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Tool geometries and plunge depth play significant roles in the stirring process involved in micro-friction stir spot welding (µFSSW). These two variables affect the hook and joint formation, which influence the static strength and failure mode characterization of a single spot weld. The present work investigated the influence of tool geometry and plunge depth on the static strength and the failure mode characterization in an AA1100 lap-shear joint with a 0.42-mm thickness by examining the macrostructure and mechanical properties. Seven tool designs and three plunge depth variations were applied to investigate the evolution of the hook and joint formation in each tool design and to determine the influence of the size and geometry on joint characteristics, respectively. Seven tool designs and three plunge depth variations were executed to obtain the highest tensile shear load. The regression and prediction interval analysis uncovered a correlation between tensile shear load (i.e., the maximum load) and real plunge depth. The results indicated that the formation of a hook, such as a straight or bending shape, depended on the features of the stir zone, which was affected by the tool's geometry. The hook's shape and location determined the possibility of the crack propagation path and ultimately affected the maximum load. The highest average max load was achieved for Tool 2 at total welding time (TWT) of 10 s at 330–400 µm, and Tool 7 had the lowest among all the tools. Partial interfacial fracture (PIF) is a failure mode that has high joint strength, while pullout fracture (PF) is a failure mode that is considered to have medium joint strength. A conversion equation has been proposed to reveal the influence of tool geometry on the max load by considering the shoulder size, thickness, and material properties. [ABSTRACT FROM AUTHOR]

This study investigated the mechanism of UVAD using numerical and analytical techniques. Silicon wafers possess challenging cutting properties due to their inherent brittleness and susceptibility to cracking along specific crystal orientation. Hence, non-traditional cutting methods like UVAD hold promise for precision micro-hole drilling in silicon wafers. In order to comprehend the mechanism of UVAD, the numerical technique utilized a direct brittle micro-cracking model within a 2D finite element (FE) method. This facilitated a comparative analysis between conventional drilling (CD) and UVAD, with a specific focus on understanding the micro-cracking mechanisms during the mechanical process. This study examined primarily the cutting force, micro-fracture analysis, and cutting energy. The numerical technique effectively predicted micro-cracks within the brittle regime, a task that is challenging to accomplish using analytical methods alone. In parallel, an analytical technique was developed to predict brittle-ductile transition (BDT) lines by analyzing the thrust force and specific cutting energy (SCE), combined with the numerical technique. Various feed rates per revolution were tested to validate the analytical force predictions. The analytical results demonstrate that the force profile corresponds to the transient cutting depth, while the numerical results indicated that the direct brittle micro-cracking model effectively demonstrated the fracture mechanisms, particularly at greater depths of cut. The SCE graph can predict the formation of a ductile regime on the cutting surface of the drilled micro-hole, although predicting micro-fractures on the side edges of the drilled micro-holes remains challenging. Additionally, UVAD demonstrated a reduction in micro-fractures on the sides of drilled micro-holes, particularly at very low feed rates per revolution. [ABSTRACT FROM AUTHOR]

An investigation of micro friction stir spot welding (μFSSW) of 0.42-mm-thick AA1100 sheets has been performed under high-speed tool rotation. This study aimed to determine the effect of the plunge rate and dwell time on the thermal history and the axial force during the welding process, and also optimizing plunge rate and dwell time to obtain the good result of the weld joint strength. Thermal histories and axial force histories during μFSSW experiments were obtained. Both showed that increasing the dwell time has no significant effect on increasing the maximum temperature at the center of the weld and the axial force. The plunge rates were the major cause of the hardening and softening of the material in the plunging stage. However, the tensile shear test results indicate that the dwell time plays a major role in increasing the tensile shear strength, while the plunge rate has a minor effect on the tensile strength. The macrostructural observation was also performed to study the hook formation and stirred zone width of μFSSW. Furthermore, the correlation of the hook shape to failure propagation has been carried out. [ABSTRACT FROM AUTHOR]

