Tool Torque Research Articles

Welding load, temperature, and material flow in ultrasonic vibration enhanced friction stir lap welding of aluminum alloy to steel

To elucidate the effect of ultrasonic vibration on the welding process (welding load, thermal cycle, and material flow) of aluminum/steel dissimilar metals in friction stir lap welding, conventional friction stir lap welding (FSLW) and ultrasonic vibration enhanced friction stir lap welding (U-FSLW) were used to weld aluminum/steel dissimilar metals. The results indicate that applying ultrasonic vibration to the FSLW of aluminum/steel dissimilar metals can effectively decrease welding loads (tool torque, axial force, and spindle power), and it was found that the reduction in welding load was inversely proportional to the welding speed. The effect of additional ultrasonic vibration on axial force was the largest. Ultrasonic vibration had a significant preheating effect, and its thermal effect in the width and depth directions of the workpiece gradually weakened. Additional ultrasound can reduce the peak temperature during the welding process. The instantaneous state of the weld was obtained using the "emergency stop+emergency cooling" technology, and the three-dimensional visualization characterization of material flow near the keyhole was achieved using X-ray based computer tomography (CT). It was found that ultrasonic vibration could increase the material's plastic flow, change the steel structure's flow path, and significantly increase the steel particles' flow range near the pin tool. Compared with conventional FSLW, the changes in the macro/microstructure of U-FSLW joints were closely related to the welding thermal cycle and material flow.

Understanding in-process responses in multi-layer friction stir additive manufacturing: Temperature, viscosity, tool torque, and mechanical properties

Most melt-based processes greatly inhibit additive manufacturing of high-strength aluminium alloys due to porosity, cracking, and distortion. Friction stir additive manufacturing (FSAM) greatly enhances the printability of such alloys by avoiding melting. However, the repeated heating and cooling during the multilayer fabrication severely degrades the structure and properties of the final build. The effects of thermal cycles, peak temperatures, and cooling rates that substantially degrade the properties are not well reported in the literature. The processing conditions that control the complex viscoplastic flow of the material and the in-process force responses on tool important in order to understand the influence of the possible defects in the final build need to be better reported. Therefore, a systematic numerical and experimental study is conducted to quantitatively understand the spatial and temporal evolution of the build properties, bead profiles, tool torque, and traverse force for the first time in the FSAM literature. The results, which have been rigorously tested and verified, show that the peak temperature, cooling rate, bead profile, tool torque and traverse force were more sensitive to the print height, followed by traverse speed and tool rotation speed. However, the degradation of mechanical properties was found to be least affected by the higher traverse speeds as a result of the lower peak temperatures and the duration of thermal exposure. The numerically computed results corroborated well with the corresponding experimentally measured results, and the results from the independent literature, further enhancing the reliability of our findings. Further, the direct correlation between process variables and the final build properties via in-process responses could substantially reduce the existing trial-and-error approaches in the manufacturing of aluminum alloy structures through the FSAM route.

Comparative numerical analysis between butt and lap joints of Mg alloy friction stir welding with considering tilted tool effect

Magnesium (Mg) alloy, as an important lightweight structural metal, can be effectively joined by the friction stir welding (FSW) method. Understanding FSW temperature and material flow coupling process in butt and lap welding configurations has important theoretical significance. In this study, the tilted tool induced incomplete contact distance is calculated by process parameters and slip rate, and the deflection of the contact interface is related to the tool torque. The non-uniform boundary conditions are considered. The numerical model is proposed and experimentally validated by using the measured temperatures and thermo-mechanically affected zone (TMAZ) profiles. The comparative numerical analysis between butt and lap welding with three levels of process parameters is further conducted. The peak temperature and material flow velocity along the specified circumferences in FSBW are more than 10 K and 4 mm/s higher than these in FSLW, respectively. When the rotation rate increases from 600 rpm to 800 rpm, the peak temperature and material flow velocity along the specified circumferences increase about 20 K and 9 mm/s, respectively. When the welding speed decreases from 150 mm/min to 30 mm/min, the temperature and material flow velocity fluctuations along the specified circumference decreases about 25 K and 14 mm/s, respectively.

