Friction Force Research Articles

Giant Enhancement of Negative Friction by Resonant Coupling Between Localized Surface Phonon Polaritons and Graphene Plasmonics

Abstract Negative friction refers to a frictional force that acts in the same direction as the motion of an object, which has been predicted in terahertz (THz) gain systems [Phys. Rev. B 108 (4), 045406(2023)]. In this work, we investigate the enhancement of the negative friction experienced by nanospheres placed near a graphene substrate. We find that the magnitude of negative friction is related to the resonant coupling between the surface plasmon polaritons (SPPs) of the graphene and localized surface phonon-polaritons (LSPhP) of nanospheres. We exam nanospheres consisted of several different materials, including SiO2, SiC, ZnSe, NaCl, lnSb. Our results suggest that the LSPhP of NaCl nanospheres match effectively with the amplified SPPs of graphene sheets. The negative friction for NaCl nanospheres can be enhanced about one-to-two orders of magnitude compared to that of silica (SiO2) nanospheres. At the resonant peak of negative friction, the required quasi-Fermi energy of graphene is lower for NaCl nanospheres. Our finds hold great prospects for the mechanical manipulations of nanoscale particles.

Extreme electromagnetic rotation, chemical reaction, Hall and ion slip effects on weakly ionized fluid in a Riga channel

The utilization of external magnetic or electric fields, particularly through a Riga setup, markedly enhances flow dynamics by mitigating frictional forces and turbulent fluctuations, thereby facilitating superior flow management. Such improvements are especially beneficial in optimizing the operational efficiency of machinery and turbines. Our research focuses on the behaviour of a weakly ionized fluid within a porous, infinitely extended Riga channel (or electromagnetic channel) set in a rotational frame work affected by Hall and ion-slip electric fields. This model integrates the cumulative repulsions of an abruptly apply pressure gradients, electro-magnetic force, electromagnetic radiation, as well as chemical reactions. The physical configuration of the model features a stationary RHS wall as well as the LHS wall subjected to transversal vibration, establishing a complex flow environment. This circumstance is analytically modeled utilizing time dependent PDE, with the Laplace transform method applied to achieve a closed-format resolution for the course controlling equations. Through detailed graphical and tabular data, the investigations explored the impacts of assorted pivotal parameters on the model's flow traits and quantities. Our results indicate that an upswing in the modified Hartmann number significantly enhances fluids flow in the conduit, with the most important resultant flow showing marked improvement as Hall and ion-slip parameters amplify, and secondly the resultant flow diminishing chemical reaction parameter. Additionally, species concentration lowers with higher Schmidt numbers and chemical reaction rates, while an expanded modified Hartmann number correlate with enhanced shear stress near the conduit wall. Moreover, an elevation in the radiating parameter reduces the rate of temperature transport at the vibrating wall, whereas this at the stationary wall improves. This study has profound implications across several fields, notably in fusion energy research, spacecraft propulsion systems, satellite operations, aerospace engineering, and advanced manufacturing technologies.

In situ monitoring of defects in steel structures using a robot‐assisted ultrasonic inspection technique

AbstractIncidents in extreme environments can bring unprecedented consequences that would endanger the lives of many humans. Real‐time and early detection of cracks and defects in the steel used for the construction of industrial sites can bring many benefits to remote operators and site managers. Although different methods and systems have been proposed in the past, they are not suitable for real‐time fault detection or long‐term operation in harsh environments. Therefore, this paper proposes a low‐power robotic platform with a magnetic actuator mechanism which is capable of wireless inspection of steel structures using the ultrasonic method. The proposed magnetic motion uses the inertia force generated by the piston vibration and the difference in frictional force during movement. The paper evaluates the performance of the steel structure defect detection system from four different perspectives: sensing principle, wireless communication network, driving part, and power supply.

