Abrasion Pattern Research Articles

The steady state abrasion of rubber: Why are the weakest rubber compounds so good in abrasion?

This paper examines the blade abrasion of four different rubber materials, unfilled natural rubber (NR), unfilled styrene butadiene rubber (SBR), unfilled butadiene rubber (BR) and carbon black filled styrene butadiene rubber. Each is abraded until the steady state abrasion pattern is developed on the surface of moulded rubber wheels. The steady state conditions are measured using the weight loss per revolution of the wheel. The abraded surface is cut to examine the typical asperity profile. Each profile is modelled using finite element analysis to calculate the stored energy release rate for each combination of material and test condition. The stored energy release rate when combined with an independent measure of the rate of crack growth measured using a fatigue crack growth test gives a reasonable prediction of the abrasion rate for both SBR materials as well as the BR. However, the NR materials appear to be about 30 times worse in abrasion than would be expected from the cyclic fatigue crack growth measurements. This is most likely to result from the strain induced crystallisation being suppressed by the very rapid loading rates that are encountered during blade abrasion. It is apparent that the low strength of the BR material results in much smaller asperities being formed under steady state abrasion. When these asperities are modelled they create very low values of strain energy release rate which results in a much slower abrasion rate. Conversely the strongest material NR has the longest tongue on the asperity and this in turn generates much larger values for the tearing energy at the tip of the asperity and this contributes to its poor abrasion resistance.

Taphonomy of debris-flow hosted dinosaur bonebeds at Dalton Wells, Utah (Lower Cretaceous, Cedar Mountain Formation, USA)

A taphonomic study of the Lower Cretaceous, Dalton Wells (DW) dinosaur bonebeds near Moab, Utah, provides insight into the origins, preservational biases, and paleobiological significance of one of the richest and most diverse Early Cretaceous dinosaur sites known. The bonebeds occur in a stacked succession of debris flows at the base of the Yellow Cat Member of the Cedar Mountain Formation, which was deposited in a seasonally-dry, alluvial-lacustrine setting. Although only 5% of the locality has been collected, more than 4200 bones were recovered, representing an assemblage overwhelmingly dominated by dinosaurs — with a minimum of 67 individuals that represent at least eight genera. The assemblage also includes eight elements from four non-dinosaurian reptiles. The dinosaur fauna is sauropod-dominated (MNI [minimum number of individuals] = 41): a basal macronarian (MNI = 15), Venenosaurus (MNI = 3), a camarasaurid (MNI = 2), and a large number (MNI = 21) of generically unassigned sauropod elements. Other dinosaurs include the theropods Utahraptor (MNI = 9), Nedcolbertia (MNI = 2), a possible ornithomimid (MNI = 2), plus a large iguanodontid (MNI = 4), and the ankylosaurid, Gastonia (MNI = 9). Patterns of skeletal articulation and clustering, ontogenetic representation, and bone surface modification indicate that the assemblage accumulated and was exposed for more than a year as the result one or more multiple mass mortality events, likely droughts, that culled large numbers of subadults from the biocoenose. Carcasses and disarticulated elements were reworked, then later transported a short distance and buried by a succession of debris flows. Skeletal representation data, patterns of sorting, breakage, burrows, abrasion, and scratch marks provide evidence for sorting, trampling, and scavenging prior to debris flow reworking. Pre-debris-flow sorting is attributed to earlier hydraulic winnowing of easily transported elements. The intensity and thoroughness of breakage involving 97% of the elements suggest highly-focused, high-load impacts, compatible with trampling by sauropods and iguanodontids. Lightly abraded and vertically displaced elements indicate episodes of trampling in soft mud. Trampling occurred before, and after, debris flow transport. Theropod tooth marks are uncommon but bone scavenging by osteophagous insects was common and severe, resulting in substantial damage to articular surfaces. Comparisons of DW and other debris-flow hosted bonebeds indicate that there are few consistent patterns among fossil-assemblage and bone-modification data. However, there are numerous similarities in the geological and spatial taphonomy datasets from these sites, resulting from the similar physico-hydraulic conditions under which elements were transported/reworked and buried. Geologically and taphonomically, Dalton Wells is similar to the Blagoveshchensk monodominant hadrosaur bonebed in the Udurchukan Formation of eastern Russia, which also is interpreted as a debris flow/hyperconcentrated flow deposit. Dalton Wells also shares geologic and taphonomic characteristics with four bonebeds southeast of the town of Green River, Utah and all occur at the base of the Yellow Cat Member. The uniform stratigraphic occurrences of the Dalton Wells, Blagoveshchensk, and the Green River sites (resting on an unconformity), and their shared sedimentologic and taphonomic features indicate that these sites originated in response to similar tectonic, depositional and biostratinomic factors.

