共查询到20条相似文献,搜索用时 15 毫秒
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Cunsheng Zhang Guoqun Zhao Hao Chen Yanjin Guan Fujun Kou 《The International Journal of Advanced Manufacturing Technology》2012,60(1-4):101-110
The most important way to improve the quality of aluminum profiles is to assure the material flow through die land exit with the same velocity. In this paper, a numerical model was developed to investigate metal flow behavior during aluminum profile extrusion. Firstly, the numerical model for a complex hollow aluminum profile was built based on the arbitrary Lagrangian–Eulerian program HyperXtrude. Then, with the numerical model, metal flow behavior at each stage during the whole extrusion process was analyzed and dead zones in the die cavity were also investigated by means of the particle tracking method. Finally, the numerical results were validated by comparing with the nose ends of two extrudates in practice, and the comparison showed that the numerical model developed in this work could provide the effective guidance for practical production. 相似文献
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概述了塑性成形的基本原理,分析了螺杆钻具接头在热镦挤成形过程中载荷随工件变形量的变化、工件表面应力以及工件在成形过程中的金属流动情况,确定了螺杆钻具接头热镦挤成形所需要的镦挤压力和成形温度,设计了热镦挤成形试验装置的基本结构,并通过试验验证了这种螺杆钻具接头加工方法的可行性。 相似文献
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A computational study of die geometry and processing conditions effects on equal channel angular extrusion of a polymer 总被引:3,自引:0,他引:3
B. Aour F. Zaïri M. Naït-Abdelaziz J.M. Gloaguen O. Rahmani J.M. Lefebvre 《International Journal of Mechanical Sciences》2008,50(3):589-602
Equal channel angular extrusion (ECAE) is an efficient process to obtain enhanced microstructures via super-plastic deformation. In view of its optimisation, it is of prime importance to assess the relationships between processing conditions and material flow. More precisely, detailed knowledge of the plastic strain distribution in the extruded material in relation to the ECAE processing variables is required. The key parameters of the ECAE process are primarily die geometry, ram speed, extrusion temperature, use of back-pressure, number of extrusion sequences and processing route (e.g. rotation of the sample between successive passes). A numerical investigation was achieved to check out the influence of these parameters on the homogeneity of plastic strain distribution in the case of a conventional thermoplastic polymer. Material parameters of a phenomenological elastic viscoplastic model were deduced from compressive deformation tests at different temperatures and strain rates on high-density polyethylene (HDPE). Recommendations on tool geometry and processing conditions can then be provided, according to the numerical results.It was found that optimum ECAE die geometry is strongly material dependent. The application of a back-pressure significantly contributes to reduce the corner gap and consequently promotes the homogeneity of the plastic strain field. A slight sensitivity of plastic strain to ram speed and friction conditions was pointed out. The extrusion temperature strongly influences the magnitude of the plastic strain and has a slight effect on its homogeneity. The number of passes has a significant effect on the magnitude of the plastic strain but has a negligible influence beyond a certain temperature. The extruded material reaches a stationary strain state after few passes. The homogeneity of the plastic strain field is strongly affected by the processing route. 相似文献
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基于ALE算法的空心薄壁铝型材模具结构优化 总被引:1,自引:0,他引:1
针对空心薄壁铝合金型材挤压成型后薄壁内凹缺陷进行了数值模拟分析,得到了其在稳态时不同方向上的金属流速分布及在焊合室内的金属压力分布状况。模拟结果表明:由于截面上不同部分之间产生了较大的流速差,且金属在不同方向上的流速不相同,从而导致了缺陷的存在。根据分析采用了增加阻流块的设计方案,以此达到阻碍金属流动,减小流速差的目的。经过仿真计算发现修改后的模具结构最终能获得合格的产品。 相似文献
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在轮胎胶料挤出生产中,口模的结构对共挤出产品的质量起着关键的作用,但在实际生产中,共挤出口模的设计主要依靠经验,口模设计质量的控制需要经过多次试模和修模。采用流体计算软件Polyflow进行轮胎胶料(TWD40/FS10)的共挤成型过程的三维数值模拟,分析共挤出过程中的速度、压力分布以及胶料熔体的流动情况,并通过试验验证模拟的可行性。针对初始口模设计的不足,提出增加窄缝区域高度和扩充口模入口的方法,有效解决初始模具设计中速度分布不均的问题,改善了口模中熔体的流动,提高了挤出质量,同时还降低了挤出过程中的能耗。利用数值方法可对共挤出口模结构进行设计,提出的口模设计方法可以对同类轮胎胶料共挤出口模结构的设计提供指 相似文献
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Cunsheng Zhang Guoqun Zhao Hao Chen Yanjin Guan Hengkui Li 《The International Journal of Advanced Manufacturing Technology》2012,60(5-8):589-599
Taguchi’s design of experiment and numerical simulation were applied in the optimization of an aluminum profile extrusion process. By means of HyperXtrude, the extrusion process was simulated and the effects of process parameters on the uniformity of metal flow and on the extrusion force were investigated with the signal to noise ratio and the analysis of variance. Through analysis, the optimum combination of process parameters for uniform flow velocity distribution was obtained, with the billet diameter of 170?mm, ram speed of 2.2?mm/s, die temperature of 465°C, billet preheated temperature of 480°C, and container temperature of 425°C. Compared with the initial process parameters, the velocity relative difference in the cross-section of extrudate was decreased from 2.81% to 1.39%. In the same way, the optimum process parameters for minimum required extrusion force were gained, with the billet diameter of 165?mm, ram speed of 0.4?mm/s, die temperature of 475°C, billet preheated temperature of 495°C, and container temperature of 445°C. A 24.7% decrease of required extrusion force with optimum process parameters was realized. Through the optimization analysis in this study, the extrusion performance has been greatly improved. Finally, the numerical results were validated by practical experiments, and the comparison showed that the optimization strategy developed in this work could provide the effective guidance for practical production. 相似文献
