Papers by Keyword: Railway

Abstract: Maintenance due to the replacement of damaged wheels and rails due to rolling contact fatigue (RCF) and wear has been found to be the major problem to rail operating companies. This problem tends to lead to unavailability of railway networks. To solve this problem, costly wear simulators are developed to predict the wear behaviour of the rails and wheels to improve the preventive maintenance in pursuit of operational efficiency. Therefore, more studies that simulate a combination of rolling and sliding wear, together with RCF, are required, specifically for the Southern African, where good and cost-effective rail wear simulators are not readily available. The problem with wear and RCF simulators is high production costs, so this work aims to solve this problem by developing a cost-effective wear test rig that is capable of simulating RCF, sliding and rolling wear as experienced by the train wheel while moving along railway tracks. For this work, it was decided that twin-disc concept would be used, since literature clearly shown that the method was able to simulate the three damage mechanisms mentioned. The developed twin-disc wear simulator was able to simulate both rolling and sliding wear and parameters including contact load and slip ratio could be changed with ease so to simulate the actual contact conditions between the wheel and rail. Outputs such as coefficient of friction and wheel disc temperature were obtained. The results showed that the severity of wear is heavily dependent on slip ratio i.e., increased with slip ratio, with both coefficient of friction and wear rate increasing with slip ratio.

Abstract: The development of the technology for laser hardening of the axle seats of rail vehicles aims to improve the high-cycle service life of these axles under wheel pressing and thus to increase safety in rail transport. Laser hardening can create high compressive stresses that increase the fatigue resistance of the material. The paper will present the results of this development on the EA1N material together with the documentation of the microstructure, hardness profiles and correlations with the internal residual stresses as well. These compressive stresses can play a crucial role in significantly increasing the fatigue resistance of the axles under operation.

Abstract: This paper present a prediction of the centrifugal force caused by the dynamic unbalanced of train wheelset on a developed scale down test bench. The wheelset dynamic unbalanced can be one of reasons for the derailment accidents on trains. Dynamic unbalance represented by the produced centrifugal force can be the main factor causing wear on bearings, noise, vibrations on the train, and the fatal cause of trains accident. The behavior prediction is carried out by applying various eccentricity values by varying the additional weights. The centrifugal force prediction of the developed equipment then compared with the actual size wheelset’s unbalance behavior. The comparison shows a similar pattern between this miniature and the actual size test-bench in terms of the magnitude of the centrifugal force at various eccentricities and rotational speeds. Keywords: train, wheelset, railway, rotating unbalance

Abstract: Silt and clay with low liquid limits do not qualify as fill materials for high-speed railway (HSR) according to Chinese standard {TB, 10001 (2016)}. The present paper proposes using these materials as fillings for HSR embankments in an attempt to reduce the costs of exploiting and transporting qualifying fill materials. Our proposal of using silt and clay with low liquid limits is rooted in German standards {DIN,18196 (2006)} and {Ril, 836(1999)} and Japanese standards {ISBN 13: 9784621046692 (1999)}, and is preliminarily verified by operation experiences of the Zhengzhou–Xi'an HSR as well as other types of projects. On the basis of proven practices, a design cross-section for an HSR embankment constructed in from silt and clay with low liquid limits area is recommended combined with corresponding engineering measures.

Abstract: Mid-Life Refurbishment (MLR) is a process conducted in many industries to improve or extend the life span of assets such as machines, infrastructures and systems. The objective of MLR works execution is to extend the life span, sustain the train performance and achieve system reliability. Typically, the refurbishment scope consists of overhaul, upgrading and rectification works. The biggest challenge is to determine) the scope of refurbishment works and to create equilibrium between the feasibility and viability of the project. Therefore, the main objective of this paper is to discuss the current practice of performing MLR maintenance through the utilization of Failure Mode and Effect Analysis (FMEA) and to transform the existing FMEA used by the automotive industry to fulfil the needs of Rolling Stock. The use of FMEA is critical in determining) the scope of train refurbishment work. It was carried out at the initial stages of the process in order to determine Risk Priority Number (RPN) to prioritize the type of refurbishment plans and scope. The design of the FMEA Worksheets, De-sign of FMEA severity Evaluation Criteria, Design of Occurrence Evaluation Criteria and Design of FMEA Prevention/Detection Criteria were adopted and adapted from the generic format so that it is coherent with Railway Industries. The results based on the transformation framework, the plan and scope of overhaul, upgrading and rectification were defined using the FMEA. Out of the 80 elements of MLR works that were analyzed using the FMEA approach, it was found that 46 elements needed overhaul, 23 elements needed upgrading and 11 elements needed rectification works. Finally, the application of the FMEA helped determine the MLR scope of work from 13 systems. The case study was taken from the Malaysia LRT Project, and currently the fleet has been in operation for more than 20 years (operated since year 1998).

