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In this paper, the effect of the differential lubrication method on the wrinkling and cracking during the hydroforming of the Y-shaped tube was discussed, as well as the effects of the initial position, counterforce, and end angle of the counter punch on the forming of the branch tube were discussed. It is of great significance to the hydroforming of thin-walled 5A02 aluminum alloy Y-shaped tube with a large transition fillet that is asymmetric in both longitudinal and transverse directions. The experiment used a counter punch with 0° and 13.5° end angles and a loading path with stepped pressure feed. MoS2 and PTFE film were chosen as lubricants for the differentiated lubrication method. The experimental results show that the flow rate of material in the bulging zone was effectively improved when MoS2-PTFE was used in this zone of Y-shaped tube, while dry friction was used in other areas, preventing the wrinkling on the main tube. The branch without cracking but with ideal height and good surface quality can be obtained when the counterforce was 13.7 KN, the initial position was 17 mm, and the counter punch end angle was 13.5°. [ABSTRACT FROM AUTHOR]

To improve the tool lubrication performance and reduce the use of cutting fluid as much as possible, a new type of tool with continuous lubrication on the tool-chip contact interface has been fabricated. The atomized cutting fluid can be directly delivered to the tool-chip contact interface through the inner microchannel. Experiments were conducted on the new lubrication method, dry cutting, and traditional MQL cutting of 45 steel. The three-dimensional cutting forces and the cutting temperatures were measured. The wear surface of the rake face was analyzed through SEM micromorphology and EDS element detection. The results showed that the main cutting force of the tool with continuous lubrication at the tool-chip interface decreased by 14.5% and 5.9% compared with the conventional tools of dry cutting and MQL cutting. Moreover, the friction coefficient decreased by 14.2% and 9.8%, the length of the tool-chip contact interface decreased by 35.4% and 19.1%, and the amount of cutting fluid was only 1/10 of that in MQL cutting. The new lubrication method had better cutting fluid penetration and lubrication film formation performance than the traditional MQL method on the tool-chip interface. Furthermore, the surface wear of the new lubrication method was significantly reduced, and the main wear form of the new lubrication method was adhesive wear. [ABSTRACT FROM AUTHOR]

In recent years, there has been a challenge: how to meet the requirements of cutting lubrication and use the least cutting fluid for environmental protection simultaneously. To resolve this problem, novel cutting tools with micro textures on the rake face for lubrication were proposed, which can directly transport the cutting fluid to the tool-chip contact interface by using a micro-pipe. Cutting tests were performed on AISI 1045 steel. Then, the cutting force, friction coefficient, tool-chip contact length as well as wear of tools were investigated. The results show that the novel tools with micro textures have better cutting performance than other tools, by using much less cutting fluid than traditional flood lubricating cutting. Especially for the TVT tool, it has the best comprehensive performance. The main lubricating mechanism is that the cutting fluids can be more widely distributed on the tool rake face by the micro textures. This leads to better lubrication and less adhesion of the rake face. [ABSTRACT FROM AUTHOR]

Functionally graded materials (FGMs) are a promising engineering material, which is highly desirable in extreme environments of aerospace, nuclear, and bio-implants. Although the surface accuracy and quality of 3D-printed Ni–Fe FGMs can meet most application scenarios, it still requires post-cutting treatment especially in nuclear industry. The FGMs, with the gradient of mechanical property, are a new type of difficult-to-cut material. However, no ready-made post milling process can be referred. The poor-machined surface quality induced by excessive tool wear still cannot be handled even with textured tool under minimum quantity lubrication (MQL). In this paper, the mechanical properties and machinability of the Ni–Fe FGMs as well as its 5 isotropic component 304LxIN625y were firstly studied and correlated. Then, two milling parameter selection strategies were proposed by minimum milling force and by minimum surface roughness, corresponding to strategy I and strategy II. The results show that tool breakage occurs in bottom cutting edge when strategy I is adopted. On the contrary, strategy II can reduce tool major flank wear 40.1% by forming an elastohydrodynamic lubrication between bottom cutting edge and the machined surface, which is a prospective method to solve the tool failure during milling of 3D-printed Ni–Fe FGMs. [ABSTRACT FROM AUTHOR]

