Attrition Wear Research Articles

Thermal and Mechanical Mechanisms of Polymer Wear at the Nanoscale.

Wear is a ubiquitous phenomenon that limits the life of many engineered components with sliding interfaces through the gradual removal of material. The wear of polymers is crucial in many applications, ranging from bearings to orthopedic implants to nanolithography processes. The wear rate of polymers is strongly affected by the stress and temperature at the interface. The effects of temperature and stress are often described empirically since the wear process involves complex interactions between multiple asperities on rough surfaces over a range of length scales. Nanoscale tribology experiments at the single-asperity level have provided new insights into the underlying mechanisms of wear. Experiments on hard covalently bonded materials, including silicon and diamond, have demonstrated that wear is an atomic attrition wear process that can be modeled using stress-assisted transition state theory. Here, we examine the wear of a common polymer, polymethylmethacrylate (PMMA), at the nanoscale as a function of stress and temperature and show that the polymer wear is controlled by a combination of atomic attrition and viscoelastic relaxation. While the wear experiments are conducted at the nanoscale via atomic force microscopy, the results show that accounting for the local stress distribution at the contact interface is critical to understanding the wear behavior, an effect that was not considered in earlier studies on hard materials. Using a model that accounts for the stress distribution, we demonstrate the ability to predict the wear volume within 8%.

Atomic-scale wear behaviors of iron oxide through the atom-by-atom attrition and plastic deformation of nano-asperities

Atomic-scale wear, behaving distinctly from macroscale wear, has been gaining significant scientific interest. We previously proposed a semi-empirical wear model for covalent bonding materials, which primarily describes an interfacial-bond-dominant atomic-scale wear process. To assess the model's broader applicability on other material types, herein we selected the iron oxide (Fe2O3) as a representative ionic bonding material and conducted the large-scale atomistic simulations. The simulations unveiled two main atomic-scale wear mechanisms of Fe2O3: plastic deformation/cracking of nano-asperities induced by the asperity collision, and atom-by-atom attrition caused by the interfacial O–Fe bond formation. Crucially, our simulations proved effective in capturing the atom-by-atom attrition wear, thus confirming its validity for ionic materials and expanding its potential usefulness to a broader range of materials.

Diagnosis and prevalence of probable awake and sleep bruxism in adolescents: an exploratory analysis.

The aims of this study were to perform an exploratory analysis of probable awake (AB) and sleep bruxism (SB) prevalence using of different diagnosis criteria based on the International Consensus; evaluate the associations between self-report and clinical signs/symptoms in adolescents. Participated in this cross-sectional study 403 adolescents aged 12- to 19-years-old enrolled in public and private schools from Belo Horizonte, Brazil. Parents/caregivers answered a questionnaire about sociodemographic status and adolescents' health status. Adolescents answered a questionnaire evaluating AB (e.g., grinding and clenching) and SB (e.g., grinding, bracing, and thrusting) activities and frequent headaches. A clinical examination was performed on adolescents to evaluate bruxism clinical signs/symptoms (pain upon palpation on masseter and temporal, linea alba, indentation on the tongue and attrition wear severity). Descriptive statistics and Pearson's Qui-square test were performed (P≤0.05). Adolescents mean age was 14.3±1.5 years, and 58.1% were female. Self-report of SB was identified in 31% of participants and self-report of AB in 51.6%. Almost all adolescents (99%) presented at least one tooth with attrition wear (98.5% on enamel and 0.5% on dentin), with a mean number of 12.4±5.7 teeth. Depending on the diagnosis criteria, the prevalence of probable SB and AB varied from 0- 99% and 0.2- 99%, respectively. A high inconsistency was found for the prevalence of probable AB and SB in adolescents, which were influenced by the different clinical sings/symptoms used as diagnosis criteria. Frequent headaches and pain upon palpation on masseter and temporal muscle were associated to self-report of AB and SB among adolescents.

