Explore the vast range of titles available.

Diamond-like carbon (DLC) films with excellent anti-friction and wear resistance, can effectively reduce the energy loss of tribosystems and the wear failure of parts, but the high residual stress limits their application and service life. Researchers found that doping heterogeneous elements in the carbon matrix can alleviate the defects in the microstructure and properties of DLC films (reduce the residual stress; enhance adhesion strength; improve tribological, corrosion resistance, hydrophobic, biocompatibility, and optical properties), and doping elements with different properties will have different effects on the structure and properties of DLC films. In addition, the comprehensive properties of DLC films can be coordinated by controlling the doping elements and their contents. In this paper, the effects of single element and co-doping of carbide-forming elements (Nb, W, Mo, Cr, Ti, Si) and non-carbide-forming elements (Cu, Al, Ag, Ni) on the properties of microstructure, mechanical, tribological, optical, hydrophobic, corrosion resistance, etc. of DLC films are reviewed. The mechanisms of the effects of doping elements on the different properties of DLC films are summarized and analyzed.

High-pressure axial piston pumps operate in high-speed and high-pressure environments. The contact state of the slipper against the swashplate can easily change from an oil film lubrication to a mixed oil film/asperity contact, or even dry friction. To improve the dry friction performance of slipper pairs and to avoid their potentially rapid failure, this study examined the effects of material matching on the dry friction performance of the slipper pair for high-pressure axial piston pumps. A FAIAX6 friction and wear tester was developed, and the dry friction coefficients of the slipper pairs matched with different materials were studied using this tester. Based on the thermo-mechanical coupling of the slipper pair with the working process, the contact surface temperatures of the slipper pairs matched with different materials were calculated and analyzed for the same working conditions. Following this, the effects of the material properties on the temperature increase at the slipper sliding contact surfaces were revealed. The reliabilities of the temperature calculations and analysis results were verified through orthogonal tests of slipper pairs matched with different materials. The results indicate that the influence of the material density on the friction coefficient is greater than that of the Poisson’s ratio or the elastic modulus, and that the slipper material chosen should have a high thermal conductivity, low density, and low specific heat, whereas the swashplate material should be high in specific heat, density, and thermal conductivity; in addition, the slipper pair should be a type of hard material to match the type of soft material applied; that is, the hardness of the swashplate material should be greater than that of the slipper material.

Layered palygorskite (PAL), commonly called attapulgite, is a natural inorganic clay mineral composed of magnesium silicate. In this study, an aqueous miscible organic solvent treatment method is adopted to prepare molybdenum-dotted palygorskite (Amo-PMo) nanoplatelets, which greatly improved the specific surface area of PAL and the dispersion effect in an oil-based lubricant system. Their layered structure and size were confirmed using transmission electron microscopy (TEM) and atomic force microscopy. Following a tribological test lubricated with three additives (PAL, organic molybdenum (SN-Mo), and Amo-PMo), it was found that the sample of 0.5 wt% Amo-PMo exhibited the best tribological properties with a coefficient of friction of 0.09. Moreover, the resulting wear scar diameter and wear volume of the sliding ball surface were 63% and 49.6% of those lubricated with base oil, respectively. Its excellent lubricating performance and self-repairing ability were mainly attributed to the generated MoS 2 adsorbed on the contact surfaces during the tribochemical reaction, thereby effectively preventing the direct collision between asperities on sliding solid surfaces. Thus, as-prepared Amo-PMo nanoplatelets show great potential as oil-based lubricant additives, and this study enriches the existing application of PAL in industry.

In this paper, a sub-pixel detection and evaluation method for roundness error of shaft workpiece is proposed by using machine vision technology. This method uses polynomial interpolation-piecewise curve fitting algorithm to accurately locate the sub-pixel edge of image contour. Based on obtaining the sub-pixel coordinates of image edge points, the least square method is used to detect the center coordinates, and then the roundness error of shaft workpiece is detected and evaluated. The experimental results show that the average absolute errors between the measured values of this method and the measured values of the vertical optical meter and the coordinate measuring machine are 7.6 µm and 6.9 µm, respectively, and the roundness error value measured by this method is more uniform, the fluctuation is the smallest and the detection accuracy is higher, which provides a feasible approach for the evaluation of the roundness error of shaft workpieces.

Due to the rapid development of the modern industry, people have higher and higher requirements on the rolling speed and quality of steel. The performance of conventional cast-iron roll cannot supply production demands because it contains higher chrome-nickel elements. The high-speed steel W6Mo5Cr4V2 with high service life, red hardness and wear resistance becomes a promising material of roll. However, the above characteristics bring great difficulties to roller repairing. Within this study, the high-speed steel W6Mo5Cr4V2 was processed with roll grinding at various grinding conditions (grain size, workpiece speed and depth of grinding) by using Taguchi design method, and the grinding process parameters are analysed and optimized according to the values of surface roughness and the depths of microhardness alterations. To obtain the optimized parameters, the values of surface roughness and microhardness alterations were analysed with grading methods of synthesizing multiple guidelines. Also, a confirmatory test was done to confirm the optimized parameters obtained from the above methods. The results of this work may provide the knowledge/database of the roll grinding process of high-speed steel W6Mo5Cr4V2 at given grinding parameters.

