NEMO Type Acrylic Plastic Spherical Hull for Manned Operation to 3000 ft Depth

1976 ◽  
Vol 98 (2) ◽  
pp. 537-549 ◽  
Author(s):  
J. D. Stachiw
Keyword(s):  
Fatigue Life ◽  
Stress Wave ◽  
Cyclic Fatigue ◽  
Short Term ◽  
Destructive Testing ◽  
Pressure Cycling ◽  
Acrylic Plastic ◽  
Scale Models ◽  
Spherical Pressure

NEMO Mod 2000 acrylic plastic pressure hull assembly represents the latest addition to the NEMO hull series represented by NEMO Mod 600 and 1000 hull assemblies. The 66 in. OD × 58 in. ID spherical acrylic hull with aluminum hatches has successfully withstood 24 hr long external hydrostatic pressurizations to 450, 900, 1350, and 1800 psi. Pressure cycling and short term destructive testing of 15 in. OD × 13 in. ID scale models has shown that the crackfree fatigue life is in excess of 1000 pressure cycles to 1500 psi and the short term implosion pressure is in the range of 4750–5000 psi. Stress wave emissions have been found to be a good indicator of incipient failure. NEMO Mod 2000 spherical pressure hulls with panoramic visibility are considered to be acceptable for manned submersibles with 3000 ft operational depth capability. The cyclic fatigue life of such hulls is conservatively predicted to be at least 12 × 106 ft hr.

Polycarbonate Plastic Inserts for Spherical Acrylic Plastic Shells Under Hydrostatic Loading

1981 ◽  
Vol 103 (1) ◽  
pp. 90-98 ◽  
Author(s):  
J. D. Stachiw ◽  
R. B. Dolan ◽  
D. L. Clayton
Keyword(s):  
Fatigue Life ◽  
Structural Integrity ◽  
Structural Parameters ◽  
Cyclic Fatigue ◽  
Pressure Vessels ◽  
Plastic Shell ◽  
Acrylic Plastic ◽  
Hydrostatic Loading ◽  
Spherical Pressure

An acrylic plastic spherical pressure hull incorporating polycarbonate inserts for mounting of penetrators has been built and pressure tested. The transparent hull will serve as one atmosphere cockpit in Johnson-Sea-Link #3 submersible for 2500 ft. service. Tests have been conducted with model scale polycarbonate inserts in acrylic plastic spherical pressure hulls and windows to evaluate the structural integrity and cyclic fatigue life of polycarbonate plastic inserts and acrylic shells in which they are mounted under repeated hydrostatic pressurizations. Test results indicate that the short term, long term and cyclic fatigue life of a polycarbonate insert, serving as a bulkhead for electric or hydraulic penetrators in spherical acrylic plastic pressure hulls or windows, exceeds that of the acrylic plastic shell in which it is mounted. Structural parameters of polycarbonate inserts are discussed and design criteria formulated for their utilization in manned submersibles and pressure vessels for human occupancy. Particular emphasis is placed on selection of material, seal configuration, and retainment design.

Flanged Acrylic Plastic Hemispherical Shells for Undersea Systems—Part 2: Static and Cyclic Fatigue Life Under Hydrostatic Loading

1978 ◽  
Vol 100 (2) ◽  
pp. 249-260
Author(s):  
J. D. Stachiw ◽  
R. Sletten
Keyword(s):  
Fatigue Life ◽  
Fatigue Cracks ◽  
Cyclic Fatigue ◽  
Bearing Surface ◽  
Short Term ◽  
Ring Groove ◽  
Working Pressure ◽  
Temperature Range ◽  
Acrylic Plastic ◽  
Hydrostatic Loading

