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A Numerical Study of Densification Behavior of Silicon Carbide Matrix Composites in Isothermal Chemical Vapor Infiltration
摘要： We studied the characteristics of two-scale pore structure of preform in the deposition process and the mass transfer of reactant gas in dual-scale pores, and observed the physiochemical phenomenon associated with the reaction. Thereby, we established mathematical models on two scales, respectively, preform and reactor. These models were used for the numerical simulation of the process of ceramic matrix composites densified by isothermal chemical vapor infiltration (ICVI). The models were used to carry out a systematic study on the influence of process conditions and the preform structure on the densification behaviors. The most important findings of our study are that the processing time could be reduced by about 50% without compromising the quality of the material, if the processing temperature is 950-1 000 ℃ for the first 70 hours and then raised to 1 100 ℃.
关键词： isothermal chemical vapor infiltration,fiber preform structure,densification behavior,ceramic matrix composites,process parameters
更新于2025-09-23 15:23:52
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Surface roughness and densification correlation for direct metal laser sintering
摘要： The increasing use of metal additive manufacturing (AM) technologies, such as direct metal laser sintering (DMLS), requires an in-depth understanding of how the optimum DMLS process parameters can be determined to achieve the target properties, such as reduced defect densities and/or desired surface characteristics. To this end, it is important to develop simple strategies that assess part quality and are fast and cost-effective. In this study, the in-plane surface roughness of components fabricated with AM is correlated with the DMLS process parameters and fractional density, enabling rapid and accurate indirect determination of the fractional density of AM components through surface roughness measurements. To this end, two sets of DMLS process parameters and a geometrical parameter are utilized to fabricate more than 150 rectangular cubic samples with varying parameters. All the samples are fabricated using Ti-6Al-4 V powder, which is a frequently used metal alloy for DMLS. Second, two line roughness parameters are defined and measured for all the samples, and their correlations with the DMLS and geometrical parameters are reported. Third, the fractional densities of all the samples are measured and their correlations with the DMLS process parameters are demonstrated. Lastly, a thorough analysis of the observed correlations between the line roughness parameters and fractional density are discussed.
关键词： Ti-6Al-4 V,Surface roughness,Densification,Process parameters,Metal additive manufacturing
更新于2025-09-23 15:21:01
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Development of metal matrix composites by laser-assisted additive manufacturing technologies: a review
摘要： Metal matrix composites (MMCs) generally possess superior properties than the monotonic matrix alloys, and thus, they have become excellent candidate materials in various applications. Also, the ability of property tailoring at an affordable cost is of particular importance to industries. Among the many manufacturing techniques for MMCs, laser-assisted additive manufacturing (AM) techniques have emerged and drawn increasing attention in the past decade. In the literature, a wealth of studies have been carried out on the synthesis of MMCs via laser-assisted AM techniques, as well as the property evaluation of the obtained MMCs. In this paper, we review and analyze the relevant literature and summarize the material preparation, optimization of process parameters, resultant improvements, and corresponding strengthening mechanisms for each major category of MMCs. Moreover, the limitations and challenges related to MMC synthesis using the laser-assisted AM techniques are discussed, and the future research directions are suggested to address those issues.
关键词： Laser-assisted additive manufacturing,Process parameters,Material preparation,Strengthening mechanisms,Metal matrix composites
更新于2025-09-23 15:21:01
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[IEEE 2018 19th International Conference on Electronic Packaging Technology (ICEPT) - Shanghai (2018.8.8-2018.8.11)] 2018 19th International Conference on Electronic Packaging Technology (ICEPT) - Simulation research on wafer warpage and internal stress in the First Passivation process of eSiFO package
摘要： In the electronics packaging process, warpage and thermal stress are two important causes which lead to packaging failure. In this paper, ABAQUS is used to perform three-dimensional numerical simulation of eSiFo packaging products from the thermodynamic point of view. The effects of different structural parameters on wafer warpage and thermal stress in electronic packages are simulated. In the simulation part, single factor analysis, Taguchi orthogonal experiment design and finite element analysis are combined to obtain the optimized process parameters and perform simulation analysis. The result shows that the structural parameter that has the greatest influence on the von Mises stress value of the wafer is the window size. And the structural parameter that has the greatest influence on the wafer warpage is the Die thickness. The thickness of the adhesive layer and the thickness of the passivation layer have a relatively small effect on the von Mises stress and the warpage value of the wafer. Under the optimized process parameters, the maximum von Mises stress and the maximum warpage value are much smaller than the initial process.
