Axle Load Research Articles

Optimization of the handling behaviour of an electric car by adjusting the kinematic gains of suspension

Abstract In this paper, within the scope of development of an electric car on a vehicle platform that is borned as internal combustion engine is presented. The vehicle dynamics behaviour changes due to the change of weight distribution and centre of gravity. Replacing the internal combustion engine with an electric motor, plus the addition of the battery moves the center of gravity towards the rear of the vehicle. Due to the increase in the rear axle load, the tendency of the vehicle to oversteer increases. To overcome this phenomenon, the rear suspension kinematic gains (camber, toe change due to vertical movement of the wheel) are adjusted thanks to the multi-link suspension. In the fist part of the study the platform is measured and Admas Car model is correlated depends on measured handling metrics. Subsequently, centre of gravity changes are applied to the verified Adams Car model. Also main platform handling metrics is defined as design targets and rear axle kinematic gains are defined as design parameters. A design of experiments (DOE)-based optimization study was performed via Adams®/Insight commercial software to achieve required handling metrics which satisfy design targets. Kinematic gains of the suspension system is analyzed via Adams car and sensitivity deepens on harpoints is determined. Design space for hardpoints is determined depends on mechanical design. The lowest and highest points are determined on the x, y and z axis and experiment list are designed according to DOE. Maneuvers that are for measuring the handling metrics are performed one after the other by changing the parameters according to the boundary conditions comes from DOE. A regression mathematical model is obtained and optimum parameters are calculated for the handling behaviour optimisation. Optimum parameters are applied on the Adams Car model again and handling manoeuvres are repeated. Results show that, although weight distribution changes, handling behaviours remain the same as based platform.

A Review on Developing HiPER Bituminous Mix Using Existing Binder and Modifier

Heavy commercial vehicles combined with high pavement temperatures induce higher stresses in base and surface courses layers resulting in premature pavement distresses such as rutting and cracking. Therefore, it's essential to create a binder that performs better in heat and is more elastic and rigid so that it may be utilized to bear heavy axle loads. For several years, efforts have been made in India and worldwide to develop new pavement materials and improve the specifications of paving mixes and their constituents. One of the emerging solutions is use of a French asphalt mix known as “Enrobé à Module Élevé (EME)” or “High-Modulus Asphalt (HiMA) Mix”. This mix offers unique performance characteristics such as high stiffness and durability, good resistance to permanent deformation and fatigue. Therefore, HiMA mixes also referred as High Performance (HiPER) Bituminous Mixes. EME mixes uses a hard grade binder (HB), have higher binder content and lower air voids. The unique challenges in preparation of HiPER bituminous mix is selection of bitumen, which shall be hard grade bitumen (stiffer than VG40). In India, binder stiffer than VG40 are not commonly available commercially. Also, selection of modifiers used to produce hard grade binders and to enhance the performance of the binders that provides higher resistance to permanent deformation as well as to cracking. The main focus of this study is to find potential of modifier(s) to develop hard grade binder (HB) and use of HB for the preparation of mixes at various binder content and evaluated with the target of producing HiPER bituminous mix. Marshall stability and indirect tensile strength (ITS) tests are conducted to assess the mixes for HiPER bituminous mix

Efficiency Analysis of Powertrain for Internal Combustion Engine and Hydrogen Fuel Cell Tractor According to Agricultural Operations.

