Frictional Problems Research Articles

A Composite Material an alternative for manufacturing of Automotive Disc Brake: A Review

The brake disc is an indispensable component of an automobile especially in this trending era of electric mobility, where gasoline engines are superseded by electric vehicles in which prominent criteria is to lower down the weight to enhance the performance of the vehicle. Aluminum Metal matrix composites (MMC) play an important role because of researchers as these are not only used in automotive industries but aircraft and locomotives also. In most vehicles, these brakes are made up of Cast Iron which has well anti-wear properties and cheap too. But in certain other cases such as high-performance vehicles, these brake discs are not up to their standards of high performance because the cast iron brake discs are heavy and so reduces the vehicle’s performance to a particular extent. This paper reviews on fundamental function of Disc brake and the crucial challenges found in this review are, the problem of evolution of hazardous wear particles in an atmosphere, thermoelectric friction problem during braking, friction-induced vibration which causes squeal, the behavior of abrasive particles, and dynamic stability analysis, etc. an alternative to cease these problems possibly is to adopt novel material

Topology optimization of elastic contact problems using B-spline parameterization

This work extends B-spline parameterization method to topology optimization of elastic contact problems. Unlike the traditional density-based method, design variables directly refer to the control parameters of the B-spline. A continuous pseudo-density field representing the material distribution over the concerned design domain is constructed by means of B-spline parameterization and then discretized onto the finite element (FE) mesh. The threshold projection is further introduced to regularize the B-spline pseudo-density field for the reduction of gray areas related to the local support property of B-spline. 2D and 3D frictionless and frictional problems are solved to demonstrate the effectiveness of the proposed method. Results are also compared with those obtained by the traditional density-based method. It is shown that the B-spline parameterization is independent of the FE model and suitable to deal with contact problems of inherent contact nonlinearity. The optimized configuration with refined details and smoothed boundaries can be obtained.

An Evolutionary Based Method for Solving the Nonlinear Gripper Problem

ABSTRACT This paper presents an Evolutionary Programming based (EP) solution for the nonlinear frictional gripper problem for both the isotropic and orthotropic cases. The presented method is compared with other methods that involve piecewise linearization of the friction law, and methods that are based on the solution of Nonlinear Complementarity Problem (NCP). The EP method could generate more optimal solutions than those of other methods. Numerical examples that illustrate the proposed method are presented.

On a New Nonlinear Reduced-Order Model for Capturing Internal Resonances in Intentionally Mistuned Cyclic Structures

Abstract Cyclic structures such as turbomachinery present material and geometrical variations between sectors. These discrepancies are called mistuning and break the cyclic symmetry of the structure. Computing the forced response of mistuned cyclic structures is thus a numerical challenge. The component nonlinear complex mode synthesis (CNCMS) is one of the few nonlinear reduced-order model (ROM) formulations that allow to compute the nonlinear response of tuned and mistuned structures. It has been validated successfully for friction problems. However, in the presence of geometric nonlinearities, internal resonances may arise and they cannot be captured correctly with the CNCMS method. The purpose of this work is therefore to present a new methodology for developing a nonlinear ROM that can successfully capture internal resonances for tuned and mistuned structures. This method, called component mode synthesis with nonlinear reevaluation (CMSNR), is based on a variation of the CNCMS approach. The final modal synthesis uses a multiharmonic procedure and a reevaluation of the nonlinear forces on each sector independently. The performance and limitations of the proposed approach are assessed using a simplified example of a blisk subject to polynomial nonlinearities. Different internal resonances are exhibited and studied depending on the type of excitation force and on the level of mistuning.

A Kind of FM-BEM Penalty Function Method for a 3D Elastic Frictional Contact Nonlinear System

In this paper, a kind of node_face frictional contact FM-BEM penalty function method is presented for 3D elastic frictional contact nonlinear problems. According to the principle of minimum potential energy, nonpenetrating constraints are introduced into the elastic frictional contact system as a penalty term. By using the least square method and penalty function method, an optimization mathematical model and a mathematical programming model with a penalty factor are established for the node_face frictional contact nonlinear system. For the two models, a penalty optimization IGMRES (m) algorithm is proposed, and the influences of different penalty factors on the solution of the whole system are analyzed. Finally, a numerical simulation is carried out for two elastic frictional contact objects, and some important results including displacements, pressures, friction forces, and friction slips in the contact area are presented. Theoretical analysis and numerical experiment show that the newly presented FM-BEM penalty function method not only is efficient and practical but also has much superiority. It is easy to implement, and it is fast convergent with good stability.

