Analysis of Friction Stir Processed Surface Quality of AA2098 Aluminum Alloy for Aeronautical Applications

FSP is a relatively new technique that changes the microstructure on the surface of the material to improve mechanical properties in the desired zone. This study aimed to investigate the surface quality of AA2098 sheets after being subjected to friction stir processing under different conditions of feed rate and rotational speed. A DoE analysis was developed with two factors, feed rate and rotational speed, and three different levels of 75, 100, 125 mm/min and 1000, 1250, 1500 rpm respectively, in order to assess the processed surface quality. The Sa parameter was used to represent the surface quality in different zones of the process, near entrance tool, middle and near exit tool, and ANOVA analysis was conducted. The results indicated that only the position and feed rate have a statistical influence on surface roughness. Additionally, the surface quality is strongly affected by the position relative to the entrance of the tool and the side (retreating or advancing sides). The roughness was found to be significantly lower on the advancing side rather than on the retreating side

Analysis of Friction stir processed surface quality of AA2098 aluminum alloy for aeronautical applications

FSP is a relatively new technique that changes the microstructure on the surface of the material to improve mechanical properties in the desired zone. This study aimed to investigate the surface quality of AA2098 sheets after being subjected to friction stir processing under different conditions of feed rate and rotational speed. A DoE analysis was developed with two factors, feed rate and rotational speed, and three different levels of 75, 100, 125 mm/min and 1000, 1250, 1500 rpm respectively, in order to assess the processed surface quality. The Sa parameter was used to represent the surface quality in different zones of the process, near entrance tool, middle and near exit tool, and ANOVA analysis was conducted. The results indicated that only the position and feed rate have a statistical influence on surface roughness. Additionally, the surface quality is strongly affected by the position relative to the entrance of the tool and the side (retreating or advancing sides). The roughness was found to be significantly lower on the advancing side rather than on the retreating side

Friction-Stir Welding of AA 2198 Butt Joints: Mechanical Characterization of the Process and of the Welds Through DOE Analysis

In this study, rolled plates of AA 2198 T3 aluminium alloy are friction-stir welded in butt configuration varying two fundamental process parameters: rotational and welding speeds. Two sets of empirical models based on regression analysis are developed. The first one predicts the stationary values of the in-plane and downwards forging welding forces in dependence of the process parameters under investigation. The second one predicts the mechanical strength, in particular yield and tensile strength, of the friction-stir welded joints as function of the same parameters. For the development of the empirical models, two 32 full factorial designs are used: one having the stationary values of the welding forces and the other having the yield and tensile strength as observed responses, respectively. Statistical tools such as analysis of variance, F tests, Mallows’ CP, coefficient of determination etc. are used to build and to validate the developed models. By using the desirability function approach, the optimum process parameters to simultaneously obtain maximum possible yield and tensile strength are found within the investigated range. The developed models can be effectively used to predict the stationary forces and the mechanical proprieties of the joints at 95% confidence level

Effects of process parameters on the deformation energy in a sheet-bulk metal forming process for an automotive component

The present study investigates the effects of the process parameters on cold forming process of an automotive component in AISI 1006 low carbon steel. The material formability was characterised up to 250°C. The material flow behaviour and the related thermal distributions during the geometrical transformations were analyzed. Coining and forming operations were investigated by using a coupled 3D Thermo-mechanical FEM with different die geometries and friction conditions in order to optimize the final die geometry and to reduce the energy consumption. FEM simulation results were validated by comparison with the experimental trials. The detailed study of the component allowed defining the energy required by the severe bending of the initial thick plate. The FEM predictions led to a reduction of deformation energy of about 20%, a mass reduction of 28% on the final product and permitted avoiding secondary machining operations

Bonding of similar AA3105 aluminum alloy by accumulative roll bonding process

Accumulative roll-bonding (ARB) is a novel plastic straining process aimed at bonding of similar and dissimilar metal combinations. Moreover, it is used recently to produce ultrafine grain materials and metal matrix reinforced composites to enhance mechanical, electrical, and corrosion resistance properties. This work presents an experimental study of roll bonding and accumulative roll bonding of similar AA3105 aluminum alloy at 300°C with a final thickness of 1.2 mm, focusing especially on bond strength evaluation and layers continuities. Tensile tests and three-points bending were performed to mechanical characterize the produced sheets in the various steps and based on the number of the cycles. The maximum strength was reached after 3 ARB cycles. After 4 cycles, the bonding interfaces have a uniform distribution through the sheet thickness, it is possible to distinguish only the interface formed in the last pass in the fracture surface, and no significant enhancement in strength was observed. Starting from 2 ARB cycles, micro-cracks were observed at the outer surface for bending angles greater than 90 deg, and at 180 deg all ARBed samples except A1 were failed

