现状铝合金低温断裂韧性研究.doc

铝合金低温断裂韧性研究Low temperature fracture toughness aluminum alloy research 姓名: 班级: 学号:  摘要：随着航空航天技术的发展，机械性能的结构材料在低温的研究也越来越多。人们更加注重断裂韧性的铝合金的低温。本文介绍了常用的测量断裂韧性的方法及判据，分析了国内外评定铝合金及其接头的断裂性能现状，并提出测试2219铝合金的断裂韧性评定方案。最后指出了我国在评定低温断裂性能方面的不足以及需要改进的方面断裂力学判据随着近年来断裂力学的进展，在评价结构使用性能时，最适当的量度已变为断裂韧性。在断裂力学上把材料抵抗裂纹扩展的能力称为断裂韧性。在实际工程应用中我们采用那个断裂力学破坏判据？如何应用断裂力学指导选材与测定断裂韧性？这些是必须要首先解决的问题。目前断裂力学断裂判据较多，其特点、出发点各有不同。如线弹性断裂力学(KIC)可以认为是应力判据，裂纹张开位移(COD)可认为是位移判据，J积分可认为是能量判据，塑性区的尺寸ρ可认为是应变判据等。这些判据在评定结构件有那些问题？采用哪个比较适宜？为此必须了解这些判据的特点、约束条件、优点及不利的地方。线弹性断裂力学适用于平面应变或小范围屈服条件下；对于大范围屈服采用 ， ， 判据，对于全面屈服状态下的 不再成立，只有用 和 ；但是 理论尚不够完善，J积分方法是弹塑性断裂力学中很有前途的方法ABSTRACT: As the development of aeronautic and astronautic techniques, the mechanical properties of structural materials at cryogenic temperature are studied more and more. People pay more attention to the fracture toughness of Al alloy at cryogenic temperature. This paper introduced manners of measuring fracture toughness, analyzed the present evaluation of fracture toughness of aluminum alloy and its welding joint, and proposed scheme of evaluation of the fracture toughness of 2219 Al alloy. In the end, it was stated that there were a lot of deficiencies in evaluation of the fracture toughness at cryogenic temperature in our country.; Fracture mechanics criterion with the recent progress in the evaluation of fracture mechanics, structural performance, the most appropriate measure has been changed to fracture toughness. In the mechanics of materials resistance to crack propagation ability is called fracture toughness. In the practical engineering application. We adopt the fracture mechanics damage criterion? How the application of fracture mechanics to guide the selection and determination of the fracture toughness? These are must first solve the problem. The fracture mechanics and fracture criterion is more, its characteristics, the starting point is different. Such as the linear elastic fracture mechanics ( KIC ) can be cons