Wear Equation Research Articles

Study on the wear characteristics of hydrodynamic seals during start-up based on cross-scale contact mechanics

Hydrodynamic seals are crucial sealing components in aero-engines, and the wear phenomenon during their start-up process is the primary cause of engine efficiency and lifetime degradation. To accurately predict the wear rate of seals, this study establishes a wear prediction model for the start-up process of hydrodynamic seals. The model solves the multi-field coupling of cross-scale contact mechanics and hydrodynamics, and calculates the wear rate of seals using the Modified Archard Wear Equation. The model's accuracy is verified through tests, and the study analyzes the influence of the force balance coefficients of the seal on the wear rate. It was observed that (i) hydrodynamic seals experience a wear-increase stage, a wear-decrease stage, a transition stage, and a no-wear stage during the start-up process; (ii) increasing the static load factor helps to reduce the duration of the wear stage; (iii) as the gap convergence rate increases, the wear-increase stage compresses the durations of the other stages, followed by the wear-decrease stage, which compresses and then decompresses the durations of the other stages; (iv) as the gap convergence rate increases from 0.00 to 6.00 × 10−6, the main wear area shifts from the outer side to the inner side; (v) increasing the spring load factor raises the wear rate and diminishes the influence of both the static load factor and the gap convergence rate.

A Contact Mechanics Model for Surface Wear Prediction of Parallel-Axis Polymer Gears.

As surface wear is one of the major failure mechanisms in many applications that include polymer gears, lifetime prediction of polymer gears often requires time-consuming and expensive experimental testing. This study introduces a contact mechanics model for the surface wear prediction of polymer gears. The developed model, which is based on an iterative numerical procedure, employs a boundary element method (BEM) in conjunction with Archard's wear equation to predict wear depth on contacting tooth surfaces. The wear coefficients, necessary for the model development, have been determined experimentally for Polyoxymethylene (POM) and Polyvinylidene fluoride (PVDF) polymer gear samples by employing an abrasive wear model by the VDI 2736 guidelines for polymer gear design. To fully describe the complex changes in contact topography as the gears wear, the prediction model employs Winkler's surface formulation used for the computation of the contact pressure distribution and Weber's model for the computation of wear-induced changes in stiffness components as well as the alterations in the load-sharing factors with corresponding effects on the normal load distribution. The developed contact mechanics model has been validated through experimental testing of steel/polymer engagements after an arbitrary number of load cycles. Based on the comparison of the simulated and experimental results, it can be concluded that the developed model can be used to predict the surface wear of polymer gears, therefore reducing the need to perform experimental testing. One of the major benefits of the developed model is the possibility of assessing and visualizing the numerous contact parameters that simultaneously affect the wear behavior, which can be used to determine the wear patterns of contacting tooth surfaces after a certain number of load cycles, i.e., different lifetime stages of polymer gears.

Development of a Novel Wear Equation by Comparing the Wear Behaviour of Hard (AA7075) and Soft (AA6063) Hybrid Composite Materials

Development of a Novel Wear Equation by Comparing the Wear Behaviour of Hard (AA7075) and Soft (AA6063) Hybrid Composite Materials

Simulation on the Effect of Braking Force and Brake Shoe Material Type on The Wear Rate of Railway Bogie Brake Block

The brake block in the railway bogie system is an important component in supporting the operational safety of trains, so it needs to be inspected to determine its performance and service life. A simulation-based study was conducted to predict the wear rate of railway brake block with oriented braking force (F = 25.66 kN - 29.54 kN) and different material types, namely grey cast iron with hardness 170 HBN and metallic composite with hardness 90 HRR. The method of the study was carried out by Finite Element Analysis (FEA) simulation and calculating the wear rate with the Archard wear equation to measure the comparison of the amount of wear volume that occurs on the two materials. The results of the braking ability calculation can be concluded that the different types of brake block materials can affect the ability to decelerate during the deceleration process, causing differences in stopping mileage according to the type of material, such as gray cast iron (μ = 0.30) which has an average mileage of 15 metres and metallic composite (μ = 0.21) has an average mileage of 66 metres. The wear simulation results obtained are that the grey cast iron brake block has an average wear rate of 2,8285e-08 /s which is greater than the metallic composite which is only 1,5391e-08 /s. With this data, it can be concluded that oriented to the braking force load, the metallic composite brake block material has the advantage of a longer service life than grey cast iron.

