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  本文選題：42CrMo鋼　切入點：Zerilli-Armstrong模型　出處：《西南交通大學》2017年碩士論文

【摘要】：42CrMo鋼屬于中碳高強度合金鋼,作為高速列車車軸等構(gòu)件的原材料,是負擔列車質(zhì)量的關鍵部件。在運行中承受沖擊和旋轉(zhuǎn)彎曲等多項復雜應力以及惡劣的工作環(huán)境。作為列車運行至關重要的部件,車軸材料除了考慮承受正常的設計載荷外,在當前形勢下更需要考慮沖擊載荷的作用。本文包括采用RPL100設備完成材料的準靜態(tài)壓縮實驗;采用MTS-858微力拉扭試驗機完成材料的準靜態(tài)拉伸實驗;采用分離式霍普金森壓桿設備(SHPB)完成材料的沖擊壓縮實驗;采用分離式霍普金森拉桿設備(SHTB)完成材料的沖擊拉伸實驗;采用Zeiss Axio Scope.Al.光鏡完成42CrMo鋼不同加載應變率下的微觀組織觀察實驗。實驗結(jié)果表明,42CrMo鋼,作為典型的BCC金屬材料,在寬應變率范圍內(nèi)具有典型的高應變率及溫度敏感性,同時在沖擊加載實驗中,出現(xiàn)絕熱剪切的變形機制,對材料塑性變形產(chǎn)生重要作用。針對材料在沖擊實驗中顯示的高應變率相關性,采用位錯理論對42CrMo鋼變形機理進行解釋,并改進了 Zerilli-Armstrong模型,引入絕熱溫升軟化項,因為Zerilli-Armstrong模型本身在應變硬化率上的獨立性,使得改進后模型,在表征材料應變硬化、溫度軟化以及應變率效應時可以很好的耦合。為了驗證改進的Zerilli-Armstrong模型的合理性和適用性,分別采用不考慮絕熱溫升的Zerilli-Armstrong模型和引入考慮絕熱溫升這一不容忽視因素的Zerilli-Armstrong模型,參數(shù)優(yōu)化后獲得的理論曲線與沖擊實驗結(jié)果進行比較。得出改進的Zerilli-Armstrong模型,可以很好地描述及預測不同應變率下42CrMo鋼的流動應力。針對42CrMo鋼材料顯示出的典型BCC金屬特性,采用熱激活位錯理論對材料塑性變形機理進行解釋,認為造成準靜態(tài)到動態(tài)力學性能不同的原因在于,不同的滑移系開動條件以及Peierls勢壘的高率敏感性。對基于晶體塑性理論的本構(gòu)模型進行了研究,結(jié)合BCC金屬塑性變形機理,在剪切變形率演化中引入宏觀應變率項,在硬化演化中引入絕熱溫升軟化項。經(jīng)驗證,模型對模擬多晶下準靜態(tài)實驗結(jié)果體現(xiàn)出很好適應性,同時,模擬多晶下沖擊實驗結(jié)果也能很好體現(xiàn)應變率效應及熱軟化效應。
[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.
【學位授予單位】：西南交通大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TG142.1

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本文編號：1689712