Moderate Wear Research Articles

Quantitative wear and wear damage analysis of composite resins in vitro

The aim of this study was to investigate volume loss and worn surfaces' morphologies of eight composite resins: Durafill VS (DUR), Clearfil AP-X (APX), Filtek Z250 (Z250), Filtek Supreme XT (FIL), Kalore (KAL), MI Flow (MFL), Venus Diamond (VED) and Venus Pearl (VEP). Disc-shaped specimens were fabricated and mounted in a ball-on-disc wear testing machine and abraded in water or with the third-body media, poppy seed slurry and polymethyl methacrylate (PMMA) slurry. Volume loss (n=5) was determined after 50k sliding cycles, and analyzed using two-way ANOVA (α=0.05). The worn surfaces were examined with SEM. Two-way ANOVA suggested significant interaction between composite and wear condition. DUR, KAL and MFL showed low wear in water. DUR, Z250 and FIL showed moderate wear with PMMA slurry, whereas APX, KAL and MFL were deeper abraded. Under the action of poppy seed slurry DUR proved high volume loss. SEM showed that Z250, FIL and MFL were uniformly abraded in water. KAL and MFL with poppy seed were heavily destructed, whereas VED and VEP appeared very smooth. KAL and MFL abraded with PMMA slurry showed many cracks, but VEP remained crack-free and smooth. Volume loss and worn surfaces' morphologies varied with type of composite and third-body media used.

Tu1776 The Risk of Dental Erosion in GERD Patients As Measured by the Basic Erosive Wear Examination

Background and aims: While symptoms and complications from gastroesophageal reflux disease (GERD) such as heartburn, esophageal stricture, bleeding, and Barrett's esophagus are commonly known, dental complications of GERD may go unrecognized. The prevalence of dental erosion in subjects with GERD is poorly described. The aim of this study was to determine the risk of dental erosion in a population diagnosed with GERD. The association between dental erosion and salivary flow, salivary buffering capacity and dietary acidic challenges was also assessed. Methods: Subjects were recruited from The University of North Carolina's Center for Esophageal Disease and Swallowing with a physician diagnosis of GERD, and typical symptoms of heartburn and regurgitation. Subjects received a basic dental exam using the Basic Erosive Wear Exam (BEWE, table); the general population has about a 10% prevalence of erosive wear. Subjects provided a stimulated salivary sample which was used to determine their stimulated salivary flow rate and salivary buffering capacity. A diet diary was given to the subjects to complete for 4 days which was used to calculate daily average acidic challenges. Xerostomia was defined as a flow rate less than 0.1mL/minute. Salivary flow was considered low risk if flow rate was between 0.7-0.1 mL/ minute. Salivary buffering was considered high risk if pH was below 4.0. while the risk was considered moderate if pH was between 4.0-4.9. Simple percentages are reported. Results: To date, 22 GERD subjects (13 female, 9 male) have been enrolled. Of these, 41% have moderate erosive wear (BEWE cumulative score 9-13), 50% have low erosive wear (BEWE score 3-8), and 9% show no erosive wear (BEWE score 0-2) Stimulated salivary flow rate was normal for 77% of the subjects, low for 18.5% and 4.5% of the subjects had xerostomia. Salivary buffering capacity was normal for 46% of the subjects while, 36% were at high risk and 18% of the subjects were at moderate risk. Dietary acidic challenges were low for 50% of the subjects, moderate for 35.7% and high for 14.3%. Conclusion: A high proportion of subjects with GERD show erosive wear of their teeth. Inadequate salivary flow or buffering capacity may in part explain this defect. BEWE Criteria for Grading Erosive Wear

The tribological properties of benzoxazine-bismaleimides composites with functionalized nano-SiO2

