Tool Rotation Rate Research Articles

Experimental investigation and optimization of surface roughness in negative incremental forming

Single Point Incremental Forming (SPIF) allows the possibility of forming components of various shapes and sizes with the use of simple and economical tooling. Investigation of surface quality of the formed components becomes necessary for selecting the optimal process parameters in order to ensure precision and safe forming of the components. Moreover, lack of available knowledge regarding the process parameters makes the process limited for industrial applications. In this paper, various input factors have been investigated on the surface roughness of formed components. The process has been optimized to obtain the optimal levels of input factors for producing better surface quality using Taguchi Method (TM) as Design of Experiment (DOE) and analysis of variance (ANOVA). Results showed that the optimal experimental condition for average roughness has been determined as tool diameter (15.66 mm), tool shape (hemispherical), the viscosity of the forming oil (320 cSt), sheet thickness (0.8 mm), wall angle (60°), step size (0.2 mm), tool rotation (1000 rpm), and feed rate (1500 mm/min). The tool diameter has been found the most dominating factor for average surface roughness of the conical frustums. Tool shape and the viscosity of forming oil have also been significant factors for average roughness. The results obtained from confirmatory experiments showed that predictive model obtained from TM is efficient and effective for estimating optimal levels of input parameters for producing the better surface quality during the SPIF process.

On performance enhancement of electrochemical discharge trepanning (ECDT) process by sonication of tool electrode

In the present work, an attempt has been made to use ultrasonic energy to augment the performance of electrochemical discharge trepanning (ECDT) process. The effect of various process parameters such as applied voltage, pulse on time, tool rotation rate and power rating on quality characteristics (over cut (OC) and depth of penetration (DOP)) of machined work materials has been experimentally investigated. The underlying process mechanism for ultrasonic assisted ECDT (UA-ECDT) process is proposed by considering the high speed images of gas film, mathematical formulations and electrical signals as evidences. A comparative analysis between ECDT and UA-ECDT has also been performed. The experimental results reveal that the integration of ultrasonic vibrations in ECDT process facilitates evacuation of the sludge/debris from the machining zone. Also, it generates thin and stable gas film over the tool electrode. Therefore, the use of UA-ECDT improves the energy channelization index (ECI), and exhibits 10 times more ECI than the ECDT process. The second-order mathematical models have been developed to determine the relationship between input process parameters and quality characteristics (OC and DOP). The developed models are in good agreement with the experimental results and exhibit an average error of less than 3%. Additionally, a desirability approach has been employed to conduct the multiobjective optimization for the minimization of OC and maximization of DOP. The parametric combination of applied voltage of 60 V, pulse on time of 3 ms, tool rotation rate of 42 rpm and power rating of 17% is recommended to perform the UA-ECDT process.

Formation of skin surface layer on aluminum foam by friction stir powder incremental forming

To improve strength–mass relationship of a closed-cell type aluminum foam, friction stir powder incremental forming (FSPIF) process was applied to form nonporous skin surface layer on the foam surface from aluminum powder. In this process, the powder was supplied to the surface pores of the foam, and then, the powder and the cell wall near the foam surface were incrementally pressed by a rod-shaped tool without rotation (incremental hammering (IH)) and incrementally stirred by the tool at a very high rotation rate (friction stir incremental forming (FSIF)). The skin layer with a maximum thickness of 1.4 mm was formed on the foam surface without deforming the porous structure of the inside of the foam under the forming conditions, a tool rotation rate of 8000 rpm, a tool feed rate of 60 mm/min, and a total forming depth of 10 mm. The formation mechanism of the skin layer from the powder was investigated by microscope observation. Due to combination of sandwich structure and increase of bulk density, the specific plateau stress and the plateau end strain of the foam specimen with the skin layers were improved up to 1.2–1.6 times greater in a uniaxial compression test.