Structure Optimization Design of Pulseoscillation Amplifier for Hydraulic Oscillator Based on Numerical Simulation

Hydraulic oscillator is one of the effective tools to solve the problem of high friction in directional drilling and horizontal drilling. However, there are some problems with this kind of tools such as high pressure loss and insufficient vibration force. Because of its self-excited oscillation characteristics, pulse oscillation amplifier can realize the amplification of pulse jet pressure under the condition of lowpressure loss, which is one of the effective ways to solve the above problems of hydraulic oscillator. In this paper, according to the working characteristics of hydraulic oscillator and the demand of pulse amplification, the structure of pulse oscillator amplifier was optimized based on numerical simulation method. Firstly, the geometric and numerical models of the pulse oscillator amplifier were constructed, and the flow field distribution and pulse amplification effect of the pulse oscillation amplifier under different structural parameters were simulated and analyzed, and the influence of different structural parameters on the pulse amplification effect was explored. Secondly, the structure of the pulse oscillator amplifier was optimized by Response Surface Method, and the optimal structure based on the effect of outlet pressure amplification was obtained: upper nozzle diameter D1=22mm, upper nozzle length L1=26mm, lower nozzle diameter D2=28mm, lower nozzle length L2=28mm, cavity length L=58mm, cavity diameter d=80mm, angle 60°. Its pressure loss was 0.3MPa and outlet pressure peak value was 4.5MPa, which was 1.8 times of the inlet pressure peak value of 2.5MPa. Finally, the minimum relative error between the experimental results and the numerical simulation results was 4%, which has verified the credibility of the numerical simulation and structural optimization results.

The application of braden scale and rough set theory for pressure injury risk in elderly male population

Background: The elderly with a limited body or bedridden are prone to pressure injury, and the Braden scale is often used as a risk assessment tool. However, few studies have explained the relationship between risk factors and risk levels using machine learning methods from Braden clinical observation data. Additionally, nearly half of the elderly over 75 years old in China are men. Purpose: This study aimed to establish a pressure injury risk prediction model for elderly male patients using a machine learning method based on hospital clinical data. It further analyses the importance of risk factors and risk levels. Methods: This study's Braden observation data were obtained from the electronic medical records of elderly male patients from 27 October 2019 to 1 November 2020 in the case hospital. Rough set theory was used to identify the perception patterns between risk factors and risk levels based on the data. Results: The importance of rough set theory showed that sensory perception and nutrition are key risk factors for identifying elderly male inpatients. Therefore, nurses should pay special attention to the measurement scores of these two risk factors. Moreover, this method also revealed conditions/decision rules for different risk levels. Among elderly male inpatients at risk of severe pressure injury, 42% of the observation data showed that their physical condition is completely limited in sensory perception, possibly insufficient nutrition, friction and shearing problems, and bedridden activities. Conclusion: This model can effectively identify the critical risk factors and decision rules for different risk levels for pressure injury in elderly male inpatients. This allows nurses to focus on patients at a high risk of possible pressure injury in the future without increasing their workload. This study also provides a way to solve the problem that the Braden scale shows insufficient predictive validity and poor accuracy in identifying patients with different pressure injury risk levels, so it cannot fully reflect patients' characteristics.

Friction properties of suspended graphene

Minimizing friction is a goal that has long been pursued in history. The role of micro-electromechanical system and nano-electromechanical system (MEMS/NEMS) in electronic devices is becoming more and more important. Due to the increasingly small size of the device, large surface-to-volume ratio leads to severe friction and wear problems of the device, thus limiting its performance. Graphene is considered as a good lubricating material in MEMS/NEMS due to its extremely thin size and excellent anti-friction effect. The study of nano-friction properties of graphene is of great significance in further developing the MEMS/NEMS. In this work, microporous arrays are prepared on a SiO<sub>2</sub>/Si substrate, and graphene is stripped on the micropores to form a suspension structure. The friction properties of suspended graphene and supported graphene are measured by using atomic force microscope. The results show that the nanofriction on suspended graphene is significantly reduced compared with that on supported graphene. The supported graphene experiences a frictional enhancement effect because of the puckering effect, while the friction enhancing effect disappears in the suspended graphene. With the increase of graphene thickness, the out-of-plane stiffness increases gradually, and the friction difference between suspended graphene and supported graphene decreases gradually. In addition, the nanofriction properties of suspended graphene under new tip and pretreated tip are also different. The friction between the pretreated tip and graphene is significantly higher than that between the new tip and graphene. The surface friction difference between the suspended graphene and the supported graphene decreases when the pretreated tip is used compared with the new tip. This work demonstrates that the deformability of atomic-scale structures can provide an additional channel of regulating the friction of contact interfaces. By comparing the changes of surface friction between the suspended graphene and the supported graphene with different thickness and tip sizes, the influence of out-of-surface deformation on the friction of graphene is revealed, thus providing theoretical guidance for effectively improving the friction performance of graphene solid lubricant.