Over 25 acrylic plastic windows with t/Ri = 0.364 in the shape of hemispherical domes with equatorial flanges have been thermoformed from flat sheets and tested under short term, long term, and cyclic pressure loading at 65–75°F ambient temperature. Two kinds of flanges with O-ring grooves on the bearing surfaces were experimented with: Type 1, a flat lip with a rounded heel and instep, and Type II, a conical lip with a rounded heel. The 14,500 psi short term critical pressure of hemispherical windows with t/Ri = 0.364 was found to be independent of the equatorial flange configuration. Both the static and cyclic fatigue lives of the windows were also found to be independent of equatorial flange configuration. In either case, the maximum acceptable working pressure for 65–75°F temperature range was found to be 1000 psi. Only by elimination of the O-ring groove in the bearing surface of the window flange and the use of a thin neoprene bearing gasket between the arylic flange and the steel is it possible to extend the working pressure to 2000 psi for 65–75°F temperature range. Operating the flanged windows at pressures in excess of the safe working pressures shown above will generate fatigue cracks in the bearing surface of the flange in less than 1000 pressure cycles; at 5000 psi pressure the cyclic fatigue life decreases to less than 100 cycles.

Fatigue Analysis of Small Bore Copper Nickel Full Encirclement Sleeve and Socket Welds Under Pressure Cycling

2017 ◽  
Author(s):  
Michael Jones ◽  
James Wilson ◽  
Alex Harris
Keyword(s):  
Fatigue Life ◽  
Nuclear Power ◽  
Structural Integrity ◽  
Destructive Testing ◽  
Butt Weld ◽  
Pressure Cycling ◽  
Lack Of Fusion ◽  
Copper Nickel ◽  
Process Plants ◽  
The Impact

Sleeve and socket welds are often used in small bore nuclear power plant pipework where access is too limited to allow a conventional butt-weld. These welds are also used in process plants and pipelines as a permanent repair to reinforce areas such as cracks and corrosion that might threaten the structural integrity of the component. The fillet weld associated with this type of joint is particularly susceptible to lack of fusion defects which can be problematic to detect using conventional volumetric inspection techniques. The stress concentration associated with this type of defect will impact the fatigue life and pressure retaining ability of the joint. This paper provides examples of Copper/Nickel (CuNi) sleeve weld defects and presents an approach for determining the fatigue life of socket welds due to pressure cycling within a Pressurised Water Reactor (PWR) environment. This approach is based on modelling lack of fusion features using a database of sleeve and socket weld Non-Destructive Testing (NDT) records and calculating the stress range in the remaining ligament using textbook calculations. Sensitivity studies presented herein show the impact of lack of fusion and pipe size/thickness on fatigue life.

Acrylic Plastic Spherical Pressure Hull for 2439 m (8000 ft) Design Depth: Phase I

1987 ◽  
Vol 109 (1) ◽  
pp. 40-47 ◽  
Author(s):  
J. D. Stachiw ◽  
A. Clark ◽  
C. B. Brenn
Keyword(s):  
Phase I ◽  
Scale Model ◽  
Test Plan ◽  
Short Term ◽  
Acrylic Plastic ◽  
Hull Design ◽  
Manned Submersible ◽  
Design Depth ◽  
Different Diameters ◽  
Spherical Pressure

A program has been initiated to provide the oceanographic community with a manned submersible with panoramic visibility for 2439 m (8000 ft) design depth. The first phase of the program is to validate the design of the acrylic plastic pressure hull utilizing model scale spheres with different diameters and thickness to inside diameter (t/Di) ratios. This papers summarizes 1) the criteria used in the design of the acrylic plastic hull for 2439 m (8000 ft) depth, 2) the experimental test plan for validation of the hull design, and 3) the fabrication, and short-term pressurization to destruction of the first scale model with an aluminum hatch. The 457-mm (18-in.) o.d. acrylic sphere with t/Di ratio of 0.2 successfully withstood 1-hr long pressurizations from 0 to 6.9, 13.8, 20.7, 27.6, 34.4 and 41.3 MPa (1000, 2000, 3000, 4000, 5000, and 6000 psi) followed by 1-hr long relaxation periods after each pressurization prior to imploding at 110.2 MPa (16,000 psi) under 4.5 MPa/min (650 psi/min) pressurization. The selected t/Di ratio 0.2 appears to exceed the design depth requirement for 2439 m (8000 ft).

