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Application of Innovative PVD Coating to Stamping Dies for Processing Ultra-High Tensile Strength Steel Sheets

SAE International Journal of Materials and Manufacturing

KOBAC, KOBELCO Advanced Coating America Inc-Yoshinobu Hosokawa, Kazuki Takahara
Kobe Steel Ltd-Kenji Yamamoto, Susumu Kujime, Tatsuya Yasunaga, Koichiro Akari
  • Journal Article
  • 2009-01-1170
Published 2009-04-20 by SAE International in United States
A novel nitride based coating system (BELCOAT-SS) was developed for the stamping dies for ultra high-tensile strength steel. It is characterized by an excellent wear resistance and low deposition temperature compare to the conventional diffusion coatings such as VC or TiC. High temperature wear test indicate that the wear rate of the new coating is 2 to 10 lower than conventional diffusion coatings. The result of stamping test using ultra-high tensile steel sheets indicate that life time of the die can be prolonged by the factor of at least 5 to 10 times.
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Axial and Bending Fatigue of a Medium Carbon Steel Including Geometry and Residual Stress Effects

SAE International Journal of Materials and Manufacturing

Eaton Corporation-Steve McCutcheon
The University of Toledo-Sean McKelvey, Ali Fatemi
  • Journal Article
  • 2009-01-0422
Published 2009-04-20 by SAE International in United States
This paper discusses the effects of changes in specimen geometry, stress gradient, and residual stresses on fully-reversed constant amplitude uniaxial fatigue behavior of a medium carbon steel. Axial fatigue tests were performed on both flat and round specimens, while four-point rotating bending tests were performed only on round specimens. All the tests were performed using shot peened and unpeened flat and round samples, to investigate the effects of compressive residual stresses on fatigue behavior. The specimens in the rotating bending tests experienced longer life for a given stress amplitude than in the axial test. Shot-peening was found to be beneficial in the long life region, while in short life tests the shot-peened samples experienced a shorter life than the unpeened samples under both axial and bending test conditions. Specimen geometry had a minimal effect on fatigue life and the difference observed between the behavior of round and flat samples is thought to be due to slightly different hardness levels of the two specimen geometries. The data generated from the aforementioned tests and conditions and the…
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A Theoretical Model for the Elastic-Plastic Behaviour of Spot Welded Joints

SAE International Journal of Materials and Manufacturing

University of Rome “Tor Vergata”-Francesco V ivio, Michele Ferracci
  • Journal Article
  • 2009-01-0026
Published 2009-04-20 by SAE International in United States
An analytical procedure for the evaluation of the elasticplastic behavior of spot welded joints is presented. The procedure is based on a new theoretical model of spot weld region: a circular plate having variable thickness with a central rigid nugget. The closed-form solution allows to describe the displacement of a rigid nugget when an axial orthogonal load is applied on the plate while plasticity and moderately large deflections are present. The goal is to reach a reliable spot weld region model which can be used as the basis to develop a spot weld element in FE analysis even when plasticity and large deflections are in effect. The analytical results obtained by using the new general relations precisely match those obtained modelling spot weld area by FEA.
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Viscosity Controlled High Penetration Wax on Paint Process

SAE International Journal of Materials and Manufacturing

Automobile R&D Center, Honda R&D Co., Ltd-Yasuhisa Shimizu, Takahide Maeda
  • Journal Article
  • 2009-01-0894
Published 2009-04-20 by SAE International in United States
The wax has been developed that is able to protect vehicle bodies from corrosion for extended periods. Vehicle bodies, composed mainly of steel components, are prone to corrosion, in particular side sills and various flanges. These sections are generally coated with wax to protect them from water, primary corrosion-promoting factor, enabling manufacturers to offer extended warranties against corrosion perforation in their catalogs. However, while corrosion prevention systems using conventional waxes contribute significantly to increased corrosion prevention, they result in increased costs, for example for dedicated wax coating lines in production lines, and require specialized lines tailored to specific vehicle bodies. Areas such as side sills and various flanges require careful attention to, and particularly high standards of, corrosion prevention. Particular attention to coating required in these areas tends to increase volume of coating material employed. Wax developed in this project displays excellent penetration. Material is able to penetrate into flanges, enabling achievement of a high level of anti-corrosion performance using a reduced amount of wax. This wax is controlling the viscosity characteristic of material, and…
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Improvements in Detector Design for X-ray Inspection of Cast Parts

SAE International Journal of Materials and Manufacturing

Fraunhofer Development Center X-ray Technology (EZRT)-N. Uhlmann
Fraunhofer Institute Integrated Circuits (IIS)-O. Scholz, P. Schmitt, M. Kube, R. Behrendt
  • Journal Article
  • 2009-01-0212
Published 2009-04-20 by SAE International in United States
The results of automatic X-ray inspection of cast parts rely heavily on the quality of the imaging components. Flat panel detectors suffer from a number of flaws, the most serious being long-term stability and image quality.This paper presents a new X-ray detector design which can increase defect detection quality, cost efficiency and long term stability of an industrial automatic X-ray inspection system.
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Mechanical Behavior and Failure Mechanism of Nb-Clad Stainless Steel Sheets

