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R. Manna Pulkit Agrawal Sushant Joshi Basavakumar K. Mudda N.K. Mukhopadhyay G.V.S. Sastry 《Scripta materialia》2005,53(12):3769
We report here the results of our physical modeling study of the equal channel angular pressing process using two-colour constituent plasticine workpieces in a metallic die. The workpieces, usually called billets, are made up of discs as well as spherical balls. They are deformed repeatedly with and without changing the orientation between successive passes. Both square and round dies with inner channel intersection angle of 90° are used. The flow patterns are revealed by sectioning the billet after a requisite number of passes. Thorough mixing of the two constituents with a drastic reduction in the section size of each constituent of the plasticine workpiece was observed after 15 passes. The initial shape of the constituents of the billet does not affect the final flow pattern of the microstructure. Material accumulation of the two colour constituents of plasticine was observed in some regions of the billet along the central region at a low and intermediate number of passes. 相似文献
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等通道转角挤压(Equal Channel Angular Pressing,ECAP)是一种制备超细晶材料的新工艺.工艺路径的选择对试样的应变分布均匀性有重要的影响.利用非线性有限元软件MSC.Marc对等通道转角多道次挤压过程进行了模拟计算.通过对ECAP中试样沿A路径和C路径6道次挤压的模拟,获得了A路径和C路径等效应变分布规律.结果表明,试样沿C路径的等效应变要比沿A路径更均匀,但C路径对试样端部等效应变的累积效果不如A路径;试样沿A、C两种路径每道次最大挤压力逐渐增加,大小基本相同. 相似文献
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Anumalasetty Venkata Nagasekhar Hyoung Seop Kim 《Metals and Materials International》2008,14(5):565-568
Plastic deformation behavior in T-shaped equal channel pressing, a modified equal channel angular pressing (ECAP) using T-shaped
channel instead of conventional L-shaped channel, is analyzed by using the commercial finite element code DEFORM. Simulations
were carried out under realistic conditions by considering the strain hardening of material and friction. The deformation
behavior is more complicated and the strain induced is highly localized. Severe plastic strain is localized in the bottom
region of the workpiece and very small strain is developed in the other region, which is in good agreement with the experimental
results reported in the literature showing the nonuniformity in microstructure and hardness distribution. In addition, the
load requirements of the T-ECAP are much higher compared to conventional ECAP. 相似文献
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Seung Chae Yoon Anumalasetty Venkata Nagasekhar Hyoung Seop Kim 《Metals and Materials International》2009,15(2):215-219
For the first time, a detailed and systematic finite element study was carried to identify the parameters which cause the
bending of the workpiece in equal channel angular pressing. These simulations were carried out by using commercial finite
element code Abaqus with different materials behavior, processing parameters, and die geometries. The results showed that
the optimal ways to reduce the bending of strain rate sensitive materials in ECAP without varying the strain homogeneity are
the usage of lower processing speed and the increase in length of the die exit-channel. 相似文献
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AZ31镁合金等通道转角挤压变形均匀性有限元分析 总被引:2,自引:0,他引:2
以AZ31镁合金为研究对象,通过对不同模具外角ECAP变形过程的有限元模拟,研究不同模具外角下AZ31镁合金ECAP变形的等效应变分布.利用微观组织观察以及硬度测试,分析等效应变分布对微观组织及力学性能影响.结果表明:当模具外角ψ为20.时,工件可以获得均匀的等效应变分布.AZ31镁合金经过ECAP挤压后,微观组织显著细化,力学性能明显改善,但平均晶粒尺寸及微观维氏硬度在工件横截面上分布不均匀,等效应变分布的不均匀性是导致材料微观组织和力学性能不均匀的主要因素之一. 相似文献
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Deformation behavior of submicron grain size Al–1.5Mg was studied using strain rate change tests. Compared to the annealed state, the strain rate sensitivity of the pressed materials increased, its peak shifted to lower temperatures and the dynamic strain aging regime at the lower temperatures was suppressed. 相似文献
