Finite Element Analysis of Conical Shells With a Constrained Viscoelastic Layer

1994 ◽  
Vol 171 (5) ◽  
pp. 577-601 ◽  
Author(s):  
T.C. Ramesh ◽  
N. Ganesan
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Viscoelastic Layer ◽  
Element Analysis ◽  
Conical Shells

Dynamic Analysis to Evaluate Viscoelastic Passive Damping Augmentation for the Space Shuttle Remote Manipulator System

1992 ◽  
Vol 114 (3) ◽  
pp. 468-475 ◽  
Author(s):  
Thomas E. Alberts ◽  
Houchun Xia ◽  
Yung Chen
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Dynamic Analysis ◽  
Active Control ◽  
Space Shuttle ◽  
Viscoelastic Layer ◽  
Passive Damping ◽  
Element Analysis ◽  
Joint Flexibility ◽  
Damping Treatments

This paper presents a NASTRAN finite element analysis for evaluation of the effectiveness of viscoelastic damping treatments as passive controls for large flexible space manipulators. The passive damping could be used alone or as an augmentation to active control. Perhaps the best existing example of a practical flexible manipulator is the space shuttle Remote Manipulator System (RMS). The authors use the RMS as an example for this investigation, subjecting it to a detailed dynamic analysis which can be used to evaluate the critical modes for control and to distinguish the modes which are good candidates for active control from those which are well suited for passive control. Modal potential energy analysis (MPE) is used to examine the modal energy distribution in each structural member of the complex flexible chained system. The results indicate that the most dominant contributors to end-point oscillations fall into two categories. These include very low frequency modes due to joint flexibility and higher frequency modes due to bending in the booms. Significant end-point motions result from each category, but the most significant motions are associated with joint flexibility. Finally, a finite element analysis is performed to evaluate the effectiveness of constrained viscoelastic layer damping treatments for passive vibration control. Passive damping augmentation is introduced through the use of a constrained viscoelastic layer damping treatment applied to the surface of the manipulator’s flexible booms. It is shown that even the joint compliance dominated modes can be damped to some degree through appropriate design of the treatment.

Decay Length in Pressure Vessels

2017 ◽  
Author(s):  
R. Adibi-Asl ◽  
R. Seshadri
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Edge Effect ◽  
Interaction Effects ◽  
Pressure Vessels ◽  
Decay Length ◽  
Internal Edge ◽  
Element Analysis ◽  
Conical Shells

In theory of shell, decay length is defined as the distance affected by localized external (applied loads) or internal (edge effect, discontinuity) forces and moments, beyond which the effect of these loads becomes negligible. The concept of decay length becomes relevant when assessing the interaction effects caused by adjacent discontinuities. In this paper, the decay lengths for several shells geometries, specifically cylindrical, spherical and conical shells, are reviewed. The available expressions for decay lengths in the literature are listed and are compared with finite element analysis to demonstrate the accuracy of some of the solutions.

Experimental and Finite Element Analysis of Stand-Off Layer Damping Treatments for Beams

2007 ◽  
Author(s):  
Jessica M. H. Yellin ◽  
I. Y. Shen ◽  
Per G. Reinhall
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Frequency Response ◽  
Viscoelastic Layer ◽  
Constrained Layer Damping ◽  
Response Functions ◽  
Element Analysis ◽  
Frequency Response Functions ◽  
Damping Treatments ◽  
Passive Constrained Layer Damping

Passive stand-off layer (PSOL) and slotted stand-off layer (SSOL) damping treatments are presently being implemented in many commercial and defense designs. In a PSOL damping treatment, a stand-off or spacer layer is added to a conventional passive constrained layer damping treatment. In an SSOL damping treatment, slots are included in the stand-off layer. A set of experiments using PSOL and SSOL beams in which the geometric properties of the stand-off layer were varied was conducted to analyze the contribution of the stand-off layer to the overall system damping. This set of experiments measured the frequency response functions for a series of beams in which the total slotted area of the stand-off layer was held constant while the number of slots in the stand-off layer was increased for a constant stand-off layer material. Finite element analysis models were developed in ANSYS to compare the predicted frequency response functions with the experimentally measured frequency response functions for the beams treated with PSOL and SSOL damping treatments. In these beams, the bonding layers used to fabricate these treatments were found to have a measurable and significant effect on the frequency response of the structure. The finite element model presented here thus included an epoxy layer between the base beam and the stand-off layer, a contact cement layer between the stand-off layer and the viscoelastic layer, and a method for modeling delamination.

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