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K. Logesh V. K. Bupesh Raja 《The International Journal of Advanced Manufacturing Technology》2017,89(1-4):113-123
The remarkable nonlinearity between the viscosity and temperature significantly reduces the extrusion formability of Nylon-66. The conventional extrusion methods, which obtain extrusion profiles with high precision through first extrusion and then sizing in calibrator, are unable to realize the extrusion of Nylon-66, especially for GF/Nylon-66 composite. In this paper, a one-step extrusion method, which realizes the fast sizing of extruded parts by taking advantages of the crystallization of GF/Nylon-66 melt, was proposed based on the viscosity change features and crystallization behavior of GF/Nylon-66 around its melting temperature (T m). Thus, the sizing and cooling processes using standardized dies in conventional extrusion methods can be eliminated. In this study, the one-step extrusion process of GF/Nylon-66 was investigated from three aspects including the extrusion rheological performance, the equilibrium property of extrusion flow and crystallization sizing behavior, based on finite element simulations and experiments. The results revealed that the melt flow property can be improved by increasing temperature and shear rate. The rheological constitutive equation can precisely describe the rheological performance of materials under different temperatures and shear rates. Increasing melt temperature and screw speed will reduce the melt flow equilibrium. With the melt temperature at neck ring mold being the peak crystallizing temperature and screw speed being appropriate, an optimized dynamic balance among the melt flow property, the flow equilibrium performance and the crystallization sizing capability can be achieved. Thus, the extrusion molding of GF/Nylon-66 can be implemented via one-step extrusion. The method proposed can realize the extrusion molding of GF/Nylon-66 with improved efficiency and reduced cost. 相似文献
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薄壁塑料异型材在生产生活中得到了越来越广泛的应用,而截面厚度不均对挤出工艺有着比较大的影响.首先对L型异型材出口速度均匀性进行了理论分析,然后对T型异型材出口速度均匀性进行了数值分析,最后着重分析了截面厚度差异对挤出工艺的影响规律.在实际生产过程中,应尽量避免截面厚度的不均匀导致的不良影响. 相似文献
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An optimization strategy for die design in the low-density polyethylene annular extrusion process based on FES/BPNN/NSGA-II 总被引:1,自引:1,他引:0
Yue Mu Guoqun Zhao Xianghong Wu Chengrui Zhang 《The International Journal of Advanced Manufacturing Technology》2010,50(5-8):517-532
An optimization strategy for die design in the polymer extrusion process is proposed in the study based on the finite element simulation, the back-propagation neural network, and the non-dominated sorting genetic algorithm II (NSGA-II). The three-dimensional simulation of polymer melts flow in the extrusion process is conducted using the penalty finite element method. The model for predicting the flow patterns in the extrusion process is established with the artificial neural network based on the simulated results. The non-dominated sorting genetic algorithm II is performed for the search of globally optimal design variables with its objective functions evaluated by the established neural network model. The proposed optimization strategy is successfully applied to the die design in low-density polyethylene (LDPE) annular extrusion process. A constrained multi-objective optimization model is established according to the characteristics of annular extrusion process. The minimum of velocity relative difference, δu, and the minimum of swell ratio, S w, that, respectively, ensure the extrinsic feature, mechanical property, and dimensional precision of the final products are taken as optimization objectives with a constrained condition on the maximum shear stress. Three important die structure parameters, including the die contraction angle α, the ratio of parallel length to inner radius L/R i, and the ratio of outer to inner radius R o /R i, are taken as design variables. The Phan-Thien–Tanner constitutive model is adopted to describe the viscoelastic rheological characteristics of LDPE whose parameters are fitted by the distributions of material functions detected on the strain-controlled rheometer. The penalty finite element model of polymer melts flowing through out of the extrusion die is derived. A decoupled method is employed to solve the viscoelastic flow problem with the discrete elastic-viscous split-stress algorithm. The simulated results are selected and extracted to constitute the learning samples according to the orthogonal experimental design method. The back propagation algorithm is adopted for the training and the establishment of the predicting model for the optimization objective. A Pareto-optimal set for the constrained multi-objective optimization is obtained using the constrained NSGA-II, and the optimal solution is extracted based on the fuzzy set theory. The optimization for die parameters in the annular extrusion process of low-density polyethylene is performed and the optimization objective is successfully achieved. 相似文献
