Frictional Work Research Articles

A fast method for determination of creep forces in non-Hertzian contact of wheel and rail based on a book of tables

The Kalker book of tables for non-Hertzian contact described in a previous work from the authors provides creep forces, but the moment generated in the contact patch is not available. The extended Kalker book of tables for non-Hertzian contact (KBTNH) presented in this paper provides creep forces, as well as the moment. The paper presents the simplified linear theory of rolling contact for a simple double-elliptical contact (SDEC) region used for regularisation of contact patches and, resulting from this theory, the full symmetry relations for creep forces and moment. The parameterisation of variables and structure of the extended book of tables are described. The extended Kalker book of tables of moderate volume has been computed in co-simulation Matlab-CONTACT. The creep forces and moment obtained from KBTNH have been compared to those obtained directly by CONTACT program and FASTSIM algorithm. The comparison shows that KBTNH is in good agreement with CONTACT for a wide range of creepage conditions and shapes of the contact patch, whereas the use of FASTSIM may lead to significant deviations from the reference CONTACT solutions. The presented example of application is a realistic case of a freight wagon curving simulation, where KBTNH has been used to assess the contribution of the moment into the unit frictional work dissipated in contacts of wheels and rails. The high calculation speed and good accuracy of determining creep forces for non-Hertzian wheel–rail contact make the proposed method a suitable tool for multibody system (MBS) simulation programs oriented for rail vehicle dynamics.

Thermal properties of S-gears in comparison with involute gears

The tests with small plastic gears, which were conducted to assess Wöhler curves for S- and E-gears indicated improved behaviour of S-gears, which is due to their geometry. However, the thermal load of the gears in contact is of a crucial importance. Therefore, the paper focusses on the differences in thermal load of cylindrical, spur, plastic involute and S-gears. Whereas there are thermal (temperature) models at disposal for the involute gears, no models are available for the S-gears. Such a model should reflect actual flank shape and difference in actual thermal behaviour deriving from there. So, frictional power along the path of contact, work of friction and deriving flash temperatures along the path of contact were calculated for both gear types, which disclosed lower thermal load of S-gears. Small E- and S-gears made of polyacetal and nylon were manufactured by milling. So, gears were of higher quality and reflected actual tooth flank geometry. The later long-term experiments were planned with smaller loads to run up to 10 or 20 million cycles; in this context they were focused on measurements of a steady state bulk temperature which helped in assessment of actual contact circumstances and contact temperatures.

Tracking control and robustness study of shifting process

Heavy dump vehicles are usually working with big load changes and bad work environment, thus change the friction performance of transmission clutches, as well as great affect the shift quality seriously, which influence the vehicle performance. Many researchers developed a lot to design a useful automatic transmission control system. Using PID tracking control and Monte Carlo method, the controller based on an dynamic model was set up to analyze the shifting process of automatic transmission and its robustness in this paper．The shift process was divided into four stages, low-gear phase, torque phase, inertia phase and high-gear phase. The model presents the process from the first gear to the second gear when the torque has big change．Since the jerk and the friction work of clutch are both related to the speed of clutch which was easier to control, it was chose as the target to control the oil pressure for satisfying the requirement of shift quality．The simulation software, Maplesim and Simulink, were used to build the vehicle model and shifting controller for simulation under different working conditions, and the maximum jerk was changed from 34 m/s3 to 12 m/s3 after the optimization. In this paper the Monte Carlo has been used to quantize and evaluate the robustness of the closed-loop system for the friction coefficients and output torque of turbine variation leading by the friction feature parameters and throttle angle changed. Monte Carlo method was used to analyze the effectiveness and robustness of PID controller, which proves that it has good control effect when the throttle is ongoing minor fluctuations. When the throttle is full opening, a quadratic optimal controller based on disturbance is designed by the method of multi-objective optimization. When it changes within 20 percent, PID controller was designed under the guidance of tracking thoughts. The results also show that the controller could still obtain better effect when the friction coefficient ranged from -40 % to 40 % as well as engine torque changed from -20 % to 20 %, which indicates the robustness of controller.