As interest in eco-friendly work vehicles grows, research on the powertrains of eco-friendly tractors has increased, including research on the development of eco-friendly vehicles (tractors) using hydrogen fuel cell power packs and batteries. However, batteries require a long time to charge and have a short operating time due to their low energy efficiency compared with hydrogen fuel cell power packs. Therefore, recent studies have focused on the development of tractors using hydrogen fuel cell power packs; however, there is a lack of research on powertrain performance analysis considering actual working conditions. To evaluate vehicle performance, an actual load measurement during agricultural operation must be conducted. The objective of this study was to conduct an efficiency analysis of powertrains according to their power source using data measured during agricultural operations. A performance evaluation with respect to efficiency was performed through comparison and an analysis with internal combustion engine tractors of the same level. The specifications of the transmission for hydrogen fuel cell and engine tractors were used in this study. The power loss and efficiency of the transmission were calculated using ISO 14179-1 equations, as shown below. Plow tillage and rotary tillage operations were conducted for data measurement. The measurement system consists of four components. The engine data load measurement was calculated using the vehicle's controller area network (CAN) data, the axle load was measured using an axle torque meter and proximity sensors, and fuel consumption was measured using the sensor installed on the fuel line. The calculated capacities, considering the engine's fuel efficiency for plow and rotary tillage operations, were 131.2 and 175.1 kWh, respectively. The capacity of the required power, considering the powertrain's efficiency for hydrogen fuel cell tractors with respect to plow and rotary tillage operations, was calculated using the efficiency of the motor, inverter, and power pack, and 51.3 and 62.9 kWh were the values obtained, respectively. Considering these factors, the engine exhibited an efficiency of about 47.9% compared with the power pack in the case of plow tillage operations, and the engine exhibited an efficiency of about 29.3% in the case of rotary tillage operations. A hydrogen fuel cell tractor is considered suitable for high-efficiency and eco-friendly vehicles because it can operate on eco-friendly power sources while providing the advantages of a motor.

Exploring Kriging metamodeling to alleviate speed reading dependence in Bridge Weigh-In-Motion predictions

Bridge Weigh-In-Motion (BWIM) systems can be installed and serviced on highway bridges to provide measurements of moving vehicle’s gross weight, axle load, axle separation, and so on, without interrupting traffic. This data can be used to provide information of the heavy traffic over the bridge to management. This article presents the application of Kriging metamodeling to BWIM through the simulation of traffic streams. The Kriging methodology, with its prediction of metamodel variance, allows for the strategic selection of vehicles to train the BWIM metamodel. The proposed approach extends the BWIM concept of influence area from response time histories to geometric input spaces from the strain response wave (RW). The simulated dynamic response of simply supported bridges in the US Interstate Highway System were performed using Finite Element Modeling (FEM) of moving loads, generating RWs captured in different sensor locations. Three independent input spaces based on geometric properties of the RWs are the input to train the Kriging metamodel of a defined training truck group. In this approach, the measurement of the vehicle speed is not needed as an improvement of traditional BWIM methods. The results show that the Kriging prediction can fulfill at least the Type II WIM Systems performance defined in the ASTM’s Standard, using a comparable number of training runs to the number of calibration runs defined in the standard.

An experimental analysis of dynamic deformation and settlement resistance in a novel prestressed railway subgrade

ABSTRACT The dynamic deformation characteristics of track-subgrade systems under moving train loads provide valuable insights for vibration and serviceability assessment of the track-subgrade. This study developed three 1:5 scale track-subgrade models incorporating the novel prestressed subgrade structure and conducted two series of dynamic tests to examine how the heavy-haul train axle loads and prestress levels affected the track-subgrade dynamic deformation. The primary frequency of the subgrade dynamic displacement was observed closely aligned with the input loading frequency of 2 Hz, indicating the validity of the test setup. The track-subgrade dynamic displacement decreased with increasing distance from the loading source, of which the elastic deformation near the subgrade shoulder attenuated by approximately 79% compared to that at the sleeper end. The elastic deformation at the monitoring points approximately linearly increased with the axle load at rates ranging from 0.0018 to 0.0029 mm/t. Conversely, increasing prestress reduced the track-subgrade elastic deformation with average rates of 22.8 and 1.63 μm/100 kPa at the sleeper end and subgrade shoulder, respectively. Furthermore, application of prestress enhanced the track stiffness, with the equivalent track stiffness rising by 16.3% and 17.7% when the prestress increased from 0 to 50 kPa and from 50 to 100 kPa, respectively. The study also showed that the prestressed reinforcement structures could significantly mitigate the cumulative track-subgrade settlement over 60%, comparing the prestressed subgrade with 50 kPa prestress to the unreinforced subgrade, which highlighted the superior deformation resistance of prestressed subgrades under the train loads.