As an important precision transmission functional component in industrial fields such as large mechanical equipment, high-speed CNC machining center, and aerospace, the service life of the ball screw are directly related to the life of high-end equipment. Fatigue failure is the main failure mode of the ball screw in the transmission application where the transmission accuracy is not high. Therefore, the fatigue life of the ball screw is studied from the perspective of fatigue. The load distribution form of the double-nut ball screw under axial load is analyzed. Based on the ball load distribution, a mixed lubrication model of the ball screw considering non-Newtonian effect of lubricant is established, and a fatigue life prediction method of the ball screw based on maximum secondary surface stress is proposed. The lubrication performance of the ball screw under maximum contact load is compared with that under equal load distribution, and the effects of ball load distribution, curvature ratio, and temperature rise on fatigue life are analyzed. Two kinds of ball screw including BT GD8020 and NSK DFD8020 are used for running test of fatigue life, and the fatigue life calculation method based on the maximum secondary surface stress is verified. The hardness distribution of the transition zone between ball and raceway is analyzed, and the fatigue failure modes of two ball screws are explored. [ABSTRACT FROM AUTHOR]

Ball screw has become a key functional component commonly used in actuators of high-end machine tools because of its high transmission efficiency, low environmental impact, and strong universality of working conditions. For the high-precision ball screw, the proper and constant preload is the premise to maintain the transmission accuracy and reliable dynamic characteristics of the ball screw. The direct measurement of the preload is difficult to be achieved. Usually, the preload of the ball screw is indirectly determined by the friction torque of the ball screw under no-load condition. In previous studies, the influence of lubrication on friction torque of the ball screw was not considered, and the influence of operating conditions on performance of lubricant was ignored, and the influence of contact elastic hysteresis effect and the sliding friction effect was not considered, which seriously affected the modeling accuracy of friction torque for the ball screw. Therefore, on the basis of considering the contact elastic hysteresis friction and the sliding friction of the ball screw in the paper, a calculation model of friction torque for the ball screw based on the coupling of the ball load distribution and the thermal elastohydrodynamic lubrication is proposed. The mechanism of different friction terms on the friction torque of the ball screw is analyzed, and the coupling relationship among preload, rotational speed, and friction torque is established. The experimental results show that the proposed method, which the ball load distribution, the thermal elastohydrodynamic lubrication, the elastic hysteresis, and the sliding friction are comprehensively considered, has a good reference significance for improving the internal preload and predicting the precision degradation of the ball screw. [ABSTRACT FROM AUTHOR]

In high-speed sawing, the penetration of cutting fluid is limited due to the narrow kerf and large cutting depth. To improve the machining performance of high-speed sawing and the lubrication and cooling efficiency of cutting fluid, a technology named electrostatic minimum quantity lubrication (EMQL) high-speed sawing with water-based nanofluid as cutting fluids was developed. The adsorption and motion characteristics of droplets on the solid surface under airflow were studied. Furthermore, the machinability of EMQL in high-speed sawing was explored. The results show that the charged droplet's surface tension, static contact angle, and velocity under tangential airflow are lower than those of the uncharged droplet, while the dynamic contact angle hysteresis is higher. This indicates that the adsorbability of charged droplets on solid surface is enhanced. In high-speed sawing processing, the principal sawing force is reduced by 19% when the fluid is charged at − 4 kV. The reason may be that charging reduces the drag force of the droplet and increases the capillary force generated by the deformation of the contact line between the droplet and the solid surface, which enhances the adsorption capacity of the charged droplets on the sawtooth surfaces and improves the lubrication performance of the sawing area. [ABSTRACT FROM AUTHOR]

In order to study the friction and wear properties of cast iron in free grinding environment under the condition of line contact, this paper presented a new method to calculate the friction coefficient by measuring the friction torque. Through the self-developed free abrasive grinding experimental device in line contact condition, this work carried out friction and wear experiment with relative speed, load, abrasive particle diameter, and abrasive mass fraction as process parameters, and studied the evolution rules of friction coefficient and wear amount of cast iron materials under different process parameters. Based on the response surface method Box-Behnken experimental design, the significance of the experimental results was analyzed, and the prediction model of the friction coefficient and wear amount of cast iron was established. According to the significance of the prediction model, the influence degree of each process parameter on the friction coefficient and wear amount was revealed. The results showed that under the action of free abrasive, the friction coefficient of cast iron material in line contact with GCr15 was between 0.18 and 0.35. When the experimental time was 1.5 h, the removal amount of cast iron material was between 20 and 65 mg, which is significantly increased compared with that without abrasive and the wearing capacity of cast iron increased with the increase of relative speed, load, abrasive particle diameter, and abrasive mass fraction. The friction coefficient had a negative correlation with relative speed, and a positive correlation with abrasive particle diameter and abrasive mass fraction. With the increase of load, the change of friction coefficient decreased first and then increased. The influence degree of each process parameter on the friction coefficient and wear amount of cast iron material: the particle diameter and relative velocity of abrasive were relatively significant, the abrasive mass fraction was the second, and the load was the smallest. Through random experiments, the prediction model of friction coefficient and wearing capacity were verified to be highly accuracy, and could be used to predict the friction and wear performance parameters of cast iron in the process of free grinding under the condition of line contact. It provided a certain theoretical basis for the friction and wear behavior of cast iron as a grinding tool material in the grinding process. [ABSTRACT FROM AUTHOR]

