High Level Of Friction Research Articles

Transient skin friction behavior associated with hemisphere-based vortex ring collisions

Global and local transient skin friction variations resulting from a large-eddy simulation study on ReΓ0=3000 vortex rings colliding with surface-mounted hemispheres of hemisphere-to-vortex-ring diameter-ratios of 0.5≤D/d≤2 are investigated here. Skin friction distribution changes due to the approaching primary vortex ring, formation of secondary/tertiary vortex rings, subsequent mutual interactions between various vortex ring structures, and azimuthal instabilities are clarified with a view to better establish their relationships when the relative hemisphere size varies. Results show that the primary vortex ring produces the highest skin friction levels when it is close to or collides with the hemisphere/flat wall. Additionally, entrainment of wavy secondary/tertiary vortex rings leads to them entangling around the primary vortex ring and resulting in segmented skin friction regions at later stages of the collision process, regardless of the diameter-ratio. Unlike smaller hemispheres, the largest D/d=2 hemisphere here restricts all skin friction changes along its surface with the flat wall unaffected. It is also revealed here that while the diameter-ratio governs the global skin friction distributions, how secondary/tertiary vortex rings interact with the primary vortex ring and how azimuthal instabilities manifest and evolve for all the various vortex rings confer strong influences on the breaking-up and dissipation of regions with high skin friction levels.

The influence of corrosive medium on the selected tribological properties of ZrSi-based nitride and oxynitride deposited on 316L stainless steel

Targeting to restore the function of load-bearing joints which are subjected to high levels of friction and wear during the normal activity, the aim of the current study was to assess the extent of the role played by the corrosive environment on the underlaying tribological mechanism. In this study we deposited by reactive cathodic arc evaporation technique ∼ 1 μm thick, stoichiometric ZrSi-based nitrides and oxynitrides coatings, either as monolayer or double-layer structure on 316L steel substrates. Tribological tests were conducted in dry and two commonly used corrosive environments: Ringer and 0.9 % NaCl solutions. We demonstrate that the ZrSiN and ZrSi(N,O) coatings improved the wear performance of 316L stainless steel in biological environments, reaching even ∼ 94 % improvement as compared with the bare substrate for the ZrSi(N,O) coating.

Use of Sustainable Transport System Approach in Tourism Zone Development at Kupang City

The augmentation of high scale social-economic activities usually triggers a great number of small-scale derived activities. However, the presence of such activities has been ignored in traffic impact analysis. The crowded traffic produced surround it then became a laten issue. This study aim is to determine the effect of roadside friction to road capacity and to provide adequate parking zone. Subsequently, this research also discusses the possible implemented solution based on land use availability and/or road environmental condition. Therefore, the traffic volume and geometrical survey have been carried out, and the road segment capacity was calculated using Indonesian Highway Capacity Manual, whereas the effect of varying roadside friction level to road capacity were simulated under 3 conditions, i.e.: 1) without on street parking, 2) with one side on street parking, and 3) with two side of on street parking. It was found that: 1) high level of roadside friction due to the existing on-street parking vehicle and pedestrian as well as entry-exit vehicles produced strongly influenced road capacity, degree of saturation 2) since only one side on street parking is allowed, then the authority should provide additional parking zone by convert potential land into off-street parking zone.

The effect of candle-soot reinforced electroless Ni-P particle interface on tribological performance in copper-based materials produced by flake powder metallurgy method: Transfer of candle-soot from waste to solid-lubricant

