Simulation Of Forming Processes Research Articles

Study of the high speed blanking proccess with the C-NEM

The C-NEM is a new approach that we apply to solve mechanical problem in the context of finite transformations as encountered in forming process simulation. The C-NEM (Constrained Natural Element Method) is based on the Voronoi diagram associated to the nodes spread on the studied domain. The Voronoi diagram is constrain to respect the geometry of the domain boundaries. Its ability for constructing the interpolation when the domain becomes highly distorted makes of that approach an appealing choice for simulation forming processes as for example 3D cutting and blanking. In this communication we present some aspects related to the C-NEM approach and we show its ability to simulate kinematics encountered in high velocity blanking process.

Simulation of Forming Process as an Educational Tool Using Physical Modeling

Metal forming process simulation requires a very high cost including the cost for dies, machine and material and tight process control since the process involve very huge pressure. A physical modeling technique is developed and initiates a new era of educational tool of simulating the process effectively. Several publications and findings have shown a potential of the techniques else where. The objective of the paper is to simulate the closed-die forging. In this work, billet material from plasticine is used and dies are fabricated from perspex. The result indicates that billet volume and geometry of the billet is significant in forming process to measure the filling-ability and forming load required in the process.

Optimization of the type of finite element representation for simulation of the forming process of elasto-plastic panels

Проведено компьютерное моделирование процесса формообразования элемента крыльевой панели с использованием программных продуктов корпорации MSC.Software: MSC.Marc 2007 и MSC.Patran 2007. Рассмотрены четыре 3D конечно-элементные модели с разными типами конечных элементов (тетраэдральными и гексагональными, с трилинейной и триквадратичной аппроксимацией геометрии и перемещений). Показано, что использование тетраэдральных конечных элементов постоянной деформации не позволяет правильно определить конфигурацию отформованной панели. Для практических расчетов рекомендуется использовать гексагональные восьмиузловые конечные элементы. Показано, что при решении типичных задач формообразования крыльевых панелей надо учитывать геометрическую нелинейность уравнений их деформирования.

Forming Process Simulation of Truss Core Panel

Honeycomb panel is widely used as flooring or wall material in various structure including buildings, aircraft, train and so on due to high stiffness and lightness at present. Honeycomb panel, however, has a disadvantage that adhesive used to glue honeycomb core and top plate may burn by fire. On the other hand truss core panel has equivalent stiffness as honeycomb panel and is expected to be an alternative to honeycomb panel as it is safer for fire. However, in general, difficulty exists to form truss core and forming techniques should be developed for practice use of truss core panel. In this paper, firstly theoretical forming limitation is discussed for tetrahedral truss core . Secondly single stage forming simulation of truss core panel using explicit FEM technique was performed for preliminary investigation to estimate formability and thickness distribution. Finally multi-stage forming simulation was presented and possibility to apply press forming for truss core panel production through the simulation. In addition some results of the simulation was compared with the experiment and good agreement of both results was shown.

A VR‐based simulation system for glass pressing

AbstractThe integration with virtual reality is a new boost to CAD and CAE. This paper presents a research effort aimed at creating a desktop‐based, low‐cost and independent VR‐based simulation system for glass pressing, which integrates the forming process simulation and mold motion simulation. The skeletal animation technique is employed for motion simulation of the mold. The stereoscopic view of the virtual system is achieved by CrystalEyes shutter glasses, with C++ language and OpenGL support library selected as the development tool. With the stereoscopic display of the mold design, pressing motion and numerical CAE results, the system enables engineers to gain a cohesive view of mold structure, assembly issues, and possible forming faults. It can also support training of students and engineers to acquire the theoretical know‐how, practical skills, and the problem troubleshooting techniques of glass pressing. © 2008 Wiley Periodicals, Inc. Comput Appl Eng Educ 16: 315–320, 2008; Published online in Wiley InterScience (www.interscience.wiley.com); DOI 10.1002/cae20216

Constitutive modeling for anisotropic/asymmetric hardening behavior of magnesium alloy sheets: Application to sheet springback