Investigation on tool wear mechanisms and machining tribology of hardened DC53 steel through modified CBN tooling geometry in hard turning

DC 53 steel has emerged as a possible replacement of AISI D2 steel possessing competitive hardness and better toughness. In the current work, turning of DC 53 steel was conducted via Xcel modified inserts by varying workpiece hardness levels (40 and 60 HRC), cutting speed (130 and 160 m/min), feed rate (0.07 and 0.112 mm/rev), and depth of cut (0.07 and 0.17 mm). A two-level 4-factor full factorial design was employed entailing 16 runs. An analysis of variance (ANOVA) was conducted to statistically analyze the effect and contributions of input parameters on response variables namely tool life, surface roughness, volume of material removed, power consumption, and machining zone temperature. Results show that the tool life, surface roughness, volume of material removed, and machining zone temperature are primarily affected by the hardness of DC53 with PCRs of ~ 96%, ~ 25%, ~ 62%, and ~ 25%, respectively. At a 40 HRC hardness value, true crater wear was observed due to continuous chips sliding at the rake face while for the workpiece having a 60 HRC, discontinuous chip formation produced less prominent crater wear. SEM images revealed complete delamination of the coating from the tool surface with adhesion and attrition wear identified as the main wear mechanisms. The formation of a groove pattern was also noticed on the flank face. The minimum surface roughness was 0.90 µm-Ra for the workpiece having a 40 HRC hardness level, and the same value was obtained for 60 HRC as well. The threshold value of the feed rate for the excellent performance of these inserts was less than 0.20 mm/rev. Additionally, the turning process proved to be productive for this material along with a lower surface roughness value in comparison to the wire EDM process.

On the Uniqueness of Wear Coefficient for Abrasive Wear at Nanoscale

AbstractMaterials wear is often characterized by empirical relations as the physical and chemical interactions at sliding interfaces are not fully understood at any length scale. Recent studies showed that these wear relations do not always hold in particular at the nanoscale. Here we discuss the validity range and limitations of two well-known wear models, i.e., Archard’s and Reye’s ones (which were principally developed for adhesive wear) for an abrasive wear process. Using systematic long-timescale molecular dynamic nanoscratching simulations, we show that, at the nanoscale, the wear coefficient increases by the adhesion strength and scratching depth and eventually saturates to a constant value. The saturation is associated with the transition from atomic attrition wear mode to plasticity-induced wear. This new understanding rationalizes discrepant experimental observations on the validity of Archard’s wear relation at the nanoscale. Furthermore, it confirms that a depth- and adhesion-independent wear coefficient can be obtained when plastic deformation dictates the abrasive wear process.

Effect of grain growth in bimodal microstructure on cutting performance of self-toughening Dy-α-SiAlON ceramic tool inserts

Although significant increase in mechanical properties has been achieved in ?-SiAlON ceramics by introducing self-toughening bimodal microstructure, the bimodal microstructure may not always result in better cutting performance of ?-SiAlON tool inserts. Herein Dy-?-SiAlON ceramics were prepared by hot-pressing at 1900?C under 30MPa. Diameter and aspect ratio of the large elongated ?-SiAlON grains pivotal to formation of bimodal microstructures were regulated by using 0-5wt.% Dy2O3 as a sintering additive. Mechanical properties and cutting performance of ?-SiAlON tool inserts were evaluated. The results showed good Vickers hardness (19.0-19.7GPa) and fracture toughness (3.61-4.18MPa?m1/2) increasing with crack propagation length. However, transverse section of the large elongated grains was revealed as critical crack to cause premature fracture of the ?-SiAlON ceramics. Fracture rather than attrition wear was recognized as dominant mechanism for tool failure, indicating that for better cutting performance of the ?-SiAlON tool inserts a selftoughening microstructure consisting of thinner grains with large aspect ratio is required.

