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.

A Three-Dimensional Geometrically Nonlinear Analysis of Pipelaying in an Ocean Environment

1981 ◽  
Vol 103 (2) ◽  
pp. 201-205
Author(s):  
S. Odorizzi ◽  
B. A. Schrefler
Keyword(s):  
Hydrostatic Pressure ◽  
Nonlinear Analysis ◽  
Dimensional Analysis ◽  
Three Dimensional ◽  
Bending Stiffness ◽  
Ocean Floor ◽  
Geometrically Nonlinear ◽  
External Hydrostatic Pressure ◽  
Geometrically Nonlinear Analysis ◽  
Ocean Environment

A three-dimensional analysis for pipelines suspended between the ocean floor and a laying barge or a stinger is presented. The analysis performed is capable of handling not only variations in bending stiffness, weight and buoyancy, crosscurrents and lateral bay drift, but also the effects of external hydrostatic pressure and buckling of the pipes. For this purpose a total Lagrangian geometrically nonlinear analysis in space. Examples are given which demonstrate the versatility of the analysis proposed.

A Study of Jones’ Equation for Buckling of Laminated Composite Cylinders Under External Hydrostatic Pressure

1993 ◽  
Vol 37 (03) ◽  
pp. 239-252
Author(s):  
Thomas Perry ◽  
Zan Miller
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Composite Materials ◽  
Hydrostatic Pressure ◽  
Analytical Solution ◽  
Laminated Composite ◽  
External Hydrostatic Pressure ◽  
Element Analysis ◽  
Composite Cylinders ◽  
Good Agreement

A classical solution derived by Jones (1968) is used to evaluate the buckling performance of unstiffened generally orthotropic and quasi-isotropic laminated Graphite/Epoxy (GREP) composite cylinders subjected to external hydrostatic pressure. The results of the analysis are compared to finite-element analysis results. Hydrostatic testing to failure of several 12-ply T300/5208 GREP cylinders demonstrated that the classical buckling solution is quite accurate. The finite-element results showed good agreement with both Jones' solution and test data, with several notable exceptions. Evaluation of strain gage data via Southwell's (1932) method indicates that the test cylinders were fabricated very nearly true. A postiori buckling predictions using Southwell plots all compared quite favorably with the Jones' equation predictions. This work demonstrates that a relatively simple analytical solution can reliably evaluate the performance of composite materials in pressure hull applications.

Inelastic Shell Instability of Geometrically Imperfect Aluminum Alloy Circular Cylinders under Uniform External Pressure

2008 ◽  
Vol 45 (03) ◽  
pp. 175-181
Author(s):  
Carl T. F. Ross ◽  
Andrew P. F. Little ◽  
Graham Brown ◽  
Aravinthan Nagappan
Keyword(s):  
Aluminum Alloy ◽  
Hydrostatic Pressure ◽  
Analytical Solution ◽  
Structural Design ◽  
External Pressure ◽  
Circular Cylinders ◽  
External Hydrostatic Pressure ◽  
Element Analysis ◽  
Uniform External Pressure ◽  
Design Chart

The paper presents new experimental results on the collapse of unstiffened aluminum alloy circular cylinders suffering elastic and plastic nonsymmetric bifurcation buckling under external hydrostatic pressure. These results complement the results given in two previous Marine Technology papers written by the senior author, which were intended for the structural design of near-perfect unstiffened and ring-stiffened circular conical shells under external hydrostatic pressure. The present paper presents a structural design chart for geometrically imperfect circular cylinders under uniform external pressure, which is more likely to be used than the design charts for the previous near-perfect vessels because it represents the more "usual" case. In addition to an experimental analysis, theoretical analyses were also carried out. An analytical solution by von Mises was used, together with a finite element analysis solution, using the Shell 93 element of the ANSYS computer package. Comparison between ANSYS and the analytical solution was reasonable. A design chart is provided, which looks like it could be quite useful for practical purposes.

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.

scholarly journals DIFFUSION NUCLEATION OF CAVITIES IN GRAIN JUNCTIONS OF SUBMICROCRYSTALLINE MATERIALS

2021 ◽  
Vol 83 (3) ◽  
pp. 276-284
Author(s):  
A.S. Pupynin ◽  
S.V. Kirikov ◽  
V.N. Perevezentsev
Keyword(s):  
Plastic Deformation ◽  
Hydrostatic Pressure ◽  
High Pressure Torsion ◽  
Vacancy Concentration ◽  
Triple Junctions ◽  
External Hydrostatic Pressure ◽  
Tensile Stresses ◽  
Boundary Triple ◽  
Junction Disclinations ◽  
Submicrocrystalline Materials