A sphere-triangle contact model with complex boundary face problems

This paper proposes a sphere-triangle contact model for three-dimensional sphere discontinuous deformation analysis to simulate complex boundary face problems often encountered in engineering. First, the detection of sphere-triangle contact and the calculation of corresponding sphere-triangle contact submatrices for building a sphere-triangle contact model are described. Then, the correctness of the proposed model is preliminarily verified by simulating the sphere-plane/edge/vertex contact, sphere-triangle friction problem and a complex boundary face problem. Furthermore, a rigorous open-close iteration is proposed to guarantee the correctness of setting penalty springs for sphere-triangle contacts, to ensure computational stability of three-dimensional sphere discontinuous deformation analysis. Meanwhile, two imperceptible fatal errors (i.e., direction deflection error and oscillation error) hidden in the sphere-triangle contact model are estimated, which reveals that a larger sphere or a higher collision velocity at a sphere-triangle contact leads to larger errors. In addition, an algorithm for excluding invalid contacts is proposed to avoid these fatal errors, enhancing the robustness of the proposed contact model. Finally, a landslide simulation with 80,974 spheres, 76,382 triangles and 150,000 calculation steps is conducted, further validating the proposed model in large-scale simulations. This work indicates the feasibility of the proposed model for simulating complex boundary face problems.

Моделирование теплообмена и трения в тонком воздушном ламинарном пограничном слое над боковой поверхностью затупленного конуса малого удлинения

It is not possible to obtain a high-quality solution to a convective heat transfer problem without numerically integrating the differential equations describing the boundary layer, which involves a whole range of computational issues. Developing relatively simple yet adequately accurate computation methods becomes crucial. Using the effective length method may be considered to be the first step towards solving this problem. This method boasts an accuracy of convective heat transfer calculation that is acceptable in practice, due to which it became prevalent in aircraft design. However, this method is also relatively labour-intensive, although significantly less so than numerical integration of the boundary layer differential equations. The most efficient approach to solving heat transfer and friction problems in engineering practice would be using simple algebraic equations based on fitting the results of rigorous numerical computations or experimental investigations. Regrettably, there is no information published regarding how accurate these equations are for various operation conditions. The paper presents a solution to this problem based on deriving systematic numerical solutions to the boundary layer equations in the most rigorous analytical statement, along with conducting a thorough analysis of the equation accuracy for both the equations derived and previously published

Numerical Analysis of the Coupling between Heat Transfer and Deformation in Rotary Air Preheater

The rotary air preheater is one of the leading heat exchangers to be employed in steam power plants. However, thermal stress induced deformation of the rotor significantly decreases the efficiency of preheating system. The countercurrent arrangement of hot flue gas and cold air is the direct cause of greater temperature difference across the rotor, which leads to a mushroom deformation, and then serious problems of air leakage and mechanical friction. In this study, a numerical investigation was newly performed by the analysis modules of Fluid Flow (FLUENT) and Static Structural through ANSYS Workbench to couple heat transfer and thermal stress deformation in the rotary air preheater. Porous media method along with the local non-equilibrium thermal model was adopted to accurately obtain the temperature distributions of both matrix and gas. Good agreements were yielded by comparing the simulation results and experimental data. The effects of operational and structural parameters, i.e., the temperature difference between the hot and the cold ends, the rotation angle, the height, and the radius on thermal deformation behavior of the entire rotor were investigated in detail. The droopy deformation at the hot and the cold ends increases with the temperature difference and radius, whereas increasing the height of rotor has the opposite influence. With the rotation of matrix, the maximum droopy deformation is located at the entrance of flue gas section and the minimum occurs when reaching the air section. Furthermore, a series of formulas were presented with nonlinear curve fitting to evaluate the deformation amount, which were proved to be of excellent accuracy and can be a better guidance for the seal system of the preheater.

