Tangential Load Research Articles

Electrical measurement method of static friction force on rough surface

Friction plays a key role in the assessment of the safety and stability of mechanical systems (such as superconducting magnet quench explosion, aerospace vehicle bearing wear, etc.). Due to the closeness of the interfaces in engineering structures and the randomness of the contact surfaces, existing methods for measuring static friction force are unable to measure it at the contact interfaces of engineering structures under service conditions. In this paper, a new method for measuring the static friction force at the interface based on electrical signals is proposed. This method enables the measurement of the static friction force at interfaces of complex engineering structures under service conditions solely through electrical signals. The results indicate that the contact resistance gradually decreases with the increase in tangential load during the static friction stage until a monotonic behavior of macroscopic sliding occurs. The evolution of contact resistance is linked to the evolution of the real contact area, and this monotonic behavior can be explained as the deformation form of contact points. The accuracy of the proposed electrical measurement method is verified by comparison with experimental results (with an error of less than 9%). The indirect measurement method of friction force proposed in this paper can effectively measure the static friction force at the interfaces of engineering structures under service conditions, and it is expected to be applied to the detection of friction performance at engineering structure interfaces in extreme service environments.

A Mathematical Model of Rod Lateral Oscillations Considering an External Tangential Load

A Mathematical Model of Rod Lateral Oscillations Considering an External Tangential Load

Clutch model for focal adhesions predicts reduced self-stabilization under oblique pulling

Cell-matrix adhesions connect the cytoskeleton to the extracellular environment and are essential for maintaining the integrity of tissue and whole organisms. Remarkably, cell adhesions can adapt their size and composition to an applied force such that their size and strength increases proportionally to the load. Mathematical models for the clutch-like force transmission at adhesions are frequently based on the assumption that mechanical load is applied tangentially to the adhesion plane. Recently, we suggested a molecular mechanism that can explain adhesion growth under load for planar cell adhesions. The mechanism is based on conformation changes of adhesion molecules that are dynamically exchanged with a reservoir. Tangential loading drives the occupation of some states out of equilibrium, which for thermodynamic reasons, leads to the association of further molecules with the cluster, which we refer to as self-stabilization. Here, we generalize this model to forces that pull at an oblique angle to the plane supporting the cell, and examine if this idealized model also predicts self-stabilization. We also allow for a variable distance between the parallel planes representing cytoskeletal F-actin and transmembrane integrins. Simulation results demonstrate that the binding mechanism and the geometry of the cluster have a strong influence on the response of adhesion clusters to force. For oblique angles smaller than about 40∘, we observe a growth of the adhesion site under force. However this self-stabilization is reduced as the angle between the force and substrate plane increases, with vanishing self-stabilization for normal pulling. Overall, these results highlight the fundamental difference between the assumption of pulling and shearing forces in commonly used models of cell adhesion.

High-precision modelling of deformation of sandwich structures under bilateral symmetric and oblique-symmetric loading

The analysis and assessment of the stress-strain state (STS) of multilayer plates with orthotropic layers under the action of stationary transverse and tangential loads is an urgent task. It includes calculations on the strength and deformability of various homogeneous and multi-layered plates with layers of constant thickness but arbitrary structure according to the thickness of the plate. Combining materials with isotropic and transversely isotropic physical characteristics into a multilayer package allows you to create multifunctional structures. The SSS of such structures, due to their structural heterogeneity and relatively low transverse stiffness of the individual layers, is significantly associated with the influence of transverse shear deformations and transverse compression deformations. Therefore, the problem of refined modeling of SSS plates, which would take into account these types of deformations, is urgent. Based on the decomposition of the SSS plate into flexural and unflexural components, it is proposed to optimize the design scheme of deformation of a rectangular multilayer plate. This significantly simplifies its modeling. For unflexural and exclusively flexural SSS, a two-dimensional, high-degree iterative approximation, but three-dimensional models of deformation of multilayer rectangular plate on a rigid foundation with isotropic, transverse-isotropic and orthotropic layers are constructed in an elastic formulation. That models takes full account deformation of transverse shear and transverse compression at transverse and the tangential loading of a plate. The model is continuous, that is, the number of equations and the order of differentiation of the calculation system of equations does not depend on the number of layers in the slab. This order of differentiation and the number of calculation equations can depend only on the order of iterative approximation of the model. A way of precise satisfaction of all defining correlations of the layers of material under keeping the conditions of their contact is found, while in the known continual models the dependence between the cross normal stress and cross deformation is only integral.The results of the analytical solution of the problem of deformation of a rectangular plate under boundary conditions of the Navier type under the action of transverse and tangential loads are given. By solving the test problems of the deformation of two-layer plates with transversally isotropic layers and three-layer plates with orthotropic layers and comparing the solutions with the exact three-dimensional solutions of these problems obtained by known methods, an assessment of the accuracy of the proposed refined models is given. The limits of admissible parameters of elastic characteristics of transversely isotropic and orthotropic plates for application of the offered models are established.

