Papers by Author: Michael J. Worswick

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Authors: O. Orlov, Éric Maire, Jérôme Adrien, Michael J. Worswick, David J. Lloyd
Abstract: A three-dimensional damage percolation model, which captures the effect of microstructural heterogeneity on damage evolution, has been developed to model damage initiation and propagation in materials containing second phase particles. It considers the three phenomena preceding ductile rupture of the material: void nucleation, growth, and coalescence. Threedimensional X-ray tomography is used to obtain measured three-dimensional second phase particle distributions in aluminum alloy sheet. Material damage evolution is studied within a tensile test simulation and compared to measured damage from an in situ tensile test utilizing X-ray tomography. Experimental and simulation results for material damage initiation and evolution are in good agreement.
Authors: Zeng Tao Chen, Michael J. Worswick, David J. Lloyd
Abstract: The numerical simulation of the stretch flange forming operation of Al-Mg sheet AA5182 was conducted with an explicit finite element code, LS-DYNA. A Gurson-Tvergaard- Needleman (GTN)-based material model was used in the finite element calculation. A strain controlled void nucleation rule was adopted with void nucleating particle fraction measured directly from the as-received Al-Mg sheet. Parametric study was performed to examine the effect of void nucleation strain on the predicted onset of ductile fracture. Critical porosity levels determined through quantitative metallurgical analysis were adopted to predict the commencement of void coalescence in the GTN model. The numerical results were compared to the experimental ones and an applicable void nucleation strain was suggested.
Authors: Zeng Tao Chen, Michael J. Worswick, David J. Lloyd
Abstract: In this paper, stretch flange forming experiments were performed on the AA5182 and AA5754 Al-Mg sheet materials. A triple-action servo-hydraulic press, developed at the University of Waterloo, was used in the experiments. A z-flange tooling, which incorporates mating drawbeads on the main and backup punches, was employed. Drawbeads are used in commercial stretch flange operations to control or limit the rate of cutout expansion. Of interest in the current research are the flange formability and the damage development induced by the bending-unbending of the sheet as it passes through the drawbeads. Both AA5182 and AA5754 were tested with thickness of 1.6 mm. Further tests were performed using 1.0 mm AA5182 to examine the effect of thickness. To examine the effect of cutout size on the formability, cutout radii in the range 88 to 98 mm in increments of 2 mm were tested to failure.
Authors: Michael J. Worswick, R. Smerd, C.P. Salisbury, S. Winkler, David J. Lloyd
Abstract: This paper presents results from quasi-static and high rate tensile testing of three aluminum sheet alloys, AA5754, AA5182 and AA6111, all of which are candidates for replacing mild steel in automotive bodies. Tests were performed at quasi-static rates using an Instron apparatus and at strain rates of 600 to 1500 s-1 using a tensile split Hopkinson bar. Additionally, an in-depth investigation was performed to determine the levels of damage within the materials and its sensitivity to strain rate. The constitutive response of all of the aluminum alloys tested showed only mild strain rate sensitivity. Dramatic increases in the elongation to failure were observed with increases in strain rate as well as greater reduction in area. Additionally, the level of damage was seen to increase with strain rate.
Authors: Mohammad Jaffar Hadianfard, Michael J. Worswick
Abstract: The effect of strain rate in the range of 10-4 to 10-1 s-1 on localization of deformation and fracture behavior of 5754 and 5182 aluminum alloys is investigated. For this study, tensile tests, interrupted tensile tests, shear band decoration, fractography and image analysis has been used. This investigation is based on experimental work and observation of the material behavior. Results show that strain rate has some effect on the mechanical properties and deformation stability of the alloys. The area of localized plastic deformation and thickness of the shear bands were found to be sensitive to the strain rate. It was also observed that localization of plastic deformation and shear band formation is an important step in the damage propagation and final fracture of the alloys. Detail of damage development, based upon micrographs of samples interrupted at different stages of straining is presented
Authors: Zeng Tao Chen, Michael J. Worswick
Abstract: Stretch flange forming experiments of AA5182 and AA5754 sheet alloys were performed to characterize the forming properties. Identical blanks with the same cutout radius were deformed to 25, 50, 75, and 90% of the measured minimum punch depth to fracture. Strain development during stretch flange forming was tracked through strain measurement of the recovered deformation-interrupted samples. Finite element modeling of stretch flange forming was performed, and the resulted strain distribution along the stretch flange profile was compared to the experimental results. Good agreement was observed between the numerical and experimental results. Two failure modes observed in the stretch flange experiments, inner edge necking and circumferential cracking in sidewall, were related to the measured strain locus and sheet thickness.
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