An Insight into the Analytical Models of Granular Particle Damping

2013 ◽  
Vol 819 ◽  
pp. 13-19
Author(s):  
D.Q. Wang ◽  
C.J. Wu ◽  
R.C. Yang
Keyword(s):  
Analytical Models ◽  
Lumped Mass ◽  
Mass Model ◽  
Complex Particle ◽  
Granular Particle ◽  
Particle Damping ◽  
Particle Dampers ◽  
The Stability ◽  
Improved Model ◽  
The Impact

Granular particle damping technique is a means for achieving high structural damping by the use of metal particles filled into an enclosure which is attached to the structure in a region of high vibration levels. The particle dampers are now preferred over traditional dampers due to the stability, robustness, cost effectiveness and the lower noise level than the impact damper. Such a promising technique has been used successfully in many fields over the past 20 years. In this paper, a state-of-art review on the development of modeling for particle damping is presented. The fundamentals and individual features of three main mathematical models of the granular particle damping are briefly summarized, i.e. the lumped mass model, the Discrete Element Method (DEM) and the approach based on the multiphase flow (MPF) theory of gas-particle. It is worth noting that an improved analytical model of the particle damping based on MPF theory is also introduced. The co-simulation of the COMSOL Multiphysics live link for MATLAB is conducted using this improved model. It can be shown that this model makes the complicated modeling problem more simply and offers the possibility to analyze the more complex particle-damping vibrating system.

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.

Coupling Simulation Algorithm of Dynamic Feature of a Plate With Particle Dampers Under Centrifugal Loads

2011 ◽  
Vol 133 (4) ◽  
Author(s):  
Zhaowang Xia ◽  
Xiandong Liu ◽  
Yingchun Shan
Keyword(s):  
Vibration Suppression ◽  
Extreme Temperature ◽  
Extreme Environment ◽  
Dynamic Feature ◽  
Simulation Algorithm ◽  
Centrifugal Forces ◽  
Granular Particle ◽  
Particle Damping ◽  
Particle Dampers ◽  
Element Method

Particle damper comprises granular particle enclosed in a container within a vibrating structure. The performance of particle damper is strongly nonlinear whose energy dissipation is derived from a combination of mechanisms including plastic collisions and friction between particles or particles and cavity walls. Particle damper containing suitable materials may be effective in a wider temperature range than most other types of passive damping devices. Therefore, it may be applied in extreme temperature environments where most conventional dampers would fail. It may also attenuate vibrations over a broad range of frequencies and cost less. Researches have indicated that particle damper could be a viable option for extreme environment applications. However, to date, no effort has come forward the can prove analytically or numerically that the particle damping is a viable solution for vibration suppression under centrifugal forces. In this paper, a coupling simulation algorithm based on the discrete element method and finite element method and the results of simulative studies aimed at understanding the effects of parameters of particle damper under centrifugal forces are presented. And the results show that the presented coupling simulation algorithm is effective and the analyses of dynamic feature of a plate with particle dampers under centrifugal loads are reasonable.

A Study of Noise Impact on the Stability of Electrostatic MEMS

2020 ◽  
Vol 15 (11) ◽  
Author(s):  
Yan Qiao ◽  
Wei Xu ◽  
Hongxia Zhang ◽  
Qin Guo ◽  
Eihab Abdel-Rahman
Keyword(s):  
Noise Intensity ◽  
Initial Conditions ◽  
Basins Of Attraction ◽  
Low Noise ◽  
Intensity Level ◽  
Lumped Mass ◽  
Mass Model ◽  
Restoring Force ◽  
Electrostatic Mems ◽  
The Stability

Abstract Noise-induced motions are a significant source of uncertainty in the response of micro-electromechanical systems (MEMS). This is particularly the case for electrostatic MEMS where electrical and mechanical sources contribute to noise and can result in sudden and drastic loss of stability. This paper investigates the effects of noise processes on the stability of electrostatic MEMS via a lumped-mass model that accounts for uncertainty in mass, mechanical restoring force, bias voltage, and AC voltage amplitude. We evaluated the stationary probability density function (PDF) of the resonator response and its basins of attraction in the presence noise and compared them to that those obtained under deterministic excitations only. We found that the presence of noise was most significant in the vicinity of resonance. Even low noise intensity levels caused stochastic jumps between co-existing orbits away from bifurcation points. Moderate noise intensity levels were found to destroy the basins of attraction of the larger orbits. Higher noise intensity levels were found to destroy the basins of attraction of smaller orbits, dominate the dynamic response, and occasionally lead to pull-in. The probabilities of pull-in of the resonator under different noise intensity level are calculated, which are sensitive to the initial conditions.

scholarly journals Certain Type Turbofan Engine Whole Vibration Model with Support Looseness Fault and Casing Response Characteristics

2014 ◽  
Vol 2014 ◽  
pp. 1-23 ◽  
Author(s):  
H. F. Wang ◽  
G. Chen
Keyword(s):  
Coupled System ◽  
Structural Features ◽  
Fault Model ◽  
System Response ◽  
Lumped Mass ◽  
Mass Model ◽  
Turbofan Engine ◽  
Response Characteristics ◽  
Rotor Support ◽  
The Impact

