scholarly journals The Influence of Manufacturing Variations on a Crash Energy Management System

2008 ◽  
Author(s):  
Philip Mallon ◽  
Benjamin Perlman ◽  
David Tyrell
Keyword(s):  
Energy Management ◽  
Energy Levels ◽  
Primary Energy ◽  
Coupling Mechanism ◽  
Lumped Mass ◽  
Mass Model ◽  
Average Force ◽  
Energy Absorber ◽  
Passenger Rail ◽  
Manufacturing Tolerances

Crash Energy Management (CEM) systems protect passengers in the event of a train collision. A CEM system distributes crush throughout designated unoccupied crush zones of a passenger rail consist. This paper examines the influence of manufacturing variations in the CEM system on the crashworthiness of CEM passenger rail equipment. To perform effectively, a CEM system must have certain features. A coupling mechanism allows coupled cars to come together in a controlled fashion and absorb energy. A load transfer mechanism ensures that the car ends mate and maintain contact. A principal energy absorber mechanism is responsible for absorbing the vast majority of crash energy. These components function by providing an increasing force-crush characteristic when they are overloaded. The force-crush behavior can vary due to manufacturing tolerances. For the purposes of this research, the pushback coupler, the deformable anticlimber, and the primary energy absorber were the devices that performed these functions. It was confirmed in this study that the force-crush characteristic of the pushback coupler and the primary energy absorber have the greatest influence on crashworthiness performance. To represent the influence of these parameters, the average force of the pushback coupler and the average force of the primary energy absorber were examined. A cab-led passenger train impacting a standing freight consist was represented as a one-dimensional lumped-mass model. The force-crush characteristic for each coach car end was adjusted to examine the effects of variation in manufacturing. Each car end was modified independently while holding all other car ends constant. The model used in this study was designed to be comparable with a 30 mph, full-scale, train-to-train CEM test. Using crush distribution and secondary impact velocity as measures of crashworthiness, the standard CEM consist performance has a maximum crashworthiness speed limit of 40 mph. Percent total energy absorbed was used as a means of comparison between cars for each consist configuration. When energy absorption levels are decreased at any particular car end, crush tends to be drawn towards this car end. Correspondingly, when available energy levels are increased at a car end, crush is drawn away from this car end. For both cases, the overall distribution of crush has more of an effect locally and less of an effect at other coupled interfaces. This paper shows that moderate variations in crush behavior may occur due to manufacturing tolerances and have little influence on the crashworthiness performance of CEM systems.

scholarly journals Performance Efficiency of a Crash Energy Management System

2007 ◽  
Author(s):  
Michael Carolan ◽  
David Tyrell ◽  
A. Benjamin Perlman
Keyword(s):  
Energy Management ◽  
Primary Energy ◽  
Baseline Characteristic ◽  
Lumped Mass ◽  
Mass Model ◽  
Passenger Train ◽  
Passenger Rail ◽  
Draft Gear ◽  
Energy Absorbers ◽  
The Individual

Previous work has led to the development of a crash energy management (CEM) system designed to distribute crush throughout unoccupied areas of a passenger train in a collision event. This CEM system is comprised of crush zones at the front and rear ends of passenger railcars. With a consist made up of CEM-equipped cars, the structural crush due to a collision can be distributed along the length of the train, crushing only unoccupied areas and improving the train’s crashworthy speed as compared with a conventional train in a similar collision. This paper examines the effectiveness of one particular CEM system design for passenger rail cars. The operating parameters of the individual components of the CEM system are varied, and this paper analyzes the effects of these variations on the behavior of the consist during a collision. The intention is to determine what modifications to the components, if any, could improve the crashworthiness of passenger railcars beyond the baseline CEM design without introducing new hazards to passengers. A one-dimensional, lumped-mass model of a passenger train impacting a heavy freight train was used in this investigation. Using this model of a collision, the force-crush behavior for each end of each car in the impacting consist was varied. The same force-crush characteristic was applied to each car end on the passenger train. The four components of the CEM system investigated were the draft gear, pushback coupler, primary energy absorbers, and occupied volume of the train car. The paper presents selected parameters of particular interest, such as the strength ratio of the primary energy absorber to the pushback coupler and the average strength of the occupied volume. The objective of this work was to ascertain the sensitivities of the various parameters on the crashworthy speed and to help optimize the force-crush characteristic. This investigation determined that modifications could be made to the baseline characteristic to improve the train’s crashworthy speed without creating new hazards to occupants.

