Friction Plane Research Articles

Self-rotation-eversion of an anisotropic-friction-surface torus

Recent experiments have revealed a new end-to-end ribbon spiral structure capable of demonstrating two interconnected periodic zero-energy-mode self-rotation-eversion in reaction to constant temperature or constant light sources, yet its fabrication is challenging due to its intricate nature. Differently, this paper develops a light-fueled self-rotating and everting liquid crystal elastomer torus on an isotropic frictional plane, by imparting anisotropic frictional properties to the surface of the torus. Based on a mature dynamic liquid crystal elastomer model, we constructed the theoretical model of the torus system. The torus is capable of absorbing the illumination energy to counteract damping dissipation and produce zero-energy-mode self-eversion-rotation. Theoretical findings demonstrate that the angular velocity of self-eversion is influenced by light intensity, light penetration depth, gravitational acceleration and anisotropic friction surface. Moreover, there is a proportional relationship between the self-rotation and self-eversion angular velocities, which is determined by the anisotropic frictional surface. The detailed criterion for the self-rotation direction is also established. Theoretical findings exhibit several similar phenomena to experimental observations. This paper proposes a new simple strategy that utilizes anisotropic friction surface to control self-eversion-rotation, which has guiding significance for the application of soft robots, active devices, and energy harvesters.

Active Brownian particles in a biased periodic potential

We study transport properties of an active Brownian particle with an Rayleigh-Helmholtz friction function in a biased periodic potential. In the absence of noise and depending on the parameters of the friction function and on the bias force, the motion of the particle can be in a locked state or in different running states. According to the type of solutions, the parameter plane of friction and bias force can be divided into four regions. In these different regimes, there is either only a locked state, only a running state, a bistability between locked and running states, or a bistability of two different running states (corresponding to a systematic motion to the left or right, respectively). In the presence of noise, the mean velocity depends in different ways on the noise intensity for the various parameter regimes. These dependences are explored by means of numerical simulations and simple analytical estimates for limiting cases.

Identification of the torsion coefficient of bolts in slip-critical connections

Introduction. The article proposes a method for identifying the coefficient of torsion of a high-strength bolt in the laboratory environment. The coefficient is found by determining the relative deformation of a drawn bolt using load cells. This method requires specialized equipment and a test bench, and it can be used to study the behavior of bolts. The value of the torsion coefficient is necessary to ensure the appropriate bolt tension force, since according to current friction concepts of bolted connections involving high-strength bolts, the design behavior of a bolted connection is ensured by the appropriate bolt tension force, determined using the required torque. Otherwise, the actual behavior of a bolt differs from its design behavior, since only a pre-set tension force ensures the necessary bearing capacity of a bolted connection in the friction planes.
 
 Materials and methods. Specimens of bolts under study are made according to the German standard DIN931 with a strength of 10.9, and the size M14 × 220; their nuts comply with the German standard DIN934 with a strength of 10 and the size M14. Instron 1000HDX tension testing machine was used to make a diagram describing the performance of steel bolts. Nut tension was determined using NOGRAU NTW24-034R torque control key, and bolt elongation was controlled using FLA 5-11 strain gauges and the National Instruments data collection system.
 
 Results. A new method for monitoring the measurement of the torsion coefficient of high-strength bolts was tested and proposed in furtherance of the research conducted by the authors.
 
 Conclusions. As a result of testing, a change in the torsion coefficient can be evaluated depending on the torque value.