The softness and ductility of copper can lead to high levels of wear and friction when it encounters other surfaces, which can be detrimental in certain applications. Therefore, improving the tribological properties of copper, such as by coatings or surface treatments, can help to mitigate these issues and make copper even more versatile and useful in a wider range of applications. Accordingly, in this study, functional particles were produced by electroless coating process by providing an electroless Ni-P/candle-soot (CS) nanoparticle (1%vol.) coating layer around each of the flake copper powders followed by production of final materials by flake powder metallurgy including hot-pressing. The wear surfaces were thoroughly analysed using SEM and EDS techniques which allows for the examination of morphological and microstructural characteristics. Due to the homogeneous distribution of Ni-P/CS additives on the interface, the tensile and wear resistances have shown approximately 250% and 1300% increase, respectively, compared to the additive-free Cu materials. While the Ni-P interface in Cu materials caused a decrease in electrical conductivity, the addition of CS resulted in approximately 14% improvement in electrical conductivity. It was showed that electroless Ni-P coatings provide a hard, wear-resistant surface with lubricative CS that protects against wear, making them ideal for use in applications such as aerospace, automotive, and electronic industries.

Parent-child language differences and ethnolinguistic minority children’s evaluations of family life

ABSTRACT Within ethnolinguistic minority families, parents and children often differ in language usage and proficiencies. In this study, we investigate the role of intergenerational language differences in cultivating and/or complicating family relations and how aspects of gender may moderate these relationships. Guided by the Family Language Policy framework, we expand the concept of intergenerational language differences beyond language use and proficiencies to incorporate language attitudes and language management indicators. Binomial logistic regression models were used to estimate the likelihood of children (N = 823; aged 10–12) reporting high levels of family friction and cohesion. Our results show that parent-child differences in language use and proficiencies are associated with family friction but not with cohesion, whereas differences in language attitudes impact family cohesion. Brokering has a significant negative impact on perceptions of family relations while language rules are not related to conflict or cohesion. Our interaction analyses suggest that the influence of parent-child language differences on family relations is more pronounced for the father-daughter dyad.

Plastic deformation of polymer matrix composites reinforced with beaded fibers

Beaded fiber composites represent promising design strategies capable of simultaneously improving strength and toughness of materials. Recent experiments have shown that plastic deformation of polymer matrix is the major energy dissipation mechanism contributing to damage tolerance of the composites reinforced with beaded fibers. Motivated by the experiments, the analyses are carried out for plastic deformation of beaded fiber composites in the course of fiber pullout. The post-yield strain softening and strain hardening of polymer matrix are accounted for, and the effect of friction between the bead and polymer matrix is incorporated in the finite element simulations. It is found that plastic deformation in beaded fiber composites is strongly dependent on the plasticity characteristics of the polymer matrix. The bead displays highly localized plastic deformation with the plastic zone located in the vicinity of fiber-bead interface. For the polymer matrix exhibiting strain softening without hardening, plastic strain in the bead is larger than that in the matrix, thereby increasing the propensity of fracture at the fiber-bead interface. The strain softening followed by hardening behavior of polymer matrix enables emergence of multiple shear bands, while strain hardening plays a role in spreading plastic deformation, giving rise to large plastic zone in the polymer matrix. We have further revealed that the high level of friction between the bead and matrix can promote coalescence of shear bands in the polymer matrix. The findings of this study shed new light on the design principles of beaded fiber composites.

Textural Evolution of 6061 Aluminum Alloy Processed by Accumulative Roll-Bonding Process

A commercial Al-Mg-Si alloy (AA 6061) was deformed by using the accumulative roll bonding (ARB) process for up to five cycles at ambient temperature. The evolution of texture in this process was studied by the X-ray diffraction (XRD) method. Experimental results indicate that the combination of the shear texture composed of Rotated cube {001} component and the rolling textures that included Copper {112} and Dillamore {4, 4, 11} components developed after the first cycle. During the first cycle, the shear texture was developed as a result of shear deformation induced by high level of friction between the rolls and the sheet. By increasing the number of cycles, the shear texture strength diminished and changed to the rolling texture. After the fifth cycle, a remarkable increase in the rolling texture intensity was observed due to homogenous deformation induced by the presence of fine non-shearable particles. Additionally, the presence of magnesium in solid solution influenced the texture evolution during ARB.

