Comparative study on wheel–rail dynamic interactions of side-frame cross-bracing bogie and sub-frame radial bogie

Railway Engineering Science - Improving freight axle load is the most effective method to improve railway freight capability; based on the imported technologies of railway freight bogie, the...     

An experimental study on the effects of friction modifiers on wheel–rail dynamic interactions with various angles of attack

By modifying friction to the desired level, the application of friction modifiers(FMs) has been considered as a promising emerging tool in the railway engineering for increasing braking/traction force in poor adhesion conditions and mitigating wheel/rail interface deterioration, energy consumption, vibration and noise. Understanding the effectiveness of FMs in wheel–rail dynamic interactions is crucial to their proper applications in practice, which has, however, not been well explained. This st...     

Intact soft clay’s critical response to dynamic stress paths on different combinations of principal stress orientation

Comprehensive tests on Hangzhou intact soft clay were performed, which were used to obtain the soils’ critical response to undrained dynamic stress paths under different combinations of principal stress orientation. The different combinations included cyclic principal stress rotation (CPSR for short), cyclic shear with abrupt change of principal stress orientation (CAPSO for short) and cyclic shear with fixed principal stress orientation (CFPSO for short). On one side, under all these stress paths, samples have obvious strain inflection points and shear bands, and the excess pore water pressure is far from the level of initial effective confining pressure at failure. Stress paths of major principal stress orientation (α) alternating from negative and positive have quite different influence on soil’s properties with those in which α is kept negative or positive. On the other side, due to the soil’s strongly initial anisotropy, samples under double-amplitudes CPSR and CAPSO (or single-amplitude CPSR and CFPSO) have similar properties on dynamic shear strength and pore water pressure development tendency when α is kept within ±45°, while have quite different properties when α oversteps ±45°.     

A dynamic problem on the edges of a mode Ι crack subjected to moving unit-step loads

Afurtherinvestigationfordynamicfractureprob lemsofamodeΙcrackundermovingsteploadshas beenperformed,andageneralexpressionofthesolu tionsisgivenwiththemethodofcomplexvariablefunc tions.Bysuchmethods,theproblemstudiedisde ducedtoaproblemofRiemann Hilbert,wh…     

Experimental study on fluid flow in arciform clearance

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Research on flow stress in ferrite deformation of a Ti-IF steel

The experiments of the ferrite warm deformation of ultra-low carbon （ULC） Ti-IF steel were carded out on a hot simulator and the influences of deformation temperature, strain, and strain rate on the flow stress were analyzed. New flow stress models suitable to ferrite warm forming of Ti-IF steel were given on the basis of analyzing the influence of deformation technology parameters on the flow stress.     

Effects of proton radiation on field limiting ring edge terminations in 4H–SiC junction barrier Schottky diodes

In this study, the effects of high-energy proton radiation on the effectiveness of edge terminations using field limiting rings(FLRs) in 4 H–SiC junction barrier Schottky(JBS) diodes were examined in detail. The devices were irradiated using 5-MeV protons at fluences ranging from 5×10~(12) cm~(-2) to 5×10~(14) cm~(-2). Further, the reverse breakdown performances of the investigated devices were measured both before and after irradiation. Proton irradiation initially decreased the breakdown voltage(BV);subsequently, the BV was increased as the proton fluence increased. At a fluence of 5×10~(13) cm~(-2), the BV was reduced by approximately 18%, whereas it was reduced by approximately 5% at a higher proton fluence of 5×10~(14) cm~(-2). The related degradation mechanism that was associated with this phenomenon was also investigated using the numerical simulations of the current-voltage(I-V) and capacitance-voltage(C-V) characteristics of the device. The main contribution to the radiation-induced changes in BV originates from the variations of charge distribution at the SiO_2/4 H–SiC interface and the reduction of the net carrier density in the drift region. Both the aforementioned variations affect the spread of the electric field in the FLR edge termination regions.     

Numerical simulation on electrolyte flow field in 156 kA drained aluminum reduction cells

Based on the commercial CFD software CFX-4.3, two-phase flow of electrolyte in 156 kA drained aluminum reduction cells with a new structure was numerically simulated by multi-fluid model and k-ε turbulence model. The results show that the electrolyte flow in the drained cells is more even than in the conventional cells. Corresponding to center point feeding, the electrolyte flow in the drained cells is more advantageous to the release of anode gas, the dissolution and diffusion of alumina, and the gradient reduction of the electrolyte density and temperature. The average velocity of the electrolyte is 8.3 cm/s, and the maximum velocity is 59.5 cm/s. The average and maximum velocities of the gas are 23.2 cm/s and 61.1 cm/s, respectively. The cathode drained slope and anode cathode distance have certain effects on the electrolyte flow.     

Experimental study on the mechanical and failure behaviors of deep rock subjected to true triaxial stress: A reviewOA

It has become an inevitable trend of human development to seek resources from the deep underground.However, rock encountered in deep underground engineering is usually in an anisotropic stress state(σ₁>σ>σ₃) due to the influences of geological structures and engineering disturbances. It is therefore essential to study the mechanical, seepage, and dynamic disaster behaviors of deep rock under true triaxial stress to ensure the safe operation of deep rock engineering an...     

