Friction Research Articles

Clamping Force Estimation for Electro-Mechanical Brake Based on Friction Torque Fusion Approach

Electromechanical brakes (EMB) are anticipated to become the standard brake system in the future, gaining favor among researchers and automobile manufacturers due to their numerous advantages. However, to achieve cost competitiveness, expensive load cells used to measure the clamping force on the disc must be replaced with a clamping force estimation algorithm. To do this, an algorithm is first developed to estimate the pad contact point, which represents the point of contact between the pad and the disc, to determine where the clamping force occurs. Subsequently, this paper proposes a novel Kalman filter approach utilizing friction torque fusion for clamping force estimation. Specifically, the estimation performance is enhanced by incorporating both dynamic and static friction torque models. The proposed estimation algorithm is validated by comparing its results with the actual clamping force measured using a load cell sensor. Furthermore, experimental tests are conducted to confirm whether the proposed estimation algorithm maintains its performance under various control reference conditions, and overall, the estimation error was within about 5% in this paper.

Investigating slope stability of multiple stopes prone to instability in the Ziluoyi iron ore mining site

The ore mining sites commonly experience slope instability, which is causing concern for the workers’ safety and the operation’s stability. Considering the Ziluoyi iron ore mining site as a case study, uniaxial compression strength and shear tests are performed on the lower disk peripheral rock, ore body, and upper disk peripheral rock, leading to the extraction of compressive strength and elastic modulus (lower disk: 77.7 MPa–9.093 GPa; ore body: 19.6 MPa–4.619 GPa; upper disk: 55.47 MPa–5.573 GPa). Further, using the Hoek–Brown criterion in conjunction with the Moher–Columb criterion, the cohesion and internal friction angle of various samples are appropriately determined (lower disk: 21.124 MPa–35.614°; ore body: 21.66 MPa–26.5°; upper disk: 42.916 MPa–25.743°). By employing an appropriate rock mass reduction model, its constants (m and s) and RMR score for the consisting layers (schist layer and ore body) of the three understudy slopes (Slope#1–Slope#3) are evaluated. An effective algorithm based on the Morgenstern–Price method is employed and its effectiveness is also proved by comparing its factor of safety results with those of Geo-Slope for various slope structures subjected to different loads. Subsequently, the stability analyses of various slopes are methodically examined by predicting the factor of safety values under multiple types of loading (i.e., self-weight + groundwater, slope self-weight + groundwater + blasting vibration force, and self-weight + groundwater + seismic force). The factor of safety values of the slopes pertinent to Slope#1/Slope#2/Slope#3 subjected to the above loading conditions are obtained as 1.354/1.273/1.188, 1.326/1.239/1.169, and 1.321/1.232/1.162, respectively. Upon comparing these results with those of a valid homeland specification, it becomes clear that the results are able to meet safety standards and ensure efficient mine operation.

Numerical evaluation of the internal fracture mechanism of horizontal loop connections in precast elements under the influence of transverse reinforcement

AbstractThis study numerically evaluated the flexural capacity and fracture mechanism of precast reinforced concrete beams connected with in situ horizontal loop connections employing the three‐dimensional rigid body spring model (3D‐RBSM) for modeling of concrete and beam elements (BEs) for modeling of steel, respectively. The research analyzed the performance of continuous horizontal loop connections with and without transverse reinforcement, considering varying vertical spacing between loops and transverse steel ratios. The numerical model effectively captured the test load displacement relationships by incorporating the model parameters like Young's modulus, tensile strength, fracture energy, compressive strength, cohesion, and angle of internal friction for concrete along with mechanical properties of steel and revealed that loop joints without transverse reinforcement exhibited loop type failure. In contrast, specimens with transverse reinforcement improved the peak load and caused compression failure. It was discovered that transverse rebars on the continuous side of the joint experience more strain; particularly, the maximum strain occurred in the corner rebars within the curved sections of U‐rebars. Moreover, the increased vertical spacing between the loop rebars increased the diagonal crack propagation and demonstrated the loop‐type failure. Further, a larger circumferential area of transverse rebar offered greater bond strength and confinement to the concrete core and reproduced the maximum deformation capacity, ductility, and compression failure.

