Friction Lining Research Articles

Failure analysis and finite element simulation of key components of PDM

As one of the most commonly used downhole drilling tools, PDM (Positive Displacement Motor) is widely used in drilling and workover. Drilling practice shows that PDM is frequently scraped for the failure of key components. The coupled thermo-mechanical finite element model of rubber linings, finite element models of thrust bearing and universal shaft petals were established respectively, and the failure reasons were discussed by simulation. It was found that there are oval holes caused by thermal failure in general rubber lining, while no oval holes in the uniform wall thickness rubber lining. Rubber layer peeling and broken appear on the surfaces of rubber linings under the load of drilling fluid and rotor. Thrust bearings experienced serious wear, corrosion and rupture in the terrible downhole environment. The universal shaft petals appear fracture in the root, and wear on contact surfaces under torque and axial load. The results obtained in the paper show that the analyzing model and evaluation methods are quite reasonable and can be generally applied, which have great significance on the enhancement of structural design and repair for PDM in the future industry.

천이효과를 고려한 BWB UCAV 형상의 공력 특성 전산해석

A computational simulation for a nonslender BWB UCAV configuration with rounded leading edge and span of 1.0m was performed to analyze its aerodynamic characteristics. The freestream is 50m/s over –4 to 26 degree A.o.A.s. Reynolds number based on the mean chord length is × . 3D multi block hexahedral grids are used which allow good grid quality and ease to capture boundary layer.  model as well as  SST model is employed to assess the effect of transition for flow behavior. Drag and lift of the UCAV were well predicted while  is under predicted at high angle of attacks and influenced by the turbulence models strongly. After assessing pressure distribution, skin friction lines and velocity field around the UCAV configuration, it was found that transition effect should be considered to enhance the prediction of aerodynamic behavior by a vortical flowfield.

Thermodynamic limit of surface layers of polymer linings in friction interaction

As the analyses of scientific studies showed, thermodynamic processes occur in the surface layers of metal-polymer friction pairs of drawworks band-shoe brake in their friction interaction. During electrothermomechanical friction of friction linings and brake pulley, the latter stores energy, its surfaces undergo forced cooling, and linings, which are placed on the band, are exposed to the physicochemical transformation. Therefore, there is a need to study the behavior of surface and subsurface layers of polymer linings in different thermodynamic states since lining is an element of friction pairs and affects the drawworks band-shoe brake friction unit efficiency. Statistical mechanics, applied to the surface layer of polymer lining and patterns of changing the studied parameters in evaluating the thermodynamic limit are first considered in the paper. Adding more and more particles (ions and electrons) causes, respectively, changes in the volume and, thus, the average environment of any particle gradually becomes virtually unchanged. The results of experimental studies of the first-order phase transition, conducted in stand conditions have shown that, at the temperature increase on the friction surfaces of friction pairs from the set, there are current fluctuations, which will continue to exist at the temperature increase, which adversely affects the friction units performance. The research results are important since they answer the questions: what processes occur in friction pairs, what leads to their rapid deterioration, and consequently failure of the drawworks band-shoe brake friction unit.

Numerical investigation on transient thermal behavior of multidisk friction pairs in hydro-viscous drive

In order to research the thermal behavior of multidisk friction pairs in hydro-viscous drive, three-dimensional transient temperature model is established for numerical simulation. As the force differences between any two adjacent friction pairs are significant, the normal pressures on all the surfaces are obtained from the principle of force equilibrium and then the heat flux acting on the related surfaces are also deduced. The process of the disks's heat conduction is analyzed in detail. The research results show that twelve frictional subregions divided by the grooves present similar temperature distributions and hot spots. The maximum temperature along the axial direction of the multidisk friction pairs occurs in the second friction pairs near the hydraulic piston. The temperature expansion at the non-grooved regions is larger than that at the grooved regions and the radial temperature gradient in the separator disks is larger than that in the friction disks. There may not be clear deformation both at the grooved regions and near the grooved regions. However, the non-grooved regions are prone to be deformed and the friction linings are more likely to be deformed.

