NEM-FEM comparison on porthole die extrusion of AA-6082

Porthole die extrusion is a forming process used to manufacture hollow components with different shapes. This forming process is optimized to improve the welding line quality. Process optimization can be achieved by determining the influences that each process parameter has on the pressure along the welding plane. The construction complexity of the die results in research difficulty from an experimental point of view. Even the finite element method (FEM) presents relevant drawbacks primarily because of numerical codes are not capable of simulating the welding phase. Hence, the natural element method (NEM), which allows the joining phase of free surfaces, presents significant advantages. In this work, experimental results obtained using a flexible porthole die are discussed. A suitable 2D geometry was extracted from the die, and both FEM and NEM were conducted. A good agreement among the numerical results was recorded.     

Multiobjective optimization design of porthole extrusion die using Pareto-based genetic algorithm

The extrusion die plays a crucial role in aluminum alloy profile production, which influences product quality and service life of extrusion die directly. In this paper, a profile with irregular shape was taken as an analysis example, and multiobjective optimization for porthole extrusion die based on modern intelligence algorithm was carried out. Aiming at achieving the uniform velocity distribution in the cross-section of the profile as well as decreasing the maximum stress on the extrusion die and the deflection of the mandrel, the angle between port bridges, the position of die orifice, and the height of welding chamber were considered as the design variables. Then Kriging model was established on the basis of Latin hypercube samplings, and above design variables were optimized using Pareto-based genetic algorithm. Finally, an optimal die structure is gained. Compared with the initial scheme, the velocity distribution in the extrudate was more even, and the stress on the die and the deflection of the mandrel were decreased obviously in the optimal scheme. The optimal design method for porthole die has strong commonality, thus, it could give useful guidelines for practical production of the same kind of aluminum profile.     

Analysis and porthole die design for a multi-hole extrusion process of a hollow,thin-walled aluminum profile

The appropriate die design for multi-hole extrusion is still a challenging task because of the complicated circumstances and large material deformation during extrusion process. In the present study, the material flow during multi-hole extrusion process for producing a hollow and thin-walled profile was revealed by means of numerical simulation based on the Arbitrary Lagrangian Eulerian (ALE) method. The effects of eccentricity ratio, shape of the second-step welding chamber, and uneven bearing length on the exit velocity distribution of extrudate were synthetically investigated, and a two-hole porthole die was designed accordingly. The exit velocity and temperature on the extrudate in this optimized die were analyzed and compared with the initial die, and it was found that both of them exhibit better uniformity, which is beneficial for the enhancement of product quality. Through performing the current work, a logical and effective route for designing multi-hole porthole die was proposed as the guidance for die designers.     

Round-to-channel section extrusion through linearly converging die: a three-dimensional analysis

Metal flow in the extrusion process is an important factor in controlling the mechanical properties of the extruded products. It is, however, difficult to predict the metal flow in three-dimensional extrusion of sections due to the involvement of re-entrant corners. The present work is an attempt to find an upper bound solution for the extrusion of channel section from round billet through the taper die. The rigid-perfectly plastic model of the material is assumed, and the spatial elementary rigid region (SERR) technique is presented for which the kinematically admissible velocity field is found out by minimizing the plastic dissipation of power. The presented analysis allows for specification of process control parameters and their relation to extrusion load, equivalent die angle, reduction ratios and friction factor.     

Three-dimensional analysis of round-to-angle section extrusion through straight converging die

The increasing interest in the modeling of metal-forming processes in recent years has brought the development of different analytical and/or numerical technique. However, due to the complexity nature of the problem, most of the attempts are made with plain strain assumptions. Among the different techniques used, the upper bound method is a convenient tool for evaluating the rate of work in processes involving predominantly plastic deformation of rigid/perfectly plastic material. The present study is an endeavor to remodel and apply the spatial elementary rigid region technique for analyzing extrusion of angle-section bars from round billets through the linearly converging die. Optimized values of the nondimensional average extrusion pressure at various area reductions have been computed and compared with experimental results. It is observed that the proposed technique can be used effectively with adequate accuracy to predict the optimal die geometry which requires a minimal forming stress at different reduction of areas and friction conditions.     

Axisymmetric extrusion and drawing through a die of arbitrary form

Axisymmetric extrusion and drawing through a die of arbitrary shape is analyzed by the Orowan method. The stress state in a representative element is determined by solving a boundary value problem of plasticity theory.     

Rotordynamic analysis and experimental validation of a high speed induction motor made by copper die casting process

A copper die casting induction motor can obtain an energy saving effect of about 2–3% compared to previous aluminum die casing induction motors. In addition, copper die casting motors can reduce the size of motors and reduce material costs. The critical speed and unbalance response of high speed machines need to be verified by rotordynamic analysis for dynamic stability of the rotors. The critical speed analysis, harmonic analysis and transient analysis by unbalance are performed for dynamic stability. The unbalance analysis results are compared with the experiment considering allowable vibration displacement (API 611) and balancing grade (ISO 1940-1). This paper dealt with the design, analysis and experimental validation of a high speed induction motor. The dynamic stability of the prototype is verified successfully, and two experimental methods by ISO 10816-3 are suitable and reliable for the allowable vibration evaluation of rotating machine.     

