Ultrasonic-assisted Electrical Discharge Research Articles

Surface integrity of Ti-6Al-4V alloy in hybrid electrical discharge machining processes

Titanium alloy is one of the difficult-to-machine materials. The final conditions of the machined surface of this alloy are influenced by electro-discharge machining. High temperatures and thermal cycles in machining operation induce undesirable alterations in the surface quality of Ti-6Al-4V. One of the ways to improve the negative effects of electrical discharge machining is to use hybrid methods. There is no comprehensive research on the effect of hybrid electrical discharge machining process on the surface integrity of the Ti-6Al-4V alloy. In this paper, hybrid electrical discharge machining techniques including ultrasonic-assisted electrical discharge machining, powder-mixed dielectric electrical discharge machining using Al2O3 nanopowders and powder-mixed dielectric combined with ultrasonic-assisted electrical discharge machining, were used for processing of this alloy. The hybrid electrical discharge machining processes were evaluated by basic specifications of surface integrity including surface cracks, heat affected area, residual stress, and corrosion resistance. It was found that in powder-mixed dielectric combined with ultrasonic-assisted electrical discharge machining process, developed microcracks were very low and this process developed a thinner heat-altered layer, compared to traditional electrical discharge machining process, which produced a thicker heat-altered layer. The findings also, demonstrated that ultrasonic waves have reduced residual stresses compared to other methods and its stress diagram was distinct in comparison with the other processes. The corrosion rate of samples machined by electrical discharge machining process was higher than other hybrid processes; in powder-mixed dielectric electrical discharge machining process, the machined samples had the highest corrosion resistance.

The numerical research on the effect of ultrasonic field on metallic powders produced by the ultrasonic-assisted electrical discharge process

The numerical research on the effect of ultrasonic field on metallic powders produced by the ultrasonic-assisted electrical discharge process

The effect of focused ultrasonic power on particles produced by the ultrasonic-assisted electrical discharge process

Metallic micro-powder mixed nanoparticles are applied as original materials in additive manufacturing (AM) and powder sintering because of the thermodynamic size effect of nanoparticles. Mechanical properties can be improved by using high density powder. The ultrasonic-assisted electrical discharge is a green and easily controlled method to generate mixed metallic powder. A new lab-made device was designed and experiments were carried out to investigate the influence of focused ultrasonic power on the dense degree and size distribution of particles. It is found that nickel particles with larger size and higher dense degree were generated by the high-density ultrasound-assisted process. The ultrasonic shock wave generated an instantaneous great force and high temperature to lead the collision and sinter between particles, which results in forming a sinter neck between particles with a large size. Meanwhile, the size and dense degree of particles increased with the increase of sound intensity.

Comparative evaluation of powder-mixed and ultrasonic-assisted rough die-sinking electrical discharge machining based on pulse characteristics

Electrical discharge machining is used in the machining of complicated shapes in hardened molds and dies. In rough die-sinking stage, attempts are made to enhance material removal rate with a consequential reduction in cycle time. Powder mix and ultrasonic assistance are employed in the electrical discharge machining process to create gap conditions favoring material removal. In the present work, experiments are carried out on hardened D3 die steel using full-factorial design based on three levels of voltage, current and pulse on time. The gap phenomena in graphite powder-mixed and ultrasonic-assisted rough electrical discharge machining are studied using a detailed analysis of pulse shapes and their characteristic trains. Two new parameters, namely, energy expended over a second ( E) and performance factor ( PF) denoting the ratio of energy associated with sparks to total discharge energy, bring out gap conditions effectively. In comparison with the conventional electrical discharge machining for the selected condition, it is seen that the graphite powder mixed in the dielectric enhances the material removal rate by 20.8% with E of 215 J and PF of 0.227, while these values are 179.8 J and 0.076 for ultrasonic-assisted electrical discharge machining with marginal reduction of 3.9%. Cross-sectional images of workpieces also reveal the influence of electrical discharge machining conditions on the machined surface. The proposed approach can be extended to different powder mix and ultrasonic conditions to identify condition favoring higher material removal.

Productivity of EDM Process Assisted by Ultrasonic Waves

Ultrasonic assisted electrical discharge machining (USEDM) is one of hybrid machining methods based on the EDM process. The effects of ultrasonic waves on EDM process were analyzed and the experimental investigation of productivity of steel induced by USEDM was reported. Results indicated that ultrasonic waves and cavitation played an important role in improving the flushing and machining efficiency during USEDM. And the material removal rate of EDM assisted by ultrasonic waves was improved greatly.