scholarly journals Locomotive Crash Energy Management Coupling Tests

2018 ◽  
Author(s):  
Patricia Llana ◽  
Karina Jacobsen
Keyword(s):  
Energy Management ◽  
New Technologies ◽  
Primary Objective ◽  
Performance Comparison ◽  
Analytical Models ◽  
Lumped Mass ◽  
Mass Model ◽  
Subsequent Test ◽  
Wide Range ◽  
The Impact

Research to develop new technologies for increasing the safety of passengers and crew in rail equipment is being directed by the Federal Railroad Administration’s (FRA’s) Office of Research, Development, and Technology. Crash energy management (CEM) components which can be integrated into the end structure of a locomotive have been developed: a push-back coupler and a deformable anti-climber. These components are designed to inhibit override in the event of a collision. The results of vehicle-to-vehicle override, where the strong underframe of one vehicle, typically a locomotive, impacts the weaker superstructure of the other vehicle, can be devastating. These components are designed to improve crashworthiness for equipped locomotives in a wide range of potential collisions, including collisions with conventional locomotives, conventional cab cars, and freight equipment. Concerns have been raised in discussions with industry that push-back couplers may trigger prematurely, and may require replacement due to unintentional activation as a result of service loads. Push-back couplers (PBCs) are designed with trigger loads meant to exceed the expected maximum service loads experienced by conventional couplers. Analytical models are typically used to determine these required trigger loads. Two sets of coupling tests have been conducted to demonstrate this, one with a conventional locomotive equipped with conventional draft gear and coupler, and another with a conventional locomotive retrofit with a push-back coupler. These tests will allow a performance comparison of a conventional locomotive with a CEM-equipped locomotive during coupling. In addition to the two sets of coupling tests, car-to-car compatibility tests of CEM-equipped locomotives, as well as a train-to-train test are also planned. This arrangement of tests allows for evaluation of the CEM-equipped locomotive performance, as well as comparison of measured with simulated locomotive performance in the car-to-car and train-to-train tests. The coupling tests of a conventional locomotive have been conducted, the results of which compared favorably with pre-test predictions. This paper describes the results of the CEM-equipped locomotive coupling tests. In this set of tests, a moving CEM locomotive was coupled to a standing cab car. The primary objective was to demonstrate the robustness of the PBC design and determine the impact speed at which PBC triggering occurs. The coupling speed was increased for each subsequent test until the PBC triggered. The coupling speeds targeted for the test were 2 mph, 4 mph, 6 mph, 7 mph, 8 mph, and 9 mph. The coupling speed at which the PBC triggered was 9 mph. The damage observed resulting from the coupling tests is described. Prior to the tests, a lumped-mass model was developed for predicting the longitudinal forces acting on the equipment and couplers. The test results are compared to the model predictions. Next steps in the research program, including future full-scale dynamic tests, are discussed.

scholarly journals Collision Safety Comparison of Conventional and Crash Energy Management Passenger Rail Car Designs

Joint Rail ◽  
2003 ◽  
Author(s):  
Kristine J. Severson ◽  
David C. Tyrell ◽  
A. Benjamin Perlman
Keyword(s):  
Energy Management ◽  
Impact Velocity ◽  
Structural Damage ◽  
Rigid Wall ◽  
Collision Dynamics ◽  
Average Force ◽  
Secondary Impact ◽  
Passenger Rail ◽  
Conventional Design ◽  
The One