Analysis of a Dry Friction Force Law for the Covariant Optimal Control of Mechanical Systems with Revolute Joints

This contribution shows a geometric optimal control procedure to solve the trajectory generation problem for the navigation (generic motion) of mechanical systems with revolute joints. The mechanical system is analyzed as a nonlinear Lagrangian system affected by dry friction at the joint level. Rayleigh’s dissipation function is used to model this dissipative effect of joint-level friction, and regarded as a potential. Rayleigh’s potential is an invariant scalar quantity from which friction forces derive and are represented by a smooth model that approaches the traditional Coulomb’s law in our proposal. For the optimal control procedure, an invariant cost function is formed with the motion equations and a Riemannian metric. The goal is to minimize the consumed energy per unit time of the system. Covariant control equations are obtained by applying Pontryagin’s principle, and time-integrated using a Finite Elements Method-based solver. The obtained solution is an optimal trajectory that is then applied to a mechanical system using a proportional–derivative plus feedforward controller to guarantee the trajectory tracking control problem. Simulations and experiments confirm that including joint-level friction forces at the modeling stage of the optimal control procedure increases performance, compared with scenarios where the friction is not taken into account, or when friction compensation is performed at the feedback level during motion control.

Decoding roughness perception in distributed haptic devices

Abstract The ability to render realistic texture perception using haptic devices has been consistently challenging. A key component of texture perception is roughness. When we touch surfaces, mechanoreceptors present under the skin are activated and the information is processed by the nervous system, enabling perception of roughness/smoothness. Several distributed haptic devices capable of producing localized skin stretch have been developed with the aim of rendering realistic roughness perception; however, current state-of-the-art devices rely on device fabrication and psychophysical experimentation to determine whether a device configuration will perform as desired. Predictive models can elucidate physical mechanisms, providing insight and a more effective design iteration process. Since existing models (1, 2) are derived from responses to normal stimuli only, they cannot predict the performance of laterally actuated devices which rely on frictional shear forces to produce localized skin stretch. They are also unable to predict the augmentation of roughness perception when the actuators are spatially dispersed across the contact patch or actuated with a relative phase difference (3). In this study, we have developed a model that can predict the perceived roughness for arbitrary external stimuli and validated it against psychophysical experimental results from different haptic devices reported in literature. The model elucidates two key mechanisms: 1) The variation in the change of strain across the contact patch can predict roughness perception with strong correlation 2) The inclusion of lateral shear forces is essential to correctly predict roughness perception. Using the model can accelerate device optimization by obviating the reliance on trial-and-error approaches.

Effect of vibration frequency on tribological characteristics of vibration-assisted micro-nano machining

Experimental findings regarding the influence of vibration frequency on the machining outcomes of vibration-assisted machining (VAM) have been inconsistent. This work aims to address this issue through both experimental and theoretical analyses. The results indicate that the circuit's frequency response is the primary source of these discrepancies. When the vibration frequency is less than half the cutoff frequency, the friction force reaches a minimum while the wear volume peaks. The solution of the heat conduction equation demonstrated that the acoustic softening effect drives the softening mechanism in nanoscale VAM. Molecular dynamics (MD) simulations further elucidate the damage mechanisms during the wear process, showing that high-frequency vibrations contribute to achieving high-precision machining.

Inelastic deformation accrued over multiple seismic cycles: Insights from an elastic-plastic slider-and-springboard model

We study a toy model designed to build physical insight into the problem of slow accumulation of non-recoverable strain in fault blocks over multiple earthquake cycles. The model consists of a thin, horizontal elastic-plastic plate (springboard) in frictional contact with a vertical, rigid wall moving downward at a steady speed. Our model produces stick-slip cycles consisting of interseismic plate downwarping and coseismic plate upwarping as long as the moment of the frictional force at the contact does not exceed the maximum (purely plastic) bending moment the plate can sustain. We show that the duration of individual earthquake cycles and the spatial pattern of interseismic deflection are controlled by two stress ratios involving the peak yield stress of the plate, the frictional strength of the fault and the coseismic stress drop. We show that non-recoverable plate deflection accumulates over successive earthquake cycles if the plate’s yield strength decreases through time, causing a progressive decrease of the aforementioned stress ratios. We derive scaling relations between the rate of accumulation of inelastic deformation, the relative tectonic plate velocity, and the rate of lithospheric weakening. Our results are consistent with observations of long-term permanent deformation of natural fault regions.