A Hybrid Lagrangian–Eulerian Formulation of Thin‐Shell Fracture

AbstractThe hybrid Lagrangian/Eulerian formulation of continuum shells is highly effective for producing challenging simulations of thin materials like cloth with bending resistance and frictional contact. However, existing formulations are restricted to materials that do not undergo tearing nor fracture due to the difficulties associated with incorporating strong discontinuities of field quantities like velocity via basis enrichment while maintaining continuity or regularity. We propose an extension of this formulation to simulate dynamic tearing and fracturing of thin shells using Kirchhoff–Love continuum theory. Damage, which manifests as cracks or tears, is propagated by tracking the evolution of a time‐dependent phase‐field in the co‐dimensional manifold, where a moving least‐squares (MLS) approximation then captures the strong discontinuities of interpolated field quantities near the crack. Our approach is capable of simulating challenging scenarios of this tearing and fracture, all‐the‐while harnessing the existing benefits of the hybrid Lagrangian/Eulerian formulation to expand the domain of possible effects. The method is also amenable to user‐guided control, which serves to influence the propagation of cracks or tears such that they follow prescribed paths during simulation.

Bearing capacity of strip footing subjected to eccentric loads found nearby prevailing footing by finite element analysis

ABSTRACT The utilisation of urban sites for the construction of buildings is undeniable due to population growth and suburbanisation. In these situations, it is compelled to build the structures in the vicinity of existing structures. The ultimate bearing capacity (UBC) of the new footing gets affected due to the interference. To study the effect of UBC on the new footing in the vicinity of an existing footing, the finite element method (FEM) analysis has been carried out to fact-finding the influence of UBC on the new footing found nearby the prevailing footing subjected to centric and eccentric loads resting on cohesionless soil. The current outcomes have been verified against the reviewed studies. The potency of UBC on the new footing has been expressed in terms of efficiency factor ξ q with regard to the spacing ratio, angle of internal friction of soil, eccentricity ratio and different width ratio. The schematic charts for practical implementation have been devised to assess the ξ q factors. The accuracy of the failure mechanism has been observed and improved by using an adaptive mesh refinement approach.

Lateral load response of a dry-joint masonry arch subject to vertical support displacements by rigid block analysis

Abstract Masonry arches play a crucial role in the seismic response of historic masonry buildings. Although masonry arches are often subjected to large support displacements that alter and deform their geometries over time, their response to seismic actions is generally analysed using idealized, perfect geometries. This paper aims to assess the effect of large support displacements on the response of masonry arches to lateral loads. To this end, a small-scale segmental dry-joint masonry arch subjected to the vertical displacement of one support was investigated. Using a rigid block modelling approach recently proposed in the literature, the arch was modelled as an assemblage of rigid voussoirs connected by no-tension frictional contact interfaces. The response of the arch to lateral loads, applied in one direction, and to vertical support displacements was assessed through nonlinear static analyses. To evaluate the effect of support displacements, lateral loads were applied to a series of deformed arch geometries resulting from the application of increasing values of the imposed vertical displacement. The results of the numerical analyses provided new insights into how support displacements affect the lateral load response of masonry arches, showing that they may significantly reduce both the horizontal action triggering collapse and the ultimate displacement capacity.