Technologies assuring the service properties of friction pairs with cellular microrelief surfaces

Article focuses on the improvement of the technologies used to improve the durability of friction pair components. The authors use the piston compressor to study cellular microrelief surfaces of cylindrical components. The cells are shaped as elliptic paraboloid with uneven positive parameters. The use of cellular microrelief surfaces is highly preferred as they reduce the attrition wear of the friction pairs through assuring the hydrodynamic load capacity of the lubrication layer with the shape of the microrelief. The research goals included the parametric analysis of the lubrication layer behavior in the gap between the microrelief cells. To do this, the authors developed an analytical model based on the theory of hydrodynamic lubrication and constructed a CFD model using the ANSYS Fluent software. To contain the transfer equations, the authors used the turbulence model SST k–ω. Both models showed that the maximum hydrodynamic load capacity coincided with the 75%-length of the major axis of the elliptic cell, which also corresponds to 0.128 mm in cell depth. The maximum lifting hydrodynamic pressure on one microrelief cell amounted to 3 kPa. Based on the results of the parametric analysis, the authors claim that the cellular microrelief can be efficiently used to assure the service properties of friction pairs in process units. Keywords: friction pair; cylinder sleeve; piston ring; cellular microrelief; hydrodynamic model; mathematical model; ANSYS Fluent; two-dimensional parametric analysis.

A tool wear analysis of an Inconel 600 turned TiAlN coated carbide insert at various cutting speeds

In the current work, to investigate the influence of cutting speeds on turning of Inconel 600 using TiAlN insert has been conducted. The turning was conducted at different cutting speeds such as 25, 38, 62, and 102 m/min. The effect cutting speeds on SEM view and EDS analysis of turned insert has been discussed. It was found that at very low cutting speeds (25 and 38 m/min), nose of the insert underwent substantial wear due to attrition wear. It was also found that relatively high flaking and scratches were observed on rake surface at 62 and 102 m/min over others due to abrasion wear. Based on the EDS analysis of turned inserts, it was observed that a minor loss of tool material and lower deposition of workpiece elements on turned insert at 102 m/min cutting speed condition.

In vitro attrition wear resistance of four types of paste-like bulk-fill composite resins

BackgroundRecently, the application of bulk-fill composite resins has increased significantly. Attrition wear and the consequently increased surface roughness of composite resins are among the causes of restoration failure in the posterior teeth. This study aimed to compare the attrition wear and surface roughness of four types of bulk-fill composite resins compared to a conventional composite resin.MethodsEverX-Posterior, X-tra fil, SonicFill 2, and Filtek Bulk-Fill composites (bulk-fill) and Z250 composite (conventional resin composite) were evaluated. Thirty cylindrical specimens (n = 6) were weighed and monitored for 24 h until their weight was stabilized. The primary surface roughness of the specimens was measured by a profilometer. The specimens were then subjected to attrition wear in a chewing simulator. Next, the specimens were weighed, and the surface roughness was measured again. Data were analyzed by one-way ANOVA and Tukey’s post-hoc test at P < 0.05 significance level.ResultsAccording to one-way ANOVA, the difference in weight loss was significant among the groups (P = 0.004) but the difference in surface roughness of the groups was not significant after the attrition wear (P > 0.05). Tukey’s post-hoc test showed that the weight loss of bulk-fill composites was not significantly different from that of Z250 conventional composite after the attrition wear (P > 0.05).ConclusionWithin the limitations of this study, it appears that the tested bulk-fill composite resins are comparable to the conventional composite regarding their attrition wear, increased surface roughness, and weight loss.

Wear mechanisms of abrasive wheel for rail facing grinding

Facing grinding by abrasive wheel is the most widely used method to maintain the rails. The wear of abrasive wheel is inevitable and influences the grinding performance significantly. Therefore, a deep understanding on the wear mechanisms of abrasive wheel is beneficial for the development of grinding wheels and optimization of grinding processes. In the present study, rail grinding experiments were conducted using whole abrasive wheels and a single abrasive grain. The wear mechanisms of abrasive wheel were revealed, including the attrition wear, fracture and pulling-out of abrasive grains, material adhesion, clogging, and chemical wear. With the degradation of abrasive grain, the attrition wear, micro-fracture, macro-fracture and pulling-out of grain successively became the primary wear mode as the function of service time. With the primary wear state changing from attrition wear to grain fracture and grain pulling-out, the grinding efficiency was improved, but the grinding quality was decreased. The grinding wheel in the wear state of grain fracture had the optimum grinding performance.