关键词： Taguchi orthogonal experiment,optimization of process parameters,numerical simulation,Warpage,thermal stress
更新于2025-09-23 15:21:01
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A review of metal additive manufacturing technologies: Mechanism of defects formation and simulation of melting and solidification phenomena in laser powder bed fusion process
摘要： In this review, the analysis of melting and solidification phenomena and the mechanism of the occurrence of defects as well as the analysis of melting and solidification using the numerical simulation in laser powder bed fusion (LPBF) process were introduced. In addition, the strategies of suppression of defects were described. The melting and solidification phenomena during LPBF process are relatively similar to those during welding. Since the plume brings about the strong recoil pressure on the melt pool, the keyhole takes place. And when the depth of keyhole becomes more than a threshold, the keyhole pore remains at the bottom of melt pool. Since the plume also brings about spattering and blows out powder, the gas pores are prone to occur easily. The micro-simulation of melting and solidification enables to reproduce the real phenomena. The macro-simulation of melting and solidification phenomena is one of the effective tools to predict the optimum fabrication condition. In order to prevent the occurrence of defects, it is significant not only to obtain the optimum fabrication condition using the process map but also to develop the simulation software. In addition, the use of the monitoring and feedback control system is greatly effective. Therefore the development of the cyber-physical system is needed.
关键词： Numerical simulation,Process parameters,Additive manufacturing,Melting phenomena,Powder bed fusion,Defect,Laser
更新于2025-09-23 15:19:57
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Coloring stability analysis of nanosecond pulsed laser induced surface coloring on stainless steel
摘要： In this paper, a nanosecond pulsed laser was used to induce the surface coloring of stainless steel. The effect of process parameters, including defocusing distance, scanning speed, scanning interval, repetition frequency and release time on color marking and coloring stability were studied. For objective evaluation of color changes, a hand-held colorimeter and the CIEL*a*b* color difference formula were used. Finally, the process parameters range of six colors was given when the stability requirement is satisfied. The effect of the above process parameters on the stability of surface coloring was also studied.
关键词： Process parameters,Nanosecond pulsed laser,Stability analysis,Surface coloring
更新于2025-09-16 10:30:52
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Influence of Process Parameters on the Porosity, Accuracy, Roughness, and Support Structures of Hastelloy X Produced by Laser Powder Bed Fusion
摘要： The manufacture of highly complex components from nickel-based superalloys with laser powder bed fusion (L-PBF) technology can reduce the production costs parts with comparable microstructural and mechanical properties when compared to casting. The purpose of this study was to investigate the characteristics of samples produced in commercial Hastelloy X (with w% composition of 21Cr-18Fe-9Mo-0.7W-1.5Co-0.1C-1Si-1Mn-0.5Al-0.15Ti-bal.Ni) with an L-PBF process in terms of build density, accuracy, surface roughness, and interface area between the part and the support structures. Samples were obtained with a high density (99.88%), without cracks and with low surface roughness. From the analysis of the support structures, it emerged that the choice of the parameters between support structures, the lower face of the part (down-skin) and the internal area of the part (in-skin) is fundamental to the correct realization of these structures in order to avoid deformation of the components that is induced by thermal stresses during part building.
