Tool Shoulder Research Articles

Ispitivanje i optimizacija površine zavara i mehaničkih performansi termoplastičnih delova proizvedenih aditivnom proizvodnjom i zavarenih zavarivanjem trenjem

This study presents an experimental investigation into the weldability of ABS M30 (acrylonitrile butadiene styrene) plates produced by Additive Manufacturing (AM) using Friction Stir Welding (FSW). The effects of FSW process parameters on the yield stress and their optimal levels were determined using the Taguchi method. The optimal welding parameters were found to be a 16 mm tool shoulder diameter, 800 rpm tool rotation speed, and 10 mm/min traverse speed. The weld area of each sample welded using FSW was examined at a macroscopic level. The direction of tool rotation significantly affects the quality and strength of the FSW. When the FSW was performed with a clockwise rotation of the welding tool, a perfect weld could not be achieved. The tunnel effect resulted in gaps in the weld area of the samples at high rotation speeds. Differences were observed in the density between the weld area of the samples and the main parts.

Using fuzzy logic to predict the influence of the tool shoulder geometry of friction stir welded Al 6082 T6 alloy

Using fuzzy logic to predict the influence of the tool shoulder geometry of friction stir welded Al 6082 T6 alloy

Влияние геометрии инструмента на формирование сварного соединения при сварке трением с перемешиванием алюминиевого сплава АМг5

One of the important parameters influencing the formation of a weld during friction stir welding is the tool geometry, which affects the processes of heat generation and stirring of metals in their connection zone. These processes influence the formation of a high quality and strength welded joint without continuity defects. In this regard, it is relevant to analyze the influence of tool geometry on the welding mode parameters, at which the welded joint is formed without continuity defects, as well as on the welded joint strength under static tension. The work considers the influence of the cylindrical and conical shapes of the tool pin, as well as the conical shape of the pin with a thread on its outer surface and a spiral groove on the end surface of the tool shoulder on the welding mode parameters, at which the welded joint is formed without continuity defects. The study shows that changing the shape of the pin working surface from cylindrical to a conical one had no effect on the range of welding mode parameters, at which the welded joint is formed without continuity defects. It has been found that the presence of a thread on the pin outer surface and a groove on the end surface of a tool shoulder allows producing welded joints without continuity defects in a wider range of welding mode parameters compared to a simpler tool geometry. The macrostructure of the resulting welded joints was considered. It has been found that the studied tool geometry has almost no influence on the maximum strength values of welded joints produced by friction stir welding and reaches 95 % of the strength of the base metal.

Predicting Axial Force in Friction Stir Welded Joints of AA7075-T6 and AA2024-T3 Using Machine Learning Techniques

The friction stir welding (FSW) process has gained popularity in joining various types of aluminum alloys. The heat generated during the process is caused by the friction between the shoulder of the welding tool and the workpiece. The axial force (Fz) of the weld plays a crucial role in the welding process. If the axial force is insufficient to generate heat will result in defective workpieces. Therefore, the aim of this study was to predict the axial force of the FSW process of dissimilar aluminum alloys (AA7075-T6 and AA2024-T3) using machine learning techniques. The data used to create the predictive model was obtained from experiments involving 5 factors, each with 2 levels: 1) welding speed (mm/min), 2) rotational speed (RPM), 3) type of tools, 4) plunge depth (mm), and 5) dwell time (sec). The axial force was measured using a dynamometer with a sampling frequency of 10 Hz. The predictive model was created using all 4 algorithms: AdaBoost, CatBoost, LightGBM, and XGBoost. The performance of the four predictive models was evaluated using four metrics: mean absolute error (MAE), mean absolute percent error (MAPE), mean square error (MSE), and root mean square error (RMSE). The results showed that the AdaBoost algorithm had the best performance, with MAE, MAPE, MSE, and RMSE values of 509.08, 0.24, 452591.73, and 672.75, respectively. The AdaBoost algorithm was then used to predict the axial force using a dataset of 29,282 data, with predicted minimum average axial force of 1871.6 N. When compared to the axial force measured in the experiment, which was 1265 N, the results showed that the AdaBoost algorithm was capable of predicting the axial force with acceptable accuracy.

