Considering that after milling titanium alloy with a ball-end milling cutter, the wear degree of different areas of the rake face is different, which indicates that the tool-chip contact conditions in this area are different, and then the micro-texture action mode is different. To improve the effect of micro-texture, this paper establishes a mathematical distribution model of variable distribution density micro-texture based on the two-zone method, builds a variable distribution density micro-texture ball-end milling titanium alloy test platform, studies the influence of variable density micro-texture parameters on tool milling behavior, and optimizes the parameters based on the improved particle swarm optimization algorithm. The results show that the micro-texture with variable distribution density has a positive effect on the milling behavior of the tool. The micro-texture parameters of the stickiness area have the greatest influence on the milling behavior of the tool. A texture parameter is optimized, and the overall milling behavior of the variable density micro-texture TiAlN coated milling cutter is optimal. This study provides a theoretical basis for the design and preparation of variable distribution density micro-textured tools. Highlights Based on the two-zone method, the mathematical distribution model of the variable distribution density micro-texture of the rake face of the tool is constructed. The influence mechanism of micro-texture parameters on the milling behavior of a ball-end milling cutter is explored. The multi-objective optimization of the variable density micro-texture parameters was carried out, and the optimal parameter combination was obtained. It is verified that the variable distribution density of the micro-texture has a positive effect on the cutting performance of the tool.

In the machining of difficult-to-machine metals, such as titanium-based alloys, the delivery of coolant with high pressure can increase machining efficiency and improve process stability through more efficient chip breaking and better cooling. Proper selection of machining conditions can also increase the productivity of the process by reducing cutting forces and tool wear rate. To investigate the effect of high-pressure jet cooling (HPJC) on cutting force, surface roughness, and chip formation of Ti-6Al-4V ELI in high-speed turning, Grade 5 Ti ELI turning tests were carried out under coolant pressure of 200 bar. A lower pressure of 6 bar was also used in this study to compare the results of the pressure change. In general, surface roughness increased as the feed rate increased at constant cutting speeds in experiments with both 6 bar and 200 bar coolant pressures. Even though 200 bar pressure provided a better cooling thus reduced cutting force, and tool wear rate; the surface roughness values ​​obtained from the experiments with 200 bar were relatively worse than the experiments with 6 bar pressure. It was also seen that 200 bar coolant pressure may result in instabilities in the turning process in terms of chip geometries and formations.

The objective of the present study is to investigate the effect of chemical composition and microstructure on machinability, mechanical properties, and crack growth of GG-20 gray cast iron for brake drum application. The effects of a reduction in C and Si on microstructural parameters such as type, size, and aspect ratio of graphite particles, interlamellar spacing of pearlite, and the presence of MnS were investigated. In the following, the effect of different microstructures on mechanical properties and machinability of cast iron were studied. The fracture surface, crack growth, worn surface, chip formation and wear on cutting tools have been studied as well. The results showed that both tensile strength and hardness increased, and the machinability reduced by decreasing C and Si. By reducing the C content from 3.4% to 3.2%, the maximum hardness value and tensile strength were obtained to be 207HB and 286 MPa, respectively. Moreover, the Ra and Rz values were increased to 4.3 μm and 25.8 μm, respectively. With an increase in the length of graphite flakes, the distance between microcracks on the machined chips decreased. In the sample with the lower hardness value, delamination occurred extensively and led to the disappearance of cracks and pores on the worn surface.

In the literature, investigations on the electrical discharge machining (EDM) process with Tungsten carbide powder mixed into dielectric fluid, also called PMEDM, are still limited. In this study, machining performances of PMEDM, including material removal rate (MRR) of AISI H13 steel and tool wear rate (TWR), were investigated in the semi-finishing process. Thereafter, recast layer properties of AISI H13 steel, including composition and content of chemical elements, recast layer thickness (RLT), and acreage percentage of micro-cracks on surfaces (APCS), were evaluated and discussed. Quantitative methods of MRR, TWR, RLT, APCS, and the composition and content of chemical elements on machined surfaces have been proposed. The results revealed that machining performances and recast layer properties were influenced by peak current (Ip), pulse on time (Ton), and powder concentration (Cp). MRR and TWR have been changed in an uptrend when Ip, Ton, and Cp increased. The chemical composition of machined surfaces was modified. APCS and RLT formed by PMEDM are notably decreased as compared with EDM, with a reduction of 41.093% and 48.982%, respectively. In addition, the changing trend of machining performances and recast layer properties were also explored.

Difficult-to-cut material, i.e., AISI D2 tool steel, has been widely adopted in metalworking industries to manufacture dies for piercing, blanking, drawing and thread rolling due to its excellent wear resistance and non-deforming properties. This article attempts an experimental study to determine the effect of cryogenic coolant (liquid nitrogen) on the grindability of AISI D2 tool steel as work material and its results are compared with the conventional dry and wet grinding methods. The effects of the cryogenic coolant on force components (i.e., tangential force, Ft and normal force, Fn ), specific grinding energy (u), force ratio, surface roughness parameters (Ra and Rz ) and microstructure were observed. The comparison results indicate a significant reduction in grindability indices such as 64% and 44% in Ft , 54% and 34% in Fn , 46% and 30% in Ra and 40% and 34% in Rz , respectively under cryogenic grinding at higher downfeed as followed to dry and wet grinding. The grinding performance in Ft , Fn , u and Ra was also improved with an increased delivery pressure of the liquid nitrogen (LN2). From the results, it is concluded that cryogenic coolant offers an influential method to improve grinding performance and surface integrity of AISI D2 tool steel.

