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Copyright of Journal of Mechanical Strength / Jixie Qiangdu is the property of Zhengzhou Research Institute of Mechanical Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The performance improvement in machining characteristics of titanium grade 5 alloy (Ti6Al4V) is investigated in this work by turning with TiC-coated inserts of dissimilar rake angle, nose radius, and relief angle. Machining Ti6Al4V is difficult as it possesses lower heat conductivity, high-temperature strength, high reactiveness to chemicals, and high hot hardness. For this, coated inserts are considered to have varying geometries that produce better output conditions. Based on Taguchi's orthogonal array, investigations were devised, an L9 array was considered, and numerical simulation of the turning process was performed on Deform-2D simulation software. The output parameters resulting from cutting force (RFC), wear depth (WD), and tool-workpiece interface temperature (TWIT) are measured and optimized using a multi-criteria decision-making (MCDM) approach. Outcomes show that with coated inserts, the WD, TWIT, and RCF produced were lower, had a higher nose radius, and had moderate relief and rake angle, which produced better results. The confirmation experiment provides a better condition than the L9 combination. [ABSTRACT FROM AUTHOR]

In order to clarify the influence of different working conditions on the wear of tapered roller bearings, the wear state of tapered roller bearings was carried out.A quasi-statics model of tapered roller bearings including roller balance equation and inner ring balance equation was established, and a wear depth calculation model suitable for wear analysis of tapered roller bearings was derived based on Archard wear theory.The wear distribution characteristics of bearing inner and outer raceways and roller elements under light load, medium load and heavy load conditions were comparative analyzed.The results show that the wear depths of the tapered roller and the inner/outer raceways on the contact line show bimodal distribution characteristics, and the wear distribution of the outer raceway is closely related to the positions of the rolling elements.For light load condition, the peak wear depth of bearing raceways and roller elements increases by 20% as bearing speed increases 25%, and for heavy load condition, the peak wear depth of bearing raceways and roller elements increases more than 17% as bearing load increases 16%.The comparison of bearing wear peaks under the three working conditions shows that the product of the equivalent load and the speed of the bearing is not the determining factor controlling bearing wear，and the load change has a significant impact on the bearing wear.

The present study uses DC magnetron sputtering for synthesis of a TiN and Ti-TiN bilayer on the surface of SS-CRM 487/1 high-speed tool steel. This coating is deposited on the substrate at 400°C. The deposited substrate is characterised by different experimental techniques. The scanning-electron microscopy (SEM) is used for film morphology, cross-sectional examination, and worn-out surfaces. The profilometer is used for measuring the film thickness and roughness. However, the nano-indentation is used to extract the intrinsic hardness and young's modulus evaluation. The ball on-disc sliding test under dry conditions is employed for tribological properties of deposited high-speed tool steels. The test results indicate the improvement in the wear resistance for the Ti-TiN bilayer except four bilayers as no of layer increases. [ABSTRACT FROM AUTHOR]

During the drilling process of large displacement wells, due to the high horizontal-vertical ratio, the movement of the drill string underground is complex, resulting in severe wear on the casing wall and a reduction in casing strength, greatly affecting subsequent drilling and production operations. A casing wear efficiency model based on energy transfer was applied. The segmented method was used to determine the lateral force on the pipe string, and the crescent-shaped wear of the casing was analyzed. Based on the API (American Petroleum Institute) minimum wall thickness method, the crescent-shaped casing wear was simplified, and a method for predicting casing wear and calculating residual strength was established. Using this model, calculations were performed on a large displacement well in the South China Sea. The results show that lateral force is the main factor affecting casing wear, and reverse circulation drilling has a significantly greater effect on casing wear than normal drilling. The most severely worn section of the entire wellbore is the section with the greatest dogleg severity, where the risk of casing failure is highest, making it the critical section for implementing anti-wear measures. After the completion of the four-stage operation in this well, the depth of casing wear at the location of the maximum dogleg severity is 1.15 mm, and the casing strength has decreased to 58. 24% of its original strength, but still meets strength requirements. The research outcome provides a basis and reference for the prevention and control of casing wear in highdisplacement wells in the South China Sea. [ABSTRACT FROM AUTHOR]

Surface tooth wear is one of the major causes of tooth failures in gear drives. Boosting tooth wear resistance is a significant research objective for designing high-quality asymmetric spur gears with longer life against wear. The main goal of the present work is to boost the wear resistance of the asymmetric spur gear by changing the tooth shape through profile modification. The proper distribution of correction factor to the pinion and gear is necessary to enhance the gear performance. The asymmetric spur gear with different values of sum of profile correction factors (−0.2, 0 and 0.2) is chosen to evaluate the wear depth. This sum of correction factors is accurately distributed between the asymmetric pinion and gear for attaining balanced sliding velocity at the tip and root, balanced slide to roll ratio at the tip and root, equal bending strength in the asymmetric drive and maximum balanced wear in the face and flank regions of the pinion. The optimum values of the correction factor of the asymmetric pinion and the maximum tooth wear are evaluated for the above four different balanced cases. The calculated tooth wear is lower in the balanced wear method than that in other balanced methods. [ABSTRACT FROM AUTHOR]