Impact of slip velocity-dependent friction coefficient on surface traction, wear, RCF and curve squeal noise prediction in wheel-rail contact

Wheel-rail contact friction coefficient is often assumed to be constant through the entire contact patch for the calculation of surface traction. In reality, however, the friction value in a certain point decreases when transitioning from adhesion to slip regimes. Including this friction coefficient behaviour in the estimations of surface traction on the contact patch can potentially provide more accurate calculations of wear and rolling contact fatigue (RCF). In the present work, a slip velocity-dependent friction coefficient is implemented in the tangential contact solver using the concept of ‘Friction Memory’. The effect of this implementation on traction estimations and on the prediction of wear and RCF is analysed by comparing the results with a case with constant friction coefficient in the contact patch. Furthermore, the slip velocity-dependent friction coefficient provides a creep curve with a maximum creep forces value, and a decreasing creep force for higher creepages. This is commonly known as one of the possible mechanisms of curve squeal noise generation. The results provide insights into the likelihood of curve squeal generation, and an on-set curve squeal noise detection technique is proposed that also accounts for the influence of profile changes due to wear.

Study on influencing factors and prediction model of strength and compression index of sandy silt on bank under freeze–thaw cycles

The Inner Mongolia section of the Yellow River is a seasonal frozen soil area, where the freeze–thaw effect can alter soil strength and compressibility, affecting bank stability. This study takes the banks sandy silt of the Inner Mongolia section of the Yellow River as the research object. It systematically investigates the relationship between shear strength parameters and compression index of sandy silt and the initial dry density, water content, and freeze–thaw cycles of the soil. It analyzes the order and significance of influencing factors, establishes prediction models of shear strength and compression index, and evaluates the effects of freeze–thaw cycles on soil cohesion and shear strength. The results show that the shear strength index of sandy silt is proportional to changes in initial dry density and inversely proportional to changes in water content. After 10 freeze–thaw cycles, the cohesion of the soil decreases by 22.53 to 58.85%, and the shear strength decreases by 22.67 to 58.91%. The internal friction angle is less affected by freeze–thaw and tends to be stable overall. The smaller the initial dry density and the greater the water content, the greater the compression index and compressibility of the soil, but freeze–thaw has little effect on compression index. The factors affecting sandy silt shear strength and compression index are ranked as dry density > moisture content > freeze–thaw cycles. The stepwise regression model of soil shear strength and compression index based on initial dry density, water content, and freeze–thaw cycles is effective, providing technical guidance for engineering practice.

Tribological behavior under adhesion and dry friction conditions of copper-steel composites manufactured by wire-feed electron beam additive technology

Tribological behavior under adhesion and dry friction conditions of copper-steel composites manufactured by wire-feed electron beam additive technology

Suppressing Friction-Induced Stick-Slip Vibration and Noise of Zinc-Coated Steel through Temper Rolling.

The stick-slip phenomenon as a prevalent friction instability poses significant challenges to industry, including frictional vibration, reduced precision, and noise generation. The interfacial interactions between asperities on the surface of materials are critical in influencing stick-slip behavior. This study focused on modifying the asperities on the surface of zinc-coated steel through temper rolling as a new approach to suppress friction-induced stick-slip vibration and noise. It was revealed that temper rolling effectively suppressed the stick-slip behavior when the deformation of zinc-coated steel exceeded 2.3%. The proposed mechanism suggested that the temper rolling reduced surface asperity density, resulting in diminished potential energy fluctuations and a subsequent decrease in the stick-slip amplitude (the difference between the static and kinetic friction coefficients). In situ observation using the digital image correlation (DIC) technique demonstrated that the decrease in the stick-slip amplitude affected the motion state of the friction pair, effectively suppressing the stick-slip vibration and noise generation. These findings highlight the potential of temper rolling as an effective strategy for tailoring the surface topography to suppress the stick-slip phenomenon along with its related vibration and noise.

