| 摘要 |
PROBLEM TO BE SOLVED: To provide an estimation method of stretch-flange crack for establishing a design guide or design limit of stretch-flange shape for parts used for automobile and electric home appliance. SOLUTION: The estimation method includes the steps of: obtaining a numerical formula on relationship among sheared surface ratioγat blanking of a material to be estimated, either one or both of strain gradients in the end ridge directionΔεθand strain gradients in the end ridge vertical directionΔεr, and critical equivalent plastic strainεcr for cracking at the blanked edge; measuring sheared surface ratioγpart of the blanked material to be estimated and performing stretch-flange forming analysis: calculating strain gradient of eitherΔεθorΔεr or both of them; obtaining critical strainεcr part for cracking in the blanked end surface by substituting the sheared surface ratioγpart and the strain gradientsΔεθ,Δεr into the numerical formula; and estimating the stretch-flange cracking by comparing the equivalent plastic strainεfor the flange part obtained by the forming analysis with the critical strainεcr part of the actual parts. COPYRIGHT: (C)2010,JPO&INPIT
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