Tool Offsets Research Articles

Mechanical and metallurgical characterization of friction stir welded AA2024 to pure copper using specific variables and positioning

A simple cylindrical pin shaped tool made economically of H13 tool steel was used to butt weld dissimilar metal plates of AA2024 and pure copper with friction stir welding with three different welding arrangements of plate positionings and tool offsets. Plunge depth, tool tilt angle and tool traverse speed remained steady while tool rotation speed varied in every arrangement. Tensile strength testing, microhardness testing, SEM, EDS and fractography were performed to evaluate the impact of plate positioning, tool offset and tool rotational speed on weld quality. The NZ showed swirl and vortex microstructures, and ductile fracture was identified as the cause of rupture in the FSWed samples. The arrangement AA2024 was placed in the advancing side without tool offset at tool rotation speed of 900 rpm demonstrated UTS, YS and microhardness as 198.98 MPa, 153.86 MPa and 251 HV respectively whereas maximum elongation, joint efficiency found 8.39%, 85.54% respectively.

Corrosion Characterization of Friction Stir Weld Dissimilar Aluminium Alloy Joints

The course of contact mix welding is quick acquiring conspicuousness in aviation, marine and car industry because of its benefits as far as mechanical strength, effect and hardness characteristics. There is as yet a requirement for sure fire consideration from the exploration local area to erosion in grating mix welding zones, hence the work introduced here centres around the consumption portrayal of the grinding mix weld divergent aluminium composite. This study looks into friction stir welding under various parametric settings and shows how corrosion happens in a sodium chloride electrolytic media under potentio-dynamic conditions. The friction stir weld joints of dissimilar alloys aluminium are constructed using three sets of parameters. Straight cylinder, taper cylinder, and straight triangular tool profiles; tool rotational speeds of 800, 1000, and 1200 rpm; tool feed rates of 100, 120, and 140 mm/min; and tool offsets of 0.5, 0 mm, and -1.5 mm. The corrosion current (Icorr) reduces as tool rotating speed increases up to 1200 rpm, after which it slightly increases due to the creation of ridges all around the periphery of the friction stir weld area.

A Novel Study on the Effect of Tool Offset in Friction Stir Processing for Mg-NiTi Composite

Mg-NiTi-based metal matrix composites are appropriate solutions for the two most important goals of material engineers in the present day, i.e., imparting functional behaviour and the light weighting of metallic structures. In recent years, due to its solid-state nature, the development of Mg-based metal matrix composites has largely benefited from friction stir processing. Despite the great effort of researchers in the domain of friction stir welding and processing, finding optimum process parameters for efficient material mixing and consolidation remains a rigorous and exhaustive challenge. Tool offset variation has been seen to aid the integrity and strength of friction stir welds; however, its effect upon the stir zone structure, material flow, particle distribution, and defect formation has not been investigated for friction stir processing. Therefore, the authors employed Mg as the base metal and NiTi shape memory alloy as the reinforcement to the targeted metal matrix composite. The tool offset was linearly varied by tilting the slotted length with respect to the traverse direction. Friction stir processing performed at a rotational speed of 560 rpm and traverse speed of 80 mm/min revealed crucial changes in defect morphology and area, which has been explicated with the quantified variation in tool offset from the advancing side to the retreating side. For the positive offset conditions, i.e., tool offset towards the advancing side, the shape of the tunnelling defect was chiefly convex from the outward direction. Meanwhile, for the negative offset conditions, i.e., tool offset towards the retreating side, the tunnelling defect exhibited a concave outward shape. A transition from rectangular to triangular morphology was also observed as the tool moved from an offset of 1.75 mm in the advancing side to 1.75 mm in the retreating side.

