Frictional Problems Research Articles

Shape Optimization for Variational Inequalities: The Scalar Tresca Friction Problem

Shape Optimization for Variational Inequalities: The Scalar Tresca Friction Problem

Modeling, simulation, and implementation of a superconducting magnetic bearing twisting system in a high‐speed ring spinning process

AbstractThe implementation of a Superconducting Magnetic Bearing (SMB) system is a promising solution for the problem of friction exhibited in the twisting elements of the conventional ring‐spinning process. This research focuses on the development of a dynamical model with six degrees of freedom of the Permanent Magnet (PM) ring used in an SMB system for a high‐speed ring spinning process. The modeling takes into account the magnetic forces and torques that enable the magnetic levitation of the PM ring. Experimental tests allow the identification of unknown parameters of the model and the validation is done through simulations.

Super-Low Friction Electrification Achieved on Polytetrafluoroethylene Films-Based Triboelectric Nanogenerators Lubricated by Graphene-Doped Silicone Oil.

The novel proposal of Wang's triboelectric nanogenerator (TENG) has inspired extensive efforts to explore energy harvesting devices from the living environment for the upcoming low-carbon society. The inevitable friction and wear problems of the tribolayer materials become one of the biggest obstacles for attaining high-performance TENGs. To achieve super-low friction electrification of the TENGs, the tribological and electrical behaviors of the sliding-mode TENGs based on polytetrafluoroethylene (PTFE) films and metallic balls under both dry friction and liquid lubrication conditions were investigated by using a customized testing platform with a ball-on-flat configuration. Most interestingly, a super-low friction coefficient of 0.008 was achieved under graphene-doped silicone oil lubrication. The corresponding wear rate of the PTFE film was drastically decreased to 8.19 × 10-5 mm3/Nm. Simultaneously, the output short-circuit current and open-circuit voltage were enhanced by 6.8 times and 3.0 times, respectively, compared to the dry friction condition. The outstanding triboelectrical performances of the PTFE film when sliding against a steel ball are attributed to the synergistic lubricating effects of the silicone oil and the graphene nanosheets. The current research provides valuable insights into achieving the macro-scale superlubricity of the TENGs in practical industrial applications.

Yarn level finite element method simulation for bending over sheaves of braided ropes

The complex problem of ropes (cyclic) bending over sheaves (CBOS) is considered in this article. Ropes that are used to manoeuvre and regulate sails undergo a variety of dynamic stresses which are crucial yet difficult to determine, due to the complexity of the multi-scaled braiding structure of ropes. A full dynamic Finite Element Method (FEM) simulation of a braided rope bending over a sheave is conducted with the commercial software Abaqus/Explicit, as it can capture the complex processes occurring inside the rope to high accuracy. A theoretical deduction is performed to determine the yarn paths in a 3D braided structure. Relative movement between braided yarns (including the interlacing point) are better assessed at yarn level through 3D element types instead of the traditional beam elements, as they allow to obtain an estimation of yarn-yarn displacement. Parametric studies are conducted to better understand the factors that affect the yarn sliding. The ratio between the diameter of the sheave and the rope, and the braiding angle, are found to be crucial for the relative movement, while the number of yarns and their diameters have little influence. The successful simulation process demonstrates the feasibility of modelling and analysing the complex interaction occurring in braided structures under specific boundary conditions. The calculated estimated displacement can contribute to further investigations such as the friction and heat generation problem in braided ropes. Simulation with this method can provide alternatives in predicting lifespan of braided products that cannot be easily inspected.

Pump-Controlled AGC Micro-Displacement Position Control of Lithium Battery Pole Strip Mill Based on Friction Model

Electrode roll-forming refers to rolling a battery electrode into a preset thickness through the electro-hydraulic servo pump-controlled hydraulic roll gap thickness automatic control system (known to as pump-controlled AGC). Compared with the motor servo system, the friction problem of the electro-hydraulic servo system is more serious and the friction problem of the actuator itself is very prominent. Moreover, low-speed performance is one of its core indicators, the friction phenomenon is the most abundant during the low-speed stage and the impact on the servo system is also the most obvious. Therefore, for high-performance electro-hydraulic servo control, friction compensation is not only unavoidable, but also a very difficult problem. Aiming to influence the friction on the position control of the pump-controlled system of a lithium battery pole strip mill, the rolling mechanism and process procedure under micro-displacement position control based on the friction model were studied and compared from the perspective of considering friction factors, and a friction compensation controller based on the LuGre model was designed. The control precision of a pump-controlled AGC system was improved through combination with an adaptive robust controller. Because of the diversity of unmeasurable states of the system, a dual observer was designed, and the known model of the system was added to the observer. In the final comparative experiment, the steady-state accuracy of the friction adaptive robust compensation controller system based on the LuGre model reached ±0.3 μm, which is superior to the fuzzy IMC compensation and traditional PID control strategies.

