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Ductile fracture occurs due to microvoid nucleation, growth and, finally, coalescence into microcracks. These microcracks grow in the presence of stresses leading to fracture. In this work, a criterion based on this phenomenon is used to simulate ductile fracture in a class of steel specimens. A critical value of the damage variable, estimated from experimental results, is used as an indicator of fracture initiation. A continuum damage mechanics model is employed to incorporate the damage in the constitutive relation of the material. A damage growth law based on experimental results is used. It is observed that the damage reaches the critical value first at the center in both the cylindrical and prenotched specimens. Thus, the failure begins at the center and then grows radially outward toward the free surface. The analysis is carried out till the damage reaches the critical value across the whole cross-section, at which point the specimen is considered to have failed. [ABSTRACT FROM AUTHOR]

Deep drawing is an extensively used press working process since it eliminates expensive machining and welding operations and enables the production of components at a very high rate. The workpiece material used in a deep drawing process is anisotropic in nature, due to a prior thermomechanical treatment. Earing is one of the major defects observed in a deep drawing process due to the anisotropic nature of the sheet material. Knowledge about the ear formation in deep drawing allows a prior modification of the process, which can result in a defect-free final product with financial savings. In this paper, a recently proposed anisotropic yield criteria by Barlat et al. for rolled sheets is used to model the anisotropy for simulating the earing defect in square and circular cup drawing processes. The effect of the tooling geometry and process parameters on the ear formation is studied. It is shown that, in the square cup, the uneven metal flow rate, rather than the material anisotropy, is mainly responsible for the flange earing. Finite element formulation, based on the updated Lagrangian approach, is employed for the analysis. The stresses are updated in a material frame and the logarithmic strain measure is used, which allows the use of a large increment size. Isotropic hardening is assumed, and it follows a power law. Inertia forces are neglected due to small accelerations. The modified Newton–Raphson iterative technique is used to solve the nonlinear incremental equations. [ABSTRACT FROM AUTHOR]

Surface roughness plays an important role in product quality, particularly in situations such as precision fits and high-strength applications. Magnetic abrasive finishing (MAF) is an advanced finishing process in which the cutting force is controlled by magnetic field. This process is capable of giving nanometer-scale surface finish. This paper describes modeling, simulation and analysis of the profiles of the surface obtained after MAF. The real-life surface profile is so complicated that a single parameter can not give a full description of surface quality. However, in the present work, the height of the surface profile distribution before MAF is considered to be Gaussian. The surface roughness model is developed which computes center-line average (Ra) surface roughness. The validity of this model is checked by comparison with the experimental results. A series of numerical experiments are performed using finite-element methods and surface roughness models of the process, to study the effect of flux density, height of working gap, size of magnetic abrasive particles and rotational speed of magnetic pole on the surface quality. Based upon the results, we concluded that Ra values of the finished workpiece surface decrease with increase in magnetic flux density, size of magnetic abrasive particles and rotational speed of flexible magnetic abrasive brush. On the other hand, the surface roughness values increase with increase in the working gap. [ABSTRACT FROM AUTHOR]