Research on contact friction characteristics of SiCp/Al tool-chip under quasi-intermittent vibration assisted swing cutting

Research on contact friction characteristics of SiCp/Al tool-chip under quasi-intermittent vibration assisted swing cutting

Global Sensitivity Analysis of Slope Stability Considering Effective Rainfall with Analytical Solutions

Abstract: Rainfall-induced landslides are widely distributed in many countries. Rainfall impacts the hydraulic dynamics of groundwater and, therefore, slope stability. We derive an analytical solution of slope stability considering effective rainfall based on the Richards equation. We define effective rainfall as the total volume of rainfall stored within a given range of the unsaturated zone during rainfall events. The slope stability at the depth of interest is provided as a function of effective rainfall. The validity of analytical solutions of system states related to effective rainfall, for infinite slopes of a granite residual soil, is verified by comparing them with the corresponding numerical solutions. Additionally, three approaches to global sensitivity analysis are used to compute the sensitivity of the slope stability to a variety of factors of interest. These factors are the reciprocal of the air-entry value of the soil α, the thickness of the unsaturated zone L, the cohesion of soil c, the internal friction angle ϕ related to the effective normal stress, the slope angle β, the unit weights of soil particles γs, and the saturated hydraulic conductivity Ks. The results show the following: (1) The analytical solutions are accurate in terms of the relative differences between the analytical and the numerical solutions, which are within 5.00% when considering the latter as references. (2) The temporal evolutions of the shear strength of soil can be sequentially characterized as four periods: (i) strength improvement due to the increasing weight of soil caused by rainfall infiltration, (ii) strength reduction controlled by the increasing pore water pressure, (iii) strength reduction due to the effect of hydrostatic pressure in the transient saturation zone, and (iv) stable strength when all the soil is saturated. (3) The large α corresponds to high effective rainfall. (4) The factors ranked in descending order of sensitivity are as follows: α > L > c > β > γs > Ks > ϕ.

Adaptive Friction Compensation for Tracking Control With Position Error Constraints of Servo Control Systems: A Switched System Point of View

ABSTRACTThis paper will investigate the adaptive backstepping friction compensator for a class of servo control systems from a switched system point of view. Firstly, by introducing a convergence‐invariant unbounded transformation, the position error bounds are incorporated into the original system. Secondly, an integral term is introduced to increase the robustness and the ‐backstepping technique is utilized to deal with the sign‐indefinite term. Then, an adaptive controller with a Coulomb friction estimator is obtained and the generated closed‐loop error system has the upper block‐triangle structure, which can be treated as a pair of cascade‐connected systems. Further, the common Lyapunov function (CLF) is obtained. The objects of asymptotical tracking with position error constraints and identification of the Coulomb friction coefficient can be realized. By similar methods, we propose adaptive friction compensators for the viscous friction model and the Coulomb & viscous model. Finally, the simulation results demonstrate the advantages of the proposed methods.

Numerical heat transfer analysis considering thermal contact conductance between rough reciprocating sliding surfaces

The frictional heat generated leads to elevated surface temperatures, which markedly influence the reliability and service life of friction pairs. Considering the dynamic changes in the thermal contact conductance and friction coefficient, the heat transfer equations which consist of heat exchange due to temperature difference and frictional heat generation at the sliding interface have been established. A finite element heat transfer model is constructed between two rough reciprocating sliding surfaces. The influences of the reciprocating motion and the interface thermal contact conductance on the heat flow distribution coefficient and surface contact temperature are solved by numerical simulations respectively. Furthermore, a prediction model is developed based on the BP neural networks. The results indicate that the heat flow distribution coefficient and surface contact temperature increase with rising motion frequency or interface thermal contact conductance and eventually reach a steady state. Moreover, for a fixed motion frequency, both parameters increase linearly with motion amplitude under different interface thermal contact conductance. The prediction model for heat flow distribution coefficient and surface contact temperature shows average relative errors of 0.45% and 3.53%, respectively. This research provides a new efficient way to analyze heat transfer in reciprocating sliding contacts and predict the contact surface temperatures.