Investigation of Tribological Properties of Inconel 601 under Environmentally Friendly MQL and Nano-Fluid MQL with Pack Boronizing

Friction and high temperatures greatly affect the hardness and processing efficiency of superalloys. Therefore, it is important to provide a coating on their surfaces with a hard layer. In this study, pack boronizing was applied on Inconel 601 to improve its microstructure and tribological properties. In this regard, tribological tests were performed under MQL, nano-MQL1 (MQL + CuO), and nano-MQL2 (MQL + TiO2) environments. The research results showed that the lowest wear depth, friction force, coefficient of friction (CoF), and volume loss values were obtained in pack-boronized Inconel 601 in a nano-MQL2 environment. In the nano-MQL2 environment, the wear depth decreased by 17.81% (from 57.922 µm to 47.605 µm) with package-boronized Inconel 601 compared to as-received Inconel 601 at a 45 N load. Pack-boronized Inconel 601 experienced an average reduction of 30.23%, 41.60%, and 52.32% in friction force when switching from dry to MQL, nano-MQL1, and nano-MQL2 environments, respectively. It was also observed that the coefficient of friction (CoF) and volume loss values decreased with pack boronizing in an MQL/nano-MQL environment. In a nano-MQL2 environment at 15 N load, volume losses for as-received and boron-coated Inconel 601 were determined as 0.288 mm3 and 0.249 mm3, respectively (13.54% decrease). The findings of this study demonstrate that pack boronizing and MQL and nano-MQL techniques enhance the tribological characteristics of Inconel 601 alloys.

Numerical simulation of friction characteristics of bionic flexible contact surface of front axle rocker arm sleeve of car

Based on the finite element software ABAQUS, the friction process of the flexible friction pair of the front axle rocker bushing of a car with a convex structure similar to the mantis head is established.The finite element model of the process is constructed and its friction characteristics are verified. By selecting a suitable hyperelastic constitutive model and changing the size of the convex structure on the surface of the sleeve,The simulation analysis of the mechanical characteristics of the flexible friction pair in radial and torsional directions shows that the bionic convex hull design changes the maximum stress of the bushing when it is subjected to force.The force and strain position are adjusted to reduce the possibility of cracking of the rubber bushing; the contact friction force and friction coefficient of the bionic bushing surface are significantly reduced, and the type 2 modelThe drag reduction and wear resistance of the profiled surface are the best.

Research Progress on Current-Carrying Friction with High Stability and Excellent Tribological Behavior

Current-carrying friction affects electrical contact systems like switches, motors, and slip rings, which determines their performance and lifespan. Researchers have found that current-carrying friction is influenced by various factors, including material type, contact form, and operating environment. This article first reviews commonly used materials, such as graphite, copper, silver, gold, and their composites. Then different contact forms like reciprocating, rotational, sliding, rolling, vibration, and their composite contact form are also summarized. Finally, their environmental conditions are also analyzed, such as air, vacuum, and humidity, on frictional force and contact resistance. Additionally, through experimental testing and theoretical analysis, it is found that factors such as arcing, thermal effects, material properties, contact pressure, and lubrication significantly influence current-carrying friction. The key mechanisms of current-carrying friction are revealed under different current conditions, including no current, low current, and high current, thereby highlighting the roles of frictional force, material migration, and electroerosion. The findings suggest that material selection, surface treatment, and lubrication techniques are effective in enhancing current-carrying friction performance. Future research should focus on developing new materials, intelligent lubrication systems, stronger adaptability in extreme environments, and low friction at the microscale. Moreover, exploring stability and durability in extreme environments and further refining theoretical models are essential to providing a scientific basis for designing efficient and long-lasting current-carrying friction systems.

