A literature survey on electrical-current-assisted friction stir welding

Electrical-current-assisted friction stir welding (EA-FSW) is a procedure developed for the joining of similar and dissimilar materials. EA-FSW is a newly invented solid-state process to increase welded components’ efficacy in various applications, such as marine structures. EA-FSW joints have investigated the dissimilar joints on aluminum–magnesium, aluminum–steel, and polymer-to-steel. Similar joints have been performed on aluminum, magnesium, and steel. The main parameters that affect the temperature of the nugget in EA-FSW are electrical current and tool rotational velocity. This review paper presents the fundamental principle of EA-FSW, its processes mechanism, and various types of tools, and discusses the different joints that EA-FSW welded. The effect of electrical current on the quality of similar and dissimilar joints is discussed. The simulation process and detailed modeling of the EA-FSW process are discussed in the last section

Effects of FSW Tool Plunge Depth on Properties of an Al-Mg-Si Alloy T-Joint: Thermomechanical Modeling and Experimental Evaluation

One of the main challenging issues in friction stir welding (FSW) of stiffened structures is maximizing skin and flange mixing. Among the various parameters in FSW that can affect the quality of mixing between skin and flange is tool plunge depth (TPD). In this research, the effects of TPD during FSW of an Al-Mg-Si alloy T-joint are investigated. The computational fluid dynamics (CFD) method can help understand TPD effects on FSW of the T-joint structure. For this reason, the CFD method is employed in the simulation of heat generation, heat distribution, material flow, and defect formation during welding processes at various TPD. CFD is a powerful method that can simulate phenomena during the mixing of flange and skin that are hard to assess experimentally. For the evaluation of FSW joints, macrostructure visualization is carried out. Simulation results showed that at higher TPD, more frictional heat is generated and causes the formation of a bigger stir zone. The temperature distribution is antisymmetric to the welding line, and the concentration of heat on the advancing side (AS) is more than the retreating side (RS). Simulation results from viscosity changes and material velocity study on the stir zone indicated that the possibility of the formation of a tunnel defect on the skin–flange interface at the RS is very high. Material flow and defect formation are very sensitive to TPD. Low TPD creates internal defects with incomplete mixing of skin and flange, and high TPD forms surface flash. Higher TPD increases frictional heat and axial force that diminish the mixing of skin and flange in this joint. The optimum TPD was selected due to the best materials flow and final mechanical properties of joints

Effects of Rapid Cooling on Properties of Aluminum-Steel Friction Stir Welded Joint

In this study, dissimilar sheets including AA3003 aluminum and A441 AISI steel were welded via cooling-assisted friction stir welding (FSW). Three different cooling mediums including forced CO2, forced water, and forced air were employed, and a non-cooled sample was processed to compare the cooling-assisted condition with the traditional FSW condition. The highest cooling rate belongs to CO2 and the lowest cooling rate belongs to the non-cooled sample as FSW. The best macrograph without any segregation at interface belongs to the water-cooled sample and the poorest joint with notable segregation belongs to the CO2 cooling FSW sample. The CO2 cooling FSW sample exhibits the smallest grain size due to the suppression of grain growth during dynamic recrystallization (DRX). The intermetallic compound (IMC) thickening was suppressed by a higher cooling rate in CO2 cooling sample and just Al-rich phase was formed in this joint. The lowest cooling rate in the FSW sample exhibits formation of the Fe rich phase. The IMC layers were thicker at the top of the weld due to closeness with the heat generation source. The water cooling sample exhibits the highest tensile strength due to proper mechanical bonding simultaneously with optimum IMC thickness to provide appropriate metallurgical bonding. Fractography observation indicates that there is a semi-ductile fracture in the water cooling sample and CO2 cooling sample exhibits more brittle fracture. Hardness evaluation reveals that the higher the cooling rate formed, the higher the hardness in stir zone, and hardness changes in the aluminum side were higher than the steel side

Fatigue properties of spot joints of metal-plastic composites with DP 800 steel prepared by ultrasound resistance spot welding

The aim of this work is to analyze the properties of spot joints of metal-plastic composites (Litecor) with DP 800 steel. The joints were made using ultrasound resistance spot welding technology. A metallographic analysis of the joints was carried out, and the basic areas of the weld structure were determined. The separation and decomposition of the polymer core was also illustrated, with no observed diffusion between the Litecor covers and the polypropylene core. Fatigue tests were the main goal of this work, therefore a fatigue curve was determined and the mechanisms of fatigue failure at various levels of fatigue load were analyzed. The tests were carried out at a frequency of 30 Hz, the cycle asymmetry coefficient was R = 0.1 and the limit number of cycles was 2 × 106. Fatigue failure mechanisms specific to particular levels of fatigue load were demonstrated, which were: 2.2, 1.9, 1.5, 1.2, and 1 kN. For joints subjected to fatigue shear has been demonstrated that the boundary between low-cycle and high-cycle fatigue is located at a cyclic shear stress level of approximately 132 MPa. However, with the assumed limit number of fatigue cycles, the fatigue shear strength was 70.576 MPa. Macro- and microscopic fractographic analysis was carried out for joints after fatigue tests in order to demonstrate the mechanisms of failure at individual levels of cyclic load.</p