During the process of starting, braking and running of the train, sliding contact between wheel and rail occurs. The wear caused by sliding contact exerts a noteworthy influence on the contact characteristics of wheel/rail. To analyze these characteristics, a three-dimensional wheel/rail contact wear model is established, and the contact characteristics at different wear depths are studied. The results indicate that at initial contact, the wheel/rail contact patch is approximately elliptical in shape and its area is 122.5 mm2. The von Mises stress of the wheel and rail is maximum in the subsurface at a distance of 2 mm from the contact interface, with maximum values of 559 MPa and 628 MPa respectively. When the wear depth is less than 0.5 mm, the wear depth, contact area and size increase quickly. As the amount of wheel contact wear increases, the maximum contact stress gradually decreases and the contact stress becomes uniform. In addition, the calculation results indicate that the contact patch shape does not always remain elliptical, the shape can change from elliptical to rectangular as the wear depth increases. As the increasing of wear amount, the contact stress gradient on the inner side of wheel contact surface increases. [ABSTRACT FROM AUTHOR]

Sliding bearings are vital components in modern industry, exerting a crucial influence on equipment performance, with wear being one of their primary failure modes. In addressing the issue of wear diagnosis in sliding bearings, this paper proposes an intelligent diagnostic method based on a multiscale gated convolutional neural network (MGCNN). The proposed method allows for the quantitative inference of the maximum wear depth (MWD) of sliding bearings based on online vibration signals. The constructed model adopts a dual-path parallel structure in both the time and frequency domains to process bearing vibration signals, ensuring the integrity of information transmission through residual network connections. In particular, a multiscale gated convolution (MGC) module is constructed, which utilizes convolutional network layers to extract features from sample sequences. This module incorporates multiple scale channels, including long-term, medium-term, and short-term cycles, to fully extract information from vibration signals. Furthermore, gated units are employed to adaptively assign weights to feature vectors, enabling control of information flow direction. Experimental results demonstrate that the proposed method outperforms the traditional CNN model and shallow machine learning model, offering promising support for equipment condition monitoring and predictive maintenance. [ABSTRACT FROM AUTHOR]

30CrNi2MoVA steel demonstrates excellent performance, meeting the requirements of a crucial material for high-load structural parts. However, after experiencing high loads and thermal cycling, the material undergoes wear on its contact surfaces, resulting in a certain wear depth that determines its service life. Therefore, accurately predicting and evaluating the wear performance and wear depth of this material is of paramount importance. This study employs a combined approach of experimental and simulation methods. Initially, friction and wear tests were conducted to investigate the wear behavior of the 30CrNi2MoVA steel. The experimental results reveal a significant influence of thermal cycling temperature on the material's wear resistance, with wear mechanisms primarily attributed to adhesive wear and abrasive wear. Subsequently, a ball-on-disc wear model was established. Based on experimental data, the modified Archard model was implemented as a user subroutine in finite element software (ABAQUS version 2020) to assess the material's wear volume. The simulation results demonstrate a close agreement with the experimental wear depths. Furthermore, a fitting formula was developed to correlate the wear depth of the material with the number of wear cycles, enabling accurate wear depth prediction. This study provides theoretical support for enhancing the performance and extending the service life of 30CrNi2MoVA steel. [ABSTRACT FROM AUTHOR]

In order to analyze the bearing wear in the spindle system considering different speed and load conditions, a four-bearing spindle system was investigated. Two different working conditions, Case I and Case II, are considered. Case I condition has lower spindle speed and higher external loads and preload than Case II condition. Based on Archard model, a new wear depth model of angular contact ball bearing is presented which takes into account the influence of lubrication on bearing wear. The wear depths of inner and outer raceways for angular contact ball bearings are calculated based on the motion parameters and contact parameters of ball elements which are obtained by spindle system model. The effects of spindle speed, angular misalignment, external load and surface roughness on the wear depths of bearings are comparatively studied. Increasing spindle speed at Case I condition can significantly increase bearing wear. Angular misalignment may be beneficial to individual bearing, but overall, no angular misalignment is the most beneficial to spindle system. The change rate of wear depth of bearing raceway with external loads at Case I condition is much greater than that at Case II condition. The surface roughness can significantly affect the bearing wear in the spindle system, especially at Case I condition. [ABSTRACT FROM AUTHOR]