Experimental Studies on Mechanism of Material Removal in Abrasive Flow Machining Process

In this article, the mechanism of material removal (MR) in Abrasive Flow Machining (AFM) process has been studied. Representative components of pure Aluminum and Brass were processed by AFM under similar process conditions. The processed surfaces were analyzed with the help of Scanning Electron Microscopy (SEM). SEM photographs reveal noticeable difference between abrasion patterns produced on the processed surfaces of both the materials. A mechanism of MR has been proposed by examining the nature of interaction between the flowing abrasive medium and target work surfaces of selected materials.

Tribological Properties of Carbon black added Acrylonitrile-butadiene Rubber

The tribological properties of acrylonitrile-butadiene rubber (NBR) filled with two kinds of carbon black filler were examined. Different types of Semi-Reinforcing Furnace (SRF), and High Abrasion Furnace (HAF) blacks were used as filler material to test the influence of carbon black particle size on the friction and wear of NBR. Results from tribological tests using a ball on disk method showed that the smaller HAF particles were more effective for reducing the wear of NBR during frictional sliding. The hardness, elastic modulus at 100% elongation, and elongation at break were measured to examine the correlation between the effects of carbon black on the mechanical and tribological properties of the NBR specimens. The wear tracks of the NBR specimens were observed with scanning electron microscopy (SEM). The wear tracks for NBR with different ratios of SRF and HAF showed clearly different abrasion patterns. Mechanisms for the friction and wear behavior of NBR with different sizes of carbon black filler were proposed using evidence from wear track observation, as well as the mechanical and tribological test results.

Statistic approach on taphonomic phenomena in shells ofGlycymeris glycymeris (Bivalvia: Glycymerididae) and its significance in the fossil record

Abrasion is a taphonomic process of three-dimensional alteration and destruction of bivalve (and other shelly biota) shell morphology. In this study, abrasion processes inGlycymeris glycymeris and their relationships are presented, quantified and compared with fossil analogues. The Recent material was sampled from sandy beaches of NW France (Normandy). As a basis for describing abrasion patterns and paths, a revised description of the non-abraded morphology ofG. glycymeris is provided. For an analysis of shell microstructure abrasion patterns, fracture samples as well as polished and etched thin-sections were studied by SEM and TLM methods. Based on 524 specimens ofG. glycymeris, abrasion patterns of nine shell characters (valve outline; external shell surface ornamentation;external colour pattern and periostracum; beak/umbo depression; beak/umbo facets;hinge plate;ligamental area; internal shell surface within palliai line and adductor scars; crenulation of the inner ventral margin) were divided into 6–10 abrasion stages, arranged in their successive order. By means of cluster and correspondence analyses, the subjective order of abrasion stages was tested. Particular abrasion stages of certain characters are quite frequent, whereas others are rare. Consequently, some stages are either biased or our subjective stages are positioned within a consecutive path and not well defined. Cluster analysis revealed that certain characters are quite closely correlated; others do not show any relationships. The results derived from the Recent material are compared with two fossil examples,Glycymeris obovata and G. pilosa deshayesi, from the Tertiary of Central Europe.

Feeding behavior of the Gondwanic Crocodylomorpha Mariliasuchus amarali from the Upper Cretaceous Bauru Basin, Brazil

Mariliasuchus amarali Carvalho and Bertini, 1999 is a Cretaceous Crocodylomorpha (Notosuchia) from the Bauru Basin, Brazil. The feeding behavior of M. amarali is analysed and interpreted based on the articular–quadrate articulation, pattern of teeth occlusion and the chemical composition of coprolites. The articulation between the articular and quadrate bones and the teeth abrasion pattern allow to infer that this notosuchian probably moved the jaw antero-posteriorly, processing the food before swallowing it. M. amarali should have kept the food inside the oral cavity during the feeding process, increasing the effectiveness of mastication. The post-caniniform tooth row is medially displaced in relation to the skull, suggesting the presence of a large conjunctive tissue. The structure and shape of the anterior caniniform and incisiform teeth exclude the possibility of an entirely herbivorous diet. Based on the morphological data and on the physical and chemical analyses of coprolites, it is interpreted that it had omnivorous feeding habits. The shape and abrasion pattern of the incisiform teeth suggest that Mariliasuchus employed the prominent anterior incisiform teeth for an active digging behavior.

