Influence Of Friction Research Articles

Hot Deformation Behavior and Microstructure Evolution of the Maraging Stainless Steel

Hot deformation behavior of the maraging stainless steel is studied in temperature range from 900 to 1150 °C and strain rate from 0.1 to 10 s−1. When the deformation temperature is 900−950 °C, the abnormal stress increase is observed at the end of the flow curves. Transmission electron micrographs reveal that the Laves phase at the interface between prior austenitic (γ) and high‐temperature ferrite (δ) impedes hot deformation. The microstructure analysis shows that the dynamic recrystallization (DRX) mechanism of γ and δ is discontinuous DRX and continuous DRX, respectively. When the specimens are deformed at 950 °C, the extent of DRX at a strain rate of 5 s−1 is higher than at 0.1 s−1. This anomaly is due to adiabatic heating causing the actual deformation temperature at high strain rate () to be higher than at low , indicating that DRX is more influenced by temperature compared to . The influences of adiabatic heating and friction are corrected. Strain‐dependent constitutive equation is developed based on the revised flow curves, yielding an average absolute relative error of 4.69% and a correlation coefficient of 0.99; the prediction accuracy exceeds 90% when the relative error is within 10%.

The Influence of Sino-US Trade Friction on the Export Volume of China's High-tech Products

With the rapid development of economy, witnessing the extraordinary progression of the economy, China has ascended as the second largest economy globally, and the gap with developed countries is getting smaller and smaller. For a long time, there has been a huge trade deficit from China to the United States. The United States provoked trade friction on the grounds of trade protectionism, restricting trade with China, high-tech industries being the focus. Employing the difference-in-differences (DID) methodology, this paper scrutinizes the influence of Sino-US trade frictions on the export value of China's high-tech industries, utilizing the export data of China's high-tech industries to the United States spanning from 2012 to 2022. It is found that after the Sino-US trade friction began, China's exports of high-tech products to the United States have declined significantly, which has caused trade destruction effect and trade deflection effect from China to the United States.

Simplified assessment of structures with clutching inertia-friction systems by equivalent linearization methods

The innovative Clutching Inertia System (CIS), has garnered increasing recognition for its effectiveness in mitigating structural vibrations. To enhance the efficiency of passive CIS, introducing suitable energy dissipation mechanisms for the rotation inertia component is imperative. This study delves into the dynamic behavior of CIS, augmented with additional friction damping. Initially, the influence of supplementary friction damping within the CIS framework is examined through a dynamic model of a Single-Degree-of-Freedom (SDOF) system, integrated with the CIS and incorporating the Coulomb friction model. Subsequently, to streamline the dynamic analysis of the CIS and optimize the friction force thereby enhancing control efficiency while minimizing inactive durations, the paper introduces two distinct Equivalent Linearization Methods (ELMs). Furthermore, an assessment of the CIS’s dynamic performance, subjected to various external excitations, is presented. The findings highlight the crucial role of supplemental friction damping in reducing the inactivity of CIS and enhancing its overall control effectiveness. The employed ELMs demonstrate commendable accuracy and practicality for both response assessment and CIS performance optimization. In essence, the CIS, when integrated with supplemental friction damping, exhibits superior performance in suppressing structural displacement responses across diverse excitations, particularly in longer-period structures. Conversely, a more pronounced efficacy in managing structural acceleration responses is observed in structures with shorter periods. The study concludes that for specific structural applications, enhancing supplemental friction damping is more advantageous for vibration control than increasing the CIS’s inertia.

System response time and optimal path

Abstract In this work we study, in general terms, the optimal path for an out-of-equilibrium process from a geometric perspective constructed from a probability density function belonging to the exponential family (PDFE). With this objective we have constructed the speed of entropy production for a system out of equilibrium. This speed of entropy production is not determined with respect to the clock time t but rather with respect to a dimensionless time ξ (t) associated with a characteristic response time of each system λ (t). In this context, we demonstrate that the constant entropy production speed condition leads to the system moving on a geodesic of the manifold constructed from the probability density function. In the last part of this work we apply our general results to study the Ornstein–Uhlenbeck process (OU), which is a well-known stochastic process that strictly speaking describes the velocity of a Brownian particle under the influence of friction. As the system evolves we find that dimensionless time ξ (t) passes slower than clock time t.

