重轨压力矫直变形残余应力的数值模拟及实验研究
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摘要
钢轨是铁路上的重要部件,钢轨内部存在的残余应力的大小和分布状态将直接影响钢轨的使用性能。矫直作为钢轨生产的最后一道工艺,对钢轨的平直度、残余应力的大小起决定性的作用。本文主要是通过压力矫直研究重轨辊式矫直过程中残余应力的形成机理和分布规律。
本文以弹塑性大变形有限元理论为基础,利用有限元软件ANSYS的静态接触分析,模拟了重轨的压力矫直过程。将辊式矫直简化为连续七次反复弯曲的过程,建立了压力矫直的反复弯曲模型,并考虑接触应力对矫直结果的影响,进行了三维有限元模拟。分析了重轨压力矫直过程中应力应变规律及矫直过程中的残余应力分布情况。在模拟的基础上进行了压力矫直过程的光塑性实验。
通过建立重轨三维压力矫直模型,分别分析了经过七次反复弯曲后中间断面等效残余应力分布情况,中间断面的纵向残余应力的大小和分布情况。分析结果表明:等效残余应力的大小分布状态都与压下量的大小有关,当压下量较大时,钢轨内部发生了较大的弹塑性变形,对等效残余应力的大小和分布都有一定影响;当压下量比较小时,钢轨内部没有发生塑性变形时,等效残余应力的大小和分布状态就没有大的变化。从应力的角度解释了重轨压力矫直过程的弹塑性变形机理,得出压力矫直过程的应力应变关系。并通过对比三个不同矫直规程的等效残余应力、截面纵向残余应力,得出了现场现行的矫直规程矫后残余应力的分布更合理。并得出了矫直过程的接触应力分布状态。
采用光塑性材料聚甲基丙烯酸甲酯(PMMA)进行了压力矫直弯曲过程的光塑性实验。实验结果表明:由于矫直过程中的弹塑性变形不是很大,故在常温下按标准规程进行矫直过程的实验中,矫后不能将残余变形很好的保留下来。而在矫直过程中能够观察到清晰的彩色条纹,说明在矫直压下过程中的有一定的弹塑性变形。并可以通过实验观察到的等差条纹看出应力分布与矫直压下量的关系。
Rail is the important parts of the railway, the magnitude and distribution of residual stresses which exist in the rail directly affect the service performance of rail. Straightening which is the final craft of the heavy rail production plays a decisive function of the straightness and the magnitude of residual stresses. The paper mainly researches the forming mechanism and law of distribution of residual stress during roller straightening by studying of the press straightening.
The basis of paper is elastoplastic finite element method of large deformation, simulate the press straightening process of the heavy rail by static contact analysis of the finite element software ANSYS. The roller straightening was simplified as the continual process of seven times reverse bend, the alternating bend model of press straightening was established, the three-dimensional simulation was simulated considering the influence of the contact press. It analyzed the law of strain-stress and the distribution of residual stresses during the straightening process. On the basis of the simulation, the photoplasticity experiment of press straightening process was carried out.
According to the simulations model,it analyzed the equivalent residual stress distribution situation of middle cross sections which went through seven times of alternating bending, the longitudinal residual stress magnitude of middle cross section and distribution. The analysis result indicated that, the equivalent residual stresses magnitude and the distribution are all related to the reduction, when the reduction is bigger, the rail interior has had the bigger elastic-plastic deformation, all has the certain influence to the equivalent residual stress magnitude and distribution; when the reduction is smaller, the rail interior has not had the plastic deformation, the equivalent residual stress magnitude and the distribution do not have the big change. The elastic-plastic deformation mechanism of heavy rail press straightening process is explained in the stress, the stress-strain relations of the press straightening process are obtained. And by contrast the equivalent residual stress and the section longitudinal residual stress of three different straightening regulations, obtained that the residual stress distribution of the present straightening regulations to be more reasonable. And it has obtained the process contact stress distribution of the straightening.
