Refinement of the rail–wheel contact pair to improve rail–wheel interaction conditions for railway vehicles with an increased axle load

At present, one of the global trends in railway transport development, which becomes clearer and clearer, is increasing the axle load of freight cars, which gives a considerable economic benefit. In this connection, of importance is not only the car design, but also the car capacity utilization factor: the higher this factor, the more economically efficient the car use. Because of this, one of the priority global lines in increasing the volume of fright traffic and the railway operation efficiency is increasing the carrying capacity of freight cars. Preparing the railways for cars with increased axle loads calls for the development of measures to decrease the track deformability, in particular by choosing appropriate wheel and rail profiles. The aim of this work was to develop recommendations on refining the wheel?rail contact pair to improve curve negotiation by railway vehicles with an increased axle loads on the Ukrainian railways. This paper presents the proprietary R-ITM wear-resistant railhead profile. The effect of the new profile on wheel?rail interaction in negotiating a curve of radius 300 m at a constant speed was studied for different cars. In doing so, emphasis was on wheel?rail interaction for a new-generation freight car on 18-9817 trucks with an axle load increased to 36 tf. The studies conducted made it possible to formulate the following recommendations: to improve curve negotiation by railway vehicles with increased axle loads, reduce the adverse effect on the track and improve traffic safety, new proprietary contact pair profiles are recommended: the ITM-73-03 wheel profile for cars, and the R-ITM railhead profile for outer rails together with the standard R65 railhead profile for inner rails.

Trajectory Tracking and Load Monitoring for Moving Vehicles on Bridge Based on Axle Position and Dual Camera Vision

Monitoring traffic loads is vital for ensuring bridge safety and overload controlling. Bridge weigh-in-motion (BWIM) technology, which uses an instrumented bridge as a scale platform, has been proven as an efficient and durable vehicle weight identification method. However, there are still challenges with traditional BWIM methods in solving the inverse problem under certain circumstances, such as vehicles running at a non-constant speed, or multiple vehicle presence. For conventional BWIM systems, the velocity of a moving vehicle is usually assumed to be constant. Thus, the positions of loads, which are vital in the identification process, is predicted from the acquired speed and axle spacing by utilizing dedicated axle detectors (installed on the bridge surface or under the bridge soffit). In reality, vehicles may change speed. It is therefore difficult or even impossible for axle detectors to accurately monitor the true position of a moving vehicle. If this happens, the axle loads and bridge response cannot be properly matched, and remarkable errors can be induced to the influence line calibration process and the axle weight identification results. To overcome this problem, a new BWIM method was proposed in this study. This approach estimated the bridge influence line and axle weight by associating the bridge response and axle loads with their accurate positions. Binocular vision technology was used to continuously track the spatial position of the vehicle while it traveled over the bridge. Based on the obtained time–spatial information of the vehicle axles, the ordinate of influence line, axle load, and bridge response were correctly matched in the objective function of the BWIM algorithm. The influence line of the bridge, axle, and gross weight of the vehicle could then be reliably determined. Laboratory experiments were conducted to evaluate the performance of the proposed method. The negative effect of non-constant velocity on the identification result of traditional BWIM methods and the reason were also studied. Results showed that the proposed method predicted bridge influence line and vehicle weight with a much better accuracy than conventional methods under the considered adverse situations, and the stability of BWIM technique also was effectively improved. The proposed method provides a competitive alternative for future traffic load monitoring.

Influence of Trajectory and Dynamics of Vehicle Motion on Signal Patterns in the WIM System

This paper presents the analyses of the signals recorded by the main sensors of a WIM test station in the cases of abnormal runs (i.e., runs with the changes of trajectory or the dynamics of vehicle motion). The research involved strain gauges which are used for measuring the weight of vehicles, inductive loops, as well as piezoelectric sensors used, inter alia, to detect twin wheels and to determine where a vehicle passes through a station. Since the designers intend the station to be able to implement the direct enforcement function, the selection of runs deviating from the normative ones constitutes an important issue for the assessment of the measurement reliability. The study considered the location of the trajectory of the runs, the dynamics (acceleration/braking) and the trajectory changes. The change in the amplitude and the value of the signal recorded by the strain gauges as a function of the location (position) of the contact between sensor and tires is a noteworthy observation which indicates the need to monitor this parameter in automatic WIM systems. Other tests also demonstrated the influence of the analysed driving parameters on the recorded results. However, by equipping the WIM station with a set of duplicate strain gauges, the measurement errors of the gross weight and axle loads are normally within the accuracy limits of class A(5) stations. Only in the case of accelerating/decelerating, does the error in measuring the load of a single axle reach several per cent.

