Die Profile Radius Research Articles

Investigation on the Crack and Thinning Behavior of Aluminum Alloy 5052 Sheet in Stretch Flanging Process

Stretch flanging is the important sheet metal-forming process which is widely used in automobile and aerospace sectors. The formability of sheet metal depends on various parameters such as material properties, geometry of the tool setup and process parameters. In the present work, effects of different die radius and sheet width on deformation behavior of sheet are studied by FEM simulation and experiments. The predicted FEM results are presented in the form of edge crack location and its propagation, crack length, forming load and strain distribution in sheet along the die profile radius. This study indicates that crack length increases with increase in the sheet width, while the crack length decreases with increase in the die radius. It is found that the crack propagation in stretch flanging process is affected by the strain distribution in sheet and this distribution of strain depends on many parameters. The crack initiates during deformation of the sheet at the die corner edge and propagates toward the center of the sheet along the die profile radius. Simulation results are compared with the experimental one in terms of crack length and variation in sheet thickness. FE simulation results are found in very good agreement with experimental results. Fractography study is also presented in terms of size, shape of the dimples along with their distribution on the fractured surface.

Finite element analysis of extrusion process using aluminum alloy

A coupled thermal-mechanical finite element analysis of axisymmetric direct extrusion process using aluminum alloy has been carried out using commercial software package ABAQUS (Standard). Effect of process parameters such as coefficient of friction, die angle and die profile radius on maximum nodal temperature, maximum contact pressure, deformation homogeneity are investigated in this paper. Heat generation due to plastic deformation and frictional heat generated between interacting surfaces of die and billet are considered in the analysis. It is found that coefficient of friction has significant effect on maximum nodal temperature while little influence on deformation homogeneity. It is also gathered that die angle has a considerable effect on deformation and on contact extrusion pressure. Besides, this it is also found that die profile radius has an appreciable influence on contact extrusion pressure. This study helps in selection of appropriate process parameters for proper designing of direct extrusion process.

Analysis of the effects of tool and process parameters in hydrodynamic deep drawing assisted by radial pressure

Among the various techniques of sheet hydroforming, hydrodynamic deep drawing assisted by radial pressure (HDDRP) has showed good results to shape parts with uniform thickness distribution and high drawing ratio. In this paper, improving formability of the parts in HDDRP is taken into consideration and the effects of some geometrical parameters such as the die profile radius and the gap between the die and the blank holder, and some process parameters such as pressure path and friction coefficient are investigated on thickness distribution of cylindrical cups and punch force. The pressure path has a great effect on the formability. The results showed that increasing the maximum pressure reduces part thinning in the critical regions. Increasing the pressure above a certain value does not have a significant effect on the part forming, but it increases the punch force. The most appropriate pressure path for forming the part studied in this paper is 27 MPa. Furthermore, thinning of the part and maximum punch force decreases by decreasing the friction between the sheet and blank holder. Moreover, increasing the friction coefficient between the punch and sheet to a certain value (0.2) improves forming condition that results in decreasing thinning of the part. Increasing the friction coefficient more than this value does not have a significant effect on forming the part. Friction between the punch and the sheet does not affect the maximum punch force. The results also illustrated that by increasing the gap between the blank holder and the die to 1.2 mm which is more than the thickness of the sheet, thickness reduction of the part and maximum punch force decreases. Increasing the gap above this value does not have a significant effect on ease of sheet flow and improving part formability.

A study on spring-back in U-draw bending of DP350 high-strength steel sheets based on combined isotropic and kinematic hardening laws

In this article, a numerical model for predicting spring-back in U-draw bending of DP350 high-strength steel sheet was presented. First, the hardening models were formulated based on combined isotropic–kinematic hardening laws, along with the traditional pure isotropic and kinematic hardening laws. A simplified method was proposed for determining the material parameters. Comparison of stress–strain curves of uniaxial tests at various pre-strains predicted by the numerical models and experiment showed that the combined isotropic–kinematic hardening model could accurately describe the Bauschinger effect and transient behavior subjected to cyclic loading conditions. Then, a finite element model was created to simulate the U-draw bending process using ABAQUS. Simulations were then conducted to predict the spring-back of DP350 high-strength steel in U-draw bending with geometry provided in the NUMISHEET’2011 benchmark problems. It was shown that the predictions of spring-back using the proposed model were in good agreement with the experimental results available in the literature. Finally, the effects of various tool and process parameters such as punch profile radius, die profile radius, blank holding force, and punch-to-die clearance on the spring-back were investigated. The simulation results suggested the significance of tool and process parameters on the final shape of the formed parts influenced by the spring-back.