A photoplastic experiment was carried on Used the photoplastic material polymethyl methacrylate (PMMA) which simulates the press straightening curving process. Experimental results indicated that: because elastic-plastic deformation quantity of straightening process is not big at room temperature, it can’t hold the residual deformation after straightening in the experiment according to standard regulations. But the clear colorized stripes could observe in straightening process, it show that the straightening press process have certain quantity plastic deformation. We can get the relations between press distribution and the reduction by the isochromatic stripes.
本文以弹塑性大变形有限元理论为基础,利用有限元软件ANSYS的静态接触分析,模拟了重轨的压力矫直过程。将辊式矫直简化为连续七次反复弯曲的过程,建立了压力矫直的反复弯曲模型,并考虑接触应力对矫直结果的影响,进行了三维有限元模拟。分析了重轨压力矫直过程中应力应变规律及矫直过程中的残余应力分布情况。在模拟的基础上进行了压力矫直过程的光塑性实验。
通过建立重轨三维压力矫直模型,分别分析了经过七次反复弯曲后中间断面等效残余应力分布情况,中间断面的纵向残余应力的大小和分布情况。分析结果表明:等效残余应力的大小分布状态都与压下量的大小有关,当压下量较大时,钢轨内部发生了较大的弹塑性变形,对等效残余应力的大小和分布都有一定影响;当压下量比较小时,钢轨内部没有发生塑性变形时,等效残余应力的大小和分布状态就没有大的变化。从应力的角度解释了重轨压力矫直过程的弹塑性变形机理,得出压力矫直过程的应力应变关系。并通过对比三个不同矫直规程的等效残余应力、截面纵向残余应力,得出了现场现行的矫直规程矫后残余应力的分布更合理。并得出了矫直过程的接触应力分布状态。
采用光塑性材料聚甲基丙烯酸甲酯(PMMA)进行了压力矫直弯曲过程的光塑性实验。实验结果表明:由于矫直过程中的弹塑性变形不是很大,故在常温下按标准规程进行矫直过程的实验中,矫后不能将残余变形很好的保留下来。而在矫直过程中能够观察到清晰的彩色条纹,说明在矫直压下过程中的有一定的弹塑性变形。并可以通过实验观察到的等差条纹看出应力分布与矫直压下量的关系。
Rail is the important parts of the railway, the magnitude and distribution of residual stresses which exist in the rail directly affect the service performance of rail. Straightening which is the final craft of the heavy rail production plays a decisive function of the straightness and the magnitude of residual stresses. The paper mainly researches the forming mechanism and law of distribution of residual stress during roller straightening by studying of the press straightening.
The basis of paper is elastoplastic finite element method of large deformation, simulate the press straightening process of the heavy rail by static contact analysis of the finite element software ANSYS. The roller straightening was simplified as the continual process of seven times reverse bend, the alternating bend model of press straightening was established, the three-dimensional simulation was simulated considering the influence of the contact press. It analyzed the law of strain-stress and the distribution of residual stresses during the straightening process. On the basis of the simulation, the photoplasticity experiment of press straightening process was carried out.
According to the simulations model,it analyzed the equivalent residual stress distribution situation of middle cross sections which went through seven times of alternating bending, the longitudinal residual stress magnitude of middle cross section and distribution. The analysis result indicated that, the equivalent residual stresses magnitude and the distribution are all related to the reduction, when the reduction is bigger, the rail interior has had the bigger elastic-plastic deformation, all has the certain influence to the equivalent residual stress magnitude and distribution; when the reduction is smaller, the rail interior has not had the plastic deformation, the equivalent residual stress magnitude and the distribution do not have the big change. The elastic-plastic deformation mechanism of heavy rail press straightening process is explained in the stress, the stress-strain relations of the press straightening process are obtained. And by contrast the equivalent residual stress and the section longitudinal residual stress of three different straightening regulations, obtained that the residual stress distribution of the present straightening regulations to be more reasonable. And it has obtained the process contact stress distribution of the straightening.