Sliding friction and wear properties of friction linings with friction-promoting grease applied

The rheological properties of a commercial friction-promoting grease (FPG) were investigated using a cone and plane rheometer. Two friction tests were conducted at a low sliding rate (1 mm/s) using a wire rope (designed for mining use) and a commercial friction lining material. One involved dry-friction and the other greased conditions. The corresponding coefficient of friction (COF) in each case was determined and used to evaluate the effect of application of the FPG on the lifting performance of a hoist under normal conditions. In addition, experiments involving high-speed sliding friction between the wire rope and the friction material were also performed (with and without the FPG). Different sliding speeds and applied loads were used. The aim was to obtain the tribological behavior of the friction material in conditions that simulate a severe working environment for the hoist. The experimental results were analyzed and combined with the rheological properties of the FPG. The FPG can substantially protect the friction lining from wear and simultaneously provide an adequate COF (about 0.356) between the friction pair under normal working conditions. When the working conditions are severe, an increase in sliding speed causes a decrease in the COF. However, a larger load does not necessarily result in a smaller COF. Increasing the sliding speed or the load both aggravate the wear of the friction lining.

Investigating the Three-dimensional Flow Separation Induced by a Model Vocal Fold Polyp

The fluid-structure energy exchange process for normal speech has been studied extensively, but it is not well understood for pathological conditions. Polyps and nodules, which are geometric abnormalities that form on the medial surface of the vocal folds, can disrupt vocal fold dynamics and thus can have devastating consequences on a patient's ability to communicate. Our laboratory has reported particle image velocimetry (PIV) measurements, within an investigation of a model polyp located on the medial surface of an in vitro driven vocal fold model, which show that such a geometric abnormality considerably disrupts the glottal jet behavior. This flow field adjustment is a likely reason for the severe degradation of the vocal quality in patients with polyps. A more complete understanding of the formation and propagation of vortical structures from a geometric protuberance, such as a vocal fold polyp, and the resulting influence on the aerodynamic loadings that drive the vocal fold dynamics, is necessary for advancing the treatment of this pathological condition. The present investigation concerns the three-dimensional flow separation induced by a wall-mounted prolate hemispheroid with a 2:1 aspect ratio in cross flow, i.e. a model vocal fold polyp, using an oil-film visualization technique. Unsteady, three-dimensional flow separation and its impact of the wall pressure loading are examined using skin friction line visualization and wall pressure measurements.

Investigating the Three-dimensional Flow Separation Induced by a Model Vocal Fold Polyp

The fluid-structure energy exchange process for normal speech has been studied extensively, but it is not well understood for pathological conditions. Polyps and nodules, which are geometric abnormalities that form on the medial surface of the vocal folds, can disrupt vocal fold dynamics and thus can have devastating consequences on a patient's ability to communicate. Our laboratory has reported particle image velocimetry (PIV) measurements, within an investigation of a model polyp located on the medial surface of an in vitro driven vocal fold model, which show that such a geometric abnormality considerably disrupts the glottal jet behavior. This flow field adjustment is a likely reason for the severe degradation of the vocal quality in patients with polyps. A more complete understanding of the formation and propagation of vortical structures from a geometric protuberance, such as a vocal fold polyp, and the resulting influence on the aerodynamic loadings that drive the vocal fold dynamics, is necessary for advancing the treatment of this pathological condition. The present investigation concerns the three-dimensional flow separation induced by a wall-mounted prolate hemispheroid with a 2:1 aspect ratio in cross flow, i.e. a model vocal fold polyp, using an oil-film visualization technique. Unsteady, three-dimensional flow separation and its impact of the wall pressure loading are examined using skin friction line visualization and wall pressure measurements.

Development of a Composite Material from Agro Waste for Wear Resistance Application

The Friction lining is an essential part of braking system. Friction materials have their significant role for transmission in various machines. Their composition keeps on changing to keep pace with technological development and environmental requirements. Earlier asbestos has been used as a friction material because of its good physical and chemical properties. But later researchers eyed that there are many health hazards associated with asbestos handling. The average disk temperature and average stopping time for pass is increased and it has poor dimensional stability. Hence it has lost favor and several alternative materials are being replaced these days. In this work a non-asbestos bio-friction material is enlighten which is developed using an Agro-waste material palm kernel shell (PKS) along with other Ingredients. Among the agro-waste shells investigated the PKS exhibited more favorable properties. The developed friction material is used to produce automobile disk brake pads. The developed brake pads were tested for functional performance on a specially designed experimental test rig. Physical properties of this new material along with wear properties have been determined and reported in this paper. When compared with premium asbestos based commercial brake pad PKS pads were found to have performed satisfactorily in terms of amount of wear and stopping time.

