Abstract
Automotive stamping is a multi-stage process where a sheet material is drawn in first stage and then redrawn, flanged and pierced in subsequent stages. In the first draw stage, continuous strain path change is induced in the material while a discontinuous strain path change occurs when the material is processed in the subsequent stages of a multi-stage stamping operation. The strain path transition can potentially alter the forming limit of the material. Previous research has investigated the effect of the discontinuous mode of strain path change by loading the sample in one strain path, unloading it, then reloading it in a second path. Thus, discontinuous strain path change was obtained. In this work, the effect of continuous strain path change was investigated with a novel experimental design that allowed cruciform samples to change strain path continuously without unloading. The work was carried out in two stages. In the first stage, the design of the cruciform sample was verified with finite element modelling to ensure the occurrence of continuous strain path change and this was validated experimentally using DX54 material by capturing full-field strain measurements data using digital image correlation technique. The size of the experimental apparatus permitted it to be placed inside a scanning electron microscope chamber. In the second stage, the validated test method was used to evaluate microstructural changes during the deformation including full-field strain and texture evolution. The micro-strain evolution showed rotation of strain bands while the texture evolution conveyed grain rotation during continuous strain path change.
Highlights
Automotive stamping is a multi-stage deformation process
To investigate the effect of material deformation on microstructure, Ghadbeigi et al [7] and Celotto et al [8] applied a recently developed technique where mechanical deformation of a material was performed inside an scanning electron microscope (SEM) chamber using a miniaturised test rig and the SEM images were captured from the sample surface while the elongation process was going on in-situ
The difference in the length of the uniaxial deformation between the experiment and simulated curve was likely to be due to the machining tolerance for the slot and thickness of the central region during manufacturing of the specimen for experimental trial
Summary
Automotive stamping is a multi-stage deformation process. In the first stage, a metal sheet is drawn into a definite shape and in the subsequent stages; the drawn component is redrawn, flanged or pierced. To investigate the effect of material deformation on microstructure, Ghadbeigi et al [7] and Celotto et al [8] applied a recently developed technique where mechanical deformation of a material was performed inside an scanning electron microscope (SEM) chamber using a miniaturised test rig and the SEM images were captured from the sample surface while the elongation process was going on in-situ They elongated the samples along the uniaxial strain path and post-processed the periodically captured SEM images using the digital image correlation (DIC) technique to examine the strain field induced on the sample surface at the meso-scale. Caër and Pesci [9] contributed to the design of sample for the in-situ deformation technique by designing a cruciform sample that ensured the strain localisation at the centre of the sample while elongating the sample along both the directions using a micromechanical rig They studied the grain rotation and misorientation development in an annealed AISI 304 stainless steel in-situ during the biaxial loading inside an SEM chamber. The micro-strain evolution showed rotation of strain bands while the texture evolution conveyed grain rotation during continuous strain path change
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