Copyright of Lubrication Engineering (0254-0150) is the property of Editorial Office of LUBRICATION ENGINEERING and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Sliding bearings are vital components in modern industry, exerting a crucial influence on equipment performance, with wear being one of their primary failure modes. In addressing the issue of wear diagnosis in sliding bearings, this paper proposes an intelligent diagnostic method based on a multiscale gated convolutional neural network (MGCNN). The proposed method allows for the quantitative inference of the maximum wear depth (MWD) of sliding bearings based on online vibration signals. The constructed model adopts a dual-path parallel structure in both the time and frequency domains to process bearing vibration signals, ensuring the integrity of information transmission through residual network connections. In particular, a multiscale gated convolution (MGC) module is constructed, which utilizes convolutional network layers to extract features from sample sequences. This module incorporates multiple scale channels, including long-term, medium-term, and short-term cycles, to fully extract information from vibration signals. Furthermore, gated units are employed to adaptively assign weights to feature vectors, enabling control of information flow direction. Experimental results demonstrate that the proposed method outperforms the traditional CNN model and shallow machine learning model, offering promising support for equipment condition monitoring and predictive maintenance.

Due to the high speed and high pressure operating conditions, wear between the finger seal and the rotor is inevitable, and this leads to an increase of leakage clearance and becomes an important factor affecting the seal life. The theory of anisotropic elasticity was employed to describe the mechanical characteristics of the seal material. An improved Archard wear model was proposed to calculate the nodal wear rate, and the local wear direction was also determined. The wear simulation model and procedure were established based on the Arbitrary Lagrangian Eulerian adaptive mesh strategy. The effects of material density, fabric orientation, pressure differential and rotor speed on the wear characteristics of finger seal and the change of leakage clearance caused by wear loss were studied. The results show that the wear first occurs at the heel area of the finger foot bottom and gradually extends to the toe area. C/C (carbon fibre reinforced carbon matrix) composite finger seal with higher material density has smaller leakage clearance and wear depth. With the increase of fabric orientation angle, the wear depth in the heel area of finger foot is smaller, and the circumferential wear area is narrower. The average wear depth of finger seal decreases with the orientation angle. When the orientation angle is 0, the seal leakage clearance is smaller. The increase of pressure differential not only aggravates the seal wear, but also expands the wear area, and also increases the average contact pressure and leakage clearance. Increasing the rotor speed make the wear depth of the heel area of finger foot gradually increase, but the wear area becomes narrower. The average contact pressure decreases and the average leakage clearance increases. This study provides a theoretical method and basis for the prediction and evaluation of the wear life and performance of C/C composite finger seal. [ABSTRACT FROM AUTHOR]

Copyright of Lubrication Engineering (0254-0150) is the property of Editorial Office of LUBRICATION ENGINEERING and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this work, a wear prediction model considering the dynamic load is proposed for spur gears in mixed elastohydrodynamic lubrication (EHL). The dynamic load is calculated by gear dynamic model. Combining gear wear model and dynamic model, the wear depth under the dynamic load is determined and compared with that under quasi-static load. The comparative results show that the maximum wear depth under dynamic load is significantly larger than that under quasi-static load near engaging-in point. The effects of fractional film defect coefficient on wear depth are considerable under dynamic load, which is closely related to gear contact temperature. Furthermore, the effects of surface roughness and gear geometrical parameters on wear depth are studied. The investigation reveals that the wear depth decreases with the increased tooth width, module and pressure angle, but increases with the surface roughness. It illustrates that gear wear depth under the dynamic load can be reduced by optimizing gear geometrical parameters. [ABSTRACT FROM AUTHOR]

This paper proposes an accurate and applicable online measurement method of wear depth using displacement signal for vertical testers under mixed lubrication. Firstly, displacement signal is revealed to be composed of temperature drift and Brownian motion. Secondly, the first order Taylor expansion of the Brownian motion is revealed to be the unified form of wear models. Further, the online measurement method is established by introducing non-integer order and amplitude coefficient to eliminate systematic randomness. Finally, the method is verified by graphite-metal tribo-pairs on a standard tester and a high speed friction and wear testing bench, relative errors between online and offline measurement results are less than 10 %, extension errors by non-integer order within its application range are less than 2 %. • Revealing the components of measured displacement signal consisting of temperature drift and Brownian motion. • Proposing a unified form of wear models. • Establishing online measurement algorithm and operation flow. • Verifying accuracy and applicability of the online measurement method. [ABSTRACT FROM AUTHOR]

This work studies the tooth surface wear of floating involute spline couplings. Based on the energy dissipation method, this study takes the floating involute spline couplings as the research object, divides the whole wear cycle into three wear stages and analyzes its wear mechanism, and proposes a wear prediction model suitable for floating involute spline couplings. By using Abaqus, the simulation of the involute spline couplings before and after carburizing was carried out when the floating distance was 0 mm, 0.3 mm and 0.6 mm, respectively. The wear depth of each tooth was compared and analyzed, and the axial and radial distributions of the wear on the tooth surface of the involute spline couplings were explored. Finally, the floating involute spline couplings test bench was used to verify the spline wear before and after carburizing. The results show that with the increase in floating distance, the wear of the tooth surface also increases, and the upper edge of the tooth surface is seriously worn. Through the comparative analysis of the spline tooth surface wear before and after carburizing treatment, it can be seen that carburizing treatment can effectively reduce the wear degree of the spline couplings tooth surface and improve the service life of the spline couplings, but at a high floating distance, carburizing treatment has no significant effect on improving the performance of the tooth surface. [ABSTRACT FROM AUTHOR]