Numerical investigation of the effects of rail vibration absorbers on wear behaviour of rail surface

Rail corrugation refers to the periodic wear of the top working surfaces of rails. This problem has plagued the railway industry over a hundred years. In the present paper, the effects of rail vibration absorbers on wear behaviour of the rail surface have been studied. The dynamic model of a wheel–rail–absorber system is established. The friction contact coupling between the wheel and the rail are fully considered in this model. A wear model, in which the mass loss of unit area in contact patch is proportional to frictional work per unit area between the wheel and the rail, is developed to analyse the wear behaviour of the rail surface. Numerical results show that the saturated creep force-induced self-excited vibration of the wheel–rail system can result in short pitch rail corrugation on the rail surface. The maximum wear depth occurs at the positions close to mid-span of each sleeper bay. After the installation of rail vibration absorbers, the formation of short pitch rail corrugation can be suppressed effectively, and the wear on the rail surface becomes uniform and the growth rate of rail corrugation reduces considerably. Increasing the connection damping between the absorber and the rail web is beneficial to preventing the formation of short pitch rail corrugation.

The influence of laser micro- and nanostructuring on the wear resistance of Grade-2 titanium surface

The development of wear-resistant surfaces supports sustainable and long-term work of friction couples. In this paper, we demonstrated laser structuring as a method for increasing Grade-2 titanium surface wear resistance. Surface treatment by a nanosecond fiber laser produces nano- and microstructures simultaneously, with composition changing to combinations of Ti, O and N. Tribological tests were conducted according to certificated ‘Ball-disk’ method in conditions of rubbing friction and Al2O3-ball as a counterbody. Investigation results demonstrate an increase in wear resistance of laser-treated titanium surface by ten times. It appears both surface structure and chemical composition influence titanium durability enhancement.

Effect of rotation speed on friction behavior of rotary friction welding of AA6061-T6 aluminum alloy

The continuous drive rotary friction welding was conducted on AA6061-T6 aluminum alloy rods under different rotation speeds. The effect of rotation speed on friction behavior was investigated via analyzing the friction torque, temperature, microstructure and axial shortening. The results show that the curves of friction time and friction work as a function of rotation speed present like “V-shape” with the minimum values locating at around 900 rpm. Besides, the ratio of friction work in the first stage to that in the whole process increases and then decreases after reaching the maximum value at 900 rpm. As the rotation speed increases, the heat pattern gradually changes from the “scissor-shape” into “double-ellipse shape” that is acquired at 900 rpm and eventually into the “disc-shape.” Additionally, the axial shortening rate at the steady stage initially reaches a high constant value and then drops to another constant value that is nearly half of the high value when the rotation speed is not less than 1500 rpm. The high axial shortening rate can be ascribed to the process of filling the unbonded area remained at the interface after the first friction stage.

Finite element simulation and experimental analysis of false brinelling and fretting corrosion

Abstract False brinelling and fretting corrosion occur in oscillating bearings. A simulation will be used to predict wear by calculating the frictional work in a contact between roller and raceway. A sub-model of the bearing is generated containing the ball and the raceway section of the inner and outer ring. This ensures a realistic approach of the problem where the degrees of freedom of the ball are only restricted by frictional forces of the contact surfaces. The appearance of wear in experimental investigations were compared with the density of frictional work of the simulations. The comparison between simulations and experimental results show good consistencies. Furthermore, the simulation results explain the characteristic shapes of false brinelling and fretting corrosion.

Modeling ignition prediction of HMX-based polymer bonded explosives under low velocity impact

Visco-SCRAM and the hot spot models are applied to predict the ignition of HMX-based polymer bonded explosives (PBXs) under low velocity impact. The model is implemented in the commercial software DYNA3D. The confined Steven test simulation is done to verify the model and to understand the mechanical and thermal response of PBXs. The ignition time as a function of the impact velocity is analyzed. Higher impact velocity results in shorter ignition time. Moreover, the empirical formula is demonstrated to predict the ignition time. Five different dimensions of the specimen ϕ70 mm × 13 mm, ϕ98 mm × 13 mm, ϕ140 mm × 13 mm, ϕ98 mm × 26 mm and ϕ98 mm × 39 mm are applied to obtain the specimen size effect on the ignition. The temperature rise distribution inside the specimen based on the hot spot model and the impact velocity threshold value are successfully predicted. The impact velocity threshold value is in agreement with the experimental data. The velocities 44 m/s, 45 m/s, 45 m/s, 66 m/s and 75 m/s are for the five specimens mentioned above respectively. In addition, the ignition due to different shape projectiles is analyzed. The simulation result shows the impact velocity threshold value is 45 m/s, 97 m/s and 21 m/s for the oval projectile, the flat projectile and the pin projectile respectively. The differences of the temperature rise among the three projectiles are analyzed in detail. In these cases above, the ignition prediction matches experimental results well and the details of mechanical and thermal response of PBXs, such as the deformation of specimens and the temperature rise histories at different positions, are further discussed. Frictional work is considered as the main ignition mechanism of HMX-based PBXs under low impact velocity.