The conditions of diffusional cavity nucleation in submicrocrystalline materials processed by the methods of intensive plastic deformation (equal-channel angular pressing, multiaxial forging, high pressure torsion, etc.) are analyzed. To date, the question of the mechanism of nucleation of cavities in such materials remains debatable due to the fact that the processing of materials by the methods of intensive plastic deformation is carried out at high hydrostatic pressures that prevent the appearance of pores. The possibility of diffusive nucleation of nanopores in the region of triple junctions of grains containing negative strain-induced wedge disclinations, generating high tensile stresses in the vicinity of triple junctions, comparable in magnitude to external hydrostatic pressure, is shown. Such junction disclinations inevitably occur at the grain junctions due to the heterogeneity of the plastic deformation through the ensemble of polycrystal grains. It is shown that an important condition for the nucleation of cavities is not only the presence of high internal tensile stresses from junction disclinations, but also an extremely high concentration of nonequilibrium strain-induced vacancies characteristic of submicrocrystalline metals, comparable in values to the vacancy concentration, at temperatures close to solidus. The influence of the strength of junction disclinations, the value of external hydrostatic pressure and the degree of supersaturation of the material by nonequilibriumstrain-induced vacancies on the rate of diffusional nucleation and the volume of critical pore nuclei is analyzed. It is established that in order to effectively suppress the process of pore formation in the grain boundary triple junctions, it is necessary to apply an external hydrostatic pressure that compensates for internal elastic fields from junction disclinations.

Finite Element Analysis of the Hydro-Mechanical Punching Process

2006 ◽  
Vol 505-507 ◽  
pp. 871-876
Author(s):  
Jong Hun Yoon ◽  
Hoon Huh ◽  
Yong Sin Lee ◽  
Seung Soo Kim ◽  
E.J. Kim ◽  
...  
Keyword(s):  
Hydrostatic Pressure ◽  
Ductile Fracture ◽  
Sheet Material ◽  
Middle Surface ◽  
Initial Crack ◽  
Fracture Criteria ◽  
Element Analysis ◽  
Final Fracture ◽  
Ductile Fracture Criteria ◽  
Punching Process

This paper investigates the characteristics of a hydro-mechanical punching process. The hydro-mechanical punching process is divided into two stages: the first stage is the mechanical half piercing in which an upper punch goes down before the initial crack is occurred; the second stage is the hydro punching in which a lower punch goes up until the final fracture is occurred. Ductile fracture criteria such as the Cockcroft et al., Brozzo et al. and Oyane et al. are adopted to predict the fracture of a sheet material. The index value of ductile fracture criteria is calculated with a user material subroutine, VUMAT in the ABAQUS Explicit. The hydrostatic pressure retards the initiation of a crack in the upper region of the blank and induces another crack in the lower region of the blank during the punching process. The final fracture zone is placed at the middle surface of the blank to the thickness direction. The result demonstrates that the hydro-mechanical punching process makes a finer shearing surface than the conventional one as hydrostatic pressure increases.

The Onset of Plastic Yielding in a Spherical Shell Compressed by a Rigid Flat

2010 ◽  
Vol 78 (1) ◽  
Author(s):  
Longqiu Li ◽  
Izhak Etsion ◽  
Andrey Ovcharenko ◽  
Frank E. Talke
Keyword(s):  
Spherical Shell ◽  
Normal Load ◽  
Empirical Relation ◽  
Solid Sphere ◽  
Plastic Yielding ◽  
Element Analysis ◽  
Shell Parameter ◽  
Shell Geometry ◽  
Limiting Value ◽  
Critical Contact

The onset of plastic yielding in a spherical shell loaded by a rigid flat is analyzed using finite element analysis. The effect of spherical shell geometry and material properties on the critical normal load, critical interference, and critical contact area, at the onset of plastic yielding, is investigated and the location where plastic yielding first occurs is determined. A universal dimensionless shell parameter, which controls the behavior of the spherical shell, is identified. An empirical relation is found for the load-interference behavior of the spherical shell prior to its plastic yielding. A limiting value of the dimensionless shell parameter is identified above which the shell behaves like a solid sphere.

Solutions for Non-Newtonian Flow Into Elliptical Openings

1991 ◽  
Vol 58 (3) ◽  
pp. 820-824 ◽  
Author(s):  
A. Bogobowicz ◽  
L. Rothenburg ◽  
M. B. Dusseault
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Steady State ◽  
Hydrostatic Pressure ◽  
Velocity Field ◽  
Velocity Fields ◽  
Newtonian Flow ◽  
Element Analysis ◽  
Elliptical Opening ◽  
Elliptical Coordinates

A semi-analytical solution for plane velocity fields describing steady-state incompressible flow of nonlinearly viscous fluid into an elliptical opening is presented. The flow is driven by hydrostatic pressure applied at infinity. The solution is obtained by minimizing the rate of energy dissipation on a sufficiently flexible incompressible velocity field in elliptical coordinates. The medium is described by a power creep law and solutions are obtained for a range of exponents and ellipse eccentricites. The obtained solutions compare favorably with results of finite element analysis.

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