Wear of runner blades is a common problem affecting the operational reliability of turbines with high head and high sediment content. In order to accurately predict the wear of the turbine runner blade, based on the solid-liquid two-phase flow equation and turbulence model, the full channel numerical simulation of the internal water and sediment flow was carried out, and the sediment volume distribution and sand water velocity on the turbine runner blade were obtained. Then, according to the digital simulation results and the operating parameters of the turbine runner, the sediment wear test scheme for the turbine blade material specimen is designed, and the sediment wear test is carried out on the runner material. According to the test results, the sediment wear curve of runner blade material is obtained and applied to numerical simulation, and the main position and wear degree of turbine blade sediment erosion are predicted. The inspection results of the runner blade wear after the unit has operated for a flood season show that obvious wear can be seen at the outlet edge of the lower band of the runner blade, and the wear position and wear amount are basically consistent with the simulation values. The study is of great importance for predicting the wear of turbine runner blades with high drop height and high sediment content, and for turbine maintenance under complex conditions.

Copyright of Lubrication Engineering (0254-0150) is the property of Editorial Office of LUBRICATION ENGINEERING and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In order to clarify the effects of different working condition parameters and quantify their influence degree on bearing wear in the spindle system, the bearing wear in the spindle system supported by multi-bearing was carried out. Firstly, the calculation method of wear coefficient considering the lubrication state is introduced, and the wear depth model of the angular contact ball bearing is deduced. Second, the wear depth of the inner and outer raceways of the bearing is calculated based on the motion parameters and contact parameters of the bearing rolling elements obtained from the system model. The influences of spindle speed, bearing angular misalignment caused by mounting error, external loads and bearing surface roughness on bearing wear are discussed. The results show that the spindle speed has a significant impact on bearing wear, and the change of spindle speed leads to a great difference of bearing wear law. Without bearing angular misalignment, the sum of the wear depth of the inner and outer raceways of each bearing in the spindle system is the smallest. The change of external loads has little effect on bearing wear, but the increase in surface roughness can significantly increase the wear depth of the bearing.

This work studies the tooth surface wear of floating involute spline couplings. Based on the energy dissipation method, this study takes the floating involute spline couplings as the research object, divides the whole wear cycle into three wear stages and analyzes its wear mechanism, and proposes a wear prediction model suitable for floating involute spline couplings. By using Abaqus, the simulation of the involute spline couplings before and after carburizing was carried out when the floating distance was 0 mm, 0.3 mm and 0.6 mm, respectively. The wear depth of each tooth was compared and analyzed, and the axial and radial distributions of the wear on the tooth surface of the involute spline couplings were explored. Finally, the floating involute spline couplings test bench was used to verify the spline wear before and after carburizing. The results show that with the increase in floating distance, the wear of the tooth surface also increases, and the upper edge of the tooth surface is seriously worn. Through the comparative analysis of the spline tooth surface wear before and after carburizing treatment, it can be seen that carburizing treatment can effectively reduce the wear degree of the spline couplings tooth surface and improve the service life of the spline couplings, but at a high floating distance, carburizing treatment has no significant effect on improving the performance of the tooth surface.

In order to improve the service life and detection accuracy of the unfolding wheels in the AVIKO series steel ball inspection system, and to improve the surface friction coefficient while reducing wear, the surface microstructures were applied to the unfolding wheels to study the friction and wear characteristics. Three kinds of pit microstructures with different diameter parameters were processed on the outer surfaces of the test pieces by laser, and the friction coefficient and wear amount were obtained through the tests with a self-designed friction and wear tester, and the distribution of stress and wear depth were obtained by numerical simulation. Compared and analyzed with smooth surface test pieces, the results show that the friction coefficient of the microstructure surface test pieces is larger and the wear amount is smaller under dry sliding friction conditions. The microstructure surface reduces wear and improves wear resistance by changing the stress distribution and dispersing the position of wear points. The established numerical simulation wear model may be used to predict the wear depth of microstructure surface, which provides a basic theory for the life prediction of microstructure surface unfolding wheels. [ABSTRACT FROM AUTHOR]

