基于小波变换模极大值的橡胶薄层厚度超声检测

为解决同一薄层界面处的各次反射回波在时域上不可分离导致无法测厚的问题,提出利用小波变换模极大值对橡胶薄层超声回波信号奇异点进行检测的方法.信号奇异点构成模极大值曲线,极大值曲线产生周期性,相邻的极大值曲线对应入射时基体/橡胶界面和反射时橡胶/基体界面回波信号的到达时间,其差值为超声波在橡胶薄层中传播时间的2倍,取其平均值,计算出橡胶薄层的厚度.仿真结果表明,该方法的相对误差均在10%以内.经实例验证该方法是可行的.

Ultrasonic testing of rubber thin-bed thickness based on wavelet transform modulus maxima

This paper presented a method for testing singular points of the ultrasonic echo of the rubber thin-bed using modulus maxima of wavelet transform as the thin-bed thickness cannot be measured due to multiple reflection waves being inseparative at the same interface in time domain.The curve of modulus maxima with periodicity is constituted by signal singular points.Adjacent curves were respectively corresponding to the arrival times of the incidence wave at substrate-rubber thin-bed interface and the reflection wave at thin-bed rubber-substrate interface.The mean value of both times difference is twice as long as the time which ultrasonic travels in the rubber thin-bed,therefore,the rubber thin-bed thickness could be calculated.Simulation result shows that comparatively error of the thin-bed thickness is less than 10%.Experiments validate the feasibility of the proposed method.