Abstract
A constitutive model for automobile steel with high elongation needs to be established to predict the dynamic deformation behavior under hydroforming applications. In order to clarify the confusing discrepancy in the essential parameters of the classical Cowper-Symonds (C-S) model, a series of automobile structural steels have been employed to investigate the strain rate response by conducting tensile dynamic deformation. Metallographic microscopy and orientation distribution functions were used to characterize the microstructure and texture components of the steels. The microstructure observation discloses that the matrix of all steels is mainly of ferrite and the texture constituent provides a framework for steel to withstand external deformation. The C-S model can be applied to simulate the dynamic deformation with satisfied expectations. It is concluded that the essential parameters D and p in the model show a specific relationship with the steel grade, and the parameter D is proportional to the steel grade and related to material anisotropy, while the parameter p is inversely proportional to the steel grade and has close links with the grain boundary characteristics.
Highlights
The mechanical behavior of automotive structural steels ensures the safety of automobile components during the occurrence of extreme collisions by the absorption of impact energy; the dependent variables of the quasi-static deformation and the dynamic response to collision must be taken into account in order to predict the failure process under varied strain rate conditions [1,2]
As for Q460 and3.Q500, theand black areas consist of pearlite and a small quantity of bainite
The microstructures for Q380 and Q420 steels consist of ferrite and pearlite, while that for Q460 and Q500 consist of ferrite, pearlite and a small quantity of bainite
Summary
The mechanical behavior of automotive structural steels ensures the safety of automobile components during the occurrence of extreme collisions by the absorption of impact energy; the dependent variables of the quasi-static deformation and the dynamic response to collision must be taken into account in order to predict the failure process under varied strain rate conditions [1,2]. A high-speed servohydraulic testing machine and modified Hopkinson bar system can be employed to record the mechanical behavior of materials over a wide range of strain rates [3,4]. A constitutive model for such steels needs to be established to predict the dynamic deformation behavior under hydroforming conditions. Zwick/Roell HTM5020 testing machine to minute the dynamic response, and discloses the inherent regularity of the observed microstructure to the parameters of the C-S model
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