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Title: Numerical Prediction of Elastic Springback in An Automotive Complex Structural Part

Abstract

The occurrence of elastic springback phenomena in sheet metal processing operations determines a relevant issue in the automotive industry. The routing and production of 3D complex parts for automotive applications is characterized by springback phenomena affecting the final geometry of the components both after the stamping operations and the trimming ones. In the present paper the full routing of a automotive structural part is considered and the springback phenomena occurring after forming and trimming are investigated through FE analyses utilizing an explicit implicit approach. In particular a sensitivity analysis on process parameter influencing springback occurrence is developed: blank holder force, draw bead penetration and blank shape.

Authors:
; ;  [1]
  1. Dipartimento di tecnologia meccanica, produzione ed ingegneria gestionale University of Palermo, Viale delle Scienze 90128, Palermo (Italy)
Publication Date:
OSTI Identifier:
21057012
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 907; Journal Issue: 1; Conference: 10. ESAFORM conference on material forming, Zaragoza (Spain), 18-20 Apr 2007; Other Information: DOI: 10.1063/1.2729513; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ALLOYS; COMPUTERIZED SIMULATION; DRAWING; ELASTICITY; FINITE ELEMENT METHOD; METALS; PROCESSING; SENSITIVITY ANALYSIS; SHAPE; SHEETS

