Increase In Rotational Speed Research Articles

Experimental Study on the Influence of Rotational Speed on Grinding Efficiency for the Vertical Stirred Mill

The rotational speed of the agitator is one of the important parameters that affect the grinding efficiency of the vertical stirred mill. Increasing the speed will improve the grinding effect, but it will increase energy consumption, and determining a reasonable speed setting is a system issue. The effects of different speeds on energy consumption, product particle size, and grinding efficiency were analyzed in this study. An experimental vertical stirred mill was used to grind iron ore, and five different speed parameters from 175 rpm to 350 rpm were set as variables. It was found that increasing the rotational speed will increase the grinding effect, but it will trigger more energy consumption. A new evaluation index to comprehensively reflect the grinding efficiency of the mill, which was defined as the ability of a mill to grind the same product per unit of time and energy consumption, was proposed. The grinding efficiency was calculated when the particle size of iron ore powder decreased to −45, −38, and −28 μm at different speeds. It can be seen that the growth rate of energy consumption is faster than that of the percentage of particle size, which leads to a continuous decrease in grinding efficiency with the increase in rotational speed. If high processing capacity is pursued within a certain period of time, high speed can be chosen, but it will result in energy loss. On the contrary, the low speed can be chosen, if considering grinding economy.

Research on magnetic force of magnetic seal in aero-engine

Aiming at the magnetic seal in an aero-engine accessory, the range of magnetic force required for the normal operation of the magnetic seal is analyzed. The finite element analysis method based on the Maxwell stress tensor method is used to calculate the magnetic force between the dynamic ring and the magnetic static ring in the magnetic sealing system. The magnetic force under different magnetization modes and gaps is tested by the magnetic measuring test bench, which verifies the correctness of the magnetic calculation method. The effects of permanent magnet material, permanent magnet magnetization direction, magnetic seal structural parameters, and working conditions on the magnetic force between the dynamic ring/magnetic static ring in the magnetic seal are analyzed. Under the same structure, the magnetic force of NeFeB35, SmCo28, Alnico5, and Ferrite as magnetic static rings is compared. The results show that NdFeB35 has the largest magnetic force, SmCo28 is second, Alnico5 and Ferrite are relatively small, and their magnetic forces are about 1/4 to 1/5 of the first two materials. When the rotor or the casing is moving axially, NeFeB35 and SmCo28 materials with large magnetic force should be selected to meet the normal working requirements. Under the same material, the magnetic forces of axial, radial, and radiative magnetization modes are compared. the ratio of magnetic force under axial, radiative, and radial magnetization is about 2.3:1.1:1. If NeFeB35 and SmCo28 materials are axially magnetized, their magnetic forces will exceed the allowable range, which will increase the seal wear. The increase in the inner diameter of the dynamic ring and the gap between the dynamic ring and the magnetic static ring causes a decrease in the magnetic force. The increase in temperature affects the magnetic properties of permanent magnetic material, which leads to the decline of magnetic force between the dynamic ring and the magnetic static ring. The increase in rotor speed leads to the acceleration of the fluctuation frequency of the magnetic force. Still, the maximum and minimum values of the magnetic force under different speeds remain unchanged, and the maximum fluctuation rate is less than 3%. According to the analysis results, the fitting formula of magnetic force calculation is presented by the orthogonal test and the least squares method.

CFD-based unsteady simulation and performance analysis of scroll compressor

The scroll compressor is an essential part of the heat pump air conditioning system in electric vehicles, with its performance and efficiency having a significant impact on the vehicle's range. This paper employs a combination of experimental and numerical simulations (using the dynamic mesh method) to study the scroll compressor in electric vehicles, exploring the effects of rotational speed and pressure ratio on compressor performance. The results reveal a significantly uneven temperature distribution across the chambers, primarily due to tangential leakage, which results in elevated temperatures in the central areas of the chambers and reduced temperatures near the meshing points. As the rotational speed increases, both the mass flow rate and the isentropic efficiency of the scroll compressor rise, whereas the discharge temperature declines; notably, discharge temperature drops by an average of 1.6 % for 600 r·min-1 increase in rotational speed. For each unit increase in the pressure ratio, the discharge temperature increases by an average of 12.22 K, while the mass flow rate decreases by 7.95 %. The study also shows that the isentropic efficiency initially rises with increasing pressure ratio, reaching a maximum of 67.06 % before starting to decline. These findings provide valuable insights into the performance characteristics of scroll compressors and offer theoretical support for optimizing compressor efficiency in practical applications.

