Number Of Wear Cycles Research Articles

Frictional Study on 30CrNi2MoVA Steel Based on Experiments and Finite Element Simulation: Wear Prediction

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.

Influence of profile modification on the transmission error of spur gears under surface wear

The load distribution, transmission error, and time-varying meshing stiffness of spur gears are all influenced by the teeth dimensions and profiles shape. Any modification on the teeth geometry, as a profile relief frequently used to avoid the mesh-in impact, will affect all these parameters and the entire dynamic behavior of the gearset. In addition, due to the friction between contacting surfaces, wear arises at the teeth flanks. This causes the shape of the meshing profiles to change, which will affect the load distribution and the transmission error for the subsequent meshing cycles. And this new load distribution causes a surfaces wear different form that of the previous meshing cycle. Consequently, the wear depth increase is different at any contact point —because the load and sliding velocity are different— and at any meshing cycle as well —because the load distribution changes with the accumulated wear—. And all the above is also influenced by the profile modification the teeth were manufactured with. In this paper, a simple, analytic model of meshing stiffness, load sharing, and transmission error for spur gears with profile modifications including the influence of surfaces wear is presented. The evolution of the transmission error with the number of wear cycles is studied, and the optimal profile modification for minimizing the dynamic load induced by the transmission error is investigated.

Nano-scratch testing on thin diamond-like carbon coatings for microactuators: friction, wear and elastic-plastic deformation

Abstract In micromechanical systems the mechanical and tribological requirements for the materials in use are getting rapidly higher. The aim is to find out the fundamental frictional and wear behavior of thin coatings by using the hitherto knowledge in mechanical characterization of coatings and selective experiments. Nanoindentation and linear oscillating microwear experiments have been performed on micro-actuator components and on thin diamond-like carbon coatings, using diamond tips and loads in the range of some millinewtons. The wear depth and friction coefficients were determined as a function of load and number of wear cycles. New methods of data analysis will be discussed, which allow a separation of the different contributions of wear due to material loss, and elastic and plastic deformation. The friction coefficient shows deviations from Amonton’s law because of the dependence of the contact area on the normal load.

Quantification of wear in glass reinforced epoxy resin composites using surface profilometry and assessing effect of surfacing film involvement

This paper investigates the performance of glass reinforced epoxy resin composites in plate-on-plate type sliding wear. Wherein the samples were subjected to wear on a specially designed wear test rig for 20,000 cycles under an external load of 10 N. Also, the effect of using carbide-based surfacing film on the intensity of resulting wear was studied. The quantification of the amount of wear, though in cubic micron volume, was uniquely done by the criteria of surface profilometry. Two methods of surface profilometry – (i) manual type using Mitutoyo SJ310 and (ii) automated setup using KLA P7 Tencor, were followed to quantify the wear. Of which the automated measurement data were further processed using a developed MATLAB code to uniquely quantify the wear volume instead of giving only the surface parameters unlike regular measurements. The designed code also allowed the visualization of the surface profile, for effective comparison of the before and after wear data. The results show that the involvement of carbide surfacing film dramatically reduces the wear, as the volumetric wear observed in such samples were almost 70% less as compared to the uncoated samples. Though, there were hardly any difference after wear between the samples having single and triple layers of surfacing film. Hence, it was concluded that single layer of surfacing film would suffice for getting the effectiveness for wear resistance over three layers for the tested 20,000 number of wear cycles.

Numerical study on wear evolution and mechanical behavior of steel wires based on semi-analytical method

Based on the elastic contact theory and Archard's theory of wear, a mathematical model for wear evolution and mechanical behavior of steel wires in perpendicularly crossed configuration is established in the present study. The mathematical model is solved with a progressive solution process, in which a semi-analytical method (SAM) is adopted to realize the precise and fast evaluation of contact pressure, deformation and internal stress of the wires. The results show that both the wear and mechanical performances depend on the number of wear cycles and the position of moving wire along the wear movement direction. The interwire wear condition changes from sliding wear to mixed wear (both sliding wear and fretting wear) during the wear process. The wear depth during a single wear cycle has a generally uniform distribution in the wear region, except for the areas near the wear edges where oscillating distributions occur. The distribution of contact pressure is more uniform at the wear center than those at the wear edges, where obvious surface stress concentrations happen. In the initial phase of the wear process, wear scars of the wires extend rapidly and the nonuniformity of contact performance at different wear positions is distinct. As the wear process continues, the increasing rate of the wear depth decreases, and the interwire contact parameters become uniformly distributed.

