Wear Equation Research Articles

Oxidative wear kinetics in unlubricated steel sliding contact

A tools lifetime absolutely depends on the material properties and lubrication. By a lubricant absence, the direct contact between the materials might cause an increase of friction and wear, which might lead to a tool's failure. That is why wear prediction and control are important requirements in industry. The wear prediction experiments in this study were performed for an unlubricated (dry) bushing/shaft system of relatively high load and low sliding speed. Two different commercially available tool steels were used for tribological investigations. Normal load and temperature were considered as independent variable in the wear testing. The results showed that the extensive oxidation of metals have a positive factor on wear. When the temperature raises formation of the protective oxide layers consequently change the wear transition to the mild oxidative wear. Based on the classical wear equations and on the chemical oxidation kinetics concepts a wear prediction model was developed and statistically evaluated in the case when metallic contact wear as the predominant wear mechanism was combined with the oxidation of metals.

Asymptotic modeling of reciprocating sliding wear with application to local interwire contact

Abstract The paper presents asymptotic modeling of the local contact of crossed elastic cylinders in reciprocating sliding wear under a prescribed constant normal load. The wear contact problem is formulated within the framework of the three-dimensional theory of elasticity in conjunction with Archard's generalized wear equation. It is shown that the asymptotic modeling approach, which maintains the experimentally related feature of contact pressure in the steady-state regime, leads to simple but sufficiently accurate analytical approximations. In particular, closed-form approximations are derived for the volumetric wear, parameters of the contact area, and the wear scar profiles. The developed asymptotic modeling approach is not capable of handling the initial period of wear process, when the contact pressure distribution transforms from the initial Hertzian form to the uniform distribution appearing in the steady-state regime. The obtained analytical results have been compared with finite-element simulations and experimental results published in the literature.

Fretting Wear Modeling of Coated and Uncoated Surfaces Using the Combined Finite-Discrete Element Method

Abstract A new approach for modeling fretting wear in a Hertzian line contact is presented. The combined finite-discrete element method (FDEM) in which multiple finite element bodies interact as distinct bodies is used to model a two-dimensional fretting contact with and without coatings. The normal force and sliding distance are used during each fretting cycle, and fretting wear is modeled by locally applying Archard’s wear equation to determine wear loss along the surface. The FDEM is validated by comparing the pressure and frictional shear stress results to the continuum mechanics solution for a Hertzian fretting contact. The dependence of the wear algorithm stability on the cycle increment of a fretting simulation is also investigated. The effects of friction coefficient, normal force, displacement amplitude, coating thickness, and coating modulus of elasticity on fretting wear are presented.

On the influence of indentation size effect on the wear of metallic alloys

In metallic alloys, apart from the linear decrease of the wear rate with decreasing load, an additional decrease of wear rate has been observed and attributed to a number of different causes. In the present paper it is shown that this effect can be properly quantified from the hardness variation of the material with indentation depth, usually referred as indentation size effect (ISE). It is shown that, due to ISE, a significant reduction of wear is expectable in metallic alloys, as the asperities penetrate the surface of these materials to depths smaller than a few microns. As a result we propose a modification to the Rabinowicz wear equation that accounts for this effect and fits experimental results.

Tool Life Estimation for High-Speed Machining of Composite Material

Tool life is an important index to judge machinability of cutting tool. Wear standard is a necessary considered factor to give tool life. Microwave printed board is composite material, wear standard should be found by tool wear experiment under definite machining environment. Life-span data of cutting tools with different combination of cutting parameters is collected through machining experiment. And then based 2 mathematic models: extended Taylor empirical equation and quadratic response surface equation, with regression analysis method, the mathematical models of relationship between cutting parameters and tool life were given respectively. Through comparison of two regression methods, response surface equation based wear equation is given, determining calculating method of tool life for High-speed Machining of Aluminum Base Microwave Printed Circuit Board. Described method can be popularized according to change of machining conditions.

A mathematical model to evaluate wear depth of an aluminium alloy reinforced with a silicon carbide particle composite using finite element analysis

In the present study, an attempt is made to synthesize an aluminium alloy—silicon carbide (SiC) particle composite using a liquid metallurgy route and to characterize the composites in terms of sliding wear behaviour and numerical simulation by finite element analysis. The sliding wear behaviour was studied using a pin-on-disc apparatus with the composite pin sliding against an EN32 steel counter surface at different applied loads and sliding speed. The experimental results for the aluminium alloy—SiC particle composite were validated using a mathematical model. A wear equation was used to predict the steady-state wear rates. It is based on an exponential transient wear volume equation and Archard's equation. An algorithm for the finite element model to simulate wear tests was also developed. The predicted results were in good agreement with the experimental values.