Effects of Ni-5 wt% Al/Bi2O3 addition and heat treatment on mechanical and tribological properties of atmospheric plasma sprayed Al2O3 coating

To solve the problem of high friction and wear of the plasma sprayed Al2O3 coating in a wide temperature range, two Al2O3-based composite coatings, namely Al2O3-(NiAl-Bi2O3) coating and Al2O3-(NiAl-Bi2O3)-H coating (heat treatment), were prepared by involving Ni-5 wt% Al and Bi2O3, and applying a simple heat treatment. Compared to the Al2O3 coating, two Al2O3-based composite coatings attained increased toughness and adhesive strength. In particular, heat treatment endowed Al2O3-(NiAl-Bi2O3)-H coating with improved compositional homogeneity and more NiBi intermetallic compound and α-Al2O3 phases. In terms of tribological behavior, when subjected to rubbing against the counterpart Al2O3 ball, Bi2O3 and NiBi were shown to have good lubricating properties, and they exerted friction-reducing and anti-wear effects in both Al2O3-based composite coatings at 25 and 400 °C, respectively. At 800 °C, under the action of thermo-mechanical coupling, a tribo-oxide layer composed of multiple oxides (Al2O3, Bi2O3, NiO and Bi2Al4O9) was generated on the worn surface of the two composite coatings, achieving the excellent lubrication and wear-resistance.

Experimental investigations with Neodymium – Iron – Boron magnets with aluminum circular plates to find deceleration, time taken and stopping distance

There are quite a lot of problems in friction brake like squealing, peddle pulsation, structural failure due to high heat, circular plate distortions. Hence, the present work tries to focus on developing no contact brakes by applying induced magnetization principles. Aluminum circular plate along with Neodymium – Iron – Boron (NdFeB) rare earth magnets are chosen for the work. Thickness of circular plates considered are 4, 6 and 8 mm. Chosen Aluminum circular plates are rotated at velocities of 20.94 m/s, 31.39 m/s, 41.89 m/s and 52.36 m/s. Considered brake parameters are brake deceleration, time elapsed for braking and stopping distance. In solitary magnet situation under steady application, aforesaid brake parameters are inferior as compared to those in solitary magnet with swift application situation. Brake parameters were found to be quite superior in 4 mm thick circular plate in solitary magnet with swift application. Considering the parameters such as time elapsed for braking and stopping distance, no contact brakes with permanent magnets are very suitable for top velocity rail applications.

Unifikasi Kelompok Keagamaan Islam Berbasis Multi Interdisipliner menuju Masyarakat Madani

The purpose of this article is to reveal the problems of friction, conflict, and divisions that occur among Muslims, which are spread across several groups such as Nahdlatul Ulama, Muhammadyah, Jama'ah Islam, Tabligh Jama'ah, Salafi, and Ahmadiyah. In general, each group claims to be the most correct group, so they are trapped in bigotry based on their group, doctrin, tafwa, or their leaders. The method of this study is based on library research in which the approach is carried out in a multi-disciplinary manner, namely through the science of interpretation, hadith, ushul fiqh, and sociology. The method of this study is based on library research in which the approach is carried out in a multi-disciplinary manner, namely through the science of interpretation, hadith, ushul fiqh, and sociology. The results of the study found: 1) Islam highly upholds unity within the ummah. The prohibition of division has been imposed since the time of the prophet before the Prophet Muhammad was sent to the world. Therefore the existence of religious groups should be to strengthen people and religion, so as to try to avoid the perception of a single truth claim, so as not to be trapped in the fanaticism of the group, schools of thought, tafwa, as well as towards their leaders; 2) Unification of religious groups can occur if it is based on intellectual awareness. Because this awareness can penetrate across ideologies, ideologies, schools of thought, and/or cultures. Without this awareness, unification is difficult to achieve; and 3) Intellectual awareness can be achieved through intellectual collaboration between religious group leaders. In fact, this intellectual awareness is a gateway to civil society, which has the characteristics of being open to knowledge, egalitarianism, and equality in the community, respecting human rights, respect for achievements, and being highly civilized and abandoning primordial attitudes.

