Axle Mass Research Articles

Bridge State and Average Train Axle Mass Estimation for Adaptive Railway Bridges

Bridge State and Average Train Axle Mass Estimation for Adaptive Railway Bridges

Bifurcation analysis of a rear axle tramp car model

Axle tramp is a self-sustaining vibration in the driven axle of a vehicle with a beam axle layout, known to occur under heavy braking or acceleration. A 6DOF mathematical model of this phenomenon is used to identify how the key parameters of driveline stiffness, axle mass and fore/aft stiffness change the system’s dynamics. A bifurcation analysis is performed to study this nonlinear system’s dynamics. Four Hopf bifurcations in the underlying equilibria, along with a fold bifurcation in the outermost limit cycle branch, are shown to bound the parameter space where tramp occurs. The severity of tramp was found to be minimised by increasing drivetrain stiffness, reducing axle mass or increasing fore/aft stiffness: the trade-off for minimising tramp severity is that it may be easier to excite tramp when the drivetrain stiffness is increased, and the speed range over which tramp can occur is increased as fore/aft stiffness is increased. A key outcome from this work is that future electrified powertrains may experience more tramp, albeit at a reduced magnitude, than their combustion-powered counterparts.

Bridge’s vehicular loads characterization through Weight-In-Motion (WIM) systems. The case study of Brescia

The growing traffic flow and the increase in transported masses negatively affect infrastructural safety. Several authors have characterized traffic loads on bridges in the American and Chinese context using Weigh-in-Motion (WIM) systems. Conversely, very few studies have been carried out in Europe and, as far as the authors know, none in Italy. This study covers this gap by providing a statistical analysis of raw WIM data collected on a main bridge near the city of Brescia (Italy). First, the traffic flow and the characteristics of vehicles were gathered by a WIM device. Second, some descriptive statistics were performed by computing the probabilistic distributions of numerous vehicular attributes. Third, as a novelty element, a K-means based Clustering technique was adopted on a wide set of vehicular features to detect heavy vehicle clusters. The results showed the existence of three main clusters: two predominately composed by lightly overloaded ordinary vehicles and construction machinery, respectively, and one by mass exceptional vehicles. This study considers a broader set of vehicular parameters than previous ones and then, provides a deeper understanding. Moreover, it shows that axle mass limits violations are noteworthy among mass exceptional vehicles in Italy highlighting the need of improving weight enforcement. These knowledges will be crucial for a rational organisation of the existing assets.

A vision for a lightweight railway wheelset of the future

Rail vehicle lightweighting using fibre reinforced polymer composite materials is essential for the future of rail. This is recognised as a means of reducing carbon dioxide production through lower energy consumption, as well as reducing the impact on track degradation, thus delivering improved rail capacity and performance. This paper presents an overview of the work conducted within work package three of the NEXTGEAR project focused on the ‘wheelset of the future’. Three concepts for a hybrid metallic-composite railway axle are proposed and their strengths and weaknesses are assessed. A finite element analysis on the selected concept was conducted, including a solution for the bonded joints of the metallic collars which provide the interface to the wheels and bearings. An axle mass reduction of over 63% was shown. An overview is also provided regarding the analysis of manufacturability of the axle, non-destructive methods for axle inspection/structural health monitoring and effects of impacts from ballast stones. Finally, a preliminary evaluation of the benefits arising from the reduction of the unsprung masses is provided, based on multibody simulations of vehicle dynamics.

Structural analysis for the design of a lightweight composite railway axle

The unsprung masses associated with the axles of a railway vehicle result in costly impact damage to the rail infrastructure. A hybrid metallic-composite (HMC) railway axle is evaluated using finite element analysis. The axle mass is 74 kg, 63% lighter than an equivalent hollow steel axle. The HMC railway axle comprises a full length, carbon fibre reinforced, epoxy matrix composite tube with secondary overwrapping for stiffness and EA1N grade steel collars creating the wheel seats and journal surfaces. Maximum axle deflection is 1.72 mm with a misalignment at the journals of 0.21°, potentially requiring a bearing reassessment. Nominal bending stress in the axle is 99.3 MPa (Tsai-Wu damage index of 0.18). Peak bending and torsional stresses result in Tsai-Wu damage indexes of 0.71 and 0.42, respectively. The methodology in this paper can be extended to the design of future lightweight composite shafts to benefit many other industries.