Abstract: The paper describes optimized measurements in field on points of railway control by the GNSS-RTK method. The purpose of measurement is to monitor the status of railroad track geometry. Good geometry extends the life of superstructure, reduces tracks and sleepers material wear during passing of the trains, and thus lowers the overall maintenance demands. In the model each of these points can be represented by node in graph and evaluation of graph edges corresponds to the distance between individual nodes. The task is to measure on every node even one times and to absolve the total route with minimal sum of distance. In fact it is searching of the Hamilton's path in a graph. The situation is complicated because the conditions for GNSS surveying in nodes are suitable only at certain time intervals during the day. Generally the above mentioned is difficult task, which is solved in the practice in many cases by heuristic methods. The authors proposed the optimization method based on Floyd algorithm and dynamic data structure - events list. The optimization of field measurement solves the time demands and brings economic effectiveness.

Abstract: Fragility curves for typical multi-span simply supported concrete box girder bridges in eastern China are presented. A set of bridge samples, of which five uncertain parameters are considered, is established using the Latin hypercube sampling. Nonlinear time history analyses are conducted to capture the structural response quantities. Probabilistic seismic demand models are formulated by quadratic regression analysis for the capacity/demand ratios. Fragility curves of bridge components are developed and the fragility of bridge system is evaluated using the first-order bound method. The results show that the columns and expansion bearings among bridge members are more fragile under earthquake excitation, and the bridge system is more fragile than any bridge component. The typical bridges have more than 50% probability when subjected to PGAs of 0.46, 0.58, 0.82, and 1.0g for four damage states, respectively. The fragility curves can be used for retrofit prioritization for this type of bridges.

Abstract: The presented paper considers approx. 5 years measurement on concrete railway bridge. The span is 39.875 + 34.877 + 37.000 + 9 x 31.500 m. The total length of the bridge is 443 m. Structure possesses typical three-box cross section. Monitoring was focused on temperature of concrete, temperature of atmosphere in the shade and mainly on measurement of movements of several bearings. Because the monitoring period of bridge structure was approx. 5 year, the probability p = 0.2 (5 years returning period) was chosen in order to compare measured data with standard values according to EN 1991-1-5. Of course, the standard value was assumed without any safety factor for this purpose. The maximal difference of measured and standard values was only 25 mm. This was achieved on the pillar where measured value of displacement range was 135 mm, standard value 160 mm and the dilatation length was 332 m. On the other hand, the minimal difference was only 3 mm on the pillar where measured value was 33 mm, standard value 36 mm and the dilatation length was 75 m. If the approx. 5 years measurement is compared with theoretical value of 5 years return period, the standard procedure cannot be classified as very conservative. It was shown that the long-time measurement is very important for the further development and improvement of the Eurocodes as well as statistical approach, i.e., returning time which shall be taken into account.

Abstract: Particle analysis methodology is presented, together with the morphology of the wear debris formed during rolling contact fatigue. Wear particles are characterised by their surface topography and in terms of wear mechanism. Rail-wheel materials are subjected to severe plastic deformation as the contact loading progresses, which contributes to a mechanism of major damage in head-hardened rail steel. Most of the current methodologies involve sectioning of the rail-wheel discs to trace material damage phenomena such as crack propagation and plastic strain accumulation. This paper proposes methodology to analyse the development of the plastically deformed layer by sectioning wear particles using the focussed ion beam (FIB) milling method. Moreover, it highlights the processes of oxidation and rail surface delamination during unlubricated rolling contact fatigue.

Abstract: The testing results obtained during investigation of 3D mat are presented in the article. The spatial mat is designed to provide a cheap, efficient and durable soil stabilization on slopes. The testing was focused on development of suitable methods to be used when assessing foil properties on-site. The tested samples were extracted from mats that were used for soil stabilization at the location of mine Nástup Tušimice (Company Severočeské doly, Czech Republic) and exposed to external environment and weathering for 2 years. The performance of the mats was compared with reference samples from unused mats stored for 2 years in laboratory conditions. The testing revealed that deterioration of the material is negligible over the period of 2 years.