The bequest ofIlegalja: contested memories and moralities in contemporary Kosovo

In this essay I explore the ways in which the internal Albanian politics of memory in Kosovo rely on a longer, lived history of militant self-organisation than the Kosovo Liberation Army (KLA) war period alone. On the basis of recent ethnographic research, I argue that the memory of prewar militant activism is symbolically codified, ritually formalized, and put on the public stage in Kosovo today. Not only has this process effectively rehabilitated and consolidated the personal, social, and political status of specific former activists, it also has produced a hegemonic morality against which the actions of those in power are judged internally. On the one hand, this process reproduces shared cultural references which idealise ethnonational solidarity, unity and pride and which have served militant mobilisation already before the 1990s. On the other, it provides the arguments through which rival representatives of the former militant underground groups (known asIlegalja)compete both socially and politically still today. Although this process demarcates some lines of social and political friction within society, it also suggests that international efforts to introduce an identity which breaks with Kosovo's past and some of its associated values, face a local system of signification that is historically even deeper entrenched than is usually assumed.

Peacebuilding and lines of friction between imagined communities in Bosnia-Herzegovina and South Africa

With specific reference to Bosnia-Herzegovina and South Africa, this article looks at how peacebuilding actors constantly recreate public space and the discourses within it. The formation of imagined political communities reflects the extent to which peacebuilding interactions can be rather horizontal or vertical in nature, producing different types of friction in the encounter between peacebuilding actors. In Bosnia, the predominantly horizontal nature of international peacebuilding processes has resulted in the emergence of fragmented local sub-spaces. Those are often in conflict with international and national political communities, with frictions emerging between local, national and international actor networks. The article will contrast those processes with the mosaic developing in South Africa, where boundaries between actors are more blurred. Due to strong vertical cooperation, sporadic frictions tend to emerge within those spaces rather than exclusively at their boundaries. The article will analyse the extent to which different patterns of peacebuilding interaction impact upon the constructive and destructive frictions that those produce.

MODELING AND ANALYSIS OF THERMAL PROCESSES IN MECHANICAL FRICTION CLUTCH — NUMERICAL AND EXPERIMENTAL INVESTIGATIONS

Thermal processes occurring in the mechanical clutch or brake systems have a great influence on the strength of elements of these systems as well as on their dynamics. The contact problems exhibited by such systems include heat generated by dry friction contact surfaces. The contact dynamics in general depends on many system parameters, and it attracted attention of many researches focused on analysis of the mentioned phenomena in different kinds of mechanical systems like clutches, brakes, and others. In this work a mathematical model describing the processes of heat generation and its propagation in the mechanical friction clutch is presented. The presented model takes into account the unequal distribution of flux density of produced heat in the clutch, the thermal conductivity of materials of friction linings, and the heat transfer between the friction linings of clutch and its environments. The analyzed object is described by a set of algebraic linear homo- and heterogeneous equations, and it is derived using a computer numerical method. Many interesting numerical and experimental results are obtained, illustrated and discussed. Presented numerical results coincide with experimental data.

Friction heat conduction and entransy of friction lining

PurposeThis paper aims to analyze the friction heat conduction and entransy of two friction linings in the high‐speed slide accident of a mine friction hoist.Design/methodology/approachFirstly, the dynamic thermophysical properties were analyzed and their fitting equations were also obtained. Additionally, the dynamic heat partition ratio was obtained according to the dynamic thermophysical properties. Then, a simple method was developed to solve the temperature rise of friction lining. Finally, based on the theoretical model of temperature rise, the entransy of friction lining with respect to T and t were gained.FindingsThe error of temperature rise between simulation result and experiment result is less than 7 per cent, which proves that the theoretical model is correct. The entransy decreases with the temperature below 40°C and it increases after 40°C. The entransy of lining K is a little higher than that of lining G within 19 s, but the entransy of lining G is much higher than lining K after 19 s and the entransy difference gets great gradually. It is indicated that the lining K has good heat‐resistant property which is of great benefit to the tribological property of friction lining.Practical implicationsThe authors' study provides a fundamental basis for developing a new friction lining with good heat‐resistant property, and it also brings forward a new quantitative method to evaluate the heat‐transfer capability of friction materials.Originality/valueA simple method was introduced to calculate the temperature rise of friction lining with the consideration of dynamic thermophysical properties and dynamic heat partition ratio. And the entransy of friction lining was obtained to evaluate the heat‐transfer capability of friction linings quantitatively.