АНАЛИЗ ВЛИЯНИЯ ОСНОВНЫХ ВНЕШНИХ СИЛ И РЕАКЦИЙ НА ВЕЛИЧИНУ БОКОВОГО УВОДА УПРАВЛЯЕМЫХ И НЕУПРАВЛЯЕМЫХ КОЛЕС ПРИ КРИВОЛИНЕЙНОМ ДВИЖЕНИИ ДВУХОСНОГО АВТОМОБИЛЯ

Pneumatic tires must have elasticity, strength, wear resistance and, taking vertical, tangential and lateral loads, must ensure vehicle stability when cornering. Optimization of their parameters and properties, often of a contradictory nature, is an urgent task, for the solution of which hypotheses were put forward based on the information and analytical research carried out and which made it possible to specify the purpose and objectives of subsequent research.

UAV Swarm Centroid Tracking for Edge Computing Applications Using GRU-Assisted Multi-Model Filtering

When an unmanned aerial vehicles (UAV) swarm is used for edge computing, and high-speed data transmission is required, accurate tracking of the UAV swarm’s centroid is of great significance for the acquisition and synchronization of signal demodulation. Accurate centroid tracking can also be applied to accurate communication beamforming and angle tracking, bringing about a reception gain. Group target tracking (GTT) offers a suitable framework for tracking the centroids of UAV swarms. GTT typically involves accurate modeling of target maneuvering behavior and effective state filtering. However, conventional coordinate-uncoupled maneuver models and multi-model filtering methods encounter difficulties in accurately tracking highly maneuverable UAVs. To address this, an innovative approach known as 3DCDM-based GRU-MM is introduced for tracking the maneuvering centroid of a UAV swarm. This method employs a multi-model filtering technique assisted by a gated recurrent unit (GRU) network based on a suitable 3D coordinate-coupled dynamic model. The proposed dynamic model represents the centroid’s tangential load, normal load, and roll angle as random processes, from which a nine-dimensional unscented Kalman filter is derived. A GRU is utilized to update the model weights of the multi-model filtering. Additionally, a smoothing-differencing module is presented to extract the maneuvering features from position observations affected by measurement noise. The resulting GRU-MM method achieved a classification accuracy of 99.73%, surpassing that of the traditional IMM algorithm based on the same model. Furthermore, our proposed 3DCDM-based GRU-MM method outperformed the Singer-KF and 3DCDM-based IMM-EKF in terms of the RMSE for position estimation, which provides a basis for further edge computing.

Quasistatic strain fields in normally- and tangentially-loaded elastomeric rollers under impending slip

Elastomeric rollers are important components in applications such as printing and roll-to-roll manufacturing. To gain insight into roller mechanics and provide a basis for further investigations into dynamic rolling problems where rolling instabilities may arise, we employ a specially-designed apparatus to obtain displacement and strain fields via digital image correlation (DIC) under applied loads. We test loading scenarios leading to impending slip of an elastomeric roller, mounted on a steel hub, and in contact with a glass (rigid) substrate. We first examine strain fields under normal loading and compare them with the closest analytical predictions. We then progress to analyzing the strain fields under combined normal and tangential loading. For each loading scenario, we discuss the displacement and strain fields of the roller sidewall and contact interface. We use a conceptual string model to explore how stick and slip zones develop within the contact area as well as how memory effects arise during cyclic loading. This memory effect is then verified experimentally using the DIC strain fields. Additionally, we demonstrate a means for identifying the stick zone area between the roller and substrate using the experimentally-obtained displacement fields. We believe the apparatus, and the ability to obtain experimental displacement and strain fields, will prove valuable in understanding roller mechanics and associated instabilities.

