Effective Strain Distribution Research Articles

A Study of Preform Design on Backward Extrusion for Improved Hardness Distribution

In this paper, the finite element method is used to investigate the effect of preform shapes on the strain hardening distribution in the wall of the extruded cup of backward extrusion. A series of simulations on the backward extrusion with three different preform shapes (flat, concave and convex) and without preform using the FEM program DEFORM 2D was carried out, respectively. The influence of preform shapes on the effective strain distribution in the extruded wall was examined. A hardness vs. effective strain curve for an annealed AL6061 Aluminum was first obtained using a simple forging test in conjunction with FE simulations, then the curve was used to convert the effective strain distribution into the hardness distribution in the extruded wall. The results of FEM calculations reveal that the concave shape preform has the best effect on the hardness strengthening at the extruded wall of backward extrusion.

Finite Element Analysis of Rim Ring Rolling Forming of Bicycle Aluminum Alloy

The bicycle is not only a pollution-free method of transportation, but also has sport and recreation functions. Therefore, the bicycle attracted attention in now society gradually. This study uses the rigid-plastic finite element (FE) DEFORMTM software to investigate the plastic deformation behavior of a 7075 aluminum alloy workpiece as it is formed through a ring rolling die. This study systematically investigates the relative influences of ring rolling velocity, entering velocity, and workpiece temperature under various ring rolling forming conditions. The effective strain, effective stress, and workpiece damage distribution in the ring rolling process are also investigated. Results confirm the suitability of the proposed design process, which allows a ring rolling manufacturer to achieve a perfect design during finite element analysis.

A novel technique to increase strain distribution homogeneity for ECAPed materials

Abstract Equal channel angular pressing as a material processing technique imposes high but in-homogeneous strain at the cross-section of the workpiece. In this research, cylindrical shaped commercial pure aluminum undergoes ECAP process up to four passes by route A using the conventional and covered tube casing (CTC) methods. The influence of CTC on strain distribution in the region of uniform longitudinal strain field was investigated experimentally and numerically. The Vickers hardness measurement at the cross-section of the aluminum samples indicated that there is more uniformity in the deformation during a single-pass ECAP in the CTC method compared with the conventional method and matched the simulated effective strain distributions. Moreover, based on volume fraction rule, an analysis has been developed to predict the required pressing force for CTC method.

Feed Speed Design and Optimization in Radial-Axial Ring Rolling Process by FEM

Radial-axial ring rolling is an important component of advanced manufacturing technology, but it has characteristics of high nonlinear on geometry and physics, so the radial-axial ring rolling process becomes very complex. In addition, the feeding mode of core roller has enormous influence on the quality of the rolled ring as well as the stability of the process. In this paper, a 3D rigid-plastic FE model of radial-axial ring rolling process is established, then three kinds of feed speed design ((1)constant of feed speed; (2)constant of feed in one rotary; (3)variation of feed speed)are offered. The difference of outer radius growth velocity, distribution of effective strain and temperature, rolling force, size of ring are analysised for the three kinds of feed methods. And, an optimized feed method is proposed base on analytic results, the optimized feed method can improve the quality of formed ring, and decrease the requirement of ring rolling mill.

Numerical Simulation and Analysis on Bending Forming of Hull Plate

Bending process is one of the important methods to form thick hull plate, whose accuracy is directly related to the quality of hull plate forming.In this paper, bending process of thick hull plate is simulated by using finite element software ANSYS, and some simulation results on bending deformation of thick hull plate such as the deformation of meshes in deformation zone, the distributions of the Von Mises stress and effective strain are obtained.

Three-Dimensional Numerical Simulation and Experimental Study of Severe Plastic Deformation of AZ31 Magnesium Alloy

Grain size refinement by using equal channel angular Extrusion (ECAE) is an effective way to improve workability and strength of the magnesium alloys. Round workpieces of ECAE processes for AZ31 magnesium alloy are investigated by using numerical simulations and experimental studies in this paper. The processing of ECAE is simulated in order to study the influence of the processing on the deformation behavior of the workpiece and extruding load. The variation trends of the effective strain distributions in the workpiece are changed little for different cross-section. Punch load for extrusion is the major factor to be considered while designing a sound ECAE die. The deformation mechanism of ECAE for grain refinement is obtained. In addition, the experimental finally workpieces shapes and extruding load results are also consistent with FE analysis results.

