Punch Corner Radius Research Articles

A Study on Yield Criteria Influence on Anisotropic Behavior and Fracture Prediction in Deep Drawing SECC Steel Cylindrical Cups.

The deep drawing process, a pivotal technique in sheet metal forming, frequently encounters challenges such as anisotropy-induced defects. This study comprehensively investigates the influence of various yield criteria on the anisotropic behavior and fracture prediction in SECC steel cylindrical cups. It integrates Hill'48R, Hill'48S, and von Mises yield criteria in conjunction with Swift's hardening law to evaluate material behavior under complex stress states. Experimental and numerical simulations assess the anisotropy effects across multiple orientations (0°, 45°, and 90°), revealing intricate relationships between stress criteria and material response. The findings indicate significant discrepancies between isotropic and anisotropic models in predicting fracture heights, emphasizing the importance of selecting appropriate yield criteria. Notably, the von Mises criterion results in lower fracture heights, suggesting higher susceptibility to fractures, while the Hill'48R model aligns closely with experimental data, validated through variations in punch corner radius and blank holder force parameters, with a maximum deviation of 3.23%. Hill'48S displays moderate plastic deformation characteristics.

Determination of optimum process parameters for minimum punch force in deep drawing using numerical simulation

This article represents the most common sheet formation method, deep drawing. This technology is employed in the production of the automotive and aerospace industries. There are various aspects that have an impact on the deep drawing process; these factors are known as the deep drawing process parameters. Finite element analysis and Taguchi Techniques are coupled to find out the optimum deep drawing parameters. Six process parameters such as die corner radius, punch corner radius, punch speed, friction between blank and die, friction between blank and blank holder and friction between blank and punch are used for analysis. Punch force is considered as response variable. The Taguchi method is employed to determine the optimal process parameters for the deep drawing process. Based on SN ratio analysis, optimum deep drawing parameters for punch force were found to be die corner radius of 7mm, punch corner radius of 7mm, punch speed of 0.2mm/s, friction between blank and die of 0.08, friction between blank and blank holder of 0.08 and friction between blank and punch of 0.10. From ANOVO, it was found that die corner radius was the most significant process parameter influencing minimum punch force.

Experimental and Numerical Investigation on the Square Hole Hydro-Piercing Process

The hydro-piercing process is an emerging approach to the direct punching of holes on complex hollow components. During tube hydro-piercing, the deformation in the region adjacent to the pierced hole may range from having a substantially flat form to having a countersunk form. To improve the understanding of deformation behavior in square hole hydro-piercing, an experimental setup was designed and the effects of internal pressure and punch corner radius on the deformation sequence, as well as the collapse behavior, were investigated in this study. At the same time, a numerical simulation was conducted using the Abaqus/Explicit software 6.13. The results showed that the degrees of collapse at three characteristic points were different when the internal pressure was low and that the differences in the degrees of collapse could be reduced by increasing the internal pressure. It was demonstrated that the collapse was related to the internal pressure but had little dependence on the punch corner radius.

Estimating Forming Conditions for Deep Drawn SUS304 Square Cups Having no Delayed Cracks Using FE Simulation

Forming conditions for deep drawn SUS304 square cups having no delayed cracks are determined using finite element (FE) simulations based on the threshold % of wall thickening for delay cracking obtained from deep drawing tests of SUS304 cylindrical cups. The maximum drawing ratio and the initial blank thickness are fixed at 1.87 and 0.8 mm, respectively in this study taken into the considerations of the capacity of the press machine i.e., 100 kN. The blank holding forces (BHF), punch corner radius, rp and die corner radius, rd are varied to obtain 75 mm x 75 mm square cups having % of local thickening less than the threshold value i.e., 47% in the cracking zones located adjacent to the top corners of the cups. A quarter 3D FE simulation model of the deep drawing process is constructed, the wall thickness distributions of the cups are calculated. The simulation results showed that the forming conditions for the crack-free cups could be obtained with BHF ≥ 47 kN, rp ≥ 8.5 mm and 6.8 mm ≤ rd ≤ 9.5 mm. A method for designing the forming conditions of deep drawn SUS304 square cups is proposed in this study.

