In order to overcome the shortages that traditional linear ultrasonic testing could not detect the micro-cracks,VAM was studied.The VAM was simulated with finite element software ABAQUS to demonstrate the validity of the proposed method.The parameter setting of experimental testing system was also depended on the simulation results.VAM experimental testing system was es-tablished to investigate the nonlinear characteristic for micro cracks with variable lengths,and a quan-titative characterization method was proposed based on information entropy of modulation signals. The results show that side-band signals are obvious when there is a micro crack in aluminum plate. The information entropy of modulation signals increases monotonically with increasing micro crack lengths and can be used as the characteristic parameter of crack length using VAM method.%为克服传统线性超声无法检测微纳级宽度裂纹的缺点，开展了振动声调制法检测金属微裂纹的研究。用有限元分析软件ABAQUS开展了仿真研究，并验证了该方法的有效性，为实验参数设置提供了参考。搭建振动声调制检测系统，分析了不同长度微裂纹的调制特性，提出了基于振动声调制信号的信息熵定量表征方法。结果表明，存在微裂纹的铝板的振动声调制信号中的旁瓣信号明显，且检测信号的信息熵随裂纹长度单调增大，可作为振动声调制法检测微裂纹长度的特征参数。
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