To improve the tribological properties of benzoxazine (BOZ) resin, bismaleimides (BMI) resin is chosen as organic phase, hyperbranched polysilane functionalized SiO2 nanoparticles (HBPSi-SiO2) are chosen as inorganic modifiers to prepare HBPSi-SiO2/BOZ-BMI composites using high shear and ultrasonic processes. The effect of content of HBPSi-SiO2 on the mechanical properties and tribological properties of the composites are investigated. The results show that suitable addition of HBPSi-SiO2 can largely enhance the impact strength, reduce the friction coefficient, and wear rate of BOZ-BMI resin. Scanning electron microscopy is employed to research the wearing mechanism of materials. The severe wear of the BOZ pure resin is owing to fatigue wear, and the moderate wear of BOZ-BMI resin is attributed to adhesive wear. While, the mild wear of the composites with HBPSi-SiO2 is due to abrasive wear. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

The wear of polished and glazed zirconia against enamel

The wear of tooth structure opposing anatomically contoured zirconia crowns requires further investigation. The purpose of this in vitro study was to measure the roughness and wear of polished, glazed, and polished then reglazed zirconia against human enamel antagonists and compare the measurements to those of veneering porcelain and natural enamel. Zirconia specimens were divided into polished, glazed, and polished then reglazed groups (n=8). A veneering porcelain (Ceramco3) and enamel were used as controls. The surface roughness of all pretest specimens was measured. Wear testing was performed in the newly designed Alabama wear testing device. The mesiobuccal cusps of extracted molars were standardized and used as antagonists. Three-dimensional (3D) scans of the specimens and antagonists were obtained at baseline and after 200 000 and 400 000 cycles with a profilometer. The baseline scans were superimposed on the posttesting scans to determine volumetric wear. Data were analyzed with a 1-way ANOVA and Tukey Honestly Significant Difference (HSD) post hoc tests (α=.05) Surface roughness ranked in order of least rough to roughest was: polished zirconia, glazed zirconia, polished then reglazed zirconia, veneering porcelain, and enamel. For ceramic, there was no measureable loss on polished zirconia, moderate loss on the surface of enamel, and significant loss on glazed and polished then reglazed zirconia. The highest ceramic wear was exhibited by the veneering ceramic. For enamel antagonists, polished zirconia caused the least wear, and enamel caused moderate wear. Glazed and polished then reglazed zirconia showed significant opposing enamel wear, and veneering porcelain demonstrated the most. Within the limitations of the study, polished zirconia is wear-friendly to the opposing tooth. Glazed zirconia causes more material and antagonist wear than polished zirconia. The surface roughness of the zirconia aided in predicting the wear of the opposing dentition.

New Aluminum Foam/Polyformaldehyde Interpenetrating Phase Composites Prepared by Injection Molding

A new type of interpenetrating phase composite was formed by filling 70%-porous open-cell aluminum foam with polyformaldehyde through injection molding process. The results showed that both mechanical properties and tribological behavior of composites were improved. The interphase behaviour of aluminum foam/polyformaldehyde composites was examined by scanning electron microscopy(SEM).The worn surfaces of composites were also examined and discussed. It could be indicated that injection molding and Al foam surface preprocessing including both alkaline wash and KH550 treatment for Al foam/ POM composites was available. The new composite could be used where moderate strength and wear properties are needed.

Wear Properties of A356/Al2O3 Metal Matrix Composites Produced by Semisolid Processing

In this study, A356/Al2O3 metal matrix composites were fabricated by conventional stirring and semisolid processing (combination of mechanical stirring in the mushy zone and cooling slope casting) and these composites were subjected to wear tests. The composites containing various weight fractions of Al2O3 particles (1%, 2.5% and 5%) were used in both conventional and rheocasting processes. In conventional stirring, the primary phase remained dendritic while in rheocasting the dendritic primary phase transformed into a globular microstructure. The influences of these processes on the hardness and wear behaviour of the composites were investigated. A pin-on-disc tribometer was used to carry out tribological tests under dry sliding conditions in air. Wear tests were carried out at 1.0 m/s sliding speed under a 20N load and four different sliding distances. A scanning electron microscope was used to examine the wear mechanism on the worn surfaces of the composites. The results showed that the volume loss of the composites produced by semisolid processing was lower than that of those produced by conventional casting. Based on wear rate ranges, all metal matrix composites exhibited moderate wear regimes. The dominant wear mechanism for all materials was ploughing, with some delimitation.