A heat transfer model for thermal distortions in high speed spiral groove gas lubricated face seals

The thermal distortions of seal face caused by heat transfer directly affect the stability of seal operation. Here, a heat transfer analysis model of spiral groove gas face seal is established taking account of gas compressibility and choked flow effect. Then, a thermoelastohydrodynamic lubrication (TEHL) analysis is carried out based on the proposed heat transfer model, frictional heat flux, surface conduction heat flux, and film adsorption heat flux are calculated, and face distortions are also analyzed under different operating parameters including rotational speed, seal temperature and seal pressure. It is shown that, the adsorption heat induced by gas expansion makes the film cooling, which often leads complex temperature distributions and plays an important and non-ignored role in thermal distortions. For the spiral groove face seal, the increase of seal pressure and rotational speed makes the adsorption heat increase significantly due to pumping effect of grooves. The more important is that the thermal distortions may be controlled by changing seal width. Here, for the spiral groove face seal, the clearance can transfer divergent to convergent with increasing seal width from 5 mm to 13.1 mm. This provides a potential way for distortion control in gas face seal design.

Micromechanical study of core barrel drilling for rotary drilling rigs based on the discrete element method

Abstract This study developed a gravel soil granular bed model using the discrete element method, elaborating on the core barrel drilling process by integrating bond-breaking and particle flow patterns. A quantitative description of the drilling process is achieved by defining bond-breaking efficiency. The results indicate that the force on particles near the drill tooth is the greatest, and this force increases with the core barrel feed rate, which enhances drilling efficiency and exacerbates wear on the drill tooth and guide bars. An increase in rotational speed raises the force on the particles in the boundary region, leading to deeper wear of the guide bar; however, the enlargement of particle voids near the drill tooth mitigates wear. Additionally, a coupled discrete element method and finite element method are developed to analyse the effects of drilling parameters on drill tooth deformation, revealing that the design of the open hole at the top of the drill can effectively reduce the maximum equivalent stress and wear depth. The conclusions drawn contribute to understanding particle mechanics, the particle bonding damage mechanism, and drilling mechanical behavior, providing a reference for optimizing drilling operations and drill design.

Study on the excess seeds removing performance of a potato precision seed metering device

In the potato mechanical planting industry, the high multi-seeding rate and miss-seeding rate are problems that exist in many potato precision seed metering devices. The main potato seeds in China are cut potatoes with different shapes and sizes. However, there is a lack of research on precision seeding technology for cut potatoes, and the adaptability of many existing potato seeding devices on cut potato is poor. The mechanized precision seeding of potato can effectively reduce labor consumption, improve the seeding effect (decrease multi-seeding rate and miss-seeding rate), improve the improve production of potato per acre and improve the quality commodity potatoes. In response to the above issues, a precision seed metering device with novel scoops, which can adapt to various sizes and shapes of cut potatoes, was developed. In this study, the different seed collecting scenarios (SCSs) were constructed. Through the statics and kinematic analysis, the excess seeds removing (ESR) process was divided in to three areas. The kinematic model of seed potato was established to study the influence of different SCSs and sprocket rotational speeds on the ESR performance, and preliminary determined the appropriate sprocket rotational speed range for ESR process. Then, the coupled simulation results of EDEM and RecurDyn revealed that different sprocket speeds and SCSs had a significant influence on the ESR performance. Finally, the bench tests and field tests were conducted to verify the actual performance of the precision seed metering device. The results showed that, with the increase of the sprocket rotational speed, the ESR performance of the device improved, the multi-seeding rate significantly decreased, but the miss-seeding rate increased. High sprocket rotational speed will remove more seed potatoes and cause high miss-seeding rate. The bench tests showed the appropriate sprocket rotational speed for medium and large potato was 35 r/ min. The field tests obtained the best qualified-seeding rate of 91.54%, the miss-seeding rate of 3.08% and the multi-seeding rate of 5.38%. This study can provide theoretical reference for the design of potato precision seed metering device.

The Study of Water Content on the Coal Loading Performance of Thin Coal Seam Shearer Drum by Discrete Element Method (DEM)

ABSTRACTAs the main component of thin coal seam shearers, the drum bears the functions of loading and cutting, and its performance has become an important factor restricting mining efficiency and production safety. In response to the problem of low efficiency in installing thin coal seam shearers, this paper uses the Discrete Element Method (DEM) to study the effects of loading methods, helical angle of drum, drum rotation speed, and particle water content on coal loading rate. Research has found that the coal loading performance of the ejection loading method is much higher than that of the pushing loading method. As the helical angle increases, the average loading rate increases. As the rotation speed increases, the loading rate of wet coal particles gradually decreases. During production and thin coal seam mining, special attentions should be paid to the control of helical angle of drum and drum rotation speed. This study has guiding importance for improving the efficiency of thin coal seam mining.