Tribological Properties and Wear Mechanism of C/C Composite Applied in Finger Seal

The application of C/C composites in finger seals can effectively solve the problem of seal wear due to its excellent tribological and mechanical behaviors. However, the designable characteristics of composites, such as the density and orientation of fabric on the friction plane, have a very important influence on the tribological properties and service life of sealing materials. In order to obtain a better material design scheme for the C/C composite on the finger seal, it is necessary to conduct research on the tribological properties and wear mechanism of the C/C composite based on the working conditions of the finger seal. Therefore, a reciprocating tribo-tester was used to conduct the test by abrading the C/C composite disk with a pin made of 1045,080M46. The effects of material density, fabric orientation, and load and sliding velocity on the tribological properties and wear mechanism of the C/C composite were studied. The results show that the friction coefficient and wear rate of the composite with a perpendicular orientation (non-woven cloth perpendicular to the friction plane) were lower than those with a parallel orientation (non-woven cloth parallel to the friction plane). The tribological properties with higher density are better than those of material with a lower density. The friction coefficient of low-density material increases with the load, whereas it decreases gradually with high-density material. The wear rate increases with the load for two-density materials. With the increase in the sliding velocity, the friction coefficient decreases. The wear rate of low-density material decreases significantly, whereas it changes little with high-density material. The influence of the sliding velocity on the friction and wear properties of the C/C composite is greater than that of the load. This study provides a feasible material design idea for effectively alleviating the wear of finger seals.

Experimental determination of the tightening coefficient of bolts according to the din standard

The use of slip-critical connections is very common in the design of critical steel structures and is seen as an effective way to transfer the force in conditions of dynamic loading. The limit state of the connection occurs when the calculated shear stress is reached, which depends on the friction coefficient of the contact planes and the value of the clamping force, equal to the bolt tension stress. In order to ensure the necessary bolt tensioning force, it is necessary to know the bolt tightening coefficient, because according to the current understanding of the slip-critical connection performance, the designed functioning of the bolt connection is ensured when the bolt tensioning force arising at the necessary torque value is achieved. Otherwise, the actual work of the connection will be different from the calculated, because only a given tension force provides the estimated bearing capacity of the bolted connection with friction planes. This article focuses on tensile testing of a bolt and determining the tightening factor of a bolt made of high-strength10.9 M14 steel. The tightening factor is determined with strain gauges by measuring the relative strain of the bolt when the nut is tightened. This method requires specialized equipment and a test bench and can be used in the study of bolt performance in the absence of a certificate or the need to verify or clarify the available data. The results show that the proposed method can provide a stable determination of the coefficient value. The examined bolts were made according to the German standard DIN931, strength 10.9 size M14x220, nuts according to the German standard DIN934, strength 10 size M14. An Instron 1000HDX tensile testing machine was used to plot the performance of the bolt steel. Nut tension control was determined with the use of NOGRAU NTW24-034R torque wrench, and bolt elongation control with FLA 5-11 strain gauges and National Instruments data acquisition system. On the basis of the conducted research, a method for determining the tightening factor of high-strength bolts has been tested and proposed. The proposed method of determining the tightening factor of a high-strength bolt can be used in research work and allows to determine the coefficient in the absence of an appropriate certificate or the need to clarify (verify) the stated value of the coefficient.

Explicit Analytic Solutions for the Subsurface Stress Field in Single Plane Contacts of Elastically Similar Truncated Cylinders or Wedges

As has been pointed out recently, a possible solution strategy to the wear–fatigue dilemma in fretting, operating on the level of contact mechanics and profile geometries, can be the introduction of “soft” sharp edges to the contact profiles, for example, by truncating an originally smooth profile. In that regard, analysis of possible mechanical failure of a structure, due to the contact interaction, requires the knowledge of the full subsurface stress state resulting from the contact loading. In the present manuscript, a closed-form exact solution for the subsurface stress state is given for the frictional contact of elastically similar truncated cylinders or wedges, within the framework of the half-plane approximation and a local-global Amontons–Coulomb friction law. Moreover, a fast and robust semi-analytical method, based on the appropriate superposition of solutions for parabolic contact, is proposed for the determination of the subsurface stress fields in frictional plane contacts with more complex profile geometries, and compared with the exact solution. Based on the analytical solution, periodic tangential loading of a truncated cylinder is considered in detail, and important scalar characteristics of the stress state, like the von-Mises equivalent stress, maximum shear stress, and the largest principal stress, are determined. Positive (i.e., tensile) principal stresses only exist in the vicinity of the contact edge, away from the pressure singularity at the edge of the profile, and away from the maxima of the von-Mises equivalent stress, or the maximum shear stress. Therefore, the fretting contact should not be prone to fatigue crack initiation.

