Three-Dimensional Finite Element Thermal Analysis in Selective Laser Melting of Al-Al2O3 Powder

The selective laser melting (SLM) of aluminium-based composites continues to be a challenge due to the high reflectivity, high thermal conductivity and oxidation of aluminium, all of which directly influence the thermal performance of each layer during SLM. Due to the extremely rapid melting and cooling rate of aluminium, however, it is difficult to measure thermal performance within practical SLM applications. A three-dimensional finite element simulation model is thus developed in this study to simulate the transient temperature distribution and molten pool dimensions of the premier layer during the SLM of Al-Al2O3 composite powder. In order to produce high-quality parts with minimum defects in a highly efficient manner, the predicted optimum volumetric energy density is found to be 40 J/mm3 , with laser power 300 W, scanning speed 1000 mm/s, hatch spacing 150 μm and layer thickness 50 μm; the molten pool size that is produced is 165 μm in length, 160 μm in width and 77 μm in depth, with a predicted maximum temperature of around 3400°C. All of these factors may contribute to the creation of good metallurgic bonding.Mechanical Engineerin

DesignGPT: Multi-Agent Collaboration in Design

Generative AI faces many challenges when entering the product design workflow, such as interface usability and interaction patterns. Therefore, based on design thinking and design process, we developed the DesignGPT multi-agent collaboration framework, which uses artificial intelligence agents to simulate the roles of different positions in the design company and allows human designers to collaborate with them in natural language. Experimental results show that compared with separate AI tools, DesignGPT improves the performance of designers, highlighting the potential of applying multi-agent systems that integrate design domain knowledge to product scheme design

On the role of melt flow into the surface structure and porosity development during selective laser melting

In this study, the development of surface structure and porosity of Ti–6Al–4V samples fabricated by selective laser melting under different laser scanning speeds and powder layer thicknesses has been studied and correlated with the melt flow behaviour through both experimental and modelling approaches. The as-fabricated samples were investigated using optical microscopy (OM) and scanning electron microscopy (SEM). The interaction between laser beam and powder particles was studied by both high speed imaging observation and computational fluid dynamics (CFD) calculation. It was found that at a high laser power and a fixed powder layer thickness (20 μm), the samples contain particularly low porosity when the laser scanning speeds are below 2700 mm/s. Further increase of scanning speed led to increase of porosity but not significantly. The porosity is even more sensitive to powder layer thickness with the use of thick powder layers (above 40 μm) leading to significant porosity. The increase of porosity with laser scanning speed and powder layer thickness is not inconsistent with the observed increase in surface roughness complicated by increasingly irregular-shaped laser scanned tracks and an increased number of discontinuity and cave-like pores on the top surfaces. The formation of pores and development of rough surfaces were found by both high speed imaging and modelling, to be strongly associated with unstable melt flow and splashing of molten material

Net-Shape Manufacturing using Hybrid Selective Laser Melting/Hot Isostatic Pressing

Purpose The purpose of this study is to develop a manufacturing technology using hybrid selective laser melting/hot isostatic pressing (SLM/HIP) process to produce full density net-shape components more rapidly and at lower cost than processing by SLM alone. Design/methodology/approach Ti-6Al-4V powder was encapsulated in situ by the production of as-SLMed shell prior to the HIP process. After HIPping, the SLM shell is an integral part of the final component. Finite element (FE) modelling based on pure plasticity theory of porous metal coupled with an iterative procedure has been adopted to simulate HIPping of the encapsulated Ti-6Al-4V powder and SLMed shell. Two demonstrator parts have been modelled, designed, produced and experimentally validated. Geometrical analysis and microstructural characterisation have been carried out to demonstrate the efficiency of the process. Findings The FE model is in agreement with the measured data obtained and confirms that the design of the shell affects the resulting deformed parts. In addition, the scanning electron microscope (SEM) and Electron backscatter diffraction EBSD (EBSD) of the interior and exterior parts reveal a considerably different grain structure and crystallographic orientation with a good bonding between the SLMed shell and HIPped powder. Originality/value An approach to improve SLM productivity by combining it with HIP is developed to further innovate the advanced manufacturing field. The possibility of the hybrid SLS/HIP supported by FEA simulation as a net shape manufacturing process for fabrication of high performance parts has been demonstrated. </jats:sec

Quantification of Myocardial Dosimetry and Glucose Metabolism Using a 17-Segment Model of the Left Ventricle in Esophageal Cancer Patients Receiving Radiotherapy

Objective Previous studies have shown that increased cardiac uptake of(18)F-fluorodeoxyglucose (FDG) on positron emission tomography (PET) may be an indicator of myocardial injury after radiotherapy (RT). The primary objective of this study was to quantify cardiac subvolume dosimetry and(18)F-FDG uptake on oncologic PET using a 17-segment model of the left ventricle (LV) and to identify dose limits related to changes in cardiac(18)F-FDG uptake after RT. Methods Twenty-four esophageal cancer (EC) patients who underwent consecutive oncologic(18)F-FDG PET/CT scans at baseline and post-RT were enrolled in this study. The radiation dose and the(18)F-FDG uptake were quantitatively analyzed based on a 17-segment model. The(18)F-FDG uptake and doses to the basal, middle and apical regions, and the changes in the(18)F-FDG uptake for different dose ranges were analyzed. Results A heterogeneous dose distribution was observed, and the basal region received a higher median mean dose (18.36 Gy) than the middle and apical regions (5.30 and 2.21 Gy, respectively). Segments 1, 2, 3, and 4 received the highest doses, all of which were greater than 10 Gy. Three patterns were observed for the myocardial(18)F-FDG uptake in relation to the radiation dose before and after RT: an increase (5 patients), a decrease (13 patients), and no change (6 patients). In a pairing analysis, the(18)F-FDG uptake after RT decreased by 28.93 and 12.12% in the low-dose segments (0-10 Gy and 10-20 Gy, respectively) and increased by 7.24% in the high-dose segments (20-30 Gy). Conclusion The RT dose varies substantially within LV segments in patients receiving thoracic EC RT. Increased(18)F-FDG uptake in the myocardium after RT was observed for doses above 20 Gy.</div

Three-dimensional finite element thermal analysis in selective laser melting of Al-Al2O3 powder

The selective laser melting (SLM) of aluminium-based composites continues to be a challenge due to the high reflectivity, high thermal conductivity and oxidation of aluminium, all of which directly influence the thermal performance of each layer during SLM. Due to the extremely rapid melting and cooling rate of aluminium, however, it is difficult to measure thermal performance within practical SLM applications. A three-dimensional finite element simulation model is thus developed in this study to simulate the transient temperature distribution and molten pool dimensions of the premier layer during the SLM of Al-Al2O3 composite powder. In order to produce high-quality parts with minimum defects in a highly efficient manner, the predicted optimum volumetric energy density is found to be 40 J/mm3 , with laser power 300 W, scanning speed 1000 mm/s, hatch spacing 150 μm and layer thickness 50 μm; the molten pool size that is produced is 165 μm in length, 160 μm in width and 77 μm in depth, with a predicted maximum temperature of around 3400°C. All of these factors may contribute to the creation of good metallurgic bondin