A photoplastic experiment was carried on Used the photoplastic material polymethyl methacrylate (PMMA) which simulates the press straightening curving process. Experimental results indicated that: because elastic-plastic deformation quantity of straightening process is not big at room temperature, it can’t hold the residual deformation after straightening in the experiment according to standard regulations. But the clear colorized stripes could observe in straightening process, it show that the straightening press process have certain quantity plastic deformation. We can get the relations between press distribution and the reduction by the isochromatic stripes.
引文
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[2] 李骏,邹慧君,熊国良等.压力矫直过程模型的有限元分析及应用[J].重型机械,2004(1): 28-30
[3] 钦明浩,柯尊忠,张向军,等.精密矫直机中轴类零件矫直工艺理论研究[J].机械工程学报,1997, 33(2 ): 48-53
[4] 蒋守仁,翟华,蒋叶青.一种行程控制精密校直工艺理论[J].锻压机械,1997(5): 10-12
[5] 翟华,韩春明,蒋守仁等.轴类零件精密校直行程算法研究[J].重型机械,2001(5): 35-38
[6] 李骏,熊国良,邹慧君.轴类零件压力矫直过程的数学模型与行程计算[J].重型机械,2004(6): 41-44
[7] 崔甫,施东成.矫直机压弯量计算法的探讨[J].冶金设备,1999, 113(1): 1-6
[8] 师汉奎.钢管压力矫直的参数计算和辅助辊道结构设计[J].天津冶金,2004, 123(5): 31-32
[9] 崔甫.矫直理论与参数计算[M].北京:机械工业出版社,1994
[10] Das Talukder NK, Singh AN. Mechanics of bar straightening, Part 1: General analysis of straightening process[J]. Journal of Engineering for Industry, 1991, 113(2): 224- 227
[11] 钦明浩,张向军,蒋守仁等.轴类零件校直理论分析[J].合肥工业大学学报(自然科学版),1996,19( 4) : 22-28
[12] 弓海霞,闫通海,王进礼.钻具校直的理论研究[J].哈尔滨工程大学学报,2002, 23( 3): 116-119
[13] 李骏,邹慧君,熊国良.压力校直工艺理论研究的现状与展望[J].机械设计与研究,2004, 20(4): 69-71
[14] 钦明浩,吴焱明,蒋守仁等.轴类零件校直的有限元解法[J].合肥工业大学学报(自然科学版),1996,19(2): 24- 29
[15] 于晓平.轴类全自动校直机[J].金属热处理,2002, 27(9): 45-46
[16] 单淑梅.液压自动校直机的应用与研究[J].汽车技术,1998(11): 27-29
[17] 李骏,熊国良,邹慧君.校直机行程计算经验公式的理论依据分析[J].锻压设备与制造技术,2003(6): 22- 24
[18] 井永水,窦忠强, 李忠富.矫直理论的新探索[J].北京科技大学学报,2002, 24(1): 64-66
[19] 黄雨华,徐有忠,杨会林.辊式矫直机的矫直变形理论新探[J].重型机械,1999(6): 28-30
[20] 弋景刚,王泽和,孙维连等.轴类零件矫直工艺理论研究[J].河北农业大学学报,2004, 27(3): 108-110
[21] 张向军,钦明浩,蒋守仁.轴类零件校直工艺的实验研究[J].合肥工业大学学报,1997, 20(3): 11-14
[22] 徐勇,程先华.钢管压扁矫正残余应力分析[J].上海交通大学学报,2003, 37(10) : 1526-1528
[23] 李学通,杜凤山,于凤琴.中厚板矫直过程的有限元研究[J].重型机械,2005(1): 44-46
[24] 周存龙,徐静,王国栋等.中厚板在矫直后的残余应力分布分析[J].重型机械,2005(2): 21-24
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