Suitable Method for Improving Friction Performance of Magnetic Wheels with Metal Yokes

A magnetic-wheeled robot is a type of robot that inspects large steel structures instead of humans, and it can run on a three-dimensional path by using wheels with built-in permanent magnets. For the robots to work safely, their magnetic wheels require both magnetic attractive forces and friction forces. Planetary-geared magnetic wheels, which we have developed, make direct contact with their yokes on the running surface to ensure their magnetic attractive force. However, this design decreases their frictional performance more than common magnetic wheels covered with soft materials. Therefore, the yokes require methods that can improve their frictional performance without decreasing their attractive force. To consider the best method for the use of magnetic wheels, this study has run experiments with five types of yokes, which have different processing. As a result, the yokes with corroded surfaces could have maintained the attractive force more than 90% of the time and increased their traction forces by about 36% in static conditions and about 30% in dynamic conditions compared to yokes with no machining. The main reasons for these experimental results are that the rust layer has stable irregularities on the surface and includes ferromagnetic materials.

Dynamic modeling and simulation of a new conceptual design of a magnetic capsule robot by application of endoscopic capsule

This paper investigates design, modeling, simulation, and dynamic issues related to self-propelled endoscopic capsule navigated inside the human body through external magnetic fields. A novel magnetic propulsion system is proposed and fabricated, which has great potential of being used in the field of noninvasive gastrointestinal endoscopy. The endoscopic capsule dynamic is studied on a medical silicone plate as the closest available material for the stomach tissue. First, the mechanical characteristics of the medical silicone plate is measured. Next, the forces acted on the endoscopic capsule which are friction, hydrodynamic and magnetic forces are determined by means of test and numerical techniques such as finite element method. Having known the magnitude of forces and torques on the endoscopic capsule, the dynamics of capsule are calculated under different initial conditions and external magnetic fields.

High-Fidelity Simulations of Flight Dynamics and Trajectory of a Parachute–Payload System Leaving the C-17 Aircraft

This article examines the flight dynamics and trajectory analysis of a parachute–payload system deployed from a C-17 aircraft. The aircraft is modeled with an open cargo door, extended flaps, and four turbo-fan engines operating at an altitude of 2000 feet Above Ground Level (AGL) and an airspeed of 150 knots. The payloads consist of simplified CONEX containers measuring either 192 inches or 240 inches in length, 9 feet in width, and 5.3 feet in height, with their mass and moments of inertia specified. At positive deck angles, gravitational forces cause these payloads to begin a gradual descent from the rear of the aircraft. For aircraft at zero deck angle, a ring-slot parachute with approximately 20% geometric porosity is utilized to extract the payload from the aircraft. This study specifically employs the CREATE-AV Kestrel simulation software to model the chute-payload system. The extraction and suspension lines are represented using Kestrel’s Catenary capability, with the extraction line connected to the floating confluence points of the CONEX container and the chute. The chute and payload will experience coupled motion, allowing for an in-depth analysis of the flight dynamics and trajectory of both elements. The trajectory data obtained will be compared to that of a payload (without chute and cables) exiting the aircraft at positive deck angles. An adaptive mesh refinement technique is applied to accurately capture the engine exhaust flow and the wake generated by the C-17, chute, and payloads. Friction and ejector forces are estimated to align the exit velocity and timing with those recorded during flight testing. The results indicate that the simulation of extracted payloads aligns with expected trends observed in flight tests. Notably, higher deck angles result in longer distances from the ramp, leading to increased exit velocities and reduced payload rotation rates. All payloads exhibit clockwise rotation upon leaving the ramp. The parachute extraction method yields significantly higher exit velocities and shorter exit times, while the payload-chute acceleration correlates with the predicted drag of the chute as demonstrated in prior studies.