Movement Characteristics of Droplet Deposition in Flat Spray Nozzle for Agricultural UAVs

At present, research on aerial spraying operations with UAVs mainly focuses on the deposition outcomes of droplets, with insufficient depth in the exploration of the movement process of droplet deposition. The movement characteristics of droplet deposition as the most fundamental factors affecting the effectiveness of pesticide application by UAVs are of great significance for improving droplet deposition. This study takes flat spray nozzles as the research object, uses the Particle Image Velocimetry (PIV) technique to obtain movement data of water droplet deposition under the influence of rotor flow fields, and investigates the variation characteristics of droplet deposition speed under different influencing factors. The results show that the deposition speed and the distribution area of high-speed (>12 m/s) particles increase with the increase of rotor speed, spraying pressure, and nozzle size. When the rotor speed increases from 0 r/min to 1800 r/min, the average increase in maximum droplet deposition speed for nozzle models LU120-02, LU120-03 and LU120-04 is 33.26%, 19.02%, and 7.62%, respectively. The rotor flow field significantly increases the number of high-speed droplets, making the dispersed droplet velocity distribution more concentrated. When the rotor speed is 0, 1000, 1500, and 1800 r/min, the average decay rates of droplet deposition speed are 36.72%, 20.00%, 15.47%, and 13.21%, respectively, indicating that the rotor flow field helps to reduce the decrease in droplet deposition speed, enabling droplets to deposit on the target area at a higher speed, reducing drift risk and evaporation loss. This study’s results are beneficial for revealing the mechanism of droplet deposition movement in aerial spraying by plant protection UAVs, improving the understanding of droplet movement, and providing data support and guidance for precise spraying operations.

A Numerical Simulation of the Effect of Drilling Fluid Rheology on Cutting Migration in Horizontal Wells at Different Drilling Fluid Temperatures

In recent years, significant breakthroughs have been made in the exploration of deep to ultra-deep oil and gas reserves onshore in China. These conventional deep to ultra-deep reservoirs are typically buried at depths exceeding 4500 m, with bottom-hole temperatures surpassing 150 °C. The high temperatures at the bottom of the well are more likely to cause deterioration in drilling fluid properties, altering its rheological properties and reducing cutting transport efficiency, which can lead to wellbore cleaning issues. In this paper, the numerical simulation method is used to analyze the influence of cutting particle size, drilling fluid flow rate, drill pipe rotation speed, and drill pipe eccentricity on the annular cutting concentration under different wellbore drilling fluid temperature conditions. The results show that at the same cutting particle size, as the drilling fluid temperature increases, the cutting concentration in the annulus increases sharply. The increase is the largest when the particle size is 3 mm, and when the drilling fluid temperature is 220 °C, the cutting concentration increases by 79.7% compared to at 200 °C and by 279% compared to at 180 °C. When the flow rate increases from 0.5 m/s to 1.0 m/s, the annular cutting concentration at drilling fluid temperatures of 220 °C and 200 °C decreases by 70.5% and 50.4%, respectively. The higher the drilling fluid temperature, the better the cutting removal effect when increasing the drill pipe rotation speed. However, when the rotation speed exceeds 120 rpm, the change in cutting concentration with increasing rotation speed becomes insignificant. When the drill pipe eccentricity is small, an increase in drilling fluid temperature leads to a significant rise in annular cutting concentration. However, when the drill pipe eccentricity is large, changes in drilling fluid temperature have a smaller impact on cutting concentration. The research findings can provide engineering guidance and theoretical support for the design of drilling fluid hydraulic parameters for cutting transport and rheological parameters in high-temperature wellbores.

