Simulation Of Stamping Process Research Articles

Hot Stamping Process Simulation of 22MnB5 Steel Based on Identified Heat Boundary Condition

Finite element (FE) simulation is the powerful tool for an analysis to thermo-mechanical coupling process and helps the manufacturer in understanding the effect of the various parameters in the hot stamping process better. The simulation results are strongly dependent on the accuracy of boundary condition. In this paper, the heat boundary condition is firstly obtained based on an inverse analysis method. The characteristics of heat transfer in the interface between the sheet and the die was also analyzed. Then, the numerical simulation to the whole hot stamping process was made with simulation software by applying the identified heat boundary condition. The good agreement between the calculated and experimental temperatures demonstrates that the inverse analysis method is a feasible and effective tool for identifying the sheet-die heat boundary condition.

Study on Simulation of Stamping Process and Optimization of Process Parameters of Fender

In order to obtain the optimum technological parameters of fender forming, the finite element analysis software DYNAFORM is used to simulate the drawing process of fender in this paper. The orthogonal test is designed and completed. On the basis of the orthogonal test, Taguchi method is used to design the orthogonal inner table, and the SNR of each factor at each level is calculated. The results of Taguchi method are analyzed with variance analysis, and the adjustable influencing variables and influence factors on quality stability that affect the forming quality of the fender are obtained. Experimental optimization of the adjustable variables is carried out again to obtain the optimal combination of process parameters that affect the shaping quality of the fender. The optimal combination of process parameters is as follows: blank holder force is 120 kN, model clearance is 1.0 t (t represents sheet thickness), friction coefficient is 0.11, and radius of die is 6 mm. Finally, the experimental results show that the fender manufactured with this combination of process parameters has better performance.

Hot stamping process simulation based on reliable heat boundary condition

The finite element analysis is an essential precondition for the process design of hot stamping processes. The quality and the significance of the simulation results are strongly dependent on the heat boundary condition used in FE models. In this work, the heat boundary condition in hot stamping simulation was determined by analyzing the characteristics of heat transfer in the interface between the blank and the tools. The numerical simulation to the hot stamping process was made by using LS-Dyna software. It is found that the temperature changes of the hot stamped part are inhomogeneous. This results in the inhomogeneous mechanical properties.

Physics-driven Shape Variation Modelling at Early Design Stage

Modern markets are becoming increasingly competitive emphasizing the importance of achieving Right First Time (RFT) during the early design stage as a key enabler facilitating cost and time-to-launch (or time-to-market) reduction. One of the leading challenges to deliver RFT is the lack of effective methods to model product errors at early design stage. Usually, the assembly process is designed under the assumption of ideal (nominal) products. On the contrary, it has been demonstrated that product errors (both geometrical and dimensional) affect the performance of the final assembly. To facilitate easy decision making at early design stage, new methods and models are required to support design engineers. In this study, a framework has been proposed for early design support to generate product variation.International standard provides guidelines for product control and inspection (ISO-GPS or ASME-GD&T); however, the integration of tolerance standard into nominal sized CAD models is not yet achieved. Current, Computer Aided Tolerancing (CAT) tools mainly capable to model orientation and position tolerance specifications, whereas part shape errors are omitted. This paper presents an innovative physics-driven simulation framework to model shape errors of compliant sheet metal parts at early design stage.The modelling framework consists of three important stages: (i) initial shape error prediction using physic-based simulation, such as, stamping process simulation; (ii) individual orthogonal shape error modes/patterns identification based on decomposition techniques, such as, Geometric Modal Analysis (GMA); and, (iii) simulation of shape error variation classes by assigning distribution to each orthogonal shape error modes. The proposed approach enables to generate shape errors at early design stage of assembly process which can be utilized to optimize the assembly process, including fixture design and joining process parameters. An industrial automotive component illustrates the proposed methodology.

