Hardening and Final Thickness Data Used in the Quasistatic Nonlinear Analysis of Stamping Parts (original) (raw)
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Numerical Effectiveness of the Simulation of an Automotive Body Part Stamping
Advances in Mechanical Engineering, 2014
The simulation of advanced high-strength steel sheet (AHSS) stamping processes by means of dedicated computer-aided engineering (CAE) software requires the use of appropriate material models, the use of complex FEM models, and the use of advanced methods for solving nonlinear problems of their analysis. In practice, the engineering design of automotive body parts often leads to the formulation of problems, the solution of which requires ample computer resources and is very time-consuming. The paper describes a methodology to simulate stamping on the example of a car body part, with special attention being paid to the numerical efficiency of the FEM model and methods of solving it. The simulations of stamping of a sample stamped part—the automotive body part—in DynaForm and AutoForm programs are compared, focusing on the numerical effectiveness and consistency of the simulation results with the reality.
IJERT-A finite elemental study of contact pressure distribution in stamping operations
International Journal of Engineering Research and Technology (IJERT), 2013
https://www.ijert.org/a-finite-elemental-study-of-contact-pressure-distribution-in-stamping-operations https://www.ijert.org/research/a-finite-elemental-study-of-contact-pressure-distribution-in-stamping-operations-IJERTV2IS100098.pdf In the present work, two types of analysis are considered. One three dimensional symmetric object is analysed for sheet metal formation for stamping process and a two dimensional analysis for irregular shaped objects. Initially the geometries for two dimensions and three dimensions are built and later meshed for finite element calculations. In three dimensional analysis, due to symmetry, quarter geometry is considered due to computational complexity to reduce the solution time. Also temperature effect is considered in the problem to find the stamping operational load. Contac174 and Targe170 elements are defined for contact definitions. The problem is converged at different steps and results are captured for stress and plastic strain effects. Final punch load comparison is done between experimental and numerical solutions. The results show slight variation of numerical and finite element results. Further two dimensional analysis for stamping also shows higher number of steps for stamping operation. The results are captured for vonmises, displacements, plastic stain and contact pressure. The contact pressure picture shows variation of contact pressure along the geometry. This contact pressure prediction helps in proper design of stamping tools to reduce errors in the stamping process. Also plastic pictures help in predicting the region of crack formation and higher residual stress formation which are the sources for reduction of life of the component
Impact Of The Material Variability On The Stamping Process: Numerical And Analytical Analysis
2007
The finite element simulation is a very useful tool in the deep drawing industry. It is used more particularly for the development and the validation of new stamping tools. It allows to decrease cost and time for the tooling design and set up. But one of the most important difficulties to have a good agreement between the simulation and the real process comes from the definition of the numerical conditions (mesh, punch travel speed, limit conditions,…) and the parameters which model the material behavior. Indeed, in press shop, when the sheet set changes, often a variation of the formed part geometry is observed according to the variability of the material properties between these different sets. This last parameter represents probably one of the main source of process deviation when the process is set up. That's why it is important to study the influence of material data variation on the geometry of a classical stamped part. The chosen geometry is an omega shaped part because of its simplicity and it is representative one in the automotive industry (car body reinforcement). Moreover, it shows important springback deviations. An isotropic behaviour law is assumed. The impact of the statistical deviation of the three law coefficients characterizing the material and the friction coefficient around their nominal values is tested. A Gaussian distribution is supposed and their impact on the geometry variation is studied by FE simulation. An other approach is envisaged consisting in modeling the process variability by a mathematical model and then, in function of the input parameters variability, it is proposed to define an analytical model which leads to find the part geometry variability around the nominal shape. These two approaches allow to predict the process capability as a function of the material parameter variability.
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.
Journal of Physics: Conference Series, 2019
The reducing of machine time during surface hardening by smoothening is possible by increasing in the contact length between the hardening element and part surface. We study the case: the indenter-working surface is a fragment of a cylindrical surface, which the symmetry axis is parallel to the axis of symmetry of the part hardened surface. We suggest that such a process scheme is corresponds to a 2D contact problem in which a cylindrical stamp moves in an inertial coordinate system along an elastic half-plane (circle). We tasking the boundary conditions in the contact zone, using the complex potentials developed in the works of L.N. Galin.
