Spherical Acrylic Pressure Hulls With Multiple Penetrations

1978 ◽  
Vol 100 (2) ◽  
pp. 261-271 ◽  
Author(s):  
J. D. Stachiw ◽  
R. B. Dolan
Keyword(s):  
Hydrostatic Pressure ◽  
Structural Response ◽  
Structural Performance ◽  
Experimental Program ◽  
External Hydrostatic Pressure ◽  
Short Term ◽  
Acrylic Plastic ◽  
Model Scale ◽  
Depth Rating

An experimental program has been conducted to determine the effect of multiple penetrations on the performance of spherical acrylic plastic hulls under external hydrostatic pressure. As test specimens served 15-in. OD × 14-in. ID model scale NEMO spheres. The distribution of strains and the magnitudes of short term critical pressures indicate that the structural response of acrylic spheres with multiple penetrations to external hydrostatic pressure is identical to spheres with only one penetration equipped with a metallic closure providing that the included angles of the penetrations are ≤46 deg and the edges of the penetrations are at least one penetration radius apart. Based on these findings it is feasible to incorporate three or more large penetrations into the spherical hulls of acrylic submersibles without decreasing their operational depth rating that has been based on the experimentally proven structural performance of spheres with only one penetration, or two penetrations 180 deg center to center apart.

Flanged Acrylic Plastic Hemispherical Shells for Undersea Application

1975 ◽  
Vol 97 (1) ◽  
pp. 1-9 ◽  
Author(s):  
J. D. Stachiw ◽  
J. R. Maison
Keyword(s):  
Finite Element ◽  
Hydrostatic Pressure ◽  
Stress Distribution ◽  
Boundary Conditions ◽  
Critical Pressure ◽  
Convex Surface ◽  
Elastic Analysis ◽  
Short Term ◽  
Acrylic Plastic ◽  
Hemispherical Shells

The effects of an equatorial flange and a nonuniform wall thickness upon the critical pressure and stress distribution in acrylic plastic hemispheres have been investigated by experimental and analytical methods. Forty acrylic hemispheres were fabricated and tested to destruction under short term hydrostatic pressure applied on the convex surface. Dome apex displacements were obtained from each specimen and strains were obtained from a selected few. A finite element elastic analysis was performed on one window configuration for two different boundary conditions and the experimentally derived stresses were used to determine which boundary conditions was the best for analytical analysis.

Acrylic Plastic Spherical Shell Windows Under Point Impact Loading

1976 ◽  
Vol 98 (2) ◽  
pp. 563-575 ◽  
Author(s):  
J. D. Stachiw ◽  
O. H. Burnside
Keyword(s):  
Hydrostatic Pressure ◽  
Spherical Shell ◽  
Impact Loading ◽  
External Hydrostatic Pressure ◽  
Element Analysis ◽  
Destructive Effect ◽  
Tensile Stresses ◽  
Acrylic Plastic ◽  
Degree Of Confidence ◽  
Ocean Environment

Acrylic plastic spherical shell sector windows with 117-deg included angle and outside radius of 24-in. (61 mm), have been impacted at their center, with a 12,500 lb (5662 kg) weight, in a simulated ocean environment. Velocities of impacts ranged from 0.205 to 10.702 ft (0.06 to 3.26 m) per second. It has been found that fracture of windows is initiated by tensile stresses on the concave surface of the window, directly below the point of impact. Compressive stresses, generated by external hydrostatic pressure, decrease the destructive effect of tensile stresses introduced by point impact loading. For 2.25 and 4.0-in. (57 and 101 mm) thick windows the critical impact velocities were found to fall into the 1.5 to 3 ft (0.45 to 0.91 m) per second range, the exact value being a function of window thickness and external hydrostatic pressure. A finite element analysis was found to agree rather well with the experimental. This analysis can be employed to predict, with a reasonable degree of confidence, the critical impact velocities for acrylic plastic spherical windows in the bows of submersibles.