Support looseness fault is a type of common fault in aeroengine. Serious looseness fault would emerge under larger unbalanced force, which would cause excessive vibration and even lead to rubbing fault, so it is important to analyze and recognize looseness fault effectively. In this paper, based on certain type turbofan engine structural features, a rotor-support-casing whole model for certain type turbofan aeroengine is established. The rotor and casing systems are modeled by means of the finite element beam method; the support systems are modeled by lumped-mass model; the support looseness fault model is also introduced. The coupled system response is obtained by numerical integral method. In this paper, based on the casing acceleration signals, the impact characteristics of symmetrical stiffness and asymmetric stiffness models are analyzed, finding that the looseness fault would lead to the longitudinal asymmetrical characteristics of acceleration time domain wave and the multiple frequency characteristics, which is consistent with the real trial running vibration signals. Asymmetric stiffness looseness model is verified to be fit for aeroengine looseness fault model.

The assessment of rockfall hazard at the base of talus slopes

1993 ◽  
Vol 30 (4) ◽  
pp. 620-636 ◽  
Author(s):  
S.G. Evans ◽  
O. Hungr
Keyword(s):  
British Columbia ◽  
Physical Modelling ◽  
Analytical Models ◽  
Lumped Mass ◽  
Mass Model ◽  
Geological Evidence ◽  
Rockfall Hazard ◽  
Rock Face ◽  
Rock Fragments ◽  
Talus Slopes

Fragmental rockfall is characterized by the independent movement of individual rock fragments after detachment from a rock face. The continued operation of the process leads to the accumulation of talus slopes. On talus slopes the rockfall shadow extends beyond the base of the talus and consists of scattered boulders that have run out beyond the base of the slope. The landing probability of boulders in the shadow is examined; return periods of the order of 1000 years relative to a house site are typical. Rockfall behaviour particularly with respect to run out into the shadow can be assessed using geological evidence, empirical methods, physical modelling, and computer-based analytical models. An empirical minimum shadow angle of 27.5° (i.e., the angle between the distal limit of the shadow and the top of the talus slope) is suggested and would be useful in rockfall vulnerability studies at the base of talus slopes as a first approximation to shadow limits. It is preferable to the use of the rockfall fahrböschung as proposed by several authors. A random collision lumped mass model (ROCKFALL) is outlined, ROCKFALL uses two restitution coefficients and a transition to rolling criterion, ROCKFALL is used to analyse two fatal rockfall accidents in southern British Columbia, at Hedley in 1939 and Sunnybrae in 1983, which are documented in detail. An additional nonfatal incident is also analysed (Barnhartvale in 1974). Results based on an initial calibration were encouraging. Documentation of the three rockfall incidents shows that, in each case, rockfall fragments impacted on homes at equivalent shadow angles of 30° or more. This would suggest that a review of existing development within rockfall shadow areas at the base of talus slopes may be in order. Key words : rockfall, dynamics, talus slopes, landslides, British Columbia

Investigation of Engine Distortion Interaction

2016 ◽  
Author(s):  
Fabian Wartzek ◽  
Heinz-Peter Schiffer ◽  
Jakob P. Haug ◽  
Reinhard Niehuis ◽  
Martin Bitter ◽  
...  
Keyword(s):  
Numerical Models ◽  
Experimental Studies ◽  
Stability Limit ◽  
Analytical Models ◽  
Test Case ◽  
Transonic Compressor ◽  
Numerical Studies ◽  
Small Distortion ◽  
The Stability ◽  
The Impact

Inflow distortions in the compression system of a jet engine are becoming increasingly important for research focus. The investigation of the emergence of a distortion, its interaction with the rotor and the resulting impact on the rotor flow is challenging. In this work a separation in the inflow of a transonic compressor was created and the impact on stage aerodynamics investigated. The separation resulted in a total pressure distortion close to the casing within a sector of 120°. Effects were studied both numerically and experimentally in a joint collaboration project. The numerical model consisted of the full rotor-stator compressor stage, the inlet duct and the distortion generator upstream of the stage. This enables both an accurate validation of the numerical results and contributes to a deeper understanding of the flow. The results of both the numerical and experimental studies were in good agreement. The rotor is locally throttled by the inlet separation, resulting in the formation of an additional loss core at the stability limit due to a local aerodynamic overload. Considering classic distortion descriptors like the DC60, it is shown that they are not able to adequately assess the impact of a strong, but small distortion close to the tip of the rotor. The data can be considered as test case for future numerical models as well as for the validation of new analytical models. Furthermore, the results of this study reveal effects in both experimental and numerical studies that would not be realized if only a model of the separation was analyzed.

scholarly journals Conventional Locomotive Coupling Tests

2016 ◽  
Author(s):  
Patricia Llana ◽  
Karina Jacobsen ◽  
David Tyrell
Keyword(s):  
New Technologies ◽  
Performance Comparison ◽  
Analytical Models ◽  
Lumped Mass ◽  
Mass Model ◽  
One Dimensional ◽  
Vehicle To Vehicle ◽  
Wide Range ◽  
Draft Gear ◽  
Lumped Mass Model

