Redesign of NEMO-Type Spherical Acrylic Submersible for Manned Operation to 3000 ft (914 m) Ocean Depth

2001 ◽  
Vol 124 (1) ◽  
pp. 97-107 ◽  
Author(s):  
Partha S. Das
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Three Dimensional ◽  
Dissimilar Materials ◽  
Cyclic Fatigue ◽  
Design Guidelines ◽  
Element Analysis ◽  
Design Guideline ◽  
Crack Generation ◽  
Generation Problem

A detailed nonlinear three-dimensional (3-D) finite element analysis (FEA) was performed in Phase I on a NEMO (naval experimental manned observatory) type HBOI (Harbor Branch Oceanographic Institution) spherical acrylic submersible in order to overcome the crack generation problem at its interfaces. An FEA has been carried out to develop a new design guideline, by reducing the higher stresses and relative displacements at the interfaces, which are believed to be two of the main reasons for crack generation at these areas. Variation of the stiffness between dissimilar materials at the interface, lower nylon gasket thickness, overdesigned aluminum hatch and bottom penetrator plug, attachment of the retainer ring with hatch ring, close placement of the rubber padding to the interface between the acrylic sphere, and the retainer ring are found to be the various causes for higher stresses within the acrylic sphere at the nylon gasket/acrylic interface. Based on the new design guidelines, in Phase II, a new spherical acrylic submersible was fabricated and tested. This design resulted in significant improvements by reducing the peak stresses and relative displacements at the gasket/acrylic interface areas. This improvement in design is expected to significantly extend the crack-free cyclic fatigue life of the acrylic submersible at 3000 ft (914 m) ocean depth.

Redesign of Spherical Acrylic Submersible for Manned Operation to 3000 ft (914.4 m) Ocean Depth

2000 ◽  
Author(s):  
Partha S. Das
Keyword(s):  
Finite Element Analysis ◽  
Cyclic Fatigue ◽  
Relative Displacement ◽  
Design Guidelines ◽  
Shear Cracks ◽  
Two Phase ◽  
Element Analysis ◽  
Ocean Exploration ◽  
Manned Submersible ◽  
Generation Problem

Abstract Harbor Branch Oceanographic Institution (HBOI) is using its spherical acrylic manned submersible for ocean exploration for last 3 decades. However, the development of tiny shear cracks at the interface areas of these submersibles following only few hundred dives require frequent, expensive repairs. To overcome this crack generation problem, a two-Phase research program is initiated at HBOI. In the Phase I of this study, a detailed nonlinear 3-D Finite Element Analysis (FEA) is performed at first to increase the understanding of the mechanical behavior at the interface of this submersible and then various analyses are carried out to develop a guidelines for redesigning the spherical acrylic submersible. Complete redesigning of the bottom of acrylic submersible is only presented here in details, as the discussion on the top of acrylic submersible is presented earlier. Based on the new design guidelines, in the Phase II of this study, a new spherical acrylic submersible is fabricated at HBOI. Brief discussion of the experimental results on the new submersible is also presented here. A significant reduction in peak stresses and a very small relative displacement at the gasket/acrylic interface which are believed to be two of the main causes for crack development at the interface areas clearly indicate a major improvement in the new design of the acrylic submersible, as they are also suggested by the extensive FEA results. This improvement in design is expected to extend the crack free cyclic fatigue life of the acrylic submersible at 3000 ft (914.4 m) ocean depth significantly.

Finite Element Analysis of Nonuniformity of Tires with Imperfections5

2007 ◽  
Vol 35 (3) ◽  
pp. 226-238 ◽  
Author(s):  
K. M. Jeong ◽  
K. W. Kim ◽  
H. G. Beom ◽  
J. U. Park
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Three Dimensional ◽  
Element Model ◽  
Radial Force ◽  
Element Analysis ◽  
The Finite Element Analysis ◽  
Dimensional Finite Element ◽  
Force Variation ◽  
Three Dimensional Finite Element

Abstract The effects of variations in stiffness and geometry on the nonuniformity of tires are investigated by using the finite element analysis. In order to evaluate tire uniformity, a three-dimensional finite element model of the tire with imperfections is developed. This paper considers how imperfections, such as variations in stiffness or geometry and run-out, contribute to detrimental effects on tire nonuniformity. It is found that the radial force variation of a tire with imperfections depends strongly on the geometrical variations of the tire.

Modeling and experimental verification on directivity of an electret cell array loudspeaker

2012 ◽  
Vol 24 (3) ◽  
pp. 326-333 ◽  
Author(s):  
Yu-Chi Chen ◽  
Wen-Ching Ko ◽  
Han-Lung Chen ◽  
Hsu-Ching Liao ◽  
Wen-Jong Wu ◽  
...  
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Three Dimensional ◽  
Digital Control System ◽  
Analysis Model ◽  
Cell Array ◽  
Element Analysis ◽  
Finite Element Analysis Model ◽  
The Finite Element Analysis ◽  
Directivity Characteristics

We propose a model to give us a method to investigate the characteristic three-dimensional directivity in an arbitrarily configured flexible electret-based loudspeaker. In recent years, novel electret loudspeakers have attracted much interest due to their being lightweight, paper thin, and possessing excellent mid- to high-frequency responses. Increasing or decreasing the directivity of an electret loudspeaker makes it excellent for adoption to many applications, especially for directing sound to a particular area or specific audio location. Herein, we detail a novel electret loudspeaker that possesses various directivities and is based on various structures of spacers instead of having to use multichannel amplifiers and a complicated digital control system. In order to study the directivity of an electret loudspeaker based on an array structure which can be adopted for various applications, the horizontal and vertical polar directivity characteristics as a function of frequency were simulated by a finite-element analysis model. To validate the finite-element analysis model, the beam pattern of the electret loudspeaker was measured in an anechoic room. Both the simulated and experimental results are detailed in this article to validate the various assertions related to the directivity of electret cell-based smart speakers.

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