Change of stress magnitudes during the polyphase tectonic history of the Cretaceous Gyeongsang basin, southeast Korea

Abstract In order to evaluate the change of stress magnitudes in the Gyeongsang basin during its tectonic history, we analyzed multiple faulting episodes in the Barremian-Aptian Hasandong Formation at the Yusu site. As elsewhere in southeast Korea, the recorded sequence consists of a succession of more than fourteen faulting episodes, and the relative chronology shows that a strike-slip faulting episode usually coexisted with a coaxial extensional episode. Likewise, seven couples of synchronous coaxial episodes recognised in the Gyeongsang basin are assigned to seven tectonic events (T_1 to T_7 events). The friction line (in the sense of Byerlee) allows us to determine the ratios between principal stress magnitudes as well as the origin of the dimensionless Mohr diagram. This line can be deduced from tension fractures on fault planes affected by friction and from the lower limit of scattered distribution of the normal stresses vs. shear stresses of faults. Dimensionless failure envelopes drawn for coaxial strike-slip and extensional episodes are adjusted to the experimental Mohr failure envelope derived from rock mechanic tests to determine the complete stress tensors. The maximum principal stress magnitudes of strike-slip episodes show a transition from 169 MPa in the Barremian-Coniacian T_1 Event through 263 MPa and 246 MPa in the T_2 and T_4 events, respectively to 235 MPa in the Quaternary T_7 Event; additional horizontal extension (ΔσT) have changed from −6 MPa in the T_1 Event through −8 MPa in the T_2 Event to −17 MPa in the T_7 Event. Because the studied site is currently exposed, the determined overburden (1.9 km) for the T_7 Event seems to be important, indicating the presumable occurrence of this event during the early Quaternary rather than at the present day.

Scaling of Resistance From Surface-Effect Ship Model Tests

In the case of conventional (displacement) hulls, model testing is based on the assumption (with or without certain refinements) that the total resistance can be expressed as:RT=RF+RR(1)where Rt is measured in the towing tank, and the frictional resistance, Rf, can be accurately estimated by the application of a friction line and the use of the calm-water wetted surface. It is assumed that the dimensionless residuary resistance RR is the same for the model and the prototype vessel. Our article may be considered to be an extension of the classic article by Wilson, Wells, and Heber (1978) to the more complex case of the surface-effect ship, as follows. Specifically, we opine that:RT=RF+RW+RH+RS+RM+RSPRAY(2)Here, Rw is the wave resistance of the vessel (caused by a combination of the actions of the cushion pressure and the two sidehulls), RH is the transom (hydrostatic) drag, Rs is the seal drag, Rm is the momentum drag, and RspRay is the spray drag. Rt is the only one of these quantities that is measured during the model test. The other components require the use of a variety of estimates. In the article, we present specific examples of our approach as applied to a number of tests on surface-effect ship models that we have studied in recent years.

Friction conditions in the friction brake system of Mi-2 helicopter

An assessment of friction conditions during braking on durability of structural elements of the drum brake is the goal of the work. The analysed brake in a symmetric system is used in Mi-2 helicopter. In the so far applied solutions a friction lining and brake shoe were fastened up by riveting. The new asbestos-free friction linings crack when using riveting technology. One way to avoid cracking is gluing instead of riveting. This paper presents a numerical analysis of the drum brake with the friction lining fastened by gluing. The numerical model includes a three-dimensional structure composed of seven structural elements and comparison of four material groups. A distribution of contact pressure between the frictional elements, and a stress state in the structural elements of the drum brake were determined for the assumed boundary and initial conditions. It was stated that the calculated distribution of the contact pressures is nonuniform and depends on the sense of rotation of the drum brake. This paper also presents the results of comparative tests of bonding strength for three different glues. The tests were carried out on a specially designed for this purpose test stand.

