In this paper a boundary element formulation is developed and used for the analysis of cathodic protection systems of buried slender structures, such as foundations of electric transmission line towers. The foundation...
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In this paper a boundary element formulation is developed and used for the analysis of cathodic protection systems of buried slender structures, such as foundations of electric transmission line towers. The foundation is basically a truss structure and the slenderness of the pieces composing it, brings numerical difficulties into the classical boundary element method. To avoid this problem, the dual boundary element method is implemented: combination of standard and hypersingular integral equations to form a mathematically well-posed system. A simple experiment is carried out where a galvanized metallic sheet is buried alongside two Copper electrodes (anodes) in parallel, with the objective of simulating a two-dimensional problem. The soil resistivity properties are measured along the depth and the non-linear polarization curves describing the relation between the current density and the electrochemical potential at the metallic sheet is investigated. Two situations are analysed: a) current is injected into the ground through both electrodes;b) current is injected through only one of the electrodes. In the numerical implementation, the soil is modeled as a homogeneous layered half-space with a different property for each layer. The validity of the proposed dual approach is discussed and compared with the measurements of potential at the ground surface.
Characteristics of both thermoplastic and thermoset composite materials as they pertain to marine vehicle applications are discussed. Comparison of various material selection factors such as strength, damage and moist...
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Characteristics of both thermoplastic and thermoset composite materials as they pertain to marine vehicle applications are discussed. Comparison of various material selection factors such as strength, damage and moisture resistance, and flammability and toxicity as well as cost and availability of thermoset and thermoplastic composite materials are presented. Methods for testing and reducing the flammability and toxicity are discussed. Many commercially available composite systems are reported to provide favorable characteristics for marine applications. Although there seems to be a need for improved production technology for thermoplastics, they present potential advantages in physical properties over thermoset composites.
A proposed cost effective alternative to current U.S. Navy structurally configured hulls is presented in this paper. This proposed design for producibility concept involves the elimination of structural stanchions and...
A proposed cost effective alternative to current U.S. Navy structurally configured hulls is presented in this paper. This proposed design for producibility concept involves the elimination of structural stanchions and transverse web frames. The potential impact of this “no frame” concept on structural design, weight and construction and material costs for naval surface frigates and destroyers is reflected in 1) reduced costs for the installation of distributive systems and 2) a reduced number and complexity of structural details providing a more reliable and less costly structure. This study was performed in three parts: 1) Determine the most feasible length between bulkheads without frames; 2) Using this length perform detail weight studies and construction and material costs analysis comparison on a 72-foot long hull module, with and without frames, for a FFG-7, and 3) Estimate the saving in man hours of labor on the installation of distributive systems and shipfitting for an FFG-7. For the feasible length studies on the “no frame” structural configuration, thirty-seven strength, weight and vertical center of gravity studies were performed on two ship classes; twenty-two on the FFG-7 class and fifteen on the DD-963 class. The detailed weight studies and construction and material cost analyses were conducted for FFG-7 “no frame” and “as built” modules. Results indicating the “no frame” concept module was 6.8% heavier and 14.8% less costly than the “as built” module. For the impact of an FFG-7 “no frame” structurally configured hull on the cost of labor required for the installation of distributive systems and for other functional work such as ship fitting, welding, and electrical, this study indicated a reduction of 169,206 labor hours per ship, representing 7.12% of the total required man hours to fabricate an FFG-7 class ship. With the employment of the “no frame” concept, certain areas of significant concern and potential risk were addressed. These include: 1) t
The structural design of a ship's section is a complicated, repetitive and time consuming task. With the advent of new technology, high speed computers have enabled the ship designer to accomplish in a matter of s...
The structural design of a ship's section is a complicated, repetitive and time consuming task. With the advent of new technology, high speed computers have enabled the ship designer to accomplish in a matter of seconds what would formerly take days to accomplish by hand. The Structural Synthesis Design program (SSDP) is a N avy developed computer-aided design tool which is used to design (or to analyze) the longitudinal scantlings for a variety of ship cross sections, consisting of any practical combinations of decks, platforms, bulkheads and materials, i.e., various steel and aluminum alloys. The final hull section design will have the lowest practical weight for the chosen geometric configuration, structural arrangements, and imposed loadings. The scantling developed by the program will satisfy all U.S. N avy ship structural design criteria. An explanation of the objective and design elements of N avy ship structures is included. The rationale behind the SSDP design philosophy is developed along with the significant program capabilities. In an attempt to highlight the influence of automated design procedures on the current naval ship design process, the effect of the SSDP on the DDG 51 destroyer structural development is addressed.
