scholarly journals Calibration of test probes and experimental monitoring of changes in moisture of selected materials of subgrade structures

2018 ◽  
Vol 196 ◽  
pp. 04058
Author(s):  
Peter Dobeš ◽  
Libor Ižvolt ◽  
Martin Mečár
Keyword(s):  
Protective Layer ◽  
Railway Track ◽  
Winter Period ◽  
Moisture Determination ◽  
Experimental Stand ◽  
Crushed Aggregate ◽  
Railway Engineering ◽  
Track Management ◽  
Structural Layer

The paper describes experimental activity carried out at the Department of Railway Engineering and Track Management of the Faculty of Civil Engineering, University of Žilina. It focuses on monitoring moisture changes in individual structural layers of the railway track body and its subgrade, performed on the railroad model, (1:1 scale). The Introduction characterizes the experimental stand models of the Department, used for monitoring the moisture changes in the structural layers. The second part of the paper focuses on the characteristics of the moisture determination method - time reflectometry (TDR method), and on the calibration of TRIME PICO IPH T3 probes for real materials of the experimental stand DRETM (crushed aggregate, fr. 0 / 31.5 mm - protective layer, crushed aggregate, fr. 0/63 mm - embankment, clay with the addition of river gravel – foundation). The calibration was a substantial prerequisite for the subsequent humidity monitoring of the railway models. The next part of the paper presents the recorded moisture values of the structural layer materials, built in the measuring profiles of the experimental stand DRETM, measured before and during the winter period 2017/2018. The Conclusion evaluates the measured values and the determination of the input moisture values that will be used for the numerical modeling of the thermal regime of subgrade structure by the SoilVision software.

scholarly journals Verification of boundary conditions of numerical modeling of the track substructure thermal regime – influence of the snow cover

2018 ◽  
Vol 4 (48) ◽  
pp. 51-60 ◽  
Author(s):  
Libor IŽVOLT ◽  
Peter DOBEŠ ◽  
Juraj PIEŠ
Keyword(s):  
Numerical Modeling ◽  
Boundary Conditions ◽  
Snow Cover ◽  
Air Temperature ◽  
Protective Layer ◽  
Railway Track ◽  
Experimental Stand ◽  
Crushed Aggregate ◽  
Railway Engineering ◽  
Track Substructure

The initial part of the paper briefly characterizes a long-term experimental activity at the Department of Railway Engineering and Track Management (DRETM). The research of the DRETM focuses, besides other research activities and specific problems in the field of railway engineering (application of new structures and construction materials in conventional and modernized railway tracks, modernisation and rehabilitation of existing railway tracks for higher speeds, track diagnostics, influence of track operation on noise emissions and design of structural measures, possibility of application of recycled ballast bed material in the track substructure, ballast recycling technologies, ecological assessment of recycled material of the track substructure), on various factors affecting track substructure freezing. In 2012-2017, in the campus of the University of Žilina (UNIZA), an Experimental stand DRETM was built for the research purposes. The experimental stand DRETM consists of 6 types of track substructure placed in an embankment or a cut, in the 1:1 scale. Besides conventional building materials (crushed aggregate), these structures also include various thermal insulation materials (Liapor concrete, Styrodur, foam concrete). A significant part of the paper deals with numerical modeling of the freezing process of track substructure (an embankment with the embedded protective layer of crushed aggregate, fr. 0/31.5 mm) for various boundary conditions (air frost index, average annual air temperature), using SoilVision software. The aim of this research is to identify the thermal insulation effects of different thicknesses of snow cover on the depth of penetration of the zero isotherm into the track substructure (railway track). The paper conclusion specifies the influence of different snow cover thicknesses, or nf factor (factor expressing the dependency between the mean daily air temperature and the temperature on the ballast bed surface) and various climatic conditions (frost indexes and average annual air temperatures), affecting the railway infrastructure, on the resulting depth of freezing of the track substructure (railway track). These outputs will be in the further research used for the design of nomogram for determining the thickness of the protective layer of the frost-susceptible subgrade surface of the track substructure.