E XPERIMENTAL AND NUMERICAL STUDY OF 6061-T6 AL- ALLOY FATIGUE LIFE USING FRICTION STIR WELDING

Welded parts are often subjected to variable loads. Paper’s aim is to evaluate the fatiguecharacteristics of friction stir welding of AA6061-T6 alloy under variable loading andobserved the influence of heat treatment for friction stir welding joint on the fatigue stressanalysis. The microstructure of the welds alloy are studied before and after heat treatment.The friction stir welding was employed using milling machine with constant tool rotation(1000 rpm) and feed rate (20 mm/min). Artificial aging are made for aluminum friction stirwelded alloy using electrical furnace at temperature of 500ºC for 20 min. Quenching at190ºC for 4 hr. via water is followed the aging process. Fatigue test were done for specimens(base metal, friction stir welding alloys before and after heat treatment) to obtain the S-Ncurves for each case. Finite element via ANSYS software is used to analysis the FSW(temperature, Von-Mises stress, deformation in the welded zone and contact friction stressdistributions) and Fatigue test (fatigue life, fatigue damage, fatigue safety factor, biaxialityindication , equivalent alternating stress and stress intensity factors) where the generalthermo-elasto plastic relation produced under thermal and mechanical loads with isotropic,kinematic and mixed hardening rule in three dimensional problems is proposed. The resultsshown that the heat treatment for the friction stir welded alloy would be increased thefatigue strength of the welded plate that the number of cycles of base metal (AA6061-T6)was 1.2×106 and the number of cycle for welded joints without heat treatment was(0.9×106), where the number of cycles was 1×107 with heat treatment with quenching within4hr. also it can be concluded that, the fracture opening mode (mode I) is exist in the unheated welded alloy and disappeared with heating treatment

Experimental study of effect of process parameters for heat generation in friction stir welding

In this study, experiments have been performed with three tools of cylindrical pin type for three sets of rotational speeds and feed rates, and the effect of processes parameters on heat generated at different zones of friction stir welded plate is examined. In friction stir welding, the base material is heated at elevated temperature for which heat generation is an important factor. Less heat reduces the rheology and mixing of material whereas more heat reduces the strength of the welded material. From this study, it was concluded that more heat is generated at higher tool rotation rate and tool shoulder diameter whereas less heat generate at high tool traverse speed. This study also reports the optimum tool shoulder diameter, rotational speed and transverse feed for having maximum joint strength.

Microstructure, mechanical properties and strengthening mechanisms of friction stir welded Kanthal APMT™ steel

Kanthal APMT™ steel (Fe-22Cr-5Al-3Mo) is being investigated for possible use as an accident-tolerant fuel cladding material in advanced light water reactors. Generally, high-chromium ferritic steels do not have good weldability because of a variety of metallurgical issues. In the present study, friction stir welding (FSW), a solid-state joining process, was applied to a Kanthal APMT™ plate in a bead-on-plate configuration using a tool rotation rate of 600 RPM and a traverse speed of 25.4 mm/min. Microstructure and mechanical properties were evaluated to determine the weld quality and examine feasibility of applying FSW as a joining technique for this steel. Microstructural characteristics were examined by optical microscopy and electron microscopy. The stir zone (SZ) contained equiaxed grain structure with an average grain size of 13.7 μm. Interestingly, Vickers microhardness profile across the processed zone revealed no significant change in microhardness. Mini-tensile testing, however, showed a marked improvement in mechanical properties of the SZ in the longitudinal direction compared to the base metal. The results are discussed in the light of fundamental strengthening mechanisms.

Machining of fluidic channels on borosilicate glass using grinding-aided electrochemical discharge engraving (G-ECDE) and process optimization

Electrochemical discharge machining (ECDM) has already been identified as a novel process for machining advanced ceramics and glass. The major limitations of this process are high overcut of the machined channels and the difficulty in controlling the roughness of the channel. This paper presents a novel technique which uses diamond-impregnated engraving tool as the tool electrode for machining accurate and smooth channels on borosilicate glass using ECDM. This technique can be called as grinding-aided electrochemical discharge engraving (G-ECDE). The new method utilizes both the grinding action of diamond grits and the thermal and chemical effects of ECDM for material removal. Preliminary experiments are performed using Placket–Burman design with center points to study the effect of machining parameters like voltage, electrolyte concentration, pulse-on time, tool rotational speed and tool feed rate on channel overcut and surface roughness of the channel. With the significant factors identified from the preliminary experiment, the main experiment was performed using a widely used response surface design called Box–Behnken design to develop second-order response models for surface roughness and channel overcut. Response surface plots are used to identify the effect of parameters and their interactions on the responses. Technique for order preference by similarity to ideal solution (TOPSIS) is used to optimize this multi-response problem. The optimum factor levels obtained from TOPSIS are a medium feed of 2 mm/min, a low voltage of 80 V, a medium pulse-on time of 0.0011 s and a low concentration of 2 M which produced channels with a surface roughness of 0.872 μm and overcut of 0.293 mm. From the microscopic images of machined channels, material removal mechanisms of G-ECDE are confirmed to be a combination of thermal melting due to electrochemical discharges, grinding action of diamond grits and high-temperature chemical etching action of the electrolyte. The performance of G-ECDE is compared with die-sinking ECDM and electrochemical discharge milling for producing channels and found that G-ECDE is the most suitable process to produce fluidic channel on glass which is free from recast layer and heat-affected zone. The results obtained from this study proved the potential of G-ECDE in producing smooth, accurate and complex fluidic channels on the glass.

