The Experts below are selected from a list of 972 Experts worldwide ranked by ideXlab platform
Dmitry G. Eskin - One of the best experts on this subject based on the ideXlab platform.
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numerical modelling of ultrasonic waves in a bubbly newtonian liquid using a high order acoustic cavitation model
Ultrasonics Sonochemistry, 2017Co-Authors: G S B Lebon, Dmitry G. Eskin, Iakovos Tzanakis, Koulis Pericleous, G DjambazovAbstract:To address difficulties in treating large volumes of liquid metal with ultrasound, a fundamental study of acoustic cavitation in liquid aluminium, expressed in an experimentally validated numerical model, is presented in this paper. To improve the understanding of the cavitation process, a non-linear acoustic model is validated against reference water pressure measurements from acoustic waves produced by an immersed horn. A high-order method is used to discretize the wave equation in both space and time. These discretized equations are coupled to the Rayleigh-Plesset equation using two different time scales to couple the bubble and flow scales, resulting in a stable, fast, and reasonably accurate method for the prediction of acoustic pressures in cavitating liquids. This method is then applied to the context of treatment of liquid aluminium, where it predicts that the most intense cavitation activity is localised below the vibrating horn and estimates the acoustic decay below the Sonotrode with reasonable qualitative agreement with experimental data.
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identifying the stages during ultrasonic processing that reduce the grain size of aluminum with added al3ti1b master alloy
Advanced Engineering Materials, 2017Co-Authors: Gui Wang, Dmitry G. Eskin, Matthew S Dargusch, D H StjohnAbstract:The combined application of UST and Al3Ti1B grain refiner changes the macrostructure of untreated commercial purity aluminum from large millimeter sized columnar grains to equiaxed grains of a few hundred microns. This research reveals three distinct stages that affect the grain size, while UST is applied during melting and solidification. Stage I applied well above the liquidus temperature improves the efficiency of the refiner, possibly by de-agglomeration and wetting of TiB2 particles, and their distribution throughout the melt by acoustic streaming. Stage I is followed by Stage II, where little further improvement occurs. Stage III causes additional grain refinement when applied at and below the liquidus temperature, where nucleation of grains maybe enhanced by cavitation, which can also facilitate fragmentation and detachment of grains formed on the Sonotrode. Convection due to acoustic streaming creates a uniformly undercooled temperature in the melt, which ensures the survival of these new grains during transport, as well as assisting the transport of grains to produce a uniform fine grain size throughout the ingot.
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Investigation of the factors influencing cavitation intensity during the ultrasonic treatment of molten aluminium
Materials & Design, 2016Co-Authors: Iakovos Tzanakis, Dmitry G. Eskin, G S B Lebon, Koulis PericleousAbstract:The application of ultrasound to casting processes is a subject of great interest: the resulting degassing, sonocrystallization, wetting, fragmentation, de-agglomeration and dispersion yield an improved cast material with fine grain structure. However, due to the lack of understanding of certain fundamentals involved in the process, the transfer and scale-up of this promising technology to industry has been hindered by difficulties in treating large volumes of liquid metal. Experimental results of ultrasonic processing of liquid aluminium with a 5-kW magnetostrictive transducer and a 20-mm niobium Sonotrode producing 17-kHz ultrasonic waves are reported in this study. A high-temperature cavitometer sensor that is placed at different locations in the liquid melt, measured cavitation activity at various acoustic power levels and in different temperature ranges. The highest cavitation intensity in the liquid bulk is achieved below the surface of the Sonotrode, at the lowest temperature, and when the applied power was 3.5 kW. Understanding these ultrasonication mechanisms in liquid metals will result in a major breakthrough for the optimization of ultrasound applications in metal industries.
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application of a plate Sonotrode to ultrasonic degassing of aluminum melt acoustic measurements and feasibility study
Journal of Materials Processing Technology, 2015Co-Authors: Dmitry G. Eskin, Kawther Alhelal, Iakovos TzanakisAbstract:Abstract A flat plate Sonotrode was used for ultrasonic melt processing (degassing) of aluminum melts. Calculations showed that this Sonotrode should have several antinodes with maximum amplitude, spaced at 16.5 mm. The direct measurements of the amplitude in air and indirect measurements of foil cavitation erosion in water validated these calculations. Unique acoustic measurements of cavitation activity in water and a liquid aluminum alloy were performed using a cavitometer and confirmed that the cavitation conditions were met with this scheme. The melt degassing efficiency using the plate Sonotrode was significantly higher (70–80%) than with a conventional cylindrical Sonotrode (45–50%) in batch operation. The new scheme was also suitable for ultrasonic melt processing in the melt flow giving about 50% degassing efficiency, which opens the way to upscaling this technology to treat larger volumes of melt.
