PAM-STAMP 2G Research Articles

Numerical Simulation of B-Pillar’s Hot Press Forming Process and its Shape Optimization

To solve the problem of part’s section thinning easily occurred in hot press forming, the numerical simulation model of hot press forming process of a B-Pillar on one domestic car was established, the forming process was simulated by PAM-STAMP 2G software, the area thinning on the part were forecasted. Then through modifying the corner radius and the tiny shape of the part, the thinning level lightened greatly, the effect was certificated by new simulation results and practical production.

Deformation Behaviors of Tube Rotary-Draw Bending Filled with Steel Balls

Wrinkling, wall thickness overthinning and cross-section distorting are main defects that seriously affect the forming quality of the tube in bending process. In this paper, numerical simulation based on PAM-STAMP 2G is conducted for the tube rotary-draw bending filled with steel balls as pressure transferring medium to analyze the deformation behaviors under various internal pressures. The results show that, tube bending filled with steel balls as pressure transferring medium can effectively restrain the defects of wrinkling and cross-section distorting. In addition, wrinkling and cross-section distorting of the bent tube decrease, the wall thickness thickening at the intrados of the bent tube decreases while the wall thickness thinning at the extrados increases with the internal pressure.

Numerical Simulation and Experimental Study of Limit Drawing Ratio of Steel Sheets

The limit drawing ratios of the steel sheets are studied by the numerical simulation using the finite element software PAM-STAMP 2G. The limit drawing ratios of the steel sheets are also measured by the practical Swift cup test. The results of the experiments and the simulations are compared and analyzed. The results show that the overall shapes of the deep drawing parts of the experiment and the simulation are roughly the same. The maximum deviation of limit drawing ratio values between the experimental results and the simulations for two steel sheets with various thicknesses is only 2.2%. The deviation of limit drawing ratio of steel sheet obtained through PAM-STAMP FEM software is small. The PAM-STAMP software is highly reliable for the steel sheet deep drawing simulation.

Using Contact-less Optical Systems to Characterize and Measure Deformation of TWIP Materials

There is evident huge progress in the contact-less systems for measuring deformation by means of the photogrammetry especially during last ten years. From the forming point of view is very important that in many cases photogrammetry can improve knowledge about material deformation behavior under plastic deformation. This paper deals with characterization and description quite special deformation behavior of so-called TWIP (TWinning Induced Plasticity) materials by these contact-less optical systems (in this paper is used system ARAMIS). Beside the revealing deformation behavior there is also effort to find out development of anisotropy during whole static tension test and comparison of results from those measured at deformation values specified by the commonly used standard ČSN ISO 12 275. Other important results can be found during measurement of FLD for TWIP materials according standard ISO 12004-2. There is also possibility to compare values of true strain measured by optical system and results from numeric simulation program – in this case it was widely used simulation program for sheet forming from ESI company (France) PAM-STAMP 2G - comparing of real values of true strain and results from simulation, their mapping and final graphical display of differences between these values.

Utilization of Forming Tool with Variable Blankholder Force for Drawing of Al Alloys

Drawing of stampings technology is nowadays the most using technology for sheets processing. Because of stamping's weight reduction is these days actual sheet processing from aluminium alloys which by their properties differ a lot from commonly using deep-drawing sheets. To achieve maximal plastic deformation with material fracture is necessary to use sheet with required mechanical properties and properly chosen forming technological properties. Common tools for deep-drawing don’t enable to lively reply of necessity to change blankholder force during sheet drawing. On the experimental tool for deep-drawing with variable blankholder force are in the paper evaluated two variants of drawing methods for irregular shape of stamping. In the first case was stamping from AA6016 alloy designed with constant blankholder force. In the second case was blankholder force optimized and during drawing was changed in dependence on drawing depth. Calculation of blankholder force in dependence on drawing depth was carried out by means of numerical simulation in software PAM-STAMP 2G. Result of optimalization was strain distribution change in critical places of stamping. Strain distribution on stamping is measured by means of optical system ARGUS.

