【摘要】 针对谐振疲劳裂纹扩展试验中，由裂纹闭合引起裂尖和背景区域图像灰度对比度不高造成的裂纹长度动态测量精度不高、稳定性不够的问题，提出一种谐振载荷状态下基于欠采样频闪图像采集疲劳裂纹长度在线测量方法。该方法首先在一个欠采样周期内通过同步控制器硬触发摄像机等间隔采集裂纹试件图像，同时载荷控制器获得与采集图像匹配的一系列载荷点，对载荷点进行最小二乘曲线拟合，拟合曲线幅值点近似谐振载荷最大点；然后将幅值点与邻近载荷点相位差对应时间反馈给同步控制器校准采集间隔，使每个欠采样周期采集接近谐振载荷最大点的裂纹张开图像；最后采用基于亚像素角点检测裂纹长度测量方法对裂纹张开图像进行在线测量。试验结果表明：测量数据稳定，测量精度可达0.025 mm。更多还原

【Abstract】 The low grayscale contrast between the crack tip area and the background area caused by the crack closure phenomenon in the resonance fatigue crack growth(FCG) test will lead to low accuracy and insufficient stability of the crack length dynamic measurement. In response to this problem, a fatigue crack online measurement method under resonant loading based on the under-sampling stroboscopic image acquisition is proposed. This method uses the synchronization controller to hardware trigger camera to acquire a series of cracked specimen images in an under-sampling period at equal intervals, and it queries the load controller to obtain a series of load points that match the image acquisition at the same time. Then the load points are fitted to obtain the curve using least-square fitting method, the amplitude point of the fitted curve is approximate to the maximum point of the resonance load, and the time corresponding to the phase difference between the amplitude point and the nearest load point is fed back to the synchronization controller to calibrate the interval of acquisition. So that the fatigue crack opening image close to the maximum resonance load point can be acquired in each under-sampling period. Using the crack length measurement method based on sub-pixel corner detection to process the fatigue crack opening image online. The experimental results show that the measurement data is stable, accuracy can reach 0.025 mm.更多还原