Study on Generating Machining Performance of Two-Dimensional Ultrasonic Vibration-Composited Electrolysis/Electro-Discharge Technology for MMCs

Ultrasonic vibration-composited electrolysis/electro-discharge machining technology (UE/DM) is effective for machining particulate-reinforced metal matrix composites (MMCs). However, the vibration of the tool or workpiece suitable for holes limits the application of UE/DM. To improve the generating machining efficiency and quality of flat and curved surfaces, in this study, we implemented two-dimensional ultrasonic vibration into UE/DM and constructed a novel method named two-dimensional ultrasonic vibration-composited electrolysis/electro-discharge machining (2UE/DM). The influence of vibration on the performance of 2UE/DM compared to other process technologies was studied, and an orthogonal experiment was designed to optimize the parameters. The results indicated that the materiel remove rate (MRR) mainly increased via voltage and tool vibration. The change current was responsible for the MRR in the process. Spindle speed and workpiece vibration were not dominant factors affecting the MRR; the spindle speed and tool and workpiece vibration, which reduced the height difference between a ridge and crater caused by abrasive grinding, were responsible for surface roughness (Ra) and form precision (δ). Additionally, the optimized parameters of 1000 rpm, 3 V, and 5 um were conducted on MMCs of 40 SiCp/Al and achieved the maximum MRR and minimum Ra and δ of 0.76 mm3/min, 3.35 um, and 5.84%, respectively. This study’s findings provide valuable process parameters for improving machining efficiency and quality for MMCs of 2UE/DM.

EFFECT OF THE TOOL SURFACE AREA AND WORKPIECE VIBRATION ON THE μEDM PERFORMANCE

This work investigates the influence of tool surface area (TSA) on the average surface roughness ([Formula: see text], tool wear rate (TWR) and material removal rate (MRR) in the micro-electrical discharge machining ([Formula: see text]EDM). The effects of three different TSAs were investigated at three different discharge energy settings. It was observed that the TSA had substantial influence on [Formula: see text]EDM performance owing to scaling effect. Therefore, the low-frequency workpiece vibration was applied to improve the [Formula: see text]EDM performance. The surface topography of machined surfaces was examined using scanning electron microscopy to disclose the effect of TSA as well as vibration frequency on [Formula: see text]EDMed surfaces.

Workpiece Vibration in Feed Direction Assisted Electrochemical Cutting Using Tube Electrode With Inclined Holes

Electrochemical cutting using tube electrode with inclined holes is a machining method that directly and obliquely injects electrolyte into the machining gap through inclined jet-flow holes on the sidewall of a tube electrode, allowing the electrochemical cutting of a workpiece. To improve the machining efficiency and accuracy of this cutting technique, a method of workpiece vibration in feed direction assisted electrochemical cutting is proposed in which workpiece vibration along the feed direction rapidly and periodically changes the machining gap. The near-instantaneous increases in the machining gap promotes the waste electrolyte containing electrolytic products to flow down the machining gap. At the same time, the electrochemical reaction time under the non-uniform flow field caused by the inclined downward injection of electrolyte is reduced. The flow field simulation of electrolyte in machining gap indicates that the near-instantaneous increases in the machining gap can improve the flow velocity of electrolyte. Experiment demonstrates that the average feed rate can be increased by 50% and the machining efficiency is superior to that of electrochemical cutting assisted by workpiece non-vibration in feed direction. The difference between the upper and lower slit widths is reduced and the machining accuracy is improved. The effect of the vibrational amplitude and frequency on the machining result is also investigated. Finally, an array slice structure is fabricated on a stainless steel block with a cross-section of 10 mm × 10 mm at average feed rate of 6 mm/s using a vibrational amplitude and frequency of 0.1 mm and 1.5 Hz, respectively.

Application of Alternative Support Fixture System in Vibration Suppression of Thin-Walled Parts

The machining vibration of thin-walled parts affects the quality of the products. Thus, this paper proposes a new alternative support fixture system for vibration suppression of thin-walled parts. The system includes two movable supporting heads, which are periodically repositioned along the machining path in the form of alternating support to support the area close to the cutter, so as to improve the rigidity of the actual machining position of the thin-walled part. Around this new system, a dynamic model is established to analyze the workpiece vibration. Takeing as an example simply suppoted thin-plate, the influence of the supporting head’s location, stiffness coefficient and damping coefficient on vibration suppression are numerically analyzed in this paper. The result of the simulation demonstrates the alternative support fixture system is effective in vibration suppression of thin-walled parts.

