C/SiC复合材料盲孔缺陷深度的红外热成像定量测量

Thermographic measurement methods for depths of the blind holes drilled in C/SiC composites

利用在三维针刺C/SiC复合材料板上设计不同直径和深度的盲孔作为试样,模拟材料表面下的孔洞缺陷。采用红外热成像技术对试样盲孔缺陷进行检测,获得盲孔缺陷信息,通过最大温差法和lnT-lnt曲线二阶导数最大值法两种分析方法测量盲孔的深度并分析所产生的误差。结果表明:两种方法都可以实现对盲孔缺陷深度的定量测量,但产生的测量误差存在差异;当径深比为1～4.4时,采用最大温差法的误差明显小于lnT-lnt曲线二阶导数最大值法,而lnT-lnt曲线二阶导数最大值法的测量精度虽然稍低,但该方法所适用的径深比范围较宽,并且测量误差随着盲孔径深比的增大而减小。

Different diameters and depths of blind holes were drilled in the samples of 3D needled C/SiC composites to simulate air void defects in this paper. Thermal imaging testing was used to detect the blind hole defects, and then the dimension and location information of the defects were obtained. Two methods, i.e. peak temperaturecontrast method and logarithmic peak second-derivative method, were used to measure the defect depths, and the errors of these measured results were discussed. The results indicate that both of the two methods can be used to successfully measure the depth of the blind holes, but the measured error for the two methods is different. The error of peak temperature contrast method is less than the other method when the ratio of diameter to depth ranges from 1 to 4.4. Though the error of logarithmic peak second-derivative method is a bit larger than the other, this method can be used for wider ratios of diameter to depth, and the error of this method decreases as the ratio of diameter to depth increases.