Semi-analytical modelling of realistic tire-pavement contact: an analysis of pavement surface cracking damage under critical driving conditions

This paper aims to evaluate the surface cracking phenomenon on a flexible pavement subjected to diverse vehicle running conditions. Top-down cracking initiation is addressed through a continuum damage framework coupled with a semi-analytical model of tire-pavement rolling contact. The acceleration, braking and cornering scenarios were selected to represent the effect of combining normal and tangential loads. The differences between these loading cases are accurately computed by simulating the realistic contact stresses on the pavement surface through semi-analytical modelling. The computational cost of this modelling technique is reduced, allowing it to be used in industrial applications. It is assumed that tires and pavement are linear elastic multilayered half-spaces. The critical locations of the cracks are identified for each loading scenario and the cracking directions are discussed. This study emphasises the influence of driving conditions on premature pavement cracking which is not typically considered in the current pavement design guides. It is shown that a standard axle load may cause about 9 times more surface damage on a circular intersection compared to a straight-line pavement section.

Finite Element Modeling for Flexible Pavement Behavior under Repeated Axle Load

Finite Element Modeling for Flexible Pavement Behavior under Repeated Axle Load

Sensitivity Analysis of Bogie Wheelbase and Axle Load for Low-Floor Freight Wagons, Based on Wheel Wear

Sensitivity Analysis of Bogie Wheelbase and Axle Load for Low-Floor Freight Wagons, Based on Wheel Wear

Development of a Practical Procedure for Data-Driven Weigh-in-Motion Equipment Calibration Scheduling to Assure Data Accuracy and Consistency over Time

Weigh-in-motion (WIM) technology is a traffic monitoring technology that highway agencies use to obtain information about the weight, axle loading, and configuration of heavy vehicles moving at operational speed. To ensure high-quality WIM data, the Federal Highway Administration (FHWA) recommends regular calibration of WIM equipment. This study addresses the need to optimize the allocation of the limited resources that agencies have for WIM equipment calibration by developing a procedure for data-driven calibration scheduling. This was accomplished through an analysis of WIM measurement errors from test truck data collected during field performance validation and calibration events and an analysis of monthly changes in truck weight and axle loading characteristics, based on WIM data collected between calibration events. The analysis results were used to draw conclusions on the functional performance of different WIM sites. The study also demonstrates how the newly developed National Cooperative Highway Research Program (NCHRP) WIM Data Quality Assurance Analysis Tool can be used to compute truck weight and axle loading parameters and visualize data analysis results using four case studies: two WIM sites with piezo quartz sensors in asphalt pavements and two WIM sites with bending plate sensors in concrete pavements. This paper provides a practical procedure and recommendations that highway agencies can use to develop data-driven WIM calibration schedules that will ensure consistent high-quality WIM data for sites managed by an agency with the aid of the NCHRP WIM Data Quality Assurance Analysis Tool.

Effect of unsupported sleepers on vertical levelling loss of heavy-haul railway track geometry under cyclic loadings

With an emphasis on the combined degradation of railway track geometry and components, an improved numerical approach is proposed for predicting the track geometrical vertical levelling loss (VLL). In contrast to previous studies, this research unprecedentedly considers the influence of unsupported sleepers (US) configuration on VLL under cyclic loadings, elasto-plastic behaviour, and different operational dynamic conditions. The nonlinear numerical models are performed adopting an explicit finite element (FE) package, and their results are validated by field data. The outcomes are iteratively regressed by an analytical logarithmic function that cumulates permanent settlements, and by a power function factor, which innovatively extends the response of US on VLL over a long term. Results shows that at 3 million cycles (or 60 MGT) the worst configuration for 20-ton axle load is at 5 US with 5-mm gap (5,51%), whereas for 30 and 40-ton axle loads is at 5 US with 2-mm gap (1.23% and 0,89%, respectively). This indicates that the axle load affects considerably the VLL as expected, however, the US condition plays an important role to accelerate it. Based on this study, the acceptable configuration of US can be specified for a minimum effect on VLL (thresholds) and, therefore, supports the development of practical maintenance guidelines to prolong the railway track service life.