Characterization of a novel fluidic friction-reduction tool used in extended-reach well considering periodic particle-laden jet

Fluidic oscillators (FOs) can be used as an efficient fluidic vibration tool to solve high friction problems in extended-reach wells. However, the complex mechanism of FOs makes the design challenging, and the dynamic erosion behavior inside FOs is still unclear. In this paper, new FOs are proposed and the working characteristics under the influence of periodic particle-laden jets are investigated. Firstly, the results reveal the working mechanism of new FOs, showing that the generation of pressure pulses is closely connected with periodic jet switching and the development of vortices. Secondly, the important performance parameters, i.e., pressure pulse and oscillation frequency, are extensively studied through numerical simulation and experimental verification. It is found that the performance can be optimized by adjusting the tool structure according to different engineering requirements. Finally, the oscillating solid-liquid two-phase flow inside FO is studied. It is demonstrated that the accumulation of particles leads to a significant reduction in performance. The results also reveal five locations that are susceptible to erosion and the erosion behavior of these locations are studied. It has been shown that the periodic jet causes fluctuations in the amount of erosion at the outlet and splitter. This research can provide valuable references for the design and optimization of vibration friction-reduction tools.

The history of the development of the regular straight stem in hip arthroplasty.

Since the middle of the 20th century, total hip arthroplasty has become a very successful treatment for all end-stage diseases of the hip joint. Charnley solved with his low frictional torque arthroplasty the problem of wear and friction with the introduction of a new bearing couple and the reduction of the head size, which set the prerequisite for the further development of stem design. This narrative review presents the major developments of regular straight stems in hip arthroplasty. It does not only provide an overview of the history but also assembles the generally scarce documentation available regarding the rationale of developments and illustrates often-unsuspected links. Charnley's success is based on successfully solving the issue of fixation of the prosthetic components to the bone, using bone cement made of polymethyl-methacrylate. In the field of cemented anchorage of the stem, two principles showing good long-term revision rates emerged over the years: the force-closed and the shape-closed principles. The non-cemented anchorage bases on prosthesis models ensure enough primary stability for osteointegration of the implant to occur. For bone to grow onto the surface, not only sufficient primary stability is required but also a suitable surface structure together with a biocompatible prosthetic material is also necessary.

Design, fabrication and experiments of a hydraulic active-passive hybrid prosthesis knee.

Due to low friction, passive mechanical prostheses move compliantly followed by the stump and are used widely. Advanced semi-active prostheses can both move passively like passive prostheses and provide active torque under specific conditions. However, the current mechanical-hydraulic coupling driven semi-active prostheses, in order to meet the low passive friction requirements with a low active transmission ratio, lead to a significant problem of insufficient active torque. A hybrid active and passive prosthesis was developed to solve the incompatibility problem of low passive friction and high active driving torque of semi-active prostheses. The mechanical structure and control strategy of the prosthesis were demonstrated. The performance of the prosthesis was tested by bench and human tests. Passive subsystem damping adjustment ranges from 0.4 N⋅(mm/s)-1 to 300 N⋅(mm/s)-1. The switching time between the damping and the active subsystem is 32 ± 2 ms. The continuous active torque output is more than 24 Nm. In level walking, the peak torque is about 28 Nm. The proposed active-passive hybrid hydraulic prosthesis could satisfy both low passive friction and high active actuation.

Influence of Functionally Graded Protective Coating on the Temperature in a Braking System.

A mathematical model of heat generation due to friction in a disc-pad braking system was developed with consideration of a thermal barrier coating (TBC) on the friction surface of the disc. The coating was made of functionally graded material (FGM). The three-element geometrical scheme of the system consisted of two homogeneous half-spaces (pad and disc) and a functionally graded coating (FGC) deposited on the friction surface of the disc. It was assumed that the frictional heat generated on the coating-pad contact surface was absorbed to the insides of friction elements along the normal to this surface. Thermal contact of friction between the coating and the pad as well as the heat contact between the coating and the substrate were perfect. On the basis of such assumptions, the thermal friction problem was formulated, and its exact solution was obtained for constant and linearly descending specific friction power over time. For the first case, the asymptotic solutions for small and large values of time were also found. A numerical analysis was performed on an example of the system containing a metal ceramic (FMC-11) pad, sliding on the surface of a FGC (ZrO2-Ti-6Al-4V) applied on a cast iron (ChNMKh) disc. It was established that the application of a TBC made of FGM on the surface of a disc could effectively reduce the level of temperature achieved during braking.