scholarly journals Calibration of TDR Test Probe for Measuring Moisture in the Body of the Railway Substructure and its Subgrade

2015 ◽  
Vol 11 (2) ◽  
pp. 84-94 ◽  
Author(s):  
Peter Dobeš
Keyword(s):  
The Body ◽  
Substantial Part ◽  
Test Probe ◽  
Rock Materials ◽  
Experimental Stand ◽  
Railway Engineering ◽  
Track Management ◽  
Railway Substructure ◽  
Basic Prerequisite

Abstract In the introduction of the paper there is characterized a way of monitoring the moisture in the railway substructure in the experimental stand, which is a part of the experimental workplace of the Department of Railway Engineering and Track Management. A substantial part of the paper is devoted to the calibration of TDR test probe for selected rock materials as a basic prerequisite for the determination of the actual moisture in the body of the railway substructure and subgrade.

Tribology of rail bogie

2018 ◽  
Vol 77 (4) ◽  
pp. 230-240
Author(s):  
D. P. Markov
Keyword(s):  
Contact Fatigue ◽  
Basic Element ◽  
Difficult Problem ◽  
Railway Track ◽  
Rolling Stock ◽  
Kinematic Parameters ◽  
Approximate Estimation ◽  
Railway Bogie ◽  
Classical Calculation

Railway bogie is the basic element that determines the force, kinematic, power and other parameters of the rolling stock, and its movement in the railway track has not been studied enough. Classical calculation of the kinematic and dynamic parameters of the bogie's motion with the determination of the position of its center of rotation, the instantaneous axes of rotation of wheelsets, the magnitudes and directions of all forces present a difficult problem even in quasi-static theory. The paper shows a simplified method that allows one to explain, within the limits of one article, the main kinematic and force parameters of the bogie movement (installation angles, clearance between the wheel flanges and side surfaces of the rails), wear and contact damage to the wheels and rails. Tribology of the railway bogie is an important part of transport tribology, the foundation of the theory of wheel-rail tribosystem, without which it is impossible to understand the mechanisms of catastrophic wear, derailments, contact fatigue, cohesion of wheels and rails. In the article basic questions are considered, without which it is impossible to analyze the movement of the bogie: physical foundations of wheel movement along the rail, types of relative motion of contacting bodies, tribological characteristics linking the force and kinematic parameters of the bogie. Kinematics and dynamics of a two-wheeled bogie-rail bicycle are analyzed instead of a single wheel and a wheelset, which makes it clearer and easier to explain how and what forces act on the bogie and how they affect on its position in the rail track. To calculate the motion parameters of a four-wheeled bogie, it is represented as two two-wheeled, moving each on its own rail. Connections between them are replaced by moments with respect to the point of contact between the flange of the guide wheel and the rail. This approach made it possible to give an approximate estimation of the main kinematic and force parameters of the motion of an ideal bogie (without axes skewing) in curves, to understand how the corners of the bogie installation and the gaps between the flanges of the wheels and rails vary when moving with different speeds, how wear and contact injuries arise and to give recommendations for their assessment and elimination.

Experimental Determination of Wheel and Guiding Forces on the Tracks

2015 ◽  
Vol 732 ◽  
pp. 203-206
Author(s):  
Lubos Pazdera ◽  
Jaroslav Smutny ◽  
Libor Topolář
Keyword(s):  
Experimental Determination ◽  
Vertical Direction ◽  
Railway Track ◽  
Experimental Basis ◽  
Force Interaction ◽  
Dynamic Forces ◽  
Passing Train ◽  
Strain Measures

Force interaction between a railway track and a vehicle affects the safety, comfort, and last but not least, economical maintenance. Train of wagons incidence on track in both transversal and vertical direction is simplified by qualifying of force wheel (FQ), guiding (FY) and perpendicular and transverse acceleration. An experimental basis for dynamic determination of vertical, FQ, and lateral, FY, forces at the wheel using strain measures in the foot of the rail is given. Measurements of the dynamic forces during passing train are normally very costly and uneasy. These method consists of measuring strains at selected points of the rail profile is very simple and therefore interesting.

