scholarly journals Ultrasonic Assisted Sintering Using Heat Converted from Mechanical Energy

Metals ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 971 ◽  
Author(s):  
Zhiyuan Liu ◽  
Yang Ge ◽  
Dandan Zhao ◽  
Yan Lou ◽  
Yong Liu ◽  
...  
Keyword(s):  
High Frequency ◽  
Volume Diffusion ◽  
Mechanical Energy ◽  
Pure Aluminum ◽  
Maximum Temperature ◽  
Sintered Aluminum ◽  
The Hierarchical Structure ◽  
Ultrasonic Assisted ◽  
Interparticle Friction ◽  
Sintering Method

A new sintering method, namely ultrasonic assisted sintering (UAS), has been proposed using mechanical heat converted from high frequency motion between particles. Pure aluminum specimens with diameter of 5 mm and thickness of ~2 mm have been successfully sintered in two seconds. Based on the thermodynamic analysis, the underlying heating mechanism is quantitatively interpreted, which involves high-frequency interparticle friction and plastic deformation driven by ultrasonic squeezing. Consequently, temperature rises rapidly at a speed of about 300 K/s, and the maximum temperature reaches up to 0.9 times of melting point of the aluminum during UAS. The sintered specimens have a high density of dislocations, under the combined effects of dislocations and undulating stress field, volume diffusion coefficient for sintering increases by several orders of magnitude, therefore, rapid densification can be accomplished in seconds. In addition, the sintered aluminum has ultrahigh nanohardness (~1.13 GPa), which can be attributed to the hierarchical structure formed during UAS process.

Numerical Simulation of Plunge Force During the Plunge Phase of Friction Stir Welding and Ultrasonic Assisted FSW

2008 ◽  
Author(s):  
Kwanghyun Park ◽  
Bongsuk Kim ◽  
Jun Ni
Keyword(s):  
Numerical Simulation ◽  
Friction Stir Welding ◽  
High Frequency ◽  
Hybrid Welding ◽  
Ultrasonic Vibrations ◽  
Welding Quality ◽  
Friction Stir ◽  
Ultrasonic Assisted ◽  
Welding Force ◽  
Welding Technique

Ultrasonic assisted friction stir welding (UaFSW) is an hybrid welding technique, where high frequency vibration is superimposed on the movement of a rotating tool. The benefit of using ultrasonic vibration in the FSW process refers to the reduction in the welding force and to the better welding quality. The UaFSW system is being developed and its mechanism needs to be understood using both the experiments and the numerical simulations. In this paper, FE simulations of FSW and UaFSW using ABAQUS/Explicit were carried out to examine plunge forces during the plunge phase of FSW and UaFSW, respectively. First, the simulations of the conventional FSW process were validated. Then, simulation of UaFSW process was performed by imposing sinusoidal horizontal ultrasonic vibrations on the tool.

scholarly journals Grain fragmentation in ultrasonic-assisted TIG weld of pure aluminum

2017 ◽  
Vol 39 ◽  
pp. 403-413 ◽  
Author(s):  
Qihao Chen ◽  
Sanbao Lin ◽  
Chunli Yang ◽  
Chenglei Fan ◽  
Hongliang Ge
Keyword(s):  
Pure Aluminum ◽  
Ultrasonic Assisted ◽  
Grain Fragmentation

scholarly journals Characterization of hydroxyapatite-reduced graphene oxide nanocomposites consolidated via high frequency induction heat sintering method

2020 ◽  
Vol 8 (4) ◽  
pp. 1296-1309
Author(s):  
Hassan Nosrati ◽  
Rasoul Sarraf-Mamoory ◽  
Mohammad Hossein Kazemi ◽  
Maria Canillas Perez ◽  
Mahdieh Shokrollahi ◽  
...  
Keyword(s):  
Graphene Oxide ◽  
Reduced Graphene Oxide ◽  
High Frequency ◽  
Induction Heat ◽  
Reduced Graphene ◽  
Sintering Method ◽  
High Frequency Induction

The Effect of Holding Time on the Mechanical Properties and Microstructure of Sintered NbC Composite

2010 ◽  
Vol 123-125 ◽  
pp. 803-806
Author(s):  
Duck Soo Kang ◽  
Kee Do Woo ◽  
Sang Hyuk Kim ◽  
In Jin Shon ◽  
Ji Young Kim ◽  
...  
Keyword(s):  
Grain Size ◽  
Relative Density ◽  
High Frequency ◽  
Holding Time ◽  
Full Width ◽  
Petch Relation ◽  
Sintering Time ◽  
Rapid Sintering ◽  
Sintering Method ◽  
High Frequency Induction

High frequency induction heated sintering (HFIHS) method is one of the rapid sintering methods. The advantage of rapid sintering method is that grain growth can be prevented during sintering at high temperature. Refinement of grains was known to increase the yield and flow stresses of crystals. The relation between the yield stress and the grain size is known as Hall-Petch relation. NbC-10vol.%Co, Ni and Fe composites were fabricated by HFIHS at 1060°C for 0 and 3 min as holding times under a pressure of 80MPa.The relative density of NbC-10vol.%Co, Ni and Fe composites which were sintered at 1060°C for 0min as holding time under 80MPa were 91.90%, 91.26% and 91.26%, respectively. These composites are difficult to use industrial parts due to low relative density. The longer sintering time was conducted for increasing relative density in this study. Nano-sized specimens, which were calculated grain size by full-width at half maximum (FWHM), can be obtained by HFIHS. The value of hardness and fracture toughness was investigated using 20kgf load Vickers indenter.