Response of bioinspired scale arrangement in a suction caisson to penetrating into clay reflected by using interface direct shear tests

The suction caisson has been used to support the offshore wind turbine in last decade. Normally, the resistance of the traditional suction caisson (TSC) to penetrating into the seabed is overcome by suction resulting in high soil plug causing early termination in installation. Therefore, this study proposes a novel scaled suction caisson (SSC) that adopts the bionic design concept of little forward resistance and large backward resistance in scaled belly of reptiles like snakes. The bioinspired scale is set on the outer sidewall of the TSC, which is called the SSC. Scale arrangement is the key factor to reduce penetration resistance of the SSC. To simulate the penetration, the interfacial direct shear tests are carried out along the cranial direction (i.e., forward direction of the snake). The interfacial behavior of the scaled steel plate and clay is studied under different consolidation pressures and normal stresses. The results show that normal stress is the key factor compared with the consolidation pressure. There are clay-scale shear zone and clay-clay shear zone during shearing with the increase of the scale height, respectively. In addition, the theoretical formula for calculating critical shear stress is proposed, and the calculated results are in great agreement with the model test. As the scale height increases from 0.5 mm to 1.5 mm, the peak shear stress first increases and then decreases. Meanwhile, it is determined that the design of the scale height in the clay cannot exceed 108 d50. Finally, the optimal geometric characteristics and scale arrangements of the SSC are determined by analyzing the peak shear stress and peak internal friction angle of various scale-clay interfaces. The results can contribute to optimizing the scales arrangement for easy penetration of the SSC in clay.

Aphron properties and application of surfactant drilling fluids in depleted reservoirs

Aphron drilling fluids (ADFs) are finding increasing application in science engineering fields because of their distinctive characteristic. As the interest in the application of aprons-based fluids continues to grow, there is a decisive need to advance a deeper understanding of the factors affecting their behavior and properties, especially for successful petroleum industries, such as drilling depleted reservoirs and production. This study delves into investigating the density, rheological behavior and properties, filtration properties, bubble size, and their distribution of Aphrons-drilling fluids utilizing two ionic surfactants. Sodium Dodecyl Benzene Sulfate (SDBS) as an anionic surfactant, Cetyl Trimethyl Ammonium Bromide (CTAB) as a cationic surfactant, described as environmentally friendly, in Iraqi depleted reservoirs drilling. With an emphasis on the concentrations balance between Aphron generator (SDBS) and Aphron stabilizer (CTAB), the study analyzes the behavior and characteristics of Aphron drilling fluid. The investigation demonstrates that adding SDBS and CTAB reduces system density by 28%, owing to microbubbles production which is utilized with near-balance drilling. Rheological testing reveals that shear-thinning behavior in all Aphron samples improved, and the presence of SDBS affects the fluid's internal friction, gel strength, and short-term gel structure. Filtering control characteristic study demonstrates that the presence of microbubbles significantly minimizes fluid loss by 33% with 0.20% SDBS during filtering. Bubble size and dispersion studies demonstrate that 0.20% SDBS concentration, along with 0.30% CTAB, gives the best microbubble size and distribution. These findings suggest that Aphron fluids will be a promising innovation in petroleum industries, during actual drilling operations in Iraqi depleted oilfields.

Modelling of a high-speed railway pantograph with non-linear head-suspension mechanism and parameter optimisation

AbstractAccurate pantograph models are crucial to obtain reliable simulations of the pantograph-catenary dynamic interaction. Non-linearities can make it a challenge to find a model design that fits the dynamic behaviour of the real pantograph. In this work, we propose a novel pantograph model including a particular non-linear mechanism, whose dynamic behaviour significantly affects the pantograph response. This mechanism is composed of two rigid bars and an oblique pre-stressed spring with dry friction and exhibits a complex non-linear behaviour. The objective is to design a model capable of reproducing the behaviour of the real pantograph, which is represented by the dataset of dynamic measurements in the pantograph tests. From a proper parametric representation of the model, the optimisation of the parameters by a genetic algorithm has achieved a good agreement with the experimental data. The resulting optimised model behaves similarly to the real pantograph for a wide range of excitations that vary in type, amplitude and position. Since the higher number of simulations performed in the optimisation makes it necessary to use an efficient simulation tool, we propose an efficient strategy to integrate systems with Coulomb’s friction.