Further results on advanced robust iterative learning control and modeling of robotic systems

Recently, calculus of general order [Formula: see text] has attracted attention in scientific literature, where fractional operators are often used for control issues and the modeling of the dynamics of complex systems. In this work, some attention will be devoted to the problem of viscous friction in robotic joints. The calculus of general order and the calculus of variations are utilized for the modeling of viscous friction which is extended to the fractional derivative of the angular displacement. In addition, to solve the output tracking problem of a robotic manipulator with three DOFs with revolute joints in the presence of model uncertainties, robust advanced iterative learning control (AILC) is introduced. First, a feedback linearization procedure of a nonlinear robotic system is applied. Then, the proposed intelligent feedforward-feedback AILC algorithm is introduced. The convergence of the proposed AILC scheme is established in the time domain in detail. Finally, simulations on the given robotic arm system confirm the effectiveness of the robust AILC method.

Influence of frictional contact on indentation of elastic layer under surface energy effects

The paper examines the influence of frictional contact on an indentation problem of a finite-thickness elastic layer under a rigid flat-ended cylindrical indenter considering surface energy effects based on Coulomb friction model. The continuum-based approach corresponding to the complete version of Gurtin-Murdoch surface elasticity model is adopted to demonstrate the influence from surface energy. Normal and radial displacement boundary conditions in the contact region corresponding to the frictional indentation problem is formulated in the term of integral equations by employing the relevant displacement Green's function obtained by the use of Hankel integral transform. The contact tractions are solved by applying a collocation technique together with the assumption of a piecewise distribution for the tractions within each discretized annular ring element. The accuracy of proposed solution scheme is validated with existing solutions from classical continuum mechanics for frictional indentation problem of an elastic half-space. Selected numerical results are presented to demonstrate the influence of friction effects on the elastic fields of the layer under the influence of surface energy. It is found that the consideration of frictional contact makes the layer stiffer when compared to the frictionless indentation, and the influence of friction effect is smaller when the surface energy effects are accounted for. In addition, the elastic fields of the layer are clearly size-dependent and the elastic layer becomes stiffer with the presence of surface stresses.

XIII International Scientific Conference “Tribology for Mechanical Engineering” (TriboMash 2020), 14-16 October 2020, Russia, Moscow

Blagonravov Mechanical Engineering Research Institute of the Russian Academy of Sciences holds a scientific conference «Tribology for Mechanical Engineering” every two years since 1982. XIII international conference «Tribology for Mechanical Engineering” was held on October 14-16, 2020 in Moscow, Russia. Purposes of the conference include discussion of current theoretical and applied problems of friction, wear and lubricant, generalization of the latest results of advanced calculation and experimental researches in relation to work of various branches of mechanical engineering (transport, machine-tool construction, space, oil and gas, etc.), the analysis of researches in the nanotribology, development of new highly effective methods of a tribomonitoring and creation new highly effective antifrictional, wear-resistant materials and lubricants.In 2020, the conference was held virtually due to restrictions related to COVID19 using the ZOOM platform. The organizers were located at the Blagonravov Mechanical Engineering Research Institute of the Russian Academy of Sciences, Moscow, Russia.The meetings were held in the format of a speech with an oral presentation. For each participant was allotted 15 minutes including questions. Plenary sessions were held on the first day of the conference. 93 scientists from various cities of Russia and Belarus participated in the conference in 2020. The organizing committee selected 26 articles of the participants for publication in the collection of works. The conference passed without major problems. Organizing committee connected many participants virtually. The exhibition part of the conference was impossible due to the remote presentation. This negatively affects the development of the experimental part of the tribological research.List of Conference Committee is available in this pdf.

A novel nonsmooth approach for flexible multibody systems with contact and friction in 3D space

For computational multibody system dynamics, contact and friction problems are very complex and important problems. Therefore, this paper proposes a novel nonsmooth method for flexible multibody systems with contact and friction in 3D space. Considering the nonsmooth effect of contact and friction on the state variable of the multibody systems, the proposed method is divided into two parts: (i) the change of state variables under the action of smooth force and (ii) the change of state variables caused by contact and friction. Furthermore, for the contact part, the Newton’s impact law and the classical Coulomb friction model are employed to deal with normal impact contact impulse and tangential friction contact impulse, respectively. In addition, Fischer–Burmeister function and Karush–Kuhn–Tucker conditions are also used to solve the normal impact contact impulse and tangential friction contact impulse. What’s more, since the symplectic discrete format performs well robustness to numerical results, the discrete format of the proposed method is based on the symplectic discreteness, and it is expected to obtain the robust numerical results. Finally, several numerical examples are tested by the proposed nonsmooth method, and the numerical simulation results verify the effectiveness of the proposed approach.