Cutting Performance and Predictive Models for End Milling Aluminum Alloy

End milling is considered to be one of the most commonly applied for both roughing and finishing operations to make flat surfaces, slots and pockets in precision molds and dies. Predictive models were developed for cutting force, flank wear and surface roughness in end milling aluminum alloy by regression analysis. The correlation coefficients for cutting force, flank wear and surface roughness equations were 91.6 %, 89.8 % and 79.6 %, respectively. The goal of these predictive equations is to become a good assistant to the researcher in understanding the machining process. Through the analysis of variance (ANOVA), however, it can be found that the cutter diameter, the helix angle and the feed rate are the important milling process parameters to obtain the machined quality on cutting force, flank wear and surface roughness. The investigations show that cutting force, flank wear and surface roughness can be improved in end milling aluminum alloy by using the lower cutter diameter, medium helix angle and lower feed rate.

Determining local wear equation based on friction and wear testing using a pin-on-disk scheme

Based on pin-on-disk friction and wear testing, the parameters of the wear rate as a function of sliding velocity and pressure with account for their distribution over the contact spot are computed. The parameters are compared to those obtained assuming a uniform distribution of velocities and pressures. It is assumed in the work that the contact spot does not vary, the disk does not wear out, and the study is carried out under steady-state wear conditions.

Wear elements generated in the elementary process of wear

To clarify the mechanism of adhesive wear and establish a wear equation, it is necessary to investigate the amounts of wear elements (the elemental debris of wear particles) that transfer. The size and the quantity of wear elements on friction surface were examined for various sliding conditions and combinations of pure metals. By using a piezoelectric actuator, micro-scale friction experiments were performed by sliding a pin specimen once for a distance of 120 μm on a block specimen. Atomic-force microscopic observations of the friction surface were conducted after the experiments. Differences in the normal load and the lubrication conditions affect the quantity of wear elements more than their size. Furthermore, the size and the quantity of wear elements differed depending on the combination of materials. The quantity of the generated wear elements is related to the adhesion force between the two materials. A model is proposed for the generation and transfer of wear elements.

An AFM study of single-contact abrasive wear: The Rabinowicz wear equation revisited

A nanoscale study of the abrasive wear behaviour of a ductile monophasic metallic alloy (the stainless steel AISI 316L) is presented. By using atomic force microscopy (AFM) based techniques, particularly a diamond tip mounted on a stiff steel cantilever, the contact of a single abrasive asperity was simulated, and it was possible to determine accurately the load threshold below which no measurable wear occurs. It was observed that, once this nanoscale threshold for wear is overcome, the worn volume increases linearly with the load, as predicted by the Rabinowicz model. However, it was found that, although this critical threshold for measurable wear is most certainly related with the yield-onset of plastic deformation, it cannot be predicted by using directly a criterion based on the bulk microhardness. Hence, the results presented in this paper strongly indicate that indentation size effects play a crucial role on the response to abrasive wear at the asperity contact level.

Prediction of Polymer Wear—An Analytical Model and Experimental Validation

Because of its industrial relevance, wear of engineering polymers has been studied extensively both experimentally and theoretically. The wear mechanism of polymers is complex due to the influence of numerous parameters and it has long been realized that a predicting tool for wear of polymers in dry and lubricated sliding is of practical importance. Polymer wear models hitherto have been largely done by fitting the experimental data to an empirical equation and some major contributions have been made by a number of authors in this area. However, a more fundamental approach would be to analyze the experimental evidence collectively on the basis of the variables involved and the mechanisms leading to particle detachment. Although some progress has been made in this direction, a need exists to consolidate the major experimental findings in order to develop a comprehensive analytical wear model. The present work attempts to develop such a wear model and validate the proposed model experimentally. The wear equations are presented in two groups, one representing primarily abrasive wear and the other the fatigue mechanism, since the two mechanisms operate in distinct roughness ranges. Each group consists of four equations representing different contact speed and temperature ranges. The results indicate that the surface forces dominate in the low roughness range while at the higher roughness ranges abrasive wear is predominant. Among other observations the results also indicate that a unique value of the ratio of equivalent elastic modulus to hardness (E//H) exists where wear may either be insignificant or very large depending on the parametric combination. These predictions are likely to be of practical importance.