Research on Vibration Law of Railway Tunnel Substructure under Different Axle Loads and Health Conditions

In this paper, 25-ton and 27-ton axle heavy trucks are used to carry out moving loading and dynamic real vehicle test on the cracked section, the intact section, and the repaired section of a railway tunnel foundation to test the dynamic performance of the tunnel basement structure with the change of axle loads and health conditions. By analyzing the influence law of dynamic response and fatigue life of heavy haul train under different basement conditions (intact, damaged, and repaired), the adaptability of railway tunnel equipment to freight trucks axle load is clarified. The results show that (1) the intact section of the tunnel can meet the normal operation of 25-ton and 27-ton axle load freight trains in good condition. (2) The normal operation of 25-ton and 27-ton axle load freight trucks is seriously affected by the cracked section of the tunnel. When the cracks in the tunnel basement are gradually hollowed out by groundwater, serious traffic accidents such as vehicle shaking and derailment are likely to occur. (3) The repaired section of the tunnel can meet the normal operation of 25-ton and 27-ton axle load freight trains after adopting the integrated comprehensive treatment of “Anchor-Injection-Drainage”. The research results will have reference significance for the condition assessment and disease treatment of the basement structure of the heavy haul railway tunnel.

Commissioning of the freight wagons with increased axle loads is a guarantee of the further development of railways of the Republic of Uzbekistan

The aim of the study is to select rational axle loads of the rolling stock and establish the conditions for their circulation on the railways of the Republic of Uzbekistan. In this work, research has been carried out to assess the indicators of the stress-strain state of rail track elements from the action of the rolling stock with various axial loads. The dynamic loads from the rolling stock wheel on the rail, tensile stresses at the edges of the rail foot, in wooden sleepers (rubber under-rail pads on reinforced concrete) under the linings, in the ballast under the sleeper, as well as stresses at the main area of the roadbed, were determined. The obtained results of studies on the determination and assessment of the loading of the elements of the permanent way and sub-grade bed under the condition of not exceeding their standard values made it possible to establish the permissible speeds of movement of freight wagons with increased axle loads of 25 and 27 tf on the railways of the Republic of Uzbekistan, depending on the design of the track and the thickness of the ballast layer, which will increase the running and carrying capacity of the most loaded sections of the railway network, reduce operating costs, increase the volume of freight traffic by rail, which will create conditions for the further development of national rail transport in the implementation of export and transit potential.

Response Characteristics of Inverted-base Asphalt Pavement Structure in Cold Area under Multi-axle Loads

In cold areas, semi-rigid base asphalt pavement is prone to generate reflection cracks due to thermal contraction and dry shrinkage, and the base layer cracks can cause surface layer cracking and shorten the service life of the pavement. Aiming at understanding the response characteristics of asphalt pavement structure under multi-axle loads in cold areas, this paper took semi-rigid base asphalt pavement and inverted-base asphalt pavement as the research objects, and employed ANSYS to conduct finite element analysis on them to figure out the response characteristics of the asphalt pavement structure under the condition of different multi-axle loads and graded macadam base course. The research results showed that, the action of multi-axal loads increased the tensile stress of the base layer of the asphalt pavement and the tensile stress of the base layer of the semi-rigid base asphalt pavement, and increased the road surface deflection, which had resulted in insufficient bearing capacity of the pavement structure, and thus causing significant damages to the asphalt pavement; analysis of the response characteristics of the two types of asphalt pavement showed that, adding a graded macadam base course as the stress-absorbing layer is conductive to reducing the tensile stress of the base layer of the semi-rigid base asphalt pavement and effectively delaying or inhibiting reflection cracks generating on the pavement. The study of this paper provided a theoretical reference for the design and construction of asphalt pavement.

AUTOMATIC DETERMINATION OF THE PARTIALLY FILLED TANK VEHICLE COMBINATION BRAKING MODE

The article considers the possibility of identification by automatic control systems of the braking mode of a vehicle combination with a partially filled tank. The algorithms of operation of modern vehicle stabilization systems are based on a reaction to approaching critical points of loss of stability, while the forces with which a fluid acts in a partially filled tank on a vehicle sometimes have a rapid rise when the speed or direction changes, which leads to a decrease in the efficiency of such systems. Automatic identification of the braking mode with a partially filled tank can make it possible to predict the negative consequences of fluid flow and carry out preventive manipulations to stabilize the vehicle until it actually approaches critical points of loss of stability. To solve the problem, a comparative analysis of changes in the magnitude of the normal reaction of the supporting surface on the axis of the vehicle combination during braking with a partially filled tank semi-trailer and an equivalent rigidly fixed load was carried out. Such an analysis showed that in the case of transportation of rigid cargo, the load on the axles of the vehicle combination varies linearly and in proportion to deceleration. In the case of a partially filled tank, the axle load varies non-linearly due to the trigonometric nature of the fluid movement relative to the tank. This feature allows you to distinguish between these modes. As a result, it was proposed to use an identifier that can detect the braking mode of a vehicle combination with a partially filled tank by determining the nature of the changes in axle loads. To calculate the identifier, the axle loads and vehicle acceleration over time are used, and data on the design features of the vehicle combination are not required. Keywords: vehicle combination, tank vehicle, partially filled tank, stability, braking.