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Firing tests of a small caliber experimental gun barrel made of a cobalt-base alloy have been conducted with the purpose of determining the degree of wear and erosion due to excessive firing durations. The small amount of barrel material loss makes the cobalt-base alloy an excellent candidate for use as a gun liner. An unusual wear pattern resulting from this loss was observed near the muzzle. Elimination of chemical and thermal effects made a plausible explanation of the wear pattern possible

Background and purpose — Cup wear in total hip arthroplasty (THA) can be affected by different manufacturing processes of the polyethylene (PE). We report the long-term wear pattern differences, as well as early creep behavior, between conventional PE and highly cross-linked PE (HXLPE) liners, as measured with radiostereometry (RSA) up to 10 years. We also compare migration and clinical outcome of 2 similar uncemented cups with different backside surface roughness. Patients and methods — We included 45 patients with primary osteoarthritis. 23 received a conventional liner and 22 an HXLPE liner in a similar uncemented cup, but with a slightly rougher surface. The patients were followed up with RSA and hip-specific outcome questionnaire (HOOS) at 3 months, 1, 2, 5, and 10 years. Results — During the first 3 months both liners showed expected deformation with mean proximal head penetration of 0.39 mm (conventional PE) and 0.21 mm (HXLPE). Between 3 months and 10 years there was a difference in annual wear with 0.12 mm/year for the conventional liner and 0.02 mm/year for the HXLPE liner. The cup with rougher surface had less initial migration but both types had stabilized after 3 months. The HOOS scores improved after surgery and remained high for both groups throughout the study period. Interpretation — Up to 10 years the HXLPE has consistent lower annual wear, possibly contributing to longer survival of the THA, compared with conventional PE. All patients reported good results regardless of liner type.

Erosion has been recognized as one of the major threats for industries involving multiphase transportation pipelines. Within the last decades, effective parameters on wear pattern have been identified. As a result, the (famous) V-shaped erosion profile has been detected for the pipes' elbow section. In this study, CFD is employed to investigate the erosion mechanism on the square duct elbows. A novel erosion pattern has been observed for square ducts in comparison with the pipes. The impact of several parameters (particle and flow velocity, secondary flow, turbulent intensity, particle streamline) has been inspected as well. It has been led to the conclusion that the erosion rate of square ducts is lower than common pipes, especially when either higher flow velocities or bigger particles size are employed.

The cyclic utilization of coated cemented carbide inserts for turning of Inconel 718 was presented, which could be described as that the worn inserts should be given priority to repair rather than to reclaim the resources of W and Co. The assessment of the cyclic utilization was based on the fuzzy matter element (FME) according to the cutting performance including productivity, tool life, cutting forces, surface roughness, and wear mechanisms. From the productivity view accompanied with a rational tool life, the recommended cutting speed for coated cemented carbide and welding PCBN tools should be lower than 55 m/min and 92 m/min, respectively. With the cutting speed increasing, the amount of material removal of coated cemented carbide tools corresponding to the wear criterion of VB = 0.3 mm changed from 35 to 16.5 cm3, while that of welding PCBN tools varied from 25.5 to 18.6 cm3. Higher machining speed with the chamfered cutting edge for the welding PCBN tools enhanced the workpiece softening accompanied with better heat resistance, acquiring lower cutting force and better surface roughness. The dominant wear mechanisms of coated cemented carbide tools were notch wear under the lower cutting speed, while the adhesive wear became the leading factor when the speed was above 50 m/min. The welding PCBN tools showed severe wear pattern with adhesion, notching, and chipping. Based on the FME, the assessment of cutting performance demonstrated that the welding PCBN tools were better, which proved that the cyclic utilization was meaningful and improved the utilization efficiency of the worn cemented carbide inserts.

The paper discusses the influence of the thickness of nanolayers in a wear-resistant layer of the Ti-TiN-(Ti,Cr,Al)N multilayered composite coating on the coating and tool cutting properties in turning 1045 steel. The coatings with nanolayer thickness in the range of 10–302 nm were investigated. The studies showed that with a decrease in the nanolayer thickness, the cutting tool life increased. The tests revealed an optimal nanolayer thickness with regard to the tool life under the given cutting conditions, and it was 16 nm. With a further decrease in the nanolayer thickness to 10 nm, the tool life reduced.