Inductive XY calibration method for multi-material fused filament fabrication 3D printers

In this work an optical and inductive calibration procedures for calibrating multi-material fused filament fabrication 3D printers in the x and y directions is presented. The inductive calibration is based on the principle that the inductance of a detection coil placed on the print bed changes when the (metallic) extrusion nozzle passes it. This calibration method shows a repeatability of up to 2 µm. To determine the accuracy of this calibration method, another calibration method is proposed that directly measures the position of the deposited material. During this alternative process, a calibration structure is printed on an A4-format sheet of paper using every tool. The paper is subsequently scanned using a digital scanner, and the resulting image is analyzed using an image-processing script. Using this method as a reference, it was determined that the inductive method has an accuracy of approximately 45 µm. For applications where this accuracy is sufficient, the inductive method provides a fast solution that requires little to no user interaction. For more demanding applications, the optical calibration might be the better choice, since it is more time-consuming but yields a more accurate solution. It is expected that the accurate calibration of tool offsets will reduce both the chance of poor adhesion between materials and the mixing of filaments due to local over- and under-extrusion at material interfaces.

Digital surface twin for ultra-precision high performance cutting

Increasing productivity of ultra-precision (UP) machining is vital to apply this technology in a broader range of applications. In order to achieve this goal, technologies such as diamond cutting with multiple cutting edges or the application of electromagnetic levitation guides are researched. Due to the additional, influencing factors from these technologies, a digital surface twin is beneficial for predicting surface features and characteristics. In this work, two approaches for generating a digital surface twin are investigated: a surface simulation based on numerical height maps and a dexel-based material removal simulation. Both incorporate multi degree of freedom position data provided by the levitation guide. Fly-cutting experiments are conducted to validate the digital twin approaches. Both approaches are able to predict surface profile, surface roughness and waviness with high accuracy. It is also shown, that the digital twin can support the development of compensation approaches for tool offsets. In conclusion digital surface twins for ultra-precision cutting offer a high potential to support productivity improvement especially in combination with axis position data. Further work will focus on real-time integration of the approaches.

Effect of tool offsetting on friction stir welding of dissimilar aluminium matrix composite and aluminium alloy

Commercial 6061 Al alloy and SiCp reinforced 6092 Al matrix composite (AMC) were joined by friction-stir welding (FSW) with different tool offsets. Results show offsetting the pin to Al alloy side could significantly reduce tool wear, while maintaining ultimate tensile strength of the joint around 180 MPa. As tool offset increased from zero to 3 mm, pin and shoulder wear length reduced from 0.17 mm to almost zero and from 0.28 to 0.02 mm, respectively. The corresponding estimated maximum safe welding length increased from 568 to 3125 mm. Fe debris were generated from the steel pin by the sharp SiC particles, then transferred into the nugget zone, eventually formed Al8Fe2Si particles during the FSW process.

Development of morphable polishing tools with labyrinth and dimple textures

Inspired by the physical nature and functionality of morphable surfaces, this paper develops the polishing tools with such surface characteristics. The surface textures of morphable polishing tools can be tuned and adapted according to the stage and requirements of the targeted surface finish and material removal rate. To investigate the performance of morphable surfaces in polishing, morphable polishing tools with labyrinth, dimple and hybrid textures were fabricated by curing silicone materials with different Young’s moduli. The morphable polishing tools can be produced with fast responsiveness and reversibility by controlling the air pressure in the tool cavity. Fixed-spot polishing experiments with the developed morphable tools were performed on a copper surface, and the surface morphology, surface roughness and removed volume of polished copper were measured with a laser confocal microscope. Furthermore, static and dynamic polishing forces, polishing pressure distribution and interfacial friction coefficient between the tool and workpiece were obtained and benchmarked in polishing experiments regarding the labyrinth, dimple and hybrid tools. The results show that under the investigated polishing parameters, the roughness of polished surface is the smallest with the dimple tool, higher with the hybrid tool and the labyrinth tool. The material removal volume, static and dynamic polishing forces under different tool offsets are larger in the polishing processes with a dimple tool. In addition, the theoretical and experimental study indicates that the tool surface texture significantly affects the polishing pressure distribution. Labyrinth tools show denser pressure distribution owing to the finer textures of a smaller characteristic length, while dimple tools show sparsely distributed pressure owing to the coarser surface texture.

