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Aiming at the high specific removal energy and heat generation rate in grinding process, and the low heat transfer efficiency in grinding arc zone of ordinary grinding wheel, the problems of local high temperature and grinding burn are easy to occur. In this paper, the plane grinding of grooving wheel with large spiral Angle is taken as the research object, and the numerical analysis model of gas-liquid two-phase flow field in wedge zone and grinding arc zone is established. The enhancement mechanism of heat transfer performance in grinding arc of large spiral Angle groove wheel was investigated. The results show that the flow of grinding fluid into the grinding arc will be hindered by the airflow around the grinding wheel, resulting in backflow and side leakage. Compared with ordinary grinding wheels without grooves, the backflow and side drainage in grinding zone of big spiral Angle grooves grinding wheels are significantly reduced, and a large amount of grinding fluid is transported in the heat exchange channel. The spiral groove has a good conduction effect on the grinding fluid, and the grinding fluid is easier to enter the grinding zone, thus significantly improving the heat transfer performance of the grinding zone and effectively reducing the grinding temperature during the grinding process.

Graphene nanosheets and ionic liquids (ILs) both have excellent heat transfer and lubricating properties and both have great potential in minimum quantity lubrication (MQL) grinding, however the grinding performance of graphene/IL nanofluids under nanofluid minimum quantity lubrication (NMQL) is still unclear. This research firstly evaluates the grinding performances of graphene/IL nanofluids under NMQL experimentally. The evaluation shows that graphene/IL nanofluids can further strengthen both the cooling and lubricating performances compared with MQL grinding using ILs only. The specific grinding energy and grinding force ratio can be reduced by over 40 percent at grinding depth of 10 μm. Workpiece machined surface roughness can be decreased by over 10 percent, and grinding temperature can be lowered over 50 ℃ at grinding depth of 30 μm. Aiming at the unclear tribological mechanism of graphene/IL nanofluids, molecular dynamics simulations for abrasive grain/workpiece grinding interface are performed to explore the formation mechanism of physical adsorption film. The simulations show that the grinding interface is in a boundary lubrication state. IL molecules absorb in groove-like fractures on grain wear flat face to form boundary lubrication film, and graphene nanosheets can enter into the grinding interface to further decrease the contact area between abrasive grain and workpiece. The interlayer shear effect and low interlayer shear strength of graphene nanosheets are the principal causes of enhanced lubricating performance on the grinding interface. EDS and XPS analyses are further carried out to explore the formation mechanism of chemical reaction film. The analyses show that IL base fluid happens chemical reactions with workpiece material, producing FeF2, CrF3, and BN. The fresh machined surface of workpiece is oxidized by air, producing NiO, Cr2O3 and Fe2O3. The chemical reaction film is constituted by fluorides, nitrides and oxides together.

Aimed at the problems such as old talents training concept, single assessment and lack of long-term continuous improvement mechanism, the undergraduate teaching quality assurance system was constructed and practised. Several crucial aspects such as the quality control of teaching process, the assessment mechanism for curriculum aim and graduation requirements, the teaching quality feedback mechanism, as well as the continuous improvement mechanism were explored. Based on the above research, the undergraduate teaching quality assurance system is formed, which is easy to operate and contains the OBE international advanced concept. Practical application shows that the teaching quality assurance system constructed in this paper can improve our teaching quality effectively.

The Co-Al coating was deposited on Ni-based superalloy DZ125 by pack cementation. The lifetime and interdiffusion behavior of the Co-Al coating on the Ni-based superalloy at 1050 °C, 1075 °C and 1100 °C were investigated. Surface oxidation and interdiffusion between the coating and the substrate led to depletion of Al in the coating, and β-Ni(Co)Al was gradually degraded into γ and γ' phases. Oxidation activation energy of the coating was calculated through oxidation weight gain curves of different temperatures. The formula of the coating lifetime related to the coating thickness and the temperature was established by calculating intermediate parameters. The lifetime determined by the formula and experiment showed good agreement.