Probing the effect of abrasive wear on the grinding performance of rail grinding stones

• Three grinding stones were fabricated individually using zirconia alumina, brown fused alumina and white fused alumina. • The main wear forms of rail grinding stones are blamed on attrition wear, abrasives pulled-out and fracture, the bond wear, material adhesion and clogging. • The grinding stones using brown fused alumina and white fused alumina exhibit better self-sharpness ascribed to the abrasives pulled-out and fracture. • The splintering mechanism of zirconia alumina is intergranular and transgranular fracture, while the brown fused alumina and white fused alumina are cleavable fracture. Grinding behaviour and wear mechanism of self-fabricated rail grinding stones (GS) using zirconia alumina (ZA), white fused alumina (WA) and brown fused alumina (A) were investigated in detail. The results illustrated that the grinding efficiency grew from GS-ZA and GS-A to GS-WA, and the GS-ZA gave the best ground rail surface quality. GS-ZA primarily consumed as attrition wear, while abrasive pull-out and fracture were dominant for the GS-WA and GS-A, thus making a better self-sharpness. The splintering mechanism of ZA was intergranular and transgranular fracture, and the macro-fracture and micro-fracture were presented by WA and A, respectively. Based on the experimental results, some suggestions about regulating the grinding performance of different GS, such as improving the grinding load of GS-ZA, reducing grinding heat of GS-WA, and the abrasive/bond interface modification of GS-A, were finally proposed.

Modified Taylor’s equation including the effects of fiber characteristics on tool wear when machining natural fiber composites

This study aims to give an understanding on the effects of diverse natural fibers on the mechanical properties and wear behavior of high-speed steel tool when machining polypropylene (PP) based natural fiber-reinforced composites (NFRCs). Rice husk (RH), jute and kenaf of 30 wt% each with notable differences in silicon content, hardness and aspect ratio values are used as reinforcements. The influence of worn-out tool on surface finish, machining force and work-tool interface temperature has also been elucidated. The microscopic analysis has enabled us to identify the distinct tool lives and wear mechanisms for the machined NFRCs demonstrating: (i) rigorous mechanical abrasion with strip chipping, cracks, galling and large nose deformation for RH/PP; (ii) less severe abrasion combined with adhesion and attrition wears for jute/PP; and (iii) mild abrasion/scratch marks with attrition wear and formation of protective/transfer layer for kenaf/PP composites. A remarkable difference has been observed in the flank wear values, such as VB = 0.25 mm after 55 min of machining for kenaf/PP composites whereas VB = 0.3 mm within 6 min for RH/PP. The machined surface textures generated by the worn tools reveal a plowing mechanism for RH/PP and jute/PP composites while shearing type for kenaf/PP composites. Overall, kenaf/PP composites prove to have superior mechanical and machinability characteristics in comparison to RH/PP composites, which reveal inferior outcomes. For the first time, a modified Taylor’s tool life equation, including silicon content and reinforcement aspect ratio has been derived with an error <18%.

Dry Machining Performance of AA7075-T6 Alloy Using Uncoated Carbide and MT-CVD TiCN-Al2O3-Coated Carbide Inserts

The present study examines dry machining performance of AA7075 T6 alloy using uncoated and MT-CVD TiCN–Al2O3-coated carbide inserts. Machining performance is assessed with regard to tangential cutting force, tool tip temperature and depth of flank wear. The performance of coated tool is compared to that of uncoated insert. In addition, different modes of tool wear and chip morphology are studied in detail. It is experienced that coated tool causes lower tool tip temperature and lesser flank wear than untreated counterpart. Apart from abrasion, adhesion and built-up layer formation; attrition wear is distinctly visible in case of uncoated tool. On the contrary, in addition to common wear modes, coated tool also experiences diffusion wear.