Impact of tool offset and friction stir welding speed on interface morphology of a dissimilar T-lap joints

: The dissimilar aluminum alloys of 5083 and 6061 were friction stir welded via T-lap configuration. The impact of the tool offsets and the tool moving velocity on the interface geometry and the bonding strength of the joints was investigated. The experimental results showed that the interface morphology was sensitive to both the tool offsets and welding rates. The hook defects were easily formed at low welding rate of 150 mm/min. The kissing bonds were ineliminable by both the tool offset and the tool speed. The joint strength was improved due to offsetting pin tool toward both retreating side and advancing side with the distance of 0.3 mm. The effect of the tool offset on the joint tensile strength was more remarkable than that of welding rate. The interface formation and fracture behavior of the joints were also revealed to clarify these findings.

Influence of tool offset on mechanical properties of solid-state-welded steel and AA7XXX joints

The objective of present work is to analyze the role of tool offset on mechanical properties of Friction Stir welded (dissimilar materials) AA7XXX and Steel joints. The major process parameters opted for current experimental study are, Tool Offset (T-OF), Tool Rotation Speed (TRS), and Tool Travel Speed (TTS). Tungsten Carbide (K-12) tool with cylindrical tapered pin is used to produce dissimilar butt welds. Steel plate is kept on advancing side and aluminum on retreating side during the joining process. Tensile, Impact, Bending and Hardness analysis are performed to assess the joint strength. Vickers Micro-hardness test was done along transverse direction of the joint to obtain hardness distribution at weld nugget. Experimental study divulge that, at tool rotational speed of 1400 rpm, tool travel speed of 16 mm/min and offset of +1 mm towards steel (advancing side) yields better results, i.e. around 23.3% improvement as compared to tool at zero offset.

Concurrent influences of tool offset and ultrasonic vibration on the joint quality and performance of dissimilar Al/Cu friction stir welds

Dissimilar joints made of aluminium alloy (Al) and copper (Cu) have great prospective applications in the electrical and electronic industries. Still, it is a challenging task to join them and obtain good performance. In this study, dissimilar AA6061-T6 and C10100 joints were produced by friction stir welding (FSW) and ultrasonic vibration-assisted friction stir welding (UVaFSW) processes with three different tool offset degrees from the Al side to the Cu side. Tool offset towards Al base material and in the Al/Cu interface produced defect-free joints with sound strengths in both joints made with and without ultrasonic vibration. On the other hand, tool offset towards Cu base material produced unsound joints with defective features such as wormholes and a lack of surface fill in both joints made with and without ultrasonic vibration. Ultrasonic vibration addition favoured a drastic reduction in the intermetallic compound (IMC) layer thickness, particularly amongst the welds made with tool offset in the Al/Cu interface, than those made with tool offset towards Al base material. In addition, the influence of tool offsets and the ultrasonic vibration addition remarkably affects the sizes (particle areas and the minimum Feret diameters) and the concentration of the Cu particles distributed in the weld nugget. In the joints produced with tool offset towards Al base material, the particle areas and the minimum Feret diameters were decreased by ~73.3% and ~42.6%, respectively, with the ultrasonic vibration addition. On the other hand, ultrasonic vibration in the joints produced with tool offset in the Al/Cu interface resulted in decreased particle areas and the minimum Feret diameters by ~60.6% and ~24.6%, respectively. The joints made with ultrasonic vibration have higher tensile strength than those made by conventional FSW.

Analysis of Friction Stir Welding Tool Offset on the Bonding and Properties of Al–Mg–Si Alloy T-Joints

Research on T-configuration aluminum constructions effectively decreases fuel consumption, increases strength, and develops aerial structures. In this research, the effects of friction stir welding (FSW) tool offset (TO) on Al–Mg–Si alloy mixing and bonding in T-configurations is studied. The process is simulated by the computational fluid dynamic (CFD) technique to better understand the material mixing flow and the bonding between the skin and flange during FSW. According to the results, the best material flow can be only achieved at an appropriate TO. The appropriate TO generates enough material to fill the joint line and results in formation of the highest participation of the flange in the stir zone (SZ) area. The results show that, in the T-configuration, FSW joints provide raw materials from the retreating side (RS) of the flange that play a primary role in producing a sound mixing flow. The selected parameters were related to the geometric limitations of the raw sheets considered in this study. The failure point of all tensile samples was located on the flange. Surface tunneling is the primary defect in these joints, which is produced at high TOs. Among the analyzed cases, the most robust joint was made at +0.2 mm TO on the advancing side (AS), resulting in more than 60% strength of the base aluminum alloy being retained.