Modeling and Simulation of Mild Wear of Spur Gear Considering Radial Misalignment

An appropriate clearance is required between mating gears for effective power transmission. In the present work, the effect of radial misalignment on mild wear of spur gear is modeled and simulated. The changes in the gear tooth contact geometry due to progressive wear have also been accounted in the model. The simulation results show that in the pinion dedendum region, pressure angle increases, while the contact pressure and wear depth decrease with increase in number of wear cycles. As far as the effect of radial misalignment is concerned, contact pressure decreases and wear depth increases with the increase in misalignment. In the pinion addendum region, pressure angle and wear depth increase with the increase in wear cycles, while the contact pressure and wear depth decrease with the increase in misalignment. The pressure angle and pitch point change from initial 20° (23rd pitch point) to 20.95° (26th pitch point) and 21.86° (28th pitch point) due to 0.5- and 1-mm radial misalignment, respectively. The wear depths after 50,000 wear cycles are − 1.32 × 10−2 μm, − 3.33 × 10−3 μm and − 4.39 × 10−4 μm at 23rd, 26th and 28th pitch points, respectively. The effect of radial misalignment on backlash, pressure angle, pitch point, contact ratio, double tooth contact region and speed ratio is also discussed.

Abrasive Wear of Polymer Fibers Investigated by Reciprocal Scratching in an Atomic Force Microscope

Three-dimensional (3D) woven fabrics have been considered by biomedical researchers to be used as load-bearing surfaces in joint and ligament replacements. In this regard, wear is a crucial phenomenon that determines material failure as well as biological response of body to wear debris. The current study evaluates various microscale screening methods with the aid of atomic force microscopy (AFM) for biocompatible polymer fibers that are used in 3D woven fabrics. Fibers in mono- and multi-filament forms were subjected to indentation, scratching, and line wear testing in dry and soaked conditions, and the effect of key parameters such as applied normal load, sliding velocity, and number of wear cycles was investigated. The area of worn material was determined by geometric approximation superimposed on the measured residual scratch of line wear. Moisture was found to lower the indentation hardness of some fibers while increasing the hardness of others. Line wear results clearly suggest ultrahigh molecular weight polyethylene (UHMWPE) to be the primary material for further investigation and that monofilament fibers should be avoided.

Reprint of Nanowear behaviour of monocrystalline silicon against SiO2 tip in water

By using an atomic force microscopy, the wear tests of Si(100) surface against SiO2 microsphere were performed both in water and in air. During the tests, the contact pressure was varied between 0.78GPa and 1.1GPa, the displacement amplitude was set as 250nm and the number of wear cycles was 200. As a comparison, the wear tests of Si(100) surface against diamond tip were also performed in water and air. The experimental results indicated that water environment played an important role in the wear behaviour of Si/SiO2 pair. Under a contact pressure of 1.1GPa, the wear depth of silicon in water was about 0.25nm, which was less than 10% of that in air. Since the wear depths of silicon in water were similar at various velocities (0.04–5μm/s), the hydrodynamic lubrication was not the main reason causing the slight wear of silicon in water. Further analysis indicated that the distinct wear behaviour of Si/SiO2 pair in air and in water could be mainly explained as the different intensity of chemical reactions in two environments for the pair of Si/SiO2. In air, the SiOSi bridges could easily form between SiO2 microsphere and silicon substrate and induced serious tribochemical wear of silicon. When the Si/SiO2 pair was immersed in water, the tribochemical reaction was largely resisted by the electrical double layer and the wear of silicon was slight. Even though, since the contact pressure was too low to induce the mechanical wear of silicon, the limited wear of silicon in water was still attributed to the tribochemical reaction. The results may help us understand the nanowear mechanism of silicon and optimize the tribological design of dynamic MEMS working in water environment.

