Design Of Experiments for the optimization the process parameters of thixotropic aluminum alloy

The success of the thixoforming process depends on the possibility to confer to material, when it is found in the semisolid state, a microstructure characterized by globular particles of solid phase surrounded by a continuous film of liquid phase; such microstructure is obtainable through particular thermo-mechanical treatments. In the present research, in order to optimize the influence of process parameters in the step in which the thixotropic properties are conferred to the AA7075 aluminum alloy, the statistic technique of the Design Of Experiments (DOE) has been used. The advantages in the application of such technique are expressible in terms of reduction the times of development of process and more efficient use of resources. A Central Composite Design factorial plan with two levels has been realized to allow the evaluation of experimental error and to check the adequacy of the model. The experimental tests foreseen from the same plan have been therefore performed. Using the method of the response surfaces (RSM), the function of response has been formulated, and the analysis of the experimental data has been realized by the linear regression method. Finally, the analysis of variance (ANOVA) allowed to value the causes of variability of the results. Statistic test has been performed on the significance of single factors and their interactions

Special Issue of Journal of Manufacturing Processes on New Trends in Manufacturing Processes Research

Special issue of journal of manufacturing processes on new trends in manufacturing processes researc

special issue of journal of manufacturing systems on new trends in manufacturing systems research

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Residual stress and part distortion prediction in L-PBF of Ti-6Al-4V using layer-by-layer FEM simulation

Due to its ability to accommodate customer demands and produce objects with complex shapes, Laser Powder Bed Fusion (LPBF) has been widely adopted in numerous industry areas, including biomedical, automotive, and aerospace. Even with all the benefits that LPBF has to offer, its use may be limited by the development of residual stress according to the strong thermal gradients produced throughout the process. Residual stresses within the samples can result in part distortion after the removal from the built platform or even in part failure during the process if the residual stresses are excessive. In order to save time and costs, numerical simulation can be an effective tool to predict residual stress and part distortion in opposition to the trial-and-error approach which involves an expansive and time-consuming experimental campaign. To this aim a finite element method (FEM) together with a layer-by-layer approach was used in this study. Numerical simulations were performed on the commercial software DEFORM-3DTM with which different values of laser power were investigated. Moreover, the influence of the voxel mesh on the FEM model accuracy was also investigated

Friction Stir Welding of Ti6Al4V complex geometries for aeronautical applications: a feasibility study

While Friction Stir Welding (FSW) of aluminium alloys can be considered a mature technology, even for complex joint morphologies, as T joints welded “in transparency”, welding of hard material still presents several open issues. In fact, welding of titanium alloys is a challenging process due to the chemical, mechanical and thermal characteristics of such materials which are subjected to atmosphere contamination resulting in joint hydrogen, oxygen and nitrogen embrittlement; additionally, due to the high melting temperature, large distortion and residual stress are found in joints obtained by traditional fusion welding processes as gas metal arc welding, electron beam welding and laser welding. In this way a solid-state process, as FSW, represents a valid choice in order to overcome problems related to the material melting. It should be noticed that FSW of titanium alloys is definitely more complex than the same process referred to aluminium alloys. In the proposed paper, a feasibility study on the production of Ti6Al4V T-joints in one welding pass, i.e. the so-called transparency welding, is presented. The main process parameters, i.e. tool rotation and feed rate have been fixed, and the main metallurgical and mechanical properties of the joint have been analysed. Macro and micro observations of the joints have been performed relating the final microstructure to the input process parameters utilized