Abrasion Pattern Research Articles

EXOSKELETAL ABRASION AS AN INDICATOR OF REPRODUCTIVE READINESS IN THE SPIDER CRAB LIBINIA EMARGINATA

ABSTRACT Patterns of exoskeletal abrasion on the carapace of long-clawed males of the spider crab Libinia emarginata appeared to follow specific sequences throughout the year. The degree of abrasion coincided with the enlargement of the reproductive system and increased levels of methyl farnesoate in the hemolymph. The patterns of abrasion apparently marked the time elapsed since the last molt, and when the abrasion extended beyond the midcarapace, it appeared to indicate increased reproductive readiness.

Contact Pressure Measurement utilizing Time-Frequency Analysis of Ultrasonic Reflected Wave at the Rubber Surface in Sliding Contact.

An ultrasonic technique was developed to study the characteristic for abrasion pattern of a rubber surface during stick slip motion and to demonstrate its applicability to the precisely contact pressure measurement utilizing Wigner distribution. Experiments were conducted using short cylindrical acril specimens pressed onto the rubber sheet bonded on a rotating disk. It was found that the contact pressure may be nearly zero soon after the locally high contact pressure area moves to the leading edge. In addition, the experimental results showed that the formation mechanism of the abrasion pattern observed on the rubber surface has close relation to locally sudden variation in the contact pressure due to a stick-slip phenomenon.

Tell-tale teeth: abrasion from the traditional clay pipe.

The long story of the once very widespread clay pipe has a minor but significant odontological aspect: some clay-pipe smokers may be characterized by a distinctive abrasion pattern of the teeth. The marks in question are of special interest to the archaeologist; attention is here directed particularly to the Scandinavian experience.

Mechanism of rubber abrasion part 3: how is friction linked to fracture in rubber abrasion?

We propose a new concept to understand the mechanism of rubber abrasion. Friction and fracture in abrasive wear of rubber are linked theoretically and experimentally through the formation of a periodic surface pattern, the abrasion pattern, generated by two kinds of periodic motion, stick-slip oscillation and microvibration. The direct driving force for fracture, i.e. the pattern formation, is the magnitude of the mean strain produced at the surface of the rubber by the two motions. The mean strain amplitude ε ∗ is governed by the friction constant μ, Young's modulus E of the material and the normal load P, as ε ∗ = μP/ES , where S is the cross-sectional area, which is correlated to the rate of abrasion loss V ̇ with the relation, V ̇ = dc(ε ∗/ dn . Thus, abrasive wear of rubber is strongly dependent on fracture resistant properties of the material under repeated deformation of the mean strain amplitude ε ∗ . Several questions in rubber abrasion remained unanswered are discussed according to the above concept.

A Characteristic on Abrasion Pattern on a Sliding Surface of Rubber under Stick-Slip Motion.

An ultrasonic technique was developed to study the characteristic abrasion pattern on a rubber surface under stick slip motion and to demonstrate the precisely contact pressure measurement at the end of contact. Experiments were conducted using short cylindrical rubber specimens pressed onto the rotating acril disk. It was observed that the abrasion pattern was significantly dependent on the variation in contact pressure. In addition, the experimental results showed that the formation of abrasion pattern on the middle area of contact was stimulated by the stick slip motion.

Mechanism of rubber abrasion: Part 2. General rule in abrasion pattern formation in rubber-like materials

The mechanism of rubber abrasion proposed in the previous paper was reconfirmed not only in unfilled and filled NR but in SBR and silicone rubber. It is an essential and general rule in rubber abrasion that the microvibration induced in the slip phase of stick-slip oscillation generates the initial abrasion patterns and the stick-slip motion propagates them to the final abrasion patterns. The initial pattern spacing agrees with the distance determined by the relation between the natural frequency of the material and the mean sliding velocity, meanwhile the final pattern spacing in the propagation reaches the distance given by the frequency of the stick-slip oscillation and the mean sliding velocity. Reinforcement by carbon blacks makes the frequencies of the both periodic motions in rubber larger, which of course gives the smaller initial and final pattern spacings in rubber abrasion. In addition, the microvibration attenuates more rapidly in more filled rubbers when it spreads over the rubber surface as a surface wave. Both phenomena have a great influence on the smaller abrasive wear of more filled rubbers.

