基于频率敏感度和振型的圆柱壳损伤检测方法研究

基于频率敏感度和振型,在损伤定位准则的基础上,提出一种确定圆柱壳中损伤位置和程度的方法.通过对比由于损伤引起的理论和测量频率改变百分比,可以确定损伤的轴向位置.由于圆柱壳的轴对称性,引入某些特定位置的振型信息来确定损伤的环向位置,并且利用一阶近似方法估计损伤程度.对三种边界条件下(自由、简支、悬臂)的圆柱壳数值算例结果表明,文中方法能准确定位单、多位置损伤,而且可以在较小的误差范围内估计出损伤程度.最后利用含噪声的测量频率研究该方法的稳定性.

DAMAGE DETECTION IN CIRCULAR CYLINDRICAL SHELLS BY FREQUENCY SENSITIVITIES AND MODE SHAPES

The damage location assurance criterion (DLAC) is extended to locate and assess damage in a circular cylindrical shell based on natural frequency sensitivities and mode shape deviations. Frequency sensitivities obtained from a defect-free finite element model are applied to calculate the theoretical frequency changes. The axial position of the damage can be easily obtained by comparing the theoretical and measured frequency changes due to damage. For the shell is axis-symmetric, additional information of mode shapes is introduced to locate the exact damage position. The damage extent can be estimated by the first order approximation method. The feasibility and practicality of the damage detection scheme are evaluated by locating and sizing damage for several damage scenarios in the free-free, simple-supports and free-clamped shells, respectively. Simulation results show that the proposed detection scheme can well locate the single or multiple positions of damage. It is also observed that damage extent can be estimated within a relatively small error. The robustness of the proposed method in the presence of measurement errors is demonstrated.