New Developments in Superplastic Forming Simulation and Industrial Applications

In this paper, the authors presented the material models and numerical algorithms adopted in PAMSTAMP 2G for superplastic forming simulation. The improvements in strain rate control, automatic stop criteria, velocity scaling and shell element formulation to include normal stress can improve the accuracy and efficiency of superplastic forming simulation.

An expert system for predicting the deep drawing behavior of tailor welded blanks

The forming behavior of tailor welded blanks (TWB) is influenced by thickness ratio, strength ratio, and weld conditions in a synergistic fashion. In most of the cases, these parameters deteriorate the forming behavior of TWB. It is necessary to predict suitable TWB conditions for achieving better-stamped product made of welded blanks. This is practically difficult and resource intensive, requiring lot of simulations or experiments to be performed under varied base material and weld conditions. Automotive sheet part designers will be greatly benefited if an ‘expert system’ is available that can deliver forming behavior of TWB for varied weld and blank conditions. This work primarily aims at developing an expert system using artificial neural network (ANN) model to predict the deep drawing behavior of welded blanks made of steel grade and aluminium alloy base materials. The important deep drawing characteristics of TWB are predicted within chosen range of varied blank and weld conditions. Through out the work, PAM STAMP 2G® finite element (FE) code is used to simulate the forming behavior and to generate output data required for training the ANN. Predicted results from ANN model are compared and validated with FE simulation for two different intermediate TWB conditions. It is observed that the results obtained from ANN based expert system are encouraging with acceptable prediction errors.

Optimisation of Can Bottom Geometry by Means of Simulations

Cans used in food industry have to be designed respecting aesthetic, technological, and security constraints. In many cases, due to the natural food fermentation, these cans are subjected to internal pressure of some bars. For that reason they must be designed so as to prevent the occurrence of defects due to the presence of this pressure. The aim of the present research is to properly modify the geometry of a pressurized can bottom to avoid wrinkles or bursting when pressure reaches a defined value. In this kind of cans the bottom is welded on the principal can body. The ability of the FEM software Pam-Stamp 2G to correctly simulate the process was verified by the FEM results comparison with the actual behaviour of can under pressure experimentally tested. Once validated the software, FE simulations were conducted with different bottom geometries. The results comparison allowed to identify the can bottom geometry that guarantees the best results in terms of avoiding wrinkles or bursting.

New Developments in Superplastic Forming Simulation and Industrial Applications

In this paper, the authors presented the material models and numerical algorithms adopted in PAMSTAMP 2G for superplastic forming simulation. The improvements in strain rate control, automatic stop criteria, velocity scaling and shell element formulation to include normal stress can improve the accuracy and efficiency of superplastic forming simulation.

English

In the present study the effect of mechanical Properties like strain hardening coefficient (n) and yield strength (σys) on the deep drawing formability is observed. In which three levels of n and σys have been considered. All the simulations were performed in the PAM STAMP 2G a FEM code and specialized sheet metal forming soft. Hill’s 1948 isotropic hardening yield criterion was used as the plasticity model. Hollomon’s power law was used as the strain hardening law. All three levels of mechanical properties were taken from experimental work of Singh and Gupta (2010) on IF steel. The data like dome height, and thickness distribution variations is taken. The results showed that dome height for the all the simulation is same and thickness distribution has got little variation with respect to mechanical properties.

금형 자동 보정 방식을 이용한 자동차 서라운드 몰딩 부품의 스프링백 현상 제어

Springback, an elastic material recovery after the unloading of stamping tools, causes variations and inconsistencies of final part dimensions. Recently, narrow and long surround molding parts around door frame are applied to high grade automobiles, but there are great difficulties in their die development, construction and tryout because of several springback modes including vertical movement and twist during flange forming process of them. So it is very important to predict springback's quantities of a surround molding part and, moreover, to compensate the die for them adequately, when they can't be corrected by the restrike operation. This paper presents a case study based on the die design for a surround molding part made of stainless steel. The forming and springback predictions, carried out using PAMSTAMP 2G, are reported and compared with the measurement data of the prototype. The predicted springback results were acceptable, so the processes of compensating die using Automatic Die Compensation Module of PAMSTAMP 2G were performed iteratively until the tolerances between the designed shape and the simulation data were satisfied.