Experimental Evaluation and Finite Element Simulation to Produce Square Cup by Deep Drawing Process

Deep drawing process to produce square cup is very complex process due to a lot of process parameters which control on this process, therefore associated with it many of defects such as earing, wrinkling and fracture. Study of the effect of some process parameters to determine the values of these parameters which give the best result, the distributions for the thickness and depths of the cup were used to estimate the effect of the parameters on the cup numerically, in addition to experimental verification just to the conditions which give the best numerical predictions in order to reduce the time, efforts and costs for producing square cup with less defects experimentally is the aim of this study. The numerical analysis is used to study the effect of some parameters such as die profile radius, radial clearance between die and punch, blank diameter on the length and thickness distributions on the cup, dynamic-explicit (ANSYS11) code based on finite element method is utilized to simulate the square deep drawing operation. Experiments were done for comparison and verification the numerical predictions. effective square cup with less defects and acceptable thickness distributions were produced in this study. It is concluded the most thinning appear in the corner cup due to excessive stretching occur in this region and also it is found the cup thickness and height prediction by numerical analysis and in general in harmony with experimental analysis.

Experimental Evaluation and Finite Element Simulation to Produce Square Cup by Deep Drawing Process

Deep drawing process to produce square cup is very complex process due to a lot of process parameters which control on this process, therefore associated with it many of defects such as earing, wrinkling and fracture. Study of the effect of some process parameters to determine the values of these parameters which give the best result, the distributions for the thickness and depths of the cup were used to estimate the effect of the parameters on the cup numerically, in addition to experimental verification just to the conditions which give the best numerical predictions in order to reduce the time, efforts and costs for producing square cup with less defects experimentally is the aim of this study. The numerical analysis is used to study the effect of some parameters such as die profile radius, radial clearance between die and punch, blank diameter on the length and thickness distributions on the cup, dynamic-explicit (ANSYS11) code based on finite element method is utilized to simulate the square deep drawing operation. Experiments were done for comparison and verification the numerical predictions. effective square cup with less defects and acceptable thickness distributions were produced in this study. It is concluded the most thinning appear in the corner cup due to excessive stretching occur in this region and also it is found the cup thickness and height prediction by numerical analysis and in general in harmony with experimental analysis.

Experimental Evaluation and Finite Element Simulation to Produce Square Cup by Deep Drawing Process

Deep drawing process to produce square cup is very complex process due to a lot of process parameters which control on this process, therefore associated with it many of defects such as earing, wrinkling and fracture. Study of the effect of some process parameters to determine the values of these parameters which give the best result, the distributions for the thickness and depths of the cup were used to estimate the effect of the parameters on the cup numerically, in addition to experimental verification just to the conditions which give the best numerical predictions in order to reduce the time, efforts and costs for producing square cup with less defects experimentally is the aim of this study. The numerical analysis is used to study the effect of some parameters such as die profile radius, radial clearance between die and punch, blank diameter on the length and thickness distributions on the cup, dynamic-explicit (ANSYS11) code based on finite element method is utilized to simulate the square deep drawing operation. Experiments were done for comparison and verification the numerical predictions. effective square cup with less defects and acceptable thickness distributions were produced in this study. It is concluded the most thinning appear in the corner cup due to excessive stretching occur in this region and also it is found the cup thickness and height prediction by numerical analysis and in general in harmony with experimental analysis.

Deep drawing mechanism, parameters, defects and recent results: state of the art

Deep drawing is a sheet metal forming process which is widely used in manufacturing parts for automobile and air craft industries. In this paper, the mechanism of deformation, effect of the geometrical parameters involved and the defects encountered in the process are presented and discussed. These include: the radial clearance percentage, punch and die profile radii. Despite the number of publications on the subject, there is still a great demand for further research. Recent experimental investigation on the effect of radial clearance percentage, punch and die profile radii on their autographic records (punch load- punch displacement curves) and on quality of the produced blanks is carried out and the results are presented and discussed. It was found that the maximum drawing force decreases with increase of the die profile radius and increases by increase of the punch profile radius. Furthermore, the liability of the produced cups to wrinkle increases by the increase of both punch and die profile radii being more influenced by the die profile radius.

