Press Formability of the Steel/Resin/Steel Laminates Vibration Damping Sheets

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Effects of the shear flow stress of resin core on the press formability of steel/resin/steel laminates vibration damping sheets were investigated. First, for several types of sheets with different core materials, conventional sheet metal formability tests, i.e. the simple tension test, Swift cup test and the hole expansion test, were performed. It mede clear that higher shear flow stress of the core resin gives more excellent press formability, both for wrinkling and fracture resistivity. The limit strain ,at which the skin steel sheet breaks, increased for high shear flow stress of resin core. Because the shear flow stress constrained the development of strain of the outer skin layer in the localized zone. M-K model,which had been proposed by Marciniak and Kczinski,was modified to predict the limit strain of the three layers sandwich sheet under uniform biaxial plane stress states. Results of numerical calculation gives the remarkable influence off the value of shear flow stress and elastic rigidity on the limit strain.Next, double-bent phenomenon in the V-type bending process was analyzed using J2-deformation theory and the results of numerical analysis make clear some effects of shear flow stress of the resin core on double-bent phenomenon. It could determine the forming condition that ensure to perform no double-bent V-bending operation. Finally, in order to decide the visco-elastic-plastic properties of resins under simple shear, we tried to construct the torsion testing machine for the sandwiched ring specimen with resin core. Trial machine is able to torsion test with any specified path of shear strain rate. For several types of resin, workhadening rules and strain rate sensitivities are decided by the test using the trial testing machine.