关键词： process parameters,nickel super-alloys,additive manufacturing,selective laser melting,Hastelloy X
更新于2025-09-16 10:30:52
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Transferability of Process Parameters in Laser Powder Bed Fusion Processes for an Energy and Cost Efficient Manufacturing
摘要： In the past decade, the sales of metal additive manufacturing systems have increased intensely. In particular, PBF-LB/M systems (powder bed fusion of metals using a laser-based system) represent a technology of great industrial interest, in which metallic powders are molten and solidified layer upon layer by a focused laser beam. This leads to a simultaneous increase in demand for metallic powder materials. Due to adjusted process parameters of PBF-LB/M systems, the powder is usually procured by the system’s manufacturer. The requirement and freedom to process different feedstocks in a reproducible quality and the economic and ecological factors involved are reasons to have a closer look at the differences between the quality of the provided metallic powders. Besides, different feedstock materials require different energy inputs, allowing a sustainable process control to be established. In this work, powder quality of stainless steel 1.4404 and the effects during the processing of metallic powders that are nominally the same were analyzed and the influence on the build process followed by the final part quality was investigated. Thus, a correlation between morphology, particle size distribution, absorptivity, flowability, and densification depending on process parameters was demonstrated. Optimized exposure parameters to ensure a more sustainable and energy and cost-efficient manufacturing process were determined.
关键词： powder characterization,stainless steel (1.4404; 316L),energy and cost-efficient manufacturing,PBF-LB/M,sustainable process parameters,additive manufacturing
更新于2025-09-16 10:30:52
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Modelling of Laser Powder Bed Fusion Process and Analysing the Effective Parameters on Surface Characteristics of Ti-6Al-4V
摘要： In this paper, we propose a model to predict the average surface roughness (Sa) and analyse the effect of related process parameters on laser powder bed fusion (LPBF) selective laser melting (SLM) of Ti-6Al-4V. The additive manufacturing (AM) process has various independent parameters that affect the quality of the produced parts and is complex to analyse. Although the process parameters can be selected separately in LPBF, they do however affect each other. Therefore, large adjustments of process parameters is not possible due to the negative effect they have on each other which can lead to problems such as cracks, balling, unmelted powders, porosity, and distortion. A range of process parameters using Taguchi L25 design of experiment (DOE) with five repetitions for each sample has been selected. Then, an artificial neural network (ANN) is applied to the model to predict the value of (arithmetical mean height)/(average surface roughness) (Sa). The selected processing parameters are laser power, scan speed, hatch spacing, laser pattern increment angle, and heat treatment (HT) condition. The present work revolves around ANN modelling and using a wide parameter range and a large number of test samples under ASTM standards as well as adding HT to the DOE to analyse the simultaneous effect of HT and changing process parameters on surface characteristics. A large and precise data set with high generality and reliability obtained by 3750 profilometries on 125 samples. The contribution of this paper is using ANN as an accurate tool in surface modeling and characterizing the effective parameters on the surface of LPBF parts. The existence phenomena and governing factors were explained by introducing new parametric mechanisms in rheology of melting pool. In AM of metals, the variation of average roughness in overlap of hatches can be 5-7 times higher than the centre of the track. Therefore, Sa was selected to have consistency in the measured roughness values. Results showed heat treatment above beta phase transus leads to a local flow of material at the surface causing an increase of Sa. The ranking of influential factors on Sa from the highest to the lowest was found to be: heat treatment > laser power > scan pattern angle > hatch space > scan speed.
关键词： Selective laser melting,Process parameters,Additive manufacturing,Average surface
更新于2025-09-12 10:27:22
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The influence of the workpiece illumination proportion in annular laser beam wire deposition process
摘要： The paper provides a description of an annular laser beam based direct wire deposition head, which can be used to perform controllable, simultaneous, and symmetrical heating of both the workpiece surface and the axially fed wire. In order to characterize the proportion of energy delivered to the workpiece and fed wire, respectively, a new process parameter, referred to as the workpiece illumination proportion, has been introduced, which is defined as the percentage of the annular laser beam power incident on the workpiece surface. The influence of this newly defined illumination parameter on the process outcome was characterized, based on single-layer deposition experiments using a 0.6 mm diameter nickel wire which was fed onto a stainless steel workpiece. The results show that the geometry of the deposited layer is influenced, as well as by the conventional process parameters, also by the newly introduced workpiece illumination parameter, which also affects the process stability and its robustness.
关键词： wire deposition,process parameters,Annular laser beam
更新于2025-09-12 10:27:22