Comparative study of ductile fracture prediction of 22MnB5 steel in hot stamping process

Damage growth and ductile fracture prediction is an urgent question for hot stamping operations. Numerous models for ductile fracture prediction in cold forming processes have been extensively developed. There is a real need to compare them to choose the best suitable one for hot stamping applications. In the present study, several ductile fracture criteria under the category of “uncoupled phenomenological criterion” and the “fully coupled damage criterion,” i.e., the continuum damage mechanics (CDM)-based Lemaitre model, were employed to compare their prediction capability on ductile failure prediction. These two categories of criteria were coded into an explicit thermo-mechanical finite element code dedicated to hot stamping simulation. Both hot forming limit and hot tensile tests of 22MnB5 steel were conducted in order to provide suitable data for calibrating these models. Numerical results of the applications of these models to the hot stamping process simulation of an automotive B-pillar were compared with the experimental ones. It is concluded that thermo-mechanical finite element analysis in conjunction with CDM-based Lemaitre model can be used as a reliable tool to predict ductile damage and fracture of 22MnB5 steel in hot stamping process.

Optimized Design and Numerical Simulation of B-Pillar Reinforcement Panel by Hot Stamping Steel

In a certain vehicle of Dongfeng Passenger Vehicle Company (DFPV), a new design of integrated hot stamping B-pillar reinforcement panel is introduced to replace the original design of two cold stamping parts connecting by spot-weld. A further light-weight design by thickness thinning is also attempted. All the schemes are validated by hot stamping process simulation and vehicle side impact simulation. The results show that by using hot-stamping steel of the same thickness as the original design, the performance of anti-vehicle side impact is improved; and an equivalent anti-side impact performance can be achieved by appropriate thickness reduction, while the weight of the part is lightened.

Estimation model for magnetic properties of stamped electrical steel sheet

AbstractLess deterioration in the magnetic properties of electrical steel sheets in the process of stamping out the iron core is necessary in order to maintain performance. First, the influence of plastic strain and stress on the magnetic properties is studied using test pieces, in which plastic strain is added uniformly and residual stress is not induced. Because the influence of plastic strain is expressed using the equivalent plastic strain, at each equivalent plastic strain state the influence of the load stress is investigated. Second, the elastic limit is determined to be about 60% of the macroscopic yield point (MYP), and this agrees with the stress limit inducing irreversible deterioration in the magnetic properties. Therefore, simulation models, in which excess elastic limit plastic deformation begins and the magnetic properties deteriorate sharply, are proposed. Additional points taken into consideration in the deformation analysis are the strain rate sensitivity of flow stress, the anisotropy under deformation, and the influence of stress triaxiality on fracture. Finally, the proposed models are shown to be valid because the magnetic properties of rectangular sheets 5 mm wide stamped out from a nonoriented electrical steel sheet (35A250 JIS grade) can be estimated with good accuracy. It is concluded that the elastic limit must be taken into account in both the stamping process simulation and magnetic field calculation. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 183(2): 1–11, 2013; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.22269

Reducing Non-Value Added Process for an Automotive Component Using Finite Element Modeling

The research work focuses on sheet metal stamping process simulation of an automotive component known as bracket assembly upper spring made from low carbon steel and has axis-symmetrical cup shape that employs four multi-stage drawing processes. Non-value added drawing stages (optimization process) reduced and portrayed from the formability simulation result using finite element modeling (FEM) method. The modified design, with reduction of one draw stage, showed that the risk of the component to form cracks is lesser, the material elements are further away from the failure zone of the forming limit diagram (FLD) and it meets the requirement for minimum thickness. The FEM simulation was able to predict the formability and optimize the design of a sheet metal forming process that lowered the product cost and improve cycle time.

Geometric compensation for automotive stamping die design integrating structure deflection and blank thinning

Targeting to improve dimensional accuracy of automotive body panels, elastic deformation of stamping die structure and blank thinning are considered for compensation on the die surfaces. The thinning distribution on the deformed blank is extracted from stamping process simulation results and converted into first quantitative compensation. The boundary load required for die structural FEM analysis can be automatically mapped from process simulation results by using an updated load mapping algorithm, and the die deflection is then calculated and the deflection of die surfaces is transferred into second quantitative compensation. These two quantitative contributions are referred together for the compensation on the die surface model. The proposed methodologies have been programmed and can be integrated with LS-Dyna and HyperWorks or with Autoform and CATIA. Additionally, a software toolkit used to calculate the contacting ratio between the formed blank and die face has also been developed to automatically evaluate the effectiveness of die face compensation rather than virtually check the contacting ratio. The proposed methodologies and developed software have been verified by a case study of process and die design for an automotive panel part, showing the benefit in improving the contacting ratio.