Exploring Fatigue Crack Initiation in Helical Gears: Impact of Carburization and Frictional Influences

A computational model is presented to analyze the fatigue crack initiation period in helical gears, incorporating considerations for heat treatment via carburization and friction effects. The aim is to determine the number of stress cycles necessary for the initiation and growth of initial cracks, while investigating the impact of dynamic behavior. This study employs a dynamic gear model with two degrees of freedom in torsion, developed using MATLAB, and incorporates the Papadopoulos criterion for fatigue analysis. The computational results are benchmarked against the strain-life method. The findings underscore the significant influence of the friction coefficient between surfaces, heat treatment, and dynamic loads on the growth of initial fatigue cracks. For instance, with a friction coefficient (μ) of 0.5, the initial crack forms on the tooth surface (y=0) in both methods, with the (ε-N) method suggesting 28-65 cycles and the Papadopoulos criterion indicating 101-156 cycles. The latter accounts for the greater influence of residual stresses. Additionally, untreated gears exhibit a minimum number of loading cycles for initial crack appearance at 1.07 × 104 cycles. In contrast, carburized gears demonstrate an extended lifespan, requiring 1.45 × 105 loading cycles for crack initiation in our example. This emphasizes the efficacy of carburization in enhancing gear durability.

Influence of separation, collision and friction of rotating ring in sleeve on vibration characteristics of gas face seals

Purpose This study aims to understand how the assembly of rotating ring affects the axial forced vibration of gas face seals. Design/methodology/approach A three-mass kinematic model is established to investigate the axial movement of the rotating ring with bilateral constraints. The separation, collision and frictional sliding of the rotating ring in sleeve are discussed under rotor excitation. The effects of operating parameters and O-ring dynamic characteristics on the separation degree and film thickness disturbance are analyzed. A dimensionless axial characteristic force is defined to determine the critical conditions for the occurrence of separation. Several effective methods to eliminate the separation are proposed based on the adjustment of typical installation parameters. Findings Under rotor excitation, there may be two collisions between the rotating ring and the sleeve surfaces in one excitation period. This will cause self-excited vibration of the fluid film, increasing the risk of seal failure. The separation and collision can be prevented by increasing the equilibrium ratio, the installation radius of the O-ring on the outer surface of the rotating ring and the friction in the sleeve. Originality/value The results develop the modeling of multibody dynamics of gas face seals, enabling more accurate prediction of vibration characteristics.

Analysis of Thickness Variation in 2219 Aluminum Alloy Ellipsoid Shell with Differential Thickness by Hydroforming

The process of spinning and machining for heavy plates has the problems of a large amount of machining, large springback, and easy cracking. Aiming to address these issues, we proposed a deep drawing forming method for a plate with differential thickness to manufacture an integral ellipsoid component with a thin zone in the middle and a thick zone in the periphery. The plate with a differential thickness was initially produced through machining, followed by the execution of deep drawing deformation. During the deformation process of plates with differential thickness, the thin zone is prone to rupture defects. Therefore, a hydroforming method utilizing an elastic auxiliary plate was adopted to solve this problem. Through mechanical analysis and deep drawing experiments, the influences of hydraulic pressure and elastic auxiliary plate on the distributions of thickness and strain were studied, and the influence of friction on hydroforming was analyzed. The results indicate that increasing the hydraulic pressure and setting elastic auxiliary plates can increase the interfacial friction, reduce the thickness thinning rate, and improve the thickness distribution and deformation uniformity within the thin zone. When the hydraulic pressure is 5.2 MPa and the thickness of the elastic plate is 5 mm, the maximum thickness thinning rate of the ellipsoid shell is 8.8%, which is 34% lower than that of the ellipsoid shell obtained via conventional deep drawing.