Tribological properties of NiCrAlYTa-Ag self-lubricating coatings at wide temperature range by detonation spraying

High-temperature self-lubricating materials are an appropriate choice to solve the problem of friction and wear for elevated temperature mechanical systems. In this study, NiCrAlYTa-Ag self-lubricating coatings used in a wide temperature range were prepared by the detonation gun spraying method. According to the findings, NiCrAlYTa-Ag coatings are composed of γ/γ', β-NiAl and Ag phases. The hardness and bonding strength of the coating decrease with the addition of Ag, and the coating with 20 % Ag has a high bonding strength of 43 MPa and a hardness of 303 Hv. The coating exhibited a friction coefficient of 0.35–0.47 and a wear rate of 4 × 10−5–6 × 10−5 mm3/N m From room temperature to 900 °C. At low temperatures, lubrication behavior was mainly attributed to the formation of Ag films. Excitingly, the AgTaO3 with good lubrication performance was created at high temperatures by a tribo-chemical reaction, which plays a synergistic lubrication role with Ta2O5, NiO, and Cr2O3.

Wear Resistance of Bio-Polymer Composite Base on Cotton Post-Harvest Line Residues

New trend in material engineering are composites with biological-based fillers. On of aim in biological-bases composite is how to use waste from agriculture production i.e. unused secondary products known as residues. The aim of this research is experimental investigation of wear resistance of bio-polymer composite reinforce by cotton post-harvest line residues. These residues come from cotton production as a waste which contain cotton stems and plant roots. Most of these residues are burned as energy source, but residues can find other utilization. Composites based on polymer can solve friction and wear problems in industry for their advantages as self-lubrication, light weight, easy of properties modification, etc. This research is part of wide study dealing with material utilization of post-harvest line residues. Mass loss of wear resistance at composite PCFC 500 with short fibres decrease against the matrix up to 21% on 19.28 mg.

Reconstruct lower‐dimensional crack paths from phase‐field point cloud

AbstractBecause of the smeared representation of phase‐field fracture, reconstructing lower‐dimensional crack paths is challenging, which may impede the further applications of the phase‐field method in the modeling of fault friction and fluid flow in fracture. In the present work, we propose to capture the crack curves or surfaces from two‐dimensional or three‐dimensional phase‐field point cloud using an optimized ridge regression algorithm, and k‐nearest neighbor and principal component analysis are used to estimate the normal direction of each segment on the identified discrete crack path. The sensitivity and computational efficiency of the proposed method are investigated thoroughly. Subsequently, this method is extended to reconstruct the complex discrete fracture networks. Finally, several benchmarks for fracture, fault friction and fluid flow problems are presented to demonstrate the strength of the proposed approach.

A fluid-structure coupled transient mixed lubrication model for piston ring lubrication property analysis with CMFF method

The bore's circumferential cross-section is not always a perfect circle, due to manufacturing errors, installation, and the influence of high-temperature and high-pressure gas, especially for a cylinder liner of the two-stroke marine diesel engine. This non-axisymmetric feature significantly impacts the lubrication properties of the piston ring and cylinder liner tribo-pair. To study the tribology and lubrication properties of the tribo-pair, a fluid-structure coupled transient mixed lubrication model is developed, which incorporates the piston ring curved beam model and mixed lubrication model. The key challenge lies in integrating the interface contact issue between the piston ring and bore with the structural deformation, requiring a multi-scale modeling strategy. To address this challenge, a method of coupling mesh between the finite difference method and the finite element method (CMFF) is proposed. The approach achieves the requirement for a fine mesh for the interface contact solution while maintaining the accuracy of the curved beam model for the structural response of the piston ring. Based on the model, the lubrication performance and deformation behavior of the piston ring in an elliptical bore are comprehensively analyzed. The results are compared with those of the rigid ring model to explore the overall differences. Results reveal that the current model predicts the friction is mostly caused by asperity contact between solids at the top dead center, whereas the rigid ring model predicts viscous shearing of the lubricant. The discrepancy is mainly due to the reduction of the oil film thickness between the piston ring and the cylinder liner following the consideration of ring deformation. Moreover, the minimum clearance exhibited at the piston ring end gap demonstrates the thorough consideration of the local and global lubrication performance of piston rings in the proposed model. This is significant for the resolution of local friction and wear problems of piston rings in engineering applications. Based on the work, a new framework is established for the study of the coupled performance of piston ring dynamics and tribology.