This study was to determine to what extent a cryogenic surface treatment technique could improve the wear resistance of a Co-Cr-Mo hip implant material. Dry and cryogenic treatments were used to create different surface and sub-surface conditions. The Co-Cr-Mo samples were wear-tested using a pin-on-disk tester in a simulated implant environment. A change in the wear response was found as a function of the material surface properties. Correlation between the treatment conditions and wear volume loss was discussed. Sample from cryogenic treatment was found to be most promising with lower wear volume due to microstructure refinement, compressive residual stresses and preferred hcp phase; moreover, the preferred hcp phase revealed to be the most influencing property in enhancing the wear resistance.

Serrated chip is a typical characteristic of high-speed cutting. It is an important aspect of high-speed cutting mechanism, and has significant influence on cutting force, cutting temperature and tool wear. For the observation of serrated chip, optical microscope (OM) and scanning electron microscope (SEM) are usually used. The main problem of OM observation is time-consuming and that of SEM observation is high cost. Therefore, a new serrated chip observation method based on digital microscope（DM）was proposed. The advantage of this method is that the experimental chip can be observed directly, so plenty of preparation time of metallographic sample is saved, and the cost of it is also lower. Relevant parameters, including segment spacing, tooth top height and tooth root height, can be measured by depth synthesis function. This will greatly facilitate the quantitative study of serrated chip, and thus promote the in-depth study of high-speed cutting. The validity of the proposed method was verified by comparing the observation results of OM and DM. The advantages and disadvantages of the proposed method were also discussed. Furthermore, the serrated chips in high-speed cutting of Ti6Al4V alloy and AISI 1045 steel were studied. The results show that whether it's Ti6Al4V alloy or AISI 1045 steel, the degree of segmentation increases with the increase of cutting speed and depth of cut, and decreases with the increase of rake angle. The segment spacing decreases with the increase of cutting speed and rake angle, but increases with the increase of depth of cut. The mechanism of serrated chip changing with cutting parameters was analyzed based on adiabatic shear theory.

The performance characteristics of micro-EDM dressing were investigated based on some real-time and offline responses for the fabrication of micro-rod(s) on a novel Ti-6Al-7Nb biomedical material. These characteristics evaluated along the micro-rod length at three different discharge energy settings were analyzed by monitoring the discharge gap condition captured through an in house developed pulse-discriminating system (PD). The experimental results show that the normal pulse was more (∼90%) in the low energy setting (E 1). In contrast, arcing was more (∼28%) in the high energy setting (E 3). Pulse frequency was found more (∼60 ) in E 1. However, due to an increase in the ‘idle’ time, it significantly decreased (∼25) along the machining length. however, was found more (∼5.7 × 103, µm3/s) in E 3. The specific energy was found very high (∼9 MJ/mm3) in E 1 since the process spent additional energy to remove the re-solidified molten metal. The was, on the other hand, found very high (∼2.1) in E 1 due to prolonged exposure to discharges and experiencing higher total discharge energy by the work-tool interface. E 3 was found more suitable for fabricating dimensionally accurate micro-rod(s) on this material because of less tool wear.

In this research, the effects of high speed milling on the main surface integrity characteristics, including surface roughness and topography, microhardness, white layer thickness, and surface chemical composition of Ti-6Al-4V were empirically studied. Totally, 18 experiments were carried out using a full factorial design of experiments method in the presence of minimum quantity lubricant. The results showed that by using high speed milling, it is possible to reach the surfaces with a higher quality and surface roughness of approximately 0.2 μm. Also, it was discovered that the microhardness variation with cutting speed has a dual nature. The maximum microhardness was obtained at the cutting speed of 375 m/min and the feed rate of 0.08 mm/tooth, which showed a 57% increase compared with the bulk material. In addition, by using the cutting speed of 450 m/min, the depth of heat-affected layer and work hardening effects declined up to 75% in comparison with the cutting speed of 300 m/min.

In order to accurately decompose the surface morphology of machined surface and trace the potential errors of the machine, a comprehensive improved algorithm is proposed, which combines wavelet packet decomposition (WPD) and improved complete ensemble empirical modal decomposition of adaptive noise (Improve CEEMDAN). Firstly, the cost function is used to find the optimal wavelet packet base and the optimal decomposition tree is obtained. Secondly, under semi-hard threshold denoising, the wavelet coefficients obtained by the optimal decomposition tree can generate the denoised signal. Finally, the white noise is preprocessed to obtain the upper limit frequency and the band white noise, and the improvement of CEEMDAN is completed. The improved CEEMDAN is used to decompose the denoised signal to obtain a series of intrinsic mode functions (IMFs). The merit of this comprehensive improved algorithm is that it can improve the calculation efficiency and decomposition accuracy by adaptively finding the optimal wavelet packet base and adding band-limited white noise. Simulations and experiments results show the feasibility, effectiveness and higher accuracy of the comprehensive algorithm in decomposing surface topography.