Two dimensional plastic waves in quasi rate independent viscoplastic materials

The subject of this work is an analysis of the experimental biaxial Hopkinson bar technique when such a device consists of a cruciform tensile specimen surrounded by four very long elastic bars. Unlike commonly applied by-pass analysis which attempts to draw conclusions from behavior of elastic bars we attempt to take into account real plastic waves inside the specimen with few hundreds of reflections. A quasi rate-independent as well as a more general rate-dependent tensor function model for ASME 537 steel are applied. Plastic wave speeds non-existent in traditional elasto-viscoplasticity are analyzed. Some preliminary numerical results for symmetric and non-symmetric loading cases valid for initial and subsequent elastic ranges are given. Predmet ovog rada je analiza talasa koji se pojavljuju tokom eksperimenta sa dvoosnim Hopkinsonovim stapom kada se taj uredjaj sastoji iz krstastog zateznog uzorka oivicenog sa cetiri veoma duga elasticna stapa. Nasuprot uobicajene analize koja pokusava da izvuce zakljucke iz ponasanja elasticnih stapova mi ovde uzimamo u obzir realne plasticne talase unutar uzorka sa nekoliko stotina odbijanja. Primenjeni su konstitutivni model prividno nezavisan od brzine kao i opstiji model sa tenzorskom funkcijom na celik ASME 537. Analiziraju se takodje i plasticne brzine talasa nepostojece u tradicionalnoj elasto-viskoplasticnosti. Dati su neki uvodni numericki rezultati za simetricne i nesimetricne slucajeve opterecenja u pocetnim i sledecim elasticnim opsezima.