Bedload abrasion and the in situ fragmentation of bivalve shells

AbstractThe aim of this study was to determine how Unio bivalve shells fragment within the channel of the Sakmara River (southern Urals, Russia). The Sakmara River has an abundant bivalve population and a highly variable flow regime which, at low flow, allowed much of the channel bed to be examined. A large data set of 1013 shells (Unio sp.) was examined and these were shown to have consistent patterns of orientation, aspect, shell abrasion, perforation and fracture. The close spatial relationship between areas of shell abrasion, shell perforation and shell fracture showed that they form part of a continuum whereby areas of abrasion evolve into perforations and perforations coalesce and enlarge into fractures. The mechanism of shell damage proposed is one of abrasion in place, whereby the shell remains stationary on the surface of the point bar and is impacted by bedload. Underpinning this process are the hydrodynamic properties of the bivalve shell, with consistency in the orientation and aspect of the valve in a flowing current producing consistency in the distribution of damage on the shell surface. Valves preferentially lie in a convex‐up position and orientate in the flow such that the umbo faces upstream. The elevated, upstream‐facing umbo region is exposed to particle impact and is the first to be abraded and perforated. The vulnerability of the umbo to perforation is greatly increased by the thinness of the shell at the umbo cavity. The in situ abrasion process is enhanced by the development of an armoured gravel bed which restricts valve mobility and maintains shells within the abrasion zone at the sediment–water interface. The in situ abrasion process shows that broken shells are not a reliable indicator of long distance transport. The study also raises the issue that tumbling barrel experiments, which are generally used to simulate shell abrasion, will not replicate the type of directionally focused sand‐blasting which appears to be the principal cause of shell fragmentation in the Sakmara River.

Effect of soft carbon black on tribology of deproteinised and polyisoprene rubbers

In this work, the tribological properties of deproteinised natural rubber (DPNR) were examined and compared with synthetic cis-1,4-polyisoprene rubber (IR), namely Natsyn 2200. The effect of adding carbon black (CB) (0, 25 and 50 phr) to both DPNR and IR on the friction and wear characteristics was investigated. Dry abrasion tests were carried out using pin-on-cylinder tribometer with abrasive paper (Diamond 50) under different operating test conditions such as applied normal load (5–35 N), sliding speed (0.3–1.5 m/s) and sliding distance (90–450 m). Experimental results showed that the addition of CB has significantly affected the wear and friction characteristics of both DPNR and IR, i.e. it reduces the abrasion weight loss by more than 70% compared to unfilled rubber, depending on the test conditions and the concentration of CB. The friction coefficient of DPNR was decreased by about 12.5% upon the addition of 50 phr CB, compared to unfilled DPNR. Meanwhile, adding (25–50 phr) CB to IR drastically deteriorates the friction coefficient, i.e. an increase in the friction by about 200% at 25 phr CB and 300% at 50 phr CB compared to unfilled IR. Finally, scanning electron microscopy (SEM) technique is employed to observe the abrasion pattern of rubber in order to correlate the experimental test results to the wear mechanisms.

The worn dentition — pathognomonic patterns of abrasion and erosion

Historically, the dental literature has revealed various causes of tooth wear, yet it has failed to provide a conclusive method of differentiation and diagnosis of the condition. The categories of tooth wear encountered most commonly in dental practice are abrasion and erosion. The major causes of wear from abrasion are bruxism and toothpaste abuse, and the major causes of wear from erosion are regurgitation, coke-swishing and fruit-mulling. Through in-depth clinical study of these causes, this paper provides a diagnostic system that will enable dental professionals to determine and differentiate the exact aetiology of the worn dentition simply by the recognition of the pathognomonic wear patterns on diagnostic casts, which are based upon the position and quantity of the non-carious loss of tooth structure.

ICP-MS trace-element analysis as a forensic tool.

Careful tracing of evidence at the site of a crime must be performed before suspects can be convicted of a crime or homicide. Fingerprints and ballistic control samples are important evidence. A common method used to examine lead bullets is comparison of physical properties such as weight, dimensions, shape, and distinctive markings. However ballistic investigations, for example comparison of characteristic scratches and marks left on fired bullets, do not always give sufficient information. Ballistic abrasion patterns can change for a variety of reasons, e.g. deformation or mechanical strain. Sometimes only particles remain in a victim's body. In such cases trace-element composition and lead-isotope ratios can be compared with those of controls. Elemental composition of particles and deformed bullets have been compared with the elemental fingerprints and isotope ratios of potential bullet types found on suspects. The applicability of the method was studied for two different cases. Data interpretation and several limitations of the technique are also discussed in this paper.

