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Technical Paper

Bending Performance of Advanced High Strength Steel Tubes

To reach safety, emissions, and cost objectives, manufacturers of automotive body structural components shape thin gauge, high strength steel tube using a series of manufacturing steps that often include bending, preforming and hydroforming. Challenging grades and bend severity require a sensitive optimization of the tubular bending process. To this end, it is necessary to achieve an understanding of efficient measurement methods capable of capturing small differences in bending formability. In preparation for an optimization of a 90o bend using Dual Phase 780 (DP780) and High Strength Low Alloy (HSLA350) thin walled tube, the measurement techniques of three formability characteristics: thinning, strain, and final geometry were statistically evaluated. In addition, the difference in the bending behaviour of the two grades was evaluated.
Technical Paper

Bending Process Optimization of Dual Phase 780 (DP780) Tubes for Body Structural and Chassis Applications

To reach safety, emissions, and cost objectives, manufacturers of automotive body structural and chassis components shape thin gauge, high strength steel tube with a bending, pre-forming and hydroforming process. Challenging grades and bend severity require a careful optimization of the bending procedure. A joint project between Ford and ArcelorMittal Tubular Products investigated suitable bending parameters for severe bends using commercially available thin-walled DP780 and HSLA350 tubes. This paper summarizes the measurement methods found to be capable of capturing small differences in bending formability and details the influence of bender variables such as boost, pressure die, center-line bend radius and bend angle on the wrinkling, thinning and springback of these tubes. As a result of this work, recommendations were made as to effective bender set-ups for these tubes.
Journal Article

Measurement of Fracture Strains for Advanced High Strength Steels (AHSS) Using Digital Image Correlation

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.
Technical Paper

NVH Analysis of Lightweight Steel Components in Full Vehicle

With tighter environmental regulations, as well as political and public opinion pressure, the reduction of automotive polluting gas emissions is subject to intense debates and interests. Before a potential transition to full electrical vehicles as the long term solution, the reduction of mass remains of prime importance to permit direct reduction of emissions in internal combustion engine (ICE) vehicles. In addition to the challenges of structural integrity and safety issues, the acoustical and vibration performance of vehicles can be greatly influenced by mass reduction. This article presents a case study of lightweight design of an automotive door with a high strength steel thin gauge outer panel. An experimental comparison between a reference and a lightweight door was conducted in a complete vehicle, allowing assessing the potential effect of the mass reduction on the acoustic and vibrational performances.
Technical Paper

Study on Metal Sheet Ductile Fracture using Square Punch Test

This study introduces a new practical calibration approach of ductile fracture models by performing square punch tests on metal sheets. During square punch tests, ductile fracture occurs at either the corner of die or punch radius when applying different clamping loads and lubrication conditions. At the corner of die radius, in-plane pure shear is induced at the intersection between the side-walls and the flange by combined tension and compression. On the other hand, the material at the corner of the punch radius is under combined bending and biaxial tension. The material studied in this paper is advanced high strength steel (AHSS) DP780 from ArcelorMittal. Isotropic J2 plasticity model with mixed Swift-Voce hardening rule is calibrated from uniaxial tensile tests.