Plasma morphology and induced airflow characterization of a DBD actuator with serrated electrode

Plasma morphology and airflow induced by a dielectric barrier discharge (DBD) actuator, whose exposed electrode geometry is designed with a serrated configuration, are investigated in quiescent air and compared with a DBD actuator consisting of electrodes designed with a standard linear strip configuration. ICCD imaging, electrical measurements and three-component laser Doppler velocimetry were carried out to compare various features of these two actuators. With the serrated configuration, ICCD images of the discharge show that streamers are bent, whereas with the linear configuration they are straight. These curved streamers induce a three-dimensional flow topology, which is confirmed by friction line visualization and velocity measurements. Whereas a two-dimensional wall-jet is induced with the linear configuration, a transverse velocity component is measured with the serrated configuration, implying the creation of spanwise-periodic vorticity. Phase-averaged velocity measurements allow the temporal variation of this transverse velocity to be highlighted. On both sides of a tooth, it has qualitatively the same variation as the longitudinal velocity with respect to the negative or positive half-cycles of the high voltage signal. Moreover, with the same electrical operating parameters, the measured longitudinal velocity was higher, particularly at the tips.

Manufacturing technology for cast inserts of new wear-resistant alloys for combined mill linings

The efficiency of combined use of elastomers (rubbers) and wear-resistant steels and cast iron for mining and metallurgical equipment is studied: mill lining, hydrocyclones, modular screens, conveyor belt grids, crushers, etc. Rubber absorbs impact loads, dampens them, and thereby prevents breakage of high-hardness wear-resistant steels and cast iron. It is established by research that combination within the structure of chromium-manganese alloys of the transition class (1.6–2.2% C) types 200G4Kh5L, 200G5Kh2L (200G5Kh2TFL) with a sufficient amount of hard carbide phases and a ductile austenite-pearlite matrix provides high indices for impact-abrasive and impact-abrasive-corrosion resistance. Inserts of combined rubber and metal linings of metals of the transition class type are effective.

Scaling of Resistance From Surface‐Effect Ship Model Tests

In the case of conventional (displacement) hulls, model testing is based on the assumption (with or without certain refinements) that the total resistance can be expressed as: RT = RF + RR where RT is measured in the towing tank, and the frictional resistance RF can be accurately estimated by the application of a friction line and the use of the calm-water wetted surface. It is assumed that the dimensionless residuary resistance RR is the same for the model and the prototype vessel. Our paper may be considered to be an extension of the classic paper by Wilson, Wells, and Heber (1978), to the more complex case of the surface-effect ship, as follows. Specifically, we opine that: RT = RF + RW + RH + RS + RM + RSPRAY Here, RW is the wave resistance of the vessel (caused by a combination of the actions of the cushion pressure and the two sidehulls), RH is the transom (hydrostatic) drag, RS is the seal drag, RM is the momentum drag, and RSPRAY is the spray drag. RT is the only one of these quantities that is measured during the model test. The other components require the use of a variety of estimates. In the paper, we present specific examples of our approach, as applied to a number of tests on SES models that we have studied in recent years.

Simulation of the flow over axisymmetric submarine hulls in steady turning

A computational study of slender axisymmetric bodies with tapered tails undergoing steady turning manoeuvres is presented. The computational modeling is based on the Reynolds Average Navier Stokes (RANS) equations and uses a novel hybrid meshing scheme designed to accurately resolve near field viscous flow features through systematic grid refinement. Turns with a range of radii 1.0<R/ℓ<10.0, and drift angles 1°<β<17°, are studied for the DRDC STR, SUBOFF, and Series 58 model submarine hulls. Detailed results for surface skin friction lines, flow separation and leeside vortex development together with longitudinal lateral force distributions and total forces and moments on the body are described. Partial validation of the computational modeling is achieved by comparison of total forces and moments to experimental data for turning radii R/ℓ=2.74±0.04 and a range of drift angles, 3.8°<β<16.5°.

Bridging the Gap Between the Dense and the Discrete: The Number Line and the “Rubber Line” Bridging Analogy

In two experiments we explored the instructional value of a cross‐domain mapping between “number” and “line” in secondary school students' understanding of density. The first experiment investigated the hypothesis that density would be more accessible to students in a geometrical context (infinitely many points on a straight line segment) compared to a numerical context (infinitely many numbers in an interval). The participants were 229 seventh to eleventh graders. The results supported this hypothesis but also showed that students' conceptions of the line segment were far from that of a dense array of points. We then designed a text-based intervention that attempted to build the notion of density in a geometrical context, making explicit reference to the number-to-points correspondence and using the “rubber line” bridging analogy (the line as an imaginary unbreakable rubber band) to convey the no-successor principle. The participants were 149 eighth and tenth graders. The text intervention improved student performance in tasks regarding the infinity of numbers in an interval; the “rubber line” bridging analogy further improved performance successfully conveying the idea that these numbers can never be found one immediately next to the other.