The Wear Behaviour of a New Eccentric Meshing Reducer with Small Teeth Difference

Eccentric meshing reducers are widely used in agriculture, industrial robots, and other fields due to their ability to achieve a high reduction ratio within a compact volume. However, the contact wear problem seriously affects the service performance of the eccentric meshing reducer, thereby limiting their range of applications. To effectively address this issue, this study involved a stress analysis of the contact pairs and a surface wear analysis of a new eccentric meshing reducer. The wear equation for the contact pairs was derived using Archard’s wear theory, incorporating geometric and material parameters from both the reducer gear contact pair and the spline contact pair. In parallel, a wear simulation was conducted by integrating the UMESHMOTION subprogram with ALE adaptive grids. Additionally, the effects of load amplitudes on contact pair stress and surface wear were systematically investigated. It is revealed that the contact pair stress of the reducer gear was higher than that of the spline contact pair. Furthermore, the internal spline exhibited the highest wear rate, followed by the output shaft gear, external spline, and input shaft gear, in that order. This work provides a comprehensive and in-depth understanding of the wear behaviors of general reducers with small teeth differences and offers valuable scientific references for design optimization, fault diagnosis, and maintenance strategy formulation.

Development of a wear coefficient equation for the A A7075-B4C composite – steel interface

In this research, an attempt was made to develop a wear equation for specific wear regimes that differs with temperature, sliding velocity, applied load, and sliding distance. The experimental runs were designed with the L25 Taguchi orthogonal array, and the uniform dispersion of reinforcement was confirmed using a scanning electron microscope. The presence of reinforcement hinders dislocation movement led to an augmentation in the composites’ hardness, while an elevation in temperature resulted in a decline in hardness due to the reduction of Pierls stresses. Owing to the formation of a Mechanical Mixed Layer (MML), the wear rate decreases with addition of volume fraction of B4C particles until 7.5%, beyond this MML break down and wear rate transit from mild to severe due to the direct metal contact. At 50 °C, the wear mode was abrasive and delamination; at 150 °C, it was abrasive plastic deformation; and at 250 °C, it was plastic flow of materials. Grooves, micro pits, micro cracks, ploughing and resolidified material were the distinct feature observed on the worn surface morphology. The modified wear equation was developed by incorporating reinforcement effect, specific wear regimes, temperature-dependent factors, and functional parameters.

Linear complementarity formulations for contact analysis and wear prediction in gears

This work presents linear complementarity based formulations for contact analysis and wear prediction in gear trains. Assuming steady motion of gears transmitting constant input torque without transmission errors, three sets of linear complementarity formulations are proposed, first for rigid gear teeth, second for gear teeth with skin compliance, and third for gear teeth with full compliance, the last two being new in linear complementarity literature. The developed formulations are used for contact analysis of two examples of gear trains, a pair of spur gears in mesh, and a planetary gear train. The accuracy of the method is tested by considering various time step sizes and stability of the formulations demonstrated for wide range of time steps. Contact forces between meshing teeth are calculated at a pre-defined set of points on the path of contact, and then wear is calculated on gear tooth flank using Archard’s wear equation. These wear calculations are compared with existing results in literature which demonstrate the applicability of the developed LC formulations. Future work is projected to include more state-of-art friction models and extension to 3D contact analysis in helical gear trains.

