Sample records for frictional elastic hard

  1. Elastic model of dry friction

    Energy Technology Data Exchange (ETDEWEB)

    Larkin, A. I.; Khmelnitskii, D. E., E-mail: [Landau Institute for Theoretical Physics (Russian Federation)


    Friction of elastic bodies is connected with the passing through the metastable states that arise at the contact of surfaces rubbing against each other. Three models are considered that give rise to the metastable states. Friction forces and their dependence on the pressure are calculated. In Appendix A, the contact problem of elasticity theory is solved with adhesion taken into account.

  2. Static friction in elastic adhesive MEMS contacts, models and experiment

    NARCIS (Netherlands)

    Tas, Niels Roelof; Gui, C.; Elwenspoek, Michael Curt


    Static friction in shearing mode can be expressed as the product of the shear strength of the interface and the real contact area. The influence of roughness on friction in elastic adhesive contact is analyzed. Special attention is paid to low loading conditions, in which the number of contact

  3. Recent Advances in Hard, Tough, and Low Friction Nanocomposite Coatings

    Institute of Scientific and Technical Information of China (English)

    A.A.Voevodin; J. S. Zabinski; C.Muratore


    Nanocomposite coatings demonstrate improved friction and wear responses under severe sliding conditions in extreme environments. This paper provides a review how thin film multilayers and nanocomposites result in hard, tough, low-friction coatings. Approaches to couple multilayered and nanocomposite materials with other surface engineering strategies to achieve higher levels of performance in a variety of tribological applications are also discussed. Encapsulating lubricious phases in hard nanocomposite matrices is one approach that is discussed in detail. Results from state-of-the-art "chameleon" nanocomposites that exhibit reversible adaptability to ambient humidity or temperature are presented.

  4. Debris-bed friction of hard-bedded glaciers (United States)

    Cohen, D.; Iverson, N.R.; Hooyer, T.S.; Fischer, U.H.; Jackson, M.; Moore, P.L.


    [1] Field measurements of debris-bed friction on a smooth rock tablet at the bed of Engabreen, a hard-bedded, temperate glacier in northern Norway, indicated that basal ice containing 10% debris by volume exerted local shear traction of up to 500 kPa. The corresponding bulk friction coefficient between the dirty basal ice and the tablet was between 0.05 and 0.08. A model of friction in which nonrotating spherical rock particles are held in frictional contact with the bed by bed-normal ice flow can account for these measurements if the power law exponent for ice flowing past large clasts is 1. A small exponent (n glacier sliding at 20 m a-1 with a geothermally induced melt rate of 0.006 m a-1 and an effective pressure of 300 kPa can exceed 100 kPa. Debris-bed friction can therefore be a major component of sliding resistance, contradicting the common assumption that debris-bed friction is negligible. Copyright 2005 by the American Geophysical Union.

  5. Surface Hardness of Friction Stir Welded AA6063 Pipe


    Ismail Azman; Awang Mokhtar


    The external surface hardness of friction stir welded aluminum alloy 6063 pipe joint was investigated in this paper. The 89mm of outside diameter pipe with 5mm of wall thickness was used as test pipe piece for this experiment on closed butt joint configuration by utilising Bridgeport 2216 CNC milling machine and orbital clamping unit specially designed to cater for this task and function. Several welded samples were produced on varying process parameters which were successfully joined by usin...

  6. Surface topography, hardness, and frictional properties of GFRP for esthetic orthodontic wires. (United States)

    Inami, Toshihiro; Tanimoto, Yasuhiro; Yamaguchi, Masaru; Shibata, Yo; Nishiyama, Norihiro; Kasai, Kazutaka


    In our previous study, glass-fiber-reinforced plastics (GFRPs) made from polycarbonate and glass fiber for esthetic orthodontic wires were prepared by using pultrusion. The purpose of the present study was to investigate the surface topography, hardness, and frictional properties of GFRPs. To investigate how fiber diameter affects surface properties, GFRP round wires with a diameter of 0.45 mm (0.018 in.) were prepared incorporating either 13 μm (GFRP-13) or 7 μm (GFRP-7) glass fibers. As controls, stainless steel (SS), cobalt-chromium-nickel alloy, β-titanium (β-Ti) alloy, and nickel-titanium (Ni-Ti) alloy were also evaluated. Under scanning electron microscopy and scanning probe microscopy, the β-Ti samples exhibited greater surface roughness than the other metallic wires and the GFRP wires. The dynamic hardness and elastic modulus of GFRP wires obtained by the dynamic micro-indentation method were much lower than those of metallic wires (p < 0.05). Frictional forces against the polymeric composite brackets of GFRP-13 and GFRP-7 were 3.45 ± 0.49 and 3.60 ± 0.38 N, respectively; frictional forces against the ceramic brackets of GFRP-13 and GFRP-7 were 3.39 ± 0.58 and 3.87 ± 0.48 N, respectively. For both bracket types, frictional forces of GFRP wires and Ni-Ti wire were nearly half as low as those of SS, Co-Cr, and β-Ti wires. In conclusion, there was no significant difference in surface properties between GFRP-13 and GFRP-7; presumably because both share the same polycarbonate matrix. We expect that GFRP wires will deliver superior sliding mechanics with low frictional resistance between the wire and bracket during orthodontic treatment.

  7. Elastic friction drive of surface acoustic wave motor. (United States)

    Kurosawa, Minoru Kuribayashi; Itoh, Hidenori; Asai, Katsuhiko


    Importance of elastic deformation control to obtain large output force with a surface acoustic wave (SAW) motor is discussed in this paper. By adding pre-load to slider, stator and slider surfaces are deformed in a few tens nanometer. Appropriate deformation in normal direction against normal vibration displacement amplitude of SAW existed. By moderate deformation, the output force of the SAW motor was enlarged up to about 10 N and no-load speed was 0.7 m/s. To produce this performance, the transducer weight and slider size were only 4.2 g and 4 x 4 mm(2).By traveling wave propagation, surface particles of the SAW device move in elliptical motion. Due to the amplitude of the elliptical motion is 10 or 20 nm order, the contact condition of the slider is very critical. To control the contact condition, namely, the elastic deformation of the slider and stator surface in nanometer order, a lot of projections were fabricated on the slider surface. The projection diameter was 20 micro m. In static condition, the elastic deformation and stress were evaluated with the FEM analysis. From this calculation and the simulation result, it is consider that the wave crest is distorted, hence the elasticity has influence on the friction drive condition. Elastic deformation of the stator surface beneath the projection from the initial position were evaluated. In 4 x 4 mm(2) square area, the sliders had from 1089 to 23,409 projections. Depression was independent to the contact pressure. However, the output force depended on the depression although the projection density were different. From the view point of the output power of the motor, the proper depression was independent to the projection density. Around 25 nm depression, the output force and output power were maximized. This depression value was almost same as the vibration displacement amplitude of the stator transducer.

  8. Development of Hard Elastic Solids from Glassy Polymers. (United States)


    elastic polypropylene (PP) as reported by Park and Noether 5 The stress-strain behavior for three intermittent cycles to 40% extension is shown in Fig. Zb...system. Such viscoelastic effects have been concluded by Park and Noether 1 5 from more extensive stress relaxation investigations of hard elastic PP...Petermann and H. Gleiter, J. Macromol. Sc.- Phys., B12(4), 523 (1976). 4. H. D. Noether , Intern. J. Polymeric Mater.,. 7, 57 (1979). 5. M. E. Mackay

  9. Friction and hardness of gold films deposited by ion plating and evaporation (United States)

    Miyoshi, K.; Spalvins, T.; Buckley, D. H.


    Sliding friction experiments were conducted with ion-plated and vapor-deposited gold films on various substrates in contact with a 0.025-mm-radius spherical silicon carbide rider in mineral oil. Hardness measurements were also made to examine the hardness depth profile of the coated gold on the substrate. The results indicate that the hardness is influenced by the depth of the gold coating from the surface. The hardness increases with an increase in the depth. The hardness is also related to the composition gradient in the graded interface between the gold coating and the substrate. The graded interface exhibited the highest hardness resulting from an alloy hardening effect. The coefficient of friction is inversely related to the hardness, namely, the load carrying capacity of the surface. The greater the hardness that the metal surface possesses, the lower is the coefficient of friction. The graded interface exhibited the lowest coefficient of friction.

  10. Thermodynamic stability in elastic systems: Hard spheres embedded in a finite spherical elastic solid. (United States)

    Solano-Altamirano, J M; Goldman, Saul


    We determined the total system elastic Helmholtz free energy, under the constraints of constant temperature and volume, for systems comprised of one or more perfectly bonded hard spherical inclusions (i.e. "hard spheres") embedded in a finite spherical elastic solid. Dirichlet boundary conditions were applied both at the surface(s) of the hard spheres, and at the outer surface of the elastic solid. The boundary conditions at the surface of the spheres were used to describe the rigid displacements of the spheres, relative to their initial location(s) in the unstressed initial state. These displacements, together with the initial positions, provided the final shape of the strained elastic solid. The boundary conditions at the outer surface of the elastic medium were used to ensure constancy of the system volume. We determined the strain and stress tensors numerically, using a method that combines the Neuber-Papkovich spherical harmonic decomposition, the Schwartz alternating method, and Least-squares for determining the spherical harmonic expansion coefficients. The total system elastic Helmholtz free energy was determined by numerically integrating the elastic Helmholtz free energy density over the volume of the elastic solid, either by a quadrature, or a Monte Carlo method, or both. Depending on the initial position of the hard sphere(s) (or equivalently, the shape of the un-deformed stress-free elastic solid), and the displacements, either stationary or non-stationary Helmholtz free energy minima were found. The non-stationary minima, which involved the hard spheres nearly in contact with one another, corresponded to lower Helmholtz free energies, than did the stationary minima, for which the hard spheres were further away from one another.

  11. Hard and low friction nitride coatings and methods for forming the same (United States)

    Erdemir, Ali; Urgen, Mustafa; Cakir, Ali Fuat; Eryilmaz, Osman Levent; Kazmanli, Kursat; Keles, Ozgul


    An improved coating material possessing super-hard and low friction properties and a method for forming the same. The improved coating material includes the use of a noble metal or soft metal homogeneously distributed within a hard nitride material. The addition of small amounts of such metals into nitrides such as molybdenum nitride, titanium nitride, and chromium nitride results in as much as increasing of the hardness of the material as well as decreasing the friction coefficient and increasing the oxidation resistance.

  12. Existence of solutions for quasistatic problems of unilateral contact with nonlocal friction for nonlinear elastic materials

    Directory of Open Access Journals (Sweden)

    Alain Mignot


    Full Text Available This paper shows the existence of a solution of the quasi-static unilateral contact problem with nonlocal friction law for nonlinear elastic materials. We set up a variational incremental problem which admits a solution, when the friction coefficient is small enough, and then by passing to the limit with respect to time we obtain a solution.

  13. Friction behavior of 304 stainless steel of varying hardness lubricated with benzene and some benzyl structures (United States)

    Buckley, D. H.


    The lubricating properties of some benzyl and benzene structures were determined by using 304 stainless steel surfaces strained to various hardness. Friction coefficients and wear track widths were measured with a Bowden-Leben type friction apparatus by using a pin-on-disk specimen configuration. Results obtained indicate that benzyl monosulfide, dibenzyl disulfide, and benzyl alcohol resulted in the lowest friction coefficients for 304 stainless steel, while benzyl ether provided the least surface protection and gave the highest friction. Strainhardening of the 304 stainless steel prior to sliding resulted in reduced friction in dry sliding. With benzyl monosulfide, dibenzyl disulfide, and benzyl alcohol changes in 304 stainless steel hardness had no effect upon friction behavior.

  14. The effect of elastic modulus and friction coefficient on rubber tube sealing performance (United States)

    Li, Zhimiao; Xu, Siyuan; Ren, Fushen; Liu, Jubao


    The packer is the key element in separating geosphere layers of water injection, water plugging and fracturing operations in the oilfield. The sealing ability of the packer is depending on the contact pressure between rubber tube and the casing. The circumferential strain of casing wall was tested by the strain gauge to get the contact pressure distribution along axial direction of the tube. The friction force between the casing and the rubber tube was taken by the pressure sensor in compression process. Under the 20,60 and 100 degrees Celsius conditions, the friction forces and the contact pressure distribution were taken in work condition of single rubber tube, double rubber tubes and combination rubber tubes after oil immersion .The result shows that elastic modulus of rubber tube has little effect on the friction force and contact pressure. With elastic modulus decreasing, the friction forces has gradually decreasing trend; The friction coefficient has much impact on friction force: the friction forces under the condition of dry friction and wet friction are respectively equivalent to 48.27% and 5.38% axial compression forces. At wet friction condition, the contact pressure distribution is more uniform and the sealing effect is better.

  15. Finite element analysis of 3D elastic-plastic frictional contact problem for Cosserat materials (United States)

    Zhang, S.; Xie, Z. Q.; Chen, B. S.; Zhang, H. W.


    The objective of this paper is to develop a finite element model for 3D elastic-plastic frictional contact problem of Cosserat materials. Because 3D elastic-plastic frictional contact problems belong to the unspecified boundary problems with nonlinearities in both material and geometric forms, a large number of calculations are needed to obtain numerical results with high accuracy. Based on the parametric variational principle and the corresponding quadratic programming method for numerical simulation of frictional contact problems, a finite element model is developed for 3D elastic-plastic frictional contact analysis of Cosserat materials. The problems are finally reduced to linear complementarity problems (LCP). Numerical examples show the feasibility and importance of the developed model for analyzing the contact problems of structures with materials which have micro-polar characteristics.

  16. Elastic Films for Cyrogenic Skin Friction Measurements Project (United States)

    National Aeronautics and Space Administration — Here we introduce a new sensor for measurement of skin friction and pressure, Surface Stress Sensitive Film (S3F). This technique can operate over a range of...

  17. A theory of static friction between homogeneous surfaces based on compressible elastic smooth microscopic inclines

    CERN Document Server

    Thun, Freeman Chee Siong; Chan, Kin Sung


    We develop a theory of static friction by modeling the homogeneous surfaces of contact as being composed of a regular array of compressible elastic smooth microscopic inclines. Static friction is thought of as the resistance due to having to push the load over these smooth microscopic inclines that share a common inclination angle. As the normal force between the surfaces increases, the microscopic inclines would be compressed elastically. Consequently, the coefficient of static friction does not remain constant but becomes smaller for a larger normal force, since the load would then only need to be pushed over smaller angles. However, a larger normal force would also increase the effective compressed area between the surfaces, as such the pressure is distributed over this larger effective compressed area. The relationship between the normal force and the common angle is therefore non-linear. Overall, static friction is shown to depend on the normal force, apparent contact area, Young's modulus, and the compr...

  18. System of elastic hard spheres which mimics the transport properties of a granular gas. (United States)

    Santos, Andrés; Astillero, Antonio


    The prototype model of a fluidized granular system is a gas of inelastic hard spheres (IHS) with a constant coefficient of normal restitution alpha. Using a kinetic theory description we investigate the two basic ingredients that a model of elastic hard spheres (EHS) must have in order to mimic the most relevant transport properties of the underlying IHS gas. First, the EHS gas is assumed to be subject to the action of an effective drag force with a friction constant equal to half the cooling rate of the IHS gas, the latter being evaluated in the local equilibrium approximation for simplicity. Second, the collision rate of the EHS gas is reduced by a factor (1/2)(1+alpha), relative to that of the IHS gas. Comparison between the respective Navier-Stokes transport coefficients shows that the EHS model reproduces almost perfectly the self-diffusion coefficient and reasonably well the two transport coefficients defining the heat flux, the shear viscosity being reproduced within a deviation less than 14% (for alpha > or = 0.5). Moreover, the EHS model is seen to agree with the fundamental collision integrals of inelastic mixtures and dense gases. The approximate equivalence between IHS and EHS is used to propose kinetic models for inelastic collisions as simple extensions of known kinetic models for elastic collisions.

  19. A new visco-elastic contact model of traveling wave ultrasonic motor with stator frictional layer

    Institute of Scientific and Technical Information of China (English)


    A new contact model of traveling wave ultrasonic motor (TWUSM) with a visco-elastic stator frictional layer was presented. In this model, the initial boundaries were revised, and the rotor revolution speed could be calculated iteratively. This model was compared with compliant slider and rigid stator model. The results of motor characteristics simulations showed that the motors based on this model would gain bigger stall torque. Then the friction and wear characteristics of two models were analyzed. The motors based on this model had lower coefficient of friction and better wear resistance.

  20. Internal friction and elastic softening in polycrystalline Nb3Sn (United States)

    Bussière, J. F.; Faucher, B.; Snead, C. L., Jr.; Welch, D. O.


    The vibrating-reed technique was used to measure internal friction and Young's modulus of polycrystalline Nb3Sn in the form of composite Nb-Nb3Sn tapes from 6 to 300 K. In tapes with only small residual strain in the A 15 layers, a dramatic increase in internal friction with decreasing temperature is observed with an abrupt onset at ~48 K. The internal friction Q-1 between 6 and 48 K is believed to be associated with stress-induced motion of martensitic-domain walls. In this temperature range, Q-1 is approximately proportional to the square of the tetragonal strain of the martensitic phase; Q-1~(ca-1)2. With residual compressive strains of ~0.2%, the internal friction associated with domain-wall motion is considerably reduced. This is attributed to a biasing of domain-wall orientation with residual stress, which reduces wall motion induced by the (much smaller) applied stress. The transformation temperature, however, is unchanged (within +/- 1 K) by residual strains of up to 0.2%. Young's modulus exhibits substantial softening on cooling from 300 to 6 K. This softening is substantially reduced in the presence of small residual compressive strains, indicating a highly nonlinear stress-strain relationship as previously reported for V 3Si.

  1. Optimisation of hardness and tensile strength of friction stir welded ...

    African Journals Online (AJOL)

    DR OKE

    Department of Mechanical Engineering, Bapatla Engineering College, Bapatla, ... surface design matrix were developed by using MINITAB14 software package. ..... search algorithm for multi-criteria optimization in hard turning of AISI D3 Steel.

  2. Active Elastic Support/Dry Friction Damper with Piezoelectric Ceramic Actuator

    Directory of Open Access Journals (Sweden)

    Liao Mingfu


    Full Text Available The basic operation principle of elastic support/dry friction damper in rotor system was introduced and the unbalance response of the rotor with elastic support/dry friction damper was analyzed theoretically. Based on the previous structure using an electromagnet as actuator, an active elastic support/dry friction damper using piezoelectric ceramic actuator was designed and its effectiveness of reducing rotor vibration when rotor traverses its critical speed and blade-out event happened was experimentally verified. The experimental results show that the active elastic support/dry friction damper with piezoelectric ceramic actuator can significantly reduce vibration in rotor system; the vibration amplitude of the rotor in critical speed region decreased more than 2 times, and the active damper can protect the rotor when a blade-out event happened, so the rotor can traverse the critical speed and shut down smoothly. In addition, the structure is much simpler than the previous, the weight was reduced by half and the power consumption was only 5 W.

  3. Role of interparticle friction and particle-scale elasticity in the shear-strength mechanism of three-dimensional granular media (United States)

    Antony, S. J.; Kruyt, N. P.


    The interlink between particle-scale properties and macroscopic behavior of three-dimensional granular media subjected to mechanical loading is studied intensively by scientists and engineers, but not yet well understood. Here we study the role of key particle-scale properties, such as interparticle friction and particle elastic modulus, in the functioning of dual contact force networks, viz., strong and weak contacts, in mobilizing shear strength in dense granular media subjected to quasistatic shearing. The study is based on three-dimensional discrete element method in which particle-scale constitutive relations are based on well-established nonlinear theories of contact mechanics. The underlying distinctive contributions of these force networks to the macroscopic stress tensor of sheared granular media are examined here in detail to find out how particle-scale friction and particle-scale elasticity (or particle-scale stiffness) affect the mechanism of mobilization of macroscopic shear strength and other related properties. We reveal that interparticle friction mobilizes shear strength through bimodal contribution, i.e., through both major and minor principal stresses. However, against expectation, the contribution of particle-scale elasticity is mostly unimodal, i.e., through the minor principal stress component, but hardly by the major principal stress. The packing fraction and the geometric stability of the assemblies (expressed by the mechanical coordination number) increase for decrease in interparticle friction and elasticity of particles. Although peak shear strength increases with interparticle friction, the deviator strain level at which granular systems attain peak shear strength is mostly independent of interparticle friction. Granular assemblies attain peak shear strength (and maximum fabric anisotropy of strong contacts) when a critical value of the mechanical coordination number is attained. Irrespective of the interparticle friction and elasticity

  4. Role of elastic deformation in determining the mixed alkaline earth effect of hardness in silicate glasses

    DEFF Research Database (Denmark)

    Kjeldsen, Jonas; Smedskjær, Morten Mattrup; Potuzak, M.


    been investigated previously, but the link between the resistance to elastic deformation and hardness has not yet been studied. In this work, we investigate the link between elastic deformation during indentation and Vickers hardness in a series of mixed magnesium-barium boroaluminosilicate glasses. We...... show that the mixed alkaline earth effect manifests itself as deviations from linearity in shear modulus, Poisson’s ratio, glass transition temperature, liquid fragility index, hardness, volume of densification, and volume of plastic flow. We find no correlation between the elastic part...... of the indentation and hardness, and we thus infer that elastic deformation does not play a dominant role in determining the mixed alkaline earth effect of hardness. However, interestingly, we find a strong correlation between Poisson’s ratio, volume of plastic flow, and hardness, by which the minimum in hardness...

  5. Asymptotic behavior of an elastic satellite with internal friction


    Haus, Emanuele; Bambusi, Dario


    We study the dynamics of an elastic body whose shape and position evolve due to the gravitational forces exerted by a pointlike planet. The main result is that, if all the deformations of the satellite dissipate some energy, then under a suitable nondegeneracy condition there are only three possible outcomes for the dynamics: (i) the orbit of the satellite is unbounded, (ii) the satellite falls on the planet, (iii) the satellite is captured in synchronous resonance i.e. its orbit is asymptoti...

  6. Elastic Properties and Internal Friction of Two Magnesium Alloys at Elevated Temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Freels, M.; Liaw, P. K.; Garlea, E.; Morrell, J. S.; Radiovic, M.


    The elastic properties and internal friction of two magnesium alloys were studied from 25 C to 450 C using Resonant Ultrasound Spectroscopy (RUS). The Young's moduli decrease with increasing temperature. At 200 C, a change in the temperature dependence of the elastic constants is observed. The internal friction increases significantly with increasing temperature above 200 C. The observed changes in the temperature dependence of the elastic constants and the internal friction are the result of anelastic relaxation by grain boundary sliding at elevated temperatures. Elastic properties govern the behavior of a materials subjected to stress over a region of strain where the material behaves elastically. The elastic properties, including the Young's modulus (E), shear modulus (G), bulk modulus (B), and Poisson's ratio (?), are of significant interest to many design and engineering applications. The choice of the most appropriate material for a particular application at elevated temperatures therefore requires knowledge of its elastic properties as a function of temperature. In addition, mechanical vibration can cause significant damage in the automotive, aerospace, and architectural industries and thus, the ability of a material to dissipate elastic strain energy in materials, known as damping or internal friction, is also important property. Internal friction can be the result of a wide range of physical mechanisms, and depends on the material, temperature, and frequency of the loading. When utilized effectively in engineering applications, the damping capacity of a material can remove undesirable noise and vibration as heat to the surroundings. The elastic properties of materials can be determined by static or dynamic methods. Resonant Ultrasound Spectroscopy (RUS), used in this study, is a unique and sophisticated non-destructive dynamic technique for determining the complete elastic tensor of a solid by measuring the resonant spectrum of mechanical resonance for a

  7. Frictional unilateral contact for hemitropic solids in micropolar elasticity and boundary element approximation (United States)

    Gwinner, Joachim


    This contribution deals with unilateral contact problems with Tresca friction (given friction model) in hemitropic mi-cropolar elasticity. Based on a boundary integral approach such problems can be reduced to boundary variational inequalities. This suggests the use of boundary element methods for their numerical treatment. With higher order approximation this leads to a nonconforming approximation what can numerically be realized by means of Gauss-Lobatto quadrature. The contribution is based on the recent papers [7, 8] of the author and on joint work [3] with A. Gachechiladze, R. Gachechi-ladze, and D. Natroshvili.

  8. Effects of the ratio of hardness to Young's modulus on the friction and wear behavior of bilayer coatings (United States)

    Ni, Wangyang; Cheng, Yang-Tse; Lukitsch, Michael J.; Weiner, Anita M.; Lev, Lenoid C.; Grummon, David S.


    We present a study of the effects of the ratio of hardness to Young's modulus on the friction and wear behavior of layered composite coatings. Layered coating structures with the same surface coating but different interlayers were prepared by physical vapor deposition. We found that the ratio of hardness to Young's modulus plays an important role in determining the friction coefficient and wear resistance of layered composite coatings. A low friction coefficient and high wear resistance can be achieved in structures with high ratio of hardness to Young's modulus and moderately high hardness.

  9. Driven self-assembly of hard nanoplates on soft elastic shells

    Institute of Scientific and Technical Information of China (English)

    章尧旸; 华昀峰; 邓真渝


    The driven self-assembly behaviors of hard nanoplates on soft elastic shells are investigated by using molecular dynamics (MD) simulation method, and the driven self-assembly structures of adsorbed hard nanoplates depend on the shape of hard nanoplates and the bending energy of soft elastic shells. Three main structures for adsorbed hard nanoplates, including the ordered aggregation structures of hard nanoplates for elastic shells with a moderate bending energy, the collapsed structures for elastic shells with a low bending energy, and the disordered aggregation structures for hard shells, are observed. The self-assembly process of adsorbed hard nanoplates is driven by the surface tension of the elastic shell, and the shape of driven self-assembly structures is determined on the basis of the minimization of the second moment of mass distribution. Meanwhile, the deformations of elastic shells can be controlled by the number of adsorbed rods as well as the length of adsorbed rods. This investigation can help us understand the complexity of the driven self-assembly of hard nanoplates on elastic shells.

  10. Asymptotic Behavior of an Elastic Satellite with Internal Friction

    Energy Technology Data Exchange (ETDEWEB)

    Haus, E., E-mail: [Università di Napoli Federico II Via Cintia, Dipartimento di Matematica e Applicazioni R. Caccioppoli (Italy); Bambusi, D., E-mail: [Università degli Studi di Milano, DIpartimento di Matematica F. Enriques (Italy)


    We study the dynamics of an elastic body whose shape and position evolve due to the gravitational forces exerted by a pointlike planet. The main result is that, if all the deformations of the satellite dissipate some energy, then under a suitable nondegeneracy condition there are only three possible outcomes for the dynamics: (i) the orbit of the satellite is unbounded, (ii) the satellite falls on the planet, (iii) the satellite is captured in synchronous resonance i.e. its orbit is asymptotic to a motion in which the barycenter moves on a circular orbit, and the satellite moves rigidly, always showing the same face to the planet. The result is obtained by making use of LaSalle’s invariance principle and by a careful kinematic analysis showing that energy stops dissipating only on synchronous orbits. We also use in quite an extensive way the fact that conservative elastodynamics is a Hamiltonian system invariant under the action of the rotation group.

  11. Asymptotic Behavior of an Elastic Satellite with Internal Friction (United States)

    Haus, E.; Bambusi, D.


    We study the dynamics of an elastic body whose shape and position evolve due to the gravitational forces exerted by a pointlike planet. The main result is that, if all the deformations of the satellite dissipate some energy, then under a suitable nondegeneracy condition there are only three possible outcomes for the dynamics: (i) the orbit of the satellite is unbounded, (ii) the satellite falls on the planet, (iii) the satellite is captured in synchronous resonance i.e. its orbit is asymptotic to a motion in which the barycenter moves on a circular orbit, and the satellite moves rigidly, always showing the same face to the planet. The result is obtained by making use of LaSalle's invariance principle and by a careful kinematic analysis showing that energy stops dissipating only on synchronous orbits. We also use in quite an extensive way the fact that conservative elastodynamics is a Hamiltonian system invariant under the action of the rotation group.


    Institute of Scientific and Technical Information of China (English)

    张洪武; 钟万勰; 顾元宪


    The solution of 3 D elastic-plastic frictional contact problems belongs to the unspecified boundary problems where the interaction between two kinds of nonlinearities should occur. Considering the difficulties for the solution of 3 D frictional contact problems, the key part is the determination of the tangential slip states at the contact points, and a great amount of computing work is needed for a high accuracy result. A new method based on a combination of programming and iteration methods, which are respectively known as two main kinds of methods for contact analysis, was put forward to deal with 3 D elastic-plastic contact problems. Numerical results demonstrate the efficiency of the algorithm illustrated here.

  13. Manufacturing Systems Demonstration: Bimetallic Friction STIR Joining of AA6061 and High Hardness Steel (United States)


    tool’s first use. In all tools made of alloy having hafnium carbide, we’ve commonly seen small voids (0.0-1.0 mm dia.) on the surface of machined...distribution unlimited 13. SUPPLEMENTARY NOTES 14. ABSTRACT Focus: HOPE (FH) has developed the process parameters to successfully join AA6061 aluminum alloy successfully join AA6061 aluminum alloy and High Hardness Armor (HHA) steel using the friction stir process (FSP). Metallographic analysis

  14. Large difference in the elastic properties of fcc and hcp hard-sphere crystals

    NARCIS (Netherlands)

    Pronk, S.; Frenkel, D.


    We report a numerical calculation of the elastic constants of the fcc and hcp crystal phases of monodisperse hard-sphere colloids. Surprisingly, some of these elastic constants are very different (up to 20%), even though the free-energy, pressure, and bulk compressibility of the two crystal structur

  15. Study of nonlinear behaviors and modal reductions for friction destabilized systems. Application to an elastic layer (United States)

    Loyer, A.; Sinou, J.-J.; Chiello, O.; Lorang, X.


    As noise reduction tends to be part of environmental directives, predicting squeal noise generated by disc brakes is an important industrial issue. It involves both the transient and stationary nonlinear dynamics of self-excited systems with frictional contact. Time simulation of the phenomenon is an attractive option for reducing experiment costs. However, since such computations using full finite element models of industrial disc brake systems is time-consuming, model reduction has to be performed. In this paper, both the transient and stationary nonlinear behaviors of the friction destabilized system and the effect of dynamical reduction on the nonlinear response of a simple friction destabilized system are carried out. The first part provides a description of the general modeling retained for friction destabilized systems. Then, discretization and solving processes for the stability analysis and the temporal evolution are presented. The third part presents an analysis of a sliding elastic layer for different operating conditions, in order to better understand the nonlinear behavior of such systems. Finally, spatial model reduction is performed with different kinds of reduction bases in order to analyze the different effects of modal reductions. This clearly shows the necessity of including static modes in the reduction basis and that nonlinear interactions between unstable modes are very difficult to represent with reduced bases. Finally, the proposed model and the associated studies are intended to be the benchmark cases for future comparison.

  16. Microstructure and mechanical properties of hard zone in friction stir welded X80 pipeline steel relative to different heat input

    Energy Technology Data Exchange (ETDEWEB)

    Aydin, Hakan, E-mail: [Engineering and Architecture Faculty, Mechanical Engineering Department, Uludag University, 16059 Gorukle-Bursa (Turkey); Nelson, Tracy W. [Mechanical Engineering Department, Brigham Young University, 435 CTB, Provo, UT 84602 (United States)


    The study was conducted to investigate the microstructure and mechanical properties of the hard zone in friction stir welded X80 pipeline steel at different heat inputs. Microstructural analysis of the welds was carried out using optical microscopy, transmission electron microscopy, and microhardness. Heat input during friction stir welding process had a significant influence on the microstructure and mechanical properties in the hard zone along the advancing side of the weld nugget. Based on the results, the linear relationships between heat input and post-weld microstructures and mechanical properties in the hard zone of friction stir welded X80 steels were established. It can be concluded that with decrease in heat input the bainitic structure in the hard zone becomes finer and so hard zone strength increases.

  17. Structure and Hardness of 01570 Aluminum Alloy Friction Stir Welds Processed Under Different Conditions (United States)

    Il'yasov, R. R.; Avtokratova, E. V.; Markushev, M. V.; Predko, P. Yu.; Konkevich, V. Yu.


    Structure and hardness of the 01570 aluminum alloy joints processed by friction stir welding at various speeds are investigated. It is shown that increasing the traverse tool speed lowers the probability of macrodefect formation in the nugget zone; however, this can lead to anomalous grain growth in the zone of contact with the tool shoulder. Typical "onion-like" structure of the weld consisting of rings that differ by optical contrast is formed for all examined welding regimes. It is demonstrated that this contrast is caused by the difference in the grain sizes in the rings rather than by their chemical or phase composition. Mechanisms of transformation of the alloy structure during friction stir welding are discussed.

  18. Elasticity, friction, and pathway of γ-subunit rotation in FoF1-ATP synthase. (United States)

    Okazaki, Kei-ichi; Hummer, Gerhard


    We combine molecular simulations and mechanical modeling to explore the mechanism of energy conversion in the coupled rotary motors of FoF1-ATP synthase. A torsional viscoelastic model with frictional dissipation quantitatively reproduces the dynamics and energetics seen in atomistic molecular dynamics simulations of torque-driven γ-subunit rotation in the F1-ATPase rotary motor. The torsional elastic coefficients determined from the simulations agree with results from independent single-molecule experiments probing different segments of the γ-subunit, which resolves a long-lasting controversy. At steady rotational speeds of ∼ 1 kHz corresponding to experimental turnover, the calculated frictional dissipation of less than k(B)T per rotation is consistent with the high thermodynamic efficiency of the fully reversible motor. Without load, the maximum rotational speed during transitions between dwells is reached at ∼ 1 MHz. Energetic constraints dictate a unique pathway for the coupled rotations of the Fo and F1 rotary motors in ATP synthase, and explain the need for the finer stepping of the F1 motor in the mammalian system, as seen in recent experiments. Compensating for incommensurate eightfold and threefold rotational symmetries in Fo and F1, respectively, a significant fraction of the external mechanical work is transiently stored as elastic energy in the γ-subunit. The general framework developed here should be applicable to other molecular machines.

  19. Understanding the effects of inter-particle contact friction on the elastic moduli of granular materials (United States)

    Taghizadeh, K.; Kumar, N.; Magnanimo, V.; Luding, S.


    Understanding the mechanical stiffness of closely packed, dense granular systems is of interest in many fields, such as soil mechanics, material science and physics. The main difficulty arises due to discreteness and disorder in granular materials at the microscopic scale which requires a multi-scale approach. The Discrete Element Method (DEM) is a powerful tool to inspect the influence of the microscopic contact properties of its individual constituents on the bulk behavior of granular assemblies. In this study, the isotropic deformation mode of polydisperse packings of frictionless and frictional spheres are modeled by using DEM, to investigate the effective stiffness of the granular assembly. At various volume fractions, for every sample, we determine the stress and fabric incremental response that result from the application of strain-probes. As we are interested first in the reversible, elastic response, the amplitude of the applied perturbations has to be small enough to avoid opening and closing of too many contacts, which would lead to irreversible rearrangements in the sample. Counterintuitively, with increasing inter-particle contact friction, the bulk modulus decreases systematically with the coefficient of friction for samples with the same volume fraction. We explain this by the difference in microstructure (isotropic fabric) the samples get when compressed to the same density.

  20. Hard diffraction from quasi-elastic dipole scattering

    CERN Document Server

    Bialas, A


    The contribution to diffraction dissociation of virtual photons due to quasi-elastic scattering of the q-\\bar q component is calculated in the framework of the QCD dipole picture. Both longitudinal and transverse components of the cross-section are given. It is shown that, at fixed mass of the diffractively produced system, quantum mechanical interference plays an important r\\^ ole. Phenomenological consequences are discussed.

  1. Elastic modulus and hardness of cortical and trabecular bovine bone measured by nanoindentation

    Institute of Scientific and Technical Information of China (English)



    The elastic modulus and hardness of several microstructure components of dry bovine vertebrae and tibia have been investigated in the longitude and transverse directions using nanoindentation. The elastic modulus for the osteons and the interstitial lamellae in the longitude direction were found to be (24.7±2.5) GPa and (30.1±2.4) GPa. As it's difficult to distinguish osteons from interstitial lamellae in the transverse direction,the average elastic modulus for cortical bovine bone in the transverse direction was (19.8±1.6) GPa. The elastic modulus for trabecular bone in the longitude and transverse direction were (20±2) GPa and (14.7±1.9) GPa respectively. The hardness also varied among the microstructure components in the range of 0.41-0.89 GPa. Analyses of variance show that the values are significantly different.

  2. Thermal Phenomena in the Friction Process of the TG15 - Hard Anodic Coating Couple

    Directory of Open Access Journals (Sweden)

    Służałek G.


    Full Text Available The paper presents a one-dimensional model of heat conduction in a couple consisting of a cylinder made of a sliding plastic material, TG15, and a cuboid made of alloy AW 6061 coated with a hard anodic coating, where the couple is heated with the heat generated during friction. TG15 is a composite material based on polytetrafluoroethylene (PTFE with a 15% graphite filler, used for piston rings in oil-free air-compressors. Measurement of temperature in the friction zone is extremely important for the understanding and analysis of the phenomena occurring therein. It is practically impossible to introduce a temperature sensor in such a place. Therefore, the interaction taking place in such a couple was modelled using numerical methods. In order to simplify and accelerate the calculations, a one-dimensional model and constant thermophysical parameters of the materials participating in friction were adopted. To solve the proposed model, the finite difference method was used (FDM. The resultant system of equations was solved by means of an explicit scheme.

  3. Friction Behavior on Contact Interface of Linear Ultrasonic Motor with Hard Contact Materials

    Institute of Scientific and Technical Information of China (English)

    Wang Jinpeng; Zhou Hongping; Jin Jiamei; Zhao Chunsheng


    How to improve the efficiency of the linear ultrasonic motor with hard contact materials (HLUSM ) or the precision motion stage driven by HLUSM ,becomes a hot issue .Analysis and testing of friction behavior on the contact interface of HLUSM is one of the key issues .Under the action of ultrasonic vibration and impact ,the fric-tion behavior on contact interface is very complex due to micro-amplitude and high frequency .Moreover ,it is diffi-cult to observe and test it .Focusing on the frictional behavior on the interface of HLUSM ,a new method ,through testing the vibration of the driving tips (scanning vibrometer PSV-400-3D) and the motion of the slider (displace-ment sensor LK-G30) ,respectively ,is proposed .Then ,take the HLUSM as an example ,theoretical analyses and experiments are carried out .Theoretical analysis shows that the average speed of the slider should be 600 mm/s when there is no slippage between the stator and slider during the contact process .Experimental results show that the average speed of the slider is about 390 mm/s .At the same time ,the tangential vibration speed of the driving tip of HLUSM is larger than 600 mm/s .Therefore ,there must be slippage between the stator and slider of HLUSM .Further experimental results show that the maximum efficiency is less than 10% .The slippage on the contact interface should be the main reason for the low efficiency of HLUSM .


    Directory of Open Access Journals (Sweden)



    Full Text Available Experimental investigations had been done in this study to explore the effects of friction stir processing (FSP on the microstructure, hardness and damping capacity of fully ferrite nodular cast iron ASTM A536, grade 65-45-12. The main process parameters employed in this study were the rotational speed, translational speed and axial applied load which were varied within selected ranges. Their influence to be analysed and optimized for best process conditions compared with as cast material. Detailed investigations were carried out using optical microscopy, hardness test and impact test. Results showed that graphite grain refinements of 2-3 times the original size and phase transformations of a fully ferritic to bainite/martensite were achieved within the processed zone and across thickness. Matrix modifications caused improvement in hardness of 3.5 times compared to hardness of original cast iron. Increment in the damping capacity up to 14% was achieved. The stated improvements were related to the process parameters employed in the test.

  5. Nano-hardness and elastic modulus of anodic aluminium oxide based Poly (2-hydroxyethylmethacrylate composite membranes

    Directory of Open Access Journals (Sweden)

    Gérrard Eddy Jai Poinern


    Full Text Available In this study we determine the elastic and hardness properties of electrochemically engineered porous anodic aluminium oxide (AAO membranes and AAO membranes infiltrated with Poly (2-hydroxyethylmethacrylate to form a unique biologically compatible AAO/polymer composite. The electrochemically-synthesised membranes have a nanometre scale porous oxide structure with a mean pore diameter of 100 nm. The membranes were characterized using field emission scanning electron microscopy before and after polymer infiltration. The polymer treated and untreated membranes were then examined using the nano-indentation technique to measure the hardness and subsequently determine the membrane elasticity.

  6. Elastic properties of two dimensional hard discs in the close packing limit

    CERN Document Server

    Wojciechowski, K W; Kowalik, M; Tretiakov, K V


    Elastic constants and the Poisson ratio of defect-free hard disc solid are determined by two independent methods: (1) analysis of the box side fluctuations in the NpT ensemble with variable box +shape and (2) numerical differentiation (with respect to strain components) of the free energy computed in the NVT ensemble. It is shown that reasonable estimates of the elastic properties can be obtained by studying small systems and that the singular behavior of the elastic constants near close packing is well described by the free volume approximation; the coefficients of the leading singularities are estimated.

  7. Computational Investigation of Hardness Evolution During Friction-Stir Welding of AA5083 and AA2139 Aluminum Alloys (United States)


    and R.S. Mishra, Effect of Friction Stir 940Processing on the Microstructure of Cast A356 Aluminum , Mater. Sci. 941Eng. A, 2006, 433, p 269–278...REPORT Computational Investigation of Hardness Evolution During Friction-Stir Welding of AA5083 and AA2139 Aluminum Alloys 14. ABSTRACT 16. combined with the basic physical metallurgy of two wrought aluminum alloys to predict/assess their FSW behaviors. The two alloys selected are AA5083

  8. Conformal growth of low friction HfB{sub x}C{sub y} hard coatings

    Energy Technology Data Exchange (ETDEWEB)

    Mohimi, E. [Department of Materials Science and Engineering, University of Illinois, Urbana, IL 61801 (United States); Ozkan, T. [Department of Mechanical Science and Engineering, University of Illinois, Urbana, IL, 61801 (United States); Babar, S. [Department of Materials Science and Engineering, University of Illinois, Urbana, IL 61801 (United States); Polycarpou, A.A. [Department of Mechanical Science and Engineering, University of Illinois, Urbana, IL, 61801 (United States); Abelson, J.R., E-mail: [Department of Materials Science and Engineering, University of Illinois, Urbana, IL 61801 (United States)


    Thin films of HfB{sub x}C{sub y} are deposited in a cold wall CVD apparatus using Hf(BH{sub 4}){sub 4} precursor and 3,3-dimethyl-1-butene, (CH{sub 3}){sub 3}CCH=CH{sub 2}, as a controllable source of carbon, at substrate temperatures of 250–600 °C. As-deposited films grown at 250 °C are highly conformal (e.g., in a very deep trench, the step coverage is above 90% at a depth/width of 30:1), exhibit dense microstructure, and appear amorphous in X-ray diffraction. Increasing the carbon content from 5 to 21 at.% decreases the hardness from 21 to 9 GPa and the reduced modulus from 207 to 114 GPa. Films grown at 600 °C with carbon contents of 28 and 35 at.% exhibit enhanced hardness of 25 and 23 GPa, and reduced modulus of 211 and 202 GPa, respectively. Annealing the 300 °C grown films at 700 °C affords a nanocrystalline structure with improved mechanical properties. For films with the highest and lowest carbon contents, respectively: the coefficient of sliding friction is in the range of 0.05–0.08 and the H/E and H{sup 3}/E{sup 2} ratios range from 0.08–0.11 and 0.15–0.40. These values indicate that C-containing films should exhibit improved wear performance in tribological applications. - Highlights: • CVD of highly conformal hard coatings of hafnium borocarbide, HfB{sub x}C{sub y}. • Deposition temperature as low at 250 °C using non-halogenated precursor and olefinic carbon source • Films have low coefficient of unlubricated sliding friction and high wear resistance. • Mechanical properties reported across the compositional range 5–35 at.% carbon.


    Directory of Open Access Journals (Sweden)

    Yanhui Huang,


    Full Text Available Compression wood is commonly found in Masson pine. To evaluate the mechanical properties of the cell wall of Masson pine compression and opposite wood, nanoindentation was used. The results showed that the average values of hardness and cell wall modulus of elasticity of opposite wood were slightly higher than those of compression wood. With increasing age of the annual ring, the modulus of elasticity showed a negative correlation with microfibril angle, but a weak correlation was observed for hardness. In opposite and compression wood from the same annual ring, the differences in average values of modulus of elasticity and hardness were small. These slight differences were explained by the change of microfibril angle (MFA, the press-in mode of nanoindentation, and the special structure of compression wood. The mechanical properties were almost the same for early, transition, and late wood in a mature annual ring of opposite wood. It can therefore be inferred that the average modulus of elasticity (MOE and hardness of the cell walls in a mature annual ring were not being affected by cell wall thickness.

  10. A Low-Stress, Elastic, and Improved Hardness Hydrogenated Amorphous Carbon Film

    Directory of Open Access Journals (Sweden)

    Qi Wang


    Full Text Available The evolution of hydrogenated amorphous carbon films with fullerene-like microstructure was investigated with a different proportion of hydrogen supply in deposition. The results showed at hydrogen flow rate of 50 sccm, the deposited films showed a lower compressive stress (lower 48.6%, higher elastic recovery (higher 19.6%, near elastic recovery rate 90%, and higher hardness (higher 7.4% compared with the films deposited without hydrogen introduction. Structural analysis showed that the films with relatively high sp2 content and low bonded hydrogen content possessed high hardness, elastic recovery rate, and low compressive stress. It was attributed to the curved graphite microstructure, which can form three-dimensional covalently bonded network.

  11. A Preliminary Report on the Strength and Metallography of a Bimetallic Friction Stir Weld Joint Between AA6061 and MIL-DTL-46100E High Hardness Steel Armor (United States)


    bimetallic friction stir weld joint between AA6061 and MIL-DTL-46100E High Hardness steel armor. ABSTRACT One half inch thick plates of 6061-T6 aluminum...alloy and High Hardness steel armor (MIL- STD-46100) were successfully joined by the friction stir welding (FSW) process using a tungsten-rhenium...4. TITLE AND SUBTITLE A preliminary report on the strength and metallography of a bimetallic friction stir weld joint between AA6061 and MIL-DTL

  12. Hardness and Elastic Modulus on Six-Fold Symmetry Gold Nanoparticles (United States)

    Ramos, Manuel; Ortiz-Jordan, Luis; Hurtado-Macias, Abel; Flores, Sergio; Elizalde-Galindo, José T.; Rocha, Carmen; Torres, Brenda; Zarei-Chaleshtori, Maryam; Chianelli, Russell R.


    The chemical synthesis of gold nanoparticles (NP) by using gold (III) chloride trihydrate (HAuCl∙3H2O) and sodium citrate as a reducing agent in aqueous conditions at 100 °C is presented here. Gold nanoparticles areformed by a galvanic replacement mechanism as described by Lee and Messiel. Morphology of gold-NP was analyzed by way of high-resolution transmission electron microscopy; results indicate a six-fold icosahedral symmetry with an average size distribution of 22 nm. In order to understand the mechanical behaviors, like hardness and elastic moduli, gold-NP were subjected to nanoindentation measurements—obtaining a hardness value of 1.72 GPa and elastic modulus of 100 GPa in a 3–5 nm of displacement at the nanoparticle’s surface. PMID:28809302

  13. Measurement of Elastic Modulus and Vickers Hardness of Surround Bone Implant Using Dynamic Microindentation - Parameters Definition


    Soares,Priscilla Barbosa Ferreira; Nunes,Sarah Arantes; Franco,Sinésio Domingues; Pires, Raphael Rezende; Zanetta-Barbosa,Darceny; Soares, Carlos José


    The clinical performance of dental implants is strongly defined by biomechanical principles. The aim of this study was to quantify the Vicker's hardness (VHN) and elastic modulus (E) surround bone to dental implant in different regions, and to discuss the parameters of dynamic microindantion test. Ten cylindrical implants with morse taper interface (Titamax CM, Neodent; 3.5 mm diameter and 7 mm a height) were inserted in rabbit tibia. The mechanical properties were analyzed using microhardnes...

  14. Microstructure, Hardness and Impact Toughness of Heat-Treated Nanodispersed Surface and Friction Stir-Processed Aluminum Alloy AA7075 (United States)

    Refat, M.; Elashery, A.; Toschi, S.; Ahmed, M. M. Z.; Morri, A.; El-Mahallawi, I.; Ceschini, L.


    Friction stir processing (FSP) is a recent surface engineering processing technique that is gaining wide recognition for manufacturing nanodispersed surface composites, which are of high specific strength, hardness and resistance to wear and corrosion. Herein, four-pass FSP was applied on aluminum alloy 7075 (AA7075-O) with and without the addition of alumina nanoparticles (Al2O3) of average size 40 nm. All FSP parameters were constant at 40 mm/min transverse speed, 500 rpm and tilt angle of 3°. FSP rotation direction was reversed every other pass. The friction stir-processed materials were sectioned and solution treated at 515 °C for 1.5 h, followed by age hardening at 120 °C for 12, 24, 36, 48 and 60 h. The effect of heat treatment regimes on microstructure, hardness and toughness was examined, as well as the fracture mode. The new friction stir-processed surfaces without and with nanodispersion showed enhancement in the hardness of the surface of the AA7075-O material (65 HV) to almost a double (100 and 140 HV) after four-pass FSP (before heat treatment) without and with incorporating nanoalumina particles, respectively. After 48-h aging at 120 °C, a significant enhancement in impact toughness was achieved for both the friction stir-processed without and with nanodispersion (181 and 134 J, respectively), compared to the reference material AA7075 in T6 condition (104 J).

  15. Abrasion resistant low friction and ultra-hard magnetron sputtered AlMgB14 coatings (United States)

    Grishin, A. M.


    Hard aluminum magnesium boride films were fabricated by RF magnetron sputtering from a single stoichiometric AlMgB14 ceramic target. X-ray amorphous AlMgB14 films are very smooth. Their roughness does not exceed the roughness of Si wafer and Corning glass used as the substrates. Dispersion of refractive index and extinction coefficient were determined within 300 to 2500 nm range for the film deposited onto Corning glass. Stoichiometric in-depth compositionally homogeneous 2 μm thick films on the Si(100) wafer possess the peak values of nanohardness 88 GPa and Young’s modulus 517 GPa at the penetration depth of 26 nm and, respectively, 35 GPa and 275 GPa at 200 nm depth. Friction coefficient was found to be 0.06. The coating scratch adhesion strength of 14 N was obtained as the first chipping of the coating whereas its spallation failure happened at 21 N. These critical loads and the work of adhesion, estimated as high as 18.4 J m-2, surpass characteristics of diamond like carbon films deposited onto tungsten carbide-cobalt (WC-Co) substrates.

  16. Granular mixtures modeled as elastic hard spheres subject to a drag force. (United States)

    Vega Reyes, Francisco; Garzó, Vicente; Santos, Andrés


    Granular gaseous mixtures under rapid flow conditions are usually modeled as a multicomponent system of smooth inelastic hard disks (two dimensions) or spheres (three dimensions) with constant coefficients of normal restitution alpha{ij}. In the low density regime an adequate framework is provided by the set of coupled inelastic Boltzmann equations. Due to the intricacy of the inelastic Boltzmann collision operator, in this paper we propose a simpler model of elastic hard disks or spheres subject to the action of an effective drag force, which mimics the effect of dissipation present in the original granular gas. For each collision term ij, the model has two parameters: a dimensionless factor beta{ij} modifying the collision rate of the elastic hard spheres, and the drag coefficient zeta{ij}. Both parameters are determined by requiring that the model reproduces the collisional transfers of momentum and energy of the true inelastic Boltzmann operator, yielding beta{ij}=(1+alpha{ij})2 and zeta{ij} proportional, variant1-alpha{ij}/{2}, where the proportionality constant is a function of the partial densities, velocities, and temperatures of species i and j. The Navier-Stokes transport coefficients for a binary mixture are obtained from the model by application of the Chapman-Enskog method. The three coefficients associated with the mass flux are the same as those obtained from the inelastic Boltzmann equation, while the remaining four transport coefficients show a general good agreement, especially in the case of the thermal conductivity. The discrepancies between both descriptions are seen to be similar to those found for monocomponent gases. Finally, the approximate decomposition of the inelastic Boltzmann collision operator is exploited to construct a model kinetic equation for granular mixtures as a direct extension of a known kinetic model for elastic collisions.

  17. Elastic properties of the nematic phase in hard ellipsoids of short aspect ratio (United States)

    Heymans, S.; Schilling, T.


    We present a Monte Carlo simulation study of suspensions of hard ellipsoids of revolution. Based on the spatial fluctuations of the orientational order, we have computed the Frank elastic constants for prolate and oblate ellipsoids and compared them to the affine transformation model. The affine transformation model predicts the right order of magnitude of the twist and bend constant but not of the splay constant. In addition, we report the observation of a stable nematic phase at an aspect ratio as low as 2.5.

  18. Quark structure of the nucleon and angular asymmetry of proton-neutron hard elastic scattering. (United States)

    Granados, Carlos G; Sargsian, Misak M


    We investigate an asymmetry in the angular distribution of hard elastic proton-neutron scattering with respect to the 90 degrees center of mass scattering angle and demonstrate that it's magnitude is related to the helicity-isospin symmetry of the quark wave function of the nucleon. Our estimate of the asymmetry within the quark-interchange model of hard scattering demonstrates that the quark wave function of a nucleon based on the exact SU(6) symmetry predicts an angular asymmetry opposite to that of experimental observations. We found that the quark wave function based on the diquark picture of the nucleon produces a correct asymmetry. Comparison with the data allowed us to show that the vector diquarks contribute around 10% in the nucleon wave function and they are in negative phase relative to the scalar diquarks. These observations are essential in constraining QCD models of a nucleon.

  19. Evaluation of elastic modulus and hardness of crop stalks cell walls by nano-indentation. (United States)

    Wu, Yan; Wang, Siqun; Zhou, Dingguo; Xing, Cheng; Zhang, Yang; Cai, Zhiyong


    Agricultural biomaterials such as crop stalks are natural sources of cellulosic fiber and have great potential as reinforced materials in bio-composites. In order to evaluate their potential as materials for reinforcement, the nano-mechanical properties of crop-stalk cell walls, i.e. those of cotton (Gossypium herbaceu) stalk, soybean (Glycine max) stalk, cassava (Manihot esculent) stalk, rice (Oryza sativa L.) straw, and wheat (Triticum aestivum L.) straw, were investigated by means of nano-indentation and atomic force microscopy (AFM). The elastic modulus of wheat straw was found to be 20.8 GPa, which was higher than that of the other four crops. The highest hardness was observed in cotton stalk at 0.85 GPa. The elastic moduli of the crop stalks were lower than those of most of the hardwood species, but higher than that of some softwoods and of lyocell fiber. The mean value of the hardness of the five crop stalks' cell walls was higher than those of wood or lyocell fiber.

  20. Parameters controlling microstructure and hardness during friction-stir welding of precipitation-hardenable aluminum alloy 6063 (United States)

    Sato, Yutaka S.; Urata, Mitsunori; Kokawa, Hiroyuki


    The aluminum (Al) alloys 6063-T5 and T4 were friction-stir welded at different tool rotation speeds ( R), and then distributions of the microstructure and hardness were examined in these welds. The maximum temperature of the welding thermal cycle rose with increasing R values. The recrystallized grain size of the weld increased exponentially with increasing maximum temperature. The relationship between the grain size and the maximum temperature satisfied the static grain-growth equation. In the as-welded condition, 6063-T5 Al was softened around the weld center, whereas 6063-T4 Al showed homogeneous hardness profiles. Different R values did not result in significant differences in the hardness profile in these welds, except for the width of the softened region in the weld of 6063-T5 Al. Postweld aging raised the hardness in most parts of the welds, but the increase in hardness was small in the stir zone produced at the lower R values. Transmission electron microscope (TEM) observations detected a similar distribution of the strengthening precipitates in the grain interiors and the presence of a precipitation-free zone (PFZ) adjacent to the grain boundaries in all the welds. Microstructural analyses suggested that the small increase in hardness in the stir zone produced at the lower R values was caused by an increase in the volume fraction of PFZs.

  1. Ultra-low friction and excellent elastic recovery of fullerene-like hydrogenated carbon film based on multilayer design

    Indian Academy of Sciences (India)



    Multilayer fullerene-like hydrogenated carbon (FL-C:H) films were synthesized by using the chemical vapourdeposition technique with a different flow rate of methane. The typical fullerene-like structure of as-prepared films wasinvestigated by using transmission electron microscopy and Raman spectra. The prepared multilayered FL-C:H films showeda high elastic recovery ($\\sim$90%), ultra-low friction coefficient ($\\sim$0.019) and low wear rate ($\\sim 3.0 \\times 10^{−9}$ mm$^3$ Nm$^{−1}$) in humid air.

  2. Hard Two-Photon Contribution to Elastic Lepton-Proton Scattering: Determined by the OLYMPUS Experiment

    CERN Document Server

    Henderson, B S; Khaneft, D; O'Connor, C; Russell, R; Schmidt, A; Bernauer, J C; Kohl, M; Akopov, N; Alarcon, R; Ates, O; Avetisyan, A; Beck, R; Belostotski, S; Bessuille, J; Brinker, F; Calarco, J R; Carassiti, V; Cisbani, E; Ciullo, G; Contalbrigo, M; De Leo, R; Diefenbach, J; Donnelly, T W; Dow, K; Elbakian, G; Eversheim, P D; Frullani, S; Funke, Ch; Gavrilov, G; Gläser, B; Görrissen, N; Hasell, D K; Hauschildt, J; Hoffmeister, Ph; Holler, Y; Ihloff, E; Izotov, A; Kaiser, R; Karyan, G; Kelsey, J; Kiselev, A; Klassen, P; Krivshich, A; Lehmann, I; Lenisa, P; Lenz, D; Lumsden, S; Ma, Y; Maas, F; Marukyan, H; Miklukho, O; Milner, R G; Movsisyan, A; Murray, M; Naryshkin, Y; Benito, R Perez; Perrino, R; Redwine, R P; neiro, D Rodríguez Pi\\; Rosner, G; Schneekloth, U; Seitz, B; Statera, M; Thiel, A; Vardanyan, H; Veretennikov, D; Vidal, C; Winnebeck, A; Yeganov, V


    The OLYMPUS collaboration reports on a precision measurement of the positron-proton to electron-proton elastic cross section ratio $R_{2\\gamma}$, a direct measure of the contribution of hard two-photon exchange to the elastic cross section. In the OLYMPUS measurement, 2.01 GeV electron and positron beams were directed through a hydrogen gas target internal to the DORIS storage ring at DESY. A toroidal magnetic spectrometer instrumented with drift chambers and time-of-flight scintillators detected elastically scattered leptons in coincidence with recoiling protons over a scattering angle range of $\\approx 20^\\circ$ to $80^\\circ$. The relative luminosity between the two beam species was monitored using tracking telescopes of interleaved GEM and MWPC detectors at $12^\\circ$, as well as symmetric M{\\o}ller/Bhabha calorimeters at $1.29^\\circ$. A total integrated luminosity of 4.5 fb$^{-1}$ was collected. In the extraction of $R_{2\\gamma}$, radiative effects were taken into account using a Monte Carlo generator to ...