ENERGY PERFORMANCE IN DISC HARROWING OPERATION IN DIFFERENT GRADIENTS AND GAUGES

ABSTRACT The operational performance of the agricultural tractor can be increased by adjusting parameters such as tire inflation pressure, axle mass distribution and gauge opening, which is a very divergent factor in controlled-traffic production. The objective of the experiment was to measure the energy performance of a 93 kW agricultural tractor in intermediate grading operation in two slopes (flat and sloping) and three gauge configurations (closed, intermediate and open) in mobilized soil. Energy performance was determined from the following parameters: slip, engine speed, actual effective speed, hourly and specific fuel consumption; strength, power and performance on the drawbar. Turbo pressure and temperature monitoring was also performed at six different engine points. The experiment was conducted in double factorial arrangement (2 slopes and 3 gauges), with four replications, totaling 24 plots. Data were analyzed for normality and homoscedasticity of the residues, after ANOVA and when significant, the means test. Tilts and tire gauges did not differ statistically, so it can be concluded that depending on the operation do not interfere with operating performance.

Two-Mass Vehicle Model for Extracting Bridge Frequencies

The dynamic response of a moving vehicle has been utilized to extract the frequencies of the supporting bridge. In most previous studies, the vehicle was modeled as a single-degree-of-freedom sprung mass moving over a simple beam, which suffers from the drawback that the sprung mass may be affected by the vehicle motion. To overcome this drawback, this paper presents a two-mass vehicle model for extracting the bridge frequencies, which contains a sprung mass (vehicle body) and an unsprung mass (axle mass). By using the response of the unsprung mass, the bridge response can be more realistically extracted. The main findings of the present study are as follows: (1) the use of unsprung mass in the vehicle model can faithfully reveal the dynamic responses of both the vehicle and bridge, (2) the increase in the unsprung mass can effectively help the extraction of bridge frequencies, including the second frequency, (3) under high levels of road roughness, the proposed model can identify the bridge frequencies, while the single-mass model cannot, and (4) in the presence of vehicle damping, the proposed model can identify the bridge frequencies under high levels of road roughness without additional techniques of processing.

Dynamic Axle Load of an Automotive Vehicle When Driven on a Mobile Measurement Platform

An analysis of the dynamic axle load of an automotive vehicle (AV) when it is driven on a mobile measurement platform is presented in this paper. During the ride, the time characteristic of the dynamic force N(t), acting on the axle, was recorded. The effect of the vehicle axle mass on the maximum dynamic force value and the dynamic coefficient were studied. On this basis it was attempted to calculate the total vehicle’s weight. Conclusions concerning the dynamic loads of the vehicle axles in relation to the reduced axle mass, were drawn. The optimal axle mass value, for which the dynamic coefficient reaches a minimum, was calculated

Structural durability design recommendations for forged automotive aluminium chassis components submitted to spectrum and environmental loadings by the example of a tension strut

The structural durability design of a tension strut of forged aluminium (EN AW 6082 T6), which is a safety component of the automotive chassis, is described. The first step of the structural durability design is the knowledge of the mechanical and environmental loadings. The mechanical loadings are the spectrum loading for the designated normal driving conditions and unintended special event loadings by e.g. braking over road bumps, which are introduced into the component through the wheels. The local stresses imposed on the component are also influenced by kinematics, stiffness, axle mass, dampers, bearings, bump geometry, etc. The environmental loading is the corrosion caused, in winter-time, by salty water on the roads. For design according to the local stress concept, the knowledge of Woehler-curves without and with salt corrosion effects is necessary. On this basis, cumulative fatigue under spectrum loading, which also comprises the special events mentioned, is assessed for a standard configuration and for an optimised one. The numerical results are verified by experimental proofs on the component in the laboratory and on the proving ground as well as by field tests with vehicles.

Study of Axle Load Conversion for Pavement with Reflective Crack Based on Stress Intensify Factor

By applying the theory of fatigue fracture, equivalent conversion of load between 3D model and plane strain model was performed according to the equivalent principle of maximal stress in undamaged semi – rigid base. Subsequently, by use of the theory of fatigue crack, axle load conversion coefficient of reflective crack under different loads based on the equivalent speed of crack expansion was presented. And then, the conversion coefficient was compared with the current specification for design of highway asphalt pavement. The result shows that (1) if axle mass is less than standard axle load, the axle load conversion coefficient based on the equivalent principle of crack propagation velocity is larger than that in existing specification; (2) on the contrary, it is smaller.

Kinematics and Dynamics Simulation Research for Roller Coaster Multi-Body System

To assess the roller coaster multi-body system security, it is need to extract the running process of kinematics, dynamics, load spectrum and other features, as basis dates of the roller coaster structural design. Based on Solidworks/motion software and in the 3D model, the calculation formula of the carrying car velocity and acceleration is derived, and the five risk points of the roller coaster track section are found by simulation in the running, and the simulation results of roller coaster axle mass center velocity are compared with theoretical calculation results, which error is less than 4.1%, indicating that the calculation and simulation have a good fit and providing the evidence for the roller coaster structure design analysis.