Microstructural characterisation and mechanical properties of dissimilar AA5083-copper joints produced by friction stir welding

This work aims to study the influence of the tool rotational speed and tool traverse speed on dissimilar friction stir butt welds on 3 mm thick AA5083 to commercially pure copper plates. Complex microstructures were formed in the thermo-mechanically affected zone, in which a vortex-like pattern and lamellar structures were found. Several intermetallic compounds were identified in this region, such as Al2Cu, Al4Cu9 and these developed an inhomogeneous hardness distribution. The highest ultimate tensile strength of 203 MPa and joint efficiency of 94.8% were achieved at 1400 rpm tool rotational speed and 120 mm/min traverse speed. Placing the softer material (aluminium) on the advancing side produced an excellent metallurgical bond with no requirement for tool offsetting.

Influence of Tool Offset on Performance of Thin Al–Cu Dissimilar Metal Friction Stir Butt Welded Joint

The 1-mm-thick Al to Cu friction stir welding is successfully performed at the tool offsets toward Al side ranging from 0 to 2 mm. With increasing tool offset, the phenomenon of material sticking to tool shoulder surface is restricted and the area of Al–Cu mixing zone is reduced progressively. As the tool offset is increased from 0 to 1 mm, the weld shows a variation of intermetallic phases from CuAl2 + Cu9Al4 to CuAl2 and exhibits a lowering in hardness and tensile properties. The 2-mm-offset weld without intermetallic phases discernible exhibits the highest hardness due to the thinness of Cu lamellar and Al-rich compound layers, and the joint featured by a failure at the relatively soft region adjacent to harder Al–Cu mixing zone in a ductile pattern shows the best tensile strength equivalent to 80% of that of the base material.

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.

Analysis of material distribution in dissimilar friction stir welded joints of Al 1050 and copper

The objective of this work is to analyse the material distribution in dissimilar friction stir welded joints of Al 1050 and Copper. During dissimilar friction stir welding, mixing of materials leads to the emergence of interfaces between two dissimilar materials. These interfaces provide venues for the formation of intermetallic compounds, which significantly affect the joint properties. Therefore it is of interest to understand the material movement and track the interfaces which are generated during friction stir welding. A three-dimensional computational fluid dynamics model is developed for the dissimilar friction stir welding. The volume of fluid method is used to track the material movement during the process. Friction stir welds of Al 1050 and Copper are prepared, with different tool rotational speeds and tool offsets towards Al 1050 side. Optical microscopy of the weld cross-sections is performed to observe the final status of material movement and material dispersion in the stir zone. Despite the absence of direct contact between copper and FS tool initially, copper is pulled into the stir region. Numerical results suggest that the temperature, stress and strain rates in the vicinity of FS tool are sufficient to pull copper into the stir zone. Relatively lower viscosities in shoulder driven region promote material mixing and uniform distribution of both materials. While pockets rich in copper or Al 1050 are observed in pin driven region. For the same strain rate and temperature, copper exhibits higher viscosity than Al 1050. This impedes the movement of copper and prevents it from moving all around the tool. This allows Al 1050 to displace copper at advancing side, which leads to shifting of initial copper-Al 1050 interface towards advancing side. Small offset towards Al 1050 and high tool rotation speed promotes pulling in of the copper and vice versa. This leads to larger interface shifts at smaller offsets and higher tool rotations speeds and vice versa. These trends are well captured by the numerical model.