A heat source model for dissimilar Al/Cu friction stir welding process based on tool torque measurement

A heat source model for dissimilar Al/Cu friction stir welding process based on tool torque measurement

Acoustic effect on the joint quality and process of friction stir lap welding of aluminum to steel

To gain a high strength-to-weight ratio and economic viability for multiple industrial applications, the Al and steel need to be joined successfully. In the present work, we used conventional friction stir welding (FSW) and ultrasonic vibration enhanced friction stir welding (UVeFSW) techniques to obtain high-strength industrial-grade dissimilar joints of Al and steel. The effects of acoustic energy on the joint quality and welding process were investigated. Macrographs of the joints revealed that ultrasonic vibrations could effectively promote the material flow and increase the mixing degree and width of the Al/steel interface. Steel strips' fragmentation and intermixing with the Al substrate were enhanced under ultrasonic effects. The tool torque, axial force, and spindle power were significantly decreased with ultrasonic vibration. Acoustic assistance was found beneficial to increase the joints’ failure load and change the fracture mechanism. The microhardness of acoustically treated regions was found to be higher compared to its counterparts. The thinning of the brittle intermetallic compounds (IMCs) layer at the interface of the UVeFSW joint was caused by decreased peak temperature during welding. In UVeFSW, when the welding speed was 50 mm/min, the maximum failure load of the joint was obtained under the joint action of the macro interlocks (interface zone), the thinner IMCs layer, and the micro interlocks (laminated structure). When the welding speed was 100 mm/min, the failure load of the joint was improved by 25.8% compared with conventional FSW.

Research on Embedded Ball Screw Diagnosis System for Mechanical Fault Based on Bispectral Image

Ball screw is one of the main basic transmission components in CNC machine tool feed system because of its high transmission efficiency, positioning accuracy, and rigidity. It plays an irreplaceable role in the process of machine tool torque transmission and positioning. However, ball screw is also one of the parts which are easy to break down in the feed system. If it breaks down, it will affect the processing accuracy of the whole machine tool and even cause shutdown. Numerical control means that digital control is a high-efficiency technology that uses digital information to control mechanical movement and processing processes. Therefore, to increase the high-speed and high-precision operation ability of CNC machine tools, research and development of efficient and reliable predictive maintenance and issue identification technology to guide maintenance of CNC machine tools are critical. Throughout this study, a bispectrum image-based embedded defect fight against the disease for cylindrical gears is provided. Firstly, the bispectrum of fault signal is generated by Wavelet Packet Threshold denoising, wavelet packet reconstruction, and bispectrum analysis, and the characteristics of bispectrum are represented by the first kind of gray moments. These feature statistics are used as input feature vectors of BP neural network pattern recognition algorithm to classify these feature sets and identify the corresponding gear fault types. Experiments show that under the condition of noise, after 14.5 hours of testing, the NGI has increased significantly and can be used to diagnose faults in the gear system, and the method achieves relatively ideal recognition rate and verifies the feasibility of gear box fault diagnosis method based on image recognition. The code compiled by OpenCV library is easy to transplant to embedded system, with high development efficiency and reliable program operation. OpenCV has the characteristics of powerful matrix computing capability and convenient and flexible interface, and it is a general algorithm that can realize real-time image processing.

Effect of Friction Stir Welding on the Mechanical and Microstructural Behaviour of AA7075 Aluminium Alloy

In this research work, an attempt was made to weld AA7075 alloy using the friction stir welding (FSW) technique. The experimental runs were designed using the Taguchi L18 orthogonal array and welds were obtained by varying tilt angle, tool rotation speed, tool feed rate, and axial load, whereas weld quality was accessed in terms of tensile strength and microhardness. The microstructure was examined using an optical microscope. The studies revealed that the tool angle was the most influential factor followed by the tool feed rate as both the parameters impacted the intensity of heat developed. It was observed that the tool tilt decreased the microhardness of the welds. The UTS values and macrostructure imply that the weld should be subjected to higher tool torque conditions. The material flow was not periodic nor coordinated, as seen by the tool-tilted weld's macrostructure. With a tool tilt, the weld pressure is lowered, and the lower pressure could not be enough to prevent volumetric defects. The reduced pressure at quicker welding rates may have had an effect on the development of flaws.