Grinding residual stress (GRS) has been understood to have a great impact on the strength of gear fatigue life. However, there are lack of detailed studies on the influences in terms of mechanism and magnitude. To fill this gap, this study proposed a new method based on finite element analysis (FEA) to calculate the overall meshing stress on a gear tooth surface by including both the GRS and elastohydrodynamic lubrication (EHL) film pressure. Applying this method to a spiral bevel gear has resulted in a number of interesting results that GRS produced to reveal its mechanism of action through a full meshing cycle. The acquired understanding would be useful for development of manufacturing processes. [ABSTRACT FROM AUTHOR]

Using pure water in comparison to water-based lubricant containing 4% TiO2 nanoparticles (NPs), the hot rolling tests of 304 stainless steel were carried out at a rolling temperature of 1050 °C under varying rolling reductions and speeds. The effects of lubrication on rolling force, torque, power and contact friction were systematically investigated. The coefficient of friction (COF) during steady-state hot steel rolling was inversely calculated using a developed flow stress model. The COF models including the effects of rolling reduction and speed were proposed via multiple linear regression. The results indicated that the use of the nanolubricant enabled a reduction of rolling force up to 6.1% and decreases in rolling torque and power up to 21.6%, compared to that of water condition. The results obtained from the linear regression agreed well with those from the inverse calculation, suggesting the developed COF models had high accuracy. The lubrication mechanisms were derived from a boundary lubrication regime, owing to ball bearing and mending effects of TiO2 NPs, and formation of thin lubricant film under high rolling pressure. [ABSTRACT FROM AUTHOR]

To improve the meshing performance and increase the bearing capacity and service life of spiral gear pairs, a cutterhead approximation machining method based on controlling geometric topological deviations was proposed to solve the problem where line contact spiral bevel gears with tapered teeth depth cannot be machined by cutterheads. First, a mathematical model of the line contact conjugate flank was established, and the geometric topological deviations model of the comparison between the machining tooth flank and the theoretical tooth flank was obtained. Second, the deviation of each tooth flank point was calculated by the topological differential calculus analysis. Finally, with the machining tooth flank approaching the theoretical tooth flank as the modification objective, the additional cutting motions and machining compensation parameters of cutterheads were obtained to control the machining tooth flank deviations and reduce them to the allowable deviations of the theoretical tooth flank, and the cutterhead approximation machining of line contact spiral bevel gear pairs with tapered teeth depth was realized. The contact simulation analysis and rolling test verified the correctness of the line contact conjugate flank model and the feasibility of the cutterhead approximation machining method. [ABSTRACT FROM AUTHOR]

In this study, the effect of flow rate and melt temperature on the film thickness during the film insert injection molding (FIM) process is investigated. Many studies have rigorously investigated viscoelastic deformation and severe warpage during the FIM process. However, very few studies have examined the change in the film thickness, despite it being an important aspect for achieving a high-quality final product. In this regard, changes in the film thickness during the FIM process are experimentally and analytically examined in this study. Some notable changes are observed in the film thickness along both center and edge paths in the melt flow direction. This is attributed to the combined effect of rapid heat transfer from the hot polymer melt and compressive effect from melt pressure. Moreover, a simple mathematical model is created based on a dimensional analysis, which helped in predicting their effects on the film thickness distribution. [ABSTRACT FROM AUTHOR]