Influence of cutting tool material on machinability of Inconel 718 superalloy

Appropriate selection of tool material is very important for effective machining of ‘difficult-to-cut’ aerospace superalloy Inconel 718, especially, under dry condition. Present work aims at investigating performance of physical vapor deposition (PVD) multi-layer (TiN/TiCN/TiN) coated cermet, and PVD TiAlN coated PCBN (Polycrystalline Cubic Boron Nitride) brazed tipped carbide inserts on machinability of Inconel 718. Machinability is assessed based on cutting force magnitude, maximum tool-tip temperature attained, tool wear morphology, chip macro/micro morphology, and end part surface integrity. Later includes detailed analysis on morphology of the machined surface, roughness, and depth of hardened layer. Results obtained thereof, are compared to that of conventional uncoated WC-Co tool. It is evidenced that coated cermet outperformed other two inserts in purview of lower cutting force, better surface finish, and tiny white layer. WC-Co causes extreme cutting temperature than other counterparts. Up to 86 m/min cutting velocity, PCBN tool exhibits minimal flank wear; afterwards, tool is severely affected by huge notch wear. On the contrary, cermet tool suffers from lower flank wear than WC-Co for all cutting speeds tested. Both cermet and PCBN inserts are found remarkably affected by notching, and coating dissipation. Attrition wear is evidenced only in case of WC-Co insert. Coated cermet, thus, appears as a better choice for dry turning of Inconel 718.

Grain wear evolution of cubic boron nitride abrasives during single grain grinding of powder metallurgy superalloy FGH96

The grain wear evolution during grinding powder metallurgy superalloy FGH96 using a single abrasive grain of cubic boron nitride (CBN) under different undeformed chip thickness and abrasive wheel speed was investigated. The wear behavior of single abrasive grain (SAG) was extracted based on the variation feature of grinding force, radial wear, grain topography and material remove characteristics. Meanwhile, acoustic emission (AE) testing is used to analyze the grain wear evolution. The results show that micro fracture firstly occurs at the original defects of SAG at the initial wear stage. Attrition wear and micro fracture are responsible for the steady wear stage, while micro and macro fracture are dominant at severe wear stage. Besides, the manner of the plastic adiabatic shear remove occurs in the process of grinding FGH96. Furthermore, sudden increase of root mean square (RMS) of AE signal can be applied to reflect the fracture of SAG, whereas the continuously gradual decrease can be considered the attrition wear or material adhesion, which can provide a technical support for monitoring the grain wear during grinding.

On the machinability of the Ni-30 high-temperature iron-based superalloy

Superalloys are high-performance materials which combine high tensile, creep and fatigue strength, besides good ductility, toughness and resistance to corrosion, properties that are also responsible for their low machinability. The VAT 30® alloy contains an austenitic stainless steel base with additions of chromium, nickel, titanium and aluminum, and it is mainly applied on the manufacture of valves of combustion engines, due to its advantageous characteristics. This alloy exhibits both high ductility and abrasiveness, features that may promote both attrition and abrasion wear mechanisms on the tool used to cut it. This work contains some investigations about the effect of cooling condition, tool rake angle and cutting speed on the machinability of Ni-30 alloy in terms of cutting power consumption, surface roughness and tool life, besides the tool wear mechanisms. Conventional and high-pressure coolant injected toward the tool rake face was compared, as well as negative rake angle and neutral tooling, besides two different cutting speeds. Results show that high-pressure coolant may reduce cutting power consumption and even increase the volume of material removed during tool life up to 45% in some cases, but this same influence has not been verified regarding the workpiece arithmetical mean roughness value. Negative and neutral rake angle tools did not present very different results in terms of power and roughness, but negative tools provided considerably higher volume of material removed per tool life (up to 75% in one condition). Cutting speed showed strong effect on the cutting power, as expected, but no reasonable effect on workpiece surface roughness; regarding tool life, the cutting speed increase typically reduced the volume of material removed per tool life with conventional cooling, but when high-pressure coolant was used, this effect was attenuated. Abrasion and attrition were the main tool wear mechanisms in any tested condition.

