基于对数二阶微分峰值法的缺陷深度测量研究

Study of Defect-depth Measurement Based on Second-order Derivative Peak Value Method

红外检测中定量分析方法常以特征时间和缺陷深度的关系为基础。本文预设6个平底洞的不锈钢为实验试件,选取一种不需要参考区域的PSDT法进行测厚计算。以对数温度曲线的二阶微分峰值时刻作为特征时间,利用特征时间与试件深度的平方成正比关系,达到测厚的目的。用VC软件编程实现任意点的数据计算,先用最小二乘多项式的方法拟合数据,再计算对数温度一对数时间的二阶微分峰值时刻,将结果用图形直观精确地显示出来,最终实现缺陷深度的自动测量。

In infrared detection, the quantitative analysis is usually based on the relationship between the specified characteristic time and the defect depth. Using a stainless steel plate with six flat-bottom holes as an experimental sample, the defect depth is calculated by using a PSDT method which need not to choose any reference. When the time of the second-order derivative of logarithmic temperature peak is taken as the characteristic time, the defect depth is measured according to the proportion of the characteristic time to the square of defect depth. The data calculation for any point can be implemented with a VC program. Firstly, the data is fitted by using the least square polynomial. Then, the second-order derivative peak time of the logarithmic temperature-logarithmic time is calculated. The result is displayed precisely in figures and the defect depth is automatically measured finally.