Development and validation of a new code for longitudinal train dynamics simulation

2020 ◽  
pp. 095440972092349
Author(s):  
Nicola Bosso ◽  
Matteo Magelli ◽  
Nicolò Zampieri
Keyword(s):  
Experimental Tests ◽  
Dynamics Simulation ◽  
Essential Information ◽  
Signaling Systems ◽  
Railway Systems ◽  
Heavy Haul ◽  
Train Dynamics ◽  
And Performance ◽  
Heavy Haul Trains ◽  
Development And Validation

Longitudinal train dynamics have a significant impact on both safety and performance of railway systems. Numerical simulation of long heavy haul trains can thus provide essential information for the development of diagnostic and signaling systems as well as coupling elements and braking systems. Long trains are usually modeled by considering only the longitudinal degree of freedom and by adding extra resistant forces to represent the track curvature and gradients. The prediction of in-train forces represents the most critical aspect in modeling the longitudinal dynamics of long trains made up of several vehicles. In fact, coupling elements have non-linear force–deflection characteristics, with different behavior in loading and unloading states, thus featuring a hysteretic loop. Look-up tables storing data from experimental tests are generally used to model these elements; however, other strategies, such as fitting curves and white-box models are witnessed in the literature. Recently, an international benchmarking of longitudinal train dynamics simulator was established in order to compare the output results obtained by different models with the same input data. The research group from Politecnico di Torino performed the simulations using the multibody software Simpack, but computational inefficiencies and numerical divergences occurred. To overcome these issues, a new dedicated in-house code was developed in the MATLAB environment. The paper focuses on the description of this new code and its validation, which was carried out by performing the simulations according to the benchmark inputs and comparing the results with the outputs from the other participants.

Methodology for Optimization of Friction Draft Gear Design

2014 ◽  
Author(s):  
Qing Wu ◽  
Colin Cole ◽  
Maksym Spiryagin
Keyword(s):  
Dynamics Simulation ◽  
Rolling Stock ◽  
System Failures ◽  
Gear Design ◽  
Simulation Techniques ◽  
Coupling System ◽  
Heavy Haul ◽  
Draft Gear ◽  
Train Dynamics ◽  
Heavy Haul Trains

Evidence gathered from industry indicates that railway coupling system failures have become a limitation for further developments of heavy haul trains. Friction draft gears have implications for both longitudinal train dynamics and rolling stock fatigue; therefore, optimization of friction draft gears could be a possible solution to conquer the limitation. In this paper, a methodology for optimization of friction draft gear design based on an advanced friction draft gear model is proposed. The methodology proposes using simulation techniques such as longitudinal train dynamics simulation and a Genetic Algorithm to develop improved parameters.

A Dynamic Model of Friction Draft Gear

2014 ◽  
Author(s):  
Qing Wu ◽  
Maksym Spiryagin ◽  
Colin Cole
Keyword(s):  
Dynamic Modeling ◽  
Field Test ◽  
Modeling And Prediction ◽  
Heavy Haul ◽  
Draft Gear ◽  
Train Dynamics ◽  
Simulation Results ◽  
Model Of Friction ◽  
Heavy Haul Trains ◽  
Force Displacement

Friction draft gears are the most widely used draft gears. Modeling and prediction of their dynamic behavior are of significant assistance in addressing various concerns. Longer, heavier and faster heavy haul trains mean larger in-train forces and more complicated force patterns, which require further improvements of dynamic modeling of friction draft gears to assess the longitudinal train dynamics. In this paper a force-displacement characteristics model named “base model” was described. The base model was simulated after the analyses of a set of field-test data. Approaches to improve the base model to a full advanced draft gear model were discussed; preliminary simulation results of an advanced draft gear model were also presented.

