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.

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.

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.

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 Rockfall-induced impact force causing a debris flow on a volcanoclastic soil slope: a case study in southern Italy

2010 ◽  
Vol 10 (9) ◽  
pp. 1995-2006 ◽  
Author(s):  
P. Budetta
Keyword(s):  
Debris Flow ◽  
Impact Force ◽  
Back Analysis ◽  
Soil Slope ◽  
Lumped Mass ◽  
Depth Of Penetration ◽  
Lumped Mass Method ◽  
Elliptical Area ◽  
Surrounding Areas ◽  
The Impact

Abstract. On 10 January 2003, a rockfall of approximately 10 m3 affected a cliff some 25 m high located along the northern slopes of Mt. St. Angelo (Nocera Inferiore, province of Salerno) in the southern Italian region of Campania. The impact of boulders on the lower sector of the slope, along which detrital-pyroclastic soils outcrop, triggered a small channelled debris flow of about 500 m3. Fortunately, no damage nor victims resulted from the landslide. Several marks of the impacts were observed at the cliff toe and outside the collapsed area, and the volumes of some fallen boulders were subsequently measured. By means of in-situ surveys, it was possible to reconstruct the cliff's geo-structural layout in detail. A rockfall back-analysis was subsequently performed along seven critical profiles of the entire slope (surface area of about 4000 m2). The results of this numerical modelling using the lumped-mass method were then used to map the kinetic iso-energy curves. In the triggering area of the debris flow, for a falling boulder of 1 m3, the mean kinetic energy was estimated at 120 kJ, this value being equivalent to an impact force, on an inclined surface, of some 800 kN. After landing, due to the locally high slope gradient (about 45°), and low angle of trajectory at impact (about 23°), some boulders slid down the slope as far as the endpoints. The maximum depth of penetration into the ground by a sliding block was estimated at about 16 cm. Very likely, owing to the high impact force of boulders on the saturated soil slope outcropping at the cliff base, the debris flow was triggered under undrained loading conditions. Initial failure was characterized by a translational slide involving a limited, almost elliptical area where the pyroclastic cover shows greater thickness in comparison with the surrounding areas.

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 Effects of the impact angle on the coefficient of restitution in rockfall analysis based on a medium-scale laboratory test

2018 ◽  
Vol 18 (11) ◽  
pp. 3045-3061 ◽  
Author(s):  
Yanhai Wang ◽  
Wei Jiang ◽  
Shengguo Cheng ◽  
Pengcheng Song ◽  
Cong Mao
Keyword(s):  
Kinetic Energy ◽  
Laboratory Test ◽  
Laboratory Tests ◽  
Impact Angle ◽  
Coefficient Of Restitution ◽  
Small Scale ◽  
Lumped Mass ◽  
Mass Model ◽  
Medium Scale ◽  
The Impact

Abstract. The reliability of a computer program simulating rockfall trajectory depends on the ascertainment of reasonable values for the coefficients of restitution, which typically vary with the kinematic parameters and terrain conditions. The effects of the impact angle with respect to the slope on the coefficients of restitution have been identified and studied using small-scale laboratory tests. To investigate whether the existing conclusion based on small-scale laboratory tests is valid when the test scale changes as well as the role of rotation in the effect of the impact angle on the coefficients of restitution, this study performed a medium-scale laboratory test using spherical limestone polyhedrons to impact concrete slabs. Free-fall tests are conducted, and the velocities before and after the impact are obtained by a 3-D motion capture system. The comparison of results between our test and the existing small-scale tests verified that several general laws occur when accounting for the effect of the impact angle, regardless of the test scales and conditions. Increasing the impact angle will induce reductions in the normal coefficient of restitution Rn, the kinematic coefficient of restitution Rv and the kinetic energy coefficient of restitution RE, whereas it will lead to increases in the tangential coefficient of restitution Rt. The rotation plays an important role in the effect of the impact angle. A higher percentage of kinetic energy converted to rotational energy always induces a higher normal coefficient of restitution Rn and a lower tangential coefficient of restitution Rt. As the impact angle decreases, the ratio between the rebound angle β and the impact angle α increases, and the percentage of kinetic energy dissipated in rotation as the collision became higher. Considering that the effect of block shape and the detailed impact orientations are not involved in the present study, the test results are valid for trajectory simulation codes based on a lumped-mass model and can be referenced in the trajectory predication of spherical rocks impacting hard surfaces using a rigid body model.

