押出し加工における中心割れ発生の多価規準による予測

概要

論文の詳細を見る
The central burst defect, also called chevron crack, in axi-symmetric extrusion is analyzed. For the prediction of central bursting the criterion based on plastic instability is used. It satisfies the sufficient condition s_uε_u=0 for multiplicity of solution, which is derived from the discussion based on its necessary condition Δs_uΔε_u=0,where s_u denotes the nominal stress rate, and Δ shows the difference of any two multiple solutions. Stress and strain in the specimen are evaluated using FEM. As the parameter representing the risk for the occurrence of central bursting the measure y_M is introduced 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 between the cone angle of die and the reduction in working. From these values the working condition predicting y_M=0 is interpolated for several work hardening exponents, which shows the boundary between workings with and without cracking. The boundary curve predicted is compared with experimental values obtained by Zimerman and Avitzur. The prediction is found to be, on the whole, similar to the experimental results.
一般社団法人日本機械学会の論文
1999-08-25