Experimental investigation and numerical simulation of swaging process of tubes for oil country tubular goods

AbstractPremium integrated seamless pipes made from high strength low alloy steels are used to produce oil country tubular goods. Operational requirements of these pipes in petroleum industry lead to an adequate tube end connection with better mechanical strength and sealing properties. Therefore a cold swaging process or calibration of pipe end is necessary for the mechanical threading process of the tube. Applications of typical calibration mandrels result in heavy wear due to higher swaging loads and the optimal necessary geometry of end tube could not be achieved. In this study, a new mandrel geometry with a finished surface was developed to modify the pipe end profile and reduce the wear tool. The investigated pipe made from P110- pipe steel was plastically preformed using a cold swaging process. Experimental measurements of the pipe end geometry after swaging process resulted an increase of the inner tube diameter of approximately 4.9% and an outer tube diameter of 3.7% respectively. Furthermore, a rather constant tube wall thickness was also observed. An Abaqus plug-in was developed to characterize the swaging process of pipe ends. The influence of friction between tool and pipe surfaces on the final geometry of pipe ends and residual stresses in pipe ends due to preforming were numerically predicted. The new designed swaging process resulted a better final pipe end geometry and low tool wear during the preforming of pipe end. The presented plug-in in this work could be used for tool optimization and characterization of swaging process of pipes in oil and gas industries.

Influence of Side Friction on Average Width Loss in Urban Roads Links; A Case Study of Nakuru Town

This study investigated the impact of side friction factors on the reduction of effective carriageway width in urban road links in Nakuru Town, Kenya. Linear regression models were developed for each road link, revealing a strong positive relationship between the frequency of side friction factors and the average carriageway width reduction (AVWR). The prediction models highlighted the varying influence of specific side friction factors, such as pedestrians, entry and exit maneuvers, parked vehicles, motorbikes, and bicycles, on AVWR across different road segments. The findings emphasize the importance of context-specific analysis and tailored interventions to effectively address traffic congestion in urban areas, as the complex interplay of side friction factors necessitates comprehensive approaches to traffic management. Regression analyses were conducted on data from 11 major arterial roads, considering factors like pedestrian activity, entry/exit maneuvers, parking situations, and presence of motorbikes, bicycles, and tuk-tuks. Results showed significant positive correlations for most links, with pedestrians, entry/exit maneuvers, and parked vehicles consistently contributing to carriageway width reduction. However, the impact of motorbikes and bicycles varied across locations, underlining the need for location-specific strategies. The study also revealed the intricate interplay among side friction factors, necessitating a holistic approach to traffic management. By understanding these relationships, urban planners and traffic managers can develop targeted strategies to mitigate the impact of side friction factors, improve traffic flow, and enhance overall road network efficiency.

New training simulator for lumbar puncture base on magnetorheological

In response to the difficulties in accurately reproducing the resistance drop generated by puncturing key tissue layers with a needle and the poor experience in existing simulators, based on the continuous controllability and rapid response of magnetorheological fluid under the influence of a magnetic field, this paper proposes a lumbar puncture training simulator(LPTS) that can accurately simulate the puncture feedback force within tissues such as the skin, subcutaneous fat, and supraspinous ligament throughout the entire process. By using a dual rod structure and reasonably arranging the damping channel gap, the influence of mechanical friction and zero-field damping force on the feedback force during tissue progression is minimized. This paper introduces the acquisition and modeling analysis of raw data, and based on this, the design, simulation, and mechanical testing of the simulator are carried out. Finally, a performance testing platform for the simulator is established to evaluate its tracking performance of the expected puncture strength and the reproducibility of the puncture sensation. The results show that the experimental puncture strength deviates from the expected puncture strength by 0.35 N to 0.61 N in the crucial steps of breaking through the supraspinous ligament, interspinous ligament, ligamentum flavum, and dura mater, with a relative error below 10 %.