The Clarity and Legibility of Students’ Translation of Arabic – Indonesian Official Text

Assessment of the quality of translation is one of the important activities in translation. The translation assessment can be seen from three aspects: accuracy, clarity, and naturalness. This study aims to reveal the accuracy and fatigue of the translation results of students' Arabic-Indonesian official manuscripts, considering that researchers rarely touch the spiciness aspect than the translation's accuracy and reasonableness. This research uses the descriptive analysis method and content analysis model. The research sample is six graduate students in Arabic Language Education at the Indonesia University of Education. The data collection techniques used were observation, interviews, documentation, and questionnaires. From the results of this study, the researchers obtained several findings, namely: first, the level of mastery was very high, spread as many as eight data (44.4%), the moderate level of intelligence was spread as many as six data (33.3%), and the level of intelligence lacked as many as four data. (22.2%). Second, the level of fatigue in the translation of the official text for high levels of friction is as many as ten data (55.5%), there are five data (27.7%) for moderate fatigue, and three data (16.6%) is less tired. So, from the results of this study, it is concluded that fatigue dominates as much as ten data (55.5%) compared to the very high level of mastery where there are only eight data (44.4%).

The influence of the pavement surface texture on the Pendulum Test Value

The article deals with the problem of finding a relation between surface texture and skid resistance represented by the Pendulum Test Value. For the texture measurements was used a new device that can capture surface irregularities up to the microtexture level. Besides Pendulum Test Values were also evaluated standard roughness parameters as well as the Mean Profile Depth widely used for pavement surface macrotexture evaluation. The texture parameters were evaluated for both macro- and micro-texture of all tested surfaces. Two groups of surfaces were measured. The first group, represented by reference surfaces with known parameters, was used for evaluation of the reliability of new device as well as for determining the relation between microtexture and pendulum test value. The second group was represented by asphalt mixture specimens designed to create various surfaces with different parameters of both macrotexture and microtexture. The obtained results show that there is no unambiguous direct relation between the size of irregularities and skid resistance. That means that high values of both macro and microtexture won’t have to necessarily mean a high level of friction. The proper size and proportion of both parts in their optimal combination are needed.

The onset of friction for rubber across an ice bead

PurposeThe exploration of the polar regions is of immeasurable potential. It brings great challenges to tribology in the extreme environment. Moreover, the static friction force is an essential index of the braking performance. The purpose of this paper is the static friction force between the rubber of marine pipe tensioner and the ice bead.Design/methodology/approachThe frictional phenomena were studied for rubber-ice bead at different contact positions (front edge, front part and end part) by means of image processing and measuring. Also, the image sequences of the contact were combined with friction force and displacement data.FindingsAs rubber across the ice bead, the forces of rubber and ice bead at different contact positions determined the order of static friction force (front edge > front part > end part). Meanwhile, there were two different contact states in this process. In addition, under the low tangential load growth rate, the higher temperature can increase the static friction force by increasing the viscoelasticity and contact area of rubber.Originality/valueThe research on the static friction of rubber-ice bead leads to more controlled and higher friction levels during marine pipeline laying.Peer reviewThe peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-12-2019-0526/

Dynamics of Neutral and Charged Nanodiamonds in Aqueous Media Confined between Gold Surfaces under Normal and Shear Loading.

The dynamics of cubo-octahedral nanodiamonds (NDs) with three different surface treatments and confined in aqueous environments between gold surfaces under shear and normal loading conditions have been characterized via molecular dynamics (MD) simulations. The treatments consisted of carboxyl (−COO–) or amino (−NH3+) groups attached to the NDs, producing either negatively or positively charged NDs, respectively, and hydrogen-terminated surfaces producing neutral NDs. Simulations were performed in the presence and absence of induced image charges to explore the impact of electrostatic interactions on friction and surface deformation. Significant deformation of the gold surfaces was observed for negatively charged NDs placed between gold surfaces under external loads that were sufficient to displace water from the contact. Rolling and relatively high friction levels were also observed for the negatively charged NDs under the same conditions. In contrast, the neutral and positively charged NDs exhibited sliding behavior with only minor deformation of the gold surfaces. The results suggest that the size of the surface functional group plays a major role in determining whether NDs slide or roll on solid contacts. Higher friction levels were also observed in conjunction with induced image charges in the gold contacts. The results demonstrate how surface functionalization and surface-induced charges can work in combination to profoundly influence tribological performance.