In conjunction with full-scale equipment tests, collision dynamics models of passenger rail cars have been developed to investigate the benefits provided by incorporating energy-absorbing crush zones at the ends of the cars. In a collision, the majority of the structural damage is generally focused at the point of impact for cars of conventional design. In contrast, cars with crush zones, or crash energy management (CEM), can better preserve occupied areas by distributing crush to the ends of cars. Impact tests of conventional equipment have already been conducted, which consisted of a single car and two coupled cars colliding with a rigid wall. Corresponding tests are planned using CEM equipment. This paper presents preliminary predictions of the one- and two-car CEM tests, and compares them to the results of the respective conventional equipment tests. The comparison will focus on loss of occupant volume, secondary impact velocity (SIV), and lateral buckling, as measures of occupant protection. The modeling results indicate that the occupant volume can be preserved in both the one-car and two-car tests of the CEM equipment, while 2 1/2 and 3 feet of occupant volume were crushed in the respective tests of conventional equipment. In the two-car model, the CEM design is able to distribute the crush between both cars, whereas the conventional design incurs nearly all the crush at the point of impact. The CEM design can absorb more energy without crushing the occupied area because it requires a higher average force per foot of crush at the vehicle ends. The trade-off associated with this higher crush force is generally a higher SIV for occupants in the CEM cars. Secondary impact velocity refers to the velocity at which an occupant strikes some part of the interior, in this analysis the back of the seat ahead of the occupant. The greatest SIV penalty is in the impacting car. The difference between the SIV for cars in a conventional and a CEM consist decreases in each trailing car. That is, the SIV generally decreases in each trailing car of a CEM consist, while the SIV remains approximately the same in each trailing car of a conventional consist.

Analysis of Mistuned Blade Vibrations Based on Normally Distributed Blade Individual Natural Frequencies

2015 ◽  
Author(s):  
Felix Figaschewsky ◽  
Arnold Kühhorn
Keyword(s):  
Probability Distribution ◽  
Development Process ◽  
Structural Model ◽  
Natural Frequencies ◽  
Rotor Blades ◽  
Lumped Mass ◽  
Mass Model ◽  
Influence Coefficients ◽  
Random Mistuning ◽  
Rotor Assembly

With increasing demands for reliability of modern turbomachinery blades the quantification of uncertainty and its impact on the designed product has become an important part of the development process. This paper aims to contribute to an improved approximation of expected vibration amplitudes of a mistuned rotor assembly under certain assumptions on the probability distribution of the blade’s natural frequencies. A previously widely used lumped mass model is employed to represent the vibrational behavior of a cyclic symmetric structure. Aerodynamic coupling of the blades is considered based on the concept of influence coefficients leading to individual damping of the traveling wave modes. The natural frequencies of individual rotor blades are assumed to be normal distributed and the required variance could be estimated due to experiences with the applied manufacturing process. Under these conditions it is possible to derive the probability distribution of the off-diagonal terms in the mistuned equations of motions, that are responsible for the coupling of different circumferential modes. Knowing these distributions recent limits on the maximum attainable mistuned vibration amplitude are improved. The improvement is achieved due to the fact, that the maximum amplification depends on the mistuning strength. This improved limit can be used in the development process, as it could partly replace probabilistic studies with surrogate models of reduced order. The obtained results are verified with numerical simulations of the underlying structural model with random mistuning patterns based on a normal distribution of individual blade frequencies.

A Comparison of Inverse Models for the Estimation of Ice-Induced Propeller Moments on a Polar Vessel

2021 ◽  
Author(s):  
Brendon M. Nickerson ◽  
Anriëtte Bekker
Keyword(s):  
Rotational Speed ◽  
Continuous Model ◽  
Full Scale ◽  
Lumped Mass ◽  
Mass Model ◽  
Inverse Models ◽  
Lumped Mass Model ◽  
Ill Posed ◽  
Shaft Torque ◽  
Measurement Location

Abstract Full-scale measurements were conducted on the port side propulsion shaft the S.A. Agulhas II during the 2019 SCALE Spring Cruise. The measurements included the shaft torque captured at two separate measurement locations, and the shaft rotational speed at one measurement location. The ice-induced propeller moments are estimated from the full-scale shaft responses using two inverse models. The first is a published discrete lumped mass model that relies on regularization due to the inverse problem being ill-posed. This model is only able to make use of the propulsion shaft torque as inputs. The second model is new and employs modal superposition to represent the propulsion shaft as a combination of continuous modes, resulting in a well-posed problem. This new model requires the additional measurement of the shaft rotational speed for the inverse solution. The continuous model is shown to be more consistent and efficient, which allows its use in real-time monitoring of propeller moments.