Simulation of the surface and volume stress in the contact archwire/bracket for classical friction and critical contact angle

AbstractAimThe occlusion of the teeth is affected due to the appearance of micro-cracks resulting from maximum stresses in the contact zones between the wire and the bracket under normal and tangential loading. The objective of this study is to evaluate the surface and volume constraints in the presence of bonding and partial sliding zones on the contact surface between wires and supports. Knowledge of these stress fields will make it possible to better limit the surfaces where most of the micro-cracks occur. Indeed, the evaluation of the stress will facilitate the modelling or application of established micro crack models on this subject, because the initiation of micro-cracks often appears on the contact surface or just below it.Materials and methodsIn this study, the two most common situations of contact between the wire and the bracket were studied; the first corresponds to the situation where the wire is positioned in the center of the support (classic friction), and the second corresponds to the situation where the inclined wire touches the ends of the supports (critical contact angle).The MATHCAD software was used to simulate the damage zones for normal loading in the two cases studied (classic friction, critical contact angle). We proposed a Hertzian loading for the first case and a linear loading for the second case. Also, the effect of the additional load during wire tightening applied by the orthodontist was studied.ResultsThe charge concentration is located above the contact zone, of the order of 0.3P0 (pressure per unit of arbitrary normal length), according to Mathcad simulation results. The adhesion zone/micro-slip zone contact generates the largest tangential load, which is directed towards the side experiencing the most stress. We also observed that the stick area shifts towards the recessed side when the additional load is applied. Additionally, comparing the configurations, the critical contact angle resulted in a higher maximum shear stress.

Cracking behavior during scratching brittle materials with different-shaped indenters

The cracking behavior greatly influences the material removal and surface integrity during the abrasive machining of brittle materials. The abrasive machining can be simplified as a series of scratching by different-shaped indenters. In this paper, a scratch-induced stress field model is built to analyze the cracking behavior during scratching brittle materials. The model considers conical, pyramidal, and spherical (CPS) indenters and correlates the scratch-induced principal stress with workpiece material properties, indenter geometries, and scratch behavior parameters (e.g., scratch normal load, tangential load, friction coefficient, scratch depth). With the model, the effects of scratch depth and indenter geometries on the scratch behavior and cracking behavior are investigated. The results show that the scratch load decreases when a sharper indenter or a spherical indenter with a smaller radius is used. The larger the scratch depth, the easier it is for radial, median, and lateral (RML) cracks to initiate. There is an optimal indenter half-apex angle at which it is most difficult to initiate radial and median cracks. The lateral crack easily initiates when the indenter becomes sharp. The initiation position of radial crack changes from being in front of the indenter to being behind it as the scratch depth increases or the half-apex angle decreases. The propagation angle of radial crack decreases, while that of median crack increases with an increase in scratch depth. The sizes of RML cracks increase with an increasing scratch depth or half-apex angle. Finally, the model is validated through scratching experiments on fused silica using CPS indenters and by referencing previous research. It demonstrates that the model can accurately determine the sizes of RML cracks, with an average relative error of less than 11%. This research provides guidance on selecting suitable process parameters or indenter geometries to increase the material removal rate and mitigate the crack damage during the abrasive machining of brittle materials.

Analysis of stress drop behavior for stick-slip friction based on total reflection observation experiment

This paper employed an experimental system based on the total reflection method to study the contact interface behavior during the stress drop process of stick-slip friction. The two-stage drop behavior was found for the first time, namely, the tangential load during the stick-slip stress drop underwent two successive drops in different rates and magnitudes, instead of a single drop. A critical location at the contact interface, where the contact areas on both sides of this location exhibited different contact behaviors during stress drop events, was found. An image recognition method was present to identify the boundary between the stick and sliding zones of the interface, the impact of stress drop events on interface contact, and the propagation velocity and direction of rupture fronts. Finally, the mechanism for the interesting phenomenon described in this paper was preliminarily discussed. The research may be useful for better understanding the stick-slip friction and its stress drop events.

