09.03.2018
Nonferrous Alloys in Shipbuilding

Aluminum Alloy Applications

Aluminum alloys find use where their special attributes such as low density and high strength to weight ratio, corrosion resistance in certain environments or retention of toughness at low temperatures are of value. Development of inert gas arc welding processes has facilitated the use of aluminum alloys for various ship structural applications. Aluminum alloys are frequently used in superstructures of large ships and for the entire hull structure of some ferries and small boats such as those serving the offshore industry.

The low density of aluminum alloys makes them particularly attractive for applications where high strength to weight ratios are of particular concern such as in surface effect and hydrofoil craft. Since aluminum alloys increase in strength and maintain toughness as temperature decreases, they have proven particularly suitable for cryogenic services such as containment of liquefied natural gas. Details of compositions, properties and methods of inspection are contained in American National Standards Institute documents...

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09.03.2018
Hull Material Properties and Tests

A major change in ship construction occurred over 100 years ago when steel was introduced to replace iron and wood as a hull material. Subsequent important developments in materials and ship construction were the all-welded ship and the application of concepts of toughness for the prevention of the brittle hull fractures experienced with the all-welded steel ships of the 1940's.

Over the past thirty years, many new designs have been introduced such as container ships, liquefied gas carriers, high speed surface-effect ships, and mobile and fixed offshore structures. To meet requirements for such designs, high strength-to-weight ratio alloys and alloys intended for low temperature service have been introduced into shipbuilding. The complex networks of intersecting members in offshore structures require that consideration be given to material properties when the applied tensile loads are perpendicular to the plate surfaces. The increasing size of ships, such as the VLCC tankers, and the concern for economy, stimulated automation of fabrication processes.

Hull Material Properties and Tests - 2

 The relatively simple concept of toughness developed to answer the brittle fracture problems in ordinary strength steel hulls required refinement and extensive development before it could be applied to the newer hull materials and structures. For some structures increased consideration had to be given to such factors as fatigue and corrosion. Accompanying all these changes, was an increased demand for the designer to provide for quality assurance by nondestructive methods. To meet the challenges presented by these new developments, the designer had to become familiar with metallurgy, welding engineering, nondestructive testing, and the materials sciences. An appreciation of the basic principles of these fields will provide more efficient and reliable hull designs through selection of appropriate materials, joining, and quality assurance requirements...

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