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.

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.

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.

Spherical Sector Windows With Restrained Edge for Undersea Applications

1977 ◽  
Vol 99 (2) ◽  
pp. 459-468
Author(s):  
J. D. Stachiw
Keyword(s):  
Spherical Shell ◽  
Experimental Evaluation ◽  
Cyclic Fatigue ◽  
Bearing Surface ◽  
Short Term ◽  
Cyclic Pressure ◽  
Fatigue Data ◽  
Vertical Bearing ◽  
Radial Thrust

A new concept for the mounting of spherical sector windows has been experimentally evaluated under short-term, long-term, and cyclic pressure loadings. The new mounting concept requires that the spherical sector windows be provided with square edges instead of conical edges. The horizontal bearing surface of the square edge carries the axial and the vertical bearing surface the radial thrust of the spherical sector window. Experimental evaluation of the new mounting concept has shown that the spherical windows with square edges are subjected to larger flexure moments than similar windows with conical edges. However, the short-term critical pressures of spherical sector windows with square edges and included angle 75 deg < α < 180 deg were found to be only 10 percent less than those of similar windows with conical edges. For spherical sectors with α < 75 deg the square edge mounting provides significantly higher short-term implosion pressures than conical edge mountings. Based on the short-term critical pressures, strains, stresses, and cyclic fatigue data generated by this study, the spherical shell sector windows with square edge mounting are considered acceptable for service in manned submersibles, habitats, or diving bells.

Structural Performance of Acrylic Plastic Plane Disk Windows With Twin Conical Bearing Surfaces

1978 ◽  
Vol 100 (2) ◽  
pp. 273-286
Author(s):  
J. D. Stachiw ◽  
N. E. Smith ◽  
O. H. Burnside
Keyword(s):  
Finite Element ◽  
Stress Analysis ◽  
Structural Performance ◽  
Bearing Surface ◽  
Test Program ◽  
Finite Element Stress Analysis ◽  
Acrylic Plastic ◽  
Hydrostatic Loading ◽  
Conical Bearing ◽  
Plane Disk

Exploratory investigation into the structural performance of acrylic plastic plane disk windows with twin conical bearing surfaces has shown that such windows behave under hydrostatic loading similarly to plane disk windows with a single conical bearing surface. This conclusion is based both on experimental data from a test program and on findings from a finite element stress analysis. The test program encompassed short term and cyclic pressure testing of plane disk windows with twin conical bearing surfaces in the 0.21 ≤ t/Di ≤ 0.423 and 60 deg ≤ α ≤ 120 deg ranges. The finite element stress analysis addressed itself only to plane disk windows with 90 deg twin conical bearing surfaces in the 0.23 ≤ t/Di ≤ 1 range. On the basis of findings reached in this investigation it is recommended that the existing criteria (ANSI/ASME PVHO-1) for the design of plane disk windows with a single bearing surface be applied also in the design of plane disk windows with twin conical bearing surfaces since their structural performance under external hydrostatic loading appears to be very similar.

scholarly journals Quantitative Analysis of Inclusion Engineering on the Fatigue Property Improvement of Bearing Steel

Metals ◽  
2019 ◽  
Vol 9 (4) ◽  
pp. 476 ◽  
Author(s):  
Chao Gu ◽  
Min Wang ◽  
Yanping Bao ◽  
Fuming Wang ◽  
Junhe Lian
Keyword(s):  
Fatigue Life ◽  
Quantitative Analysis ◽  
Critical Size ◽  
Fatigue Behavior ◽  
Fatigue Cracks ◽  
Fatigue Property ◽  
Bearing Steel ◽  
Fatigue Properties ◽  
Bearing Steels ◽  
Inclusion Distribution

The fatigue property is significantly affected by the inner inclusions in steel. Due to the inhomogeneity of inclusion distribution in the micro-scale, it is not straightforward to quantify the effect of inclusions on fatigue behavior. Various investigations have been performed to correlate the inclusion characteristics, such as inclusion fraction, size, and composition, with fatigue life. However, these studies are generally based on vast types of steels and even for a similar steel grade, the alloy concept and microstructure information can still be of non-negligible difference. For a quantitative analysis of the fatigue life improvement with respect to the inclusion engineering, a systematic and carefully designed study is still needed to explore the engineering dimensions of inclusions. Therefore, in this study, three types of bearing steels with inclusions of the same types, but different sizes and amounts, were produced with 50 kg hot state experiments. The following forging and heat treatment procedures were kept consistent to ensure that the only controlled variable is inclusion. The fatigue properties were compared and the inclusions that triggered the fatigue cracks were analyzed to deduce the critical sizes of inclusions in terms of fatigue failure. The results show that the critical sizes of different inclusion types vary in bearing steels. The critical size of the spinel is 8.5 μm and the critical size of the calcium aluminate is 13.5 μm under the fatigue stress of 1200 MPa. In addition, with the increase of the cleanliness of bearing steels, the improvement of fatigue properties will reach saturation. Under this condition, further increasing of the cleanliness of the bearing steel will not contribute to the improvement of fatigue property for the investigated alloy and process design.

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

A new approach for pre-stressing of rail-end-bolt holes

2016 ◽  
Vol 231 (12) ◽  
pp. 2275-2283 ◽  
Author(s):  
JT Maximov ◽  
GV Duncheva ◽  
IM Amudjev ◽  
AP Anchev ◽  
N Ganev
Keyword(s):  
Fatigue Life ◽  
Fatigue Cracks ◽  
New Technology ◽  
Innovative Technology ◽  
Bolted Joint ◽  
Compressive Stresses ◽  
Process Formation ◽  
Technology Process ◽  
Bolt Holes ◽  
Hoop Stresses

Bolted joint railroad is the subject matter of this paper. Rail joint elements are subjected to cyclic and impact loads as a result of the passage of trains, which causes the origination and growth of fatigue cracks occurring, in most cases, around the bolt holes. Fatigue failure around rail-end-bolt holes is particularly dangerous because it leads to derailment of trains and, consequently, to inevitable accidents. Moreover, the cracking at rail-ends, which starts from bolt hole surface, causes premature rails replacement. The presence of residual compressive hoop stresses around the bolted holes, which is achieved by prestressing of these holes, extends the fatigue life of bolted joint railroads. This article presents an innovative technology for pre-stressing of rail-end-bolt holes, implemented on a vertical machining centre of Revolver vertical (RV) type. Two consecutive operations are involved in the manufacturing technology process: formation of the hole by drilling, reaming and making of a chamfer through a new combined cutting tool; cold hole working by spherical motion cold working through a new tool equipment, which minimizes the axial force on the reverse stroke. The new technology introduces beneficial residual compressive stresses around the bolted holes thereby preventing the fatigue cracks growth and increasing the fatigue life of these openings.

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