  3. Hard Two-Photon Contribution to Elastic Lepton-Proton Scattering Determined by the OLYMPUS Experiment (United States)

    Henderson, B. S.; Ice, L. D.; Khaneft, D.; O'Connor, C.; Russell, R.; Schmidt, A.; Bernauer, J. C.; Kohl, M.; Akopov, N.; Alarcon, R.; Ates, O.; Avetisyan, A.; Beck, R.; Belostotski, S.; Bessuille, J.; Brinker, F.; Calarco, J. R.; Carassiti, V.; Cisbani, E.; Ciullo, G.; Contalbrigo, M.; de Leo, R.; Diefenbach, J.; Donnelly, T. W.; Dow, K.; Elbakian, G.; Eversheim, P. D.; Frullani, S.; Funke, Ch.; Gavrilov, G.; Gläser, B.; Görrissen, N.; Hasell, D. K.; Hauschildt, J.; Hoffmeister, Ph.; Holler, Y.; Ihloff, E.; Izotov, A.; Kaiser, R.; Karyan, G.; Kelsey, J.; Kiselev, A.; Klassen, P.; Krivshich, A.; Lehmann, I.; Lenisa, P.; Lenz, D.; Lumsden, S.; Ma, Y.; Maas, F.; Marukyan, H.; Miklukho, O.; Milner, R. G.; Movsisyan, A.; Murray, M.; Naryshkin, Y.; Perez Benito, R.; Perrino, R.; Redwine, R. P.; Rodríguez Piñeiro, D.; Rosner, G.; Schneekloth, U.; Seitz, B.; Statera, M.; Thiel, A.; Vardanyan, H.; Veretennikov, D.; Vidal, C.; Winnebeck, A.; Yeganov, V.; Olympus Collaboration


    The OLYMPUS Collaboration reports on a precision measurement of the positron-proton to electron-proton elastic cross section ratio, R2 γ , a direct measure of the contribution of hard two-photon exchange to the elastic cross section. In the OLYMPUS measurement, 2.01 GeV electron and positron beams were directed through a hydrogen gas target internal to the DORIS storage ring at DESY. A toroidal magnetic spectrometer instrumented with drift chambers and time-of-flight scintillators detected elastically scattered leptons in coincidence with recoiling protons over a scattering angle range of ≈20 ° to 80°. The relative luminosity between the two beam species was monitored using tracking telescopes of interleaved gas electron multiplier and multiwire proportional chamber detectors at 12°, as well as symmetric Møller or Bhabha calorimeters at 1.29°. A total integrated luminosity of 4.5 fb-1 was collected. In the extraction of R2 γ, radiative effects were taken into account using a Monte Carlo generator to simulate the convolutions of internal bremsstrahlung with experiment-specific conditions such as detector acceptance and reconstruction efficiency. The resulting values of R2 γ, presented here for a wide range of virtual photon polarization 0.456 <ɛ <0.978 , are smaller than some hadronic two-photon exchange calculations predict, but are in reasonable agreement with a subtracted dispersion model and a phenomenological fit to the form factor data.

  4. Hardness, elastic modulus, and wear resistance of hafnium oxide-based films grown by atomic layer deposition

    Energy Technology Data Exchange (ETDEWEB)

    Berdova, Maria; Liu, Xuwen; Franssila, Sami, E-mail: [Department of Materials Science and Engineering, Aalto University, 02150 Espoo (Finland); Wiemer, Claudia; Lamperti, Alessio; Tallarida, Grazia; Cianci, Elena [Laboratorio MDM, IMM CNR, Via C. Olivetti 2, 20864 Agrate Brianza (MB) (Italy); Fanciulli, Marco [Laboratorio MDM, IMM CNR, Via C. Olivetti 2, 20864 Agrate Brianza (MB), Italy and Dipartimento di Scienza dei Materiali, Università degli studi di Milano Bicocca, 20126 Milano (Italy)


    The investigation of mechanical properties of atomic layer deposition HfO{sub 2} films is important for implementing these layers in microdevices. The mechanical properties of films change as a function of composition and structure, which accordingly vary with deposition temperature and post-annealing. This work describes elastic modulus, hardness, and wear resistance of as-grown and annealed HfO{sub 2}. From nanoindentation measurements, the elastic modulus and hardness remained relatively stable in the range of 163–165 GPa and 8.3–9.7 GPa as a function of deposition temperature. The annealing of HfO{sub 2} caused significant increase in hardness up to 14.4 GPa due to film crystallization and densification. The structural change also caused increase in the elastic modulus up to 197 GPa. Wear resistance did not change as a function of deposition temperature, but improved upon annealing.

  5. Analysis of the elastic-plastic indentation properties of materials with varying ratio of hardness to Young's modulus

    Institute of Scientific and Technical Information of China (English)


    The elastic-plastic indentation properties of materials with varying ratio of hardness to Young's modulus (H/E) were analyzed with the finite element method. And the indentation stress fields of materials with varying ratio H/E on the surface were studied by the experiment. The results show that the penetration depth, contact radius, plastic pileup and the degree of elastic recovery depend strongly on the ratio H/E. Moreover, graphs were established to describe the relationship between the elastic-plastic indentation parameters and H/E. The established graphs can be used to predict the H/E of materials when compared with experimental data.

  6. Impact resistance and hardness modelling of Aluminium alloy welds using square-headed friction-stir welding tool (United States)

    Sudhakar, U.; Srinivas, J., Dr.


    This paper proposes modelling and optimization issues relating to friction-stir welding process of aluminium alloys. A specially prepared SS tool of square headed pin profile with cylindrical shoulder is used with a vertical milling machine. Effects of process variables including tool rotation and tool velocity on the weld performance are studied in terms of impact strength and hardness. Three different rotational motions and three welding speeds (feeds) of tool are considered at constant axial load (depth of cut) condition and altogether nine experiments are conducted on a vertical milling machine with specially prepared fixture. Each weld sample is then tested for its impact strength (IS) and hardness independently. A model is developed to correlate the relations between the hardness/impact strength with tool rotation and weld speed using neural networks. The optimized process conditions are predicted to improvise the impact strength and hardness of the weld. Further, the morphology of the weld is studied using SEM to know the material flow characteristics.

  7. Geometry explains the large difference in the elastic properties of fcc and hcp crystals of hard spheres

    NARCIS (Netherlands)

    Sushko, N; van der Schoot, P


    As is well known, hard-sphere crystals of the fcc and hcp type differ very little in their thermodynamic properties. Nonetheless, recent computer simulations by Pronk and Frenkel indicate that the elastic response to mechanical deformation of these two types of crystal are quite different [S. Pronk

  8. Evaluation of elastic modulus and hardness of highly inhomogeneous materials by nanoindentation (United States)

    Epshtein, Svetlana A.; Borodich, Feodor M.; Bull, Steve J.


    The experimental and numerical techniques for evaluation of mechanical properties of highly inhomogeneous materials are discussed. The techniques are applied to coal as an example of such a material. Characterization of coals is a very difficult task because they are composed of a number of distinct organic entities called macerals and some amount of inorganic substances along with internal pores and cracks. It is argued that to avoid the influence of the pores and cracks, the samples of the materials have to be prepared as very thin and very smooth sections, and the depth-sensing nanoindentation (DSNI) techniques has to be employed rather than the conventional microindentation. It is shown that the use of the modern nanoindentation techniques integrated with transmitted light microscopy is very effective for evaluation of elastic modulus and hardness of coal macerals. However, because the thin sections are glued to the substrate and the glue thickness is approximately equal to the thickness of the section, the conventional DSNI techniques show the effective properties of the section/substrate system rather than the properties of the material. As the first approximation, it is proposed to describe the sample/substrate system using the classic exponential weight function for the dependence of the equivalent elastic contact modulus on the depth of indentation. This simple approach allows us to extract the contact modulus of the material constitutes from the data measured on a region occupied by a specific component of the material. The proposed approach is demonstrated on application to the experimental data obtained by Berkovich nanoindentation with varying maximum depth of indentation.

  9. Strain Localization of Elastic-Damaging Frictional-Cohesive Materials: Analytical Results and Numerical Verification. (United States)

    Wu, Jian-Ying; Cervera, Miguel


    Damage-induced strain softening is of vital importance for the modeling of localized failure in frictional-cohesive materials. This paper addresses strain localization of damaging solids and the resulting consistent frictional-cohesive crack models. As a supplement to the framework recently established for stress-based continuum material models in rate form (Wu and Cervera 2015, 2016), several classical strain-based damage models, expressed usually in total and secant format, are considered. Upon strain localization of such damaging solids, Maxwell's kinematics of a strong (or regularized) discontinuity has to be reproduced by the inelastic damage strains, which are defined by a bounded characteristic tensor and an unbounded scalar related to the damage variable. This kinematic constraint yields a set of nonlinear equations from which the discontinuity orientation and damage-type localized cohesive relations can be derived. It is found that for the "Simó and Ju 1987" isotropic damage model, the localization angles and the resulting cohesive model heavily depend on lateral deformations usually ignored in classical crack models for quasi-brittle solids. To remedy this inconsistency, a modified damage model is proposed. Its strain localization analysis naturally results in a consistent frictional-cohesive crack model of damage type, which can be regularized as a classical smeared crack model. The analytical results are numerically verified by the recently-proposed mixed stabilized finite element method, regarding a singly-perforated plate under uniaxial tension. Remarkably, for all of the damage models discussed in this work, the numerically-obtained localization angles agree almost exactly with the closed-form results. This agreement, on the one hand, consolidates the strain localization analysis based on Maxwell's kinematics and, on the other hand, illustrates versatility of the mixed stabilized finite element method.

  10. Nanoindentation hardness and elastic modulus of nano-grained titanium produced by asymmetric and symmetric rolling. (United States)

    Li, Zhiming; Fu, Liming; Fu, Bin; Yang, Xiaoping; Shan, Aidang


    To understand the nanomechanical properties of nano-grained (NG) Ti produced by combination of asymmetric and symmetric rolling, nanoindentation hardness (H(n)) and elastic modulus (E(n)) of different planes within the NG Ti specimens were measured using continuous stiffness measurement mode at room temperature. For comparison, the nanomechanical properties of the as-received hot-rolled coarse-grained (CG) Ti and ultrafine-grained (UFG) Ti with only asymmetric rolling process were also investigated. It was found that H(n) of the Ti samples increased significantly with the decrease of grain sizes, while E(n) exhibited a slight decrease as the grain sizes decreased from CG to NG regime. The increase of H(n) was expected to be caused by higher density of dislocations and finer grains attained by severer plastic deformation, while the slight decrease of E(n) was considered as a result of the increased density of lattice defects and volume fraction of the grain boundary atoms. Furthermore, the nanomechanical properties of different planes of the Ti specimen exhibited a little difference which can be expressed as H(n(RD-TD)) > H(n(N-RD)) > H(n(TD-ND)) and E(n(RD-TD)) > E(n(ND-RD)) > E(n(TD-ND)). These differences were ascribed to crystallographic textures formed by rolling deformation.

  11. Computational Studies of Hard Disks: Contact Percolation, Fragility, Frictional Families and Basin Volumes (United States)

    Shen, Tianqi

    This thesis presents four computational and theoretical studies of the structural, mechanical, and vibrational properties of purely repulsive disks, dimer-, and ellipse-shaped particles with and without friction. The first study investigated the formation of interparticle contact networks below jamming onset at packing fraction φJ, where the pressure of the system becomes nonzero. We generated ensembles of static packings of frictionless disks over a range of packing fraction. We find that the network of interparticle contacts forms a system spanning cluster at a critical packing fraction φP missing contacts relative to the isostatic value N0c We show that the probability Pm(micro) to obtain a static packing with m missing contacts at micro can be expressed as a power series in micro. Using Pm(micro), we find that the average contact number versus micro agrees quantitatively with that from simulations of the Cundall-Strack model for frictional disks. In the final project, we performed calculations of the structure of the basin volumes of mechanically stable packings in configuration space as a function packing fraction. Using the basin volumes, we show that the probability to obtain a given MS packing depends strongly on the packing fraction of the initial configuration.

  12. Elastic contact conditions to optimize friction drive of surface acoustic wave motor. (United States)

    Kuribayashi Kurosawa, M; Takahashi, M; Higuchi, T


    The optimum pressing force, namely the preload, for a slider to obtain superior operation conditions in a surface acoustic wave motor have been examined. We used steel balls as sliders. The preload was controlled using a permanent magnet. The steel balls were 0.5, 1, and 2 mm diameter, with the differences in diameter making it possible to change contact conditions, such as the contact pressure, contact area, and deformation of the stator and the slider. The stator transducer was lithium niobate, 128 degrees rotated, y-cut x-propagation substrate. The driving frequency of the Rayleigh wave was about 10 MHz. Hence, the particle vibration amplitude at the surface is as small as 10 nm. For superior friction drive conditions, a high contact pressure was required. For example, in the case of the 1 mm diameter steel ball at the sinusoidal driving voltage of 180 V(peak), the slider speed was 43 cm/sec, the thrust output force was 1 mN, and the acceleration was 23 times as large as the gravitational acceleration at a contact pressure of 390 MPa. From the Hertz theory of contact stress, the contact area radius was only 3 microm. The estimation of the friction drive performance was carried out from the transient traveling distance of the slider in a 3 msec burst drive. As a result, the deformation of the stator and the slider by the preload should be half of the vibration amplitude. This condition was independent of the ball diameter and the vibration amplitude. The output thrust per square millimeter was 50 N, and the maximum speed was 0.7 m/sec. From these results, we conclude that it is possible for the surface acoustic wave motor to have a large output force, high speed, quick response, long traveling distance, and a thin micro linear actuator.

  13. Experimental studies of translation-rotational motions of rolling bodies under elastic-frictional interaction with the bases (United States)

    Plotnikov, P. K.


    Experimental studies and their results are described for the translation-rotational motion of rolling bodies subjected to forces and elastic deformations of the contact tribological conjunction regions between such bodies and the bases. Most attention is paid to the motion of such bodies outside the contact surfaces in the regions of preliminary displacements and behind these regions. In several experiments, the processes are recorded and analyzed from the very beginning to the termination of the rolling body finite displacements. All displacement stages exhibit oscillations due to variations in the character of motions of the rolling bodies. In the case where the body is only under the action of its weight, the regions of normal strains symmetric with respect to the axis of the weight action are shown as surface indentations outside the region of direct contact between the base and the rolling body. The photographs of the base nonsymmetric deformations due to the additional action of the tangential force on the rolling body are presented. One can see that the indentation slope in the motion or the force action direction is steeper and the indentation depth and length are smaller than those on the opposite side. This suggests that, on the side where the rolling body surface enters the base, the volumes of their deformations and hence the elastic force are greater than on the opposite side. The graphs are constructed for the variation in the values of preliminary and kinematic (in motion) displacements and the arm of rolling friction force for two motor cars, for a solid steel roller, and for a steel roller with two foam rubber wheels. The graphs show that, quantitatively, the displacement values are by one and more orders of magnitude greater than the values of these arms of force. Qualitatively, the arms of rolling friction force, just as the displacements, are characterized by the presence of proportionality and saturation segments of their characteristics. The

  14. The transition of dynamic rupture styles in elastic media under velocity-weakening friction

    KAUST Repository

    Gabriel, A.-A.


    Although kinematic earthquake source inversions show dominantly pulse-like subshear rupture behavior, seismological observations, laboratory experiments and theoretical models indicate that earthquakes can operate with different rupture styles: either as pulses or cracks, that propagate at subshear or supershear speeds. The determination of rupture style and speed has important implications for ground motions and may inform about the state of stress and strength of active fault zones. We conduct 2D in-plane dynamic rupture simulations with a spectral element method to investigate the diversity of rupture styles on faults governed by velocity-and-state-dependent friction with dramatic velocity-weakening at high slip rate. Our rupture models are governed by uniform initial stresses, and are artificially initiated. We identify the conditions that lead to different rupture styles by investigating the transitions between decaying, steady state and growing pulses, cracks, sub-shear and super-shear ruptures as a function of background stress, nucleation size and characteristic velocity at the onset of severe weakening. Our models show that small changes of background stress or nucleation size may lead to dramatic changes of rupture style. We characterize the asymptotic properties of steady state and self-similar pulses as a function of background stress. We show that an earthquake may not be restricted to a single rupture style, but that complex rupture patterns may emerge that consist of multiple rupture fronts, possibly involving different styles and back-propagating fronts. We also demonstrate the possibility of a super-shear transition for pulse-like ruptures. Finally, we draw connections between our findings and recent seismological observations.

  15. Elasticity

    CERN Document Server

    Soutas-Little, Robert William


    According to the author, elasticity may be viewed in many ways. For some, it is a dusty, classical subject . . . to others it is the paradise of mathematics."" But, he concludes, the subject of elasticity is really ""an entity itself,"" a unified subject deserving comprehensive treatment. He gives elasticity that full treatment in this valuable and instructive text. In his preface, Soutas-Little offers a brief survey of the development of the theory of elasticity, the major mathematical formulation of which was developed in the 19th century after the first concept was proposed by Robert Hooke

  16. Anisotropic elasticity and abnormal Poisson’s ratios in super-hard materials

    Directory of Open Access Journals (Sweden)

    Chuanwei Huang


    Full Text Available We theoretically investigated the variable mechanical properties such as Young’s modulus, Poisson’s ratios and compressibility in super-hard materials. Our tensorial analysis reveals that the mechanical properties of super-hard materials are strongly sensitive to the anisotropy index of materials. In sharp contrast to the traditional positive constant as thought before, the Poisson’s ratio of super-hard materials could be unexpectedly negative, zero, or even positive with a value much larger than the isotropic upper limit of 0.5 along definite directions. Our results uncover a correlation between compressibility and hardness, which offer insights on the prediction of new super-hard materials.


    Institute of Scientific and Technical Information of China (English)

    徐曾和; 徐小荷


    The rockburst of the coal pillar under a thick hard roof stratum is modelled as the instability failure problem of coal pillars under strata subject to elastic support. The instability mechanism of rockburst is studied by applying cusp catastrophic theory. The effects of the stiffness ratio of the system and loads imposed on the system on the rockburst are explicated.The factors affecting rockbursts are discussed. Based on them, the "evolution process, the forewarning regularity and forewarning sings of rockbursts are studied. It is indicated that the subsidence velocity of roof stratum, which increases quickly and tends to infinity, is the forewarning measurable signs of the rockbursts of coal pillar.

  18. Theoretical investigation on the electronic structure,elastic properties, and intrinsic hardness of Si2N2O

    Institute of Scientific and Technical Information of China (English)

    Ding Ying-Chun; Chen Min; Gao Xiu-Ying; Jiang Meng-Heng


    According to the density functional theory we systematically study the electronic structure,the mechanical properties and the intrinsic hardness of Si2N2O polymorphs using the first-principles method.The elastic constants of four Si2N2O structures are obtained using the stress-strain method.The mechanical moduli (bulk modulus,Young's modulus,and shear modulus) are evaluated using the Voigt-Reuss-Hill approach.It is found that the tetragonal Si2N2O exhibits a larger mechanical modulus than the other phases.Some empirical methods are used to calculate the Vickers hardnesses of the Si2N2O structures.We further estimate the Vickers hardnesses of the four Si2N2O crystal structures,suggesting all Si2N2O phases are not the superhard compounds.The results imply that the tetragonal Si2N2O is the hardest phase.The hardness of tetragonal Si2N2O is 31.52 GPa which is close to values of β-Si3N4 and γ-Si3N4.

  19. Intrinsic Correlation between Hardness and Elasticity in Polycrystalline Materials and Bulk Metallic Glasses


    Chen, Xing-Qiu; Niu, Haiyang; Li, Dianzhong; Li, Yiyi


    Though extensively studied, hardness, defined as the resistance of a material to deformation, still remains a challenging issue for a formal theoretical description due to its inherent mechanical complexity. The widely applied Teter's empirical correlation between hardness and shear modulus has been considered to be not always valid for a large variety of materials. Here, inspired by the classical work on Pugh's modulus ratio, we develop a theoretical model which establishes a robust correlat...

  20. Elastic Modulus and Hardness of Cr-Nb Nano-Multilayers

    Institute of Scientific and Technical Information of China (English)

    YANG Meng-Jin; LAI Wen-Sheng; PAN Feng


    Cr-Nb nano-multilayered films with various modulation wavelengths ∧ are prepared by e-gun evaporation and their mechanical properties are investigated. Cr and Nb both have bcc structures with large differences in lattice constants and Young's modulus, which are supposed to favour modulus enhancement. Nevertheless,nano-indention measurements show no enhancement for the modulus and a slight decrease for the hardness with decreasing ∧ down to 6 nm. This is mainly due to counter-contribution to modulus from adjacent layers subjected to reverse strains, in agreement with recent theoretical study, while the decrease of hardness arises from grain boundary sliding. Interestingly, at ∧ = 3 nm, the hardness of the film has an increase of 44% relative to the value of a rule of mixture, owing to the emergence of a new phase for reconciling the structure difference at the interfaces.

  1. On the nature of the static friction, kinetic friction and creep

    DEFF Research Database (Denmark)

    Persson, B. N. J.; Albohr, O.; Mancosu, F.


    In this paper, we discuss the nature of the static and kinetic friction, and of (thermally activated) creep.We focus on boundary lubrication at high confining pressure (∼1GPa), as is typical for hard solids, where one or at most two layers of confined molecules separates the sliding surfaces. We...... may depend linearly on ln (v/v0), as usually observed experimentally, rather than non-linearly [−ln (v/v0)]2/3 as predicted by a simple theory of activated processes. We also discuss the role of elasticity at stop and start. We show that for "simple" rubber (at low start velocity), the static friction...

  2. Effect of elastic-plastic behavior of coating layer on drawability and frictional characteristic of galvannealed steel sheets

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Seong Won; Lee, Jung Min [Korea Institute of Industrial Technology, Jinju (Korea, Republic of); Joun, Man Soo [Gyeongsang National University, Jinju (Korea, Republic of); Kim, Dong Hwan [International University of Korea, Jinju (Korea, Republic of)


    During a galvannealed sheet metal forming, the failures of coating layers (powdering, flaking and cracking) frequently affect the strain state of sheets and deteriorate the frictional characteristic between sheets and tools. Two FE-models in this study were suggested to investigate the effects of the mechanical behavior of coating layers on the formability and friction of the coated steel sheets in FE analysis; the first is one-layer model to express the coated sheet as one stress-strain curve and the second is a multiple-layer model which is composed of substrates and coating layers, separately. First, the frictional properties and the formability of the coated sheets were experimentally investigated using a cup deep-drawing trial. After, the drawing process was simulated by FE analysis of the two models. In the multiplelayer model, the mechanical behavior of the coating is defined as a stress-strain curve which was determined using the nanoindentation test of the coating, its FE analysis and artificial neural network method. The result showed that the multiple-layer model provides more accuracy predictions of drawing loads than the one-layer model in the FE analysis, compared to the actual cup drawing test.

  3. Extended-Kalman-filter-based regenerative and friction blended braking control for electric vehicle equipped with axle motor considering damping and elastic properties of electric powertrain (United States)

    Lv, Chen; Zhang, Junzhi; Li, Yutong


    Because of the damping and elastic properties of an electrified powertrain, the regenerative brake of an electric vehicle (EV) is very different from a conventional friction brake with respect to the system dynamics. The flexibility of an electric drivetrain would have a negative effect on the blended brake control performance. In this study, models of the powertrain system of an electric car equipped with an axle motor are developed. Based on these models, the transfer characteristics of the motor torque in the driveline and its effect on blended braking control performance are analysed. To further enhance a vehicle's brake performance and energy efficiency, blended braking control algorithms with compensation for the powertrain flexibility are proposed using an extended Kalman filter. These algorithms are simulated under normal deceleration braking. The results show that the brake performance and blended braking control accuracy of the vehicle are significantly enhanced by the newly proposed algorithms.

  4. Effect of TiO2 Particles on Micro-Hardness Corrosion, Wear and Friction of Ni-P-TiO2 Composite Coatings at Different Annealing Temperatures (United States)

    Gadhari, Prasanna; Sahoo, Prasanta


    The present study investigates the effect of titania particles on the micro-hardness, wear resistance, corrosion resistance and friction of electroless Ni-P-TiO2 composite coatings deposited on mild steel substrates at different annealing temperatures. The experimental results confirmed that the amount of TiO2 particles incorporated in the coatings increases with increase in the concentration of particles in the electroless bath. In presence of TiO2 particles, hardness, wear resistance and corrosion resistance of the coating improve significantly. At higher annealing temperature, wear resistance increases due to formation of hard Ni3P phase and incorporation of titania particles in the coated layer. Charge transfer resistance and corrosion current density of the coatings reduce with an increase in TiO2 particles, whereas corrosion potential increases. Microstructure changes and composition of the composite coating due to heat treatment are studied with the help of scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDXA) and X-ray diffraction (XRD) analysis.

  5. Theory of nonlinear elasticity, stress-induced relaxation, and dynamic yielding in dense fluids of hard nonspherical colloids. (United States)

    Zhang, Rui; Schweizer, Kenneth S


    We generalize the microscopic naïve mode coupling and nonlinear Langevin equation theories of the coupled translation-rotation dynamics of dense suspensions of uniaxial colloids to treat the effect of applied stress on shear elasticity, cooperative cage escape, structural relaxation, and dynamic and static yielding. The key concept is a stress-dependent dynamic free energy surface that quantifies the center-of-mass force and torque on a moving colloid. The consequences of variable particle aspect ratio and volume fraction, and the role of plastic versus double glasses, are established in the context of dense, glass-forming suspensions of hard-core dicolloids. For low aspect ratios, the theory provides a microscopic basis for the recently observed phenomenon of double yielding as a consequence of stress-driven sequential unlocking of caging constraints via reduction of the distinct entropic barriers associated with the rotational and translational degrees of freedom. The existence, and breadth in volume fraction, of the double yielding phenomena is predicted to generally depend on both the degree of particle anisotropy and experimental probing frequency, and as a consequence typically occurs only over a window of (high) volume fractions where there is strong decoupling of rotational and translational activated relaxation. At high enough concentrations, a return to single yielding is predicted. For large aspect ratio dicolloids, rotation and translation are always strongly coupled in the activated barrier hopping event, and hence for all stresses only a single yielding process is predicted.

  6. Measurement of elastic modulus and Vickers hardness of surround bone implant using dynamic microindentation--parameters definition. (United States)

    Soares, Priscilla Barbosa Ferreira; Nunes, Sarah Arantes; Franco, Sinésio Domingues; Pires, Raphael Rezende; Zanetta-Barbosa, Darceny; Soares, Carlos José


    The clinical performance of dental implants is strongly defined by biomechanical principles. The aim of this study was to quantify the Vicker's hardness (VHN) and elastic modulus (E) surround bone to dental implant in different regions, and to discuss the parameters of dynamic microindantion test. Ten cylindrical implants with morse taper interface (Titamax CM, Neodent; 3.5 mm diameter and 7 mm a height) were inserted in rabbit tibia. The mechanical properties were analyzed using microhardness dynamic indenter with 200 mN load and 15 s penetration time. Seven continuous indentations were made distancing 0.08 mm between each other perpendicularly to the implant-bone interface towards the external surface, at the limit of low (Lp) and high implant profile (Hp). Data were analyzed by Student's t-test (a=0.05) to compare the E and VHN values obtained on both regions. Mean and standard deviation of E (GPa) were: Lp. 16.6 ± 1.7, Hp. 17.0 ± 2.5 and VHN (N/mm2): Lp. 12.6 ± 40.8, Hp. 120.1 ± 43.7. No statistical difference was found between bone mechanical properties of high and low profile of the surround bone to implant, demonstrating that the bone characterization homogeneously is pertinent. Dynamic microindantion method proved to be highly useful in the characterization of the individual peri-implant bone tissue.

  7. Role of nitrogen in the formation of hard and elastic CNx thin films by reactive magnetron sputtering (United States)

    Hellgren, Niklas; Johansson, Mats P.; Broitman, Esteban; Hultman, Lars; Sundgren, Jan-Eric


    Carbon nitride films, deposited by reactive dc magnetron sputtering in Ar/N2 discharges, were studied with respect to composition, structure, and mechanical properties. CNx films, with 0<=x<=0.35, were grown onto Si (001) substrates at temperatures between 100 and 550 °C. The total pressure was kept constant at 3.0 mTorr with the N2 fraction varied from 0 to 1. As-deposited films were studied by Rutherford-backscattering spectroscopy, x-ray photoelectron spectroscopy, electron-energy loss spectroscopy, Raman and Fourier transform infrared spectroscopy, and nanoindentation. Three characteristic film structures could be identified: For temperatures below ~150 °C, an amorphous phase forms, the properties of which are essentially unaffected by the nitrogen concentration. For temperatures above ~200 °C, a transition from a graphitelike phase to a ``fullerenelike'' phase is observed when the nitrogen concentration increases from ~5 to ~15 at. %. This fullerenelike phase exhibits high hardness values and extreme elasticity, as measured by nanoindentation. A ``defected-graphite'' model, where nitrogen atoms goes into substitutional graphite sites, is suggested for explaining this structural transformation. When a sufficient number of nitrogen atoms is incorporated, formation of pentagons is promoted, leading to curving of the basal planes. This facilitates cross-linking between the planes and a distortion of the graphitic structure, and a strong three-dimensional covalently bonded network is formed.

  8. Structure, elastic stiffness, and hardness of Os 1- xRu xB 2 solid solution transition-metal diborides

    KAUST Repository

    Kanoun, Mohammed


    On the basis of recent experiments, the solid solution transition-metal diborides were proposed to be new ultra-incompressible hard materials. We investigate using density functional theory based methods the structural and mechanical properties, electronic structure, and hardness of Os 1-xRu xB 2 solid solutions. A difference in chemical bonding occurs between OsB 2 and RuB 2 diborides, leading to significantly different elastic properties: a large bulk, shear moduli, and hardness for Os-rich diborides and relatively small bulk, shear moduli, and hardness for Ru-rich diborides. The electronic structure and bonding characterization are also analyzed as a function of Ru-dopant concentration in the OsB 2 lattice. © 2012 American Chemical Society.

  9. Microstructural Characterization and Hardness Evaluation of Friction Stir Welded Composite AA6061-4.5Cu-5SiC (Wt.%

    Directory of Open Access Journals (Sweden)

    A.K. Shettigar


    Full Text Available Recent developments in advanced materials research have led to the emergence of new materials having features like low density, high strength to weight ratio, excellent mechanical properties, heat and corrosion resistance. In friction stir welding (FSW, a non-consumable rotating welding tool is used to generate the frictional heat and plastic deformation of the material in the welding zone, which is in the solid state. The advantages of FSW as compared to the fusion welding are high joint strength, less defect weld, uniform distribution of grain structure in the weld zone and low power consumption. AA6061with 4.5 % weight of copper and 5 % weight of SiC composite material has been prepared to conduct experiment and carry out characterization, evaluation of the mechanical properties. Micro-structural characterization of the weld zone is carried out by scanning electron microscope (SEM. Evaluation of hardness was also carried out across the weld zone. A successful method for FSW of AA6061-4.5(wt.% Cu-5(wt.% SiC has been developed.Defence Science Journal, 2013, 63(4, pp.429-434, DOI:

  10. Microstructural Characterization and Hardness Evaluation of Friction Stir Welded Composite AA6061-4.5Cu-5SiC (Wt.%

    Directory of Open Access Journals (Sweden)

    A.K. Shettigar


    Full Text Available Recent developments in advanced materials research have led to the emergence of new materials having features like low density, high strength to weight ratio, excellent mechanical properties, heat and corrosion resistance. In friction stir welding (FSW, a non-consumable rotating welding tool is used to generate the frictional heat and plastic deformation of the material in the welding zone, which is in the solid state. The advantages of FSW as compared to the fusion welding are high joint strength, less defect weld, uniform distribution of grain structure in the weld zone and low power consumption. AA6061with 4.5 % weight of copper and 5 % weight of SiC composite material has been prepared to conduct experiment and carry out characterization, evaluation of the mechanical properties. Micro-structural characterization of the weld zone is carried out by scanning electron microscope (SEM. Evaluation of hardness was also carried out across the weld zone. A successful method for FSW of AA6061-4.5(wt.% Cu-5(wt.% SiC has been developed.

  11. Influence of microstructural evolution on mechanical behavior of Fe–Nb–B ultrafine composites with a correlation to elastic modulus and hardness

    Energy Technology Data Exchange (ETDEWEB)

    Kim, J.T.; Hong, S.H.; Park, H.J.; Park, G.H. [Hybrid Materials Center (HMC), Faculty of Nanotechnology and Advanced Materials Engineering, Sejong University, 209 Neugdong-ro, Gwangjin-gu, Seoul 143-747 (Korea, Republic of); Suh, J.Y. [High Temperature Energy Materials Research Center, Korea Institute of Science and Technology, Hwarangno 14-gil 5, Seoungbuk-gu, Seoul 136-791 (Korea, Republic of); Park, J.M., E-mail: [Global Technology Center, Samsung Electronics Co., Ltd, 129 Samsung-ro, Yeongtong-gu, Suwon-si, Gyeonggi-do 443-742 (Korea, Republic of); Kim, K.B., E-mail: [Hybrid Materials Center (HMC), Faculty of Nanotechnology and Advanced Materials Engineering, Sejong University, 209 Neugdong-ro, Gwangjin-gu, Seoul 143-747 (Korea, Republic of)


    In this study, we explore the microstructural modulation and mechanical properties of Fe–Nb–B ultrafine composites by the addition of boron. According to the evolution of microstructure, mechanical properties including yield strength and plastic strain were significantly changed. With increase of boron content, Fe–B type compounds were newly formed and eutectic structured matrix was concurrently altered. Newly formed phases with high hardness/elastic modulus leads to considerably increase the yield strength up to 3110 MPa but macroscopic plasticity is deteriorated inadequately. To understand the origin of critically changed macroscopic mechanical properties, the values of hardness and elastic modulus obtained from nanoindentation test were plotted and demonstrated as a contour map. The structural characterization and nano-scale mechanical analysis are capable of providing the clear evidence to understand the relationship between microstructure and mechanical properties of the ultrafine multi-phase composites. - Highlights: • Fe–Nb–B heterogeneous ultrafine eutectic composites. • Nano-scale mechanical analysis has been performed by nanoindentation test. • Relationship between microstructural heterogeneity and mechanical coherency. • Hardness and elastic modulus were plotted as a mechanical contour map.

  12. Analysis of Equilibrium with Friction of an Elastic Rod Constrained by a Cylindrical Surface%受圆柱面约束弹性细杆的摩擦平衡分析

    Institute of Scientific and Technical Information of China (English)

    薛纭; 刘昭


    Under background of a class of engineering object,the problem of equilibrium with friction of an elastic rod constrained by a cylindrical surface was investigated in this paper.On the basis of the analysis of the configuration and the motion of the circular-cross-section elastic rod constrained by the cylindrical surface,differential equations of the equilibrium with the distributed friction were derived and transformed into dimensionless form.Conditions for the existence of solutions of the screw rod without the friction were obtained,as well as conditions for no relative sliding between the elastic rod and the cylinder surface with the friction.It was found that the deformation expressed by the first derivative of nutation angle and the second derivative of since angle with respect to the arc coordinate was induced by the distributed friction.For five types of special configuration of elastic rod in equilibrium,principal vector of internal forces on cross sections of the rod and distributions of friction force were predicted analytically.Then some types were discussed numerically to determine whether the rod would be balanced.This paper provides possible methods and ideas for further studying the statics and the dynamics of elastic rods constrained by surfaces with friction.%以一类工程对象为背景,研究圆柱面约束下的弹性杆的摩擦平衡问题.在对圆柱面上圆截面弹性杆位形和运动分析的基础上,导出了计入分布摩擦力的弹性杆平衡微分方程并无量纲化.由此得到了无摩擦时螺旋杆解的存在条件,以及存在摩擦时的不滑动的条件.分析表明,截面章动角对弧坐标的一阶导数和自转角对弧坐标的二阶导数表达的变形是分布摩擦力所致.就5类特殊的平衡位形,分别计算了内力和分布摩擦力集度,部分进行了数值计算,给予了静止与否的判定.为曲面上弹性杆的摩擦平衡或动力学分析提供方法和思路.

  13. Tribological properties of metal-matrix composite materials reinforced by superelastic hard carbon particles (United States)

    Ushakova, I. N.; Drozdova, E. I.; Chernogorova, O. P.; Blinov, V. M.; Ekimov, E. A.


    Metal-matrix composite materials (CMs) are synthesized from a mixture of a metal powder (Ti, Fe, Co, Ni, Cu, Al-based alloy) and fullerenes (10 wt %). The thermobaric synthesis conditions (700-1000°C, 5-8 GPa) ensure the collapse of fullerene molecules and their transformation into superelastic carbon phase particles with an indentation hardness H IT = 10-37 GPa, an elastic modulus E IT = 60-260 GPa, and an elastic recovery of >80% upon indentation. After reinforcing by superelastic hard carbon, the friction coefficient of CM decreases by a factor of 2-4 as compared to the friction coefficient of the matrix metal, and the abrasive wear resistance increases by a factor of 4-200. Superelastic hard carbon particles are a unique reinforcing material for an increase in the wear resistance and a simultaneous decrease in the friction coefficient of CM.

  14. Friction characteristics of trocars in laparoscopic surgery. (United States)

    Alazmani, Ali; Roshan, Rupesh; Jayne, David G; Neville, Anne; Culmer, Peter


    This article investigates the friction characteristics of the instrument-trocar interface in laparoscopic surgery for varying linear instrument velocities, trocar seal design and material, and trocar tilt. Furthermore, the effect of applying lubrication at the instrument-trocar seal interface on friction was studied. A friction testing apparatus was designed and built to characterise the resistance force at the instrument-trocar interface as a function of the instrument's linear movement in the 12-mm trocar (at constant velocity) for different design, seal material, and angle of tilt. The resistance force depended on the trocar seal design and material properties, specifically surface roughness, elasticity, hardness, the direction of movement, and the instrument linear velocity, and varied between 0.25 and 8 N. Lubricating the shaft with silicone oil reduced the peak resistance force by 75% for all trocars and eliminated the stick-slip phenomenon evident in non-lubricated cases. The magnitude of fluctuation in resistance force depends on the trocar design and is attributed to stick-slip of the sealing mechanism and is generally higher during retraction in comparison to insertion. Trocars that have an inlet seal made of rubber/polyurethane showed higher resistance forces during retraction. Use of a lubricant significantly reduced frictional effects. Comparisons of the investigated trocars indicate that a low friction port, providing the surgeon with improved haptic feedback, can be designed by improving the tribological properties of the trocar seal interface.

  15. Structural, elastic constants, hardness, and optical properties of pyrite-type dinitrides (CN 2, SiN 2, GeN 2) (United States)

    Ding, Y. C.; Xiang, A. P.; He, X. J.; Hu, X. F.


    The crystal structures, band structures, elastic constants, hardness, and optical properties of pyrite-type dinitrides (CN 2, SiN 2, and GeN 2) are obtained from the density functional theory using the plane-wave pseudopotential (PWP) method within the local density and generalized gradient approximations. The formation enthalpies for AN 2 (A=C, Si, and Ge) compounds suggest the three structures that are stable. The calculated band structures show the indirect gaps ( Γ-R) in CN 2, SiN 2, and GeN 2. The intrinsic hardnesses of AN 2 (A=C, Si, and Ge ) compounds are calculated. Our results show that the cubic CN 2 and SiN 2 are superhard materials. Furthermore, we studied the optical properties such as the complex dielectric function and the electron energy loss spectra.

  16. Correlation between Mechanical Properties with Specific Wear Rate and the Coefficient of Friction of Graphite/Epoxy Composites


    Mahdi Alajmi; Abdullah Shalwan


    The correlation between the mechanical properties of Fillers/Epoxy composites and their tribological behavior was investigated. Tensile, hardness, wear, and friction tests were conducted for Neat Epoxy (NE), Graphite/Epoxy composites (GE), and Data Palm Fiber/Epoxy with or without Graphite composites (GFE and FE). The correlation was made between the tensile strength, the modulus of elasticity, elongation at the break, and the hardness, as an individual or a combined factor, with the specific...

  17. A Pedagogical Model of Static Friction

    CERN Document Server

    Pickett, Galen T


    While dry Coulombic friction is an elementary topic in any standard introductory course in mechanics, the critical distinction between the kinetic and static friction forces is something that is both hard to teach and to learn. In this paper, I describe a geometric model of static friction that may help introductory students to both understand and apply the Coulomb static friction approximation.

  18. Design of Milling Cutter of Frictional Hard Alloy Mechanical Clamped Grooves%可磨式机夹硬质合金铣槽刀的设计

    Institute of Scientific and Technical Information of China (English)



    The problems of production in mechanical processing was prescribed because of cutter factors, such as pieces with grooves when that were processing with normal cutter, which maybe occur the problems as low production efficiency, poor product quality, vulnerable cutter, hard respiring cutter and serious waste. But the design and making of new type of frictional hard alloy mechanical clamped grooves have soled the difficult problem of processing. After milling the cutter tooth, the cutter tooth can be took off for milling knife edge, collate knifepoint of knife edge with own made tool setting gauge, and process cutter edge installed on tool shank again. The new type of groove knife can be applied in normal milling lather or CNC milling lather, which can milling grooves, planes and head faces, and can set tool outside machine, reduce occupation time with the characteristics of convenient operation, simple structure, high efficiency, low cost. It is proved that it can meet the requirements of processing.%主要阐述了机械加工中刀具因素给生产带来的困扰,如经常会遇到加工一些带沟槽的零件,使用常规刀具加工零件,生产效率低、产品质量难保证、刀具易损坏且修复困难、浪费严重.而新型可磨式机夹硬质合金铣槽刀的设计与制作,解决了加工中的难题.当刀齿磨后,可将刀齿取下修磨刀刃,用自制的对刀仪校对刀齿刀尖,重新把刀齿安装在刀柄上加工.这种新型铣沟槽刀可在普通铣床或数控铣床上使用,可铣沟槽、平面和端面,可机外对刀,减少占机时间,操作简便,结构简单,工效高,成本低.实践证明,新型可磨式机夹硬质合金铣槽刀能满足加工需求.

  19. Energy Balance of Friction and Friction Coefficient in Energetical Interpretation

    Directory of Open Access Journals (Sweden)

    S.V. Fedorov


    Full Text Available Sliding friction energy model is proposed. In this model, generalized mechanism of transformation and dissipation of energy under friction the model of elastic-plastic deformation and fracture contact volumes is considered. Energy model of the process of plastic deformation and destruction of solid bodies is based on the concept of ergodynamic of deformable bodies. Equations of energy balance of friction within the structural and energetic interpretation of deformation are proposed. The energy interpretation of the coefficient of friction is showed. From this position the friction coefficient is the most informative characteristic of the process. Experimental friction curves have been generalized. As a result of the energy analysis of friction, the energy diagram of the structural evolution of the friction surfaces is suggested.

  20. 水分对猪牙表面硬度和摩擦系数的影响%Effect of Water Content on the Hardness and Friction Coefficient of Swine Teeth Enamel

    Institute of Scientific and Technical Information of China (English)

    华李成; 郑靖; 周仲荣


    本文采用猪牙为研究对象,通过干燥和浸泡处理来控制猪牙釉质中的水分含量,利用维氏硬度仪和纳米压痕/划痕仪,研究了水分对离体生物硬组织力学性能和摩擦学特性的影响.结果表明:水含量能引起猪牙釉质表层硬度和摩擦系数的恢复性变化.猪牙表层硬度会随着水分的减少而升高,在水分再次增加后回落.猪牙表面摩擦系数随着水分的减少而降低,在水分再次增加后回升.%The mechanical properties and micro-friction behavior of swine tooth were investigated after various drying treatments,using Vicker's indentation test machine and nano-hardness/scratch tester.Moreover,the recovery of swine tooth's mechanical properties in water was investigated by immersing the dried enamel specimens in deionized water.The objective of this study is to explore the effect of water on biological hard tissue.The results show that the hardness and friction coefficient of swine tooth enamel were associated with its water content.The surface hardness of swine tooth enamel increased with the reduction of water,but the friction coefficient of swine tooth enamel decreased,and they were recovered significantly after water-immersing treatment.

  1. Friction in orthodontics (United States)

    Prashant, P. S.; Nandan, Hemant; Gopalakrishnan, Meera


    Conventional wisdom suggests that resistance to sliding (RS) generated at the wire-bracket interface has a bearing on the force transmitted to the teeth. The relative importance of static and kinetic friction and also the effect of friction on anchorage has been a topic of debate. Lot of research work has been done to evaluate the various factors that affect friction and thus purportedly retards the rate of tooth movement. However, relevancy of these studies is questionable as the methodology used hardly simulates the oral conditions. Lately studies have concluded that more emphasis should be laid on binding and notching of archwires as these are considered to be the primary factors involved in retarding the tooth movement. This article reviews the various components involved in RS and the factors affecting friction. Further, research work should be carried out to provide cost effective alternatives aimed at reducing friction. PMID:26538873

  2. Polymer friction Molecular Dynamics

    DEFF Research Database (Denmark)

    Sivebæk, Ion Marius; Samoilov, Vladimir N.; Persson, Bo N. J.

    We present molecular dynamics friction calculations for confined hydrocarbon solids with molecular lengths from 20 to 1400 carbon atoms. Two cases are considered: a) polymer sliding against a hard substrate, and b) polymer sliding on polymer. In the first setup the shear stresses are relatively...... independent of molecular length. For polymer sliding on polymer the friction is significantly larger, and dependent on the molecular chain length. In both cases, the shear stresses are proportional to the squeezing pressure and finite at zero load, indicating an adhesional contribution to the friction force....

  3. Influence of Stress History on Elastic and Frictional Properties of Core Material from IODP Expeditions 315 and 316, NanTroSEIZE Transect: Implications for the Nankai Trough Accretionary Prism (United States)

    Knuth, M. W.; Tobin, H. J.; Marone, C.; Saffer, D. M.; Hashimoto, Y.


    We present results of ultrasonic P and S-wave velocity measurements on core material recovered during NanTroSEIZE Stage 1 Expeditions 315 and 316 to the Nankai Trough Accretionary Margin, focusing on how different stress paths during subduction and exhumation along regional thrust faults influence the elastic moduli and anisotropy of various components of the accretionary prism. The influence of changes in pore pressure and confining pressure on the elastic properties of prism material has important implications for its mechanical strength, and understanding how elastic properties change along various stress paths will help us use 3D seismic tomography to draw inferences about overpressurization and fluid flow within the accretionary prism. We compare the velocities measured during shipboard physical properties characterization and logging-while-drilling data from Expedition 314 with 3D seismic velocity data and the results of previous shore-based studies to establish in situ conditions for material at various locations within the prism. We test both intact core material and disaggregated gouge and unlithified sediments from the upper prism, subjecting both samples types to a progression of confining pressure, pore pressure, and axial loading conditions representing normal consolidation and overconsolidation stress paths due to compaction and dewatering during burial and subsequent uplift by thrust faulting. While making continuous ultrasonic velocity measurements to determine changes in dynamic and quasistatic elastic moduli during axial and isotropic loading, we also subject granular material to frictional shear in a biaxial double-direct shearing configuration to measure how its frictional properties vary as a function of stress history.

  4. Elasticity, Hardness and Thermal Conductivity of Si-Ge-Based Oxynitrides (SiGeN2O) (United States)

    Ding, Yingchun; Chen, Min; Wu, Wenjuan; Xu, Ming


    Capitalizing on density functional theory, the novel Si-Ge-based oxynitrides (SiGeN2O) have been studied in terms of mechanical and thermal properties. Regarding α- or β-SiGeN2O, the SiGeN2O exhibits smaller mechanical moduli, suggesting a compressible and soft material. Our calculated lattice constants of two SiGeN2O phases are very consistent with other values. In addition, the hardness for SiGeN2O is investigated in details according to different semi-empirical methods. The results indicate a small hardness of two phases of SiGeN2O. Furthermore, the mechanical anisotropy, Debye temperature and the minimum thermal conductivity of two SiGeN2O compounds are clearly estimated for both SiGeN2O compounds. It is found that the SiGeN2O compounds show low thermal conductivity, which is suitable to be used as a thermal barrier coating.

  5. Elasticity, Hardness and Thermal Conductivity of Si-Ge-Based Oxynitrides (SiGeN2O) (United States)

    Ding, Yingchun; Chen, Min; Wu, Wenjuan; Xu, Ming


    Capitalizing on density functional theory, the novel Si-Ge-based oxynitrides (SiGeN2O) have been studied in terms of mechanical and thermal properties. Regarding α- or β-SiGeN2O, the SiGeN2O exhibits smaller mechanical moduli, suggesting a compressible and soft material. Our calculated lattice constants of two SiGeN2O phases are very consistent with other values. In addition, the hardness for SiGeN2O is investigated in details according to different semi-empirical methods. The results indicate a small hardness of two phases of SiGeN2O. Furthermore, the mechanical anisotropy, Debye temperature and the minimum thermal conductivity of two SiGeN2O compounds are clearly estimated for both SiGeN2O compounds. It is found that the SiGeN2O compounds show low thermal conductivity, which is suitable to be used as a thermal barrier coating.

  6. Structural, phase stability, electronic, elastic properties and hardness of IrN{sub 2} and zinc blende IrN: First-principles calculations

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Zhaobo [Key Laboratory of Advanced Materials of Yunnan Province & Key Laboratory of Advanced Materials of Non-Ferrous and Precious Rare Metals Ministry of Education, Kunming University of Science and Technology, Kunming 650093 (China); Zhou, Xiaolong, E-mail: [Key Laboratory of Advanced Materials of Yunnan Province & Key Laboratory of Advanced Materials of Non-Ferrous and Precious Rare Metals Ministry of Education, Kunming University of Science and Technology, Kunming 650093 (China); Zhang, Kunhua [State Key Laboratory of Rare Precious Metals Comprehensive Utilization of New Technologies, Kunming Institute of Precious Metals, Kunming 650106 (China)


    First-principle calculations were performed to investigate the structural, phase stability, electronic, elastic properties and hardness of monoclinic structure IrN{sub 2} (m-IrN{sub 2}), orthorhombic structure IrN{sub 2} (o-IrN{sub 2}) and zinc blende structure IrN (ZB IrN). The results show us that only m-IrN{sub 2} is both thermodynamic and dynamic stability. The calculated band structure and density of states (DOS) curves indicate that o-IrN{sub 2} and ZB Ir-N compounds we calculated have metallic behavior while m-IrN{sub 2} has a small band gap of ~0.3 eV, and exist a common hybridization between Ir-5d and N-2p states, which forming covalent bonding between Ir and N atoms. The difference charge density reveals the electron transfer from Ir atom to N atom for three Ir-N compounds, which forming strong directional covalent bonds. Notable, a strong N-N bond appeared in m-IrN{sub 2} and o-IrN{sub 2}. The ratio of bulk to shear modulus (B/G) indicate that three Ir-N compounds we calculated are ductile, and ZB IrN possesses a better ductility than two types IrN{sub 2}. m-IrN{sub 2} has highest Debye temperature (736 K), illustrating it possesses strongest covalent bonding. The hardness of three Ir-N compounds were also calculated, and the results reveal that m-IrN{sub 2} (18.23 GPa) and o-IrN{sub 2} (18.02 GPa) are ultraincompressible while ZB IrN has a negative value, which may be attributed to phase transition at ca. 1.98 GPa.

  7. Solid friction between soft filaments

    CERN Document Server

    Ward, Andrew; Schwenger, Walter; Welch, David; Lau, A W C; Vitelli, Vincenzo; Mahadevan, L; Dogic, Zvonimir


    Any macroscopic deformation of a filamentous bundle is necessarily accompanied by local sliding and/or stretching of the constituent filaments. Yet the nature of the sliding friction between two aligned filaments interacting through multiple contacts remains largely unexplored. Here, by directly measuring the sliding forces between two bundled F-actin filaments, we show that these frictional forces are unexpectedly large, scale logarithmically with sliding velocity as in solid-like friction, and exhibit complex dependence on the filaments' overlap length. We also show that a reduction of the frictional force by orders of magnitude, associated with a transition from solid-like friction to Stokes' drag, can be induced by coating F-actin with polymeric brushes. Furthermore, we observe similar transitions in filamentous microtubules and bacterial flagella. Our findings demonstrate how altering a filament's elasticity, structure and interactions can be used to engineer interfilament friction and thus tune the prop...

  8. Frictional and mechanical properties of diamond-like carbon-coated orthodontic brackets. (United States)

    Muguruma, Takeshi; Iijima, Masahiro; Brantley, William A; Nakagaki, Susumu; Endo, Kazuhiko; Mizoguchi, Itaru


    This study investigated the effects of a diamond-like carbon (DLC) coating on frictional and mechanical properties of orthodontic brackets. DLC films were deposited on stainless steel brackets using the plasma-based ion implantation/deposition (PBIID) method under two different atmospheric conditions. As-received metal brackets served as the control. Two sizes of stainless steel archwires, 0.018 inch diameter and 0.017 × 0.025 inch cross-section dimensions, were used for measuring static and kinetic friction by drawing the archwires through the bracket slots, using a mechanical testing machine (n = 10). The DLC-coated brackets were observed with a scanning electron microscope (SEM). Values of hardness and elastic modulus were obtained by nanoindentation testing (n = 10). Friction forces were compared by one-way analysis of variance and the Scheffé test. The hardness and elastic modulus of the brackets were compared using Kruskal-Wallis and Mann-Whitney U-tests. SEM photomicrographs showed DLC layers on the bracket surfaces with thickness of approximately 5-7 μm. DLC-coated brackets deposited under condition 2 showed significantly less static frictional force for the stainless steel wire with 0.017 × 0.025 inch cross-section dimensions than as-received brackets and DLC-coated brackets deposited under condition 1, although both DLC-coated brackets showed significantly less kinetic frictional force than as-received brackets. The hardness of the DLC layers was much higher than that of the as-received bracket surfaces. In conclusion, the surfaces of metal brackets can be successfully modified by the PBIID method to create a DLC layer, and the DLC-coating process significantly reduces frictional forces.

  9. Rubber friction on (apparently) smooth lubricated surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Mofidi, M; Prakash, B [Division of Machine Elements, Luleaa University of Technology, Luleaa SE-97187 (Sweden); Persson, B N J [IFF, FZ-Juelich, 52425 Juelich (Germany); Albohr, O [Pirelli Deutschland AG, 64733 Hoechst/Odenwald, Postfach 1120 (Germany)


    We study rubber sliding friction on hard lubricated surfaces. We show that even if the hard surface appears smooth to the naked eye, it may exhibit short-wavelength roughness, which may make the dominant contribution to rubber friction. That is, the observed sliding friction is mainly due to the viscoelastic deformations of the rubber by the counterface surface asperities. The results presented are of great importance for rubber sealing and other rubber applications involving (apparently) smooth surfaces.

  10. Rubber friction on (apparently) smooth lubricated surfaces (United States)

    Mofidi, M.; Prakash, B.; Persson, B. N. J.; Albohr, O.


    We study rubber sliding friction on hard lubricated surfaces. We show that even if the hard surface appears smooth to the naked eye, it may exhibit short-wavelength roughness, which may make the dominant contribution to rubber friction. That is, the observed sliding friction is mainly due to the viscoelastic deformations of the rubber by the counterface surface asperities. The results presented are of great importance for rubber sealing and other rubber applications involving (apparently) smooth surfaces.

  11. Dynamics of Elastic Excitable Media

    CERN Document Server

    Cartwright, J H E; Hernández-García, E; Piro, O; Cartwright, Julyan H. E.; Eguiluz, Victor M.; Hernandez-Garcia, Emilio; Piro, Oreste


    The Burridge-Knopoff model of earthquake faults with viscous friction is equivalent to a van der Pol-FitzHugh-Nagumo model for excitable media with elastic coupling. The lubricated creep-slip friction law we use in the Burridge-Knopoff model describes the frictional sliding dynamics of a range of real materials. Low-dimensional structures including synchronized oscillations and propagating fronts are dominant, in agreement with the results of laboratory friction experiments. Here we explore the dynamics of fronts in elastic excitable media.

  12. Friction surfaced Stellite6 coatings

    Energy Technology Data Exchange (ETDEWEB)

    Rao, K. Prasad; Damodaram, R. [Department of Metallurgical and Materials Engineering - Indian Institute of Technology Madras, Chennai 600 036 (India); Rafi, H. Khalid, E-mail: [Department of Metallurgical and Materials Engineering, Indian Institute of Technology Madras, Chennai 600 036 (India); Ram, G.D. Janaki [Department of Metallurgical and Materials Engineering, Indian Institute of Technology Madras, Chennai 600 036 (India); Reddy, G. Madhusudhan [Metal Joining Group, Defence Metallurgical Research Laboratory (DMRL) Kanchanbagh, Hyderabad 500 058 (India); Nagalakshmi, R. [Welding Research Institute, Bharat Heavy Electricals Limited, Tiruchirappalli 620 014 (India)


    Solid state Stellite6 coatings were deposited on steel substrate by friction surfacing and compared with Stellite6 cast rod and coatings deposited by gas tungsten arc and plasma transferred arc welding processes. Friction surfaced coatings exhibited finer and uniformly distributed carbides and were characterized by the absence of solidification structure and compositional homogeneity compared to cast rod, gas tungsten arc and plasma transferred coatings. Friction surfaced coating showed relatively higher hardness. X-ray diffraction of samples showed only face centered cubic Co peaks while cold worked coating showed hexagonally close packed Co also. - Highlights: Black-Right-Pointing-Pointer Stellite6 used as coating material for friction surfacing. Black-Right-Pointing-Pointer Friction surfaced (FS) coatings compared with casting, GTA and PTA processes. Black-Right-Pointing-Pointer Finer and uniformly distributed carbides in friction surfaced coatings. Black-Right-Pointing-Pointer Absence of melting results compositional homogeneity in FS Stellite6 coatings.

