Strengthening by Plastic Corrugated Reinforcements: An Efficient Way for Strain-Hardening Improvement by Architecture
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1188-LL05-01
Strengthening by Plastic Corrugated Reinforcements: An Efficient Way for Strain-Hardening Improvement by Architecture O. Bouaziz, S. Allain , D. Barcelo, R. Niang ArcelorMittal Research, Voie Romaine-BP30320, 57283 Maizières-lès-Metz Cedex, France
ABSTRACT The particular plastic behaviour of corrugated metallic strips under tension has been investigated and it has been exploited to propose a new design of structural material using strengthening by plastic corrugated reinforcement. It is reported that the proposed approach is suitable to strongly improve the strain-hardening by this specific architecture. . INTRODUCTION In material science the improvement of the strain-hardening is often a crucial challenge for the development of alloys or composites suitable to be formed without localization of the plastic strain. Unfortunately strain-hardening tends to decrease with an increasing strength. This problem has been widely investigated and metallurgical solutions such metal matrix composites [1,2], multiphase alloys ( as steels [3] or Ti-based [4]) and using also dynamic hardening mechanism as Tranformation Induced Plasticity [5] or Twinning Induced Plasticity [6] have been proposed. As mentioned by pioneering work of Ashby [7] and as illustrated in a recent review [8] the metallurgical limitations to combine contradictory properties could be overcome changing the architecture of the materials at a scale between microstructure and samples or part. In this paper a method is proposed to combine more efficiently strength and strain-hardening. The approach is based on the interest of the use of plastic corrugated reinforcement embedded in a matrix has been investigated. In a first part the particular plastic behaviour of a corrugated metal under tension is characterized. In a second part the improvement of the matrix strengthened by corrugated reinforcements is reported.
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Fig1. Usual morphology of the reinforcement by particle (a.) and by fiber (b.) . Comparison with the approach based on corrugated reinforcement (c.)
EXPERIMENTAL PROCEDURE Strips of Interstitial Free steel have been used. The thickness is 1 mm. Tensile specimen have been first machined to 20mm width and 80mm gauge length. In a second step different corrugations have been obtained by deformation at room temperature using uniaxial compression of the tensile specimen between two anvils where metallic cylinders have been added as shown in Fig.2a. This device is suitable to produce varying corrugation geometries changing the diameter of the cylinders and/or the spacing between cylinders. One of the obtained corrugated patterns is shown in Fig2.b. The tensile behaviour have been characterized for the flat sample (i.e. without any corrugations) and for two samples with 2 and 4 corrugations with the geometry shown in Fig.2b. The experimental evolution of the engineering stress (force divided by the initial area) as a function of the elongation is drawn in Fig3. Initially the elongation of the corrugated samples is provided by un-bendin
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