SAE International Journal of Materials and Manufacturing

Pacific Northwest National Laboratory-K. S. Weil
University of Michigan-K. Asim, W. F. Hosford, J. Pan
  • Journal Article
  • 2009-01-1393
Published 2009-04-20 by SAE International in United States
Because niobium-clad 304L stainless steel sheets are considered for use as bipolar plates in polymer electrolyte membrane (PEM) fuel cells, their mechanical behavior and failure mechanism are important to be examined. As-rolled and annealed specimens were tested in tension, bending and flattening. The effects of annealing temperature and time on the mechanical behavior and failure mechanism were investigated. Micrographic analyses of bent and flattened specimens showed that the as-rolled specimens have limited ductility and that the annealed specimens can develop an intermetallic layer of thickness of a few microns. The annealed specimens failed due to the breakage of intermetallic layer causing localized necking and the subsequent failure of Nb layer. The springback angles of the as-rolled and annealed specimens were also obtained from guided-bend tests. Nano-indentation tests indicated that the intermetallic layer exhibit much higher values of hardness and elastic modulus as compared to those of the stainless steel and Nb sheets.
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Measurement of Fracture Strains for Advanced High Strength Steels (AHSS) Using Digital Image Correlation

SAE International Journal of Materials and Manufacturing

ArcelorMittal-Gang Huang, Benda Yan, Hong Zhu
  • Journal Article
  • 2009-01-1174
Published 2009-04-20 by SAE International in United States
Predicting fracture behavior of Advanced High Strength Steels (AHSS) on both manufacturing and crash simulations is becoming more and more important with the wide use of AHSS in automotive industry. The accurate measurement of fracture strains is a critical input for predicting failure in FEA simulations. It is well known that fracture is a highly localized behavior and fracture strain is gauge or size dependent. In this paper, a full field measurement technique, Digital Image Correlation (DIC), is employed to measure gauge-dependent fracture strains for several Advanced High Strength Steels (AHSS) under tensile test conditions and Limit Dome Height (LDH) tests. Applications of the fracture strains for FEA simulation are discussed.
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Robust Optimization of Drawbead Forces for a B-pillar Stamping

SAE International Journal of Materials and Manufacturing

Ford Motor Company-Z. Cedric Xia
Severstal North America-Tony Chang, Yu-Wei Wang
  • Journal Article
  • 2009-01-0980
Published 2009-04-20 by SAE International in United States
Many uncertainties exist in the sheet metal stamping such as the variation of incoming material properties, die and press setup conditions, long-term tool wear and degradations. They are interacting in a way to make the process less robust, thus contributing to increased scrap rates and more unscheduled downtime. This paper presents a new approach for the die design optimization where these uncertainties are taken into account. A Tailor-Welded B-pillar consisting of 1.65mm DP600 and 0.9mm DDQ is selected as the focal part to demonstrate the new design process. The study is divided into two phases. The focus of the first phase is to understand the complexity of the formability window and determine effective optimization techniques under deterministic conditions. It is found that the formability window is highly nonlinear, or even discontinuous if a global objective function such as the Maximum Failure Factor is used. It is therefore more advantageous to adopt a regional approach where the split-prone zones and wrinkle-prone zones are identified. Optimization can then take place for each region with a multi-objective approach…
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Drawbead Restraining Force Modeling: Nonlinear Friction

SAE International Journal of Materials and Manufacturing

Ford Motor Company-Feng Ren, Laurent Chappuis, Z. Cedric Xia
  • Journal Article
  • 2009-01-1391
Published 2009-04-20 by SAE International in United States
A detailed investigation of influence of friction on drawbead restraining force modeling is presented in this paper. It is motivated by the need to accurately correlate line bead strengths, which are usually the output of an optimized draw development for controlling materials flow and achieving desired formability, and the physical drawbead geometries required for die face engineering. A plane-strain drawbead model with linear Coulomb friction is first established and the restraining forces corresponding to a range of bead penetration depths are obtained. The comparison of the simulation results with experimental data indicates that, while a larger Coefficient of Friction (COF) has better correlation for smaller bead penetrations and smaller COF does better for deeper bead penetrations, no single COF matches satisfactorily for overall range of bead penetration depths. Nonlinear friction models are subsequently proposed where the friction coefficient is dependent on the contact pressure, justified by a comprehensive review of theoretical and experimental evidences. Their applications to the drawbead modeling yield improved correlations for the restraining forces. The paper focuses on the investigation of the…
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Bayesian Probabilistic PCA Approach for Model Validation of Dynamic Systems

SAE International Journal of Materials and Manufacturing

Ford Motor Company-Ren-Jye Yang, Saeed Barbat, Para Weerappuli
General Electric Company-Xiaomo Jiang
  • Journal Article
  • 2009-01-1404
Published 2009-04-20 by SAE International in United States
In the automobile industry, the reliability and predictive capabilities of computer models for a dynamic system need to be assessed quantitatively. Quantitative validation allows engineers to assess and improve model reliability and quality objectively and ultimately lead to potential reduction in the number of prototypes built and tests. A good metric, which is essential in model validation, requires considering uncertainties in both testing and computer modeling. In addition, it needs to be able to compare multiple responses simultaneously, as multiple quantities are often encountered at different spatial and temporal points of a dynamic system. In this paper, a state-of-the-art validation technology is developed for multivariate complex dynamic systems by exploiting a probabilistic principal component analysis method and Bayesian statistics approach. The probabilistic principal component analysis approach is developed to address multivariate correlation, data uncertainty, and dimensionality reduction. The multivariate Bayesian hypothesis testing method is exploited to quantitatively assess the quality of the computer models for dynamic systems. The proposed method is illustrated with a rear seat child restraint system example with a Hybrid III 3-year…
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