Research on Response of Ultrasonics to Closed Cracks and Nondestructive Evaluation

1.为了建立一种对裂纹回波幅度进行自动二维扫描的高精度、高速度的采样方法，采用水和超声波设备作为超声波传播和波数采样的介质。将数据安装在采样速度较快的数字示波器中。2.从闭合裂纹的理论方程出发，推导出简化的评价方程。利用简化的评价方程，通过对反问题的分析，给出了计算裂纹长度和裂纹闭合相对不敏感性的计算机程序。3.为了探索一种改进的检测和信号处理方案，对单探头超声技术进行了新的实验研究，以获得更好的超声特征响应。4.在垂直入射超声自动系统的基础上，研制了一种高灵敏度的自动采集斜角裂纹回波数据的系统。5.实验研究了超声波入射波束倾斜角与反射波和模式转换的关系。6.利用斜入射超声对两个极窄、0.1 mm宽、深度分别为1 mm和3 mm的小裂纹进行了无损检测。该方法可用于小裂纹的评定。

1.In order to establish a high accuracy and high speed sampling method by using an automatic two dimensional scanning for an amplitude of echo from crack, water and an ultrasonic equipment were used as medium for ultrasonic wave propagation and sampling of wave date. The data was installed in a digital oscilloscope which has a high sampling speed.2.An evaluation equation which was simplified from a theoretical equation of a closed crack was derived. The evaluation method and a program of a computer to get a length of crack and a relative insensitivity of crack closure was shown by analyzing an inverse problem using the simplified evaluation equation.3.In a quest to develop an improved detection and signal processing scheme, a new experimental study of a single probe ultrasonic technique concerning a beam angle has been conducted in an attempt to achieve better characteristic response of ultrasonics.4.A high sensitive and automatic sampling system applied for crack echo data with oblique angle was developed from the automatic system using normal incident ultrasonics.5.The relation between the oblique angle of ultrasonic incident beam and the reflection of the wave and also mode conversion were examined experimentally. The possibility of a nondestructive evaluation by ultrasonics with oblique angle was shown.6.Two simulated small cracks extremely narrow width, 0.1 mm-wide slit, having depths of 1 and 3mm, wer evaluated by using oblique incident ultrasonics. The method can be applied for an evaluation of small cracks.