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e Schematic diagram of ultrasonic wave in one period (a) and sound pressure distribution near the tool on horizontal plane Z ¼ 1.5 mm at different times (bej).
Source publication
To understand the synchronous interaction mechanism between the ultrasonic vibration exerted on the tool and the tool induced thermo-mechanical behavior in ultrasonic vibration-assisted friction stir welding (UVaFSW) process, the geometric shape of the contact surface between the horn and the tool was considered, and a previous point source of ultr...
Contexts in source publication
Context 1
... the sound pressure changes periodically in the aforementioned, a period is divided into t 1 -t 9 , a total of 9 time points (Fig. 9 (a)) and the sound pressure field in Z ¼ 1.5 mm horizontal plane at different times is extracted (Fig. 9bej). The periodic change of sound pressure can be divided into four stages: firstly, it can be seen as the rising stages of sound pressure, and the sound pressure reaches its peak value at the time t 2 in Fig. 9bec. Then it begins to ...
Context 2
... the sound pressure changes periodically in the aforementioned, a period is divided into t 1 -t 9 , a total of 9 time points (Fig. 9 (a)) and the sound pressure field in Z ¼ 1.5 mm horizontal plane at different times is extracted (Fig. 9bej). The periodic change of sound pressure can be divided into four stages: firstly, it can be seen as the rising stages of sound pressure, and the sound pressure reaches its peak value at the time t 2 in Fig. 9bec. Then it begins to drop with time and reaches zero (Fig. 9dee). After that, the sound pressure changes its direction and ...
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... 9 , a total of 9 time points (Fig. 9 (a)) and the sound pressure field in Z ¼ 1.5 mm horizontal plane at different times is extracted (Fig. 9bej). The periodic change of sound pressure can be divided into four stages: firstly, it can be seen as the rising stages of sound pressure, and the sound pressure reaches its peak value at the time t 2 in Fig. 9bec. Then it begins to drop with time and reaches zero (Fig. 9dee). After that, the sound pressure changes its direction and reaches the maximum negative pressure at the time t 6 (Fig. 9feg). Later, the sound pressure starts to rise and reaches zero at the time t 8 , and then starts another period of sound pressure, as shown in Fig. 9hej. ...
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... field in Z ¼ 1.5 mm horizontal plane at different times is extracted (Fig. 9bej). The periodic change of sound pressure can be divided into four stages: firstly, it can be seen as the rising stages of sound pressure, and the sound pressure reaches its peak value at the time t 2 in Fig. 9bec. Then it begins to drop with time and reaches zero (Fig. 9dee). After that, the sound pressure changes its direction and reaches the maximum negative pressure at the time t 6 (Fig. 9feg). Later, the sound pressure starts to rise and reaches zero at the time t 8 , and then starts another period of sound pressure, as shown in Fig. 9hej. Fig. 10 shows the sound pressure distribution along welding ...
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... can be divided into four stages: firstly, it can be seen as the rising stages of sound pressure, and the sound pressure reaches its peak value at the time t 2 in Fig. 9bec. Then it begins to drop with time and reaches zero (Fig. 9dee). After that, the sound pressure changes its direction and reaches the maximum negative pressure at the time t 6 (Fig. 9feg). Later, the sound pressure starts to rise and reaches zero at the time t 8 , and then starts another period of sound pressure, as shown in Fig. 9hej. Fig. 10 shows the sound pressure distribution along welding direction on the horizontal section of the workpiece (Z ¼ 1.5 mm). At instant t ¼ 1.01250 ms, the tool is driven to vibrate ...
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... time t 2 in Fig. 9bec. Then it begins to drop with time and reaches zero (Fig. 9dee). After that, the sound pressure changes its direction and reaches the maximum negative pressure at the time t 6 (Fig. 9feg). Later, the sound pressure starts to rise and reaches zero at the time t 8 , and then starts another period of sound pressure, as shown in Fig. 9hej. Fig. 10 shows the sound pressure distribution along welding direction on the horizontal section of the workpiece (Z ¼ 1.5 mm). At instant t ¼ 1.01250 ms, the tool is driven to vibrate toward positive x-axis, and the sound pressure is positive for x > 0 but negative for x < 0. At instant t ¼ 1.03750 ms, the tool is driven to vibrate ...
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... better comparison of the heat flux on pin side, two circumferences at the pin/workpiece contact interface are taken in Fig. 19a, which locate at the horizontal plane 1.5 mm and 2.5 mm away from the bottom of the workpiece. As shown in Fig. 19b, r q is the radius direction; q q is the included angle between the welding direction and the radius direction. Fig. 19ced shows the heat flux versus q q at the tool/workpiece contact interface at different ...
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... better comparison of the heat flux on pin side, two circumferences at the pin/workpiece contact interface are taken in Fig. 19a, which locate at the horizontal plane 1.5 mm and 2.5 mm away from the bottom of the workpiece. As shown in Fig. 19b, r q is the radius direction; q q is the included angle between the welding direction and the radius direction. Fig. 19ced shows the heat flux versus q q at the tool/workpiece contact interface at different ...