Performance evaluation of MQL with AL2O3 mixed nanofluids prepared at different concentrations in milling of Hastelloy C276 alloy

Since some deficiencies in mist lubri-cooling techniques i.e., minimum quantity lubrication (MQL) in heavy cutting conditions have been noticed, recently nano-cutting fluids which have enrich thermal conductivity than base fluid, are begun to be used in MQL system. One of the critical issues arising in this process is the addition of the appropriate nanoparticle ratio to the base liquid. Therefore, this study aimed to find the optimum distribution rate of Al2O3 nanoparticles having excellent properties and machining parameters. For this purpose, by adding Al2O3 nanoparticles to vegetable-based cutting fluid, nano-cutting fluids were prepared in different volumetric concentrations (0.5, 1.0 and 1.5 vol%). These prepared nanofluids were used in the MQL system when milling of Hastelloy C276. Three cutting speeds (60, 75 and 90 m/min) and three different feed rates (0.10, 0.15 and 0.20 mm/rev) were added to the experimental design to study the performance of nanofluids under several cutting parameters. Apart from this experimental design, to clearly see the effect of concentration rates on tool wear and tool life, three experiments were carried out at each concentration ratio by keeping the machining parameters. Eventually, 1 vol% Al2O3 concentration clearly provided an improvement by up to 23% and 10% in tool life, compared to 0.5 vol% and 1.5 vol% concentration, respectively. In addition, while chipping/fracture, attrition wear and peeling of coating were observed under all cutting conditions, there was no evidence for workpiece material adhesion at 1 vol% and 1.5 vol% Al2O3 based nanofluid-MQL.

Influence of agglomerated diamond abrasive wear on sapphire material removal behavior

Further to explore the effect of the agglomerated diamond (AD) abrasive wear on material removal behavior of sapphire in lapping, the pin-on-disk test with an AD abrasive was carried out. The classifications of AD abrasive wear, material removal behavior of sapphire, friction coefficient of sliding contact and removal ratio of sapphire material were thoroughly investigated. The wear behavior of the AD abrasive shows two types: attrition wear and micro-fracture. Three wear statuses of the active cutting diamond grains fixed on the AD abrasive surface, including attrition wear, worn-flat and pull-out, occur in the tests. The sapphire material is mainly removed by the AD abrasive via plastic deformation. The micro-fracture feature of the AD abrasive improves its self-sharpening ability. Therefore, the micro-cutting action of the AD abrasive on the sapphire wafer has behaved well.

Microstructural analysis of failure progression for coated carbide tools during high-speed milling of Ti-6Al-4V

In this study, the microstructural failure progression of coated carbide tools was analyzed during milling Ti-6Al-4V under dry conditions. The microstructure and compositional characterization of worn tool inserts were examined using SEM and EDS analysis. It was found that the coated carbide cutting tools undergo several stages during interrupted cutting Ti-6Al-4V alloy: coating delamination, cobalt diffusion, attrition wear, cracking and flaking. Firstly, coating delamination firstly occurred around the cutting edge and then extended to the rake face and flank face as cutting process proceeds. The diffusion of the binder phase cobalt (Co) was observed after coating delamination and cutting speed significantly promoted the process of cobalt diffusion. Then, attrition wear occurred around the cutting edge as the WC particles were pulled out and removed from the tool substrate. In addition, Microcracks initiated and propagated from the voids introduced by cobalt diffusion due to cyclic thermomechanical loadings. Brittle fractures were found to be the main failure modes of coated carbide tools at high cutting speeds.

Effects of abrasive material and hardness of grinding wheel on rail grinding behaviors

Abrasive material and hardness of grinding wheel are two important factors affecting the grinding efficiency and quality. In this study, two kinds of abrasive grains (i.e., zirconium corundum (ZA) and brown fused alumina (BA)) were used to produce eight grinding wheels, among which five with different contents of abrasive grains and four with different hardness levels. Rail grinding experiments were conducted to investigate their grinding efficiency (grinding amount of rail), grinding quality (including surface roughness, surface burn, white etching layer (WEL), and residual stress), and wear types of grinding wheels. The results show that ZA grinding wheel produced larger grinding amount, higher surface roughness, but lower level of surface burn, thinner WEL, and smaller parallel residual stress than BA grinding wheel. With the increase in grinding wheel hardness, the surface roughness and residual stress of ground rail showed decrease trends, but the thickness of WEL increased. The wear type of ZA grains was macro-fracture and the wear type of BA grains was attrition wear. With the increase in grinding wheel hardness, the wear type was changed from grain pullout wear to macro-fracture. Based on the analysis of results, the appropriate grinding wheel was recommended that can improve the grinding process and reduce the grinding cost.