铝合金薄壁柱壳电磁胀形塑性失稳实验研究
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摘要
利用高速相机记录电磁驱动6063-T6铝合金薄壁柱壳膨胀变形过程,结合二维数字图像相关法分析试样表面应变场演化,对金属柱壳电磁膨胀塑性失稳过程开展研究,探讨金属高速成形极限及影响因素。实验结果表明:6063-T6铝合金薄壁柱壳电磁高速膨胀成形开始为均匀变形,随变形发展试样表面应变场出现局域化集中并沿45°或135°方向失稳扩展,裂纹沿局域化集中带发展导致碎裂;电磁膨胀局域化过程中分散性失稳时的平均应变与准静态拉伸失稳应变相比并没有明显变化,而局域化带形成时的应变随加载率提高显著增大,分析认为薄壁板电磁高速胀形成形极限提高的"增塑性"主要与惯性效应与结构效应相关。
The deformation in electromagnetic bulging process for 6063-T6 aluminum alloy thin-walled cylindrical was recorded with high-speed camera,combined with 2-D digital image correlation method,the evolution of strain field of cylinders surface was analyzed,and the plastic instability of electromagnetic bulging for thin-walled alloy cylinder was studied to discuss the dynamic forming limit and the influence factors on the forming process. The experiment results show that the electromagnetic bulging for thin-walled aluminum alloy cylinder begin with homogeneous deformation and with the development of the deformation,there is localization band of the strain filed of cylinders surface,and unstable propagation at an angle of 45° to 135° to the axial direction of shell approximately was monitored,the crack develop with the localization band and cause fracture. When instability occur in the electromagnetic bulging localization process,the mean strain have no significant variation compared with the quasi-static tensile instability strain,while the strain increase obviously with the increase of strain rate in the formation process of the localized band. It is suggested that the"hyper-plasticity"which means the increase of the dynamic forming limits of electromagnetic bulging for thin-wall alloy is mainly related to the inertial effect and structural effect.
The deformation in electromagnetic bulging process for 6063-T6 aluminum alloy thin-walled cylindrical was recorded with high-speed camera,combined with 2-D digital image correlation method,the evolution of strain field of cylinders surface was analyzed,and the plastic instability of electromagnetic bulging for thin-walled alloy cylinder was studied to discuss the dynamic forming limit and the influence factors on the forming process. The experiment results show that the electromagnetic bulging for thin-walled aluminum alloy cylinder begin with homogeneous deformation and with the development of the deformation,there is localization band of the strain filed of cylinders surface,and unstable propagation at an angle of 45° to 135° to the axial direction of shell approximately was monitored,the crack develop with the localization band and cause fracture. When instability occur in the electromagnetic bulging localization process,the mean strain have no significant variation compared with the quasi-static tensile instability strain,while the strain increase obviously with the increase of strain rate in the formation process of the localized band. It is suggested that the"hyper-plasticity"which means the increase of the dynamic forming limits of electromagnetic bulging for thin-wall alloy is mainly related to the inertial effect and structural effect.
引文
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[2]DEVIS J R.American society for metals handbooks Vol 14,forming and forging[M].Ohio:Metal Parks ASM International,1988.
[3]BALANETHIRAM V S,HU X Y.ALTYNOVA M,et al.Hyperplasticity:enhanced formability at high rates[J].Journal of Material Processing Technology,1994,45(1):595-600.
[4]BALANETHIRAM V S,DAEHN G S.Hyperplasticity:increased forming limits at high workpiece velocity[J].Scripta Metallurgica Et Materialia,1994,30(4):515-520.
[5]OLIVEIRA D A,WORSWICK M J,FINN M,et al.Electromagnetic forming of aluminum alloy sheet:free-form and cavity fill experiments and model[J].Journal of Materials Processing Tech,2005,170(1):350-362.
[6]THOMAS J D,SETH M,DAEHN G S,et al.Forming limits for electromagnetically expanded aluminum alloy tubes:theory and experiment[J].Acta Materialia,2007,55(8):2863-2873.
[7]ZHANG H,RAVI-CHANDAR K.On the dynamics of necking and fragmentation—I.Real-time and post-mortem observations in Al6061-O[J].International Journal of Fracture,2006,142(3):183-217.
[8]ZHANG H,RAVI-CHANDAR K.On the dynamics of necking and fragmentation-II.Effect of material properties,geometrical constraints and absolute size[J].International Journal of Fracture,2008,150(1):3-36.
[9]ZHANG H,LIECHTI K M,RAVI-CHANDAR K.On the dynamics of localization and fragmentation-III.Effect of cladding with a polymer[J].International Journal of Fracture,2009,155(2):101-118.
[10]ZHANG H,MURATA M,SUZUKI H.Effects of various working conditions on tube bulging by electromagnetic forming[J].Journal of Material Processing Technology,1995,48(1-4):113-121.
[11]LEE S H,DONG N L.Estimation of the magnetic pressure in tube expansion by electromagnetic forming[J].Journal of Material Processing Technology,1996,57(3):311-315.
[12]LAI G K,HILLIER M J.The electrodynamics of electromagnetic forming[J].International Journal of Mechanical Sciences,1968,10(6):491-500.
[13]HIDEO S.Finite element analysis of tube deformation under impulsive internal pressure[J].Advanced Technology of Plasticity.1984,1(6):367-372
[14]TAKATSU N,KATO M,SATO K,et al.High-speed forming of metal sheets by electromagnetic force[J].JSME International Journal,1988,31(1):142-148.