Wire arc additive manufacturing (WAAM) technique became an emerging manufacturing technology because of its cost-effective in creating large-scale metal parts with moderately high deposition rates. ...Mainly, WAAM works through the utilization of heat source as an electric arc by melting the metal wire to build the three-dimensional metal parts in a layer-by-layer approach, which may significantly minimize the fabrication costs compared to powder and other additive manufacturing techniques such as laser and electron beam, similarly. This article reviews WAAM processes and methods and gives an exhaustive overview of the residual stresses, microstructures, and material properties of the as-fabricated and post-fabrication treated WAAM components. The typical defects during the fabrication of metal components by the WAAM process are residual stresses, deformity, porosity, and cracking. And also, methods on controlling residual stresses, improving material properties, and effects of post-processing treatments to enhance the part quality fabricated by using the WAAM process are recommended in this review. Finally, the measurement methods of residual stresses in the metal parts and FEA simulations in the WAAM are discussed. FEA simulations provide better insights on moving heat source model, temperature distributions, and residual stresses in the WAAM process. This article concludes that selecting process parameters affects the quality WAAM component during the deposition process. And also, approaches to improving the part quality are proposed. The materials fabrication issues in the WAAM processes were outlined, and the advanced WAMM processes were suggested to obtain high quality and defect-free WAAM parts.
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Overhead conductors enduring aeolian vibrations are subjected to fretting fatigue damage. To predict the fretting fatigue cracking risk along the conductor-clamp assembly involving a multitude of ...crossed-strands contacts, a multi-scale analysis is considered. First, a global model provides the spatial distribution of normal, tangential and fatigue loadings for every contact. “Specific” loading cases were simulated using a local FEM model involving a Crossland fatigue stress analysis and a critical distance approach to correct the stress-gradient effects. Mono-contact fretting fatigue experiments were then performed reproducing the exact same loading cases. The comparison between numerical predictions and experimental results showed that a very good prediction of crack-nucleation is achieved using this strategy. However, total failures were not systematically observed. It is believed to be related to the manufacturing process. Wire drawing induces a longitudinal microstructure which promotes cracks with a low diving angle, rather than cracks propagating directly into the bulk. 3D-surface-crack simulations confirm a crack arrest phenomenon induced by the contact-induced compressive stress field.
•Global modeling of a conductor-clamp assembly and assessment of fretting loadings distribution.•Local modeling of mono-contact between two aluminium strands to perform crack nucleation predictions.•Reverse identification of the optimal distance to use a non-local approach, based on experimental fretting tests.•Experimental fretting fatigue tests of a mono-contact subjected to fretting fatigue, comparison with simulations.•Stress Intensity Factor calculations to illustrate experimental fretting fatigue results.
Multi-material selective laser melting (SLM) is a new development direction in additive manufacturing technologies to realize the incorporation of different materials within a single component. In ...this work, processing parameters, cross-sectional features and surface morphologies of TiB2 tracks on SLM-processed Ti6Al4V alloy layer were investigated. A processing window was determined by examining the type of molten pools and continuity of scanned tracks. Formation mechanism of microstructures at the cross-sections of TiB2 tracks was also discovered. At a high scan speed above 700 mm/s, the tracks all exhibited an unstable surface consisting of excessive shrinkage, spatters and cracks. Consequently, based on the experimental analysis and numerical simulations, a range of laser energy density from 0.67 J/mm to 1.50 J/mm at laser powers of 400–450 W was found to be a feasible scope of processing parameters to fabricate stable tracks of TiB2 on Ti6Al4V alloy by SLM.
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•Stable TiB2 tracks were formed on Ti6Al4V alloy during selective laser melting of ceramic-metal multi-material.•Formation mechanisms of different microstructures in the cross-sectional molten pool were determined.•TiB2 tracks at high scan speed exhibited an unstable surface consisting of excessive shrinkage, spatters and cracks.•Numerical simulations of temperature distribution and cooling rate during SLM process were given.
The authors deal with the use of electrostatic shielding to mitigate the electric discharge machining (EDM) currents on the induction machine bearings. Employing 2D and 3D models, several finite ...element analysis (FEA) simulations were thoroughly made addressing the shielding effectiveness to attenuate the shaft-to-frame voltage and the associated eddy current losses for different shield widths, thicknesses and materials. The obtained results provide very good guidelines for the practical design of the shielding device. In addition, comparisons between frequency- and time-domain models highlight the importance of considering factors such as the saturation of the iron core, the rotor movement and non-sinusoidal sources to compute the eddy current losses in the shield. Besides, the authors present a comprehensive theoretical review of the EDM currents, where the main influencing factors and action mechanisms are compiled in a clear and didactic approach, for the purpose of broad comprehension.