Shear Waves in an Elastic Plate with a Hole Resting on a Rough Base

The article is devoted to the analytical and numerical study of the pattern of propagation and attenuation, due to Coulomb friction, of shear waves in an infinite elastic thin plate with a circular orifice of radius r0 lying on a rough base. Considering the friction forces and their influence on the sample of wave propagation in extended rods or thin plates is important for calculating the stress–strain state in them and the size of the area of motion. An exact analytical solution of a nonlinear boundary value problem for tangential stresses and velocities is obtained in quadratures by the Laplace transform, with respect to time. It turned out that the complete exhaustion of the wave front of a strong rupture occurs at a finite distance r* from the center of the orifice, and an elementary formula is given for this distance (the case of tangential shock stresses suddenly applied to the orifice boundary is considered). For various ratios of the magnitude of the limiting friction force to the amplitude of the applied load, the stopping (trailing) wave fronts are calculated. After passing them, a state of static equilibrium between the elastic and friction forces with a nonlinear distribution of residual stresses is established in the region r0≤r≤r*. For the first time, a precise analytical solution was obtained for the boundary value problem of the propagation of elastic shear waves in an infinite isotropic space with a cylindrical cavity, when a tangential shock load is set on its surface.

An Approach to Measure Slips in Friction Contacts Using a Self-Powered Sensor

The accumulation of small tangential slip will occur on the contact surfaces of components in mechanical structures when subjected to cyclic loadings, which will lead to system failure. However, the small tangential slip is difficult to measure directly. In this paper, a method for measuring the contact slip by using a self-powered displacement sensor based on triboelectric nanogenerator (TENG) is proposed, and the accuracy is verified by the finite element analysis (FEA). The contact slips for a flat-on-flat contact configuration are measured by this method. When the test piece is subjected to a cyclic tangential load with a frequency of 10Hz, the average obtained slip displacement of the test piece under single load cycle is less than 10μm. Then the finite element simulation of the contact configuration is carried out using software Abaqus 6.14. The analysis results are close to the test results, which verifies the effectiveness of the measurement method. Moreover, the slips of the flat-on-flat contact configuration under different frequency and amplitude of cyclic tangential load are investigated.

Stress Distribution in Wear Analysis of Nano-Y2O3 Dispersion Strengthened Ni-Based μm-WC Composite Material Laser Coating.

Oxide-dispersion- and hard-particle-strengthened (ODS) laser-cladded single-layer multi-tracks with a Ni-based alloy composition with 20 wt.% μm-WC particles and 1.2 wt.% nano-Y2O3 addition were produced on ultra-high-strength steel in this study. The investigation of the composite coating designed in this study focused on the reciprocating friction and wear workpiece surface under heavy load conditions. The coating specimens were divided into four groups: (i) Ni-based alloy, nano-Y2O3, and 2 μm-WC (2 μm WC-Y/Ni); (ii) Ni-based alloy with added 2 μm-WC (2 μmWC/Ni); (iii) Ni-based alloy with added 80 μm-WC (80 μmWC/Ni); and (iv) base metal ultra-high-strength alloy steel 30CrMnSiNi2A. Four conclusions were reached: (1) Nano-Y2O3 could effectively inhibit the dissolution of 2 μm-WC. (2) It can be seen from the semi-space dimensionless simulation results that the von Mises stress distribution of the metal laser composite coating prepared with a 2 μm-WC particle additive was very uniform and it had better resistance to normal impact and tangential loads than the laser coating prepared with the 80 μm-WC particle additive. (3) The inherent WC initial crack and dense stress concentration in the 80 μm-WC laser coating could easily cause dislocations to accumulate, as shown both quantitatively and qualitatively, resulting in the formation of micro-crack nucleation. After the end of the running-in phase, the COF of the 2 μm-WC-Y2O3/Ni component samples stabilized at the minimum of the COF of the four samples. The numerical order of the four COF curves was stable from small to large as follows: 2 μm-WC-Y2O3/Ni, 2 μm-WC/Ni, 80 μm-WC/Ni, and 30CrMnSiNi2A. (4) The frictional volume loss rate of 2 μm-WC-Y2O3/Ni was 1.3, which was significantly lower than the corresponding values of the other three components: 2.4, 3.5, and 13.

