Study on Detecting Existence of Flaws in Materials by Observing Radiation Temperature distribution by means of infrared radiometry

提出了一种利用红外辐射计进行热辐射检测的新技术，用于检测材料内部的夹杂、裂纹、缝隙和针孔等缺陷。在本研究中，将太阳、灯和热气体等多种入射热能注入具有人工内部缺陷的试验材料。用红外辐射计在阴极射线管上显示出内部缺陷上方表面的瞬态辐射温度。表面与缺陷之间的辐射温差代表了内部缺陷的存在。用金属、陶瓷、塑料和绝缘体试件比较了正向加热和侧向加热等各种热注入方法的特点，并在正向加热的情况下，用卤素灯和镀金抛物面不锈钢镜进行了分步高通量热注入试验。在横向加热的情况下，从试件侧面注入的热量通过热传导流到试件的另一侧。在正常加热条件下，内部缺陷上方的温度分布呈现出山脉状和山谷状;在侧向加热条件下，内部缺陷上方的温度分布呈现出不连续的温差。试验结果表明，横向加热法检测狭缝型缺陷优于常规加热法，检测针孔型缺陷低于常规加热法，内部缺陷的检测极限取决于被测材料表面温度的变化。通过求解二维热传导方程，数值分析了内部缺陷周围的瞬态热流，验证了缺陷上方的表面温度分布。

A new thermal radiation technique using an infrared radiometer had been developed to detect internal flaws of materials used, such as inclusion, crack, gap and pinhole. In this study, several incident thermal energies like sun, lamp and hot gas, were injected to the test material with artifical internal flaws. Transient radiation temperature of the surface above the internal flaws were displayd on the CRT by means of the infrared radiometer. The radiation temperature difference between the surface and flaws represents the existance of the internal flaws. Characteristics of various heat injection methods, such as normal and lateral heatings were compared with each others by using test pieces of metal, ceramic, plastic and insulator.Stepwise high-flux heat injection test had been undertaken, using a Halogen lamp with a parabolic stainless mirror coated by gold in case of the normal heating. And the injected heat from lateral side of the test piece flows to the other side of the piece by heat conduction in case of the lateral heating. We visualized the mountainous and valley-like temperature distribution above the internal flaws at the normal heating and discontinuous temperature difference above the flaws at the lateral heating. Test results show that the lateral heating method is more superior than the normal heating in case of detecting the slit flaw and inferior than the normal heating in case of detecting the pin-hole flaw.The detection limit of internal flaws is determined by the surface tempeature variance of the tested material. The transient heat flow arround the internal flaws were numerically analyzed by solving a 2-dimensional heat conduction equation to verify the surface temperature distribution above the flaws.