THE HEAVY VECHICLES INTERACTION WITH ROAD PAVEMENT INFLUENCE TO CONSTRUCTION LAYERS ANALYZIS / SUNKIŲJŲ AUTOMOBILIŲ SĄVEIKOS SU KELIO DANGA IR JŲ ĮTAKOS KONSTRUKCIJOS SLUOKSNIAMS ANALIZĖ

Smoothness is the main feature of road exploitation. It particularly affects movement speed, safety and driving comfort. Evenness of the road belongs of three factors: strength of the pavement construction, heavy vehicle traffic and the impact of the axle mass over it’s term of exploitation. The main negative influence on Lithuanian roads has a overloaded heavy vehicle in excess of the permissible axle load limits. Static and dynamic vehicle weighing equipment and technologies were presented in the article. This article explores overloaded heavy vehicle damage done to Lithuanian roads and its intensity increase. Discuss the basic preventive techniques and methods to prevent the rapid wear of pavements. Also analysis of changes in axial load data through the 2009 August is done.

Structural durability of forged automotive aluminium chassis components submitted to spectrum loading and salt-corrosion by the example of a tension strut

The structural durability design of a tension strut of forged aluminium (EN AW 6082 T6), which is a safety component of the automotive chassis, is described. The first step of the structural durability design is the knowledge of the mechanical and environmental loadings. The mechanical loadings are the spectrum loading for the designated normal driving conditions and unintended special event loadings by e.g. braking over road bumps, which are introduced into the component through the wheels. The local stresses imposed on the component are also influenced by kinematics, stiffness, axle mass, dampers, bearings, bump geometry etc. The environmental loading is the corrosion caused, in winter-time, by salty water on the roads. For design according to the local stress concept, the knowledge of Woehler-curves without and with salt corrosion effects is necessary. On this basis, cumulative fatigue under spectrum loading, which also comprises the special events mentioned, is assessed for a standard configuration and for an optimized one. The numerical results are verified by experimental proofs on the component in the laboratory and on the proving ground as well as by field tests with vehicles.

Accident assessment of vehicles on long-span bridges in windy environments

Currently, there are very few systematic analyses of vehicle performance on bridges in windy environments. There are thus no scientific data to support bridge management in this regard, such as when to close traffic on bridges. This paper presents a framework of vehicle accident analysis model on long-span bridges in windy environments. In the accompanying paper, a three-dimensional analysis of the coupled bridge–vehicle–wind system is developed. Each vehicle is modeled as a combination of several rigid bodies, axle mass blocks, springs, and dampers. Dynamic interaction analysis is then conducted on the vehicle–bridge system to predict the “global” bridge and vehicle dynamic responses without considering accident occurrences. The results of the global bridge–vehicle vibrations serve as the basis for the present accident analysis of the “local” vehicle vibrations. With the global vibrations as inputs of the accident model, the lateral response, yaw response of the vehicle, and the reaction forces of each individual wheel are obtained and the stability condition of the vehicles are analyzed. The vehicle accidents on long-span bridges are then identified with given accident criteria. The developed framework can be used in not only analyzing the vehicle performance on highways and on bridges, but also in predicting useful information for emergency preparedness agencies in developing evacuation plans.

Framework of vehicle–bridge–wind dynamic analysis

This paper presents a framework of dynamic analysis of coupled three-dimensional vehicle–bridge system under strong winds. A general formulation of this system is introduced to simulate a series of vehicles consisting of different numbers and different types of vehicles running on bridges under hurricane-induced strong winds. Each vehicle is modeled as a combination of several rigid bodies, axle mass blocks, springs, and dampers, considering wind and road roughness loads. With this vehicle–bridge model, coupled dynamic analysis of vehicles running on bridges is conducted with a numerical example. Effects of driving speeds on the dynamic performance of the vehicles as well as the bridge are discussed. It is found that the driving speeds mainly affect the vehicle's vertical relative response while they have insignificant effect on the rolling response of vehicles. Vehicle's absolute response is dominated by the bridge response when wind speed is high, while it is dominated by road roughness when the wind speed is low. Detailed accident analysis of vehicles on bridges under strong winds will be reported in an accompanying paper.

Wheel/rail noise— Part I: Characterization of the wheel/rail dynamic system

Field and laboratory measurements of the point impedance, response, radiation efficiency, and directivity of rapid transit steel wheels and rails are presented and compared with appropriate analytical models. The rail impedance can be well modeled by the impedance of an infinitely long beam with the same bending stiffness. Measurements of the wheel impedance in the radial direction are closely approximated (up to ∼ 1000 Hz) by the impedance of a mass equivalent to that of the wheel plus one-third of the axle mass. Above 1000 Hz, the wheel impedance is approximated by the impedance of an infinite beam with the same cross-section as the wheel tread without the web. At low frequencies (below 1000 Hz), the decay of vibration along the length of a rail away from the point of excitation is rapid enough so that most rail vibration occurs within a few feet of the exciting wheel. Measurements of the wheel radiation efficiency agree with predictions that are based on the radiation efficiency of a rigid disk with the same radius vibrating in the axial direction. The directivity of radiation from the wheel and rail is approximately uniform.