The constitutive model for the unusual asymmetric hardening behavior of magnesium alloy sheet presented in a companion paper (Lee, M.G., Wagoner, R.H., Lee, J.K., Chung, K., Kim, H.Y., 2008. Constitutive modeling for anisotropic/asymmetric hardening behavior of magnesium alloy sheet, Int. J. Plasticity 24(4), 545–582) was applied to the springback prediction in sheet metal forming. The implicit finite element program ABAQUS was utilized to implement the developed constitutive equations via user material subroutine. For the verification purpose, the springback of AZ31B magnesium alloy sheet was measured using the unconstrained cylindrical bending test of Numisheet (Numisheet ’2002 Benchmark Problem, 2002. In: Yang, D.Y., Oh, S.I., Huh, H., Kim, Y.H. (Eds.), Proceedings of 5th International Conference and Workshop on Numerical Simulation of 3D Sheet Forming Processes, Jeju, Korea) and 2D draw bend test. With the specially designed draw bend test the direct restraining force and long drawn distance were attainable, thus the measurement of the springback could be made with improved accuracy comparable with conventional U channel draw bend test. Besides the developed constitutive models, other models based on isotropic constitutive equations and the Chaboche type kinematic hardening model were also considered. Comparisons were made between simulated results by the finite element analysis and corresponding experiments and the newly proposed model showed enhanced prediction capability, which was also supported by the simple bending analysis adopting asymmetric stress–strain response.

Faster to Sound Parts by Advanced Forming Process Simulation - Advanced Forming Process Model Including the Elastic Effects of the Forming Press and Tool

This article addresses process, stamping, and manufacturing engineers, as well as tool designers (prototype and series production tools), and press shop planners in the range of metal forming. The paper deals with methods of modelling and simulating the metal forming process and their application in product design, production, and forming process planning. In models usually applied major effects on the forming process are neglected. For instance, the elastic behaviour of presses and die tools is not considered in process and tool planning. Thus, reworking of tools is a consequence of this model oversimplification. The paper illustrates how interactions between forming press, die tool and metal forming processes can be modelled by enhancing conventional FE models. Several examples demonstrate the information value of the Advanced Forming Process Model (AFPM).

Bulk metal forming process simulation based on rigid-plastic/viscoplastic element free Galerkin method

A rigid-plastic/viscoplastic element free Galerkin method is established based on the flow formulation for rigid-plastic/viscoplastic materials to simulate bulk metal forming processes. According to incomplete generalized variational principle, stiffness equations and solution formulas are derived. The transformation method is adopted to impose the essential boundary condition in the local coordinate system. The arctangent frictional model is used to implement the frictional boundary conditions, and the transform matrix from the global coordinate system to local coordinate system is given. The analysis software is developed. The method for dealing with the rigid region is introduced. Pressure projection method is used to solve volumetric locking and pressure oscillation problems. The contact and detachment criterion for the workpiece and die is given to judge the contact state. Numerical examples of bulk metal forming process are analyzed based on rigid-plastic/viscoplastic element free Galerkin method. The material flow, field variable distributions, etc. are analyzed. The numerical analysis results obtained by the method proposed in the paper are in good agreement with those obtained by the finite element method and experiment. The correctness of the presented method is demonstrated.

Massive metal forming process simulation based on rigid/visco-plastic element-free Galerkin method

Abstract The advantages of meshless method are analyzed. Applications of meshelss method in numerical simulations of metal forming processes are summarized. The element-free Galerkin method based on the hypothesis of the rigid/visco-plastic material is introduced. Using the incomplete generalized variational principle and employing penalty function method to introduce volume constancy, the stiffness matrix equation is established. The meshless analysis techniques for metal forming processes with arbitrarily shaped die, such as the description of dies or workpieces with arbitrarily shaped boundary, iteration convergence criterions and detachment and contact criterion, are developed. The phenomenon of volumetric locking and pressure oscillation is released. The rigid/visco-plastic element-free Galerkin method nalysis of the non-steady metal forming processes with arbitrarily shaped dies is realized. The simulation results of the meshless method are in agreement with those obtained by using the rigid/visco-plastic FEM, and the effectiveness of the model and key techniques is verified.

