Simulation Of Forming Processes Research Articles

Numerical simulation of 3D angle-interlock woven fabric forming and compression processes

Numerical simulation of 3D angle-interlock woven fabric forming and compression processes

High-efficiency computation for electromagnetic forming process: An explicit-implicit GPU approach

Low computational efficiency is one of the crucial challenges in electromagnetic forming process simulation. However, the huge gap in switching from the electromagnetic field to mechanics hinders the development of high-efficiency parallel coupling. A graphics processing unit (GPU)-based explicit-implicit coupling method is proposed to address the high-computational cost in simulations of the electromagnetic forming process, in which the large deformation (explicit) and electromagnetic field (implicit) are intimately coupled. The electromagnetic-mechanical coupling is achieved by constructing five parallel algorithms, which include the parallel operations of vector-vector, matrix-matrix, matrix-vector, vector assembly, and matrix-free assembly parallel preconditioned conjugate gradient algorithm. The high-efficiency GPU parallel computing is realized through the special data storage structure and parallel strategies. The explicit-implicit GPU method is validated against the experimental results, and several examples are presented for simulations of the electromagnetic forming process to illustrate both the accuracy and high-efficiency parallel acceleration performance of the present program.

Surface and subsurface material modifications and graded material properties in sheet steel 1.0338 (DC04) and their influence on forming processes

For bulk material it is very well known, that the material properties differ between the material near the surface and the inner material (i.e. segregations). However, for sheet material a gradient of material properties in depth direction and its influence on forming processes was not yet investigated. Within experiments on sheet steel 1.0338 (DC04) a gradient in material properties was proven by hardness measurements for both unprocessed material as well as after conducting forming and milling processes. The characterisation shows a gradient in material hardness over the entire sheet thickness. The experimental results regarding forming processes, such as rolling and bending, additionally show an increase of the materials hardness due to work hardening. The problem from the inhomogeneous material properties leads to an inaccurate prediction of the forming behaviour of the workpiece in further processing. Machining experiments were conducted for transferring the knowledge of modified surface and subsurface layers onto forming processes and their simulation. The bending experiments and the corresponding process simulation of the spring back behaviour show, that the implementation of an inhomogeneous material property increases the prediction accuracy. Notably the prediction of the spring back behaviour of thinner sheet metals is highly improved. Therefore, an analysis of sheet metal properties in thickness direction and their consideration in forming process simulations is inevitable for the implementation of accurate material models.

Effect of cooling rate on the phase transformation and post strength of Ti-6Al-4V under hot forming conditions: experiments and modelling

A systematic experimental and numerical study of the cooling rate effects on the post-formed strength and microstructure evolutions of a dual phase Ti-6Al-4V alloy under hot forming conditions was performed in this study. A series of cooling treatment tests were designed to achieve typical cooling scenarios in current hot forming processes, i.e. air cooling, water quenching and die quenching. The post-treated mechanical properties and phase volume fractions were characterized and quantified. The results show that higher temperatures and higher cooling rate would facilitate the β phase transformation and martensite transformation of α′ phases, leading to the higher yield strength in the formed part. Based on the macro- and micro- properties relations and observed data, a unified model for the hot forming and cooling of Ti-6Al-4V was proposed and calibrated, enabling the accurate prediction of both the macro-strength and microstructures under different cooling conditions of the material. The proposed model was further implemented into FE simulation for practical forming process simulations. A typical hot gas forming process of a rectangular cross-sectioned titanium alloy hollow tubular part was investigated. Experiments of hot gas forming with different cooling conditions, i.e. forming temperatures and cooling rates, were carried out and used to validate the established material model and simulation model. Good prediction accuracy was obtained under all the tested conditions, with the maximum prediction errors of 5.55% for macro-strength and of 9.79% for average grain size. The results and the model developed in this paper provides an effective way to facilitate the process designs and optimization for hot forming titanium alloy parts in various applications.

Characterization and computational modeling of continuous-fiber prepreg ply-ply interaction behavior

Ply-ply interaction behavior critically affects wrinkle formation during composite forming. This paper presents a computational model of the ply-ply interaction behavior of woven thermoset prepreg fabrics. The computational model includes visco-elastic, pressure-sensitive adhesion behavior, as well as a yield behavior that allows the deformation to transition from adhesion to friction. The model is based on the analysis and observations of double-lap shear factor effect screening tests and of total slip test measurements. To validate the computational model, finite element simulations are compared to experimental response surface tests for various pressures and deformation rates. The comparison shows that the computational model closely captures the load-deformation response of the ply-ply interaction. This computational model can be used in a forming process simulation to predict wrinkle formations.