Effect of Processing Parameters on Plastic Flow and Defect Formation in Friction-Stir-Welded Aluminum Alloy

The effect of processing parameters on material flow and defect formation during friction stir welding (FSW) was investigated on 6.0-mm-thick 2014Al-T6 rolled plates with an artificially thickened oxide layer on the butt surface as the marker material. It was found that the “S” line in the stir zone (SZ) rotated with the pin and stayed on the retreating side (RS) and advancing side (AS) at low and high heat inputs, respectively. When the tool rotation rate was extremely low, the oxide layer under the pin moved to the RS first and then to the AS perpendicular to the welding direction, rather than rotating with the pin. The material flow was driven by the shear stresses produced by the forces at the pin–workpiece interface. With increases of the rotation rate, the depth of the shoulder-affected zone (SAZ) first decreased and then increased due to the decreasing shoulder friction force and increasing heat input. Insufficient material flow appeared in the whole of the SZ at low rotation rates and in the bottom of the SZ at high rotation rates, resulting in the formation of the “S” line. The extremely inadequate material flow is the reason for the lack of penetration and the kissing bonds in the bottom of the SZ at extremely low and low rotation rates, respectively.

Characteristic study on Al7020 friction stir joints with various rotational speeds

This article provides information on the weld quality of joints which are made by friction stir welding (FSW) based on industrial application especially aerospace and automotive. Here, two aluminium 7020 plates were welded. The joints were produced using same welding parameters only the variation is done in the rpm of the tool. Here the characterisation is done against mechanical properties and microstructure. Using the selected welding parameters, excellent weldment forms, but the micrographs for each joint cross-section made with different rpm are different. With the change of tool's rotary speed, a number of particles stirred into the stir zone are varied. Moreover, the failure loads of the joints also vary with relevant to the rpm of the tool. The results of the analysis show that the specimen joint made with 1,400 rpm tool rotation and feed rate of 32 mm/min has achieved higher mechanical properties, better metal dispersion with poor defects. Finally, the direction of future research and potential applications are examined and explained.

A case study of mechanical and metallurgical properties of friction stir welded AA6063 AMC

This experimental work deals with the comparative examination of microstructural and mechanical properties of as cast and friction stir welded, AA6063/SiC matrix composite. AA6063/10.5 wt. % SiC aluminium matrix composite was produced by employing stir casting route. Specimen Plates having thickness 6mm were cut from the fabricated composite matrix and friction stir welded successfully. The friction stir welding (FSW) was performed by using a tool rotational rate of 1400 rpm and tool transverse rate of 124 mm/min. A square pin profiled tool made of AISI H13 tool steel was used. The microstructural study revealed that FSW produced a notable reduction in the size of reinforcement agents and their homogeneous distribution in the stir zone as compared to the base metal composite matrix. Frictional heat generated during FSW had impacts on the growth, dissolution and reprecipitation of the hardening precipitates. The microstructural changes resulted in improved mechanical properties. The scanning electron microscopic (SEM) fracture analysis revealed that the fracture behaviour was changed from ductile to brittle after FSW.

A case study of mechanical and metallurgical properties of friction stir welded AA6063 AMC

This experimental work deals with the comparative examination of microstructural and mechanical properties of as cast and friction stir welded, AA6063/SiC matrix composite. AA6063/10.5 wt. % SiC aluminium matrix composite was produced by employing stir casting route. Specimen Plates having thickness 6mm were cut from the fabricated composite matrix and friction stir welded successfully. The friction stir welding (FSW) was performed by using a tool rotational rate of 1400 rpm and tool transverse rate of 124 mm/min. A square pin profiled tool made of AISI H13 tool steel was used. The microstructural study revealed that FSW produced a notable reduction in the size of reinforcement agents and their homogeneous distribution in the stir zone as compared to the base metal composite matrix. Frictional heat generated during FSW had impacts on the growth, dissolution and reprecipitation of the hardening precipitates. The microstructural changes resulted in improved mechanical properties. The scanning electron microscopic (SEM) fracture analysis revealed that the fracture behaviour was changed from ductile to brittle after FSW.