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Equal channel angular pressing (ECAP) is an important process for producing ultra fine grains in bulk metallic materials by means of severe plastic deformation. Workability of metals and alloys is an important parameter as it influences the fracture resistance of the material and the ease of subsequent forming by conventional techniques. In this study, the effect of various passes and processing routes of ECAP on the workability of commercially pure aluminum has been investigated. Aluminum specimens were subjected to ECAP using 90° angle ECAP die. ECAP was carried out using two processing routes for up to three passes. Microstructure characterization and mechanical property measurements were carried out. Workability was determined by means of upsetting tests on hexagonal collar specimens machined from specimens processed by ECAP. A Cockcroft fracture criterion was used to evaluate experimental results. It is observed that processing to two passes through Route C results in enhanced mechanical properties with only a slight decrease in workability. 相似文献
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概述了等径角挤压(Equal ChannelAngular Pressing)制备超细晶材料工艺的研究进展;介绍了ECAP的技术原理和工艺特点;着重分析了ECAP模具对ECAP细晶材料的显微组织的影响,优化ECAP模具结构。 相似文献
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《Intermetallics》2017
Multiple-stage transformation of Ti49.2Ni50.8 alloy processed by equal channel angular pressing (ECAP) was investigated as a function of pass number and aging treatment before ECAP. When the pass number is no more than four passes, three stage transformation, namely A→R, R1→M1 and R2→M2, occurs in the as-ECAP processed alloy initially aged at 450 °C for 60 min. Only the A→R→M forward transformation occurs provided that the aging duration was decreased/increased to 10/600min. The transformation sequence was discussed based on the microstructure evolution of as-ECAP processed alloy with different initial microstructure and pass number. 相似文献
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纯铝等径角挤技术(Ⅱ)--变形行为模拟 总被引:19,自引:5,他引:19
通过有限元模拟和坐标网格,对纯铝等径角挤过程的变形行为进行了模拟和试验。结果表明,纯铝在单道次等径角挤压过程中所需的载荷随着样品位移的增加大致可分为快速增加、缓慢增加、快速增加、载荷值趋于稳定、载荷下降5个阶段。由于样品外部在主要变形区的流动速率比样品内部的快,因而样品在等径角挤压过程中会出现不均匀变形,样品底部沿宽度方向的塑性变形量明显少于样品顶部和中部的,坐标网格法实验结果也证明了这一点。在等径角挤压过程中,样品不同部位的应力状态不一致,样品内部存在压应力→拉应力的转变,样品外部存在压应力→拉应力→压应力的转变。摩擦消除后,有效应变有所增加,但并不能降低样品变形的不均匀性;采用尖角模具既能产生更大的剪切应变,又能提高变形的均匀性。 相似文献
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Jun-Hyun Han Hyung-Jun Chang Kwang-Koo Jee Kyu Hwan Oh 《Metals and Materials International》2009,15(3):439-445
The deformation behavior within the deformation zone of a workpiece during equal channel angular pressing (ECAP) was investigated
using the finite element method. The effects of die geometry on the variations of normal and shear deformations were studied
with a deformation rate tensor (D). The zero dilatation line, at which the normal components (D11 and D22) of the deformation rate tensor (D) are zero, in the die coincided with the line of intersection of the two die channels irrespective of die geometry such as
curvature angle (Ψ) and oblique angle (Φ), while the maximum shear line, at which the shear components (D12 and D21) of the deformation rate tensor (D) have maximum value, is dependant on the die geometry 相似文献
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粉末多孔材料等径角挤压热力耦合有限元数值分析 总被引:6,自引:2,他引:4
等径角挤压是获得块体超细晶材料的一种重要工艺方法。针对粉末多孔材料,采用体积可压缩刚粘塑性热力耦合有限元法对其等径角挤压过程进行模拟分析。结果显示,等径角挤压工艺对粉末多孔材料具有强烈的致密效果,变形温度和接触摩擦状况对变形及致密存在明显的影响。研究表明,材料所处的静水压力状态对多孔材料的挤压效果影响显著,高的静水压力状态有利于提高粉末材料的变形能力及致密效果,改进的带背压工艺有利于提高变形的均匀性,扩大工艺的应用范围。 相似文献
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等通道弯角挤压变形机理模拟与工艺参数优化 总被引:10,自引:0,他引:10
通过等通道弯角挤压工艺 (EqualChannelAngularPressing ECAP)能够获得块状超细晶粒材料 (包括亚微米和纳米材料 )。模具几何形状、摩擦条件等工艺参数对挤压过程具有重要影响。本文应用作者自主开发的商品化软件 ,通过大量的有限元模拟 ,研究了过程参数对挤压件变形分布、挤压载荷的影响规律 ,给出了不同模具拐角和圆心角对ECAP挤压件变形区产生的累积等效应变、等效应力和载荷 行程曲线的影响 ,为优化模具形状和获得所要求的挤压件变形分布提供了大量有效的结果和规律。 相似文献