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Yuguang Wu 《The International Journal of Advanced Manufacturing Technology》2018,95(5-8):1697-1714
In this paper, the rheological behaviors of a silicone rubber used in sheet metal flexible-die forming were analyzed experimentally and numerically. Firstly, six silicone rubber samples with different molecular weights were subjected to three tests: oscillation, creep recovery, and shear viscosity test by using dynamic shear rheometer (DSR). Then, the responses of the silicone rubber to the load were categorized into three groups as elasticity, viscoelasticity, and viscoplasticity depending on whether they were time dependent and recoverable during the unloading period. By applying Perzyna’s theory, a visco-elasto-plastic model was proposed to simulate the rheological behaviors of the silicone rubber numerically. Finally, a finite element-element-free Galerkin (FE-EFG) code was implemented on the basis of this numerical model. Employing the program into polymer extrusion and sheet metal flexible-die forming process, on the substation of parameters obtained from experiments, good matches were found between numerical results and experimental ones. 相似文献
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针对聚合物熔体在微尺度通道中流动时的黏性耗散效应对其流动行为的影响,通过自行构建的带有温度传感器和超声振子的微注塑成型试验系统,采用单因素成型试验方法,对聚丙烯(Polypropylene, PP)和高密度聚乙烯(High-density polyethylene, HDPE)两种聚合物材料在不同工艺参数和超声外场作用下,流经矩形截面微通道时由黏性耗散效应引起的通道出口熔体温升进行试验测量。结果表明,微通道中熔体的黏性耗散效应随注射速度的增加而增强,随入口熔体温度和模具温度的升高而减弱;与不加超声振动相比,施加超声振动使两种材料的微通道出口熔体温升值明显升高;但材料自身的微观分子结构及其热物理性能不同,其温升增幅差别较大。试验注射速度下,施加超声振动比不加超声振动时的PP熔体温升增幅高出34.7%,而HDPE熔体的温升增幅则高达71.7%。当超声频率和工艺参数一定时,增大超声功率使PP熔体的微通道出口温升增加了24.8%,HDPE熔体的温升增加了83.6%。可见施加超声外场作用能使微通道中聚合物熔体的黏性耗散效应明显增强。 相似文献
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Injection molding has been one of the most important polymer processing methods for manufacturing plastic parts. In the process, the temperature is an important parameter that influences process features such as cycle times, crystallization rates, degree of crystallinity, melt flow properties, and molded product qualities. This study aims to, experimentally and numerically, examine the three-dimensional temperature distribution along the melt flow path of injection molded parts. A special experimental set-up, which includes an injection mold equipped with protruding microprobes for guiding embedded thermocouples, was designed and built to measure the temperature field along the flow path, i.e., inside the runner and the cavity, of injection molded products. The experimental results suggested that the disturbance induced by the probes remained negligible and precise temperature profiles could be measured at various positions inside the cavity. A significant increase of melt temperature was found to result from the viscous dissipation of the polymeric materials in the runner. Additionally, a commercially available code was employed to simulate and predict the temperature variation in injection molded parts. It was shown that the numerical simulation predicted better the temperature distributions inside the cavity than those along the runner. 相似文献
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Rheology forming is a novel semi-solid processing method, which is different from traditional mold forging and conventional casting processes. The rheological behavior of metallic alloys containing both solid and liquid phases investigated the low and high solid fraction ranges. Rheology forming has several obvious advantages including its excellent forming ability resulting in the easier production of complex work pieces, more flexibility in shaping pieces, and more compact inner quality because of its high pressure. This research paper presents the theory of the rheology forming process and the results of a finite element simulation of rheology forming for aluminum alloys. The algorithms for both a single- and two-phase flow model, developed for this study, gives the die filling patterns, velocities, temperatures and solid fractions of the rheology material during the rheology process. To calculate the velocity and temperature fields, the respective governing equations corresponding to the liquid and solid regions were used. Therefore, the respective numerical models that take the co-existing solid and liquid phases within the rheology material into consideration have been developed to predict the defects of parts manufactured by the rheology process. This study compares of the velocity, temperature, and solid fraction between the single- and two-phase flow models. And, to predict the liquid segregation in the parts, the deviation of velocity between the liquid and solid regions in the two-phase flow model was analyzed. 相似文献
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将聚合物熔体和低速热空气均视作不可压流体,针对一聚苯乙烯(PS)片材的全气体辅助挤出,建立了描述其气体-熔体两相分层流动的三维有限元模型,采用黏弹应力分离法(EVSS)和非协调流线迎风法(SU)等有限元方法,利用PolyFlow求解器对气体辅助流道中气体和熔体流动进行了计算,分析了熔体截面变化的规律及原因。研究结果表明:气体辅助流道内,气体对熔体有拖曳作用;沿挤出方向,熔体速度逐渐增大,而截面积逐渐减小,都在口模出口面上达到极值,同时截面形状有微小改变;口模出口面上熔体沿挤出方向的速度随入口气体体积流率的增大而近似线性增大,熔体截面积则近似线性减小。 相似文献