Influence of friction on initial setting position of preform for final forging process of large-scale titanium alloy strut

Influence of friction on initial setting position of preform for final forging process of large-scale titanium alloy strut

A novel cohesive interlayer model considering friction

To understand the influence of friction on the shear-slip behavior of heterogeneous brittle composites, a novel cohesive interlayer model that can effectively capture the friction effect was proposed based on the classical Park-Paulino-Roesler model. Meanwhile, the unified potential energy function governing the interface tangential and normal behaviors was introduced to realize the mechanical interaction between Mode I fracture and Mode II fracture, and a smooth friction growth function was added in the elastic deformation stage for calculating the accurate contact pressure and friction force. Furthermore, the capability of the proposed model in addressing unloading and reloading was improved, and the fracture energy can vary accordingly during cyclic loading. To verify the effectiveness of the proposed model, it was examined by modelling the shear behavior of a masonry wallette. The results show that the relative error of the proposed model is 14.92% which is much lower than those of the other three pre-existing models when calculating the displacement corresponding to peak shear stress. Meanwhile, in terms of peak shear stress and initial displacement at residual stage, the relative errors of the proposed model are only 1.82% and 5.04%, respectively, indicating the high accuracy. Besides, the tangent stiffness determined by the second-order integration of the potential energy function is also continuous and smooth, which ensures the effective convergence of the proposed cohesive model.

A new solution to force analysis including Coulomb friction in mechanism joints

The objective of this paper is to propose a novel approximate solution for determining the reactions of joints in mechanical systems, which involves the influence of Coulomb friction. It is widely acknowledged that if Coulomb friction is used in determining an exact solution to the equilibrium equations for a mechanism, then it will involve nonlinear systems of equations. With the abundance of computer tools now available, tasks of this kind, especially numerical computations, are not particularly challenging. However, new analytically tractable approximate methods are still valuable as a straightforward way of solving the problem. Several studies have been carried out in this field to find a simple solution. In this paper, a new approach based on friction circle concept and Babylonian algorithm is developed for various mechanisms, which is exceptionally well-suited for calculating and streamlining the solution process for mechanical systems by eliminating the necessity for iterative steps at each stage of the force analysis.

Experimental study of the end effect on the mechanical behaviors of rocks under true 3D compressions

AbstractIn true triaxial compression tests, all three principal stresses are imposed independently. This allows for a more comprehensive analysis of the material's mechanical properties. The end effect in true triaxial compression tests is a crucial phenomenon that impacts the accuracy and reliability of the test results. In this study, a series of true triaxial compression tests is conducted to examine the influence of the end friction on the mechanical properties. The laboratory results show that the presence of the end friction could bring about an apparent increase in rock strength and also restrict the deformation in each direction showing that the stiffness (the slope of the curves) increased slightly. The rock strength could be enhanced from 24.7 to 90.7 () when the end friction is increased, which is mainly caused by the lateral interface friction. The failure mode and fracture angle of the specimen are also influenced by the end effect, showing that under high friction conditions, the failure is more ductile, and a larger fracture angle is observed. At last, in comparison with the published experimental data, the actual specific friction angle (corresponding friction coefficient is about 0.19) for the direct specimen–metal contacts in a true 3D test is numerically identified, which is empirically reasonable and higher than the tested range 0.146–0.157 obtained from double‐shear test system.

The stick-slip bending behavior of the multilevel helical structures: A 3D thin rod model with frictional contact