Measurement of the Deformation Distribution on Friction Surface of Rubber under the Sliding Condition with the Correlation Method

It is important to analyze the deformation distribution on friction surface under friction condition in order to clarify growth and wear mechanism of the abrasion pattern of rubber. In this paper, the aspect of the contact surface under sliding friction of rubber and glass plate was observed, and it was tried that the displacement vectors on friction surface that abrasion pattern was created was calculated by the digital image correlation method. As a result, the displacement on contact surface of rubber repeated the reciprocating motion. As abrasion patterns grew, the amplitude of reciprocating motion increased and the period was long. Even if the position of friction direction is different, the deformation of friction surface was similar the period and the amplitude, but there was a time lag. The normal strain and shearing strain on friction surface were calculated by the displacement vectors. Their strain repeated increase and decrease as well as the displacement. The range of strain increased, as the load was bigger.

ゴムのパターン摩耗時のアブレージョンパターン成長機構に関する研究(OS9-2 摩擦・摩耗)

ゴムのパターン摩耗時のアブレージョンパターン成長機構に関する研究(OS9-2 摩擦・摩耗)

Fracture behavior of NR and SBR vulcanizates filled with ground rubber having uniform particle size

AbstractThe use of recycled rubber including ground scrap vulcanizates in rubber compounds was studied. When ground rubber was incorporated into rubber compounds, the physical properties, especially the tensile strength, were deteriorated compared to the virgin rubber compound. Also, incorporating ground rubber caused a change of the cure behavior via migration of sulfur or an accelerator between the virgin rubber matrix and the ground rubber vulcanizate. In this study, the fracture behavior and abrasion property of carbon black‐filled SBR and NR compounds containing ground rubber vulcanizate were investigated. Also, the effect of the particle size or loading volume of ground rubber powder on those properties was studied. Four different sizes, 420–600, 177–250, 125–150, and 75–88 μm, of ambient ground rubber powder recycled from waste tire were selected and used in the compounding. The loading amounts of ground rubber powder were 10, 30, and 50 phr. The flex crack growth of SBR‐ and NR‐based compounds was altered by the addition of ground rubber particles. More delayed crack growth was observed with an increasing loading volume and decreasing particle size of the ground rubber powders, and this behavior was more prominent in SBR than in NR compounds. Tangent delta, a direct measure of internal energy dissipation, increased with an increasing loading volume of the ground rubber particles. The abrasion rate of ground rubber‐filled compounds was more dependent on the size of the abrasion pattern than on the loading level or particle size of the ground rubber powders. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2491–2500, 2002

Laboratory simulation of clast abrasion

AbstractExperimental abrasion of river‐bed materials has been widely undertaken, producing ‘downstream’ fining rates that generally are believed to be much less than those observed in the field. A conclusion commonly adopted has been that sorting processes are more effective than abrasion processes. A comparative evaluation of results from an abrasion tank and a tumbling barrel are presented, which show that abrasion patterns and rates differ according to the equipment used, clast size and shape, the clast charge (barrel) and water velocity and bed material (tank). Abrasion is a composite process, and the effects achieved appear to be dominated by percussion in the tank and grinding in the barrel. Breakage, crushing and sandblasting are not modelled effectively, nor are effects achieved on clasts when they form part of the bed. Comparisons are made with other equipment used, the very limited amount of direct field abrasion monitoring, and with the probable suite of processes that may occur under field conditions. Also reviewed are the problems that arise when laboratory weight‐loss abrasion coefficients are used or converted into ones of size diminution, as usually derived from field observations of down‐channel trends. It is concluded that field abrasion rates generally have been underestimated, as the processes involved are at best only selectively represented by the experimental equipment so far used, and because the results obtained experimentally are capable of misinterpretation when related to field trends. Copyright © 2002 John Wiley & Sons, Ltd.

ゴムのアブレージョンパターン面の摩擦 摩擦方向が摩擦係数に及ぼす影響

In this study, the coefficients of friction on the rubber surfaces having abrasion patterns which were abraded by abrasive cloth were examined. When a mating glass specimen was perpendicularly rubbed against parallel ridges of abrasion patterns, the effects of sliding direction and the spacing of the abrasion patterns on the coefficients of friction were investigated. From the experiments, the variations of the coefficients of friction were explained by the variation of contact area.The coefficients of friction on the abrasion patterns were examined with same direction of abrasion by abrasive cloth and the counter direction of abrasion. The coefficients of friction on the abrasion patterns in a direction of abrasion were from twenty-five to fifty percents larger than those rubbed in a counter direction of abrasion. When the abrasion patterns were rubbed in a direction of abrasion, the coefficients of friction increased because of the increment of apparent applied load by friction force. While the abrasion patterns were rubbed in the counter direction of abrasion, the coefficients of friction decreased by the decrement of apparent applied load by friction force. The coefficients of friction decreased when the spacing of abrasion patterns and applied load increased. The load dependence was dominant as the spacing of patterns was large.