Nanowear behaviour of monocrystalline silicon against SiO2 tip in water

By using an atomic force microscopy, the wear tests of Si(100) surface against SiO2 microsphere were performed both in water and in air. During the tests, the contact pressure was varied between 0.78GPa and 1.1GPa, the displacement amplitude was set as 250nm and the number of wear cycles was 200. As a comparison, the wear tests of Si(100) surface against diamond tip were also performed in water and air. The experimental results indicated that water environment played an important role in the wear behaviour of Si/SiO2 pair. Under a contact pressure of 1.1GPa, the wear depth of silicon in water was about 0.25nm, which was less than 10% of that in air. Since the wear depths of silicon in water were similar at various sliding velocities (0.04–5μm/s), the hydrodynamic lubrication was not the main reason causing the slight wear of silicon in water. Further analysis indicated that the distinct wear behaviour of Si/SiO2 pair in air and in water could be mainly explained as the different intensity of chemical reactions in two environments for the pair of Si/SiO2. In air, the SiOSi bridges could easily form between SiO2 microsphere and silicon substrate and induced serious tribochemical wear of silicon. When the Si/SiO2 pair was immersed in water, because of the different structure of the adsorbed water layer on silicon surface and the effect of the electrical double layer, the tribochemical reaction was largely resisted and the wear of silicon was slight. Even though, since the contact pressure was too low to induce the mechanical wear of silicon, the limited wear of silicon in water was still attributed to the tribochemical reaction. The results may help us understand the nanowear mechanism of silicon and optimize the tribological design of dynamic MEMS working in water environment.

Nano-scale Tribological Behavior of Polycrystalline Silicon Structural Films in Ambient Air

ABSTRACTDynamic friction, wear volumes and wear morphology have been studied for sliding wear in polysilicon in ambient air at μN normal loads using on-chip micron-scale test specimens. With increasing number of wear cycles, the friction coefficients show two distinct types of behavior: (i) an increase by a factor of two and a half to a steady-state regime after peaking at three times the initial value of about 0.10 ± 0.04, with no failure after millions of cycles; (ii) an increase by a factor larger than three followed by failure after ∼105 cycles. Additionally, the average nano-scale wear coefficient sharply increased in the first ∼105 cycles up to about 10−4 and then decayed by an order of magnitude over the course of several million cycles. For both modes of behavior, abrasive wear is the governing mechanism, the difference being attributed to variations in the local surface morphology (and wear debris) between the sliding surfaces. The oxidation of worn polysilicon surfaces only affects the friction coefficient after periods of inactivity (>30 min).

Changes in gloss after simulated generalized wear of composite resins

Generalized wear of composite resins in the noncontact area may result in changes of gloss, which can influence esthetics of restorations. The purpose of this study was to determine the changes in gloss of composite resins after generalized wear simulation. Surface roughness and amount of wear were measured for comparison. Generalized wear simulation was performed with a wear tester for 400,000 cycles with 6 composite resins (Estelite Sigma, Esthet X improved, Filtek Supreme, Heliomolar, Renamel Microfill, and Tetric-Ceram). Composite resin was placed into a mold (8 mm in diameter, 3 mm in depth) in an acrylic resin block, and 8 specimens were prepared per group. A flat-planed stylus made with polyacetal was loaded perpendicularly. Gloss was measured after every 100,000 cycles with a glossmeter in gloss units (GU). Average surface roughness (R(a)) of each specimen before and after 400,000 cycles of wear was determined. The amount of wear was measured with a 3-dimensional profilometer. Changes in gloss were analyzed by repeated-measures analysis of variance, and mean values were compared by Fisher's PLSD interval (alpha=.05). Gloss was influenced by the number of wear cycles and the composite resin, and there was a significant interaction (P=.000) between the number of wear cycles and the brand of composite resin. There were no significant correlations between the wear depth and the gloss or changes in gloss after 400,000 cycles. Generalized wear simulation for approximately 3 years of clinical use resulted in gloss changes of 36 to 64 GU, and maximum wear depth was in the range of 35 to 75 mum. Change in gloss varied among the composite resins, but average surface roughness was not influenced by the various composite resins.