Modelling and control of a novel two-speed transmission for electric vehicles

Multiple speed transmissions adopted by electric vehicles (EVs) provide the probability of further improving the global efficiency of the drivetrain, as well as extending limited driving range for the fixed power storage. This paper proposes a novel two-speed transmission for an electric vehicle (EV), which is capable of realizing power-on gear shifting by operating the band brake to lock or unlock the one-way-clutch. The band brake controlled by the actuator provides a smooth and efficient gear shifting. To achieve power-on gear shifting, three alternative control strategies are proposed and applied in this novel two-speed transmission system. To verify the transient behaviour during the gear shifting, the EV powertrain equipped with the proposed two-speed transmission is undertaken. Firstly, a mathematical model is developed, including the electric motor, the proposed two-speed transmission, the vehicle, etc. Then, model-based alternative power-on gearshift strategies are developed, and a torque-based gearshift closed-loop controller with the desired speed trajectory is proposed. The vehicle jerk and the friction work are taken as the foremost metrics to evaluate the gearshift quality. The simulation results demonstrate that all strategies can achieve power-on gearshifts. The disadvantages and advantages of these strategies are exhibited clearly, which provides beneficial knowledge and reference to the researchers engaged in the development of the transmission controller.

Study of the welding parameters effect on the tunnel void area during friction stir welding of 1060 aluminum alloy

Friction stir welding is a relatively novel solid state method which produces ultra fine-grained microstructure and promoted mechanical properties due to the severe plastic deformation induced during welding. These features, of course, would be obtained if the welding parameters have been justified so that the welding zone becomes free of any defect specially tunnel cavity. This defect was primarily caused by an insufficient heat input during welding. In this study, a mathematical model has been presented to estimate the heat input generation during welding pertaining to the frictional work dissipated between the tool/workpiece interface, and moreover, the heat produced by the mechanical stirring of the plastically deformed material around the pin. The aim was to correlate the heat input generation and the tunnel void area. Aluminum plates with commercial purity were used for experimental efforts. During friction stir welding, a thermal camera was utilized to measure the maximum temperature of the material. After welding, samples cut through the transverse direction and examined for the area of tunnel cavity, and the extent of thermo-mechanically affected zone, as well. Comparison among the tunnel cavity areas with the heat input generations showed that to eliminate the tunnel cavity, at least a minimum heat input of about 800 J mm−1 was required.

A study and comparison of frictional losses in free-piston engine and crankshaft engines

Friction work in free-piston engines is expected to be lower than in crankshaft engines due to the elimination of the crank mechanism. In this paper, friction mechanisms were reviewed and compared between a free-piston and crankshaft engine of similar size. The main friction mechanisms were identified to be the piston assembly including piston rings and piston skirt, valve train system, the crank and bearing system for the CSE, and the linear electric generator for the FPE. The frictional loss of each friction mechanism was estimated and discussed. A Stribeck diagram was used to simulate the piston ring friction during hydrodynamic lubrication, mixed lubrication, and boundary condition. It is found that the FPE doesn’t show advantage on piston ring friction force over the CSE, and the frictional loss from the piston ring is even higher. While the elimination of the crankshaft system reduces the frictional loss of the FPE, and the total friction loss of the FPE is nearly half of the CSE.