Wear life prediction of piston ring and cylinder liner based on integration of experiment and bench test data

The wear data of piston ring-cylinder liner (PRCL) of high-power diesel engines faces the problems of small samples, randomness, and underutilization, which leads to the wear life prediction of PRCL has been a difficult task in the engineering field. A wear life prediction method of PRCL based on the integration of experimental data and bench test data is proposed. First, a large amount of wear data is rapidly obtained through accelerated wear tests on specimens, and the distribution type of wear depth of PRCL is determined. Secondly, based on Rhee's wear equation, the nonlinear relationship between time, load, temperature, and wear depth is considered, and the acceleration models of temperature and load were introduced as the Arrhenius model and the inverse power law model, respectively. The wear life prediction model (WLPM) for specimens and parts with stochasticity is developed. The eigenvalues of WLPM’s parameters of specimens and parts were utilized to construct the mapping relationship from the specimen to the part. Finally, the Bayesian statistical method is used to merge the wear data of specimens and the parts, and the WLPM of specimens and the mapping relationship are taken as the a priori information, the bench data are taken as the new sample information, and the MCMC-Gibbs sampling method is used to estimate the mapping-based WLPM of parts. The results show that through the validation test, the method predicts the wear depth of PRCL with 100 % falling into the 95 % confidence interval better than the WLPM prediction results of a single specimen or part, and the errors of predicting the mean wear life of PRCL are all within 10 %. The method can provide a reference for the quality evaluation and engineering application of PRCL.

Development of Novel Wear Equation of AA7050/SiC-Steel Interface for High Temperature Application

AA7050 aluminium alloy used for the main landing gear link was reinforced with SiC particles utilizing stir casting and uniform dispersion of reinforced particles was analyzed through SEM with EDS mapping. Wear test were performed on pin on disc apparatus by varying the process parameters and experimental runs were designed using response surface methodology. The influence of SiC particles on wear resistance at high temperatures was explored and the findings led to the development of a novel wear equation. The hardness of composites increased due to impediments of dislocation movement, and it declines with an increase in temperature owing to a reduction of Pierls stresses. The formation of a Mechanically Mixed Layer (MML) enhances wear resistance with the inclusion of reinforced particles, and the breakdown of this layer swifts the wear from moderate to severe. The mode of wear was a combination of shearing and abrasive at room temperature, shearing and adhesive until the temperature 200ᵒC, and plastic deformation when the temperature exceeded 200 °C, which was confirmed by worn surface morphology.

Prediction of Tool Wear in Fine Blanking Punch with PVD Coating with TiCN for JIS.SKH51 High Speed Tool Steel Using Archard Wear Model

The aim of this study is predict tool wear in the fine-blanking process using a tribometer tester with ASTM G99-17 standard. Then, the result of wear volume and tool life were confirmed with finite element simulation and experiment. The punch material used in fine blanking process was selected to be hight speed steel JIS.SKH51 with surface coating thickness 4 µm of TiCN, the work piece material was used as hot-rolled steel JIS.SPHD P/O, with a thickness of 8 mm. The experimented and simulated results were found that the pressure, and sliding velocity were increase in term of linear curve with slope K = 2.09x10-6 and K = 2.07x10-6 ,respectively, and the hardness of material was increase in term of power at 1.983 and slope of K = 2.14 x10-6. These three factors were effect to the wear volume and tool life, simultaneously, the summation of three factors will average as K = 2.10 x10-6. From comparison of the applied wear equation model with tribology tester the simulated and experimented results were similarly equal with 0.05 by significance at 95% reliability confident. The resulted were precisely confirmed according to the previous research.

