平面ひずみ押出し加工の中心割れ発生の予測

概要

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The central burst defect, also called chevron crack, in the extruded product worked under plane strain is analyzed. To the prediction of central bursting the criterion based on plastic instability is used. It satisfies the sufficient condition s_iε_i=0 for multiplicity of solution, which is derived from the consideration based on its necessary condition Δs_iΔε_i=0,where s_i denotes the nominal stress rate, and Δ shows the difference of any two multiple solutions. The criterion gives the limit strain identical to the one derived from Swift's criterion under plane stress condition, but its concept is quite different with Swift's. Stress and strain in the specimen are evaluated using FEM. The measure y_M to present the occurrence of central bursting is proposed and it is calculated using the stress and strain on the central line of the product. When y_M<0,the bursting occurs. The value of y_M is shown in the range of combination of cone angle and reduction. It is found that the zone denoting the central burst is very similar to the one obtained by slip line method.
一般社団法人日本機械学会の論文
1998-09-25