Effects of friction stir processing and minor Sc addition on the microstructure, mechanical properties, and damping capacity of 7055 Al alloy

This study investigated the effects of friction stir processing (FSP) and addition of 0.25% (mass ratio) Sc on the microstructure, mechanical properties, and damping capacity of AA 7055 alloy. Microstructure analyses revealed that a low tool rotation rate of 300rpm effectively inhibited the grain coarsening in the recrystallization of the alloy during FSP. Sc addition prevented the coarsening of grains and precipitated η phase and the annihilation of dislocations in the FSP AA 7055 alloy. After being subjected to FSP at 300rpm, the AA 7055 alloy containing Sc exhibited good mechanical and damping properties, which were mainly attributed to the fine recrystallized grain structure, fine precipitated η phase, and large number of nano-sized Al3(Sc, Zr) particles located at the grain boundaries and dislocations. This work provides an effective strategy for preparing commercial Al alloys with excellent damping capacity and mechanical properties.

Mechanical properties optimization of AZX612-Mg alloy joint by double-sided friction stir welding

AZX612 (Mg-6% Al-1% Zn-2% Ca) non-combustive magnesium alloy joints formed by asymmetric double-sided friction stir welding with different lower tool rotation rates were investigated. Compared with the conventional one-sided friction stir welding, joints fabricated by the asymmetric double-sided friction stir welding showed better tensile strength and elongation values. EBSD observations of the stir zone indicate that the stir zone formed at the upper and lower tool rotation rates of 600rpm and 500rpm exhibits the lowest 〈0001〉 texture intensity thereby showing the best balance of tensile strength and ductility. With defect-free joining parameters, the complexity of the material flow caused by the asymmetric layout of the double tools needs both a small difference between the upper and lower tool rotation rates and a proper heat input.

Improving joint performance of friction stir welded wrought Mg alloy by controlling non-uniform deformation behavior

Macroscopic non-uniform deformation is usually found in deformed joints of friction sir welded (FSW) wrought Mg alloys, detrimental to the joint performance. In the present work, two kinds of FSW joints with different stirred zone (SZ) structures were generated for extruded AZ31 plates. Comparative studies were conducted aiming to unravel the underline mechanism of the non-uniform deformation and their effect on tensile properties. It was found that the occurrence of non-uniform deformation was associated with the special texture distribution and twinning behavior in the SZ. The shape of concave sub-regions in the SZ coincided with the distribution area of extension twins. Texture evolution showed that consistent lattice rotation occurred across the SZ during tensile process. Schmid factor analysis revealed the role acted by basal slip and extension twinning in sub-regions at various deformation stages. In addition, the non-uniform deformation behavior could be suppressed by modifying the texture distribution through increasing the tool rotation rate, which meanwhile could improve both the tensile strength and ductility of the joints. Digital image correlation measurements provided detailed examination of the actual strain distribution evolved in the joints and demonstrated the dominant contribution of strain localization to the tensile properties.

Effect of welding parameters and B4C contents on the microstructure and mechanical properties of friction stir welded B4C/6061Al joints

Annealed 2.8mm thick B4C/6061Al composite sheets with various B4C particle contents (15, 20, 25, 30wt%) were friction stir welded (FSW) at a tool rotation rate of 1000rpm and traverse speeds of 50 and 150mm/min using a single simple-shaped wear-resistant cermet tool. Sound FSW joints were obtained without severe abrasion of the tool. FSW resulted in obvious homogenization and fragmentation of B4C and the re-distribution of the interfacial products, thereby remarkably increased the hardness of the nugget zone. The hardness profiles of the welded joints were hardly influenced by B4C contents but significantly by the welding speeds. “S” line and a B4C depleted region were formed at the top and the bottom of the nugget zone, respectively. However, they did not deteriorate the mechanical properties of the joints. The tensile strength of all the joints was close or even up to that of the base material with the fracture occurring at the base material.

Process mechanics in Friction Stir Extrusion of magnesium alloys chips through experiments and numerical simulation

Friction Stir Extrusion (FSE) is a novel process designed to directly recycle machining chips. An experimental campaign was carried out on AZ31 milling chips using variations in extrusion ratio, force and tool rotation rate. The process mechanics were studied and correlated to the material flow, which was elucidated through use of a copper marker. A 3D, Lagrangian, thermo-mechanically coupled dedicated numerical model was set up and validated through temperature measurements. The combination of experimental and numerical results permitted to reconstruct the complex 3D material flow induced by tool rotation and plunge into the extrusion billet chamber.