Optimization of friction stir processing parameters for improving structural and mechanical properties in in situ AA5083-H111/Al–Fe composites

The primary focus of this study is the application of friction stir processing to produce surface composites of in situ AA5083-H111/Al–Fe. These composites were fabricated by mixing mechanically alloyed Fe–40 wt% Al powder for 40 h. The AA5083 substrate underwent a two-pass friction stir processing with changes in the tool’s movement direction during fabrication. This experiment used Taguchi’s L9 orthogonal array design to gather and analyse data efficiently. Following each friction stir processing pass, the fabricated aluminium metal matrix composite microstructure, hardness and ultimate tensile strength were conducted. In this study, the maximum tensile strength of 225.8 MPa after the first pass and 253.6 MPa after the second pass. Additionally, microhardness measurements indicated values of 123.3 and 128.3 Hv after the first and second passes, respectively. These impressive mechanical properties were achieved by optimizing specific process parameters, including a tool shoulder diameter of 21 mm, a tool rotational speed of 900 rpm, a tool traverse speed of 63 mm/min and a tilt angle of 1.5°. Furthermore, examining the fracture surface of the friction stir processed sample revealed ductile failure behaviour, suggesting that the material experienced deformation and stretching before fracture. This observation aligns with the inherent ductile nature of the AA5083/Al–Fe composite.

Role of tool shoulder profile and tool rotational speed on the mechanical performance of friction stir welded Al5083 joints

AbstractIn the current work, Al5083 weld joints have been produced by friction stir welding using three different tool shoulder profiles (flat, concave and convex) at three different tool rotational speeds (900 min−1, 1120 min−1 and 1400 min−1) with an objective to investigate the role of tool shoulder profile and welding parameters on the joint quality. The cross sectional microstructural observations revealed the development of perfect weld joint at 900 min−1 and 1120 min−1 with flat and concave shoulder profiles due to the better material flow in the stir zone. Other weld joints revealed the presence of tunneling defect at the bottom of the nugget zone. Hardness measurements of the weld joints showed increased values at 1120 min−1 with concave shoulder. From the impact test data, all the weld joints exhibited similar impact energy compared with the base material except the weld joint produced with concave shoulder at 1120 min−1. Tensile tests of the weld joints demonstrated better joint strength for the weld joints obtained with both the flat and concave shoulder profiles at 1120 min−1 without losing the ductility similar to that of the base alloy.

Effect of pin geometry, rotational speed, and dwell time of tool in dissimilar joints of low-carbon galvanized steel and aluminum 6061-T6 by friction stir spot welding

In this study, aluminum 6061-T6 plates were joined with low-carbon galvanized steel using friction stir spot welding. Three conical pins with varying lengths (short, medium, and long) were utilized, along with different dwell times and rotation speeds of the tool. The objective of this research was to compare the simultaneous effects of several important process parameters on mechanical and welding properties. The results indicate that the use of short conical pins significantly increased the microhardness in the upper aluminum plate. Conversely, increasing the pin length led to higher microhardness in the lower steel plate. Tensile shear loading was greater for short pins compared to medium pins, attributed to the influence of the tool shoulder. However, with increasing pin length, failure loading reached its highest value due to the dispersion of particles in the weld. The failure mode for short pins exhibited a mixed pattern, which transitioned to a ductile shape in all conditions as pin length increased. Overall, the most influential parameter was the tool penetration depth, which positively affected the obtained properties. The rotational speed of the tool was the second most significant parameter, followed by the dwell time.

An experimental method for choosing the tool pin profile and shoulder size to join dissimilar aluminum alloys AA7075-T651 and AA6061-T6 joints

Many military and light weight aircraft designs call for joints between two different grades of aluminium alloy. This present study looked at the effect of tool shoulder diameter and tool pin profile on the tensile strength properties of dissimilar aluminium alloy AA6061-T6 and AA7075-T651 joints created by friction stir welding. The joints were fabricated utilizing three distinct tool shoulder diameters 15 mm, 20 mm and 25 mm along with two distinct tool pin profiles namely taper and square. The microstructure and microhardness of weld stir zone (WSZ) were examined and linked with the strength parameters of the joints. Adequate frictional heat generation from 20 mm shoulder diameter and pulsating stirring action of square pin revealed the formation of very fine grains in the weld nugget zone (WNZ). Due to enhanced material flow and the production of a defect-free stir zone, the joint created using a tool with a 20 mm shoulder diameter and square pin profile had the maximum hardness of 117 HV and the highest tensile strength of 284 MPa. The ductile mechanism of fracture is revealed by the presence of fine dimples accumulating in the tensile fractured surface of the joint fabricated by 20 mm tool shoulder diameter and square pin.