Mechanism of oxide film removal and analysis of diffusion behavior of interfacial elements during magnetic pulse-assisted semi-solid brazing

The magnetic pulse-assisted semi-solid brazing (MPASSB) for Cu/Al tubes is proposed, in order to effectively remove oxide film to ensure the metallurgical bonding of Cu/Al brazing and joint performance. By designing a field shaper with a specific taper angle, the axial distribution of the electromagnetic force, tube deformation, and filler metal shear rheology are controlled to obtain the interface joining characteristics under different mechanical conditions. The relationship between the deformation behavior of the tube and filler metal with the interface element diffusion and metallurgical bonding is analyzed through the forming process simulation and interface microscopic characterization. In addition, the mechanical mechanism of oxide film removal is discussed as well. The results show that metallurgical bonding and element diffusion depend on the comprehensive effect of the interface compressive stress and the shear rheology of the filler metal. The larger the compressive stress, the better the oxide film removal. The stress at the bottom Cu/filler metal interface is the weakest, with an oxide layer thickness of 11.5 µm. The higher the shear rheological rate, the less the element diffusion depth. The filler metal flow rate at the bottom Cu/filler metal interface is the slowest, with a maximum depth of element diffusion of 13.5 µm. On the premise of ensuring the effective removal of the oxide film, the shear rheological rate (compressive stress) should not be too high.

Simulation of Cross Wedge Rolling and Hot Extrusion-Combined Forming Process for Axle Sleeve

In this paper, an axle sleeve is formed through a combined cross wedge rolling (CWR) and hot extrusion process, and the combined forming process is simulated via finite element analysis software Deform-3D. The forming mechanism is revealed by analyzing the stress and strain distribution, the temperature variation and the metal flow law of the workpiece during CWR and hot extrusion. Combined with CWR and hot extrusion forming experiments, the feasibility of a combined rolling and extrusion process to produce an axle sleeve is verified. It has been proven that the outer steps of the axle sleeve produced through the rolling extrusion composite process are well formed, the flange extrusion cavity is full, the metal streamline is continuous, the axis of the inner hole does not easily deviate, the product quality is good and the production efficiency is high.

Numerical Modelling and Simulation of Sheet Metal Forming Process

Simulation and modelling of sheet metal forming process are well common today in different industries (automotive, aerospace) and several research centers regarding its huge impact for both on production and reliability of the lifecycle of the equipment, and the quality of the product. However, to obtain the best configuration possible with the inputs parameters to achieve high level of production and increasing the durability of the tools needs some extra methods for the optimization for this problem using mostly finite element method cooperated with iterative algorithms based on Artificial Neural Network (ANN) [1]. Whereas this research is focused on modelling of stamping process of stainless steel AISI 304 to investigate to formability of the material, and studying the influence of the friction factor on the quality of the product as well the energy required for each set configuration.

Simulation of Electromagnetic Forming Process and Optimization of Geometric Parameters of Perforated Al Sheet Using RSM

Electromagnetic forming (EMF) is a kind of high-speed forming technology that can be useful for materials like aluminum. EMF helps to overcome the limitations of traditional forming. Due to this ability, the use of EMF in automotive applications has risen in recent years. The application of finite element software packages such as ANSYS 22 gives numerical modelling capabilities to simulate the EMF process and to design the forming process. Hence, the aim of this research work is to build and study the three-dimensional finite element model for the electromagnetic forming process and analyze the geometric parameters influencing the deformation of the perforated sheet with a design of experiments (DOE) approach. The finite element simulation is used in two stages. In the first stage, the electromagnetic force or Lorentz force striking the workpiece (i.e., Al sheet) is predicted using the ANSYS 22 Emag module. In the second stage, the predicted Lorentz force is then applied on an Al sheet to calculate the sheet deformation. The deformation of the sheet is predicted for different combinations of the geometric parameters of the sheet, such as open area percentage, ligament ratio (LR) and size of the hole, using ANSYS 22 Structural. In the DOE, response surface methodology (RSM) is used by considering the geometric parameters of perforated sheet such as open area percentage, ligament ratio (LR) and size of the hole. To minimize the number of experiments, an RSM model named central composite design (CCD) is employed. Further, the optimization study finds that the maximum deformation 0.0435 mm is calculated for the optimized combination of 25% open area, 0.14 LR and 4 mm hole size.

