泡沫铝疲劳性能研究进展

Research Progress on Fatigue Properties of Al Foams

泡沫铝因其出色的力学、电学、热力学性能而被人们广泛关注和应用。目前,对泡沫铝的研究主要集中在准静态以及高应变率单轴压缩性能上。然而,随着泡沫铝应用环境的复杂化,其在服役过程中承受循环载荷的情况不可避免。因此,充分了解泡沫铝的疲劳性能以及承受循环加载时的失效机理对其在工程中的进一步应用具有重大意义。根据疲劳试验时加载方式的不同,可将泡沫铝的疲劳分为压-压疲劳、拉伸疲劳两种。由于泡沫铝内部结构不规则,试样个体间差异较大,其疲劳性能离散性明显,因此对疲劳寿命、疲劳强度等参数的定义方式也不尽相同。此外,学者们针对泡沫铝疲劳性能的影响因素展开了一系列研究,并取得了一定成果。目前被广泛认可的泡沫铝疲劳性能的影响因素包括:泡孔结构与形貌、试样尺寸、基体与增强相材料以及热处理等,深入了解影响疲劳性能的因素有助于提高泡沫铝在复杂应用环境下的疲劳寿命与疲劳强度。由于试样结构与研究方法的局限性,目前对于泡沫铝疲劳失效机制的分析尚未得出统一结论,针对其疲劳裂纹扩展方式的研究报道相对较少。研究者们多从疲劳应变-循环次数曲线及内部缺陷等方面入手来分析泡沫铝的失效机理。本文综合分析国内外文献并结合笔者课题组工作,针对泡沫铝疲劳性能研究中的一些关键问题进行了论述。重点介绍了压-压疲劳、拉伸疲劳两种不同疲劳载荷加载方式下泡沫铝的疲劳性能,包括疲劳寿命、疲劳强度以及应力水平等参数的定义方式;讨论了不同因素对泡沫铝疲劳性能的影响,提出通过减小泡孔尺寸和优化泡孔结构均匀性等方法来改善其疲劳性能。此外,从宏观、微观角度出发,对泡沫铝的疲劳失效机理进行了分析讨论。

Aluminum foams have been widely applied due to its excellent mechanical,electrical and thermodynamic properties.At present,the re-search of aluminum foams mainly focus on quasi-static and high strain rate uniaxial compression properties.However,with the diversifica-t ion of the application environment of aluminum foams,it is inevitable that the cyclic loading will act on the aluminum foams.Therefore,it is of great significance to fully understand the fatigue properties of aluminum foams and the failure mechanism under cyclic loading.According to the different loading modes in the fatigue test,the fatigue of aluminum foams can be divided into two types,compression-compression fatigue and tension fatigue.Because of the irregular internal structure and the individual differences among specimens,the fatigue performance is discrete.Therefore,the definition of fatigue life and fatigue strength is not the same.In addition,scholars have carried out a series of studies on the factors affecting the fatigue properties of aluminum foams,and have made certain progress.The factors affecting the fatigue properties which are widely accepted include the structure and morphology of the foams,the size of the specimen,the matrix and the reinforcement materials,and the heat treatment.The in-depth understanding of the factors affecting the fatigue properties will help to improve the fatigue life and fatigue strength in the complex application environment.Due to the limitations of sample structure and research methods,the failure analysis of aluminum foams have not reached a unified conclusion at present.Meanwhile,there are relatively few reports on the mode of fatigue crack propagation.The researchers mainly analyzed the failure mechanisms of aluminum foams from the aspects of fatigue strain-number of circles curve and internal defects.This paper analyze the domestic and foreign literature combined with the work of the author’s group,and then discuss some important problems in the study of fatigue properties of aluminum foams.The fatigue properties of aluminum foams under two kinds of fatigue loading modes(compression-compression and tension fatigue)are mainly introduced.The different definitions of parameters such as fatigue life,fatigue strength and stress level are discussed.The influence of different factors on fatigue properties of aluminum foams is discussed.In order to improve the fatigue performance,reduction of the pore size and increment of the uniformity of the pore structure were proposed.In addition,the fatigue failure mechanism of aluminum foams is discussed from macroscopic and microscopic perspectives.