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 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 are planned to demonstrate this, one with a conventional locomotive equipped with conventional draft gear and coupler, and another with a conventional locomotive equipped 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. This paper describes the results of the coupling tests of conventional equipment. In this set of tests, a moving locomotive was coupled to a standing cab car. The coupling speed for the first test was 2 mph, the second test 4 mph, and the tests continued with the speed incrementing by 2 mph until the last test was conducted at 12 mph. The damage observed resulting from the coupling tests is described. The lowest coupling speed at which damage occurred was 6 mph. Prior to the tests, a one-dimensional lumped-mass model was developed for predicting the longitudinal forces acting on the equipment and couplers. The model predicted that damage would occur for coupling speeds between 6 and 8 mph. The results of these conventional coupling tests compare favorably with pre-test predictions. Next steps in the research program, including future full-scale dynamic tests, are discussed.

scholarly journals A New Formula of Impact Stiffness in Linear Viscoelastic Model for Pounding Simulation

2016 ◽  
Vol 2016 ◽  
pp. 1-7 ◽  
Author(s):  
Xiuli Xu ◽  
Xiang Xu ◽  
Weiqing Liu ◽  
Ding Zhou
Keyword(s):  
Impact Force ◽  
Viscoelastic Model ◽  
Lumped Mass ◽  
Mass Model ◽  
Linear Viscoelastic ◽  
Lumped Mass Model ◽  
New Formula ◽  
The Impact ◽  
Linear Viscoelastic Model ◽  
Viscoelastic Contact

The phenomenon of earthquake-induced structural pounding was extensively studied by some researchers using different models for the impact force. The aim of this paper is to provide a new formula of impact stiffness in the linear viscoelastic contact model, based on the assumption that the maximum impact deformation from the distributed mass model should be equal to that from the equivalent lumped mass model. The correctness and accuracy of the proposed formula have been confirmed by comparing the pounding simulation using the present formula of impact stiffness with those using the existing formulae.

SIMPLIFIED ANALYSIS OF LOW VELOCITY IMPACT ACTIONS ON SHALLOW DOMES

2013 ◽  
Vol 05 (02) ◽  
pp. 1350013 ◽  
Author(s):  
YI YANG ◽  
NELSON LAM ◽  
LIHAI ZHANG ◽  
EMAD GAD
Keyword(s):  
Nonlinear Behavior ◽  
Low Velocity Impact ◽  
Elastic Behavior ◽  
Response Behavior ◽  
Lumped Mass ◽  
Low Velocity ◽  
Mass Model ◽  
Simplified Approach ◽  
Lumped Masses ◽  
The Impact

This paper is concerned with a simplified approach of estimating the effects of the impact of a projectile on a circular dome. The procedure to be introduced involves simplifying the impactor (projectile) and the target (the dome) by a two-degree-of-freedom (2DOF) system which is made up of two lumped masses connected by elastic springs. This modeling approach has only been adapted for analyzing the impact response behavior of beams and plates. The original contributions of this paper is the development of equations and charts for estimating the value of the lumped mass and spring stiffness in the 2DOF lumped mass model to emulate the response behavior of circular domes. Linear elastic behavior of the dome is assumed but nonlinear behavior of the impactor has been taken into account. The developed calculation procedure has been validated and illustrated by case studies.

scholarly journals Investigation of Lumped-Mass Method on Coupled Torsional-longitudinal Vibrations for a Marine Propulsion Shaft with Impact Factors

2019 ◽  
Vol 7 (4) ◽  
pp. 95
Author(s):  
Qianwen Huang ◽  
Haiyun Liu ◽  
Jiyin Cao
Keyword(s):  
Propulsion System ◽  
Impact Factors ◽  
Dynamical Response ◽  
Longitudinal Vibrations ◽  
Lumped Mass ◽  
Mass Model ◽  
Coupled Vibrations ◽  
Lumped Mass Method ◽  
Marine Propulsion ◽  
The Impact

Severe vibrations of the marine propulsion shaft can evidently affect the dynamical response of the propulsion system and degrade the performance of a ship. As the vibration forms couples which interact with each other, a better understanding of the coupled vibrations is essential for dynamic prediction to improve the efficiency and reliability of the marine propulsion system. Thus, an investigation of the lumped-mass method for coupled torsional-longitudinal vibrations of the shaft is proposed. First, a theoretical solution for the coupled ordinary differential equations demonstrates the accuracy of the proposed lumped-mass model. This model allows for the bifurcation diagram and the Poincare surface, and transient accelerations of the coupled vibrations are numerically calculated. Furthermore, the impact factors including various length-diameter ratios, coupling stiffness coefficients, and damping coefficients are respectively discussed. These impact factors are found to affect the coupled vibrations to different extents through the comparison of the transient accelerations. Finally, an accurate and applicative lumped-mass method for the coupled torsional-longitudinal vibrations of the marine propulsion shaft has been obtained. An optimal design and vibration reduction of the shaft, considering the above-mentioned impact factors, can be achieved.

Sign in / Sign up

Export Citation Format

Share Document