Numerical Simulation of Cold Press Forging Forming for Stepped Hole of Thin Sheet Metal

An optimum process for a two-step press forging of stepped holes in a metal sheet was proposed .Numerical simulation on the two-step process was carried out by using DEFORM-3D. Distributions of effective strain and effective stress were obtained. The study showed that the process not only can form the stepped, but also can increase the surface quality and strength of stepped holes in sheet metal parts, According to the numerical simulation’s process parameter , an experimental die was designed, the simulation results were in good agreement with the experimental data

Novel Plasticity Integration Algorithm in Improved Inverse Analysis Method and its Verification in Clover-Shaped Cup Drawing

An improved inverse analysis method is developed based on the final workpiece in Euler coordinate system. The drawbeads and the radius of the die introduce a complex bending-unbending loading history as the material passes through these regions. Unlike the widespread inverse analysis using deformation theory of plasticity, in order to consider loading history, the improved inverse analysis method uses the constitutive equation based on flow theory of plasticity. In order to avoid numerous iterations to ensure the numerical stability in Newton-Raphson scheme to obtain plastic multiplier , a novel plastic integration algorithm is proposed to consider bending–unbending effects. A clover-shaped cup drawing example is numerically simulated with the inverse analysis method based on deformation theory of plasticity and the improved one based on flow theory of plasticity. These simulated results are compared with those of the incremental forward finite element solver LS-DYNA simultaneously. The comparisons of blank configurations and the effective strain distribution show that the proposed plasticity integration algorithm is effective and reliable.

Investigation of Precision Forging Process of Spur Gears: Numerical Analysis and Experiments

In this study, the precision forging process of spur gears has been investigated by means of numerical analysis. The effect of some parameters such as teeth number and module on the forming force and specific pressure were presented. The simulation works were performed rigid-plastic finite element method using DEFORM 3D software. In order to validate the estimated numerical results, they were compared with those obtained experimentally during precision forging of spur gear using lead as a model material. Results showed that the optimum number of gear teeth is between 10 to 20, that is because of being the specific pressure in its minimum value. Also the results obtained from analyzing the effective strain distribution showed that the maximum strain is located on the root area of the teeth. The work presented in this paper might be used for basic data in the design of the precision forging process.

Experimental investigation of bond characteristics between CFRP fabrics and steel plate joints under impact tensile loads

In recent years, the use of adhesively-bonded fibre-reinforced composite materials has attracted widespread attention as a viable alternative for the retrofitting of civil infrastructure such as buildings and bridges. This has been particularly the case for concrete structures. The retrofitting of metallic bridges and buildings with FRP materials, however, is still in its early stages. In real life, these structures are subjected to dynamic loads. Therefore, it is necessary to understand the bond behaviour between steel and the strengthening materials for both static and dynamic loads. To examine the bond between steel plates and carbon fibre-reinforced polymers (CFRP) fabrics, this paper describes the experimental procedures and results of double strap steel joints loaded at different loading rates (2 mm/min, 3.35, 4.43 and 5 m/s). In this test program, ultimate load-carrying capacity, effective bond length, failure mechanism and strain distribution were examined for all loading rates. Different numbers of CFRP layers with different bond lengths were investigated. Experimental findings reveal that the maximum improvement in joint capacity occurs at a rate of 3.35 m/s. It was observed that the effective bond length is insensitive to loading rate for both joints. The failure modes and strain distributions, however, exhibit little difference between static and dynamic conditions.

Using finite element modeling to examine the flow processes in quasi-constrained high-pressure torsion

Finite element modeling was used to examine the flow processes in high-pressure torsion (HPT) when using quasi-constrained conditions where disks are contained within depressions on the inner surfaces of the upper and lower anvils. Separate simulations were performed using applied pressures from 0.5 to 2.0 GPa, rotations up to 1.5 turns and friction coefficients from 0 to 1.0 outside of the depressions. The simulations demonstrate the distribution of effective strain within the depressions is comparable to the prediction by ideal torsion, and the applied pressure and the friction coefficient outside the depressions play only a minor role in the distribution of effective strain. The mean stresses during processing vary linearly with the distance from the center of the disk such that there are higher compressive stresses in the disk centers and lower stresses at the edges. The torque required for rotation of the anvil is strongly dependent upon the friction coefficient between the sample and the anvil outside the depressions.

