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增材制造TC4钛合金的动态力学行为研究

DYNAMIC MECHANICAL BEHAVIOR OF ADDITIVE MANUFACTURING TC4 ALLOY

  • 摘要: 增材制造TC4钛合金是具有优良的力学性能和工艺性能的金属材料, 在航空航天领域已得到重要应用. 近年来, 在塑性力学的研究中, 探究应力状态对金属材料变形和失效行为的影响得到广泛关注, 然而大部分的研究都是在准静态下完成的, 对于中高应变率下金属材料变形失效的研究较少. 本文从增材制造TC4钛合金的基本力学性能出发, 考虑应力状态和应变率对其变形和失效行为的影响, 采用应力三轴度 \eta 和罗德角参数 \overline \theta 表征应力状态, 设计了相应的试样形式和实验方法. 利用电子万能实验机、高速液压伺服实验机以及分离式Hopkinson杆, 结合数字图像相关法分析对材料在不同应变率、不同应力状态下的力学性能进行了测试, 获得其变形和失效特性. 为得到试样内部应力状态历程参数和应变场, 通过ABAQUS进行数值仿真, 得到试样应变最大处的应力状态历程参数和失效应变. 以实验测试和仿真分析结果为基础, 对传统MMC失效模型进行了修正, 建立了全面考虑应变率、应力三轴度和罗德角效应的增材制造TC4材料的失效模型; 同时建立了考虑应力三轴度η和应变率效应的 Johnson-Cook 失效模型. 并通过对增材制造TC4钛合金平板进行高速冲击实验和数值仿真, 验证了本文拟合的该材料的本构模型和失效模型描述高应变率下变形失效行为的有效性.

     

    Abstract: Additive manufacturing TC4 alloy is a kind of metal material with excellent mechanical properties and process properties. It has been widely used in the aerospace field. In recent years, the effect of stress state on the deformation and failure behavior of metal materials has been widely concerned in the research field of plastic mechanics. However, most of these studies were performed considering quasi-static state only, but few of them took into account the high strain rates. In this paper, the effects of stress state on the deformation and failure behavior of additive manufacturing TC4 alloy were systematically investigated. Starting from the basic mechanical properties of additive manufacturing TC4 alloy, the stress triaxiality \eta and Lode angle parameters \overline \theta are used to characterize the stress state. Using electronic universal testing machine, high-speed hydraulic servo testing machine and split Hopkinson bar, combined with digital image correlation analysis, the mechanical properties of additive manufacturing TC4 alloy under different strain rates and different stress states were tested. The deformation and failure characteristics of the material under various working conditions are obtained. In order to obtain the internal stress state history parameters and strain field of the sample, this article passes ABAQUS performs numerical simulation to obtain the stress state history parameters and failure strain at the maximum strain of the specimen. Based on the results of experimental testing and simulation analysis, the traditional MMC failure model was revised, and the failure model of material was established that fully considered the strain rate, stress triaxiality and Lode angle effect. At the same time, a Johnson-Cook failure model considering the effects of stress triaxiality η and strain rate is established. A high-speed impact experiment was carried out on the additive manufacturing TC4 alloy plate, and numerical simulation was carried out for the experiment, which verified the usability of the established constitutive model and failure model.

     

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