The Impact of Anglicizing Former German-Language Psychology Journals on Authorship and Citation Frequencies

2012 ◽  
Vol 17 (3) ◽  
pp. 190-198 ◽  
Author(s):  
Günter Krampen ◽  
Thomas Huckert ◽  
Gabriel Schui
Keyword(s):  
Side Effects ◽  
English Language ◽  
General Trend ◽  
Native Language ◽  
Impact Factors ◽  
German Language ◽  
Journal Articles ◽  
Number Of Citations ◽  
The Impact ◽  
Number Of Authors

Exemplary for other than English-language psychology journals, the impact of recent Anglicization of five former German-language psychology journals on (1) authorship (nationality, i.e., native language, and number of authors, i.e., single or multiple authorships), (2) formal characteristics of the journal (number of articles per volume and length of articles), and (3) number of citations of the articles in other journal articles, the language of the citing publications, and the impact factors (IF) is analyzed. Scientometric data on these variables are gathered for all articles published in the four years before anglicizing and in the four years after anglicizing the same journal. Results reveal rather quick changes: Citations per year since original articles’ publication increase significantly, and the IF of the journals go up markedly. Frequencies of citing in German-language journals decrease, citing in English-language journals increase significantly after the Anglicization of former German-language psychology journals, and there is a general trend of increasing citations in other languages as well. Side effects of anglicizing former German-language psychology journals include the publication of shorter papers, their availability to a more international authorship, and a slight, but significant increase in multiple authorships.

scholarly journals Exploring Factors Influencing Scenarios Evolution of Waste NIMBY Crisis: Analysis of Typical Cases in China

2021 ◽  
Vol 18 (4) ◽  
pp. 2006
Author(s):  
Ling He ◽  
Qing Yang ◽  
Xingxing Liu ◽  
Lingmei Fu ◽  
Jinmei Wang
Keyword(s):  
Network Theory ◽  
Development Process ◽  
Dynamic Bayesian Network ◽  
Impact Factors ◽  
Social Stability ◽  
Ground Theory ◽  
Evolution Path ◽  
Dynamic Scenario ◽  
The Impact

As the impact factors of the waste Not-In-My-Back Yard (NIMBY) crisis are complex, and the scenario evolution path of it is diverse. Once the crisis is not handled properly, it will bring adverse effects on the construction of waste NIMBY facilities, economic development and social stability. Consequently, based on ground theory, this paper takes the waste NIMBY crisis in China from 2006 to 2019 as typical cases, through coding analysis, scenario evolution factors of waste NIMBY crisis are established. Furtherly, three key scenarios were obtained, namely, external situation (E), situation state (S), emergency management (M), what is more, scenario evolution law of waste NIMBY crisis is revealed. Then, the dynamic Bayesian network theory is used to construct the dynamic scenario evolution network of waste NIMBY crisis. Finally, based on the above models, Xiantao waste NIMBY crisis is taken as a case study, and the dynamic process of scenario evolution network is visually displayed by using Netica. The simulation results show that the scenario evolution network of Xiantao waste NIMBY crisis is basically consistent with the actual incident development process, which confirms the effectiveness and feasibility of the model.

scholarly journals Design of Hybrid-Electric Megayachts: The Impact of Operative Profile and Smart Berthing Infrastructures

2021 ◽  
Vol 9 (2) ◽  
pp. 186
Author(s):  
Francesco Mauro ◽  
Elia Ghigliossi ◽  
Vittorio Bucci ◽  
Alberto Marinó
Keyword(s):  
Electric Propulsion ◽  
Propulsion System ◽  
Storage Devices ◽  
Electric Propulsion System ◽  
Hybrid Electric ◽  
The Impact

Nowadays, sustainable navigation is becoming a trending topic not only for merchant ships but also for pleasure vessels such as motoryachts. Therefore, the adoption of a hybrid-electric propulsion system and the installation of on-board storage devices could increase the greenness of a megayacht. This paper analyses the performance of three commercial propulsive solutions, using a dynamic operative profile and considering the influences of the smart berthing infrastructures. Results compare the yearly fuel consumptions of the analysed configurations for a reference megayacht.

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