The residual stress distribution in the surface layer of bearing ring raceway has a significant impact on the fatigue life of rolling bearings. Grinding is the critical manufacturing process for bearing rings, and directly determines the residual stress distribution. However, the residual stress distribution is generally not detected in the manufacturing procedure of rolling bearings, and there are no corresponding control standards or measures. This research intensively investigated the grinding mechanism of bearing ring raceway, and performed an integrated modeling to achieve controlled stress grinding. The integrated modeling starts from the grain/workpiece interaction, through modeling of the distributions of interaction stresses and heat flux, and ends up with the numerical model for coupled thermal-mechanical residual stress analysis. The integrated modeling was validated experimentally through the comparisons between the measured and simulated temperatures and residual stresses. With the integrated model, the generating mechanism of the residual stress distribution was revealed, the influences of grinding parameters and cooling conditions were investigated, and the control strategy was finally put forward. The investigations show that grinding can produce compressive residual stresses in the surface layer of bearing ring raceway. Heat flux is still detrimental to the formation of compressive residual stresses, although thermally induced tensile residual stresses are prevented. To produce compressive residual stresses in the surface layer of bearing ring raceway, the rotational speed of bearing ring should be increased, the rotational speed of grinding wheel and the transverse feed speed should be reduced, and increasing convective heat transfer coefficient is more effective than reducing the initial temperature of grinding fluid.

To perform grinding temperature field analysis, the heat source on the finished surface is more convenient compared with the heat source on the workpiece/wheel contact surface. Therefore, many profiles of the heat source on the finished surface were proposed. However, these profiles were based on the specific grinding conditions, and were not universally applicable. In this research, the changing trend of the PHSF (profile of the heat source on the finished surface) under different grinding conditions was investigated. The contact angle and the Peclet Number are two critical parameters to clarify the changing trend. At small contact angles, the PHSF is right triangular. Under the conditions of very low Peclet Numbers and large contact angles, the PHSF is triangular. Under the conditions of large contact angles and high Peclet Numbers, the PHSF is parabolic. Two PHSFs were proposed and were described by mathematical formulas. A figure to serve as the selection guide for the two PHSFs was obtained, which took the error of the maximum dimensionless temperature less than 15% as the engineering permissible range. The figure contains almost all the general grinding conditions, and can be conveniently used in engineering for the grinding temperature analysis.

Bearing raceway grinding process has a large influence on the work quality and the rotate accuracy of the bearings. Surface roughness and heat affected layer, which have a strong relationship with grinding process quality, are important factors relevant to the bearing raceway surface quality. Based on the integrated grinding process model proposed previously by the author, which can calculate ground surface roughness, grinding forces, grinding temperature field, and dark layer thickness, from the investigation on the microscopic interaction mechanism between grinding wheel and workpiece surface in the grinding contact zone, the calculation results had been validated through a series of experiments which were conducted on the raceway grinding experimental platform. Based on the simulated and experimental results, both the surface quality and the process efficiency were taken as the optimize objectives, and the determination method on the process parameters was proposed. The optimized process parameters could not only avoid the dark layer occurrence, satisfying the technical requirement on the roughness, but also reached the highest process efficiency. The determination method and the optimized process parameter set could directly be used in the practical machining processes.

Grinding temperature field analysis is very significant to achieve controlled stress grinding and controlled grinding of affected layer depth. Heat source profile is an important basis for the grinding temperature field analysis. The heat source on the finished surface is more convenient than the heat source on the contact surface to perform grinding temperature field analysis both analytically and numerically. At present, the heat source profile on the finished surface was modeled to be rectangular, right triangular, triangular, or other shapes. However, all the modeled heat source profiles are not universally applicable under different grinding conditions. Therefore, the heat source profile on the finished surface under different grinding conditions needs to be further investigated. In this research, the inverse heat transfer analysis was performed to investigate the heat source profile on the finished surface under different grinding conditions. The investigation showed that the heat source profile on the finished surface is nearly right triangular in conventional shallow grinding, is triangular in creep feed grinding, and is close to be parabolic in HEDG (high efficiency deep grinding). Based on the investigation, the heat source profile on the finished surface was modeled as simple shapes to accommodate different grinding conditions. It was modeled to be right triangular in conventional shallow grinding and in creep feed grinding, and was modeled to be parabolic in HEDG. Error analyses of the predicted grinding temperatures obtained from the modeled heat source profiles were performed. The results showed that the modeled right triangular heat source profile is applicable in conventional shallow grinding and in creep feed grinding. The modeled parabolic heat source profile is applicable to most of the grinding parameters employed in HEDG. The modeled heat source profiles can conveniently serve as useful tools for grinding temperature field analysis in engineering.