Evaluation of axial force, tool torque and weld quality of friction stir welded dissimilar 6061/5083 aluminum alloys

In this research, the welding parameters of the friction stir welding (FSW) of dissimilar 6061/5083 aluminum alloys were optimized, and the significance of each welding parameter was determined. The effect of welding parameters on weld quality was obtained by testing the mechanical properties of welded joints. The influences of welding parameters on material mixing were studied through metallography and microhardness. The data acquisition system of axial force and tool torque was designed, and the relationships between the data and welding parameters were analyzed. The results showed that the materials were not sufficiently mixed and thus void type defects were formed at higher traverse speeds. The optimum welding parameters, namely rotational speed, traverse speed, and plunge depth were 2400 rpm, 1200 mm/min, and 0.25 mm, respectively.

Realization of Super-Large-Diameter Slurry Shield Passing through Settlement-Sensitive Area Based on Unreinforced Disturbance Control Technology.

Due to the complex construction conditions of shield tunnels, ground disturbance is inevitable during the construction process, which leads to surface settlement and, in serious cases, damage to surrounding buildings (structures). Therefore, it is especially important to effectively control the constructive settlement of subway tunnels when crossing settlement-sensitive areas such as high-density shantytowns. Based on the project of Wuhan Metro Line 8 Phase I, the shield of Huangpu Road Station-Xujiapang Road Station interval crossing high-density shantytowns, we study the disturbance control technology of oversized diameter mud and water shield crossing unreinforced settlement-sensitive areas during the construction process. By optimizing the excavation parameters and evaluating the ground buildings, the excavation process can be monitored at the same time, and the water pressure, speed, and tool torque required during the excavation during the construction process can be finely adjusted; the control of tunneling process parameters can provide reference and basis for analyzing the construction control of large-diameter shield through old shantytowns.

The effect of tool pin size and taper angle on the thermal process and plastic material flow in friction stir welding

Friction stir welding (FSW) tool pin, as a critical component of FSW tool, plays an important role in determining the final joint properties by affecting the heat generation, plastic material flow, welding loads, and so on. However, the effects of tool pin on heat and mass transfer in FSW are not elucidated and quantitative studied. In the present study, a validated model was adopted to quantitatively analyze the effects of pin size and taper angle on the thermal process and plastic material flow in FSW. The effects of pin root diameter, pin tip diameter, and pin taper angle on heat and mass transfer in FSW were quantitatively investigated, respectively. It reveals that the torque and transverse force imposed on the pin are increased with the increase of the pin diameters (including its root diameter, its tip diameter, and its size in condition of constant taper angle), while the total tool torque varies a little for the tool pin diameter considered in this study. When the pin diameters increase, the viscosity of the materials near the pin is decreased, while the temperature as well as the flow velocity is increased. More plastic material near the tool could rotate around the tool with an increase of the pin diameter. The TMAZ boundary is enlarged with larger pin diameters in FSW. Particularly, the shear layer thickness of the same horizontal plane in the range of 1 mm < z < 5 mm is significantly enlarged with an increase of pin root diameters. However, the shear layer thickness of the same horizontal plane in the region of z < 5 mm is increased when using a larger pin tip diameter. In addition, maximum width of TMAZ boundary at the top surface of workpiece was not affected by pin diameters. The model is validated by experimental results. It could lay a solid foundation for optimizing the tool pin size and taper angle in FSW.

