基于Lyapunov指数的GMAW喷射过渡稳定性分析

Analysis of gas metal arc welding spray transfer stability based on Lyapunov exponent

基于Takens相空间重构理论及Lyapunov指数的wolf法,通过优化原始时间序列选取方法,对GMAW喷射过渡的混沌特性进行研究,依据Lyapunov指数变化规律分析喷射过渡的稳定性。结果表明,喷射过渡过程处于混沌状态,其最大Lyapunov指数均大于0,Lyapunov指数可用于分析喷射过渡过程的稳定性。在射滴阶段,随着电流增加,Lyapunov指数逐渐增大,混沌的复杂程度有所增加,焊接过程稳定性降低,在射流阶段,随着电流的增大,Lyapunov指数逐渐减小,混沌的复杂程度降低,焊接过程的稳定性提高。从射滴过渡到射流过渡是一个渐变过程,转变临界电流存在于一个较小的电流区间内;在此区间熔滴过渡形态为射滴、射流混合过渡,过渡频率不规律导致Lyapunov指数不稳定,实际焊接过程中应该尽量避开此电流区间。

Based on the Takens phase space reconstruction theory and wolf method of Lyapunov exponent,by optimizing the original time sequence selection method,the chaotic characteristics of gas metal arc welding spray transfer was studied.Lyapunov exponent can be used to analyze the spray transfer process stability,and the stability of spray transfer was analyzed by means of Lyapunov exponent variation.The results show that,for spray transfer process in a chaotic state,its largest Lyapunov exponent is greater than 0.In the projected transfer stage,as the current increases,Lyapunov exponent increases gradually,and Chaos complexity increases,and the stability of the welding process becomes poor.In spray transfer stage,as the current increases,Lyapunov exponent gradually decreases,and Chaos complexity decreases,and the stability of the welding process is improved.It is a gradual process of transition from projected transfer to spray transfer,and the critical transition current is in a narrow current range.In this range of welding current,the droplet transfer if the mixed tranfer of projected transfer and spray transfer,the transfer frequency is irregular,which leads to unstable Lyapunov exponent,should be avoided in the welding process in production.