Numerical Investigation on the Hysteretic Performance of Self-Centering Precast Steel–Concrete Hybrid Frame

To improve the construction performance and seismic resilience of precast reinforced-concrete frame structures, an innovative self-centering precast steel–concrete hybrid frame has been proposed and subjected to cyclic loading tests. In this paper, a comprehensive numerical analysis was conducted to further investigate the frame’s hysteretic behavior. Initially, a numerical model was developed using the finite element software OpenSees. Numerical analyses of two frame specimens were conducted, demonstrating good agreement between the numerical and experimental hysteretic characteristics, thus validating the model’s accuracy. Subsequently, based on the numerical simulations, a quantitative comparison of hysteretic performance between a novel frame and a traditional reinforced-concrete frame of the same scale was performed. While the proposed frame exhibited slightly lower initial stiffness and energy dissipation capacity than the traditional frame, it outperformed in terms of load-carrying capacity and self-centering ability. Finally, parametric analyses were carried out to assess the influence of various design parameters on the hysteretic performance, including friction force in the web frictions devices, initial post-tensioned force of the prefabricated steel–concrete hybrid beams, the steel arm length, and the column longitudinal reinforcement ratio. The results showed that increases in these four parameters improved the load-carrying capacity and initial stiffness of the proposed frame. Additionally, an increase in the friction force, steel arm length, or column longitudinal reinforcement ratio enhanced the frame’s energy dissipation capacity, while an increase in the initial post-tensioned force or a decrease in the friction force enhanced the frame’s self-centering capacity.

Classification of The Analog Informative Parameters of the Rod Deepwell Pump Dynamograph Signals

In mechanized oil production, rod deep-well pumps are widely used. They consist of surface and underground parts. The above-ground part includes pump drive and wellhead fittings. The wellhead fitting is designed to seal the well. The underground part is the pump itself. The pump consists of a plunger, rod string and tubing. The main method of diagnosing a rod deep-well pump is dynamometry. Dynamometry allows to determine the equipment defects and control the efficiency of the pump operation mode without stopping the well operation. Dynamometry is a process of measuring the loads, which are perceived by the polished rod during the operation of the well. There are theoretical and practical dynamograms. Practical dynamogram is a closed non-periodic curve with variable amplitude. There are various methods to automate the process of the dynamometry result processing. In this paper we analyze the analog informative parameters of dynamometer signals. These parameters depend on the friction forces in the underground part of the rod pump, inertial forces, tightness of valve assemblies, dynamic liquid level, etc. The results obtained can be used in the development of the pumping process. The obtained results can be also applied to develop processing algorithms of practical dynamograms.

Penerapan Model Problem Based Learning untuk Meningkatkan Hasil Belajar IPAS Siswa Kelas IV-A SDN Pakis 1 Surabaya

This study aims to improve the learning outcomes of students in class IV-A in IPAS subjects, especially on the material of friction and muscle force, by using the Problem Based Learning (PBL) Learning Model at SDN Pakis 1 Surabaya. This research is a Classroom Action Research (PTK) conducted in two cycles, each of which consists of planning, implementation, observation, and reflection stages. The subjects of this study were 28 students of class IV-A. The instruments used include learning outcome tests to measure students' understanding of the material taught. The results showed a significant increase in student learning outcomes. At the pre-cycle stage, only 39% of students achieved mastery, while 61% of students were not yet complete. After the implementation of PBL, in cycle 1 student completeness increased to 71%, and in cycle 2 all students reached completeness with a percentage of 100%. PBL proved to be effective in improving students' understanding of the concepts of friction and muscle force through problem solving that is relevant to everyday life. Thus, the application of Problem Based Learning (PBL) can significantly improve student learning outcomes in IPAS subjects, especially in understanding abstract concepts such as force. This method is also effective in developing students' critical and collaborative thinking skills.

