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等截面侧向挤压的力学分析 总被引:6,自引:0,他引:6
等截面侧向挤压是实现材料纯剪切变形的有效方法。通过网格实验研究了等截面侧向挤压过程中材料的变形情况 ,结果表明塑性变形区仅位于模具通道拐点连线附近。通过几何分析推导出等截面侧向挤压等效应变计算公式 ,通过上限分析推导出等截面侧向挤压变形力计算公式 ,理论计算结果与实测值进行了对比。 相似文献
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针对搅拌摩擦焊(friction stir welding,FSW)的特点,建立了基于固体力学的刚粘塑性热力耦合有限元方程,并采用网格局部加密自适应跟随技术对FSW过程进行数值模拟,获得了焊接过程的温度、应力、应变分布特征及金属流动规律,预测焊接过程中所产生的缺陷.结果表明,FSW过程中试件的温度分布不对称,应变沿板厚的方向分布不一致,焊缝区产生了剧烈的塑性变形,因此FSW是一个典型的三维剧烈的塑性变形过程,热塑性变形机制是焊接接头形成的主要机制. 相似文献
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STRAIN ANALYSIS OF LATERAL EXTRUSION PROCESS 总被引:2,自引:0,他引:2
Liu Zuyan Wang Erde School of Materials Science Engineering Harbin Institute of Technology Harbin P. R. China 《中国有色金属学会会刊》1999,9(1)
INTRODUCTIONInrecentyears,anewkindofmethod,equalcrossectionlateralextrusion(ECSLE),hasbeensuccesfulyusedtomakeultrafinegra... 相似文献
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Twist extrusion, a promising severe plastic deformation technique for grain refinement down to ultrafine/nanocrystalline microstructures, was introduced as an attempt to provide large plastic deformation conditions similar to those in high pressure torsion while allowing large workpiece dimensions for industrial applications. As a relatively new severe plastic deformation technique, twist extrusion requires in-depth investigation of its plastic deformation characteristics. In this study, the twist extrusion process with a square shape die cavity has been analyzed using an upper bound solution to estimate the required power, deformation pattern, and optimum process condition. The analysis has been performed based on two kinematically admissible velocity fields while the effects of friction condition, die geometry, and mean equivalent strain have been considered. The results indicate that the die geometry and process parameters can dramatically change the deformation pattern and extrusion power. 相似文献
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FE simulation of the influence of die-elasticity on component dimensions in forward extrusion 总被引:1,自引:0,他引:1
The elastic behaviour of the forming die has a direct influence on the quality of the formed component. Simulation of material flow and of die deflection during forward extrusion was conducted using elastic and plastic considerations to establish the influence of die-elasticity on the form of the component under different processing conditions.The simulations show that the dimensions of the work-material are affected by die-elasticity during both, loading and unloading of the die. The change of the die-geometry does not produce obvious differences in the dimensions of the extrudate; however, it influences the geometric errors of the workpiece which is retained in the die. Larger values of friction in the injection chamber result in the corresponding increase of punch pressure which results in larger radial deflection of the die during extrusion (loading), the consequence being a greater variation in extrudate geometry. High levels of friction reduce the elastic contraction of the die during punch retraction (unloading), and hence, larger form-errors are sustained after unloading. The contraction of the die during unloading phase of the process causes plastic deformation of the work-material remaining in the injection-chamber; this plastic deformation is significant to the overall form-error of the component. 相似文献
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利用有限元法研究ZK60镁合金在多道次往复挤压过程中的应变分布。为优化往复挤压工艺,研究摩擦条件和模具结构尺寸对ZK60合金总等效塑性应变分布的影响。结果表明:ZK60合金试样经往复挤压后内应变分布不均匀。试样两个端部的应变量低于试样中间部位的应变量。工艺参数对应变分布的影响很大。试样和模具间的摩擦不利于试样内应变量的均匀分布,因而应尽量降低摩擦。为了提高应变量的均匀分布,应该使用较大的过渡圆角半径和较低的挤压角度。 相似文献
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楔横轧工艺成形阶梯轴类件时轧件表面缺陷形成条件分析 总被引:4,自引:1,他引:3
依据文献 [4]的模拟实验结果 ,拟定了楔横轧工艺成形阶梯轴类件时轧件表面出现表面缺陷 (蛇皮状或鱼鳞状缺陷 )时的金属流动速度场。以此为基础 ,并借助于上限原理和最小能量原理 ,获得了楔横轧成形阶梯轴时轧件表面缺陷形成的必要条件。同时 ,研究了表面缺陷产生与变形程度、摩擦因数及模具整形段相对长度的关系。从而为估测楔横轧成形阶梯轴类件时轧件表面是否会产生缺陷提供理论指导。 相似文献
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《中国有色金属学会会刊》2021,31(7):1939-1950