Jaw movement in fossil mammals: analysis, description and visualization

A terminology for and visualizations of different mammalian mastication paths are provided, resulting from orientation of attritional and abrasional facets and striation on fossil (and extant) teeth. The occlusal motion of the left lower jaw is considered, and a moderate wear stage (IDAS 3) is used as standard. In contrast to conventional terminologies, the proposed nomenclature differentiates between the inclination and the direction of the lower jaw movement as projected onto a horizontal plane for each phase of the power stroke. The proposed mastication compass attempts to combine three aspects of the power stroke: (1) the number of phases, (2) the occlusal direction, and (3) the inclination of each phase. Descriptions and visualizations are given for several taxa in order to demonstrate its general applicability. The proposed new terminology and the mastication compass simplify comparisons of different modes of mastication in different mammalian taxa.

Severe muscular waste in university student of nutrition science

The aim of this study was to evaluate the protein status of young students of Nutrition attending to the University of Querétaro in central México. A total of 39 students, (35 women and 4 men), aged between 19 and 25 years old participated in this study. The average age of participants was 20.8±1.3 years. The average body mass index (BMI) was 22.1±4.1 kg/m2 (within normal range); however, 14.3% of women were underweight and 11.4% presented overweight and/or obesity. In contrast, 33% of men were overweight. 42% of women and 33% of the men had elevated body fat. Over 94% of participants had some type of muscle wasting with the diagnosis of creatinine‐height index. Of those who had normal weight, 36% of them had severe muscle wasting and an additional 20% showed moderate wear, which indicates that, the students of nutrition in order to maintain a healthy weight; they are succeeding at the expense of muscle protein. It is necessary to pay more attention to maintain body compartments and not just the weight of people, avoiding to compromise important structural and metabolic roles.University of Querétaro‐CONCYTEQ

Novel Modeling of Tool Edge Wear

In this article, modeling of the entire curve of the tool edge wear, covering all of its characteristic segments relating to the cutting process (first, without any detectable wear; second, initial wear; third, moderate wear; fourth, accelerated wear), from the beginning to its end, is presented. The excessive tool edge wear ends with the loss of the tool's ability to cut. First, the description of tool life in the entire range of velocity variation is provided. Then the characteristics of the tool edge wear are presented. The need to model other phenomena (material resistance to machining; strenghthening or hardening of the solid; thermal expansion of solid; entropy growth of heated solid, etc.) using a similar method is stressed.

Tradeoffs amongst fatigue, wear, and oxidation resistance of cross-linked ultra-high molecular weight polyethylene

This study evaluated the tradeoffs amongst fatigue crack propagation resistance, wear resistance, and oxidative stability in a wide variety of clinically-relevant cross-linked ultra-high molecular weight polyethylene. Highly cross-linked re-melted materials showed good oxidation and wear performance, but diminished fatigue crack propagation resistance. Highly cross-linked annealed materials showed good wear and fatigue performance, but poor oxidation resistance. Moderately cross-linked re-melted materials showed good oxidation resistance, but moderate wear and fatigue resistance. Increasing radiation dose increased wear resistance but decreased fatigue crack propagation resistance. Annealing reduced fatigue resistance less than re-melting, but left materials susceptible to oxidation. This appears to occur because annealing below the melting temperature after cross-linking increased the volume fraction and size of lamellae, but failed to neutralize all free radicals. Alternately, re-melting after cross-linking appeared to eliminate free radicals, but, restricted by the network of cross-links, the re-formed lamellae were fewer and smaller in size which resulted in poor fatigue crack propagation resistance. This is the first study to simultaneously evaluate fatigue crack propagation, wear, oxidation, and microstructure in a wide variety of clinically-relevant ultra-high. The tradeoff we have shown in fatigue, wear, and oxidation performance is critical to the material’s long-term success in total joint replacements.