A simulation and experimental study on the deep drawing process of SPCC sheet using the graphical method

This study presents a method for finite element (FE) simulation of a deep drawing process of a cold-rolled carbon steel (SPCC) sheet material based on the graphical method. First, uniaxial tensile specimens were prepared and experimental tests were conducted to determine the flow stress curves. The calculation of the fracture points at special strain modes (plane strain, uniaxial tensile strain, and biaxial tensile strain) was presented using the modified maximum force criterion (MMFC). After that, the graphical method was adopted for the estimation of the forming limit curve (FLC) based on several hardening laws. FE models for a deep drawing process of the SPCC sheet were then built using the calculated FLCs. Using FE simulations, the fracture heights of cylinder cups formed by the deep drawing process were finally determined and compared with those from experiments. The results showed a good agreement between simulated and measured fracture height with a maximum of 3.6 % deviation. Additionally, simulations and corresponding experiments were performed to investigate the effects of the blank holder force, punch corner radius, and drawing ratio on the fracture height of cylinder cups.

Numerical investigation of the effect of punch corner radius and die shoulder radius on the flange earrings for AA1050 and AA1100 aluminum alloys in cylindrical deep drawing process

In aeronautic sectors, lightweight materials are very demanded in order to reduce fuel consumption. Therefore, thinning drawn cups are very recommended. Reduction of thickness led to many geometrical and physical failures that damage the final product. Since most lightweight materials had a high level of anisotropic, the presence of earrings is one of the most significant failures faced in the deep drawing process. Many functions were developed in order to control these undesirable earrings in sheet metal parts. In this paper, a simulation of a 3D cylindrical deep drawing model for AA1050 and AA1100 aluminum alloys using ABAQUS finite element software was achieved. Prediction of earing phenomenon in deep drawing process was carried out. Moreover, the impact of punch corner radius and die shoulder radius on flange earrings was analyzed and a reduction of the percentage of earring heights was investigated.

Numerical analysis on the influence of process parameters on the deep drawn product by using Taguchi method

Deep drawing is a metal forming process that involves complex metal flow and widely used in various manufacturing. The process parameters such as punch corner radius and die corner radius affect the product quality. The punch velocity is also important to obtain the desired product shape. However, it is rare to observe the combination of process parameters effects such as punch and di corner radii and punch speed. In this study, the influences of punch corner radius, die corner radius, and punch speed on deep drawn formability and defect formation are analysed. Taguchi Method is applied to build the design of simulations, and the axisymmetric model is used to simulate with Finite Element Analysis-based ABAQUS software. The results showed that the punch corner radius and die corner radius mainly affect stress and strain distribution and the punch velocity affect the formability of the product and the production time.

Effect of process parameters on micro flexible deep drawing of stainless steel 304 cups utilizing floating ring: Simulation and experiments

Due to its simplicity, versatility of process and feasibility of prototyping, using flexible tools in sheet forming seems appropriate for producing cups at microscales. This article presents a novel micro deep drawing technique in which a cooperation of a floating ring, as a primary rigid die, with a rubber pad, as a main flexible die, is employed for forming micro-cups. The function of the floating ring is to overcome minor wrinkles that commonly occur at flange portion, while the flexible die is to complete the forming stroke. The influence of initial sheet thickness, drawing ratio, punch corner radius and rubber height is studied through simulations and experiments. Furthermore, three size scales are adopted to investigate the possibility of using the proposed technique under different process dimensions. The code ABAQUS/Standard is utilized to build the finite element models and thereafter micro-forming experiments are carried out to verify the numerical results. For this purpose, a special setup is developed to be compatible with simulation models. The results show that the formed cups are characterized by very accurate dimensions, high surface quality, homogeneous wall thickness distribution in terms of maximum thinning and thickening and relatively large aspect ratio.