Development and Validation of a Cognitive Reserve Index in HIV

2021 ◽  
pp. 1-9
Author(s):  
Navaldeep Kaur ◽  
Lesley K. Fellows ◽  
Marie-Josée Brouillette ◽  
Nancy Mayo
Keyword(s):  
Cognitive Reserve ◽  
Study Entry ◽  
Video Gaming ◽  
Everyday Functioning ◽  
Data Set ◽  
Multiple Indicators ◽  
And Performance ◽  
Competitive Games ◽  
Development And Validation

Abstract Objectives: In the neuroHIV literature, cognitive reserve has most often been operationalized using education, occupation, and IQ. The effects of other cognitively stimulating activities that might be more amenable to interventions have been little studied. The purpose of this study was to develop an index of cognitive reserve in people with HIV, combining multiple indicators of cognitively stimulating lifetime experiences into a single value. Methods: The data set was obtained from a Canadian longitudinal study (N = 856). Potential indicators of cognitive reserve captured at the study entry included education, occupation, engagement in six cognitively stimulating activities, number of languages spoken, and social resources. Cognitive performance was measured using a computerized test battery. A cognitive reserve index was formulated using logistic regression weights. For the evidence on concurrent and predictive validity of the index, the measures of cognition and self-reported everyday functioning were each regressed on the index scores at study entry and at the last follow-up [mean duration: 25.9 months (SD 7.2)], respectively. Corresponding regression coefficients and 95% confidence intervals (CIs) were computed. Results: Professional sports [odds ratio (OR): 2.9; 95% CI 0.59–14.7], visual and performance arts (any level of engagement), professional/amateur music, complex video gaming and competitive games, and travel outside North America were associated with higher cognitive functioning. The effects of cognitive reserve on the outcomes at the last follow-up visit were closely similar to those at study entry. Conclusion: This work contributes evidence toward the relative benefit of engaging in specific cognitively stimulating life experiences in HIV.

Flow Coefficient Evaluation of Poppet Valves Used in Reciprocating Compressors for LDPE

2008 ◽  
Author(s):  
Enzo Giacomelli ◽  
Massimo Schiavone ◽  
Fabio Manfrone ◽  
Andrea Raggi
Keyword(s):  
Pressure Drop ◽  
Time Pressure ◽  
Experimental Tests ◽  
Operating Conditions ◽  
Flow Coefficient ◽  
Operating Life ◽  
High Fatigue ◽  
Strongly Connected ◽  
And Performance ◽  
Poppet Valves

Poppet valves have been used for a long time for very high pressure reciprocating compressors, as for example in the case of Low Density Polyethylene. These applications are very critical because the final pressure can reach 350 MPa and the evaluation of the performance of the machines is strongly connected to the proper operation and performance of the valve itself. The arrangement of cylinders requires generally a certain compactness of valve to withstand high fatigue stresses, but at the same time pressure drop and operating life are very important. In recent years the reliability of the machines has been improving over and over and the customers’ needs are very stringent. Therefore the use of poppet valves has been extended to other cases. In general the mentioned applications are heavy duty services and the simulation of the valves require some coefficients to be used in the differential equations, able to describe the movement of plate/disk or poppet and the flow and related pressure drop through the valves. Such coefficients are often determined in an experimental way in order to have a simulation closer to the real operating conditions. For the flow coefficients it is also possible today to use theoretical programs capable of determining the needed values in a quick and economical way. Some investigations have been carried out to determine the values for certain geometries of poppet valves. The results of the theory have been compared with some experimental tests. The good agreement between the various methods indicates the most suitable procedure to be applied in order to have reliable data. The advantage is evident as the time necessary for the theoretical procedure is faster and less expensive. This is of significant importance at the time of the design and also in case of a need to provide timely technical support for the operating behavior of the valves. Particularly for LDPE, the optimization of all the parameters is strongly necessary. The fatigue stresses of cylinder heads and valve bodies have to match in fact with gas passage turbulence and pressure drop, added to the mechanical behavior of the poppet valve components.