Characterizing the contact force of a high-speed rotating fluid on brush wire

Abstract To study the effect of coolant fluid on rotor-brush wire contact in high-speed conductive slip rings, the rotor-brush wire contact model is simplified to two cylindrical vertical contacts. The theoretical formula of the force on the near-wall surface of the brush wire is derived by combining the distribution of the characteristics of the cylindrical rotating fluid domain. A three-dimensional model of high-speed rotor-brush wire fluid-solid coupling is created. The initial preload and coolant disturbance on the near-wall surface of the brush wire is considered to analyze the force characteristics of the brush wire. The force characteristics of the near-wall surface and the three-dimensional surface velocity cloud diagram of the fluid domain are obtained. The results show that the growth rate of the fluid domain force on the wall surface of the brush wire increases with the increase of rotational speed. A change of only 0.5 mm near the wall leads to a change of nearly 40% in the speed.

Optimizing waste heat recovery for hydrogen production: Modeling and simulation of ternary size metallic granule flow in a cooling cylinder

In order to recover the waste heat of high temperature metallic granules to produce steam for hydrogen production, a waste heat recovery cooling cylinder with cooling water channel is innovatively developed. The simulation is carried out based on DEM and soft sphere model to study the flow characteristics of ternary size metallic granules. The model of cooling cylinder is established and verified by comparing to the experiment data. The change rule of bed shape in the waste heat recovery cooling cylinder is examined, and the inclination angle, rotational speed and filling rate are assessed to find their influence on the flow characteristics of ternary size metallic granules. The results indicated that, with the increase of inclination angle, the axial velocity increases by 482.76%, which means the reduce of residence time of granules. With the increase of rotational speed, the axial velocity has an increase of 161.54%, the sum velocity increases by 158.49%, leading to a decrease of residence time. As the filling rate increases from 1.5% to 15.5%, the contact number has an increase of 91.53%, which lead to the increase of heat transfer area. The residence time and heat transfer area will directly affect the waste heat recovery efficiency, so a proper arrangement of granule flow is significant for enhancing the heat transfer efficiency.

DEM simulation of an impact crusher using the fast-cutting breakage model

The impact crusher that exploits impact rather than pressure to break down materials has been widely used in the mineral industry. To further improve its performance in material crushing, numerical simulation capable of providing a deeper insight into the complicated dynamics of feed materials than experimental study has emerged as a promising tool. However, the field of the accurate prediction of product quality and explicit simulation of breakage events inside an industrial-scale crusher remains underexplored on account of the absence of a robust breakage model and heavy computational cost. In this study, a numerical investigation of an industrial-scale crusher using the fast-cutting breakage model is conducted within the DEM (Discrete Element Method) framework. The accuracy of the breakage simulation is quantitatively validated by comparing the predicted results with the measurements from actual production. Furthermore, the influence of operating conditions including the rotation speed of the rotor and the feeding rate on the interested parameters, i.e., the power consumption of the equipment, the size distribution of the products, and the impact-induced wear is investigated comprehensively. The results illustrate that (i) the size of the product increases with the rotor speed until a critical value, after which a further increase in rotor speed will exert no significant influence on the size distribution; (ii) The feeding rate is not a critical operating condition that largely determines the fineness of the product and the efficiency of the equipment almost remain stable under a certain range of feeding rates; (iii) The wear of the devices concentrates on the rotor and the impact plates, and the distribution of the wear exhibits different characteristics in different parts, caused by the complex collision between the particles and the devices.

Revealing microstructure evolution and mechanical properties of Al/Cu joints during high-speed friction stir welding

Friction stir welding provides several advantages, including relatively low welding temperature, no thermal crack, and excellent joint performance. However, due to the narrow process window, the research on the friction stir welding of aluminum and copper is mainly focused on the lower welding speed range, which greatly affects the welding efficiency. Addressing the challenge of increasing welding speed and optimizing process parameters has become an urgent priority. In addition, the dynamic recrystallization behavior during high-speed Al–Cu friction stir welding is complex, and the microstructure evolution is still unclear. In order to clarify these issues, the high-speed friction stir welding (HSFSW) experiment was carried out, and the influence of rotation speeds on microstructure evolution and mechanical properties of joints at high welding speed was investigated. The results show that when welding speed is fixed at 400 mm/min and rotational speeds are in the range of 2000∼2500r/min, the joints can be obtained with good surface morphology and no internal defects. The ultimate tensile strength of specimen is 191 MPa at the process parameters of 2250r/min-400 mm/min, which is 77% of the strength of copper base material. As the rotation speed increases, a thick intermetallic compounds layer appears inside the joint. Due to the influence of thermal cycle and stirring of pin, the nugget zone undergoes a large amount of recrystallization behaviors and forms fine equiaxed grains, which is conducive to refined crystalline strengthening, thus improving mechanical properties of joints.

