半透明材料红外热像检测的光谱特性和光源选择

Spectrum characteristics and light source selection for infrared thermal imaging testing of semitransparent materials

对半透明材料的光激励红外检测,其热激励机理与不透明材料不同,试件的吸热依赖于材料的光学特性和光源的辐射光谱。基于半透明材料的光谱特性,提出了体加热的物理机制和建模方法。为了获得材料的光谱吸收率,测试了不同厚度下玻璃纤维复合材料在一定波长范围内光的反射率和透射率。以色温模型来描述加热灯的光谱特性,用有限单元法分析了闪光灯色温对缺陷检测效果的影响,给出了可检信息参数(最大温差和最大对比度)与闪光灯色温的关系。结果表明,最大温差和最大对比度与色温呈非线性关系,它们随色温升高先减小后增大,因此低色温和高色温闪光灯对半透明复合材料检测更有利。所得结论为半透明复合材料的闪光灯激励红外检测提供了理论参考。

In the case of infrared thermography of semitransparent materials, the heat stimulation mechanism differs from that of opaque materials, and the heat absorption of a specimen depends on its optical properties and the radiation spectrum of a light source used. Based on the spectrum characteristics of semitransparent materials, a body heating mechanism and modelling were proposed. To obtain the spectrum absorptivity of the materials, the reflectivity and transmittance of the glass fiber reinforced plastics with different thicknesses were measured in a certain wavelength range. The spectrum characteristics of heating lamps were described by a color temperature model, the effect of the color temperature of a flash on the flaw detection was analyzed by using finite element method, and the relationships between the detectable information parameters（the maximum temperature difference and maximum contrast） and the flash color temperature were presented. The results show that the maximum temperature difference and maximum contrast are a nonlinear function of the color temperature, and they decrease first and then increase when the color temperature increases, so a low or high color temperature is more favorable for the inspection of semitransparent composite materials. The conclusions provide a theoretical reference for the flash infrared thermography of semitransparent composite materials.