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... comparison of the heat flux on pin side, two circumferences at the pin/workpiece contact interface are taken in Fig. 19a, which locate at the horizontal plane 1.5 mm and 2.5 mm away from the bottom of the workpiece. As shown in Fig. 19b, r q is the radius direction; q q is the included angle between the welding direction and the radius direction. Fig. 19ced shows the heat flux versus q q at the tool/workpiece contact interface at different ...
Citations
... Friction stir welding (FSW), a solid-state joining technology, has been widely employed to join various dissimilar material combinations due to its unique joining mechanism [14,15]. In FSW, the joining of dissimilar materials can be achieved successfully by the heat generated during the friction between the tool-workpiece interface and the material flowinduced plastic deformation [16][17][18]. ...
The present study investigates the impact of complex material flow-induced interfacial reaction layers on the fatigue performance of friction stir-welded (FSW) S45C steel and 6061-T6 aluminum alloy. The material flow analysis reveals that the intermixing between aluminum and steel forms intermetallic compounds (IMCs) mainly limited to the upper side of the stir zone (SZ). The IMC layers in various regions of the aluminum/steel interface within the SZ are visualized by scanning electron microscopy, and their possible chemical compositions are identified using energy-dispersive spectroscopy analysis. The chemical composition, morphology, and thickness of IMC layers exhibit significant heterogeneity owing to the asymmetric material flow of aluminum and steel between the top and bottom sides of the SZ. The non-uniform IMC layers considerably influence surface microhardness values and the fatigue behavior of the FSW joint. Moreover, the significance of IMC thickness on the morphology of the fatigue failure mechanism is examined using detailed microstructural analysis in proximity to fatigue fracture locations of the FSW joint. SEM images suggest that fatigue cracks inside the FSW joint initiate more frequently in thick IMC lamella than in the comparatively thinner Al-rich reaction layers.
... The second is the thermal effect generated by acoustic energy absorption. The third is the acoustic antifriction effect [44,45]. The three effects do not exist alone but interact on each other in UVaFSW process. ...
... The other details of the model, such as the calculation of ultrasonic field, ultrasonic antifriction mechanism and boundary conditions are introduced in detail in our previous publications [31,45]. ...
... When the radial distance is equal, the heat flux on the AS (Mg) is slightly lower than that on the RS (Al). With applying UV, due to the acoustic antifriction effect, the distribution of the interfacial heat generation determined by two j o u r n a l o f m a t e r i a l s r e s e a r c h a n d t e c h n o l o g y 2 0 2 3 ; 2 6 : 1 8 8 2 e1 9 0 2 models corresponds to the butterfly-shaped antifriction zone [44,45]. UV significantly reduces the friction coefficient at the pin root, and the friction heat generation is low in UVaFSW. ...
... The workpiece is assumed to be an in-compressible non-Newtonian fluid, the viscosity is written as [38], ...
Experiments have proven tool tilting in friction stir welding (FSW) can effectively suppress the formation of void defects. However, the mechanism of tool tilting on suppressing the formation of void defects has not been revealed. In this study, a CFD model considering the influence of tool tilting is established. A non-uniform distribution of normal pressure at the tool-workpiece contact interfaces is proposed to relate to the tool tilt angle. The discrete particle tracing method is used to characterize the formation of void defects in FSW. The heat generation, temperature distribution and plastic flow behaviors between the case without (i.e. 0° tool tilt angle) and with (i.e. 2.5° tool tilt angle) tool tilting are quantitatively compared and analyzed. The results show the tool tilting in FSW leads to higher heat flux and temperature near the pin side in the middle and low parts of the workpiece. Moreover, the frictional shear stress at the pin side/workpiece contact interface significantly increases when the tool is tilting, leading to a higher driving force for the plastic material to flow. As a result, the material flows farther to the advancing side of the workpiece after bypassing the tool when the tool is tilting at 2.5°, which helps to heal the voids on the advancing side of the FSW joints. The higher temperature with higher frictional shear stress enhances the plastic material flow in the middle and low part of the joints when the tool is tilting, which is attributed to suppressing the void defects. The model is validated by experimental results.
... They found that the heat generation at the tool-workpiece interface is decreased and the viscous dissipation of the plastic deformation zone is also decreased with superimposing ultrasound vibration in FSW. Zhang et al. [16] established a model of ultrasonic vibration-assisted FSW by considering the ultrasonic at tool horn and FSW tool as a line source of sound. It was found that superimposing ultrasonic vibration leads to a slight overall decrease in total amount of heat generation in FSW due to the dual effects of acoustic softening and ultrasonic antifriction. ...