Experimental and Numerical Modal Analysis of Composite Laminated Shells

2019 ◽  
Vol 161 (A1) ◽  
Keyword(s):  
Heat Dissipation ◽  
Mass Matrix ◽  
Experimental Studies ◽  
Free Vibration Analysis ◽  
Mode Shapes ◽  
Radius Of Curvature ◽  
Lumped Mass ◽  
Auxiliary Equipment ◽  
Mass Model ◽  
Laminated Shells

The presence of cut outs at different positions of laminated shell component in marine and aeronautical structures facilitate heat dissipation, undertaking maintenance, fitting auxiliary equipment, access ports for mechanical and electrical systems, damage inspection and also influences the dynamic behaviour of the structures. The aim of the present study is to establish a comprehensive perspective of dynamic behavior of laminated deep shells (length to radius of curvature ratio less than one) with cut-out by experiments and numerical simulation. The glass epoxy laminated composite shell has been prepared in the laboratory by resin infusion. The experimental free vibration analysis is carried out on laminated shells with and without cut-out. The mass matrix is developed by considering rotary inertia in a lumped mass model in the numerical modeling. The results obtained from numerical and experimental studies are compared for verification and the consistency between mode shapes is established by applying modal assurance criteria.

Coupled Torsional Vibration and Fatigue Damage of Turbine Generator Due to Grid Disturbance

2014 ◽  
Vol 136 (6) ◽  
Author(s):  
Chao Liu ◽  
Dongxiang Jiang ◽  
Jingming Chen
Keyword(s):  
Fatigue Damage ◽  
Torsional Vibration ◽  
Coupled System ◽  
Lumped Mass ◽  
Mass Model ◽  
Turbine Generator ◽  
Failure Prevention ◽  
Lumped Mass Model ◽  
Continuous Mass ◽  
Fatigue Evaluation

Crack failures continually occur in shafts of turbine generator, where grid disturbance is an important cause. To estimate influences of grid disturbance, coupled torsional vibration and fatigue damage of turbine generator shafts are analyzed in this work, with a case study in a 600MW steam unit in China. The analysis is the following: (i) coupled system is established with generator model and finite element method (FEM)-based shafts model, where the grid disturbance is signified by fluctuation of generator outputs and the shafts model is formed with lumped mass model (LMM) and continuous mass model (CMM), respectively; (ii) fatigue damage is evaluated in the weak location of the shafts through local torque response computation, stress calculation, and fatigue accumulation; and (iii) failure-prevention approach is formed by solving the inverse problem in fatigue evaluation. The results indicate that the proposed scheme with continuous mass model can acquire more detailed and accurate local responses throughout the shafts compared with the scheme without coupled effects or the scheme using lumped mass model. Using the coupled torsional vibration scheme, fatigue damage caused by grid disturbance is evaluated and failure prevention rule is formed.

Combining Physics-Based and Data-Driven Models for Estimation of WOB During Ultra-Deep Ocean Drilling

2018 ◽  
Author(s):  
Tatsuya Kaneko ◽  
Ryota Wada ◽  
Masahiko Ozaki ◽  
Tomoya Inoue
Keyword(s):  
Hybrid Model ◽  
Numerical Models ◽  
Drill String ◽  
Operating Conditions ◽  
Data Driven ◽  
High Frequency Oscillation ◽  
Lumped Mass ◽  
Unknown Parameters ◽  
Mass Model ◽  
Time Operation