Usually, constant process parameters are used for turning. These process parameters result in a thermomechanical load of the tool, which leads to a specific wear pattern. Varying the process parameters along the toolpath, e.g. linear or sinusoidal, can extend tool life by distributing wear over a wider area and reducing the thermal tool load. In this paper, a method for designing process parameter variations during turning is presented. It is shown that tool wear can be reduced using process parameter variation. This reduction in wear is due to a decrease in thermal tool load. In addition, a method for designing processes with modulated process parameters is being developed.

A high-speed milling experiment on wood-plastic composites was performed using cemented carbide tools, and the resulting wear pattern was studied. The influence of the cutting parameters, the cutting speed, feed speed, and axial cutting depth on the tool wear was studied via response surface methodology, and the influence of the interaction of the cutting parameters on tool wear was analyzed. Three-dimensional surface graphs and contour plots of the tool wear results were established. According to the experimental results, a mathematical model of the tool wear based on the second-order response surface methodology was established, and the model was utilized to verify its feasibility. The results show that the nose width (NW) increases with the increase of the cutting speed and axial cutting depth and decreases with the increase of feed speed. Among the factors affecting tool wear, the cutting speed had the greatest influence, followed by the feed rate, with the axial cutting depth affecting tool wear the least. According to the results of the interaction between the tool wear and the cutting parameters, a low feed speed and small axial cutting depth can be selected to ensure long tool life; for low-speed cutting, a high feed speed and large axial cutting depth can be adopted to ensure tool life while improving machining efficiency.

Knee instability is the second most common cause of revision after total knee arthroplasty (TKA). Genu recurvatum (GR) is the rarest form of instability usually occurring in patients with underlying conditions such as neuromuscular disorders and fixed valgus deformities. The literature regarding de novo post-TKA GR and its treatment is scarce. In this case series and review of literature, we aimed to review the treatment strategies of post-TKA GR and to present our experience in the treatment of late-onset de novo GR after TKA by isolated polyethylene exchange. To our knowledge, isolated polyethylene exchange has not been so far described for GR correction after TKA. We found a unique wear pattern at the base of the liner post in all 3 patients. They showed a satisfactory outcome with no recurrence on a mean follow-up of 26.67 months.

Objectives Carabelli is a nonmetric dental trait variably expressed as a small pit to a prominent cusp in the maxillary molars of modern humans. Investigations on the occurrence and expression rates of this trait have been conducted extensively, tracing its origin to genetic sources. However, there remains a lack of understanding about its potential role in chewing. In this study, we examine molar macrowear with the aim of reconstructing Carabelli trait occlusal dynamics occurring during chewing. Methods We have examined 96 deciduous and permanent maxillary molars of children and young adults from Yuendumu, an Australian Aboriginal population that was at an early stage of transition from a nomadic and hunter-gatherer way of life to a more settled existence. We apply a well-established method, called Occlusal Fingerprint Analysis, which is a digital approach for analyzing dental macrowear allowing the reconstruction of jaw movements required to produce wear pattern specific to each tooth. Results Carabelli trait slightly enlarges the surface functional area, especially in those molars where this feature is expressed in its cuspal form and it is closer to the occlusal plane. Moreover, the highly steep contact planes would also indicate that Carabelli wear areas contribute to increasing the shearing abilities of the occluded teeth, which are particularly important when processing fibrous and tough foods. Conclusions The macrowear analysis suggests that Carabelli trait in the Aboriginal people from Yuendumu slightly enhanced occlusion and probably played some functional role during mastication. Future biomechanical and microwear analyses could provide additional information on the mechanical adaptation of Carabelli trait in modern human dentition.

This study presents the results of detailed wear process examination on polyformaldehyde gears under both dry and lubricated conditions. A multi-purpose durability test rig was employed to study the wear performance of polyformaldehyde gear pairs. The wear behaviors of polyformaldehyde gears under dry and oil-lubricated operating conditions were characterized via measurements of gear tooth surface micro-topography and tooth profile deviation. Under the dry running condition, a hump and a gully appear on the tooth surface in the pitch line area of the driving gear and the driven wheel, respectively. The largest amount of wear was observed around the tooth root of the driving gear. However, the gear tooth wear pattern with lubrication is different from that under the dry running condition.

