基于红外成像技术的铝锂合金2198疲劳裂纹监测机制研究

红外成像技术提供了一种快速、非接触、全区域的表面温度监测手段。在超声疲劳试验中,大多数金属材料均具有明显的温度效应。将采用这种技术手段系统地对铝锂合金2198-T8材料在疲劳试验过程中的升温情况开展研究。结果表明,材料从试验开始到疲劳断裂现象的发生,试件表面温度通常要经历三个阶段:快速升温阶段、缓慢升温阶段和急剧升温阶段。快速升温阶段通常与施加应力的大小有关;施加应力和疲劳微裂纹萌生是缓慢升温阶段的主要影响因素;宏观裂纹的扩展以及裂纹面之间的碰撞和摩擦则可导致材料表面的急剧升温。验证了红外成像技术在探索疲劳失效规律问题上作为一种可靠技术手段的正确性。

A Research on Monitoring Fatigue Crack Growth of Al-Li Alloy 2198 Based on Infrared Thermographic Technology

Infrared thermographic technology provides a fast, non-contact and whole region temperature monitoring means. In the ultrasonic fatigue experiments, almost all metallic materials have obvious thermal effect. In this paper, we used this infrared imaging method to do some systematical researches on temperature rise of the surface of Al-Li alloy 2198-T8 during fatigue experiments. The results shows that the temperature on the surface of specimens usually goes through three stages from the beginning of tests to the occurrence of the fatigue fracture: rapid heating stage, slow warming stage and sharp warming stage. The rapid heating stage is usually related to the magnitude of the stress; the magnitude of the stress and micro-crack initiation is the main factors of the slow warming stage; the expansion of the macro-cracks and the collision and friction between the crack surfaces can lead to the rapid temperature increase of the material surface. The infrared thermograghic method can be used as a reliable technical means in fatigue failure researches and has proved to be true in some other papers.