  13. Kinetic Friction Coefficient of Ice, (United States)


    For the hardest ice tested (xi = 0.33 described by Rabinowicz (1965), where To is inter- mm, H, = 1525 kPa), the calculated values of a preted as...material with a low elastic pressures. The frictional force was measured at modulus ( Rabinowicz 1965). It has been observed the application point of...tion 10, pp. 8-16. Barnes, P. and D. Tabor (1966) Plastic flow and Rabinowicz , E. (1965) Friction and Wear of Mate- pressure melting in the deformation

  14. 船舶齿轮箱硬弹性隔振技术研究%Research of Hard Elastic Isolation Technology of Marine Gearboxes

    Institute of Scientific and Technical Information of China (English)


      船舶齿轮箱是中高速柴油机主推进系统的重要组成设备,随着柴油机隔振性能不断提升,齿轮箱的振动源不断突出,已成为影响船舶声学性能的重要振源,迫切需要突破齿轮箱隔振技术,对齿轮箱采取与柴油机一致的振动控制措施。论文以带齿轮箱的某双机并车柴油机推进系统进行隔振设计研究,设计硬弹性隔振器实现齿轮箱的振动控制,用有限元方法对隔振装置进行模态分析,通过试验验证预期的隔振效果。%Ship gearbox is the important equipment in the mid-high speed diesel propeller system. As the diesel vibration isolation performance promoting, the vibration source from gearbox has become the main factor influencing the ship’s sound performance. The vibration isolation technology of gearbox is crying for break-through, and the vibration isolation measures of the gearbox corresponding to the diesel engine’s are necessary. Taking a twin-engine parallel operation propeller system along with the gearbox as a vibration isolation research object, the hard elastic vibration isolators were designed for gearbox’s vibration control. The modal was analyzed for the vibration isolator set by FEM. And the expectant vibration isolation effect was verified by the test.

  15. Tribological Properties of Mo-N Hard Coatings on Ti6Al4V by Double Glow Discharge Technique

    Institute of Scientific and Technical Information of China (English)

    Xiuyan LI; Bin TANG; Junde PAN; Daoxin LIU; Zhong XU


    Mo-N hard coatings on Ti6Al4V were formed using double glow discharge technique. The fundamental coating properties,such as the phase, hardness and elastic modulus were investigated. The tribological performances of the coatings in dry wear condition were studied by means of ball-on-disc wear machine. The experimental results showed that the thickness of the Mo-N hard coating was about 10 μm. The coating was single fcc γ-Mo2N phase with (200) preferred orientation. The hardness and the elastic modulus of the coating was 13.80 GPa and 261.65 GPa respectively. The surface treatment enhanced the hardness and elastic modulus of the surface of Ti6Al4V base greatly. With GCr15 slider ball, the friction coefficient of the Mo-N hard coatingwas in the range of 0.56~0.65 at the steady state. Though the coating did not show friction reducing effect, it improved the wear resistance of Ti6Al4V greatly.

  16. Modeling the Effects of Velocity, Spin, Frictional Coefficient, and Impact Angle on Deflection Angle in Near-elastic Collisions of Phenolic Resin Spheres

    CERN Document Server

    Crown, S C


    A simple model is outlined to describe the collision of cast phenol-formaldehyde resin spheres such as the balls used in the parlor game of pocket billiards, based in part on the famous analysis of elastic collisions developed by Heinrich Hertz over 100 years ago. The analysis treats the normal and tangential components of the initial sphere's velocity independently as it collides with a stationary identical second sphere. The collective effects of these and other parameters on the trajectory of the second sphere are provided in the conclusions.

  17. Sliding without slipping under Coulomb friction: opening waves and inversion of frictional force

    CERN Document Server

    Yastrebov, Vladislav A


    An elastic layer slides on a rigid flat governed by Coulomb's friction law. We demonstrate that if the coefficient of friction is high enough, the sliding localizes within stick-slip pulses, which transform into opening waves propagating at intersonic speed in the direction of sliding or, for high Poisson's ratios, at supersonic speed in the opposite one. This sliding mode, characterized by small frictional dissipation, rapidly relaxes the shear elastic energy via stress waves and enables the contact surface slide ahead of the top one, resulting in inversion of the frictional force direction.

  18. Frictional properties of confined polymers

    DEFF Research Database (Denmark)

    Sivebæk, Ion Marius; Samoilov, Vladimir N; Persson, Bo N J


    We present molecular dynamics friction calculations for confined hydrocarbon solids with molecular lengths from 20 to 1400 carbon atoms. Two cases are considered: a) polymer sliding against a hard substrate, and b) polymer sliding on polymer. In the first setup the shear stresses are relatively...... independent of molecular length. For polymer sliding on polymer the friction is significantly larger, and dependent on the molecular chain length. In both cases, the shear stresses are proportional to the squeezing pressure and finite at zero load, indicating an adhesional contribution to the friction force...

  19. Financial Frictions

    DEFF Research Database (Denmark)

    Vestergaard Jensen, Mads

    frictions, a call option should never be exercised early, but only at expiration or just before the underlying stock pays a dividend. Chapter one of this thesis shows that suffciently severe frictions can make early exercise optimal. Short-sale costs especially represent an important driver of early...

  20. 考虑摩擦热的弹塑性平面接触应力及塑性应变分析%Analysis of Elastic-Plastic Plane Contact Stress and Plastic Strain Considering Frictional Heat

    Institute of Scientific and Technical Information of China (English)

    李鹏阳; 陈欢; 王世军; 王权岱; 傅卫平


    The influence of surface contact friction heat on the failure and the life of the parts was studied .The thermal stress of elastic-plastic surface contact was calculated using Fortran language ,the contact surface temperature distribution and the influence of friction heat on the surface pressure distribution were analyzed ,and the subsurface of the Mises stress field and the influence of plastic strain of the contact surface were discussed .The results show :With the increase of surface friction heat flux , the surface maximum pressure is increased .The maximum stress under the surface is decreased and the maximum stress zone of subsurface is always moving gradually to the contact surface .The contact surface temperature increases with the increase of sliding speed .The location of highest temperature point slowly shifts ,with increase of sliding speed ,to the sliding velocity direction .%研究了降低表面接触摩擦热对材料失效和零件寿命的影响。应用Fortran编程语言对弹塑性表面接触中产生的热应力进行了计算,分析了接触表面温度分布及摩擦热对接触表面压力分布、表面下米塞斯应力场及塑性应变的影响。分析结果表明:随着表面摩擦热流的增加,表面上最大接触压力逐渐变大,而表面下最大应力值逐渐减小,最大应力区域逐渐向接触表面上移动。接触表面温度的大小随滑动速度的提高而升高,且最高温度点的位置随滑动速度的提高缓慢向滑动速度方向偏移。


    Directory of Open Access Journals (Sweden)

    I. K. Badalakha


    Full Text Available The article presents the results of solving several problems of a flat deformation of elastic infinitely long massifs of different width and limited thickness. Various cases of conditions at the massif/base contact. The relationships between stressed and strained states previously suggested by the author, which differ from the generalized Hooke’s law, are used in the solutions.

  2. The Use of Instrumental Hardness Measurements in Determining Stresses in the Elastic Elements of a Manipulator for Servicing Water and Sewage Networks

    Directory of Open Access Journals (Sweden)

    Kaczyński R.


    Full Text Available The paper presents the design of a manipulator for servicing the elements of water and sewage infrastructure, in particular for installation and dismantling of pressure transducers without the need for earthmoving. To build this device the resilient elements, cold shaped, responsible for centering the manipulator in the technical tube were used. In their construction a method was applied of estimating the value of residual stresses in the cold shaped material, based on measurements of instrumental hardness. The experimental verification of numerical simulation of instrumental hardness measurements of flat springs made of 1.1274 steel is described.

  3. 种植牙用钛合金Ti-30Nb-8Zr-2Mo硬度及弹性模量%Micro-hardness and elastic modulus of Ti-30Nb-8Zr-2Mo alloy for dental implants

    Institute of Scientific and Technical Information of China (English)

    邓嘉胤; 崔春翔; 刘双进; 戚玉敏; 杨薇; 高平; 彭诚; 宫崎隆


    BACKGROUND: As dental implants, pure titanium and Ti-6Al-4V has achieved broad clinical applications, but they also contain toxic vanadium and aluminum element. Moreover, their elastic modulus is so high as to produce stress shield. OBJECTIVE: To examine the micro-hardness and elastic modulus of the self-made Ti-30Nb-8Zr-2Mo titanium alloy. DESIGN, TIME AND SETTING: An observational experiment was performed at the laboratory of College of Material Science and Engineering at Hebei University of Technology between March 2003 and February 2006. MATERIALS: Titanium alloy was prepared using titanium sponge (≥ 99% purify), niobium strip (≥ 99.9% purify), molybdenum powder (≥ 99% purify) and zirconium sponge (≥ 99.4% purify).METHODS: The micro-hardness of the specimens was determined after uniformly annealing, hot-forging and solution. Compression test was conducted on post-aging samples. MAIN OUTCOME MEASURES: Hardness and stress-strain curve.RESULTS: The maximal alloy strength was obtained after solution under 800 ℃ for 0.5 hours. Post-aging alloy's hardness was improved significantly although little change occurred on solution alloy. Compressive strength of alloy samples was 1 054 MPa, while elastic modulus reached 16.5 GPa. CONCLUSION: Both micro-hardness and elastic modulus of the self-made Ti-30Nb-8Zr-2Mo titanium alloy have satisfied performance requirements for dental implant materials.%背景:目前广泛应用于临床的纯钛和Ti-6AI-4V种植体材料中存在着铝和钒的潜在毒性及弹性模量太大易造成界面应力屏障等问题.目的:对自行研制的新型钛合金Ti-30Nb-8Zr-2Mo进行硬度及弹性模量性能测试.设计、时间及地点:观察实验,于2003-03/2006-02在河北工业大学材料学实验室完成.材料:钛合金制备用原材料海绵钛纯度≥99%、钼粉纯度≥99%、铌条≥99.9%、海绵锆≥99.4%.方法:在均匀化退火、热煅、固溶后对试样显微硬度进行测量,对时效后的样品

  4. Effect of electrostatic field on dynamic friction coefficient of pistachio

    Directory of Open Access Journals (Sweden)

    M. H Aghkhani


    Full Text Available Introduction: Separation and grading of agricultural products from the production to supply, has notable importance. The separation can be done based on physical, electrical, magnetic, optical properties and etc. It is necessary for any development of new systems to study enough on the properties and behavior of agricultural products. Some characteristics for separation are size (length, width and thickness, hardness, shape, density, surface roughness, color, speed limit, aerodynamic properties, electrical conductivity, elasticity and coefficient of static friction point. So far, the friction properties of agricultural products used in the separating process, but the effect of electrostatic charging on static and dynamic coefficients of friction for separation had little attention. The aim of this study was to find out the interactions between electrostatic and friction properties to find a way to separate products that separation is not possible with conventional methods or not sufficiently accurate. In this paper, the separation of close and smiley pistachios by electrostatic charging was investigated. Materials and Methods: Kallehghoochi pistachio cultivar has the top rank in production in Iran. Therefore, it was used as a sample. The experimental design that used in this study, had moisture content at three levels (24.2, 14.5 and 8.1 percent, electric field intensity at three levels (zero, 4000 and 7000 V, speed of movement on the surface at three levels (1300, 2500 and 3300 mm per minute, friction surface (galvanized sheet iron, aluminum and flat rubber and pistachio type at two levels (filled splits and closed that was measured and analyzed in completely randomized factorial design. A friction measuring device (built in Ferdowsi University of Mashhad used to measure the friction force. It has a removable table that can move in two directions with adjustable speed. The test sample put into the vessel with internal dimensions of 300 × 150

  5. Friction self-oscillation decrease in nonlinear system of locomotive traction drive (United States)

    Antipin, D. Ya; Vorobiyov, V. I.; Izmerov, O. V.; Shorokhov, S. G.; Bondarenko, D. A.


    The problems of the friction self-oscillation decrease in a nonlinear system of a locomotive traction drive are considered. It is determined that the self-oscillation amplitude decrease in a locomotive wheel pair during boxing in traction drives with an elastic linkage between an armature of a traction electric motor and gearing can be achieved due to drive damping capacity during impact vibro-damping in an axle reduction gear with a hard driven gear. The self-oscillation amplitude reduction in a wheel pair in the designs of locomotive traction drives with the location of elastic elements between a wheel pair and gearing can be obtained owing to the application of drive inertial masses as an anti-vibrator. On the basis of the carried out investigations, a design variant of a self-oscillation shock absorber of a traction electric motor framework on a reduction gear suspension with an absorber located beyond a wheel-motor unit was offered.

  6. The Influence of Small Quantities of Oxygen in the Structure, Microstructure, Hardness, Elasticity Modulus and Cytocompatibility of Ti-Zr Alloys for Dental Applications

    Directory of Open Access Journals (Sweden)

    Fábio B. Vicente


    Full Text Available The mechanical properties of Ti alloys are changed significantly with the addition of interstitial elements, such as oxygen. Because oxygen is a strong stabilizer of the α phase and has an effect on hardening in a solid solution, it has aroused great interest in the biomedical area. In this paper, Ti-Zr alloys were subjected to a doping process with small amounts of oxygen. The influence of interstitial oxygen in the structure, microstructure and some selected mechanical properties of interest for use as biomaterial and biocompatibility of the alloys were analyzed. The results showed that in the range of 0.02 wt% to 0.04 wt%, oxygen has no influence on the structure, microstructure or biocompatibility of the studied alloys, but causes hardening of the alloys, increasing the values of the microhardness and causing variation in the elasticity modulus values.

  7. Phase stability, elasticity, hardness and the minimum thermal conductivity of Si{sub 2}N{sub 2}O polymorphs from first principles calculations

    Energy Technology Data Exchange (ETDEWEB)

    Ding, Ying-chun, E-mail:; Chen, Min; Wu, Wenjuan


    Some fundamental properties of Si{sub 2}N{sub 2}O polymorphs are calculated using first principles calculations based on density functional theory. The results indicate that orthorhombic-Si{sub 2}N{sub 2}O is the most stable phase at ambient conditions; it transforms into tetragonal-Si{sub 2}N{sub 2}O at a relatively low pressure (10 GPa). PBEsol predicts lattice constants and mechanical properties better than PBE, but PBE gives better phase transition parameters. The mechanical properties, such as bulk modulus, Young's modulus and shear modulus, are evaluated by the Voigt–Reuss–Hill approach. The tetragonal-Si{sub 2}N{sub 2}O exhibits larger mechanical moduli than other phases. The obtained Vickers hardness of Si{sub 2}N{sub 2}O structures shows that the hardness of tetragonal-Si{sub 2}N{sub 2}O is slightly higher than those of monoclinic and orthorhombic phases. The minimum thermal conductivities of Si{sub 2}N{sub 2}O polymorphs in crystalline and amorphous states are estimated, and we conclude that the thermal conductivities of amorphous Si{sub 2}N{sub 2}O phases are comparable to typical thermal barrier coatings.

  8. Dynamic hardness of metals (United States)

    Liang, Xuecheng

    Dynamic hardness (Pd) of 22 different pure metals and alloys having a wide range of elastic modulus, static hardness, and crystal structure were measured in a gas pulse system. The indentation contact diameter with an indenting sphere and the radius (r2) of curvature of the indentation were determined by the curve fitting of the indentation profile data. r 2 measured by the profilometer was compared with that calculated from Hertz equation in both dynamic and static conditions. The results indicated that the curvature change due to elastic recovery after unloading is approximately proportional to the parameters predicted by Hertz equation. However, r 2 is less than the radius of indenting sphere in many cases which is contradictory to Hertz analysis. This discrepancy is believed due to the difference between Hertzian and actual stress distributions underneath the indentation. Factors which influence indentation elastic recovery were also discussed. It was found that Tabor dynamic hardness formula always gives a lower value than that directly from dynamic hardness definition DeltaE/V because of errors mainly from Tabor's rebound equation and the assumption that dynamic hardness at the beginning of rebound process (Pr) is equal to kinetic energy change of an impact sphere over the formed crater volume (Pd) in the derivation process for Tabor's dynamic hardness formula. Experimental results also suggested that dynamic to static hardness ratio of a material is primarily determined by its crystal structure and static hardness. The effects of strain rate and temperature rise on this ratio were discussed. A vacuum rotating arm apparatus was built to measure Pd at 70, 127, and 381 mum sphere sizes, these results exhibited that Pd is highly depended on the sphere size due to the strain rate effects. P d was also used to substitute for static hardness to correlate with abrasion and erosion resistance of metals and alloys. The particle size effects observed in erosion were

  9. An elastic mechanics model and computation method for geotechnical material

    Institute of Scientific and Technical Information of China (English)

    Zheng Yingren; Gao Hong; Zheng Lushi


    Internal friction characteristic is one of the basic properties of geotechnical materials and it exists in mechanical elements all the time.However,until now internal friction is only considered in limit analysis and plastic mechanics but not included in elastic theory for rocks and soils.We consider that internal friction exists in both elastic state and plastic state of geotechnical materials,so the mechanical unit of friction material is constituted.Based on study results of soil tests,the paper also proposes that cohesion takes effect first and internal friction works gradually with the increment of deformation.By assuming that the friction coefficient is proportional to the strain,the internal friction is computed.At last,by imitating the linear elastic mechanics,the nonlinear elastic mechanics model of friction material is established,where the shear modulus G is not a constant.The new model and the traditional elastic model are used simultaneously to analyze an elastic foundation.The results indicate that the displacements computed by the new model are less than those from the traditional method,which agrees with the fact and shows that the mechanical units of friction material are suitable for geotechnical material.

  10. Elasticity limits structural superlubricity in large contacts (United States)

    Sharp, Tristan A.; Pastewka, Lars; Robbins, Mark O.


    Geometrically imposed force cancellations lead to ultralow friction between rigid incommensurate crystalline asperities. Elastic deformations may avert this cancellation but are difficult to treat analytically in finite and three-dimensional systems. We use atomic-scale simulations to show that elasticity affects the friction only after the contact radius a exceeds a characteristic length set by the core width of interfacial dislocations bcore. As a increases past bcore, the frictional stress for both incommensurate and commensurate surfaces decreases to a constant value. This plateau corresponds to a Peierls stress that drops exponentially with increasing bcore but remains finite.

  11. Slow frictional waves (United States)

    Viswanathan, Koushik; Sundaram, Narayan; Chandrasekar, Srinivasan

    Stick-slip, manifest as intermittent tangential motion between two dry solid surfaces, is a friction instability that governs diverse phenomena from automobile brake squeals to earthquakes. We show, using high-speed in situ imaging of an adhesive polymer interface, that low velocity stick-slip is fundamentally of three kinds, corresponding to passage of three different surface waves -- separation pulses, slip pulses and the well-known Schallamach waves. These waves, traveling much slower than elastic waves, have clear distinguishing properties. Separation pulses and Schallamach waves involve local interface separation, and propagate in opposite directions while slip pulses are characterized by a sharp stress front and do not display any interface detachment. A change in the stick-slip mode from separation to slip pulse is effected simply by increasing the normal force. Together, these three waves constitute all possible stick-slip modes in adhesive friction and are shown to have direct analogues in muscular locomotory waves in soft bodied invertebrates. A theory for slow wave propagation is also presented which is capable of explaining the attendant interface displacements, velocities and stresses.


    Institute of Scientific and Technical Information of China (English)

    Yu Chunxiao; Shen Guangxian; Liu Deyi


    A mathematical program is proposed for the highly nonlinear problem involving frictional contact. A program-pattern using the fast multipole boundary element method (FMBEM) is given for 3-D elastic contact with friction to replace the Monte Carlo method. A new optimized generalized minimal residual (GMRES) algorithm is presented. Numerical examples demonstrate the validity of the program-pattern optimization model for node-to-surface contact with friction. The GMRES algorithm greatly improves the computational efficiency.

  13. Mathematical Programming Solution for the Frictional Contact Multipole BEM

    Institute of Scientific and Technical Information of China (English)

    YU Chunxiao; SHEN Guangxian; LIU Deyi


    This paper presents a new mathematical model for the highly nonlinear problem of frictional contact. A programming model, multipole boundary element method (BEM), was developed for 3-D elastic contact with friction to replace the Monte Carlo method. A numerical example shows that the optimization programming model for the point-to-surface contact with friction and the fast optimization generalized minimal residual algorithm (GMRES(m)) significantly improve the analysis of such problems relative to the conventional BEM.

  14. Hard electronics; Hard electronics

    Energy Technology Data Exchange (ETDEWEB)



    Hard material technologies were surveyed to establish the hard electronic technology which offers superior characteristics under hard operational or environmental conditions as compared with conventional Si devices. The following technologies were separately surveyed: (1) The device and integration technologies of wide gap hard semiconductors such as SiC, diamond and nitride, (2) The technology of hard semiconductor devices for vacuum micro- electronics technology, and (3) The technology of hard new material devices for oxides. The formation technology of oxide thin films made remarkable progress after discovery of oxide superconductor materials, resulting in development of an atomic layer growth method and mist deposition method. This leading research is expected to solve such issues difficult to be easily realized by current Si technology as high-power, high-frequency and low-loss devices in power electronics, high temperature-proof and radiation-proof devices in ultimate electronics, and high-speed and dense- integrated devices in information electronics. 432 refs., 136 figs., 15 tabs.

  15. Velocity dependence of friction of confined polymers

    DEFF Research Database (Denmark)

    Sivebæk, Ion Marius; Samoilov, V.N.; Persson, B.N.J.


    We present molecular dynamics friction calculations for confined hydrocarbon solids with molecular lengths from 20 to 1400 carbon atoms. Two cases are considered: (a) polymer sliding against a hard substrate, and (b) polymer sliding on polymer. We discuss the velocity dependence of the frictional...... cases the frictional shear stress increases monotonically with the sliding velocity. For polymer sliding on polymer [case (b)] the friction is much larger, and the velocity dependence is more complex. For hydrocarbons with molecular lengths from 60 to 140 C-atoms, the number of monolayers of lubricant...... shows no dependence on the sliding velocity, and for the shortest hydrocarbon (20 C-atoms) the frictional shear stress increases nearly linearly with the sliding velocity....

  16. Steady accretion of an elastic body on a hard spherical surface and the notion of a four-dimensional reference space (United States)

    Tomassetti, Giuseppe; Cohen, Tal; Abeyaratne, Rohan


    Taking the cue from experiments on actin growth on spherical beads, we formulate and solve a model problem describing the accretion of an incompressible elastic solid on a rigid sphere due to attachment of diffusing free particles. One of the peculiar characteristics of this problem is that accretion takes place on the interior surface that separates the body from its support rather than on its exterior surface, and hence is responsible for stress accumulation. Simultaneously, ablation takes place at the outer surface where material is removed from the body. As the body grows, mechanical effects associated with the build-up of stress and strain energy slow down accretion and promote ablation. Eventually, the system reaches a point where internal accretion is balanced by external ablation. The present study is concerned with this stationary regime called "treadmilling". The principal ingredients of our model are: a nonstandard choice of the reference configuration, which allows us to cope with the continually evolving material structure; and a driving force and a kinetic law for accretion/ablation that involves the difference in chemical potential, strain energy and the radial stress. By combining these ingredients we arrive at an algebraic system which governs the stationary treadmilling state. We establish the conditions under which this system has a solution and we show that this solution is unique. Moreover, by an asymptotic analysis we show that for small beads the thickness of the solid is proportional to the radius of the support and is strongly affected by the stiffness of the solid, whereas for large beads the stiffness of the solid is essentially irrelevant, the thickness being proportional to a characteristic length that depends on the parameters that govern diffusion and accretion kinetics.

  17. Tribological characterization of selected hard coatings


    Karlsson, Patrik


    Hard coatings are often used for protection of tool surfaces due to coating properties like low friction and high wear resistance. Even though many of the hard coatings have been tested for wear, it is important to try new wear test setups to fully understand tribological mechanisms and the potential of hard coatings. Few experiments have been performed with dual-coated systems where the sliding contact surfaces are coated with the same, or different, hard coating. The dual-coated system coul...

  18. Close packing density of polydisperse hard spheres. (United States)

    Farr, Robert S; Groot, Robert D


    The most efficient way to pack equally sized spheres isotropically in three dimensions is known as the random close packed state, which provides a starting point for many approximations in physics and engineering. However, the particle size distribution of a real granular material is never monodisperse. Here we present a simple but accurate approximation for the random close packing density of hard spheres of any size distribution based upon a mapping onto a one-dimensional problem. To test this theory we performed extensive simulations for mixtures of elastic spheres with hydrodynamic friction. The simulations show a general (but weak) dependence of the final (essentially hard sphere) packing density on fluid viscosity and on particle size but this can be eliminated by choosing a specific relation between mass and particle size, making the random close packed volume fraction well defined. Our theory agrees well with the simulations for bidisperse, tridisperse, and log-normal distributions and correctly reproduces the exact limits for large size ratios.

  19. Friction drive of an SAW motor. Part II: analyses. (United States)

    Shigematsu, Takashi; Kurosawa, Minoru Kuribayashi


    The mechanics of the friction drive of a surface acoustic wave motor were investigated by means of contact mechanics theory. As a means to control the contact condition, the motor's slider had projections on its frictional surface. Assuming the projection was a rigid circular punch and the slider body was an elastic half-space allowed application of contact mechanics formulae to the analyses of the friction drive. Because the projection contacted the Rayleigh wave vibration, the projection's responses were considered dynamic; thus, the dynamics were also analyzed in the same framework of contact mechanics formulae. Moreover, the analyses were applied to measurements of the projection's displacement to examine the detailed mechanics during the friction drive. We calculated the contact/frictional forces based on the measurement and indicated the necessity of further investigation of the surface acoustic wave motor's friction drive, because the usual friction law was unable to explain the measurement.

  20. Hard electronics; Hard electronics

    Energy Technology Data Exchange (ETDEWEB)



    In the fields of power conversion devices and broadcasting/communication amplifiers, high power, high frequency and low losses are desirable. Further, for electronic elements in aerospace/aeronautical/geothermal surveys, etc., heat resistance to 500degC is required. Devices which respond to such hard specifications are called hard electronic devices. However, with Si which is at the core of the present electronics, the specifications cannot fully be fulfilled because of the restrictions arising from physical values. Accordingly, taking up new device materials/structures necessary to construct hard electronics, technologies to develop these to a level of IC were examined and studied. They are a technology to make devices/IC of new semiconductors such as SiC, diamond, etc. which can handle higher temperature, higher power and higher frequency than Si and also is possible of reducing losses, a technology to make devices of hard semiconducter materials such as a vacuum microelectronics technology using ultra-micro/high-luminance electronic emitter using negative electron affinity which diamond, etc. have, a technology to make devices of oxides which have various electric properties, etc. 321 refs., 194 figs., 8 tabs.

  1. Contact mechanics, friction and adhesion with application to quasicrystals

    DEFF Research Database (Denmark)

    Persson, Bo; Carbone, Giuseppe; Samoilov, Vladimir N.;


    We discuss the origin of friction and adhesion between hard solids such as quasicrystals. We emphasize the fundamental role of surface roughness in many contact mechanics problems, in particular for friction and adhesion between solid bodies. The most important property of rough surfaces is the s...

  2. Acoustics of friction. (United States)

    Akay, Adnan


    This article presents an overview of the acoustics of friction by covering friction sounds, friction-induced vibrations and waves in solids, and descriptions of other frictional phenomena related to acoustics. Friction, resulting from the sliding contact of solids, often gives rise to diverse forms of waves and oscillations within solids which frequently lead to radiation of sound to the surrounding media. Among the many everyday examples of friction sounds, violin music and brake noise in automobiles represent the two extremes in terms of the sounds they produce and the mechanisms by which they are generated. Of the multiple examples of friction sounds in nature, insect sounds are prominent. Friction also provides a means by which energy dissipation takes place at the interface of solids. Friction damping that develops between surfaces, such as joints and connections, in some cases requires only microscopic motion to dissipate energy. Modeling of friction-induced vibrations and friction damping in mechanical systems requires an accurate description of friction for which only approximations exist. While many of the components that contribute to friction can be modeled, computational requirements become prohibitive for their contemporaneous calculation. Furthermore, quantification of friction at the atomic scale still remains elusive. At the atomic scale, friction becomes a mechanism that converts the kinetic energy associated with the relative motion of surfaces to thermal energy. However, the description of the conversion to thermal energy represented by a disordered state of oscillations of atoms in a solid is still not well understood. At the macroscopic level, friction interacts with the vibrations and waves that it causes. Such interaction sets up a feedback between the friction force and waves at the surfaces, thereby making friction and surface motion interdependent. Such interdependence forms the basis for friction-induced motion as in the case of

  3. Correlation between Mechanical Properties with Specific Wear Rate and the Coefficient of Friction of Graphite/Epoxy Composites

    Directory of Open Access Journals (Sweden)

    Mahdi Alajmi


    Full Text Available The correlation between the mechanical properties of Fillers/Epoxy composites and their tribological behavior was investigated. Tensile, hardness, wear, and friction tests were conducted for Neat Epoxy (NE, Graphite/Epoxy composites (GE, and Data Palm Fiber/Epoxy with or without Graphite composites (GFE and FE. The correlation was made between the tensile strength, the modulus of elasticity, elongation at the break, and the hardness, as an individual or a combined factor, with the specific wear rate (SWR and coefficient of friction (COF of composites. In general, graphite as an additive to polymeric composite has had an eclectic effect on mechanical properties, whereas it has led to a positive effect on tribological properties, whilst date palm fibers (DPFs, as reinforcement for polymeric composite, promoted a mechanical performance with a slight improvement to the tribological performance. Statistically, this study reveals that there is no strong confirmation of any marked correlation between the mechanical and the specific wear rate of filler/Epoxy composites. There is, however, a remarkable correlation between the mechanical properties and the friction coefficient of filler/Epoxy composites.

  4. Correlation between Mechanical Properties with Specific Wear Rate and the Coefficient of Friction of Graphite/Epoxy Composites. (United States)

    Alajmi, Mahdi; Shalwan, Abdullah


    The correlation between the mechanical properties of Fillers/Epoxy composites and their tribological behavior was investigated. Tensile, hardness, wear, and friction tests were conducted for Neat Epoxy (NE), Graphite/Epoxy composites (GE), and Data Palm Fiber/Epoxy with or without Graphite composites (GFE and FE). The correlation was made between the tensile strength, the modulus of elasticity, elongation at the break, and the hardness, as an individual or a combined factor, with the specific wear rate (SWR) and coefficient of friction (COF) of composites. In general, graphite as an additive to polymeric composite has had an eclectic effect on mechanical properties, whereas it has led to a positive effect on tribological properties, whilst date palm fibers (DPFs), as reinforcement for polymeric composite, promoted a mechanical performance with a slight improvement to the tribological performance. Statistically, this study reveals that there is no strong confirmation of any marked correlation between the mechanical and the specific wear rate of filler/Epoxy composites. There is, however, a remarkable correlation between the mechanical properties and the friction coefficient of filler/Epoxy composites.

  5. Composites materials for friction and braking application (United States)

    Crăciun, A. L.; Pinca-Bretotean, C.; Birtok-Băneasă, C.; Josan, A.


    The brake pads are an important component in the braking system of automotive. Materials used for brake pads should have stable and reliable frictional and wear properties under varying conditions of load, velocity, temperature and high durability. These factors must be satisfied simultaneously which makes it difficult to select effective brake pads material. The paper presents the results of the study for characterisation of the friction product used for automotive brake pads. In the study it was developed four frictional composites by using different percentages of coconut fibres (0%, 5%, 10%, 15%) reinforcement in aluminium matrix. The new composites tested in the laboratory, modelling appropriate percentage ratio between matrix and reinforcement volume and can be obtained with low density, high hardness properties, good thermal stability, higher ability to hold the compressive force and have a stable friction coefficient. These characteristics make them useful in automotive industry.


    Institute of Scientific and Technical Information of China (English)

    潘岳; 顾士坦


    ,supporting action of soft rock under hard roof was often simplified as the Winkler elastic foundation. To accurately analyze the mechanical characteristics and activity of overlying strata,this simplification cannot be contented with the actual requirements. In view of peak of abutment pressure in front of the coal wall,mechanics properties of hard roof model that was thought as soften foundation between coal wall and the peak of abutment pressure and elastic foundation ahead of the peak of abutment pressure were analyzed before the periodic weighting. Methods for determinating peak value of the abutment force were presented. Examples were given to illustrate how to calculate the peak value of the abutment and verify the accuracy using the development approaches. Analysis results were compared with mechanics properties of roof based on full elastic foundation. The research results are shown as follows:Reaction force near the coal wall to the roof obtained by full elastic foundation is 4 times as big as that of the roof calculated by the soften foundation in the depths of 200-300 m. Bending degree of roof,scope of the bend,the distance between peak of bending moment and the coal wall,storage area of strain energy and storage capacity become small near the coal wall, which result from the powerful reaction near coal wall. Reaction near the coal wall to the roof,which is caused by the soften foundation is a fourth as big as that of the former. Owning to the small reaction near coal wall,bending degree of roof and scope of the bend become increase for resisting on overly roof,which lead to the peak of bending moment and the distance between peak of bending moment and the coal wall increase remarkably. Meanwhile,storage area of strain energy and storage capacity outstanding aggrandize in front of coal wall. Then the roof′s deflection increase overall and remarkably when compared with the roof supported by full elastic foundation. Position of peak of bending moment in front of coal

  7. Wear and Friction Characteristics of AlN/Diamond-Like Carbon Hybrid Coatings on Aluminum Alloy (United States)

    Nakamura, Masashi; Kubota, Sadayuki; Suzuki, Hideto; Haraguchi, Tadao


    The use of diamond-like carbon (DLC) coatings has the potential to greatly improve the wear resistance and friction of aluminum alloys, but practical application has so far been limited by poor adhesion due to large difference in hardness and elasticity between the two materials. This study investigates the deposition of DLC onto an Al-alloy using an intermediate AlN layer with a graded hardness to create a hybrid coating. By controlling the hardness of the AlN film, it was found that the wear life of the DLC film could be improved 80-fold compared to a DLC film deposited directly onto Al-alloy. Furthermore, it was demonstrated through finite element simulation that creating a hardness gradient in the AlN intermediate layer reduces the distribution of stress in the DLC film, while also increasing the force of adhesion between the DLC and AlN layers. Given that both the DLC and AlN films were deposited using the same unbalanced magnetron sputtering method, this process is considered to represent a simple and effective means of improving the wear resistance of Al-alloy components commonly used within the aerospace and automotive industries.

  8. Role of Friction in Cold Ring Rolling

    Institute of Scientific and Technical Information of China (English)

    He YANG; Lianggang GUO; Mei ZHAN


    Cold ring rolling is an advanced but complex metal forming process under coupled effects with multi-factors, such as geometry sizes of rolls and ring blank, material, forming process parameters and friction, etc. Among these factors,friction between rolls and ring blank plays animportant role in keeping the stable forming of cold ring rolling. An analytical method was firstly presented for proximately determining the critical friction coefficient of stable forming and then a method was proposed to determine thecritical friction coefficient by combining analytical method with numerical simulation. And the influence of friction coefficient on the quality of end-plane and side spread of ring,rolling force, rolling moment and metal flow characteristic in the cold ring rolling process have been explored using the three dimensional (3D) numerical simulation based on the elastic-plastic dynamic finite element method (FEM)under the ABAQUS software environment, and the results show that increasing the friction on the contact surfaces between rolls and ring blank is useful not only for improving the stability of cold ring rolling but also for improving the geometry and dimension precision of deformed ring.

  9. Velocity Dependence of Friction of Confined Hydrocarbons

    DEFF Research Database (Denmark)

    Sivebæk, Ion Marius; Samoilov, Vladimir N.; Persson, Bo N. J.


    We present molecular dynamics friction calculations for confined hydrocarbon “polymer” solids with molecular lengths from 20 to 1400 carbon atoms. Two cases are considered: (a) polymer sliding against a hard substrate and (b) polymer sliding on polymer. We discuss the velocity dependence of the f......We present molecular dynamics friction calculations for confined hydrocarbon “polymer” solids with molecular lengths from 20 to 1400 carbon atoms. Two cases are considered: (a) polymer sliding against a hard substrate and (b) polymer sliding on polymer. We discuss the velocity dependence...... in the polymer film is always close to the thermostat temperature. In the first setup (a), for hydrocarbons with molecular lengths from 60 to 1400 carbon atoms, the shear stresses are nearly independent of molecular length, but for the shortest hydrocarbon C20H42 the frictional shear stress is lower. In all...... cases the frictional shear stress increases monotonically with the sliding velocity. For polymer sliding on polymer (case b) the friction is much larger, and the velocity dependence is more complex. For hydrocarbons with molecular lengths from 60 to 140 C atoms, the number of monolayers of lubricant...

  10. Friction Model for FEM Simulation of Sheet Metal Forming Operations (United States)

    Keum, Y. T.; Wagoner, R. H.; Lee, J. K.


    In order to find the effect of frictional characteristics, lubricant viscosity, tool geometry, and forming speed on the sheet metal forming, a friction tester was designed and manufactured. Friction tests were performed using drawing oils, various tool radii and forming speeds for aluminum alloy sheets, galvanized steels sheets and cold rolled steel sheets. From the experimental observation, the mathematical friction model considering lubricant viscosity, sheet surface roughness and hardness, punch corner radii, and punch speed is developed. By comparing the punch load found by FEM using the proposed friction model with that of experimental measurement when the steel sheets are formed in 2-D geometry in dry and lubricating conditions, the validity and accuracy of the mathematical friction model are demonstrated.

  11. Simulation of Strip Rolling Using Elastoplastic Contact BEM With Friction

    Institute of Scientific and Technical Information of China (English)

    LI Yu-gui; HUANG Qing-xue; SHEN Guang-xian; XIAO Hong; PANG Si-qin; WANG Jian-mei


    With rollers as elastic bodies and workpieces as elastoplastic bodies, the rolling problem can be viewed as a friction elastic-plastic contact problem. With fewer assumptions in the simulation of strip-rolling process, a boundary element method (BEM) for two-dimensional elastoplastic finite strain and finite deformation analysis of contact problems with friction was presented. All the equations for contact problems, which include multi-nonlinearities, were obtained. Incremental and iterative procedures were used to find contact pressure and friction stress. Moreover, initial strain rate algorithm and work-hardening material behavior can be assumed in the plastic analysis. Several examples were presented, and the results of contact pressure and friction stress were in excellent agreement with those of analysis.

  12. Static and dynamic friction of hierarchical surfaces (United States)

    Costagliola, Gianluca; Bosia, Federico; Pugno, Nicola M.


    Hierarchical structures are very common in nature, but only recently have they been systematically studied in materials science, in order to understand the specific effects they can have on the mechanical properties of various systems. Structural hierarchy provides a way to tune and optimize macroscopic mechanical properties starting from simple base constituents and new materials are nowadays designed exploiting this possibility. This can be true also in the field of tribology. In this paper we study the effect of hierarchical patterned surfaces on the static and dynamic friction coefficients of an elastic material. Our results are obtained by means of numerical simulations using a one-dimensional spring-block model, which has previously been used to investigate various aspects of friction. Despite the simplicity of the model, we highlight some possible mechanisms that explain how hierarchical structures can significantly modify the friction coefficients of a material, providing a means to achieve tunability.

  13. Aftershocks in a frictional earthquake model. (United States)

    Braun, O M; Tosatti, Erio


    Inspired by spring-block models, we elaborate a "minimal" physical model of earthquakes which reproduces two main empirical seismological laws, the Gutenberg-Richter law and the Omori aftershock law. Our point is to demonstrate that the simultaneous incorporation of aging of contacts in the sliding interface and of elasticity of the sliding plates constitutes the minimal ingredients to account for both laws within the same frictional model.

  14. On the origin of Amonton’s friction law

    DEFF Research Database (Denmark)

    Persson, Bo N J; Sivebæk, Ion Marius; Samoilov, Vladimir N


    Amonton's law states that the sliding friction force increases linearly with the load. We show that this result is expected for stiff enough solids, even when the adhesional interaction between the solids is included in the analysis. As a function of the magnitude of the elastic modulus E, one can...... on the load and is non-vanishing at zero load. In this last case a finite pull-off force is necessary in order to separate the solids. Based on molecular dynamics calculations, we also discuss the pressure dependence of the frictional shear stress for polymers. We show that the frictional shear stress...

  15. Time dependent friction in a free gas (United States)

    Fanelli, Cristiano; Sisti, Francesco; Stagno, Gabriele V.


    We consider a body moving in a perfect gas, described by the mean-field approximation and interacting elastically with the body, we study the friction exerted by the gas on the body fixed at constant velocities. The time evolution of the body in this setting was studied in Caprino et al. [Math. Phys. 264, 167-189 (2006)], Caprino et al. [Math. Models Methods Appl. Sci. 17, 1369-1403 (2007)], and Cavallaro [Rend. Mat. Appl. 27, 123-145 (2007)] for object with simple shape; the first study where a simple kind of concavity was considered was in Sisti and Ricciuti [SIAM J. Math. Anal. 46, 3759-3611 (2014)], showing new features in the dynamic but not in the friction term. The case of more general shape of the body was left out for further difficulties, and we believe indeed that there are actually non-trivial issues to be faced for these more general cases. To show this and in the spirit of getting a more realistic perspective in the study of friction problems, in this paper, we focused our attention on the friction term itself, studying its behavior on a body with a more general kind of concavity and fixed at constant velocities. We derive the expression of the friction term for constant velocities, we show how it is time dependent, and we give its exact estimate in time. Finally, we use this result to show the absence of a constant velocity in the actual dynamic of such a body.

  16. Static and kinetic friction characteristics of nanowire on different substrates (United States)

    Kim, Hyun-Joon; Nguyen, Gia Hau; Ky, Dinh Le Cao; Tran, Da Khoa; Jeon, Ki-Joon; Chung, Koo-Hyun


    Friction characteristics of nanowires (NWs), which may be used as building blocks for nano-devices, are crucial, especially for cases where contact sliding occurs during the device operation. In this work, the static and kinetic friction characteristics of oxidized Si NWs deposited on thermally grown SiO2 and chemical vapor-deposited single layer graphene were investigated using an atomic force microscope (AFM). Kinetic friction between the oxidized Si NWs and the substrates was directly measured by the AFM. Static friction was also obtained from the most bent state of the NWs using the individually determined elastic moduli of the NWs from kinetic friction experiments based on elastic beam theory. Furthermore, the shear stress between the oxidized Si NWs and the substrates was estimated based on adhesive contact theory. It was found that both static and kinetic friction increased as the radius of the NWs increased. The friction of the oxidized Si NWs on the graphene substrate was found to be smaller than that on the SiO2 substrate, which suggests that chemical vapor-deposited graphene can be used as a lubricant or as a protective layer in nano-devices to reduce friction. The shear stress estimated from the kinetic friction data between the oxidized Si NWs and the SiO2 substrate ranged from 7.5 to 12.3 MPa while that between the oxidized Si NWs and the graphene substrate ranged from 4.7 to 7.0 MPa. The result also indicated that the dependence of shear stress on the radius of the NWs was not significant. These findings may provide insight into the friction characteristics of NWs.

  17. Self-lubricating Hard Coatings for Extreme Environment Project (United States)

    National Aeronautics and Space Administration — This program will develop low friction hard coatings for lubricating mechanical and tribological components used for exploring Mars, the Moon, asteroids, comets and...

  18. Biopolymer Elasticity

    CERN Document Server

    Sinha, S


    In recent years molecular elasticity has emerged as an active area of research: there are experiments that probe mechanical properties of single biomolecules such as DNA and Actin, with a view to understanding the role of elasticity of these polymers in biological processes such as transcription and protein-induced DNA bending. Single molecule elasticity has thus emerged as an area where there is a rich cross-fertilization of ideas between biologists, chemists and theoretical physicists. In this article we present a perspective on this field of research.

  19. Torsional friction damper optimization (United States)

    Ye, Shaochun; Williams, Keith A.


    A new approach for the analysis of friction dampers is presented in this work. The exact form of the steady-state solution for a friction damper implemented on a primary system is developed and numerical solutions are used to determine the optimum friction in a friction damper applied to a specific primary system. When compared to classical results presented by earlier authors, the new approach provides a more optimal solution. In addition, viscous damping in the primary system may be included with the new analysis approach. The ability to optimize a friction damper when viscous damping is included in the primary system is a significant improvement over earlier methods and shows potential for serving as a guide to realizing a more accurate estimate of the optimal damping for friction dampers.


    Institute of Scientific and Technical Information of China (English)

    H.Zhang; S.B.Lin; L.Wu; J.C.Feng


    Friction stir welding achieves the weld in solid phase by locally introducing frictional heating and plastic flow arising from rotation of the welding tool, which results in changes in the local microstructure of magnesium alloy. The purpose in the paper is to study the microstructures of friction stir welded AZ3I magnesium alloy. Residual microstructures,including dynamic re-crystallization zone and nugget structures have been systematically investigated utilizing optical microscopy (OM), scanning electric microscopy (SEM),transmission electron microscopy (TEM) with energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and micro-hardness. AZ31 magnesium alloy has been successfully friction stir welded and exhibits the variations of microstructure including dynamically recrystallized,equaxied grains in the weld nugget. Residual hardness in the nugget was found slightly lower than the parent but not too obvious.

  1. Microstructure analysis in friction welding of copper and aluminum (United States)

    Wibowo, A. G. Wahyu; Ismail, Rifky; Jamari, J.


    The Friction welding is a welding method with utilizing heat generated due to friction. Surfaces of two materials to be joined, one rotates the other being idle, is contacted by a pressure force. Friction on the second contact surface is done continuously so that the heat generated by the continuous friction will continue to rise. With the heat and the pressure force on the second surface to the second meeting of the material reaches its melting temperature then there is the process of welding. This paper examines the influence of the pressure force, rotational speed and contact time on friction welding of Aluminum (Al) and Copper (Cu) to the quality of welded joints. Friction welding process is performed on a friction welding machine that is equipped with the loading mechanism. The parameters used are the pressure force, rotational speed and friction time. Determination of the quality of welding is done by testing the tensile strength, hardness, and micro structure on the weld joint areas. The results showed that the friction welding quality is very good, this is evidenced by the results of a tensile strength test where the fault occurs outside the weld joint and increased violence in the weld joint. On the results visually cuts the welding area did not reveal any porosity so that it can be concluded that each metal contacts have melted perfectly and produce a connection with good quality.

  2. Applications of Friction Stir Processing during Engraving of Soft Materials

    Directory of Open Access Journals (Sweden)

    V. Kočović


    Full Text Available Friction stir processing has extensive application in many technological operations. Application area of friction stir processing can be extended to the processing of non-metallic materials, such as wood. The paper examines the friction stir processing contact between a specially designed hard and temperature-resistant rotating tool and workpiece which is made of wood. Interval of speed slip and temperature level under which the combustion occurs and carbonization layer of soft material was determined. The results of the research can be applied in technological process of wood engraving operations which may have significant technological and aesthetic effects.

  3. Friction Stir Processing for Efficient Manufacturing

    Energy Technology Data Exchange (ETDEWEB)

    Mr. Christopher B. Smith; Dr. Oyelayo Ajayi


    Friction at contacting surfaces in relative motion is a major source of parasitic energy loss in machine systems and manufacturing processes. Consequently, friction reduction usually translates to efficiency gain and reduction in energy consumption. Furthermore, friction at surfaces eventually leads to wear and failure of the components thereby compromising reliability and durability. In order to reduce friction and wear in tribological components, material surfaces are often hardened by a variety of methods, including conventional heat treatment, laser surface hardening, and thin-film coatings. While these surface treatments are effective when used in conjunction with lubrication to prevent failure, they are all energy intensive and could potentially add significant cost. A new concept for surface hardening of metallic materials and components is Friction Stir Processing (FSP). Compared to the current surface hardening technologies, FSP is more energy efficient has no emission or waste by products and may result in better tribological performance. FSP involves plunging a rotating tool to a predetermined depth (case layer thickness) and translating the FSP tool along the area to be processed. This action of the tool produces heating and severe plastic deformation of the processed area. For steel the temperature is high enough to cause phase transformation, ultimately forming hard martensitic phase. Indeed, FSP has been used for surface modification of several metals and alloys so as to homogenize the microstructure and refine the grain size, both of which led to improved fatigue and corrosion resistance. Based on the effect of FSP on near-surface layer material, it was expected to have beneficial effects on friction and wear performance of metallic materials. However, little or no knowledge existed on the impact of FSP concerning friction and wear performance the subject of the this project and final report. Specifically for steel, which is the most dominant

  4. Comparison of different hardness definitions usable for micro- and nanoindentation

    Energy Technology Data Exchange (ETDEWEB)

    Pohlenz, F.; Herrmann, K.; Seemann, R.; Menelao, F. [Physikalisch-Technische Bundesanstalt, Braunschweig (Germany)


    In order to describe the hardness of substrates and layers, different definitions are used which consider the plastic or the elastic-plastic behavior of the material. For a chosen spectrum of substrate and layer materials the absolute hardness values according to these definitions are compared with each other. Moreover, relationships between the hardness values are derived. For the investigation of differences in the accuracy of the various hardness definitions the variance coefficients of different hardnesses were determined. (orig.)

  5. Nanomechanical properties of friction stir welded AA6082-T6 aluminum alloy

    Energy Technology Data Exchange (ETDEWEB)

    Koumoulos, E.P. [National Technical University of Athens, Department of Chemical Engineering 9 Heroon, Polytechneiou st., Zografos, Athens, GR-157 80 (Greece); Charitidis, C.A., E-mail: [National Technical University of Athens, Department of Chemical Engineering 9 Heroon, Polytechneiou st., Zografos, Athens, GR-157 80 (Greece); Daniolos, N.M.; Pantelis, D.I. [National Technical University of Athens, Department of Naval Architecture and Marine Engineering 9 Heroon, Polytechneiou st., Zografos, Athens, GR-157 80 (Greece)


    Lightweight alloys are of major concern, due to their functionality and applications in transport and industry applications. Friction stir welding (FSW) is a solid-state welding process for joining aluminum and other metallic alloys and has been employed in aerospace, rail, automotive and marine industries. Compared to the conventional welding techniques, FSW produces joints which do not exhibit defects caused by melting. The objective of the present study is to investigate the surface hardness (H) and elastic modulus (E) in friction stir welded aluminum alloy AA6082-T6. The findings of the present study reveal that the welding process softens the material, since the weld nugget is the region where the most deformations are recorded (dynamic recrystallization, production of an extremely fine, equiaxial structure), confirmed by optical microscopy and reduced nanomechanical properties in the welding zone. A yield-type pop-in occurs upon low loading and represents the start of phase transformation, which is monitored through a gradual slope change of the load-displacement curve. Significant pile-up is recorded during nanoindentation of the alloy through SPM imaging.

  6. Crecimiento, estructura y comportamientode la fricción de recubrimientos duros delnanocompuesto WS2-Ti Growth, structure and friction behavior of the nanocomposite hard coatings WS2-Ti

    Directory of Open Access Journals (Sweden)

    Federico Sequeda


    ambientes húmedos y altas temperaturas, reduciendo la oxidación y mejorando el tiempo de vida de las piezas. Esta forma de obtener mejores condiciones de trabajo ha sido poco estudiada en detalle y se presenta un mecanismo de reacción que permite explicar dicho fenómeno utilizando técnicas novedosas de análisis como FIB.Tungsten disulphide (WS2 and titanium doped tungsten disulphide (Ti-WS2 nanocomposites were deposited on silicon substrates, varying substrate temperature and target power, using magnetron co–sputtering in order to obtain different Ti contents in the nanocomposite. The films were analyzed using X-ray difraction (XRD, high resolution scanning electron micrscopy (HRSEM/EDS and high resolution transmision electron microscopy (HRTEM to observe the crystallinity and morphology behavior respect the induced Ti percentage and the substrate temperature variation. The inclusion of Ti on the co–sputtering process prevents the WS2 crystallization forming dispersed amorphous nanocrystals (1-3 nm. The friction tests performed in a Pin on Disk (POD at low temperatures, shows that the room temperature and low Ti concentrations films (between 5 and 14%at possesses higher life times that pure WS2 films but no significant changes in friction coefficients (COF were observed. The same effect is determined in high temperature POD tests (500◦C with higher changes in COF. To study solid lubricant mechanisms, samples prepared by focus ion bean (FIB, were analyzed by Raman spectroscopy, determining surface deformation and tribo-chemical compounds formation in the wear track. The formation of WO3 in the surface during wear (tribo–oxidation and transfer to the counterface (third body generation was observed. Ti doping, producing a nanocomposite, is a procedure that improves tribological properties of the material in humid and high temperature environments. Obtaining these improvements by means of element doping has been poorly studied in detail and a reaction mechanism is

  7. Elastic Beanstalk

    CERN Document Server

    Vliet, Jurg; Wel, Steven; Dowd, Dara


    While it's always been possible to run Java applications on Amazon EC2, Amazon's Elastic Beanstalk makes the process easier-especially if you understand how it works beneath the surface. This concise, hands-on book not only walks you through Beanstalk for deploying and managing web applications in the cloud, you'll also learn how to use this AWS tool in other phases of development. Ideal if you're a developer familiar with Java applications or AWS, Elastic Beanstalk provides step-by-step instructions and numerous code samples for building cloud applications on Beanstalk that can handle lots

  8. The effects of porosity in friction performance of brake pad using waste tire dust

    Directory of Open Access Journals (Sweden)

    İbrahim Mutlu


    Full Text Available Abstract This research is focused on the effect of porosity on the friction-wear properties of automotive brake pads. Waste Tire Dust (WTD was used as a new friction material in brake pads. Newly formulated brake pad materials with five different components have been produced by conventional techniques. In the experimental studies, the change of the friction coefficient, the temperature of the friction surface, the specific wear rate, and the hardness, density and porosity were measured. In addition, the micro-structural characterizations of brake pads are determined using Scanning Electron Microscopy (SEM. The mean coefficient of friction, porosity and specific wear are increased due to a WTD rate increases, on the other hand, hardness and density are decreased. As a result, WTD can be considered as an alternative to revalorize this kind of waste products in the brake pads and the amount of porosity of the brake pad affected the friction coefficient and wear behavior of the pad.

  9. Static and kinetic friction characteristics of nanowire on different substrates

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Hyun-Joon [Department of Precision Mechanical Engineering, Kyungpook National University, Sangju 37224 (Korea, Republic of); Nguyen, Gia Hau; Ky, Dinh Le Cao; Tran, Da Khoa [School of Mechanical Engineering, University of Ulsan, Ulsan 44610 (Korea, Republic of); Jeon, Ki-Joon [Department of Environmental Engineering, Inha University, Incheon 22212 (Korea, Republic of); Chung, Koo-Hyun, E-mail: [School of Mechanical Engineering, University of Ulsan, Ulsan 44610 (Korea, Republic of)


    Highlights: • Direct measurement of kinetic friction of oxidized Si NW using AFM. • Determination of static friction of oxidized Si NW from most bent state. • Friction characteristics of oxidized Si NW on SiO{sub 2} and graphene. • Estimation of shear stress between cylindrical NW and flat substrate. • No significant dependence of shear stress on NW radius. - Abstract: Friction characteristics of nanowires (NWs), which may be used as building blocks for nano-devices, are crucial, especially for cases where contact sliding occurs during the device operation. In this work, the static and kinetic friction characteristics of oxidized Si NWs deposited on thermally grown SiO{sub 2} and chemical vapor-deposited single layer graphene were investigated using an atomic force microscope (AFM). Kinetic friction between the oxidized Si NWs and the substrates was directly measured by the AFM. Static friction was also obtained from the most bent state of the NWs using the individually determined elastic moduli of the NWs from kinetic friction experiments based on elastic beam theory. Furthermore, the shear stress between the oxidized Si NWs and the substrates was estimated based on adhesive contact theory. It was found that both static and kinetic friction increased as the radius of the NWs increased. The friction of the oxidized Si NWs on the graphene substrate was found to be smaller than that on the SiO{sub 2} substrate, which suggests that chemical vapor-deposited graphene can be used as a lubricant or as a protective layer in nano-devices to reduce friction. The shear stress estimated from the kinetic friction data between the oxidized Si NWs and the SiO{sub 2} substrate ranged from 7.5 to 12.3 MPa while that between the oxidized Si NWs and the graphene substrate ranged from 4.7 to 7.0 MPa. The result also indicated that the dependence of shear stress on the radius of the NWs was not significant. These findings may provide insight into the friction characteristics

  10. Application of response surface methodology to maximize tensile strength and minimize interface hardness of friction welded dissimilar joints of austenitic stainless steel and copper alloy%响应面方法在奥氏体不锈钢与铜合金异种材料摩擦焊接头的抗拉强度最大化和界面硬度最小化中的应用

    Institute of Scientific and Technical Information of China (English)



    在奥氏体不锈钢与铜合金异种材料摩擦焊接过程中,采用响应面方法优化摩擦焊接工艺参数,以获得抗拉强度最大和界面硬度最小的焊接接头。采用三因素、五水平中心复合正交矩阵来确定实验条件。得到20个焊接接头,测定了焊接接头的抗拉强度和界面硬度。采用方差分析(ANOVA)方法来确定起显著作用的、主要的及相互作用的参数,使用回归分析得到经验关系模型。用设计专家软件构造响应图和等高线图来优化摩擦焊接工艺参数。用得到的经验关系模型可以有效地预测焊接接头的抗拉强度和界面硬度,其置信水平达95%。从形成的等高线图可以得到所需的摩擦焊接的最佳条件。%An attempt was made to optimize friction welding parameters to attain a minimum hardness at the interface and a maximum tensile strength of the dissimilar joints of AISI 304 austenitic stainless steel (ASS) and copper (Cu) alloy using response surface methodology (RSM). Three-factor, five-level central composite design matrix was used to specify experimental conditions. Twenty joints were fabricated using ASS and Cu alloy. Tensile strength and interface hardness were measured experimentally. Analysis of variance (ANOVA) method was used to find out significant main and interaction parameters and empirical relationships were developed using regression analysis. The friction welding parameters were optimized by constructing response graphs and contour plots using design expert software. The developed empirical relationships can be effectively used to predict tensile strength and interface hardness of friction welded ASS−Cu joints at 95%confidence level. The developed contour plots can be used to attain required level of optimum conditions to join ASS−Cu alloy by friction welding process.

  11. Packing of elastic wires in flexible shells (United States)

    Vetter, R.; Wittel, F. K.; Herrmann, H. J.


    The packing problem of long thin filaments that are injected into confined spaces is of fundamental interest for physicists and biologists alike. How linear threads pack and coil is well known only for the ideal case of rigid containers, though. Here, we force long elastic rods into flexible spatial confinement borne by an elastic shell to examine under which conditions recently acquired knowledge on wire packing in rigid spheres breaks down. We find that unlike in rigid cavities, friction plays a key role by giving rise to the emergence of two distinct packing patterns. At low friction, the wire densely coils into an ordered toroidal bundle with semi-ellipsoidal cross-section, while at high friction, it packs into a highly disordered, hierarchic structure. These two morphologies are shown to be separated by a continuous phase transition. Our findings demonstrate the dramatic impact of friction and confinement elasticity on filamentous packing and might drive future research on such systems in physics, biology and even medical technology toward including these mutually interacting effects.

  12. Iliotibial band friction syndrome. (United States)

    Lavine, Ronald


    Published articles on iliotibial band friction syndrome have been reviewed. These articles cover the epidemiology, etiology, anatomy, pathology, prevention, and treatment of the condition. This article describes (1) the various etiological models that have been proposed to explain iliotibial band friction syndrome; (2) some of the imaging methods, research studies, and clinical experiences that support or call into question these various models; (3) commonly proposed treatment methods for iliotibial band friction syndrome; and (4) the rationale behind these methods and the clinical outcome studies that support their efficacy.