Investigation of material flow and thermomechanical behavior during friction stir welding of an AZ31B alloy for threaded and unthreaded pin geometries using computational solid mechanics simulation

In the friction stir welding process, the tool role in the material flow and its thermomechanical behavior is still not entirely understood. Several modeling approaches attempted to explain the material and tool relationship, but to this date, insufficient results were provided in this matter. Regarding this issue and the urgent need for trustful friction stir welding models, a computational solid mechanic's model capable of simulating material flow and defect formation is presented. This model uses an Arbitrary Lagrangian-Eulerian code comparing a threaded and unthread pin profile. The model was able to reproduce the tool's torque, temperatures, and material flow along the entire process, including the underreported downward flow effect promoted by threaded pin's. A point tracking analysis revealed that threads increase the material velocity and strain rate to almost 30% compared to unthreaded conditions, promoting a temperature increment during the process, which improved the material flow and avoided filling defects. The presented results showed the model's capability to reproduce the defects observed in real welded joints, material thermomechanical characteristics and high sensitivity to welding parameters and tool geometries. Nevertheless, the outcomes of this work contribute to essential guidelines for future friction stir welding modeling and development, tool design, and defect prediction.

Experimental study on the working performance of different milling tools for multistage fracturing ball seats

To achieve the secondary production in multistage fracturing wells of tight oil, milling tools are usually used to remove the multistage fracturing ball seats to achieve production with a large diameter in later. In this paper, first of all, the working mechanism of milling tools for multistage fracturing ball seats was studied and a mechanical analysis model of single abrasive grain was established. Then, an experimental system for milling tools was developed, and the experimental tests of the flat, the blade, and the slope milling tool were conducted in order. Besides, the morphology of chips and the surface morphology of the workpiece after the experiment were analyzed. Also, the working performance of milling tools was evaluated from the perspectives of working safety, working efficiency, and wear resistance of the milling tool. The results show that the torque of the milling tool increases nonlinearly with the increase in the cutting depth of the abrasive grain and increases linearly with the increase in the cutting width. Also, the chips are irregular particles and the size is mainly from 10 to 50 μm. So, the chips should be pumped up with a small pump pressure and a large displacement. Besides this, the cutting depths of the abrasive grains are from 216.20 to 635.47 μm and the bottom surface of the milling tool should be eccentric to avoid the zero point of cutting speed. Furthermore, the torque of the slope milling tool is 23.8% larger than that of the flat milling tool, which is also 30.4% smaller than that of the blade milling tool. Compared with the flat milling tool, the working efficiency of the blade milling tool improves by 79.9% and the slope milling tool improves by 111.1%. Also, the wear resistance of the blade milling tool decreases by 102.7%, while the slope milling tool declines by 32.6% when compared with the flat milling tool. Therefore, the slope milling tool has the characteristics of moderate torque, stable working conditions, the highest working efficiency, and fine wear resistance, which is preferably used to mill multistage fracturing ball seats. This study provides a theoretical basis and guidance for milling multistage fracturing ball seats on-site and realizing production with a large diameter in later stages of multistage fracturing wells.

Acoustic induced antifriction and its effect on thermo-mechanical behavior in ultrasonic assisted friction stir welding

The developed ultrasonic assisted friction stir welding (UaFSW) process can reduce the welding load and improve the joint quality, but the interaction mechanism between the exerted ultrasonic vibration and the thermo-mechanical behavior induced by friction stir welding is not yet elucidated. In this study, the classical Norton friction model is modified with the acoustic stress work, and the effect of ultrasonic vibration on the contact state at the tool/workpiece interface is analyzed. The relative velocity between the tool and its adjacent contacting material is taken as one of the main influencing factors to calculate the interfacial friction shear stress. A non-uniform interfacial friction model is combined with the modified constitution equation. And a fully coupled model of UaFSW process is developed to analyze the ultrasonic field, interfacial contact state, heat generation, plastic material flow and heat transfer phenomena. It is found that ultrasound can effectively reduce the interfacial friction stress, and this antifriction effect is more obvious in the welding direction which coincides with ultrasonic vibration. The ultrasound exerted along the radial direction of tool in UaFSW process results in acoustic softening of base material and friction reduction at the tool/material interface. Both effects change the heat generation, material flow and temperature field in UaFSW. Thus, the torque and traverse force are lowered with the ultrasonic induced reduction of interfacial stress, and the high quality of welds are obtained with the improvement of material flow. The model is experimentally validated by comparison of predicted and measured tool torque, heat input and thermal cycles.