The isothermal extrusion process of hollow aluminium profile was investigated using incremental proportional–integral–derivative (PID) control algorithm and finite element simulations. The range of extrusion speed was determined by considering the maximum extrusion load and production efficiency. By taking the optimal solution temperature of the secondary phase as the target temperature, the extrusion speed–stroke curve for realizing the isothermal extrusion of the aluminium profile was obtained. Results show that in the traditional constant extrusion speed process, the average temperature of the cross-section of the aluminium profile at the die exit rapidly increases and then slowly rises with the increase in ram displacement. As the extrusion speed increases, the temperature difference at the die exit of the profile along the extrusion direction increases. The exit temperature difference between the front and back ends of the extrudate along the extrusion direction obtained by adopting isothermal extrusion is about 6.9 °C. Furthermore, the heat generated by plastic deformation and friction during extrusion is balanced with the heat transfer from the workpiece to the container, porthole die and external environment. 相似文献
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利用三维有限元方法模拟了圆形工件的等通道转角挤压过程,分析了工件上应变分布情况,其与理论值和二维模拟的结果符合较好.通过对稳定变形阶段塑性变形区的分析,探讨了应变分布不均匀的原因,所得结果有利于理解工件变形过程和优化工艺设计. 相似文献
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应用有限元分析软件中的显式动力学求解器模拟筒形零件缩口成形工艺过程中应力、应变和位移流向的分布云图,分析了工件成形时的塑性变形特点及其对成形质量的影响关系.研究表明:筒形件冲压缩口成形工艺主要失效形式是缩径区的裂纹、定径区的起皱和传力区部分的失稳等;工件失效的主要原因是塑性变形区材料流动速度不均匀导致的应力集中;冲压缩口力随着摩擦系数和模具锥角的增大而增大,但是会随着模具型腔内圆角半径的增大而减小. 相似文献
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Using numerical simulation and experiment, the metal flow behavior mechanical mechanisms in the extrusion process with active
friction were investigated. The characteristic variables, second invariant of the stress deviator J
2 and the Lode’s coefficient μ were employed to partition the deformation region. It is shown that no metal flow interface
occurred at the container bottom in the extrusion with active friction and the dead zone disappeared completely. The strain
types of the material in the plastic deformation area decreased from three types into a single type of tension, and the homogeneity
of metal deformation as well as metal flow was greatly improved. It was also indicted that the active friction was beneficial
to the extrusion process and the promotion of product quality. After contrasting the result of experiment and the simulation,
the displacement and the load were well correlated on both values and trends. 相似文献
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With the help of Complex Function Mapping theory, the complicated three-dimensional deformation problems are transferred into two-dimensional problems, and the function of strain ratio field is analyzed in the metal plastic extruding deformation. Taking the strain-hardening effect of metal deformation into account, the relationship between friction behavior and optimized mathematical model is analyzed by the numerical analysis friction energy dissipation function. As a result, the method of lowering the material hardening and decreasing the reduction ratio over multi-procedures can be used to improve the surface quality of metal special-shape extrusion products. 相似文献
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金属液体凝固中直接挤压过程的数值模拟 总被引:3,自引:0,他引:3
根据稳定的交替方向隐式(SADI)有限差分方法、上限元法(UBET)等数值计算方法提出了一种数值模拟方法.使用这种方法成功地模拟了融凝固和大塑性变形为一体的金属液体凝固过程中直接挤压(简称液体挤压)的工艺过程.计算机生成的动画图象直观地表现了工件的整个成型过程.模拟结果有助于掌握液体挤压这一新工艺的各种工艺规律. 相似文献
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镦,挤,摆辗复合工艺实验研究与工艺参数的优化 总被引:1,自引:0,他引:1
采用物理模拟技术对镦,挤,摆辗复合工艺进行了实验研究。用视塑性法研究了变形体子午面内金属的流动规律,从而阐明变形方式,进给时、工件原始高径比、变形温度及变形量对正反挤出长度及法兰盘外缘形状的影响,对大量实验数据进行回归处理后,得出了根据产品尺寸选择最佳毛坯尺寸和最佳变形方式的经验曲线为复杂零件成形提供实验依据。 相似文献
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Yuepeng Song Wenke Wang Dongsheng Gao Eun Yoo Yoon Dong Jun Lee Hyoung Seop Kim 《Metals and Materials International》2014,20(3):445-450
High pressure torsion (HPT) is one of the most important techniques among various methods that create severe plastic deformation in the production of bulk materials with nano/ultrafine grained microstructures. Since the driving force in deforming the workpiece in HPT is surface friction, understanding of the friction effect is critical for successful application of HPT. In this study, the friction effect in HPT was analyzed using the finite element method. The distribution of effective strain on the contact surface of the HPT samples under different friction conditions was investigated. The friction force influenced the effective strain more in the middle and edge regions than in the central region. The condition for the minimum friction factor that could achieve a sticking condition between the surfaces of the dies, and the samples in the middle and edge regions, was investigated. There was a critical friction coefficient in which the effective strain varies sharply with an increasing friction coefficient. 相似文献