Effect of Cu Particles Precipitation on Wear Behaviour of Fe-3mass%Cu under Dry Sliding Condition

Effect of peak-aged and over-aged Cu particles on wear behaviour of ferritic iron was investigated by means of Pin-on-Disc wear test under dry sliding condition. It was found that hardness of the peak-aged sample was higher than the over-aged sample. The specific wear rates of peak-aged samples were in the range of 0.20 × 10-4 to 0.89 × 10-4 mm3/(Nm) while the over-aged samples were in the range of 0.21 × 10-4 to 1.29 × 10-4 mm3/(Nm). Although both samples possessed moderate wear behaviours, the peak-aged samples had better wear resistance. Scanning Electron Microscopy observation found that most wear mechanism were due to plastic ploughing phenomenon. Transferred materials from the counterface tool was also proven by Energy Dispersive Spectroscopy test. However, the roughness test showed that the peak-aged sample surface was finer than the over-aged sample surface. Average roughness of peak-aged samples were in the range of 0.49 to 1.79 μm while the over-aged samples were in the range of 3.28 to 4.02 μm. Hence, it can be concluded that the peak-aged Cu particles can improve the wear resistance of steel.

Dry sliding wear behaviour of Al–12Si–4Mg alloy with cerium addition

The purpose of this work is to understand the effect of cerium addition on wear resistance behaviour of as-cast alloys. Al–12Si–4 Mg alloys with 1–5 wt% cerium addition were prepared using the casting technique. A sliding wear test was carried out under applied loads of 10 N, 30 N and 50 N at a fixed sliding speed of 1 m/s using a pin-on-disc configuration. The wear test was conducted in dry conditions at room temperature of ∼25 °C. Detailed analysis of the microstructure, worn surface, collected debris and microhardness was undertaken in order to investigate the differences between the as-cast alloys with different levels of cerium addition. The addition of 1–5 wt% cerium was found to lead to the precipitation of intermetallic phases (Al–Ce), resulting a needle-like structures. Increasing cerium content up to 2 wt% improved both wear resistance and microhardness of as-cast alloys. Addition of more than 2 wt% cerium, however, led to a decrease in microhardness, resulting in lower wear resistance of the alloys. Moderate wear was observed at all loads, with specific wear rates ( K′) ranging from 6.82 × 10 −5 with 2 wt% Ce at applied load of 50 N to 21.48 × 10 −5 mm 3/N m without added Ce at an applied load of 10 N. Based on K′ ranges, the as-cast alloys exhibited moderate wear regimes, and the mechanism of wear is a combination of abrasion and adhesion. Alloy containing 2 wt% Ce, with the highest hardness and lowest K′ value, showed the greatest wear resistance.

Structural and optical properties of diamond like thin films deposited by asymmetric bipolar pulsed-DC reactive magnetron sputtering

In contrast with PECVD technology, reactive sputtering of graphite allows an independent control of the substrate bias. This characteristic permits the modification of film properties without varying the plasma composition. In the present study, the characteristics of DLC films grown by pulsed-DC reactive sputtering were determined as a function of substrate bias. Asymmetric bipolar pulsed-DC in a gas mixture of Ar and 7.5% CH 4 with substrate bias in the range of − 300 V to 0 V, provided wear resistant a-C:H films with wear rate values in the range of 15 to 23 · 10 − 15 m 3 m − 1 N − 1 . DLC exhibit characteristics associated to hydrogenated DLC films (DLCH), namely: moderate sp 3 content and mass density (up to 1.8 g/cm 3), low hydrogen content (∼ 30%) and high transparency (> 90%) up to wavelengths of 700 nm with a Tauc gap energy up to 1.9 eV. Moreover, they also showed low stress values and moderate wear rates, as shown in previous studies.

