快速傅里叶变换分析6061铝合金在不同自然时效时间下的PLC效应  

Fast Fourier transform analysis on Portevin-Le Chartelier effect in 6061 Al-based alloy at different nature aging

作　　者：许建飞 符师桦 黄锋 秦培成 XU Jianfei;FU Shihua;HUANG Feng;QIN Peicheng(School of Civil Engineering and Architecture,Hainan University,Haikou 570228,Hainan,China)

机构地区：[1]海南大学土木工程学院,海南海口570228

出　　处：《实验力学》2021年第3期340-349,共10页Journal of Experimental Mechanics

基　　金：国家自然科学基金(11802080);海南省自然科学基金(118QN182和520CXTD433)资助。

摘　　要：快速傅里叶变换对复杂波形曲线的频率组成分析具有高效性和独特性。利用该方法对不同自然时效时间的6061铝合金在恒定应变率下的拉伸应力曲线,进行了整体及局部的频谱分析,实验发现,随自然时效时间延长,材料的屈服强度和抗拉强度逐渐增大,应力跌落幅值逐渐减小,应力锯齿类型由B型向A型过渡。整体频谱分析中,自然时效0~2h在1.9Hz处呈峰状分布,峰频和峰值随自然时效时间延长而减小;自然时效3~7h频谱上无峰状。局部频谱分析中,自然时效0~1h的峰值先逐渐增大后趋于平稳,二者的峰频先逐渐减小后趋于平稳;自然时效2h的峰值和峰频保持平稳。此外,本文提出一种简化频谱分析方法,获得了最优简化频谱曲线,更好地呈现了应力锯齿的频谱特征。结合动态应变时效微观机制,从溶质原子浓度与可动位错之间“钉扎-脱钉”的相互作用角度,对应力锯齿的频谱特征进行了解释。Fast Fourier transform(FFT)is a highly efficient method for analysis of complex signal curves.The frequency domain feature of the Portevin-Le Chartelier(PLC)effect is investigated by FFT in 6061 Al-based alloy with different nature aging time of 0~7 h.The stress-time curves obtained via tensile test at a constant strain rate show that the serrations change from type B to type A with increasing nature aging time.The FFT results show that a peak appears at near 1.9 Hz in the frequency spectrum of the whole range for the samples nature aged 0~2 h and disappears for the samples nature aged 3~7 h.The evolutions of the peaks are expressed by the frequency spectrum of subsections.Firstly,the peak value increases,and the peak frequencies decrease and then fluctuate in a steady range for the samples nature aged 0~1 h.For the samples nature aged 2 h,both the peak value and the peak frequency fluctuate in a steady range.Finally,a simplified spectrum analysis method based on conservation of power is proposed to obtain the optimal simplified spectrum,which presents more concisely the characteristics of serrated stress curves in frequency domain.Moreover,the discussion combined with dynamic strain aging is conducted to explain the behaviors in frequency domain.

关 键 词：Portevin-Le Chatelier效应 自然时效 动态应变时效 快速傅里叶变换 

分 类 号：O348[理学—固体力学] O17[理学—力学]