Wear Equation Research Articles

Stress-enhanced dissolution and delamination wear of crystal CaF2 in water condition

The role of water in the material removal of single crystal calcium fluoride (CaF2) was studied using a scratch tester with a diamond tip. Water can facilitate the sliding wear of CaF2, and the degree strongly depended on the amount of water molecules involved in the wear process. CaF2 wear increases with the increase of relative humidity (RH). When the sliding wear tests were conducted in dry condition, the wear rate increases linearly with applied load, obeying the Archard wear equation. When water participated in the wear process, the Archard wear equation was failure and a exponential dependence of wear rate on contact stress was given under water condition. The transformation of the applied load (or contact stress) dependence indicates the change of wear mechanism in water condition. In dry condition, the surface damage of CaF2 is mainly attributed to mechanical wear where the stress-induced plastic flow under the activation of the slip systems results in a relatively smooth worn surface. In humid nitrogen or water condition, the plastic wear of CaF2 weakens due to the stress-associated dissolution though the wear volume increases compared to that in dry case. Both the water-associated dissolution itself and induced delamination promote the sliding wear of CaF2 in water. The results may help elucidate the water-associated wear mechanism of CaF2 and optimize the processing parameters in the ultra-precision machining to reduce the residual surface/subsurface defects.

Formation of lubricated tribo layer, grain boundary precipitates, and white spots on titanium-coated graphite–reinforced hybrid composites

In this present investigation, AA7050 hybrid composite reinforced with boron carbide (B4Cp) and graphite (Gr) was fabricated through stir casting. The AA7050/B4Cp/Gr hybrid composites were prepared with 7.5 wt.% boron carbide particles added with 2.5, 5, 7.5 and 10 wt.% of graphite. Addition of potassium titanium fluoride (K2TiF6) flux improved the bonding of matrix and reinforcement due to the titanium interface. The influence of graphite particles on mechanical, wear, sulphide stress corrosion cracking and electric discharge machining was analysed. A new wear equation for graphite-reinforced composites based on transient wear equation and Archard’s equation was derived. The hardness, tensile strength and wear resistance of hybrid composites reduce with increase in graphite weight percentage. The graphite-reinforced hybrid composites showed improvement in sulphide stress corrosion cracking due to grain boundary precipitates. The material removal rate of hybrid composites increases with increase in graphite weight percentage, and it exhibits poor surface finish due to poor heat dissipation.

Correlation of wear and work in dual pivoted jaw crusher tests

A laboratory sized jaw crusher with uniform movement of the jaws, the dual pivoted jaw crusher, was used to determine the relationship between wear and work. Wear was concentrated on the jaw plates opposing each other and was measured as mass loss of the specimens. Work was measured directly from the force and displacement of the instrumented jaw, which allowed work to accumulate only from the actual crushing events. The tests were conducted with several jaw geometries and with two motional settings, where the relation of compressive and sliding motion between the jaws was varied. The tests showed that the relation between wear and work was constant in many of the tested cases. In certain tests with larger lateral and faster contact speed, wear occurred at relatively lower amounts of work. This behavior was more definite when the relation of wear and work was investigated using modified Archards wear equation. The results indicate that the lower amount of needed work could stem from the material reaching a dynamic situation, where the flow stress becomes increasingly strain-rate dependent.

A population balance model of ball wear in grinding mills: An experimental case study

A general and realistic population balance model is applied to a ceramic ball mill. The experimental data are obtained for three differently sized balls. The mill is operated 500 h with silica sand during 8 cycles. After each cycle, the mill is stopped to measure the ball wear to obtain the kinetics wear equations. It turns out that the wear law for all three different sized balls is of zero order. These experimental results are introduced into the model to obtain the ball charge of the mill at steady state and the alumina consumption by wear.

Assessment of wear behaviour of copper-based nanocomposite at the nanoscale

Nanoscale wear behaviour of copper-based nanocomposite with Al2O3 nanoparticles have been investigated with the help of the circular mode atomic force microscopy (CM-AFM). The occurrence of running-in and steady-state wear regimes is similar to macroscopic behaviour described by Barwell. Archard's macroscopic wear equation, which states that the wear value is proportional to the applied load and independent on the sliding speed, is also valid at the nanoscale, with the limitation that the normal load should reach a threshold value to generate wear. Eventually, it is shown that the wear value at the nanoscale is highly dependent on the nature of the counter-body (AFM tip) material.