Tribological Behavior and Corrosion Resistance of Kolsterized AISI316L Austenitic Stainless Steel: Existing Applications in the Automotive Industry

Abstract In this paper the effect of Kolsterizing, a commercial low temperature carburizing process, on the dry sliding wear behaviour and corrosion resistance of the AISI316L austenitic stainless steel is presented and discussed, together with some applications of the process in the automotive field. The treatment significantly enhances the surface hardness of the steel; this hardness increase is due to the formation of a carbon-supersaturated austenite phase, without carbide precipitation. The Kolsterizing process also significantly increases the dry sliding wear resistance of the steel, both against metallic and ceramic countermaterials. Severe wear occurs in the case of the untreated steel, with strong adhesion, abrasion, and severe plastic deformation; while a moderate oxidative wear regime is observed for the low temperature carburized steel. The corrosion resistance in H2SO4 0.5 M and chloride-containing electrolytes is also significantly improved, thanks to the formation of a C-rich surface layer that ennobles the treated steel. At very high anodic potentials this surface layer is locally penetrated, producing a pitting-like corrosion form.

Inferring parrotfish (Teleostei: Scaridae) pharyngeal mill function from dental morphology, wear, and microstructure

Morphology, occlusal surface topography, macrowear, and microwear features of parrotfish pharyngeal teeth were investigated to relate microstructural characteristics to the function of the pharyngeal mill using scanning electron microscopy of whole and sectioned pharyngeal jaws and teeth. Pharyngeal tooth migration is anterior in the lower jaw (fifth ceratobranchial) and posterior in the upper jaw (paired third pharyngobranchials), making the interaction of occlusal surfaces and wear-generating forces complex. The extent of wear can be used to define three regions through which teeth migrate: a region containing newly erupted teeth showing little or no wear; a midregion in which the apical enameloid is swiftly worn; and a region containing teeth with only basal enameloid remaining, which shows low to moderate wear. The shape of the occlusal surface alters as the teeth progress along the pharyngeal jaw, generating conditions that appear suited to the reduction of coral particles. It is likely that the interaction between these particles and algal cells during the process of the rendering of the former is responsible for the rupture of the latter, with the consequent liberation of cell contents from which parrotfish obtain their nutrients.

Vacuum tribological behaviour of self‐lubricating quasicrystalline composite coatings

AbstractHigh‐temperature‐resistant self‐lubricating coatings are needed in space vehicles for components that operate at high temperatures and/or under vacuum. Thick composite lubricant coatings containing quasicrystalline alloys as the hard phase for wear resistance can be deposited by a thermal spray technique. The coatings also contain lubricating materials (silver and BaF2CaF2 eutectic) and NiCr as the tough component. This paper describes the vacuum tribological properties of TH103, a coating of this type, with a very good microstructural quality. The coating was deposited by high‐velocity oxygen fuel spraying and tested under vacuum using a pin‐on‐disc tribometer. Different loads, linear speeds, and pin materials were studied. The pin scars and disc wear tracks were characterised using a combination of scanning electron microscopy and energy dispersive spectrometry. A minimum mean steady friction coefficient of 0.32 was obtained when employing an X750 Ni superalloy pin in vacuum conditions under 10 N load and 15 cm/s linear speed, showing moderate wear of the disc and low wear of the pin.