The influence of indenter bluntness on the apparent contact stiffness of thin coatings
Thin Solid Films, 2009
In the present paper, the influence of punch tip sharpness on the interpretation of indentation measurements is considered. Firstly, in order to obtain analytical insight into the nature of the problem, closed form solutions are presented for the indentation of a homogeneous elastic half-space by an axisymmetric indenter of arbitrary shape, including Hertzian, conical, and conical indenter with a rounded tip. Next, a fast and efficient numerical implementation of a semi-analytical approach to the solution of problems about frictionless ...
Journal of Physics: Conference Series, 2019
The development of manufacturing engineering leads to the bill of goods expansion that work in extreme conditions and are made of new steels and alloys. Unfortunately, the traditional technological methods are not able to ensure the necessary performance characteristics of parts surfaces. Diamond smoothening is a well-behaved technological method that allows to finely controlling the quality parameters of the layer surface. However, we consider that the physical processes that occur in the interface between the indenter and the hardened surface are not well understood. A deeper understanding of the physical processes occurring in the contact zone will expand the scope of surface hardening by smoothening. In our work, we tasking the physical boundary conditions in the contact zone between the hardening tool and part surface.
Determination of the Mechanical Properties of Hot Stamped Parts from Numerical Simulations
Procedia CIRP, 2015
Hot stamping is a well-established process in car manufacturing today. However, the resulting mechanical properties of a hot stamped part and its behaviour during a crash are still open questions. The usual procedure includes destructive experiments to determine the mechanical properties resulting from the forming and quenching process. The gained information is then used for crash simulation. Using images from micrographs to determine the proportion of bainite and martensite resulting from the hot stamping process has proved to be difficult, as these structures are fairly similar and hard to distinguish. Sophisticated numerical simulations of the hot stamping process are available. The hardness resulting from the hot stamping process can be predicted fairly well from these process simulations. However, information like the tensile strength that is more relevant for the crash behaviour cannot be predicted that easily. It is not yet state of the art to map the results from the hot stamping simulation directly into the crash simulation. The approach to be presented in detail in this contribution uses the forming speed and the quenching velocity to predict the relevant mechanical properties of the hot stamped parts. Both input parameters, the forming speed and the quenching velocity, can be derived from the numerical hot stamping simulation. By means of experiments using a thermomechanical test system Gleeble well defined process parameters were used. Micro tensile test specimens were manufactured out of the Gleeble specimens to eliminate the effect of the Gaussian temperature profile created during the Gleeble experiments. Afterwards, tensile tests were carried out to derive a response surface for 22MnB5. The validated results allow the determination of the tensile strength of hot stamped parts from the numerical simulation of the hot stamping process with good accuracy.
Computational Materials Science, 2009
We proposed an application of inverse approach to experimental indentation data in order to determine combined hardening models parameters. It was shown that the use of a model combining isotropic and kinematic hardening allows a better description of cyclic indentation than isotropic hardening models. It was also shown that inverse analysis applied to experimental cyclic indentation curves can give a quite good approximation of the monotonic stress-strain curve and the beginning of cyclic tensile test. However, it appeared that the combined hardening model, used in this paper, is not sufficient to take into account all phenomenons coming in the steels behaviour under cyclic indentation.
Elastic-plastic property evaluation using a nearly flat instrumented indenter
International Journal of Solids and Structures, 2017
A 100-µm diameter, nearly flat, instrumented, indenter is used to indent aluminum AA-6463 and X80 pipeline steel. In contrast to sharp and spherical indenters, a rising load-displacement response is followed by a concave-downwards response during indentation. The substrate materials are characterized using tension and compression tests. Yield strengths measured under compression are within +/-10% of the tensile values thereby providing partial support for assuming symmetric tension-compression response. Based on imaging of the actual indenter using a Scanning Electron Microscope, a model of the indenter that accounts for the curved contact profile was created, assumed to be rigid and used in the finite element simulations. In the simulations, tensile yield strength and flow properties, obtained by tensile testing are used to describe the behavior of the substrate and good agreement with measured indentation force-displacement curves was obtained when the exact shape of the indenter was used. The agreement is poor when the contact profile of the indenter was idealized as flat. In the context of the inverse approach, using the Efficient Global Optimization technique, fits to the stress-strain curves of both of the alloys were obtained, and again the curvature of the indenter contact profile is found to be crucial. This work sets the stage for a large-scale deployment of the inverse approach to map the stress-strain response of heterogeneous microstructures such as welds.