Modelling of the Forming Limit Band –A new Method to Increase the Robustness in the Simulation of Sheet Metal Forming Processes

Forming Limit Curves are valid for one particular material alloy, temper and gauge combination. However material properties vary from batch to batch due to variation in the production process. For there a single Forming Limit Curve can not be an exact description of the forming limit. Several researchers have proposed a more general concept, namely the Forming Limit Band (FLB) as a region covering the entire dispersion of the Forming Limit Curves. A Forming Limit Band can successfully be predicted using the normal statistical distribution found in different production lots, of the yield stresses. Until now, the study of the dispersion was only experimental. Using the FORM-CERT software the influence of the different material parameters on the FLC has been studied. Using the normal distribution of mechanical properties the plus and minus 3-Sigma limits are used to determine the Upper- and the Lower FLC. The region between these two curves represents the Forming Limit Band. The paper presents for the first time the numeric modelling of the FLB concept. This method is illustrated on the AA 6111-T43 aluminum alloy.

Study of the Strain Rate Effect on Cold-Reduced Carbon Steel and Aluminium Alloy with Numerical Simulations

In this paper, the effect of strain rate has been considered in the simulation of forming process with a simple form combined into the material law. Quite a few researchers have proposed various hardening laws and strain rate functions to describe the material tensile curve. In this study, the strain rate model Cowper-Symonds is used with anisotropic elasto-plastic material law in the simulation process. The strain path evolution of certain elements, when the strain rate is considered and not, is compared. Two sheet materials, Cold-reduced Carbon Steel (SPCC) JIS G3141 and Aluminum alloy 6112 are used in this study. Two yield criteria, Hill 48 and Hill 90, are applied respectively to improve the accuracy of simulation result. They show different performance when strain rate effect is considered. Strain path of the elements in the fracture risk area of SPCC (JIS G3141) varies much when the strain rate material law is used. There is only little difference of the strain distribution of Al 6112 when the strain rate effect is included and excluded in the material law. The simulation results of material SPCC under two conditions indicate that the strain rate should be considered if the material is the rate-sensitive material, which provides more accurate simulation results.

A cascade optimization methodology for automatic parameter identification and shape/process optimization in metal forming simulation

Computer simulations of metal forming processes using the finite element method (FEM) are, today, well established. This form of simulation uses an increasing number of sophisticated geometrical and material models, relying on a certain number of input data, which are not always readily available. The aim of inverse problems, which will be considered here, is to determine one or more of the input data relating to these forming process simulations, thereby leading to a desired result. In this paper, we will focus on two categories of such inverse problems. The first category consists of parameter identification inverse problems. These involve evaluating the material parameters for material constitutive models that would lead to the most accurate results with respect to physical experiments, i.e. minimizing the difference between experimental results and FEM simulations. The second category consists of shape/ process optimization inverse problems. These involve determining the initial geometry of the specimen and/or the shape of the forming tools, as well as some parameters of the process itself, in order to provide the desired final geometry after the forming process. These two categories of inverse problems can be formulated as optimization problems in a similar way, i.e. by using identical optimization algorithms. In this paper, we intend firstly to solve these two types of optimization problems by using different non-linear gradient based optimization methods and secondly to compare their efficiency and robustness in a variety of numerical applications.

Meshless methods with application to metal forming

In recent years, a new family of computational methods has emerged. The so-called meshless or mesh-free methods have been investigated and used by many researchers for treating a large variety of engineering problems, involving usually large displacements as encountered for example in forming process simulations. The main advantage of meshless methods is the fact that the interpolation accuracy is not significantly affected by the nodal distribution. Nevertheless, a troublesome task in these techniques is the imposition of essential boundary conditions, as in general the Kronecker delta property is not satisfied. Despite of several techniques have been proposed to overcome this problem, an appealing alternative technique which allows to circumvent this difficulty lies in the use of the natural neighbor interpolation (NEM). This paper focuses on the description and analysis of the natural element method, and its application for simulating some forming processes involving large displacements as well as fixed or moving discontinuities.

Meshless Methods and Partition of Unity Finite Elements

This paper encompasses the main conclusions obtained in the mini-symposium New and Advanced Numerical Strategies in Forming Processes Simulation, held during the 6th International ESAFORM Conference on Material Forming (Salerno 2003), particularly those aspects dealing with meshless and partition of unity methods applied to the simulation of forming processes.