Evaluation of square deep drawn AA6061-T6 blank based on thinning pattern

Deep drawing can be generally described as a process of converting a metal sheet into a desired shape and geometry. Material flow and formability of the blank depends on the die and the punch geometries and it is important to predict the material behavior during square deep drawing to reduce possibility of defect and part rejection. In this research, a 3D Finite Element (FE) model is developed to simulate the square deep drawing process of an AA6061-T6 material using ANSYS Explicit Dynamics. The developed model can be used to predict the thinning pattern of the blank especially at the corner area. This research focus on the effect of design parameters namely punch corner radius (R1), punch nose radius (R2), die corner radius (R3) and die shoulder radius (R4) towards thinning pattern.

Contribution in analyzing dimensional deviations in ellipsoidal steel heads during deep drawing

The present work is a contribution in analyzing dimensional deviations in ellipsoidal thin-layer steel heads used for high-pressure air brake reservoirs. The dimensional deviations are attributed to the thickness distribution during the drawing process with regard to input geometrical parameters such as punch and die diameter, and also die and punch fillet. The aim of the present work is therefore optimizing the input data in order to respect the initial geometrical requirement. Investigation has been carried out using FEM code Abaqus, on a case example produced by the Algerian truck company according to G.R.C E81-102 standard. FEM simulations followed the process of deep drawing and concerned the effect of the most influencing factors such as the die corner radius, the punch corner radius, and the blank radius. Dimensional deviations are analyzed in terms of variations of thinning along the true dish path and hence engineering models of the corresponding true strain in the straight zone, the knuckle zone, and the crown zone of the dish are proposed.

An Investigation into Deep Drawing Parameters on Deformation-Induced Martensitic Microstructure Transformation of an Austenitic Stainless Steel

Stainless steel is one of the most widely used engineering materials due to high strength and excellent corrosion resistance. In this paper, the deformation-induced martensitic behavior of austenitic stainless steel 304 was investigated by the finite element method. For this purpose, the process parameters of forming speed and punch corner radius were examined during the warm deep drawing process under gradient condition from room temperature to 300 °C for sheets with 1 mm thickness. Also, their effects were studied on deformation-induced martensitic transformation. To apply thermal gradient, the blank in flange region was heated by die heating, and the blank center has been cooled by water circulating punch for strength enhancement. Results showed that when the temperature was increased to 150 and 300 °C, the martensitic transformation stopped in wall and flange regions, and the maximum punch force decreased. In addition, the faster forming speed and the sharper punch corners transformed higher martensitic content especially in the punch corner regions.

The Investigation and Optimization of Process Parameters in Warm Deep Drawing of ASS304 Steel Using Box Behnken Design and Applying Temperature Gradient

Warm deep drawing of high specific strength materials has attracted more attention in automotive and aerospace industries. Optimization of process parameters is a very important task in deep drawing process to reduce the production costs. In this paper, four process parameters, namely temperature, blank holder force, punch corner radius and matrix cavity corner radius have been planned and utilized according to the Box-Behnken design of response surface methodology in gradient warm deep drawing process. Their effects have been investigated on thickness distribution limiting drawing ratio and maximum forming force at ambient temperature up to 300 °C on an austenitic stainless steel 304 sheet. The optimum setting of mentioned factors has been reported to minimize an objective function response targets individually and simultaneously. Results show that the optimum setting to simultaneously satisfy the response targets includes the blank holder force of about 2200 N, a punch corner radius equal to 7.5 mm, a matrix cavity corner radius near 5 mm and a temperature of about 160 °C.