Development of Slurry Surfacing with Electric Arc Furnace Slag for Pavements with Friction Problems

Pavement maintenance is an essential activity for maintaining the quality of the pavements. It is common for the ageing pavement to present problems of friction, so a proper solution must be provided. In this work, electric arc furnace slags are incorporated in slurry surfacing to provide adequate friction with this technique. The electric arc furnace slag was studied with physical, chemical, and mechanical tests to evaluate its suitability in the formation of the bituminous mixture. At the same time, different groups of samples were made with increasing percentages of bitumen emulsion and slag as coarse aggregate, determining the wear of the different families and the cohesion. The results reflected the excellent characteristics of the electric arc furnace slags, and an optimal combination of materials (slag, aggregate, water, and bitumen emulsion) could be obtained to develop slurry surfacing applicable to important traffic roads. This provided a use for the electric arc furnace slag in which its mechanical properties were used and a sustainable bituminous mixture with excellent characteristics and respectful of the environment was developed.

Modeling and Experimental Verification of a Cable-Constrained Synchronous Rotating Mechanism Considering Friction Effect

Cable-Constrained Synchronous Rotating Mechanism (CCSRM) has an important application prospect in the field of cable-driven robots, which can greatly reduce the number of driving motors while ensuring the light and slender body. However, there are obvious cable friction effect and elastic deformation in CCSRM. These nonlinear characteristics have a significant impact on synchronous motion performance. In this letter, a model of CCSRM considering cable friction is proposed, which integrates the effects of cable pretension, elastic deformation, and friction between cable and pulley on system characteristics. The distribution law of cable tension under the influence of friction force and the phenomenon of motion hysteresis caused in reverse rotation are emphatically discussed. Then, an improved LuGre friction model is proposed to solve the problem of line contact friction between cables and pulleys. Further a dynamic model of CCSRM is established to simulate the motion characteristics of the whole process, including the discontinuous friction phenomenon in reverse rotation. Finally, an experimental prototype of two-axis synchronous rotating system is built, and the friction coefficient is identified. The experimental results show that the dynamic model can well simulate the motion characteristics of CCSRM.

Research on Non - contact Electromagnetic Loading Device for Water - lubricated Bearing

In order to deeply study the characteristics of water-lubricated bearing under load condition, a non-contact electromagnetic loading device is designed to solve the problems of friction, vibration and noise in the traditional contact loading methods such as hydraulic cylinder and weight, etc. The device consists of loading plate, E magnets, coil, programmable dc power supply, first of all, is derived by Maxwell’s three laws of the theoretical equation of electromagnetic force, and then, application of Solidworks, Ansoft Maxwell 18.2 software modeling and simulation of electromagnetic loading device structure, the final will be the electromagnetic simulation, comparing the theoretical results, the results show that the simulation and the theoretical value is less than 11.4%, validate the rationality and accuracy of the device.

Editorial: Friction and Multi-Field Problems in Sliding Contacts

Editorial: Friction and Multi-Field Problems in Sliding Contacts

Investigation of tribological characteristics of nickel alloy-based solid-lubricating composites at elevated temperatures under vacuum

The development of a high-performance solid-lubricating composite with excellent self-lubricity over a broad temperature range in vacuum is significant to solve the frictional problems of spatial mechanisms. In this study, the vacuum tribological behaviors of nickel-matrix/Ag/(Ca, Ba)F2/graphite (0–2 wt%) composites were studied from 25 to 800 °C. The results show that the synergistic effects of solid lubricants can significantly improve the tribological properties of the composites in vacuum, with the graphite content contributing considerably. For 2 wt% graphite, a low friction coefficient (0.14–0.25) and the lowest wear rate ((0.12−4.78)×10−5 mm3·N−1·m−1) were observed in vacuum over the entire testing temperature range. Moreover, the wear mechanisms were clarified via analysis of the chemical composition and morphologies of the sliding surfaces.