基于应变模态方法的飞机蒙皮分布动载荷识别

目的解决飞机蒙皮分布动态载荷确定的工程实际问题。方法将基于广义正交多项式的复杂分布动载荷识别技术与应变模态理论相结合,建立利用有限个测点的应变响应和结构应变频响函数作为已知参数的飞机蒙皮分布动载荷识别模型。利用Nastran软件,以某型飞机机身中段外蒙皮为例,分别采用位移模态方法和应变模态方法进行了70、80、90、100 Hz下的蒙皮分布动载荷识别,并进行对比分析。结果以应变响应作为已知参数的应变模态载荷识别方法,在各计算频率下均具有较好的识别精度,最大识别误差为8.9%,能够满足工程应用。在各识别频率下,采用应变方法识别过程中的积分矩阵条件数小于位移方法。在100 Hz识别频率下增加3%随机误差干扰后,位移识别方法最大误差为19.4%,采用应变方法的载荷识别最大误差为9.8%。结论相比于传统的采用位移模态的载荷识别方法,以应变响应作为已知参数的应变模态载荷识别方法具有更好的数值稳定性,对于解决结构共振频率附近频响函数矩阵奇异性问题具有很好的应用价值。

Identification of Aircraft Skin Distributed Dynamic Load Based on Strain Modal Method

To solve the practical engineering problem of distributed dynamic load identification on aircraft skin, this paper combined the strain modal theory and the complex distributed dynamic load identification technology based on the generalized orthogonal polynomials, established a distributed dynamic load identification model of aircraft skin with the structural strain response of limited measuring points and strain transfer function as the known parameters. Taking the outer skin of a certain aircraft fuselage as an example, the distributed dynamic load identification of skin was carried out at 70, 80, 90 and 100 Hz by both displacement mode method and strain mode method with NASTRAN software, and a comparative analysis was carried out. The example showed that the method of dynamic load identification of aircraft skin distribution using strain mode method had good accuracy of load identification and the maximum identification error was 8.9%, which can meet the needs of engineering application. The condition number of integral matrix based on strain modal method was lower than those based on displacement method at each frequency. The maximum identification error of displacement method reached 19.4% when 3% random noise was applied, while the identification error of the maximum strain method was 9.8%. Compared with the traditional method of load identification using displacement mode, the strain modal load identification method with strain response as a known parameter has better numerical stability, which has a good application value for solving the singularity problem of frequency response function matrix near the resonance frequency of structure.