Deformation Behavior and Microstructure Characterization of AZ31 Processed by Equal Channel Angular Extrusion: Effect of Extrusion Temperature

In this paper, influence of temperature on warm temperature equal channel angular of AZ31 alloy was investigated by using numerical simulation and experimental investigation. The effective stress distribution rules and load-stroke curves viartions were obtained at different temperature. And the distribution of effective strain and the rules of deformation uniformity of three temperatures extrusion processing for round workpiece are obtained. The proper temperatures extrusion processing is acquired through comparing the results of three extrusion routes. The effect of the temperature on the accelerated grain refining during the ECAE operation was discussed in the numerical calculations with a view to the use of the process to bulk AZ31 alloys. On the basis of the simulations, the warm ECAE experiments are carried out. The geometries of finally pressed workpieces of the different temperature pressed samples are in good agreement with finite element analysis results．

Simulation and experimental investigation of FSP of AZ91 magnesium alloy

A thermo-mechanical simulation of the friction stir processing (FSP), using the DEFORM 3D software based on Lagrangian implicit, was developed and verified by the experimental results. Simulation can successfully predict the temperature and effective strain distributions. Material flow around the tool pin was examined using the point tracking. It was found that the major part of material flow occurs at the advancing side, and consequently, stirred zone (SZ) stretches toward the advancing side. However, material at the retreating side moves slightly in backward direction. The material deformation and the peak temperature influence on the microstructural characters and can determine the width of SZ. Based on the simulation, effective strain and temperature histories of material around the tool pin were also calculated. The amount of effective strain and peak temperature required for recrystallization at the advancing and retreating sides as well as at the bottom of SZ was determined. Therefore, the width of SZ can be predicted by the simulation.

Study on Cross Section Geometry of Preform for the Forming Laws of a Symmetrical Rib-Web Component

In order to reveal the forming laws，eliminate the forming defects appearing in the typical aluminum alloy web-rib parts，two types of preforms have been used in the final forging with numerical simulation software.Based on the simulation，the comparisons of metal flow，effective strain distribution are obtained between the two types of preforms applied in the final forging process，the forming laws of a symmetrical rib-web component have been obtained ,and the forming mechanism of defects often happened in web- rib parts also has been analyzed,the relationship between the fillet radius and metal flow velocity/ final load was obtain. The results show that the fiber breaking,vortex could be avoided，a high forming quality of rib-web part could be gained by the method of using the thin web-high rib preform in finish-forging.

Numerical and Experimental Studies of Splines Produced by Injection Forging Process

This article presents numerical and experimental study of spline production with an injection forging process, in terms of load requirement and material flow. A three-dimensional finite element model has been developed to analyze the effect of initial billet diameter, number of spline teeth, and die corner radius on the required forging load, pattern of material flow, and effective strain distribution. For this purpose, the finite element-based DEFORM-3D software has been used. Also, a series of experimental tests has been carried out using solid commercial lead billets with two different billet diameters and three different die cavities (two, three, and six teeth). The results obtained using the numerical solutions were compared with the experimental data for each case study and good agreement was observed. Both the simulation and experimental results highlight the major role of the above-mentioned parameters on the required forming load and material flow pattern. It has been shown that the initial billet diameter and the number of spline teeth have significant effects on the forming load. Although, the die corner radius has little effect on the required forming load, it is an important factor in forming the material flow pattern and strain distribution.

Simulation of large forging flat-anvil stretching process and its optimization

In this paper, a kind of mathematic method for optimizing stretching process of large forgings is proposed. Distributions of effective strain within forged ingots is described by a Gauss function, which is obtained from the simulation of flat-anvil stretching process. Successive stretching is expressed by the superimposing Gauss functions. Optimized stretching process, with both homogeneous and certain strain in the center of forgings, is presented by derivation of this function. The relationship between effective strain and the values of feed is obtained during the successive stretching with a rotation angle of 90° and a feed displacement of 1/2 anvil width. The optimization result is verified by finite element simulation. Optimized value of feed obtained using this method can ensure both uniformity and forging penetration. It provides mathematic model and theoretic basis of optimizing large forging stretching process.