In this study, samples of worn spindle hook teeth were collected under different field working times to investigate their loss of ability to pick seed cotton owing to wear failure of the geometric structure. The wear characteristics of the surface of the hook teeth were tested and analyzed, and the development process of the wear region and the average value of the wear depth were obtained. This research established a wear process model for the surface of hook teeth. The results show that wear originates from the tip of the hook teeth, and a parallelogram-like wear region is gradually formed along the direction of the teeth edge. The size of the wear region and wear depth gradually decreased in the following order: hook teeth 1, hook teeth 2, and hook teeth 3. The relative errors of the front three hook teeth of simulated wear depth and wear depth were Δ 1 = 2.55%, Δ 2 = 1.43%, and Δ 3 = 4.02%, respectively. Thus, the accuracy of the picking spindle hook teeth wear process model was verified. Accordingly, the failure process of hook teeth wear can be predicted, laying a foundation for the subsequent optimization design of the spindle picking hook teeth geometric structure. • The development of the wear region on the picking spindle hook teeth is analyzed. • The wear depth leads to structural failure of the picking spindle hook teeth. • The picking spindle hook teeth wear process model close to the field test conditions was constructed. • The linear relationship between the working time of the picking spindle hook teeth and the wear depth was established. [ABSTRACT FROM AUTHOR]

We carried out wear tests with material combination of a hard-drawn copper contact wire and an iron-based sintered alloy contact strip by changing the apparent contact area with four steps to clarify the influence of the apparent contact area on wear properties under electric current flowing condition. And we focused on a film resistance such as an oxide film and a wear particle on the contact wire surface, and considered the relationship between wear depth and wear mode transition phenomena. Based on wear properties obtained from the wear test results and microscopic observations, we clarify the phenomena that the wear mode which maximizes the wear rate of contact wire will be changed depending on the apparent contact area, and that the wear depth determined by the apparent contact area and the load are important parameters for melting of contact wire. Finally, the possibility of suppressing the maximum wear of contact wire is suggested by decreasing the film resistance of contact wire with changing the apparent contact area.

Abstract The spherical plain bearing test bench is a necessary detecting equipment in the research process of self-lubricating spherical plain bearings. The varying environmental temperatures cause the thermal deformation of the wear-depth detecting system of bearing test benches and then affect the accuracy of the wear-depth detecting data. However, few researches about the spherical plain bearing test benches can be found with the implementation of the detecting error compensation. Based on the self-made modular spherical plain bearing test bench, two main causes of thermal errors, the friction heat of bearings and the environmental temperature variation, are analysed. The thermal errors caused by the friction heat of bearings are calculated, and the thermal deformation of the wear-depth detecting system caused by the varying environmental temperatures is detected. In view of the above results, the environmental temperature variation is the main cause of the two error factors. When the environmental temperatures rise is 10.3 °C, the thermal deformation is approximately 0.01 mm. In addition, the comprehensive compensating model of the thermal error of the wear-depth detecting system is built by multiple linear regression (MLR) and time series analysis. Compared with the detecting data of the thermal errors, the comprehensive compensating model has higher fitting precision, and the maximum residual is only 1 μm. A comprehensive compensating model of the thermal error of the wear-depth detecting system is proposed, which provides a theoretical basis for the improvement of the real-time wear-depth detecting precision of the spherical plain bearing test bench.

Abstract In this study, based on the classical Archard adhesion wear theory, a three-dimensional finite element model was established, with the aim of simulating the failure process of self-lubricating spherical plain bearings in the swinging wear condition. The results show that the self-lubricating spherical plain bearings go through two different stages during the wear process, namely, initial wear stage and stable wear stage. Because the large contact points wear out during the initial wear stage, the maximum contact pressure decreases as the test period increases. The relatively larger wear depth region shows elliptical distribution, and the maximum distribution appears in the central contact area. The wear depth reaches 0.974 mm after swinging 25,000 times. PTFE fibers, which possess a good friction performance but poor abrasion resistance, abundantly exist on the friction surfaces of the fabric liner. Consequently, the friction torque during the initial wear stage is slightly smaller than the friction torque during the stable wear stage; however, the wear rate during the initial wear stage is high. The reliability and effectiveness of the finite element model are verified by experiment. The developed finite element model can be used for the analysis of the wear mechanisms of bearings and the prediction of the service life of bearings.

Objectives: To test the hypotheses that (a) the chairside/handheld dental scanner combined with a metrology software will measure clinical wear in vivo in agreement with measurements from X‐ray computed microtomography and; (b) polished monolithic zirconia does not cause accelerated wear of opposing enamel. Materials and methods: Thirty single crowns were randomized to receive a monolithic zirconia or metal‐ceramic crown. Two non‐restored opposing teeth in the same quadrants were identified to serve as enamel controls. After cementation, quadrants were scanned using an intraoral dental scanner. Patients were recalled at 6‐months and 1‐year for re‐scanning. Scanned images were compared using a metrology software to determine maximum vertical wear of teeth. The accuracy of the scanning measurements from this new method was compared with X‐ray computed microtomography (micro‐CT) measurements. Statistical analysis was performed using Mann–Whitney U test to determine significant differences between wear of enamel against zirconia, metal‐ceramic or enamel. Linear regression analysis determined agreement between measurements obtained using intraoral scanning and micro‐CT. Results: Regression analysis demonstrated that there is a quantitative agreement between depth and volume measurements produced using intraoral scanning and the micro‐CT methodologies. There was no significant difference between the wear of enamel against polished monolithic zirconia crowns and enamel against enamel. Conclusions: Intraoral scanning combined with a matching software can accurately quantify clinical wear to verify that monolithic zirconia exhibited comparable wear of enamel compared with metal‐ceramic crowns and control enamel. Agreement between the intraoral scanner and the micro‐CT was 99.8%. Clinical Trials.gov NCT02289781. [ABSTRACT FROM AUTHOR]