The Stamping Process Simulation of Plate Using CAE Technology

Stamping process of sheet metal is widely used in the automobile industry. How to improve the quality of plate molding is a challenge for stamping process workers. With the development of the numerical analysis method and the computer technology, Computer Aided Engineering (CAE) technology is widely applied in the industrial areas. As the CAE technology comes up, a qualitative change has happened in the stamping process of automobile sheet metal parts. This paper presents one stamping process simulation of auto rearview mirror installation plate by using the software DYNAFORM.

Optimization Technology Applied to Automotive Stamping Process Simulation

Optimization Technology Applied to Automotive Stamping Process Simulation

電磁鋼板の打抜き加工による磁気特性劣化量の推定技術の開発

Less deterioration in the magnetic properties of electrical steel sheets in the process of stamping out the iron core is necessary in order to maintain performance. First, the influence of plastic strain and stress on the magnetic properties is studied using test pieces, in which plastic strain is added uniformly and residual stress is not induced. Because the influence of plastic strain is expressed using the equivalent plastic strain, at each equivalent plastic strain state the influence of the load stress is investigated. Second, the elastic limit is determined to be about 60% of the macroscopic yield point (MYP), and this agrees with the stress limit inducing irreversible deterioration in the magnetic properties. Therefore, simulation models, in which excess elastic limit plastic deformation begins and the magnetic properties deteriorate sharply, are proposed. Additional points taken into consideration in the deformation analysis are the strain rate sensitivity of flow stress, the anisotropy under deformation, and the influence of stress triaxiality on fracture. Finally, the proposed models are shown to be valid because the magnetic properties of rectangular sheets 5 mm wide stamped out from a nonoriented electrical steel sheet (35A250 JIS grade) can be estimated with good accuracy. It is concluded that the elastic limit must be taken into account in both the stamping process simulation and magnetic field calculation. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 183(2): 1–11, 2013; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.22269

Equivalent drawbead models for sheet forming simulation

Equivalent drawbead models associated with drawbead types, with which the geometrical modeling of drawbeads can be replaced in a numerical simulation of the stamping process, are introduced. The accuracy of the equivalent drawbead models rapidly computing the drawbead restraining and opening forces, based on the hybrid membrane/bending method accommodating Barlat’s anisotropic yield function for the plane stress state and the modified Chaboche model considering the Bauschinger effect and transient behavior under the plane strain condition, is verified by comparing the equivalent drawbead forces with those obtained from the finite element simulation. Moreover, the drawbead forces computed by equivalent drawbead models are employed in a finite element simulation of the automotive fender stamping process, from which the effectiveness and applicability of equivalent drawbead models are observed by comparing strains and draw-ins with those measured in the tryout panel.

Industrial challenges for finite element and multiscale methods for material modeling

The automotive industry promotes lightweight design to reduce the CO2-emission and enhances the passenger’s safety using high strength steel grades. One limiting factor to the accuracy of modern stamping simulation are the empirical constitutive models. In particular for high strength multiphase steels the modelling techniques like multi-scale methods are becoming more interesting. However they should meet the industrial needs. Not only the accuracy but also features like time, costs and complexity are rapidly increasing. The challenge is the development of finite element technologies and multi-scale methods in an appropriate framework for industrial projects. The crystal plasticity finite element method bridges the gap between the micro level and macroscopic mechanical properties that opens the way for more profound consideration of metal anisotropy in stamping process simulation. Nevertheless new empirical constitutive models are favourable for spring back prediction in forming simulations, even if the number of material parameters and the amount of tests for their identification increases. In this paper the application of crystal plasticity FEM within the concept of virtual material testing with a representative volume element (RVE) is demonstrated.