An adhesive wear prediction method for double helical gears based on enhanced coordinate transformation and generalized sliding distance model

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.

Development of a fretting corrosion model for metallic interfaces using adaptive finite element analysis

A new adaptive finite element model was successfully developed to simulate fretting corrosion at metallic interfaces. To do this, the Archard wear equation and a previously established electrochemical equation were simultaneously employed. The algorithm of this finite element approach is able to determine the volume of passive oxide layers removed from the interface and/or re-generated onto the surface; and also, material loss caused by both fretting wear and corrosion at each cycle of fretting wear in a corrosive environment. The fretting corrosion simulation method developed in this work was then used to simulate the fretting corrosion process for a CoCr/CoCr interface under a varying profile of fretting sliding and two different normal contact stresses of 250 and 500 MPa. The results showed that with increasing the normal stress, material loss caused by fretting increases; however, the material loss caused by corrosion and the oxide layer volume decrease. This new model can be employed for various fretting corrosion situations with different material combinations, interface geometries and mechanical loading and sliding profiles.

Effect of tooth profile modification on wear in internal gears

Internal gears are often used in the automotive industry when two gears are required to rotate in the same direction. Tooth shapes, slippage speeds at the beginning and end of meshing are different according to the external gears. Manufacturing of internal gears is more difficult than external gears. Thus, it is necessary to determine the working conditions and wear behavior of internal gears carefully. The profile modification method in terms of strength and surface tension of the gear mechanism are performed in order to increase the load-carrying capability. In this study, profile modification method was performed in the internal gears to reduce the wear on the teeth. For this purpose, the wear of the internal gears was theoretically investigated by adapting the Archard wear equation to the internal gears. Closed circuit power circulation system was designed and manufactured to experimentally investigate the wear in internal gears. With this system, wear tests of gears made of St 50 material without profile modification and different profile modifications were made and the results were compared. Experimental study was performed in the same loading and cycle time conditions to validate the theoretical results and it was seen that the results are compatible. According to the experimental results, it is seen that in the internal gears, when profile modification done the wear is decreased in the teeth tip region.

Combined experimental and numerical simulation of abrasive wear and its application to a tillage machine component

Abstract Abrasive wear of key components is a critical process limiting the lifetime of machinery for mining or farming. However, materials and process parameters are mostly based on empirical data since the underlying wear mechanisms in the field are not well known. In order to assess and predict the effects of abrasive wear on typical tillage machine components, the authors developed a combined experimental and numerical simulation procedure based on a time- and space-resolved version of the Archard wear equation. The applicability of the aforementioned procedure is demonstrated on a tooth of a circular harrow. The simulated worn geometry is in good agreement with the real geometry of a tooth worn in a soil bin.

Simulation Methodology for Prediction of the Wear on Silver-Coated Electrical Contacts With a Sphere/Flat Configuration

A protective coating is generally applied on base materials for better performance and a longer lifetime of electrical contacts. Silver is a widely used coating material, due to the good balance between the high resistance to corrosion caused by oxidation and the cost. Moreover, it possesses high electrical conductivity. Before the wear through of silver coatings, the electrical contact resistance is stable and remains at a low value, and thus, the reliability of electrical contacts can be guaranteed. After the wear through of silver coatings, the base material, typically a copper alloy, is exposed to the environment. The oxides of base materials are generated and accumulated, leading to blocking of the current path and an electrical failure of the contacts. Consequently, it is critical to predict the wear through of the silver coatings, when assessing the reliability of the electrical contacts. However, for a thick coating, it is difficult to forecast the wear through, since the linear wear rate of coatings decreases disproportionately with increasing coating thickness, and various phases exist, such as the running-in phase and the steady-state phase. In this paper, a simulation methodology based on Archard’s wear equation and consideration of both the surface roughness and geometry of the contact area is established in order to interpret the wear process of thick silver coatings with an as-received roughness applied in the electrical contacts with a sphere/flat configuration. The specific wear coefficient is regressed by curve fitting, according to the experimental results in the running-in phase and results from finite element analysis computation. Then, a modification of the regressed specific wear coefficient is conducted, considering the simplification of the roughness on the flat part and the gaps on the roughness ribs introduced by the rolling process. This modified specific wear coefficient is applied in the calculation model for the steady-state phase in order to predict the wear through of silver coatings. A good correlation between the simulated wear curve and the experimental results is obtained.