Loose abrasive edge wear effects and final surface topography in conventional grinding machines

Applying Cordero-Davila's edge ring pressure increase to upper disk kinematics equations has led to excellent agreement between theoretical loose abrasive wear computer simulations and their experimental counterparts. Experiments to verify Cordero's ring equations over long grinding periods, up to 40 min, and their computer simulations are presented in detail. These experiments led to a new improved version of Kumanin's loose abrasive wear equation. Maximum wear rate and final topography errors, between theory and experiment, were slightly larger than instrumental uncertainty. Now it became possible to compute exact pressure, relative speed and wear, at any contacting point pair and over the entire upper free disk surface.

Modeling and Prediction of Erosion Response of Glass Reinforced Polyester-Flyash Composites

Solid particle erosion of polymer composites is a complex surface damage process, strongly affected by material properties and operational conditions. To avoid repeated experimentation, it is important to develop predictive equations to assess material loss due to erosion wear under any impact conditions. This paper presents the development of a mathematical model for estimating erosion damage caused by solid particle impact on flyash filled glass fiber reinforced polyester composites. The model is based upon conservation of particle kinetic energy and relates the erosion rate with composite properties and test conditions. Another correlation derived from the results of Taguchi experimental design is proposed as a predictive equation for erosion wear of these fiber reinforced composites. Further, considering the complexity and high degree of nonlinearity in the erosion process, an artificial neural networks (ANN) technique is implemented as an effective tool for prediction of wear response of these composites in a larger space. Finally, the results of a mathematical model and the ANN model are compared with those obtained from experimentation.

Relative velocity and loose abrasive wear in conventional grinding machines

A model to compute relative velocity for arbitrary tool-work point pairs in conventional grinding machines is presented. This model is based on experimental data collected by means of an electronic system to measure kinematics variables in real time. Exact machine kinematics equations and an approximate equation representing upper disk rotational speed as a function of machine operation regime are introduced. With these equations, it became possible to calculate relative velocity among arbitrary tool-work point pairs. As a consequence, the amount of wear produced on optical elements, applying Preston's or Kumanin's abrasive wear equations, can be calculated.

An evaluation of high velocity wear

The Holloman High Speed Test Track (HHSTT) is a rocket-powered sled track facility used for testing a variety of hypervelocity aerospace applications at speeds approaching 3000 m/s. Research conducted at the HHSTT has to consider several features that result from the physics of high velocity. The feature of gouging has been noted to be a significant factor at speeds above 1.5 km/s. This characteristic has been studied in recent years by several authors including the senior author of this paper. Another feature that is always present is that of wear between the shoe and the rail resulting from their sporadic contact as the sled travels down the rail. This paper attempts to establish a proof concept that can eventually be extended into future understanding of wear at high velocities. The authors approached wear using two separate techniques. The first technique involves the use of equations that have been successfully used to represent wear at low speeds. This technique relies on the research of Lim and Ashby and the equations they developed to model the different modes of wear. Included in this technique is the use of Archard's wear equation. The second technique, completely independent of the first, relies on the physics of frictional movement displayed by a model produced using CTH, a hydrocode developed by Sandia National Laboratory for analyzing hypervelocity impact problems. This technique considers features that are potentially present in the overall phenomenon but are limited to the use of the code. The authors have found it necessary to make simplifying assumptions in both techniques, but the end result is a better appreciation of what is needed to put together a more accurate model of wear at high velocities.

Proposed procedure and trial simulation of rail profile evolution due to uniform wear

A procedure for numerical simulation of rail wear and the corresponding profile evolution has been formulated. The wear is assumed to be uniform in the sense that the profiles remain constant along the track portion to be investigated. A simulation set is selected defining the vehicles running on the track, their operating conditions, and contact parameters. Several variations of input data may be included together with the corresponding occurrence probability. Simulation of multi-body dynamics is used to calculate contact forces and positions, and Archard's wear equation is applied for the calculation of wear depth. Wear coefficients as a function of contact pressure and relative sliding velocity are collected from different test results. Trial calculations of four non-lubricated and two lubricated curves with radii from 303 to 802m show qualitatively reasonable results in terms of profile shape development and difference in wear mechanisms between gauge corner and rail head. The wear rates related to traffic tonnage are, however, overestimated and the lubrication efficiency underestimated. It is expected that model refinements in terms of environmental influence and contact stress calculation are useful to improve the quantitative results.

