1,721,038 research outputs found
Magnesium and Aluminium alloys Dissimilar Joining by Friction Stir Welding
No full textMulti-material lightweight structures are gaining a great deal of attention in several industries, in particular where a trade-off between reduced weight, improved performances, and cost compression is required. Magnesium alloys, such as the zinc-rare earth elements ZE41A alloy, fulfill the first two requirements; however, they are susceptible to corrosion and relatively expensive. Lightweight structures hybridization, for instance combining Magnesium alloys and Aluminium alloys, is currently under consideration as a potential solution to this problem. Nevertheless, dissimilar joining of Magnesium and Aluminium alloys is challenging due to the significant differences in physical properties, as well as to the precipitation of brittle intermetallic compounds, such as Al12Mg17 and Al3Mg2. In this study, the dissimilar joining of Magnesium and Aluminium alloys by friction stir welding process is discussed. In particular, 4 mm thick plates of ZE41A Mg alloy and AA2024-T3 Al alloy were welded in the butt joint configuration. The feasibility of the process was assessed by means of microstructure and mechanical analysis. The formation of brittle intermetallic compounds was investigated as well
Friction Stir Welding of Ti6Al4V complex geometries for aeronautical applications: a feasibility study
Full text linkWhile 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
Investigating the influence of deposition techniques and processing conditions on AA2024/SiC FSW joints: Evaluation of microstructural and mechanical properties
Full text linkFriction Stir Welding (FSW) has become a mature technology for most metal alloys. The current frontier is the
development of in-situ alloyed or reinforced materials to further spread the field of application of this technique.
In the paper, SiC-reinforced 2024-T3 aluminum joints were produced by integrating micro-size SiC particles by
creating proper features in the sheets. A new joint design was proposed in order to overcome the issues of powder
dispersion occurring with the more conventional hole design. The influence of distinct parameters viz., tool
rotation speed, traverse speed, and joint configuration on SiC dispersion, microstructure, and mechanical
properties of the prepared joints has been corroborated. Standard FSW was also carried out for comparison. The
rotation and travel speeds varied ranging 700–1100 rpm and 50–90 mm/min, respectively. The distribution of
reinforcement particles in various zones of the FSW process was examined by using optical microscopy (OM) and
scanning electron microscopy (SEM). It was found that the velocity ratio variation influences the heat generation
and thereby the microstructural and mechanical properties owing to distinct SiC particulate dispersion
throughout the joint area. The welded joints produced at the 1100 rpm and 70 mm/min (S1100–70) combination
exhibit an increment in hardness by 30 % as compared to base material resulting from grain size reduction and
better dispersion of SiC powder. Finally, the analysis of power consumption and temperature during the process
was carried out. These additional measurements were crucial in determining the overall performance and
feasibility of using SiC powder in the welding process
Assessing the Economic Impacts of Government Incentives on SMEs through Monte Carlo Simulations: A Framework for Sustainable Growth and Technological Adoption
No full textIn the contemporary economic landscape, small and medium-sized enterprises (SMEs) are vital for innovation and growth but face barriers like limited capital access and digital skill gaps. This study employs Monte Carlo simulations to assess governmental incentives' economic impacts on SMEs, focusing on variables like revenue growth, employment, and R&D outputs. By evaluating profitability indices (e.g., ROI, ROS) and using synthetic-realistic data, it provides insights into optimizing assistance programs. The Monte Carlo method, in conjunction with more traditional statistical approaches, offers a sophisticated framework for modeling complex scenarios and variables, ensuring reliable and informative results for effective policymaking
An accurate and refined nonlinear beam model accounting for the Poisson effect
No full textIn this paper, an enhanced beam model based on a 5-parameter displacement field, recently proposed by the authors and able to reproduce the Poisson effect in transverse direction is presented, and utilized to simulate the fully geometrically nonlinear response of elastic beam structures. The adoption of the linear solution as approximation functions for the nonlinear case allows prediction of nonlinear response of problems involving complex geometries with a relatively small computational effort. Several numerical examples of benchmark problems are analyzed, highlighting the characteristic features of the proposed five-parameter model and comparing the results with those obtained using the classical Bernoulli beam model and 3D finite element model
Finding Damage in Truss Structures Exploiting Modal Strains
Full text linkThe detection of potentially damaged elements in planar truss structures is a challenging
task. Among the different methods proposed in literature, one promising procedure exploits the
modal strains of the structure that are calculated from the flexibility matrix, which is, in turn,
estimated from the lowest frequencies and corresponding modes of vibration. The benefit of this
approach stems from the possibility of using a reduced number of mode shapes, usually available
from the dynamic monitoring of the structure to perform the damage detection. In this work, a
novel damage detection index based on modal strains is proposed, and its reliability in detecting
stiffness reduction in elements of a planar truss is tested numerically
Mechanical properties of cables made with helically wound carbon-nanotube fibers for advanced structural applications
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