42CrMo钢力学性能研究及其动态本构描述

发布时间：2018-03-31 07:17

本文选题：42CrMo钢　切入点：Zerilli-Armstrong模型　出处：《西南交通大学》2017年硕士论文

【摘要】：42CrMo钢属于中碳高强度合金钢,作为高速列车车轴等构件的原材料,是负担列车质量的关键部件。在运行中承受冲击和旋转弯曲等多项复杂应力以及恶劣的工作环境。作为列车运行至关重要的部件,车轴材料除了考虑承受正常的设计载荷外,在当前形势下更需要考虑冲击载荷的作用。本文包括采用RPL100设备完成材料的准静态压缩实验;采用MTS-858微力拉扭试验机完成材料的准静态拉伸实验;采用分离式霍普金森压杆设备(SHPB)完成材料的冲击压缩实验;采用分离式霍普金森拉杆设备(SHTB)完成材料的冲击拉伸实验;采用Zeiss Axio Scope.Al.光镜完成42CrMo钢不同加载应变率下的微观组织观察实验。实验结果表明,42CrMo钢,作为典型的BCC金属材料,在宽应变率范围内具有典型的高应变率及温度敏感性,同时在冲击加载实验中,出现绝热剪切的变形机制,对材料塑性变形产生重要作用。针对材料在冲击实验中显示的高应变率相关性,采用位错理论对42CrMo钢变形机理进行解释,并改进了 Zerilli-Armstrong模型,引入绝热温升软化项,因为Zerilli-Armstrong模型本身在应变硬化率上的独立性,使得改进后模型,在表征材料应变硬化、温度软化以及应变率效应时可以很好的耦合。为了验证改进的Zerilli-Armstrong模型的合理性和适用性,分别采用不考虑绝热温升的Zerilli-Armstrong模型和引入考虑绝热温升这一不容忽视因素的Zerilli-Armstrong模型,参数优化后获得的理论曲线与冲击实验结果进行比较。得出改进的Zerilli-Armstrong模型,可以很好地描述及预测不同应变率下42CrMo钢的流动应力。针对42CrMo钢材料显示出的典型BCC金属特性,采用热激活位错理论对材料塑性变形机理进行解释,认为造成准静态到动态力学性能不同的原因在于,不同的滑移系开动条件以及Peierls势垒的高率敏感性。对基于晶体塑性理论的本构模型进行了研究,结合BCC金属塑性变形机理,在剪切变形率演化中引入宏观应变率项,在硬化演化中引入绝热温升软化项。经验证,模型对模拟多晶下准静态实验结果体现出很好适应性,同时,模拟多晶下冲击实验结果也能很好体现应变率效应及热软化效应。
[Abstract]:42CrMo steel belongs to medium carbon high strength alloy steel. As the raw material of high speed train axle and other components, 42CrMo steel is the key component to load train quality.In operation, many complex stresses such as impact and rotating bending, and harsh working environment.As one of the most important components in train operation, axle materials not only take into account the normal design load, but also need to consider the impact load in the current situation.In this paper, the quasi-static compression experiment of materials is completed by using RPL100 equipment, the quasi-static tensile test of materials is completed by using MTS-858 micro-force tensioning test machine, the impact compression experiment of materials is completed by using split Hopkinson compression bar equipment.Zeiss Axio Scope.Al.The microstructure of 42CrMo steel at different strain rates was observed by light microscope.The experimental results show that, as a typical BCC metal material, the steel 42CrMo has a typical high strain rate and temperature sensitivity in a wide strain rate range. At the same time, the adiabatic shear deformation mechanism appears in the impact loading experiment.It plays an important role in plastic deformation of materials.In view of the high strain rate dependence of the material in the impact test, the dislocation theory is used to explain the deformation mechanism of 42CrMo steel, and the Zerilli-Armstrong model is improved to introduce the adiabatic temperature rise softening term because of the independence of the Zerilli-Armstrong model in the strain hardening rate.The improved model can be well coupled to characterize material strain hardening, temperature softening and strain rate effect.In order to verify the rationality and applicability of the improved Zerilli-Armstrong model, the Zerilli-Armstrong model without adiabatic temperature rise and the Zerilli-Armstrong model with adiabatic temperature rise are adopted, respectively.The theoretical curves obtained after parameter optimization are compared with the experimental results.The improved Zerilli-Armstrong model can well describe and predict the flow stress of 42CrMo steel at different strain rates.According to the typical BCC metal characteristics of 42CrMo steel, the plastic deformation mechanism of 42CrMo steel is explained by the thermosetting dislocation theory, and the reason for the difference between quasi-static and dynamic mechanical properties is considered.Different moving conditions of slip system and high rate sensitivity of Peierls barrier.The constitutive model based on the theory of crystal plasticity is studied. Combined with the plastic deformation mechanism of BCC, the macroscopic strain rate term is introduced in the evolution of shear deformation rate and the adiabatic temperature rise softening term is introduced in the hardening evolution.It is verified that the model is very adaptable to the quasi-static experimental results under simulated polycrystals, and the results of simulated shock tests under polycrystals can also well reflect the strain rate effect and thermal softening effect.
【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG142.1

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