Numerical analysis of vibration effect on friction stir welding by smoothed particle hydrodynamics (SPH)

A numerical analysis is improved to study the effect of vibration on temperature history, heat generation, and mechanical properties during the friction stir welding process with different welding speeds. In this investigation, smoothed particle hydrodynamics (SPH) was applied to improve the 3D numerical analysis for simulation of the friction stir welding (FSW) process and friction stir vibration welding (FSVW) under different welding speeds. According to the experimental analysis, the grain size of the FSVW-ed sample is finer compared with that of the FSW-ed sample. The analysis was validated through a comparison of the simulated thermal cycles with the experimental results. There was a close agreement between FEM and experimental values. The results indicated that the vibration increased the mechanical properties such as von Misses stress and also thermal properties of the FSW-ed sample. The vibration in the FSW process can lead to an enhanced plastic material flow and also improve the weld quality by enhancing the plastic material flow near the tool. The shear zone volume (SZV) develops from 289.56 mm3 for the FSW process to 367.34 mm3 for the FSVW process. It was found that the axial forces, traverse force, and tool torque with respect to different steps (plunging, preheating, or dwelling time and traveling) in FSVW is lower than those in the FSW.

Dissimilar Friction Stir Welding of Austenitic and Duplex Stainless Steel: Effect of Material Position and Tool Offset

Dissimilar friction stir welding (FSW) of 2205 duplex stainless steel (2205 DSS) and 304 austenitic stainless steel (304 ASS) is carried out with various parameters. The effect of material position and tool offset on material flow and mixing, the microstructure, and the mechanical properties of joints are investigated, and the relationship between tool torque and material flow is determined. With tool offset to retreating side (RS), defect‐free joints with proper material mixing are fabricated. When 304 ASS is placed on the advancing side (AS), the material mixing is better than is the case with the opposite material position, but results in a larger stirring zone (SZ) width. A large amount of mixed zone (MXZ) with a different phase ratio (γ–α) from both base metals (BMs) is formed in the defect‐free joints due to the alloying element diffusion between the two steels and severe plastic deformation. Due to the dynamic recrystallization, the SZ of all joints has higher hardness than 304 BM. The defect‐free dissimilar joints have higher tensile strength than 304 BM and good ductility.

Evolution of process parameters in friction stir welding of AA6061 aluminum alloy by varying tool eccentricity

The evolution of processing parameters by varying tool eccentricity in AA6061 alloy friction stir welding was examined using a combination of detailed force/torque measurements and thermal history as well as high-speed camera (HSC) observations. Tri-axial forces show larger oscillations during the steady-state phase of welding if the tool eccentricity is increased. However, the tool torque remains similar for up to 0.4 mm eccentricity versus the aligned tool even with varying weld speed. In situ HSC observation indicates that tool eccentricity is reduced during the welding process for larger eccentric setups. Stir zone thermal measurements reveal that the temperature peaks and stabilizes near the solidus temperature of the AA6061 base material.

Optimizing the tool pin with three flats in friction stir welding of aluminum alloy

The role of tool pin profile is crucial in friction stir welding (FSW) process, but its optimization design still requires sufficient quantitative data and a comprehensive understanding of the thermomechanical behavior around the tool. The present work gives a systematic investigation of FSW process for tool pin with three flats by using a three-dimensional computational fluid dynamics model. The thermal response, material flow behavior, and welding loads are analyzed for tool pin with various proportion of the flat feature. The feasibility of the numerical model is verified by comparing the results with measured thermal cycle, macrostructure, tool torque, and traverse force for both tool pins with and without flat feature. Based on the numerical model, a methodology is proposed for the optimization design of tool pin profile with three flats by identifying different torque components on flat area, and also considering the material flow behavior and tool wear tendency. Furthermore, the proposed methodology is utilized for optimizing tool pin profile for a wide range of process parameters, and the precision of the optimization result is also discussed. The present approach provides an explicit solution for the computer-aided optimization design and reliability assessment of the tool pin profile in FSW.