Offshore drilling with drill string over 10,000m long has many technical challenges. Among them, the challenge to control the weight on bit (WOB) between a certain range is inevitable for the integrity of drill pipes and the efficiency of the drilling operation. Since WOB cannot be monitored directly during drilling, the tension at the top of the drill string is used as an indicator of the WOB. However, WOB and the surface measured tension are known to show different features. The deviation among the two is due to the dynamic longitudinal behavior of the drill string, which becomes stronger as the drill string gets longer and more elastic. One feature of the difference is related to the occurrence of high-frequency oscillation. We have analyzed the longitudinal behavior of drill string with lumped-mass model and captured the descriptive behavior of such phenomena. However, such physics-based models are not sufficient for real-time operation. There are many unknown parameters that need to be tuned to fit the actual operating conditions. In addition, the huge and complex drilling system will have non-linear behavior, especially near the drilling annulus. These features will only be captured in the data obtained during operation. The proposed hybrid model is a combination of physics-based models and data-driven models. The basic idea is to utilize data-driven techniques to integrate the obtained data during operation into the physics-based model. There are many options on how far we integrate the data-driven techniques to the physics-based model. For example, we have been successful in estimating the WOB from the surface measured tension and the displacement of the drill string top with only recurrent neural networks (RNNs), provided we have enough data of WOB. Lack of WOB measurement cannot be avoided, so the amount of data needs to be increased by utilizing results from physics-based numerical models. The aim of the research is to find a good combination of the two models. In this paper, we will discuss several hybrid model configurations and its performance.

Identification of firefly algorithm-based fluctuation coefficient of the exciting torque for vehicle driveline

2018 ◽  
Vol 233 (2) ◽  
pp. 317-326
Author(s):  
Qiaobin Liu ◽  
Wenku Shi ◽  
Zhiyong Chen
Keyword(s):  
Torsional Vibration ◽  
Firefly Algorithm ◽  
Vibration Response ◽  
Theoretical Modelling ◽  
Lumped Mass ◽  
Mass Model ◽  
Engine Torque ◽  
Lumped Mass Model ◽  
Vibration Performance ◽  
Engine Excitation

The unbalanced excitation force and torque generated by an engine that resonate with the natural frequency of drivetrain often causes vibration and noise problems in vehicles. This study aims to comprehensively employ theoretical modelling and experimental identification methods to obtain the fluctuation coefficients of engine excitation torque when a car is in different gear positions. The inherent characteristics of the system are studied on the basis of the four-degree-of-freedom driveline lumped mass model and the longitudinal dynamics model of vehicle. The correctness of the model is verified by torsional vibration test. The second order's engine torque fluctuation coefficients are identified by firefly algorithm according to the curves of flywheel speed in different gears under the acceleration condition of the whole open throttle. The torque obtained by parameter identification is applied to the model, and the torsional vibration response of the system is analysed. The influence of the key parameters on the torsional vibration response of the system is investigated. The study concludes that proper reduction of clutch stiffness can increase clutch damping and half-axle rigidity, which can help improve the torsional vibration performance of the system. This study can provide reference for vehicle drivetrain modelling and torsional vibration control.

An Efficient Response Analysis Method for a Non-Linear/Parameter Changing System Using Sub-Structure Modes

1993 ◽  
Vol 207 (1) ◽  
pp. 41-52
Author(s):  
H K Kim ◽  
Y-S Park
Keyword(s):  
Equations Of Motion ◽  
Forced Response ◽  
Suggested Method ◽  
Response Analysis ◽  
Synthesis Methods ◽  
Lumped Mass ◽  
State Equations ◽  
Mass Model ◽  
Non Linear ◽  
Forced Responses

An efficient state-space method is presented to determine time domain forced responses of a structure using the Lagrange multiplier based sub-structure technique. Compared with the conventional mode synthesis methods, the suggested method can be particularly effective for the forced response analysis of a structure subjected to parameter changes with time, such as a missile launch system, and/or having localized non-linearities, because this method does not need to construct the governing equations of the combined whole structure. Both the loaded interface free-free modes and free interface modes can be employed as the modal bases of each sub-structure. The sub-structure equations of motion are derived using Lagrange multipliers and recurrence discrete-time state equations based upon the concept of the state transition matrix are formulated for transient response analysis. The suggested method is tested with two example structures, a simple lumped mass model with a non-linear joint and an abruptly parameter changing structure. The test results show that the suggested method is very accurate and efficient in calculating forced responses and in comparing it with the direct numerical integration method.

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