Casing wear is a serious problem in highly-deviated wells because serious wear will lead to casing deformation, drilling tool sticking and failure of subsequent operations. The purpose of this paper is to predict casing wear depth and evaluate its effect on casing strength degradation in highly-deviated well drilling operation. Special attention has been given to the algorithm to achieve the prediction and evaluation. The effect of tool joint on contact force distribution is considered in contact force model. Then a wear depth prediction model and its solution method are proposed based on crescent-shaped wear morphology and wear-efficiency model. Besides, strength degradation of worn casing is analyzed in bipolar coordinate system and the model is verified by finite element method. Therefore, the technology of casing wear prediction and residual strength evaluation is completed systematically. Then, to apply casing wear prediction and residual strength evaluation technologies to an actual highly-deviated well, casing wear experiment and friction coefficient experiment are carried out to obtain wear coefficient and friction coefficient. Finally, based on the established models as well as experimental results, the distribution of casing wear is predicted and residual strength is evaluated. The method presented in this paper will contribute greatly to casing wear prediction and evaluation in highly-deviated wells. [ABSTRACT FROM AUTHOR]

In this research work, a new incremental slab method analysis has been derived to calculate extrusion force and its die pressure distribution during an extrusion process, while a die of arbitrary shape is used. In addition, a computational algorithm has been presented based on the proposed analysis method and Archard's wear model to investigate the effect of die profile on its working life. Three different die profiles including optimum curved, optimum constant angle, and cylindrical shaped are numerically evaluated. The results revealed that the predicted extrusion loads and die pressure distributions through the implementation of the applied method are in an acceptable agreement with FEM analysis results. Moreover, it has been demonstrated that the maximum wear depth on all die profiles is located at the die exit area, which indicates the predominant effect of the material velocity profile. It is also found that the die life of the two optimum dies would be the same, but the least working life estimated is the working lifetime of the cylindrical die profile. [ABSTRACT FROM AUTHOR]

Copyright of Transactions of Nanjing University of Aeronautics & Astronautics is the property of Editorial Department of Journal of Nanjing University of Aeronautics & Astronautics and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The hip joint envisages the prime load bearing structure among other joints in the human body. Hip joint failure leads to the replacement of the hip joint prosthesis. This research work focuses on the proper selection of bearing couple materials for the hip joint to improve the performance and life. Herein, the stress and deformation of different bearing couple materials are analysed in the perspective of transient dynamic analysis under jogging load cycle. Selective hip joint bearing (femoral head-liner) couples are SS316L on UHMWPE (MoP), CoCrMo on UHMWPE (MoP), Ti6Al4V on SrO-ZTA (MoC), SrO-ZTA on UHMWPE (CoP) and SrO-ZTA on SrO-ZTA (CoC) encountered, respectively. The SrO-ZTA on SrO-ZTA (CoC) bearing couple generates the less Von Mises stress of 180.88 MPa. Load bearing pressure and Archard law predict the wear depth of CoCrMo on UHMWPE (MoP) and SrO-ZTA on SrO-ZTA (CoC) bearing couples are 0.141 mm/year and 0.031 mm/year, respectively. In simultaneous, the theoretical wear volume for CoCrMo on UHMWPE (MoP) and SrO-ZTA on SrO-ZTA (CoC) bearing couples are found as 35.46 mm3/year and 2.62 mm3/year, respectively. The wear depth and wear volume are supporting the available clinical retrievals and exist in well acceptable range. Competitive wear analysis data ensures 15 years safe life of SrO-ZTA on SrO-ZTA (CoC) hip prosthesis bearing. [ABSTRACT FROM AUTHOR]

The paper aims to predict the cam and follower wear in direct acting valve train considering the effects of operating conditions. A numerical approach has been developed using frictional and lubrication analysis which is applied in the cam/follower wear study. Loading and motion parameters have been determined from dynamic and kinematic analysis whereas the wear profiles are obtained by linear wear relation. The wear of cam/follower is largely dependent on the lubrication film thickness, normal loading/contact pressure and sliding velocity. At low camshaft speeds, the wear depth of cam/follower pair is higher whereas it decreases at higher speeds due to relatively thicker oil film. It is an original research work and is strongly believed that it would help to further improve the performance of engine valve train and would also provide an opportunity to control the operating conditions promoting wear. [ABSTRACT FROM AUTHOR]

