裂纹参数和筋条布局对共振九宫板动态应力强度因子的影响

由于裂纹的出现会改变振动结构的断裂行为，本文建立了含中心裂纹九宫板结构的有限元模型并采用模态叠加原理快速求解出该结构在共振条件下的裂纹尖端应力强度因子（SIF），然后分析并讨论了裂纹参数（偏转角度和裂纹长度）及筋条布局对应力强度因子的影响。结果表明：随着裂纹偏转角度的增加，Ⅰ、Ⅱ和Ⅲ型应力强度因子最大值分别表现出不同的变化趋势（单调增加、无显著变化、先增加后减小）；裂纹长度同时影响应力强度因子最大值和裂纹类型；对于裂纹参数相同的九宫板，筋条布局改变了结构的模态振型，从而导致不同裂纹类型出现；特别地，当九宫板中央区域为正方形时，应力强度因子最大值和裂纹类型对裂纹偏转角度不敏感。

Effect of crack parameters and stiffener layout on dynamic stress intensity factor of 3×3 grid stiffened panel at resonance

The fatigue crack generated during vibration would affect the fracture in structures. The 3×3 grid stiffened panel with the center crack was modeled using the finite element method. The modal recombination method was applied to rapidly compute the values of the Stress Intensity Factor (SIF) of crack tip in the panel at resonance. The influence of crack parameters (inclined angle and crack length) and the stiffener layout on SIF values was analyzed. The result shows that the maximum SIF values of the structures for Mode Ⅰ, Mode Ⅱ and Mode Ⅲ showed different trends as the inclined angle of the crack increased (monotonically increase, no significant change, and increase first and then decrease). The maximum SIF values and crack mode were affected by the crack length. For the panels with the same crack parameters, different distribution of the stiffener results in different vibration shape, and thus causes different types of cracks. In particular, effect of the crack inclined angle on the SIF amplitude and crack mode can be ignored when the center region of the panel is square.