Parameter optimization analysis of plane friction coupling effect

When the ground motion is input into a Spring-Viscous damping-Coulomb friction plane isolation system with XY shear keys along a certain inclined angle, XY shear keys will be sheared asynchronously, which will lead to the structural violent curvilinear movement in the plane, resulting in the plane friction coupling effect. In this paper, the influence of the plane friction coupling on the relative displacement response of the structure is studied, and the variation of the structural peak relative displacement with the spring stiffness coefficient, damping constant and friction coefficient is analyzed in detail, so as to find the optimal parameter design of the plane isolation system under the plane friction coupling effect. The results indicate that the plane friction coupling can amplify the peak relative displacement, and the smaller the peak ground acceleration is, the more significant the amplification effect is. Although the mechanism of friction and viscous damping is different, the peak relative displacement will decrease with the increase of friction coefficient or damping constant, and it will decrease rapidly at first and then slowly, so the optimal parameters can be obtained at the cutoff point of the reduction rate. However, with the increase of spring stiffness coefficient, the amplification effect of relative displacement caused by plane friction coupling will be significantly reduced, and the amplification effect will decrease rapidly at first, and then decrease slowly, so there is also a dividing value for spring stiffness coefficient, and this value will not cause resonance phenomenon.

Influence on the seismic isolation performance of friction pendulum system when XY shear keys are sheared asynchronously

When the friction pendulum system and shear keys work together to resist the ground motion, which obliquely inputs (non 45°) to the bridge structure, the shear keys in XY direction will be sheared asynchronously, so that the friction pendulum system will have a violent changing direction curve movement on the sliding surface under the earthquake, and there is a strong plane friction coupling effect during this process. In view of this situation, this paper constructs a Spring-Viscous damping-Coulomb friction plane isolation system with XY shear keys, which realizes the detailed and accurate mechanical analysis under the plane friction coupling effect of friction pendulum system, and adopts self-programming to realize the calculation of the time history response. The results indicate that when XY shear keys are sheared asynchronously, on the one hand, it will change the motion state of system, caused the influence of the plane friction coupling, on the other hand, it will cause a sudden change of the structural acceleration at the moment of the shear key sheared. While the shearing force of XY shear keys is small, the plane friction coupling effect will play a leading role, which will reduce the maximum acceleration of the structure. Meanwhile, the plane friction coupling effect caused by XY sheared asynchronously will increase the maximum relative displacement of the structure, and this amplification effect needs to be more importantly considered in the design of structural seismic isolation when the PGA is small.

Tribological Behaviour of Additively Manufactured Fiber-Reinforced Thermoplastic Composites in Various Environments.

Polymer composites with increased utility properties are becoming competition for conventional materials, in conjunction with additive manufacturing techniques. The aim of this study was to evaluate tribological characteristics of fibrous composites produced in fused deposition modeling (FDM) with the use of an innovative head with symmetrical feeding of the matrix material. Analysis of the influence of composite-forming temperature on their tribological properties allowed the determining of the optimal printing process parameters for this group of composites. Significant differences in the friction process of the same reinforced materials were observed in dry and wet environments. Fibrous composites showed 10 times lower wear intensity as well as two times lower friction value in water than in air. Research shows friction in the water environment ensures more even wear of the surface of the composites involved in the work. The article contains 3D microscopic imaging of the friction plane of the tested composites and a description of a typical course of material wear is described.