Citation Formats

Fratini, Livan, Ingarao, Giuseppe, and Micari, Fabrizio. Numerical Prediction of Elastic Springback in An Automotive Complex Structural Part. United States: N. p., 2007. Web. doi:10.1063/1.2729513.
Fratini, Livan, Ingarao, Giuseppe, & Micari, Fabrizio. Numerical Prediction of Elastic Springback in An Automotive Complex Structural Part. United States. doi:10.1063/1.2729513.
Fratini, Livan, Ingarao, Giuseppe, and Micari, Fabrizio. Sat . "Numerical Prediction of Elastic Springback in An Automotive Complex Structural Part". United States. doi:10.1063/1.2729513.
@article{osti_21057012,
title = {Numerical Prediction of Elastic Springback in An Automotive Complex Structural Part},
author = {Fratini, Livan and Ingarao, Giuseppe and Micari, Fabrizio},
abstractNote = {The occurrence of elastic springback phenomena in sheet metal processing operations determines a relevant issue in the automotive industry. The routing and production of 3D complex parts for automotive applications is characterized by springback phenomena affecting the final geometry of the components both after the stamping operations and the trimming ones. In the present paper the full routing of a automotive structural part is considered and the springback phenomena occurring after forming and trimming are investigated through FE analyses utilizing an explicit implicit approach. In particular a sensitivity analysis on process parameter influencing springback occurrence is developed: blank holder force, draw bead penetration and blank shape.},
doi = {10.1063/1.2729513},
journal = {AIP Conference Proceedings},
number = 1,
volume = 907,
place = {United States},
year = {Sat Apr 07 00:00:00 EDT 2007},
month = {Sat Apr 07 00:00:00 EDT 2007}
}
  • With the drive towards implementing Advanced High Strength Steels (AHSS) in the automotive industry; stamping engineers need to quickly answer questions about forming these strong materials into elaborate shapes. Commercially available codes have been successfully used to accurately predict formability, thickness and strains in complex parts. However, springback and twisting are still challenging subjects in numerical simulations of AHSS components. Design of Experiments (DOE) has been used in this paper to study the sensitivity of the implicit and explicit numerical results with respect to certain arrays of user input parameters in the forming of an AHSS component. Numerical results weremore » compared to experimental measurements of the parts stamped in an industrial production line. The forming predictions of the implicit and explicit codes were in good agreement with the experimental measurements for the conventional steel grade, while lower accuracies were observed for the springback predictions. The forming predictions of the complex component with an AHSS material were also in good correlation with the respective experimental measurements. However, much lower accuracies were observed in its springback predictions. The number of integration points through the thickness and tool offset were found to be of significant importance, while coefficient of friction and Young's modulus (modeling input parameters) have no significant effect on the accuracy of the predictions for the complex geometry.« less
  • Springback prediction and compensation is nowadays a widely recommended discipline in finite element modeling. Many researches have shown an improvement of the accuracy in prediction of springback using advanced modeling techniques, e.g. by including the Bauschinger effect. In this work different models were investigated in the commercial simulation program AutoForm for a large series production part, manufactured from the dual phase steel HC340XD. The work shows the differences between numerical drawbead models and geometrically modeled drawbeads. Furthermore, a sensitivity analysis was made for a reduced kinematic hardening model, implemented in the finite element program AutoForm.
  • To reduce weight and increase fuel efficiency and safety, more and more automotive sheet stamping parts are being made of aluminum and high strength steels. Forming of such materials encounters not just reduced formability but also dimensional quality problems. Springback prediction accuracy and compensation effectiveness have been the major challenge to die development, construction and tryout. In this paper, the factors that affect the accuracy of springback prediction are discussed, which includes the effect of material models, the selection of element size, and the contact algorithms. Springback predictions of several automotive aluminum and high strength panels are compared with measurementmore » data. The examples show that the prediction correlates with measurement data in both springback trend and magnitude. The effect of springback on final product can be reduced or eliminated through process control and die face compensation. The process control method involves finding the root causes of springback and eliminating them through process modification. The geometrical compensation of die surface is a direct way to eliminate the springback effect. The global scaling compensation method is normally limited to parts with relatively small springback. For large springback and twisting, a new approach is discussed, which takes into account of the effect of deformation and springback history. The compensation is achieved iteratively by solving a system of non-linear equations. Production dies were cut to the compensated surface, which shows that the die compensation is an efficient way to reduce springback-induced geometry deviation.« less
  • In the sheet metal forming simulation, the shell element widely used is assumed as a plane stress state based on the Mindlin-Reissner theory. Numerical prediction with the conventional shell element is not accurate when the bending radius is small compared to the sheet thickness. The main reason is because the strain and stress formulation of the conventional shell element does not fit the actual phenomenon. In order to predict precisely the springback of a bent sheet with a severe bend, a measurement method for through-thickness strain has been proposed. The strain was formulated based on measurement results and calculation resultsmore » from solid element. Through-thickness stress distribution was formulated based on the equilibrium. The proposed shell element based on the formulations was newly introduced into the FEM code. The accuracy of this method's prediction of the springback shape of two bent processes has been confirmed. As a result, it was found that the springback shape even in severe bending can be predicted with high accuracy. Moreover, the calculation time in the proposed shell element is about twice that in the conventional shell element, and has been shortened to about 1/20 compared to a solid element.« less
  • Advanced high strength steels (AHSS) are increasingly being used in the automotive industry to reduce vehicle weight while improving vehicle crash performance. One of the concerns in manufacturing is springback control after stamping. Although computer simulation technologies have been successfully applied to predict stamping formability, they still face major challenges in springback prediction, particularly for AHSS. Springback analysis is very complicated and involves large deformation problems in the forming stage and mechanical multiplying effect during the elastic recovery after releasing a part from the die. Therefore, the predictions are very sensitive to the simulation parameters used. It is very criticalmore » in springback simulation to choose an appropriate material model, element formulation and contact algorithm. In this study, a springback benchmark test, the slit ring cup, is used in the springback simulation with commercially available finite element analysis (FEA) software, LS-DYNA. The sensitivity of seven simulation variables on springback predictions was investigated, and a set of parameters with stable simulation results was identified. Final simulations using the selected set of parameters were conducted on six different materials including two AHSS steels, two conventional high strength steels, one mild steel and an aluminum alloy. The simulation results are compared with experimental measurements for all six materials and a favorable result is achieved. Simulation errors as compared against test results falls within 10%.« less