Experimental and numerical investigations of sliding wear behaviour of an Fe-based alloy for PWR wear resistance applications

The excellent wear and corrosion resistance of Co-based alloys make them desirable for tribological applications in the nuclear industry. However, neutron activation of the Co-based alloys leads to significant occupational radiation doses. An alternative Fe-based alloy called RR2450 was developed by Rolls-Royce plc to replace these alloys. This paper presents the first comprehensive study evaluating the sliding wear resistance of RR2450 alloy in representative PWR conditions. The sliding counterface of RR2450 balls was a Co-based alloy, Haynes 25 discs. Four tests were performed at temperatures up to 80 °C, and 12 tests were performed up to 200 °C. Results showed wear performance of RR2450 balls degraded at higher loads and temperatures, with temperature having a significant role. Microstructural investigation revealed voids and hard silicide phases, negatively impacting wear resistance. Nonetheless, the wear performance of RR2450 was similar to a Co-based alloy, a=Stellite 20, at nuclear reactor conditions. Two wear tests with uneven wear tracks were selected for 3D finite element analysis. The wear simulation procedure is based on Archard’s wear equation and is implemented in a commercial FE package, ABAQUS. The FEA method was used to capture the wear on both surfaces, and was shown to predict nominal wear profiles. These comparisons with experiments show that the FEA results can provide representative wear profiles when wear depths and widths are asymmetrical and irregular.

Finite element analysis and experimental validation of polymer–metal contacts in block-on-ring configuration

The wear profile analysis, obtained by different tribometers, is essential to characterise the wear mechanisms. However, most of the available methods did not take the stress distribution over the wear profile in consideration, which causes inaccurate analysis. In this study, the wear profile of polymer–metal contact, obtained by block-on-ring configuration under dry sliding conditions, was analysed using finite element modelling (FEM) and experimental investigation. Archard’s wear equation was integrated into a developed FORTRAN–UMESHMOTION code linked with Abaqus software. A varying wear coefficient (k) values covering both running-in and steady state regions, and a range of applied loads involving both mild and severe wear regions were measured and implemented in the FEM. The FEM was in good agreement with the experiments. The model reproduced the stress distribution profiles under variable testing conditions, while their values were affected by the sliding direction and maximum wear depth (hmax). The largest area of the wear profile, exposed to the average contact stresses, is defined as the normal zone. Whereas the critical zones were characterized by high stress concentrations reaching up to 10 times of that at the normal zone. The wear profile was mapped to identify the critical zone where the stress concentration is the key point in this definition. The surface features were examined in different regions using scanning electron microscope (SEM). Ultimately, SEM analysis showed severer damage features in the critical zone than that in the normal zone as proven by FEM. However, the literature data presented and considered the wear features the same at any point of the wear profile. In this study, the normal zone was determined at a stress value of about 0.5 MPa, whereas the critical zone was at about 5.5 MPa. The wear behaviour of these two zones showed totally different features from one another.

Experimental study of plastic cutting in laser-assisted machining of SiC ceramics

In this paper, the cutting process of laser-assisted machining (LAM) of SiC ceramics is studied. Three processing states of brittleness, plasticity and thermal damage are determined based on the characterization analysis of surface integrity, tool wear and chip morphology, and the surface roughness and tool wear regression model established under the plastic processing state are verified. Firstly, the surface integrity, tool wear and chip morphology are investigated by the single-factor experiment of laser power to explain the material removal mechanism according to the material fracture theory and to determine the laser power range of plastic cutting (185 W–225 W). Then the Box-Benhnken experimental scheme is designed to establish a multivariate prediction model based on the response surface methodology (RSM) to obtain the regression equation of surface roughness and tool wear and further analyze the interaction between process parameters. Finally, the experimental values of surface roughness and tool wear are compared with the predicted values through optimization analysis. The results show that the maximum error is 5 % and 7.57 % respectively, which proves that the model has good prediction ability. The surface roughness and tool wear regression prediction models provide guidance for the selection of plastic cutting process parameters for SiC ceramics.

