为实现无损在线探测缸盖内部热裂纹，提出一种基于红外热成像技术，由缸盖表层温度直接判断其内部热缺陷的新方法。以某型柴油机缸盖为研究对象，分析了缸盖的传热机理，结合缸盖温度场的三维分布，确定了其内部易产生热裂纹的部位，并对裂纹结构进行了加工模拟。构建缸盖温度场检测台架，对正常结构缸盖与裂纹缸盖开展了外部特征区域温度场的检测。结果表明，在缸盖传热边界一定的情况下，缸盖表层温度场的变化能直接反映缸盖内部热裂纹缺陷，具体表现为传热受阻的左表面特征区域最高温度值降低，而其他特征表面由于传热量的增强使得表面上的温度升高，这与缸盖实际的传热规律相符。

A new method is put forward to detect thermal flaw inner cylinder head on-line based on infrared thermograph technology. Aiming at some diesel engine, heat transfer rule for cylinder head is analyzed. Combined with three-dimension temperature distribution, areas in which flaws can be produced are studied and flaw inner cylinder head is machined. Testing platform on detecting flaw is set up and temperature tests on cylinder head are developed. Results show that when there is a flaw inner cylinder head, maximum temperature value of outer surface hindered by flaw will be decreased. On other surfaces, maximum temperature value will be increased, which is accordant with actual heat transfer rule.