Investigation of dynamic effects during cold upset-forging of sintered aluminium truncated conical preforms

The present paper deals with the upper bound analysis, experimental investigation and computer simulation of upset-forging of sintered aluminium truncated conical preforms, which considers heterogeneous deformation due to barreling of preform slant sides, composite die–workpiece interfacial friction conditions, preform densification along with compression and inertia effects. A generalized theoretical expression for average forging load and preform bulged profile based on the exponential velocity field and strain rate has been established. The upset-forging experiments were conducted using the sintered preforms prepared by compacting aluminium metal powder in the closed dies and various deformation characteristics were measured. Finally, the computer simulation of the upset-forging of the sintered aluminium truncated conical preforms was performed using DEFORM software and the deformation behavior velocity, effective strain and effective stress distribution were critically studied. The effect of die speed, i.e. dynamic effects on average die load has been investigated using energy and load factors. The DOE (Design of Experiment) and RSM (Response Surface Methodology) techniques were also used to investigate and determine interrelationships between important upset-forging characteristics and the results were presented graphically. During the present investigations, it was found that inertia energy dissipation and energy factor increases, where as die load and load factor decreases exponentially with die speed. It is expected that the present work will be useful for effective assessment of various deformation characteristics during processing of sintered materials, especially at high-speed.

Numerical and Experimental Investigation of Strain Inhomogeneity during Cyclic Channel Die Compression

Severe plastic deformation (SPD) can refine conventional coarse-grained materials to submicrometer or even nanometer level. In this paper, effective strain distribution was simulated by rigid-plastic finite element method (FEM) after multi-pass cyclic channel die compression (CCDC) by two different processing routes, and the Vickers microhardness was examined to verify the deformation distribution. The results show that large strain can be accumulated in the material by CCDC. The deformation distribution is non-uniform. Apart from the edges or corners of the specimen, the effective strain is higher in the central region and lower at the surrounding region. The effective strain gradient increases with the number of compression. The microhardness distribution features of two routes are in agreement with the simulation results of strain distribution. The microhardness increases globally with the number of compression and its distribution is inhomogeneous at the small and medium strain stage. But with the increasing of strain, the microhardness homogeneity is improved.

Chip morphology of normalized steel when machining in different atmospheres with ceramic composite tool

Dry cutting tests in air and nitrogen atmospheres with a ceramic cutting tool were carried out on normalized AISI 1045 steel. SEM and EDX techniques are employed to observe the chip morphology and tribological mechanisms are simultaneously discussed. The finite element model of chip formation was created to determine the effective stress and strain distributions in the chip and workpiece. Compared in nitrogen, the friction coefficient in air was reduced when the cutting speed is at 160 m/min and the feed rate is 0.1 mm/r. Experimental data and observation revealed the formation of a lubricating film at the tool–chip interface, which related to the difference chip morphology in air and nitrogen.

Influence of ECAR Processing on OFHC Cu Material Properties

The influence of severe plastic deformation (SPD) on distribution of effective stresses, effective strains and temperatures during equal channel angular rolling (ECAR) process is mathematically simulated. Effect of ECAR processing on substructural and mechanical properties of oxygen free high conductivity (OFHC) Cu material is investigated too. Mathematical simulations in software DEFORM-3D, ECAR technology, tensile tests, EBSD analysis were used as experimental methods. Mathematical simulations of first ECAR pass referred on following results: effective normal stress had low heterogeneity with value 385 MPa, effective strain was distinguished with high heterogeneity in cross section of sample (φ=1,5-3) and temperature in deformation zone achieved value 150 °C. Mechanical properties after cold drawing were: Rp0,2 = 217 MPa, Rm = 260 MPa, Z = 63 % and after sixth ECAR pass were: Rp0,2 = 412 MPa, Rm = 426 MPa, Z = 72 %. From experiments is resulting the stabilization of mechanical properties after fourth ECAR pass were obtained.