Drawing of Hexagonal Cup

The main aim of this work is to produce hexagonal cup drawn from flat sheet (blank Ø80) and effect of wall corner radii of die on drawing process. The dimension of diagonal and side hexagonal cup are (41,36mm) and (36 mm) respectively, and (0.7mm) thickness made from low carbon steel (1006–AISI), has been produced. A commercially available finite element program code (ANSYS11.0), was used to perform the numerical simulation of drawing operation. Two types of wall corner radii of die ( =0.7, 4 mm) with constant punch profile radius equal to ( =4) mm and die profile radius equal to ( =8 mm (were used to investigate the effect of die corner radius on punch force, variation of cup wall thickness and the strain distribution over the cup wall. The numerical results of this model were compared with experimental results and the results show that, the greatest thinning occurs when used wall corner radius of die equal to ( = 0.7mm) due to great stretching of the metal over the corner radius. The best strain and thickness distribution over all zones in produced cup obtained when using wall corner radius of die is equal to = 4 mm).

Punchless Drawing of Magnesium Alloy Sheet Under Cold Condition and its Computation

Shallow cup drawing of magnesium alloy AZ31-O sheet was performed under cold condition using the Maslennikov’s technique. A deformable rubber pad was used, instead of the “hard” punch, in this technique. A small die profile radius was adopted, which was twice or four-times the sheet thickness. A semisolid lubricant was used for lubrication of the blank-die interface. On the other hand, the rubber-blank interface was degreased to increase friction. A limiting drawing ratio of 1.31 was obtained in the circular cup drawing. A peculiar fracture mode appeared in which the material suddenly fractured with the crack evolution emanating from the flange periphery. In the square cup drawing, an adequate blank shape was found to be circular compared with the other ones. Numerical simulation was also conducted using dynamic explicit finite element method. Adequate setting including speed scaling enabled us to predict the accurate deformation pattern and the forming force.

The Influence of the Blank Holder Force during Forming Process of a U-Shaped Part Made from AZ31 Magnesium Alloy

In case of sheet metal forming the main dimensional errors are caused by the springback phenomena. The present work deals with numerical simulation related to draw bending and springback of U - shaped part made from magnesium alloy. The current paper is trying to prove out the important role of the blank holder force with respect to the forming process. Though novel approaches relating to the formality of magnesium alloy sheets, the change of springback due to the characteristic of each process should be verified by finite element method. Springback refers to the elastic recovery of deformed parts. Springback occurs because of the elastic relief from the bending moment imparted to the sheet metal during forming. Springback is mainly influenced by the sheet thickness, the punch and die profile radii, initial clearance between punch and die, friction conditions, rolling direction of the materials, blankholder force and by material properties. In this study, the magnesium alloy strips with two types of material having the thickness of 1mm, are used to investigate springback characteristics in U-shape bending. The Dynaform 5.6 software was used to simulate the forming process, in which the blank holder force takes values between 15 and 35 kN. In this study, the springback was analyzed by U-forming at room temperature conditions with different blank holder forces. Springback decreased with the increase of the blank holding force. Excessive holding force cause irregular thinning of the material, especially in the radius area.

Fracture Prediction for Ultralow Carbon Steel Sheet Subjected to Draw-Bending Using Forming Limit Stress Criterion

A fracture criterion for sheet metals subjected to draw-bending is investigated using the concept of forming limit stress criterion. The test material used is a 1.0-mm-thick ultralow carbon steel sheet. Draw-bending experiment of a wide specimen is performed for a die profile radius of 4mm. A specimen undergoes bending-unbending under tension when passing over the die profile radius. The drawing speed was set to 5mm/s. The magnitude of true stress when a specimen fractured has been precisely determined from the measured data of a drawing force and the cross sectional area of the draw-bent specimen after fracture. Moreover, multiaxial tube expansion tests of the test material are performed to measure the forming limit stress of the test material under plane strain tension. It is found that the is larger than by approximately 10 %. Therefore, it is concluded that the forming limit stress criterion is effective as a fracture criterion for a mild steel sheet subjected to draw-bending.