  13. Systematic hardness measurements on some rare earth garnet crystals

    Indian Academy of Sciences (India)

    D B Sirdeshmukh; L Sirdeshmukh; K G Subhadra; K Kishan Rao; S Bal Laxman


    Microhardness measurements were undertaken on twelve rare earth garnet crystals. In yttrium aluminium garnet and gadolinium gallium garnet, there was no measurable difference in the hardness values of pure and nominally Nd-doped crystals. The hardness values were correlated with the lattice and elastic constants. An analysis of hardness data in terms of the interatomic binding indicated a high degree of covalency.

  14. Fundamental considerations in adhesion, friction and wear for ceramic-metal contacts (United States)

    Miyoshi, Kazuhisa


    Fundamental studies of friction, wear and adhesion of ceramics in contact with metals are evaluated. It is shown that friction and adhesion are strongly dependent on the ductility of the metals. The surface energy, friction, adhesion and hardness of a metal are related to its Young's modulus and shear modulus, which have a marked dependence on the electron configuration of the metal. Generally, the greater the sheer modulus, the less metal transfer there is to the ceramic.

  15. Elastic scattering of hadrons (United States)

    Dremin, I. M.


    Colliding high-energy hadrons either produce new particles or scatter elastically with their quantum numbers conserved and no other particles produced. We consider the latter case here. Although inelastic processes dominate at high energies, elastic scattering contributes considerably (18-25%) to the total cross section. Its share first decreases and then increases at higher energies. Small-angle scattering prevails at all energies. Some characteristic features can be seen that provide information on the geometrical structure of the colliding particles and the relevant dynamical mechanisms. The steep Gaussian peak at small angles is followed by the exponential (Orear) regime with some shoulders and dips, and then by a power-law decrease. Results from various theoretical approaches are compared with experimental data. Phenomenological models claiming to describe this process are reviewed. The unitarity condition predicts an exponential fall for the differential cross section with an additional substructure to occur exactly between the low momentum transfer diffraction cone and a power-law, hard parton scattering regime under high momentum transfer. Data on the interference of the Coulomb and nuclear parts of amplitudes at extremely small angles provide the value of the real part of the forward scattering amplitude. The real part of the elastic scattering amplitude and the contribution of inelastic processes to the imaginary part of this amplitude (the so-called overlap function) are also discussed. Problems related to the scaling behavior of the differential cross section are considered. The power-law regime at highest momentum transfer is briefly described.

  16. Nanoscience friction and rheology on the nanometer scale

    CERN Document Server

    Meyer, E; Gyalog, T; Overney, R M


    Friction force microscopy is an important analytical tool in the field of tribology on the nanometer-scale. The contact area between the probing tip and the sample is reduced to some square nanometers, corresponding to the ideal of a single asperity contact. Traditional concepts, such as friction coefficients, adhesion and elasticity and stick-slip are re-examined with this novel technique. New concepts based upon classical and quantum mechanics are investigated.Contents: Introduction and Motivation; Instruments; Normal Forces at the Atomic Scale; Understanding of Lateral Forces; Dissipation Mechanisms; Nanorheology and Nanoconfinement; Generation of Ultrasonic Waves in Sliding Friction; Friction Force Microscopy Experiments; Appendix: Instrumental Aspects of Force Microscopy.Readership: Graduate and researchers in physics, chemistry and materials science.

  17. Rotational elasticity (United States)

    Vassiliev, Dmitri


    We consider an infinite three-dimensional elastic continuum whose material points experience no displacements, only rotations. This framework is a special case of the Cosserat theory of elasticity. Rotations of material points are described mathematically by attaching to each geometric point an orthonormal basis that gives a field of orthonormal bases called the coframe. As the dynamical variables (unknowns) of our theory, we choose the coframe and a density. We write down the general dynamic variational functional for our rotational theory of elasticity, assuming our material to be physically linear but the kinematic model geometrically nonlinear. Allowing geometric nonlinearity is natural when dealing with rotations because rotations in dimension three are inherently nonlinear (rotations about different axes do not commute) and because there is no reason to exclude from our study large rotations such as full turns. The main result of the talk is an explicit construction of a class of time-dependent solutions that we call plane wave solutions; these are travelling waves of rotations. The existence of such explicit closed-form solutions is a non-trivial fact given that our system of Euler-Lagrange equations is highly nonlinear. We also consider a special case of our rotational theory of elasticity which in the stationary setting (harmonic time dependence and arbitrary dependence on spatial coordinates) turns out to be equivalent to a pair of massless Dirac equations. The talk is based on the paper [1]. [1] C.G.Boehmer, R.J.Downes and D.Vassiliev, Rotational elasticity, Quarterly Journal of Mechanics and Applied Mathematics, 2011, vol. 64, p. 415-439. The paper is a heavily revised version of preprint

  18. Computational investigation of the tensile behaviour of the hard coated Ti-6Al-4V alloy

    Directory of Open Access Journals (Sweden)

    W. Ziaja


    Full Text Available Purpose: Modification of the surface layer of the titanium alloys is frequently applied in order to improve their tribological properties. Various surface engineering techniques can be used to produce hard coatings, e.g. composed of metallic carbides, nitrides or more recently DLC. The coating and substrate materials possess significantly different stiffness and strength properties. This can lead to premature failure of the usually elastic coating in case of plastic deformation of the substrate when the high stresses are encountered. Cracking of the hard coating leads to stress concentration and localized plastic deformation of the substrate that can modify macroscopic deformation behaviour of the system. In the paper the influence of coating and substrate properties on local plastic deformation of substrate material was numerically investigated.Design/methodology/approach: Two dimensional finite element analysis of the process of tensile deformation of titanium alloy with hard elastic coating was carried out. Two cases were analyzed, i.e. with and without diffusion strengthened layer underlying the coating.Findings: The influence of the difference in Young’s modulus between coating and substrate material, yield strength of substrate material, coating thickness and depth of the crack in the coating on local plastic deformation of substrate material was determined.Research limitations/implications: Some extension of the numerical model should be pursued in order to take into account initiation of microcracks in surface layer of the coated material and process of coating delamination.Practical implications: The results could be used in the element design process for selection of parameters of surface layer with complex structure for load bearing applications.Originality/value: The mechanical behaviour of hard coated material was most frequently studied for indentation and friction conditions and much less investigations were carried out for

  19. Science 101: What Causes Friction? (United States)

    Robertson, Bill


    Defining friction and asking what causes it might seem like a trivial question. Friction seems simple enough to understand. Friction is a force between surfaces that pushes against things that are moving or tending to move, and the rougher the surfaces, the greater the friction. Bill Robertson answers this by saying, "Well, not exactly".…

  20. Friction stir welding tool (United States)

    Tolle; Charles R. , Clark; Denis E. , Barnes; Timothy A.


    A friction stir welding tool is described and which includes a shank portion; a shoulder portion which is releasably engageable with the shank portion; and a pin which is releasably engageable with the shoulder portion.

  1. Dependence of friction on roughness, velocity, and temperature. (United States)

    Sang, Yi; Dubé, Martin; Grant, Martin


    We study the dependence of friction on surface roughness, sliding velocity, and temperature. Expanding on the classic treatment of Greenwood and Williamson, we show that the fractal nature of a surface has little influence on the real area of contact and the static friction coefficient. A simple scaling argument shows that the static friction exhibits a weak anomaly mu ~ A(0)(-chi/4), where A0 is the apparent area and chi is the roughness exponent of the surface. We then develop a method to calculate atomic-scale friction between a microscopic asperity, such as the tip of a friction force microscope (FFM) and a solid substrate. This method, based on the thermal activation of the FFM tip, allows a quantitative extraction of all the relevant microscopic parameters and reveals a universal scaling behavior of atomic friction on velocity and temperature. This method is extended to include a soft atomic substrate in order to simulate FFM scans more realistically. The tip is connected with the support of the cantilever by an ideal spring and the substrate is simulated with a ball-spring model. The tip and substrate are coupled with repulsive potentials. Simulations are done at different temperatures and scanning velocities on substrates with different elastic moduli. Stick-slip motion of the tip is observed, and the numerical results of the friction force and distribution of force maxima match the theoretical framework.

  2. Study of lubrication behavior of pure water for hydrophobic friction pair

    Institute of Scientific and Technical Information of China (English)


    The perfluorooctyltrichlorosilane molecular layer was self-assembled on glass plate. The tribological properties of the molecular layer in water were studied with the method of ball on disk. An interesting phenomenon was found that low friction coefficients of 0.02―0.08 were obtained when the friction pair was lubricated with only a water droplet. Whereas, when the friction pair was encircled with large amount of water or fully immersed in water, the friction coefficient was higher than that under a droplet lubrication. A mechanism of water droplet lubrication was proposed that the surface tension caused by the solid-liquid-air three-phase interface makes water molecules enter into the contact zone, which separates the two friction surfaces and provides a low friction coefficient. However, water film can hardly form when more water encircles the friction pair, due to the attraction between water molecules.

  3. Effects of surface coating on reducing friction and wear of orthopaedic implants

    Directory of Open Access Journals (Sweden)

    Hee Ay Ching


    Full Text Available Coatings such as diamond-like carbon (DLC and titanium nitride (TiN are employed in joint implants due to their excellent tribological properties. Recently, graphite-like carbon (GLC and tantalum (Ta have been proven to have good potential as coating as they possess mechanical properties similar to bones—high hardness and high flexibility. The purpose of this systematic literature review is to summarize the coating techniques of these four materials in order to compare their mechanical properties and tribological outcomes. Eighteen studies published between January 2000 and February 2013 have met the inclusion criteria for this review. Details of their fabrication parameters, material and mechanical properties along with the tribological outcomes, such as friction and wear rate, were identified and are presented in a systematic way. Although experiment conditions varied, we conclude that Ta has the lowest wear rate compared to DLC, GLC and TiN because it has a lower wear rate with high contact pressure as well as higher hardness to elasticity ratio. However, a further tribology test is needed in an environment which replicates artificial joints to confirm the acceptability of these findings.

  4. Microstructural and Residual Stress Development due to Inertia Friction Welding in Ti-6246 (United States)

    Attallah, Moataz M.; Preuss, Michael; Boonchareon, Chatri; Steuwer, Axel; Daniels, John E.; Hughes, Darren J.; Dungey, Christopher; Baxter, Gavin J.


    A thorough investigation has been performed to assess the microstructural properties, mechanical properties (hardness and elastic modulus), and residual stress development in Ti-6Al-2Sn-4Zr-6Mo (Ti-6246) inertia friction welds in the as-welded and postweld heat-treated conditions. It was evident that the thermomechanical deformation in the weld region occurred above the β transus, forming dynamically recrystallized β grains and precipitating acicular α within the β grains, which resulted in a localized hardness increase. In the heat-affected zone, a ghost microstructure of the base metal formed because of the absence of sufficient time for diffusion, resulting in Mo segregation in the prior primary α plates. Energy-dispersive synchrotron X-ray diffraction and neutron diffraction were used to assess the residual stress development in the three principal directions. The variation in the unstrained lattice parameters across the weld regions was established by imposing a stress balance on the axial stress component in the radial direction. It was found that the maximum stresses occurred in the hoop direction, with significantly lower stresses present in the radial and axial directions. The maximum tensile hoop stresses were located at ~4 mm from the weld centerline and not at the dynamically recrystallized β-rich weld zone. This was associated with the α → β phase transformation and the subsequent acicular α precipitation within the region surrounding the weld centerline.

  5. Effect of ZrSiO4 on the Friction Performance of Automotive Brake Friction Materials

    Institute of Scientific and Technical Information of China (English)


    Friction-wear properties of the ZrSiO4 reinforced samples were measured and compared with those of plain bronze based ones. For this purpose, density, hardness, friction coefficient wear behaviour of the samples were tested. Microstructures of samples before and after sintering and worn surfaces were also investigated by scanning electron microscopy (SEM), and the wear types were determined. The optimum friction-wear behaviour was obtained in the sample compacted at 500 MPa and sintered at 820℃. Density of the final samples decreased with increasing the amount of reinforcing elements (ZrSiO4) before pre-sintering. However after sintering, there is no change in density of the samples including reinforcing elements (ZrSiO4). With increasing friction surface temperature, a reduction in the friction coefficient of the samples was observed.However, the highest reductions in the friction coefficients were observed in the as-received samples containing 0,5% reinforced ZrSiO4. The SEM images of the sample indicated that while bronze-based break lining material without ZrSiO4 showed abrasive wear behaviour, increasing the amount of ZrSiO4 resulted a change in abrasive to adhesive wear mechanism. All samples exhibited friction-wear values, which were within the values shown in SAE-J661 standard. With increasing the amount of reinforcing ZrSiO4, wear resistance of the samples was increased. However samples reinforced with 5% and 6% ZrSiO4 showed the best results.

  6. Friction in volcanic environments (United States)

    Kendrick, Jackie E.; Lavallée, Yan


    Volcanic landscapes are amongst the most dynamic on Earth and, as such, are particularly susceptible to failure and frictional processes. In rocks, damage accumulation is frequently accompanied by the release of seismic energy, which has been shown to accelerate in the approach to failure on both a field and laboratory scale. The point at which failure occurs is highly dependent upon strain-rate, which also dictates the slip-zone properties that pertain beyond failure, in scenarios such as sector collapse and pyroclastic flows as well as the ascent of viscous magma. High-velocity rotary shear (HVR) experiments have provided new opportunities to overcome the grand challenge of understanding faulting processes during volcanic phenomena. Work on granular ash material demonstrates that at ambient temperatures, ash gouge behaves according to Byerlee's rule at low slip velocities, but is slip-weakening, becoming increasingly lubricating as slip ensues. In absence of ash along a slip plane, rock-rock friction induces cataclasis and heating which, if sufficient, may induce melting (producing pseudotachylyte) and importantly, vesiculation. The viscosity of the melt, so generated, controls the subsequent lubrication or resistance to slip along the fault plane thanks to non-Newtonian suspension rheology. The shear-thinning behaviour and viscoelasticity of frictional melts yield a tendency for extremely unstable slip, and occurrence of frictional melt fragmentation. This velocity-dependence acts as an important feedback mechanism on the slip plane, in addition to the bulk composition, mineralogy and glass content of the magma, that all influence frictional behaviour. During sector collapse events and in pyroclastic density currents it is the frictional properties of the rocks and ash that, in-part, control the run-out distance and associated risk. In addition, friction plays an important role in the eruption of viscous magmas: In the conduit, the rheology of magma is integral

  7. Creep motion of a model frictional system

    CERN Document Server

    Blanc, Baptiste; Géminard, Jean-Christophe


    We report on the dynamics of a model frictional system submitted to minute external perturbations. The system consists of a chain of sliders connected through elastic springs that rest on an incline. By introducing cyclic expansions and contractions of the springs we observe a reptation of the chain. We account for the average reptation velocity theoretically. The velocity of small systems exhibits a series of plateaus as a function of the incline angle. Due to elastic e ects, there exists a critical amplitude below which the reptation is expected to cease. However, rather than a full stop of the creep, we observe in numerical simulations a transition between a continuous-creep and an irregular-creep regime when the critical amplitude is approached. The latter transition is reminiscent of the transition between the continuous and the irregular compaction of granular matter submitted to periodic temperature changes.

  8. Reflections on Friction in Quantum Mechanics

    Directory of Open Access Journals (Sweden)

    Yair Rezek


    Full Text Available Distinctly quantum friction effects of three types are surveyed: internalfriction, measurement-induced friction, and quantum-fluctuation-induced friction. We demonstrate that external driving will lead to quantum internal friction, and critique the measurement-based interpretation of friction. We conclude that in general systems will experience internal and external quantum friction over and beyond the classical frictional contributions.

  9. Skin friction on a flat perforated acoustic liner (United States)

    Boldman, D. R.; Brinich, P. F.


    The report concerns the measurement of friction coefficients of a typical perforated acoustic liner installed in the side of a wind tunnel. The results are compared with measured friction coefficients of a smooth hard wall for the same mean flow velocities in a wind tunnel. At a velocity of 61 m/sec, an increase in the local skin coefficient of only a few percent was observed, but at the highest velocity of 213 m/sec an increase of about 20% was obtained. This velocity is a realistic velocity for turbo-machinery components utilizing such liners, so a loss in performance is to be expected. Some tests were also performed to see if changes in the mean boundary layer induced by imposed noise would result in friction increase, but only at low velocity levels was such an increase in friction noted.

  10. Linear and nonlinear stiffness and friction in biological rhythmic movements. (United States)

    Beek, P J; Schmidt, R C; Morris, A W; Sim, M Y; Turvey, M T


    Biological rhythmic movements can be viewed as instances of self-sustained oscillators. Auto-oscillatory phenomena must involve a nonlinear friction function, and usually involve a nonlinear elastic function. With respect to rhythmic movements, the question is: What kinds of nonlinear friction and elastic functions are involved? The nonlinear friction functions of the kind identified by Rayleigh (involving terms such as theta3) and van der Pol (involving terms such as theta2theta), and the nonlinear elastic functions identified by Duffing (involving terms such as theta3), constitute elementary nonlinear components for the assembling of self-sustained oscillators, Recently, additional elementary nonlinear friction and stiffness functions expressed, respectively, through terms such as theta2theta3 and thetatheta2, and a methodology for evaluating the contribution of the elementary components to any given cyclic activity have been identified. The methodology uses a quantification of the continuous deviation of oscillatory motion from ideal (harmonic) motion. Multiple regression of this quantity on the elementary linear and nonlinear terms reveals the individual contribution of each term to the oscillator's non-harmonic behavior. In the present article the methodology was applied to the data from three experiments in which human subjects produced pendular rhythmic movements under manipulations of rotational inertia (experiment 1), rotational inertia and frequency (experiment 2), and rotational inertia and amplitude (experiment 3). The analysis revealed that the pendular oscillators assembled in the three experiments were compositionally rich, braiding linear and nonlinear friction and elastic functions in a manner that depended on the nature of the task.

  11. Numerical-analytical investigation into impact pipe driving in soil with dry friction. Part I: Nondeformable external medium

    CERN Document Server

    Aleksandrova, Nadezhda


    The study focuses on propagation of longitudinal waves in an elastic pipe partly embedded in a medium with dry friction. Mathematical formulation of the problem on the impact pipe driving into the soil is based on the model of longitudinal vibration of an elastic rod with taking into account lateral resistance. The lateral resistance of soil is described by the law of the contact dry friction. Numerical and analytical solutions to problems on longitudinal impulse loading of a pipe are compared.

  12. Wet Friction-Elements Boundary Friction Mechanism and Friction Coefficient Prediction

    Directory of Open Access Journals (Sweden)

    WANG Yanzhong


    Full Text Available The friction mechanism for the boundary friction course of friction elements engagement was explicitly expressed. The boundary friction model was built up by the surface topography. The model contained the effect of boundary film, adhesion, plough and lubrication. Based on the model, a coefficient for weakening plough for the lubrication was proposed. The modified model could fit for the working condition of wet friction elements. The friction coefficient as a function curve of rotating speed could be finally obtained by the data k and s/sm. The method provides a well interpretation of friction condition and friction coefficient prediction and the agreement between theoretical and experimental friction coefficients is reasonably good.

  13. Standard hardness conversion tables for metals relationship among brinell hardness, vickers hardness, rockwell hardness, superficial hardness, knoop hardness, and scleroscope hardness

    CERN Document Server

    American Society for Testing and Materials. Philadelphia


    1.1 Conversion Table 1 presents data in the Rockwell C hardness range on the relationship among Brinell hardness, Vickers hardness, Rockwell hardness, Rockwell superficial hardness, Knoop hardness, and Scleroscope hardness of non-austenitic steels including carbon, alloy, and tool steels in the as-forged, annealed, normalized, and quenched and tempered conditions provided that they are homogeneous. 1.2 Conversion Table 2 presents data in the Rockwell B hardness range on the relationship among Brinell hardness, Vickers hardness, Rockwell hardness, Rockwell superficial hardness, Knoop hardness, and Scleroscope hardness of non-austenitic steels including carbon, alloy, and tool steels in the as-forged, annealed, normalized, and quenched and tempered conditions provided that they are homogeneous. 1.3 Conversion Table 3 presents data on the relationship among Brinell hardness, Vickers hardness, Rockwell hardness, Rockwell superficial hardness, and Knoop hardness of nickel and high-nickel alloys (nickel content o...

  14. On the Indeterminacy in Hardness of Shape Memory Alloys

    Institute of Scientific and Technical Information of China (English)



    The present communication addresses an interesting problem related to the indeterminacy in hardness of superelastic NiTi reported by Xu et al.[1]. The origin of the indeterminacy is attributed to the inadequacy of the conventional Vickers hardness testing measurement which does not record elastic deformation, and thus the indeterminacy may be removed with suitable techniques. Concepts of hardness in relation to deformation are clarified. Recommendations for measuring the hardness of NiTi and other elastic-plastic materials are suggested, together with comments on the advantages and disadvantages of each of these methods.

  15. Characteristics of Deformation Layer for Vermicular Iron under Dry Sliding Friction

    Institute of Scientific and Technical Information of China (English)

    SUN Le-min; SHANG Guan-bao; ZHANG Yong-zhen; CHEN Yue


    At room temperature, dry sliding wear tests were carried out using pin-on-disc test rig, in which the pin is made of vermicular iron and the disc is made of 40Cr steel. The microstructures of the frictional surfaces for the pin specimens were investigated. Under the action of both frictional heat and frictional shearing stress, a plastic deformation layer under the frictional surface is formed. The morphology and properties of the plastic deformation layer depend on specimen material, contact pressure and frictional shearing stress. In the plastic deformation layer, the phosphorous mass percent varies at different depth and results in different hardness. On the outer side of surface, the hardness is the biggest and the phosphorous mass percent is the highest. They become gradually small from outer side to inner side of the surface.

  16. Partial squeeze film levitation modulates fingertip friction. (United States)

    Wiertlewski, Michaël; Fenton Friesen, Rebecca; Colgate, J Edward


    When touched, a glass plate excited with ultrasonic transverse waves feels notably more slippery than it does at rest. To study this phenomenon, we use frustrated total internal reflection to image the asperities of the skin that are in intimate contact with a glass plate. We observed that the load at the interface is shared between the elastic compression of the asperities of the skin and a squeeze film of air. Stroboscopic investigation reveals that the time evolution of the interfacial gap is partially out of phase with the plate vibration. Taken together, these results suggest that the skin bounces against the vibrating plate but that the bounces are cushioned by a squeeze film of air that does not have time to escape the interfacial separation. This behavior results in dynamic levitation, in which the average number of asperities in intimate contact is reduced, thereby reducing friction. This improved understanding of the physics of friction reduction provides key guidelines for designing interfaces that can dynamically modulate friction with soft materials and biological tissues, such as human fingertips.

  17. Friction Modeling in Concentric Tube Robots. (United States)

    Lock, Jesse; Dupont, Pierre E


    Concentric tube robots are a novel class of continuum robots that are constructed by combining pre-curved elastic tubes such that the overall shape of the robot is a function of the relative rotations and translations of the constituent tubes. Frictionless kinematic and quasistatic force models for this class of robots have been developed that incorporate bending and twisting of the tubes. Experimental evaluation of these models has revealed, however, a directional dependence of tube rotation on robot shape that is not predicted by these models. To explain this behavior, this paper models the contributions of friction arising from two sources: the distributed forces of contact between the tubes along their length and the concentrated bending moments generated at discontinuities in curvature and at the boundaries. It is shown that while friction due to distributed forces is insufficient to explain the experimentally observed tube twisting, a simple model of frictional torque arising from concentrated moments provides a good match with the experimental data.

  18. Dynamic friction of self-affine surfaces (United States)

    Schmittbuhl, Jean; Vilotte, Jean-Pierre; Roux, Stéphane


    We investigate the velocity dependence of the friction between two rigid blocks limited by a self-affine surface such as the one generated by a crack. The upper solid is subjected either to gravity or to an external elastic stiffness, and is driven horizontally at constant velocity, V, while the lower solid is fixed. For low velocities, the apparent friction coefficient is constant. For high velocities, the apparent friction is shown to display a velocity weakening. The weakening can be related to the variation of the mean contact time due to the occurrence of jumps during the motions. The cross-over between these two regimes corresponds to a characteristic velocity which depends on the geometry of the surfaces and on the mean normal force. In the case of simple gravity loading, the velocity dependence of the apparent friction at high velocities is proportional to 1/V^2 where V is the imposed tangential velocity. In the case of external elastic stiffness, two velocity weakening regimes can be identified, the first is identical to the gravity case with a 1/V^2 dependence, the second appears at higher velocities and is characterized by a 1/V variation. The characteristic velocity of this second cross-over depends on the roughness and the elastic stiffness. The statistical distribution of ballistic flight distances is analysed, and is shown to reveal in all cases the self-affinity of the contacting surfaces. Nous analysons la dépendence en vitesse du frottement entre deux solides limités par une surface rugueuse auto-affine comme celle d'une surface de fracture. Le solide supérieur est soumis soit à la gravité, soit à une raideur élastique externe, et est entraîné à vitesse horizontale constante V sur le solide inférieur fixe. A faible vitesse, le coefficient de friction apparent, est constant. A forte vitesse, le coefficient de friction apparent devient inversement proportionnel à la vitesse. Cette dépendance peut être reliée à la variation du temps

  19. Indentation of elastically soft and plastically compressible solids

    DEFF Research Database (Denmark)

    Needleman, A.; Tvergaard, Viggo; Van der Giessen, E.


    The effect of soft elasticity, i.e., a relatively small value of the ratio of Young's modulus to yield strength and plastic compressibility on the indentation of isotropically hardening elastic-viscoplastic solids is investigated. Calculations are carried out for indentation of a perfectly sticking...... rigid sharp indenter into a cylinder modeling indentation of a half space. The material is characterized by a finite strain elastic-viscoplastic constitutive relation that allows for plastic as well as elastic compressibility. Both soft elasticity and plastic compressibility significantly reduce...... the ratio of nominal indentation hardness to yield strength. A linear relation is found between the nominal indentation hardness and the logarithm of the ratio of Young's modulus to yield strength, but with a different coefficient than reported in previous studies. The nominal indentation hardness decreases...

  20. Strain hardening and damage in 6xxx series aluminum alloy friction stir welds

    DEFF Research Database (Denmark)

    Simar, Aude; Nielsen, Kim Lau; de Meester, Bruno


    A friction stir weld in 6005A-T6 aluminum alloy has been prepared and analyzed by micro-hardness measurements, tensile testing and scanning electron microscopy (SEM). The locations of the various weld zones were determined by micro-hardness indentation measurements. The flow behavior of the various...

  1. Microstructural evolution of 6063 aluminum during friction-stir welding

    Energy Technology Data Exchange (ETDEWEB)

    Sato, Y.S.; Kokawa, Hiroyuki [Tohoku Univ., Sendai (Japan). Dept. of Materials Processing; Enomoto, Masatoshi [Showa Aluminum Corp., Oyama City, Tochigi (Japan); Jogan, Shigetoshi [Showa Aluminum Corp., Sakai, Osaka (Japan)


    The microstructural distribution associated with a hardness profile in a friction-stir-welded, age-hardenable 6063 aluminum alloy has been characterized by transmission electron microscopy (TEM) and orientation imaging microscopy (OIM). The friction-stir process produces a softened region in the 6063 Al weld. Frictional heating and plastic flow during friction-stir welding create fine recrystallized grains in the weld zone and recovered grains in the thermomechanically affected zone. The hardness profile depends greatly on the precipitate distribution and only slightly on the grain size. The softened region is characterized by dissolution and growth of the precipitates during the welding. Simulated weld thermal cycles with different peak temperatures have shown that the precipitates are dissolved at temperatures higher than 675 K and that the density of the strengthening precipitate was reduced by thermal cycles lower than 675 K. A comparison between the thermal cycles and isothermal aging has suggested precipitation sequences in the softened region during friction-stir welding.

  2. Intelligent Flow Friction Estimation

    Directory of Open Access Journals (Sweden)

    Dejan Brkić


    Full Text Available Nowadays, the Colebrook equation is used as a mostly accepted relation for the calculation of fluid flow friction factor. However, the Colebrook equation is implicit with respect to the friction factor (λ. In the present study, a noniterative approach using Artificial Neural Network (ANN was developed to calculate the friction factor. To configure the ANN model, the input parameters of the Reynolds Number (Re and the relative roughness of pipe (ε/D were transformed to logarithmic scales. The 90,000 sets of data were fed to the ANN model involving three layers: input, hidden, and output layers with, 2, 50, and 1 neurons, respectively. This configuration was capable of predicting the values of friction factor in the Colebrook equation for any given values of the Reynolds number (Re and the relative roughness (ε/D ranging between 5000 and 108 and between 10−7 and 0.1, respectively. The proposed ANN demonstrates the relative error up to 0.07% which had the high accuracy compared with the vast majority of the precise explicit approximations of the Colebrook equation.

  3. Skin tribology: Science friction?

    NARCIS (Netherlands)

    Heide, van der E.; Zeng, X.; Masen, M.A.


    The application of tribological knowledge is not just restricted to optimizing mechanical and chemical engineering problems. In fact, effective solutions to friction and wear related questions can be found in our everyday life. An important part is related to skin tribology, as the human skin is fre

  4. Gravitomagnetic dynamical friction

    CERN Document Server

    Cashen, Benjamin; Kesden, Michael


    A supermassive black hole moving through a field of stars will gravitationally scatter the stars, inducing a backreaction force on the black hole known as dynamical friction. In Newtonian gravity, the axisymmetry of the system about the black hole's velocity $\\mathbf{v}$ implies that the dynamical friction must be anti-parallel to $\\mathbf{v}$. However, in general relativity the black hole's spin $\\mathbf{S}$ need not be parallel to $\\mathbf{v}$, breaking the axisymmetry of the system and generating a new component of dynamical friction similar to the Lorentz force $\\mathbf{F} = q\\mathbf{v} \\times \\mathbf{B}$ experienced by a particle with charge $q$ moving in a magnetic field $\\mathbf{B}$. We call this new force gravitomagnetic dynamical friction and calculate its magnitude for a spinning black hole moving through a field of stars with Maxwellian velocity dispersion $\\sigma$, assuming that both $v$ and $\\sigma$ are much less than the speed of light $c$. We use post-Newtonian equations of motion accurate to $...



    Ugues, Daniele; Maizza, Giovanni


    In the modern technology, tribologically suitable components and devices are important to increase the energy efficiency. It is possible when one can reduce the friction coefficient and wear of sliding components. The economic effectiveness can be achieved by better tribological system and therefore research in tribology is aimed at minimizing the energy losses resulting from friction and wear. In this view, hard coatings deposited by physical vapor deposition (PVD) are adequate solutions for...

  6. Effect of Al2O3 on the friction performance of P/M composite materials for friction applications (United States)

    Ivǎnuş, R. C.; ǎnuş, D., IV; Cǎlmuc, F.


    Bronze bearings are one of most used friction materials. In those applications where higher mechanical properties are needed, iron base bearings can be an alternative to bronze base materials, or other alloying elements added to bronze. The paper presents the results obtained in metal matrix composites field with friction characteristics, for automotive brakes, by P/M. The scope of these researches was the improvement of wear resistance and friction properties of metal matrix composites. Friction-wear properties of the Al2O3 reinforced samples were measured and compared with those of plain bronze based ones. For this purpose, density, hardness, friction coefficient wear behaviour of the samples were tested.Microstructures of samples before and after sintering and worn surfaces were also investigated by scanning electron microscopy (SEM), and the wear types were determined. The optimum friction-wear behaviour was obtained in the sample compacted at 500 MPa and sintered at 820°C. Density of the final samples decreased with increasing the amount of reinforcing elements (Al2O3) before presintering. However after sintering, there is no change in density of the samples including reinforcing elements (Al2O3). With increasing friction surface temperature, a reduction in the friction coefficient of the samples was observed. However, the highest reductions in the friction coefficients were observed in the as-received samples containing 0,5% reinforced Al2O3. The SEM images of the sample indicated that while bronze-based break lining material without Al2O3 showed abrasive wear behaviour, increasing the amount of Al2O3 resulted in a change of abrasive to adhesive wear mechanism. With increasing the amount of reinforcing Al2O3, wear resistance of the samples was increased. However samples reinforced with 5% and 6% Al2O3 showed the best results.

  7. Effect of Coulomb friction on orientational correlation and velocity distribution functions in a sheared dilute granular gas. (United States)

    Gayen, Bishakhdatta; Alam, Meheboob


    From particle simulations of a sheared frictional granular gas, we show that the Coulomb friction can have dramatic effects on orientational correlation as well as on both the translational and angular velocity distribution functions even in the Boltzmann (dilute) limit. The dependence of orientational correlation on friction coefficient (μ) is found to be nonmonotonic, and the Coulomb friction plays a dual role of enhancing or diminishing the orientational correlation, depending on the value of the tangential restitution coefficient (which characterizes the roughness of particles). From the sticking limit (i.e., with no sliding contact) of rough particles, decreasing the Coulomb friction is found to reduce the density and spatial velocity correlations which, together with diminished orientational correlation for small enough μ, are responsible for the transition from non-gaussian to gaussian distribution functions in the double limit of small friction (μ→0) and nearly elastic particles (e→1). This double limit in fact corresponds to perfectly smooth particles, and hence the maxwellian (gaussian) is indeed a solution of the Boltzmann equation for a frictional granular gas in the limit of elastic collisions and zero Coulomb friction at any roughness. The high-velocity tails of both distribution functions seem to follow stretched exponentials even in the presence of Coulomb friction, and the related velocity exponents deviate strongly from a gaussian with increasing friction.

  8. Friction and Wear Behaviors of Nanostructured Metals

    Institute of Scientific and Technical Information of China (English)

    Zhong HAN; Yusheng ZHANG; Ke LU


    Nanostructured (ns) materials, i.e., polycrystalline materials with grain sizes in the nanometer regime (typically below 100 nm), have drawn considerable attention in the past decades due to their unique properties such as high strength and hardness. Wear resistance of ns materials, one of the most important properties for engineering materials, has been extensively investigated in the past decades. Obvious differences have been identified in friction and wear behaviors Between the ns materials and their corresponding coarse-grained (cg) counterparts, consistently correlating with their unique structure characteristics and mechanical properties. On the other hand, the superior tribological properties of ns materials illustrate their potential applications under contact loads. The present overview will summarize the important progresses achieved on friction and wear behaviors of ns metallic materials, including ultrafine-grained (ufg) materials in recent years. Tribological properties and effects on friction and wear behaviors of ns materials will be discussed under different wear conditions including abrasive wear, sliding wear, and fretting wear. Their correlations with mechanical properties will be analyzed. Perspectives on development of this field will be highlighted as well.

  9. Friction measurement and modelling in forward rod extrusion

    DEFF Research Database (Denmark)

    Tan, Xincai; Bay, Niels; Zhang, Wenqi


    Forward extrusion is one of the important processes in bulk metal forming. Friction stress can be estimated from the slope of the load±displacement curve at the steady state after the maximum load in a forward extrusion test. In this paper, forward rod extrusion tests are carried out to determine...... experimentally friction stress at various normal pressures, reductions in area, billet heights and lubrications. Tested materials include aluminium alloy, low carbon steel and stainless steel. Two lubrication methods are applied, conversion coating followed by either alkaline soap or molybdenum disulphide...... as the lubricant. Friction stresses are obtained from measurements of slopes of extrusion pressure±punch travel curves at the steady state stage. Normal pressures are evaluated by using Mohr’s circle, in which shear ¯ow stresses are estimated at the maximum elastic deformation points from the same extrusion...

  10. On the generalized cost - demand elasticity of intermodal container transport

    NARCIS (Netherlands)

    Jourquin, B.; Tavasszy, L.A.; Duan, L.


    Elasticities for freight transport in the context of mode choice are hardly available for markets in which intermodal container transport competes with truck only transport. These elasticities are expected to be different, however, from values found in the literature for traditional freight

  11. Multi-objective Optimization of Continuous Drive Friction Welding Process Parameters Using Response Surface Methodology with Intelligent Optimization Algorithm

    Institute of Scientific and Technical Information of China (English)



    The optimum friction welding (FW) parameters of duplex stainless steel (DSS) UNS S32205 joint was determined. The experiment was carried out as the central composite array of 30 experiments. The selected input parameters were friction pressure (F), upset pressure (U), speed (S) and burn-off length (B), and responses were hardness and ultimate tensile strength. To achieve the quality of the welded joint, the ultimate tensile strength and hardness were maximized, and response surface methodology (RSM) was applied to create separate regression equations of tensile strength and hardness. Intelligent optimization technique such as genetic algorithm was used to predict the Pareto optimal solutions. Depending upon the application, preferred suitable welding parameters were selected. It was inferred that the changing hardness and tensile strength of the friction welded joint inlfuenced the upset pressure, friction pressure and speed of rotation.

  12. DAE for Frictional Contact Modeling of Constrained Multi-Flexible Body Systems

    Institute of Scientific and Technical Information of China (English)

    Ray P.S.Han; S. G. Mao


    A general formulation for modeling frictional contact interactions in a constrained multi-flexible body system is outlined in this paper. The governing differential-algebraic equations (DAE) for the constrained motion contains not only a frictional term but also, the unknown contact conditions. These contact conditions are characterized by a set of nonlinear complementarity equations. To demonstrate the model, a falling-spinning beam impacting a rough elastic ground with damping is solved and comparison with Stewart-Trinkles' results provided.

  13. Series Elastic Actuators for legged robots (United States)

    Pratt, Jerry E.; Krupp, Benjamin T.


    Series Elastic Actuators provide many benefits in force control of robots in unconstrained environments. These benefits include high force fidelity, extremely low impedance, low friction, and good force control bandwidth. Series Elastic Actuators employ a novel mechanical design architecture which goes against the common machine design principal of "stiffer is better." A compliant element is placed between the gear train and driven load to intentionally reduce the stiffness of the actuator. A position sensor measures the deflection, and the force output is accurately calculated using Hooke"s Law (F=Kx). A control loop then servos the actuator to the desired output force. The resulting actuator has inherent shock tolerance, high force fidelity and extremely low impedance. These characteristics are desirable in many applications including legged robots, exoskeletons for human performance amplification, robotic arms, haptic interfaces, and adaptive suspensions. We describe several variations of Series Elastic Actuators that have been developed using both electric and hydraulic components.

  14. Whether It's Hard for Poor Family to have a Talent from the Perspective of Psychological Theory of Elasticity%心理弹性理论视野下看寒门是否再难出学子

    Institute of Scientific and Technical Information of China (English)

    谢颖; 毛晋平


    心理弹性研究表明保护性因素通过各种途径对贫困学子产生重要的积极影响。人格倾向性、支持性家庭环境和外部支持系统三个保护性因素促使寒门学子积极应对生活逆境而赢得正常发展。公共教育资源向处境不利学子倾斜,为其提供学习和生活环境,促进智力、情绪、社会性等方面的健康发展。%The psychological elasticity study shows that the protective factors will have a significant positive influence on poverty students through various ways.The three protective factors of personality tendencies,supportive family environment and external support systems contribute to poor family students to cope with adversity and win the normal development of life.Resources for public education inclinable to disadvantaged students will provide them a rich learning and living environment and promote healthy development of the intellectual,emotional and social aspects.

  15. Quantum tunneling with friction (United States)

    Tokieda, M.; Hagino, K.


    Using the phenomenological quantum friction models introduced by P. Caldirola [Nuovo Cimento 18, 393 (1941), 10.1007/BF02960144] and E. Kanai [Prog. Theor. Phys. 3, 440 (1948), 10.1143/ptp/3.4.440], M. D. Kostin [J. Chem. Phys. 57, 3589 (1972), 10.1063/1.1678812], and K. Albrecht [Phys. Lett. B 56, 127 (1975), 10.1016/0370-2693(75)90283-X], we study quantum tunneling of a one-dimensional potential in the presence of energy dissipation. To this end, we calculate the tunneling probability using a time-dependent wave-packet method. The friction reduces the tunneling probability. We show that the three models provide similar penetrabilities to each other, among which the Caldirola-Kanai model requires the least numerical effort. We also discuss the effect of energy dissipation on quantum tunneling in terms of barrier distributions.

  16. Friction in rail guns (United States)

    Kay, P. K.


    The influence of friction is included in the present equations describing the performance of an inductively driven rail gun. These equations, which have their basis in an empirical formulation, are applied to results from two different experiments. Only an approximate physical description of the problem is attempted, in view of the complexity of details in the interaction among forces of this magnitude over time periods of the order of milisecs.

  17. Numerical-analytical investigation into impact pipe driving in soil with dry friction. Part II: Deformable external medium

    CERN Document Server

    Aleksandrova, Nadezhda


    Under analysis is travel of P-waves in an elastic pipe partly embedded in soil with dry friction. The mathematical formulation of the problem on impact pipe driving in soil is based on the model of axial vibration of an elastic bar, considering lateral resistance described using the law of solid dry friction. The author solves problems on axial load on pipe in interaction with external elastic medium, and compares the analytical and numerical results obtained with and without accounting for the external medium deformability.

  18. Hard and Soft Multilayered SiCN Nanocoatings with High Hardness and Toughness

    Directory of Open Access Journals (Sweden)

    S. K. Mishra


    Full Text Available Alternate hard and soft layers increase deformation accommodation as thin hard layers slide relative to each other due to shear deformation of low modulus layers. However, the processing of such multilayers is challenging. In the present paper the alternating soft and hard multilayered SiCN coating deposited by magnetron sputtering has been studied and presented. A hardness and modulus of 37 GPa and 317 GPa with elastic recovery of 62% are achieved by alternate hard and soft layer of Si–C–N by magnetron sputtering. The trilayer films sustained even 2000 gf under indentation without failure though substrate plastically deformed. The fracture toughness value KIC was measured to be 9.5–10 MPa m1/2, significantly higher than many reported hard coatings.

  19. High Speed Friction Microscopy and Nanoscale Friction Coefficient Mapping


    Bosse, James L.; Lee, Sungjun; Huey, Bryan D; Andersen, Andreas Sø; Sutherland, Duncan S


    As mechanical devices in the nano/micro length scale are increasingly employed, it is crucial to understand nanoscale friction and wear especially at technically relevant sliding velocities. Accordingly, a novel technique has been developed for Friction Coefficient Mapping (FCM), leveraging recent advances in high speed AFM. The technique efficiently acquires friction versus force curves based on a sequence of images at a single location, each with incrementally lower loads. As a result, true...

  20. A phase-plane analysis of localized frictional waves (United States)

    Putelat, T.; Dawes, J. H. P.; Champneys, A. R.


    Sliding frictional interfaces at a range of length scales are observed to generate travelling waves; these are considered relevant, for example, to both earthquake ground surface movements and the performance of mechanical brakes and dampers. We propose an explanation of the origins of these waves through the study of an idealized mechanical model: a thin elastic plate subject to uniform shear stress held in frictional contact with a rigid flat surface. We construct a nonlinear wave equation for the deformation of the plate, and couple it to a spinodal rate-and-state friction law which leads to a mathematically well-posed problem that is capable of capturing many effects not accessible in a Coulomb friction model. Our model sustains a rich variety of solutions, including periodic stick-slip wave trains, isolated slip and stick pulses, and detachment and attachment fronts. Analytical and numerical bifurcation analysis is used to show how these states are organized in a two-parameter state diagram. We discuss briefly the possible physical interpretation of each of these states, and remark also that our spinodal friction law, though more complicated than other classical rate-and-state laws, is required in order to capture the full richness of wave types.

  1. Computational Elastic Knots

    KAUST Repository

    Zhao, Xin


    Elastic rods have been studied intensively since the 18th century. Even now the theory of elastic rods is still developing and enjoying popularity in computer graphics and physical-based simulation. Elastic rods also draw attention from architects. Architectural structures, NODUS, were constructed by elastic rods as a new method of form-finding. We study discrete models of elastic rods and NODUS structures. We also develop computational tools to find the equilibria of elastic rods and the shape of NODUS. Applications of elastic rods in forming torus knot and closing Bishop frame are included in this thesis.

  2. Physically representative atomistic modeling of atomic-scale friction (United States)

    Dong, Yalin

    Nanotribology is a research field to study friction, adhesion, wear and lubrication occurred between two sliding interfaces at nano scale. This study is motivated by the demanding need of miniaturization mechanical components in Micro Electro Mechanical Systems (MEMS), improvement of durability in magnetic storage system, and other industrial applications. Overcoming tribological failure and finding ways to control friction at small scale have become keys to commercialize MEMS with sliding components as well as to stimulate the technological innovation associated with the development of MEMS. In addition to the industrial applications, such research is also scientifically fascinating because it opens a door to understand macroscopic friction from the most bottom atomic level, and therefore serves as a bridge between science and engineering. This thesis focuses on solid/solid atomic friction and its associated energy dissipation through theoretical analysis, atomistic simulation, transition state theory, and close collaboration with experimentalists. Reduced-order models have many advantages for its simplification and capacity to simulating long-time event. We will apply Prandtl-Tomlinson models and their extensions to interpret dry atomic-scale friction. We begin with the fundamental equations and build on them step-by-step from the simple quasistatic one-spring, one-mass model for predicting transitions between friction regimes to the two-dimensional and multi-atom models for describing the effect of contact area. Theoretical analysis, numerical implementation, and predicted physical phenomena are all discussed. In the process, we demonstrate the significant potential for this approach to yield new fundamental understanding of atomic-scale friction. Atomistic modeling can never be overemphasized in the investigation of atomic friction, in which each single atom could play a significant role, but is hard to be captured experimentally. In atomic friction, the

  3. Friction laws for lubricated nanocontacts (United States)

    Buzio, R.; Boragno, C.; Valbusa, U.


    We have used friction force microscopy to probe friction laws for nanoasperities sliding on atomically flat substrates under controlled atmosphere and liquid environment, respectively. A power law relates friction force and normal load in dry air, whereas a linear relationship, i.e., Amontons' law, is observed for junctions fully immersed in model lubricants, namely, octamethylciclotetrasiloxane and squalane. Lubricated contacts display a remarkable friction reduction, with liquid and substrate specific friction coefficients. Comparison with molecular dynamics simulations suggests that load-bearing boundary layers at junction entrance cause the appearance of Amontons' law and impart atomic-scale character to the sliding process; continuum friction models are on the contrary of limited predictive power when applied to lubrication effects. An attempt is done to define general working conditions leading to the manifestation of nanoscale lubricity due to adsorbed boundary layers.

  4. Friction stir welding of AZ31 magnesium alloy

    Institute of Scientific and Technical Information of China (English)

    林三宝; 张华; 吴林; 冯吉才; 戴鸿滨


    Friction stir welding (FSW) is an new solid-phase joining technology which has more advantages over fusion welding methods in welding of aluminum and other non-ferrous metals. The effects of welding parameters on mechanical properties and microstructure during friction stir welding of AZ31 magnesium alloy were studied in this paper. Microstructures and mechanical properties of the joints were investigated by means of optical microscopy, scanning electric microscopy (SEM), micro-hardness analysis, and tensile test. Experimental results show that the magnesium alloy can be successfully welded by FSW method, and the ultimate tensile strength (UTS) of FSW joint reaches up to 90 percent of base metal. The microstructures of welded joints exhibit the variation from dynamically recrystallized fine grains to greatly deformed grains. Hardness in nugget zone was found lower than the base metal but not too obvious.

  5. Elastic and mechanical softening in boron-doped diamond (United States)

    Liu, Xiaobing; Chang, Yun-Yuan; Tkachev, Sergey N.; Bina, Craig R.; Jacobsen, Steven D.


    Alternative approaches to evaluating the hardness and elastic properties of materials exhibiting physical properties comparable to pure diamond have recently become necessary. The classic linear relationship between shear modulus (G) and Vickers hardness (HV), along with more recent non-linear formulations based on Pugh’s modulus extending into the superhard region (HV > 40 GPa) have guided synthesis and identification of novel superabrasives. These schemes rely on accurately quantifying HV of diamond-like materials approaching or potentially exceeding the hardness of the diamond indenter, leading to debate about methodology and the very definition of hardness. Elasticity measurements on such materials are equally challenging. Here we used a high-precision, GHz-ultrasonic interferometer in conjunction with a newly developed optical contact micrometer and 3D optical microscopy of indentations to evaluate elasticity-hardness relations in the ultrahard range (HV > 80 GPa) by examining single-crystal boron-doped diamond (BDD) with boron contents ranging from 50–3000 ppm. We observe a drastic elastic-mechanical softening in highly doped BDD relative to the trends observed for superhard materials, providing insight into elasticity-hardness relations for ultrahard materials. PMID:28233808

  6. Elastic and mechanical softening in boron-doped diamond. (United States)

    Liu, Xiaobing; Chang, Yun-Yuan; Tkachev, Sergey N; Bina, Craig R; Jacobsen, Steven D


    Alternative approaches to evaluating the hardness and elastic properties of materials exhibiting physical properties comparable to pure diamond have recently become necessary. The classic linear relationship between shear modulus (G) and Vickers hardness (HV), along with more recent non-linear formulations based on Pugh's modulus extending into the superhard region (HV > 40 GPa) have guided synthesis and identification of novel superabrasives. These schemes rely on accurately quantifying HV of diamond-like materials approaching or potentially exceeding the hardness of the diamond indenter, leading to debate about methodology and the very definition of hardness. Elasticity measurements on such materials are equally challenging. Here we used a high-precision, GHz-ultrasonic interferometer in conjunction with a newly developed optical contact micrometer and 3D optical microscopy of indentations to evaluate elasticity-hardness relations in the ultrahard range (HV > 80 GPa) by examining single-crystal boron-doped diamond (BDD) with boron contents ranging from 50-3000 ppm. We observe a drastic elastic-mechanical softening in highly doped BDD relative to the trends observed for superhard materials, providing insight into elasticity-hardness relations for ultrahard materials.

  7. Elastic and mechanical softening in boron-doped diamond (United States)

    Liu, Xiaobing; Chang, Yun-Yuan; Tkachev, Sergey N.; Bina, Craig R.; Jacobsen, Steven D.


    Alternative approaches to evaluating the hardness and elastic properties of materials exhibiting physical properties comparable to pure diamond have recently become necessary. The classic linear relationship between shear modulus (G) and Vickers hardness (HV), along with more recent non-linear formulations based on Pugh’s modulus extending into the superhard region (HV > 40 GPa) have guided synthesis and identification of novel superabrasives. These schemes rely on accurately quantifying HV of diamond-like materials approaching or potentially exceeding the hardness of the diamond indenter, leading to debate about methodology and the very definition of hardness. Elasticity measurements on such materials are equally challenging. Here we used a high-precision, GHz-ultrasonic interferometer in conjunction with a newly developed optical contact micrometer and 3D optical microscopy of indentations to evaluate elasticity-hardness relations in the ultrahard range (HV > 80 GPa) by examining single-crystal boron-doped diamond (BDD) with boron contents ranging from 50–3000 ppm. We observe a drastic elastic-mechanical softening in highly doped BDD relative to the trends observed for superhard materials, providing insight into elasticity-hardness relations for ultrahard materials.

  8. Raising the heat and wear resistances of hardened carbon steels by friction strengthening treatment (United States)

    Makarov, A. V.; Korshunov, L. G.; Malygina, I. Yu.; Solodova, I. L.


    The effect of friction treatment by a hard-alloy indenter on the microhardness and resistance to the heat-induced softening upon tempering of hardened medium-and high-carbon steels at 100-600°C is studied. The x-ray and electron microscopy methods are used to determine the causes of the increase in the heat resistance of the friction-strained steel surfaces. A comparative analysis of the effect of the hardening treatment by a hard-alloy indenter and by abrasive particles on the friction-induced heat resistance is performed for the case of high-speed friction treatment of a high-carbon laser-hardened steel.

  9. Micromechanical study of macroscopic friction and dissipation in idealised granular materials: the effect of interparticle friction

    NARCIS (Netherlands)

    Kruyt, N.P.; Rothenburg, L.; Gutkowski, Witold; Kowalewski, Tomasz A.


    Using Discrete Element Method (DEM) simulations with varying interparticle friction coefficient, the relation between interparticle friction coefficient and macroscopic continuum friction and dissipation is investigated. As expected, macroscopic friction and dilatancy increase with interparticle fri

  10. Frictional granular mechanics: A variational approach

    Energy Technology Data Exchange (ETDEWEB)

    Holtzman, R.; Silin, D.B.; Patzek, T.W.


    The mechanical properties of a cohesionless granular material are evaluated from grain-scale simulations. Intergranular interactions, including friction and sliding, are modeled by a set of contact rules based on the theories of Hertz, Mindlin, and Deresiewicz. A computer generated, three-dimensional, irregular pack of spherical grains is loaded by incremental displacement of its boundaries. Deformation is described by a sequence of static equilibrium configurations of the pack. A variational approach is employed to find the equilibrium configurations by minimizing the total work against the intergranular loads. Effective elastic moduli are evaluated from the intergranular forces and the deformation of the pack. Good agreement between the computed and measured moduli, achieved with no adjustment of material parameters, establishes the physical soundness of the proposed model.

  11. Friction welding; Magnesium; Finite element; Shear test.

    Directory of Open Access Journals (Sweden)

    Leonardo Contri Campanelli


    Full Text Available Friction spot welding (FSpW is one of the most recently developed solid state joining technologies. In this work, based on former publications, a computer aided draft and engineering resource is used to model a FSpW joint on AZ31 magnesium alloy sheets and subsequently submit the assembly to a typical shear test loading, using a linear elastic model, in order to conceive mechanical tests results. Finite element analysis shows that the plastic flow is concentrated on the welded zone periphery where yield strength is reached. It is supposed that “through the weld” and “circumferential pull-out” variants should be the main failure behaviors, although mechanical testing may provide other types of fracture due to metallurgical features.

  12. Frictional granular mechanics: A variational approach

    Energy Technology Data Exchange (ETDEWEB)

    Holtzman, R.; Silin, D.B.; Patzek, T.W.


    The mechanical properties of a cohesionless granular material are evaluated from grain-scale simulations. Intergranular interactions, including friction and sliding, are modeled by a set of contact rules based on the theories of Hertz, Mindlin, and Deresiewicz. A computer generated, three-dimensional, irregular pack of spherical grains is loaded by incremental displacement of its boundaries. Deformation is described by a sequence of static equilibrium configurations of the pack. A variational approach is employed to find the equilibrium configurations by minimizing the total work against the intergranular loads. Effective elastic moduli are evaluated from the intergranular forces and the deformation of the pack. Good agreement between the computed and measured moduli, achieved with no adjustment of material parameters, establishes the physical soundness of the proposed model.

  13. Friction and wear calculation methods

    CERN Document Server

    Kragelsky, I V; Kombalov, V S


    Friction and Wear: Calculation Methods provides an introduction to the main theories of a new branch of mechanics known as """"contact interaction of solids in relative motion."""" This branch is closely bound up with other sciences, especially physics and chemistry. The book analyzes the nature of friction and wear, and some theoretical relationships that link the characteristics of the processes and the properties of the contacting bodies essential for practical application of the theories in calculating friction forces and wear values. The effect of the environment on friction and wear is a

  14. Control rod drop surveillance using two friction coefficients


    Blázquez, Juan; Vallejo, I.; García-Berrocal Sánchez, Agustin; Balbás Antón, Miguel


    In the case of large burnup, a control rod (CR) guide tube in the pressurized water reactor of a commercial nuclear power plant might bend. As a consequence, a CR drop experiment may indicate an event of a CR partially inserted and whether the CR should be deemed inoperable. Early prevention of such an event can be achieved by measuring two friction coefficients: the hydraulic coefficient and the sliding coefficient. The hydraulic coefficient hardly changes, so that the curvature of the guide...

  15. Friction or Closure

    DEFF Research Database (Denmark)

    Lundahl, Mikela


    . The anthropologist Anna Tsing has developed the concept-metaphor friction as a way to discuss the energy created when various actors narrate “the same” event(s) in different ways, and see the other participants’ accounts as fantasies or even fabrications. I will use my position as researcher and my relations...... is Stone Town in Zanzibar and the de-velopment and dissolution going on under the shadow of the UNESCO World Heritage flag; a growing tourism; a global and local increase in islamisation; and the political tension within the Tanzanian union. My main focus is narratives of the identity of Zanzibar since...

  16. Effects of water-vapor on friction and deformation of polymeric magnetic media in contact with a ceramic oxide (United States)

    Miyoshi, K.; Buckley, D. H.


    The effects of humidity (water-vapor) in nitrogen on the friction and deformation behavior of magnetic tape in contact with a Ni-Zn ferrite spherical pin were studied. The coefficient of friction is markedly dependent on the ambient relative humidity. In elastic contacts the coefficient of friction increased linearly with increasing humidity; it decreased linearly when humidity was lowered. This effect is the result of changes in the chemistry and interaction of tape materials such as degradation of the lubricant. In plastic contacts there was no effect of humidity on friction below 40 percent relative humidity. There is no effect on friction associated with the breakthrough of the adsorbed water-vapor film at the interface of the tape and Ni-Zn ferrite. The coefficient of friction, however, increased rapidly with increasing relative humidity above 40 percent in plastic contacts.

  17. Friction analysis of kinetic schemes : the friction coefficient

    NARCIS (Netherlands)

    Lolkema, Juke S.


    Friction analysis is proposed as the application of general control analysis to single enzymes to describe the control of elementary kinetic steps on the overall catalytic rate. For each transition, a friction coefficient is defined that measures the sensitivity of the turnover rate to the free ener


    NARCIS (Netherlands)



    Friction analysis is proposed as the application of general control analysis to single enzymes to describe the control of elementary kinetic steps on the overall catalytic rate. For each transition, a friction coefficient is defined that measures the sensitivity of the turnover rate to the free ener

  19. Friction analysis of kinetic schemes : the friction coefficient

    NARCIS (Netherlands)

    Lolkema, Juke S.


    Friction analysis is proposed as the application of general control analysis to single enzymes to describe the control of elementary kinetic steps on the overall catalytic rate. For each transition, a friction coefficient is defined that measures the sensitivity of the turnover rate to the free ener

  20. The study on the properties of AISI 4140 and AISI 1040 steel rods welded by friction welding


    Thanee Toomprasen; Chawalit Thinvongpituk; Sukangkana Talangkun


    This paper is aimed to investigate the properties of joint between AISI 4140 and AISI 1040 welded by friction welding. The specimens were prepared in round shape of 13 mm diameter and 100 mm long. They were welded by friction welding method under the following conditions; friction pressure of 183 MPa, friction time of 12 sec, upset pressure of 428 MPa, upset time of 7 sec. and rotational speed of 1400 rpm. The strength and hardness were tested on the welded area. The result showed finer grain...

  1. Nanoscale friction as a function of activation energies (United States)

    Chong, W. W. F.; Rahnejat, H.