Process Parametric Dependency of Axial Downward Force and Macro- and Microstructural Morphologies in Ultrasonically Assisted Friction Stir Welding of Al/Mg Alloys

An elementary analysis is proposed to quantify the effects of ultrasonic vibrations during friction stir welding (FSW) of AA6061-T6 to AZ31B Mg alloy. In the present context, the ultrasonic vibrations are applied in the stirred zone (SZ) via a specially designed welding tool. The influence of ultrasonic vibration has been analyzed for a wide range of welding and rotation speeds. The acoustic addition has proven beneficial to enhance joint strength. Significant diminutions in axial downward force, tool torque, and tool input power equal to ~ 38, 38.7, and 38.75 pct, respectively, have been observed during the ultrasonic addition. Melioration in interfacial bonding, enhanced material mixing, and an improvement in weldment surface quality are observed for ultrasonic joints. For conventional joints, the intermetallic phases βAl3Mg2 and γAl12Mg17 have been found in the SZ and are fragmented under the acoustic influence. The microstructural analysis of the fracture surface shows a ductile fracture mechanism at ultrasonically treated surfaces. A noteworthy grain refinement cum recrystallization is observed in the SZ as well as the immediate deformation zone. The maximum ultrasonic effects are apparent at the weld center and gradually diminish as they move ahead from it.

Effects of tool shoulder size on the thermal process and material flow behaviors in ultrasonic vibration enhanced friction stir welding

To improve the joint quality and lower the welding loads, ultrasonic vibration enhanced friction stir welding (UVeFSW) had been developed and had shown several benefits. The most important geometric parameter in UVeFSW tool design is the shoulder diameter, but its effect on the thermal process and plastic material flow behaviors has not been quantitatively analyzed. To elucidate these effects, an integrated computational fluid dynamics (CFD) model was adopted to quantitatively study the effects of tool shoulder diameter on the thermal process and plastic material flow behaviors in UVeFSW. It is found that UVeFSW process can have significant effects in enhancing plastic material flow and reducing the welding loads without increasing the process temperature when compared to that in FSW by using larger tool shoulder to enhance the plastic material flow. It revealed that the maximum width of the shear zone at the top surface of the workpiece was highly dependent on the shoulder diameter. However, the minimum width of the shear zone at the bottom surface of the workpiece was insensitive to the shoulder diameter. Based on the combination of the integrated CFD model with the theory of maximum traction of the tool torque on the plastic material, the optimum shoulder diameter at various welding parameters had been systematically studied. It was found that the optimum shoulder diameter decreases with an increase of the tool rotation speed, while it increases with an increase of the welding speed. This model provides a reasonable method for optimum the shoulder diameter in UVeFSW process. The integrated CFD model is validated by a comparison of the predicted and measured thermal cycles and welding loads.

A method for evaluating dynamic viscosity of alloys during friction stir welding

The constitutive laws for dynamic viscosity, used today in CFD-models for the analysis of viscous flows during friction stir welding, aggregate data obtained from diverse standard mechanical trials (including, among others, hot compression, tension, torsion, etc.). However, the real stress–strain condition in the stir zone during FSW is that the metal dwells in the condition of overall, multiaxial deformation at high strain rates. Therefore, a method for determining the dynamic viscosity of alloys via spot-FSW trials has been proposed. The method is based on the measurements of the forge force and spindle torque of a pinless tool during the spot-FSW trials as well as the thickness of the stir zone. The results of the measurements are then processed by means of a computational procedure, which reproduces: the temperature field in the workpiece based on the torque and forge force data; strain rate in the stir zone based on its thickness; dynamic viscosity based on the strain rate and temperature. The method has allowed the calculation of a variety of discrete values of the dynamic viscosity for aluminum alloy AA5083 in dependence on the temperature and strain rate at various locations of the stir zone boundary. These discrete data have finally been approximated to receive a corresponding temperature-and-strain rate dependent polynomial.