Optimization of Hydroforming Process for Deep Drawing of AA7075 Using Finite Element Simulation and Response Surface Methodology

Aluminum 7075 is a functional aerospace alloy that has high strength and low formability during room temperature deep drawing. Therefore, to avoid warm forming process and relative difficulties, careful control in the process design is needed to enhance quality of drawn part and improve die life. In the present work, an attempt was made to experimentally and numerically study the effect of hydrodynamic deep drawing process such as die geometry and fluid pressure on thinning ratio and punch force. Statistical analysis based on response surface methodology was carried out to correlate empirical relationship between die corner radius, punch corner radius and die fluid pressure as process factors and maximum thinning ratio and punch force as responses. Sensitivity analysis was also performed to find out the factor having greatest impact on aforementioned responses. Further, optimization was carried out by using desirability approach to find out optimal parameter setting to attain minimum thinning and forming force simultaneously. Results indicated that punch and die corner radius followed by fluid had significant effect on the process quality characteristics. Moreover, setting of 9.3 mm punch corner radius, 2 mm die corner radius and 26 MPa fluid pressure resulted in 71% desirability incorporating 31% thinning and 175 MPa punch force. The obtained optimal results were then verified through both FE simulation and confirmatory experiment.

Process window calculation and pressure locus optimization in hydroforming of conical box with double concave cavities

With the enhancement in the functional integration of components and concentration on lightweight materials, complex sheet metal parts are widely used in automobile and aviation industrial clusters. Consequently, the sheet hydroforming process has become an attractive fabricating technology for forming lightweight materials and complicated products. In this research, the hydrodynamic deep drawing (HDD) process of a composite conical box with double concave cavities was investigated through theoretical analysis, numerical simulation, and process experimentation. Furthermore, the process window diagram (PWD) was calculated using the stress analytical model combining material properties with workpiece geometrical features. The influence of cavity pressure loading locus on the forming quality of the fabricated part and the deformation behavior of aluminum alloy was explored. The forming results indicated that the initial pressure, full pressure, and loading locus are the fundamental parameters directly related to the forming quality and dimensional accuracy. For the conical part with composite features, the reasonable initial pressure value is crucial for the thickness homogeneity of the double concave characteristics, whereas the magnitude of the full pressure is vital for improving the quality of the conical feature. In addition, the optimal loading locus of the cavity pressure is characterized by two turning points, which are related to the punch corner radius, die shoulder radius, blank thickness, and angle of the conical feature.

Optimization of geometrical design of clinching tools in flat-clinching

Owing to the importance of geometrical design of clinching tools, the flat-clinching were investigated numerically and experimentally to determine the optimal geometrical parameters in this study. The geometrical parameters in flat-clinching, including punch corner radius, draft angle of the punch, blank holder corner radius, blank holder radius, and punch velocity, were optimized using the orthogonal experimental design simulation method based on the evaluation of interlocking. The simulation results show that the punch corner radius and the blank holder radius have a significant impact on the clinched joint, whereas the draft angle of the punch and blank holder corner radius have little influence on the clinched joint. The simulation results were validated through an experimental setup testing on material aluminum alloy Al5052. The experimental results have a good agreement with the orthogonal experimental design simulation.

Optimization of geometrical design of clinching tools in clinching process with extensible dies

Due to the importance of geometrical design of clinching tools, the clinching process with extensible dies was investigated numerically and experimentally to seek for optimal parameters of clinching tools in this study. The joining parameters, including punch corner radius, sliding distance, die depth and bottom thickness, were optimized using the orthogonal experimental design simulation method based on the evaluation of tensile strength. The simulation results were validated through an experimental setup testing on material aluminum alloy Al5052. The orthogonal experimental design simulation results showed reasonably good agreement with the experimental results. To further investigate the validation of the simulation model, the different bottom thicknesses within a reasonable range of value were studied. The results also indicated that the simulation model could be employed to predict the joint forming by the clinching process with extensible dies.

