基于声发射技术和数字散斑测量法的铝合金成形性能研究

发布时间：2018-08-23 15:10

【摘要】：铝合金材料以其质量轻、强度高、具有良好的耐腐蚀性、易于成形等优点,被广泛运用于建筑、汽车制造、包装运输以及航空航天等行业中。铝合金材料的破坏过程是位错运动到裂纹的产生及扩展直至断裂的变化过程。应用声发射检测技术可以实时记录和反映铝合金板材塑性变形和微裂纹的产生及扩展的变化情况。数字散斑相关方法是一种能够对金属全场应变进行精确测量的一种方法。本文结合数字散斑测量法,利用AMARIS三维应变测试系统和声发射检测系统,通过铝合金单向拉伸试验和刚性凸模胀形试验,对铝合金单向拉伸和刚性凸模胀形过程不同时刻应变场特点和声发射信号特征进行研究。本文主要研究内容和结论如下:(1)基于数字散斑测量法,采用AMARIS光学应变测试系统,得到单向拉伸过程应变场。结合单向拉伸应变场,分析了铝合金拉伸过程中变形破坏机制。针对于颈缩失稳直至断裂的应变场深入研究,发现试件变形集中部位出现局部失稳,且裂纹沿着变形集中部位扩张直至断裂。(2)对不同尺寸铝合金试件进行单向拉伸试验,运用声发射检测系统,得到拉伸过程声发射信号。利用特征参数法、波形分析法、频谱分析法三种方法对单向拉伸整个过程进行声发射信号特征进行分析,结合铝合金拉伸过程应变场,分析了铝合金拉伸过程中声发射产生的机理。(3)结合拉伸过程铝合金变形破坏机制及声发射产生机理,对刚性凸模胀形过程应变场和声发射信号特征进行分析,以确定胀形过程成形极限状态。结合AMARIS应变图,得到在此状态下极限应变点。这为板材成形极限状态的确定提供一种切实可行的方法,且与AMARIS数字图像法确定极限状态获得的成形极限曲线图相比,这种方法在安全设计方面更加可靠。
[Abstract]:Aluminum alloy is widely used in construction, automobile manufacturing, packaging and transportation, aerospace and other industries because of its light weight, high strength, good corrosion resistance, easy forming and so on. The failure process of aluminum alloy is from the dislocation motion to the generation and propagation of cracks and to the fracture. The change of plastic deformation and microcrack generation and propagation of aluminum alloy sheet can be recorded and reflected in real time by using acoustic emission detection technique. Digital speckle correlation is a method that can accurately measure the field strain of metal. In this paper, the digital speckle measurement method is used to measure aluminum alloy in uniaxial tension test and bulging test of rigid punch by using AMARIS three-dimensional strain measurement system and acoustic emission testing system. The characteristics of strain field and acoustic emission signal at different times in the process of uniaxial tensile and bulging of aluminum alloy are studied. The main contents and conclusions of this paper are as follows: (1) based on digital speckle measurement and AMARIS optical strain measurement system, the strain field of uniaxial tensile process is obtained. Combined with uniaxial tensile strain field, the deformation and failure mechanism of aluminum alloy during tensile process was analyzed. Based on the deep study of strain field from necking instability to fracture, it is found that the local instability occurs in the concentrated deformation area of the specimen, and the crack expands along the concentrated deformation site until fracture. (2) uniaxial tensile tests are carried out on aluminum alloy specimens of different sizes. Acoustic emission signal of stretching process is obtained by using acoustic emission detection system. The characteristic parameter method, waveform analysis method and spectrum analysis method are used to analyze the characteristics of acoustic emission signal in the whole process of uniaxial stretching, combined with the strain field of aluminum alloy tensile process. The mechanism of acoustic emission in the process of aluminum alloy drawing is analyzed. (3) the strain field and the characteristics of acoustic emission signal in bulging process of rigid punch are analyzed in combination with the deformation failure mechanism and acoustic emission generation mechanism of aluminum alloy during tensile process. To determine the forming limit state of bulging process. Combined with AMARIS strain diagram, the limit strain point is obtained in this state. This method provides a feasible method for determining the limit state of sheet metal forming and is more reliable in safety design than that obtained by AMARIS digital image method.
【学位授予单位】：南昌大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG146.21

【参考文献】