A magnetohydrodynamic flow of a water-based hybrid nanofluid past a convectively heated rotating disk surface: A passive control of nanoparticles

Abstract One of the basic fluid mechanics problems of fluid flows over a revolving disk has both theoretical and real-world applications. The flow over a rotating disk has been the subject of numerous theoretical studies because it has many real-world applications in areas like rotating machinery, medical equipment, electronic devices, and computer storage. It is also crucial for engineering processes. Therefore, this article deals with a time-independent water-based hybrid nanofluid flow containing copper oxide and silver nanoparticles past a spinning disk. The Newtonian flow is taken into consideration in this analysis. The influence of magnetic field, thermophoresis, nonlinear thermal radiation, Brownian motion, and activation energy has been considered. The present analysis is modeled in a partial differential equation form and is then converted to ordinary differential equations using appropriate variables. A numerical solution using the bvp4c technique is accomplished using MATLAB software. The current results are matched with the previous literature and established a close relationship with previous studies. The purpose of this investigation is to numerically investigate the time-independent hybrid nanofluid flow comprising copper oxide and silver nanoparticles over a rotating disk surface. The results show that the increased magnetic parameters increase the friction force at the surface, which decreases the radial and azimuthal velocity distribution. At the sheet surface, the radial velocity of the hybrid nanofluid shows dominant performance compared to the nanofluid. On the other hand, the magnetic factor has dominant behavior on the azimuthal velocity component of the nanofluid flow compared to the hybrid nanofluid flow. The higher volume fraction and magnetic factor enhance the skin friction at the disk surface. Furthermore, greater surface drag is found for the hybrid nanofluid flow. The higher solid volume fraction, temperature ratio, and Biot number enhance the rate of heat transmission. Also, a higher rate of heat transmission is observed for the hybrid nanofluid flow.

The effect of disc deformation on the dynamic response of multi-disc systems: A tilting-impact model originating from the wet clutch

Analyzing the dynamic response of a wet multi-disc clutch is crucial for relevant fault diagnosis research. However, characterizing the tilting-impact phenomenon between the friction discs remains ambiguous. This paper presents a tilting-impact model of a multi-disc system under dry conditions and investigates the effect of disc deformation on the system dynamics. Firstly, Euler angles and Euler kinematic differential equations are introduced to describe the spatial position and orientation of the spinning-tilting disc. The aligning centrifugal moment, spline friction force, and tilting-impact forces for both flat and deformed discs are derived. A bench test is conducted to validate the model by comparing simulation and experimental signals at various rotation speeds. The results indicate that the occurrence of tilting-impact phenomena in dry conditions requires external disturbances, and the discs eventually stop tilting-impacting once the disturbance subsides, and the system with deformed discs experiences longer recovery times. Furthermore, the tilting-impact forces in systems with deformed discs are smaller than those with flat discs only.

Experimental and FE Investigation on the Influence of Impact Load on the Moment Transmission of Smooth Shaft–Hub Connections

A well-known phenomenon in machinery systems is the easing of a blocked connection of mechanical parts after an impact hit close to the connection. Such impact hits may also arise in shaft–hub connections such as gears, crankshafts, or other parts. The objective of this study is to investigate the influence of local impact loads on the transmittable torque of smooth shaft–hub connections. In a specially designed test rig, it was demonstrated that the transmittable torque of the shaft–hub connection is reduced as a consequence of the impact, resulting in a reduction in the frictional force and slippage of the hub. Increasing the impact load leads to an increase in the reduction in the frictional force as well as the slippage and reduces the transmittable torque. By carrying out a modal analysis of the relevant parts and FE simulations of the impact, two possible reasons have been identified: (i) the impact load excites a vibration mode in the connection which reduces the frictional force and the transmittable torque; and (ii) the impact causes local deformation of the shaft, which results in local slip.

Traction on Rods within Cylinders Containing Grains: An Analogy with the Upward Movement of Trees in Tornadoes

In this work, the frictional traction forces developing in the annular space between two concentric vertical cylinders consisting of the outer surface of a cylindrical rod and the inner sidewall of a wider circular cylinder will be analyzed. The experiments carried out for this study allowed us to measure the traction on the rod for several filling heights, H. For the rod, it is possible to find a linear relation between the theoretically computed traction Trod and the traction measured experimentally, TrodM. Based on these results, it is possible to understand the fascinating phenomenon of the lifting, by the rod, of the weights of the mass of grains and of the outer cylinder. Finally, a physical analogy between this problem and the upward movement of trees in tornadoes can be identified.