Non-slipping adhesive contact between dissimilar elastic solids under normal and tangential loads

In this paper, a model of two-dimensional non-slipping adhesive contact between dissimilar elastic solids under normal and tangential loads is proposed, and the general analytical solution is derived. The interaction of adhesion and friction along the contacting interface is studied. Specifically, (i) the shear-off force of adhesive contact is proposed; (ii) the effect of tangential load on the puff-off force is presented; (iii) the influence of the normal load on the shear-off force is obtained; (iv) in the context of these results, the nominal static friction coefficient is defined and analyzed, and it is shown that the static friction coefficient is a function of external normal load, which can well explain some experimental results in the literature. The proposed model appears to be consistent with the available experimental data, which offers new insight into the interplay mechanism between friction and adhesion. These results provide the foundation for understanding and modelling some tribological phenomena at the macro-, micro- and nano- scales.

Research on the monitoring friction hysteresis for the bolted interface by electromechanical impedance

Friction hysteresis manifests at the bolted interface when subjected to external excitation, leading to nonlinear structural responses. But the interface evolution is rarely considered in the health monitoring. In this paper, we introduce the pioneering concept of effective mechanical impedance of the contact interface (EMICI) and formulate a coupled structural impedance model that comprehensively incorporates both tangential loading and contact impedance considerations. EMICI was deemed to encapsulate intricate information pertaining to contact nonlinearity, and the theoretical equation was derived using principles of contact mechanics. Tangential loading experiments, time domain impedance analysis and impact hammer tests were conducted to confirm the close relationship between EMICI and the structural properties. The coupled structural impedance model is proved to be effective, in which EMICI can be identified by changing the tangential force and torque. Subsequent analysis revealed that the proposed model could additionally serve in the identification of system-related parameters. The loading coefficient in the model is linearly related to the tangential force, and the calculated EMICI corresponds to the slip characteristics of the bolted interface. The introduced concept of EMICI could be considered as a metric for assessing interface properties, offering dependable insights into contact evolution, and facilitating a deeper understanding of interface dynamics.

Influence of contact curvature on frictional energy dissipation under varying tangential loads

This study investigates the effect of contact surface curvatures on the friction response under varying tangential loadings using a finite element (FE) model. The results showed that the geometry of the surface influences the contact force at the interface and reduces the friction effect through an unsteady distribution of the contact force. The relationship between the friction effect, excitation, and contact surface shape was also examined, revealing a linear inverse relationship between the friction and curvature. The findings provide a comprehensive understanding of the frictional interactions between elastic bodies and highlight the role of curvature as a design parameter for regulating the friction effect.

Determination of the stress-deformed state of the grinding circle adjustment pencil

Using the Ery stress function in a linear formulation, using the methods of the classical theory of elasticity, an algorithm for analytically determining the stress-strain state of the working part of the abrasive wheel straightening tool as a two-layer composite material was developed. The algorithm allows considering arbitrarily distributed normal and tangential loads of the working surface of the abrasive grain of the tool. It considers the mandrel's limitation of deformations of the grain and the material that attaches it to it, the compatibility of the deformation of the grain and the material of its attachment to the mandrel, and their mechanical properties.
 Calculations performed according to the obtained algorithm allowed the following to be established. The maximum standard stresses on the working face of the grain exceed the corresponding stresses on the opposite face due to their more uniform distribution. The tangential stresses are almost uniformly distributed along the specified face. The material connecting the grain to the tool mandrel deforms almost uniformly due to its lower modulus of elasticity and smaller thickness than the abrasive grain's modulus of elasticity and thickness. Determining the stress-deformed state of the executive part of the pencil for correcting the working surfaces of grinding wheels for abrasive processing of materials makes it possible to specify the known mechanism of their interaction and increase the efficiency of the technological process of restoring the working surfaces of the tool for abrasive processing of metals.
 Taking into account the simultaneous deformation of the abrasive grain and the material that attaches it to the pencil mandrel, determining their stress-strain states using the methods of the classical theory of elasticity allows us to consider the results obtained by the given algorithm as sufficiently reliable within the limits of linear deformation. It is advisable to direct further research to determine the durability of the "abrasive grain-bond" system under variable cyclic loads.