Enhancement of mechanical and microstructural properties of friction stir welded AA2024 by eccentric square tool pin

Grain size significantly affects joint strength and mechanical properties after friction stir welding (FSW). The tool pin shape/feature is an important factor influencing weld quality and microstructural features. The current work investigates the FSW of AA2024 with eccentric (distance between the axis of tool pin and shoulder) square tool pin and its influence on mechanical and microstructural characteristics. A square tool pin with three different eccentricities (0.0, 0.1, and 0.2 mm) is considered with a tilt angle of zero, one and two degrees. A defective weld is observed for the zero eccentricity, while the defect is reduced for the eccentricity of 0.2 mm with the reduction in grain sizes. Ultimate tensile strength enhanced to 407 MPa, contributing to a weld efficiency of 87 % obtained with a 0.2 mm pin eccentricity and two-degree tool tilt angle. Also, the average grain size and hardness at the stirred zone are 3.4 μm and 164 HV, respectively. Tool eccentricity produced 50, 14.7, and 11.2 % increase in tensile strength for 0o, 1o, and 2o tool tilt angles respectively, while increasing eccentricity from 0.0 to 0.2 mm. It is also found that eccentricity results in a higher dynamic area of 8 and 16 % for 0.1 and 0.2 mm, leading to more plastic deformation and better material mixing, resulting in enhanced mechanical and microstructural features. Also, higher rotational paths due to eccentricity cause interacting material to deform more with enhanced plasticization. Average grain size reduces by 25 %, 18.5 %, and 46 % when tool pin eccentricity is increased from 0 to 0.2 mm for a tilt angle of zero, one and two degrees, respectively. thermomechanical and mechanistic models are developed to explain the grain refinement and defect reduction mechanism due to eccentricity.

Fatigue life simulation of AA7075-T651 FSW joints using experimental data

The friction stir welding (FSW) process is a solid phase type applied in this study to connect AA7075-T651 aluminum alloy plates. This study investigates the impact of welding input quantities such as tool rotational speed, welding speed, shoulder radius, and tool geometry on welding joint quality, including strength, toughness, hardness, fractography, and fatigue behavior. Also, in this study, the fatigue life in the base material (BM) and joints obtained from the simple, threaded, and truncated triangular pyramid pins as an FSW effective input parameter was obtained by the finite element analysis (FEA). The experimental outcomes represented that the mechanical attributes of the threaded pin are higher than that of the simple and truncated triangular pyramid pins with the same input parameters. Also, the outcomes of the numerical simulation with the experimental outcomes of fatigue life for the BM were in acceptable agreement, and the error value of the validation result for σmax=0.5σy for the stress ratio R=-1 was equal to 0.4%. In addition, the FEA results indicated that the fatigue strength of FSW joints in the stir zone for the threaded, simple, and truncated triangular pyramid pins in the fatigue life of 107 cycles was 64%, 63%, and 43% of the BM, respectively.

Numerical assessment of temperature and stresses in friction stir welding of dissimilar Mg-Al-Zn alloys

ABSTRACT Magnesium (Mg) alloys are used more frequently as a replacement for heavier structural materials because of their advantageous specific strength and eco-friendly attributes. Their fusion welding is a difficult process, but the friction stir welding (FSW) offers a potential solution to these issues. In this study, a thermal analysis is carried out to obtain the temperature distribution and residual stresses related to FSW of different Mg-Al-Zn series Mg alloys under different processing conditions. The highest temperature recorded at the centre of the weld was 544.04°C, while the average von Mises stress during welding was 185.07 MPa. These values were achieved with a tool rotational speed of 1000 rpm, welding speed of 40 mm/min, and a tool shoulder diameter of 21 mm. The temperatures obtained through the numerical model were validated by comparing them with experimental data. During the experimental analysis, small cracks were observed at the centre of the welded joint, resulting from the formation of MgO. The welded joint exhibited a maximum tensile strength of 234.86 MPa, which is approximately 90% of the stronger AZ31 Mg alloy.

The impact of process parameters and pin-to-shoulder diameter ratio on the welding performance of polycarbonate in FSW

The utilization of friction stir welding (FSW) for the joining of polymers and composites is gaining increasing recognition due to its capabilities. In this study, the weldability of 4 mm thick polycarbonate (PC) plates in FSW is examined. Statistical modeling tools were employed to investigate the effect of four control parameters, i.e., rotational speed, travel speed, weld tool shoulder, and pin diameter, on the geometrical characteristics (residual thickness) of the weld region and the mechanical performance of the weld components under flexural and tensile loads. A screening experimental procedure with an L9 Taguchi was initially performed to calibrate the control parameter levels. During the welding procedure, the temperature profiles were continuously recorded to verify the materials’ solid state. The welding efficiency of the joint was also assessed, with a 90% welding efficiency achieved in the study. The morphological characteristics of the welded zones were assessed through optical and scanning electron microscopy. The samples welded with 4 mm/min travel speed, 10 mm shoulder diameter, 1000 rpm rotational speed, and 3 mm pin diameter had the highest mechanical performance. Overall, a shoulder-to-pin diameter ratio between 2.5 and 3 achieved the best results. The findings provide valuable information for the weld performance optimization of PC sheets, which can be employed successfully in real-life uses.Graphical abstract

Grain Structure Evolution in 6013 Aluminum Alloy during High Heat-Input Friction-Stir Welding.