Predicting earthquake-induced sliding displacements using effective incremental ground velocity

This article evaluates a pulse intensity measure, the effective incremental ground velocity ( EIGV), for predicting sliding displacements induced by real ground motions. EIGV is based on computing the additional incremental velocity of a pulse after a system begins to slide. Predictions of peak sliding displacements are made using multiple ground motion and pulse intensity measures, and it is found that at high friction levels, defined here as friction coefficient above 0.15, EIGV is a very effective parameter with a lognormal standard deviation of predicted displacements around 0.5, despite including only the properties of the largest pulse in a record. For high-friction systems, very few pulses usually cause the peak sliding displacement during the response history, hence the potential for an effective pulse intensity measure. EIGV improves sliding displacement predictions compared to existing intensity measures, which are geared toward conventional hysteretic systems. Prediction equations are developed for peak relative sliding displacement as a function of EIGV, the sliding interface coefficient of friction, and the radius of curvature for concave sliding surfaces.

High-velocity impact onto a high-frictional fabric treated with adhesive spray coating and shear thickening fluid impregnation

The ballistic performance of a bullet-proof fabric can be increased by an increment in the friction between fibres. For enhancement of this performance, numerous studies on the shear thickening fluid (STF)-impregnated fabric have been conducted. The STF as a fluid, however, has inherent shortcomings. Our research aim is to understand and compare experimentally two different bullet-proof fabrics treated with a simple spray coating and STF impregnation. In this study, 71 single yarn pull-out and 90 high-velocity impact experiments were carried out. It was remarkable that the newly proposed Heracron fabric coated with a commercial coating spray increased by more than 90% the energy absorption before penetration, with only less than 15% of add-on weight. It was found that the polymeric anchors created on the fibre produce an exceptionally high level of friction between fibres, according to a microscopic morphological analysis and the single-yarn pull-out experiment. This study revealed the physical explanation of this coating method, showed its feasibility, and considered its effectiveness with excellent results.

Comparison of frictional coefficient and surface roughness between three different active self-ligating brackets: An experimental in vitro study

Aim: In orthodontic treatment, the high levels of friction may reduce the effectiveness of the mechanical and decrease tooth movement efficiency. The use of active self-ligating brackets is claimed to possibly reduce friction in orthodontic treatment. The aim of this study was to investigate the three-different active self-ligating orthodontic brackets in frictional coefficient and surface roughness. Materials and Methods: This study was true-experiment laboratory with posttest group design to collect the frictional coefficients data from three different active self-ligating brackets. Friction tests were performed on three different active self-ligating brackets—In-Ovation R, Empower, and BioQuick. Each group consists of seven samples of active self-ligating brackets—and stainless steel wire which has been stored in artificial saliva solutions for 14 days. After the friction coefficients of every sample obtained, the bracket clips were separated from the bodies and set on resin acrylic medias. Surface roughness of the bracket clips was evaluated using the atomic force microscope (AFM). A one-way analysis of variance (ANOVA) followed by Scheffe test for comparisons was performed statistically (P < 0.05). Results: BioQuick and Empower orthodontic brackets produced lower frictional coefficients compared to In-Oviation-R brackets. BioQuick showed least frictional coefficients. Based on the statistical analysis, there was no significant difference of frictional coefficients between Empower and BioQuick. Surface roughness test showed that the clip surface of In-Ovation R produced the maximum roughness, followed by Empower and BioQuick. Conclusion: In-Ovation R brackets offered more frictional coefficients and surface roughness than Empower and BioQuick brackets, whereas BioQuick brackets offered the least among all the brackets studied.

