1,720,982 research outputs found
Numerical prediction of lack-of-fusion defects in selective laser melted AlSi10Mg alloy
No full textDespite the emerging research, it is still troublesome to control the defect formation in selective laser melted parts. In this paper, a mechano-thermo-fluid dynamical FEM model at meso-scale was proposed. The model calculates and predicts the volume and dimensions of lack-of-fusion (LOF) defects according to the applied process parameters. The numerical model was validated with experimentally assessed volume of lack-of-fusion defects and melt pool dimensions. Results shown the lowest volume of LOF defects (0.41%) in specimen produced with 275 W and scanning speed of 400 mm/s. Laser power was determined as a parameter majorly impacting the volume and dimensions of LOF in selective laser melted parts
Defects and residual stresses finite element prediction of FDM 3D printed wood/PLA biocomposite
Full text linkThe exploited enthusiasm within the research community for harnessing PLA-based biocomposites in fused deposition modeling (FDM) is spurred by the surging demand for environmentally sustainable and economically viable materials across diverse applications. While substantial strides have been taken in unravelling the intricacies of the process-structure–property relationship, the intricate interdependencies within this context remain only partially elucidated. This current gap in knowledge presents formidable obstacles to achieving the pinnacle of quality and dimensional precision in FDM-fabricated specimens crafted from biocomposites. Despite the existence of numerous numerical models for simulating the FDM process, an unmistakable need exists for models that are custom-tailored to accommodate the distinct characteristics inherent to biocomposites. As a reaction to those pressing needs, this study presents a 3D coupled thermomechanical numerical model designed to predict dimensions, defect formation, residual stresses, and temperature in PLA/wood cubes produced by FDM, considering various process parameters and composite-like nature of wood-filled PLA filaments. The accuracy of the proposed numerical model was validated by comparing its results with experimental measurements of biocomposite cubes manufactured under the same process parameters. Encouragingly, the simulated dimensions showed a maximum relative error of 9.52% when compared to the experimental data, indicating a good agreement. The numerical model also successfully captured the defect formation in the manufactured cubes, demonstrating consistent correspondence with defects observed in the experimental specimens. Therefore, the presented model aims to substantially contribute to the progress in the field of additive manufacturing of PLA-based biocomposites
On modelling Nd:Yag nanosecond laser milling process by neural network and multi response prediction methods
Full text linkIn this paper, the milling effects on AISI 316 L steel by nanosecond pulsed laser was studied under different parameters as laser pulse peak power, laser repetition rate, scanning speed and focal point. Based on a full factorial design, 108 tests were conducted. MD varied from 15.58 to 60.14 μm; MRR from 0.0028 to 0.0195 mm3/s; Ra from 0.13 to 1.49 μm. The study showed that the laser power and scanning speed have a great influence on material removal. When the laser spot was focused on the upper sample surface, the removing material process was improved. Moreover, Response Surface Methodology and Artificial Neural Network were used to analyze and predict the milling depth, the material removal rate, and the surface roughness. The predictive capabilities of the methods were compared. The predicted R-square for RMS model were 99.70%, 77.79% and 67.73%, while for FF-BPNN were 99.99%, 99.85% and 81.98% for MD, MRR and Ra respectively. Therefore, both models demonstrated strong ability to match the responses. Neural network model exhibited superior predictive power
Strain behaviour of a friction stir processed superplastic aluminium alloy sheet during free inflation tests
No full textIn this work, the strain behaviour of friction stir processed aluminium superplastic sheet was investigated. The aim was to study the feasibility of the combination of the friction stir processing technique with the superplastic forming process. Main friction stir process parameters (tool rotational speed and transverse speed) were varied in order to study the effect of these changes on the strain behaviour and on the formability of the processed sheet. For this purpose, free inflation tests were carried out on the processed sheet at a temperature at which the base material exhibits an optimal superplastic behaviour. A strong influence of the stirring parameters on the strain behaviour of the processed sheet was found denoting only a specified set of friction stir parameters made the processed sheet behave like the base material. The microstructure evolution of the stirred zone played an important role in this direction. Higher tool rotational speeds led to abnormal grain growth and, consequently, to a slower deformation in the processed material. Thickness measurements made after free inflation tests also confirmed this behaviour: the material processed with a higher tool rotational speed had a thickness that is twice the unprocessed one
On the role of the Thermal Contact Conductance during the Friction Stir Welding of an AA5754-H111 butt joint
No full textIn Friction Stir Welding (FSW), the clamping conditions affect the mechanical and metallurgical properties of friction stir welded joints. Due to the involved forces is necessary rigidly lock the two sheets by means of an appropriate rigid fixing system on the underlying support plate. The temperature distribution and the trend of the heat flow is required to predict the properties of the joints and to optimize the welding parameters. Moreover, the evaluation of the Thermal Contact Conductance (TCC) is necessary to predict the heat fraction that is channeled to the tool, the one toward the sheet metal and to the clamping system. A three-dimensional finite element model (FEM) was developed to predict the evolution of the thermal flux in an FS-welded joint of aluminum alloy, considering the presence of the backing plate and the clamping system. The Thermal Contact Conductance (TCC) was measured under different temperature and pressure conditions. Experiments on a welding on 6 mm of AA5754 H111 were also carried out, to compare the model with the experimental results
Modeling of Probeless Friction Stir Spot Welding of AA2024/AISI304 Steel Lap Joint