Simulation and sensitivity analysis of wear on the automotive brake pad

In this paper, an algorithm is proposed for finite element simulation of wear employing the Archard's wear equation. To evaluate the accuracy of a FE model, an experimental test is performed on a standard-sized pin, made of a known brake pad. Comparison of worn masses, obtained by experimental and numerical approaches shows good accuracy of the developed algorithm. As the next step, passenger car single-piston and double-piston brake pad wear cases are simulated using the proposed algorithm. The rotor/pad contact area and worn mass are compared between the two cases. It is shown that usage of a double-piston brake pad over a single-piston one, can improve brake performance. The Taguchi Method with an orthogonal array L9 is then applied to optimize the design parameters, meaning maximization of the ``contact area'' and minimization of the ``worn mass''. The ANOVA method is also used for evaluating the impact of each design parameter on desired outputs. It is shown that the contact area is most likely to be affected by back plate thickness, while the worn mass is more sensitive to the diameter of the piston, closer to the leading edge of the pad.

Microstructure and Tribological Properties of Sub-Microcrystalline Carbon Steel Produced by Severe Plastic Deformation

The microstructure, hardness, and sliding wear properties of high-pressure torsion (HPT)-processed pure Fe and S45C carbon steel were comprehensively investigated. The grains of Fe and S45C were significantly refined to the submicron size range using the HPT process, and the grain sizes were found to decrease with an increased number of turns (N). The Vickers hardness of HPT-processed specimens increased with increasing N or with distance from the center (i.e., with an increase in the strain), which is attributed to grain refinement. In addition, the hardness of HPT-processed Fe was saturated with a further increase in the number of turns owing to the saturation of grain refinement. However, saturation with hardening was not observed in the case of S45C and the hardness values of S45C were much higher than those of Fe. The wear amount was considerably reduced by HPT processing for both Fe and S45C. A linear correlation was determined between the specific wear rate and the inverse of hardness, which agrees with the Archard wear equation. The experimental results show that the reduction in the wear of Fe and S45C is considered to be due to hardening by the HPT process.

Sensitivity analysis of DEM prediction for sliding wear by single iron ore particle

PurposeSliding wear is a common phenomenon in the iron ore handling industry. Large-scale handling of iron ore bulk-solids causes a high amount of volume loss from the surfaces of bulk-solids-handling equipment. Predicting the sliding wear volume from equipment surfaces is beneficial for efficient maintenance of worn equipment. Recently, the discrete element method (DEM) simulations have been utilised to predict the wear by bulk-solids. However, the sensitivity of wear prediction subjected to DEM parameters has not been systemically investigated at single particle level. To ensure the wear predictions by DEM are accurate and stable, this study aims to conduct the sensitivity analysis at the single particle level.Design/methodology/approachIn this research, pin-on-disc wear tests are modelled to predict the sliding wear by individual iron ore particles. The Hertz–Mindlin (no slip) contact model is implemented to simulate interactions between particle (pin) and geometry (disc). To quantify the wear from geometry surface, a sliding wear equation derived from Archard’s wear model is adopted in the DEM simulations. The accuracy of the pin-on-disc wear test simulation is assessed by comparing the predicted wear volume with that of the theoretical calculation. The stability is evaluated by repetitive tests of a reference case. At the steady-state wear, the sensitivity analysis is done by predicting sliding wear volumes using the parameter values determined by iron ore-handling conditions. This research is carried out using the software EDEM® 2.7.1.FindingsNumerical errors occur when a particle passes a joint side of geometry meshes. However, this influence is negligible compared to total wear volume of a wear revolution. A reference case study demonstrates that accurate and stable results of sliding wear volume can be achieved. For the sliding wear at steady state, increasing particle density or radius causes more wear, whereas, by contrast, particle Poisson’s ratio, particle shear modulus, geometry mesh size, rotating speed, coefficient of restitution and time step have no impact on wear volume. As expected, increasing indentation force results in a proportional increase. For maintaining wear characteristic and reducing simulation time, the geometry mesh size is recommended. To further reduce simulation time, it is inappropriate using lower particle shear modulus. However, the maximum time step can be increased to 187% TR without compromising simulation accuracy.Research limitations/implicationsThe applied coefficient of sliding wear is determined based on theoretical and experimental studies of a spherical head of iron ore particle. To predict realistic volume loss in the iron ore-handling industry, this coefficient should be experimentally determined by taking into account the non-spherical shapes of iron ore particles.Practical implicationsThe effects of DEM parameters on sliding wear are revealed, enabling the selections of adequate values to predict sliding wear in the iron ore-handling industry.Originality/valueThe accuracy and stability to predict sliding wear by using EDEM® 2.7.1 are verified. Besides, this research accelerates the calibration of sliding wear prediction by DEM.