Modelling of Nanoindentation of TiAlN and TiN Thin Film Coatings for Automotive Bearing

Bearings are critical components for the transmission of motion in machines. Automotive components, especially bearings, will wear out over a certain period of time because they are constantly subjected to high levels of stress and friction. Studies have proven that coatings can extend the lifespan of bearings. Hence, it is necessary to conduct studies on coatings for bearings, particularly the mechanical and wear properties of the coating material. This detailed study focused on the mechanical properties of single-coatings of TiN and TiAIN using the finite element method (FEM). The mechanical properties that can be obtained from nano-indentation experiments are confined to just the Young’s modulus and hardness. Therefore, nanoindentation simulations were conducted together with the finite element method to obtain more comprehensive mechanical properties such as the yield strength and Poisson’s ratio. In addition, various coating materials could be examined by means of these nanoindentation simulations, as well the effects of those parameters that could not be controlled experimentally, such as the geometry of the indenter and the bonding between the coating and the substrate. The simulations were carried out using the ANSYS Mechanical APDL software. The mechanical properties such as the Young’s modulus, yield strength, Poisson’s ratio and tangent modulus were 370 GPa, 19 GPa, 0.21 and 10 GPa, respectively for the TiAlN coating and 460 GPa, 14 GPa, 0.25 and 8 GPa, respectively for the TiN coating. The difference between the mechanical properties obtained from the simulations and experiments was less than 5 %.

A Novel Method of Assessing Floor Friction in Cowsheds and Its Association with Cow Health.

Simple SummaryThe objective of this paper was to test a simple method of measuring the extent of the slipperiness of different types of floors in cow shelters. Excessively slippery floors, which are less abrasive, are known to reduce a cow’s ability to walk, lie down, and get up without slipping and causing injury to herself. A moderate level of friction between the cows’ hooves and the floor is required for cow comfort and prevention of foot disease and injuries. This study developed a rapid method that welfare assessors can use to measure the slipperiness of floors in cowsheds. The data obtained were then validated by comparing them with the various animal-based and resource-based welfare parameters assessed in each shelter. The analyses done in this study show that there is a link between excessively slippery floors and various parameters such as frequency of cleaning the floors, the gradient of floors, wounds on the bodies and joints of the cows, and the presence of dirty hind limbs. All of these ultimately affect the welfare of cows in shelters. These results suggest that this simple measure of floor friction could be useful in cow welfare assessments. Further work on the repeatability of this method is recommended.Measurement of friction of cowshed floors to determine slipperiness potential is important for cow comfort. Existing methods require elaborate equipment and procedures. A quick method for assessment of friction characteristics is proposed. Friction was measured in 54 cattle housing and yard facilities with earth, brick, concrete, and stone floors, and its association with cattle health parameters was investigated through assessment of 30 animals per facility. A 156 g cuboidal wooden block attached to a spring balance was pulled over 3 m, and the coefficient of friction was recorded as the force required to move the block at a constant speed. The coefficient of friction ranged from 0.3 to 0.7 and was lowest for concrete and highest for earth floors. A multivariate analysis found that cows were standing more and could be more easily approached when they were on floors with high friction levels. The proportion of cows with dirty hind limbs declined with increasing friction of the floor, probably reflecting the fact that they felt more confident to stand rather than lie on high friction floors. This simple measure of frictional characteristics of cattle floors offers promise to be included in welfare measures as an indicator of cow welfare.

Research on the vibration damping performance of hydro-pneumatic suspension of mine dump truck

The working environment of mine dump truck is relatively harsh, thus the suspension system with poor performance will directly affect driver's driving comfort and physical and mental health. An oil cylinder is one of the key components of the hydro-pneumatic suspension system, however, the high friction levels between cylinder and piston would lead to ‘friction locking’ phenomenon in the practical application. In order to improve the vibration damping performance of hydro-pneumatic suspension system and enhance the comfortability of whole vehicle, a 110 t mine dump truck was studied by theoretical and experimental method. The results of this study show that increasing the length of cylinder guide can effectively decrease the cylinder vibration transmission rate and improve the driving comfortability of vehicle.