Fatigue Damage in Asphalt Pavement Based on Axle Load Spectrum and Seasonal Temperature

In asphalt pavement structure design, traffic axle loads and pavement layer temperatures are crucial factors affecting fatigue damage calculations. To investigate the differences in fatigue damage calculations caused by different characterizations of traffic axle loads and temperature, fatigue damage calculations were conducted under equivalent standard axle loads (ESALs), axle load spectra (ALS), constant temperatures, and seasonal temperature variations using the field data from an expressway in Shandong Province, China under seven calculation plans. The results indicated: (1) the annual traffic composition is dominated by vehicle Type 9, with a proportion of about 43% in all the vehicle types, and its load level is also high, with a proportion about of 80% in the heavy load interval at all axle types; (2) The ESALs method underestimates the actual fatigue damage incurred in asphalt pavement by 6.04 times, with an accumulated damage of 2.34 × 10−9 (ESALs), 1.69 × 10−8 (ALS), respectively; (3) The fatigue damage results from a single month with consistent temperature showed similar trends, with an accumulated damage of 1.50 × 10−5, 9.07 × 10−5, respectively; (4) The cumulative fatigue damage calculated using the ALS method across the four seasons, respectively, is 6.51, 5.88, 6.42, and 4.60 times that of the fatigue damage calculated using the ESALs method. Although the ratio of fatigue damage between the two characterizations of traffic axle loads remains consistent, which is 6.04, the fatigue damage calculation that accounts for temperature variations can reveal seasonal trends in fatigue damage development. Based on the axle load spectra and considering temperature variations, fatigue damage calculation will be more closely related to the actual service state of asphalt pavement. These research findings provide insights for estimating asphalt pavement fatigue damage to some extent.

Dynamic Response Characteristics of Foundation of Mined-out Areas under High-speed Railway Load

To reveal the dynamic response characteristics of the foundation of mined-out areas (MOA) under the high-speed railway (HSR) load is important for predicting settlement and safety assessment of the foundation. Taking MOA of Dianshang under the Taiyuan-Jiaozuo HSR as the engineering background, the model experiments and numerical analysis were employed to reveal the dynamic response of both subgrade and the foundation of the HSR, as well as the attenuation law of the acceleration in the overlying strata of the MOA. Results show that within the full frequency range of the HSR load, the dynamic response of the foundation increases with the increase in load frequency. When the depth exceeds 6 m, the dynamic response of the foundation initially increases and subsequently decreases with the increase in load frequency. Contrasted with single-point loading, the superposition effect and moving effect of the HSR load will form a dynamic response superposition zone within 1-4 m below the subgrade, leading to a significant enhancement of the dynamic response of the foundation. Compared to HSR axle load, the driving speed of HSR has a greater impact on the acceleration of both the subgrade and foundation. The obtained conclusions provide a reference for the safety operation of the HSR crossing the MOA

The method of determining design assumptions for bogie platform

This article is devoted to the methods of designing running gear in compliance with recently changed requirements, regulations of rail authorities, technical specification for interoperability, and safety certification. Changes are focused on the certification process. According to ERA these changes are recommended for bogies holding IC certificate issued according to the former TSI WAG, without assessment of the strength of the bogie frame. The presented methods allow designing a bogie platform with a wide range of applications in regional, and long-distance trains. Issues related to calculations, and studies of bogie frames are described. Particular attention is paid to methods for determining loads applied to the bogie frame based on assumed axle loads, determining reference forces for the projected shock absorbers, and compiling computational cases for strength analysis of traction units.

Dynamic response of a permafrost railway subgrade with 3D train-track-subgrade-ground model simulations

Studying train-induced response characteristics is essential for safely operating permafrost railway subgrades. A three-dimensional thermal-mechanical coupling nonlinear dynamic model of train-track-subgrade-ground relationships was established to analyse the train-induced dynamic stress, acceleration and stress path characteristics of a permafrost railway subgrade, and field monitoring data were used to verify this model. The differences between the 2D and 3D models are also discussed, along with the seasonal changes, train speed, axle load, and train type affecting permafrost subgrades. The main results are as follows. First, the vibration load significantly impacts the subgrade 6 m below the sleeper, producing distinct vertical dynamic stress waves due to the wheels and bogies. Dynamic compression stress dominates the subgrade and is influenced by the train structure, speed, and sleeper spacing. While the 2D model tends to underestimate the dynamic stress in shallower layers, it concurs with the 3D model in deeper subgrade dynamics within a 10% margin of error. Then, the principal stress axis of the subgrade soil rotates synchronously with train movements, exhibiting regular stress paths in the YZ plane (longitudinal section) with depth-dependent variations in the stress cycles and deviatoric stress. Finally, predominantly originating from sleeper-induced vibrations, the subgrade vibration acceleration varies with the train speed, sleeper spacing, and season and is most pronounced in the vertical direction. This study provides theoretical guidance for the vibration response of permafrost subgrades on the Qinghai-Tibet Railway (QTR).