Effect of steel hardness on soot wear

Due to incomplete combustion, high levels of soot can accumulate in engine lubricants between drain intervals. This soot can promote wear of engine parts such as timing chains and cam followers. One standard approach to reducing wear is to increase the hardness of the rubbing components used. According to the Archard wear equation, wear rate should be broadly inversely proportional to hardness.To explore this approach for controlling soot wear, wear tests have been conducted in a High Frequency Reciprocating Rig (HFRR) with HFRR steel discs of various hardness against a hard steel ball. Carbon black (soot surrogate) dispersions in model lubricants based on solutions of ZDDP and dispersant in GTL base oils have been studied. Wear volumes have been measured and wear scars and tribofilms analysed using scanning white light interferometry and SEM-EDS.It is found that, while most oils show wear that reduces with increasing hardness, for blends that contain both ZDDP and carbon black, wear rate markedly increases with disc hardness as the latter approaches the hardness of the ball. The results support the prevalence of a corrosive-abrasive wear mechanism when carbon black and ZDDP are both present in a lubricant and suggests that selection of very hard surfaces may not be a useful way to control soot.

Engineering modeling of wear profiles in tooth flank of polyamide spur gears

The present paper is a contribution in developing an engineering model expressing the evolution of tooth flank wear in polyamide spur gears as a function of number of cycles. The method is based on first observing the behavior of wear on tooth flanks in real test conditions. Then, progressive flank wear profiles are plotted in order to sort out the corresponding fitting curves together with the associated mathematical equations. The general engineering model controlling the evolution of wear profile is found of the form of quadratic equation where the variable is the circular thickness of a tooth at a given depth from the top land of the tooth. The respective parameters of the engineering wear equation are determined as a function of number of revolutions of the spur gear. A wear correction parameter k w is added in order to catch up the measuring errors when plotting the wear profile curves using the proposed engineering wear model for spur gears. The data are in good agreement with that obtained from experimental measurements.

An adaptive finite element simulation of fretting wear damage at the head-neck taper junction of total hip replacement: The role of taper angle mismatch.

An adaptive finite element simulation was developed to predict fretting wear in a head-neck taper junction of hip joint implant through a two dimensional (2D) model and based on the Archard wear equation. This model represents the most critical section of the head-neck junction which was identified from a 3D model of the junction subjected to one cycle of level gait loading. The 2D model was then used to investigate the effect of angular mismatch between the head and neck components on the material loss and fretting wear process over 4 million gait cycles of walking. Generally, junctions with distal angular mismatches showed a better resistance to fretting wear. The largest area loss in the neck after 4 million cycles of loading was 1.86E-02mm2 which was found in the junction with a proximal mismatch angle of 0.124°. While, the minimum lost area (4.30E-03mm2) was found in the junction with a distal angular mismatch of 0.024°. Contact stress, amplitude of sliding and contact length were found as the key parameters that can influence the amount of material loss and the process of fretting wear damage. These parameters vary over the fretting wear cycles and are highly dependent on the type and magnitude of the taper angle mismatch. This study also showed that lost area does not have a linear relationship with the mismatch angle of taper junctions.

