摘要
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。
The tensile experiments were carried out under the condition of different pulse currents on pure tantalum. The results showed that pulse current decreased the function of strain hardening and improved the metal plastic deformation ability. With the increase of pulse current density,the tensile strength decreased and elongation increased; while the pulse current density maintained at7. 64 × 10^2A·cm^- 2,the elongation of tantalum increased to 50. 7%,rising by 10%. Meanwhile,its tensile strength dropped from 380 to 300 MPa,declining by 25%. With the measured flow stress and strain curve and the influence of pulse current on strain hardening,a H-V comprehensive model was proposed and a synthetic plasticity constitutive equation was built up on the bases of Hollomon and Voce models to describe the function of pulse current on stress and strain. Under a condition of pulse current,nine parameters of each model were determined,and then the simulation of the stretch stress and strain curve based on the three models was done to compare with the measured one. The results showed that the simulations based on the three models made little difference,especially,their simulation values were quite close to the actual ones,all of which could provide accurate predictions in the initial stage of deformation.With the increase of strain,the differences among H model,V model and H-V model were more and more obvious and the prediction precision increased in turn. Finally,the simulation results showed that the fitting coefficients（ R^2） of the trend line determined by HV,V and H models were 0. 99900,0. 96409 and 0. 88368. The mean square error of the H-V,V and H models was respectively2. 42,26. 32 and 39. 26. So H-V model provided more accurate predictions of strain behaviors than the other two during the tensile with pulse current.
出处
《稀有金属》
EI
CAS
CSCD
北大核心
2014年第6期973-977,共5页
Chinese Journal of Rare Metals
基金
国家自然科学基金项目(51071077)资助
关键词
电致塑性效应
脉冲电流
本构方程
加工硬化
应力
应变
electro plastic effect
pulse current
constitutive equation
strain hardening
strain
stress
