疲劳裂纹扩展试验裂纹图像采集系统

针对目前金属疲劳裂纹扩展检测方法存在效率低、操作繁琐、精度不高，不能实现实时性等缺点，文章提出了基 于机器视觉的裂纹检测方法。根据金属疲劳裂纹扩展试验过程中裂纹图像的采集要求，设计了摄像头位置可自动调整 的疲劳裂纹图像采集系统，包括摄像头安装运动装置，裂纹图像采集装置以及摄像头运动控制系统。图像采集装置由高 分辨率黑白面阵CCD摄像头、光学镜头，光源照明装置和图像采集卡组成，前3者安装在摄像头支架上，与摄像头运动 装置相连。摄像头运动装置中的X，Y，，Z轴运动机构由步进电机带动滚珠导轨机构。在基于ARM技术的运动控制系统 的控制下摄像头可沿X，Y，，Z轴作高精度直线运动，实现和试件之间精确位置的调整。实验结果表明，所设计的系统可 采集到疲劳裂纹扩展试验过程中高清晰度、高分辨率的试件裂纹图像，满足下一步裂绞尺寸计算的要求；摄像头运动定 位精度可达到0. 02 mm，满足精确的系统聚焦、位置调整、跟踪采集的要求。

Crack Image Acquisition System in Fatigue Crack Propagation Test

At present metal fatigue crack growth detection methods have the shortcomings of low efficiency and accuracy, complicated operation. and not real-time achievement. so the new crack detection method was given based on machine vision. A crack image acquisition system with auto-adjusting camera in the fatigue crack propagation test was designed, in order to meet the crack image acquiring requirement for the machine vision fatigue crack propagation test. The designed system included image acquisition device composed of black white area CCD camera with high resolution, optical lens, lighting device, and image acquisition card. The camera movement and installation device composed of X, Y.Z axis moving mechanism which was the ball screw and LM guide rail structure with the high movement precision was driven by a highly-subdivided stepper motor and the installation mechanism. and the camera moving control system has been designed based on the ARM technology. The CCD could perform the high precision straight movement along X, Y, Z axis direction controlled by the camera moving control system. accurate position adjustment between the sample and CCD coul be achieved. The experiment results show that this design system can capture the crack images which are very clear and with high resolution in the fatigue crack propagation test. and can satisfy the requirement for the precise crack length measurement. The camera movement accuracy reaches 0. 02 mm.and can meet the requirements of accurate focusing, position adjustment and image tracking acquisition.