Study of Ductile-to-Brittle Transition in Single Grit Diamond Scribing of Silicon: Application to Wire Sawing of Silicon Wafers

2012 ◽  
Vol 134 (4) ◽  
Author(s):  
Hao Wu ◽  
Shreyes N. Melkote
Keyword(s):  
Hydrostatic Pressure ◽  
Silicon Wafers ◽  
Depth Of Cut ◽  
Critical Depth ◽  
External Hydrostatic Pressure ◽  
Tensile Stresses ◽  
Brittle Transition ◽  
Ductile Mode Cutting ◽  
Critical Depth Of Cut ◽  
Ductile To Brittle Transition

The ductile-to-brittle cutting mode transition in single grit diamond scribing of monocrystalline silicon is investigated in this paper. Specifically, the effects of scriber tip geometry, coefficient of friction, and external hydrostatic pressure on the critical depth of cut associated with ductile-to-brittle transition and crack generation are studied via an eXtended Finite Element Method (XFEM) based model, which is experimentally validated. Scribers with a large tip radius are shown to produce lower tensile stresses and a larger critical depth of cut compared with scribers with a sharp tip. Spherical tipped scribers are shown to generate only surface cracks, while sharp tipped scribers (conical, Berkovich and Vickers) are found to create large subsurface tensile stresses, which can lead to nucleation of subsurface median/lateral cracks. Lowering the friction coefficient tends to increase the critical depth of cut and hence the extent of ductile mode cutting. The results also show that larger critical depth of cut can be obtained under external hydrostatic pressure. This knowledge is expected to be useful in optimizing the design and application of the diamond coated wire employed in fixed abrasive diamond wire sawing of photovoltaic silicon wafers.

scholarly journals Verification of the Structural Performance of Textile Reinforced Reactive Powder Concrete Sandwich Facade Elements

2019 ◽  
Vol 9 (12) ◽  
pp. 2456 ◽  
Author(s):  
Mathias Flansbjer ◽  
Natalie Williams Portal ◽  
Daniel Vennetti
Keyword(s):  
Structural Model ◽  
Structural Performance ◽  
Wind Loading ◽  
Experimental Program ◽  
Reactive Powder Concrete ◽  
Uniaxial Tensile ◽  
Material Development ◽  
Pull Out ◽  
Glass Fiber Reinforced ◽  
Reactive Powder

As a part of the SESBE (Smart Elements for Sustainable Building Envelopes) project, non-load bearing sandwich elements were developed with Textile Reinforced Reactive Powder Concrete (TRRPC) for outer and inner facings, Foam Concrete (FC) for the insulating core and Glass Fiber Reinforced Polymer (GFRP) continuous connectors. The structural performance of the developed elements was verified at various levels by means of a thorough experimental program coupled with numerical analysis. Experiments were conducted on individual materials (i.e., tensile and compressive tests), composites (i.e., uniaxial tensile, flexural and pull-out tests), as well as components (i.e., local anchorage failure, shear, flexural and wind loading tests). The experimentally yielded material properties were used as input for the developed models to verify the findings of various component tests and to allow for further material development. In this paper, the component tests related to local anchorage failure and wind loading are presented and coupled to a structural model of the sandwich element. The validated structural model provided a greater understanding of the physical mechanisms governing the element’s structural behavior and its structural performance under various dead and wind load cases. Lastly, the performance of the sandwich elements, in terms of composite action, was shown to be greatly correlated to the properties of the GFRP connectors, such as stiffness and strength.

scholarly journals OPTIMUM BUCKLING DESIGN OF CYLINDRICAL STIFFENER SHELL UNDER EXTERNAL HYDROSTATIC PRESSURE

2018 ◽  
Vol 18 (2) ◽  
pp. 239-252 ◽  
Author(s):  
Rawa Hamed M. Al-Kalali
Keyword(s):  
Hydrostatic Pressure ◽  
Numerical Optimization ◽  
Collapse Load ◽  
Ansys Software ◽  
External Hydrostatic Pressure ◽  
Buckling Mode ◽  
Design Elements ◽  
Design Variables ◽  
Thick Cylinder ◽  
Strength Constraints

This paper present an investigation of the collapse load in cylinder shell under uniformexternal hydrostatic pressure with optimum design using finite element method viaANSYS software. Twenty cases are studied inclusive stiffeners in longitudinal and ringstiffeners. Buckling mode shape is evaluated. This paper studied the optimum designgenerated by ANSYS for thick cylinder with external hydrostatic pressure. The primarygoal of this paper was to identify the improvement in the design of cylindrical shell underhydrostatic pressure with and without Stiffeners (longitudinal and ring) with incorporativetechnique of an optimization into ANSYS software. The design elements in this researchwas: critical load, design variable (thickness of shell (TH), stiffener’s width (B) andstiffener’s height (HF). The results obtained illustrated that the objective is minimizedusing technique of numerical optimization in ANSYS with optimum shell thickness andstiffener’s sizes. In all cases the design variables (thickness of shell) was thicker than themonocoque due to a shell’s thicker is essential to achieve the strength constraints. It can beconcluded that cases (17,18,19, and 20) have more than 90% of un-stiffened critical load.The ring stiffeners causes increasing buckling load than un-stiffened and longitudinalstiffened cylinder.