This study investigated the friction and wear pattern of silica-reinforced Styrene-Butadiene Rubber (SBR) in sliding friction with a steel blade indenter. The experiments were conducted using a pin-on-disc tribometer at various applied loads and examined under dry and wet contact conditions. Analysis was focused on investigating the coefficient of friction and length of wear pattern spacing. Related to coefficient of friction identification, the abrasion theory was applied here. In addition, the stick-slip theory to identify the wear pattern spacing was also applied. Results of the experiments show that the overall coefficient of friction (COF) decreases along with the increasing applied loads. The COF in wet conditions is much lower at the beginning of sliding time than the COF in dry conditions. The wear pattern spacing increases with increasing loads. However, it seems that there is no significant difference in pattern spacing between the dry and wet contact condition. In general, the experimental results agree qualitatively with the analytical results.

Purpose The purpose of this paper is to study friction and wear properties of three types of steels against paper-based friction disc, including 65Mn, 20#steel and 30CrAl, so as to obtain the appropriate working conditions for different friction materials in the transmission system. Design/methodology/approach Based on actual working conditions, pin-on-disc tests are conducted on a universal material tester. The two evaluation indexes, including average friction coefficient and variation coefficient, are introduced to analyze the different friction properties among three types of steel. Furthermore, the temperature-dependent wear pattern and wear depth are subsequently studied. Findings The results show that 65Mn is more suitable for working under heavy load and low velocity, but 30CrAl and 20#steel are suitable for working under light load and high velocity. Moreover, wear primarily occurs on paper-based material and peaks at about 325. Practical implications This research of different materials and friction property for friction pairs is helpful to improve the performance and prolong the service life of transmission systems. Originality/value Suitable working conditions of different friction materials are obtained, and the correlation between wear and decomposition in high temperature is verified.

Due to thermal degradation, the tribological performance of fluororubber (FKM) at high temperature is not satisfactory, despite its excellent temperature resistance. In this paper, the friction and wear process of FKM O-rings were traced by the tribo-test, which compares the wear behaviors at different stages of the wear process. Results showed that under the influence of thermal degradation of FKM, the wear rate and friction coefficient decrease, while the friction instability increases. This phenomenon is caused by the deterioration of the mechanical properties affects the development of the typical wear pattern of FKM in unsteady state (running-in stage). The wear debris is more likely to adhere to the surface of the wear scar, which causes the friction form to change from two-body abrasion to three-body abrasion. Findings from this study can enhance understanding of tribology behaviors of FKM O-ring seals under the high temperature condition and can help develop higher-performance alternatives.

The long term performance of total knee arthroplasty (TKA) with regards to the bearing materials is related to the aging behaviour of these materials. The use of highly crosslinked materials in hip arthroplasty improved the clinical outcome. Nevertheless, the outcome for these materials compared to conventional UHMWPE (ultra-high molecular weight polyethylene) remains controversial in TKA and alternative bearing materials may be advantageous to improve its outcome in the second and third decade. The aim of this study is the evaluation of the influence of radiation conditions on the wear behaviour of Vitamin E blended UHMWPE gliding components for TKA by simulation of extended aging and high demanding daily patient activities. For a medium radiation dose (30 kGy), the influence of the irradiation type (E-beam or Gamma radiation) and the thermal conditions (room temperature (RT) or heated to 115 °C) are evaluated in comparison to non-irradiated material. Significant influences on the wear behaviour were found for the radiation source and temperature during irradiation. Furthermore, no relevant degradation of the tested materials was observed after extended artificial aging. There was a good correspondence between the wear pattern in this study and retrievals.

