Feasibility of Forming Twist in Structural Shapes for Shipbuilding
Abstract
Large steel sections are used extensively as reinforcing structural members in the shipbuilding industry. T-sections, for example, often measure 30 in. x 1/2 in. in the web region and 10 in. x 1 in. in the flange region, and are over 40 ft long. These structural sections have to be twisted, with the toe of the web as the axis, to conform with the curving profile of the ship body. The twisting is generated primarily near each end of the section length, and is normally in the range of 1-2 degrees/f t with a maximum of about 3 degrees/f t. The current procedure employed for this purpose by Newport News Shipbuilding (NNS) involves heating each end of the section separately in a furnace to 1600 degrees F, removing them, and then loading the end with a 4-5 ton dead load while using suitable positioned wedges. Once the setup is ready, it takes nearly 30-40 min per end with a five- man crew. The daily twist production rate is 10-12 ends/shift including setup time. The objective of this venture was to investigate the feasibility of forming the twist, preferably at room temperature, using a set of forming dies in a hydraulic press. The structural T-sections were to be scaled down linearly by a factor of 5 to enable the experiments to be conducted in IITRI's 75 ton press. The main requirement on the twist was that it be accurate enough to allow joining of two consecutive members with as little mismatch as possible. Successful application of the twist forming technique would result in a higher production rate and elimination of heating furnaces and also the oxidation problem caused by heating to elevated temperatures, through the use of existing hydraulic presses (250, 1000, and 2500 ton capacities) at NNS.
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 24, 1978
- Accession Number
- ADA450398
Entities
People
- S. Rajagopal
Organizations
- IIT Research Institute