一种基于非线性超声谐波幅值比的微裂缝探测方法

超声波穿过受损材料后,都会产生一定程度的非线性效应,如谐波.利用非线性波动理论中二阶谐波幅值与基波幅值的关系,探讨了通过测试谐波比关系的变化,获得材料非线性特征改变,进而判断材料损伤的方法,并进行了试验研究.试验中制作了两组水泥砂浆试棒,采用了相同活性碱骨料砂、相同水灰比,其中一组中通过碱骨料反应引入不同程度的微裂缝;另一组保持无损状态.两组水泥砂浆试验的对比试验结果表明,材料经碱骨料损伤后,其超声非线性特征变化十分明显.证明本方法对混凝土材料微裂缝的探测非常敏感,对于水泥基材料而言,是一种极具潜力的材料退化评估方法.

A method for microcrack detection based on harmonic amplitude ratio of nonlinear ultrasonic

The nonlinear acoustic features,such as harmonics will appear with ultrasound through a damaged material.Based on the relationship between the harmonics,a method that uses nonlinear acoustic harmonic amplitude ratio to distinguish microcracks in cement-based materials.Experimental tests were performed by two groups of mortar samples.Portland cement mortar samples prepared with alkali-reactive aggregate were exposed to an aggressive environment to induce microcracking and were compared to control samples of the same composition,but which were not exposed to aggressive conditions.The test results show that acoustic features were very obvious for the damaged group samples.The method presented is sensitive to the microcrack,demonstrating the potential of nonlinear acoustic waves to provide a quantitative evaluation of the deterioration of cement-based materials.