Anteromedial osteoarthritis (AMOA) is a common wear pattern in primary osteoarthritic knees. In patients with bone-on-bone disease, the most appropriate surgical intervention is still a matter of debate. Knee arthroplasty is a well-accepted treatment to relieve symptoms and regain function. Unfortunately, satisfaction is limited, especially related to activities. A cross-sectional study was performed among patients treated with total knee arthroplasty (TKA) and unicondylar arthroplasty (UKA) to determine if the osteoarthritis wear pattern or type of prosthesis affects knee-specific function scores and satisfaction related to activities. All UKA patients (N = 100) were treated for AMOA. Based on radiological assessment of the wear pattern, TKA patients were divided into two groups: TKA for AMOA (N = 68) and true TKA (N = 99). The Knee injury and Osteoarthritis Outcomes Score (KOOS), new Knee Society score (KSS), anterior knee pain scale, visual analog scales (VASs) for satisfaction about activities, and net promoter score were collected. After 2 years' follow-up, the anterior knee pain scale and VAS satisfaction showed significantly better scores for patients treated with TKA for AMOA compared with the true TKA group. Also in the KOOS subscales, some differences were seen in favor of the TKA for AMOA group. The new KSS was not in favor of a specific wear pattern, but patients with AMOA treated with UKA performed better on the symptoms subscale compared with patients treated with TKA. In conclusion, patients treated with TKA for AMOA showed better knee-specific function scores and satisfaction scores compared with patients treated with TKA for other wear patterns, and only slight differences were found between both the AMOA groups (TKA for AMOA and UKA). Thus, the radiologic assessment of wear patterns might be useful to take into account the shared decision-making process, when discussing expectations, timing, and outcomes with knee osteoarthritis patients considering knee arthroplasty. When AMOA is present, it might be beneficial to choose UKA over TKA.

Background A common bearing combination in total hip arthroplasty today is a metal femoral head articulating with polyethylene in the cup. Ceramic heads are thought to be more resistant to third-body damage, and have better wettability and decreased surface roughness, which taken together have been suggested to result in less polyethylene wear. The purpose of this study is to compare the initial creep deformation and follow wear pattern, using radiostereometric analysis, of ceramic and metal femoral heads that articulate with a modern highly cross-linked polyethylene cup liner. Methods Fifty patients with primary osteoarthritis and scheduled for an uncemented total hip arthroplasty were randomized 1:1 to either a ceramic (BIOLOX delta) or a metal (CoCr) femoral head. The patients were followed up for 5 years with repeated radiostereometric analysis examinations (postoperatively, then at 14 days, 3, 12, 24, and 60 months), as well as a hip-specific outcome questionnaire. Results During the first 3 months both groups showed expected creep within the liner of 0.12 mm (standard deviation 0.03) for the ceramic and 0.08 mm (standard deviation 0.02) for the metal heads. Between 3 months and 5 years there was very little wear of the liner in either group, corresponding to 0.003 mm/y for ceramic and 0.007 mm/y for metal heads. There was no difference in cup migration or clinical outcome between the groups and no cups were revised. Conclusion With the introduction of modern highly cross-linked polyethylene, the ceramic head demonstrates no superiority when it comes to either early deformation or polyethylene wear compared with the metal head.

Context: Edentulous patients often complain about the instability of mandibular denture. To overcome that, implant-supported overdentures (IODs) have been applied as a good prosthetic option. Aims: The current study compared the changes in retentive force and patterns of surface wear of nylon rings of two stud attachments (ball and locator) upon cyclic loading. Subjects and Methods: Two implant analogs were fixed parallel to each other, 22 mm apart, in custom-made rectangular blocks for each attachment system. Ten nylon inserts of each attachment system were tested. Universal testing machine was used to measure the retentive force, and a low-value fatigue testing machine was used for cyclic loading of 2500 insertion–removal cycles. Surface changes of the components were evaluated by scanning electron microscope (SEM). Statistical Analysis Used: Paired Student's t-test was used to determine groups that were statistically significant. Results: The greatest retention loss rate, i.e., the difference between the initial retentive force and final retentive force was observed in the ball attachment (6.20 N) followed by locator attachment (3.70 N). The results were found to be statistically significant (d ≤ 0.001**). Upon SEM analysis, the nylon inserts of ball attachment revealed more surface wear compared to that of locator attachment. Conclusions: For greater retention and longer function, locator overdenture attachment should be preferred for implant overdentures over ball attachment.

Scholars have long recognized the importance of organic artifacts to an improved understanding of the economic and social behavior of Palaeolithic hominins. However, in contrast to archaeological studies in other parts of the world, osseous industries from China have received only limited attention. As one of the first steps aiming at tipping this balance, the current paper examines, therefore, a shaped boar tusk—one particular element of hunter-gatherers’ tool kit at Shuidonggou Locality 12 (SDG12). Morphological and metrical comparisons of the tusk with both paleontological specimens and bone artifacts from the same site demonstrate that wear pattern on one of the dentin surfaces of the tooth is not significant different from occlusal attritions in living animals, while linear striations on the other dentin facet are most probably artificial grinding marks formed by prehistoric toolmakers in attempts to manufacture a scraper. The tusk specimen from SDG12 represents the first evidence of a ground tooth in Upper Palaeolithic China. The current study indicates that hominins in Shuidonggou area had achieved a deepened understanding of physical properties of osseous material available in environs and ultimately broadened their range of raw material selection by adding a particular element to the inventory of subsistence tools.