Effects of tool offset, pin offset, and alloys position on maximum temperature in dissimilar FSW of AA6061 and AA5086

Friction stir welding (FSW) is a solid-state welding technique, which two workpieces join by pressure and large plastic deformation near their melting points. The tool offset, pin offset, and position of dissimilar alloys can highly affect the maximum temperature and heat distribution in FSW process. In current research, the effects of three mentioned variables on the maximum temperature of FSW of AA6061 and AA5086 alloys have been investigated. In this manner, Response Surface Methodology (RSM) as an auxiliary method has been used. The results show that pin offset is the most effective parameter affecting maximum achieved temperature. In all pin and tool offsettings, placing the harder alloy (AA6061) at advancing side results in more maximum temperature increment compared to the case which the harder alloy is at the retreating side.

Effect of Tool Offset on the Microstructure and Properties of AA6061/AZ31B Friction Stir Welding Joints

Friction stir welding was carried out on AA6061/AZ31B alloy, and the influence of tool offset on microstructures and mechanical properties of the joints was studied. The results showed that preferred properties were obtained when Mg was placed in the Advancing Side (AS) and offset was positioned into Mg. The distribution of Al3Mg2 and Al12Mg17 intermetallic compounds (IMCs) could be improved with offset in a certain range. The tensile strength of the joints was elevated with the increase of the offset due to the superior distribution and diminished size of IMCs, and when the offset was 1.5 mm, the joint strength reached the maximum value of 107 MPa. The microhardness of the stirring zone decreased with the increased offset.

Influence of tool offsetting and base metal positioning on the material flow of AA5052-AA6061 dissimilar friction stir welding

This study examines dissimilar friction stir welding of AA5052-AA6061 aluminum alloys with varying tool offsets. The base metals were positioned and fixed at a slight diagonal positioning such that varying tool offset position from the centreline can also be varied along the length of the weld. After the fabrication process, microstructural and mechanical property characterization was subsequently conducted. The results show that, above a certain threshold for tool offset, incomplete consolidation (i.e. kissing bond defects) will occur. Regardless of the base material positioning, a zero tool offset shows optimum intermixing in the stir zone. EDX mapping confirms the presence of a distinct interface between both materials in the stir zone region. However, enhanced material intermixing and better elongation are observed when AA6061 alloy is positioned at the tool advancing side.

Friction stir butt-lap welding of A7N01P-T4 aluminum alloy: Efforts to mitigate defects and the resultant mechanical properties

Butt-lap configuration of aluminum alloys was friction stir welded under various tool offsets, rotational speeds, and tool geometries. The tool offset was introduced to mitigate the inherent retreating side hook. As the probe was placed inwards, the retreating side hook was mitigated, but a severe S-line was formed. Since the inherent retreating side hook was difficult to further mitigate, the S-line was selected to be mitigated by increasing the rotational speed. But an excessive rotational speed (2000 r/min) could cause a severe upward-bending retreating side hook, which decreased the effective plate thickness. Subsequently, two-section stepped probes were employed to mitigate the defects. The S-line and retreating side hook were both mitigated and its ultimate tensile strength (369 MPa) reached 91% of the base material.

Controlling of compliant grinding for low-rigidity components

The machining of low-rigidity components (e.g. thin-walled) with compliant tools presents accuracy challenges as both sides in contact are being deformed. The controlling method presented in this paper enables, for the first time, to obtain the desired and uniform material removal rate by controlling the nominal tool offset when two bodies (workpiece and tool) are compliant in grinding. A contact deformation model is proposed to predict the relation between the nominal and actual tool offsets. The function of nominal tool offsets and material removal rates is obtained based on the calibration tests. Spot grinding tests have been performed for the validation of the calculated material removal rates, normal grinding forces and spot sizes, presenting position-dependent characteristics. The controlling method has been tested for the case of continuous grinding the whole area of a circular aluminium thin wall. The surfaces ground under the time-variant tool offsets (proposed approach) reach the desired removal depth with an average error of ≤10% and achieve 11.2 μm–24.2 μm (P–V) accuracy in the elastic domain, compared with the error of 76.8%~113.7% and accuracy of 42.6 μm–50.1 μm (P–V) in the circumstance of constant tool offsets (conventional approach).