缺陷表面温度分布及空腔自然对流对红外检测的影响

对存在内部缺陷的板状结构的传热建立了二维物理和教学模型。通过有限差分法求 解得到了检测表面的温度分布。得到了缺陷尺寸、深度以及缺陷的当量导热系数对检测表面温度分布的影响规律;通过建立一维模型,分析了缺陷空腔内自然对流换热对检测表面温度分布的影响。研究认为,随着缺陷厚度的增加,缺陷的导热系数与被检材料的导热系数差异扩大,表面的最大温差增大;表面最大温差随缺陷的长度和缺陷深度的增大先增加后减小;缺陷厚度大概在10mm范围内自然对流开始起作用,高于此值后,自然对流换热对表面的温度分布具有显著的影响,并且此缺陷的厚度值受试件材料、表面对流换热系数的影响可以忽略。

Temperature Distribution of Defect Surface and Effect of Natural Convection on Thermographic Inspection

A two dimensional physical and mathematical model on the heat transfer in the fiat plate with rectangular inner defect is presented and is solved by finite difference method, by which the temperature distribution rules on the inspection surface by infrared thermography are investigated with different defect dimensions, depths and effective thermal conductivities. In addition, the effect of the convective heat transfer in the defect on the temperature distribution of the inspection surface is also studied by building a one dimensional model. From these investigations the conclusions can be drown that the maximum temperature difference increases with the increase of the defect thickness, thermal conductivity difference between the plat material and the defect, but the maximum temperature difference has a extremum with the increase of the defect length or the depth of the defect. The convective heat transfer becomes effective when the defect thickness is about 10mm, which changes little with different plate materials and surface convective heat transfer coefficients.