A computational model of wear evolution for shot peened surfaces of gear steel

In mechanical engineering, shot peening is frequently used to reinforce the surfaces of some crucial components. Currently, there are no models available which can accurately predict the long-term wear behavior of surfaces treated with shot peening. This research proposes a computational model and technique for simulating the evolution of wear on gear steels with shot-peened surfaces in a ball-on-flat contact. Based on the fundamental Archard’ s equation, a wear equation is derived from the perspective of a contacting point on the static flat to represent the wear loss. The model takes into account the effects of abrasive particles and variations in hardness along the vertical direction by introducing a scaling factor in the wear equation and stratification of the flat material, respectively. The proposed model and developed method are validated through experiments and can be utilized to predict the wear evolution of shot peened surfaces on gear steels under the application of various loads and friction duration. Furthermore, the model and method can be easily extended to other materials as well.

Developing a steady state wear equation for AA7050 hybrid composites/steel interface at elevated temperature

ABSTRACT In this research work, an attempt was made to reinforce AA7050/5Gr composites with multi-walled carbon nanotube (MWCNT) of varying weight percentages processed through stir casting route. SEM with EDS mapping revealed that the particles were uniformly distributed over the composites. Hardness reduces with increasing MWCNT weight percentage owing to the inverse hall petch effect and increment in void content. A third-body abrasion, which happens when the CNT in the aluminium matrix material detaches from the surface and erodes material from the composites pin as well as the counter face, causes the wear resistance to rise with the addition of CNT particles. A mechanically mixed layer, which avoids direct metal-to-metal contact and thus increases wear resistance, was created at the abraded surface and at high temperature, where the reduction of wear rate was due to the development of oxide protective layer. A steady-state wear equation for the contacting surface at high temperature (R = 1/Y √(ln W/2X)) for AA7050 hybrid composites–steel interface was developed. The enhancement in wear resistance was directly proportional to the proportion of ferrous content present on the surface, which was confirmed on the elemental analysis. Pock marks, micropits, craters and cracks were the features observed on the worn surface morphology, whereas delamination and plasticisation were the observed modes of wear mechanism.

Numerical analysis and formula correction of mechanical seal ring wear of slurry pump based on thermal deformation

In view of the excessive wear of the mechanical seal of the slurry pump in the project and the inconsistency between the theoretical wear and the actual wear, this article studies the wear of the mechanical seal of the slurry pump. In this article, a numerical model of mechanical seal wear based on thermal deformation is established. The hardness, wear coefficient and dry friction coefficient of the sealing ring were obtained through experiments, and the wear morphology was collected by the ultra-depth microscope. In this article, the precise calculation of mechanical seal wear is realized, and the seal ring wear depth under single and multiple field conditions is obtained. The wear formula of the mechanical seal is optimized by adding a correction index, and the end face structure of the mechanical seal is improved. The results show that: the seal ring forms a converging surface due to thermal deformation resulting in more severe wear of the inner diameter relative to the outer diameter; the revised wear equation can more accurately predict the life of the nickel-based tungsten carbide alloy mechanical seal, with a 3.2 times increase in expected life after comprehensive end face improvement.

HAp-Ti-6Al-4V Interface Fretting Wear Failure Prediction in Different Bio-lubricants using FEM

Plasma-sprayed hydroxyapatite (HAp) coated titanium alloy (Ti-6Al-4V) has been widely used as the material for artificial hip implants. However, studies have greatly challenged their long-time usage due to fretting wear behavior at the HAp-Ti-6Al-4V interface. Wear particles from the HAp coating may activate inflammation at surrounding organs, further leading to implant loosening, implant failures and even total hip replacement (THR) revision surgeries. Hence, present research aims to adopt the finite element methodology (FEM) in predicting fretting wear failure at the HAp-Ti-6Al-4V interface of uncemented hip implant femoral stem component under different body environments (bio-lubricants). A finite element (FE) model based on the half-cylinder on flat contact configuration subjected to actual mechanical and tribological properties under different bio-lubricants is developed with the modified Archard wear equation adopted to examine the fretting wear behavior through simulations. A parametric study is then conducted to evaluate the combined effects of different mechanical and tribological properties, including HAp coating thickness, bone elastic modulus and loading condition, under different bio-lubricants on the fretting wear behavior of HAp-Ti-6Al-4V interface. Lastly, single and multiple regression analyses are performed to formulate fretting wear predictive equation that acts as a fast-fretting wear failure prediction tool. The FE predicted results in this paper prove that the maximum wear depth at HAp-Ti-6Al-4V interface is promoted under lower coefficient of friction (COF), smaller HAp coating thickness, smaller bone elastic modulus and larger intensity of fatigue loading. The formulated predictive equations suggest a strong correlation between independent and dependent variables due to R-squared (R2) values being larger than 0.75 which guarantee goodness of fit.