This work was undertaken to evaluate the influence of friction-stir welding (FSW) under a high-heat input condition on microstructural evolution. Given the extreme combination of deformation conditions associated with such an FSW regime (including the highest strain, temperature, and strain rate), it was expected to result in an unusual structural response. For this investigation, a commercial 6013 aluminum alloy was used as a program material, and FSW was conducted at a relatively high spindle rate of 1100 rpm and an extremely low feed rate of 13 mm/min; moreover, a Ti-6Al-4V backing plate was employed to reduce heat loss during welding. It was found that the high-heat-input FSW resulted in the formation of a pronounced fine-grained layer at the upper weld surface. This observation was attributed to the stirring action exerted by the shoulder of the FSW tool. Another important issue was the retardation of continuous recrystallization. This interesting phenomenon was explained in terms of a competition between recrystallization and recovery at high temperatures. Specifically, the activation of recovery should reduce dislocation density and thus retard the development of deformation-induced boundaries.

Effect of tool pin profile on the heat generation model of the friction stir welding of aluminium alloy

Abstract The present work aims to model the three-dimensional heat transfer coupled with the material flow model of 7075-T6 aluminium alloy material using the three tool pin profiles, square, pentagon, and hexagon, in the friction stir welding process. The temperature rise and fluid flow behaviour from the top to the bottom of the tool were evaluated. Also, the strain rate and dynamic viscosity variation were found near the tool pin and shoulder region. The results showed that the frictional contact heat between the shoulder surface and workpiece was responsible for the maximum heat generation. The probe area was minimum in the square tool pin geometry, which results in high heat generation due to the maximum shoulder surface contact area with the workpiece model. Furthermore, the analytical formula for calculating the heat generation on the tool shoulder/workpiece interface and the tool pin/workpiece contact region were also evaluated. The numerical modelling of heat generation was evaluated by COMSOL Multiphysics V5.3a software.

Microstructural Evolution and Material Flow during Friction Stir Welding of 6013 Aluminum Alloy Studied by the Stop-Action Technique

This work is part of a wide-ranging study aiming to enhance the technology of dissimilar friction-stir welding of aluminum and titanium. In the previous study, a new approach was proposed that provided an exceptionally narrow intermetallic layer. However, an essential disadvantage of this technique was the significant material softening in the aluminum part. Hence, the present work was undertaken in order to obtain insight into microstructural processes and material flow in the aluminum part. To this end, the stop-action technique was applied. It was found that the microstructural evolution included several stages. Specifically, the initial material underwent the discontinuous static recrystallization in the heat-affected zone. With the approach of the rotating tool, the recrystallized grains experienced continuous dynamic recrystallization, which resulted in grain refinement. The subsequent transportation of material around the rotating tool provided no significant alterations in microstructure. This “superplastic-like” character of material flow was attributed to a dynamic balance between grain refinement and grain coarsening. It was also found that the stirred material experienced a secondary deformation induced by the rotating tool shoulder far behind the welding tool. The concomitant microstructural changes were most pronounced at the upper weld surface and gave rise to a fine-grained layer.

Effect of tool concavity on flash formation during fabrication of tubes through friction stir welding

Tubular components are challenging to weld using friction stir welding (FSW) process due to its curvature. In the present work, a novel strategy involving concave shoulder tool with three different concavities (3°, 6° and 9°) coupled with double pass was devised to fabricate longitudinal FSWed tubes of AA5083-O. An increase in concavity resulted in formation of flash and thinning of weld zone (WZ) due to excessive heat generation caused by enhanced tool contact with tube curvature. The flash generation led to the formation of porosity in the WZ. The tool with 6° concavity resulted in spherical pores whereas long and needle shaped pores were witnessed in case of 9° concave tool. However, negligible pores were observed with 3° concave tool leading to excellent WZ strength. Therefore, it was inferred that concave shoulder tool with small concavity along with double pass was suitable for welding tubes using FSW.