Gradient recovery type a posteriori error estimates of virtual element method for an elliptic variational inequality of the second kind

In this paper, gradient recovery type a posteriori error estimators of virtual element discretization are derived for a simplified friction problem, which is a typical elliptic variational inequality of the second kind. Both the reliability and the efficiency of the error estimators are proved. In addition, one numerical example is presented to show the efficiency of the adaptive VEM based on the derived error estimators.

A Study of the Thermal Behavior of Some Materials Used to Prevent Corrosion in Mechanical Parts

Thermal deterioration of Machines is the change in the properties of the basic material as a result of thermal reaction with its environment as a result of the presence of moisture in the bodies of machines such as the bodies of aircraft, cars, engineering equipment and related to the mechanics of the machines in the field of mechanical engineering, which is called the medium of deterioration and not as a result of a mechanical process such as friction in the machines as a result of work Continuous in these machines, according to this definition there is a possibility of corrosion not only in metals, but other materials such as concrete and containers that are in direct contact with moisture, air and environmental factors that are a catalyst for mechanical deterioration. Many researchers in mechanical engineering were interested in the thermal processes of machines, so the problem of corrosion and friction of machines and other important problems that have been studied extensively by finding engineering solutions to reduce or eliminate them. Corrosion of Machines be a limiting factor for various materials in many applications. Thus, it is necessary to have a better understanding of the deterioration processes, their prevention and reduction of the associated damage. In this research the preparation of some reagents and their use as deterioration inhibitors to reduce the deterioration process in engineering machinery by measuring the loss in weights resulting from the phenomenon of deterioration in engineering machinery. These thermal reagents were prepared as a thermal inhibitor painting, diagnosed in spectroscopic techniques, and then some thermal measurements were made to studying them as inhibitors of engineering corrosion in machines. The results appeared that the prepared reagents are good deterioration’s inhibitors due to the inhibition efficiency of the selected thermal reagents increased with increasing of concentration, and decreased with increasing of temperature.

3D Surface-to-Surface Contact Algorithm for SPH Method and Its Application to Simulation of Impact Failure of Ceramic Plate

This work presents a three-dimensional (3D) surface-to-surface contact algorithm for SPH method and its application to the simulation of material failure during high velocity impact of a projectile on a ceramic plate. In the present contact algorithm, surfaces of 3D objects represented by SPH particles are reconstructed. Based on the reconstructed surfaces, a box test followed by a crossover test is employed to detect contacts between different objects, and a penalty method is employed to enforce contact conditions between contact pairs identified by contact detection. Validation examples are presented to demonstrate the accuracy and capability of the algorithm. The calculated results show that the present contact algorithm can achieve high accuracy and it is capable of handling various contact problems, including frictionless and frictional problems as well as small and significant deformation problems. The algorithm is then used to simulate the high velocity impact of a projectile on a ceramic plate. The material failure of the projectile and the ceramic plate is reproduced, and the residual velocity of the projectile is well predicted.

Use of Functionally Graded Material to Decrease Maximum Temperature of a Coating–Substrate System

A mathematical model for determining the temperature distribution in the system consisting of a coating deposited on the surface of substrate was proposed. The foundation material is homogeneous, while the coating is made of a functionally gradient material (FGM) with thermal conductivity increasing exponentially along the thickness. Heating processes of the outer surface of the coating were considered with a constant and linearly decreasing in time intensity of the heat flux. Such thermal loads are common in thermal problems of friction, particularly regarding frictional heating during braking. An exact (in quadrature) solution of the corresponding boundary-value problems of parabolic heat conduction was obtained. Asymptotic solutions to these problems were also found for small and large values of the Fourier number. Calculations were performed for a coating made of two-component FGM ZrO2-Ti-6Al-4V, applied on a cast iron substrate. In order to explain the effect of FGM on temperature, corresponding analysis was carried out for the coating made of a homogeneous (ZrO2) material.