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点阵桁架夹芯板作为一种特殊的超轻多孔材料,具有广阔应用前景。针对其加工和服役过程中经常发生的脱焊损伤,本文提出一种基于结构振动特性进行金字塔型点阵桁架夹芯板无损评价的方法。首先,基于有限元理论对夹芯板在不同损伤状态(损伤个数、位置)下的振动特性进行数值模拟;然后基于计算所得振动特性参数,运用切比雪夫多项式逼近法计算相应均布载荷曲面的曲率,进而通过此参数与原始未损伤模型参数作差进行损伤识别;最后运用曲面拟合算法解决该检测方法对原始未损伤模型参数的依赖性问题。数值计算结果表明:四周简支金字塔型点阵桁架夹芯板中存在损伤时,损伤前后结构损伤位置处的均布载荷曲面的曲率差值比较明显,基于此差分方法可精确识别各种损伤状况下夹芯板脱焊损伤的位置和数量;利用曲面拟合算法可以消除损伤结构参数中因损伤造成的尖点,从而不需以原始未损伤模型参数为依据即可精确识别损伤。
Lattice truss sandwich panel as a special ultra-light porous material, has broad application prospects. In this paper, aiming at the desalting damage often occurred in the process of machining and service, a method of nondestructive evaluation based on the structural vibration characteristics of the pyramid lattice truss sandwich panel is proposed. First of all, based on the finite element theory, the vibration characteristics of the sandwich panel under different damage conditions (damage number and position) are numerically simulated. Then, based on the calculated vibration characteristic parameters, the Chebyshev polynomial approximation method is used to calculate the corresponding uniform load surface , And then the parameters of this model are used to identify the damage from the parameters of the original undamaged model. Finally, the algorithm of surface fitting is used to solve the dependence of this method on the parameters of the original undamaged model. The numerical results show that the difference of the curvature of the uniformly distributed load surface at the location of structural damage before and after damage is obvious when the damage occurs in the simply supported pyramid lattice sandwich panel. Based on this difference method, various damage conditions can be accurately identified The location and number of the lower core plate desoldering damage; the use of surface fitting algorithm can eliminate the damage caused by the structural parameters of the sharp point, so that the original model can not be damaged based on the parameters to accurately identify damage.