An evaluation of five methods for the determination of moisture in grass seeds

2002 ◽  
Vol 82 (2) ◽  
pp. 401-405
Author(s):  
N. A. Fairey
Keyword(s):  
Key Words ◽  
Rapid Determination ◽  
Performance Characteristics ◽  
Grass Species ◽  
Moisture Determination ◽  
Fresh Weight ◽  
Seed Moisture ◽  
Seed Crops ◽  
Time Of Harvest

Seed of four grass species was re-hydrated to 11 pre-determined moisture concentrations ranging from 100 to 600 g kg-1 fresh weight ( FW) to simulate seed maturation during swathing and combining. The performance characteristics of three thermogravimetric and two electronic capacitance methods of moisture determination were evaluated. The thermogravimetric methods had no moisture range limitations and were, in general, more accurate than the electronic methods. The thermogravimetric Koster tester is suitable for grass seeds of all moisture concentrations, and can be easily adapted for use at field sites. The John Deere Moisture- Chek electronic tester is suitable for the rapid determination of moisture in grass seeds but is limited to concentrations of 80–250 g kg-1 FW. Key words: Grass seed crops, seed moisture measurement, swathing, combining, time of harvest

scholarly journals Features of the Surface and Subsurface Waves Application for Ultrasonic Evaluation of Physicomechanical Properties of Solids. Part 1. Influence of the Geometrical Parameters

2018 ◽  
Vol 9 (4) ◽  
pp. 325-326
Author(s):  
A. R. Baev ◽  
A. L. Mayorov ◽  
M. V. Asadchaya ◽  
V. N. Levkovich ◽  
K. G. Zhavoronkov
Keyword(s):  
Protective Coating ◽  
Layer Structure ◽  
Base Material ◽  
Protective Layer ◽  
Body Waves ◽  
Measuring System ◽  
Geometrical Parameters ◽  
Small Aperture ◽  
Ultrasonic Evaluation

Application of surface and subsurface waves for control of objects with a double-layer structure allows to extend possibilities of diagnostics of their physico-mechanical properties. The purpose of work was to determine conditions and offer recommendations providing measuring of ultrasonic velocity and amplitude of the former modes in protective layers and in basis of object at one-sided access to its surface.The analysis of an acoustic path of a measuring system in relation to ultrasonic evaluation of the objects having the restricted sizes and the protective coating according to velocity data of the surface and subsurface waves propagation is made. On the basis of representations of beam acoustics the dependences connecting a wavelength of the excited surface and subsurface modes, thickness and width of a controlled object, acoustic base of a sounding are defined. There are to provide a condition leveling of the influence of an acoustical noise created by the reflected and accompanying waves on parameters of acoustic signal with the given quantity of oscillations in an impulse.The principle opportunity is shown and conditions for determination of velocity of subsurface body waves in the base material which is under a protective coating layer are established. For these purposes on the basis of use of the block of ultrasonic probes the optimum scheme of a sounding is offered and the analytical expression for calculation of required velocity considering varying of thickness of a covering is received.The method of acoustical measuring realized by a direct and reverse sounding of the objects with small aperture and angle probes was analysed and formulas for determination of speed of subsurface wave under protective layer of the wedge form have been got. An ultrasonic device is suggested for the excitationreception of subsurface waves with different speed in objects (on 20–35 %) using for the acoustic concordance of environments of metallic sound duct as a wedge. Possibility of leveling of interference in a protective layer to control efects in basis of material by a volume wave by creation of supporting echo-signal of longitudinal wave of the set frequency and entered normally to the surface of object was studied.

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