Thermal and tribological characterizations of millscale-particles-reinforced ceramic matrix composites

ABSTRACTThis paper evaluates some basic functional properties of iron-millscale-reinforced ceramic matrix composites (CMCs) as potential material for automobiles and aircraft brake pads’ application. The particulate CMCs were produced by the powder metallurgy method. Iron millscale particles’ addition varied from 3 to 18 wt.% in a matrix comprising a mixture of silica, magnesia and bentonite. After sintering, the composites were subjected to coefficient of friction (COF), wear, thermal and microstructural characterizations. Microstructure of the composites showed a uniform distribution of millscale particles in the ceramic matrix with a strong interfacial bonding between the particles. The composites demonstrated a comparatively high resistance to wear, appreciable COF (0.506–0.561) and a modest thermal conductivity (0.39–0.53 W/m K) coupled with high thermal stability. Contributions to these superlative performances were provided by the high level of friction induced on composites’ surfaces and strong interfacial bonding developed during sintering.

Escaping the Ashby limit for mechanical damping/stiffness trade-off using a constrained high internal friction interfacial layer

The development of new materials with reduced noise and vibration levels is an active area of research due to concerns in various aspects of environmental noise pollution and its effects on health. Excessive vibrations also reduce the service live of the structures and limit the fields of their utilization. In oscillations, the viscoelastic moduli of a material are complex and it is their loss part – the product of the stiffness part and loss tangent – that is commonly viewed as a figure of merit in noise and vibration damping applications. The stiffness modulus and loss tangent are usually mutually exclusive properties so it is a technological challenge to develop materials that simultaneously combine high stiffness and high loss. Here we achieve this rare balance of properties by filling a solid polymer matrix with rigid inorganic spheres coated by a sub-micron layer of a viscoelastic material with a high level of internal friction. We demonstrate that this combination can be experimentally realised and that the analytically predicted behaviour is closely reproduced, thereby escaping the often termed ‘Ashby’ limit for mechanical stiffness/damping trade-off and offering a new route for manufacturing advanced composite structures with markedly reduced noise and vibration levels.

Experimental and numerical analysis of high and low velocity impacts against neat and shear thickening fluid (STF) impregnated weave fabrics

This investigation aims to study the efficiency of STF impregnated plain-weave fabric made of Kevlar under high and low velocity impact conditions. The shear thickening fluid (STF) was prepared by ultrasound irradiation of silica nanoparticles (diameter ≈30 nm) dispersed in liquid polyethylene glycol polymer. STF impregnation effect was determined from single yarn pull-out test and penetration at low velocity using drop weight machine equipped with hemi-spherical penetrator and dynamic force sensor. Force-displacement curves of neat and impregnated Kevlar were analysed and compared. Also, the STF impregnation effect on Kevlar multilayers was analysed from high velocity impact tests using 9mm FMJ bullet at 390 m/s. After impact, Back face deformation (BFD) of neat and impregnated Kevlar layers were measured and compared. Results showed that STF impregnated fabrics have better energy absorption and penetration resistance as compared to neat fabrics without affecting the fabric flexibility. When relative yarn translations are restricted (e.g. at very high levels of friction), windowing and yarn pull-out cannot occur, and the fibres engaged with the projectile fail in tension that leads to fabric penetration. Microscopy of these fabrics after testing have shown pitting and damage to the Kevlar filaments caused by the hard silica particles used in the STF. Mesoscopic 3D Finite Element models were developed using explicit LS-DYNA hydrocode to account for STF impregnation by employing the experimental results of yarn pull-out tests, low and high velocity impacts. It was found that friction between fibers and yarns increase the dissipation of energy upon impact by restricting fiber mobility, increasing the energy required for relative yarn translations and transferring the impact energy to a larger number of fibers.