钛合金Ti6Al4V激光加热辅助车削过程的仿真分析与实验研究

发布时间：2019-01-26 07:17

【摘要】：钛合金是以钛为基础加入其他元素组成的合金,具有比强度高、热强度高、低温性能好、耐腐蚀能力强等优点,广泛应用于航空航天、医疗、化工等行业。但是由于钛合金的导热性差、化学活性高等性能特点,导致其切削加工时切削温度高、刀具磨损快,是典型的难加工金属,故其大规模应用受到了加工效率和加工成本的制约,因此探究钛合金的新型加工技术、改善其加工性能具有重要的研究意义。激光加热辅助切削技术是一种新型的混合加工技术,可以降低切削力和切削能量、延长刀具使用寿命、提高加工表面质量。目前国内激光辅助加工技术的研究主要集中在陶瓷材料领域,研究方法多局限于实验研究。本文采用有限元仿真和实验相结合的方法,针对应用广泛的Ti6Al4V钛合金的激光辅助车削技术进行了研究,具体研究内容如下:首先基于经典传热学理论建立了激光预热钛合金的三维有限元模型,针对多组激光参数进行了数值仿真研究。采用实验和仿真对比的方法,确定了钛合金对激光能量的吸收率这一重要参数。通过比较仿真结果,分析了激光功率、激光移动速度、光斑半径和刀具/激光距离等加工参数对预热温度场的影响,并选取了合适的加工参数用于后续的切削过程仿真和实验研究。基于Johnson-Cook材料本构模型和对应的断裂准则,建立了正交车削钛合金工件的完全热-力耦合有限元模型,进行了多组加工参数下传统加工和激光辅助加工的仿真研究。通过分析仿真得到的应力场、温度场和切削力等结果,揭示了激光辅助加工改善加工状态的机理,并分析了各加工参数对激光辅助切削效果的影响。进行了激光辅助正交车削钛合金的实验研究。设计了激光辅助车削钛合金的实验系统,进行了多组不同加工参数下的切削实验,测量了切削过程中的切削力,观察并分析了激光加热钛合金后的材料微观结构和切削得到的切屑形态,分析了激光辅助加工对加工状态的影响。最后通过比较仿真和实验结果,证实了有限元模型的合理性和准确性。
[Abstract]:Titanium alloy is a kind of alloy with high specific strength, high thermal strength, good low temperature performance and strong corrosion resistance, which is based on titanium. It is widely used in aerospace, medical, chemical and other industries. However, because of the poor thermal conductivity and high chemical activity of titanium alloy, the cutting temperature is high and the tool wear is fast, so the large-scale application of titanium alloy is restricted by machining efficiency and processing cost. Therefore, it is of great significance to explore the new processing technology of titanium alloy and improve its processing performance. Laser heating assisted cutting is a new hybrid machining technology, which can reduce cutting force and cutting energy, prolong tool life and improve surface quality. At present, the research of laser assisted processing is mainly focused on ceramic materials, and the research methods are limited to experimental research. In this paper, the laser-assisted turning technology of Ti6Al4V titanium alloy is studied by means of finite element simulation and experiment. The main contents are as follows: firstly, based on the classical theory of heat transfer, the 3D finite element model of laser preheating titanium alloy is established, and the numerical simulation of multiple laser parameters is carried out. The laser energy absorptivity of titanium alloy is determined by the method of experiment and simulation. By comparing the simulation results, the effects of laser power, laser moving speed, spot radius and tool / laser distance on the preheating temperature field are analyzed. Suitable machining parameters are selected for subsequent simulation and experimental study. Based on the constitutive model of Johnson-Cook material and the corresponding fracture criterion, the complete thermal-mechanical coupling finite element model of orthogonal turning titanium alloy workpiece is established. The simulation of traditional machining and laser assisted machining under multiple processing parameters is carried out. By analyzing the simulation results of stress field, temperature field and cutting force, the mechanism of laser assisted machining to improve machining state is revealed, and the influence of processing parameters on laser assisted cutting effect is analyzed. An experimental study on laser assisted orthogonal turning of titanium alloy was carried out. An experimental system for laser assisted turning of titanium alloy was designed. The cutting experiments with different machining parameters were carried out, and the cutting force in the cutting process was measured. The microstructure and chip morphology of titanium alloy after laser heating were observed and analyzed. The influence of laser assisted machining on the processing state was analyzed. Finally, the rationality and accuracy of the finite element model are verified by comparing the simulation and experimental results.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TG51;TN249

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