    Understanding the scale-dependence of friction is increasingly viewed as a critical quest. With progressively thinner films, mixed and boundary regimes of lubrication have become commonplace. Therefore, at the micro-scale a greater need for mitigating friction is desired in order to improve operational efficiency of many machines and mechanisms. Furthermore, there is a growing tendency to use low friction hard wear-resistant advanced coatings to guard against wear. In parallel, there has been much attention paid to lubricant rheology and formulation. However, only in recent times there has been an emerging view of lubricant-surface combination as a system. In this perspective it is essential to relate the observed and measured friction at component level to the underlying interactions in micro/nano-scales. This is the approach in this paper. Observed phenomenon at micro-scale are related back to the activation energies of lubricant-surface system, providing in particular results for surface modified Ni-SiC coated specimen in combination with formulated lubricants, the combination of which represent the lubricant-surface system of choice in cylinders of high performance race engine. The nano-scale conjunction of an AFM tip with lubricated surface-engineered specimen, subjected to various conjunctional loading and sliding kinematics is investigated. It is shown that the measured frictional characteristics can be adequately described in terms of activation energies in line with the Eyring’s thermal activation model for cases of fairly smooth asperity tip contact conjunctions.

  2. Stir zone microstructure of commercial purity titanium friction stir welded using pcBN tool

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Yu [Department of Materials Processing, Graduate School of Engineering, Tohoku University, 6-6-02 Aramaki-aza-Aoba, Aoba-ku, Sendai 980-8579 (Japan)], E-mail:; Sato, Yutaka S.; Kokawa, Hiroyuki [Department of Materials Processing, Graduate School of Engineering, Tohoku University, 6-6-02 Aramaki-aza-Aoba, Aoba-ku, Sendai 980-8579 (Japan); Park, Seung Hwan C.; Hirano, Satoshi [Hitachi Research Laboratory, Hitachi Ltd., Omika 7-1-1, Hitachi 319-1292 (Japan)


    In the present study, friction stir welding was applied to commercial purity titanium using a polycrystalline cubic boron nitride tool, and microstructure and hardness in the weld were examined. Additionally, the microstructural evolution during friction stir welding was also discussed. The stir zone consisted of fine equiaxed {alpha} grains surrounded by serrate grain boundaries, which were produced through the {beta} {yields} {alpha} allotropic transformation during the cooling cycle of friction stir welding. The fine {alpha} grains caused higher hardness than that in the base material. A lath-shaped {alpha} grain structure containing Ti borides and tool debris was observed in the surface region of the stir zone, whose hardness was the highest in the weld.

  3. Friction Stir Welding (United States)

    Nunes, Arthur C., Jr.


    Friction stir welding (FSW) is a solid state welding process invented in 1991 at The Welding Institute in the United Kingdom. A weld is made in the FSW process by translating a rotating pin along a weld seam so as to stir the sides of the seam together. FSW avoids deleterious effects inherent in melting and promises to be an important welding process for any industries where welds of optimal quality are demanded. This article provides an introduction to the FSW process. The chief concern is the physical effect of the tool on the weld metal: how weld seam bonding takes place, what kind of weld structure is generated, potential problems, possible defects for example, and implications for process parameters and tool design. Weld properties are determined by structure, and the structure of friction stir welds is determined by the weld metal flow field in the vicinity of the weld tool. Metal flow in the vicinity of the weld tool is explained through a simple kinematic flow model that decomposes the flow field into three basic component flows: a uniform translation, a rotating solid cylinder, and a ring vortex encircling the tool. The flow components, superposed to construct the flow model, can be related to particular aspects of weld process parameters and tool design; they provide a bridge to an understanding of a complex-at-first-glance weld structure. Torques and forces are also discussed. Some simple mathematical models of structural aspects, torques, and forces are included.

  4. Mechanical and Microstructural Properties of Friction Welded AISI 304 Stainless Steel to AISI 1060 Steel AISI 1060

    Directory of Open Access Journals (Sweden)

    Ates H.


    Full Text Available Rotary Friction welding is one of the most popular methods of joining similar and dissimilar materials. It is widely used with metals and thermoplastics in a wide variety of aviation, transport and aerospace industrial component designs. This study investigates the influence of friction and upsetting pressures on the hardness, tensile properties and microstructure of the welds. The experimental results showed that as the friction and upsetting pressures increased, the hardness and tensile strength values increased, as well. The tensile fracture of welded joint occurred in the AISI 1060 side. The friction processed joints were evaluated for their integrity and quality aspects by optical and scanning electron microscopy. For the perfect interfacial bonding, sufficient upsetting and friction pressures are necessary to reach the optimal temperature and severe plastic deformation to bring these materials within the attraction range.

  5. An engineering approach to dry friction behaviour of numerous engineering plastics with respect to the mechanical properties

    Directory of Open Access Journals (Sweden)

    G. Kalacska


    Full Text Available Twenty-one different commercial-grade engineering polymers, including virgin and composite types, were selected for testing, based on mechanical engineering practices. Three groups were formed according to typical applications: 1 Sliding machine element materials; 2 Mechanically load-carrying machine element materials that are often subjected to friction and wear effects; and 3 Additional two amorphous materials used as chemically resistant materials that have rare sliding load properties. The friction running-in state was tested using a dynamic pin-on-plate test rig. During steady-state friction tests, two pv regimes (0.8 and 2 MPa"ms–1 were analysed by a pin-on-disc test system. Based on the measured forces on ground structural steel, surface friction coefficients were calculated and analysed with respect to the mechanical effects of friction. The friction results were evaluated by the measured mechanical properties: yield stress, Shore D hardness, Young’s modulus and elongation at the break. The three material groups exhibited different trends in friction with respect to changing mechanical properties. Linear (with varying positive and negative slopes, logarithmic and exponential relationships were observed, and occasionally there were no effects observed. At steady-state friction, the elongation at the break had less effect on the friction coefficients. The dynamic sliding model, which correlates better to real machine element applications, showed that increasing hardness and yield stress decreases friction. During steady-state friction, an increase in pv regime often changed the sign of the linear relationship between the material property and the friction, which agrees with the frictional theory of polymer/steel sliding pairs.

  6. Corrosion effects on friction factors

    Energy Technology Data Exchange (ETDEWEB)

    Magleby, H.L.; Shaffer, S.J.


    This paper presents the results of NRC-sponsored material specimen tests that were performed to determine if corrosion increases the friction factors of sliding surfaces of motor-operated gate valves, which could require higher forces to close and open safety-related valves when subjected to their design basis differential pressures. Friction tests were performed with uncorroded specimens and specimens subjected to accelerated corrosion. Preliminary tests at ambient conditions showed that corrosion increased the friction factors, indicating the need for additional tests duplicating valve operating parameters at hot conditions. The additional tests showed friction factors of corroded specimens were 0.1 to 0.2 higher than for uncorroded specimens, and that the friction factors of the corroded specimens were not very dependent on contact stress or corrosion film thickness. The measured values of friction factors for the three corrosion films tested (simulating three operating times) were in the range of 0.3 to 0.4. The friction factor for even the shortest simulated operating time was essentially the same as the others, indicating that the friction factors appear to reach a plateau and that the plateau is reached quickly.

  7. Estimating Stresses, Fault Friction and Fluid Pressure from Topography and Coseismic Slip Models (United States)

    Styron, R. H.; Hetland, E. A.


    Stress is a first-order control on the deformation state of the earth. However, stress is notoriously hard to measure, and researchers typically only estimate the directions and relative magnitudes of principal stresses, with little quantification of the uncertainties or absolute magnitude. To improve upon this, we have developed methods to constrain the full stress tensor field in a region surrounding a fault, including tectonic, topographic, and lithostatic components, as well as static friction and pore fluid pressure on the fault. Our methods are based on elastic halfspace techniques for estimating topographic stresses from a DEM, and we use a Bayesian approach to estimate accumulated tectonic stress, fluid pressure, and friction from fault geometry and slip rake, assuming Mohr-Coulomb fault mechanics. The nature of the tectonic stress inversion is such that either the stress maximum or minimum is better constrained, depending on the topography and fault deformation style. Our results from the 2008 Wenchuan event yield shear stresses from topography up to 20 MPa (normal-sinistral shear sense) and topographic normal stresses up to 80 MPa on the faults; tectonic stress had to be large enough to overcome topography to produce the observed reverse-dextral slip. Maximum tectonic stress is constrained to be >0.3 * lithostatic stress (depth-increasing), with a most likely value around 0.8, trending 90-110°E. Minimum tectonic stress is about half of maximum. Static fault friction is constrained at 0.1-0.4, and fluid pressure at 0-0.6 * total pressure on the fault. Additionally, the patterns of topographic stress and slip suggest that topographic normal stress may limit fault slip once failure has occurred. Preliminary results from the 2013 Balochistan earthquake are similar, but yield stronger constraints on the upper limits of maximum tectonic stress, as well as tight constraints on the magnitude of minimum tectonic stress and stress orientation. Work in progress on

  8. Research on measurement and modeling of the gastro intestine's frictional characteristics (United States)

    Wang, Kun Dong; Yan, Guo Zheng


    The frictional characteristics of an intestine are required basically for the development of a noninvasive endoscope for the human intestine. The frictional force is tested by measuring the current of the motor hauling the frictional coupons at an even speed. A multifunction data acquisition device with model NI-6008 USB is used and the data process is performed on the Labview software. Two kinds of materials with aluminum and copper are used. The surfaces are designed as triangle, rectangular, cylindrical and plane forms. The tested results indicate that the frictional resistance force includes the nominal frictional force and the visco-adhesive force. When the surface contour changes from the triangle to the rectangular, to the cylindrical and finally to the plane, the nominal frictional coefficients will decrease and the visco-adhesive force will increase. The nominal frictional force is related to the elastic restoring force, the real frictional force and the contact angle. The cohesive force is determined by the contact area and the contact angle. This research will provide some preliminary references to the design and the parameter selection of locomotion devices in the human gastro-intestine.

  9. Friction in surface micromachined microengines

    Energy Technology Data Exchange (ETDEWEB)

    Miller, S.L.; Sniegowski, J.J.; LaVigne, G.; McWhorter, P.J.


    Understanding the frictional properties of advanced Micro-Electro- Mechanical Systems (MEMS) is essential in order to develop optimized designs and fabrication processes, as well as to qualify devices for commercial applications. We develop and demonstrate a method to experimentally measure the forces associated with sliding friction of devices rotating on a hub. The method is demonstrated on the rotating output gear of the microengine recently developed at Sandia National Laboratories. In-situ measurements of an engine running at 18300 rpm give a coefficient of friction of 0.5 for radial (normal) forces less than 4 {mu}N. For larger forces the effective coefficient of friction abruptly increases, suggesting a fundamental change in the basic nature of the interaction between the gear and hub. The experimental approach we have developed to measure the frictional forces associated with the microengine is generically applicable to other MEMS devices.

  10. Stable and Critical Noncohesive Coulomb Wedges: Exact Elastic Solutions (United States)

    Wang, K.; Hu, Y.


    The theory of critically tapered Coulomb wedge has been successfully applied to model active fold-and-thrust belts or submarine accretionary prisms. Brittle mountain building is episodic in nature, controlled by changes in basal friction, erosion and sedimentation, and hydrogeology. Sediment accretion may be modulated by great subduction earthquakes. Between deformation episodes and/or during transition between compressional and extensional tectonics, the Coulomb wedges are stable (i.e., supercritical), to which the critical taper theory does not apply. In this work, we provide an exact elastic solution for stable wedges based on Airy stress functions. The stress equilibrium equation and definition of basal friction and basal and internal pore fluid pressure ratios are exactly the same as those used for Dahlen's [1984] exact solution for critical noncohesive Coulomb wedges, but internal friction μ becomes irrelevant. Given elastic - perfectly Coulomb-plastic rheology, for stresses in a wedge on the verge of Coulomb failure there must co-exist a critical taper solution involving μ and a unique equivalent elastic solution not involving μ . Our elastic solution precisely reduces to Dahlen's critical taper solution for critical conditions. For stable conditions, normal stress perpendicular to the surface slope σ z and shear stress τ xz are identical with those in a critical taper, but the slope-parallel normal stress is different. The elastic solution is also generally applicable to purely elastic wedges and useful for modeling geodetic observations. A stable noncohesive Coulomb wedge differs from a general elastic wedge in that its upper and lower surfaces stay at zero curvature during loading. Dahlen, F.A. (1984), Noncohesive critical Coulomb wedges: An exact solution, JGR, 89, 10,125-10,133.

  11. Tactile friction of topical formulations. (United States)

    Skedung, L; Buraczewska-Norin, I; Dawood, N; Rutland, M W; Ringstad, L


    The tactile perception is essential for all types of topical formulations (cosmetic, pharmaceutical, medical device) and the possibility to predict the sensorial response by using instrumental methods instead of sensory testing would save time and cost at an early stage product development. Here, we report on an instrumental evaluation method using tactile friction measurements to estimate perceptual attributes of topical formulations. Friction was measured between an index finger and an artificial skin substrate after application of formulations using a force sensor. Both model formulations of liquid crystalline phase structures with significantly different tactile properties, as well as commercial pharmaceutical moisturizing creams being more tactile-similar, were investigated. Friction coefficients were calculated as the ratio of the friction force to the applied load. The structures of the model formulations and phase transitions as a result of water evaporation were identified using optical microscopy. The friction device could distinguish friction coefficients between the phase structures, as well as the commercial creams after spreading and absorption into the substrate. In addition, phase transitions resulting in alterations in the feel of the formulations could be detected. A correlation was established between skin hydration and friction coefficient, where hydrated skin gave rise to higher friction. Also a link between skin smoothening and finger friction was established for the commercial moisturizing creams, although further investigations are needed to analyse this and correlations with other sensorial attributes in more detail. The present investigation shows that tactile friction measurements have potential as an alternative or complement in the evaluation of perception of topical formulations. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  12. Analysis of a Frictional Contact Problem with Adhesion

    Directory of Open Access Journals (Sweden)

    Z. Lerguet


    Full Text Available We consider a mathematical model which describes the contact between a deformable body and an obstacle, the so-called foundation. The contact is frictional and is modelled with aversion of normal compliance condition and the associated Coulomb's law of dry friction in which the adhesion of contact surfaces is taken into account. The evolution of the bonding fieldis described by a first order differential equation and the material's behavior is modelled with a nonlinear elastic constitutive law. We derive a variational formulation of the problem then, under a smallness assumption on the coefficient of friction, we prove the existence of a unique weak solution for the model. The proof is based on arguments of time-dependent variational inequalities, differential equations and Banach'sfixed point theorem. Finally, we extend our results in the case when the piezoelectric effect is taken into account, i.e. in the case when the material's behavior is modelled with a nonlinear electro-elastic constitutive law.

  13. Fabricated and friction test anisotropy material of ultrasonic motor

    Institute of Scientific and Technical Information of China (English)

    QU Yan-yan; QU Jian-jun; KUANG Nai-hang


    The twisters for composed of anisotropic material were designed and manufactured.And two kinds of directional-composites were made:one was fiber direction vertical with frictional interface and another was parallel with frictional interface and moving direction.By varying the proportions of epoxy resin and fiber and arranging the orientations of fiber,the composites anisotropy along longitudinal and circumferential were got.Using density measurement,the mass fraction of resin and fiber were calculated.According to composite mesoscopic mechanics,the elasticity constants of composite were analyzed and calculated.The composite different thicknesses were sliced,and attach to the rotor,then the load characteristics,no-load speed,stop load of ultrasonic motor(USM) were test.The output properties of USM with 0.6 mm thickness composite were superior.The effect of friction material on ultrasonic motor was analyzed.Elastic modulus,thickness and micro-morphology of material are main factors which affect characteristics of ultrasonic motor.

  14. Friction stir processing on carbon steel

    Energy Technology Data Exchange (ETDEWEB)

    Tarasov, Sergei Yu., E-mail: [Institute of Strength Physics and Materials Science SB RAS, Tomsk, 634055, Russia and National Research Tomsk Polytechnic University, Tomsk, 634050 (Russian Federation); Melnikov, Alexander G., E-mail: [National Research Tomsk Polytechnic University, Tomsk, 634050 (Russian Federation); Rubtsov, Valery E., E-mail: [Institute of Strength Physics and Materials Science SB RAS, Tomsk, 634055 (Russian Federation)


    Friction stir processing of medium carbon steel samples has been carried out using a milling machine and tools made of cemented tungsten carbide. Samples have been machined from 40 and 40X steels. The tools have been made in the shape of 5×5×1.5 mm and 3×3×1.5 mm tetrahedrons. The microstructure of stirred zone has been obtained using the smaller tool and consists of fine recrystallized 2-3 μm grains, whereas the larger tool has produced the 'onion-like' structures comprising hard quenched 'white' 500-600 MPa layers with 300-350 MPa interlayers of bainite needles. The mean values of wear intensity obtained after measuring the wear scar width were 0.02 mm/m and 0.001 mm/m for non-processed and processed samples, respectively.

  15. Ductile damage development in friction stir welded aluminum (AA2024) joints

    DEFF Research Database (Denmark)

    Nielsen, Kim Lau


    Ductile damage development in a friction stir welded aluminum joint subjected to tension is analyzed numerically by FE-analysis, based on a total Lagrangian formulation. An elastic-viscoplastic constitutive relation that accounts for nucleation and growth of microvoids is applied. Main focus...

  16. Multigrid with FFT smoother for a simplified 2D frictional contact problem

    NARCIS (Netherlands)

    Zhao, J.; Vollebregt, E.A.H.; Oosterlee, C.W.


    This paper aims to develop a fast multigrid (MG) solver for a Fredholm integral equation of the first kind, arising from the 2D elastic frictional contact problem. After discretization on a rectangular contact area, the integral equation gives rise to a linear system with the coefficient matrix bein

  17. The effect of interlayers on dissimilar friction weld properties (United States)

    Maldonado-Zepeda, Cuauhtemoc

    The influence of silver interlayers on the metallurgical and mechanical properties of dissimilar aluminium alloy/stainless steel friction welds are investigated. An elastic contact model is proposed that explains the conditions at and close to the contact surface, which produce Al2O3 particle fracture in dissimilar MMC/AISI 304 stainless steel friction welds. Intermixed (IM) and particle dispersed (PD) regions are formed in Ag-containing dissimilar friction welds. These regions form very early in the joining operation and both contain Ag3Al. Therefore, an interlayer (Ag) introduced with the specific aim of preventing FexAly compound formation in MMC/AISI 304 stainless steel friction welds promotes the formation of another intermetallic phase at the bondline. Since IM and PD regions are progressively removed as the friction welding operation proceeds thinner intermetallic layers are produced when long friction welding times are applied. This type of behavior is quite different from that observed in silver-free dissimilar MMC/AISI 304 stainless steel welds. Nanoparticles of silver are formed in dissimilar MMC/Ag/AISI 304 stainless steel welds produced using low friction pressures. Nanoparticle formation in dissimilar friction welds has never been previously observed or investigated. The introduction of silver interlayers decreases heat generation during welding, produces narrower softened zone regions and improved notch tensile strength properties. All research to-date has assumed per se that joint mechanical properties wholly depend on the mechanical properties and width of the intermetallic layer formed at the dissimilar joint interface. However, it is shown in this thesis that the mechanical properties of MMC/AISI 304 stainless steel joints are determined by the combined effects of intermetallic formation at the bondline and softened zone formation in MMC base material immediately adjacent to the joint interface. A methodology for calculating the notch tensile

  18. Student figures in friction

    DEFF Research Database (Denmark)

    Nielsen, Gritt B.

      This thesis analyses how ‘the student', as a contested figure, is negotiated and enacted in a period of extensive university reform in Denmark. Through a combination of historical and anthropological research, it focuses on students' changing participation in the shaping of Danish society......, students' room for participation in their own learning, influenced by demands for efficiency, flexibility and student-centred education. The thesis recasts the anthropological endeavour as one of ‘figuration work'. That is, ‘frictional events' are explored as moments when conflicting figures......, the university and their own education. Detailed studies explore, first, politically active students' various attempts to influence national educational policies; second, student participation in the development of the university, especially regarding debates over consumer conduct versus co-ownership; and third...

  19. Effect of Weissenberg number on turbulent heat transfer and friction factor of viscoelastic fluids (United States)

    Kwack, E. Y.

    The effect of the elasticity of viscoelastic fluids on heat transfer and drag reduction behavior was investigated with aqueous polyacrylamide solutions flowing turbulently in circular pipes. A new dimensionless number called the Weissenberg number was used to account for the elasticity of the fluid. It was found that the fully established friction factor and dimensionless heat transfer coefficient, decrease with increasing Weissenberg number for a fixed Reynolds number up to certain critical Weissenberg numbers for friction and for heat transfer which are 5 to 10 and 200 to 250 respectively. The Powell-Eyring model was used to calculate the characteristic time of each test fluid for determining the Weissenberg number. The influence of polymer concentration, fluid degradation, pipe diameter and solvent chemistry on the behavior of friction and heat transfer of viscoelastic fluids was found to be adequately accounted for in the Weissenberg and Reynolds numbers.

  20. Application of hard coatings for blanking and piercing tools

    DEFF Research Database (Denmark)

    Podgornik, B.; Zajec, B.; Bay, Niels


    The aim of the present investigation was to examine the possibility of reducing lubrication and replacing expensive tungsten carbide material in blanking/piercing through introduction of hard tool coatings. Results show that hard PVD coatings can be successfully used in blanking/piercing...... critical value under dry friction conditions and leads to tool failure. Therefore, at present oxidation and temperature resistant hard coatings can give improved wear resistance of stamping tools, but elimination of lubricants in blanking and piercing processes is still not feasible....

  1. Token-Aware Completion Functions for Elastic Processor Verification

    Directory of Open Access Journals (Sweden)

    Sudarshan K. Srinivasan


    Full Text Available We develop a formal verification procedure to check that elastic pipelined processor designs correctly implement their instruction set architecture (ISA specifications. The notion of correctness we use is based on refinement. Refinement proofs are based on refinement maps, which—in the context of this problem—are functions that map elastic processor states to states of the ISA specification model. Data flow in elastic architectures is complicated by the insertion of any number of buffers in any place in the design, making it hard to construct refinement maps for elastic systems in a systematic manner. We introduce token-aware completion functions, which incorporate a mechanism to track the flow of data in elastic pipelines, as a highly automated and systematic approach to construct refinement maps. We demonstrate the efficiency of the overall verification procedure based on token-aware completion functions using six elastic pipelined processor models based on the DLX architecture.

  2. Structural and phase transformations in Hadfield steel upon frictional loading in liquid nitrogen (United States)

    Korshunov, L. G.; Sagaradze, V. V.; Chernenko, N. L.


    Structural transformations that occur in 110G13 steel (Hadfield) upon sliding friction in liquid nitrogen (-196°C) have been investigated by metallographic, electron-microscopic, and X-ray diffraction methods. The frictional action was performed through the reciprocating sliding of a cylindrical indenter of quenched 110G13 steel over a plate of the studied steel. A like friction pair was immersed into a bath with liquid nitrogen. It has been shown that the Hadfield steel quenched from 1100°C under the given temperature conditions of frictional loading retains the austenitic structure completely. The frictional action forms in a surface layer up to 10 μm thick the nanocrystalline structure with austenite grains 10-50 nm in size and a hardness 6 GPa. Upon subsequent low-temperature friction, the tempering of steel at 400°C (3 h) and at 600°C (5 min and 5 h) brings about the formation of a large amount (tens of vol %) of ɛ (hcp) martensite in steel. The formation of this phase under friction is supposedly a consequence of the reduction in the stacking fault energy of Hadfield steel, which is achieved due to the combined action of the following factors: low-temperature cooling, a decrease in the carbon content in the austenite upon tempering, and the presence of high compressive stresses in the friction-contact zone.


    Energy Technology Data Exchange (ETDEWEB)

    Ron Matthews


    This Final Technical Report discusses the progress was made on the experimental and numerical tasks over the duration of this project regarding a new technique for decreasing engine friction and wear via liner rotation. The experimental subtasks involved quantifying the reduction in engine friction for a prototype rotating liner engine relative to a comparable baseline engine. Both engine were single cylinder conversions of nominally identical production four-cylinder engines. Hot motoring tests were conducted initially and revealed that liner rotation decreased engine friction by 20% under motoring conditions. A well-established model was used to estimate that liner rotation should decrease the friction of a four-cylinder engine by 40% under hot motoring conditions. Hot motoring tear-down tests revealed that the crankshaft and valve train frictional losses were essentially the same for the two engines, as expected. However, the rotating liner engine had much lower (>70%) piston assembly friction compared to the conventional engine. Finally, we used the Instantaneous IMEP method to compare the crank-angle resolved piston assembly friction for the two engines. Under hot motoring conditions, these measurements revealed a significant reduction in piston assembly friction, especially in the vicinity of compression TDC when the lubrication regime transitions from hydrodynamic through mixed and into boundary friction. We have some remaining problems with these measurements that we expect to solve during the next few weeks. We will then perform these measurements under firing conditions. We also proposed to improve the state-of-the-art of numerical modeling of piston assembly friction for conventional engines and then to extend this model to rotating liner engines. Our research team first modeled a single ring in the Purdue ring-liner test rig. Our model showed good agreement with the test rig data for a range of speeds and loads. We then modeled a complete piston

  4. Studies in molecular dynamics of the friction coefficient and the Lorentz gas

    Energy Technology Data Exchange (ETDEWEB)

    Alley, W.E.


    The thesis consists of three hard-sphere molecular dynamics studies. The first describes a modification of Fick's diffusion law, required whenever long-time correlations are present. The second study concerns the mass and size dependence of the friction coefficient as well as its dependence on boundary conditions. The study presents a molecular dynamics method which calculates the infinite-mass friction coefficient of finite size hard-sphere particles. The third study presents the applicability of hydrodynamics to describe fluctuations in fluids on the molecular level. This study shows that the fluctuations present in a system of hard spheres when placed between closely spaced parallel hard walls lead to an acoustical resonance for those wavelengths which correspond to the spacing, or integer fractions thereof.

  5. Stability of sliding frictional surfaces with varying normal force

    Energy Technology Data Exchange (ETDEWEB)

    Dupont, P.E.; Bapna, D. (Boston Univ., MA (United States))


    This paper presents the stability analysis of a single degree-of-freedom elastic system following a rate- and state-dependent friction law. Normal force is assumed to depend on the displacement, velocity, and acceleration of the sliding interface. The history dependence of friction on normal force is included in the analysis. It is shown that to achieve steady sliding, system stiffness must exceed a critical value which depends on the expression for normal force. A system in which normal force depends on spring displacement is analyzed in detail. These results indicate that the functional dependence of normal force on system state can have a significant effect on the stability of low-velocity motion. 15 refs.

  6. Micro-structure and frictional characteristics of beetle's joint

    Institute of Scientific and Technical Information of China (English)

    DAI; Zhendong; Stanislav; N.; Gorb


    Geometric and micro-structure design, tribology properties of beetle joints were experimentally studied, which aimed to enlighten ideas for the joint design of MEMS.The observation by using SEM and microscopy suggested that beetle's joints consist of a concave surface matched with a convex surface. The heads of the beetles, rubbing with flat glass, were tested in fresh and dried statuses and compared with sapphire ball with flat glass. Frictional coefficient of the joint material on glass was significantly lower than that of the sapphire sphere on glass. The material of the joint cuticle for convex surface is rather stiff (the elastic modulus 4.5 Gpa) and smooth. The surface is hydrophobic (the contact angle of distilled water was 88.3° ). It is suggested here that the high stiffness of the joint material and hydrophobicity of the joint surface are parts of the mechanism minimizing friction in insect joints.

  7. Precipitation sequence in friction stir weld of 6063 aluminum during aging

    Energy Technology Data Exchange (ETDEWEB)

    Sato, Y.S.; Kokawa, Hiroyuki; Enomoto, Masatoshi; Jogan, Shigetoshi; Hashimoto, Takenori


    The precipitation sequence in friction stir weld of 6063 aluminum during postweld aging, associated with Vickers hardness profiles, has been examined by transmission electron microscopy. Friction stir welding produces a softened region in the weld, which is characterized by dissolution and growth of the precipitates. The precipitate-dissolved region contains a minimum hardness region in the as-welded condition. In the precipitate-dissolved region , postweld aging markedly increases the density of strengthening precipitates and leads to a large increase in hardness. On the other hand, aging forms few new precipitates in the precipitate-coarsened region, which shows a slight increase in hardness. The postweld aging at 443 K for 43.2 ks (12 hours) gives greater hardness in the overall weld than in the as-received base material and shifts the minimum hardness from the as-welded minimum hardness region t the precipitate-coarsened region. These hardness changes are consistent with the subsequent precipitation behavior during postweld aging. The postweld solution heat treatment (SHT) and aging achieve a high density of strengthening precipitates and bring a high hardness homogeneously in the overall weld.

  8. Multimodal Friction Ignition Tester (United States)

    Davis, Eddie; Howard, Bill; Herald, Stephen


    The multimodal friction ignition tester (MFIT) is a testbed for experiments on the thermal and mechanical effects of friction on material specimens in pressurized, oxygen-rich atmospheres. In simplest terms, a test involves recording sensory data while rubbing two specimens against each other at a controlled normal force, with either a random stroke or a sinusoidal stroke having controlled amplitude and frequency. The term multimodal in the full name of the apparatus refers to a capability for imposing any combination of widely ranging values of the atmospheric pressure, atmospheric oxygen content, stroke length, stroke frequency, and normal force. The MFIT was designed especially for studying the tendency toward heating and combustion of nonmetallic composite materials and the fretting of metals subjected to dynamic (vibrational) friction forces in the presence of liquid oxygen or pressurized gaseous oxygen test conditions approximating conditions expected to be encountered in proposed composite material oxygen tanks aboard aircraft and spacecraft in flight. The MFIT includes a stainless-steel pressure vessel capable of retaining the required test atmosphere. Mounted atop the vessel is a pneumatic cylinder containing a piston for exerting the specified normal force between the two specimens. Through a shaft seal, the piston shaft extends downward into the vessel. One of the specimens is mounted on a block, denoted the pressure block, at the lower end of the piston shaft. This specimen is pressed down against the other specimen, which is mounted in a recess in another block, denoted the slip block, that can be moved horizontally but not vertically. The slip block is driven in reciprocating horizontal motion by an electrodynamic vibration exciter outside the pressure vessel. The armature of the electrodynamic exciter is connected to the slip block via a horizontal shaft that extends into the pressure vessel via a second shaft seal. The reciprocating horizontal

  9. Multiple solutions of stick and separation type in the Signorini model with Coulomb friction

    Energy Technology Data Exchange (ETDEWEB)

    Hild, P. [Univ. de Franche-Comte, 25 - Besancon (France). Lab. de Mathematiques


    This paper proves the existence of multiple solutions to the Coulomb friction problem with Signorini contact conditions in continuum linear elasticity. We consider a body lying on a rigid foundation and we propose a method in order to exhibit two solutions to the frictional contact problem when the friction coefficient is large enough: one solution which separates from the foundation and another one which remains stuck on the foundation. We apply the method to the simple class of problems with triangular bodies and linear displacement fields and we describe the cases in which such multiple solutions exist. Denoting by {mu} the friction coefficient, we come to the conclusion that such nonuniqueness cases may appear when {mu}>1. (orig.)

  10. Rolling Friction in Loose Media and its Role in Mechanics Problems (United States)

    Klishin, S. V.; Revuzhenko, A. F.; Kazantsev, A. A.


    Rolling friction between particles is to be set in problems of granular material mechanics alongside with sliding friction. A classical problem of material passive lateral pressure on the retaining wall is submitted as a case in point. 3D method of discrete elements was employed for numerical analysis. Material is a universe of spherical particles with specified size distribution. Viscose-elastic properties of the material and surface friction are included, when choosing contact forces. Particles' resistance to rolling relative to other particles and to the boundary is set into the model. Kinetic patterns of medium deformations are given. It has been proved that rolling friction can significantly affect magnitude and nature of passive lateral pressure on the retaining wall.

  11. Low-temperature growth of low friction wear-resistant amorphous carbon nitride thin films by mid-frequency, high power impulse, and direct current magnetron sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Bakoglidis, Konstantinos D., E-mail:; Schmidt, Susann; Garbrecht, Magnus; Ivanov, Ivan G.; Jensen, Jens; Greczynski, Grzegorz; Hultman, Lars [Department of Physics, Chemistry and Biology (IFM), Linköping University, SE-581 83 Linköping (Sweden)


    GPa. Nanoindentation showed a significant increase in film hardness and reduced elastic modulus with increasing V{sub s} for all techniques. The harder films were produced by MFMS with hardness as high as 25 GPa. Low friction coefficients, between 0.05 and 0.06, were recorded for all films. Furthermore, CN{sub x} films produced by MFMS and DCMS at V{sub s} = 100 and 120 V presented a high wear resistance with wear coefficients of k ≤ 2.3 × 10{sup −5} mm{sup 3}/Nm. While all CN{sub x} films exhibit low friction, wear depends strongly on the structural and mechanical characteristics of the films. The MFMS mode is best suited for the production of hard CN{sub x} films, although high compressive stresses challenge the application on steel substrates. Films grown in HiPIMS mode provide adequate adhesion due to low residual stress values, at the expense of lower film hardness. Thus, a relatively wide mechanical property envelope is presented for CN{sub x} films, which is relevant for the optimization of CN{sub x} film properties intended to be applied as low friction and wear resistant coatings.

  12. Hard-sphere limit of soft-sphere model for granular materials: Stiffness dependence of steady granular flow


    Mitarai, Namiko; Nakanishi, Hiizu


    Dynamical behavior of steady granular flow is investigated numerically in the inelastic hard sphere limit of the soft sphere model. We find distinctively different limiting behaviors for the two flow regimes, i.e., the collisional flow and the frictional flow. In the collisional flow, the hard sphere limit is straightforward; the number of collisions per particle per unit time converges to a finite value and the total contact time fraction with other particles goes to zero. For the frictional...

  13. Bamboo Fibre-reinforced Semi-Metallic Brake Friction Materials for Automotive Applications

    Directory of Open Access Journals (Sweden)

    Talib R. J.


    Full Text Available Three friction material formulations composed of bamboo fiber along with binder, friction modifiers and filler have been prepared through powder metallurgy process. Sample F1 and F2 are composed of 10 wt. % of copper and barium, respectively, while the other ingredients in both formulations have the same wt. %. The wt. % of bamboo fiber in sample F3 is, however, increased by 100%, while the compositions of the other ingredients are proportionally decreased. The samples were examined for their porosity, hardness, and friction and wear properties using hot bath, Rockwell hardness tester, and CHASE friction dynamometer, respectively. The test results are compared with those of a commercial sample as the benchmark. Normal and hot frictions of all the three samples developed comply with the requirements specified by Automotive Manufacturer Equipment Companies Agency (AMECA. However, sample F3 which is composed of 20 wt. % of bamboo fiber does not comply with the minimum requirement of friction coefficient. Whereas, sample F2, which is composed of 10 wt. % of bamboo fiber and 10 wt. % of barium, has lower friction coefficient than the commercial sample, and has a sudden drop in friction coefficient at a temperature of 500°F. Out of three developed samples, sample F1, which is composed of 10 wt. % of bamboo fiber and 10 wt. % of copper, complies with all the requirements and has higher friction coefficient than the commercial sample, and has higher fade resistance. Thus, it could be postulated that bamboo fiber could be used as a reinforcing fiber with composition of 10 wt. %.

  14. Friction Stir Weld Failure Mechanisms in Aluminum-Armor Structures Under Ballistic Impact Loading Conditions (United States)


    Sheet) Continuation for Block 13 ARO Report Number Friction Stir Weld Failure Mechanisms in Alumin Block 13: Supplementary Note © 2013 . Published in...nose, steel jacketed, hard tungsten core (1400 Hv), armor piercing (AP) projectile (Ref 1). As mentioned above, this failure mechanism is often...zones being impacted with blunt, lower hardness projectiles [e.g., 20-mm caliber, 53 g, blunt, chamfered right circular cylindrical steel fragment

  15. Friction Material Composites Materials Perspective

    CERN Document Server

    Sundarkrishnaa, K L


    Friction Material Composites is the first of the five volumes which strongly educates and updates engineers and other professionals in braking industries, research and test labs. It explains besides the formulation of design processes and its complete manufacturing input. This book gives an idea of mechanisms of friction and how to control them by designing .The book is  useful for designers  of automotive, rail and aero industries for designing the brake systems effectively with the integration of friction material composite design which is critical. It clearly  emphasizes the driving  safety and how serious designers should  select the design input. The significance of friction material component like brake pad or a liner as an integral part of the brake system of vehicles is explained. AFM pictures at nanolevel illustrate broadly the explanations given.


    Institute of Scientific and Technical Information of China (English)

    唐立强; 李永东; 刘长海


    A mechanical model was established for mode Ⅱ interfacial crack static growing along an elastic-elastic power law creeping bimaterial interface. For two kinds of boundary conditions on crack faces, traction free and frictional contact, asymptotic solutions of the stress and strain near tip-crack were given. Results derived indicate that the stress and strain have the same singularity, there is not the oscillatory singularity in the field; the creep power-hardening index n and the ratio of Young' s module notably influence the cracktip field in region of elastic power law creeping material and n only influences distribution of stresses and strains in region of elastic material. When n is bigger, the creeping deformation is dominant and stress fields become steady, which does not change with n.Poisson ' s ratio does not affect the distributing of the crack- tip field.

  17. Friction stir welding of 5052 aluminum alloy plates

    Institute of Scientific and Technical Information of China (English)

    Yong-Jai KWON; Seong-Beom SHIM; Dong-Hwan PARK


    Friction stir welding between 5052 aluminum alloy plates with a thickness of 2 mm was performed. The tool for welding was rotated at speeds ranging from 500 to 3 000 r/min under a constant traverse speed of 100 mm/min. The results show that at all tool rotation speeds, defect-free welds are successfully obtained. Especially at 1 000, 2 000 and 3 000 r/min, the welds exhibit very smooth surface morphologies. At 500, 1 000, and 2 000 r/min, onion ring structure is clearly observed in the friction-stir-welded zone (SZ). In addition, the onion ring structure region becomes wider as the tool rotation speed is increased. The gain size in the SZ is smaller than that in the base metal, and is decreased with a decrease of the tool rotation speed. In all tool rotation speeds, the SZ exhibits higher average hardness than the base metal. Especially at 500 r/min, the average hardness of the SZ reaches a level about 33% greater than that of the base metal. At 500, 1 000 and 2 000 r/min, the tensile strength of the friction stir welded (FSWed) plates is similar to that of the base metal (about 204 Mpa). The elongation of the FSWed plates is lower than that of the base metal (about 22%). However, it is noticeable that the maximum elongation of about 21% is obtained at 1 000 r/min.

  18. Peak mass and dynamical friction

    CERN Document Server

    Del Popolo, A


    We show how the results given by several authors relatively to the mass of a density peak are changed when small scale substructure induced by dynamical friction are taken into account. The peak mass obtained is compared to the result of Peacock \\& Heavens (1990) and to the peak mass when dynamical friction is absent to show how these effects conspire to reduce the mass accreted by the peak.

  19. Tire/runway friction interface (United States)

    Yager, Thomas J.


    An overview is given of NASA Langley's tire/runway pavement interface studies. The National Tire Modeling Program, evaluation of new tire and landing gear designs, tire wear and friction tests, and tire hydroplaning studies are examined. The Aircraft Landing Dynamics Facility is described along with some ground friction measuring vehicles. The major goals and scope of several joint FAA/NASA programs are identified together with current status and plans.

  20. Labor Supply and Optimization Frictions

    DEFF Research Database (Denmark)

    Søgaard, Jakob Egholt


    In this paper I investigate the nature of optimization frictions by studying the labor market of Danish students. This particular labor market is an interesting case study as it features a range of special institutional settings that affect students’ incentive to earn income and comparing outcomes...... theory. More concretely I find the dominate optimization friction to be individuals’ inattention about their earnings during the year, while real adjustment cost and gradual learning appears to be of less importance....

  1. Structure, tribological and electrochemical properties of low friction TiAlSiCN/MoSeC coatings

    Energy Technology Data Exchange (ETDEWEB)

    Bondarev, A.V.; Kiryukhantsev-Korneev, Ph.V.; Sheveyko, A.N.; Shtansky, D.V., E-mail:


    Highlights: • TiAlSiCN/MoSeC coatings for tribological applications. • Doping with MoSeC reduces friction coefficient in humid air from 0.8–0.9 to 0.05. • Doping with MoSeC increases wear resistance by one-two orders of magnitude. • TiAlSiCN/MoSeC coatings demonstrated low friction coefficient in distilled water. • TiAlSiCN/MoSeC coatings showed superior tribological properties at moderate temperatures. - Abstract: The present paper is focused on the development of hard tribological coatings with low friction coefficient (CoF) in different environments (humid air, distilled water) and at elevated temperatures. TiAlSiCN/MoSeC coatings were deposited by magnetron sputtering of four-segment targets consisting of quarter circle TiAlSiCN segments, obtained by self-propagating high-temperature synthesis, and one or two cold pressed segments made of MoSe{sub 2} and C powders in a ratio 1:1 wt%. The structure and phase composition of coatings were investigated by means of X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy. The coatings were characterized in terms of their hardness, elastic modulus, and elastic recovery. The tribological properties of coatings were investigated first at room temperature against Al{sub 2}O{sub 3} and WC–Co balls, after which studied in distilled water and during continuous heating in air in the temperature range of 25–400 °C against Al{sub 2}O{sub 3} counterpart material. To evaluate their electrochemical characteristics, the coatings were tested in 1 N H{sub 2}SO{sub 4} solution. The obtained results show that the coating hardness depends on the amount of MoSeC additives and decreased from 40 to 28 (one MoSeC segment) and 12 GPa (two MoSeC segments). Doping with MoSeC resulted in a significant reduction of CoF values measured in humid air (RH 60 ± 5%) from 0.8–0.9 to 0.05 and an increase of wear resistance by one or two orders of magnitude depending on

  2. Frictional Effects on Gear Tooth Contact Analysis


    Zheng Li; Ken Mao


    The present paper concentrates on the investigations regarding the situations of frictional shear stress of gear teeth and the relevant frictional effects on bending stresses and transmission error in gear meshing. Sliding friction is one of the major reasons causing gear failure and vibration; the adequate consideration of frictional effects is essential for understanding gear contact behavior accurately. An analysis of tooth frictional effect on gear performance in spur gear is presented us...

  3. Thermodynamic hardness and the maximum hardness principle (United States)

    Franco-Pérez, Marco; Gázquez, José L.; Ayers, Paul W.; Vela, Alberto


    An alternative definition of hardness (called the thermodynamic hardness) within the grand canonical ensemble formalism is proposed in terms of the partial derivative of the electronic chemical potential with respect to the thermodynamic chemical potential of the reservoir, keeping the temperature and the external potential constant. This temperature dependent definition may be interpreted as a measure of the propensity of a system to go through a charge transfer process when it interacts with other species, and thus it keeps the philosophy of the original definition. When the derivative is expressed in terms of the three-state ensemble model, in the regime of low temperatures and up to temperatures of chemical interest, one finds that for zero fractional charge, the thermodynamic hardness is proportional to T-1(I -A ) , where I is the first ionization potential, A is the electron affinity, and T is the temperature. However, the thermodynamic hardness is nearly zero when the fractional charge is different from zero. Thus, through the present definition, one avoids the presence of the Dirac delta function. We show that the chemical hardness defined in this way provides meaningful and discernible information about the hardness properties of a chemical species exhibiting integer or a fractional average number of electrons, and this analysis allowed us to establish a link between the maximum possible value of the hardness here defined, with the minimum softness principle, showing that both principles are related to minimum fractional charge and maximum stability conditions.

  4. Wear of hard materials by hard particles

    Energy Technology Data Exchange (ETDEWEB)

    Hawk, Jeffrey A.


    Hard materials, such as WC-Co, boron carbide, titanium diboride and composite carbide made up of Mo2C and WC, have been tested in abrasion and erosion conditions. These hard materials showed negligible wear in abrasion against SiC particles and erosion using Al2O3 particles. The WC-Co materials have the highest wear rate of these hard materials and a very different material removal mechanism. Wear mechanisms for these materials were different for each material with the overall wear rate controlled by binder composition and content and material grain size.

  5. Frictional heating of total hip implants. Part 1: measurements in patients.

    NARCIS (Netherlands)

    Bergmann, G.; Graichen, F.; Rohlmann, A.; Verdonschot, N.J.J.; Lenthe, G.H. van


    Hip implants heat up due to friction during long lasting, high loading activities like walking. Thermal damage in the surrounding soft and hard tissues and deteriorated lubrication of synovial fluid could contribute to implant loosening. The goal of this study was to determine the implant temperatur

  6. Experimental Study on Friction Characteristics of Caragana korshinskii Kom

    Institute of Scientific and Technical Information of China (English)

    Xiao LlU; Yuming GUO


    Caragana korshinski Kom, which is a kind of excel ent shrubs, has strong resistance to windstorms, and it is also a kind of forage that is of high nutritional value as wel as a forming fuel conversion resource that is of high caloric. Cara-gana korshinski Kom is of high lignifications after growing for a few years and the toughness of it is considerably high. Currently in China, equipments of harvesting and processing for ripe crops can hardly finish the mechanized production for Cara-gana korshinski Kom. Friction characteristics of woody material for Caragana kor-shinski Kom under different conditions should be given when the relevant operation machinery is designed, which can provide physical parameters for transportation of Caragana korshinski Kom as wel as the designing of relevant machinery. The pa-per bases on the research of friction characteristics between Caragana korshinski Kom whose diameter of 7, 10, and 13 mm under sampling directions of 0° , 45° , and 90° and machinery materials that are commonly used such as steel plate, rub-ber sheet and so on, and meanwhile the test considers factors such as different conditions of Caragana korshinski Kom, different materials of machines, different angles and so on. The data strongly suggests that the average static, dynamic fric-tion coefficient between Caragana korshinski Kom and steel plate is 0.399 711 and 0.353 022, respectively; The average static and dynamic friction coefficient between Caragana korshinski Kom and rubber sheet is 0.965 178 and 0.883 667, respec-tively. The maximum of static and dynamic friction coefficients is when the angle between the direction of sampling and the direction of movement is vertical. As the angle increased, the dynamic and static friction coefficient decreased. The friction coefficient between Caragana korshinski Kom and steel plate were increased with the increase of the diameter of Caragana korshinski Kom, but the diameter have no effect on the dynamic friction

  7. Elastically Decoupling Dark Matter

    CERN Document Server

    Kuflik, Eric; Lorier, Nicolas Rey-Le; Tsai, Yu-Dai


    We present a novel dark matter candidate, an Elastically Decoupling Relic (ELDER), which is a cold thermal relic whose present abundance is determined by the cross-section of its elastic scattering on Standard Model particles. The dark matter candidate is predicted to have a mass ranging from a few to a few hundred MeV, and an elastic scattering cross-section with electrons, photons and/or neutrinos in the $10^{-3}-1$ fb range.

  8. Elastically Decoupling Dark Matter. (United States)

    Kuflik, Eric; Perelstein, Maxim; Lorier, Nicolas Rey-Le; Tsai, Yu-Dai


    We present a novel dark matter candidate, an elastically decoupling relic, which is a cold thermal relic whose present abundance is determined by the cross section of its elastic scattering on standard model particles. The dark matter candidate is predicted to have a mass ranging from a few to a few hundred MeV, and an elastic scattering cross section with electrons, photons and/or neutrinos in the 10^{-3}-1  fb range.

  9. ElasticSearch cookbook

    CERN Document Server

    Paro, Alberto


    Written in an engaging, easy-to-follow style, the recipes will help you to extend the capabilities of ElasticSearch to manage your data effectively.If you are a developer who implements ElasticSearch in your web applications, manage data, or have decided to start using ElasticSearch, this book is ideal for you. This book assumes that you've got working knowledge of JSON and Java

  10. Hard-on-hard lubrication in the artificial hip under dynamic loading conditions.

    Directory of Open Access Journals (Sweden)

    Robert Sonntag

    Full Text Available The tribological performance of an artificial hip joint has a particularly strong influence on its success. The principle causes for failure are adverse short- and long-term reactions to wear debris and high frictional torque in the case of poor lubrication that may cause loosening of the implant. Therefore, using experimental and theoretical approaches models have been developed to evaluate lubrication under standardized conditions. A steady-state numerical model has been extended with dynamic experimental data for hard-on-hard bearings used in total hip replacements to verify the tribological relevance of the ISO 14242-1 gait cycle in comparison to experimental data from the Orthoload database and instrumented gait analysis for three additional loading conditions: normal walking, climbing stairs and descending stairs. Ceramic-on-ceramic bearing partners show superior lubrication potential compared to hard-on-hard bearings that work with at least one articulating metal component. Lubrication regimes during the investigated activities are shown to strongly depend on the kinematics and loading conditions. The outcome from the ISO gait is not fully confirmed by the normal walking data and more challenging conditions show evidence of inferior lubrication. These findings may help to explain the differences between the in vitro predictions using the ISO gait cycle and the clinical outcome of some hard-on-hard bearings, e.g., using metal-on-metal.

  11. Hard-on-hard lubrication in the artificial hip under dynamic loading conditions. (United States)

    Sonntag, Robert; Reinders, Jörn; Rieger, Johannes S; Heitzmann, Daniel W W; Kretzer, J Philippe


    The tribological performance of an artificial hip joint has a particularly strong influence on its success. The principle causes for failure are adverse short- and long-term reactions to wear debris and high frictional torque in the case of poor lubrication that may cause loosening of the implant. Therefore, using experimental and theoretical approaches models have been developed to evaluate lubrication under standardized conditions. A steady-state numerical model has been extended with dynamic experimental data for hard-on-hard bearings used in total hip replacements to verify the tribological relevance of the ISO 14242-1 gait cycle in comparison to experimental data from the Orthoload database and instrumented gait analysis for three additional loading conditions: normal walking, climbing stairs and descending stairs. Ceramic-on-ceramic bearing partners show superior lubrication potential compared to hard-on-hard bearings that work with at least one articulating metal component. Lubrication regimes during the investigated activities are shown to strongly depend on the kinematics and loading conditions. The outcome from the ISO gait is not fully confirmed by the normal walking data and more challenging conditions show evidence of inferior lubrication. These findings may help to explain the differences between the in vitro predictions using the ISO gait cycle and the clinical outcome of some hard-on-hard bearings, e.g., using metal-on-metal.

  12. Low temperature friction stir welding of P91 steel

    Directory of Open Access Journals (Sweden)

    Prasad Rao Kalvala


    Full Text Available Bead-on-plate friction stir welds were made on P91 alloy with low and high rotational speeds (100 and 1000 RPM to study their effects on weld microstructural changes and impression creep behavior. Temperatures experienced by the stir zone were recorded at the weld tool tip. Different zones of welds were characterized for their microstructural changes, hardness and creep behavior (by impression creep tests. The results were compared with submerged arc fusion weld. Studies revealed that the stir zone temperature with 100 RPM was well below Ac1 temperature of P91 steel while it was above Ac3 with 1000 RPM. The results suggest that the microstructural degradation in P91 welds can be controlled by low temperature friction stir welding technique.

  13. Process optimization of friction stir welding based on thermal models

    DEFF Research Database (Denmark)

    Larsen, Anders Astrup


    This thesis investigates how to apply optimization methods to numerical models of a friction stir welding process. The work is intended as a proof-of-concept using different methods that are applicable to models of high complexity, possibly with high computational cost, and without the possibility...... information of the high-fidelity model. The optimization schemes are applied to stationary thermal models of differing complexity of the friction stir welding process. The optimization problems considered are based on optimizing the temperature field in the workpiece by finding optimal translational speed....... Also an optimization problem based on a microstructure model is solved, allowing the hardness distribution in the plate to be optimized. The use of purely thermal models represents a simplification of the real process; nonetheless, it shows the applicability of the optimization methods considered...

  14. Friction anisotropy in boronated graphite

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, N., E-mail: [Materials Science Group, Indira Gandhi Centre for Atomic Research, Kalpakkam (India); Radhika, R. [Crystal Growth Centre, Anna University, Chennai (India); Kozakov, A.T. [Research Institute of Physics, Southern Federal University, Rostov-on-Don (Russian Federation); Pandian, R. [Materials Science Group, Indira Gandhi Centre for Atomic Research, Kalpakkam (India); Chakravarty, S. [UGC-DAE CSR, Kalpakkam (India); Ravindran, T.R.; Dash, S.; Tyagi, A.K. [Materials Science Group, Indira Gandhi Centre for Atomic Research, Kalpakkam (India)


    Graphical abstract: - Highlights: • Friction anisotropy in boronated graphite is observed in macroscopic sliding condition. • Low friction coefficient is observed in basal plane and becomes high in prismatic direction. • 3D phase of boronated graphite transformed into 2D structure after friction test. • Chemical activity is high in prismatic plane forming strong bonds between the sliding interfaces. - Abstract: Anisotropic friction behavior in macroscopic scale was observed in boronated graphite. Depending upon sliding speed and normal loads, this value was found to be in the range 0.1–0.35 in the direction of basal plane and becomes high 0.2–0.8 in prismatic face. Grazing-incidence X-ray diffraction analysis shows prominent reflection of (0 0 2) plane at basal and prismatic directions of boronated graphite. However, in both the wear tracks (1 1 0) plane become prominent and this transformation is induced by frictional energy. The structural transformation in wear tracks is supported by micro-Raman analysis which revealed that 3D phase of boronated graphite converted into a disordered 2D lattice structure. Thus, the structural aspect of disorder is similar in both the wear tracks and graphite transfer layers. Therefore, the crystallographic aspect is not adequate to explain anisotropic friction behavior. Results of X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy shows weak signature of oxygen complexes and functional groups in wear track of basal plane while these species dominate in prismatic direction. Abundance of these functional groups in prismatic plane indicates availability of chemically active sites tends to forming strong bonds between the sliding interfaces which eventually increases friction coefficient.

  15. Numerical Studies of Friction Between Metallic Surfaces and of its Dependence on Electric Currents (United States)

    Meintanis, Evangelos; Marder, Michael


    We will present molecular dynamics simulations that explore the frictional mechanisms between clean metallic surfaces. We employ the HOLA molecular dynamics code to run slider-on-block experiments. Both objects are allowed to evolve freely. We recover realistic coefficients of friction and verify the importance of cold-welding and plastic deformations in dry sliding friction. We also find that plastic deformations can significantly affect both objects, despite a difference in hardness. Metallic contacts have significant technological applications in the transmission of electric currents. To explore the effects of the latter to sliding, we had to integrate an electrodynamics solver into the molecular dynamics code. The disparate time scales involved posed a challenge, but we have developed an efficient scheme for such an integration. A limited electrodynamic solver has been implemented and we are currently exploring the effects of currents in the friction and wear of metallic contacts.

  16. Wear and friction of oxidation-resistant mechanical carbon graphites at 650 C in air (United States)

    Allen, G. P.; Wisnader, D. W.


    Studies were conducted to determine the friction and wear properties of experimental carbon-graphites. Hemispherically tipped carbon-graphite rider specimens were tested in sliding contact with rotating Inconel X-750 disks in air. A surface speed of 1.33 m/sec, a load of 500 g, and a specimen temperature of 650 C were used. Results indicate: (1) hardness is not a major factor in determining friction and wear under the conditions of these studies. (2) Friction and wear as low as or lower than those observed for a good commercial seal material were attained with some of the experimental materials studied. (3) The inclusion of boron carbide (as an oxidation inhibitor) has a strong influence on wear rate. (4) Phosphate treatment reduces the friction coefficient when boron carbide is not present in the base material.

  17. Experimental study of mechanical properties of friction welded AISI 1021 steels

    Indian Academy of Sciences (India)

    Amit Handa; Vikas Chawla


    Friction welding is widely used as a mass production method in various industries. In the present study, an experimental set-up was designed in order to achieve friction welding of plastically deformed AISI 1021 steels. In this study, low alloy steel (AISI 1021) was welded under different welding parameters and afterwards the mechanical properties such as tensile strength, impact strength and hardness were experimentally determined. On the basis of the results obtained from the experimentation, the graphs were plotted. It is the strength of welded joints, which is fundamental property to the service reliability of the weldments and hence present work was undertaken to study the influence of axial pressure and rotational speed in friction welded joints. Axial pressure and rotational speed are the two major parameters which can influence the strength and hence the mechanical properties of the friction welded joints. Thus the axial pressure and rotational speed were taken as welding parameters, which reflect the mechanical properties.

  18. The effect of friction on simulated containment of underground nuclear explosions

    Energy Technology Data Exchange (ETDEWEB)

    Attia, A.V.


    The strength of the residual stress field is used as an important indicator in assessing the containment of underground nuclear explosions. Containment analysis using the COTTAGE geology shows considerable cracking in the hard Paleozoic layer, just below the cavity. The coefficient of friction is the ratio of total shear stress applied to a closed fracture surface to normal applied compressive total stress. Without any friction, the Paleozoic residual stress field is weakest. As the friction coefficient is increased from 0 to 0.5, the Paleozoic residual stress field is strengthened. A further increase of the friction coefficient from 0.5 to 0.8 shows strengthened where cracks are closed and weakening where cracks remain open. 4 refs., 4 figs., 1 tab.

  19. Modeling of contact mechanics and friction limit surfaces for soft fingers in robotics, with experimental results

    Energy Technology Data Exchange (ETDEWEB)

    Xydas, N.; Kao, I.


    A new theory in contact mechanics for modeling of soft fingers is proposed to define the relationship between the normal force and the radius of contact for soft fingers by considering general soft-finger materials, including linearly and nonlinearly elastic materials. The results show that the radius of contact is proportional to the normal force raised to the power of {gamma}, which ranges from 0 to 1/3. This new theory subsumes the Hertzian contact model for linear elastic materials, where {gamma} = 1/3. Experiments are conducted to validate the theory using artificial soft fingers made of various materials such as rubber and silicone. Results for human fingers are also compared. This theory provides a basis for numerically constructing friction limit surfaces. The numerical friction limit surface can be approximated by an ellipse, with the major and minor axes as the maximum friction force and the maximum moment with respect to the normal axis of contact, respectively. Combining the results of the contact-mechanics model with the contact-pressure distribution, the normalized friction limit surface can be derived for anthropomorphic soft fingers. The results of the contact-mechanics model and the pressure distribution for soft fingers facilitate the construction of numerical friction limit surfaces, and will enable us to analyze and simulate contact behaviors of grasping and manipulation in robotics.

  20. Development of method for evaluating cell hardness and correlation between bacterial spore hardness and durability

    Directory of Open Access Journals (Sweden)

    Nakanishi Koichi


    Full Text Available Abstract Background Despite the availability of conventional devices for making single-cell manipulations, determining the hardness of a single cell remains difficult. Here, we consider the cell to be a linear elastic body and apply Young’s modulus (modulus of elasticity, which is defined as the ratio of the repulsive force (stress in response to the applied strain. In this new method, a scanning probe microscope (SPM is operated with a cantilever in the “contact-and-push” mode, and the cantilever is applied to the cell surface over a set distance (applied strain. Results We determined the hardness of the following bacterial cells: Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, and five Bacillus spp. In log phase, these strains had a similar Young’s modulus, but Bacillus spp. spores were significantly harder than the corresponding vegetative cells. There was a positive, linear correlation between the hardness of bacterial spores and heat or ultraviolet (UV resistance. Conclusions Using this technique, the hardness of a single vegetative bacterial cell or spore could be determined based on Young’s modulus. As an application of this technique, we demonstrated that the hardness of individual bacterial spores was directly proportional to heat and UV resistance, which are the conventional measures of physical durability. This technique allows the rapid and direct determination of spore durability and provides a valuable and innovative method for the evaluation of physical properties in the field of microbiology.