Effect of Neurodynamic Mobilization on Precision Grip among Healthy Individuals

Over the last three decades, insights into the role of the median nerve in precision grip control have been documented in the study of healthy volunteers using Microneurography Technique 1 or a nerve anesthesia block at the wrist or hand . Accurate grip requires proper adjustment of the grip force (GF) perpendicular to the grip surface of the object and the tangential load (LF). Prevents objects from slipping and prevents premature muscle fatigue. Neurodynamic techniques (NDT) are a type of manual therapy in which forces are supposed to be directed to neural regions via the positioning and movement of several joints . The Changes in the mechanics or physiology of the nervous system can cause other system dysfunctions or dysfunctions in the musculoskeletal tissues that receive its innervations, according to the theory of neural mobilization. The objective of the study is to determine the effects of neuromobilisation on key pinch, three jaw chuck and tip to tip pinch among the healthy individual.

Effect of Magnetic Field and Inclined Load on a Two-Dimensional Thermoelastic Medium Under Gravity

This work aims to investigate the effects of magnetic field and inclined load on a two-dimensional thermoelastic medium under gravitational field. The problem is formulated in the context of refined dual-phase-lag Green–Naghdi (DPL GN) model. The bounding plane surface is heated by a non-Gaussian laser beam. The inclined load is supposed to be a linear combination of a normal load and a tangential load. Analytical formulas for several physical quantities are generated on the transformed domain using the Laplace and Fourier transform techniques. The inversion of double transform has been done numerically by using MATHEMTICA 10. The numerical inversion of Laplace transform is done by using the Zakian method (Halsted and Brown [Zakians technique for inverting Laplace transforms, J. Chem. Eng. 3 (1972) 312–313]). All physical quantities have been graphically depicted for the dual-phase-lag Green–Naghdi type III model (DPL GN-III), simple Green–Naghdi type III model (simple GN-III), Lord–Shulman model (LS) and classical thermoelasticity theory (CTE) to indicate the effect of magnetic field and the angle of inclination of the medium.

Analysis of the Disc Cutter Cutting Load and Performance during TBM Tunneling in Soft-Hard Varied Strata through Laboratory Cutting Test

Abstract Tunnel boring machine (TBM) disc cutters are specially designed for breaking hard rocks and always exhibit unsatisfactory performance during the soft-hard varied stratum tunneling process. To figure out the load and cutting performance of the disc cutter and avoid unsatisfying excavation face crushing effects, a soft-hard varied strata excavation face model was made and rotary cutting tests with full-scale disc cutters were conducted. The load and cutting performance of the disc cutter under different TBM operating conditions were monitored and analyzed based on the test. It was found that the variation of the disc cutter load did not meet the CSM model completely, and the tangential force of the disc cutters in the heterogeneous areas was only about 30–40 % of that in the uniform areas of the excavation face model. An ideal criterion for the excavation face to be crushed successfully was established and the unknown parameters in it were obtained by fitting the test data. The gradation information and fractal dimension of crushing debris were obtained by the sieved-and-weighed method, which can provide indicators for the crushing effect of the disc cutters. Three different disc cutter poor performance modes in the heterogeneous strata cutting process were analyzed: (1) rotating starting failure of the disc cutters caused by tangential load insufficiency, (2) excavation face crushing failure caused by low crack extending capacities of the materials being cut and improper operating parameters (too small cutting depths or too large disc cutter spacing), and (3) adverse excavation face crushing forms (large or powdery debris). These analyses can help with the performance evaluation of disc cutters and the tunneling parameter adoption of the TBM in soft-hard varied strata tunneling engineering.