Modeling of 3-D thickness distribution of a head plate based on forming process simulation analysis

Modeling of 3-D thickness distribution of a head plate based on forming process simulation analysis

Shared mechanism between flow drill screw and friction stir welding and its impact on failure prediction of steel-aluminum joints

Severe plastic deformation and heat generation during the flow drill screw (FDS) process led to profound changes in the microstructures and mechanical properties of the heat-affected zone (HAZ). Microhardness measurements, electron backscattered diffraction (EBSD), and forming process simulation results showed that the HAZ was located within 1.0 mm from the thread tip. According to the simulated results of the joint forming process, the HAZ was divided into four subzones. The challenge in the numerical simulation of FDS joints lied in how to accurately acquire the mechanical properties of HAZ with limited size. In the present study, large-sized equivalent specimens were prepared with the friction stir welding (FSW) process. Based on the mechanical testing results of the equivalent specimens, a three-dimensional numerical model was established. Simulation results revealed that considering the material softening of HAZ was crucial for accurately predicting the mechanical behaviour of the joints under the tensile loading condition. The prediction accuracy of the peak force and failure displacement was improved by 7.0% as compared with that obtained using the numerical model without considering the material softening of HAZ. Under shear and mixed loading conditions, the error difference of predicted peak force and failure displacement with the two models was less than 3.0%. The deformation and failure characteristics of the joints could be accurately predicted by both the models.

Deformation behavior and forming process simulation of semi-solid powder rolling based on the combined constitutive model

Semi-solid powder forming (SPF) as a novel technology has been widely used to prepare composite materials. However, most of the present models used to simulate the complicated SPF process are based on the constitutive relationship of single dense or porous material, which cannot well satisfy the actual conditions. In this study, the process of semi-solid powder rolling was simulated by the combined constitutive formula of sintered and dense Al-Cu-Mg alloy materials obtained from semi-solid compression experiments. The results show that the semi-solid compression curves of dense and sintered materials are similar, and their peak stresses increase with the decreasing porosities. The grain or particle size of sintered materials after semi-solid compression becomes finer as powders crushed, but the grain size of dense materials becomes larger due to grain coarsening and deformation, which is the key advantage of SPF with fine microstructures. The combined constitutive model of semi-solid powder materials was established and verified, and then the numerical simulation of semi-solid powder rolling based on the model was proved that can well describe the rolling process, which provides a guidance for process optimization.

Multiphysics numerical modelling of backward flow forming process of AISI 5140 steel

Flow forming is a cold working process that makes it possible to produce high-precision thin-walled rotational symmetric parts leading to increased mechanical properties. The backward flow forming process is numerically modelled with the finite element method (FEM) based on FORGE® NxT 3.2 software, which is used in this work. In order to obtain all elasticity, thermal, physical, and plasticity properties of the AISI 5140 steel material, JmatPro Software is used. The obtained material parameters are defined in FORGE® NxT 3.2 software. For this purpose, microstructural characterization, hardness properties, stress distribution, and strains of samples are figured out. The experimental results are compared with the FEM. The thermomechanical properties and power distributions are carried out in this work. It is well understood that the plastic deformation mechanism plays a significant role in the workpiece temperature during the flow forming process. The hardness and mechanical properties of the AISI 5140 preform increase significantly after flow forming. The grain direction in the longitudinal direction with grain refinement is also observed. The results show that Arbitrary Lagrangian Eulerian (ALE) formulation is a very efficient method for providing very high accurate hardness properties of the workpiece during the flow forming process simulation. The stress distribution, mechanical properties, process temperature, strain rate, dimensional changes, radial, and axial forces are investigated using ALE formulation. In order to validate the FEM results, the same forming process parameters are experimentally performed on annealed AISI 5140 steel tube with a 65% flow forming reduction ratio. Furthermore, axial and radial forces are compared between experimental and simulation. The results show that the final part hardness difference is around 1.5%, and reaction forces error is less than 10% for both radial and axial directions.

Research and Analysis of Out-of-Tolerance Problem in Mold Processing Based on Intelligence

Out-of-tolerance is one of the most common problems in mold processing. For the out-of-tolerance problem in mold processing, the cold stamping die for motorcycle fuel tank shell is taken as the research object to solve the problem of out-of-tolerance, that is, easy to occur in the process of mold forming. Based on knowledge engineering, case-based reasoning (CBR) and numerical simulation are combined to study the intelligent design method of stamping die. The factors of overtolerance in stamping die processing are analyzed, and combined with the stamping process, the intelligent design system framework of cold stamping die for fuel tank shells is constructed. Numerical simulation of the double-cover forming (DCF) process of the fuel tank shell shows that sidewall wrinkling and local cracking are the main defects. Through the analysis of orthogonal table data and evaluation indicators, the optimal parameter scheme is F = 250 kN and H = 5 mm. At this time, the interaction effect (K2 = 0.738) of the two is the largest. Through test verification, the distribution trend of the simulated thickness is consistent with the experimental thickness, and the deviation range is within 10%. According to the numerical simulation results, the reasoning mechanism of an intelligent design system including instance and rule knowledge is designed, and an uncertain knowledge reasoning algorithm based on the reliability factor is proposed to improve the accuracy of mold size and reduce the overtolerance of the mold.