Experimental Study Improving The Friction in The Surface of Cold Form Steel Connections Using Adhesive

The purpose of this study is to test the strength of light steel joints using screws and the addition of adhesives to the surface of the joint. The addition of adhesive is done to increase the frictional force on the surface of the joint. The study was carried out experimentally by giving axial tensile strength to the specimens. The specimen is a mild steel connection made from a lip channel profile that is connected back to back with 2 screws and has 2 variables, namely adhesive and without adhesive. Each variable has 3 samples. The experimental results show that the addition of adhesives to the joint system is proven to increase friction. This shows that the joints that use adhesives have a greater strength of 17.20% than the joints without adhesives. The mechanism of collapse of the joint using adhesive starts from the collapse in the friction plane, then the screw undergoes tilting and subsequently experiences a collapse in the fused plane. From the results of this study it was concluded that the use of adhesives can be used as an alternative to increase the frictional force on the surface of the mild steel joints.

Natural endogenous factors of geoecological transformation of the mountain part of North Ossetia

Geoecological transformation of the biocenosis habitat is an evolutionary process, predetermined by the interaction of the lithosphere with the hydrosphere, atmosphere and the solar system as a whole, under the condition of anthropogenic impact absence. Geoecological transformation occurs under the influence of many natural factors of an endogenous and exogenous nature, the effects of which in the mountainous areas are especially intensive and damageable, due to the sharp and intense exposure forms of exogenous factors of the erosive destruction, the presence of a large gravitational potential for a spatial removal of the destroyed material, poor protection of the bedrocks by biogeocenosis, low strength of terrigenous rocks, etc. The main factors of the intensive geoecological transformation of the mountain landscape are endogenous geodynamic processes. The Greater Caucasus, as the geosynclinal region of young Alpine orogenesis, is characterized by the active deep geodynamics, the focal zones of which can be activated in time and migrate in the lithosphere, as evidenced by the interchange of the periods of seismic activity and relative passivity of deep geodynamic processes (fault tectonics, seismicity and magmatic manifestations). A high density of the tectonic faults contributes to the weakening of rock strength in the zone of a faulting crop out due to jointing and claying along the friction planes.

Wave reflection and transmission test with pipe wall roughness and without roughness on the perforated breakwater

Waves towards the shore that have a porous breakwater building will experience reflection and transmission, to determine the height of reflection and transmission wave is needed a study by the process of generating waves on the flume with a porous breakwater building, the effect of wave changes in its propagation requires an experiment in the laboratory. This study was aimed to determine the height ratio of reflection and transmission wave by using a model of pipe structure as a wave reducer by adding the friction plane of the roughness of the walls in the pipe. A method of laboratory experiment on the wave generation flume has several variations consisting of 3 periods (T; 1,0 seconds, T; 1,1 seconds, T; 1.2 seconds) and 3 water depth (d) are 15, 30 and 36 cm, stroke to regulate the flap motion that determines the wave height (H) as a wave generator that is 4, 5 and 6 by comparing the model that uses pipe wall roughness and without roughness. The result of testing indicates that the height of reflection wave (Hr) and transmission (Ht) is strongly influenced by the period (T). If the period increases, Hr and Ht significantly decrease, the height ratio of reflection wave using pipe wall roughness is greater than without roughness. However, it inversely proportional to the height of transmission wave (Ht) were a model using pipe roughness is more efficient to reduce Ht than a model without pipe roughness.

