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It is significant to study railway wheel tread wear laws and predict wheel tread wear for the safe operation of trains. In this paper, a wheelset-rail finite element model was established for contact analysis, and simulation results were verified by contact tests carried out on a self-built wheel-rail test rig. Based on the physical work, the FE friction work calculation method was proposed to obtain the node friction work of contact area, and the wheel tread friction work was obtained by superposition of node friction work along the train running direction. Based on FE results of the wheel tread friction work, a wheel tread wear calculation method was proposed to predict wear amounts and worn profiles under different operating mileage conditions. It was found that the difference between predicted wear amounts and measured data is less than 5%, and the predicted worn profiles have the same change trend as the measured profiles. The wheel tread wear calculation method based on the FE friction work has high computational efficiency and reliability, and it has good research significance and practical value. [ABSTRACT FROM AUTHOR]

The accurate prediction of disc-cutter wear has been a longstanding topic that affects the tunneling efficiency and performance of tunnel boring machines, especially the prediction of flat wear extent in mixed ground. In the present study, a novel method for predicting the wear depth of the disc cutter is proposed based on energy analysis. Initially, the critical condition for the occurrence of normal and flat wear is determined. Subsequently, according to the geometry of disc cutters and the relationship between wear loss and friction work, the normal and flat wear depth of the disc cutter are obtained, respectively. By comparing calculated wear with Ren's prediction model and a case study, the effectiveness of the present model was verified. Finally, the influences of penetration depth and installation radius on cutter wear in mixed ground were analyzed. The research results indicate that the critical condition for the occurrence of flat wear is that the resistance moments acting on disc cutters exceed the driving moment. In addition, it was found that flat wear extent was much larger than the normal one. The disc cutter is prone to wear abnormally in mixed ground. Sensitivity analyses on penetration depth and installation radius show that wear from of disc cutters is determined by penetration depth. Furthermore, both normal and flat wear exert positive correlations with installation radius. The present work may provide some primary understanding about the determination of the critical condition for the occurrence of flat wear under different engineering environments. [ABSTRACT FROM AUTHOR]

Highlights • A simplified starting dynamic model of the new power-cycling continuously variable transmission system (PCVT) is developed. • The two PCVT starting control mode, which include pure-throttle starting control and first-gear-clutch starting control, are proposed. • The throttle control strategy in the pure-throttle starting and the clutch oil pressure control strategy in the clutch starting control are formulated in stages respectively. • An optimization starting method of PCVT system is proposed based on the analytic hierarchy process and genetic algorithm. • After optimization, the starting jerk is effectively reduced by 36.6% in the pure-throttle starting mode and 34.2% in the first-gear-clutch starting mode. Abstract Based on a detailed introduction of the working principle and starting process of a new power-cycling continuously variable transmission (PCVT), a starting dynamic model of the system is established. According to its special structure and the characteristics of power reflux, pure-throttle and first-gear-clutch starting controls are proposed. Pure-throttle starting control of PCVT can realize accurate throttle control in stages, by using start time and jerk as control objectives and combining them with driver starting intentions. The clutch-starting control takes the jerk, friction work, and starting time as control objectives. Furthermore, its control strategy of the clutch-oil pressure change rate is formulated in stages, combined with driver starting intentions. To achieve the optimal starting performance, an optimization method is proposed, based on the analytic hierarchy process and genetic algorithm. Simulation results show that the two strategies can effectively guarantee the quality of vehicle starting with consideration of driver intentions. After optimization, the starting jerk is effectively reduced by 36.6% in the pure-throttle starting mode and 34.2% in the first-gear-clutch starting mode. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Disc cutter wear is a crucial problem that influences the working efficiency and security of hard rock tunnel boring machines (TBMs). This wear results from friction energy accumulation and conversion. In this study, the process of hard rock TBM disc cutter wear is identified and analyzed by quantifying the collective energy change. This study starts with an analysis of the friction process between the disc cutter and hard rock. The relationship between the rolling force work and thrust force work of the disc cutter is examined. As a result, the disc cutter energy equation is determined, and the meaning of the upper and lower bounds of this equation are discussed. Based on the above results, the hard rock TBM cutterhead energy equation is then deduced. A method to identify the friction work is developed. According to the energy wear theory, the cutter wear law on hard rock for a TBM cutterhead is revealed, and a method for predicting disc cutter wear for a hard rock TBM cutterhead is advanced. Furthermore, the validity of this prediction method is confirmed by utilizing data from project cases. [ABSTRACT FROM AUTHOR]