Molecular Dynamics Simulation of AFM-Based Nanomachining Processes

2011 ◽  
Author(s):  
Rapeepan Promyoo ◽  
Hazim El-Mounayri ◽  
Kody Varahramyan ◽  
Ashlie Martini
Keyword(s):  
Molecular Dynamics ◽  
Friction Coefficient ◽  
Md Simulation ◽  
Computational Models ◽  
Dynamics Simulation ◽  
Radius Of Curvature ◽  
Force Microscopy ◽  
Indentation Force ◽  
Atomic Force ◽  
Development And Validation

Recently, atomic force microscopy (AFM) has been widely used for nanomachining and fabrication of micro/ nanodevices. This paper describes the development and validation of computational models for AFM-based nanomachining (nanoindentation and nanoscratching). The Molecular Dynamics (MD) technique is used to model and simulate mechanical indentation and scratching at the nanoscale in the case of gold and silicon. The simulation allows for the prediction of indentation forces and the friction force at the interface between an indenter and a substrate. The effects of tip curvature and speed on indentation force and friction coefficient are investigated. The material deformation and indentation geometry are extracted based on the final locations of atoms, which are displaced by the rigid tool. In addition to modeling, an AFM was used to conduct actual indentation at the nanoscale, and provide measurements to validate the predictions from the MD simulation. The AFM provides resolution on nanometer (lateral) and angstrom (vertical) scales. A three-sided pyramid indenter (with a radius of curvature ∼ 50 nm) is raster scanned on top of the surface and in contact with it. It can be observed from the MD simulation results that the indentation force increases as the depth of indentation increases, but decreases as the scratching speed increases. On the other hand, the friction coefficient is found to be independent of scratching speed.

Non-Stationary Random Vibration Analysis of Railway Bridges Under Moving Heavy-Haul Trains

2018 ◽  
Vol 18 (03) ◽  
pp. 1850035 ◽  
Author(s):  
Zhihui Zhu ◽  
Lidong Wang ◽  
Zhiwu Yu ◽  
Wei Gong ◽  
Yu Bai
Keyword(s):  
Random Vibration ◽  
Vertical Acceleration ◽  
Railway Bridges ◽  
Coupling System ◽  
Ballasted Track ◽  
Heavy Haul ◽  
Train Speed ◽  
Track Irregularity ◽  
Heavy Haul Trains ◽  
Track Bridge

This paper presents a non-stationary random vibration analysis of railway bridges under moving heavy-haul trains by the pseudo-excitation method (PEM) considering the train-track-bridge coupling dynamics. The train and the ballasted track-bridge are modeled by the multibody dynamics and finite element (FE) method, respectively. Based on the linearized wheel-rail interaction model, the equations of motion of the train-ballasted track-bridge coupling system are then derived. Meanwhile, the excitations between the rails and wheels caused by the random track irregularity are transformed into a series of deterministic pseudo-harmonic excitation vectors by the PEM. Then, the random vibration responses of the coupling system are obtained using a step-by-step integration method and the maximum responses are estimated using the 3[Formula: see text] rule for the Gaussian stochastic process. The proposed method is validated by the field measurement data collected from a simply-supported girder bridge (SSB) for heavy-haul trains in China. Finally, the effects of train speed, grade of track irregularity, and train type on the random dynamic behavior of six girder bridges for heavy-haul railways are investigated. The results show that the vertical acceleration and dynamic amplification factor (DAF) of the midspan of the SSB girders are influenced significantly by the train speed and track irregularity. With the increase in the vehicle axle-load, the vertical deflection-to-span ratio ([Formula: see text]) of the girders increases approximately linearly, but the DAF and vertical acceleration fail to show clear trend.

