涡流脉冲热像技术中传热学分析与数值模拟

Heat Transfer Analysis and Numerical Simulation using Eddy Current Pulsed Thermography

涡流脉冲热像技术中,对含裂纹被测试件施加短时高频电流激励,裂纹面因涡流积聚会产生瞬时热量,进而由热传导引起试件表面温度分布的变化。为了分析裂纹传热特性,建立了涡流分布模型和简化传热模型,探索了试件表面温度分布的特点。制作了一系列含不同长度的贯穿疲劳裂纹金属试件,深入研究了裂纹区域热响应和裂纹长度之间的关系。数值模拟和实验结果表明:在特定的检测条件下,裂纹区域热响应与裂纹长度接近线性关系,满足正相关性,从而证明了简化传热模型的正确性。研究成果丰富了涡流脉冲热像技术的传热理论,为该技术的工程实践奠定了理论基础。

In eddy current pulsed thermography, the short-high-frequency current excitation is applied to the test piece. The crack surface generates instantaneous heat due to the accumulation of the eddy current, and then the temperature distribution of the specimen is caused by heat conduction. In this paper, the current distribution model and simplified heat transfer model were established to explore the characteristics of the surface temperature distribution of the specimen. Furthermore, a series of penetrating fatigue cracked metal specimens with different lengths were made, and the relationship between the thermal response and the crack length was studied. The numerical simulation and experimented results show that the thermal response of the crack region is linear with the crack length under certain detection conditions, and satisfying the positive correlation, which prove the correctness of the simplified heat transfer model. The research results enriched the heat transfer theory of ECPT, which laid a theoretical foundation for the engineering practice of the technology.