The multilevel helical structures in various engineering and natural fields offer excellent deformation flexibility and load bearing capabilities. Understanding the interplay between the local frictional contact and the geometric characteristics of the helical structure under complex external loads has attracted considerable interest. In this work, the effect of local frictional contact behaviors on the bending in multilevel helical structures is investigated by using a combination of theoretical modeling, finite element (FE) simulations, and experiments. In the case of pure bending, the kinematic parameters of the bent multi-stage helix are derived concisely by the idea of the kinematic analogy. The bending stiffness of the multi-stage helix is further obtained. In the case of the combined tension/torsion and bending, the 3D thin rod model incorporating Coulomb’s friction is established to describe the mechanical responses. It is found that the relationship between equivalent bending stiffness and the laying angle exhibits nonlinearity. A comparison with the classical Papailiou model reveals that, for helical structures at large laying angles, the influence of friction is primarily determined by the internal force in the tangential direction, which is the core assumption of the Papailiou model. However, in the case of small laying angles, the helical twisting characteristics and the contribution of the internal forces and moments in the other two directions (normal and binormal directions) to the friction cannot be ignored. Subsequently, a multilevel frictional contact transmission formulation is proposed according to the force action–reaction principle. Based on the above formulation, the non-simplified thin rod equations with Coulomb’s friction are extended to describe the multilevel stick-slip bending behaviors of the second stage cable (3*3). The dissipation capacity of helical structures is evaluated quantitatively under the hysteretic bending. Finally, the theoretical model is verified by FE simulations and experimental results. This work provides insights for unveiling the intrinsic relationship between the nonlinear bending and local frictional contact behaviors in the multilevel helical structures.

Atomic-scale wear behavior of two-phase TiAl alloys by vibrational horizontal friction

To investigate the influence of vibrational horizontal friction on the microscopic distortion of γ/α2 biphasic TiAl alloys, a molecular dynamics approach was used for simulation by analyzing the mechanical properties, atomic displacements, shear strains, and defect distributions of the substrate in vibrational horizontal friction and conventional friction. The friction force and coefficient of friction in vibrational horizontal friction were found to be less than conventional friction. Vibrational horizontal friction has a shallower depth of abrasion marks and a larger wear area compared to conventional friction. At the same time, this γ/α2 phase boundary changes the direction of motion of the atom so that they move in the same orientation as parallel to the interfacial boundary. Vibrational horizontal friction has a larger strain concentration area than conventional friction. The existent γ/α2 interface impedes the strain transmission so that some of the stresses are concentrated near the interface, and the γ-phase accumulates a large proportion of dislocations, which leads to work-hardening of the material. The slip of the horizontal stacking faults in the vibrational horizontal friction releases internal stresses. The formation of structures such as stacking fault tetrahedrons has a significant strengthening effect on the material.

Experimental investigations and material modeling of an elastomer jaw coupling

Abstract This work investigates the hyper-viscoelastic behavior of a thermoplastic polyurethane IROGRAN A 92 E 5670 FCM used in the gear rim of a jaw coupling. The aim is to provide the material parameters for the modeling of jaw couplings in engineering tasks. Uniaxial compression tests were conducted at various temperatures and loading speeds to fit a hyper-viscoelastic material model. The material model uses the Yeoh free energy and the power law model with one Maxwell element. The parametrized material model showed very good results in comparison to experimental data. In addition, the influence of friction on the experiments was modeled, investigated, and discussed. Further component tests for a jaw coupling of size 28 were conducted with two different specimen types. The original gear rim and a modified gear rim with central boreholes for integrated sensors were used in the test. The influence of such a modification was investigated with four different loading cases, focusing on the torsion-torque characteristic and the relative damping. These component tests enable the validation of numerical models of jaw couplings.

Viscosity of Clayey Soils: Experimental Studies

Due to the high rate of the development of housing, transportation and hydraulic engineering construction in the last hundred years, the study of the phenomenon of creep of clay soils has become a subject of scientific research. In the study, experimental investigations of clay soil were conducted using a simple shear device in kinematic loading mode, aimed at examining the influence of shear rate on the viscosity coefficient of the clay soil and its strength characteristics. The tests were performed at four different shear rates and three different vertical load values. Based on the results of experimental and theoretical studies, the viscosity coefficients of clay soil were obtained, and a new rheological equation was proposed, which simultaneously takes into account the influence of Coulomb friction, structural cohesion, cohesion of water–colloidal bonds and viscous resistance of the soil. It has been shown that the shear rate has a significant impact on the viscosity coefficient of clay soil, and the viscosity coefficient itself is a variable quantity, depending both on the magnitude of the applied load and the duration of its application. The obtained results can be used for further improvement of methods for calculating the settlement of structures over time, as well as for predicting the time until the bearing capacity of foundation soils is exhausted.