Gold-based micro-electro-mechanical-systems (Au-MEMS) capacitive accelerometers can simultaneously realize high sensitivity and miniaturization because of the high mass density of Au. In order to ...further improve the sensitivity of the Au-MEMS capacitive accelerometers, Young's modulus of the cantilever-like spring part connected to the movable component is a key parameter. Considering the size effect in the mechanical property of metallic materials on micro-scale, the design of the spring part is expected to reflect their Young's modulus; that is, effective Young's modulus (Eeff). In this study, we clarify effects of the structural designs of the Au-based micro-cantilevers on their Eeff by experiments and finite element analyses (FEA) simulations. The Eeff of the Au micro-cantilevers having Ti/Au multi-layered structures is evaluated by resonance frequency method, which demonstrates the key structural parameters affecting their Eeff. The FEA calculations show a consistent trend with that observed in the experimental results.
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•A total of 120 micro-cantilevers with Ti/Au multi-layered structure are prepared.•Their effective Young's modulus (Eeff) are evaluated by LDV methods.•The beam width scarcely affected their Eeff regardless of the layered structure.•The Eeff is governed by the distance between the beam and the fixed electrode.
Many research works on tolerance analysis have been carried out in the last thirty years. In this paper, a new idea is proposed, aiming to investigate the effect of form error and mechanical behavior ...of parts on the stack-up result by combining the recent novelties on the tolerance analysis of rigid and flexible bodies. The real parts are simulated considering the non-nominal Skin Model Shape and the mechanical properties in order to simulate the assembly of a realistic case study. A manufacturing signature model to generate the features with geometric deviations and Finite Element Analysis (FEA) are used.
Loss values are key parameters for designing high-performance high-frequency magnetic components for power electronics (PE) converters. With the increase of PE switching frequencies, copper losses ...have to be precisely quantified, ideally until some megahertz. In the literature, many 2D numerical simulations based on finite element analysis (FEA) are performed for such computations. 3D FEA studies of planar components are still limited because of modelling problems, computational resources and computing time. In this study, quantitative comparisons between 2D and 3D simulation results for planar inductors are achieved focusing on copper loss computation. Results are compared in terms of simulation performances and accuracy. The aim of the study is to highlight benefits of 2D and 3D FEA simulations in order to choose the appropriate model according to the studied problem.
•An original 1D analytical model dedicated to Rosen type piezoelectric transformers is described.•Different electro-mechanical transfer functions were derived from the matrix representation of this ...model.•The 1D analytical model results were compared with both 3D Finite Element Analysis and experimental measurements.•Eight parameters of the 1D analytical model were fitted by performing a least squares adjustment of the voltage gain.•The Rosen type piezoelectric transformer’s output impedance was calculated analytically.
This article is dedicated to the study of Piezoelectric Transformers (PTs), which offer promising solutions to the increasing need for integrated power electronics modules within autonomous systems. The advantages offered by such transformers include: immunity to electromagnetic disturbances; ease of miniaturisation for example, using conventional micro fabrication processes; and enhanced performance in terms of voltage gain and power efficiency. Central to the adequate description of such transformers is the need for complex analytical modeling tools, especially if one is attempting to include combined contributions due to (i) mechanical phenomena owing to the different propagation modes which differ at the primary and secondary sides of the PT; and (ii) electrical phenomena such as the voltage gain and power efficiency, which depend on the electrical load.
The present work demonstrates an original one-dimensional (1D) analytical model, dedicated to a Rosen-type PT and simulation results are successively compared against that of a three-dimensional (3D) Finite Element Analysis (COMSOL Multiphysics software) and experimental results. The Rosen-type PT studied here is based on a single layer soft PZT (P191) with corresponding dimensions 18mm×3mm×1.5mm, which operated at the second harmonic of 176kHz. Detailed simulational and experimental results show that the presented 1D model predicts experimental measurements to within less than 10% error of the voltage gain at the second and third resonance frequency modes. Adjustment of the analytical model parameters is found to decrease errors relative to experimental voltage gain to within 1%, whilst a 2.5% error on the output admittance magnitude at the second resonance mode were obtained. Relying on the unique assumption of one-dimensionality, the present analytical model appears as a useful tool for Rosen-type PT design and behavior understanding.
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