  1. Investigation on Behavior of Rare Earth Element Cerium in Aluminum-Lithium Alloys by Internal Friction Method

    Institute of Scientific and Technical Information of China (English)


    The behavior of rare earth element Ce in 2090 Al-Li alloys was studied by the method of low frequency internal friction.The results showed that rare earth element Ce can increase the activation energy of grain boundary and improve the grain boundary strength of alloys.Rare earth element Ce can decrease the tendency of softening of elastic modulus of 2090 Al-Li alloys after heat cycle and keep high elastic modulus of initial state.

  2. Investigation Antiwear Properties of Lubricants with the Geo-Modifiers of Friction

    Directory of Open Access Journals (Sweden)

    I. Levanov


    Full Text Available The article describes the influence of the geo-modifiers of friction on the antiwear properties of lubricants. Geo-modifiers of friction are the fine powders of mineral materials. This work is directed on the investigation the influence of the geo-modifiers of friction in the form of the hard lubricant compositions, which based on a mineral serpentine, on the anti-wear properties of greases and gear oils. This composition is the fine powder serpentine with the addition of components such as chalk, borax, kaolin and talc. We compared the antiwear properties of the greases without geo-modifiers of friction and the antiwear properties of greases containing the geo-modifiers of friction from 0.5 % to 3 %. The Litol-24 and transmission oil TAD-17 was used for testihg. The four-ball machine of friction was used for tests accordance with GOST 9490-75. As geo-modifiers the serpentine was used, the fraction of which has a size from 0.87 microns to 2.2 microns. Such parameter as the wear scar diameter was used for evaluation of the antiwear properties of lubricants. As a result of tests it was established that the antiwear greases properties improved on 26-50 % depending on the concentration of the geo-modifiers of friction based on the pure serpentine.

  3. Versatile Friction Stir Welding/Friction Plug Welding System (United States)

    Carter, Robert


    A proposed system of tooling, machinery, and control equipment would be capable of performing any of several friction stir welding (FSW) and friction plug welding (FPW) operations. These operations would include the following: Basic FSW; FSW with automated manipulation of the length of the pin tool in real time [the so-called auto-adjustable pin-tool (APT) capability]; Self-reacting FSW (SRFSW); SR-FSW with APT capability and/or real-time adjustment of the distance between the front and back shoulders; and Friction plug welding (FPW) [more specifically, friction push plug welding] or friction pull plug welding (FPPW) to close out the keyhole of, or to repair, an FSW or SR-FSW weld. Prior FSW and FPW systems have been capable of performing one or two of these operations, but none has thus far been capable of performing all of them. The proposed system would include a common tool that would have APT capability for both basic FSW and SR-FSW. Such a tool was described in Tool for Two Types of Friction Stir Welding (MFS- 31647-1), NASA Tech Briefs, Vol. 30, No. 10 (October 2006), page 70. Going beyond what was reported in the cited previous article, the common tool could be used in conjunction with a plug welding head to perform FPW or FPPW. Alternatively, the plug welding head could be integrated, along with the common tool, into a FSW head that would be capable of all of the aforementioned FSW and FPW operations. Any FSW or FPW operation could be performed under any combination of position and/or force control.

  4. Friction Properties of Polished Cvd Diamond Films Sliding against Different Metals (United States)

    Lin, Zichao; Sun, Fanghong; Shen, Bin


    Owing to their excellent mechanical and tribological properties, like the well-known extreme hardness, low coefficient of friction and high chemical inertness, chemical vapor deposition (CVD) diamond films have found applications as a hard coating for drawing dies. The surface roughness of the diamond films is one of the most important attributes to the drawing dies. In this paper, the effects of different surface roughnesses on the friction properties of diamond films have been experimentally studied. Diamond films were fabricated using hot filament CVD. The WC-Co (Co 6wt.%) drawing dies were used as substrates. A gas mixture of acetone and hydrogen gas was used as the feedstock gas. The CVD diamond films were polished using mechanical polishing. Polished diamond films with three different surface roughnesses, as well as the unpolished diamond film, were fabricated in order to study the tribological performance between the CVD diamond films and different metals with oil lubrication. The unpolished and polished CVD diamond films are characterized with scanning electron microscope (SEM), atomic force microscope (AFM), surface profilometer, Raman spectrum and X-ray diffraction (XRD). The friction examinations were carried out by using a ball-on-plate type reciprocating friction tester. Low carbide steel, stainless steel, copper and aluminum materials were used as counterpart balls. Based on this study, the results presented the friction coefficients between the polished CVD films and different metals. The friction tests demonstrate that the smooth surface finish of CVD diamond films is beneficial for reducing their friction coefficients. The diamond films exhibit low friction coefficients when slid against the stainless steel balls and low carbide steel ball, lower than that slid against copper ball and aluminum ball, attributed to the higher ductility of copper and aluminum causing larger amount of wear debris adhering to the sliding interface and higher adhesive

  5. Analysis and Comparison of Friction Stir Welding and Laser Assisted Friction Stir Welding of Aluminum Alloy. (United States)

    Campanelli, Sabina Luisa; Casalino, Giuseppe; Casavola, Caterina; Moramarco, Vincenzo


    Friction Stir Welding (FSW) is a solid-state joining process; i.e., no melting occurs. The welding process is promoted by the rotation and translation of an axis-symmetric non-consumable tool along the weld centerline. Thus, the FSW process is performed at much lower temperatures than conventional fusion welding, nevertheless it has some disadvantages. Laser Assisted Friction Stir Welding (LAFSW) is a combination in which the FSW is the dominant welding process and the laser pre-heats the weld. In this work FSW and LAFSW tests were conducted on 6 mm thick 5754H111 aluminum alloy plates in butt joint configuration. LAFSW is studied firstly to demonstrate the weldability of aluminum alloy using that technique. Secondly, process parameters, such as laser power and temperature gradient are investigated in order to evaluate changes in microstructure, micro-hardness, residual stress, and tensile properties. Once the possibility to achieve sound weld using LAFSW is demonstrated, it will be possible to explore the benefits for tool wear, higher welding speeds, and lower clamping force.

  6. Analysis and Comparison of Friction Stir Welding and Laser Assisted Friction Stir Welding of Aluminum Alloy

    Directory of Open Access Journals (Sweden)

    Sabina Luisa Campanelli


    Full Text Available Friction Stir Welding (FSW is a solid-state joining process; i.e., no melting occurs. The welding process is promoted by the rotation and translation of an axis-symmetric non-consumable tool along the weld centerline. Thus, the FSW process is performed at much lower temperatures than conventional fusion welding, nevertheless it has some disadvantages. Laser Assisted Friction Stir Welding (LAFSW is a combination in which the FSW is the dominant welding process and the laser pre-heats the weld. In this work FSW and LAFSW tests were conducted on 6 mm thick 5754H111 aluminum alloy plates in butt joint configuration. LAFSW is studied firstly to demonstrate the weldability of aluminum alloy using that technique. Secondly, process parameters, such as laser power and temperature gradient are investigated in order to evaluate changes in microstructure, micro-hardness, residual stress, and tensile properties. Once the possibility to achieve sound weld using LAFSW is demonstrated, it will be possible to explore the benefits for tool wear, higher welding speeds, and lower clamping force.

  7. Friction Stir Welding of very thin plates

    Directory of Open Access Journals (Sweden)

    Ivan Galvão


    Full Text Available The results obtained in present research, relative to friction stir welding of 1 mm thick plates of aluminium, copper, copper-zinc and zinc alloys, prove that the application of the process in the joining of very thin plates is feasible and desirable. In fact, independently of the base material, the welds produced presented very good morphological characteristics and significant grain refinement in the nugget. Tensile and hardness tests proved that all the welds were at least in even-match relative to the base material properties. Based on the AA 5182 aluminium alloy results it was also possible to conclude that augmenting the welding speed, which improves process productivity, increases grain refinement in the nugget, improving the mechanical properties of the welds.Os resultados obtidos no presente estudo, referentes a friction stir welding de chapas de alumínio, cobre, cobre-zinco e zinco com 1 mm de espessura, provam que a aplicação desta tecnologia para a ligação de chapas muito finas é possível e desejável. De fato, independentemente do material de base, as soldas produzidas apresentaram características morfológicas muito boas e um significativo refinamento do grão na zona do nugget. Ensaios de dureza e tração provaram que todas as soldas apresentavam, no mínimo, propriedades mecânicas semelhantes às dos materiais de base. Com base nos resultados da liga de alumínio AA 5182 foi também possível concluir que ao aumentar a velocidade de soldagem, o que melhora a produtividade do processo, aumenta-se o refinamento do grão no nugget, melhorando as propriedades mecânicas das soldas.

  8. The Reality of Casimir Friction

    Directory of Open Access Journals (Sweden)

    Kimball A. Milton


    Full Text Available For more than 35 years theorists have studied quantum or Casimir friction, which occurs when two smooth bodies move transversely to each other, experiencing a frictional dissipative force due to quantum electromagnetic fluctuations, which break time-reversal symmetry. These forces are typically very small, unless the bodies are nearly touching, and consequently such effects have never been observed, although lateral Casimir forces have been seen for corrugated surfaces. Partly because of the lack of contact with observations, theoretical predictions for the frictional force between parallel plates, or between a polarizable atom and a metallic plate, have varied widely. Here, we review the history of these calculations, show that theoretical consensus is emerging, and offer some hope that it might be possible to experimentally confirm this phenomenon of dissipative quantum electrodynamics.

  9. The Reality of Casimir Friction

    CERN Document Server

    Milton, K A; Brevik, I


    For more than 35 years theorists have studied quantum or Casimir friction, which occurs when two smooth bodies move transversely to each other, experiencing a frictional dissipative force due to quantum fluctuations. These forces are typically very small, unless the bodies are nearly touching, and consequently such effects have never been observed, although lateral Casimir forces have been seen for corrugated surfaces. Because of the lack of contact with phenomena, theoretical predictions for the frictional force between parallel plates, or between a polarizable atom and a metallic plate, have varied widely. Here we review the history of these calculations, show that theoretical consensus is emerging, and offer some hope that it might be possible to experimentally confirm this phenomenon of dissipative quantum electrodynamics.

  10. Elastic limit of silicane. (United States)

    Peng, Qing; De, Suvranu


    Silicane is a fully hydrogenated silicene-a counterpart of graphene-having promising applications in hydrogen storage with capacities larger than 6 wt%. Knowledge of its elastic limit is critical in its applications as well as tailoring its electronic properties by strain. Here we investigate the mechanical response of silicane to various strains using first-principles calculations based on density functional theory. We illustrate that non-linear elastic behavior is prominent in two-dimensional nanomaterials as opposed to bulk materials. The elastic limits defined by ultimate tensile strains are 0.22, 0.28, and 0.25 along armchair, zigzag, and biaxial directions, respectively, an increase of 29%, 33%, and 24% respectively in reference to silicene. The in-plane stiffness and Poisson ratio are reduced by a factor of 16% and 26%, respectively. However, hydrogenation/dehydrogenation has little effect on its ultimate tensile strengths. We obtained high order elastic constants for a rigorous continuum description of the nonlinear elastic response. The limitation of second, third, fourth, and fifth order elastic constants are in the strain range of 0.02, 0.08, and 0.13, and 0.21, respectively. The pressure effect on the second order elastic constants and Poisson's ratio were predicted from the third order elastic constants. Our results could provide a safe guide for promising applications and strain-engineering the functions and properties of silicane monolayers.

  11. ElasticSearch cookbook

    CERN Document Server

    Paro, Alberto


    If you are a developer who implements ElasticSearch in your web applications and want to sharpen your understanding of the core elements and applications, this is the book for you. It is assumed that you've got working knowledge of JSON and, if you want to extend ElasticSearch, of Java and related technologies.

  12. Molecular dynamics simulations of metallic friction and of its dependence on electric currents - development and first results (United States)

    Meintanis, Evangelos Anastasios

    We have extended the HOLA molecular dynamics (MD) code to run slider-on-block friction experiments for Al and Cu. Both objects are allowed to evolve freely and show marked deformation despite the hardness difference. We recover realistic coefficients of friction and verify the importance of cold-welding and plastic deformations in dry sliding friction. Our first data also show a mechanism for decoupling between load and friction at high velocities. Such a mechanism can explain an increase in the coefficient of friction of metals with velocity. The study of the effects of currents on our system required the development of a suitable electrodynamic (ED) solver, as the disparity of MD and ED time scales threatened the efficiency of our code. Our first simulations combining ED and MD are presented.

  13. The microphysics of phyllosilicate friction (United States)

    den Hartog, Sabine A. M.; Faulkner, Daniel R.; Spiers, Christopher J.


    Phyllosilicate-rich foliations in fault rocks are often thought to reduce overall fault strength and promote fault stability when forming an interconnected network. Indeed, laboratory measurements have shown that the average friction coefficient of dry phyllosilicates of 0.5 is reduced to 0.3 when wet or even 0.1 for smectite. A widely accepted interpretation of these observations is that the strength of phyllosilicates is controlled by breaking of interlayer bonds to form new cleavage surfaces when dry and by the low strength of surface-bound water films when wet. However, the correlation between phyllosilicate shear strength and interlayer bond strength, which formed the basis for this interpretation, was not reproduced in recent experiments (Behnsen and Faulkner, 2012) and is not supported by the latest calculations of the interlayer bond energies (Sakuma and Suehara, 2015). The accepted explanation for phyllosilicate friction also fails to account for the velocity dependence or (a-b) values, which decrease with temperature, reaching a minimum at intermediate temperatures, before increasing again at higher temperatures (Den Hartog et al., 2013, 2014). In this study, we developed a microphysical model for phyllosilicate friction, involving frictional sliding along atomically flat phyllosilicate grain interfaces, with overlapping grain edges forming barriers to sliding. Assuming that the amount of overlap is controlled by crystal plastic bending of grains into pores, together with rate-dependent edge-site cleavage, our model predicts most of the experimentally observed trends in frictional behaviour and provides a basis for extrapolation of laboratory friction data on phyllosilicates to natural conditions.

  14. Low temperature friction force microscopy (United States)

    Dunckle, Christopher Gregory

    The application of friction force techniques within atomic force microscopy (AFM) allows for direct measurements of friction forces at a sliding, single-asperity interface. The temperature dependence of such single-asperity contacts provides key insight into the comparative importance of dissipative mechanisms that result in dry sliding friction. A variable temperature (VT), ultrahigh vacuum (UHV) AFM was used with an interface consisting of a diamond coated AFM tip and diamond-like carbon sample in a nominal sample temperature range of 90 to 275K. The results show that the coefficient of kinetic friction, mu k, has a linear dependence that is monotonically increasing with temperature varying from 0.28 to 0.38. To analyze this data it is necessary to correlate the sample temperature to the interface temperature. A detailed thermal model shows that the sample temperature measured by a macroscopic device can be very different from the temperature at the contact point. Temperature gradients intrinsic to the design of VT, UHV AFMs result in extreme, non-equilibrium conditions with heat fluxes on the order of gigawatts per squared meter through the interface, which produce a discontinuous step in the temperature profile due to thermal boundary impedance. The conclusion from this model is that measurements acquired by VT, UHV AFM, including those presented in this thesis, do not provide meaningful data on the temperature dependence of friction for single-asperities. Plans for future work developing an isothermal AFM capable of the same measurements without the introduction of temperature gradients are described. The experimental results and thermal analysis described in this thesis have been published in the Journal of Applied Physics, "Temperature dependence of single-asperity friction for a diamond on diamondlike carbon interface", J. App. Phys., 107(11):114903, 2010.

  15. Micromechanical Simulation of Deformation of Friction Stir Welded Components (United States)

    Sidle, B. C.; Dawson, P. R.; Boyce, D. E.


    A microstructure-based finite element formulation for the mechanical response of friction stir welded AL-6XN stainless steel is presented. The welding process generates regions of substantial variations in material state and properties that contribute to strong heterogeneities in the mechanical behavior of welded components We modeled the system with a multiscale elastoplastic formulation in which polycrystalline behavior is computed as the integrated responses of constituent crystals. Model validation is made through comparisons to post-test measurements of shape and hardness and to lattice strain measurements from in situ neutron diffraction experiments.

  16. Hybrid Friction Stir Welding of High-carbon Steel

    Institute of Scientific and Technical Information of China (English)

    Don-Hyun Choi; Seung-Boo Jung; Chang-Yong Lee; Byung-Wook Ahn; Jung-Hyun Choi; Yun-Mo Yeon; Keun Song; Seung-Gab Hong; Won-Bae Lee; Ki-Bong Kang


    A high-carbon steel joint, SK5 (0.84 wt% C), was successfully welded by friction stir welding (FSW), both without and with a gas torch, in order to control the cooling rate during welding. After welding, the weld zone comprised gray and black regions, corresponding to microstructural variation: a martensite structure and a duplex structure of ferrite and cementite, respectively. The volume fraction of the martensite structure and the Vickers hardness in the welds were decreased with the using of the gas torch, which was related with the lower cooling rate.

  17. Developing Friction Stir Welding Process Model for ICME Application (United States)

    Yang, Yu-Ping


    A framework for developing a product involving manufacturing processes was developed with integrated computational materials engineering approach. The key component in the framework is a process modeling tool which includes a thermal model, a microstructure model, a thermo-mechanical, and a property model. Using friction stir welding (FSW) process as an example, development of the process modeling tool was introduced in detail. The thermal model and the microstructure model of FSW of steels were validated with the experiment data. The model can predict reasonable temperature and hardness distributions as observed in the experiment. The model was applied to predict residual stress and joint strength of a pipe girth weld.

  18. Tidal Friction: Darwin's Theory Re-Visited (United States)

    Ferraz-Mello, Sylvio


    Our knowledge of tidal friction is even today directly founded on Darwin's theory. Many progresses from studies done in the past century deserve mention. To quote just a few, we may mention Love's theory on the elastic response of one body submitted to an external potential and the understanding of the role played by tides in generating heat in synchronous planetary satellites. We may also mention the many applications that leaded to the understanding of the evolution of systems with close-in satellites, the Earth-Moon system in the first place, and those concerning systems formed by close binary stars. However, notwithstanding the existence of some high-order formal theories, the essential of our knowledge is yet nowadays the one established by Darwin and crucial questions on the action of viscosity, for instance, remains unanswered. We still are strongly tied to Darwin's assumption that the tidal waves lag proportionally to frequency or, in some favorable cases (e.g. the Earth), that the lags are constants. We intend to critically review our current understanding of Darwin's theory and some of its limitations.

  19. Simulation of the frictional stick-slip instability (United States)

    Mora, Peter; Place, David


    A lattice solid model capable of simulating rock friction, fracture and the associated seismic wave radiation is developed in order to study the origin of the stick-slip instability that is responsible for earthquakes. The model consists of a lattice of interacting particles. In order to study the effect of surface roughness on the frictional behavior of elastic blocks being rubbed past one another, the simplest possible particle interactions were specified corresponding to radially dependent elastic-brittle bonds. The model material can therefore be considered as round elastic grains with negligible friction between their surfaces. Although breaking of the bonds can occur, fracturing energy is not considered. Stick-slip behavior is observed in a numerical experiment involving 2D blocks with rough surfaces being rubbed past one another at a constant rate. Slip is initiated when two interlocking asperities push past one another exciting a slip pulse. The pulse fronts propagate with speeds ranging from the Rayleigh wave speed up to a value between the shear and compressional wave speeds in agreement with field observations and theoretical analyses of mode-II rupture. Slip rates are comparable to seismic rates in the initial part of one slip pulse whose front propagates at the Rayleigh wave speed. However, the slip rate is an order of magnitude higher in the main part of pulses, possibly because of the simplified model description that neglected intrinsic friction and the high rates at which the blocks were driven, or alternatively, uncertainty in slip rates obtained through the inversion of seismograms. Particle trajectories during slip have motions normal to the fault, indicating that the fault surfaces jump apart during the passage of the slip pulse. Normal motion is expected as the asperities on the two surfaces ride over one another. The form of the particle trajectories is similar to those observed in stick-slip experiments involving foam rubber blocks ( Brune

  20. Processing-Microstructure Relationships in Friction Stir Welding of MA956 Oxide Dispersion Strengthened Steel (United States)

    Baker, Bradford W.; Menon, E. Sarath K.; McNelley, Terry R.; Brewer, Luke N.; El-Dasher, Bassem; Farmer, Joseph C.; Torres, Sharon G.; Mahoney, Murray W.; Sanderson, Samuel


    A comprehensive set of processing-microstructure relationships is presented for friction stir welded oxide dispersion strengthened MA956 steel. Eight rotational speed/traverse speed combinations were used to produce friction stir welds on MA956 plates using a polycrystalline cubic boron nitride tool. Weld conditions with high thermal input produced defect-free, full-penetration welds. Electron backscatter diffraction results showed a significant increase in grain size, a persistent body centered cubic torsional texture in the stir zone, and a sharp transition in grain size across the thermo-mechanically affected zone sensitive to weld parameters. Micro-indentation showed an asymmetric reduction in hardness across a transverse section of the weld. This gradient in hardness was greatly increased with higher heat inputs. The decrease in hardness after welding correlates directly with the increase in grain size and may be explained with a Hall-Petch type relationship.

  1. Damage tolerant functionally graded materials for advanced wear and friction applications (United States)

    Prchlik, Lubos

    The research work presented in this dissertation focused on processing effects, microstructure development, characterization and performance evaluation of composite and graded coatings used for friction and wear control. The following issues were addressed. (1) Definition of prerequisites for a successful composite and graded coating formation by means of thermal spraying. (2) Improvement of characterization methods available for homogenous thermally sprayed coating and their extension to composite and graded materials. (3) Development of novel characterization methods specifically for FGMs, with a focus on through thickness property measurement by indentation and in-situ curvature techniques. (4) Design of composite materials with improved properties compared to homogenous coatings. (5) Fabrication and performance assessment of FGM with improved wear and impact damage properties. Materials. The materials studied included several material systems relevant to low friction and contact damage tolerant applications: MO-Mo2C, WC-Co cermets as materials commonly used sliding components of industrial machinery and NiCrAlY/8%-Yttria Partially Stabilized Zirconia composites as a potential solution for abradable sections of gas turbines and aircraft engines. In addition, uniform coatings such as molybdenum and Ni5%Al alloy were evaluated as model system to assess the influence of microstructure variation onto the mechanical property and wear response. Methods. The contact response of the materials was investigated through several techniques. These included methods evaluating the relevant intrinsic coating properties such as elastic modulus, residual stress, fracture toughness, scratch resistance and tests measuring the abrasion and friction-sliding behavior. Dry-sand and wet two-body abrasion testing was performed in addition to traditional ball on disc sliding tests. Among all characterization techniques the spherical indentation deserved most attention and enabled to

  2. Nonlinear mechanics of hyper elastic polyurethane furniture foams

    Directory of Open Access Journals (Sweden)

    Jerzy Smardzewski


    Full Text Available Upholstered furniture intended to provide better sleep and rest, especially furniture for disabled persons, require careful design of elastic spring systems. In the majority of cases, when designing new articles, both furniture designers and manufacturers rely on long-term experience and craftsman’s intuition. On the other hand, the accumulated interdisciplinary knowledge of modern medical laboratories as well as furniture certification offices indicate that it is necessary to carry out investigations related to the mechanical properties of raw materials used to manufacture furniture and to conduct virtual modelling of the phenomena connected with the contact of the human body with the elastic base. The aim of this study was to determine the elastic properties of hyper-plastic polyurethane foams applied in furniture industry, to elaborate mathematical models of these materials on the basis of non-linear Mooney-Rivlin models and to conduct a non-linear numerical analysis of contact strains in a deformed seat made of polyurethane foam. The results of the experiments revealed that the mechanical properties of polyurethanefoams are described properly by the Mooney-Rivlin model. Knowing the mechanical properties of these foams, it is possible to create freely complex furniture elastic systems. The state of strains in the contact of the human body with foam depends on the friction between these bodies. Therefore, in practice, it is advisable to design seatsystems resulting in minimal frictions between the user’s clothes and the furniture seat.


    Institute of Scientific and Technical Information of China (English)

    J.P.Gong; G.Kagata; Y.Iwasaki; Y.Osada


    The sliding friction of various kinds of hydrogels has been studied and it was found that the frictional behaviors of the hydrogels do not conform to Amonton's law F =μW which well describes the friction of solids. The frictional force and its dependence on the load are quite different depending on the chemical structures of the gels, surface properties of the opposing substrates, and the measurement condition. The gel friction is explained in terms of interfacial interaction, either attractive or repulsive, between the polymer chain and the solid surface. According to this model, the friction is ascribed to the viscous flow of solvent at the interface in the repulsive case. In the attractive case, the force to detach the adsorbing chain from the substrate appears as friction. The surface adhesion between glass particles and gels measured by AFM showed a good correlation with the friction, which supported the repulsion-adsorption model proposed by the authors.

  4. The Friction of Saline Ice on Aluminium

    Directory of Open Access Journals (Sweden)

    Christopher Wallen-Russell


    Full Text Available The friction of ice on other materials controls loading on offshore structures and vessels in the Arctic. However, ice friction is complicated, because ice in nature exists near to its melting point. Frictional heating can cause local softening and perhaps melting and lubrication, thus affecting the friction and creating a feedback loop. Ice friction is therefore likely to depend on sliding speed and sliding history, as well as bulk temperature. The roughness of the sliding materials may also affect the friction. Here we present results of a series of laboratory experiments, sliding saline ice on aluminium, and controlling for roughness and temperature. We find that the friction of saline ice on aluminium μice-al=0.1 typically, but that this value varies with sliding conditions. We propose physical models which explain the variations in sliding friction.

  5. Modeling of friction-induced deformation and microstructures.

    Energy Technology Data Exchange (ETDEWEB)

    Michael, Joseph Richard; Prasad, Somuri V.; Jungk, John Michael; Cordill, Megan J. (University of Minnesota); Bammann, Douglas J.; Battaile, Corbett Chandler; Moody, Neville Reid; Majumdar, Bhaskar Sinha (New Mexico Institure of Mining and Technology)


    Frictional contact results in surface and subsurface damage that could influence the performance, aging, and reliability of moving mechanical assemblies. Changes in surface roughness, hardness, grain size and texture often occur during the initial run-in period, resulting in the evolution of subsurface layers with characteristic microstructural features that are different from those of the bulk. The objective of this LDRD funded research was to model friction-induced microstructures. In order to accomplish this objective, novel experimental techniques were developed to make friction measurements on single crystal surfaces along specific crystallographic surfaces. Focused ion beam techniques were used to prepare cross-sections of wear scars, and electron backscattered diffraction (EBSD) and TEM to understand the deformation, orientation changes, and recrystallization that are associated with sliding wear. The extent of subsurface deformation and the coefficient of friction were strongly dependent on the crystal orientation. These experimental observations and insights were used to develop and validate phenomenological models. A phenomenological model was developed to elucidate the relationships between deformation, microstructure formation, and friction during wear. The contact mechanics problem was described by well-known mathematical solutions for the stresses during sliding friction. Crystal plasticity theory was used to describe the evolution of dislocation content in the worn material, which in turn provided an estimate of the characteristic microstructural feature size as a function of the imposed strain. An analysis of grain boundary sliding in ultra-fine-grained material provided a mechanism for lubrication, and model predictions of the contribution of grain boundary sliding (relative to plastic deformation) to lubrication were in good qualitative agreement with experimental evidence. A nanomechanics-based approach has been developed for characterizing the

  6. Creep of metal-type organic compounds. 3: Friction stress models for creep in particle-hardened systems

    Energy Technology Data Exchange (ETDEWEB)

    Davies, G.C.; Jones, D.R.H. [Univ. of Cambridge (United Kingdom). Engineering Dept.


    The effect of a dispersed phase of small, hard particles on the creep behavior of two plastic crystals, camphene and succinonitrile, is investigated experimentally. Three models describing the creep deformation of a material containing hard particles are compared to the experimental data. Previous work has considered the particles to result in a constant friction stress which opposes creep deformation. The experimental results for plastic crystals are shown to be equally consistent with a model in which the friction stress is a linear function of the applied stress.

  7. Asymptotic bifurcation solutions for compressions of a clamped nonlinearly elastic rectangle: transition region and barrelling to a corner-like profile

    CERN Document Server

    Dai, H H


    Buckling and barrelling instabilities in the uniaxial compressions of an elastic rectangle have been studied by many authors under lubricated end conditions. However, in practice it is very difficult to realize such conditions due to friction. Here, we study the compressions of a two-dimensional nonlinearly elastic rectangle under clamped end conditions.

  8. Coordination Frictions and Job Heterogeneity

    DEFF Research Database (Denmark)

    Kennes, John; le Maire, Christian Daniel

    This paper develops and extends a dynamic, discrete time, job to worker matching model in which jobs are heterogeneous in equilibrium. The key assumptions of this economic environment are (i) matching is directed and (ii) coordination frictions lead to heterogeneous local labor markets. We de- rive...

  9. Frictional heating of tribological contacts

    NARCIS (Netherlands)

    Bos, Johannes


    Wherever friction occurs, mechanical energy is transformed into heat. The tem­ perature rise associated with this heating can have an important influence on the tribological behaviour of the contacting components. Apart from determining per­ formance, thermal phenomena affect reliability and may cau

  10. Friction Sensitivity of Primary Explosives (United States)


    potassium dinitrobenzofuroxan none tetrazene 407913 tetrazene 7902454 The mixes which were tested are: NOL 130 (basic lead styphnate , barium nitrate, lead...azide, tetrazene, and antimony sulfide); PA 100 (normal lead styphnate , barium nitrate, tetrazene, lead dioxide, calcium silicide, and antimony...styuhnate, basic lead styphnate , potassium dinitrobenzofuroxan, and tetrazene were tested to determine the- 10% and 50% probability of friction

  11. Friction of atomically stepped surfaces (United States)

    Dikken, R. J.; Thijsse, B. J.; Nicola, L.


    The friction behavior of atomically stepped metal surfaces under contact loading is studied using molecular dynamics simulations. While real rough metal surfaces involve roughness at multiple length scales, the focus of this paper is on understanding friction of the smallest scale of roughness: atomic steps. To this end, periodic stepped Al surfaces with different step geometry are brought into contact and sheared at room temperature. Contact stress that continuously tries to build up during loading, is released with fluctuating stress drops during sliding, according to the typical stick-slip behavior. Stress release occurs not only through local slip, but also by means of step motion. The steps move along the contact, concurrently resulting in normal migration of the contact. The direction of migration depends on the sign of the step, i.e., its orientation with respect to the shearing direction. If the steps are of equal sign, there is a net migration of the entire contact accompanied by significant vacancy generation at room temperature. The stick-slip behavior of the stepped contacts is found to have all the characteristic of a self-organized critical state, with statistics dictated by step density. For the studied step geometries, frictional sliding is found to involve significant atomic rearrangement through which the contact roughness is drastically changed. This leads for certain step configurations to a marked transition from jerky sliding motion to smooth sliding, making the final friction stress approximately similar to that of a flat contact.

  12. Rotary Engine Friction Test Rig Development Report (United States)


    5  4.  Friction Rig Development 7  5.  AutoCAD ...Figure 4. Engine friction test rig AutoCAD model. ........................................................................8  Figure 5. dead center. 8 5. AutoCAD Model Development A model of the rotary engine friction test rig was developed to determine the optimal

  13. Asbestos free friction composition for brake linings

    Indian Academy of Sciences (India)

    Arnab Ganguly; Raji George


    An asbestos free friction material composite for brake linings is synthesized containing fibrous reinforcing constituents, friction imparting and controlling additives, elastomeric additives, fire retarding components and a thermosetting resin. The composite shows exemplary friction characteristics and has great resistance to wear and shows good temperature stability.

  14. Multiscale friction modeling for sheet metal forming

    NARCIS (Netherlands)

    Hol, J.; Cid Alfaro, M.V.; de Rooij, Matthias B.; Meinders, Vincent T.; Felder, Eric; Montmitonnet, Pierre


    The most often used friction model for sheet metal forming simulations is the relative simple Coulomb friction model. This paper presents a more advanced friction model for large scale forming simulations based on the surface change on the micro-scale. The surface texture of a material changes when

  15. A thermodynamic model of sliding friction

    Directory of Open Access Journals (Sweden)

    Lasse Makkonen


    Full Text Available A first principles thermodynamic model of sliding friction is derived. The model predictions are in agreement with the observed friction laws both in macro- and nanoscale. When applied to calculating the friction coefficient the model provides a quantitative agreement with recent atomic force microscopy measurements on a number of materials.

  16. Nanocomposite TiSiBC Hard Coatings with High Resistance to Wear, Fracture and Scratching (United States)

    Mahato, P.; Nyati, G.; Singh, R. J.; Mishra, S. K.


    The sliding wear under fretting condition, scratch adhesion, deformation behavior during micro- and nanoscratch studies have been studied for nanocomposite TiSiBC hard coating deposited on steel substrate by magnetron sputtering. The nanocomposite coatings having hardness and modulus around 30 and 300 GPa, respectively, showed a very significant decrease in fretting wear as compared to the uncoated steel. Pileup occurred along the sides of the scratch track due to plastic deformation of the substrate at the scratch load; however, cracks were not seen in films. The coefficient of friction remained scratch, higher wear resistance, higher toughness and low coefficient of friction.

  17. Elastic scattering phenomenology

    Energy Technology Data Exchange (ETDEWEB)

    Mackintosh, R.S. [The Open University, School of Physical Sciences, Milton Keynes (United Kingdom)


    We argue that, in many situations, fits to elastic scattering data that were historically, and frequently still are, considered ''good'', are not justifiably so describable. Information about the dynamics of nucleon-nucleus and nucleus-nucleus scattering is lost when elastic scattering phenomenology is insufficiently ambitious. It is argued that in many situations, an alternative approach is appropriate for the phenomenology of nuclear elastic scattering of nucleons and other light nuclei. The approach affords an appropriate means of evaluating folding models, one that fully exploits available empirical data. It is particularly applicable for nucleons and other light ions. (orig.)

  18. Dynamics of the rotor on elastic-damping supports under action of kinematic effects (United States)

    Chernyshev, V.; Savin, L.; Fominova, O.


    The article describes the elements of the theory of dynamic analysis of rotor systems. The mathematical model of a gyroscopic rotor as an elementary object on elastic-damping supports. The results of simulation of the trajectories of the rotor under kinematic loading with amplitude commensurate with the clearance in bearing assemblies of fluid friction.

  19. Analysis of the moment caused by friction of cardan joint. Cardan joint no friction kishinryoku kaiseki

    Energy Technology Data Exchange (ETDEWEB)

    Ono, K.; Yagi, Shida, T. (Atsugi Unisia Corp., Kanagawa (Japan))


    Analyzing the vibromotive force, generated by the friction, in generation morphology, level, dynamical characteristics, etc., through measurement of joint unit friction simulation of frictional vibromotive force and on-platform measurement of propeller shaft in vibromotive force, the present report investigated the influence of friction on the vehicle in sound vibration performance. By a vibromotive force measurement system, internally equipped with a piezoelectric type force meter, frictional vibromotive force could be quantitatively grasped. The friction must be appropriately controlled, because the moment, generated by it, is expected to be put in the vehicle by intermediation of a supporting point and adversely influence the sound vibration performance. Apart from the above, elucidation was made of relation between the ordinal number components of rotation of vibromotive force and friction, calculation of reaction force at the supporting point by the frictional measurement, relation between the joint angle and frictional vibromotive force, second couple force due to the friction, etc. 3 refs., 15 figs.

  20. Friction and Wear Performance of Boron Doped, Undoped Microcrystalline and Fine Grained Composite Diamond Films

    Institute of Scientific and Technical Information of China (English)

    WANG Xinchang; WANG Liang; SHEN Bin; SUN Fanghong


    Chemical vapor deposition (CVD) diamond films have attracted more attentions due to their excellent mechanical properties. Whereas as-fabricated traditional diamond films in the previous studies don’t have enough adhesion or surface smoothness, which seriously impact their friction and wear performance, and thus limit their applications under extremely harsh conditions. A boron doped, undoped microcrystalline and fine grained composite diamond (BD-UM-FGCD) film is fabricated by a three-step method adopting hot filament CVD (HFCVD) method in the present study, presenting outstanding comprehensive performance, including the good adhesion between the substrate and the underlying boron doped diamond (BDD) layer, the extremely high hardness of the middle undoped microcrystalline diamond (UMCD) layer, as well as the low surface roughness and favorable polished convenience of the surface fine grained diamond (FGD) layer. The friction and wear behavior of this composite film sliding against low-carbon steel and silicon nitride balls are studied on a ball-on-plate rotational friction tester. Besides, its wear rate is further evaluated under a severer condition using an inner-hole polishing apparatus, with low-carbon steel wire as the counterpart. The test results show that the BD-UM-FGCD film performs very small friction coefficient and great friction behavior owing to its high surface smoothness, and meanwhile it also has excellent wear resistance because of the relatively high hardness of the surface FGD film and the extremely high hardness of the middle UMCD film. Moreover, under the industrial conditions for producing low-carbon steel wires, this composite film can sufficiently prolong the working lifetime of the drawing dies and improve their application effects. This research develops a novel composite diamond films owning great comprehensive properties, which have great potentials as protecting coatings on working surfaces of the wear-resistant and anti-frictional

  1. Friction and wear performance of boron doped, undoped microcrystalline and fine grained composite diamond films (United States)

    Wang, Xinchang; Wang, Liang; Shen, Bin; Sun, Fanghong


    Chemical vapor deposition (CVD) diamond films have attracted more attentions due to their excellent mechanical properties. Whereas as-fabricated traditional diamond films in the previous studies don't have enough adhesion or surface smoothness, which seriously impact their friction and wear performance, and thus limit their applications under extremely harsh conditions. A boron doped, undoped microcrystalline and fine grained composite diamond (BD-UM-FGCD) film is fabricated by a three-step method adopting hot filament CVD (HFCVD) method in the present study, presenting outstanding comprehensive performance, including the good adhesion between the substrate and the underlying boron doped diamond (BDD) layer, the extremely high hardness of the middle undoped microcrystalline diamond (UMCD) layer, as well as the low surface roughness and favorable polished convenience of the surface fine grained diamond (FGD) layer. The friction and wear behavior of this composite film sliding against low-carbon steel and silicon nitride balls are studied on a ball-on-plate rotational friction tester. Besides, its wear rate is further evaluated under a severer condition using an inner-hole polishing apparatus, with low-carbon steel wire as the counterpart. The test results show that the BD-UM-FGCD film performs very small friction coefficient and great friction behavior owing to its high surface smoothness, and meanwhile it also has excellent wear resistance because of the relatively high hardness of the surface FGD film and the extremely high hardness of the middle UMCD film. Moreover, under the industrial conditions for producing low-carbon steel wires, this composite film can sufficiently prolong the working lifetime of the drawing dies and improve their application effects. This research develops a novel composite diamond films owning great comprehensive properties, which have great potentials as protecting coatings on working surfaces of the wear-resistant and anti-frictional

  2. Natural Aging Behavior Of Friction Stir Welded Al-Zn-Mg-Cu Aluminum Alloys

    Directory of Open Access Journals (Sweden)

    Kalemba I.


    Full Text Available The long term natural aging behavior of friction stir welded aluminum 7136-T76 and 7042 T6 extrusions was investigated. The microstructural characteristics and mechanical properties in the as-welded and six years naturally aged conditions were studied and correlated to a coupled thermal/material flow model of the joining process. Hardness profiles for the 7136 alloy taken along the mid-plane thickness of the workpiece displayed the characteristic W-shape. With natural aging, hardness recovery occurred on both sides of the weld, but the position of the hardness minima, particularly on the advancing side, shifted away from the weld centerline. The hardness profile for the 7042 alloy displayed U-shape in the as-welded condition and W-shape after natural aging. The hardness behavior upon natural aging correlated to the temperature profile developed during welding and the degree to which phase dissolution occurred in the regions adjacent to the stir zone.

  3. Focused Acoustic Beam Evaluation of Aluminum — Lithium Friction Stir Weld (United States)

    Sathish, Shamachary; Jata, Kumar V.; Martin, Richard W.; Reibel, Richard


    Local elastic variations were measured across a friction stir welded zone in Al-Li alloy with the use of a focused acoustic beam. The near surface microstructure was investigated by measuring both the amplitude and the local velocity of the Rayleigh Surface Waves (RSW). Both the amplitude and velocity of the focused longitudinal acoustic waves propagating through the thickness of the sample has been used for examination of the variations in the localized bulk elastic properties. The variations observed across the weld zone are explained based on microstructure and residual stress variations.


    Directory of Open Access Journals (Sweden)

    Vardhan Harsh


    Full Text Available Transdermal drug delivery is hardly an old technology, since 1800’s and the technology is no longer just adhesive patches. Due to recent advances in technology and the ability to apply the drug to the site of action without rupturing the skin membrane, transdermal route is becoming a widely accepted route of drug administration. Recently, various strategies have been used to augment the transdermal delivery of bioactives. Mainly, they include iontophoresis, electrophoresis, sonophoresis, chemical permeation enhancers, micro needles, and vesicular system. Among these strategies elastic liposomes appear promising. Elastic liposomes possess an infrastructure consisting of hydrophobic and hydrophilic moieties together and as a result can accommodate drug molecules with wide range of solubility. It is an ultra deformable vesicle, elastic in nature which can squeeze itself through a pore which is many times smaller than its size owing to its elasticity. They can deform and pass through narrow constriction (from 5 to 10 times less than their own diameter without measurable loss. This high deformability gives better penetration of intact vesicles. This system is much more efficient at delivering a low and high molecular weight drug to the skin in terms of quantity and depth. The article speaks specifically on various phenomenon associated with the properties of these vesicles and their transport mechanisms. It also throws light on the effectiveness of conventional and deformable vesicles as drug delivery systems as well as their possible mode of action as transdermal drug carriers.

  5. Effect of viscosity on material behavior in friction stir welding process

    Institute of Scientific and Technical Information of China (English)

    ZHANG Hong-wu; ZHANG Zhao; BIE Jun; ZHOU Lei; CHEN Jin-tao


    Temperature-dependent elastic viscoplastic material model was used for the numerical simulation of the friction stir welding process. The non-elastic response of the rate-dependent material in the large deformation problems was calculated by using the closest point algorithm. The numerical results show that the shape of the equivalent plastic strain looks like onion rings and the spacing of the rings is approximately equal to the forward movement of the tool in one rotation. The equivalent plastic strain is increased with the increase of viscosity coefficient due to the increase of friction stress in the pin-plate interface. The region which is influenced by the rotating tool is decreased with the decrease of viscosity coefficient. The radial and circumferential stresses in front of the pin are greater than the ones behind the pin. This difference can be reduced with the decrease of viscosity.

  6. Nemato-elastic crawlers

    CERN Document Server

    Zakharov, A P


    A propagating "beam" triggering a local phase transition in a nematic elastomer sets it into a crawling motion, which may morph due to buckling. We consider the motion of the various configurations of slender rods and thin stripes with both uniform and splayed nematic order in cross-section, and detect the dependence of the gait and speed on flexural rigidity and substrate friction.

  7. Statistical mechanics of elasticity

    CERN Document Server

    Weiner, JH


    Advanced, self-contained treatment illustrates general principles and elastic behavior of solids. Topics include thermoelastic behavior of crystalline and polymeric solids, interatomic force laws, behavior of solids, and thermally activated processes. 1983 edition.

  8. Friction and wear evaluation of high-strength gel (United States)

    Kameyama, Toshiki; Wada, Masato; Makino, Masato; Kawakami, Masaru; Furukawa, Hidemitsu


    In the last decade, several innovative polymer gel materials with enhanced mechanical proper ties have been invented by Japanese researches. In 2003, a most effective but simple way was proposed to synthesize double network gels, with compression fracture stress of about 30MPa, compared to several tens of kPa for common gels. In this study, we evaluate the wear of a double network gel, both with and without water lubrication. In the un-lubricated experiment, the gel surface is worn with a stainless steel ball. In the other experiment with water lubrication, the gel surface is worn by different counter surfaces because the stainless steel ball was too smooth to wear. It was found that frictional vibration of wear gel is transitioning to steady sliding in lubricated. As conventional reduction method of the friction by the contact between general solids, there are surface processing such as the texturing, attachment of lubrication materials. In the case of gel, the minute processing to the surface such as the texturing is difficult, because the gel is soft in comparison with the hard materials such as the metal. By proceeding with this study, the surface processing of low-frictional gels will be enabled.

  9. Implicit frictional-contact model for soft particle systems (United States)

    Nezamabadi, Saeid; Radjai, Farhang; Averseng, Julien; Delenne, Jean-Yves


    We introduce a novel numerical approach for the simulation of soft particles interacting via frictional contacts. This approach is based on an implicit formulation of the Material Point Method, allowing for large particle deformations, combined with the Contact Dynamics method for the treatment of unilateral frictional contacts between particles. This approach is both precise due to the treatment of contacts with no regularization and artificial damping parameters, and robust due to implicit time integration of both bulk degrees of freedom and relative contact velocities at the nodes representing the contact points. By construction, our algorithm is capable of handling arbitrary particle shapes and deformations. We illustrate this approach by two simple 2D examples: a Hertz contact and a rolling particle on an inclined plane. We also investigate the compaction of a packing of circular particles up to a solid fraction well above the jamming limit of hard particles. We find that, for the same level of deformation, the solid fraction in a packing of frictional particles is above that of a packing of frictionless particles as a result of larger particle shape change.

  10. Repair welding process of friction stir welding groove defect

    Institute of Scientific and Technical Information of China (English)

    LIU Hui-jie; ZHANG Hui-jie


    The groove defect formed in the friction stir welding dramatically deteriorates weld appearances and mechanical properties of the joints owing to its larger size and penetration. Therefore, the friction stir repair welding was utilized to remove such a groove defect, and the focus was placed on the mechanical properties and microstructural characteristics of the repair joints so as to obtain an optimum repair welding process. The experimental results indicate that the groove defect can be removed by friction stir repair welding, and the offset repair welding process is superior to the symmetrical repair welding process. In the symmetrical repair welding process, a large number of fine cavity defects and an obvious aggregation of hard-brittle phase Al2Cu occur, accordingly the mechanical properties of the repair joint are weakened, and the fracture feature of repair joint is partially brittle and partially plastic. A good-quality repair joint can be obtained by the offset repair welding process, and the repair joint is fractured near the interface between the weld nugget zone and thermal-mechanically affected zone.


    Institute of Scientific and Technical Information of China (English)

    CHENG Wei-ping; MAO Gen-hai; LIU Guo-hua


    Channel friction is an important parameter in hydraulic analysis.A channel friction parameter inversion method based on Kalman Filter with unknown parameter vector is proposed.Numerical simulations indicate that when the number of monitoring stations exceeds a critical value, the solution is hardly affected.In addition, Kalman Filter with unknown parameter vector is effective only at unsteady state.For the nonlinear equations, computations of sensitivity matrices are time-costly.Two simplified measures can reduce computing time, but not influence the results.One is to reduce sensitivity matrix analysis time, the other is to substitute for sensitivity matrix.

  12. Energy Partition During In-plane Dynamic Rupture on a Frictional Interface (United States)

    Needleman, A.; Shi, Z.; Ben-Zion, Y.


    We study properties of dynamic ruptures and the partition of energy between radiation and dissipative mechanisms using two-dimensional in-plane calculations with the finite element method. The model consists of two identical isotropic elastic media separated by an interface governed by rate- and state-dependent friction. Rupture is initiated by gradually overstressing a localized nucleation zone. Our simulations with model parameters representative of Homalite-100 indicate that different values of parameters controlling the velocity dependence of friction, the strength excess parameter and the length of the nucleation zone, can lead to the following four rupture modes: supershear crack-like rupture, subshear crack-like rupture, subshear single pulse and supershear train of pulses. High initial shear stress and weak velocity dependence of friction favor crack-like ruptures, while the opposite conditions favor the pulse mode. The rupture mode can switch from a subshear single pulse to a supershear train of pulses when the width of the nucleation zone increases. The elastic strain energy released over the same propagation distance by the different rupture modes has the following order: supershear crack, subshear crack, supershear train of pulses and subshear single pulse. The same order applies also to the ratio of kinetic energy (radiation) to total change of elastic energy for the different rupture modes. Decreasing the dynamic coefficient of friction increases the fraction of stored energy that is converted to kinetic energy. In the current study we use model parameters representative of rocks instead of Homalite-100, by modeling recent results of Kilgore et al. (2007) who measured and estimated various energy components in laboratory friction experiments with granite. We are also incorporating into the code ingredients that will allow us to study rupture properties and energy partition for cases with a bimaterial interface and dynamic generation of plastic strain

  13. Adhesive friction based on finite element study and n-point asperity model (United States)

    Sahoo, Prasanta; Waghmare, Ajay K.


    The present work considers analysis of adhesive friction of rough surfaces using n- point asperity concept for statistical definition of surface roughness features, and accurate finite element analysis of elastic-plastic deformation of single asperity contact. Well defined adhesion index and plasticity index are used to study the prospective contact situations arising out of variation in material properties and surface roughness features. From the present results it is possible to locate the combinations of adhesion index and plasticity index that may yield very low coefficient of friction. Thus suitable choice of surface and material parameters for the contact of two rough surfaces can be made in order to minimize friction typically at low load and micro scale roughness situations.

  14. Hardness Tester for Polyur (United States)

    Hauser, D. L.; Buras, D. F.; Corbin, J. M.


    Rubber-hardness tester modified for use on rigid polyurethane foam. Provides objective basis for evaluation of improvements in foam manufacturing and inspection. Typical acceptance criterion requires minimum hardness reading of 80 on modified tester. With adequate correlation tests, modified tester used to measure indirectly tensile and compressive strengths of foam.

  15. Carbide Type Influence on Tribological Properties of Hard Faced Steel Layer Part II- Experimental Results

    Directory of Open Access Journals (Sweden)

    V. Lazic


    Full Text Available In this paper is presented a preceding procedure that should be conducted in order to successfully regenerate damaged forging dies by the hard facing process. After the tool damage types identification, as well as their causes, we have chosen the procedure and the parameters of hard facing that we further corrected by conducting the test hard facings on models. Thus, we were able to relate the experimental results outputs with the repair technology, taking as a criterion the quality of the surface layers wear resistance such as friction coefficient and width of hard faced zone, hardness and its distribution in cross section, then microstructure of characteristic of hard faced zones, etc. This research points out significancy of tribological properties of certain types of carbides and their effects on metal matrix, in which carbides are embedded. Our tribological investigations have shown that the working life of the hard faced tool can be longer than that of the new tool.

  16. Mastering ElasticSearch

    CERN Document Server

    Kuc, Rafal


    A practical tutorial that covers the difficult design, implementation, and management of search solutions.Mastering ElasticSearch is aimed at to intermediate users who want to extend their knowledge about ElasticSearch. The topics that are described in the book are detailed, but we assume that you already know the basics, like the query DSL or data indexing. Advanced users will also find this book useful, as the examples are getting deep into the internals where it is needed.

  17. Study of the Thermal Decomposition of PFPEs Lubricants on a Thin DLC Film Using Finitely Extensible Nonlinear Elastic Potential Based Molecular Dynamics Simulation

    Directory of Open Access Journals (Sweden)

    S. K. Deb Nath


    Full Text Available Perfluoropolyethers (PFPEs are widely used as hard disk lubricants for protecting carbon overcoat reducing friction between the hard disk interface and the head during the movement of head during reading and writing data in the hard disk. Due to temperature rise of PFPE Zdol lubricant molecules on a DLC surface, how polar end groups are detached from lubricant molecules during coating is described considering the effect of temperatures on the bond/break density of PFPE Zdol using the coarse-grained bead spring model based on finitely extensible nonlinear elastic potential. As PFPE Z contains no polar end groups, effects of temperature on the bond/break density (number of broken bonds/total number of bonds are not so significant like PFPE Zdol. Effects of temperature on the bond/break density of PFPE Z on DLC surface are also discussed with the help of graphical results. How bond/break phenomenonaffects the end bead density of PFPE Z and PFPE Zdol on DLC surface is discussed elaborately. How the overall bond length of PFPE Zdol increases with the increase of temperature which is responsible for its decomposition is discussed with the help of graphical results. At HAMR condition, as PFPE Z and PFPE Zdol are not suitable lubricant on a hard disk surface, it needs more investigations to obtain suitable lubricant. We study the effect of breaking of bonds of nonfunctional lubricant PFPE Z, functional lubricants such as PFPE Zdol and PFPE Ztetrao, and multidented functional lubricants such as ARJ-DS, ARJ-DD, and OHJ-DS on a DLC substrate with the increase of temperature when heating of all of the lubricants on a DLC substrate is carried out isothermally using the coarse-grained bead spring model by molecular dynamics simulations and suitable lubricant is selected which is suitable on a DLC substrate at high temperature.

  18. Comprehensive hard materials

    CERN Document Server


    Comprehensive Hard Materials deals with the production, uses and properties of the carbides, nitrides and borides of these metals and those of titanium, as well as tools of ceramics, the superhard boron nitrides and diamond and related compounds. Articles include the technologies of powder production (including their precursor materials), milling, granulation, cold and hot compaction, sintering, hot isostatic pressing, hot-pressing, injection moulding, as well as on the coating technologies for refractory metals, hard metals and hard materials. The characterization, testing, quality assurance and applications are also covered. Comprehensive Hard Materials provides meaningful insights on materials at the leading edge of technology. It aids continued research and development of these materials and as such it is a critical information resource to academics and industry professionals facing the technological challenges of the future. Hard materials operate at the leading edge of technology, and continued res...

  19. Hybrid manufacturing processes for fusion welding and friction stir welding of aerospace grade aluminum alloys (United States)

    Gegesky, Megan Alexandra

    Friction stir welding and processing can provide for joints in aerospace grade aluminum alloys that have preferable material properties as compared to fusion welding techniques. Aerospace grade aluminum alloys such as AA2024-T3 and AA7075-T6 are considered non-weldable by traditional fusion welding techniques. Improved mechanical properties over previously used techniques are usually preferable for aerospace applications. Therefore, by combining traditional fusion welding and friction stir processing techniques, it could be plausible to create more difficult geometries in manufactured parts instead of using traditional techniques. While this combination of fusion welding and friction stir processing is not a new technology, its introduction to aerospace grade aluminum alloys as well as non-weldable alloys, is new. This is brought about by a lowered required clamping force required by adding a fusion weld before a friction stir processing technique. The changes in properties associated with joining techniques include: microstructural changes, changes in hardness, tensile strength, and corrosion resistance. This thesis illustrates these changes for the non-weldable AA2024-T351 and AA7075-T651 as well as the weldable alloy AA5052-H32. The microhardness, tensile strength and corrosion resistance of the four processing states: base material, fusion welded material, friction stir welded material, and friction stir processed fusion welded material is studied. The plausibility of this hybrid process for the three different materials is characterized, as well as plausible applications for this joining technique.

  20. Semi-Smooth Newton Method for Solving 2D Contact Problems with Tresca and Coulomb Friction

    Directory of Open Access Journals (Sweden)

    Kristina Motyckova


    Full Text Available The contribution deals with contact problems for two elastic bodies with friction. After the description of the problem we present its discretization based on linear or bilinear finite elements. The semi--smooth Newton method is used to find the solution, from which we derive active sets algorithms. Finally, we arrive at the globally convergent dual implementation of the algorithms in terms of the Langrange multipliers for the Tresca problem. Numerical experiments conclude the paper.

  1. The nature of the frictional force at the macro-, micro-, and nano-scales


    Broitman, Esteban


    Nowadays it is accepted that the friction force is a combined effect arising from various phenomena: adhesive forces, capillary forces, contact elasticity, topography, surface chemistry, and generation of a third body, etc. Any of them can dominate depending on the experimental force and length scales of the study. Typical forces in macro-tribology are in the Newtons, while are reduced to milli-/micro-Newtons, and nano-Newtons in micro- and nano-tribology, respectively. In this paper, experim...

  2. Collective behavior of asperities as a model for friction and adhesion (United States)

    Hulikal, Srivatsan

    Understanding friction and adhesion in static and sliding contact of surfaces is important in numerous physical phenomena and technological applications. Most surfaces are rough at the microscale, and thus the real area of contact is only a fraction of the nominal area. The macroscopic frictional and adhesive response is determined by the collective behavior of the population of evolving and interacting microscopic contacts. This collective behavior can be very different from the behavior of individual contacts. It is thus important to understand how the macroscopic response emerges from the microscopic one. In this thesis, we develop a theoretical and computational framework to study the collective behavior. Our philosophy is to assume a simple behavior of a single asperity and study the collective response of an ensemble. Our work bridges the existing well-developed studies of single asperities with phenomenological laws that describe macroscopic rate-and-state behavior of frictional interfaces. We find that many aspects of the macroscopic behavior are robust with respect to the microscopic response. This explains why qualitatively similar frictional features are seen for a diverse range of materials. We first show that the collective response of an ensemble of one-dimensional independent viscoelastic elements interacting through a mean field reproduces many qualitative features of static and sliding friction evolution. The resulting macroscopic behavior is different from the microscopic one: for example, even if each contact is velocity-strengthening, the macroscopic behavior can be velocity-weakening. The framework is then extended to incorporate three-dimensional rough surfaces, long- range elastic interactions between contacts, and time-dependent material behaviors such as viscoelasticity and viscoplasticity. Interestingly, the mean field behavior dominates and the elastic interactions, though important from a quantitative perspective, do not change the

  3. Controlling Force and Depth in Friction Stir Welding (United States)

    Adams, Glynn; Loftus, Zachary; McCormac, Nathan; Venable, Richard


    Feedback control of the penetration force applied to a pin tool in friction stir welding has been found to be a robust and reliable means for controlling the depth of penetration of the tool. This discovery has made it possible to simplify depth control and to weld with greater repeatability, even on workpieces with long weld joints. Prior to this discovery, depths of penetration in friction stir welding were controlled by hard-tooled roller assemblies or by depth actuators controlled by feedback from such external sensors as linear variable-differential transformers or laser-based devices. These means of control are limited: A hard-tooled roller assembly confines a pin tool to a preset depth that cannot be changed easily during the welding process. A measurement by an external sensor is only an indirect indicative of the depth of penetration, and computations to correlate such a measurement with a depth of penetration are vulnerable to error. The present force-feedback approach exploits the proportionality between the depth and the force of penetration Unlike a depth measurement taken by an external sensor, a force measurement can be direct because it can be taken by a sensor coupled directly to the pin tool. The reading can be processed through a modern electronic servo control system to control an actuator to keep the applied penetration force at the desired level. In comparison with the older depth-control methods described above, this method offers greater sensitivity to plasticizing of the workpiece metal and is less sensitive to process noise, resulting in a more consistent process. In an experiment, a tapered panel was friction stir welded while controlling the force of penetration according to this method. The figure is a plot of measurements taken during the experiment, showing that force was controlled with a variation of 200 lb (890 N), resulting in control of the depth of penetration with a variation of 0.004 in. (0.1 mm).