• Laser surface texturing improves lipophilicity of gear surfaces. • Static contact angle of sample decreases from 47° ± 2.8° to nearly 0° after texturing. • Spreading speed of oil droplets on processed surface is increased by 1.27 times. • Processed sample shows a 33.5 % reduction in surface wear depth compared to unprocessed one. Gear transmission is crucial in mechanical engineering, extensively used in automobiles, ships, machine tools, and airplanes. However, as gear systems advance towards higher speeds, heavier loads, and smaller sizes, the tooth surface becomes more prone to pitting, wear, and other failures. The use of laser surface texturing technology has shown great promise in enhancing the hydrophobic and lipophilic properties of material surfaces. Thus, this paper presents a novel approach for machining equally spaced parallel and perpendicular microgrooves on the surface of gear steels (20CrMnTi) to facilitate lubricant storage and enhance the material's surface lipophilicity. Laser power and scanning speed are optimized as parameters for laser processing to investigate the lipophilic properties, including the contact angle, diffusion velocity, and contact behavior of oil droplets. Comparative analysis of the processed and unprocessed specimens revealed that both static and dynamic contact behaviors are significantly changed. Compared with the unprocessed specimens, the static contact angle of the processed specimens decreases from 47° to 0° and is super lipophilic at different temperatures; the oil droplet diffusion distance increases by a maximum of 1.27 times; the vertical diffusion height increases by a maximum of 2.8 mm; and the wetting hysteresis coefficient increases by a maximum of 2.55 times. Additionally, the friction coefficient decreases during the stable wear phase, and the wear depth is reduced by 33.53 %. The research has demonstrated that the oil-attracting properties of 20CrMnTi can be greatly enhanced using laser micro-nano texture technology. This improves lubrication conditions and wear resistance, providing a novel approach to mitigating failure risks such as pitting and wear in various gear mechanisms. Furthermore, this method effectively extends the service life of gears, making it a valuable tool for gear engineering applications. [ABSTRACT FROM AUTHOR]

The piston rings are the most important part in engine which controls the lubricating oil consumption and blowby of the gases. The lubricating film of oil is provided to seal of gases towards crankcase and also to give smooth friction free translatory motion between rings and liner. Of the three rings present top ring is more crucial as it does the main work of restricting gases downwards the crankcase. Boundary lubrication is present at the Top dead centre (TDC) and Bottom dead centre (BDC) of the liner surface. In addition to this, top ring is exposed to high temperature gases which makes the oil present near the top ring to get evaporated and decreasing its viscosity, making metal-metal contact most of the time. Due to this at TDC, excess wear happens on the liner which is termed as Top ring reversal bore wear. The wear rate depends upon many parameters such as lubrication condition, viscosity index, contact type, normal forces acting on ring, geometry of ring face, surface roughness, material property. The present work explores the wear depth for different geometries of barrel ring using Finite Element model with the help of Archard wear law and the same is validated through experimentation. The study reveals that Asymmetric barrel rings have less contact pressure which in turn reduces the wear at Top dead centre.

Electroless Ni-P-W coating has enhanced tribological properties compared to the conventional binary alloys. Hence, electroless Ni-W-P, which is a ternary alloy, is synthesized on mild steel substrates. The coatings are heat treated at 400 °C for 1 hr to obtain a high hardness. Their tribological behavior is investigated on a pin–on–disc tribo–tester under dry condition. Three test parameters which include the applied normal load (L), sliding speed (S) and sliding time (T) are varied and their effects on wear depth and coefficient of friction are analyzed. An attempt is made to ascertain the optimum combination of the parameters that would minimize the coefficient of friction and wear depth of the deposits simultaneously using Grey Fuzzy logic. Optimum tribological behavior of the deposits is obtained at an applied normal load of 10 N, sliding speed of 80 rpm and sliding duration of 5min. Load and time are seen to be the most significant factors in influencing the friction and wear of the deposits. The variation of coefficient of friction and wear depth considering the combined effect of the aforesaid parameters is analyzed from three dimensional surface plots. The wear mechanism is found to be predominantly abrasive in nature.

The surface tooth wear which occurs at the gear contact region due to inadequate contact strength of the tooth is one of the predominant modes of gear failures. Currently, higher contact ratio spur gears are increasingly used in power transmission applications such as aircraft, wind turbine, automobiles and compact tracked vehicles due to their high load carrying capacity. In this work, the direct design is found to be one of the efficient gear design methods to reduce the tooth surface wear on high contact ratio asymmetric spur gears. Asymmetric gear tooth is defined, as one whose tooth geometry of the drive and coast sides is not symmetric. Asymmetry between tooth sides is achieved by providing two different pressure angles at the respective coast and drive side pitch circles. The area of existence diagrams for normal and high contact ratio gears have been developed to select suitable design solution with the given variables of gear ratio, contact ratio and teeth number. The contact load capacity, wear resistance, power losses and mechanical efficiency have also been deduced for directly designing normal and high contact ratio asymmetric spur gears. [ABSTRACT FROM AUTHOR]