New acoustical technology of sound absorption based on reverse horn

2016 ◽  
Vol 30 (34) ◽  
pp. 1650403 ◽  
Author(s):  
Yong Yan Zhang ◽  
Jiu Hui Wu ◽  
Song Hua Cao ◽  
Pei Cao ◽  
Zi Ting Zhao
Keyword(s):  
High Frequency ◽  
Sound Absorption ◽  
Mechanical Energy ◽  
Low Frequency ◽  
Acoustic Energy ◽  
Absorption Mechanism ◽  
Structure Changes ◽  
Potential Applications ◽  
Energy Focusing ◽  
The One

In this paper, a novel reverse horn’s sound-absorption mechanism and acoustic energy focusing mechanism for low-frequency broadband are presented. Due to the alternation of the reverse horn’s thickness, the amplitude of the acoustic pressure propagated in the structure changes, which results in growing energy focused in the edge and in the reverse horn’s tip when the characteristic length is equal to or less than a wavelength and the incident wave is compressed. There are two kinds of methods adopted to realize energy dissipation. On the one hand, sound-absorbing materials are added in incident direction in order to overcome the badness of the reverse horn’s absorption in high frequency and improve the overall high-frequency and low-frequency sound-absorption coefficients; on the other hand, adding mass and film in its tip could result in mechanical energy converting into heat energy due to the coupled vibration of mass and the film. Thus, the reverse horn with film in the tip could realize better sound absorption for low-frequency broadband. These excellent properties could have potential applications in the one-dimensional absorption wedge and for the control of acoustic wave.

Performance of a Solar Chimney With a Modified Collector Geometry: A Case Study From Erbil to the North of Iraq

2019 ◽  
Vol 142 (1) ◽  
Author(s):  
Dara Khalid Khidhir ◽  
Soorkeu A. Atrooshi
Keyword(s):  
Solar Radiation ◽  
Ambient Temperature ◽  
Temperature Difference ◽  
Mechanical Energy ◽  
Maximum Temperature ◽  
Geometrical Shape ◽  
Solar Chimney ◽  
Air Velocity ◽  
Temperature Loss ◽  
Solar Intensity

Abstract The principle of solar chimney power plant (SCPP) is based on harvesting the thermal spectrum of solar radiation and converting it to mechanical energy by the means of a collector, a wind turbine, and a chimney. In this work, a number of experiments were performed on a modified model made up of one-third of the circular collector area. Field data from selected clear, sunny days were recorded and studied. The analysis focused on time-temperature relations for ambient, near chimney entry point and the collector periphery, in addition to hourly solar radiation intensity and air velocity inside the chimney. The results show that for this geometry arrangement, the maximum temperature of the air entering the chimney is achieved before the ambient temperature reaches its peak value. Air velocity inside the chimney depends on the intensity of solar radiation and the temperature difference between the air temperature entering the chimney and the ambient temperature. Solar intensity directly affects the temperature of air beneath the collector, and a part of this energy is stored in the ground. Later, when the solar radiation is impaired, the stored energy can be utilized. Air velocity of 2.1 m/s is obtained after the solar noon, when the solar intensity is 737 W/m2 and the maximum temperature difference is 11.2 °C. Due to the unique geometrical shape of the rig, a minor temperature loss of up to 1.3 °C occurs for the air near the center of the chimney.

Ultraschallunterstützte Umformung von Metallen*/Ultrasonic-assisted forming of metals - Development of a test bench for material characterization with 15 kHz ultrasonic vibrations

2015 ◽  
Vol 105 (10) ◽  
pp. 715-721
Author(s):  
M. Michalski ◽  
M. Merklein
Keyword(s):  
High Frequency ◽  
Material Characterization ◽  
Test Bench ◽  
Flow Behavior ◽  
High Frequency Oscillation ◽  
Experimental Investigations ◽  
Metallic Materials ◽  
Frequency Oscillation ◽  
Ultrasonic Assisted ◽  
Forming Tools

Umformwerkzeuge, die mit einer hochfrequenten mechanischen Schwingung überlagert werden, ermöglichen eine deutliche Reduzierung der benötigten Umformkräfte. Darauf aufbauend werden am Lehrstuhl für Fertigungstechnologie experimentelle Untersuchungen mit verschiedenen metallischen Werkstoffen durchgeführt, um deren Fließverhalten bei Ultraschallüberlagerung mit 15 kHz zu charakterisieren. Die aktuelle Studie befasst sich mit der Entwicklung und der Qualifizierung eines geeigneten Prüfstands.   Forming tools that are superimposed with a high frequency oscillation enable a considerable reduction of the required forming forces. On this basis experimental investigations with various metallic materials are conducted at the Institute of Manufacturing Technology to characterize the flow behavior during ultrasonic-assisted forming with 15 kHz oscillation frequency. This study is concerned with the development and the qualification of a suitable test bench.

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