  4. Low friction and wear resistant coating systems on Ti6Al4V alloy

    Directory of Open Access Journals (Sweden)

    B.G. Wendler


    Full Text Available Purpose: Development of an original multiplex hybrid treatment of Ti6Al4V alloy: diffusion hardening+intermediate hard gradient TiCxNy layer with use of continuous CAE+top low friction and wear resistant hard amorphous a-C layer with use of pulsed CAE method.Design/methodology/approach: Ti6Al4V substrates were diffusion hardened with interstitial O or N atoms with use of glow discharge plasma in the atmosphere Ar+O2 or Ar+N2. Next they were deposited with a hard gradient TiCxNy layer and with a hard amorphous a-C coating as the top one. The morphology, microstructure, chemical and phase composition, chemical bonds, microhardness and tribological properties during dry friction of the alloy after multiplex treatment have been investigated with use of SEM, EDS, XRD, XPS, Vickers diamond indenter and ball-on-plate test.Findings: An important increase of hardness of the near surface zone of the Ti6Al4V alloy has been achieved (from ~350VHN to ~1000 VHN, good adhesion between the gradient TiCxNy coating and the Ti6Al4V substrate as well as an important decrease of dry friction coefficient (down to ~0.15 and a substantial increase of the resistance to wear (up to two orders of magnitude in comparison with non treated Ti alloy.Research limitations/implications: The research will be continued on greater number of specimens and against other counterbodies.Practical implications: It looks like that the Ti alloys can be used as mobile parts of machines due to high resistance to wear and low friction.Originality/value: A novel original multiplex hybrid treatment of Ti alloys has been developed at the Lodz University of Technology.

  5. Nonlinear elastic waves in materials

    CERN Document Server

    Rushchitsky, Jeremiah J


    The main goal of the book is a coherent treatment of the theory of propagation in materials of nonlinearly elastic waves of displacements, which corresponds to one modern line of development of the nonlinear theory of elastic waves. The book is divided on five basic parts: the necessary information on waves and materials; the necessary information on nonlinear theory of elasticity and elastic materials; analysis of one-dimensional nonlinear elastic waves of displacement – longitudinal, vertically and horizontally polarized transverse plane nonlinear elastic waves of displacement; analysis of one-dimensional nonlinear elastic waves of displacement – cylindrical and torsional nonlinear elastic waves of displacement; analysis of two-dimensional nonlinear elastic waves of displacement – Rayleigh and Love nonlinear elastic surface waves. The book is addressed first of all to people working in solid mechanics – from the students at an advanced undergraduate and graduate level to the scientists, professional...

  6. Elastic Properties of Several Silicon Nitride Films

    Energy Technology Data Exchange (ETDEWEB)

    Liu, X.; Metcalf, T. H.; Wang, Q.; Photiadis, D. M.


    We have measured the internal friction (Q{sup -1}) of amorphous silicon nitride (a-SiN{sub x}) films prepared by a variety of methods, including low-pressure chemical-vapor deposition (LPCVD), plasma-enhanced chemical-vapor deposition (PECVD), and hot-wire chemical-vapor deposition (HWCVD) from 0.5 K to room temperature. The measurements are made by depositing the films onto extremely high-Q silicon double paddle oscillator substrates with a resonant frequency of {approx}5500 Hz. We find the elastic properties of these a-SiN{sub x} films resemble those of amorphous silicon (a-Si) films, demonstrating considerable variation which depends on the film growth methods and post deposition annealing. The internal friction for most of the films shows a broad temperature-independent plateau below 30 K, characteristic of amorphous solids. The values of Q{sup -1}, however, vary from film to film in this plateau region by more than one order of magnitude. This has been observed in tetrehedrally covalent-bonded amorphous thin films, like a-Si, a-Ge, and a-C. The PECVD films have the highest Q{sup -1} just like a normal amorphous solid, while LPCVD films have an internal friction more than one order of magnitude lower. All the films show a reduction of Q{sup -1} after annealing at 800 C, even for the LPCVD films which were prepared at 850 C. This can be viewed as a reduction of structural disorder.

  7. Numerical simulation of friction stir welding (FSW): Prediction of the heat affect zone using a softening model (United States)

    Paulo, R. M. F.; Carlone, P.; Valente, R. A. F.; Teixeira-Dias, F.; Palazzo, G. S.


    In this work a numerical model is proposed to simulate Friction Stir Welding (FSW) process in AA2024-T3 plates. This model included a softening model that account for the temperature history and the hardness distribution on a welded plate can thus be predicted. The validation of the model was performed using experimental measurements of the hardness in the plate cross-section. There is an acceptable prediction of the material softening in the Heat Affected Zone (HAZ) using the adopted model.


    Institute of Scientific and Technical Information of China (English)

    蒲军平; 姚振汉


    Using a sub-regional boundary element method, an algorithm for the two-dimensionalelastic bodies with a closed crack loaded by a moving contact elastic body is proposed. Since the extentand status of the contact surface of two elastic bodies and the crack within the body are all not knownin advance, a double iterative contact algorithm is used. The BEM program for solving the closedcrack problems is developed, some numerical examples are calculated, and the results of the centercrack cases are shown to be in good agreement with the analytical solution in the classical fracturemechanics. In the condition of friction and non-friction, some coupling computational results of theSIF for the closed crack, with different angles and loaded by a moving contact elastic body, are alsoobtained by a numerical computation.

  9. High temperature skin friction measurement (United States)

    Tcheng, Ping; Holmes, Harlan K.; Supplee, Frank H., Jr.


    Skin friction measurement in the NASA Langley hypersonic propulsion facility is described. The sensor configuration utilized an existing balance, modified to provide thermal isolation and an increased standoff distance. For test run times of about 20 sec and ambient-air cooling of the test section and balance, the modified balance performed satisfactorily, even when it was subjected to acoustic and structural vibration. The balance is an inertially balanced closed-loop servo system where the current to a moving-coil motor needed to restore or null the output from the position sensor is a measure of the force or skin friction tending to displace the moving element. The accuracy of the sensor is directly affected by the position sensor in the feedback loop, in this case a linear-variable differential transformer which has proven to be influenced by temperature gradients.

  10. Deformation behaviors of 21-6-9 stainless steel tube numerical control bending under different friction conditions

    Institute of Scientific and Technical Information of China (English)

    方军; 鲁世强; 王克鲁; 姚正军


    For contact dominated numerical control (NC) bending process of tube, the effect of friction on bending deformation behaviors should be focused on to achieve precision bending forming. A three dimensional (3D) elastic-plastic finite element (FE) model of NC bending process was established under ABAQUS/Explicit platform, and its reliability was validated by the experiment. Then, numerical study on bending deformation behaviors under different frictions between tube and various dies was explored from multiple aspects such as wrinkling, wall thickness change and cross section deformation. The results show that the large friction of wiper die−tube reduces the wrinkling wave ratioη and cross section deformation degreeΔD and increases the wall thinning degreeΔt. The large friction of mandrel−tube causes largeη,Δt andΔD, and the onset of wrinkling near clamp die. The large friction of pressure die−tube reducesΔt andΔD, and the friction on this interface has little effect onη. The large friction of bending die−tube reducesη andΔD, and the friction on this interface has little effect onΔt. The reasonable friction coefficients on wiper die−tube, mandrel−tube, pressure die−tube and bending die−tube of 21-6-9 (0Cr21Ni6Mn9N) stainless steel tube in NC bending are 0.05−0.15, 0.05−0.15, 0.25−0.35 and 0.25−0.35, respectively. The results can provide a guideline for applying the friction conditions to establish the robust bending environment for stable and precise bending deformation of tube bending.

  11. Influence of ligation method on friction resistance of lingual brackets with different second-order angulations: an in vitro study (United States)

    Pereira, Graziane Olímpio; Gimenez, Carla Maria Melleiro; Prieto, Lucas; Prieto, Marcos Gabriel do Lago; Basting, Roberta Tarkany


    ABSTRACT Objective: To evaluate stainless steel archwire static friction in active and passive self-ligating lingual and conventional brackets with second-order angulations. Methods: Two conventional lingual brackets for canines (STb light/Ormco; PSWb/Tecnident), and two self-ligating brackets, one active (In-Ovation L/GAC) and the other passive (3D/ Forestadent), were evaluated. A stainless steel archwire was used at 0°, 3° and 5° angulations. Metal ligatures, conventional elastic ligatures, and low friction elastic ligatures were also tested. A universal testing machine applied friction between brackets and wires, simulating sliding mechanics, to produce 2-mm sliding at 3 mm/minute speed. Results: Two-way analysis of variance demonstrated a significant effect of the interaction between brackets and angulations (p < 0.001). Tukey test indicated that the highest frictional resistance values were observed at 5° angulation for In-Ovation L, PSWb bracket with non conventional ligature, and STb bracket with metal ligature. As for 3D, PSWb with conventional or metal ligatures, and STb brackets with non conventional ligature, showed significantly lower static frictional resistance with 0° angulation. At 0° angulation, STb brackets with metal ties, In-Ovation L brackets and 3D brackets had the lowest frictional resistance. Conclusions: As the angulation increased from 0° to 3°, static friction resistance increased. When angulation increased from 3° to 5°, static friction resistance increased or remained the same. Self-ligating 3D and In-Ovation L brackets, as well as conventional STb brackets, seem to be the best option when sliding mechanics is used to perform lingual orthodontic treatment. PMID:27653262

  12. Thermodynamic aspects of rock friction

    CERN Document Server

    Mitsui, Noa


    Rate- and state-dependent friction law for velocity-step tests is analyzed from a thermodynamic point of view. A simple macroscopic non-equilibrium thermodynamic model with a single internal variable reproduces instantaneous jump and relaxation. Velocity weakening appears as a consequence of a plasticity related nonlinear coefficient. Permanent part of displacement corresponds to plastic strain, and relaxation effects are analogous to creep in thermodynamic rheology.

  13. Fault rheology beyond frictional melting. (United States)

    Lavallée, Yan; Hirose, Takehiro; Kendrick, Jackie E; Hess, Kai-Uwe; Dingwell, Donald B


    During earthquakes, comminution and frictional heating both contribute to the dissipation of stored energy. With sufficient dissipative heating, melting processes can ensue, yielding the production of frictional melts or "pseudotachylytes." It is commonly assumed that the Newtonian viscosities of such melts control subsequent fault slip resistance. Rock melts, however, are viscoelastic bodies, and, at high strain rates, they exhibit evidence of a glass transition. Here, we present the results of high-velocity friction experiments on a well-characterized melt that demonstrate how slip in melt-bearing faults can be governed by brittle fragmentation phenomena encountered at the glass transition. Slip analysis using models that incorporate viscoelastic responses indicates that even in the presence of melt, slip persists in the solid state until sufficient heat is generated to reduce the viscosity and allow remobilization in the liquid state. Where a rock is present next to the melt, we note that wear of the crystalline wall rock by liquid fragmentation and agglutination also contributes to the brittle component of these experimentally generated pseudotachylytes. We conclude that in the case of pseudotachylyte generation during an earthquake, slip even beyond the onset of frictional melting is not controlled merely by viscosity but rather by an interplay of viscoelastic forces around the glass transition, which involves a response in the brittle/solid regime of these rock melts. We warn of the inadequacy of simple Newtonian viscous analyses and call for the application of more realistic rheological interpretation of pseudotachylyte-bearing fault systems in the evaluation and prediction of their slip dynamics.

  14. Bond-orientational analysis of hard-disk and hard-sphere structures. (United States)

    Senthil Kumar, V; Kumaran, V


    We report the bond-orientational analysis results for the thermodynamic, random, and homogeneously sheared inelastic structures of hard-disks and hard-spheres. The thermodynamic structures show a sharp rise in the order across the freezing transition. The random structures show the absence of crystallization. The homogeneously sheared structures get ordered at a packing fraction higher than the thermodynamic freezing packing fraction, due to the suppression of crystal nucleation. On shear ordering, strings of close-packed hard-disks in two dimensions and close-packed layers of hard-spheres in three dimensions, oriented along the velocity direction, slide past each other. Such a flow creates a considerable amount of fourfold order in two dimensions and body-centered-tetragonal (bct) structure in three dimensions. These transitions are the flow analogs of the martensitic transformations occurring in metals due to the stresses induced by a rapid quench. In hard-disk structures, using the bond-orientational analysis we show the presence of fourfold order. In sheared inelastic hard-sphere structures, even though the global bond-orientational analysis shows that the system is highly ordered, a third-order rotational invariant analysis shows that only about 40% of the spheres have face-centered-cubic (fcc) order, even in the dense and near-elastic limits, clearly indicating the coexistence of multiple crystalline orders. When layers of close-packed spheres slide past each other, in addition to the bct structure, the hexagonal-close-packed (hcp) structure is formed due to the random stacking faults. Using the Honeycutt-Andersen pair analysis and an analysis based on the 14-faceted polyhedra having six quadrilateral and eight hexagonal faces, we show the presence of bct and hcp signatures in shear ordered inelastic hard-spheres. Thus, our analysis shows that the dense sheared inelastic hard-spheres have a mixture of fcc, bct, and hcp structures.

  15. Friction characteristics of floppy disks

    Institute of Scientific and Technical Information of China (English)


    This note presents the principle and structure of a tribological measure for floppy disks.The precision of the force measuring system is 1 mN in loading and 3×10-6 N in friction.The resolution of the film thickness between head and floppy disk is 0.5 nm in the vertical and 1.5 nm in the horizontal direction.In order to investigate the tribological characteristics of floppy disks,six types of floppy disks have been tested and the floating properties of these disks are also studied with film measuring system.The experimental results of the surface morphology and friction coefficient of these floppy disks using the atomic force microscope/friction force mcroscope (AFM/FFM) are in accordance with the conclusion made by our own measuring system.The experimental results show that the air film thickness between head and disk is of the same order as the surface roughness of floppy disks.

  16. Hardness and excitation energy

    Indian Academy of Sciences (India)

    Á Nagy


    The concept of the ensemble Kohn-Sham hardness is introduced. It is shown that the first excitation energy can be given by the Kohn-Sham hardness (i.e. the energy difference of the ground-state lowest unoccupied and highest occupied levels) plus an extra term coming from the partial derivative of the ensemble exchange-correlation energy with respect to the weighting factor in the limit → 0. It is proposed that the first excitation energy can be used as a reactivity index instead of the hardness.

  17. Comparative Evaluation of Frictional Properties, Load Deflection Rate and Surface Characteristics of Different Coloured TMA Archwires - An Invitro Study. (United States)

    Aloysius, Arul Pradeep; Vijayalakshmi, Devaki; Deepika; Soundararajan, Nagachandran Kandasamy; Manohar, Vijaykumar Neelam; Khan, Nayeemullah


    During tooth movement the success of sliding mechanics is dependent upon various factors which include frictional resistance at bracket-archwire interface, surface roughness of archwire materials and elastic properties of archwires. Ion implantation techniques reduce the frictional force and allow better tooth movement clinically. The main objective of this study was to evaluate and compare the frictional properties, load deflection rate and surface characteristics of Honey dew and Purple coloured (Ion implanted) TMA wires with uncoated TMA wires. Fifteen archwire samples were divided into three groups comprising of five samples in each group namely, Group I - Uncoated TMA wires (Control), Group II - Purple coloured TMA wires and Group III- Honey dew TMA wires. Friction and load deflection rate testing were performed with the Instron Universal testing machine and the surface characteristics of the wires were evaluated before and after sliding using Scanning Electron Microscope. The mean frictional characteristics and surface roughness for Honey dew TMA wires was lesser than Purple coloured TMA wires which was statistically significant. Both the coloured TMA wires showed low frictional characteristics and less surface roughness than uncoated TMA wires (the control). The mean load deflection rate was low for both coloured ion implanted TMA wires when compared to uncoated TMA wires which was statistically significant. Coloured ion implanted TMA wires, especially Honey dew TMA wires have low friction, low load deflection rate and improved surface finish. Hence they can be used in frictionless as well as sliding mechanics, where uncoated TMA wires are inefficient.

  18. The study on the properties of AISI 4140 and AISI 1040 steel rods welded by friction welding

    Directory of Open Access Journals (Sweden)

    Thanee Toomprasen


    Full Text Available This paper is aimed to investigate the properties of joint between AISI 4140 and AISI 1040 welded by friction welding. The specimens were prepared in round shape of 13 mm diameter and 100 mm long. They were welded by friction welding method under the following conditions; friction pressure of 183 MPa, friction time of 12 sec, upset pressure of 428 MPa, upset time of 7 sec. and rotational speed of 1400 rpm. The strength and hardness were tested on the welded area. The result showed finer grains. in the welded area. This is the result of friction pressure and upset pressure in the welding process. In addition, the observation result indicated some changes of Ferrite and Pearlite in welded zone. This phase change resulted in the increment of hardness in AISI 4140 at the contact area and adjacent. In part of AISI 1040, the portion of Pearlite and Ferrite are not significantly changed, therefore the value of hardness is almost constant.

  19. The study of nanoscratch and nanomachining on hard multilayer thin films using atomic force microscope. (United States)

    Huang, Jen-Ching; Li, Chia-Lin; Lee, Jyh-Wei


    In this study, nanoscratching and nanomachining were conducted using an atomic force microscope (AFM) equipped with a doped diamond-coated probe (DDESP-10; VEECO) to evaluate the fabrication of nanopatterns on hard, Cr₂N/Cu multilayer thin films. The influence of normal force, scratch speed, and repeated scratches on the properties of hard multilayer thin films was also investigated. The nanoscratch experiments led researchers to establish a probe preparation and selection criteria (PPS criteria) to enhance the stability and accuracy of machining hard materials. Experimental results indicate that the depth of grooves produced by nanoscratching increased with an increase in normal force, while an increase in the number of scratches in a single location increased the groove depth but decreased friction. Therelationships among normal force and groove depth more closely resembled a logarithmic form than other mathematical models, as did the relationship between repeated scratching and its effect on groove depth and friction. The influence of scratch speed on friction was divided into two ranges. Between 0.1 and 2 µm/s, friction decreased logarithmically with an increase in scratch speed; however, when the speed exceeded 2 µm/s, the friction appeared stable. In this study, multilayered coatings were successfully machined, demonstrating considerable promise for the fabrication of nanopatterns in multilayered coatings at the nanoscale.

  20. Elastic properties of terbium

    DEFF Research Database (Denmark)

    Spichkin, Y.I.; Bohr, Jakob; Tishin, A.M.


    The temperature dependence of the Young modulus along the crystallographic axes b and c (E(b) and E(c)), and the internal friction of a terbium single crystal have been measured. At 4.2 K, E(b) and E(c) are equal to 38 and 84.5 GPa, respectively. The lattice part of the Young modulus and the Debye...

  1. Hard probes 2006 Asilomar

    CERN Multimedia


    "The second international conference on hard and electromagnetic probes of high-energy nuclear collisions was held June 9 to 16, 2006 at the Asilomar Conference grounds in Pacific Grove, California" (photo and 1/2 page)

  2. Elastic characteristics and microplastic deformation of amorphous alloys on iron base

    Energy Technology Data Exchange (ETDEWEB)

    Pol' dyaeva, G.P.; Zakharov, E.K.; Ovcharov, V.P.; Tret' yakov, B.N. (Tsentral' nyj Nauchno-Issledovatel' skij Inst. Chernoj Metallurgii, Moscow (USSR))


    Investigation results of elasticity and microplasticity properties (modulus of normal elasticity E, elasticity limit sigmasub(0.01) and yield limit sigmasub(0.2)) of three amorphous alloys on iron base Fe/sub 80/B/sub 20/, Fe/sub 70/Cr/sub 10/B/sub 20/ and Fe/sub 70/Cr/sub 5/Ni/sub 5/B/sub 20/ are given. Amorphous band of the alloys is obtained using the method of melt hardening. It is shown that amorphous alloys on iron base possess high elasticity and yield limits and hardness and are very perspective for the use as spring materials.

  3. Hard and Soft


    Claes H. de Vreese; Boomgaarden, Hajo G.; Semetko, Holli A.


    Abstract Support for European integration is a function no longer only of `hard' economic and utilitarian predictors but also of `soft' predictors such as feelings of identity and attitudes towards immigrants. Focusing on the issue of the potential membership of Turkey in the European Union (EU), this study demonstrates that the importance of `soft' predictors outweighs the role of `hard' predictors in understanding public opinion about Turkish membership. The study draws on survey...

  4. Microstructure and Functional Mechanism of Friction Layer in Ni3Al Matrix Composites with Graphene Nanoplatelets (United States)

    Xue, Bing; Zhu, Qingshuai; Shi, Xiaoliang; Zhai, Wenzheng; Yang, Kang; Huang, Yuchun


    Microstructure and functional mechanism of friction layer need to be further researched. In the present work, the friction coefficients and wear rates are analyzed through response surface methodology to obtain an empirical model for the best response. Fitting results show that the tribological performance of Ni3Al matrix composites (NMCs) with graphene nanoplatelets (GNPs) is better than that of NMCs without GNPs, especially at high sliding velocities and high loads. Further research suggests that the formation of integrated friction layer, which consists of a soft microfilm on a hard coating, is the major reason to cause the differences. Of which, the wear debris layer (WDL) with a low shear strength can reduce the shear force. The ultrafine layer (UL), which is much harder and finer, can effectively avoid fracture and improve the load support capacity. Moreover, the GNPs in WDL and UL can be easily sheared and help to withstand the loads, trending to be parallel to the direction of shear force.

  5. Dry sliding friction and wear characteristics of Fe-C-Cu alloy containing molybdenum di sulphide

    Energy Technology Data Exchange (ETDEWEB)

    Dhanasekaran, S. [Department of Mechanical Engineering, Indian Institute of Technology Madras, Chennai 600 036 (India); Gnanamoorthy, R. [Department of Mechanical Engineering, Indian Institute of Technology Madras, Chennai 600 036 (India)]. E-mail:


    Sintered steels find increasing application as bearings and gears due to economical and technical reasons. Materials used for making these machine elements need to have high strength, good wear resistance and low coefficient of friction. An attempt is made to develop molybdenum di sulphide added iron-copper-carbon sintered steels using simple single stage compaction and sintering elemental powders. Friction and wear characteristics of the developed materials were evaluated using cylindrical specimens in a pin-on-disc sliding apparatus. Addition of molybdenum di sulphide increases the compressibility and increases the part density. Strength and hardness of the molybdenum di sulphide added compositions are better than the base composition. Addition of the 3% molybdenum di sulphide is found to be beneficial in improving friction and wear characteristics. Higher amount of brittle phases in the 5% molybdenum di sulphide added sample contributes to the reduction in the wear resistance.

  6. Parameter design and analysis in continuous drive friction welding of Al6061/SiCp composites

    Energy Technology Data Exchange (ETDEWEB)

    Adalrasan, R. [Saveetha Engineering College, Chennai (India); Sundaram, A. Shanmuga [Sree Sastha Institute of Engineering and Technology, Chennai (India)


    Continuous drive friction welding (FW) had found profound industrial applications as an economical solid state joining process. The welding parameters such as frictional pressure, upset pressure, burn off length and rotational speed were found to influence the quality of joints. In the present study, Al6061/SiC{sub p} rods were joined by friction welding. The welding trials were designed by using Taguchi's L{sub 9} orthogonal array. Tensile strength and micro hardness of the joints were observed as the quality characteristics after each trial. The urge for parameter design had prompted the disclosure of a new integrated methodology based on technique for order of preference by similarity to ideal solution (TOPSIS) and grey relational analysis (GRA). The effectiveness of the proposed approach of T-GRA was validated by conducting a confirmation test and the field emission scanning electron microscope (FESEM) images of the fractured surface were also examined.

  7. Sliding wear and friction behavior of ZA-27 alloy reinforced by Mn-containing intermetallic compounds

    Institute of Scientific and Technical Information of China (English)

    龙雁; 李元元; 张大童; 邱诚; 陈维平


    A ZA-27 alloy reinforced with M n-containing intermeta llic compounds was prepared and its tribological behaviors were investigated. By adding Mn, RE, Ti and B into ZA-27 alloy, the test alloy (ZMJ) was fabricated by sand casting. Microstructural analysis shows that considerable amount of Mn-containing intermetallic compounds such as Al5MnZn, Al9(MnZn)2 and Al65 Mn(RE)6Ti4Zn36 are formed. Compared to ZA-27, ZMJ shows better wear resistance, lower friction coefficient and lower temperature rise of worn surface under lubricated sliding condition. ZMJ also shows the lowest steady friction coefficient under dry friction condition. The wear resistance improvement of ZMJ is mainly attributed to the high hardness and good dispersion of these Mn-containing intermetallic compounds. It is indicated that the intermetallic compounds play a dominant role in reducing the sever adhesive and abrasive wear of the ZA-27 alloy.

  8. Elastic anisotropy of crystals

    Directory of Open Access Journals (Sweden)

    Christopher M. Kube


    Full Text Available An anisotropy index seeks to quantify how directionally dependent the properties of a system are. In this article, the focus is on quantifying the elastic anisotropy of crystalline materials. Previous elastic anisotropy indices are reviewed and their shortcomings discussed. A new scalar log-Euclidean anisotropy measure AL is proposed, which overcomes these deficiencies. It is based on a distance measure in a log-Euclidean space applied to fourth-rank elastic tensors. AL is an absolute measure of anisotropy where the limiting case of perfect isotropy yields zero. It is a universal measure of anisotropy applicable to all crystalline materials. Specific examples of strong anisotropy are highlighted. A supplementary material provides an anisotropy table giving the values of AL for 2,176 crystallite compounds.

  9. Elastic constants of calcite (United States)

    Peselnick, L.; Robie, R.A.


    The recent measurements of the elastic constants of calcite by Reddy and Subrahmanyam (1960) disagree with the values obtained independently by Voigt (1910) and Bhimasenachar (1945). The present authors, using an ultrasonic pulse technique at 3 Mc and 25??C, determined the elastic constants of calcite using the exact equations governing the wave velocities in the single crystal. The results are C11=13.7, C33=8.11, C44=3.50, C12=4.82, C13=5.68, and C14=-2.00, in units of 1011 dyncm2. Independent checks of several of the elastic constants were made employing other directions and polarizations of the wave velocities. With the exception of C13, these values substantially agree with the data of Voigt and Bhimasenachar. ?? 1962 The American Institute of Physics.

  10. Elastic scattering of hadrons

    CERN Document Server

    Dremin, I M


    When colliding, the high energy hadrons can either produce new particles or scatter elastically without change of their quantum num- bers and other particles produced. Namely elastic scattering of hadrons is considered in this review paper. Even though the inelastic processes dominate at high energies, the elastic scattering constitutes the notice- able part of the total cross section ranging between 18 and 25% with some increase at higher energies. The scattering proceeds mostly at small angles and reveals peculiar dependences at larger angles disclos- ing the geometrical structure of the colliding particles and di?erent dynamical mechanisms. The fast decreasing Gaussian peak at small angles is followed by the exponential (Orear) regime with some shoul- ders and dips and then by the power-like decrease. Results of various theoretical approaches are compared with exper- imental data. Phenomenological models pretending to describe this process are reviewed. The unitarity condition requires the exponen- tial re...

  11. An elastic second skin (United States)

    Yu, Betty; Kang, Soo-Young; Akthakul, Ariya; Ramadurai, Nithin; Pilkenton, Morgan; Patel, Alpesh; Nashat, Amir; Anderson, Daniel G.; Sakamoto, Fernanda H.; Gilchrest, Barbara A.; Anderson, R. Rox; Langer, Robert


    We report the synthesis and application of an elastic, wearable crosslinked polymer layer (XPL) that mimics the properties of normal, youthful skin. XPL is made of a tunable polysiloxane-based material that can be engineered with specific elasticity, contractility, adhesion, tensile strength and occlusivity. XPL can be topically applied, rapidly curing at the skin interface without the need for heat- or light-mediated activation. In a pilot human study, we examined the performance of a prototype XPL that has a tensile modulus matching normal skin responses at low strain (<40%), and that withstands elongations exceeding 250%, elastically recoiling with minimal strain-energy loss on repeated deformation. The application of XPL to the herniated lower eyelid fat pads of 12 subjects resulted in an average 2-grade decrease in herniation appearance in a 5-point severity scale. The XPL platform may offer advanced solutions to compromised skin barrier function, pharmaceutical delivery and wound dressings.

  12. Friction and morphology of magnetic tapes in sliding contact with nickel-zinc ferrite (United States)

    Miyoshi, K.; Buckley, D. H.; Bhushan, B.


    Friction and morphological studies were conducted with magnetic tapes containing a Ni-Zn ferrite hemispherical pin in laboratory air at a relative humidity of 40 percent and at 23 C. The results indicate that the binder plays a significant role in the friction properties, morphology, and microstructure of the tape. Comparisons were made with four binders: nitrocellulose; poly (vinyledene) chloride; cellulose acetate; and hydroxyl-terminated, low molecular weight polyester added to the base polymer, polyester-polyurethane. The coefficient of friction was lowest for the tape with the nitrocellulose binder and increased in the order hydroxylterminated, low molecular weight polyester resin; poly (vinyledene) chloride; and cellulose acetate. The degree of enclosure of the oxide particles by the binder was highest for hydroxyl-terminated, low molecular weight polyester and decreased in the order cellulose acetate, poly (vinyledene) chloride, and nitrocellulose. The nature of deformation of the tape was a factor in controlling friction. The coefficient of friction under elastic contact conditions was considerably lower than under conditions that produced plastic contacts.


    Directory of Open Access Journals (Sweden)

    Mikhail Popov


    Full Text Available Sliding friction can be reduced substantially by applying ultrasonic vibration in the sliding plane or in the normal direction. This effect is well known and used in many applications ranging from press forming to ultrasonic actuators. One of the characteristics of the phenomenon is that, at a given frequency and amplitude of oscillation, the observed friction reduction diminishes with increasing sliding velocity. Beyond a certain critical sliding velocity, there is no longer any difference between the coefficients of friction with or without vibration. This critical velocity depends on material and kinematic parameters and is a key characteristic that must be accounted for by any theory of influence of vibration on friction. Recently, the critical sliding velocity has been interpreted as the transition point from periodic stick-slip to pure sliding and was calculated for purely elastic contacts under uniform sliding with periodic normal loading. Here we perform a similar analysis of the critical velocity in viscoelastic contacts using a Kelvin material to describe viscoelasticity. A closed-form solution is presented, which contains previously reported results as special cases. This paves the way for more detailed studies of active control of friction in viscoelastic systems, a previously neglected topic with possible applications in elastomer technology and in medicine.

  14. Friction role in deformation behaviors of high-strength TA18 tubes in numerical control bending (United States)

    Fang, Jun; Liang, Chuang; Lu, Shiqiang; Wang, Kelu; Zheng, Deliang


    In order to reveal the friction role in deformation behaviors of high-strength TA18 tubes in numerical control (NC) bending, a three dimensional (3D) elastic-plastic finite element (FE) model of high-strength TA18 tubes for whole process in NC bending was established based on ABAQUS code, and its reliability was validated by the experimental results in literature. Then, the bending deformation behaviors under different friction coefficients between tube and various dies were studied with respect to multiple defects such as wall thinning, wall thickening and cross section deformation. The results show that the wall thinning ratio and cross section deformation ratio increase with the increase of the friction coefficient between mandrel and tube f m or decrease of the friction coefficient between pressure die and tube f p, while the friction coefficient between bending die and tube f b has no obvious effect on these. The wall thickening ratio decreases with the increase of f b, f m or decrease of f p.

  15. Measurement of Thin-film Coating Hardness in the Presence of Contamination and Roughness: Implications for Tribology (United States)

    Demas, Nicholaos G.; Lorenzo-Martin, Cinta; Ajayi, Oyelayo O.; Erck, Robert A.; Shareef, Iqbal


    Standard nanoindentation measurements on commercially available TiAlN, CrN, metal-containing diamond-like carbon, and TiN coatings, deposited on steel substrates were performed to determine coating hardness and elastic modulus. It was found that the coating surface roughness/morphology present after deposition can significantly affect the measurements of nanomechanical properties so that measurements of these properties on the as-deposited coating surface may be significantly different from the bulk. In addition, a surface measurement may produce a lower nanohardness due to the existence of a soft surface contamination layer. A simple method was developed to enable accurate measurement of the nanomechanical properties of coatings, while avoiding errors introduced by surface topography and the presence of superficial contamination layers on thin films. Friction and wear behavior, as well as the wear mechanisms in dry reciprocating sliding contact of the various coatings with a steel ball can be correlated to the surface attributes of each coating in terms of roughness and the presence of contamination layers, both of which are shown to also affect the nanohardness measurements.

  16. Hardness amplification in nondeterministic logspace


    Gupta, Sushmita


    A hard problem is one which cannot be easily computed by efficient algorithms. Hardness amplification is a procedure which takes as input a problem of mild hardness and returns a problem of higher hardness. This is closely related to the task of decoding certain error-correcting codes. We show amplification from mild average case hardness to higher average case hardness for nondeterministic logspace and worst-to-average amplification for nondeterministic linspace. Finally we explore possible ...

  17. The friction coefficient evolution of a MoS2/WC multi-layer coating system during sliding wear (United States)

    Chan, T. Y.; Hu, Y.; Gharbi, Mohammad M.; Politis, D. J.; Wang, L.


    This paper discusses the evolution of friction coefficient for the multi-layered Molybdenum Disulphide (MoS2) and WC coated substrate during sliding against Aluminium AA 6082 material. A soft MoS2 coating was prepared over a hard WC coated G3500 cast iron tool substrate and underwent friction test using a pin-on-disc tribometer. The lifetime of the coating was reduced with increasing load while the Aluminium debris accumulated on the WC hard coating surfaces, accelerated the breakdown of the coatings. The lifetime of the coating was represented by the friction coefficient and the sliding distance before MoS2 coating breakdown and was found to be affected by the load applied and the wear mechanism.

  18. The Effect of Tool Press Force to Weldability of AA5754 and AA6061 Alloys with Friction Stir Welding Method

    Directory of Open Access Journals (Sweden)

    Tevfik Küçükömeroğlu


    Full Text Available In this study AA5754 and A6061 alloys have been butt welded to each other by using friction stir welding (FSW. At constant tool geometry and tool angle experiments were carried out, joints were performed using different welding speed, rotation speed and especially tool press force. The mechanical properties of the welded samples were determined by using tensile test, bending test and micro hardness. Generated microstructure and hardness profile was obtained in the welding zone. In this friction stir welding study the parameters which affect the joint structure are the tool press force, welding speed and tool rotation speed which were determined. At the end of study it is determined that AA5754 and AA6061 alloys can be successfully welded by using Friction Stir Welding method under different tool press forces at least 6kN.

  19. Reversible Simulations of Elastic Collisions

    CERN Document Server

    Perumalla, Kalyan S


    Consider a system of N identical hard spherical particles moving in a d-dimensional box and undergoing elastic, possibly multi-particle, collisions. We develop a new algorithm that recovers the pre-collision state from the post-collision state of the system, across a series of consecutive collisions, with essentially no memory overhead. The challenge in achieving reversibility for an n-particle collision (where, n << N) arises from the presence of nd-d-1 degrees of freedom during each collision, and from the complex geometrical constraints placed on the colliding particles. To reverse the collisions in a traditional simulation setting, all of the particular realizations of these degrees of freedom during the forward simulation must be saved. This limitation is addressed here by first performing a pseudo-randomization of angles, ensuring determinism in the reverse path for any values of n and d. To address the more difficult problem of geometrical and dynamic constraints, a new approach is developed whic...

  20. Cracking in soft-hard latex blends: theory and experiments. (United States)

    Singh, Karnail B; Deoghare, Girish; Tirumkudulu, Mahesh S


    Volatile organic compounds (VOCs) in the traditional paint and coating formulations are an important health and environmental concern, and current formulations are increasingly moving toward water-based dispersions. However, even within the water-based systems, small quantities of organic solvents are used to promote particle coalescence. One route to achieving this goal has been to use mixtures of soft and hard particles, also known as latex blends. We investigate the drying of colloidal films containing mixtures of silica and acrylic particles. Since both the particles deform only slightly at room temperature, this work investigates the cracking behavior of films containing elastic particles of two different elastic moduli. We extend an existing model for the stress versus strain relation for identical particles in a colloidal film to that containing a mixture of equal-sized hard and soft elastic spheres while accounting for the nonaffine deformation. A transition from soft to rigidlike behavior is observed beyond a critical hard particle volume fraction ratio that matches with published results obtained from computer simulations. The model predictions are validated with extensive experimental data on the critical stress and critical cracking thickness for various ratios of hard and soft particle volume fraction.

  1. Anisotropic elastic plates

    CERN Document Server

    Hwu, Chyanbin


    As structural elements, anisotropic elastic plates find wide applications in modern technology. The plates here are considered to be subjected to not only in plane load but also transverse load. In other words, both plane and plate bending problems as well as the stretching-bending coupling problems are all explained in this book. In addition to the introduction of the theory of anisotropic elasticity, several important subjects have are discussed in this book such as interfaces, cracks, holes, inclusions, contact problems, piezoelectric materials, thermoelastic problems and boundary element a

  2. Hybrid elastic solids

    KAUST Repository

    Lai, Yun


    Metamaterials can exhibit electromagnetic and elastic characteristics beyond those found in nature. In this work, we present a design of elastic metamaterial that exhibits multiple resonances in its building blocks. Band structure calculations show two negative dispersion bands, of which one supports only compressional waves and thereby blurs the distinction between a fluid and a solid over a finite frequency regime, whereas the other displays super anisotropy-in which compressional waves and shear waves can propagate only along different directions. Such unusual characteristics, well explained by the effective medium theory, have no comparable analogue in conventional solids and may lead to novel applications. © 2011 Macmillan Publishers Limited. All rights reserved.

  3. Mechanics of elastic composites

    CERN Document Server

    Cristescu, Nicolaie Dan; Soós, Eugen


    This is a comprehensive, reader-friendly treatment of the theory behind modern elastic composite materials. The treatment includes recently developed results and methods drawn from research papers published in Eastern Europe that until now were unavailable in many western countries. Among the book''s many notable features is the inclusion of more than 400 problems, many of which are solved at the end of the book. Mechanics of Elastic Composites is an outstanding textbook for graduate-level course work and a valuable reference for engineers and researchers. Developed over many years by leading

  4. ElasticSearch server

    CERN Document Server

    Rogozinski, Marek


    This book is a detailed, practical, hands-on guide packed with real-life scenarios and examples which will show you how to implement an ElasticSearch search engine on your own websites.If you are a web developer or a user who wants to learn more about ElasticSearch, then this is the book for you. You do not need to know anything about ElastiSeach, Java, or Apache Lucene in order to use this book, though basic knowledge about databases and queries is required.

  5. Liner surface improvements for low friction piston ring packs (United States)

    Anderberg, C.; Dimkovski, Z.; Rosén, B.-G.


    The development of engine components in the automotive industry is governed by several constraints such as environmental legislation and customer expectations. About a half of the frictional losses in an internal combustion engine come from the interactions between the piston assembly and cylinder liner surface. The tribological considerations in the contact between the piston ring and cylinder liner have attracted much attention over the past few decades. Many non-conventional cylinder liner finishes have been, and are being, developed with the aim to reduce friction losses and oil consumption, but the effects of the surface finish on piston ring pack performance is not well understood. One way of reducing friction in the cylinder system is to reduce the tangential load from the piston ring pack, focusing on the oil control ring. However, the side-effect of this is a disappointingly increased oil consumption. In this study a number of different cylinder liner surface specifications were developed and implemented in test engines with the aim of maintaining the level for oil consumption when decreasing the tangential load for the piston ring pack. To improve our understanding of the result, the same surfaces were evaluated in elastic and elasto-plastic rough contact and hydrodynamic flow simulation models. It is shown that oil consumption is strongly related to surface texture on the cylinder liners and at lower speeds (900-1200 rpm), a ‘rougher surface’ with a high core (e.g. Sk) and valley roughness (e.g. Svk) results in higher oil consumption. At the medium speed range (1200-3600 rpm), oil consumption continues to dominate for the ‘rough’ surfaces but with a visible influence of a lower oil consumption for a decreased roughness within the ‘rough’ surface group. ‘Smooth’ surfaces with a ‘smooth’ core (Sk), irrespective of the valley component (Svk), show similar oil consumption. For engine speeds above 3600 rpms, an increase in plateau

  6. The effect of hydration on the risk of friction blister formation on the heel of the foot. (United States)

    Kirkham, Suzanne; Lam, Sharon; Nester, Christopher; Hashmi, Farina


    Friction blister research has focused on prevention and treatment approaches rather than exploring the pathophysiology of the friction blister. Increased skin hydration has been purported to be a key risk factor in friction blister development. This study aimed to test the effect of increased skin surface hydration on the risk of friction blister creation. The skin on one foot was hydrated by soaking the foot in water. Intermittent loading was carried out until an observable change of 3°C was evident using infrared thermography. The contra lateral foot acted as a control. Skin hydration and elasticity was measured using electrical capacitance and negative pressure respectively. The rate of temperature change of the hydrated group was significantly greater than that of the non-hydrated foot group (P = 0.001) and showed a strong positive correlation (r = 0.520) with skin surface hydration. Weak negative correlations were seen between skin elasticity and rate of temperature change in response to load application (r = -0.166) and skin surface hydration and elasticity at baseline (r = -0.195). In controlled experimental conditions increased skin surface hydration increases the rate of temperature change of the skin in response to load application and consequently increases the risk of blister creation. © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  7. Friction and Wear in Timing Belt Drives

    Directory of Open Access Journals (Sweden)

    B. Stojanovic


    Full Text Available Timing belt tooth goes into contact with a drive pulley, stretched to the maximum, because of the previous tension. When the contact begins the peak of the belt tooth makes the contact with the outer surface of the pulley teeth. The process of the teeth entering into the contact zone is accompanied with the relative sliding of their side surfaces and appropriate friction force. The normal force value is changing with the parabolic function, which also leads to the changes of the friction force. The biggest value of the normal force and of the friction force is at the tooth root. Hollow between teeth and the tip of the pulley teeth are also in contact. Occasionally, the face surface of the belt and the flange are also in contact. The friction occurs in those tribomechanical systems, also. Values of these friction forces are lower compared with the friction force, which occurs at the teeth root.

  8. Static friction between rigid fractal surfaces. (United States)

    Alonso-Marroquin, Fernando; Huang, Pengyu; Hanaor, Dorian A H; Flores-Johnson, E A; Proust, Gwénaëlle; Gan, Yixiang; Shen, Luming


    Using spheropolygon-based simulations and contact slope analysis, we investigate the effects of surface topography and atomic scale friction on the macroscopically observed friction between rigid blocks with fractal surface structures. From our mathematical derivation, the angle of macroscopic friction is the result of the sum of the angle of atomic friction and the slope angle between the contact surfaces. The latter is obtained from the determination of all possible contact slopes between the two surface profiles through an alternative signature function. Our theory is validated through numerical simulations of spheropolygons with fractal Koch surfaces and is applied to the description of frictional properties of Weierstrass-Mandelbrot surfaces. The agreement between simulations and theory suggests that for interpreting macroscopic frictional behavior, the descriptors of surface morphology should be defined from the signature function rather than from the slopes of the contacting surfaces.

  9. Friction coefficient dependence on electrostatic tribocharging (United States)

    Burgo, Thiago A. L.; Silva, Cristiane A.; Balestrin, Lia B. S.; Galembeck, Fernando


    Friction between dielectric surfaces produces patterns of fixed, stable electric charges that in turn contribute electrostatic components to surface interactions between the contacting solids. The literature presents a wealth of information on the electronic contributions to friction in metals and semiconductors but the effect of triboelectricity on friction coefficients of dielectrics is as yet poorly defined and understood. In this work, friction coefficients were measured on tribocharged polytetrafluoroethylene (PTFE), using three different techniques. As a result, friction coefficients at the macro- and nanoscales increase many-fold when PTFE surfaces are tribocharged, but this effect is eliminated by silanization of glass spheres rolling on PTFE. In conclusion, tribocharging may supersede all other contributions to macro- and nanoscale friction coefficients in PTFE and probably in other insulating polymers.

  10. Friction tensor concept for textured surfaces

    Indian Academy of Sciences (India)

    K R Y Simha; Anirudhan Pottirayil; Pradeep L Menezes; Satish V Kailas


    Directionality of grinding marks influences the coefficient of friction during sliding. Depending on the sliding direction the coefficient of friction varies between maximum and minimum for textured surfaces. For random surfaces without any texture the friction coefficient becomes independent of the sliding direction. This paper proposes the concept of a friction tensor analogous to the heat conduction tensor in anisotropic media. This implies that there exists two principal friction coefficients $\\mu_{1,2}$ analogous to the principal conductivities $k_{1,2}$. For symmetrically textured surfaces the principal directions are orthogonal with atleast one plane of symmetry. However, in the case of polished single crystalline solids in relative sliding motion, crystallographic texture controls the friction tensor.

  11. Shear flow of dense granular materials near smooth walls. II. Block formation and suppression of slip by rolling friction. (United States)

    Shojaaee, Zahra; Brendel, Lothar; Török, János; Wolf, Dietrich E


    The role of rotational degrees of freedom and of microscopic contact properties at smooth walls in two dimensional planar shear has been investigated by contact dynamics simulations of round hard frictional particles. Our default system setup consists of smooth frictional walls, giving rise to slip. We show that there exists a critical microscopic friction coefficient at the walls, above which they are able to shear the granular medium. We observe distinctive features at this critical point, which to our knowledge have not been reported before. Activating rolling friction at smooth walls reduces slip, leading to similar shear behavior as for rough walls (with particles glued on their surface). Our simulations with rough walls are in agreement with previous results, provided the roughness is strong enough. In the limit of small roughness amplitude, however, the distinctive features of shearing with smooth walls are confirmed.

  12. Study of Composite Hardcoat Anodizing of Aluminum Alloy 6063 and Its Friction Behaviors

    Institute of Scientific and Technical Information of China (English)

    LIUShi-yong; ZHANGHui-chen; GAOXue-min; LIUWei; SHIYa-qin


    A composite hard-anodized coating containing micro PTFE (polytetrafluoroethylene) particles on aluminum alloy 6063 was produced by adding micro PTFE particles into the traditional hardcoat anodizing solution. The size of the PTFE particles is around 2μm in diameter and the content of the PTFE particles in the composite coating is within 2%-3% by area percentage. Thickness of the composite coating cart reach up to 70μm after one hour's anodizing. Surface hardness of the composite coating is between 4(RI-480 HV0.1, The average friction coefficient of the composite coating against steel under dry friction tost is 0.11, which is 17% lower than that obtained by traditional hardcoat anodizing.

  13. Improvement the wear behavior of low carbon steels by friction stir processing (United States)

    Sekban, D. M.; Aktarer, S. M.; Yanar, H.; Alsaran, A.; Purcek, G.


    A low carbon structural steel was surface-hardened by friction stir processing (FSP) through 4 mm thickness from the surface. The hardness of the alloy increased from 140 Hv0.1 to about 240 Hv0.1 after single-pass FSP. This improvement came from the substantial microstructural refinement due to both severe plastic deformation and dynamic recrystallization. Both yield and tensile strength of the alloy increased without a considerable decrease in ductility after FSP. Friction and wear behavior of the alloy before and after FSP was investigated by a pin-on-disk type tribometer according to ASTM-G133. The substantial increase in both hardness and yield strength resulted in a considerable improvement in wear resistance of the alloy depending on applied pressure. In this study, metallurgical and mechanical reasons for such improvement in wear behavior and any change in wear mechanisms after FSP were investigated.

  14. Process of friction-stir welding high-strength aluminum alloy and mechanical properties of joint

    Institute of Scientific and Technical Information of China (English)

    王大勇; 冯吉才; 郭德伦; 孙成彬; 栾国红; 郭和平


    The process of friction-stir welding 2A12CZ alloy has been studied. And strength and elongation tests have been performed, which demonstrated that the opportunity existed to manipulate friction-stir welding parameters in order to improve a range of material properties. The results showed that the joint strength and elongation arrived at their parameters changing, joint tensile strength and elongation had similar development. Hardness measurement indicated that the weld was softened. However, there was considerable difference in softening degree for different joint zone. The weld top had lower hardness and wider softening zone than other zone of the weld. And softening zone at advancing side was wider than that at retreating side.

  15. Microstructure of friction stir welded joints of 2017A aluminium alloy sheets. (United States)

    Mroczka, K; Dutkiewicz, J; Pietras, A


    The present study examines a friction stir welded 2017A aluminium alloy. Transmission electron microscope investigations of the weld nugget revealed the average grain size of 5 microm, moderate density of dislocations as well as the presence of nanometric precipitates located mostly in grains interiors. Scanning electron microscope observations of fractures showed the presence of ductile fracture in the region of the weld nugget with brittle precipitates in the lower part. The microhardness analysis performed on the cross-section of the joints showed fairly small changes; however, after the artificial ageing process an increase in hardness was observed. The change of the joint hardness subject to the ageing process indicates partial supersaturation in the material during friction stir welding and higher precipitation hardening of the joint.

  16. Design of Friction Stir Spot Welding Tools by Using a Novel Thermal-Mechanical Approach

    Directory of Open Access Journals (Sweden)

    Zheng-Ming Su


    Full Text Available A simple thermal-mechanical model for friction stir spot welding (FSSW was developed to obtain similar weld performance for different weld tools. Use of the thermal-mechanical model and a combined approach enabled the design of weld tools for various sizes but similar qualities. Three weld tools for weld radii of 4, 5, and 6 mm were made to join 6061-T6 aluminum sheets. Performance evaluations of the three weld tools compared fracture behavior, microstructure, micro-hardness distribution, and welding temperature of welds in lap-shear specimens. For welds made by the three weld tools under identical processing conditions, failure loads were approximately proportional to tool size. Failure modes, microstructures, and micro-hardness distributions were similar. Welding temperatures correlated with frictional heat generation rate densities. Because the three weld tools sufficiently met all design objectives, the proposed approach is considered a simple and feasible guideline for preliminary tool design.

  17. Study of Composite Hardcoat Anodizing of Aluminum Alloy 6063 and Its Friction Behaviors

    Institute of Scientific and Technical Information of China (English)

    LIU Shi-yong; ZHANG Hui-chen; GAO Xue-min; LIU Wei; SHI Ya-qin


    A composite hard-anodized coating containing micro PTFE (polytetrafluoroethylene) particles on aluminum alloy 6063 was produced by adding micro PTFE particles into the traditional hardcoat anodizing solution. The size of the PTFE particles is around 2 μ m in diameter and the content of the PTFE particles in the composite coating is within 2%-3% by area percentage. Thickness of the composite coating can reach up to 70 μ m after one hour's anodizing. Surface hardness of the composite coating is between 400-480 HV0.1. The average friction coefficient of the composite coating against steel under dry friction test is 0.11, which is 17% lower than that obtained by traditional hardcoat anodizing.

  18. Study on deformation and microstructure characterizations of mild steel joints by continuous drive friction welding

    Institute of Scientific and Technical Information of China (English)

    Li Wenya; Yu Min; Li Jinglong; Gao Dalu


    Macro-deformation characteristics of continuous drive friction welded mild steel joints were examined by using one deformable workpiece (objective) and the other undeformable one (rigid). The microstructure evolution and hardness change across the joint were studied. The results show that the axial shortening and radial increment of joints increase with increasing the friction time at 1 200rpm. The cementite particles of pearlites in the weld center are uniformly distributed on the ferrite matrix, while the cementites of the pearlite in the thermal-mechanically affected zone are broken and discontinuously dispersed in the pearlite. The hardness decreases rapidly from the weld center to the parent metal under the coupled effects of heat and deformation during the rapid heating and cooling processes.

  19. Low friction wear resistant graphene films (United States)

    Sumant, Anirudha V.; Berman, Diana; Erdemir, Ali


    A low friction wear surface with a coefficient of friction in the superlubric regime including graphene and nanoparticles on the wear surface is provided, and methods of producing the low friction wear surface are also provided. A long lifetime wear resistant surface including graphene exposed to hydrogen is provided, including methods of increasing the lifetime of graphene containing wear surfaces by providing hydrogen to the wear surface.

  20. Modelling cohesive, frictional and viscoplastic materials (United States)

    Alehossein, Habib; Qin, Zongyi


    Most materials in mining and civil engineering construction are not only viscoplastic, but also cohesive frictional. Fresh concrete, fly ash and mining slurries are all granular-frictional-visco-plastic fluids, although solid concrete is normally considered as a cohesive frictional material. Presented here is both a formulation of the pipe and disc flow rates as a function of pressure and pressure gradient and the CFD application to fresh concrete flow in L-Box tests.

  1. The role of friction in orthodontics


    Mariana Ribeiro Pacheco; Wellington Corrêa Jansen; Dauro Douglas de Oliveira


    INTRODUCTION: Sliding mechanics is widely used during orthodontic treatment. One of the disadvantages of this mechanics is the friction generated at the bracket/archwire interface, which may reduce the amount of desired orthodontic movement obtained. Due to the application and great acceptance of this type of mechanics, the role of friction in Orthodontics has been of interest for both clinicians and scientists. OBJECTIVE: Therefore, this article discussed how friction affects orthodontic too...

  2. Friction and wear behavior of electrodeposited amorphous Fe-Co-W alloy deposits

    Institute of Scientific and Technical Information of China (English)

    何凤姣; 雷惊天; 陆欣; 黄宇宁


    The microstructures, friction and wear behavior under dry sliding condition of electrodeposited amorphous Fe-Co-W alloy deposits heat treated at different temperatures were studied. A comparative study of hard chrome deposit under the same testing condition was also made. The experimental results show that the hardness and wear resistance of amorphous Fe-Co-W alloy deposits are improved with the increasing of heat treatment temperature, and reach the maximum value at 800 ℃, then decrease above 800 ℃. Under 40 N load, the wear resistance properties of the alloy deposits heat treated at 800 ℃ are superior to those of hard chrome deposit. The main wear mechanisms of amorphous Fe-Co-W alloy deposits heat treated below 600 ℃ are peeling, plastic and flowing deformation; when the deposits are heat treated above 700 ℃, they are plastic and flowing deformation. While the main wear mechanisms of hard chrome are abrasive wear, fatigue and peeling.

  3. Lateral vibration effects in atomic-scale friction

    Energy Technology Data Exchange (ETDEWEB)

    Roth, R. [Climate and Environment Physics, Physics Institute, University of Bern, Bern (Switzerland); Oeschger Centre for Climate Change Research, University of Bern, Bern (Switzerland); Fajardo, O. Y.; Mazo, J. J. [Departamento de Física de la Materia Condensada and Instituto de Ciencia de Materiales de Aragón, CSIC-Universidad de Zaragoza, 50009 Zaragoza (Spain); Meyer, E. [Department of Physics, University of Basel, Klingelbergstrasse 82, 4056 Basel (Switzerland); Gnecco, E. [Instituto Madrileño de Estudios Avanzados en Nanociencia, IMDEA Nanociencia, 28049 Madrid (Spain)


    The influence of lateral vibrations on the stick-slip motion of a nanotip elastically pulled on a flat crystal surface is studied by atomic force microscopy measurements on a NaCl(001) surface in ultra-high vacuum. The slippage of the nanotip across the crystal lattice is anticipated at increasing driving amplitude, similarly to what is observed in presence of normal vibrations. This lowers the average friction force, as explained by the Prandtl-Tomlinson model with lateral vibrations superimposed at finite temperature. Nevertheless, the peak values of the lateral force, and the total energy losses, are expected to increase with the excitation amplitude, which may limit the practical relevance of this effect.

  4. Subsurface contrast due to friction in heterodyne force microscopy (United States)

    Verbiest, G. J.; Oosterkamp, T. H.; Rost, M. J.


    The nondestructive imaging of subsurface structures on the nanometer scale has been a long-standing desire in both science and industry. A few impressive images were published so far that demonstrate the general feasibility by combining ultrasound with an atomic force microscope. From different excitation schemes, heterodyne force microscopy seems to be the most promising candidate delivering the highest contrast and resolution. However, the physical contrast mechanism is unknown, thereby preventing any quantitative analysis of samples. Here we show that friction at material boundaries within the sample is responsible for the contrast formation. This result is obtained by performing a full quantitative analysis, in which we compare our experimentally observed contrasts with simulations and calculations. Surprisingly, we can rule out all other generally believed responsible mechanisms, like Rayleigh scattering, sample (visco)elasticity, damping of the ultrasonic tip motion, and ultrasound attenuation. Our analytical description paves the way for quantitative subsurface-AFM imaging.

  5. bessel functions for axisymmetric elasticity problems of the elastic ...

    African Journals Online (AJOL)



  6. Acquired disorders of elastic tissue: Part II. decreased elastic tissue. (United States)

    Lewis, Kevan G; Bercovitch, Lionel; Dill, Sara W; Robinson-Bostom, Leslie


    Elastic fibers in the extracellular matrix are integral components of dermal connective tissue. The resilience and elasticity required for normal structure and function of the skin are attributable to the network of elastic tissue. Advances in our understanding of elastic tissue physiology provide a foundation for studying the pathogenesis of elastic tissue disorders. Many acquired disorders are nevertheless poorly understood owing to the paucity of reported cases. Several acquired disorders in which loss of dermal elastic tissue produces prominent clinical and histopathologic features have recently been described, including middermal elastolysis, papular elastorrhexis, and pseudoxanthoma-like papillary dermal elastolysis, which must be differentiated from more well-known disorders such as anetoderma, acquired cutis laxa, and acrokeratoelastoidosis. Learning objective At the conclusion of this learning activity, participants should have an understanding of the similarities and differences between acquired disorders of elastic tissue that are characterized by a loss of elastic tissue.

  7. Determination of the Mechanical Properties of Friction Welded Tube Yoke and Tube Joint

    Directory of Open Access Journals (Sweden)

    Efe Işık


    Full Text Available This paper deals with the friction welding of the tube yoke and the tube of the drive shaft used in light commercial vehicles. Tube yoke made from hot forged microalloyed steel and the tube made from cold drawn steel, with a ratio (thickness/outside diameter ratio of less than 0.1, were successfully welded by friction welding method. Hardness distributions on both sides of the welded joint across the welding interface were determined and the microstructure of the joint was investigated. Furthermore, joint strength was tested under tensile, static torsional, and torsional fatigue loadings. The tested data were analyzed by Weibull distribution. The maximum hardness value along the welded joint was detected as 553 Hv1. The lowest detected tensile strength of the joint was 13% less than the base materials’ tensile strength. The torsional load carrying capacity of the friction welded thin walled tubular joint without any damage was obtained as 4.252,5 Nm in 95% confidence interval. After conducting fully reversed torsional fatigue tests, the fatigue life of friction welded tubular joints was detected as 220.066,3 cycles.

  8. Effects of elastic indenter deformation on spherical instrumented indentation tests: the reduced elastic modulus (United States)

    Aida Rodríguez, Sara; Alcalá, Jorge; Martins Souza, Roberto


    of correction with the ratio E/Ei . The most affected parameter in the indentation curve, as a consequence of the indentation deformation, was the ratio between the residual indentation depth after complete unloading and the maximum indenter displacement, δr/δmax (up to 26%), but this variation did not significantly decrease the capability to estimate hardness and elastic modulus based on the ratio of the residual indentation depth to maximum indentation depth, hr/hmax . In general, the results confirm the convenience of the use of the reduced modulus in the spherical instrumented indentation tests.