Nano-scratch testing on thin diamond-like carbon coatings for microactuators: friction, wear and elastic-plastic deformation

Abstract In micromechanical systems the mechanical and tribological requirements for the materials in use are getting rapidly higher. The aim is to find out the fundamental frictional and wear behavior of thin coatings by using the hitherto knowledge in mechanical characterization of coatings and selective experiments. Nanoindentation and linear oscillating microwear experiments have been performed on microactuator components and on thin diamond-like carbon coatings, using diamond tips and loads in the range of some millinewtons. The wear depth and friction coefficients were determined as a function of load and number of wear cycles. New methods of data analysis will be discussed, which allow a separation of the different contributions of wear due to material loss, and elastic and plastic deformation. The friction coefficient shows deviations from Amonton's law because of the dependence of the contact area on the normal load.

Finite element simulation and experimental validation of fretting wear

A finite element-based method is presented for simulating both the fretting wear and the evolution of fretting variables with number of wear cycles in a cylinder-on-flat fretting configuration for application to aeroengine transmission components. The method is based on a modified version of Archard’s equation and is implemented within a commercial finite element code. Fretting tests are employed to determine the coefficient of friction (COF) and the wear coefficient applicable to the contact configuration and loading conditions. The wear simulation technique is incremental in nature and the total simulation time has been minimised via mesh and increment size optimisation. The predicted wear profiles have been compared with profilometer measurements of fretting test scars.

Analysis of microwear experiments on thin DLC coatings: friction, wear and plastic deformation

Linear oscillating microwear experiments have been performed on thin diamond-like carbon (DLC) coatings on glass, using a Hysitron Triboscope with a conical diamond tip of 0.6 μm tip radius and loads in the range of some milliNewtons. The friction coefficient μ has been determined as a function of load L and the number of wear cycles. The results can be understood in terms of a combination of Hertzian elastic contact and an additional ploughing term: μ=c 1L −1/3+c 2L m where m changes strongly during the first wear cycles. The residual wear depth of the wear trace has been compared to the residual indentation depth on the same material using the same tip. The comparison shows that in some cases the apparent wear volume is not due to a real material loss, but mainly to plastic deformation or densification of the material, while in other cases plastic deformation and material loss both contribute to the observed wear volume.

Behavior of surface layers during the reciprocating wear of SiC-Al/Si metal matrix composites

SiC particulate reinforced Al-Si matrix composite has been studied to determine the microscopic characteristics of surface layers including re-distribution of SiC particles during unlubricated reciprocal sliding wear at ambient temperature. Using a ball-on-block reciprocal test jig resulted in a surface mixed layer (SML) with fragmented SiC particles. The occurrence of the SML depends upon the number of sliding cycles and contact stress. The depth of the SML is also affected by the applied load and number of wear cycles.

Application of radioactivation analysis to the tribological study of gold-plated connectors

A radioactivation method is presented which allows high resolution determination of gold transfer during the wear of HE-11-type connectors. The method is shown to be very suitable because of the composition and the low weight of the contact elements. Wear tests are presented. These consist of mating an irradiated contact element with a non-irradiated one with or without lubrication. The quantities of gold transferred are measured by counting the gamma radiations on the non-irradiated samples. They are well described by analytical laws, including a damping exponential part and a part linearly increasing with the number of wear cycles. The linear contribution which is null when a good lubricant is used is ascribed to adhesive wear. A transient component is attributed to the progressive “breaking in” of the surfaces. The results show that radioactivation is a powerful method of investigating gold contacts.