A literature survey on electrical-current-assisted friction stir welding

Electrical-current-assisted friction stir welding (EA-FSW) is a procedure developed for the joining of similar and dissimilar materials. EA-FSW is a newly invented solid-state process to increase welded components’ efficacy in various applications, such as marine structures. EA-FSW joints have investigated the dissimilar joints on aluminum–magnesium, aluminum–steel, and polymer-to-steel. Similar joints have been performed on aluminum, magnesium, and steel. The main parameters that affect the temperature of the nugget in EA-FSW are electrical current and tool rotational velocity. This review paper presents the fundamental principle of EA-FSW, its processes mechanism, and various types of tools, and discusses the different joints that EA-FSW welded. The effect of electrical current on the quality of similar and dissimilar joints is discussed. The simulation process and detailed modeling of the EA-FSW process are discussed in the last section

Study on the effects of tool tile angle, offset and plunge depth on friction stir welding of poly(methyl methacrylate) T-joint

The effects of tilt angle (TTA), plunge depth (TPD) and offset (TO) of tool in friction stir welding of poly(methyl methacrylate) T-joint were investigated. To understand better the effects of process parameter, thermomechanical simulation of joint was assessed. The results seem to show that at higher TPD and TTA, frictional heat increases. Woven tissue structure joint line forms after friction stir welding of poly(methyl methacrylate) sheets. The distance of woven layers was affected by TPD and TTA, while TO do not significantly affect heat generation of joint. The best material flow and adequate heat are generated at 0 mm TA, 2� TTA and 0.2 mm TPD, respectively. The highest flexural and tensile strength of friction stir welded joint were approximately 93% and 90% of as-received poly(methyl methacrylate), respectively. Crack forking was detected on the fractured surface of flexural samples and crack path was detected in the vicinity of shrinkage holes at fracture surface of tensile samples. These holes and degradation of poly(methyl methacrylate) during friction stir welding process decrease strength and hardness of the joint. - IMechE 2019.Scopu

Investigation on polypropylene friction stir joint: effects of tool tilt angle on heat flux, material flow and defect formation

Tool tilt angle (TTA) is a critical factor that can control material flow in polymeric materials' friction stir joining (FSJ). This study selected a TTA range between 0° to 4° for FSJ of polypropylene (PP) polymer sheet. A modified computational fluid dynamic (CFD) technique was implemented to gain a deep understanding of the effects of TTA during FSJ of PP. The PP joint's internal flow, defect formation, heat generation, and tensile strength were investigated experimentally. The fracture surface of tensile samples was analyzed by scanning electron microscopy (SEM). Heat generation, heat flux, and defect formation results from simulation were evaluated by experimental tests output. The results indicate that the PP flow during FSJ is susceptible to TTA. Non-uniform volumetric weight transfer was caused at higher TTA in the joint line, which leads to tilted heat flux. At higher TTA, the generated heat increases, leading to PP exit from the joint line and internal gaps. According to selected parameters, the most robust joint (66 MPa) was produced at 1° TTA. The main reason for the mechanical properties of the PP joint was a dimension of the stir zone and internal defects. Shrinkage gaps were the root of crack initiation during the tensile test, and some local stretching in the fracture surface of the tensile sample after the test was detected

The effect of temperature and strain rate on the mechanical properties and microstructure of super Cr13 martensitic stainless steel

In this study, the formability of super Cr13 martensitic stainless steel (MSS) is examined by means of hot tensile tests at different temperatures (900oC-1100oC) and t strain rates (0.01s-1-10s-1). The potential effect of strain rates and temperatures on the mechanical properties, microstructure and fracture surface of super Cr13 MSS were examined. The post-test analysis, which includes hardness measurements, X-ray diffraction (XRD), fracture analysis by scanning electron microscope (SEM), and Energy-dispersive X-ray spectroscopy (EDS), was carried out. Results show that ultimate tensile stress (UTS) decreases with temperature, this way, the highest UTS was obtained at 900oC-10s-1 (187MPa), while the lowest UTS (38MPa) was obtained in the 1100oC-0.01s-1 sample. By contrast the elongation of the material increases with strain rate, since the elongation of the sample at 900oC-10s-1 was near 16% and the elongation of the sample at 1100oC-0.01s-1 was 57%. The XRD and EDS analysis indicated that Cr23C6 and Cr2N are formed inside the microstructure of samples tested between 900oC and 1000oC, and these carbides are dissolved above 1000º C. Temperature affects also retained austenite which increases with temperature. Fractography analysis indicated that the δ-ferrite phase has a primary role in high-temperature rapture. Fracture surface evaluation of samples revealed semi-ductile fracture behaviour below 1000°C and low strain rates, while ductile fracture was detected on the tensile samples at temperatures higher than 1000°C and high strain rates. Furthermore, the ductility of super Cr13 MSS was increased by increasing strain rate.Validerad;2023;Nivå 2;2023-07-20 (sofila)</p