The microscopic interaction mechanism between grains and workpiece material in grinding contact zone is extremely complicated which will take many interrelated and coupled factors into consideration, such as grinding wheel topographies, grain distributions, physical and mechanical properties of material, the emergence of grinding forces and heat energies, the partitioning and transfer of grinding heat, etc. However, the current theories and models are unable to integrate all of the above factors into an organic-whole model. Former researchers usually focused on several of above aspects and made assumptions to simplify those theories. However, these assumptions will weaken the mathematical relationship between grinding conditions and ground surface qualities and will increase the difficulties of understanding on the nature of grinding process. The work of this paper is an attempt on this purpose. It is based on the author's previous work of a microscopic interaction mechanism model between grains and workpiece material in grinding contact zone which will describe the interaction situation of a grain with any size, protrusion height and location, then the distributions of each type of grains were obtained. Single plowing and cutting grain force models were developed based on R.L. Hecker's single grain force model and M.E. Merchant's metal cutting theory, then led into grinding force distribution. The heat partition ratio model of W.B. Rowe was applied on the discrete grinding contact zone, a new developed heat flux profile transferred into workpiece surface was obtained, which was usually assumed to be rectangular, triangular and parabolic in shape in former researches. In order to confirm the rationality of this new heat flux profile, a comparison on temperature fields and grinding forces has been made between results from FE-models and experiments, under both wet and dry grinding conditions. Comparison results showed that this new developed integrated grinding process model has more precise prediction ability on grinding forces and grinding temperatures.

This paper presents an analytical solution for the vibration response of a ribbed L-shaped plate using a modal expansion solution approach. The analytical model is then employed to study the ribbing effect on vibration reduction and transmission between the two plate components of the L-shaped plate. It is found that for the system considered in the study, a rib inserted between the excitation force and the source plate can lead to a large vibration reduction for both source and receiving plates except at a frequency band near the fundamental resonant frequency of the rib where the rib's flexural stiffness is negligible. A reduced vibration transmission to the receiving plate can also be achieved by placing a rib near the plate/plate junction, attributed to the increased moment impedance at the coupling after the rib insertion. Increasing the rib's flexural stiffness under this condition can further reduce vibration transmission in the low frequency bands while increasing the rib's mass can lead to a reduced vibration transmission in the higher frequency bands. The insights obtained from this study are relevant to vibration control of structures such as transformer tanks and machine covers.

In this study, an experiment was conducted to obtain the heat flux and heat transfer coefficient of a mixed molten salt (60% NaNO3, 40% KNO3) and water at subcritical pressure in a tube in tube heat exchanger. The control variable method was used in this study. Experimental parameters covered the molten salt and water flow fluxes of 283.1–305.9 kg/m2s, 38.7–64.4 kg/m2s, the water pressures of 15–19 MPa, the water and molten salt inlet temperature of 260 °C/ 360–560 °C, and heat fluxes of 43–266 kW/m2, respectively. The heat transfer performance of molten salt and water in the single-phase and subcooled boiling regions were analysed with respect to molten salt flow fluxes and inlet temperature, water flow fluxes and pressure. Based on the experimental data, the heat transfer characteristics of molten salt to subcooled water was compared to the classical Grimson correlation, with a maximum deviation of −20%. Finally, the fitting correlation of the thermal performance of molten salt to the subcooled boiling water was presented, the fitting values demonstrated good consistency with the experimental data, with a maximum deviation of –10%.

In this study, an experiment was conducted to obtain the heat flux and heat transfer coefficient of a mixed molten salt (60% NaNO3, 40% KNO3) and water at subcritical pressure in a tube in tube heat exchanger. The control variable method was used in this study. The experimental parameters included the molten salt and water mass fluxes of 38.7–54.1 kg/m2s and 212.8–259.6 kg/m2s, respectively, water pressure of 15–19 MPa, water and molten salt inlet temperatures of 200–400 °C and 440–500 °C, respectively, and heat flux of 12–160 kW/m2. The heat transfer performances of the molten salt and water in the subcooled, subcooled boiling, saturated boiling, dryout and superheated regions were analysed with respect to the molten salt and water mass flow rate, inlet salt temperature, water pressure, and inlet water temperature. The fitting correlation of the thermal performance of molten salt to the subcooled boiling or vapor-liquid two-phase flow was presented; the fitting values demonstrated good consistency with the experimental data, with a maximum deviation of –6% and +8%.