Dynamics and energy provision of cargo transportation systems in food packing lines

The work is related to the search for the possibilities of using internal energy resources in transport and technological systems by the example of food packaging lines packed in glass containers. Trends in switching to high-performance lines have led to the need for their equipment with dual-purpose transport systems. Obviously, the first task is to ensure the movement of artificial products in the respective sections between units of technological machines, and the second component of their task - to fulfill the role of storage devices in combination with the need for restructuring mass flows. This combination of tasks has led to the exclusive use of closed circuit circuits with two friction planes in transport systems. Meanwhile, it is known that energy costs in mechanical systems are associated with the need to achieve the specified levels of kinetic energy of the moving masses in order to overcome the forces of harmful and useful resistance. The peculiarity of such transport systems is the constant presence of transients and dynamic components of loads. The study complements the known dynamic manifestations with new ratios of indicators for the possibility of energy recovery. In the transportation systems for glass production of foodstuffs, the driving factors in most cases are represented by friction forces. Simultaneously, the closure of kinematic pairs between the products and the supporting moving planes is due to gravity forces, which, in cases where their velocities do not coincide, leads to the formation of an additional friction plane with a corresponding increase in energy costs and dynamic components of the loads. The uneven velocity of the closed circuit circuits is accompanied by additional relative displacements at certain ratios of kinematic and geometric parameters. An appropriate set of parameters is achievable by eliminating these additional displacements of the product arrays relative to the reference planes and limiting energy costs. The use of rigid kinematic bonds in parallel systems allows for changes in velocities in counter-phases and provides energy recovery. With stabilized kinematic parameters, compared to single-stream systems, higher loads of drive motors with improved performance are achieved.

Physical and numerical studies of stability of soil blocks reinforced by brittle shear pins

In this paper, the stability and failure mechanism of soil blocks that were reinforced by brittle shear pins and rested on a low-interface friction plane were studied by means of physical and numerical models. The humid silica sand no. 6 was employed to build the physical models of soil blocks, while the Teflon sheet was employed as the low-interface friction plane. To study the effect of stabilizing piles on slopes, the soil blocks were reinforced by brittle shear pins using pencil leads with 2 mm in diameter. Three-dimensional finite element analyses were employed to analyze the stability of this problem. The effects of numbers and patterns of shear pins on the stability and failure mechanisms of physical and numerical models were compared and discussed.

Nonlinear analysis of the friction-induced vibrations of a rotor-stator system

In this paper, the vibratory dynamics of a system consists of a rotor and a stator with friction at the interface is studied. The main goal is to study how taking into account the deviation of the relative velocities associated with each point of the interface (rotor/stator) influences the model. The inclusion of this deviation, not usually modeled for this type of system, allows taking the friction plane into account. However, introducing this mechanism in a model with a friction interface leads to damping that in turn has an impact on the values and the convergence of the amplitudes of vibration. In addition, the deviation has a significant impact only when the rotation frequency of the rotating part is low. Thus this paper also focuses on the separation occurring at the interface. The method used to take this separation into account is presented. The addition of this separation in the model makes it possible to obtain more physically realistic limit cycles in the case of high rotation frequency. These two phenomena are combined in order to obtain physical amplitudes.

Effects of welding parameters on microstructure and mechanical properties of underwater wet friction taper plug welded pipeline steel

Microstructure and mechanical properties of underwater wet friction taper plug-welded API X52 pipeline steel with 6500–7500-rpm rotational speed at 30–45-kN axial force have been investigated, and the defect-free friction taper plug-welded joints were obtained. It was found that the microstructure in welded joint was remarkably inhomogeneous and very different from the X52 base metal. The weld region could be divided into forged zone (FZ), final frictional plane (FFP), shear deformation zone (SDZ), bonding zone (BZ), and heat-affected zone (HAZ). The HAZ has the coarsest grain and mainly consists of martensite and bainite, and the FZ and SDZ are mainly characterized by a mixture of martensite, bainite, and various shapes of ferrites. The BZ is represented by the banding pattern of fine equi-axed grain ferrites because of local decarbonization around frictional interface in wet welding condition. The axial force has a greater impact on microstructure of welded joint as compared with rotational speed. The hardness profiles measured on cross section of welded joints are severely non-uniform, ranging from 200 to 400 HV1, due to the inhomogeneity of microstructures. The impact absorbed energy of bonding interface sites in welds was considerably lower than that of base metal (about 20% of parent metal) because of the local obviously coarse grain, Widmanstatten ferrites, and banding ferrite defects. The principle of “close mode” friction welding is illustrated, and the microstructural characteristics and mechanical properties of welds can be predicted by judging the type of friction welding.