Numerical study on the effect of the frequency and amplitude of the tool on the material removal rate in ultrasonic-assisted electrical discharge machining

This paper investigates the effects on the rate of material removal of the frequency and amplitude of the ultrasonic vibration of the tool used in ultrasonic-assisted electrical discharge machining. It is shown that increases in the amplitude and frequency of the tool vibration increase the rate of pressure drop inside the bubble and consequently increase the rate of pressure drop on the surface of the workpiece. The latter facilitates the escape of the molten material from the crater and consequently increases the rate of material removal from the workpiece.

Comparative Study and Mathematical Modeling of Machining Parameters in Ultrasonic-Assisted EDM of AISI H13 Tool Steel by the Application of Workpiece Vibration

The correct selection of the machining parameters is one of the most significant issues to take into consideration in Ultrasonic-assisted Electrical Discharge Machining (US-EDM) and EDM processes. In the present work, a study has been made to develop and extract statistical models to show the relationship between important machining performance data (material removal rate (MRR), tool wear ratio (TWR) and surface roughness Ra) and the input machining parameters (pulse current, and pulse-on time) in the EDM and US-EDM of AISI H13. The models obtained were used to analyze the effects of input parameters on machining performance. In addition, a comparative study was carried out to investigate the effect of ultrasonic vibration of the workpiece on machining performance. The results show that Ultrasonic vibration of the workpiece can significantly reduce the inactive pulses and improves the stability of process. Also US-EDM is effective in attaining a high material removal rate (MRR) in finishing regime in comparison with conventional EDM. The results of Analysis of Variance (ANOVA) indicate that the proposed mathematical models can adequately explain the performance within the limits of the factors being studied.

Mathematical modelling and comparative study of the machining characteristics in ultrasonic-assisted electrical discharge machining of cemented tungsten carbide (WC—10%Co)

The phenomena occurring between the electrodes in electrical discharge machining (EDM) are still not fully understood. Poor quantitative knowledge of the sources of variability affecting this process hinders the identification of its natural tolerance limits. This paper presents a systematic methodology for developing statistical models to show the relationship between important machining performance data (material removal rate (MRR), tool wear ratio (TWR), and surface roughness Ra) and the input machining parameters (pulse current and pulse-on time) in the EDM and ultrasonic-assisted EDM (US/EDM) of tungsten carbide. The models obtained were used to analyse the effects of input parameters on machining performance. A comparative study was conducted to determine the influence of ultrasonic vibration of the tool on machining performance. The results show that the MRR is significantly increased in ultrasonic-assisted EDM of cemented tungsten carbide (WC—10%Co), especially in finishing modes, and can be up to four times greater than that of conventional EDM. The TWR and Ra values are also increased slightly in US/EDM. The mathematical models presented can be used for optimization of the machining parameters.

An investigation of ultrasonic-assisted electrical discharge machining in gas

This study focuses on using ultrasonic to improve the efficiency in electrical discharge machining (EDM) in gas medium. The new method is referred to as ultrasonic-assisted electrical discharge machining (UEDM). In the process of UEDM in gas, the tool electrode is a thin-walled pipe, the high-pressure gas medium is applied from inside, and the ultrasonic actuation is applied onto the workpiece. In our experiment, the workpiece material is AISI 1045 steel and the electrode material is copper. The experiment results indicate that (a) the Material Removal Rate (MRR) is increased with respect to the increase of the open voltage, the pulse duration, the amplitude of ultrasonic actuation, the discharge current, and the decrease of the wall thickness of electrode pipe; and (b) the surface roughness is increased with respect to the increase of the open voltage, the pulse duration, and the discharge current. Based on experimental results, a theoretical model to estimate the MRR and the surface roughness is developed.

A theoretical model of surface roughness in ultrasonic vibration assisted electrical discharge machining in gas

A new method, named Ultrasonic vibration assisted electrical discharge machining (UEDM) in a gas environment is proposed in this paper. It is shown that ultrasonic assisted electrical discharge can be achieved well in a gas medium. The tool electrode is made of a thin-walled pipe, and the high pressure gas medium is supplied from inside. During machining, ultrasonic vibration of the workpiece can improve the process. A theoretical model to estimate the roughness of the finished surface has been developed. AISI 1045 steel and copper are selected as the workpiece material and electrode material respectively. Experiments have been carried out, and the results show that the roughness of finished surface increases with an increase in the discharge voltage (Ue), the discharge current (Ie) and the pulse duration (tS ).