Yukui Wang’s research while affiliated with Harbin Institute of Technology and other places

Cf-UHTC is an ideal aerospace material because of its exceptional properties, but its machinability is facing great challenges. Electrical discharge machining (EDM) offers a potential solution, but its removal mechanism remains unclear, lacking reliable prediction tools to guide the actual production. This paper deeply explores the EDM removal mechanism of Cf-ZrB2-SiC through single-pulse experiments, high-speed camera observations, and thermal–fluid coupling simulations, revealing key processes like heat transfer, phase transformation, molten pool dynamics, crater formation, and reinforcing phase effects. And the prediction of single-pulse removal with different parameters is also realized. Based on experimental and simulation results, a random continuous discharge model is developed, which deeply studies the dynamic erosion process, reconstructs EDM surfaces, and accurately predicts surface roughness. Furthermore, the thickness of the recast layer can be predicted based on the equivalent temperature method. Undoubtedly, this model provides an ideal approach for efficient production.

TiBw mesh reinforced titanium matrix composites were investigated by rotary ultrasonic grinding experiments using nickel-based electroformed diamond grinding wheel and building a single diamond abrasive grain model and a 2D rotary ultrasonic grinding finite element model. Surface residual stress is obtained by simulation and verified by univariate experiments. Combined with nanoindentation experiments, the changes of residual stress and hardness were acquired. The results show that the reinforced phase fibers will be subjected to high mechanical stress which break the fibers and turn into chips with matrix material. The residual stress of TiBw-rich region is closer to the actual value due to the high elastic modulus and low residual strain of TiB. Residual compressive stress around − 500MPa exists in the surface of workpiece under different process parameters. As the grinding depth increases, the residual stress increases first and then decrease. At the same time, the residual stress increases as the feed speed increase. And the residual stress decreases remarkably as the spindle speed increases. Meanwhile, the work hardening of workpieces changes similarly as the residual stress. The error between experiment and simulation is under 10%, which verified the effectiveness of the finite element model.

SiCp/Al, as a new material, is widely used for its excellent wear resistance, corrosion resistance and other properties. Micro-holes are important but difficult to obtain on this ceramic material especially in curved surface. In this paper, taking micro bearing bush as an example, a micro-EDM and in-situ micro-reaming method is put forward for preparing micro through holes and micro eccentric holes on SiCp/Al cambered surface, without secondary clamping or tool change. High machining efficiency, low wear and no recasting layer can be achieved by this method. Here, machining characteristics is studied in hole micro-EDM on SiCp/Al, small taper and high efficiency machining is realized by comparing four electrical discharge drilling technique. Carbon deposition and tool wear are related to electrical parameters according to experimental exploration. After determining the discharge gap, taper and recast layer thickness, a segmented tool is designed, which can use the lower part to perform micro-EDM with the taper of 1.04°, MRR is 0.069 mm3/min, and the TWR is 3.22%. Then only needs to continue feeding the tool, the upper part of the tool can be used to achieve reaming, which can fully remove the recast layer, and decreases the roughness of hole wall from Ra 1.452 μm to Ra 0.803 μm.

Cf-ZrB2-SiC is a new composite material with excellent properties for making the next-generation aerospace component. This material is extremely difficult to removal by mechanical machining, and there is a lack of research on feasible secondary processing methods of this composite at present. Micro-EDM is not limited by material hardness, so it is very suitable for machining this material. In this paper, the Material removal mechanisms and processing characteristics of Cf-ZrB2-SiC by micro-EDM is analyzed. The removal mechanism of composite materials is explored though the discharge crater morphology, and the single-discharge experiments of each phase materials with different medium and different energies are also carried out as a reference. Electrical discharge milling experiments of Cf-ZrB2-SiC are performed to explore the medium on processing index, and found that the best surface quality and maximum processing efficiency can be realized in kerosene. An experiment with four factors (pulse width, voltage, peak current, capacitance) and three indexes (surface roughness, MRR, TWR) is designed to analyze the Cf-ZrB2-SiC process characteristics of micro-EDM and the response surface diagram and second-order regression equation are obtained. Milling the Cf-ZrB2-SiC by electrical discharge according to the optimal combination of surface roughness parameters deduced above, the as-machined surface is analyzed including the surface morphology by SEM, element content by EDS and the surface phase by XRD. The feasibility and advantages of micro-EDM on machining Cf-ZrB2-SiC are prove.

