论文部分内容阅读
在不同脉冲电流条件下对纯钽试样进行拉伸实验,结果表明脉冲电流降低了加工硬化程度,可改善金属的塑性变形能力,并且随着脉冲电流密度的增加,其抗拉强度降低,延伸率提高,当电流密度J=7.64×102A·cm-2时,延伸率达到50.7%,提高幅度为10%,同时抗拉强度从380 MPa降低至300 MPa,降幅为21%。针对实测的流动应力应变曲线,结合Hollomon模型和Voce模型,考虑脉冲电流对加工硬化的影响,提出H-V综合模型,建立塑性变形本构方程,反映脉冲电流对应力应变的影响。在一定脉冲电流条件下,确定了每种模型的9个最佳参数,利用已确定的模型对拉伸应力应变曲线进行模拟,并与实测的曲线对比验证。模拟结果显示,在变形初期阶段,3种模型之间模拟结果差别都很小,并且模拟值与实际值差异很小,预测准确度较高。随着应变的增大,差异越来越明显,H-V综合模型、Voce模型、Hollomon模型对大应变的模拟精度依次增加,3种模型的趋势线拟合决定系数R2分别为0.99900,0.96409和0.88368,均方差分别为2.42,26.32,39.26。H-V模型模拟效果最佳,能更准确地描述纯钽在电致塑性效应过程中的应力流动行为。
Tensile tests on pure tantalum samples under different pulse current conditions show that the pulse current reduces the degree of work hardening and improves the plastic deformation ability of the metal. With the increase of the pulse current density, the tensile strength decreases and extends When the current density is J = 7.64 × 102A · cm-2, the elongation reaches 50.7% and the increase rate is 10%, while the tensile strength decreases from 380 MPa to 300 MPa, a decrease of 21%. According to the measured flow stress-strain curve, combined with Hollomon model and Voce model, considering the effect of pulse current on work-hardening, H-V integrated model was proposed to establish the plastic deformation constitutive equation, which reflected the influence of pulse current on the stress and strain. Under certain pulse current conditions, the nine optimal parameters of each model were determined. The tensile stress-strain curve was simulated by the established model and compared with the measured curve. The simulation results show that there is little difference between the three models in the initial stage of deformation and the difference between the simulated value and the actual value is small and the prediction accuracy is high. With the increase of strain, the difference becomes more and more obvious. The simulation precision of HV integrated model, Voce model and Hollomon model increases with large strain. The fitting coefficients R2 of the trend lines of the three models are 0.99900, 0.96409 and 0.88368, Mean square deviations were 2.42, 26.32, 39.26 respectively. The H-V model has the best simulation results and can describe the stress flow behavior of pure tantalum more accurately during the electrical plasticity effect.