Physical Properties of Wool Treated with Multifunctional Epoxides

We have investigated the physical properties of tropical wool fabrics. Samples were woven with yam from loose fibers treated with a water soluble multifunctional epoxide, i.e., glycerol polyglycidyl ether (GPE) in an aqueous medium catalyzed with a reductive agent (Na2S2O5) in the presence and absence of saturated NaCl. The resin treatment stiffened the fabrics somewhat and decreased their ability to regain moisture a little. Scanning electron microscopy revealed a difference in the abrasive breakdown pattern between the GPE/saturated aqueous NaCl treated wool and the untreated one. A good state of preservation of the hydrophobic nature of the scale surface after treatment was confirmed by soiling measurements of the wool with an oleophilic mixture/carbon black complex. There were fewer carbon black particle deposits in surfactant solution on the untreated and GPE/saturated aqueous NaCl treated wool than on the GPE/ H2O treated wool.

Mechanism of rubber abrasion. Part I: Abrasion pattern formation in natural rubber vulcanizate

The driving force to generate the periodic surface patterns, and thus rubber abrasion consists of two kinds of periodic motions, stick-slip oscillation and the microvibration generated during frictional slidings of rubber. The stick-slip oscillation is the driving force to propagate cracks, then abrasion patterns and the microvibration with the natural frequency of the rubber induced in the slip phase of the stick-slip oscillation is another driving force for the initiation of the cracks. Although initial cracks originate in the slip region of the rubber surface, the propagation of the cracks is strongly excited in the stick region. Accordingly, the initial size of the abrasion pattern, pattern spacing, equals the distance determined by the natural period of the rubber and the mean sliding velocity while the constant pattern spacing after the critical number of frictional slidings agrees with the distance given by the period of the stick-slip oscillation and the mean sliding velocity. Consequently, during rubber abrasion, two driving forces produce bimodal size distribution of abraded particles, small particles of the order of ten micrometres by microvibrations and large ones of the order of a few hundred micrometres by the stick-slip motions.

The Continuous Abrasion Index for the Assessment of Rock Abrasion

Abstract The continuous abrasion test is a new and simple test for evaluating the abrasive potential of rock material where attrition or low-stress sliding wear problems exist. The test is sensitive to the abrasive mineral content in the host rock and was found to be very suitable in comparing the degree of abrasiveness of various sedimentary rocks and in particular coal measures rocks. The wear area generated on a tested ball bearing is used as the Continuous Abrasive Index value for the tested rock. Several types of abrasive wear pattern were recognized on the tested steel ball; these can be used as a guide for the assessment of the abrasive potential of the rock. The exploitation of this new test has led to a new rock classification index according to the abrasive potential of the rock.

Friction and wear of short-fibre-reinforced rubber composites under various sliding speeds and loads

Friction and wear properties of short-fibre-reinforced chloroprene rubber composites were examined in the longitudinal (L), transverse (T) and normal (N) directions of the oriented polyamide fibres. The experiments were conducted for various sliding speeds of rubbing against abrasive papers. The rubbing experiments were also conducted under various loads, using both metal gauze and abrasive paper. When rubbed against abrasive paper and metal gauze, the wear rates of the short-fibre-reinforced rubber (SFRR) composites were lower than those of the unreinforced chloroprene rubber. A marked difference in the wear rates for these two specimens was observed when each was rubbed against metal gauze. A considerable difference was also observed when each was rubbed against abrasive paper. The minimum wear rates were obtained for rubbing in the N direction of the SFRR under the conditions examined. The maximum wear rates were observed for rubbing in the T direction. The wear rate for rubbing in the L direction exhibited medium values. The load dependence of the wear rates was greater for the SFRR than for the unreinforced rubber when rubbed against metal gauze. However, the load dependence of the wear rates for the SFRR was similar to that for the unreinforced rubber when rubbed against coarse abrasive paper. With decreasing load, the wear states of the unreinforced rubber rubbed against metal gauze changed from pattern abrasion to milder wear that arose from the hardening of the rubber surface. The speed dependence of the wear rate and frictional coefficient was very small for rubbing against coarse abrasive paper. When rubbed against fine abrasive paper, the variation of the friction with sliding speed was observed to be peak-shaped for the SFRR rubbed in both the N and L directions. The peak of friction was manifested by the transfer of rubber to the mated abrasive paper. Following the transfer of rubber, the wear rate decreased. Abrasion patterns were observed only for the unreinforced rubber rubbed against fine abrasive paper. The spacing of the patterns became wider with decreasing sliding speeds.