Digitized die forming system for sheet metal and springback minimizing technique

A flexible production system for sheet metal parts was developed based on the “digitized die” concept. The system can produce a variety of three-dimensional parts without the need for conventional dies, and given only the geometry and the material information of the desired part. The digitized die forming (DDF) system includes the forming press, the shape control system, and software modules with the functions of forming process planning, digitized die shape design, forming process numerical simulation, and springback correction. The digitized die installed in the forming press is the kernel component of the system, it is composed of a pair of matrices of punches, and sheet metal is formed by the enveloping surface of the punches. The working surface of the digitized die are modeled by Non-Uniform Rational B-Spline (NURBS) and constructed by adjusting the height of each punch. Forming process simulation software was developed based on updated Lagrangian formulation and elastic-plastic material model of the finite element, it conducts the numerical simulation to predict the springback and forming defect that may occur in the forming process. A simulation-based approach to compensate for material springback was developed, by correcting the forming surface numerically, an accurate digitized die surface for desired part is obtained. In this paper, the overall structure of the DDF system and the methods of design and control of digitized die shape are described, the detailed steps of the die shape correction for springback and forming process simulation are explained. Applications of the system for the forming of typical sheet metal parts are described .

Simulation of the Process Influencing Behaviour of Forming Machines

In the design of sheet metal components and associated tools the use of forming process simulation based on finite element method is state of the art. The modelling of the forming process, however, neglects fundamental influences of the forming machine. But today, the machine behaviour influencing the process can be described with simulation tools sufficiently.The article presented here describes the current state of simulation for forming machines in regard to static and dynamic influences on the forming process. Furthermore, two examples and a proposal for enhancing the model are given.

A quasi-flow constitutive model with strain-rate dependence

In this paper, the proposed is a quasi-flow constitutive model with strain-rate sensitivity for elastic plastic large deformation. The model is based on the Quasi-flow Corner theory, and is suitable for the sheet metal forming process simulation with a variable punch machine velocity. Uniaxial tensile tests and deep-drawing tests of a circular blank with square punch are carried out and numerically simulated. The consistency between the experimental and the numerically simulated results shows the validity of the present new constitutive model.

Gas detonation forming process and modeling for efficient spring-back prediction

Aluminum cylindrical cups are formed with gas detonation forming technology and finite element modeling of aluminum cylindrical cup production with the detonation forming technology is performed. The forming process simulation is carried out in two-step analysis. 2D and 3D computational models are constructed with both explicit and implicit dynamic analyses are performed. The effects of detonation pressure and die design parameters also are investigated. The thickness distribution and deformed geometry of the cups are compared with the experimentally determined values. The spring-back predictions based on the explicit and implicit methods are criticized in terms of deformed shape accuracy and elapsed time.

Inverse design of glass forming process simulation using an optimization technique and distributed computing

In this paper, an inverse problem of heat transfer in the glass forming process is studied to determine a number of unknown heat transfer coefficients. An analysis program for transient heat conduction is developed to simulate the forming and cooling processes. The analysis involves the contact and separation of glass and molds and it is repeated until the process reaches a periodic state. Temperature measurements are taken at several available times and spatial positions of glass and molds during the forming operation. Heat removal by the cooling water from the plunger is also recorded. An optimization problem is formulated to determine the heat transfer coefficients that minimize the difference between the measured data and the analysis results. Significant time savings are achieved in computing finite difference-based sensitivity during the optimization by employing a distributed computing techniques over a cluster of computers. The analysis results of the optimum heat transfer coefficients are found to agree well with the measured data.

Model of dynamic compression tests on hydraulic testing machines: Influence of dynamic phenomena

The forming process simulation requires models describing the materials behaviour at large strains and at strain rates up to hundreds of s -1 . The major difficulty then encountered is that few experimental tests enable to reach these two criteria. For a few years, several studies have been carried out on hydraulic machines provided with a dynamic jack. However, for higher strain rates tests, the load measurement is disturbed by the response of the experimental set-up and oscillations appear. In this article, the experimental test is developed and a finite element model of the set-up is introduced.