IMPROVING APPROACHES TO DETERMINING THE LEVEL OF FILLING OF THE PIPE BODY WITH PUMPED PRODUCT

As of 2015, there were more than 200 permanent and variable gravity sections of crude oil and petroleum product pipelines in the pipeline system of PJSC Transneft, the natural monopoly for pipeline transportation of crude oil and petroleum products in the Russian Federation. The operation of gravity sections in oil pipelines in Russia is a very important safety and environmental issue, and Russian oil transportation companies are constantly working on improving approaches to monitor and control pipeline operation modes. When these sections occur, special attention is given to determining the geometric capacity of the pipeline section, as pumping is done in batches and commercial pumping product remains in the gravity section during periodic shutdowns. Due to the limited technical equipment of these sections and the likely illegal unrecorded product withdrawals in these pipeline sections, the most demanding approach is to determine the fill factor of the pipe body. The fill factor is influenced by many factors, including the presence of gas phase and water accumulations, correct geometry of the pipe body and other factors. Given the given initial data, it can be seen that the solution to the problem of determining the filling level of a stopped oil pipeline is reduced to the construction of a multifactor model. For accurate determination, in addition to the model, there is a need for relevant software, an algorithm for solving the problem ofcalculating the filling factor. Correspondingly, operating organisations need a system for accounting and control of the product filling level at these sections at the level of improvement of the state system for ensuring unity of measurements and metrological support of accounting for the long-distance pipeline transport of oil and oil products - a strategic resource, the revenues from the sale of which account for about 23 % of the budgetary system of the Russian Federation.The calculation created and proposed by the authors is divided into stages in which the initial data is sequentially collected, the voltages on the capacitors are calculated, the data is processed using the interpolation method, an image is constructed using the Newton-Gauss method, and the filling factor is calculated with various multiphase pumping products. The calculation is made based on voltage readings from sensors located orthogonally to the axis of the pipe body. Using the approximation method and the Newton-Gauss method, you can get rid of the «noise» and level the phase boundary. When tested and implemented at pipeline pumping facilities, it will be possible to clarify the existing dependences of the influence of gas phase friction on the fluid flow rate, and, therefore, evaluate the effect on the filling factor. This calculation can become a tool in the fight against illegal tappings.

Influence of friction and back stresses evolution on cyclic softening of laser powder bed fusion Ti-6Al-4V ELI alloy

Laser Powder Bed Fusion (LPBF) of Ti-6Al-4V ELI enables the fabrication of complex and individualized load-bearing patient-specific implants (PSI). These PSI are subjected to cyclic loading, which necessitates their fatigue performance evaluation. In this work, the fatigue properties of LPBF Ti-6Al-4V ELI in heat-treated conditions were characterized by studying the low cycle fatigue (LCF) behavior and underlying deformation mechanism. The fully reversed strain-controlled fatigue tests were performed at various strain amplitudes at room temperature. The ratio of fatigue life of conventional wrought alloy and LPBF Ti-6Al-4V ELI at the lowest (0.8 %) and the highest (1.8 %) strain amplitudes were found to be approximately 2.7 and 4.5, respectively. Further, the softening response during fatigue loading was correlated to the variation in the back and friction stresses. The TEM observations revealed that the dislocation pileup along α/β interfaces caused an increase in dislocation density, which drives the increase in back stress. However, the ease of slip transmission at high strain amplitude (1.8 %) reduced the heterogeneity between α and β phases, causing a decrease in the back stress. The TEM observations further suggested that the dislocation annihilation and subsequent rise in dislocation-free zones in α-phase reduced the friction stress at all strain amplitudes, which resulted in cyclic softening of LPBF Ti-6Al-4V ELI.