Virtual material testing for stamping simulations based on polycrystal plasticity

In the modern practice of stamping simulation of complex industrial parts the prediction of springback still lacks accuracy. In commercial software packages various empirical constitutive laws for stamping are available. Limited to simple empirical models for material anisotropy they do not take into account in a full manner the effects of microstructure and its evolution during the deformation process. The crystal plasticity finite element method bridges the gap between the polycrystalline texture and macroscopic mechanical properties that opens the way for more profound consideration of metal anisotropy in the stamping process simulation. In this paper the application of crystal plasticity FEM within the concept of virtual material testing with a representative volume element (RVE) is demonstrated. Using virtual tests it becomes possible, for example, to determine the actual shape of the yield locus and Lankford parameters and to use this information to calibrate empirical constitutive models. Along with standard uniaxial tensile tests other strain paths can be investigated like biaxial tensile, compressive or shear tests. The application of the crystal plasticity FEM for the virtual testing is demonstrated for DC04 and H320LA steel grades. The parameters of the Vegter yield locus are calibrated and the use case demonstration is completed by simulation of a typical industrial part in PAMSTAMP 2G.

자동차 스템핑 금형의 드로우비드력 특성에 관한 연구

The drawbeads, which are used for controlling the flow of the sheet into die cavity by imposing the tension and for preventing the forming defects like wrinkling, springback, etc. during the sheet forming process, affect the formability strongly because of the differences in the restraint and opening forces according to the drawbead shapes and dimensions. In this study, the experimental device enabling to measure the drawbead restraining and opening forces is manufactured and the drawing forces of circular, square, and step drawbeads are measured. The drawbead restraining and opening forces of a circular drawbead are increased as its drawbead height is increased. Similarly, those of a square drawbead are increased as its height is increased and shoulder radii decreased. The drawbead forces obtained from the experiment were compared with those calculated in the numerical simulation of stamping process of automotive fender. Good agreement was found so that the experimental measurements can be used in the simulation of auto-body stamping process.

PAM-STAMP in the simulation of stamping process of an automotive component

The present study focuses on the stamping process simulation of automotive component using PAM-STAMP TM simulation software. A die geometry of an automotive component has been simulated in this study. Safe limit of blank holder forces have been identified with respect to different parametric conditions. Plain carbon steel, reinforced steel and aluminum alloys have been used as the work materials for simulation. Safe limit of blank holder forces with respect to strain hardening exponent ( n), friction coefficient between the blank sheet and the die ( μ) and punch speed ( v) have been evaluated and analyzed. The result shows that the upper and lower limits of blank holder forces for plain carbon steel are 240 kN and 125 kN while for aluminum alloy AC120; the limit is between 85 kN and 50 kN. This indicates that plain carbon steel can be deformed without having any tear for a higher value of the blank holder force while aluminum alloy can be deformed without having any wrinkles at much lower value of the blank holder force. The upper bound limit BHF values for reinforced steel and aluminum–magnesium alloy are 220 kN and 200 kN respectively. It has also been observed that if the strain hardening exponent ( n) of the work material increases, the blank holder force also increases. However, with the increase of friction coefficient ( μ) or the punch speed ( v), the blank holder force decreases.

Essential algorithms to minimize dynamic effects in using explicit codes for stamping process simulations

AbstractA key problem, when using dynamic codes to run the static or quasi‐static jobs, in particular, for a stamping process simulation attaching spring‐back calculation, is the dynamic effect. In order to minimize the dynamic effects, some kinds of loading algorithms should be performed. The enhancement of these is proposed in this paper, as well as making up for a deficiency that current damping models have when used to reduce the dynamic effects. Essential conditions that can be followed to generate an ideal loading curve are brought forward here including the starting and ending condition. A concerned model is recommended that satisfies all ideal requirements, which can be used directly for the stamping process simulation. Associated criteria and how to optimize the loading curves are also presented. Finally, a simple case has been done to describe its practical application in simulations. Meanwhile, several kinds of loading curves, which have been used commonly in the stamping process simulation, are selected to compare with the proposed loading curve. The different features of them are also discussed. Copyright © 2003 John Wiley & Sons, Ltd.