Bio-Mediated Improvement of Soil Geotechnical Parameters by the Native Acinetobacter

The application of microorganisms to improve the mechanical properties of soil is a new developing research area. A new native bacteria extracted from soil was introduced for the biological improvement of soil geotechnical parameters. The isolate was identified as Acinetobacter calcoaceticus S1. Sporosarcina pasteurii was used as a positive control. Direct shear tests were performed on the nontreated soil and soils treated with bacteria to determine the shear strength, adhesion and angle of internal friction. The treatment period was 40 days. The shear wave velocity was measured.The results showed that the untreated sample had relatively constant shear strength, but the shear strength of the treated soils increased significantly. The soil treated with A. calcoaceticus had greater shear strength. The angle of internal friction increased for the treated soils with A. calcoaceticus (39.3%) and S. pasteurii (28.6%). The greatest cohesion was found for soil treated with A. calcoaceticus, reaching 0.66 and 0.56 kg/cm2 for S. pasteurii. The shear wave velocity in the treated soils increased significantly. The results confirmed the ability of native A. calcoaceticus to improve soil geotechnical parameters. Calcium carbonate precipitation fills the voids between soil particles and forms a gel, which makes effective connections between soil particles and makes them coalesce and grow larger.

Experimental study on optimization of pipe jacking mud mixture ratio based on MICP technology

In the course of pipe jacking construction, the carrying-soil effect frequently arises, influenced by factors such as excavation unloading, ongoing disturbance from successive pipe sections, and the progressive accumulation of soil adhesion. The pipe jacking slurry serves as a critical agent for friction reduction and strata support, essential for the secure advancement of the construction process. This study introduces the Microbial-Induced Calcium Carbonate Precipitation (MICP) technology into the realm of pipe jacking slurry, aiming to enhance its friction-reduction capabilities and the stability of the soil enveloping the pipe. An optimal MICP-slurry formulation was determined using the uniform design approach. Subsequent model tests were carried out to assess the friction-reducing efficacy of the MICP-slurry, while the mechanism by which the MICP-slurry reinforces strata stability was investigated through soil mechanics and scanning electron microscopy (SEM) analyses. The findings indicate that the optimal MICP-slurry composition is as follows: bentonite: sodium carboxymethyl cellulose: soda ash: polyacrylamide: xanthan gum = 12%: 0.31%: 0.36%: 0.25%: 0.54%. The MICP-slurry achieves a 42.2% reduction in the friction coefficient between the test block and the sand. In comparison with the untreated sample, the cohesion of the MICP-treated sample is enhanced by 38.12%, and the internal friction angle increases by 14.01%. SEM examination reveals that the calcium carbonate crystals precipitated by the MICP-slurry within the soil populate the pores, increase the inter-particle bite force, and bolster the soil’s mechanical characteristics.

Estimating the internal friction and the rotational inertia of a homemade oscillatory system

Abstract In this work, we apply the dynamics of translation and rotation to a real system-a homemade mass-spring system composed of a cart-in which the rolling without slipping constraint of the cart's wheels may be violated at any moment. In this case, we demonstrate how modeling combined with video analysis can be powerful in determining the constraint forces acting on the system. In this case, the translational and rotational accelerations are determined, and the temporal behavior of all constraint forces can be identified. Initially, we show how rotations with slipping of the cart's wheels at the return points of the system's motion impact the system's kinematics. Finally, we apply the developed methodology to estimate the system's internal friction and rotational inertia. The estimates are compared with results from the literature and with a theoretical limit, in the case of rotational inertia, achieving good agreement.