Micro-Scale Abrasive Wear Testing of CrN Duplex PVD Coating on Pre-Nitrided Tool Steel

Specific wear rates were calculated from a series of micro-scale abrasive tests by means of the calotte-grinding method. The tested material was a CrN coating deposited by arc evaporation on ion-nitrided AISI H13 steel. Characterizations included: phase analysis, chemical composition, metallography, microhardness, micro-scratch resistance and nano-indentation hardness. On wear testing, the counter body was a 30 mm diameter steel ball rotating at a tangential speed of 9.42 m/min and normal load of 0.54 N. The abrasive was a mono-crystalline diamond micro abrasive paste, 1 micrometer grit. Wear volumes were calculated by measuring the wear scars at various test intervals. In non-perforating tests, Archard's wear equation was directly employed for calculating coating wear rate as the slope of the linear least square data fit. In perforating tests, Allsopp's method was employed for the simultaneous determination of coating and substrate wear rates, from the slope and intercept values of the linear least square data fit. Coating specific wear rate values obtained from both non-perforating and perforating tests were very consistent, with a relative difference within 6%. Relative errors in specific wear rate values were estimated to be of the order of 0.05 for the coating and 0.2 for the substrate.

Microstructure and Wear Properties of High-Pressure Torsion Processed Iron

Microstructure and sliding wear properties of the sub-microcrystalline pure iron produced by an HPT process were investigated in detail. It was found the grains of pure iron were significantly refined to the submicron size range by an HPT process, and the Vickers hardness of HPT-processed specimens increased with increasing number of turns and distance from the center due to the grain refinement. A linear relationship between the hardness and the inverse square root of grain size (the Hall-Petch relationship) was realized. The HPT process clearly increased the wear resistance, and a linear correlation between the specific wear rate and the inverse of the Vickers hardness was found, which agreed with the Archard wear equation. The wear in SUJ2 ball wear tests was much higher than that in WC-Co ball wear tests owing to the high adhesion between the specimen materials.

Numerical Simulation & Experimental study of wear depth and Contact pressure distribution Of Aluminum MMC Pin on Disc Tribometer.

This paper is focused on Simulation and analysis of a simple tribo system confirming to ASTM G99, constituted by a deformable cylindrical pin that rotates around a rigid disc surface with friction. Aluminum6061 Metal Matrix Composite samples have been experimentally analyzed to investigate the Tribological characteristics of wear for various loading conditions with a constant sliding rotational velocity. The finite element software ANSYS 15 is used for this wear simulation. Assumptions were made that wear depth is not enough to change the contact pressure magnitude. The wear depth and contact pressure are being evaluated by the Archad’s linear wear law with the Euler integration formulation absorbed in Ansys. The wear coefficient (k) obtained from the experimental results which also accounted the effect of oxide formation & debris during dry slide wear. Simulation of wear involves solution of a general contact problem, which is highly non-linear due to the contact boundary conditions between the interfaces. The prediction of wear depth is evaluated from contact pressure, which is obtained from finite element simulation results & it is an input into Archard’s wear equation. It is found that simulation results are confirming in line with the experimental results.

An implicit finite wear contact formulation based on dual mortar methods

SummaryFinite deformation contact problems with frictional effects and finite shape changes due to wear are investigated. To capture the finite shape changes, a third configuration besides the well‐known reference and spatial configurations is introduced, which represents the time‐dependent worn state. Consistent interconnections between these states are realized by an arbitrary Lagrangean–Eulerian formulation. The newly developed partitioned and fully implicit algorithm is based on a Lagrangean step and a shape evolution step. Within the Lagrangean step, contact constraints as well as the wear equations are weakly enforced following the well‐established mortar framework. Additional unknowns due to the employed Lagrange multiplier method for contact constraint enforcement and due to wear itself are eliminated by condensation procedures based on the concept of biorthogonality and the so‐called dual shape functions. Several numerical examples in both 2D and 3D are provided to demonstrate the performance and accuracy of the proposed numerical algorithm. Copyright © 2016 John Wiley & Sons, Ltd.