Part distortion is a critical issue during Additive Manufacturing (AM) of metallic parts since it prevents this technology from being implemented at industrial level. To this regard, distortion prediction even from design stage has become crucial. Actually, numerical modelling methodologies play an important role here. Different modelling approaches have been developed but one of the most computationally efficient methodology to predict distortion is the so called inherent strain method. In this work an empirical methodology to determine inherent strains is presented. This is the input data in simplified Finite Element (FE) models in order to predict distortion and residual stress fields. These inherent strains are calculated considering layer lumping strategies that might be adopted in the numerical model as well. The procedure has been developed and validated using the wellknown twin-cantilever beam structure. Ti-6Al-4V beams have been manufactured by LPBF technology following different scanning strategies. Distortion after support removal has been measured in order to be compared against numerical results. The methodology has been applied at coupon level giving accurate results and providing a preliminary validation.
In the present paper, residual stresses induced by honing processes on hardened steel cylinders were determined. Cubic boron nitride (CBN) abrasives were employed. Both surface measurements and depth profiles were obtained by means of XRD. SEM observations were performed on samples’ surface. Roughness and material removal rate were also measured. Compressive residual stresses, which are known to increase fatigue life of components, were reported both in the axial and in the tangential direction. Shearing stresses were negligible. If only rough honing is taken into account, as a general trend, the lower cutting conditions used, the higher surface stresses are. A similar situation was found when only semifinish or only finish honing is considered. In most cases studied, stress profiles similar to those obtained in grinding processes, in which compressive stresses decrease with depth, were observed. However, in rough honing at hard cutting conditions, a typical hook-shaped profile was found with maximum compressive stress at 80-µm depth. Such shape is usual in turning processes. In order to obtain high surface stresses a rough, semifinish or finish honing operation with low cutting conditions is recommended. However, if stresses are to be obtained at a certain depth, rough honing at high cutting conditions is to be selected.Postprint (author's final draft
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