Experimental study on expansion and cracking properties of static cracking agents in different assembly statesOA

Rolled static cracking agent(RSCA) can solve the intractable problem of traditional bulk static cracking agent(BSCA) in engineering applications. This paper innovatively studies the rational water-cement ratio of BSCA and the immersion soaking time of RSCA under the condition of controlling temperature.Through the expansion and cracking performance experiments, the development characteristics of expansion pressure, the cracking effect of the single-hole specimen and the performance of hole spray...     

Geometry deviation effects of railway catenaries on pantograph–catenary interaction: a case study in Norwegian Railway System

This paper presents a non-contact measurement of the realistic catenary geometry deviation in the Norwegian railway network through a laser rangefinder. The random geometry deviation is included in the catenary model to investigate its effect on the pantograph–catenary interaction. The dispersion of the longitudinal deviation is assumed to follow a Gaussian distribution. A power spectrum density represents the vertical deviation in the contact wire. Based on the Monte Carlo method, several geometry deviation samples are generated and included in the catenary model. A lumped mass pantograph with flexible collectors is employed to reproduce the high-frequency behaviours. The stochastic analysis results indicate that the catenary geometry deviation causes a significant dispersion of the pantograph–catenary interaction response. The contact force standard deviations measured by the inspection vehicle are within the scope of the simulation results. A critical cut-off frequency that covers 1/16 of the dropper interval is suggested to fully describe the effect of the catenary geometry deviation on the contact force. The statistical minimum contact force is recommended to be modified according to the tolerant contact loss rate at high frequency. An unpleasant interaction performance of the pantograph–catenary can be expected at the catenary top speed when the random catenary geometry deviation is included.

     

Guest editorial–special issue on ground control in mining in 2020

正Ground control is the science of studying and controlling the behavior of rock strata in response to mining operations.Ground-control-related research has seen significant advancements over the last 40 years, and these accomplishments are well documented in the proceedings of the annual International Conference on Ground Control in Mining (ICGCM)[1].     

Experimental study on time-dependent stress and strain of in-plane shear(ModeⅡ) fracture process of rock

Shear-box test with strain measurement was used to study time-dependent stress and strain of in-plane shear(Mode Ⅱ) fracture process of rock and to reveal the mechanism of Mode Ⅱ fracture.Numerical results show that the maximum shear stress τmax at the crack tip is much larger than the maximum tensile stress σ1 and the ratio of τmax/σ1 is about 5,which favors Mode Ⅱ fracture of rock.Test results indicate that the strain—time curve comprises three stages:the linear deformation stage,the micro-cracking stage ...     

Guest Editorial–Special issue on Ground Control in Mining

<正>Ground control is the science of studying and controlling the behavior of rock strata in response to mining operations.Ground control related research has made significant advancements over the last 35 years and these accomplishments are well documented in the proceedings of the annual International Conference on     

Experimental study on pore pressure in rock-soil slope during reservoir water level fluctuation

1 Introduction The effect of seepage flow is a key problem in the investigation on the landslide fail- ure. Water in landslide comes mainly from the infiltration of rainwater and seepage flow of ground water. Rivers and reservoirs are the dominant sources of ground water in landslide. The infiltration of water will cause variations of the ground water level in landslides, which sometimes play a key role in the landslide stability. In particular, the fluctuation of water level varies remarkabl…     

Guest Editorial–Special issue on recent advances in mine safety

正Mine safety has always been a priority to operating mines. The topic has captured the attention of researchers and scientists over the last two decades, and thanks to the support and commitment of the mining industry, a whole slew of new safety innovations has been developed, particularly in areas like mining automationrobotics, virtual reality, remote sensing, machine learning and others. As a result, remarkable progress has been made in both     

Numerical study on maximum rebound ratio in blasting wave propagation along radian direction normal to joints

1 INTRODUCTION For one dimensional wave, such as seismic wave, passing across single joint or multiple parallel joints, combining the theory of displacement discontinuities and the method of characteristics, solutions in terms of magnitudes of the reflection ratio and the transmission ratio have been obtained by several researchers[1?6] for P-wave and S-wave respectively. However, for a practical dynamic problem in a rock mass involving blasting wave propagation from a tunnel or borehole,…     

Experimental study on upward bubble velocity and pierce length distributions in a water model of copper converter

The upward bubble velocity and the pierce length distributions in a sectional water model of the copper converter in Guixi Smelter in Jiangxi, China, were measured using a two-contact electro-resistivity probe. In the case of using a single tuyere, the bubble velocity distribution along longitudinal direction was similar to that derived from Guassian function. Beyond the center of the longitudinal range, the bubble pierce length exhibited a sudden increase. The upward bubble velocity at a specified location could go up to meters per second. Its probability at a fixed location obeys a lognormal function; the bubble pierce length there varies bellow a few centimeters. In the case of using multi-tuyeres, the upward bubble velocity was roughly uniform right above the tuyeres and showed a slow decrease beyond this region. The bubble pierce length within both of these two regions was roughly uniform. Its average value in the former region, however, was found to be somewhat lower than that in the later.     

Orthogonal analysis of water model study on the optimization of flow control devices in a six-strand tundish

Improper flow control devices in a multi-strand tundish can cause some problems, for example, liquid steel cannot reach every nozzle at the same time and the liquid steel in nozzles far away from the entry zone has a lower temperature. The water model experiment of a six-strand tundish of Tianjin Iron ＆ Steel Co. Ltd. was performed, a new ＂U＂ type baffle was obtained, and its parameters were defined by perpendicular analysis. The ＂U＂ baffle can not only improve those imperfections, but also prolong the residence time of nonmetallic inclusions, which is good for their flotation and separation.