Simultaneously improving mechanical properties and damping capacity of Al-Mg-Si alloy through friction stir processing

In this study, friction stir processing (FSP) was performed on an Al-Mg-Si alloy (AA 6082-T4) at a low tool rotation rate of 200rpm, and good mechanical and damping properties were simultaneously obtained after FSP. The combination of excellent ductility, moderate strength and excellent room/high temperature damping capability at FSP sample was attributed to the ultrafine recrystallized grains with predominant high-angle grain boundaries and moderate dissolution of metastable phases, and the fragmentation of micron-sized second phase during FSP. This work provided an effective strategy to improve the damping capacity of commercial Al alloys without sacrificing their mechanical properties.

Effect of friction stir processing on tensile and fracture behaviour of AZ91 alloy

Multipass friction stir processing (FSP) was performed on as-cast (AC) AZ91 magnesium alloy with different tool probe lengths to introduce layered microstructure through the thickness. Three microstructural variations were developed. They were, half thickness fine grain microstructure (HFG), surface modified-fine grain microstructure (SFG) and full thickness fine grain microstructure (FFG). FSP was performed at tool rotation rate of 720rpm and transverse speed of 150mm/min. The coarse α-Mg dendrites of 100μm were refined to approximately 2μm. Network of β-Mg17Al12 interdendritic particles were broken and distributed uniformly after multipass FSP. Tensile test and notch fracture toughness test were conducted to understand the effect of layered microstructure on mechanical properties. The tensile properties, namely, yield strength, tensile strength and percentage elongation of AC material were found to be 92MPa, 100MPa and 0.8% respectively and the corresponding values for FFG were improved to 242MPa, 327MPa and 4.7%. For HFG and SFG, these values were found to follow the rule of mixture. Similarly, apparent fracture toughness (KQ) values of single edge notch bend (SENB) specimen without precrack were compared and the results showed improvement from 6.2MPa√m in AC to 12.3MPa√m in FFG.

Characterization of the Microstructure, Mechanical Properties, and Corrosion Resistance of a Friction-Stir-Welded Joint of Hyper Duplex Stainless Steel

This study investigates the microstructure, mechanical properties, and corrosion resistance of a friction-stir-welded joint of the hyper duplex stainless steel SAF2707. Friction stir welding (FSW) is performed at a tool rotation rate of 400 rpm and a welding speed of 100 mm/min. The microstructure of the joints is examined using scanning electron microscopy and X-ray diffraction. Tensile test and fractography are subsequently employed to evaluate the mechanical properties of the joints. Results show that the grain size of the stir zone (SZ) is smaller than that of the base metal (BM). Electron back-scattered diffraction analysis reveals that fine-equiaxed grains form in the SZ because of the dynamic recrystallization during the FSW. These grains become increasingly pronounced in the austenite phase. The tensile specimens consistently fail in the BM, implying that the welded joint is an overmatch to the BM. Moreover, the welded joints consist of finer grains and thus display higher tensile strength than their BMs. Potentiodynamic polarization curves and impedance spectroscopy both demonstrate that the corrosion resistance of the SZ is superior to that of the base material.

Effect of backing material and clamping system on the tensile strength of dissimilar AA7075-AA2024 friction stir welds

Friction stir welding of dissimilar aluminum alloys has become an important application in the modern industries. Joint strength is a major consideration in this advanced technology. This paper presents an attempt made to improve the weld tensile strength by controlling the temperature distribution during the joining process. High-strength AA7075-T651 and AA2024-T351 aluminum alloys were friction stir welded using different backing and clamping materials. The tool rotation rate was preliminarily investigated to estimate the optimal spindle speed. Next, three composite backing plates and clamping systems were tested in conjunction with varying levels of traverse speeds and materials position. The transient temperatures were experimentally measured at different distances from the welding line. Asymmetric temperature distributions were observed with maximum records on the advancing side of the weld. Moreover, the influence of backing and cover materials on the joint strength was found to be varied with the applied level of the welding traverse speed. Based on these results, an idea to use asymmetric system of backing and cover materials was inspired. This system assisted to improve the temperature distribution and resulted in a sound weld with higher tensile strength. The detailed results of this work were discussed and the main outputs were outlined in the conclusions.