The dynamic rolling force model in the coexistence regime of boundary lubrication friction and hydrodynamic lubrication friction was established in this paper, mainly aiming at the common mixed lubrication friction state in the actual rolling process, while the research of rolling mixed lubrication is relatively few. Combining Karman differential equation of unit pressure with Celikoff equation, a linearized differential equation of unit pressure was obtained. The expression of total friction stress under mixed lubrication state was given according to the oil film thickness at any position in the working area and the surface real contact area ratio. It is characterized by the consideration of the mixed lubrication friction state of the coexistence of boundary lubrication and hydrodynamic lubrication, which is applicable to the whole deformation zone and the general rolling mixed lubrication friction regime. The expressions of the unit normal pressure in the front-slip zone and the backward slip zone were obtained by considering the boundary conditions at the entry and exit cross sections. The dynamic rolling force model of cold rolling strip was established by numerical integral calculation. It is based on the above expression of total friction stress; therefore, this dynamic rolling force model is more universal, the prediction accuracy is higher, and it is closer to the actual industrial production. Based on the dynamic rolling force model, the effects of friction coefficient, reduction ratio, shear strength, and roll flattening on the unit normal pressure along the contact arc and the rolling force was also analyzed in this paper. Verification with actual industrial production data showed that the prediction model of rolling force had high precision, and it could provide guidance for calibration of rolling mill equipment and parameter optimization of production technology. [ABSTRACT FROM AUTHOR]

This work is on the study of the synergetic effect of anodized Al alloy surfaces, with thin tungsten disulphide films alloyed with carbon and fluorine (WS-CF) deposited by magnetron sputtering. The surface roughness and surface chemistry were changed to tune the surface wettability and improve the frictional behaviour of the hybrid surfaces. The SEM analysis of these surfaces showed that, although the film growth has led to the progressive pore narrowing, pores were still visible after deposition of an ~ 200 nm thick film. Even though the film deposition has induced the surface smoothening, the surface free energy (SFE) of the hybrid surfaces was not substantially altered, when compared to bare anodized surface with large dimple (LD). Accordingly, the contact angles measured with water (WCA) and α-bromonaphthalene (OCA) on the hybrid surfaces suggested that the film surface chemistry was the main responsible for the wettability results, having the bottom dimple-shaped surface roughness just a low effect. LD surface coated with pure WS2 coating (LD + WS2) showed a remarkable high hydrophobicity combined with a high oleophilicity. Pin-on-disc testing carried out at room temperature in dry conditions showed much lower coefficient of friction (COF) values for the coated samples (hybrid surfaces), comparatively to uncoated ones. Furthermore, the friction performance of the hybrid surfaces was better for the F-alloyed thin film (sample named as WS-CF5 and having 9.5 at% of F) than for the WS2 film. In lubricated testing with a polyalphaolefin oil (PAO-8), the soft uncoated surfaces presented lower COF values, since the rapid smoothening of the contact surface turned the lubrication regime from mixed to hydrodynamic-like. For the LD surfaces coated with the F-alloyed WS film (named as LD + WS-CF5), the higher hardness of WS-CF5 was responsible for keeping the lubrication regime in partial lubricated conditions, leading to higher initial COF. Afterwards, a WS2-based tribolayer is formed in the solid-solid contacts which, together with the progressive film smoothening, change the lubricated regime toward hydrodynamic. Therefore, the friction of LD + WS-CF5 was reduced with the elapsed time and approached the one of the uncoated samples (LD). Concluding, both these hybrid surfaces can have a role on oil-water separation processes, self-cleaning of building outdoors or on microfluidic and printing applications. [ABSTRACT FROM AUTHOR]

Due to the characteristics of the grinding process, thermal damage may occur in the workpiece surface, resulting in the rejection of a component and considerably increasing the production costs. This study aims to analyze the heat fluxes, energy partition, and temperatures during surface grinding process with both conventional and MQL lubrication. Through the proposed analysis, the heat fluxes and maximum temperature can be predicted, enabling the avoidance of thermal damages and increasing the efficiency of the process. A comparison between the calculated and experimental value has shown that the difference is acceptable for various situations, in the order of 4.72% for the conventional method and 7.38% for the MQL method. A thermal model was developed. The transient two-dimensional heat diffusion equation was discretized by finite volume method in space and explicit discretized in time. The heat fluxes were estimated using inverse problem technique of heat transfer aiming the obtainment of the temperature of certain workpiece points. A comparison of the methods of lubrication showed that the conventional method was way more efficient than MQL, presenting considerably lower total heat flux and maximum reached temperature and any kind of thermal damage wasn't observed. On the other hand, thermal damage occurred in the workpieces. Also, clogging phenomenon in the grinding wheel surface after the process in MQL condition was observed. [ABSTRACT FROM AUTHOR]