Prediction of crack location and propagation in stretch flanging process of aluminum alloy AA-5052 sheet using FEM simulation

The stretch flanging process is significantly affected by various geometrical, material and process parameters. The punch-die clearance and initial flange length are main parameters which have major effects on the edge crack location and strain distribution along die profile radius in the flange. Non-axisymmetric stretch flanging process of AA-5052 sheet metal blanks was carried out by numerical simulation to predict the deformation behavior of flange, location and propagation of crack in flange and to investigate the effect of punch die clearance, flange length, die and punch profile radius and friction in the stretch flanging process. The experimental investigations were made to validate the simulations results. The results reveal that the crack length increases with the increase in the flange length. It is found that the flange length has a significant effect in circumferential direction as compared with the radial direction. The punch die clearance has the most significant effect in crack propagation in comparison with flange length. The circumferential strain is found to be larger in the case of punch having the profile radius less than the die profile radius, which leads to faster edge crack propagation. A close agreement is found between simulation and experimental results in terms of location of edge crack and forming load.

Investigation of the Effects of Pressure Path and Tool Parameters in Hydrodynamic Deep Drawing

In recent years, hydroforming process has been applied in different industries such as aerospace, automotive and military industries due to its advantages, such as high dimensional accuracy, capability of forming complicated parts and high drawing ratio. Hydrodynamic deep drawing with radial pressure is one type of hydroforming process. In this paper, forming of cylindrical cups in hydrodynamic deep drawing with radial pressure is numerically and experimentally investigated and the effects of significant parameters such as pressure path, punch corner radius and die profile radius on the cup thickness distribution and punch force were studied. The results obtained showed that increasing the pressure affects the thickness reduction in critical regions of cup and from the certain pressure, the pressure does not have a significant effect on the thickness of part. On the other hand, increasing the pressure, increases the force needed for forming the cup. Also, it was found that by increasing the punch corner radius, the cup thickness will be more uniform and maximum punch force does not change. Results of studying the effect of die profile radius on thickness distribution and punch force showed that increasing the die profile radius has a positive effect on the cup thickness distribution and the force needed to form part.

Blanking and piercing theory, applications and recent experimental results

Blanking and piercing are manufacturing processes by which certain geometrical shapes are sheared off a sheet metal. If the sheared off part is the one required, the processes referred to as blanking and if the remaining part in the sheet is the one required, the process is referred to as piercing. In this paper, the theory and practice of these processes are reviewed and discussed The main parameters affecting these processes are presented and discussed. These include: the radial clearance percentage, punch and die geometrical parameters, for example punch and die profile radii. The abovementioned parameters on the force and energy required to effect blanking together with their effect on the quality of the products are also presented and discussed. Recent experimental results together with photomacrographs and photomicrographs are also included and discussed. Finally, the effect of punch and die wear on the quality of the blanks is alsogiven and discussed.

Finite Element Analysis of Non-axisymmetric Stretch Flanging Process for Prediction of Location of Failure

Stretch flanging is an important sheet metal forming process which is applied in automotive industry. In this paper, finite element simulation of stretch flanging process of AA 5052 has been carried out. It is found that both punch-die clearance and initial flange length has great effect on strain distribution and edge cracking along die profile radius. A good agreement has been obtained between results of simulation and experimental results, in terms of edge crack, punch load and punch stroke. From this investigation, finite element simulation is found to be quite useful in predicting deformation behavior of stretch flange quite efficiently.