Multi objective optimization of clinching joints quality using Grey-based Taguchi method

Clinching joint quality and functionality may have undesirable features because of the choice of the forming process parameters. In fact, there are different factors controlling the mechanical connection strength such as the tools’ geometry and the joint final shape. This paper presents the implementation of the Taguchi-based Grey optimization of the mechanical clinching with fixed dies for dissimilar materials (Aluminum alloy 7075 and Mild Steel) to derive the optimal process parameters combination that leads to a high strength connection subjected to multiple characteristics, namely, the bottom thickness, the interlock length, and the neck thickness of the joint. LS-DYNA explicit and implicit finite element (FE) software was used to simulate the process in order to evaluate the joint strength by loading the sheets vertically. Taguchi’s L27 orthogonal array design and the notion of signal-to-noise (S/N) ratio were utilized to obtain the objective function. Analysis of variance (ANOVA) showed the importance of factors on overall output. The output of the study provided the optimal geometrical parameters of the punch, die, and blank holder. Indeed, the die groove height, die diameter, punch diameter, punch corner radius, and clearance between punch and blank holder were found to be the most influential parameters on the bottom and neck thicknesses. In addition, the output indicated that when bottom thickness or neck thickness increased, the interlock decreased.

A simplified approach for distinguishing between spring-back and spring-go in free U-die bending process of SPFC 440 sheets

This study proposed a simplified approach to distinguish between spring-back and spring-go in free U-die bending process of SPFC 440 sheets. A U-die bending model for unloading process is developed based on an elementary bending theory. The accuracy of prediction for distinguishing between spring-back and spring-go approaches 91.67%. A series of experiments are carried out to verify the proposed model, and further to explore the effects of process parameters on the conversion of the unloading behavior from spring-back to spring-go. Experimental results show that spring-back angle increases as sheet thickness decreases. The thin sheet is easier to induce spring-back than the thick sheet. In addition, spring-back angle increases as punch corner radius increases. Accordingly, spring-back angle slightly increases as the radius of die corner increases. Moreover, the key factor to distinguish between spring-back and spring-go seems the clearance between punch and die. The small clearance is easier to induce spring-go than the large clearance under the small radius of punch corner. A better understanding for distinguishing between spring-back and spring-go is achieved.

Parametric Optimization of Micro Deep Drawing Process using Fem Based Taguchi Method

In this work, a FEM based Taguchi method is used to predict the influence of forming parameters on the quality of formed part and punch force in micro deep drawing process. Three important forming parameters like punch corner radius, die corner radius and friction co- efficient are considered in this investigation. For optimization, the full factorial design of Taguchi's L27 orthogonal array is used for conducting FE simulation analysis for all the experimental runs and it is validated with set of experimental results. The FE simulation results agree with the experimental results. The signal-to-noise (S/N) ratio and the ANOVA techniques are used to calculate the significance of each parameters on the output characteristic. From the results, it is evident that the die corner radius and friction coefficient are the most influential parameters. Further a mathematical model has been developed for thickness variation in formed cup and punch force. The results of the confirmatory experiments are found to be in good agreement with the predicted results. Based on the results there is a scope to improve the micro forming process.

The study of forming concave-bottom cylindrical parts in hydroforming process

Among the sheet-hydroforming techniques, hydrodynamic deep drawing assisted by radial pressure has introduced good results for forming parts with high drawing ratio. Forming concave-bottom cylindrical parts is complicated through conventional deep drawing and requires several steps. Hydroforming is one of the techniques that can resolve such problems. In this paper, forming of concave-bottom parts has been studied by using finite element simulation and experiment through hydrodynamic deep drawing assisted by radial pressure. The effects of pressure path and geometrical parameters of the punch on thickness distribution and punch force have also been investigated. The results illustrate that after forming the concave profile of the part, by increasing the maximum fluid pressure, the thickness of critical regions does not change. Thus, the pressure path with the lowest maximum pressure that can form the concave profile of the part is the best pressure path for forming a concave-bottom part. Meanwhile, increasing the concavity height and punch corner radius affects thickness reduction in critical regions, but these parameters do not have any significant effects on maximum punch force.