Aiming at the problem about misjudging sheet fracture in hydroforming process, the different mechanisms between drawing and hydraulic bulging are analyzed. In this paper, a method to test the forming limit diagram (FLD) based on uniform load in thickness direction is adopted by using laminated plate hydroforming, and the quality of hydroforming process is judged more accurately. By the numerical simulation analysis, the shape of the specimen on five different linear paths is preliminarily determined, and the forming limit diagram of the sheet is obtained under the stretch-compression condition. At the same time, the influence of method of lubrication such as non-lubrication, oil, grease, and thin film on FLD is analyzed. The results show that the first principal strain and the second principal strain increase, and the bulging height decreases with the decrease of friction factor. Among them, the friction factor of thin film is reduced to the lowest. In the process of laminated sheet hydroforming, the thin film lubrication between pieces is more relatively accord with the experimental condition of stretch-compression bulging, and the FLD is more reliable to judge the quality of component formed by hydroforming. [ABSTRACT FROM AUTHOR]

Electrohydraulic forming is a typical high-speed forming which can significantly improve the formability of sheet metal. The objectives of this paper are to explore the influence of preset wire length and lifting height on the equi-biaxial stretching forming limit of DP600 steel sheets during electrohydraulic forming. The results showed that the maximum equi-biaxial stretching forming limit was obtained at the optimal wire length of 45 mm and lifting height of 37 mm, then the entire FLC was generated to evaluate the formability of DP600 steel sheets with these optimal parameters: a relative increase of 17.5–70% in major strain obtained by EHF was observed in all three regions of the FLC (tension-tension, plane strain, and tension-compression) relative to that obtained by quasi-static forming. Numerical simulation using ANSYS/LS-DYNA was conducted to reproduce the dynamic deforming behavior of a DP600 blank bulged by EHF, with an error of about 8%. A narrower radiation zone, a wider shear lip zone, and a mass of deeper and larger dimples on the fracture morphologies during EHF were observed compared with quasi-static conditions. [ABSTRACT FROM AUTHOR]

A spherical surface with a radius of R500 was used as the target surface for this study. The forming processes of three different forming methods, namely, using a fixed punch unit, using a polyurethane elastic pad, and using a swinging punch unit, were studied by numerical simulations and experimental methods. The forming process, forming principle, and mechanical structure of the three forming methods were discussed, and the effects of the three forming methods on the forming quality and accuracy of the sheet metal were analyzed in detail with respect to surface quality, curvature distribution, material thickness distribution, and spring-back. The results show that using the swinging punch unit can effectively restrain dimple and wrinkle defects, increase the plastic deformation degree of the sheet, and reduce spring-back. [ABSTRACT FROM AUTHOR]

Aluminum–copper alloys are widely employed in automobile and aerospace industries owing to their marvelous mechanical and physical attributes. But the major hindrance in their application is that these materials are more susceptible to casting defects such as porosity, hot tears, and shrinkage occurring during solidification. The said issues have a negative impact on the mechanical properties of the casted materials and thus limit their use. Squeeze casting is a promising choice for these materials that has an ability to manufacture near-net shape parts with superior surface finish and better mechanical properties. Although, the potential of this method is tested for a variety of materials, but its capability for casting AA2026 alloy is yet to be comprehensively explored which is the primary focus of this research. Three key parameters of squeeze casting process, namely squeeze pressure, die temperature, and pouring temperature are selected for investigating their influence on surface roughness, ultimate tensile strength, and hardness using response surface methodology. Experimental results are analyzed using analysis of variance to find the control factor's significance and adequacy of models. It has been found that squeeze pressure is the most influencing parameter for surface roughness whereas for ultimate tensile strength and hardness, pouring temperature is the major contributing factor. SEM analysis is carried out to reveal the micro-details of the fractured samples. In addition to finding optimal ranges of control variables (using contour plot analysis) for each response individually, a multi-response optimization has also been carried out using desirability approach. Furthermore, mathematical models are also developed and validated through confirmatory tests. The results of confirmatory runs depict that the proposed models have a high degree of prediction accuracy. [ABSTRACT FROM AUTHOR]