Improved Multi-Body Dynamic Simulation of Landing Gear Drop Test Incorporating Structural Flexibility and Bearing Contact

The investigation of multi-body dynamics (MBD) modeling for landing gear drop tests is a hot topic in the realm of landing gear design. The current results were primarily focused on the multi-rigid body simulation or a simple multi-flexible body simulation, with little regard for the correctness of longitudinal loads and their experimental confirmation, particularly wheel–axle loads. Based on a genuine oleo-pneumatic landing gear drop test of a large civil aircraft, enhanced multi-body dynamics simulation research is carried out, considering the structural flexibility and bearing support by adopting flexible multi-bodies modeling and rigid-flex coupling contacts. When compared to the test data, which purposefully measured the longitudinal wheel–axle loads, the simulation results show that the loads, shock absorber compression, and shock absorber inner pressures are all within good agreement. Furthermore, the influence of structural stiffness and bearing contact was investigated by adjusting the model settings to confirm their importance.

Pavement Service Life Prediction with PLAXIS 3D in Bangladesh

This research aims to forecast the service life of the flexible pavement in Bangladesh. The service life of flexible pavement is greatly affected by the climate and traffic load. Pavements are severely deteriorated by the overweight trucks, shortening their lifespan. The study aims to predict the service life of a flexible road using the PLAXIS 3D software. The PYTHON algorithm was utilized for the pre- and post-processing of new mechanistic empirical approach based on the AASHTO 2008 design standard. PLAXIS 3D was used for realistic soil & damage modelling and to obtain a reliable service life. Rajshahi City Bypass Nowhata Road was chosen as the study area for this study because the road condition of Nowhata is defected day by day and the number of moving vehicles with high axle load also increasing. This research has established to give the valid data to the authority according to the construction materials of flexible pavement to get better performance and proper use of materials. This road is constructed under the Road & Highway Department (RHD), Rajshahi Zone. This study shows realistic results based on temperature, soil data of subgrade and the materials property used in the PLAXIS 3D software and PYTHON programming language.

Analysis of wheel-rail contact under oil lubrication conditions

Abstract This investigation centers on the characteristics of the contact between the wheel and rail when lubricated with oil, with a consideration of the impact of surface roughness. Confronting significant challenges related to low adhesion, a thorough examination is undertaken to analyze the changes in film thickness under oil lubrication, investigating trends at varying vehicle speeds and axle loads. Employing detailed modeling based on micro-elastohydrodynamic theory, the distribution of oil film thickness under diverse operational conditions is determined. The findings indicate that, under oil lubrication, a film thickness in the range of several tens of micrometers is established, effectively insulating the surfaces of the wheel and rail, thereby reducing adhesion. With increasing vehicle speed, the thickness of the oil film also rises, whereas an elevation in axle load results in a marginal decrease in film thickness. This research contributes to a comprehensive comprehension of the wheel-rail contact mechanism in oil lubrication scenarios, providing theoretical backing to address concerns related to low adhesion. The implications are substantial for improving the safety and economic efficiency of efficient railway transportation.

Evaluation of equivalent axle load factors for multi axles based on fatigue tests using actual strain waveforms

Equivalent axle load factor (EALF) is used to characterize the fatigue damage effect of multi-axle loads on asphalt pavement. EALF is calculated as the ratio of the pavement’s fatigue resistance under a single axle load to that under a multi-axle load. Existing studies use the same fatigue life function to predict the fatigue life of asphalt mixture under both single- and multi-axle loads, primarily focusing on the differences in pavement strains under these two configurations. However, strain waveforms in asphalt pavement caused by multi-axle loads differ from those under single-axle loads, altering the mixture’s fatigue behavior. To address this issue, this research tests the fatigue responses of asphalt mixtures under actual loading waveforms from single-axle, tandem-axle, and tridem-axle loads. Based on the test results, fatigue life functions are developed for each axle configuration and used to establish an updated EALF model. Since the applied fatigue life functions are based on test results from more realistic strain waveforms, the calculated EALFs provide more reliable predictions of the damaging effect of multi-axle loads on asphalt mixtures.