Circular Cup Drawing of Magnesium Alloy Sheet under Cold Condition Using Rubber Tool and Improvement of Surface Appearance

In order to accomplish the circular cup drawing of the sheet material whose ductility is extremely poor under the cold forming condition, the Maslennikov's technique was applied. A deformable rubber ring was used instead of the hard punch. Test material was magnesium alloy AZ31-O sheet. Small die profile radius was applied, which was twice or 4 times of the sheet thickness. A semisolid lubricant was used for the lubrication of the blank - die interface, on the other hand, the rubber - blank interface was degreased to increase friction. The limiting drawing ratio of 1.31 was attained. A peculiar fracture mode arises, where the material suddenly fractured with crack evolution emanating from the flange periphery. The fracture strain is found approximately equal to the work hardening exponent n-value in plastic property. Another kind of crack arose in the circumferential direction of the cup during unbending process with smaller die profile radius. To decrease the scratched lines of the cup surface caused by very high sliding contact pressure to the die, high-speed drawing was tested using a drop-weight. The surface was improved, because the material - tool contact was successfully prevented by the hydrodynamic lubrication film.

A study on high ratio cup drawing by Maslennikov’s process

Deep drawing of sheet metals using Maslennikov’s technique has been analyzed by analytical and finite element simulation approaches. A new friction model based on local contact conditions has been used in the finite element (FE) simulations of the process. Compared to traditional Coulomb friction model, the results of FE simulations with the new friction model show good correlation with analytical calculations. The effects of key process parameters such as rubber ring thickness, ring inner diameter, die hole diameter, and die profile radius on the results have been investigated. The results showed that very deep cups without thinning in the side wall portion can be achieved with this process. Based on the results of FE analysis, it was found that the maximum drawing ratio can be achieved by adopting a combination of process parameters which correspond to points nearest to the fracture limit.

Blank Optimization in Elliptical-Shape Sheet Metal Forming Using Response Surface Model Coupled with Reduced Basis Technique and Finite Element Analysis

The present study aims to determine the optimum blank shape design for the deep drawing of Elliptical-shape cups with a uniform trimming allowance at the flange i.e. cups without ears. This earing defect is caused by planar anisotropy in the sheet and the friction between the blank and punch/die. In this research, a new method for optimum blank shape design using finite element analysis has been proposed. Present study describes the approach of applying Response Surface Methodology (RSM) with Reduced Basis Technique (RBT) to assist engineers in the blank optimization in sheet metal forming. The primary objective of the method is to reduce the enormous number of design variables required to define the blank shape. RBT is a weighted combination of several basis shapes. The aim of the method is to find the best combination using the weights for each blank shape as the design variables. A multi-level design process is developed to find suitable basis shapes or trial shapes at each level that can be used in the reduced basis technique. Each level is treated as a separated optimization problem until the required objective – minimum earing function – is achieved. The experimental design of RSM method is used to build the approximation model and to perform optimization. MATLAB software has been used for building RSM model. Explicit non-linear finite element (FE) Code Abaqus/CAE is used to simulate the deep drawing process. FE models are constructed incorporating the exact physical conditions of the process such as tooling design like die profile radius, punch corner radius, etc., material used, coefficient of friction, punch speed and blank holder force. The material used for the analysis is Stainless steel St12. A quantitative earing function is defined to measure the amount of earing and to compare the deformed shape and target shape set for each stage of the analysis. The cycle is repeated until the converged results are achieved. This iterative design process leads to optimal blank shape. So through the investigation the proposed method of optimal blank design is found to be very effective in the deep drawing process and can be further applied to other stamping applications.

Investigation of draw-trimming springback of laser tailor-welded blanks

By the numerical simulation and experiments,the process analysis of draw-bending and draw-trimming of the tailor-welded blanks (TWBs) with the thickness ratio 1.2 mm/0.8 mm are made,in which the effect of the blank holder force (BHF), friction factor and die profile radius,etc.on the springback are mainly investigated.The TWBs' springhack angle in the corner of punch and die,the total springhack angle and the sidewall curvature are surveyed in draw-bending and draw-trimming.And the welded line movement,the stress distribution in TWBs forming and their interact relationship are analyzed.The TWBs' springback in draw-bending and draw-trimming are badly influenced by the BHF,friction factor,die profile radius etc.,in which the BHF is the key factor;there is an intimate relationship between TWBs' draw-bending springback/draw-trimming springhack and welded-line movement,by which it will be advantageous to reduce the TWBs' springback through controlling the welded-line movement.In comparison,the TWBs' draw-trimming springhack is smaller than the TWBs' draw-bending springback,so it is better to use draw-trimming process for controlling TWBs' springback and improving the shape precision of TWBs' forming.