This paper presents an automated or intermittent wire feeding method in tungsten inert gas (TIG) welding. The preliminary investigation shows the macrostructure, microstructure, and mechanical property effects on various welding parameters using one combination proportion of filler metal with various welding parameters. The result of microstructure has shown that the localized segregation occurred at the center area weld metal with high-density eutectic phase and energy dispersive X-ray spectroscopy (EDS) study has found that Mg content was higher compared to the outside region. Other sample microstructure shows columnar structure was formed in dilution boundaries, and it reveals that fast cooling rates happened when the filler wire was inserted. Also, microstructure on weld traverse section shows that the wavy-like structure depended on the heat input. The fracture mode shows that lack of heat input is susceptible to oxidation; therefore, the fracture tends to occur at weld metal in the brittle manner with reduced strength of more than 40%. Also this article presented the method to calculate length ratio (RL) and the volume ratio (RV) to estimate the minimum value of ratio under the condition of a good welded surface profile. [ABSTRACT FROM AUTHOR]

A new configuration of permanent magnet as a source of external magnetic field has been established to an autogenous tungsten inert gas (TIG) welding. The external magnetic field is generated by rectangle shape NdFeB permanent magnets of 260 mT and arranged in cups-type magnetic field (CMF). A charge-coupled device (CCD) is applied to monitor the phenomenon of the arc shape. The material used in this experiment is SS304 with a thickness of 2 mm. This study aims at investigating the effect of external magnetic field towards the arc shape and finding the configuration, which can reduce the power consumption and improve penetration. A significant effect on the improvement of welding efficiency can be achieved by using PR-NNSS-SD (50 or 70 mm), PP-NNSS-SD (70 or 90 mm), or PP-NSNS-Pull (50 mm). These configurations can reduce the power consumption up to 11%. [ABSTRACT FROM AUTHOR]

This research report deals with an experimental and analytical study of the ultrasonic elliptical vibration cutting (UEVC) process on medium steel alloy (AISI 1045) for sustainable machining of round-shaped (R-shaped) microgrooves via relatively low-speed machining (0.5-2.5 m/min). The need for microgroove patterns on planar surfaces in the tribology field has increased significantly owing to superior lubrication performance in decreasing the coefficient of friction. Analyzing the surface roughness, microgroove morphology, cutting force, and chip formation during microgrooving are the main objectives of this experimental study. The experimental results showed that the UEVC process evidently produces lower surface roughness, lower cutting forces, better groove shape morphology, thinner chip thickness, and higher flow shear angle when compared to the conventional cutting process. A new approach in methods to analyze surface roughness and cutting force in UEVC microgrooving has also been developed and validated with the experimental results. Finally, these experimental studies indicate the achievement of sustainable machining of the R-shaped microgroove pattern using the UEVC process. [ABSTRACT FROM AUTHOR]

This paper presents a new method to determine the cutter-workpiece engagement (CWE) for a toroidal cutter during free-form surface machining in five-axis milling. A hybrid method, which is a combination of a discrete model and an analytical approach, was developed. Although the workpiece surface was discretized by a number of normal vectors, there was no calculation to determine the intersection between the normal vector and the cutting tool. The normal vectors were used to define the workpiece surface mathematically; next, the engagement point was calculated using a combination of the workpiece surface equation, the parametric equation of the cutting tool, and the tool orientation data. Three model parts with different surface profiles were tested to verify the validity of the proposed method; the results indicated that the method was accurate. The method also eliminated the need for a large number of discrete vectors to define the workpiece surface. A comparison showed that the proposed method was computationally more efficient. The CWE model was subsequently applied to support the cutting force prediction model. A validation test demonstrated that in terms of trends and amplitudes, the predicted cutting forces exhibit good agreement with the cutting force generated experimentally. [ABSTRACT FROM AUTHOR]