Microstructure in the joining zone during the friction welding of the two dissimilar steels

PurposeThe purpose of this paper is to point out the possibilities for friction welding of dissimilar steels which are used in various industries. In addition, friction welding is a welding method that is applied for executing the very responsible joints. This research is focused on friction and tribological processes in the friction plane of the two pieces during the welding.Design/methodology/approachThe present study research has been conducted based on the experimental testing of cylindrical specimens and results are analyzed.FindingsThe austenite grain size is affected by several factors through the friction process phase and the compacting phase during the welding. The very fine grain is the consequence of the high degree of the plastic deformation of the near-the-contact layers even in the friction phase. The viscous layer, which is formed during the stable friction phase, is the area where the moving of matter occurs according to a very complex mechanism.Originality/valueThe paper contains useful results from the area of conventional friction welding of dissimilar steels and it can be very useful to researchers and engineers who deal with similar problems.

A Study of Cutting Temperatures in Turning Carbon-Fiber-Reinforced-Plastic (CRFP) Composites with Nose Radius Worn Tools

Nine kinds of carbide nose radius worn tools were used in turning of high-strength carbon-fiber-reinforced-plastics (CFRP) materials to study the cutting temperature of tip's surface. A new cutting temperature model using the variations of shear and friction plane areas occurring in tool nose wear situations are presented in this paper. The frictional forces and heat generated in the cutting process are calculated by using the measured cutting forces and the theoretical cutting analysis. The heat partition factor between the tip and chip is solved by using the inverse heat transfer analysis, which utilizes temperature on the K type carbide tip's surface measured by infrared as the input. The tip's surface temperature is determined by finite element analysis (FEA) and compared with temperatures obtained from experimental measurements. Good agreement demonstrates the proposed model.

Investigation of Stability and Failure Mechanism of Undercut Slopes by Three-Dimensional Finite Element Analysis

Slope failures along a bedding plane were critical issues and mostly happened in an open pit mining project such as the Mae Moh Mine, Thailand. The prediction of maximum width to maintain stable slope after an excavation process is required. This paper presents an investigation of 3D finite element analysis for the stability and failure mechanism of undercut slopes resting on a low interface friction plane. In numerical models, the soil slope was modeled as volume elements with the hardening soil material. Interface elements were used at the bottom plane to simulate the low interface friction plane and at the side support to simulate fully rough surface for the models with side supports. Stage analyses in numerical models were performed following excavation processes in physical models until failure. The effects of the side support and the slope length to increase the stability of undercut slopes were considered. Failure widths, failure mechanisms, and stress distributions associated with slope angles and boundary conditions of side support were discussed and compared.

Finite element analyses of the stability of a soil block reinforced by shear pins

The assessment of slope stability is an essential task in geotechnical engineering. In this paper, a threedimensional (3D) finite element analysis (FEA) was employed to investigate the performance of different shear pin arrangements to increase the stability of a soil block resting on an inclined plane with a low-interface friction plane. In the numerical models, the soil block was modeled by volume elements with linear elastic perfectly plastic material in a drained condition, while the shear pins were modeled by volume elements with linear elastic material. Interface elements were used along the bedding plane (bedding interface element) and around the shear pins (shear pin interface element) to simulate the soil-structure interaction. Bedding interface elements were used to capture the shear sliding of the soil on the low-interface friction plane while shear pin interface elements were used to model the shear bonding of the soil around the pins. A failure analysis was performed by means of the gravity loading method. The results of the 3D FEA with the numerical models were compared to those with the physical models for all cases. The effects of the number of shear pins, the shear pin locations, the different shear pin arrangements, the thickness and the width of the soil block and the associated failure mechanisms were discussed.