Tooth fracture and surface wear are the major failure causes in a gearing system. With increasing demand for high power density gear applications, the need of effective gear design becomes an important requirement to improve gear life. This article presents a method to enhance the load carrying capacity in bending and contact, as well as wear resistance to increase gear efficiency through asymmetric tooth. Asymmetric gear is the one whose pressure angles at pitch circle on drive and coast sides are different. In the present investigation, the load shared by a teeth pair, fillet and contact stresses, wear resistance, frictional power losses and the respective mechanical efficiencies have been determined for comparative performance assessment of symmetric and asymmetric spur gears. [ABSTRACT FROM AUTHOR]

Adhesive wear in mixed elastohydrodynamic lubrication (EHL) has been one of the most prominent problems for heavy-loaded helical gears. However, this issue was rarely investigated in previous researches. In this work, an adhesive wear model for helical gears is established in line-contact mixed EHL. The contact parameters of the pinion and gear are derived according to the equivalent tapered roller contact model, and the load is attained in consideration of the varying contact line ratio. Then the asperity contact pressure is calculated according to Hertz's elastic contact theory and load sharing. Moreover, the sliding distances of the points on tooth surface of driving pinion and driven gear are achieved by a single point observation method, and Archard theory in dry contact is extended to the mixed lubrication to estimate the wear rate in mixed EHL by using fractional film defect. The modified Archard's wear model is then employed in formulating and accounting for the gear tooth wear. Effects of surface roughness, geometrical parameters and working parameters on wear depth of the driving pinion are furtherly investigated. The results show that the wear depth in mixed EHL is lower than that under dry contact, which indicates that tooth wear can be reduced with the reasonable lubricants. As the surface roughness becomes large, the asperity contact pressure, the tooth surface temperature and wear depth are increased. Additionally, the wear depths decrease with the increase in module, helix angle, pressure angle, tooth width or rotation speed but increase with input torque. • An adhesive wear prediction method is developed for helical gears in mixed EHL. • Effects of tooth surface roughness on the wear of helical gear are investigated. • Efficient lubrication can greatly reduce the wear depth of tooth surface. • Geometrical and working parameters optimization is beneficial for wear resistance. [ABSTRACT FROM AUTHOR]

The aim of this study is to investigate the effects of implant orientation and implant material on tibia bone strain, implant-bone micromotion, maximum contact pressure, and wear depth at the articulating surface due to total ankle replacement. Three-dimensional finite element models of intact and implanted ankle were developed from computed tomography scan data. Four implanted models were developed having varus and valgus orientations of 5° and 10°, respectively. In order to determine the effect of implant material combination on tibia bone strain, micromotion, contact pressure, and wear depth, three other finite element models were developed having a different material combination of the implant. Dorsiflexion, neutral, and plantarflexion positions were considered as applied loading condition, along with muscle force and ligaments. Implant orientation alters the strain distribution in tibia bone. Strain shielding was found to be less in the case of the optimally positioned implant. Apart from the strain, implant orientation also affects implant-bone micromotion, contact pressure, and wear depth. Implant materials have less influence on tibia bone strain and micromotion. However, wear depth was reduced when ceramic and carbon fibre-reinforced polyetheretherketone material combination was used. Proper orientation of the implant is important to reduce the strain shielding. The present result suggested that ceramic can be used as an alternative to metal and carbon fibre-reinforced polyetheretherketone as an alternative to ultra-high molecular weight polyethylene to reduce wear, which would be beneficial for long-term success and fixation of the implant. [ABSTRACT FROM AUTHOR]

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Highlights • A novel adhesive wear prediction method is developed for double helical gears. • An enhanced coordinate transformation for wear depth calculation is proposed. • A generalized sliding distance model for computing gear wear depth is presented. • Geometrical and working parameters optimization is beneficial for wear resistance. Abstract An adhesive wear prediction method for double helical gears is proposed according to enhanced coordinate transformation and generalized sliding distance model in conjunction with Archard's wear equation. To describe transient contact ellipse and identify the contact point pairs conveniently, a transform coordinate plane is set in coincidence with the plane of action and a coordinate axe parallels to the contact line. The contact pressure distribution is determined by contact line length, contact width and normal force, and a modified sliding distance model is proposed by generalized moving distance replacement of Hertz contact width. As the wear coefficient, contact pressure and sliding distance are given, the tooth wear depths are predicted by a developed numerical procedure. Effects of major geometrical and working parameters on the wear depth are investigated. The results show that the wear depth becomes smaller, which is mainly determined by the contact force per unit length, equivalent curvature radius and sliding distance as normal module, normal pressure angle, helix angle, tooth width or transmission ratio increases. However, the wear depth becomes larger when input torque is improved. It is indicated that rational parameters match in gear design and uniform wear distribution are beneficial for wear resistance. Graphical abstract Image, graphical abstract [ABSTRACT FROM AUTHOR]