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.

An expert system based on artificial neural network for predicting the tensile behavior of tailor welded blanks

The forming behavior of tailor welded blanks (TWB) is influenced by thickness ratio, strength ratio, and weld conditions in a synergistic fashion. In most of the cases, these parameters deteriorate the forming behavior of TWB. It is necessary to predict suitable TWB conditions for achieving better-stamped product made of welded blanks. This is quite difficult and resource intensive, requiring lot of simulations or experiments to be performed under varied base material and weld conditions. Automotive sheet part designers will be greatly benefited if an ‘expert system’ is available that can deliver forming behavior of TWB for varied weld and blank conditions. This work primarily aims at developing an artificial neural network (ANN) model to predict the tensile behavior of welded blanks made of steel grade and aluminium alloy base materials. The important tensile characteristics of TWB are predicted within chosen range of varied blank and weld condition. Through out the work, PAM STAMP 2G ® finite element (FE) code is used to simulate the tensile behavior and to generate output data required for training the ANN. Predicted results from ANN model are compared and validated with FE simulation for two different intermediate TWB conditions. It is observed that the results obtained from ANN are encouraging with acceptable prediction errors. An expert system framework is proposed using the trained ANN for designing TWB conditions that will deliver better formed TWB products.

Hydromechanical Deep Drawing of Funerary Vases: A Suitable Alternative to the Traditional Forming Processes

In the present paper a feasibility study of a funerary vase, made of stainless steel, using the Hydromechanical Deep Drawing process, is presented. The component is currently made of bronze and manufactured by die casting technology in a low volume production environment. To investigate the part feasibility, several FE simulations were implemented using the Aquadraw tool of the explicit FE code Pam Stamp 2G 2005®. The FE simulations showed that HDD process can produce the part in one single step without the requirement of finishing operations such as painting or polishing. Furthermore experimental tests were conducted and the first prototypes were successfully produced.

Developments for Rapid Tooling Application in Sheet Metal Forming

The market is changing very quickly, demanding the companies the capability of producing better and/or more performing products. This changing market leads the companies to be more flexible and agile. In particular, for the tool makers and the stamping companies, they are requested to participate in the design phase of the product and process, as well as to produce prototypes and small series in very short time and with low costs. To answer to these demands in the stamping steps design and consequently in the tool design, several finite elements packages are widely used, allowing the tool designers to foresee the results of their options/decisions without the need to manufacture and test tools, with the inherent excessive cost of money and time. Following this methodology, CAE analysis, the final phase of tool try out, always necessary, will be certainly shorter and less expensive, once they start with a solution quite more worked and, for sure, closer to the final solution. In this industrial context, appeared the great motivation for the development of competences on the rapid manufacturing of stamping tools (active elements: punch, die and blankholder), on the numerical simulation of the process and, on the development of the modular tool concept. In this paper the main results of the development of these areas of research, are presented. In particular, the use of the numerical simulation, using PAM-STAMP 2G software, for the validation of the stamping phases, the realisation of laboratorial stamping tests using tools produced by the several techniques available on Portugal for rapid prototyping. At the same time, it was developed the modular tool concept, i.e., a tool in which by fast and easy change of the active elements, different parts can be formed. The active elements of the tool have been manufactured by several rapid tooling techniques, like DMLS - Direct Metal Laser Sintering, LOM - Laminate Object Manufacturing, HSM – High Speed Milling and also the machining of non-traditional materials such as nylon, ureol and aluminium. Some inserts have been produced by indirect techniques such as reinforced resins (polyurethane, epoxy and urethane) using shells produced by SLstereolithography. Finally some conclusions are drawn.