Failure analysis of a railway copper contact strip

The present work investigated the causes of premature wear of the contact strips of a railway line working under voltage of 1.500 Vcc, current of 1120 A, normal force of 70 N and presence of graphite in the wire/strip interface. In all investigated regions (without apparent wear, moderate wear and severe wear), the presence of cracks in the hardened tribo-surface of the Cu-strip – which is caused either by work hardening or thermal cycling is usually followed by material detachment and production of hard abrasive debris. The presence of hard abrasive particles (such as SiO 2 and Al 2O 3,) and wear debris (Cu 2O and hardened Cu) promotes a regime of severe abrasion. The debris showed preferentially a flake-like morphology, being composed of graphite and highly deformed copper, suggesting the dominant action of mechanical wear mechanisms. The presence of some raindrop-like debris featuring an as-cast microstructure confirmed the occurrence of incipient fusion on the copper strip tribo-interface, possibly caused by electrical discharge (electrical induced wear). The results indicated that the wear mechanism of the Cu strip is divided into different stages. First, there is a mixed wear regime (adhesive and abrasive wear) of the graphite layer associated with lubricated adhesive wear of the Cu strip. After, there is the occurrence of a mixed wear regime between the strip/wire tribo surfaces, with simultaneous action of unlubricated adhesive wear, third body abrasive wear and electrical induced wear (local fusion). Finally, once the graphite has been completely consumed, the wear grooves are parallel to the sliding direction and the centre of the strip shows a much more severe wear rate.

Friction and wear properties of thermo-reactive diffusion coatings against titanium nitride coated steels

Abstract In this work, the tribological behavior of hardened, tufftrited, titanium nitride coated, boronized, chromium carbide coated and vanadium carbide coated AISI 52100 steel balls against titanium nitride coated AISI 1020 steel disc have been studied under 0.5, 1 and 2 N loads. Titanium nitride, chromium carbide, vanadium carbide coating were performed by pack method. Tufftriting and boronizing treatment were performed by slurry salt bath techniques. The wear test was carried out ball-on-disc configuration system. Materials tested were hardened, tuftrided, boronized, and chromium carbide, vanadium carbide and titanium nitride coated AISI 52100 steel balls against titanium nitride coated AISI 1020 steel disc. These results showed that wear rate of hardened, tufftrided, titanium nitride and chromium carbide coated, boronized and vanadium carbide coated AISI 52100 steel balls coated by thermo-chemically steel were approximately linearly proportional to load. The contacting AISI 52100 steel ball showed even greater wear rate when tested on the titanium nitride coated AISI 1020 steel samples from thermo-chemically coated AISI 52100 steel samples. Vanadium carbide coated and chromium carbide coated steel balls have the highest wear resistance to titanium nitride coated samples, boronized, and tufftrided AISI 52100 steel balls have moderate wear rate and AISI 52100 steel ball have the lowest wear resistance to titanium nitride coated steel sample. The wear constant rate value of hardened, tufftrided, titanium nitride coated, chromium carbide coated, boronized and vanadium carbide coated steel balls against titanium nitride coated AISI 1020 steel disc are with in the range of 1.6367 × 10 −6 , 1.356 × 10 −6 , 4.744 × 10 −7 , 2.2543 × 10 −7 , 2.339 × 10 −7 and 1.715 × 10 −7 mm 3 /(N m), respectively.

Role of PET in improving wear properties of PP in dry sliding condition

The sliding wear of isotactic polypropylene (PP), polyethylene terephthalate (PET) and their blends was evaluated as a function of applied pressure and composition against a stainless steel counter face in dry condition. Wear rate decreases with the addition of PET in the blend. The wear was observed in two stages, the moderate wear and high wear while increasing the applied pressure on test samples. The addition of PET in PP helps in increasing the limit of moderate wear towards the high-pressure side. Microstructure and worn surfaces of samples were observed by scanning electron microscope. The wear phenomenon has been discussed based on wear losses and worn surfaces.

The mechanism of sliding friction wear in polycrystalline solids

A new micromechanical model describing the sliding friction wear of polycrystalline solids is proposed. The model is consistent with a hypothesis suggested previously, according to which the transition from intensive to moderate wear (for the nonconforming bodies in sliding friction contact) is related to attaining a definite, sufficiently small shear strain rate at the friction surface, depending on the absolute value of the normal force applied to the friction contact. In addition, the model explains some well-known empirical relationships between the wear intensity and friction coefficient for steel on steel in a wide range of loads and pressures in the friction contact.