Head wear reduction in future hard-disk drives

Head wear and head vibration due to head-disk contact are two main issues that must be resolved for the future high-density Hard Disk Drives (HDDs). To reduce head wear, disk lubricant, carbon overcoat films on head and disk surfaces, head flying characteristics and so on have been studied. In this paper, we first show the effects of several parameters on head wear, including lubricant types, their MW, and disk burnishing. Our recent results on the effects of humidity and temperature on head wear are also explained. We then explain our extended wear equation and estimate the head wear life with present technologies.

Prediction of Tread Pattern Wear by an Explicit Finite Element Model

Abstract Tread pattern wear is predicted by using an explicit finite element model (FEM) and compared with the indoor drum test results under a set of actual driving conditions. One pattern is used to determine the wear rate equation, which is composed of slip velocity and tangential stress under a single driving condition. Two other patterns with the same size (225/45ZR17) and profile are used to be simulated and compared with the indoor wear test results under the actual driving conditions. As a study on the rubber wear rate equation, trial wear rates are assumed by several constitutive equations and each trial wear rate is integrated along time to yield the total accumulated wear under a selected single cornering condition. The trial constitutive equations are defined by independently varying each exponent of slip velocity and tangential stress. The integrated results are compared with the indoor test results, and the best matching constitutive equation for wear is selected for the following wear simulation of two other patterns under actual driving conditions. Tens of thousands of driving conditions of a tire are categorized into a small number of simplified conditions by a suggested simplification procedure which considers the driving condition frequency and weighting function. Both of these simplified conditions and the original actual conditions are tested on the indoor drum test machines. The two results can be regarded to be in good agreement if the deviation that exists in the data is mainly due to the difference in the test velocity. Therefore, the simplification procedure is justified. By applying the selected wear rate equation and the simplified driving conditions to the explicit FEM simulation, the simulated wear results for the two patterns show good match with the actual indoor wear results.

Development of computational wear simulation of metal-on-metal hip resurfacing replacements

As one of the alternatives to traditional metal-on-polyethylene total hip replacements, metal-on-metal hip resurfacing prostheses demonstrating lower wear have been introduced for younger and more active patients during the past decade. However, in vitro hip simulator testing for the predicted increased lifetime of these surface replacements is time-consuming and costly. Computational wear modelling based on the Archard wear equation and finite element contact analysis was developed in this study for artificial hip joints and particularly applied to metal-on-metal resurfacing bearings under simulator testing conditions to address this issue. Wear factors associated with the Archard wear equation were experimentally determined and based on the short-term hip simulator wear results. The computational wear simulation was further extended to a long-term evaluation up to 50 million cycles assuming that the wear rate stays constant. The prediction from the computational model shows good agreement with the corresponding simulator study in terms of volumetric wear and the wear geometry. The simulation shows the progression of linear wear penetrations, and the complexity of contact stress distribution on the worn bearing surfaces. After 50 million cycles, the maximum linear wear was predicted to be approximately 6 and 8 μm for the cup and head, respectively, and no edge contact was found.

Dynamic interaction between contact loads and tooth wear of engaged plastic gear pairs

This study investigates the interaction between the dynamic contact load and the tooth profile wear of POM and Nylon 66 plastic gear pairs. A dynamic model of a plastic gear pair is presented. This model incorporates the effects of position-varying tooth mesh stiffness, damping ratio, load sharing, tooth profile wear and temperature on the dynamic contact load. The tooth wear equation developed by Flodin and Andersson [Simulation of mild wear in spur gears. Wear 1997;207:16–23] is utilized to simulate tooth wear and tooth profile variation. The variation of the contact load generated by the cumulative tooth profile wear is simulated and examined. A computational algorithm is developed to simulate the interaction between a dynamic contact load and tooth profile wear. Numerical results demonstrate that the dynamic load histogram of an engaged plastic gear pair can change markedly due to tooth wear.