| Dynamic expansion deformation and fragmentation of the metal tubes is widely interesting inthe industrial and military fields. On one hand, the study focuses on the high strain-rate dynamicdeformation and fragmentation of the thin-wall cylinders under electromagnetic load. On the otherhand, in the electromagnetic forming fields, researches pay close attention to the forming-limit ofmetal cylinders sheet that means deformation would be uniform and there will be localized on thesurface of parts if the plastic strain out of the forming-limit which should be avoided. Therefore, ithas important academic and engineering significance to study dynamic deformation andfragmentation of the thin-wall tubes in the process of electromagnetic expansion.This paper investigated the studies on dynamic localization and fragmentation of3104aluminum alloy thin-wall cylinders in the process of electromagnetic expansion under severalloading rates combined with experimental and FEM methods. The conclusions are as follows.(1)The localized deformation occurs firstly at the edge of the cylinder sheet subjected to a uniformexpansion loading, and those localization zones develop at an angel of45°or135°to the axialdirection for the cylinder sheet. Then the cracks initiate and propagate along the localization bandsand lead to the fragmentation. Furthermore, the quantity of fragment increases with loading rateenhanced.(2) For the cylinder (60mm) under local pressure, its localized deformation occurs firstlyat the center place and develops to be cracks along with the axial direction. With the loading rateenhanced, the distance between cracks increase.(3) Simulation results show that the loading ratemay lead to different failure mode. As shown in the paper, when the peak load is up to70MP or80MP, localized deformation just appears on the central of the cylinder and there is no localizationphenomenon at the edge of cylinders. |
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