以小阻尼简支梁为例，讨论了交叉模态对随机振动疲劳损伤累积的贡献；结构的响应分析采用模态叠加方法，随机振动疲劳损伤累积分析采用Miner线性疲劳损伤准则。数值模拟结果表明,即使是小阻尼稀疏模态结构，交叉模态对结构振动疲劳损伤累积的贡献也是不容忽视的。

The contribution level of cross modality to vibration response of structure is governed by damp and modality. The larger the damping and the denser the modality, the higher the contribution. In engineering vibration analysis' a system hypothesis with lightly damping and sparse modality is generally applied to solve approximately vibration response of structure where the contribution of cross modality is neglected due to the contribution small enough. Approximate solution of displacement response can satisfy engineering requirement with certain precision but the error between approximate response and exact one, maybe tiny, can heavily effect the peak frequency and irregular factors of spectral diagram in time domain vibration analysis and change the results of fatigue damage accumulation identification. With a simple supported beam in this paper the contribution of cross modality to fatigue damage accumulation is investigated. Random response is obtained by means of superposition methods and fatigue damage accumulation of structure under random vibration is analysised with Miner's linear damage ruler. Numerical simulation shows that the contribution of cross modality to fatigue damage accumulation of structure can not be neglected even if the structure is characterized with lightly damping and sparse modality.

朱学旺（1963－），男，湖北鄂州市人，中国工程物理研究院总体工程研究所研究员，研究方向为复杂结构动力学与振动环境试验