Analysis of Brake Failure and Runaway Accidents in Mountain Terrain in Canada

2013 ◽  
Author(s):  
Daoxing Chen
Keyword(s):  
Dynamics Simulation ◽  
Contributing Factors ◽  
Friction Heat ◽  
Mountain Terrain ◽  
Maintenance Practice ◽  
Train Operation ◽  
Brake Application ◽  
Property Loss ◽  
Train Dynamics ◽  
Mountain Terrains

A number of serious rail runaway accidents have occurred in recent years on long and high grade downhill tracks in mountain terrains in Canada, causing fatal injuries and huge property loss. They were caused by brake failure, misunderstanding of brake features, maintenance deficiency and/or improper brake application on the trains. Train dynamics simulation, brake ratio testing, and dynamometer testing on friction heat fade helped disclose the causes and contributing factors in the cases presented in this paper. Guidelines were revised for safer train operation, equipment requirements and maintenance practice in the mountain terrain conditions.

scholarly journals Comparisons Between Braking Experiments and Longitudinal Train Dynamics Using Friction Coefficient and Braking Pressure Modeling in a Freight Train

2020 ◽  
Vol 14 (1) ◽  
pp. 154-163
Author(s):  
Don Bum Choi ◽  
Rag-Gyo Jeong ◽  
Yongkook Kim ◽  
Jangbom Chai
Keyword(s):  
Friction Coefficient ◽  
Time Integration ◽  
Expansion Method ◽  
Dynamics Simulation ◽  
Dynamic Simulations ◽  
Freight Train ◽  
Emergency Braking ◽  
Braking Distance ◽  
Train Dynamics ◽  
Simulation Results

Background: This paper describes the predictions and validation of the pneumatic emergency braking performance of a freight train consisting of a locomotive and 20 wagons, generally operated in Korea. It suggests the possibility of replacing the expensive and time-consuming train running tests with longitudinal train dynamic simulations. Methods: The simulation of longitudinal train dynamics of a freight train uses the time integration method of EN 14531. For reasonable simulation results, the characteristics of the train and brake equipment must be considered. For the train characteristics, specifications provided by the vehicle manufacturer are used. The braking characteristics are analyzed by friction coefficient tests and a braking pressure model. The friction coefficients of a locomotive and wagons are tested with a dynamo test bench and statistically expanded to account for variability. Freight trains should take into account the braking delay time. To reflect this in the simulation, the brake cylinder pressure pattern model uses pressures and exponential empirical equations measured at selective positions in a train of 50 vehicles. The simulation results are validated in comparison with those of the braking tests of a freight train consisting of 1 locomotive and 20 wagons. Results: The results of the longitudinal dynamics simulation show very similar results to the running test results based on the speed profile and braking distance. Conclusion: In particular, the statistical expansion method of the friction coefficient enables robust prediction of the distribution of the braking distance. The simulation can reduce or make up for costly and time-consuming repeated braking tests and reduce the risks that may arise during testing.

Design and Performance Study of a 3-DOF Micropositioning Table

2006 ◽  
Vol 315-316 ◽  
pp. 450-454
Author(s):  
Yan Ling Tian ◽  
Da Wei Zhang ◽  
Cheng Zu Ren ◽  
Bing Yan
Keyword(s):  
Control Method ◽  
Piezoelectric Actuators ◽  
Experimental Tests ◽  
Control Voltage ◽  
Performance Study ◽  
Coupling Characteristic ◽  
And Performance ◽  
Grinding Machine ◽  
Relationship Of ◽  
Wheel Vibration

In order to implement dynamic compensation for the wheel vibration of surface grinding machine, a micropositioning table with high stiffness and response frequency is designed. The micropositioning table is driven by three piezoelectric actuators with stiffness of 400 N/μm. Three capacitive sensors are utilized to form feedback control and flexure hinges are used to guide the moving part and preload for the piezoelectric actuators. The kinetics of the micropositioning table has been analyzed to understand the relationship of the control voltage and the posture of the moving part. Due to the coupling characteristic of the system, the decoupling control method is introduced to improve the performance of the table. Experimental tests are carried out to investigate the performance of the micropositioning table.

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