Abstract
This paper presents a novel calibration procedure of the modified Mohr-Coulomb (MMC) fracture model by use of localization analyses and applies it for three tempers of an AA6016 aluminium alloy. The localization analyses employ the imperfection band approach, where metal plasticity is assigned outside the band and porous plasticity is assigned inside the band. Ductile failure is thus assumed to occur when the deformation localizes into a narrow band. The metal plasticity model is calibrated from notch tension tests using inverse finite element modelling. The porous plasticity model is calibrated by use of localization analyses where the deformation histories from finite element simulations of notch and plane-strain tension tests are prescribed as boundary conditions. Subsequently, localization analyses are used to establish the failure locus in stress space for proportional loading conditions and thus to determine the parameters of the MMC fracture model. Finite element simulations of notch tension and in-plane simple shear tests as well as two load cases of the modified Arcan test are used to validate the calibrated fracture model. The predictions by the simulations are in good agreement with the experiments, even though some deviations are seen for each temper. The results demonstrate that localization analyses are a cost-effective and reliable tool for predicting ductile failure, reducing the number of mechanical tests required to calibrate the MMC fracture model compared to the hybrid experimental-numerical approach usually applied.
Highlights
Modelling and simulation of ductile fracture in metallic materials is an active research field where significant progress has been made over the last decades
This paper has presented a novel calibration procedure of the modified Mohr-Coulomb (MMC) fracture model by use of localization analyses of the imperfection band type and applied it for three tempers of the aluminium alloy AA6016
Notch tension (NT10) and plane-strain tension (PST) tests were used in the calibration of the metal and porous plasticity models assigned to the material outside and inside the imperfection band, respectively
Summary
Modelling and simulation of ductile fracture in metallic materials is an active research field where significant progress has been made over the last decades. This research is important since industries like the automotive industry want to utilize the materials to the brink of failure. The demand for accurate predictions of fracture by numerical simulations is increasing. Reliable design of structural components against ductile fracture requires a robust numerical framework able to accurately describe the damage and fracture properties of the material. In many lightweight metals, which have received special attention by the automotive industry in recent years, strength and ductility are inversely proportional properties. As strength is often favoured in this case, the ductility imposes a great challenge in design of safety components of such materials
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