  9. Numerical simulation of the seismic behavior of self-centering steel beam-column connections with bottom flange friction devices (United States)

    Guo, Tong; Song, Lianglong; Zhang, Guodong


    A new type of steel moment resisting frame with bottom flange friction devices (BFFDs) has been developed to provide self-centering capacity and energy dissipation, and to reduce permanent deformations under earthquakes. This paper presents a numerical simulation of self-centering beam-column connections with BFFDs, in which the gap opening /closing at the beam-column interfaces is simulated by using pairs of zero-length elements with compression-only material properties, and the energy dissipation due to friction is simulated by using truss elements with specified hysteretic behavior. In particular, the effect of the friction bolt bearing against the slotted plate in the BFFDs was modeled, so that the increase in lateral force and the loss of friction force due to the bolt bearing could be taken into account. Parallel elastic-perfectly plastic gap (ElasticPPGap) materials in the Open System for Earthquake Engineering Simulation (OpenSees) were used with predefined gaps to specify the sequence that each bolt went into the bearing and the corresponding increase in bending stiffness. The MinMax material in OpenSees is used to specify the minimum and maximum values of strains of the ElasticPPGap materials. To consider the loss of friction force due to bolt bearing, a number of parallel hysteretic materials were used, and the failure of these materials in sequence simulated the gradual loss of friction force. Analysis results obtained by using the proposed numerical model are discussed and compared with the test results under cyclic loadings and the seismic loading, respectively.

  10. How to teach friction: Experiments and models (United States)

    Besson, Ugo; Borghi, Lidia; De Ambrosis, Anna; Mascheretti, Paolo


    Students generally have difficulty understanding friction and its associated phenomena. High school and introductory college-level physics courses usually do not give the topic the attention it deserves. We have designed a sequence for teaching about friction between solids based on a didactic reconstruction of the relevant physics, as well as research findings about student conceptions. The sequence begins with demonstrations that illustrate different types of friction. Experiments are subsequently performed to motivate students to obtain quantitative relations in the form of phenomenological laws. To help students understand the mechanisms producing friction, models illustrating the processes taking place on the surface of bodies in contact are proposed.

  11. Noise and vibration in friction systems

    CERN Document Server

    Sergienko, Vladimir P


    The book analyzes the basic problems of oscillation processes and theoretical aspects of noise and vibration in friction systems. It presents generalized information available in literature data and results of the authors in vibroacoustics of friction joints, including car brakes and transmissions. The authors consider the main approaches to abatement of noise and vibration in non-stationary friction processes. Special attention is paid to materials science aspects, in particular to advanced composite materials used to improve the vibroacoustic characteristics of tribopairs The book is intended for researchers and technicians, students and post-graduates specializing in mechanical engineering, maintenance of machines and transport means, production certification, problems of friction and vibroacoustics.

  12. Frictional Effects on Gear Tooth Contact Analysis

    Directory of Open Access Journals (Sweden)

    Zheng Li


    Full Text Available The present paper concentrates on the investigations regarding the situations of frictional shear stress of gear teeth and the relevant frictional effects on bending stresses and transmission error in gear meshing. Sliding friction is one of the major reasons causing gear failure and vibration; the adequate consideration of frictional effects is essential for understanding gear contact behavior accurately. An analysis of tooth frictional effect on gear performance in spur gear is presented using finite element method. Nonlinear finite element model for gear tooth contact with rolling/sliding is then developed. The contact zones for multiple tooth pairs are identified and the associated integration situation is derived. The illustrated bending stress and transmission error results with static and dynamic boundary conditions indicate the significant effects due to the sliding friction between the surfaces of contacted gear teeth, and the friction effect can not be ignored. To understand the particular static and dynamic frictional effects on gear tooth contact analysis, some significant phenomena of gained results will also be discussed. The potentially significant contribution of tooth frictional shear stress is presented, particularly in the case of gear tooth contact analysis with both static and dynamic boundary conditions.

  13. Friction Stir Processing of Cast Superalloys Project (United States)

    National Aeronautics and Space Administration — This SBIR effort examines the feasibility of an innovative fabrication technology incorporating sand casting and friction stir processing (FSP) for producing...

  14. Microstructural Characterization of Friction Stir Welded Aluminum-Steel Joints (United States)

    Patterson, Erin E.; Hovanski, Yuri; Field, David P.


    This work focuses on the microstructural characterization of aluminum to steel friction stir welded joints. Lap weld configuration coupled with scribe technology used for the weld tool have produced joints of adequate quality, despite the significant differences in hardness and melting temperatures of the alloys. Common to friction stir processes, especially those of dissimilar alloys, are microstructural gradients including grain size, crystallographic texture, and precipitation of intermetallic compounds. Because of the significant influence that intermetallic compound formation has on mechanical and ballistic behavior, the characterization of the specific intermetallic phases and the degree to which they are formed in the weld microstructure is critical to predicting weld performance. This study used electron backscatter diffraction, energy dispersive spectroscopy, scanning electron microscopy, and Vickers micro-hardness indentation to explore and characterize the microstructures of lap friction stir welds between an applique 6061-T6 aluminum armor plate alloy and a RHA homogeneous armor plate steel alloy. Macroscopic defects such as micro-cracks were observed in the cross-sectional samples, and binary intermetallic compound layers were found to exist at the aluminum-steel interfaces of the steel particles stirred into the aluminum weld matrix and across the interfaces of the weld joints. Energy dispersive spectroscopy chemical analysis identified the intermetallic layer as monoclinic Al3Fe. Dramatic decreases in grain size in the thermo-mechanically affected zones and weld zones that evidenced grain refinement through plastic deformation and recrystallization. Crystallographic grain orientation and texture were examined using electron backscatter diffraction. Striated regions in the orientations of the aluminum alloy were determined to be the result of the severe deformation induced by the complex weld tool geometry. Many of the textures observed in the weld

  15. Multi-Response Optimization of Friction-Stir-Welded AA1100 Aluminum Alloy Joints (United States)

    Rajakumar, S.; Balasubramanian, V.


    AA1100 aluminum alloy has gathered wide acceptance in the fabrication of light weight structures. Friction stir welding process (FSW) is an emerging solid state joining process in which the material that is being welded does not melt and recast. The process and tool parameters of FSW play a major role in deciding the joint characteristics. In this research, the relationships between the FSW parameters (rotational speed, welding speed, axial force, shoulder diameter, pin diameter, and tool hardness) and the responses (tensile strength, hardness, and corrosion rate) were established. The optimal welding conditions to maximize the tensile strength and minimize the corrosion rate were identified for AA1100 aluminum alloy and reported here.

  16. Friction and Wear Reduction of Eccentric Journal Bearing Made of Sn-Based Babbitt for Ore Cone Crusher

    Directory of Open Access Journals (Sweden)

    Auezhan Amanov


    Full Text Available An anti-friction Babbitt alloy-coated bearing made by a casting process is a journal bearing, which is used in an ore cone crusher eccentric. The main purpose of the Babbitt coated eccentric is to provide a low friction to support and guide a rotating shaft. Despite the fact that the Babbitt-coated eccentric offers a low friction coefficient and can be operated without a continuous supply of lubricant, it suffers from mining environments and short service life. In this study, an ultrasonic nanocrystalline surface modification (UNSM technique was used to further reduce the friction coefficient, to increase the wear resistance, and to extend the service life of the Sn-based Babbitt metal. The friction and wear behavior of the Sn-based Babbitt metal was investigated using a block-on-ring tester under both dry and oil-lubricated conditions. The results of the experiments revealed that the friction and wear behavior of Sn-based Babbitt metal could be improved by the application of the UNSM technique. The friction and wear mechanisms of the specimens were explained and discussed in terms of changes in surface properties—microstructure, surface hardness, surface roughness, etc.


    Institute of Scientific and Technical Information of China (English)

    J. G(o)ken; M. Maikranz-Valentin; K. Steinhoff; T.S. Pavlova; T.V. Ivleva; I.S. Golovin


    The simultaneous influence of thermal and mechanical treatment was applied to produce a geometrically complex shaft from 51CrV4 steel leading to the formation of microstructures which were significantly different from each other. These microstructural differences were accompanied by a local change of mechanical properties in terms of hardness, electrical resistivity and especially internal friction. The Snoek-Koster peak was recognized and analyzed in the structure of this steel.

  18. Effect of Interface Modified by Graphene on the Mechanical and Frictional Properties of Carbon/Graphene/Carbon Composites

    Directory of Open Access Journals (Sweden)

    Wei Yang


    Full Text Available In this work, we developed an interface modified by graphene to simultaneously improve the mechanical and frictional properties of carbon/graphene/carbon (C/G/C composite. Results indicated that the C/G/C composite exhibits remarkably improved interfacial bonding mode, static and dynamic mechanical performance, thermal conductivity, and frictional properties in comparison with those of the C/C composite. The weight contents of carbon fibers, graphene and pyrolytic carbon are 31.6, 0.3 and 68.1 wt %, respectively. The matrix of the C/G/C composite was mainly composed of rough laminar (RL pyrocarbon. The average hardness by nanoindentation of the C/G/C and C/C composite matrices were 0.473 and 0.751 GPa, respectively. The flexural strength (three point bending, interlaminar shear strength (ILSS, interfacial debonding strength (IDS, internal friction and storage modulus of the C/C composite were 106, 10.3, 7.6, 0.038 and 12.7 GPa, respectively. Those properties of the C/G/C composite increased by 76.4%, 44.6%, 168.4% and 22.8%, respectively, and their internal friction decreased by 42.1% in comparison with those of the C/C composite. Owing to the lower hardness of the matrix, improved fiber/matrix interface bonding strength, and self-lubricating properties of graphene, a complete friction film was easily formed on the friction surface of the modified composite. Compared with the C/C composite, the C/G/C composite exhibited stable friction coefficients and lower wear losses at simulating air-plane normal landing (NL and rejected take-off (RTO. The method appears to be a competitive approach to improve the mechanical and frictional properties of C/C composites simultaneously.

  19. Job Heterogeneity and Coordination Frictions

    DEFF Research Database (Denmark)

    Kennes, John; le Maire, Daniel

    the job ladder, how the identification of assortative matching is fundamentally different in directed and undirected search models, how our theory accounts for business cycle facts related to inter-temporal changes in job offer distributions, and how our model could also be used to identify......We develop a new directed search model of a frictional labor market with a continuum of heterogenous workers and firms. We estimate two versions of the model - auction and price posting - using Danish data on wages and productivities. Assuming heterogenous workers with no comparative advantage, we...

  20. Friction of Plastic Rotating Bands (United States)


    for speeds eve ., the rdnge: 10 - 300 cm/s. Overwhelming evidence was presented to support a melt phenomena. Melt depth of: polymer, pins on a glass disk...Polymers," Proc. Roy. Soc., (London),. A291 (1966), p. 186. 24. Rabinowicz , S., et al., "The Effect of Hydrostatic Pressure on the Shear Yield Behavior of...34 Proc. Roy.,Soc., (London), A269. (19620 p. 368. 51. Carignan, F. J., and Rabinowicz , E., "Friction and Wear at ligh Sliding Speeds," ASLE Trans., 24

  1. Fractional trajectories: Decorrelation versus friction (United States)

    Svenkeson, A.; Beig, M. T.; Turalska, M.; West, B. J.; Grigolini, P.


    The fundamental connection between fractional calculus and subordination processes is explored and affords a physical interpretation of a fractional trajectory, that being an average over an ensemble of stochastic trajectories. Heretofore what has been interpreted as intrinsic friction, a form of non-Markovian dissipation that automatically arises from adopting the fractional calculus, is shown to be a manifestation of decorrelations between trajectories. We apply the general theory developed herein to the Lotka-Volterra ecological model, providing new insight into the final equilibrium state. The relaxation time to achieve this state is also considered.

  2. Distribution of tensile property and microstructure in friction stir weld of 6063 aluminum (United States)

    Sato, Yutaka S.; Kokawa, Hiroyuki


    Dominant microstructural factors governing the global tensile properties of a friction-stir-welded joint of 6063 aluminum were examined by estimating distribution of local tensile properties corresponding to local microstructure and hardness. Yield and ultimate tensile strengths of the as-welded weld were significantly lower than those of the base material. Postweld aging and postweld solution heat-treatment and aging (SHTA) restored the strengths of the weld to the levels of the base material. Elongation was found to increase with increasing strength. Hardness tests showed that the as-welded weld was soft around the weld center and that the aged weld and the SHTA weld had relatively homogeneous distributions of high hardness. Hardness profiles of the welds were explained by precipitate distributions and precipitation sequences during the postweld heat treatments. The strengths of the welds were related to each minimum hardness value. In a weld having a heterogeneous hardness profile, the fracture occurred in the region with minimum hardness. When a weld had a homogeneous hardness profile, its fracture site depended on both crystallographic-orientation distribution of the matrix grains and strain tensor of the imposed deformation, i.e., it fractured in the region with a minimum average Taylor factor.

  3. Inelastic Seismic Response of Building with Friction Damper (United States)

    Banerjee, Susanta; Patro, Sanjaya K.


    Dampers are used to control response of structure in recent years. Seismic response is reduced by adding energy dissipation capacity to the building. Dampers are provided to dissipate energy to reduce the damages on buildings. Relative displacement of two floors are opposed by damper elements. Dampers dissipate energy with no or little degradation in strength and stiffness. This work presents the response of structure with energy dissipation device i.e. friction damper built on soft soil when the structure is subjected to a ground motion. Parameters that influence strength and stiffness of structure and energy dissipating device are studied. Response of structure with energy dissipating device is analyzed and it is shown that building with damper shows better performance during earthquake. Building structures are designed using results from elastic analysis, though inelastic behavior well observed during the earthquake. Actual response of the structure can be estimated in the inelastic range by using nonlinear structural analysis programs. Inelastic Damage indices of structural component, overall building are computed by formulating Modified Park and Ang model. Nonlinear analysis program IDARC 2D is used for modeling and analysis. Modeling of friction damper is done using a Wen-Bouc model without stiffness and strength or strength degradation. These devices are modeled with an axial diagonal element. Pseudo force approach is introduced to consider the forces in damper elements, that is, forces in damper elements are subtracted from external load vector. Smooth hysteretic model is used to model response of friction dampers. Nonlinear dynamic analysis is carried out using Newmark-Beta integration method and the pseudo-force method. Damaged state of structure is obtained to observe whether elements are cracked, yielded or failed during analysis. Response parameters such as lateral floor displacement, storey drift, base shear are also computed.

  4. Collisions of Constrained Rigid Body Systems with Friction

    Directory of Open Access Journals (Sweden)

    Haijun Shen


    Full Text Available A new approach is developed for the general collision problem of two rigid body systems with constraints (e.g., articulated systems, such as massy linkages in which the relative tangential velocity at the point of contact and the associated friction force can change direction during the collision. This is beyond the framework of conventional methods, which can give significant and very obvious errors for this problem, and both extends and consolidates recent work. A new parameterization and theory characterize if, when and how the relative tangential velocity changes direction during contact. Elastic and dissipative phenomena and different values for static and kinetic friction coefficients are included. The method is based on the explicitly physical analysis of events at the point of contact. Using this method, Example 1 resolves (and corrects a paradox (in the literature of the collision of a double pendulum with the ground. The method fundamentally subsumes other recent models and the collision of rigid bodies; it yields the same results as conventional methods when they would apply (Example 2. The new method reformulates and extends recent approaches in a completely physical context.

  5. Friction Stir Additive Manufacturing: Route to High Structural Performance (United States)

    Palanivel, S.; Sidhar, H.; Mishra, R. S.


    Aerospace and automotive industries provide the next big opportunities for additive manufacturing. Currently, the additive industry is confronted with four major challenges that have been identified in this article. These challenges need to be addressed for the additive technologies to march into new frontiers and create additional markets. Specific potential success in the transportation sectors is dependent on the ability to manufacture complicated structures with high performance. Most of the techniques used for metal-based additive manufacturing are fusion based because of their ability to fulfill the computer-aided design to component vision. Although these techniques aid in fabrication of complex shapes, achieving high structural performance is a key problem due to the liquid-solid phase transformation. In this article, friction stir additive manufacturing (FSAM) is shown as a potential solid-state process for attaining high-performance lightweight alloys for simpler geometrical applications. To illustrate FSAM as a high-performance route, manufactured builds of Mg-4Y-3Nd and AA5083 are shown as examples. In the Mg-based alloy, an average hardness of 120 HV was achieved in the built structure and was significantly higher than that of the base material (97 HV). Similarly for the Al-based alloy, compared with the base hardness of 88 HV, the average built hardness was 104 HV. A potential application of FSAM is illustrated by taking an example of a simple stiffener assembly.

  6. Non-linear elastic deformations

    CERN Document Server

    Ogden, R W


    Classic in the field covers application of theory of finite elasticity to solution of boundary-value problems, analysis of mechanical properties of solid materials capable of large elastic deformations. Problems. References.

  7. Micro Structural Comparison of Friction Stir Weldment and Shielded Metal Arc Welding in API-X65 Pipe Line

    Directory of Open Access Journals (Sweden)

    Amin Shahinfar


    Full Text Available The study was conducted to investigate the microstructure and microhardness properties of the friction stir welded zones and shielded metal arc welded. Microstructural analysis of the weld was carried out using optical microscopy. Under FSW process base metal microstructure fully changed. Different heat inputs were obtained using a fix travel (welding speed in combination with several spindle speeds. Heat input during welding process had a significant influence on the microstructure and mechanical proprieties in the various weld can be concluded that with decrease in heat input the bainitic structure in the hard zone becomes finer and so hard zone hardness increase.

  8. Friction and wear measurements of 50 keV N implanted stainless steels (United States)

    Ikeyama, Masami; Miyagawa, Soji; Clissold, Ronald A.; Wielunski, Leszek S.; Swain, Michael V.


    Features of friction, wear and hardness of 50 keV nitrogen implanted 13Cr type, C and V rich stainless steel was studied. The implantation was carried out at room temperature (300 K) or about 800 K to the doses of 1 × 10 18 and 5 × 10 17 ions/cm 2. Friction coefficient was measured using steel or silicon nitride balls with the loads of 98 to 980 mN. Friction coefficient depended on upper contact ball materials and loads, and changed from an initial value of 0.1 to final values between 0.2 and 0.8. After implantation, the surface became softer due to amorphization, however, it became relatively harder around the projected range of implanted N. 800 K implantation reduced the amorphization and enhanced diffusion of nitrogen. For the silicon nitride ball, implanted surfaces showed a lower friction coefficient than unimplanted region, particularly for 800 K implantation. When the friction coefficient increased, a considerable amount of adhered debris was observed on stainless steel surfaces.

  9. Hard and superhard nanocomposite coatings

    Energy Technology Data Exchange (ETDEWEB)

    Musil, J. [Univ. of West Bohemia, Plzen (Czech Republic). Dept. of Phys.


    This article reviews the development of hard coatings from a titanium nitride film through superlattice coatings to nanocomposite coatings. Significant attention is devoted to hard and superhard single layer nanocomposite coatings. A strong correlation between the hardness and structure of nanocomposite coatings is discussed in detail. Trends in development of hard nanocomposite coatings are also outlined. (orig.)

  10. Friction Characteristics of Nitrided Layers on AISI 430 Ferritic Stainless Steel Obtained by Various Nitriding Processes

    Directory of Open Access Journals (Sweden)

    Hakan AYDIN


    Full Text Available The influence of plasma, gas and salt-bath nitriding techniques on the friction coefficient of AISI 430 ferritic stainless steel was studied in this paper. Samples were plasma nitrided in 80 % N2 + 20 % H2 atmosphere at 450 °C and 520 °C for 8 h at a pressure of 2 mbar, gas nitrided in NH3 and CO2 atmosphere at 570 °C for 13 h and salt-bath nitrided in a cyanide-cyanate salt-bath at 570 °C for 1.5 h. Characterisation of nitrided layers on the ferritic stainless steel was carried out by means of microstructure, microhardness, surface roughness and friction coefficient measurements. Friction characteristics of the nitrided layers on the 430 steel were investigated using a ball-on-disc friction-wear tester with a WC-Co ball as the counter-body under dry sliding conditions. Analysis of wear tracks was carried out by scanning electron microscopy. Maximum hardness and maximum case depth were achieved on the plasma nitrided sample at 520 ºC for 8 h. The plasma and salt-bath nitriding techniques significantly decreased the average surface roughness of the 430 ferritic stainless steel. The friction test results showed that the salt-bath nitrided layer had better friction-reducing ability than the other nitrided layers under dry sliding conditions. Furthermore, the friction characteristic of the plasma nitrided layer at 520 ºC was better than that of the plasma nitrided layer at 450 °C.DOI:

  11. Mathematical methods in elasticity imaging

    CERN Document Server

    Ammari, Habib; Garnier, Josselin; Wahab, Abdul


    This book is the first to comprehensively explore elasticity imaging and examines recent, important developments in asymptotic imaging, modeling, and analysis of deterministic and stochastic elastic wave propagation phenomena. It derives the best possible functional images for small inclusions and cracks within the context of stability and resolution, and introduces a topological derivative-based imaging framework for detecting elastic inclusions in the time-harmonic regime. For imaging extended elastic inclusions, accurate optimal control methodologies are designed and the effects of uncertai

  12. Comparison of Frictional Heating Models

    Energy Technology Data Exchange (ETDEWEB)

    Davies, Nicholas R [ORNL; Blau, Peter Julian [ORNL


    The purpose of this work was to compare the predicted temperature rises using four well-known models for frictional heating under a few selected conditions in which similar variable inputs are provided to each model. Classic papers by Archard, Kuhlmann-Wilsdorf, Lim and Ashby, and Rabinowicz have been examined, and a spreadsheet (Excel ) was developed to facilitate the calculations. This report may be used in conjunction with that spreadsheet. It explains the background, assumptions, and rationale used for the calculations. Calculated flash temperatures for selected material combinations, under a range of applied loads and sliding speeds, are tabulated. The materials include AISI 52100 bearing steel, CDA 932 bronze, NBD 200 silicon nitride, Ti-6Al-4V alloy, and carbon-graphite material. Due to the assumptions made by the different models, and the direct way in which certain assumed quantities, like heat sink distances or asperity dimensions, enter into the calculations, frictional hearing results may differ significantly; however, they can be similar in certain cases in light of certain assumptions that are shared between the models.

  13. Application of Hard Coatings for Improved Tribological Performance of Blanking and Piercing Tools

    DEFF Research Database (Denmark)

    Podgornik, B.; Zajec, B.; Bay, Niels


    The aim of the present investigation was to examine the possibility of reducing lubrication and replacing expensive tungsten carbide material in blanking/piercing through introduction of hard tool coatings. Results show that hard PVD coatings can be successfully used in blanking/piercing...... critical value under dry friction conditions and leads to tool failure. Therefore, at present oxidation and temperature resistant hard coatings can give improved wear resistance of stamping tools, but elimination of lubricants in blanking and piercing processes is still not feasible....


    Institute of Scientific and Technical Information of China (English)

    Y.P. Ma


    After three-body abrasion, the hardness re-distribution near the worn surface has aclose relationship with the carbon content of martensite steel. It is considered thatthere is a competition between the work-hardening and the temper softening, whichresults from deformation and friction heat of material. When the carbon content ofmartensite steel is below about 0.6%, the subsurface hardness distribution of materialis a softened layer sandwiched between two hardened layers, but above 0.6%C, nosoftened region appears on the hardness re-distribution curve.

  15. Session: Hard Rock Penetration

    Energy Technology Data Exchange (ETDEWEB)

    Tennyson, George P. Jr.; Dunn, James C.; Drumheller, Douglas S.; Glowka, David A.; Lysne, Peter


    This session at the Geothermal Energy Program Review X: Geothermal Energy and the Utility Market consisted of five presentations: ''Hard Rock Penetration - Summary'' by George P. Tennyson, Jr.; ''Overview - Hard Rock Penetration'' by James C. Dunn; ''An Overview of Acoustic Telemetry'' by Douglas S. Drumheller; ''Lost Circulation Technology Development Status'' by David A. Glowka; ''Downhole Memory-Logging Tools'' by Peter Lysne.

  16. Hard-hat day

    CERN Multimedia


    CERN will be organizing a special information day on Friday, 27th June, designed to promote the wearing of hard hats and ensure that they are worn correctly. A new prevention campaign will also be launched.The event will take place in the hall of the Main Building from 11.30 a.m. to 2.00 p.m., when you will be able to come and try on various models of hard hat, including some of the very latest innovative designs, ask questions and pass on any comments and suggestions.

  17. Hardness of metallic crystals

    Indian Academy of Sciences (India)

    Wuhui Li; Fengzhang Ren; Juanhua Su; Zhanhong Ma; Ke Cao; Baohong Tian


    This paper presents a new formula for calculating the hardness of metallic crystals, resulted from the research on the critical grain size with stable dislocations. The formula is = 6 /[(1 – )], where is the hardness, the coefficient, the shear modulus, the Poisson’s ratio, a function of the radius of an atom () and the electron density at the atom interface (). The formula will not only be used to testify the critical grain size with stable dislocations, but also play an important role in the understanding of mechanical properties of nanocrystalline metals.

  18. Hard exclusive QCD processes

    Energy Technology Data Exchange (ETDEWEB)

    Kugler, W.


    Hard exclusive processes in high energy electron proton scattering offer the opportunity to get access to a new generation of parton distributions, the so-called generalized parton distributions (GPDs). This functions provide more detailed informations about the structure of the nucleon than the usual PDFs obtained from DIS. In this work we present a detailed analysis of exclusive processes, especially of hard exclusive meson production. We investigated the influence of exclusive produced mesons on the semi-inclusive production of mesons at fixed target experiments like HERMES. Further we give a detailed analysis of higher order corrections (NLO) for the exclusive production of mesons in a very broad range of kinematics. (orig.)

  19. Approximation by planar elastic curves

    DEFF Research Database (Denmark)

    Brander, David; Gravesen, Jens; Nørbjerg, Toke Bjerge


    We give an algorithm for approximating a given plane curve segment by a planar elastic curve. The method depends on an analytic representation of the space of elastic curve segments, together with a geometric method for obtaining a good initial guess for the approximating curve. A gradient......-driven optimization is then used to find the approximating elastic curve....


    Energy Technology Data Exchange (ETDEWEB)

    Tang, Wei [ORNL; Chen, Gaoqiang [ORNL; Chen, Jian [ORNL; Yu, Xinghua [ORNL; Frederick, David Alan [ORNL; Feng, Zhili [ORNL


    Reduced-activation ferritic/martensitic (RAFM) steels are an important class of structural materials for fusion reactor internals developed in recent years because of their improved irradiation resistance. However, they can suffer from welding induced property degradations. In this paper, a solid phase joining technology friction stir welding (FSW) was adopted to join a RAFM steel Eurofer 97 and different FSW parameters/heat input were chosen to produce welds. FSW response parameters, joint microstructures and microhardness were investigated to reveal relationships among welding heat input, weld structure characterization and mechanical properties. In general, FSW heat input results in high hardness inside the stir zone mostly due to a martensitic transformation. It is possible to produce friction stir welds similar to but not with exactly the same base metal hardness when using low power input because of other hardening mechanisms. Further, post weld heat treatment (PWHT) is a very effective way to reduce FSW stir zone hardness values.

  1. Rolling Friction on a Wheeled Laboratory Cart (United States)

    Mungan, Carl E.


    A simple model is developed that predicts the coefficient of rolling friction for an undriven laboratory cart on a track that is approximately independent of the mass loaded onto the cart and of the angle of inclination of the track. The model includes both deformation of the wheels/track and frictional torque at the axles/bearings. The concept of…

  2. On the Blasius correlation for friction factors

    CERN Document Server

    Trinh, Khanh Tuoc


    The Blasius empirical correlation for turbulent pipe friction factors is derived from first principles and extended to non-Newtonian power law fluids. Two alternative formulations are obtained that both correlate well with the experimental measurements of Dodge, Bogue and Yoo. Key words: Blasius, turbulent friction factor, power law fluids


    surface roughness, crystalline structure , and velocity. The coefficients of friction for manganese phosphate coatings did not differ to any practical...The coefficient of friction was independent of the applied load. Velocity during dynamic testing, surface finish, and crystalline structure influenced

  4. Gimbaled-shoulder friction stir welding tool (United States)

    Carter, Robert W. (Inventor); Lawless, Kirby G. (Inventor)


    A gimbaled-shoulder friction stir welding tool includes a pin and first and second annular shoulders coupled to the pin. At least one of the annular shoulders is coupled to the pin for gimbaled motion with respect thereto as the tool is rotated by a friction stir welding apparatus.

  5. The Gulf Stream: Inertia and friction




    The inertial theory of the Gulf Stream (Charney, 1955) is extended to include vertical friction in the cyclonic shear zone (the western side) of the stream. The vertical friction is assumed to be controlled by local Froude conditions.DOI: 10.1111/j.2153-3490.1977.tb00717.x

  6. Graphite friction coefficient for various conditions

    Institute of Scientific and Technical Information of China (English)


    The friction coefficient the graphite used in the Tsinghua University 10MW High Tem-perature Gas-Cooled Reactor was analyzed for various conditions. The variation of the graphitefriction coefficient was measured for various sliding velocities, sliding distances, normal loads, en-vironments and temperatures. A scanning elector microscope (SEM) was used to analyze the fric-tion surfaces.

  7. Wiping Metal Transfer in Friction Stir Welding (United States)

    Nunes, Arthur C., Jr.; Whitaker, Ann F. (Technical Monitor)


    Much evidence suggests that as the friction stir pin-tool moves along a weld seam the displacement of metal takes place by a wiping action at the surface of a plug of metal that rotates with the tool. The wiping model is explained and some consequences for the friction stir welding process are drawn.

  8. Trial manufacture of rotary friction tester and frictional force measurement of metals

    CERN Document Server

    Abe, T; Kanari, M; Tanzawa, S


    In the plasma confinement type fusion reactor, in-vessel structures such as a blanket module slide at the joints each other when plasma disruption occurs, and then frictional heat is generated there. Therefore, for the selection of material and the use as the design data, it is important to understand the frictional characteristics of metals and ceramic films in the vacuum. In the present study, we have manufactured a prototype of rotary friction tester and examined the performances of the tester. The frictional characteristics of metals in the room air was measured using the friction tester, and the results obtained are as follows. A drifting friction force for a constant time and a friction force during the idling were 98 mN and 225 mN, respectively. These values were sufficiently small as compared to pressing load (9.8 - 57.8 N) used in the friction test. In a friction force measurement of stainless steel, dynamic friction force obeyed Amontons' law which indicated that dynamic friction force is not depend...

  9. Hard Carbon Films Deposited under Various Atmospheres (United States)

    Wei, M.-K.; Chen, S.-C.; Wu, T. C.; Lee, Sanboh


    Using a carbon target ablated with an XeCl-excimer laser under various gas atmospheres at different pressures, hard carbon was deposited on silicon, iron and tungsten carbide substrates. The hardness, friction coefficient, and wear rate of the film against steel are better than pure substrate material, respectively, so that it has potential to be used as a protective coating for micromechanical elements. The influences of gas pressure, gas atmosphere, and power density of laser irradiation on the thermal stability of film were analyzed by means of Raman-spectroscope, time-of-flight method, and optical emission spectrum. It was found that the film deposited under higher pressure has less diamond-like character. The film deposited under rest gas or argon atmosphere was very unstable and looked like a little graphite-like character. The film deposited at high vacuum (10-5 mbar rest gas) was the most stable and looked like the most diamond-like character. The film deposited at higher power density was more diamond-like than that at lower power density.

  10. Elastic platonic shells. (United States)

    Yong, Ee Hou; Nelson, David R; Mahadevan, L


    On microscopic scales, the crystallinity of flexible tethered or cross-linked membranes determines their mechanical response. We show that by controlling the type, number, and distribution of defects on a spherical elastic shell, it is possible to direct the morphology of these structures. Our numerical simulations show that by deflating a crystalline shell with defects, we can create elastic shell analogs of the classical platonic solids. These morphologies arise via a sharp buckling transition from the sphere which is strongly hysteretic in loading or unloading. We construct a minimal Landau theory for the transition using quadratic and cubic invariants of the spherical harmonic modes. Our approach suggests methods to engineer shape into soft spherical shells using a frozen defect topology.

  11. Series elastic actuators (United States)

    Williamson, Matthew M.


    This thesis presents the design, construction, control and evaluation of a novel for controlled actuator. Traditional force controlled actuators are designed from the premise that 'Stiffer is better'. This approach gives a high bandwidth system, prone to problems of contact instability, noise, and low power density. The actuator presented in this thesis is designed from the premise that 'Stiffness isn't everything'. The actuator, which incorporates a series elastic element, trades off achievable bandwidth for gains in stable, low noise force control, and protection against shock loads. This thesis reviews related work in robot force control, presents theoretical descriptions of the control and expected performance from a series elastic actuator, and describes the design of a test actuator constructed to gather performance data. Finally the performance of the system is evaluated by comparing the performance data to theoretical predictions.

  12. Introduction to linear elasticity

    CERN Document Server

    Gould, Phillip L


    Introduction to Linear Elasticity, 3rd Edition, provides an applications-oriented grounding in the tensor-based theory of elasticity for students in mechanical, civil, aeronautical, and biomedical engineering, as well as materials and earth science. The book is distinct from the traditional text aimed at graduate students in solid mechanics by introducing the subject at a level appropriate for advanced undergraduate and beginning graduate students. The author's presentation allows students to apply the basic notions of stress analysis and move on to advanced work in continuum mechanics, plasticity, plate and shell theory, composite materials, viscoelasticity and finite method analysis. This book also:  Emphasizes tensor-based approach while still distilling down to explicit notation Provides introduction to theory of plates, theory of shells, wave propagation, viscoelasticity and plasticity accessible to advanced undergraduate students Appropriate for courses following emerging trend of teaching solid mechan...

  13. Hard nanocomposite Zr-Y-N coatings, correlation between hardness and structure

    Energy Technology Data Exchange (ETDEWEB)

    Musil, J.; Polakova, H. [Univ. of West Bohemia, Plzen (Czech Republic). Dept. of Phys.


    The article reports on structure and mechanical properties of Zr-Y-N nanocomposite films containing two immiscible elements (Zr,Y) as metals. Films were prepared by d.c.-reactive magnetron sputtering of alloyed targets ZrY (80/20 at.%) and ZrY (93/7 at.%) in a mixture of Ar+N{sub 2} using round planar unbalanced magnetrons of diameter 100 mm. It was shown that: (i) there is a strong correlation between the structure of the film and its hardness, H; (ii) the film structure can be controlled with the interlayer inserted between the substrate and the Zr-Y-N film; and (iii) the film hardness depends on the ratio N/(Zr+Y) in the film and the crystallographic orientation of ZrN grains. Superhard nanocomposite films with hardness greater than 40 GPa were prepared. These films are characterized by (i) the X-ray reflection from ZrN(200) grains and no reflection from the second phase containing Y; and (ii) the ratio N/(Zr+Y){approx}1. Also, it was found that the incorporation of nitrogen into the pure ZrY alloy film results in dramatic changes of its mechanical properties. The Zr-Y-N film can be very hard (up to 47 GPa), exhibits the high elastic recovery (W{sub e} up to 83%) and the high resistance to plastic deformation [H{sup 3}/E*{sup 2} up to approx. 0.75, where E*=E/(1-{nu}{sup 2}), E is the Young's modulus and {nu} is the Poisson's ratio]. On the contrary, the ZrY alloy film is soft (H{approx}6 GPa) and exhibits a low elastic recovery (W{sub e}=32%). (orig.)

  14. CSI: Hard Drive (United States)

    Sturgeon, Julie


    Acting on information from students who reported seeing a classmate looking at inappropriate material on a school computer, school officials used forensics software to plunge the depths of the PC's hard drive, searching for evidence of improper activity. Images were found in a deleted Internet Explorer cache as well as deleted file space.…

  15. Hard Probes at ATLAS

    CERN Document Server

    Citron, Z; The ATLAS collaboration


    The ATLAS collaboration has measured several hard probe observables in Pb+Pb and p+Pb collisions at the LHC. These measurements include jets which show modification in the hot dense medium of heavy ion collisions as well as color neutral electro-weak bosons. Together, they elucidate the nature of heavy ion collisions.

  16. Rock-hard coatings

    NARCIS (Netherlands)

    Muller, M.


    Aircraft jet engines have to be able to withstand infernal conditions. Extreme heat and bitter cold tax coatings to the limit. Materials expert Dr Ir. Wim Sloof fits atoms together to develop rock-hard coatings. The latest invention in this field is known as ceramic matrix composites. Sloof has sign

  17. Budgeting in Hard Times. (United States)

    Parrino, Frank M.


    Interviews with school board members and administrators produced a list of suggestions for balancing a budget in hard times. Among these are changing calendars and schedules to reduce heating and cooling costs; sharing personnel; rescheduling some extracurricular activities; and forming cooperative agreements with other districts. (MLF)

  18. Hard and Soft Governance

    DEFF Research Database (Denmark)

    Moos, Lejf


    The governance and leadership at transnational, national and school level seem to be converging into a number of isomorphic forms as we see a tendency towards substituting 'hard' forms of governance, that are legally binding, with 'soft' forms based on persuasion and advice. This article analyses...

  19. Running in Hard Times (United States)

    Berry, John N., III


    Roberta Stevens and Kent Oliver are campaigning hard for the presidency of the American Library Association (ALA). Stevens is outreach projects and partnerships officer at the Library of Congress. Oliver is executive director of the Stark County District Library in Canton, Ohio. They have debated, discussed, and posted web sites, Facebook pages,…

  20. Hard times; Schwere Zeiten

    Energy Technology Data Exchange (ETDEWEB)

    Grunwald, Markus


    The prices of silicon and solar wafers keep dropping. According to market research specialist IMS research, this is the result of weak traditional solar markets and global overcapacities. While many manufacturers are facing hard times, big producers of silicon are continuing to expand.

  1. Elastic plate spallation (United States)

    Oline, L.; Medaglia, J.


    The dynamic finite element method was used to investigate elastic stress waves in a plate. Strain displacement and stress strain relations are discussed along with the stiffness and mass matrix. The results of studying point load, and distributed load over small, intermediate, and large radii are reported. The derivation of finite element matrices, and the derivation of lumped and consistent matrices for one dimensional problems with Laplace transfer solutions are included. The computer program JMMSPALL is also included.


    Directory of Open Access Journals (Sweden)



    Full Text Available OBJECTIVE: Most fixed appliance techniques involve some degree of sliding between brackets and arch wires. A sound knowledge of the various factors affecting the magnitude of friction is of paramount importance to the clinician. The present study was performed to evaluate and compare the frictional resistance and characteristics between self-ligating brackets and pre-adjusted edgewise brackets with different types of ligation. MATERIALS AND METHODS: Tidy's frictional test design was used to simulate retraction of tooth along with artificial saliva to simulate wet conditions in oral cavity. The jig with this assembly was mounted on the Instron machine with the cross head moving upwards at a speed of 5mm/min. The movable bracket was suspended from the load cell of the testing machine, while the jig was mounted on cross head of machine and the load cell readings were recorded on digital display. Following wires are used 0.016 HANT, 0.019X 0.025HANT, 0.019X 0.025 SS, 0.021X 0.025 SS wires are used. The brackets used were 0.022 slot Damon, 0.022 Smart clip and 0.022 slot MBT system. RESULTS: Self ligating brackets were shown to produce lesser friction when compared to the conventional brackets used with modules, and stainless steel ligatures. Damon self-ligating brackets produce a least friction of all the brackets used in the study. Stainless steel ligatures produced the least friction compared to elastomeric. CONCLUSION: Self ligation brackets produce lesser friction than the conventional brackets ligated with elastomeric modules and stainless steel ligature. Damon self-ligating brackets produce a least friction of all the brackets used in the study width of the bracket was also found to be directly proportional to the friction produced 0.0016HANT with elastomeric modules produce more friction due increase in flexibility of wire.

  3. Extension of elastic stiffness formula for leaf type holddown spring assembly

    Energy Technology Data Exchange (ETDEWEB)

    Song, Kee Nam; Kang, Heung Seok; Yoon, Kyung Ho; Kim, Hyung Kyu [Korea Atomic Energy Research Institute, Taejon (Korea)


    Based on the Euler beam theory and the strain energy method, an elastic stiffness formula of the holddown spring assembly consisting of several leaves was previously derived. The formula was known to be useful to estimate the elastic stiffness of the holddown spring assembly only with the geometric data and the material properties of the leaf. Recently, it was reported that the elastic stiffness from the formula deviated much from the test results as the number of leaves was increased. In this study, in order to resolve such an increasing deviation as the increasing number of leaves, the formula has been extended to be able to consider normal forces and friction forces acting on interfaces between the leaves. The elastic stiffness analysis on specimens of leaf type holddown springs has been carried out using the extended formula and the analysis results are compared with the test results. As a result of comparisons, it is found that the extended formula is able to evaluate the elastic stiffness of the holddown spring assembly within an error range of 10%, irrespective of the number of leaves. In addition, it is found that the effect of shear forces and axial forces on the elastic stiffness of the holddown spring assembly is only below 0.2% of the elastic stiffness, and therefore the greatest portion of the elastic stiffness of the holddown spring assembly is attributed to the bending moment. (author). 13 refs., 10 figs., 12 tabs.

  4. A flexible multi-body approach for frictional contact in spur gears (United States)

    Lundvall, O.; Strömberg, N.; Klarbring, A.


    In the present paper, a large rotational approach for dynamic contact problems with friction is proposed. The approach is used for modelling a spur gear pair with shafts and bearings. The model is obtained by superposing small displacement elasticity on rigid-body motions, and postulating tribological laws on the gear flanks. The finite element method is used to model the elastic properties of the gear pair. Shafts and bearings are represented by linear springs. The tribological laws of the contact interface are Signorini's contact law and Coulomb's law of friction. An important feature of the approach is that the difficulties of impacting mass nodes are avoided. The governing equations of the model are numerically treated by use of the augmented Lagrangian approach. In such manner the geometry of the gear flanks are well represented in the numerical simulations. It is possible to study accurately the consequences of different types of profile modifications as well as flank errors. In this work, the dynamic transmission error is studied. For instance, it turns out that the effect from profile modification is less significant for the transmission error when frictional effects are included.

  5. Biomimetic design of elastomer surface pattern for friction control under wet conditions. (United States)

    Huang, Wei; Wang, Xiaolei


    In this paper, an observation on the toe pad of a newt was carried out. It was found that the pad surface is covered with an array of polygonal cells separated by channels, similar to those of a tree frog's pad. With this micro-structure, a newt can move on wet and smooth surfaces without slipping. Inspired by the surface structure of newt toe pads, elastic micro-patterned surfaces were fabricated to understand the function of such micro-structures in friction systems. The tribological performance of the patterned surfaces was evaluated using a tribometer. Different tribological performances between micro-dimple and -pillar patterned surfaces were observed. The area density (r) of the micro-pattern is crucial for controlling the friction of the elastic surface. Distinguished from unpatterned and micro-dimple patterned surfaces, the pillar patterned surface with high area density can remain high friction at high sliding speed. It could be one of the reasons of such polygonal structures on newt's toe pads.

  6. Friction Stir Welding of ODS and RAFM Steels (United States)

    Yu, Zhenzhen; Feng, Zhili; Hoelzer, David; Tan, Lizhen; Sokolov, Mikhail A.


    Advanced structural materials such as oxide dispersion strengthened steels and reduced-activation ferritic/martensitic steels are desired in fusion reactors as primary candidate materials for first wall and blanket structures, due to their excellent radiation and high-temperature creep resistance. However, their poor fusion weldability has been the major technical challenge limiting practical applications. For this reason, solid-state friction stir welding (FSW) has been considered for such applications. In this work, the effect of FSW parameters on joining similar and dissimilar advanced structural steels was investigated. Scanning electron microscopy and electron backscatter diffraction methods were used to reveal the effects of FSW on grain size, micro-texture distribution, and phase stability. Hardness mapping was performed to evaluate mechanical properties. Post weld heat treatment was also performed to tailor the microstructure in the welds in order to match the weld zone mechanical properties to the base material.

  7. Spectroscopic signatures of quantum friction (United States)

    Klatt, Juliane; Bennett, Robert; Buhmann, Stefan Yoshi


    We present a formula for the spectroscopically accessible level shifts and decay rates of an atom moving at an arbitrary angle relative to a surface. Our Markov formulation leads to an intuitive analytic description whereby the shifts and rates are obtained from the coefficients of the Heisenberg equation of motion for the atomic flip operators but with complex Doppler-shifted (velocity-dependent) transition frequencies. Our results conclusively demonstrate that for the limiting case of parallel motion the shifts and rates are quadratic or higher in the atomic velocity. We show that a stronger, linear velocity dependence is exhibited by the rates and shifts for perpendicular motion, thus opening the prospect of experimentally probing the Markovian approach to the phenomenon of quantum friction.

  8. Friction Stir Welding and Processing

    Energy Technology Data Exchange (ETDEWEB)

    Hovanski, Yuri; Carsley, John; Clarke, Kester D.; Krajewski, Paul E.


    With nearly twenty years of international research and collaboration in friction stir welding (FSW) and processing industrial applications have spread into nearly every feasible market. Currently applications exist in aerospace, railway, automotive, personal computers, technology, marine, cutlery, construction, as well as several other markets. Implementation of FSW has demonstrated diverse opportunities ranging from enabling new materials to reducing the production costs of current welding technologies by enabling condensed packaging solutions for traditional fabrication and assembly. TMS has sponsored focused instruction and communication in this technology area for more than fifteen years, with leadership from the Shaping and Forming Committee, which organizes a biannual symposium each odd year at the annual meeting. A focused publication produced from each of these symposia now comprises eight volumes detailing the primary research and development activities in this area over the last two decades. The articles assembled herein focus on both recent developments and technology reviews of several key markets from international experts in this area.

  9. Mapping Instabilities in Polymer Friction (United States)

    Rand, Charles; Crosby, Alfred


    Schallamach waves are instabilities that occur as interfaces between a soft elastomer and rigid surface slide past each other.(1) The presence of Schallamach waves can lead to drastic changes in frictional properties. Although the occurrence of Schallamach waves has been studied for the past several decades, a general map relating fundamental material properties, geometry, and operating conditions (i.e. speed and temperature) has not been established. Using a combinatorial approach, we illustrate the role of modulus, testing velocity and surface energetics of crosslinked poly(dimethyl siloxane) on the generation Schallamach waves. This knowledge will be used with polymer patterning processes to fabricate responsive coatings for applications such as anti-fouling coatings. (1)Schallamach, A.;Wear 1971,17, 301-312.

  10. Dynamical Friction on extended perturbers

    CERN Document Server

    Esquivel, O


    Following a wave-mechanical treatment we calculate the drag force exerted by an infinite homogeneous background of stars on a perturber as this makes its way through the system. We recover Chandrasekhar's classical dynamical friction (DF) law with a modified Coulomb logarithm. We take into account a range of models that encompasses all plausible density distributions for satellite galaxies by considering the DF exerted on a Plummer sphere and a perturber having a Hernquist profile. It is shown that the shape of the perturber affects only the exact form of the Coulomb logarithm. The latter converges on small scales, because encounters of the test and field stars with impact parameters less than the size of the massive perturber become inefficient. We confirm this way earlier results based on the impulse approximation of small angle scatterings.

  11. Shape transitions in soft spheres regulated by elasticity (United States)

    Fogle, Craig; Rowat, Amy; Levine, Alex; Rudnick, Joseph


    Soft core shell structures abound in nature. Examples of these structures, comprised of a thin outer membrane bounding an elastic core, include raisins, gel-filled vesicles, and a variety of membrane-bound organelles in the cell. We study the elasticity-driven morphological transitions of spherical core shell structures when either their surface area is increased or their interior volume is decreased. We demonstrate a transition, which is related to the Euler buckling, from the spherical initial shape to a lower symmetry one. We discuss the dependence of the critical excess surface area (relative to that of a bounding sphere) for buckling, the internal stresses in the core, and the symmetry of the buckled state on the elastic parameters of the system. We compare these predictions to a variety of observed morphological transitions in hard and soft materials, and discuss extensions of this work to growing viscoelastic media.

  12. Modeling frictional melt injection to constrain coseismic physical conditions (United States)

    Sawyer, William J.; Resor, Phillip G.


    Pseudotachylyte, a fault rock formed through coseismic frictional melting, provides an important record of coseismic mechanics. In particular, injection veins formed at a high angle to the fault surface have been used to estimate rupture directivity, velocity, pulse length, stress drop, as well as slip weakening distance and wall rock stiffness. These studies have generally treated injection vein formation as a purely elastic process and have assumed that processes of melt generation, transport, and solidification have little influence on the final vein geometry. Using a pressurized crack model, an analytical approximation of injection vein formation based on dike intrusion, we find that the timescales of quenching and flow propagation may be similar for a subset of injection veins compiled from the Asbestos Mountain Fault, USA, Gole Larghe Fault Zone, Italy, and the Fort Foster Brittle Zone, USA under minimum melt temperature conditions. 34% of the veins are found to be flow limited, with a final geometry that may reflect cooling of the vein before it reaches an elastic equilibrium with the wall rock. Formation of these veins is a dynamic process whose behavior is not fully captured by the analytical approach. To assess the applicability of simplifying assumptions of the pressurized crack we employ a time-dependent finite-element model of injection vein formation that couples elastic deformation of the wall rock with the fluid dynamics and heat transfer of the frictional melt. This finite element model reveals that two basic assumptions of the pressurized crack model, self-similar growth and a uniform pressure gradient, are false. The pressurized crack model thus underestimates flow propagation time by 2-3 orders of magnitude. Flow limiting may therefore occur under a wider range of conditions than previously thought. Flow-limited veins may be recognizable in the field where veins have tapered profiles or smaller aspect ratios than expected. The occurrence and

  13. First-principles study of structural, elastic and thermodynamic properties of AuIn2 (United States)

    Wu, Hai Ying; Chen, Ya Hong; Deng, Chen Rong; Yin, Peng Fei; Cao, Hong


    The structural, elastic and thermodynamic properties of AuIn2 in the CaF2 structure under pressure have been investigated using ab initio plane wave pseudopotential method within the generalized gradient approximation. The calculated structural parameters and equation of state are in excellent agreement with the available experimental and theoretical results. The elastic constants of AuIn2 at ambient condition are calculated, and the bulk modulus obtained from these calculated elastic constants agrees well with the experimental data. The pressure dependence of the elastic constants, bulk modulus, shear modulus and Young’s modulus has also been investigated. The Debye temperature presents a slight increase with pressure. AuIn2 exhibits ductibility and low hardness characteristics, the ductibility increases while the hardness decreases with the increasing of pressure. The pressure effect on the heat capacity and thermal expansion coefficient for AuIn2 is much larger.

  14. Temperature dependent effective friction coefficient estimation in friction stir welding with the bobbin tool

    Directory of Open Access Journals (Sweden)

    Mijajlović Miroslav M.


    Full Text Available The friction coefficient in many friction stir welding researches is generally used as an effective, constant value without concern on the adaptable and changeable nature of the friction during welding sequence. This is understandable because the main problem in analyzing friction in friction stir welding are complex nature of the friction processes, case-dependent and time dependent contact between the bodies, influence of the temperature, sliding velocity, etc. This paper is presenting a complex experimental-numerical-analytical model for estimating the effective friction coefficient on contact of the bobbin tool and welding plates during welding, considering the temperature at the contact as the most influencing parameter on friction. The estimation criterion is the correspondence of the experimental temperature and temperature from the numerical model. The estimation procedure is iterative and parametric - the heat transport parameters and friction coefficient are adapted during the estimation procedure in a realistic manner to achieve relative difference between experimental and model’s temperature lower than 3%. The results show that friction coefficient varies from 0.01 to 0.21 for steel-aluminium alloy contact and temperature range from 406°C to 22°C.

  15. Mechanical and microstructural characterization of single and double pass Aluminum AA6061 friction stir weld joints (United States)

    Othman, N. H.; Shah, L. H.; Ishak, M.


    This study focuses on the effect of single pass (SP), double sided pass (DSP) and normal double pass (NDP) method on friction stir welding of aluminum AA6061. Two pieces of AA6061 alloy with thickness of 6 mm were friction stir welded by using conventional milling machine. The rotational speeds that were used in this study were 800 rpm, 1000 rpm and 1200 rpm, respectively. The welding speed is fixed to 100 mm/min. Microstructure observation of welded area was studied by using optical microscope. Tensile test and Vickers hardness test were used to evaluate the mechanical properties of this specimen. Mechanical property analysis results indicate that at low rotational speeds, defects such as surface lack of fill and tunneling in the welded area can be observed. Vickers hardness of specimens however did not vary much when rotational speed is varied. Welded specimens using single pass method shows higher tensile strength and hardness value compared to both double pass methods up to 180.61 MPa. Moreover, DSP showed better tensile test and hardness test compared to NDP method. The optimum parameters were found to be single pass method with 1200 rpm of rotational speed. Therefore economically sound to only perform SP method to obtain maximum tensile strength for AA6061 FSW with thickness of 6 mm.

  16. High hardness in the biocompatible intermetallic compound β-Ti3Au (United States)

    Svanidze, Eteri; Besara, Tiglet; Ozaydin, M. Fevsi; Tiwary, Chandra Sekhar; Wang, Jiakui K.; Radhakrishnan, Sruthi; Mani, Sendurai; Xin, Yan; Han, Ke; Liang, Hong; Siegrist, Theo; Ajayan, Pulickel M.; Morosan, E.


    The search for new hard materials is often challenging, but strongly motivated by the vast application potential such materials hold. Ti3Au exhibits high hardness values (about four times those of pure Ti and most steel alloys), reduced coefficient of friction and wear rates, and biocompatibility, all of which are optimal traits for orthopedic, dental, and prosthetic applications. In addition, the ability of this compound to adhere to ceramic parts can reduce both the weight and the cost of medical components. The fourfold increase in the hardness of Ti3Au compared to other Ti–Au alloys and compounds can be attributed to the elevated valence electron density, the reduced bond length, and the pseudogap formation. Understanding the origin of hardness in this intermetallic compound provides an avenue toward designing superior biocompatible, hard materials. PMID:27453942

  17. Thermal activation in boundary lubricated friction

    Energy Technology Data Exchange (ETDEWEB)

    Michael, P.C. [Francis Bitter National Magnet Lab. and Dept. of Mechanical Engineering, Massachusetts Inst. of Tech., Cambridge, MA (United States); Rabinowicz, E. [Francis Bitter National Magnet Lab. and Dept. of Mechanical Engineering, Massachusetts Inst. of Tech., Cambridge, MA (United States); Iwasa, Y. [Francis Bitter National Magnet Lab. and Dept. of Mechanical Engineering, Massachusetts Inst. of Tech., Cambridge, MA (United States)


    The friction coefficients for copper pairs lubricated with fatty acids and fluorinated fatty acids have been measured over a wide range of sliding speeds and temperatures. Sliding speeds in the range 10{sup -7}-10{sup -2} m s{sup -1} and temperatures in the range 4.2-300 K were used. The friction coefficients near 300 K are generally low and increase with sliding speed, while the friction coefficients at low temperatures are markedly higher and relatively independent of velocity. Each lubricant`s friction vs. velocity behavior over the temperature range 150-300 K can be described by a friction-velocity master curve derived from a thermal activation model for the lubricant`s shear strength. The activation energies deduced from this friction model are identical to those obtained in the same temperature range for a vibrational mode associated with low temperature mechanical relaxations in similarly structured polymers. These results suggest that thermally activated interfacial shear is responsible for the fatty acids` positive-sloped friction vs. velocity characteristics at low sliding speeds near room temperature. (orig.)

  18. Load-Dependent Friction Hysteresis on Graphene. (United States)

    Ye, Zhijiang; Egberts, Philip; Han, Gang Hee; Johnson, A T Charlie; Carpick, Robert W; Martini, Ashlie


    Nanoscale friction often exhibits hysteresis when load is increased (loading) and then decreased (unloading) and is manifested as larger friction measured during unloading compared to loading for a given load. In this work, the origins of load-dependent friction hysteresis were explored through atomic force microscopy (AFM) experiments of a silicon tip sliding on chemical vapor deposited graphene in air, and molecular dynamics simulations of a model AFM tip on graphene, mimicking both vacuum and humid air environmental conditions. It was found that only simulations with water at the tip-graphene contact reproduced the experimentally observed hysteresis. The mechanisms underlying this friction hysteresis were then investigated in the simulations by varying the graphene-water interaction strength. The size of the water-graphene interface exhibited hysteresis trends consistent with the friction, while measures of other previously proposed mechanisms, such as out-of-plane deformation of the graphene film and irreversible reorganization of the water molecules at the shearing interface, were less correlated to the friction hysteresis. The relationship between the size of the sliding interface and friction observed in the simulations was explained in terms of the varying contact angles in front of and behind the sliding tip, which were larger during loading than unloading.

  19. Assessment of semi-active friction dampers (United States)

    dos Santos, Marcelo Braga; Coelho, Humberto Tronconi; Lepore Neto, Francisco Paulo; Mafhoud, Jarir


    The use of friction dampers has been widely proposed for a variety of mechanical systems for which applying viscoelastic materials, fluid based dampers or other viscous dampers is impossible. An important example is the application of friction dampers in aircraft engines to reduce the blades' vibration amplitudes. In most cases, friction dampers have been studied in a passive manner, but significant improvements can be achieved by controlling the normal force in the contact region. The aim of this paper is to present and study five control strategies for friction dampers based on three different hysteresis cycles by using the Harmonic Balance Method (HBM), a numerical and experimental analysis. The first control strategy uses the friction force as a resistance when the system is deviating from its equilibrium position. The second control strategy maximizes the energy removal in each harmonic oscillation cycle by calculating the optimal normal force based on the last displacement peak. The third control strategy combines the first strategy with the homogenous modulation of the friction force. Finally, the last two strategies attempt to predict the system's movement based on its velocity and acceleration and our knowledge of its physical properties. Numerical and experimental studies are performed with these five strategies, which define the performance metrics. The experimental testing rig is fully identified and its parameters are used for numerical simulations. The obtained results show the satisfactory performance of the friction damper and selected strategy and the suitable agreement between the numerical and experimental results.


    Institute of Scientific and Technical Information of China (English)

    姚振汉; 蒲军平; 金哲植


    A scheme of boundary element method for moving contact of two dimensional elastic bodies using conforming discretization is presented. Both the displacement and the traction boundary conditions are satisfied on the contacting region in the sense of discretization. An algorithm to deal with the moving of the contact boundary on a larger possible contact region is presented. The algorithm is generalized to rolling contact problem as well. Some numerical examples of moving and rolling contact of 2D elastic bodies with or without friction, including the bodies with a hole-type defect, are given to show the effectiveness and the accuracy of the presented schemes.