It is widely accepted that surface textures can significantly improve the tribological properties of surfaces. The purpose of this research was to study surface texture formation mechanism through the ultrasonic vibration-assisted grinding process. First, a single grain cutting process model was established, and the cutting trajectory length and shape were calculated. Second, the single grain profile models were established that considered the dressing effect. Then, by considering continuous cutting process of large amounts of grains, the surface texture formation mechanism model was established. The calculation results were verified by experiments. Finally, the characteristic parameters that described the surface texture topography were proposed and the influence law of the process parameters was analyzed. The results of this research showed that the established theoretical model could accurately describe the ultrasonic vibration-assisted grinding process and the topographical characteristics of the surface texture. By controlling the process parameters, surface textures with controllable topography could be processed. This work can provide a substantially theoretical basis for processing surface textures efficiently.

To achieve controlled stress grinding and controlled grinding of the depth of modificative layer, coupled analysis of grinding force and grinding heat is required. Therefore, this paper investigated grinding force and energy partition to lay a foundation for the coupled analysis. Firstly, a new grinding force model based on the analyses of grain trajectory and grain workpiece contact. In the modeling of grinding force, critical grain indention depths for plowing and cutting were calculated and the grinding force models of a single grain were established. This model can analyze the contributions of sliding, plowing, and cutting to total grinding forces. Secondly, an energy partition model was established based on the analyses of grain trajectory and grain workpiece contact. In the modeling of energy partition, the real contact area ratio and the grain contact radius were calculated. Finally, experiments were pursued to validate the grinding force model by comparing the experimental measurements to the theoretical results. Comparisons showed reasonable agreement quantitatively.

Roughness is usually regarded as one of the most important factors to evaluate the quality of grinding process and ground surface. Many grinding parameters are affecting ground surface roughness with different extents, however, the most influential factors are wheel dressing and wear effects which were unfortunately not get seriously attention in the previous researches. On the other hand, as a most common indicator, roughness is only a statistical evaluation which is not enough to describe the topography characteristics of a surface, especially under higher demands on grinding process and functional ground surface quality. Thus in this work, a 2D and 3D ground surface topography models were established based on the microscopic interaction mechanism model between grains and workpiece in grinding contact zone. In this study, besides grinding parameters, the wheel dressing and wear effects were taken into consideration, including dressing depth, dressing lead, geometry of diamond dressing tool and wear effects of both wheel and diamond dressing tool. A dressing and wear profile line, L dw , which will describe how the grains’ shapes are changed, was established and added into a former 2D ground surface roughness prediction model. In order to obtain a better visual effect, a 3D topography model was established which is based on the interaction situations in real grinding process. Both 2D and 3D models will predict ground surface roughness more precisely and stably than traditional models by comparing with a dressing lead single-factor experiment. Results also showed that the selection of dressing parameters and dressing tools can refer to the formed shape of L dw by comparing with grinding depth, a e , and the dressing lead should be carefully chosen which will greatly influence ground surface topography the most.

In the research on grinding process modeling, the stochastic nature of grain sizes and locations need to be considered. A new numerical model was developed which will describe the micro-interacting situations between grains and workpiece material in grinding contact zone. The model was established based on a series of reasonable assumptions, the critical conditions of starting points of plowing and cutting stages, and the redefined grinding contact zone. It indicated that there are four types of grain existing in grinding contact zone: uncontact, sliding, plowing, and cutting grains. The number of grains per unit wheel volume (Nv) and the undeformed chip thickness (hcu,max), which are key parameters in grinding process modeling, were firstly obtained. The numbers and distributions of different grain types along grinding contact zone were then obtained and analyzed. Calculation results showed that only a small fraction of grains participate in cutting interactions and the changing laws of each grain types along grinding contact length are very different from each other, which gives a deeper insight into grinding process and can be a good foundation for more precise grinding force prediction and thermal analysis. Another important application of this model is for ground surface roughness prediction and a new method on this purpose was developed. At last, two comparisons were made between calculation results and existing experimental data for validating the work on paper. Comparison results showed that the roughness of ground surface can be well predicted and gave the method theoretically to reduce ground surface roughness.