Elastomeric materials are used in daily applications, such as tires and conveyor belts. Sliding friction of elastomeric materials often produces a unique periodic wear pattern. In general, the periodic wear pattern has to be prevented because it generates surface instabilities and, as a result, vibration. Sliding contact between an elastomer and a rigid ball may cause the development of a periodic wear pattern like a wave on the elastomer surface, called a wavy wear track. The present study has investigated the occurrence of the wavy wear track on the elastomers under several operating conditions. The elastomers used were a Styrene-Butadiene Rubber (SBR) and Butadiene Rubber (BR) reinforced with two types of fillers, i.e., highly dispersible silica and short-cut aramid fiber. A pin-on-disc tribometer was used to study the wavy wear track of the materials under several operating conditions. An analytical model was used to predict the wave length of the wear pattern and to study the occurrence of the wavy wear track. The results show that the occurrence of the wavy wear track depends on the mechanical properties of the elastomer, the operating conditions (such as sliding velocity and force), the inertia mass of the counter surface frame and the circumferential length of the wear track. The analytical model is in good agreement with the experimental results.

Purpose This paper aims to study the upgradation of the lubricating performance of the renewable base oil , and to study the tribological behavior of graphene oxide (GO) sheets used as lubricating additives in bio-oil for iron/steel contact. Design/methodology/approach A multifunctional end-face tribometer was used to characterize the friction coefficient and wear loss of the tribosystem under different lubricants. Findings The experimental results show that GO sheets with small size benefit lubricating effects and the optimal concentration of GO sheets in bio-oil is 0.4-0.6 per cent, which can form a complete lubricating film on the frictional interfaces and obtain a low friction coefficient and wear loss. Higher concentration of GO sheets can result in a significant aggregation of the sheets, reducing the content of the lubricating components in the bio-oil, which results in the increase in friction and wear; at this stage, the main wear pattern was ascribed to adhesive wear. Practical implications These results show a promising prospect of improving the tribological performance of renewable base oil with the introduction of GO sheets as additives. Originality/value No literature has covered the tribological behaviour of GO sheets in bio-oil. This study contributes to accelerating the application of bio-oil.

The wear pattern of working rolls that accompanies the hot graded rolling of electric copper in a combined process of casting and deformation has been studied. The depth of the worn layer over the contour of grooves in the first four rolling passages were measured. The increased wear of the grooves that roll the metal at the highest temperature has been revealed. The areas of wear localization over the contour of grooves have been stated. A conclusion has been drawn on the significant differences in the wear pattern during the rolling of steel and copper. It has been revealed that wear during electric copper rolling happens due to the flame erosion of the surface layers of rolls made from heat-resistant steel, as well as due to the intensive adhesion of copper to them; furthermore, there is hardly any mechanical or abrasive wear. Recommendations on the need to develop a special material for manufacturing rolls just for copper rolling have been made.

Polygonal wear seriously decreases the lifespan of a tire of a passenger car and adversely affects vehicle dynamic safety. The present paper builds a model that reflects the dynamic contact characteristics of the tire and reveals the mechanism and conditions of polygonal wear of a tire. The model describes the dynamic contact behavior of the tread block and considers the characteristics of dynamic friction between the road and tread of a rolling tire. Conducting numerical bifurcation analysis, the paper reveals the conditions for self-excited vibration of the tread, i.e., the improper combination of the vertical load, wheel slip angle, tire pressure and vehicle speed considerably strengthen the lateral self-excited vibration of the tread, which is the direct vibrational source of abnormal circumferential polygonal wear. The polygonal wear of a tire occurs when a vehicle travels for a certain long distance at a so-called polygonal wear speed. The polygonal wear speed should induce lateral self-excited vibration on the contact tread of the tire and the frequency of the lateral self-excited vibration should be divisible by the rolling frequency of tire that is determined by the polygonal wear speed. Visible polygonal wear requires that the vehicle travels at a certain polygonal wear speed for a minimal distance to produce a stably developing polygonal wear pattern even for subsequent driving at variable speed.