F Rivillas - One of the best experts on this subject based on the ideXlab platform.
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assessing a stepped Sonotrode in ultrasonic molding technology
Journal of Materials Processing Technology, 2016Co-Authors: J Grabalosa, Osca Martinezromero, Ale Eliaszuniga, X Planta, I Ferre, F RivillasAbstract:Abstract Ultrasonic molding is a new technology used to process polymeric micro-molded parts. An ultrasonic horn, or Sonotrode, transmits ultrasonic energy which melts the material and pushes it into a mold cavity to configure a shape. Sonotrode design – and any transformations to the dimensions or shape caused by tool wear – strongly affects efficient operation. The Sonotrode may go beyond the generator operating frequency range, thus affecting process performance. This paper assesses two issues involving a stepped Sonotrode employed in ultrasonic molding: (i) a design procedure that can predict the sonotode’s behavior during the molding process and (ii) a method for creating a Sonotrode operating frequencies map which will facilitate the design of new Sonotrodes and be able to determine the extent to which they can be re-machined after a certain period of wear. Numerical simulations carried out by finite element methods were compared to experimental measurements performed to capture the Sonotrode frequency vibrational modes. A frequency map provides the dimensional range within which the Sonotrode can be re-machined in order to eliminate tool wear and allow the Sonotrode to work properly again, thus extending the lifecycle of the tool.
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Study of the Ultrasonic Molding Process Parameters for Manufacturing Polypropylene Parts
Procedia Engineering, 2015Co-Authors: P. Negre, J Grabalosa, I. Ferrer, Joaquim Ciurana, Alex Elías-zúñiga, F RivillasAbstract:Applications of polymeric materials are becoming a huge opportunity to innovate in new manufacturing technologies. In this sense Ultrasonic Molding (USM) process is an innovative technology to produce polymeric micro parts. Here, ultrasonic energy is used for melting polymeric pellets and fill a mold cavity. This paper presents a preliminary study to analyse the influence of three process parameters of USM on filling cavity, porosity, part weight and dimension. The process parameters studied are: humidity of the pellets, Sonotrode velocity and mold temperature. The results show that dried pellets, velocities lower than 7mm/s or using increasing ramps velocities provide better parts. Although in future works the effect of the ultrasonic time on filling cavity and part dimensions should be studied and more material tested to extend the knowledge to this new technology
S Bouvier - One of the best experts on this subject based on the ideXlab platform.
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relation between roughness and processing conditions of aisi 316l stainless steel treated by ultrasonic shot peening
Tribology International, 2015Co-Authors: J Marteau, Maxence Bigerelle, Pierreemmanuel Mazeran, S BouvierAbstract:Abstract This article assessed the roughness induced by ultrasonic shot peening. Surface properties of AISI 316L steel specimens were modified through the variation of ultrasonic shot-peening parameters (shot material, shot diameter, Sonotrode amplitude vibration and coverage). Each surface was characterized using fifty surface roughness parameters and two types of robust Gaussian filter (low pass and high pass) associated with twenty one cut-off lengths. For each type of processing parameter, the most relevant roughness parameter and its corresponding length scale and filter were found. A linear relationship was identified between the four ultrasonic shot-peening parameters and the mean density of furrows with a coefficient of determination equal to 0.97.
J Grabalosa - One of the best experts on this subject based on the ideXlab platform.
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assessing a stepped Sonotrode in ultrasonic molding technology
Journal of Materials Processing Technology, 2016Co-Authors: J Grabalosa, Osca Martinezromero, Ale Eliaszuniga, X Planta, I Ferre, F RivillasAbstract:Abstract Ultrasonic molding is a new technology used to process polymeric micro-molded parts. An ultrasonic horn, or Sonotrode, transmits ultrasonic energy which melts the material and pushes it into a mold cavity to configure a shape. Sonotrode design – and any transformations to the dimensions or shape caused by tool wear – strongly affects efficient operation. The Sonotrode may go beyond the generator operating frequency range, thus affecting process performance. This paper assesses two issues involving a stepped Sonotrode employed in ultrasonic molding: (i) a design procedure that can predict the sonotode’s behavior during the molding process and (ii) a method for creating a Sonotrode operating frequencies map which will facilitate the design of new Sonotrodes and be able to determine the extent to which they can be re-machined after a certain period of wear. Numerical simulations carried out by finite element methods were compared to experimental measurements performed to capture the Sonotrode frequency vibrational modes. A frequency map provides the dimensional range within which the Sonotrode can be re-machined in order to eliminate tool wear and allow the Sonotrode to work properly again, thus extending the lifecycle of the tool.