This paper develops a new method to restrain the fracture of monocrystalline silicon machining in EDM (Electrical discharge machining) through controlling the topography of single discharge crater. By this method, the complex 3D micro-cavity can be machined without obvious fracture. The fracture of monocrystalline silicon in EDM was revealed according to the EDM pits and the machining debris, then it is inferred that there are two ways to cause fractures, one is the breakages at the edge of the effective-removing crater, and the other way is the deformation accumulation caused by the superposition of the ineffective-removing crater. Then, it was found that if the morphology of single discharge crater can be controlled, the less fracture can be guaranteed during the manufacturing. Using narrow pulse width discharge, plenty of experimental tests were carried out focused on carters and surface of monocrystalline silicon with different machining parameters, with the assistance of characterization and analysis. Using these new results, the complex 3D structure is machined by layered compensation strategy and step-by-step milling strategy. It is found from the as-machined complex 3D cavity that it has no obvious defects at the edges, and the fracture is controlled.

An integrated method of micro-milling and micro electrical discharge machining (EDM) is proposed for micro-structures array manufacture in this paper. In order to obtain micro-cavity array with high accuracy and consistency, in situ machining on the same coordinate system ensures the positioning precision. After studying micro-milling graphite, the effect of parameters on the machining accuracy is found. Further, suitable mode is chosen for high-dimensional consistency and good surface quality array electrodes according to comparison of one-by-one and layer-by-layer milling tool trajectory. Workpiece lifting control is used to strengthen the debris clear; then, it is verified beneficial of lifting through flow simulation and adding discrete particles. In order to solve poor precision of the micro-cavity contour caused by electrode wear, a multi-step machining by group electrodes is proposed, rough machining for material removal and finishing machining for trimming. Finally, a micro-cavity with clear edge, small fillets, and high shape accuracy is obtained. This method improves the machining performance of the array micro-structures and shows good prospects in micro-fabrication.

It is necessary to theoretically research wettability in superhydrophobic surface fabrication. Here, a numerical calculation approach is proposed for determining the contact angle of the water droplets on array micropillars by wire electrical discharge machining (WEDM). A hierarchical model is employed for these array microstructures, including mechanical analysis for a water droplet placed on a smooth array and wettability evaluation on the morphology of the WEDM surface. On pillars, equations are listed to solve the apparent contact angle according to force balance of gravity, tension, and pressure. As for the WEDM morphology, temperature simulation and measurement are carried out, and then the effect of roughness on surface wettability is studied. Constructed formulas predict the contact angle, and then the effect of geometric dimensions is obtained. In order to verify the assumption, array micropillars with different cross-profiles are prepared using high-speed WEDM on the Al alloy surface. Through the results of contact angle determination, the numerical calculation is carried out. This theoretical prediction is beneficial for improving the fabrication of the superhydrophobic surface by WEDM.

In this paper, it is proposed a method that using mathematical equation to describe the surface morphology of electrical discharge machining (EDM). In particular, response surfaces and the effect of current and pulse width are established by measuring diameter and depth of the pits. A matrix of surface heights is collected by scanning EDM surface with appropriate magnification. Combined with the fractal theory, the suitable fitting frequency range is obtained by analyzing power spectral density of one of the row profiles. Wavelet decomposition is used to separate the profile into signal layers in different frequency ranges. Through picking five suitable signal layers, the characteristic frequencies and corresponding amplitudes of each layer are obtained based on the sizes of the single-pulse pit. These five groups of characteristic parameters are used to reconstruct row profile and surface topography. The mathematical equation of the EDM surface is obtained, and it is verified effective. Keys words: EDM; surface morphology; wavelet; surface reconstruction; spectral analysis