Pressure Cycling Monitoring Helps Ensure the Integrity of Energy Pipelines

2010 ◽  
Author(s):  
Peter Song ◽  
Doug Lawrence ◽  
Sean Keane ◽  
Scott Ironside ◽  
Aaron Sutton
Keyword(s):  
Fatigue Life ◽  
Pipeline System ◽  
Outer Diameter ◽  
Operating Pressure ◽  
Potential Growth ◽  
Integrity Assessment ◽  
Pressure Cycling ◽  
Pressure Cycle ◽  
Primary Focus ◽  
Pump Stations

Liquids pipelines undergo pressure cycling as part of normal operations. The source of these fluctuations can be complex, but can include line start-stop during normal pipeline operations, batch pigs by-passing pump stations, product injection or delivery, and unexpected line shut-down events. One of the factors that govern potential growth of flaws by pressure cycle induced fatigue is operational pressure cycles. The severity of these pressure cycles can affect both the need and timing for an integrity assessment. A Pressure Cycling Monitoring (PCM) program was initiated at Enbridge Pipelines Inc. (Enbridge) to monitor the Pressure Cycling Severity (PCS) change with time during line operations. The PCM program has many purposes, but primary focus is to ensure the continued validity of the integrity assessment interval and for early identification of notable changes in operations resulting in fatigue damage. In conducting the PCM program, an estimated fatigue life based on one month or one quarter period of operations is plotted on the PCM graph. The estimated fatigue life is obtained by conducting fatigue analysis using Paris Law equation, a flaw with dimensions proportional to the pipe wall thickness and the outer diameter, and the operating pressure data queried from Enbridge SCADA system. This standardized estimated fatigue life calculation is a measure of the PCS. Trends in PCS overtime can potentially indicate the crack threat susceptibility the integrity assessment interval should be updated. Two examples observed on pipeline segments within Enbridge pipeline system are provided that show the PCS change over time. Conclusions are drawn for the PCM program thereafter.

Cyclic fatigue life characteristics of ceramic balls under variable thermal shock loadings

2021 ◽  
pp. 107924
Author(s):  
Shinya Matsuda ◽  
Jinya Takenaka ◽  
Kimito Arii ◽  
Keiji Ogi
Keyword(s):  
Fatigue Life ◽  
Thermal Shock ◽  
Cyclic Fatigue

Investigation on the Probabilistic Distribution of the Stress Range of Net Cage Floater of Fish Cage for Fatigue Life Prediction

2018 ◽  
Author(s):  
Xiao-Dong Bai ◽  
Yun-Peng Zhao ◽  
Guo-Hai Dong ◽  
Chun-Wei Bi
Keyword(s):  
Fatigue Life ◽  
Probability Density ◽  
Limit State ◽  
Frequency Domain Analysis ◽  
Random Wave ◽  
Stress Range ◽  
Fish Farms ◽  
Short Term ◽  
Element Analysis ◽  
Distribution Of Stress

The failure risk of fish cages has increased in the harsher environmental conditions as fish farms have moved into the open sea in recent years. Fatigue failure is an important limit state for the floating system of the fish cage under the long-term action of waves. This study is presented to investigate the applicable probability density function for estimating fatigue life of the high-density polyethylene (HDPE) floating collars. The stress response of the floating collars system in random wave is firstly analyzed based on the finite element analysis combined with a hydrodynamic model. The stress histories of floating collars under each sea state are counted using the rainflow method as a benchmark for fatigue frequency domain analysis. The distribution of stress range was fitted by various probability density functions including Rayleigh, Weibull, Gamma and generalized extreme value (GEV) distributions. Comparisons of the estimated fatigue life using different distributions with rainflow statistic results were performed. Results indicate fatigue estimation based on the GEV and Gamma distributions by removing the negligible low stress range give much more accurate fatigue damage results of the short-term stress range distribution. While Weibull distribution overestimates the fatigue lifetime of the floating collar based on the short-term distribution of stress ranges.

scholarly journals Prediction of Cyclic Fatigue Life of Nickel-Titanium Rotary Files by Virtual Modeling and Finite Elements Analysis

2015 ◽  
Vol 41 (11) ◽  
pp. 1867-1870 ◽  
Author(s):  
Alessandro Scattina ◽  
Mario Alovisi ◽  
Davide Salvatore Paolino ◽  
Damiano Pasqualini ◽  
Nicola Scotti ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Finite Elements ◽  
Cyclic Fatigue ◽  
Nickel Titanium ◽  
Finite Elements Analysis ◽  
Virtual Modeling
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