Wear and Leakage Behaviors of Brush Seal Considering Eccentricity and Radial Deformation

Brush seals can improve engine performance by reducing leakage. Wear models of brush seals provide methods to predict wear and leakage. However, rotor eccentricity, radial deformation, and hysteresis effect of bristles are not considered systematically in the existing models, which may lead to large errors in some cases. To investigate the influence of rotor-stator eccentricity and radial deformation on the wear process and leakage performance of brush seal, a brush seal test was planned and executed, in which the air leakage rates were measured at different testing times and operating conditions, the eccentricity and radial deformation was measured using eddy current sensors. The test results showed that the eccentricity and radial deformation significantly affected the wear behavior and leakage performance. In the theoretical research, the abrasive wear equation is adopted to describe the material loss of bristles, and a simplified description is used to express the rotor-stator eccentric motions. To describe the effect of hysteresis on wear behavior, the deformation of the bristle pack is divided into rebounding deformation and locked deformation, and the two deformation modes are modeled separately. Then a brush seal wear model considering rotor-stator eccentricity and radial deformation is obtained, in which the hysteresis effect is especially represented. The wear model was verified quantitatively based on the brush seal test data, and the results show that there is an error of 20% with the calculated wear loss when rotor eccentricity, radial deformation, and hysteresis effect are comprehensively considered. In contrast, ignoring the hysteresis effect may increase the error by several times. This study provides a quantitative and practical method for predicting the wear and leakage of brush seals.

Numerical study on the abrasive wear of screw flights considering the scaffolding near the bustle pipe zone in a COREX shaft furnace

Scaffolding near the bustle pipe zone is a common problem in the operation of the COREX shaft furnace. To study the asymmetrical abrasive wear of screw flights in the presence of scaffolding, a three-dimensional COREX shaft furnace model with two representative locations of scaffolding is established based on the Discrete Element Method. Two different structures of the screw are investigated and the abrasive wear is calculated using Archard wear equation. The results show that the maximum abrasive wear of the screw flights occurs on the opposite side of the scaffold. The abrasive wear of screw flights is greater when the scaffold is located directly above the middle of two adjacent screws than above a certain screw. The abrasive wear of equidistant screw flights is about twice the modified screw under the same scaffold condition. The findings of this study provide a theoretical basis for the optimization of the COREX shaft furnace.

Multiscale Wear Simulation in Textured, Lubricated Contacts

Specific surface textures may reduce the friction and increase the lifting forces in lubricated contacts. For the detrimental operating condition of mixed friction, wear is induced by the solid contact. In this study, a methodology for wear calculation in textured, lubricated contacts is presented that considers the wear-induced surface topography evolution. Based on the Reynolds differential equation, the mass-conserving cavitation model according to Jakobsson, Floberg, and Olsson (JFO), a wear-dependent asperity contact pressure curve and the wear equation according to Archard, wear in a wedge-shaped, textured lubrication gap was calculated. The results show the wear behavior of textured lubrication gaps. Based on the wear simulations, the tribological behavior of the textured surfaces compared to smooth surfaces is discussed. It is evident that textures, which improve the tribological performance in the hydrodynamic lubrication regime, are not necessarily associated with low wear values in a lubrication condition in the mixed friction regime. The analysis of the wear-dependent parameters initially showed a ‘recovery’ of the tribological system with increasing wear until the performance decreased again after a specific reversal point. This behavior is attributed to the relative position of the surface textures in the lubrication gap.