Plastic buckling of ring-stiffened conical shells under external hydrostatic pressure

2005 ◽  
Vol 32 (1) ◽  
pp. 21-36 ◽  
Author(s):  
Carl T.F. Ross ◽  
Andrew P.F. Little ◽  
Kehinde A. Adeniyi
Keyword(s):  
Hydrostatic Pressure ◽  
External Hydrostatic Pressure ◽  
Plastic Buckling ◽  
Conical Shells

Numerical Modelling of Historic Vaulted Timber Structures

2013 ◽  
Vol 778 ◽  
pp. 517-525 ◽  
Author(s):  
Carina Fonseca Ferreira ◽  
Dina D’Ayala ◽  
Jose L. Fernandez Cabo ◽  
Rafael Díez
Keyword(s):  
Finite Element Method ◽  
Software Package ◽  
Structural Response ◽  
Shear Stiffness ◽  
Timber Structure ◽  
Structural Performance ◽  
Timber Structures ◽  
Global Response ◽  
Historic Structures ◽  
Numerical Approaches

Historic timber structures forming vaulted roofs of public and ecclesiastical buildings are present worldwide. The structural response of these constructions is usually governed by the structural performance of the joints, the interaction between the timber structure and the masonry parts, and the current condition of both joints and timber members. At present, numerical approaches, such as finite element method-based approaches are well-established tools for investigating the global response of complex historic structures. Using a FE-based software package, the authors developed a numerical model of a portion of an existing historic vaulted timber structure, which is part of the roof of the Cathedral of Ica in Peru, considering the in-plane semi-rigid response of the planked arches in the elastic range. For this purpose, the rotational and shear stiffness of the joints and the properties of the materials, which are assumed in good conditions, are calibrated by comparing the numerical outputs with experimental results available in literature. The aim of the work presented here is to compare the response of the same vault assuming either continuous (planks continuously connected) or discontinuous arches (modelling of the semi-rigid response of the joints which connect the planks together).

Responses of growth cones to changes in osmolality of the surrounding medium

1991 ◽  
Vol 98 (4) ◽  
pp. 507-515
Author(s):  
D. Bray ◽  
N.P. Money ◽  
F.M. Harold ◽  
J.R. Bamburg
Keyword(s):  
Hydrostatic Pressure ◽  
Growth Cone ◽  
Culture Medium ◽  
Vapor Pressure Deficit ◽  
Surrounding Medium ◽  
Culture Fluid ◽  
Short Term ◽  
Area Reduction ◽  
Osmotic Response ◽  
Upper Limits

The possible involvement of osmotically generated hydrostatic pressure in driving actin-rich extensions of the cell surface was examined using cultures of chick neurons. Estimation of the excess internal osmotic pressure of chick neural tissue by vapor pressure deficit osmometry, and of the excess internal hydrostatic pressure in cultured chick neurons using a calibrated pressure pipette, gave upper limits of 10 mosM and 0.1 atmosphere (1 atmosphere = 101325 Pa), respectively. Increases in the osmolality of the medium surrounding cultured neurons by addition of sucrose, mannitol or polyethylene glycol by amounts that should eliminate any internal pressure not only failed to arrest the growth of filopodia but caused them to increase in length up to twofold in 3–5 min. Lamellipodia remained unchanged following hyperosmotic shifts of 20 mosM, but higher levels caused a small decrease in area. Reduction of osmolality by the addition of water to the culture fluid down to 50% of its normal value failed to show any detectable change in either filopodial length or lamellipodia area. These observations argue against an osmotic mechanism for growth cone extension and show that the growth of filopodia, in particular, is unlikely to be driven by osmotically generated hydrostatic pressure. In contrast to the short-term effects on growth cone morphology, the slower elongation of the neuritic cylinder showed a consistent osmotic response. Growth rates were reduced following addition of osmolytes and increased in rate (as much as sixfold) following addition of water to the culture medium.(ABSTRACT TRUNCATED AT 250 WORDS)

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