Pattern Abrasion and Other Mechanisms of Wear of Tank Track Pads

Abstract Wear of tank track pads has been studied under different conditions. With T142 pads tested on an M-60 tank, the mode of failure was found to depend on the test conditions. Among eighteen experimental compounds tested, improved wear (vs. the standard compound) under one test condition was generally at the expense of poorer wear under one or both of the other test conditions. However, in agreement with previous results, an HNBR/Zn-methacrylate/peroxide compound gave improved wear rate under all three test conditions. Wear of the T142 pads on a hilly cross-country course and on a combination course was generally by massive chunking. On a paved road course, most compounds wore by pattern abrasion. A few compounds worn on this course formed deep pockets parallel to the surface, resulting in the eventual loss of the large flaps between the pocket and the surface. Pattern abrasion was also found on T156 pads of four different compounds, tested on an M-1 tank on the paved road course. The abrasion patterns of both types of pads had a shingled appearance, with the ridges pitched so as to bite into the road surface. The abrasion patterns were characterized quantitatively by profilometry, using standard parameters calculated for surface roughness of metals and other materials. The ridge height and its ratio to ridge spacing correlated positively with wear rate on the paved road; whereas there was no correlation of ridge spacing with wear rate. The compounds which gave the lowest wear rate on the paved road, including the HNBR compounds, gave shallow ridges with little or no pattern.

A Laboratory Facility for the Study of Rubber Traction and Wear Resistance

Abstract Phenomena occurring at the interface between the tread compound and the road surface are responsible for at least two main tire characteristics: traction capability and wear resistance. Both depend on the road surface geometry, the presence of thin films of water, local contact pressure, tread element stiffness, temperature, tangential slip, etc. To discount the effect of tire construction, a laboratory test using a small solid rubber wheel has been considered. A rig is designed to easily change the “road” surface, and convert it from wet to dry conditions, run the rubber wheel on such surfaces under high braking or driving torque, and measure torque against longitudinal slip. The rig features a flat disk on which different surfaces can be simulated and two separate electric motors driving the disk and the test wheel in order to control slip instead of torque and to avoid instability at high driving or braking torques. Results show longitudinal characteristics versus slip in different test conditions and simulation of severe abrasion conditions leading to typical abrasion patterns.

Basic study of coupled damage caused by silt abrasion and cavitation erosion. 1st Report, Experiments with submerged water jets.

Damage due to the coupled action of cavitation erosion and silt abrasion was experimentally studied using submerged jets in which artificial silts (Al2O3) were included. It was shown that the magnitude of the acoustic emission energy, impact pressure and material damage rate caused by the cavitating jet impingement were greater than those caused by the noncavitating one. Good correlations between the above three erosion intensity parameters were also confirmed. SEM photographs of damaged surfaces showed that the edge of the abrasion trace was partially broken into pieces by cavitation. The material surface was smoother and the abrasion pattern was changed compared to that of pure abrasion.

Dental abrasion pattern in a selected group of Malaysians.

Among 350 inhabitants of two villages, 31 (8.9%) cleaned their teeth using table salt and charcoal applied to their forefinger or a Melastoma brush. As a result, all had distinct forms of abrasion cavity on the labial surfaces of their teeth. All of the above three agents are highly abrasive and injurious to both the hard and soft oral tissues. This dying practice is only popular among a very small number of persons in the older age group, and should be discouraged.

