Experimental and finite element analysis on oscillating cold forming in consideration of nonlinear loading-unloading-reloading behavior. (December 2018)

• Record Type: Journal Article
• Authors: Ben, Ning-yu; Zhang, Qi; Choi, Hongjin; Bandyopadhyay, Kaushik; Lee, Myoung-Gyu
• Is Part Of: Journal of manufacturing processes. Volume 36(2018)
• Page Start: 520
• Page End: 534
• Publication Date: 2018-12
• Subjects: Oscillating cold forming -- Constitutive model -- Simulation -- Nonlinear elasticity; Production management -- Data processing -- Periodicals; Manufacturing processes -- Periodicals; Procestechnologie; Productietechniek; Production -- Gestion -- Informatique -- Périodiques; Fabrication -- Périodiques; Manufacturing processes; Production management -- Data processing; Periodicals; 670.5
• DOI: 10.1016/j.jmapro.2018.10.043
• Languages: English
• ISSNs: 1526-6125

Abstract

Highlights: Effects of loading-unloading-reloading behavior in oscillating forming were analyzed by experiments and simulations. Novel multi-surface nonlinear elasticity model combined with strain-rate dependent hardening was applied to the simulations. The prediction for product geometry was improved by the advanced modeling. Mechanism of force reduction and material flow in oscillating forming could be analyzed by the FE simulations. Abstract: Oscillating cold forming (OCF) has gained attentions in automotive and aerospace industries owing to force reduction and enhanced precision. However, the mechanism of force reduction and material flow in the OCF compared to those of conventional cold forming (CCF) was not clear. Therefore, the implementation of realistic elastic response under loading–unloading–loading (LUL) cyclic condition, which is the one of main deformation mechanism of current application, was studied through experiments and simulations. Constitutive models that describe the nonlinear elastic modulus change as a function of plastic deformation and the strain rate dependent hardening were implemented in the finite element simulations. Two models for elasticity, i.e., the Chord and multi-surface models, were employed in the simulations and the results were compared with experiments. The influences of nonlinear elasticity in the OCF were investigated from the aspects of forming force, material flow, and stress distribution. In each aspect, the differences that lead to force reduction and effective material flow were explained. The forming force and product geometry in the OCF were appropriately described by the Johnson-Cook type hardening law coupled with the multi-surface elasticity model. The material in nonlinear elastic state after prior plastic deformation softened the workpiece, which enhances material flow toward the tooth tip by preventing material accumulation in the die entrance.