Sustainability Study of a New Solid-State Aluminum Chips Recycling Process: A Life Cycle Assessment Approach

Nowadays, reducing greenhouse gas emissions in all human activities has become crucial. This article presents a life cycle assessment (LCA) investigation conducted to evaluate the environmental benefits of a newly developed solid-state recycling process for aluminum chips, involving two steps: direct rolling and accumulative roll bonding. A comparison was made between this process and two current industrial methods of recycling aluminum scraps to obtain wrought products, which involve melting, casting, and subsequent rolling. The LCA analysis considered a scenario where 50% of the total electric requirement was met by photovoltaic energy. The results of the study indicate that in all examined impact categories, direct rolling has a lower environmental footprint compared to both traditional recycling and twin-roll cast technology. These results suggest that this new solid-state recycling procedure has significant potential to replace environmentally harmful melting processes

Effects of milling parameters on roughness and burr formation in 3D- printed PLA components

This study investigated the 3D-printed PLA (Polylactic Acid) workability during the operation of milling. It is difficult to obtain as a result of a Fused Deposition Modeling (FDM) 3D printing a very strict tolerance, and a good roughness surface. A possible solution can be the usage of the last milling operation that can complete the workpiece in terms of desired roughness and dimension tolerances. A design of experiments (DOE) analysis has been applied to observe the optimizing result. Three factors have been analyzed: feed rate, depth of cut, and rotational speed. Two responses were investigated: roughness (Ra) and burr height. The results show that these two parameters present optimum results in two different values of the process parameters: the Ra is better at a higher feed rate and low depth cut, but the situation reverses for the burr height, for which lower heights are obtained when using higher feed rate and depth cut

Integration of serum metabolomics into clinical assessment to improve outcome prediction of metastatic soft tissue sarcoma patients treated with trabectedin

Soft tissue sarcomas (STS) are a group of rare and heterogeneous cancers with few diagnostic or prognostic biomarkers. This metabolomics study aimed to identify new serum prognostic biomarkers to improve the prediction of overall survival in patients with metastatic STS. The study enrolled 24 patients treated with the same trabectedin regimen. The baseline serum metabolomics profile, targeted to 68 metabolites encompassing amino acids and bile acids pathways, was quantified by liquid chromatography-tandem mass spectrometry. Correlations between individual metabolomics profiles and overall survival were examined and a risk model to predict survival was built by Cox multivariate regression. The median overall survival of the studied patients was 13.0 months (95% CI, 5.6–23.5). Among all the metabolites investigated, only citrulline and histidine correlated significantly with overall survival. The best Cox risk prediction model obtained integrating metabolomics and clinical data, included citrulline, hemoglobin and patients’ performance status score. It allowed to distinguish patients into a high-risk group with a low median overall survival of 2.1 months and a low-to moderate-risk group with a median overall survival of 19.1 months (p < 0.0001). The results of this metabolomics translation study indicate that citrulline, an amino acid belonging to the arginine metabolism, represents an important metabolic signature that may contribute to explain the high inter-patients overall survival variability of STS patients. The risk prediction model based on baseline serum citrulline, hemoglobin and performance status may represent a new prognostic tool for the early classification of patients with metastatic STS, according to their overall survival expectancy

Two Auction-Based Resource Allocation Environments: Design and Experience

Many computer systems have reached the point where the goal of resource allocation is no longer to maximize utilization; instead, when demand exceeds supply and not all needs can be met, one needs a policy to guide resource allocation decisions. One natural policy is to seek efficient usage, which allocates resources to the set of users who have the highest utility for the use of the resources. Researchers have frequently proposed market-based mechanisms to provide such a goal-oriented way to allocate resources among competing interests while maximizing overall utility of the users.Engineering and Applied Science