INFLUENCE OF DESIGN AND OPERATIONAL FACTORS ON THE STABILITY OF THE CAR WITH TRAILER OF CATEGORY O2 DURING BRAKING MODE

In recent years, enterprises and private manufacturers in Ukraine have mastered the production of a wide range of towed vehicles. Significant attention is given to the issues of road safety for road trains, particularly those of category M1, which have found widespread use not only among state and private enterprises but also among amateur motorists. Ensuring the safety of such road trains is a pressing task. The movement characteristics of a road train fundamentally differ from those of a single vehicle. This difference is explained by the presence of additional forces in the articulated connections of the vehicle components, as well as the forces and moments acting on its individual components, which influence the movement of the vehicle as a whole. This influence is particularly noticeable during the braking of a road train, which can be accompanied by the folding of components and a loss of vehicle stability. Ensuring the safety of such road trains is a pressing task that requires a more detailed analysis of the impact of the distribution of braking forces on the stability of the road train’s movement. Such research was conducted on a spatial mathematical model of the road train. To determine the longitudinal and lateral forces acting on the wheels of a road train during braking, the normal reactions of the support surface on the wheels of the vehicle and trailer were determined. These reactions, along with the specific braking forces, determine the braking forces acting on the wheels of the vehicle and trailer. For example, with a deceleration of 6.0 m/s², the normal reaction of the support surface on the twin axle of the trailer decreases by 25%. In the absence of an anti-lock braking system in the trailer’s brake drive, wheel lockup and loss of road train stability are possible. Therefore, it is advisable to brake the road train with decelerations not exceeding 4.0 m/s². In this case, the initial braking speed that ensures the stability of the road train’s movement is higher than its maximum speed. When changing the trailer’s load while the vehicle’s load remains unchanged at a speed of 25 m/s, the road train remains stable throughout the entire range of the trailer’s total mass variation, whereas at a speed of 30 m/s, the critical mass of the trailer remains at 2500 kg. This is explained by the fact that the trailer’s mass affects the magnitude of the maximum braking force created by the braking system and the braking force that can be realized. The loading of the trailer, particularly the side loading of its wheels, is very important as it can lead to uneven braking forces on the trailer’s axles. It is shown that with the nominal loading of the vehicle and trailer, increasing the unevenness of the braking forces on the trailer’s axles up to 30% reduces the initial braking speed, which still ensures the stability of the road train’s movement, by almost half from 35.3 to 19.7 m/s. Therefore, the unevenness of the braking forces on the trailer’s axles should be limited to 15%. This will ensure the stability of the road train’s movement and the safety of its operation. Keywords: аutomobile, trailer, road train, side and axle load, braking, initial speed, movement stability.

Non-linear influences of track dynamic irregularities on vertical levelling loss of heavy-haul railway track geometry under cyclic loadings

Abstract With an emphasis on the combined degradation of railway track geometry and components, a new numerical-analytical method is proposed for predicting the track geometrical vertical levelling loss (VLL). In contrast to previous studies, this research unprecedentedly considers the influence of initial track irregularities (ITI) on VLL under cyclic loadings, elastic-plastic behaviour, and different operational dynamic conditions. The non-linear numerical models are simulated using an explicit finite element package known as LS-Dyna, and their results are validated by full-scale experimental and field measurement data. The outcomes are iteratively regressed by an analytical logarithmic function that cumulates permanent settlements, which innovatively extends the effect of ITI on VLL in a long-term behaviour. For a typical heavy-haul railway operating under 30 tons axle load and 60 km/h train velocity, the result indicates that the set of ITI with the highest standard deviation (SD) of vertical profile (VP) degrades faster (37% on average) than that with the lowest SD. Additionally, our new findings reveal that the worst scenario is related to a train running at 60 km/h and carrying a load of 20 tons/axle in an uneven track whose SD of VP evolves from 3.23 mm at N = 0 (ITI) to 7.20 mm, whereas the best one corresponds to a train at 60 km/h and 30 ton axle load in an uneven track whose SD of VP downgrades from 0.48 to 1.50 mm, both at 3 M cycles (or 60 million gross tons). These findings indicate the importance of considering the ITI for predicting track geometrical VLL under cyclic loadings. Therefore, based on this research, an acceptable condition (thresholds) of ITI can be redefined for a minimum effect on VLL, which can support the development of practical maintenance guidelines to extend the railway track service life.