An improved two-phase model for saturated steam flow in multi-point injection horizontal wells under steady-state injection condition

Previous models neglected the effect of frictional heating on steam quality and enthalpy in wellbores when saturated steam is injected into multi-point injection horizontal wellbores.In this paper, new energy conservation equations were developed for increasing the calculation accuracy of steam quality in inner tubing (IT) and annuli. Then, coupled with the momentum balance equations, the distributions of steam quality and pressure along the IT and annuli were obtained by using the straight forward numerical method. The predicted results from the new model were compared against field data and previous models. It is found that: (a). The effect of heat loss to surrounding formation on the temperature profiles is weak. However, the heat loss has a significant influence on the profile of steam quality in wellbores. (b) When removing the item of frictional work from the energy balance equations, the predicted values of steam quality and enthalpy are lower than actual data. This error in energy conservation equation may be hidden when the predicted temperatures showed good agreement with field data. (c) With the help of multi-point injection technique, formation heating effect at both heel-point and toe-point can be improved.

Wear Behaviors of GH4169 Super Alloy and 3Cr2W8V Tool Steel Under Dry Rolling Condition

Wear behaviors of 3Cr2W8V and GH4169 with H70, including surface property, wear performance and friction work, were investigated. 3Cr2W8V and H70 friction pair suffered severer wear and surface damage than GH4169 and H70 friction pair. The wear process had an impact on GH4169 subsurface hardening, but no effect on 3Cr2W8V. Heat energy was a proportion of the total friction work, and 3Cr2W8V consumed more energy than GH4169 during temperature rise. From the numerical calculations, 3Cr2W8V had a more concentrated heat distribution and produced more wear than GH4169. Ultimate tensile strength (σUTS) and uniform elongation (eUE) were considered to evaluate the wear resistance of two materials, and GH4169 had a higher σUTS × eUE value and lower wear degree. In conclusion, the wear mechanism of GH4169 is adhesive wear, and 3Cr2W8V is a combination of abrasive and adhesive wear. Cooling can reduce the wear volume for GH4169 due to good thermal conductivity. The results show that GH4169 is more reliable for the tool material, with a better wear resistance under dry rolling condition.

Effect of rotation speed on friction behavior and radially non-uniform local mechanical properties of AA6061-T6 rotary friction welded joint

The rotary friction welding of AA6061-T6 was conducted and the influence of rotation speed was investigated on friction behavior and on radially non-uniform mechanical properties of AA6061-T6 rotary friction welded (RFWed) joint. The results show that, as the rotation speed increases from 500 to 2100 rpm, the curves of friction time and friction work present like ‘V- curve’ with a minimum value at 900 rpm and the ratio of friction work in the first stage to that in the whole process increases and then decreases after reaching a maximum value at 900 rpm. The local strength of the joint correlates positively to the thickness of the deformation layer and radially uniform joint is just achieved at 900 rpm. In addition, the maximum local strength of 295 MPa, corresponding to the joint efficiency of 88%, achieves in the peripheral region at 900 rpm.

Effect of friction work on key parameters of steam at different state in toe-point injection horizontal wellbores

When modeling of steam flow in wellbores, the effect of friction work on temperature/steam quality of both fluid in wellbores and reservoir should be considered. A model that can describe the energy re-distribution in the system should be built.In this paper, new energy balance equations for steam flow in inner tubing (IT) and annuli are developed with consideration of the effect of frction work on the energy re-distribution process in the system. The heat energy caused by shear stress has an obvious influence on the increase of steam quality or superheated steam temperature, especially under high injection speed condition.Firstly, a model for steam flow is developed in wellbores based on the energy and momentum balance equations. The energy balance equation controlls the predicted values of steam quality or superheated steam temperature, and the momentum balance equation controlls mainly the steam pressure. Secondly, coupled with the seepage model in oil layer, a comprehensive mathematical model is establiehed for single, two-phase flow of steam in horizontal wells with toe-point injection technique.Results show that: (a) when the effect of friction work was neglected, the predicted steam quality or superheated steam temperature were obviously smaller than field data. (b) While seam quality decreases with distance when wet steam flows in wellbores, superheated steam temperature in annuli has an increase at the heel-point in annuli. This is because the fluid with lower temperature in annuli absorbs heat from steam with higher temperature in IT. (c). In order to obtain a satisfactory oil recovery ratio, field engineers are suggested to increase the injection pressure to a reasonable level based on the rock fracture pressure experiment.