On the reliability of yield functions in deep drawing simulations

In sheet metal forming simulations, the yield functions are usually calibrated based on experimental data, and validated by comparing the modelled and measured r-values and (in more advanced models) yield stresses along various in-plane directions. The fitted yield function should ideally reproduce (or interpolate) all the experimental values used for the fitting. However, this requirement does not guarantee accurate results in a forming process simulation, and it can even lead to unexpected results. The performance of a yield function, in addition to the fitting procedure, depends on the active loading modes which the material experiences during the simulation. The active loading modes are in turn determined by the die geometry as well as the process parameters like blank holder force and lubrication. As a consequence, the performance of a yield function, which is fitted to simple experimental data, is not identical for different forming conditions. Therefore, the application of each model is usually limited to a range of materials and processes, and this applicability is often evaluated based on experience. In the present study, we examine three phenomenological yield functions and a new crystal plasticity based material model for cup drawing process simulation with an AA6016-T4 aluminium alloy. These functions are different in their input data types used for the calibration. The results surprisingly shows that the models with more experimental data (in particular, yield stresses in different directions) in their formulation not only predict unexpectedly wrong results, but also show strong sensitivity to some of those additional input data and even to modelling parameters like the friction coefficient.

Evaluation of meridional thickness distribution of a head plate based on forming process simulation analysis

In FBR plants the head plate constitutes a part of the boundary of the containment vessel (CV), therefore, it is a very important issue if the function as the boundary is maintained or not in the case of severe accident (SA). Buckling and post-buckling behaviors due to pressure loading must be affected by the thickness distribution of the head plate during press forming process. In this paper non-linear finite element simulation analyses assuming press forming process of a head plate are improved after the previous paper and the discussion is made comparing the analysis results with the measured results of thickness distribution of the head plate specimen used for the pressure endurance test. And also, the modelling for finite element analyses of head plates is discussed. In this study, axisymmetric analyses are implemented focused on the thickness distribution along the meridional direction of the head plate.

Design Simulation and Structure Optimization of Plunger Assembly Closing

Hydraulic motors and pumps are the core components in hydraulic systems. The plunger assembly is a key component for the realization of the function of the axial piston pump and motor. The coupling between the slipper and the plunger body is completed through the closing process. With the application of computational science and finite element technology, DEFORM-3D metal forming process simulation is used to establish the corresponding closing device model of the plunger assembly. Through simulation, we analyze the change law of metal flow during plastic deformation process, and carry out structural optimization design based on the simulation results. We found that the closing is completed under the appropriate cone angle and distance line of the shoe, the quality is relatively uniform, and there is no closing defects such as metal flow overflow and cracks. The pull-off force and the clearance value after rolling can meet the design requirements. This method not only can effectively shorten the product verification cycle and reduce the cost, but also can reduce the defects of the finished product and improve the yield rate, providing a new way for the design of the closing structure and closing model of the plunger assembly.

Temperature Dependent Modelling of Fibre-Reinforced Thermoplastic Organo-Sheet Material for Forming and Joining Process Simulations

Joining and local forming processes for fibre-reinforced thermoplastics (FRTP) like hole-forming or variations of the clinching process require an in-depth understanding of the process induced effects on meso-scale. For numerical modelling with a geometrical description of a woven fabric, adequate material models for a representative unit cell are identified. Model calibration is achieved employing a mesoscopic finite-element-approach using the embedded element method based on tensile tests of the consolidated organo-sheets and a phenomenological evaluation of photomicrographs. The model takes temperature dependent stiffness and fibre tension failure into account.

Broad stress triaxiality ratio band fracture experiments in DP900 metal sheets and corresponding predictive capability of advanced phenomenological and micromechanical fully coupled damage models

Correct prediction of the fracture time and location and their evolution in metallic materials has always been a research hotspot in the field of metal forming. To this end, and in the context of metal forming process simulation, an advanced mathematical material model is crucial. In this paper, we investigate the accuracy of two fully-coupled damage models, one of which is phenomenologically-based and the other one micromechanically-based, in predicting the failure in DP900 steel plates subject to various loading paths. These are applied throughout tests, including tensile tests on unnotched and notched specimens with different notch radii as well as butterfly wing shear tests. Through the comparisons of the numerical and experimental results, in terms of force-displacement curves and fracture strains (or ductility) under wide range of strain paths, the accuracy of the proposed two coupled damage models are discussed.

Numerical simulation for fracture network evolution in coal-bearing gas reservoir reconstruction based on damage theory

Based on the characteristics of mechanical response of coal rock under loading, an elastic-brittle damage constitutive relation of coal rock has been proposed, which has been extended to the 3-D stress state, based on the geological strength index. Besides, a numerical calculation method based on the elastic-brittle damage the?ory has been developed, by analyzing the seepage-stress coupling effect. Then, a computing program for fracture network transformation has been composed to perform numerical simulation of forming process of coal rock under different working conditions, by the APDL language in the ANSYS software platform. The mechanical mechanism of fracture network forming process of coal rock has been further analyzed.