No full textIn the present study, AA2024 aluminum alloy and AISI304 stainless steel were welded in a lap joint configuration by Probeless Friction Stir Spot Welding (P-FSSW) with a flat surface tool. A full factorial DOE plan was performed. The effect of the tool force (4900, 7350 N) and rotational speed (500, 1000, 1500, 2000 RPM) was analyzed regarding the microstructure and microhardness study. A two-dimensional arbitrary Eulerian–Lagrangian FEM model was used to clarify the temperature distribution and material flow within the welds. The experimental results for the weld microstructures were used to validate the temperature field of the numerical model. The results showed that the tool rotation speed had an extensive influence on the heat generation, whereas the load force mainly acted on the material flow
Metal Wire Additive Manufacturing: A Comparison between Arc Laser and Laser/Arc Heat Sources
Full text linkIn this paper, the authors introduce the reader to the state of the art of Metal Wire Additive Manufacturing (MWAM) and provide a comparison between Wire Arc Additive Manufacturing (WAAM), Wire Laser Additive Manufacturing (WLAM), and Laser Arc Hybrid Wire Deposition (LAHWD) based on their characteristics and potential future applications, since MWAM is expected to have a promising future in various areas, such as aerospace, automotive, biomedical, and energy fields. A detailed discussion of the benefits and drawbacks of each Metal Wire Additive Manufacturing process can help to improve our understanding of the unique characteristics of metal wire application. Therefore, this paper offers a comprehensive analysis that can serve as a reference for upcoming industrial projects and research initiatives, with the aim of helping industries choose the most appropriate WAM technique for their specific applications
On the influence of building position on dimensional accuracy and surface quality of aluminum blocks manufactured by L-PBF
Full text linkThe precision of the objects fabricated by laser powder bed fusion (LPBF) and their overall quality is currently commonly increased by process optimization, however the relatively complicated process-structure–property relationship may represent a significant obstacle to its efficiency. This study aims to determine the effects of the position of L-PBF manufactured blocks on the building plate on their geometrical dimensions, tolerances (GD&T) and surface roughness. Within the study, 9 cubical specimens were manufactured from AlSi10Mg powder via LPBF using optimized process parameters, consistent for all the samples, and their GD&T and surface roughness were subsequently analyzed by CMM and perthometer. The system utilized to manufacture the samples was supplied with 200 W Yb-laser with the 90 μm diameter of the laser spot. The fabrication of the blocks and their subsequent GD&T analysis were simulated numerically to further explain the mechanisms of distortion creation. Numerical results were validated by experiments, where the maximal relative error reached 6.88 %. Statistical significance of position on GD&T was demonstrated for dimensional deviations, bottom faces planarity, parallelism of top and bottom faces and perpendicularity of top and x-oriented faces and the regression equations were assessed (with R2 96.30 %, 93.09 % and 99.79 %, 94.54 %, 98.47 %, 99.65 %, and 99.28 %, respectively). The lowest dimensional errors (0.0738 mm in x-, 0.1048 mm in y-, and −0.3844 mm in z-direction) were detected in the block located in the middle of the building plate, which can be reasoned by favorable thermal fields as the specimens are surrounded from all sides by other blocks cumulating heat. Similarly as with dimensional errors, the errors of planarity, parallelism and perpendicularity correlated with the thermal fields over the building platform, resulting in the least distorted cube located in the middle of the base plate
Design and fabrication of random metal foam structures for laser powder bed fusion
No full textWith the development of additive manufacturing, the building of new categories of lightweight structures such as random foams have been offered. Nevertheless, given the complexity of the required parts, macroscopic defects may result or the process may even fail. Therefore, proper actions must be taken at the design stage. In this paper, a method of design for additive manufacturing (DfAM) to build metal random foam structures is proposed. Namely, a procedure is suggested to generate a structure that has interconnected porosity. This procedure is based on the aimed fractional density and several technical requirements, and then the geometry is optimized and meshed. To validate the algorithm, a test article consisting of a metal cylinder with spherical random pores ranging from 1 to 6 mm in diameter with a resulting fractional density of 40 ± 2% has been conceived and manufactured by means of laser powder bed fusion (LPBF). On the basis of the outcome of the manufacturing process, crucial information has been gathered to update the algorithm
Effects of Cold Gas Tungsten Arc Welding on Dissimilar DHP-CW024A Copper/304 SS Thin Lap Joint
No full textCopper and stainless steel possess distinct properties that make them suitable for different applications (i.e. e-mobility, nuclear power plants, etc.). However, the high thermal conductivity of copper presents a significant challenge in welding. In fact, researchers have explored various fusion welding processes for joining copper to steel and concluded that fusion welding is generally difficult or even unsuitable for obtaining sound and defects free joints. The present study investigated the feasibility of dissimilar lap joint between copper and stainless-steel thin plates using Cold Gas Tungsten Arc Welding (CGTAW) without a filler material and with no significant geometrical distortion of welded plates. The weld was created by consecutive partially overlapped spots, whose welding time varied between 100 and 150 ms, in upgraded conventional TIG machine equipped with cold TIG welding function. Samples made with 150 ms welding time showed a near-uniform distribution of equiaxed copper grain microstructure, while those obtained with 100 ms exhibited significant differences in grain size with the presence of steel inclusions in globule and vortex shapes. The joints demonstrated exceptional flexibility, allowing it to be bent up to a 180o angle without any visible damage. The maximum tensile strength of sample obtained with a welding time of 150 ms was 220 MPa with a fracture located in the heat-affected zone. The sample welded with a welding time of 100 ms exhibited 171 MPa of tensile strength with the fracture along the melting spot area due to pronounce mixing of welded materials. All the samples showed ductile behavior in the fracture zone. Eventually, the application of CGTAW resulted in promising at obtaining joint with good mechanical properties
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