Evaluation of a pyramid die extrusion for a hollow aluminum profile using FE simulation

The pyramid die extrusion for a hollow aluminum profile was analyzed to investigate the potential of such innovative dies. For this purpose, the pyramid and conventional porthole dies were respectively designed for a given hollow aluminum profile. And the extrusion process was comprehensively studied by performing different types of finite element simulation, such as the analysis of steady state, transient state and billet skin tracking. The effects of pyramid angle on the evaluation parameters of extrusion, such as extrusion load, material flow, exit temperature, length of transverse weld, quality of longitudinal weld, back end defect and die stress were overall analyzed and compared with the conventional porthole die. Through this study, the advantages and shortcomings of pyramid die were well concluded, which should be important information for die designers and makers.

     

Design and analysis of streamlined extrusion die for round to hexagon using area mapping technique,upper bound technique and finite element method

Extrusion is one of the most important metal forming process commonly used for the manufacturing of the hexagonal rods. Extrusion of metal through a conventional shear faced die experiences few practical limitations such as dead metal zone, more redundant work etc. Most of the research works have proved that the streamlined die used for extrusion is more efficient than the conventional shear faced die. Design of streamlined die using arbitrarily shaped curves and conventional curves have been done by many researchers. In this study, a new approach of transforming the peripheral point on the surface of round to corresponding point on the extruded hexagon has been obtained by an analytical method. Further the prediction of force required to extrude, the development of stresses and strain have been solved with a combined approach of upper bound theorem and finite element technique by considering the profile as cosine curve. Later the experimental study has been conducted for validating these approaches to register the benefit of cosine profile.     

Estimation of die service life for a die cooling method in a hot forging process

Dies may have to be replaced for a number of reasons, such as changes in dimensions due to wear or plastic deformation, deterioration of the surface finish, breakdown of lubrication, and cracking or breakage. In this paper, die cooling methods are suggested to improve die service life with regards to wear and plastic deformation in a hot forging process. The yield strength of die decreases at higher temperatures and is dependent on hardness. Also, to evaluate die life due to wear, a modified Archard’s wear model has been proposed by considering the thermal softening of die expressed in terms of the main tempering curve. This paper describes the effects of die cooling methods such as cooling hole and direct spray cooling on the life of finisher die during the hot forging of an automobile part. It is shown that the cooling hole method during hot forging is necessary for an effective die service life to be obtained.     

Numerical analysis of friction influence and die geometry on the quality of product in the forward extrusion process of tubular copper electrodes

The results of a numerical analysis of the extrusion of tubular electrolytic-copper electrodes are presented. The numerical analysis is based on the finite-element method (FEM) in DEFORM software. This method makes it possible to predict the formation of a microstructure, characteristics of the material, and factors in the process that improve the mechanical properties of the articles.     

铝型材挤压成形过程金属流动状态的数值模拟

运用基于有限元法的模拟软件MSC.Marc对一复杂空心铝合金型材挤压过程进行数值模拟,在模拟过程中采用了一种既可以避免网格畸变和重划分,又能保证分析准确性的有限元模拟方法,研究了金属在模腔内的流动规律,利用出口质点轴向流速的SDV值定量的判定截面出口速度分布的均匀程度,揭示了金属的流动速度对产品形状及尺寸的影响,并将模拟仿真结果与试模结果进行比照分析,证明该方法可以成功地预测实际挤压过程中可能出现的潜在缺陷.     

Numerical and experimental study on the three-dimensional extrusion of square section from square billet through a polynomial shaped curved die

The geometry of die profile plays a major role in reducing the extrusion pressure and ensuring the smooth flow of material. In general, the extrusion process is mostly affected by billet geometry, die geometry, and interface frictional force at the die billet geometry. In the present investigation, an analysis using three-dimensional upper bound method using fifth-order die profile function has been carried out for extrusion of square sections from square billet. The extrusion pressure and optimum die length have been computed by multivariable optimization technique. The present die shape profile is found to be superior to many other profiles. The results obtained will help in design of optimum die profile and investigation of its performance.     

An analysis of the extrusion process of the straight-fin heat sink in a computer

In this paper, the finite element method is used to investigate the extrusion process of the straight-fin heat sink in computers. A series of simulations on the straight-fin extrusion using the program DEFORM 2D was carried out. The influences of the process parameters such as straight-fin thickness, straight-fin clearance and friction factor between the die and workpiece on the difference of maximum and minimum extruded fin lengths are examined.     

Analysis and improvement of material flow during extrusion process using spreading pocket die for large-size,flat-wide,and multi-ribs profile

Spreading extrusion is an advanced technology to produce the solid aluminum profiles with large-size, flat-wide, and thin-walled structures. Currently, lit     

大口径弯头挤压弯曲成形数值模拟分析

对挤压弯曲成形大口径弯头的变形过程进行了有限元模拟分析.对压扁工序和弯头成形工序分别进行建模和模拟,并对模拟结果进行了应力、应变分析和成形过程载荷分析.对影响弯头成形的关键区域--内弧和外弧区域进行了速度场分析.将模拟成形后的弯头与工厂实际生产的弯头相对比,成形情况良好.     

Axi-symmetric tube extrusion through a flat-faced circular die: Numerical construction of slip-line fields and associated velocity fields

A numerical method of construction of axi-symmetric slip-line fields and their associated velocity fields [13–15] is applied to investigate the problem of axi-symmetric tube extrusion through smooth and rough flat-faced circular dies and the salient results presented in a computographic manner. A reasonably satisfactory agreement was observed between the estimated values of the non-dimensionalised specific extrusion pressures in each case when these were compared with the analytical and experimental work of Kudo [6] and that carried out by the authors. The deficiency in the technique used, the difficulties encountered and also some specific errors noticed during the construction of the fields, are highlighted and the results commented upon.