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Study of the Ultrasonic Molding Process Parameters for Manufacturing Polypropylene Parts
Procedia Engineering, 2015Co-Authors: P. Negre, J Grabalosa, I. Ferrer, Joaquim Ciurana, Alex Elías-zúñiga, F RivillasAbstract:Applications of polymeric materials are becoming a huge opportunity to innovate in new manufacturing technologies. In this sense Ultrasonic Molding (USM) process is an innovative technology to produce polymeric micro parts. Here, ultrasonic energy is used for melting polymeric pellets and fill a mold cavity. This paper presents a preliminary study to analyse the influence of three process parameters of USM on filling cavity, porosity, part weight and dimension. The process parameters studied are: humidity of the pellets, Sonotrode velocity and mold temperature. The results show that dried pellets, velocities lower than 7mm/s or using increasing ramps velocities provide better parts. Although in future works the effect of the ultrasonic time on filling cavity and part dimensions should be studied and more material tested to extend the knowledge to this new technology
Iakovos Tzanakis - One of the best experts on this subject based on the ideXlab platform.
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numerical modelling of ultrasonic waves in a bubbly newtonian liquid using a high order acoustic cavitation model
Ultrasonics Sonochemistry, 2017Co-Authors: G S B Lebon, Dmitry G. Eskin, Iakovos Tzanakis, Koulis Pericleous, G DjambazovAbstract:To address difficulties in treating large volumes of liquid metal with ultrasound, a fundamental study of acoustic cavitation in liquid aluminium, expressed in an experimentally validated numerical model, is presented in this paper. To improve the understanding of the cavitation process, a non-linear acoustic model is validated against reference water pressure measurements from acoustic waves produced by an immersed horn. A high-order method is used to discretize the wave equation in both space and time. These discretized equations are coupled to the Rayleigh-Plesset equation using two different time scales to couple the bubble and flow scales, resulting in a stable, fast, and reasonably accurate method for the prediction of acoustic pressures in cavitating liquids. This method is then applied to the context of treatment of liquid aluminium, where it predicts that the most intense cavitation activity is localised below the vibrating horn and estimates the acoustic decay below the Sonotrode with reasonable qualitative agreement with experimental data.
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Investigation of the factors influencing cavitation intensity during the ultrasonic treatment of molten aluminium
Materials & Design, 2016Co-Authors: Iakovos Tzanakis, Dmitry G. Eskin, G S B Lebon, Koulis PericleousAbstract:The application of ultrasound to casting processes is a subject of great interest: the resulting degassing, sonocrystallization, wetting, fragmentation, de-agglomeration and dispersion yield an improved cast material with fine grain structure. However, due to the lack of understanding of certain fundamentals involved in the process, the transfer and scale-up of this promising technology to industry has been hindered by difficulties in treating large volumes of liquid metal. Experimental results of ultrasonic processing of liquid aluminium with a 5-kW magnetostrictive transducer and a 20-mm niobium Sonotrode producing 17-kHz ultrasonic waves are reported in this study. A high-temperature cavitometer sensor that is placed at different locations in the liquid melt, measured cavitation activity at various acoustic power levels and in different temperature ranges. The highest cavitation intensity in the liquid bulk is achieved below the surface of the Sonotrode, at the lowest temperature, and when the applied power was 3.5 kW. Understanding these ultrasonication mechanisms in liquid metals will result in a major breakthrough for the optimization of ultrasound applications in metal industries.
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application of a plate Sonotrode to ultrasonic degassing of aluminum melt acoustic measurements and feasibility study
Journal of Materials Processing Technology, 2015Co-Authors: Dmitry G. Eskin, Kawther Alhelal, Iakovos TzanakisAbstract:Abstract A flat plate Sonotrode was used for ultrasonic melt processing (degassing) of aluminum melts. Calculations showed that this Sonotrode should have several antinodes with maximum amplitude, spaced at 16.5 mm. The direct measurements of the amplitude in air and indirect measurements of foil cavitation erosion in water validated these calculations. Unique acoustic measurements of cavitation activity in water and a liquid aluminum alloy were performed using a cavitometer and confirmed that the cavitation conditions were met with this scheme. The melt degassing efficiency using the plate Sonotrode was significantly higher (70–80%) than with a conventional cylindrical Sonotrode (45–50%) in batch operation. The new scheme was also suitable for ultrasonic melt processing in the melt flow giving about 50% degassing efficiency, which opens the way to upscaling this technology to treat larger volumes of melt.