Clutch control of a hybrid electrical vehicle based on neuron-adaptive PID algorithm

This paper presents the detailed analysis of a pneumatic clutch actuator with an artificial intelligence control algorithm. The low cost of pneumatic actuator makes it an advantage in automotive applications, but fast and precise control is difficult on account of its time-varying and nonlinear character. In order to achieve good performance and save cost, the development of a fast, accurate, and inexpensive automatic pneumatic actuator clutch system for a single-axle parallel hybrid electrical is important. Targeted for the working principle of electric-drive automated mechanical transmission parallel hybrid system for shifting and clutch dynamic control during operation mode switch course, the design adopts single neuron-adaptive PID-based clutch operation process, proposed the clutch actuator piston non-contact cylinder lock control method to overcome time-varying and nonlinear characteristics’ impact present in the pneumatic actuator closed-loop control, and through the effective control of segment displacement self-diagnosis during the clutch operation process, performs variable clutch control and improve the actuator fault tolerance. Experiments show that the proposed control algorithm is feasible, which has effectively reduced the torque shock and clutch friction work during clutch engaging process.

Effects of longitudinal valley slopes on runup of the 2011 Tohoku tsunami on the Sanriku coast, northeastern Japan

The 2011 Tohoku earthquake and tsunami caused heavy damage in low-lying river valleys of the Sanriku coast, northeastern Japan. The landward extent of inundation by the tsunami varied considerably among the valleys, indicating that tsunami runups were strongly affected by the subaerial fluvial morphology of the valleys. We used detailed tsunami inundation maps to investigate tsunami runups along river valleys along the Sanriku coast, considering both the protected areas landward of coastal seawalls and levees (protected zone) and areas on the river side of levees (channel zone). We determined the mean longitudinal slopes of all river valleys and used them in conjunction with published tsunami inundation maps to determine the distances and heights of tsunami runups in 68 valleys along the Sanriku coast. Runup heights tended to be higher and inundation distances longer in the channel zone than in the protected zone. Comparisons of runups among valleys with different longitudinal valley slopes showed that inundation distance decreased with increasing valley slope, and that runup height increased with increasing slope. During runup, some of the kinetic energy of a tsunami is consumed as frictional work and some is transformed upslope to potential energy. The steeper the longitudinal slope, the greater the amount of energy transformed and stored as potential energy and, consequently, the amount of energy consumed by frictional work declines and inundation distance shortens. In the protected zone, more energy is consumed by frictional work during destruction of artificial structures such as houses, and inundation distance is shorter than in the channel zone. Our analysis of 2011 tsunami data clarified relationship among tsunami runups, shoreline-tsunami heights, geometry of the coastline, and longitudinal valley slopes. Among Sanriku ria coast, coastline geometry appears to be a secondary influence on the shoreline-tsunami height and runup. That the shoreline-tsunami height was not the dominant influence on tsunami runup emphasizes the importance of subaerial topography on tsunami runup, especially in narrow steep valleys, which are often of the topography along coasts that face plate margins.

Behavior of acoustic emissions at the onset of sliding friction

Abstract Detecting the slip using the acoustic emission (AE) technique is useful for condition-monitoring of machinery and equipment. However, the characteristics of the AE signals at the onset of a slip are insufficiently clarified. We conducted friction tests and simultaneously measured the AE signal, friction, and relative displacement of a brass ball in contact with a flat steel plate. The AE signal clearly increased during the slip, and the effective value of the AE signal well-mimicked the sliding speed. In a frequency analysis of the AE signals, the characteristic frequency components increased significantly during the slip. From the obtained data, we also calculated the AE energy and the friction work during the slip. Both values shared a strong proportional relationship.

Wear of the rope and the work of friction

Wear of the rope and the work of friction

Stuy on Fatigue Life of Aluminum Alloy Considering Fretting

To study the influence of fretting on Aluminum Alloy, a global finite element model considering fretting was performed using the commercial code ABAQUS. With which a new model for predicting fretting fatigue life has been presented based on friction work. The rationality and effectiveness of the model were validated according to the contrast of experiment life and predicting life. At last influence factor on fretting fatigue life of aerial aluminum alloy was investigated with the model. The results revealed that fretting fatigue life decreased monotonously with the increasing of normal load and then became constant at higher pressures. At low normal load, fretting fatigue life was found to increase with increase in the pad radius. At high normal load, however, the fretting fatigue life remained almost unchanged with changes in the fretting pad radius. The bulk stress amplitude had the dominant effect on fretting fatigue life. The fretting fatigue life diminished as the bulk stress amplitude increased.