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收稿：2024-06-28，
纸质出版：2024-08-25
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本构方程是搅拌摩擦焊过程热-力-流全耦合仿真模型的重要部分。针对6 mm铝合金6061-T6板材FSW过程开展热-力-流全耦合仿真分析。为分析本构方程的形式对仿真效果的影响，在模型中分别采用Chen-Liu本构模型、Sellars-Tegart模型和Johnson-Cook模型，并对仿真结果进行对比分析。仿真结果表明，Chen-Liu模型计算得到的FSW温度场及流动场与实验结果的吻合程度均高于Sellars-Tegart模型和Johnson-Cook模型。究其原因，在搅拌头-工件界面附近的温度条件下，Sellars-Tegart模型和Johnson-Cook模型预测的流变应力较高，使得材料流动困难，搅拌头与工件之间的界面状态主要为滑动摩擦。相比之下，Chen-Liu模型能够体现材料在温度升高时的迅速软化现象，在搅拌头-工件界面附近的温度条件下，材料的剪切流变应力低于搅拌头/工件界面的摩擦应力，因而在摩擦作用下工件发生塑性流动，这降低了搅拌头/工件之间的滑动摩擦速度，从而使得滑动摩擦产热减少，且其减少量大于工件发生塑性流动产生的额外热量，从而使得采用Chen-Liu模型预测得到的焊接温度更低。综合来看，FSW过程温度场与材料流动速度场受材料本构模型影响归因于FSW的热-力-流全耦合效应。
The constitutive equation is a crucial component of the fully coupled thermal-mechanical-flow simulation model for the friction stir welding (FSW) process. This paper conducts a fully coupled thermal-mechanical-flow simulation analysis of the FSW process for 6mm thick aluminum alloy 6061-T6 plates. To analyze the impact of the form of the constitutive equation on the simulation results
the Chen-Liu constitutive model
the Sellars-Tegart model
and the Johnson-Cook model were used in the simulation
and their results were compared. The simulation results show that the FSW temperature field and flow field calculated by the Chen-Liu model aligned more closely with experimental results than those calculated by the Sellars-Tegart model and the Johnson-Cook model. The reason was that under the temperature conditions near the tool-workpiece interface
the Sellars-Tegart model and the Johnson-Cook model predicted higher flow stresses
making material flow difficult. As a result
the interface state between the tool and the workpiece was primarily sliding friction. In contrast
the Chen-Liu model accurately reflected the rapid softening of the material as the temperature increases. Under the temperature conditions near the tool-workpiece interface
the shear flow stress of the material was lower than the friction stress at the tool/workpiece interface. Consequently
the workpiece undergoes plastic flow due to friction
reducing the sliding friction speed between the tool and the workpiece. This reduction in sliding friction heat generation was greater than the additional heat generated by the plastic flow of the workpiece
resulting in a lower predicted welding temperature using the Chen-Liu model. Overall
the influence of the material constitutive model on the FSW process's temperature field and material flow velocity field is due to the fully coupled thermal-mechanical-flow effects of FSW.
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