Investigating the Surface Quality of Aramid Honeycomb Materials Through Longitudinal–Torsional Ultrasonic Milling

During the milling process of aramid honeycomb, residual stresses arise, which will affect the surface quality of the honeycomb. Studies have shown that reasonable processing techniques can reduce residual stresses, indicating a close relationship between residual processing stresses and the processing parameters, such as technique. By investigating the changes in residual stresses after the processing of aramid honeycomb materials, the influence of processing techniques on these changes is analyzed. Leveraging the correlation between residual stresses and surface quality, this study proposes the use of residual stress as an indicator for evaluating processing techniques. The longitudinal–torsional ultrasonic vibration milling method is applied to the processing of aramid honeycombs. A single-factor experimental approach is adopted, utilizing ABAQUS 2020 software to mimic the longitudinal–torsional ultrasonic milling process. This study explores the influence patterns of various process parameters on the residual stresses generated during the milling of honeycombs. The simulation results indicate that within the selected range, the residual stress decreases as the tool rotation speed increases, while it increases with the increase in feed rate. The influence of milling depth on residual stress can be negligible. Furthermore, experiments were conducted based on the proposed correlation between residual stress and surface quality. The experimental results show good agreement with the simulation results, indicating that under reasonable process parameters, the residual stress values decrease, thereby improving the milling surface quality of aramid honeycomb materials. Therefore, measuring residual stress can serve as an effective method for evaluating the processing technique.

Bifurcation Characteristics Analysis of Gear System Considering Time-varying Gear Backlash

Dynamical models for super gear systems have been established, considering both fixed gear backlash and time-varying gear backlash. The focus is on analyzing the modeling process of the time-varying gear backlash. Based on this, a six degrees of freedom bending-twisting dynamical model for super gears has been developed. Then, using rotational speed as the control variable, numerical simulations have been conducted to compare the bifurcation characteristics of super gear systems with fixed gear backlash and time-varying gear backlash. The results indicate that the overall trends of the bifurcation characteristics for both systems are consistent, with their vibration periods decreasing as the rotational speed increases, leading to a gradual stabilization of the system. However, the bifurcation characteristics of the super gear system considering the time-varying gear backlash exhibit a distinct leading trend, showing significant jump phenomena at relatively low rotational speeds.

Study on the wear performance of 304 stainless steel aerospace joint bearings

In order to investigate the influence of surface micro-texture on the oil film carrying capacity, a theoretical model of dynamic pressure lubrication is constructed based on CFD, and dynamic pressure lubrication simulation and friction and wear experimental research are used to analyse the influence of speed and load on the friction behaviour of the bearing pair, and the wear performance of the specimen is evaluated by means of the surface morphology and friction coefficient. The results show that the carrying capacity of the oil film on the textured surface is relatively large compared with that of the non-textured surface, showing regular fluctuations, and that the pressure values of turbulent flow are greater than those of laminar flow. As the rotational speed increases, the cavitation effect becomes more and more obvious, and the carrying capacity of the oil film increases. The smaller the thickness of the surface oil film, the higher the load carrying capacity and the lower the degree of wear; The surfaces of the textured specimens showed the best friction reduction and anti-wear properties, followed by the smooth surfaces and the worst rough surfaces. With the increase of rotational speed, the friction coefficient tends to decrease. When the rotational speed is 0.4 m s−1, the wear of the textured surface is reduced. With the increase of load, the thickness of the formed oil film decreases, the friction coefficient decreases, and the anti-friction effect of the textured surface increases. This indicates that the surface texure treatment of 304 stainless steel, and the selection of appropriate working condition parameters can effectively reduce wear during the friction process, and improve the wear resistance of bearings.

Modelling Method and Meshing Characteristics of a Novel Curve-Surface Conjugate Internal Gear Drive

Space exploration has become a major focus in the field of technology, with gear transmissions in aerospace equipment playing a crucial role. In the extreme environment of space, gear transmissions face challenges like large temperature differentials, deformation and maintenance difficulties, which will severely impact transmission accuracy and service life. To meet the growing demands for high-performance gear transmissions with high transmission efficiency and error adaptability in the aerospace field, this paper proposes a novel curve-surface conjugate internal gear drive consisting of an involute internal gear and a curve-surface gear. The fundamental theory of curve-surface conjugation is introduced, and the construction method for curve-surface gear based on a selected contact path and meshing tube is presented. The analysis models including induced curvature, sliding ratio and tooth contact analysis with errors (ETCA) are simulated to evaluate the meshing characteristics. Additionally, prototypes are manufactured and experimental setups are established to validate the transmission performance. These results indicate that as the rotational speed increases, the transmission efficiency of the curve-surface conjugate internal gear drive improves, which is contrary to the trend observed in involute gear drives. And the transmission efficiency of the curve-surface conjugate internal gear drive surpasses that of the involute gear drive at higher rotational speeds. Moreover, this novel gear drive exhibits excellent error adaptability, maintaining intact contact paths and high transmission efficiency even in the presence of assembly errors. This study provides new ideas for the design and manufacture of high-performance gear transmissions from the perspective of spatial geometric elements.

