红外系统的定量缺陷识别算法研究

A New Quantitative Thermographic Identification Method of Subsurface Defect for Infrared Sensor System

对带有二维内部缺陷的试件的传热建立了物理和数学模型,并根据Levenberg-Marquardt法提出了根据表面红外测温确定内部缺陷尺寸和深度的识别算法,并通过正反问题的求解对计算方法进行了验证。同时,分析了表面测温误差,表面最大温差等对计算结果的影响。通过计算分析可以得到结论:本方法可以精确地识别试件内部的缺陷尺寸和深度;温度测量误差对计算结果的影响不大;表面最大温差越大,缺陷的识别精度越高。本方法适用于可用有限个参数描述的任何形状缺陷的识别。

A two-dimensional physical and mathematical heat transfer model of a test piece with one subsurface defect is built and the thermal characters at the inspection surface of the subsurface defect are studied, and at the same time a new method, based on the Levenberg-Marquardt method, of evaluating the size, depth of the defect from the temperature distribution at the inspection surface obtained from the infrared image is presented in the paper and certified by the numerical experiments. The effects of the temperature measurement error and the maximum temperature difference on the inspection surface on the computational results are also analyzed. From solving both the direct and the inverse heat conduction problems the conclusions can be drown as follows： the precise size, position of the defect can be estimated and the effect of the temperature measurement error is negligible; the larger the maximum temperature difference, the more accurate the calculational results. The method is suitable to detect any subsurface defect as long as the shape and depth of the defect can be described by a finite number of parameters.