A Hypothetical Mechanism for Rubber Abrasion

Abstract A hypothetical mechanism for creating subsurface cracks during frictional sliding has been proposed as part of the process of abrasive wear of rubber. It consists of the unbounded elastic expansion of microscopic precursor voids until they burst open as cracks, under the action of internal pressure or of a triaxial tension in the surrounding rubber. This conjecture accounts for enhanced resistance to abrasion for compounds reinforced with carbon black, in terms of increased stiffness without much loss of extensibility, and for the lack of correlation of abrasion resistance with other measures of strength. It. should be noted that it is specific to soft, extensible materials, and thus it also accounts for marked differences in the nature of the wear process in rubbery materials compared to plastics and metals. Only rubbery materials appear to abrade away by a linking up of microcracks at right angles to the sliding direction to produce characteristic wear ridges known as the Schallamach abrasion pattern. Three mechanisms of generating a sufficiently large inflation pressure or triaxial tension are discussed. The most probable one seems to be thermal decomposition of rubber, generating volatile decomposition products—a microscale blowout process. This would be aggravated by a simultaneous softening of the rubber on heating. Although strictly conjectural, the proposed wear mechanism suggests a number of interesting experiments. For example, it would be helpful to know whether the character of wear changes when abrasion is carried out under a large superimposed hydrostatic pressure. Also, not enough is known about abrasion in vacuo. Is the process altered in kind, as well as in rate? And if thermal decomposition is, indeed, an important mechanism of initating subsurface cracks, what is the effect of changes in thermal conductivity of the abrading material on the rate of wear?

Taphonomic signature as a function of environmental process: Shells and shell beds in a hurricane-influenced inlet on the Texas coast

Criteria for taphonomic processes, including dissolution, breakage, abrasion, size sorting and shell orientation, were statistically correlated against environmental parameters representing shell source, depositional environment and depth of burial, using samples obtained from San Luis Pass, a microtidal inlet on the Texas coast. Core intervals were differentiated by cluster analysis into shell-poor sands, slightly shelly sands, shell-rich sands and shell gravels based on their percent carbonate and percent shell gravel content. Boundaries between these sedimentary classes represent thresholds in physical processes forming the shell deposits. We propose that this classification scheme for shelly sediments may be useful for field descriptions in a variety of depositional and tectonic settings. The death assemblages were predominantly composed of whole and fragmental molluscan shells. Most shells show the effects of physical taphonomic processes such as shell breakage, edge rounding, surface abrasion and size sorting. A significant minority of the shells show evidence of minor chemical alteration (dissolution). Patterns of dissolution, edge rounding and surface abrasion differed significantly on shells in a mixed-faunal assemblage derived from different habitats (bay, inlet/beach, inner shelf and unrestricted). Thus, the habitat where a species lived, rather than its final depositional environment, controlled most aspects of its taphonomy. Only shell orientation and size-frequency distribution were significantly affected by final environment of deposition. The hypothesis that a discrete high energy (hurricane) “event” can imprint a unique taphonomic signature is, consequently, false. Although hurricanes physically winnow shell material, a single “event” merely concentrates shells with preexisting characteristics without further significant alteration. Depth of burial was poorly correlated with most biostratinomic effects, including dissolution. Significant dissolution must occur only near the sediment-water interface. Accordingly, quantified taphonomic characteristics might be useful in identifying the original habitats of species deposited in mixed accumulations; “taphofacies” reflect not only the final depositional process, but also taphonomic processes in the habitat of origin.

Activity-induced patterns of dental abrasion in prehistoric Pakistan: evidence from Mehrgarh and Harappa.

