy. Meanwhile,the low-velocity impact response of star-shaped negative Poisson’s ratio sandwich panels is also compared with the negative Poisson’s ratio concave hexagonal honeycomb sandwich panels, and the influence of the parameters of sandwich panels is also discussed. When the impact velocity increases, the maximum contact force and the maximum lateral displacement of the sandwich plate also increase, while the duration of the impact response decreases. The greater the thickness ratio of the sandwich plate is,the better the impact performance of the sandwich plate will be. The smaller the side length ratio of cell is, the better the impact performance of sandwich plate will be. The increase of the cell concave angle enhances the impact performance of the sandwich panel. This study can provide some reference for the study of impact resistance of negative Poisson’s ratio metamaterial structures and sandwich panels.