The high-speed projectile often has significant mass loss and nose blunting when it penetrates into the concrete target, which usually decreases the penetration performance of projectile. A shape-evolvement model is constructed to predict the shape evolvement and penetration performance of projectile in the present manuscript. The penetration process and projectile are respectively discretized in the temporal and spatial dimensions. The shape evolvement is obtained by the projectile outer surface receding point by point. During a discrete time step, the governing equation is derived for the receding displacement based on the thermal mechanism of mass loss. The related friction work between the projectile and target is obtained based on the energy conservation law, which avoids the determination of the specific form for friction. The model is validated by the experimental results. Furthermore, two suggestions are provided to reduce the projectile nose blunting by distributing the refractory material in the projectile nose. Both schemes achieve the prescribed aim and then enhance the penetration performance of the projectile. Finally, the underlying assumptions in the model are analyzed, and the possible reasons are discussed for the deviation between the model prediction and the experimental result. [ABSTRACT FROM AUTHOR]

A series of mathematical models were proposed to calculate the roll force, torque and power for cold strip asymmetrical rolling by means of the slab method, taking the percentages of the forward-slip, backward-slip and cross-shear zones into account. The friction power, plastic work and total energy consumption can be obtained by the models. The effects of variable rolling parameters—such as the speed ratio, entry thickness, friction coefficient and front and back tension—on the process of asymmetrical rolling are analyzed. In all cases, an increase in speed ratio leads to an increase in friction work and its proportions. The increase in entry thickness and deformation resistance causes both friction work and plastic deformation work to increase. The proportion of friction work decreases with increasing deformation resistance, entry thickness, front tension and back tension. In the circumstances of a thin strip being rolled with a large speed ratio, the proportion of friction work could exceed that of plastic deformation work. The concept of a threshold point of friction work was proposed to explain this phenomenon. As an example, threshold points T1, T2, T3 with the effect of the entry thickness and S1, S2, S3 with the effect of the friction coefficient have been obtained by computation. Finally, the experiment of the strip asymmetrical rolling was conducted, and a maximum error of 9.7% and an RMS error of 5.9% were found in the comparison of roll forces between experimental measurement values and calculated ones. [ABSTRACT FROM AUTHOR]

In this paper an open wagon equipped with three pieces bogies has been simulated as multi body dynamics model with non-linear effects of wedges and structural clearances using Universal Mechanism software. Analyses have been performed on closed loop track with tangent and curved sections considering random irregularities in the vertical and lateral directions of the track. Simulation results are used to calculate the friction work, wheel wear depth and worn wheel profiles for different velocities and radii of curvature. "Specht" model based on "Archard's Theory" is used for wear calculations. The wear depth of outer wheels is assessed to determine the effect of velocity, track curvature and Pivot friction of bogie on the wear pattern of wheels. The results show that Pivot friction has a great effect on the non-uniform wear of wheels even in short distances and the friction work is found to be dependent on the velocity. [ABSTRACT FROM AUTHOR]

This work presents a computational framework based on finite element methods to simulate the fibre-embedding process using ultrasonic consolidation process. The computational approach comprises of a material model which takes into account thermal and acoustic softening effects and a friction model which indicates the realistic friction behaviour at the interfaces. The derived material model and developed friction model have been incorporated in finite element model. Using the implemented material and friction model, thermo-mechanical analyses of embedding of fibre in aluminium alloy 3003 has been performed. Effect of different process parameters, such as velocity of sonotrode, displacement amplitude of ultrasonic vibration and applied loads, is studied and compared with the experimental results. The presented work has specially focused on the quality of the developed weld which could be evaluated by the friction work and the coverage of the fibre which is estimated by the plastic flow around the fibre. The computed friction work obtained from the thermomechanial analyses performed in this study show a similar trend as that of the experimentally found fracture energies. [ABSTRACT FROM AUTHOR]

The simulative assessment of brake squeal is commonly performed by applying the complex eigenvalue analysis (CEA) to large finite-element-method (FEM) models. Despite many advantages, this method has two major drawbacks: First, the resulting negative damping value gives no quantitative measure for the actual squeal propensity and second, no reliable experimental technique to measure the negative damping is available. Therefore, a direct validation and comparison of simulated and experimental squeal propensity is not possible. In this work, the energy analysis of friction-induced vibrations, proposed by Guan et al. [1] and Wagner et al. [2], is considered to overcome these drawbacks. Equations for computing the mechanical work proportions of a general multi-degrees-of-freedom (DOF) system, including the external work, are derived. These work proportions are compared to the results of the CEA for a self-excited linear and nonlinear two-DOF system exhibiting a mode coupling instability. It is shown that the work proportions of the linear and nonlinear system yield to the same stability boundaries as the CEA. The energy analysis enables the separate investigation of the dissipative and exciting work. In addition, the external work was found to predict the onset of an instability even before its actual occurrence. [ABSTRACT FROM AUTHOR]