A detailed investigation of worn teeth should reveal a record of past activity patterns including information regarding diet, food preparation methods, and craft or occupational activities. Anthropological studies of the extensive dental samples from Neolithic (MR 3) and Chalcolithic (MR 2) levels at Mehrgarh, Baluchistan, and Bronze Age Harappa, Punjab, yielded several interesting examples of unusual dental abrasion. This paper provides macro- and microscopic (scanning electron microscope) descriptions of three types of activity-induced dental abrasion: 1) interproximal tooth grooving and interproximal abrasion patches, 2) facial abrasion of maxillary anterior teeth, and 3) lingual abrasion of maxillary incisors in association with rounded wear of lower incisors. The gross size and shape of abrasion features, the orientation of microscopic wear striae, and ethnographic parallels are employed in inferring causal factors involved in their formation. Behavioral activities and dietary explanations possibly associated with each type of dental wear are considered and their implications for reconstructing prehistoric activity patterns discussed. The need for extensive ethno-anthropology research into variations of tooth use among living people with different diets, subsistence bases, and craft specializations is essential to further progress in this field.

Nonpenetrating subclavian artery trauma

Nonpenetrating injury to the subclavian vessels is uncommon. During a 6-year period we have treated 167 patients with injuries to the subclavian and superior mediastinal arteries. Fifteen of these injuries (9%) occurred after blunt trauma. In 10 patients the proximal segment (first and second parts) of the artery was involved. No patient had an isolated injury; the most frequent associated injuries were rib fractures (n = 11), with the first rib being involved in four of these. Total brachial plexus disruption was found in nine patients. All patients with distal artery involvement had a clavicular fracture. All had an absent radial pulse and eight had critical ischemia of the hand. Four patients were treated nonoperatively and the remainder were treated along standard lines. Brachial plexus reconstruction was not feasible in any patient. Within 2 weeks of operation, one patient died as a result of head injuries and one required amputation because of sepsis. During a 12-month period, five regained full function, one additional patient requested above-elbow amputation after 6 months, and seven had a flail anesthetic limb. Twelve of these patients were involved in automobile accidents, eight of whom were wearing lap-shoulder harness seat belts with a loose-fitting shoulder strap component that created a characteristic abrasion pattern on the torso and chest. We conclude that the torsion-shearing motion allowed by this situation contributed significantly to the pattern of injury and a plea is made for correctly fitted restraining devices.

Nonpenetrating subclavian artery trauma.

Nonpenetrating injury to the subclavian vessels is uncommon. During a 6-year period we have treated 167 patients with injuries to the subclavian and superior mediastinal arteries. Fifteen of these injuries (9%) occurred after blunt trauma. In 10 patients the proximal segment (first and second parts) of the artery was involved. No patient had an isolated injury; the most frequent associated injuries were rib fractures (n = 11), with the first rib being involved in four of these. Total brachial plexus disruption was found in nine patients. All patients with distal artery involvement had a clavicular fracture. All had an absent radial pulse and eight had critical ischemia of the hand. Four patients were treated nonoperatively and the remainder were treated along standard lines. Brachial plexus reconstruction was not feasible in any patient. Within 2 weeks of operation, one patient died as a result of head injuries and one required amputation because of sepsis. During a 12-month period, five regained full function, one additional patient requested above-elbow amputation after 6 months, and seven had a flail anesthetic limb. Twelve of these patients were involved in automobile accidents, eight of whom were wearing lap-shoulder harness seat belts with a loose-fitting shoulder strap component that created a characteristic abrasion pattern on the torso and chest. We conclude that the torsionshearing motion allowed by this situation contributed significantly to the pattern of injury and a plea is made for correctly fitted restraining devices.

Scanning electron microscopy studies on wear properties of blends of plasticized poly(vinyl chloride) and thermoplastic copolyester elastomer

Wear properties of blends of plasticized poly(vinyl chloride) (PVC) and thermoplastic copolyester elastomer (Hytrel 40D) have been studied with special reference to the effects of blend ratios and time of abrasion. The experiment was conducted in a Du Pont abrader using silicon carbide abrasive paper of grit size 320. The wear resistance of the blends was found to increase with increasing Hytrel content. In order to study the development of the abrasion pattern with the time of abrasion, samples were abraded for different abrasion times. The abraded surfaces were examined using scanning electron microscopy (SEM). Blends containing higher proportions of Hytrel (greater than or equal to 50 wt.%) showed frictional-type wear while those containing higher proportions of PVC showed abrasive wear. Attempts have been made to correlate the SEM micrographs with wear resistance.