Search results for "GAS"
showing 10 items of 12601 documents
The use of exploratory experimental designs combined with thermal numerical modelling to obtain a predictive tool for hybrid laser/MIG welding and co…
2011
Abstract While hybrid laser welding and coating processes involve a large number of physical phenomena, it is currently impossible to predict, for a given set of influencing factors, the shape of the molten zone and the history of temperature fields inside the parts. This remains true for complex processes, such as the hybrid laser/MIG welding process, which consists in combining a laser beam with a MIG torch. The gains obtained result essentially from the synergy of the associated processes: the stability of the process, the quality of the seam realized, and the productivity are increased. This article shows how, by means of a reduced number of experiments (8), it is possible to predict th…
Effect of active heating and cooling on microstructure and mechanical properties of friction stir–welded dissimilar aluminium alloy and titanium butt…
2019
A butt joint configuration of AA6061–pure Ti was welded using friction stir welding (FSW) with an assisted cooling and heating conditions, aiming to attain a flawless joint. Cooling-assisted friction stir welding (CFSW) was carried out with a different cooling medium such as CO2, compressed air and water at controlled flow rate. However, heating-assisted friction stir welding (HFSW) was performed with heating source of GTAW torch just before FSW tool at different current density. Prepared specimens were subjected to optical microscopy (OM), scanning electron microscopy (SEM) and electrodischarge spectroscopy (EDS) for microstructural characterizations. The tensile strength and microhardness…
A new approach to simulate coating thickness in cold spray
2020
Abstract In the process of cold spray on complex components, the coating thickness is an important indicator to monitor and control. Current methods such as destructive tests or direct mechanical measurements can only be performed after spraying. Besides, these methods lead to production shutdown and additional costs . This article presents a novel approach predicting coating thickness for components with complex curved surfaces, especially in the case of shadow effects. Firstly, a three-dimensional geometric model of the coating profile based on Gaussian distribution was developed. In addition, the relative deposition efficiency (RDE) resulting from the different robot kinematic parameters…
Friction Stir Welding of Ti6Al4V complex geometries for aeronautical applications: a feasibility study
2020
Abstract 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 l…
The numerical simulation of heat transfer during a hybrid laser–MIG welding using equivalent heat source approach
2014
International audience; The present study is dedicated to the numerical simulation of an industrial case of hybrid laser-MIG welding of high thickness duplex steel UR2507Cu with Y-shaped chamfer geometry. It consists in simulation of heat transfer phenomena using heat equivalent source approach and implementing in finite element software COMSOL Multiphysics. A numerical exploratory designs method is used to identify the heat sources parameters in order to obtain a minimal required difference between the numerical results and the experiment which are the shape of the welded zone and the temperature evolution in different locations. The obtained results were found in good correspondence with …
Stable layer-building strategy to enhance cold-spray-based additive manufacturing
2020
Abstract Cold spray (CS) has recently become one of the popular additive manufacturing (AM) processes for its advantages: high-forming efficiency, low temperature, and no phase changing of materials. These advantages may make CS able to form large volume objects and possibly directly iterate with material-removing processes to become a hybrid AM process. Current research proposes using a bulk-based volume-forming strategy (e.g. a tessellation-based method) for volume building. Although it can form 3D volumes, the control of the process is difficult and it has limitations in forming complex 3D near-net-shapes with acceptable accuracy. This also conflicts with the basic principle of AM, where…
El ?Alivio de las Indias?. la Real Hacienda Filipina, 1565-1800
2019
Previo al estudio de la Real Hacienda filipina, el trabajo se centrará en la definición del marco territorial, la función del archipiélago en la estrategia imperial y la gran transformación de finales del siglo xVIII que afectó a su situación en el conjunto colonial. En segundo lugar, se expondrá el estado de la cuestión y las principales hipótesis sobre la evolución del Tesoro filipino y los problemas que planteaba su viabilidad, así como las fuentes y la metodología empleadas. A continuación se examinarán las grandes tendencias de la Hacienda en el largo plazo y los componentes del ingreso y el gasto, para finalizar con algunas conclusiones, en especial la respuesta a la siguiente pregunt…
The impact of the volumetric swelling behavior on the water uptake of gas shale
2018
Abstract Water uptake of gas shales is commonly considered one of the most important factors responsible for fluid loss during flowback operations after hydraulic fracturing. Imbibition experiments cover a key role in this context to analyze the impact of several factors (such as mineralogical composition, fluids composition, anisotropic structure, volumetric swelling) that contribute to the water uptake in these unconventional reservoirs. The aim of this study is the quantification of the impact of the volumetric response (swelling and shrinkage) of gas shales on the water uptake during imbibition and desiccation processes. An experimental methodology to quantify the volumetric response du…
A flexible robotic cell for in-process inspection of multi-pass welds
2020
Welds are currently only inspected after all the passes are complete and after allowing sufficient time for any hydrogen cracking to develop, typically over several days. Any defects introduced between passes are therefore unreported until fully buried, greatly complicating rework and also delaying early corrections to the weld process parameters. In-process inspection can provide early intervention but involves many challenges, including operation at high temperatures with significant gradients affecting acoustic velocities and, hence, beam directions. Reflections from the incomplete parts of the weld would also be flagged as lack-of-fusion defects, requiring the region of interest (ROI) t…
Sharing R&D investments in breakthrough technologies to control climate change
2017
This paper examines international cooperation on technological development as an alternative to international cooperation on GHG emission reductions. In order to analyze the scope of cooperation, a three-stage technology agreement formation game is solved. First, countries decide whether or not to sign up to the agreement. Then, in the second stage, the signatories (playing together) and the non-signatories (playing individually) select their investment in R&D. In this stage, it is assumed that the signatories not only coordinate their levels of R&D investment but also pool their R&D efforts to fully internalize the spillovers of their investment in innovation. Finally, in the third stage, …