Mechanical characteristic variation of ballastless track in high-speed railway: effect of train–track interaction and environment loads

Railway Engineering Science - Due to the fact that ballastless tracks in high-speed railways are not only subjected to repeated train–track dynamic interaction loads, but also suffer from...     

An overview of a unified theory of dynamics of vehicle–pavement interaction under moving and stochastic load

Railway Engineering Science - This article lays out a unified theory for dynamics of vehicle–pavement interaction under moving and stochastic loads. It covers three major aspects of the...     

Vibration and sound radiation of a rotating train wheel subject to a vertical harmonic wheel–rail force

Railway Engineering Science - The rapid development of high-speed railway networks requires advanced methods for analysing vibration and sound radiation characteristics of a fast rotating train...     

Gauge-meter model building based on the effect of elastic deformation of rolls in a plate mill

The calculation error of the gauge-meter model will affect the gap setting precision and the self-learn precision of rolling force. The precision of the gauge-meter model is strongly influenced by plate width, working roll radius, backup roll radius, working roll crown, backup roll crown, and rolling force. The influence rules are hard to get by measuring. Taking a conventional 4-h plate mill as the research subject, these influences were transferred into the calculation of roll deflection and flattening deformation. To calculate these deformations, the theory of the influence function method was adopted. By modifying the traditional gauge-meter model, a novel model of the effect of roll elastic deformation on the gap setting was built by data fitting. By this model, it was convenient to analyze the variation caused by the rolling condition. Combining the elastic deformation model of rolls with the kiss-rolls method, a gauge-meter model was put forward for plate thickness prediction. The prediction precision of thickness was greatly improved by the new gauge-meter model.     

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.     

Reflection and Transmission of the Level Step to the Waves in a Linear and Continuous Layer Liquid

1 Introduction Owing to the hot radiation of the sun, the den- sity distribution of water is usually perpendicular in actual oceans and river bayoux. The source of the disturbance will not only produce water waves of a surface mode, but also of an internal mode[1–2]. In layered liquids the internal mode will induce some dynamic water phenomena which are different from those in the single layer liquid[3]. Considering the propagation of waves in deep upheaval terrain, the problem can be simplif…     

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.

     

Testing of NAPL simulator to predict migration of a light nonaqueous phase liquid (LNAPL) under water table fluctuation in a sandy medium简

Nanoqueous phase liquid （NAPL） simulator is a powerful and popular mathematical model for modeling the flow and transport of non-aqueous phase liquids in subsurface, but the testing of its feasibility under water table fluctuation has received insufficient attention. The feature in a column test was tested through two cycles of water table fluctuation. The sandy medium in the column was initially saturated, and each cycle of water table fluctuation consisted of one water table falling and one rising, resulting in a drainage and an imbibition of the medium, respectively. It was found that the difference between the simulated and measured results in the first drainage of the column test was minor. However, with the propagation of the water table fluctuations, the simulation errors increased, and the simulation accuracy was not acceptable except for the first drainage in the two fluctuation cycles. The main reason was proved to be the estimation method of residual saturation used in this simulator. Also, based on the column tests, it was assumed that the resulting residual saturation from an incomplete imbibition process was a constant, with a value equal to that of the residual value resulting from the main imbibition process. The results obtained after modifying NAPL simulator with this assumption were found to be more accurate in the first cycle of water table fluctuation, but this accuracy decreased rapidly in the second one. It is concluded that NAPL simulator is not adequate in the case of LNAPL migration under water table fluctuation in sandy medium, unless a feasible assumption to estimate residual saturation is put forward.     

The non-local theory solution of a Griffith crack in functionally graded materials subjected to the harmonic anti-plane shear waves

In this paper, the dynamic stress field near crack tips in the functionally graded materials subjected to the harmonic anti-plane shear stress waves was investi- gated by means of the non-local theory. The traditional concepts of the non-local theory were extended to solve the fracture problem of functionally graded materials. To make the analysis tractable, it was assumed that the material properties vary exponentially with coordinate parallel to the crack. By use of the Fourier transform, the problem can be solved with the help of a pair of dual integral equations, in which the unknown variable was the displacement on the crack surfaces. To solve the dual integral equations, the displacement on the crack surfaces was expanded in a series of Jacobi polynomials. Unlike the classical elasticity solutions, it is found that no stress singularities are present at crack tips. The non-local elastic solutions yield a finite hoop stress at crack tips, thus allowing us to use the maximum stress as a fracture criterion. The magnitude of the finite dynamic stress field depends on the crack length, the parameter describing the functionally graded materials, the circular frequency of the incident waves and the lattice parameter of materials.     

A fixed point theorem for a class of β-constrictive operators and its application to the integral equation in L~1(0,∞)

0　ＩＮＴＲＯＤＵＣＴＩＯＮＩｎ 1977,Ｆ .Ｓ .ＤｅＢｌａｓｉ[1] ｄｅｆｉｎｅｄｔｈｅｍｅａｓｕｒｅｏｆｗｅａｋｎｏｎｃｏｍｐａｃｔｎｅｓｓｆｏｒａｎｏｎｅｍｐｔｙｂｏｕｎｄｅｄｓｕｂｓｅｔＧｏｆａＢａｎａｃｈｓｐａｃｅＥａｓｆｏｌｌｏｗ :β(Ｇ) =ｉｎｆ {ｒ>0｜ｔｈｅｒｅｅｘｉｓｔｓａｗｅａｋｌｙｃｏｍｐａｃｔｓｅｔＣｓｕｃｈｔｈａｔＧ Ｃ+Ｂｒ}ｗｈｅｒｅＢｒ ={ｘ ∈Ｅ｜‖ｘ‖ ≤ｒ} ,ａｎｄｄｉｓｃｕｓｓｅｄｉｔｓｐｒｏｐｅｒｔｉｅｓｉｎｄｅｔａｉｌ .Ｉｎ 1981,ｂｙｍｅａｎｓｏｆｍｅａｓｕｒｅｓｏ…     

A fixed point theorem for a class ofβ-constrictive operators and its application to the integral equation in L1 (O, ∞ )

Presents the fixed point theorem for a class ofβ-constrictive increasing operators without continuity and discusses the existence of solution of the integral equation with the discontinuous term in L1(0, ∞ ) by using this theorem.