作者：
LITVIN, DASMITH, DEDavid A. Litvin
a native of Baltimore graduated in 1969 from Drexel Institute of Technology with a Degree in Metallurgical Engineering. While attending Drexel he worked as a co-op student at NSRDL in Annapolis Md. where he developed a special interest in stress-corrosion cracking of titanium alloys. Upon graduation he joined the Naval Ship Engineering Center as a Materials Engineer. He is a member of the Association of Senior Engineers the American Society for Metals the American Institute of Mining Metallurgical and Petroleum Engineers and the Alpha Sigma Mu Metallurgy Honorary Fraternity. David E. Smith was born in Brooklyn
and attended Rensselaer Polytechnic Institute where he graduated in 1959 with a Degree in Metallurgical Engineering. After spending three years as a communications officer for the Air Force he joined the Dow Chemical Company as a Welding Engineer. After two and a half years he then worked for Ling-Tempco-Vought prior to joining the Naval Ship Engineering Center as a Materials Engineer in 1967. One of his most important projects has been the Structural Titanium Alloy Development Program which he has monitored over the lost three years. He is a member of the American Society for Metals the American Welding Society and the Association of Senior Engineers.
Titanium, “the wonder metal of the future” is rapidly becoming the metal of the seventies. The high strength to weight ratio, the excellent corrosion resistance in many aggressive environments, and good elevated tem...
Titanium, “the wonder metal of the future” is rapidly becoming the metal of the seventies. The high strength to weight ratio, the excellent corrosion resistance in many aggressive environments, and good elevated temperature properties have resulted in the widespread use of titanium and its alloys, particularly in the aerospace and chemical industries. Titanium has demonstrated its superiority in sea water environments, yet the marine industry has been slow to utilize titanium's benefits. The intent of this paper is twofold—First to inform the marine industry on many advantages of titanium alloys for sea water use by describing properties and successful applications. Second, to show how susceptibility to stress corrosion cracking of certain titanium alloys, which became evident several years ago, is now understood and controllable. Well documented research has substituted knowledge for doubt and fear. Titanium and several titanium alloys are considered ready for use as engineeringmaterials in the marine industry. Today, they are competitive with nickel base alloys in cost. Naval architects and design engineers may now use titanium in certain applications to provide superior performance over traditional marine materials.
作者：
JENKINS, J.W.GUERRY, J.B.TheAuthor: J. W. Jenkins
born at Fort Reno Indian Territory on October 25 1892 attended Case Institute of Technology for 3 years transferred to and graduated from University of Wisconsin in 1917 with Degree B. S. He served during World War I as a field artillery and (later) as a flying officer in the old Aviation Section of the Signal Corps U. S. Army. He resigned in 1919 to enter on 15 years of industrial engineering experience including consulting work involving specification design and application of engineering materials. He joined the force of the Inspector of Naval Materials Chicago Illinois in May 1934 serving as Supervisor of the South Bend District and as Technical Assistant to the Inspector of Machinery Beloit Wisconsin. He joined the Bureau of Ships in July 1940 and has since served in the Metallurgical Branch of the Material Development Division presently as Head of this Branch. He has for the past decade carried on Standardization matters for the Branch. During this period he has served as Navy Department Member of the Interdepartmental Screw-Thread Committee. TheAuthor: Commander John Benjamin Guerry
U. S. Navy born January 10 1916 in Montezuma Georgia attended Georgia School of Technology 1933–1935 and was graduated from the Naval Academy in 1939. He was on sea duty from 1939 through 1946 and served in Destroyers during the War. He had command of the USS IZARD (DD 589) from March 1945 to June 1946. He attended the Post graduate school at the Naval Academy 1946–1947 and Cornegie Tech 1947–1949. He received B. S. and M. S. Degrees from Carnegie Tech in Metallurgy. Upon graduation he returned to sea duty as engineering officer aboard the USS LEYTE (CV 32). He reported to the Bureau of Ships in February 1952 where he is now stationed as the Assistant for Material Development.
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