Relation between Wavelength Analysis of the Surface Topography of Rubber and the Frictional Characteristic under the Reciprocating Sliding Condition.

The characteristics of surface topography have a great influence on the frictional features. Wavelength analysis for the frictional surface topography of rubber is an important method to elucidate the complicated frictional phenomena. In this paper, a method is proposed to evaluate the power spectral density function of the frictional surface topography of rubber under the reciprocating sliding conditions by using fractal dimension, and the relationship among fractal dimension, the friction coefficient and test conditions are examined. As abrasion patterns grew, the power spectra of long wavelength became larger and fractal dimensions were dec-reased. There was a proportional correlation between the fractal dimension and the friction coefficient. The equation of estimation on the friction coefficient with a high multiple correlation coefficient of 0.749 was represented from power spectrum function density by using multiple regression analysis. As a result of simulation on the wavy patterns that made use of fractal dimension and phase, the simulated wavy patterns were similar to the experimental results.

Analysis of the Taber Test in Characterization of Automotive Side Windows

The Taber test, as described in ASTM D-1044, combined with haze-level measurement, as described in ASTM 1003, is a commonly used method in many industries to evaluate resistance of material surfaces to abrasion. Attempts were made to use the Taber test to characterize a coated polycarbonate automotive window. However, the results did not represent the performance of the product in actual service very well. Atomic force microscopy was used to examine the abraded surfaces after the Taber test and carry out a statistical analysis to explain the observed haze development (the haze after abrasion less the haze before abrasion). It was found that the Taber test data in evaluation of the layered material had a larger standard of deviation than glass due to the occasional occurrence of delamination and chipping at the surface. In addition, its crossed-scratch abrasion pattern might not be a good simulation of the real abrasion experience of the automotive windows.

Initiation and development of wear of an elastomeric surface by a blade abrader

Experimental work is reported to study abrasion between a metal blade and an elastomeric material. It has been suggested that high frequency “microvibration” and stick-slip oscillation lead to the initiation of cracks and the formation of a distinctive abrasion pattern. Experiments have been performed to test the hypothesis. High frequency microvibration could not be detected prior to the formation of an abrasion pattern but was observed after an abrasion pattern had developed. The spacing in the abrasion pattern was, however, approximately what would be expected from the stick-slip frequency and the sliding velocity.

ゴムのパターン摩耗過程における摩擦力と接触面積の変化

In this study variation in the frictional force of rubber was examined at the initial stage of pattern abrasion. The abrasion patterns′ lengths on the contact surface were also investigated to deduce the frictional force per unit length of abrasion patterns.In the experiments, a rubber specimen was rubbed against a mating flat glass and the contact surface was observed through the mating glass. As a result, the contact area observed at the initial stage was decreased to reach a constant value after repeated sliding. At the initial stage many small abrasion patterns were observed. At the steady state of rubbing the size of individual abrasion pattern became larger and the number of abrasion patterns was reduced. The frictional force per unit length of abrasion patterns gradually increased with the prolonged sliding and then attained to a constant value. In the experiments examined the frictional forces were ranging from 0.3N/mm to 0.5N/mm. Therefore it is found that the cracks underneath the abrasion patterns are propagated by the frictional force.

Analysis of two dow corningbreast implants removed after 28 years of implantation

A pair of intact silicone gel breast implants that had been implanted for 28 years was analyzed after surgical removal in 1997 because of severe capsular contracture and heavily calcified capsules. The implants, manufactured by Dow Corning Corporation, were seamless, teardrop-shaped Cronin style (Silastic® 0) with Dacron® fixation patches. To determine the effects of long-term implantation, the material properties of tensile strength, elongation, tear resistance, 200% modulus, 400% modulus, and cross-link density were measured and found to be within the minimum-to-maximum range of properties for control implants of this type. This analysis indicates there was little or no large-scale material degradation of the elastomer shells after 28 years of implantation. Scanning electron microscopy examination of the shells was also performed and revealed that one implant wall had a defect caused by a scalpel cut accidentally induced at the time of explantation. The other explant had a very small area containing an unusual abrasion pattern of unknown origin. Otherwise, the surface structure of the 28-year-old explants showed no significant signs of wear, abrasion, or other indications of elastomer degradation. It may be true that breast implants are more likely to fail over time. However, our analysis of these implants indicates that these particular silicone shells showed no significant degradation after 28 years of implantation.