Ultrasonic vibration–enhanced friction stir welding (UVeFSW) possesses the advantages of improving the welding quality and reducing welding loads as a novel variant of conventional friction stir welding (FSW). The tool pin geometry determines the final joint properties by affecting the welding temperature and material flow behaviors in the novel UVeFSW. However, there is a lack of quantitatively analyzing the effects of tool pin geometry on heat and mass transfer during UVeFSW. Thus, an integrated computational fluid dynamics model was used to elucidate the effects of tool pin geometry (i.e., pin diameter and taper angle) on the heat generation, temperature field, plastic material flow, and welding loads in UVeFSW. It revealed that the pin diameter and taper angle have little influence on the total heat generation in the UVeFSW process, whereas they significantly affect the temperature field near the tool by affecting the pin heat generation fraction. Although the total torque and transverse force did not significantly vary with the pin diameter, the torque and force acting on the tool pin severely increase with an increase in pin diameter resulting in a higher fraction of pin torque and force. Furthermore, the plastic material flow behaviors were severely affected by the tool geometry due to different torque and transverse forces acting on the tool pin. The model was verified by experimental thermal cycles and weld cross-section. It provides a basis for optimizing the tool pin diameter and its taper angle in the UVeFSW process.
... Ultrasound and the usual acoustic wave propagation in the medium is a linear motion. The speed of motion is related to the medium, and all kinds of sound transmission mediums have a fixed acoustic impedance rate [8,34]. As the resistance of iron and oil, water is very different, therefore when the ultrasonic wave travels to the interface of the two media with a large difference in acoustic impedance, the main reflection occurs, the reflection of the ultrasonic wave back and forward in the synthesis of the ultrasonic wave, when each point of the phase difference remains stable, resonance occurs, and in some fixed positions superimposed on each other to strengthen the medium in these positions easy to produce cavities. ...
The extraction process of Tarim oil field in Xinjiang is accompanied by a large amount of oily sludge generation, which seriously restricts the progress of oil and gas development and causes serious pollution to the environment due to its large production, complex composition, and difficult treatment. Nanomaterials combined with ultrasound have been demonstrated to be a promising method for the disposal of hazardous oily sludge. In this paper, a magnetic material Nano-β[email protected]3O4 was prepared by hydrothermal method and surface modification method. Nano-β[email protected]3O4 can be intelligently enriched at the oil-water interface and oil-solid interface, and it can be stably dispersed to form nanofluid under the action of ultrasound. Nano-β[email protected]3O4 can cause changes in oil composition when it is exposed to ultrasound, resulting in the decrease of viscosity and increase of fluidity. The experimental results of treating oily sludge in Xinjiang Tarim showed that the best treatment effect was achieved when the concentration of Nano-β[email protected]3O4 was 0.5%, the ultrasonic frequency was 60Hz and the temperature was 60℃. This solution can reach 90.17% oil removal efficiency within 45 minutes, and the secondary oil removal efficiency of Nano-β[email protected]3O4 recovered by magnetic separation could still reach 85.65%. This efficient oily sludge treatment method proposed in our study provides valuable information for the development of oily sludge treatment technology.
The growing demand for lightweight materials in the automotive and aerospace industries has driven research on joining dissimilar lightweight alloys, particularly Al and Mg alloys (Al/Mg). Friction stir welding (FSW) is a promising technique for joining Al/Mg alloys, as it works below the base metal's melting temperature, leading to refined microstructures, reduced porosity, and enhanced productivity. The strength of Al/Mg friction stir weldment depends on the evolved interface, which is primarily characterized by micromechanical interlocks, type, and intermetallic compounds (IMCs) distribution. Different interfaces for butt joints have been discussed in the literature. However, the mechanism of interfacial interaction together with the ways to enhance the interface have not been reviewed yet. This review article fills the gap by analyzing the retrospective data for process parameters and mechanical properties. Joining mechanisms and the evolution of different interfaces at the microstructural level have been discussed. Lastly, ways to enhance the interface for improved mechanical properties are explained. By offering essential insights into FSW techniques and Al/Mg weld interfaces, this review article paves the way for developing FSW procedures for Al/Mg butt welds aiming for enhanced strength and performance. This review article is expected to be of interest to researchers and engineers working in the field of FSW, particularly for Al/Mg lightweight applications. It provides an overview of the current state of knowledge and identifies key areas for future research.
Tool tilt angle (TTA) is a critical factor that can control material flow in polymeric materials' friction stir joining (FSJ). This study selected a TTA range between 0o to 4o for FSJ of polypropylene (PP) polymer sheet. A modified computational fluid dynamic (CFD) technique was implemented to gain a deep understanding of the effects of TTA during FSJ of PP. The PP joint's internal flow, defect formation, heat generation, and tensile strength were investigated experimentally. The fracture surface of tensile samples was analyzed by scanning electron microscopy (SEM). Heat generation, heat flux, and defect formation results from simulation were evaluated by experimental tests output. The results indicate that the PP flow during FSJ is susceptible to TTA. Non-uniform volumetric weight transfer was caused at higher TTA in the joint line, which leads to tilted heat flux. At higher TTA, the generated heat increases, leading to PP exit from the joint line and internal gaps. According to selected parameters, the most robust joint (66MPa) was produced at 1o TTA. The main reason for the mechanical properties of the PP joint was a dimension of the stir zone and internal defects. Shrinkage gaps were the root of crack initiation during the tensile test, and some local stretching in the fracture surface of the tensile sample after the test was detected.