The main pressure regulating valve (MPRV) is a critical component for automatic transmissions, controlling the pressure regulating of the complex hydraulic control system. Its performance is directly related to the automatic transmissions’ operational performance and service life. However, few studies have focused on the optimal design and dynamic optimization of MPRV in the main oil pressure regulating system (MOPRS) for automatic transmissions. This work focused on the MPRV used in the heavy-duty automatic transmission (HDAT) for the hydraulic system nonlinearities and the parameters uncertainties of the MOPRS for pressure regulating capability. The idea is to improve pressure regulation performance from the structural parameters optimization and control methods. Firstly, based on the MOPRS working principle analysis of HDAT, the mathematical models of the design and calculation of the MPRV and the pressure regulation system were established. Then, a genetic algorithm (GA) was used to optimize structural parameters of MPRV using AMESim. Finally, the particle swarm optimization (PSO) algorithm was used to adjust the PID parameters, and comparative with the other PID parameters, the main pressure regulation (MPR) was investigated in MATLAB/Simulink. As a result, the simulation results indicated that the optimized structural parameters of MPRV were significantly better than the original parameters. Compared to the “cut and try” PID control, the proposed PSO PID control method results significantly improved the pressure regulation characteristics of MOPRS and further ensure the shift quality during the shift operating. Therefore, this work provides a general and systematic approach to hydraulic valves theoretically on the design, performance analysis, and optimization of the valve are investigated based on its working principle. Furthermore, the critical problems involved in the valve were comprehensively revealed theoretically, and finally, which will lay a solid foundation for designing and developing the HDAT’s hydraulic control block.

High-speed steel (HSS) work rolls have good wear resistance, fatigue resistance, and oxidation resistance, and are widely used in the production of hot rolled strips. The excellent performance of HSS work rolls brings significant challenges to the conventional dressing (i.e., grinding). As a typical difficult-to-machine material, the electrochemical machining (ECM) of work rolls grade HSS is a promising alternative method for dressing. The design of cathode tools for ECM is affected by the multi-physical fields (i.e., electric field, flow field, and temperature field), which is the main factor determining the forming accuracy. However, cathode design for ECM has long been a time and cost-intensive process. To effectively solve the design problem of the cathode tool for ECM of HSS, this paper proposes a design and optimization method based on multi-physics coupling analysis. Subsequently, the ECM experiment of HSS was carried out to verify the accuracy of the optimization method. Experimental results show that coupling analysis based on multiple physical fields is an effective method for optimizing cathode tool design. This method can improve the design efficiency of the cathode tool in ECM and reduce the modification time of the cathode tool.

High-speed steel (HSS) rolls are essential critical components in the steel rolling industry. Unfortunately, the working layer material has poor machinability via conventional grinding process for surface dressing because they have excellent properties. Electrochemical grinding (ECG) is a common machining approach that is used for metal materials. A significant factor for the machining quality of metal materials is the electrolytes, and thus, the selection of a suitable electrolyte for ECG is a primary problem. However, the previous studies have presented very little information on the electrolyte selection for ECG of HSS roll material. This paper proposes a method for investigating the selection of a suitable electrolyte for ECG of HSS roll material using electrochemical testing techniques and uniform design (UD) experiments. Electrochemical behavior, such as electrochemical corrosion and passivation behavior, was assessed to select a suitable electrolyte composition. The results indicate that the electrochemical passivation of composite electrolytes is better than that of single-component electrolytes. From the UD-ECG experiments, an optimal electrolyte content is obtained using a stepwise linear regression model and a multi-objective fuzzy programming approach. The results show that the surface machining quality of the optimal composite electrolyte is better than those of groups with other ratio combinations. Therefore, the method and results used to select a suitable electrolyte obtained using a combination of electrochemical testing techniques and ECG experiments may provide the knowledge for ECG machining, such as that of HSS roll materials and other metal materials.

Ultrasonic-assisted electrolytic in-process dressing (ELID) grinding can be used in the high-efficiency and high-precision machining of difficult-to-process materials. This paper establishes a prediction model of oxide film thickness growth. We conducted ultrasonic-vibration-assisted experiments on an electrolytic cast-iron-bonded grinding wheel and carried out high-speed steel ball friction and wear tests. The mechanical properties and surface morphology of the oxide film were characterized by nanoindentation, SEM, and three-dimensional morphology. The relative error between the theoretical model and the measured data did not exceed 7%. With the increase in oxide film thickness, the oxide film on the surface of the cast-iron-bonded grinding wheel became looser, the film surface exhibited more defects, and the hardness and elastic modulus of the oxide film were far lower than those of the cast-iron-bonded grinding wheel substrate. The adhesion of the oxide film first increased and then decreased with the increase in film thickness; the complete peeling distance increased with the increase in film thickness. The thicker the oxide film was, the more likely it was to fracture and fall off, the larger the average coefficient of friction (COF), the higher the wear rate of the cast-iron-bonded grinding wheel, and the lower the cast-iron-bonded grinding wheel’s service life.

Molecular dynamics (MD) simulations were conducted to investigate the interactions between a palygorskite coating and linear chain alkanes (dodecane C12, tetradecane C14, hexadecane C16, and octadecane C18), representing base oils in this study. The simulation models were built by placing the alkane molecules on the surface of the palygorskite coating. These systems were annealed and geometrically optimized to obtain the corresponding stable configurations, followed by the analysis of the structural changes occurring during the MD process. The interfacial interaction energies, mean square displacements, and self-diffusion coefficients of the systems were evaluated to characterize the interactions between base lubricant molecules and palygorskite coating. It was found that the alkanes exhibited self-arrangement ability after equilibrium. The interfacial interaction was attractive, and the electrostatic energy was the main component of the binding energy. The chain length of the linear alkanes had a significant impact on the intensity of the interfacial interactions and the molecular diffusion behavior. Moreover, the C12 molecule exhibited higher self-diffusion coefficient values than C14, C16 and C18. Therefore, it could be the best candidate to form an orderliness and stable lubricant film on the surface of the palygorskite coating. The present work provides new insight into the optimization of the structure and composition of coatings and lubricants, which will guide the experimental development of these systems for practical applications.