The high temperature generated when machining aerospace alloys namely, titanium and nickel alloys, accelerate the tool wear rate and affects the physical properties of the machined surface. Flood coolant is usually the effective traditional solution to dissipate the heat and reduce its negative impact on tool performance and surface integrity. The disposal of the coolant causes environmental concerns, and the generated fumes during machining also present health concerns. Minimum quantity lubricant is presented as an alternative coolant strategy to reduce the amount of used coolant and environmental concerns associated with flood coolant. Experimental investigations showed that MQL does not offer the same results obtained when using flood coolant during machining titanium and Inconel. However, the addition of nano-additives significantly improved the performance of MQL. In this work, an integrated model (i.e., finite element and finite volume) is developed to analyze various unique aspects of machining with nano-fluids under minimum quantity lubrication during cutting Inconel 718 and Ti-6Al-4V alloys. These aspects include the heat transfer characteristics of the resultant nano-cutting fluid, the interactions between the cutting tool and workpiece, the generated cutting temperature at different zones, and resulting residual stresses. The investigation was carried out through two main phases. A 2-D axisymmetric computational fluid dynamics (CFD) model is developed to simulate the thermal effect of resultant nano-mist and obtain the thermal characteristics of the nano-fluid. The obtained results are then used in the finite element model to simulate the machining process with nano-fluid. The average heat convection coefficients results provided from the proposed CFD model at standard room temperature demonstrated a good agreement with the theoretical values calculated throughout this work. Also, the simulated and experimental cutting forces showed better agreement in the case of cutting test performed without nano-additives (accuracy % ≈ 90%) than the cutting test performed with nano-additives (accuracy % ≈ 82.3%). This work presents a first attempt in the open literature to simulate the machining processes using MQL-nano-fluid. [ABSTRACT FROM AUTHOR]

Mixed elastohydrodynamic lubrication (EHL) model has been used to study slurry flow and contact pressure distribution in the chemical mechanical polishing (CMP) process. However, in various mixed EHL simulation frameworks, only a single-layer polishing pad is considered. Consequently, the double-layer polishing pad, which is widely used in semiconductor industry, cannot be designed and optimized from the tribology perspective with the assistance of theoretical simulation. In this paper, multi-layered elastic theory (MLET), which is frequently used to calculate flexible pavement response to truck loading, is introduced into the mixed EHL model. Pad deformation calculated by the MLET has a similar accuracy to that by the 3D finite element method, but its computational cost is much lower. It is very important for accurate and efficient simulation of the tribological behavior and material removal rate (MRR) in CMP. Based on the new simulation method, advantages of a different double-layer structure of polishing pad are discussed. It is found that the upper-hard lower-soft pad has better performance for improving the uniformity of MRR when the wafer surface is uneven, but the boundary exclusion region is bigger than single-layer pad and upper-soft lower-hard pad. The upper-soft lower-hard pad has advantage to reducing the edge exclusion, but the effect is not remarkable when the thickness of the upper layer is not extremely thinner than the lower layer. [ABSTRACT FROM AUTHOR]

Mixed elastohydrodynamic lubrication (mixed EHL) model has been successfully used to study phenomena in chemical mechanical polishing (CMP) process. However, in various mixed EHL simulation frameworks, a polishing pad's deformation cannot correctly be described by adopted models for pad deformation such as elastic half-space model and Winkler elastic foundation model. Thus, a more accurate model for pad deformation is needed, since this is the prerequisite for an accurate prediction of contact pressure and material removal rate, which is critical for improvement of polishing quality. In this paper, a layered elastic theory, which is frequently used to calculate flexible pavement response to truck loading, is introduced into the mixed EHL model. It is found that this theory has a similar accuracy to the traditional 3D finite element method for calculating the pad deformation. However, its computational cost is much lower, which is especially important for accurate and efficient simulation of mechanical behavior and material removal rate (MRR) in CMP. In order to highlight benefits of the proposed theory, simulations are carried out based on three different pad deformation models with the mixed EHL model. The pad deformation behavior is found to have a significant influence on the final simulation results, especially the MRR prediction. By comparing the different simulation models, the proposed layer elastic theory is found to be an optimal model for describing the polishing pad deformation behavior in CMP and can provide accurate simulation results on contact pressure distribution and the material removal rate. [ABSTRACT FROM AUTHOR]