Metallurgical Characterization of Penetration Shape Change in Workpiece Vibration-Assisted Tandem-Pulsed Gas Metal Arc Welding

Tandem-pulsed gas metal arc welding (TP-GMAW) simultaneously uses two wire-electrodes to enhance the material deposition rate, leading to the generation of a finger-shaped penetration as one of the arcs penetrates deeper than the other. On the other hand, workpiece vibration is one of the techniques used to control the microstructure of weld metal and a heat-affected zone. It is incidentally found that a specific vibration condition changes the finger-shaped penetration into pan-bottom shaped penetration in the TP-GMAW even though the vibration energy is much lower than the arc energy. Microstructure observation and elemental analysis are carried out for the welds fabricated without vibration and with three kinds of vibration modes, namely sine, random, and shock. The specific sine-mode vibration exhibits pan-bottom. The other modes of vibration in the same welding conditions exhibited invariable finger-shaped penetration. The Si atoms as a tracer distribute uniformly in the sine-mode. However, Si atoms segregate at the bottom of the finger-shaped weld metal with the random-mode and shock-mode workpiece vibrations. The weld pool shape change is prominent at a specific frequency. A resonance phenomenon between the droplet flow pattern and the molten material flow in the weld pool is likely to play a vital role in the change.

On-Machine Measuring Instrument of Workpiece Compliance Using Laser Interferometer

Workpiece vibration is a crucial issue in machining of thin-walled workpieces because of their large compliance. The workpiece compliance should be considered in setting machining conditions to suppress the vibration. However, the conventional impact test is laborious, and its result depends on the operator’s skill. In this study, an on-machine measurement instrument was developed to measure the compliance of thin-walled workpieces. The developed measuring instrument can be attached to the machine tool spindle for automatic compliance measurement. The workpiece compliance measured by a swept sine excitation using the developed instrument was comparable to the compliance by the conventional impact test.

New method to enhance the mechanical characteristics of Al-5052 alloy weldment produced by tungsten inert gas

Tungsten inert gas welding method is widely used to weld aluminum alloys. However, the development of some defects such as porosity and undercutting which form during tungsten inert gas welding may decrease the quality of the weld. Processing of the joint by friction stir processing is a method to enhance weld quality. In the current work, the weld area produced by tungsten inert gas is processed by friction stir processing as well as a novel processing method entitled “friction stir vibration processing.” In friction stir vibration processing, the specimen is vibrated while friction stir processing is carried out. The results show that both processing methods lead to grain refinement in the weld region and increase the strength and ductility of the tungsten inert gas–welded specimen. The stir zone grain sizes of friction stir vibration–processed samples are less than those of friction stir–processed ones. It is believed that workpiece vibration in friction stir vibration processing increases the material straining and intensifies the dynamic recrystallization. By application of friction stir processing on tungsten inert gas–welded specimen, ultimate tensile strength and ductility increase by about 10% and 22%, respectively. They increase by about 17% and 33%, respectively, as friction stir vibration processing is applied. The results also indicate that the effect of friction stir vibration processing on the microstructure of the weld region and its mechanical properties increases as vibration frequency increases. Friction stir vibration processing is a good alternative for friction stir processing, and it is recommended for application in industry.

The investigation into vibration effect on microstructure and mechanical characteristics of friction stir spot vibration welded aluminum: Simulation and experiment

In this study, an innovative technique is employed to modify the microstructure and increase the mechanical characteristics of the Al5083 joint made by friction stir spot welding (FSSW). In this technique entitled FSSVW (friction stir spot vibration welding), the workpiece is vibrated during FSSW. Noted processes were modeled and finite element simulation results were also analyzed. The results showed that workpiece vibration during FSSW led to grain refinement, larger weld region, and improvement of the mechanical properties, namely tensile shear strength and hardness, of the joint. Stir zone grain size decreased by about 25% and tensile shear strength value increased by about 20% by applying workpiece vibration during FSSW. The results also indicated that the tensile shear strength and hardness enhanced, as vibration frequency increased. It was concluded that the presence of vibration increased the material deformation in the stir zone and led to enhanced deformation of the material. This intensified the dynamic recrystallization and resulted in grain refinement. It was also found that tensile residual stresses developed in the stir zone of FSS and FSSV welded specimens and tensile residual stress values for FSSV welded specimens were higher than those for FSS welded specimens for about 10%. It was concluded that the effect of grain size on hardness is higher than the effect of residual stress. Higher ductility is predicted for FSSV welded specimen with higher vibration frequency and also for specimen welded with less dwell time; finite element simulation was also applied to analyze the effects of workpiece vibration during FSSW on strain distribution as well as hardness and residual stress distribution within the joint during FSSW and FSSVW processes. Finite element simulation results had good compatibility with experimental results. It was concluded that the strain values and flow velocity relating to the FSSVW process are higher than those relating to the FSSW process.