Defects Analysis of Tee-Section Welding Using Friction Stir Welding Process of Aluminum

Friction stir welding (FSW) of Tee-joints is obtained by inserting a specially designed rotating pin into the clamped blanks, through top plate (skin) to bottom plate (stringer), and then moving it along the joint, limiting the contact between the tool shoulder and the skin. The present work aims to investigate the defects occur for Tee-joint of an Aluminum alloy (Al 5456) with dimensions (180mm x 70mm) for the skin plate, (180mm x 30mm) for stringer plate and thickness of (4mm).The effects of welding parameters such as rotational speed, linear speed, plunging depth, tool tilting, and die radii of welding fixture on the welding quality of Aluminum Alloy will be studied. Weld defects had been summarized and studied, and then the best conditions that led to good welds had been estimated.

Quasi-in-situ characterization of microstructure evolution in friction stir welding of aluminum alloy

The in-situ investigation of microstructure evolution during friction stir welding (FSW) can provide very important theoretical guidance to control the microstructure and mechanical properties of the FSW joint. In this study, a quasi-in-situ investigation method of the microstructure evolution in friction stir welding of AA1050 aluminum alloy was developed. The microstructure along the material flow path was characterized and analyzed by taking the strain, strain rate, and temperature into account simultaneously. The results show that the microstructure evolution during the FSW of aluminum alloy can be divided into four stages according to the material flow state and thermal history. Firstly, grain coarsening by static recovery and static recrystallization occurs at the static preparatory stage (or called the preheating stage). Secondly, grain refining by continuous dynamic recrystallization occurs at the acceleration stage, where the temperature gradually increases to nearly a constant. The grain size is mainly controlled by the accumulative total strain. The strain rate only affects the rate of dislocation generation and the type of β-fiber simple shear texture components. Thirdly, at the high-velocity flow stage, a dynamic equilibrium between plastic deformation and dynamic recrystallization is maintained, and the grain size only fluctuates within a small range. Finally, a second grain-coarsening process occurs through normal grain growth due to thermal activation at the deceleration stage. This process is inevitable because it occurs under the cover of the tool shoulder. The grain coarsening during the normal cooling stage was avoided in this study due to the rapid cooling used, which has been widely reported by published documents.

Influence of Tool–Base Metal Interference on the Performance of an Aluminium–Magnesium Alloy Joined via Bobbin Tool Friction Stir Welding

Bobbin tool friction stir welding (BTFSW) is a variant of the FSW process which uses the special two-shoulder tool that forms the top and bottom of a weld surface. As such, a significant simplification of the welding setup is achieved. One of the dominant parameters of the BTFSW process is the interference between the tool shoulder pinch gap and the weld metal thickness. In this research, the influence of interference of the square pin tool with convex shoulders on process temperature, microstructure, tensile, impact, and bend performance were studied, and appropriate correlations were devised. The base metal was an aluminum–magnesium alloy in which the interference varied in the range of 0.1 to 0.5 mm. Wormhole defects and irregularities were found in all specimens except in the specimen welded with 0.4 mm interference. An optimal interference of 0.4 mm resulted in the best mechanical properties, which, in terms of tensile strength and reduction of area, were similar to the base metal. Furthermore, the impact strength was significantly higher, which was attributed to the grain refinement effect in the nugget zone.

Temperature Distribution of Friction Stir Welded Al 7075 alloy using Finite Element Simulation along with Experimental Validation

Finite element simulation (FE simulation) and experimental validation of Friction Stir Welding (FSW) has been performed on 3 mm thick plates of AA7075 at rotational speed 1000 rpm and transverse speed 50 mm/min. It is difficult to determine the temperature distribution of the workpiece and tool interface experimentally, wherein temperature distribution of workpiece is responsible for frictional heat generation. The frictional heat generation is one of the important factors affecting the material flow and joint quality of FSW. In present work, finite element simulation using Coupled Eulerian Lagrangian approach has been performed to estimate the temperature of the workpiece and the tool. The simulation result shows the temperature distribution of the workpiece and the tool. The maximum temperature was attained by the tool. The FE simulation predicts 308 C temperature adjacent to the shoulder which corresponds to experimentally measured temperature ∼ 290 C. The simulation predicts 531 C as the maximum temperature at the tool shoulder whereas the experimentally measured maximum temperature at the tool shoulder is found to be > 400 C, showing good agreement between simulation and experiment. The tensile strength 62.74 % of the base alloy and elongation of 11.5 % have been achieved in the experimentally produced FSW sample at 1000 rpm rotational speed and 50 mm/min transverse speed. The nugget zone of FSW has higher hardness due to the recrystallized fine grain and HAZ has comparatively lower hardness due to grain coarsening.