Investigation of discharge valve in ultra-high-speed rotary compressors: An experimental and FSI simulation-based study

The rotary compressors are currently witnessing a trend towards high-speed operation, resulting in an increased frequency of valve motion and a higher mass flow rate through the discharge valve. Consequently, high-speed operation leads to intensified impact between the valve and both the valve stopper and valve seat, thereby posing challenges to the reliability of the valve. Simultaneously, the dynamic characteristics of the valve at high operating speeds exert a significant influence on the compressor's performance. This paper develops a three-dimensional fluid-structure interaction (FSI) model to investigate the dynamic characteristics and reliability of the valve in a high-speed rotary compressor while considering heat transfer during the flow process within the cylinder. The proposed model shows better agreement with the experiment. The study revealed that as the rotational speed increases, there is an obvious rise in over-compression loss and a pronounced valve closure delay, which increases the impact velocity of the valve. The valve experiences two peaks of equivalent stress within one cycle, rendering it susceptible to fail at high speeds. The adoption of a double-valve structure at a rotational speed of 12,000 rpm leads to a significant reduction in over-compression loss by 62.9 %, an increase in volumetric efficiency by 6.7 %, a maximum decrease in impact velocity by 54.5 %, and a maximum decrease in equivalent stress by 25.6 %. The reliability of the double-valve structure under 12,000 rpm was proved by an endurance experiment. Besides, the asymmetry in the opening process of the two valves has been unveiled for the first time.

Study of transient pressure and fluctuation characteristics in a centrifugal pump using the delayed detached-eddy simulation method

This study employed OpenFOAM, the delayed detached-eddy simulation (DDES) turbulence model, and structured grids to develop numerical models for three centrifugal pumps with twisted blades. The internal pressure field, velocity field, forces, and fluctuation characteristics of the centrifugal pumps are comprehensively analyzed under various operating conditions. The findings indicate that the pressure is relatively higher in the flow passages near the volute tongue and the outlet within the impeller. Regions of high relative velocity (slip velocity) are mainly found on the suction side of the blades, indicating that the design of the blade suction side affects the fluid outward slip performance. As the flow rate increases, the forces and force fluctuation amplitudes of each pump component also rise. Conversely, as the rotational speed increases, the force on the blades or impeller gradually increases while the fluctuation amplitude decreases. In the stationary domain, the force on the volute gradually decreases while the fluctuation amplitude of this force increases. The shape of the volute tongue influences the rate at which pressure inside the volute is converted to outlet pressure. The power spectral density (PSD) of pressure fluctuations is smallest at the nominal flow rate, displaying a clear and distinct axial frequency pattern without complex low-frequency fluctuations. Under low flow and high-speed conditions, the PSD at the axial frequency is relatively small, whereas the pressure PSD at other low frequencies is relatively large. This indicates instability in the flow under these conditions.

Simulation of Friction Stir Welding of AZ31 Mg Alloys.

Friction stir welding has been extensively applied for the high-quality bonding of Mg alloys. The welding temperature caused by friction and plastic deformation is essential for determining the joint characteristics, especially the residual stress and weld microstructure. In this work, a modified moving heat source model was proposed by considering the variations in heat generation caused by friction shear stress at both the side and bottom surfaces of the tool. The application of this model was further extended to the entire welding process, especially in the plunging stage. The relative errors between the experimental and simulated peak temperatures at characteristic points were small, with a maximum of 10%, thereby validating the model for accurate temperature prediction. Furthermore, the influence of welding and rotational speed on temperature fields was systematically investigated. At relatively low welding and rotational speeds, the welding temperature increased significantly with either an increase in rotational speed or a decrease in welding speed. However, this effect gradually diminished at higher welding and rotational speeds. These results provide some valuable guidelines for controlling heat generation to improve the quality of Mg alloy welds.