STUDY OF AE WAVE GENERATION BY STRESS WAVE VISUALIZATION METHOD

通过应力波可视化技术模拟了声发射的产生、传播及其与接收信号的关系。为了模拟声发射波的产生，我在玻璃模型试件上引入一个缝隙来模拟裂纹，并将压电传感器放置在缝隙尖端，通过施加电脉冲使其产生类似裂纹尖端断裂的变形，使用了两种矩形形状的压电传感器来模拟实际的裂纹尖端断裂;一种是沿厚度方向变形的Ⅰ型断裂，另一种是剪切变形的Ⅱ型断裂。应用应力波可视化技术，我使用玻璃模型标本，具有类似的声速的钢。本文采用方形和条形试件研究了试件形状对声发射波产生的影响。本研究所用的应力波显示系统最初是为固体中的超声波显示而开发的。两种宽带声发射传感器和两种宽带声发射传感器的设计结果表明，它们的结构和性能对声发射波的产生有重要的影响。 ...更多信息 声发射类型1被用来接收AE波，以表征这些AE传感器。在这种模拟方法中，可以重复产生相同的AE波，因此可以通过接收相同的AE波来进行准确的比较，以评估AE传感器的接收特性。1.尽管不同类型的PZT放在狭缝尖端，无论是纵向和剪切波作为AE波从狭缝尖端发射。然而，由厚度变形模式PZT产生的主波是纵波，而由剪切变形模式PZT产生的波是剪切波，并且每个波具有不同的方向性。2.不同形状的试件在声发射波的产生和传播方面存在差异。在杆型试件中，沿试件表面沿着传播的部分纵波被转换为横波。3.声发射传感器接收到的声发射信号与实际的突发型声发射信号相似。当接收由放置在狭缝尖端的PZT产生的相同AE波时，从每个AE传感器观察到不同的信号。少

I simulated AE generation, propagation and its relation to received signal by means of stress wave visualization techniques. In order to simulate the AE wave generation, I introduced a slit into a glass model specimen as a simulation of a crack and put a piezoelectric transducer in the slit tip to deform like crack tip fracture by applying an electric pulse.Two types of PZT transducers, having rectangular shape, were used to simulate the actual crack tip fracture; one was deformed to thickness direction as mode I fracture and the other made shear deformation as mode II fracture. Applying the stress wave visualization technique, I used glass model specimens which have similar sound velocities to that of steel. Square shape and bar type specimens were used to study the effects of specimen shape to the AE wave generation.The system for stress wave visualization used in this study was originally developed for ultrasonic wave visualization in a solid.Two types of wide band AE sensors and re … More sonant type one were used to receive the AE wave for characterizing these AE sensors. In this simulation method, the same AE wave can be generated repeatedly so that exact comparison is enable to evaluate receiving characteristics of the AE sensors by receiving the same AE wave.Results obtained in this study are as follows. 1. In spite of the different types of PZT put in the slit tip, both longitudinal and shear wave were emitted as an AE wave from the slit tip. However, a main wave generated by the thickness deformation mode PZT was a longitudinal wave and the wave generated by the shear deformation mode PZT was a shear wave, and each wave has different directivity. 2. There are differences in the AE wave generation and propagation between the specimen shapes. In the bar type specimen, part of longitudinal waves propagating along the specimen surface were inode-coriverted to shear waves. 3. Received AE signals by the AE sensors were similar to actual burst type AE signal. When receiving the same AE wave generated by the PZT put at the slit tip, different signal were observed from each AE sensor. Less