Improved accuracy for radiation damping in coupled finite element/equivalent source computations

2021 ◽  
Vol 150 (4) ◽  
pp. 2375-2387
Author(s):  
John B. Fahnline
Keyword(s):  
Finite Element ◽  
Radiation Damping ◽  
Equivalent Source ◽  
Improved Accuracy

A Finite Element Approach to Drum Brake Analysis

1979 ◽  
Vol 193 (1) ◽  
pp. 401-406 ◽  
Author(s):  
A. J. Day ◽  
P. R.J. Harding ◽  
T. P. Newcomb
Keyword(s):  
Finite Element ◽  
Element Model ◽  
Practical Experience ◽  
Drum Brake ◽  
Engineering Department ◽  
Element Approach ◽  
Rigorous Treatment ◽  
Improved Accuracy ◽  
The Finite Element Model ◽  
Development Capability

Conventional methods of brake analysis ignore the distortions of shoe and drum and are acknowledged to give inaccurate predictions of brake torque. Whilst they are adequate for very general design purposes the problem of advanced design demands a more rigorous treatment. The modern technique of finite elements, adapted to deal with the case of a friction interface, where contact is not necessarily maintained over the whole lining area, appears to be a logical approach to the problem. A simple model of shoe and lining is presented as a means of obtaining both improved accuracy and a development capability for including drum distortions and thermal effects. This model is supported by the theory of a beam on an elastic foundation in order to illustrate the importance of the relative stiffnesses of shoe and lining. Validation of the finite element model is undertaken by carrying out performance tests on a brake mounted on an inertia dynamometer and the results are used to show that the divergent types of pressure distribution predicted by earlier theories and by recent research are all compatible with practical experience and that they can account for some of the differences in performance which are found in service under various conditions. * Program for Automatic Finite Element Calculations—a commercially available software package developed by the Mechanical Engineering Department of Nottingham University and associates.

Rotordynamic Morton Effect Simulation With Transient, Thermal Shaft Bow

2016 ◽  
Vol 138 (3) ◽  
Author(s):  
Xiaomeng Tong ◽  
Alan Palazzolo ◽  
Junho Suh
Keyword(s):  
Finite Element ◽  
Temperature Distribution ◽  
Dynamic Model ◽  
Computation Time ◽  
Mass Imbalance ◽  
Hybrid Beam ◽  
Morton Effect ◽  
Transient Thermal ◽  
Improved Accuracy ◽  
Model Rotor

The Morton effect (ME) is characterized by an asymmetric journal temperature distribution, slowly varying thermal bow and intolerable synchronous vibration levels. The conventional mass imbalance model is replaced by a more accurate thermal shaft bow model. Rotor permanent bow and disk skew are synchronous excitation sources and are incorporated in the dynamic model to investigate their influence on the ME. A hybrid beam/solid element finite element shaft model is utilized to provide improved accuracy for predicting the rotor thermal bow and expansion, with practical computation time. ME is shown to be induced by initial shaft bow and disk skew. The conventional mass imbalance approach is shown to have some limitations.

Finite Element Analysis of Subsea Pipelines Subjected to Underwater Explosion

2013 ◽  
Author(s):  
F. Van den Abeele ◽  
P. Verleysen
Keyword(s):  
Shock Wave ◽  
Finite Element ◽  
Transient Response ◽  
Acoustic Pressure ◽  
Underwater Explosion ◽  
Structural Response ◽  
Added Mass ◽  
Radiation Damping ◽  
Time Response ◽  
Subsea Pipelines

Underwater mines and explosives, left in ports and harbours after World War II, can still pose a threat to subsea pipelines. In case of an accidental explosion, or even during controlled detonation, such explosives can cause significant damage to subsea pipelines. To assess the safety of pipelines exposed to an underwater explosion, finite element analyses are performed to predict the transient response of the pipeline to an acoustic pressure shock wave. This type of problem is characterized by a strong coupling between the structural response of the pipe and the acoustic pressure on the wetted interface between the pipe surface and the surrounding seawater. The spherical pressure wave induced by an underwater explosion is characterized by a very steep wave front, where the maximum pressure is attained over an extremely short rise time. The pressure then drops off exponentially over a significantly longer period of time. As a result, the structural behaviour is a combination of a long time response, dominated by an added mass effect (low frequency), a short time response, governed by radiation damping (high frequency), and an intermediate time-frequency response, where both added mass and radiation damping effects are present. In this paper, a finite element model is presented to simulate the transient response of a subsea pipeline subjected to an underwater explosion. The close coupling between acoustic pressure and structural response gives rise to numerical challenges like the accurate formulation and representation of the shock wave, the mesh requirements for the acoustic domain, and the position of the surface based absorbing radiation boundaries. An explicit dynamic solver is used to tackle these challenges, and to predict the behaviour of subsea pipelines exposed to an underwater explosion. The numerical results are compared to published experimental data, and can be used to assess the safety of submerged pipelines in the vicinity of explosives.

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