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|저자명||Kwanghyun Ahn Hoon Huh Lee Ju Park|
This paper is concerned with the suggestion of the best dynamic hardening equation that is capable of quantifying the dynamic hardening properties of metallic materials for warhead. The dynamic response of metallic materials is indispensable for analysis of high speed condition. There is, however, no unique equation that is capable of representing the dynamic hardening characteristics of all kinds of materials although various dynamic hardening equations have been suggested by many researchers. Dynamic hardening equations reported and proposed have been investigated using the dynamic hardening characteristics of three kinds of representative materials for warhead: 4340Steel (BCC); OFHC (FCC); and Ti6Al4V (HCP). Three kinds of materials which have different crystalline structures were chosen to investigate the dynamic hardening characteristics with the variation of crystalline structure. Dynamic hardening characteristics of each material have been obtained by uniaxial tensile tests and SHPB tests. Uniaxial tensile tests have been performed with the variation of the strain rate from 0.001/sec to 100/sec and SHPB tests have been conducted at the strain rate ranging up to 4000/sec. Several existing models have been constructed and evaluated for Johnson-Cook model, Zerilli-Armstrong model, and Preston-Tonks-Wallace model using test results of three materials. Several proposed models by KAIST have been also evaluated for modified Johnson-Cook model, modified Khan-Huang model, and Lim-Huh model. The change of the strain rate and temperature during the deformation process were investigated for accurate application of hardening equations. The most applicable equation for each material has been suggested by comparison of constructed results.