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Optimization of strain field distribution for generation of compound curve surfaces using line heating technique

Nisith R. Mandal ,  Pankaj Biswas ,  Om P. Sha 

Indian Institute Of Technology,Kharagpur (IIT), Kharagpur, India

Abstract

In shipbuilding, one of the most tedious and human skill dependent operations is plate forming for producing compound curve plates. Line heating technique can be gainfully utilized to develop necessary thermal strains in the plate to generate the desired shapes. Thereby the process of plate forming becomes amenable to mechanization once the line heating pattern and heating parameters become available.

For generating a curved surface one needs to know the extent of strain that is to be applied and its direction. The deformation occurs perpendicular to the line of heating. Clearly there is no single way to form a given curved plate by line heating. The same curved plate can be formed from various starting templates using various amounts of strains. So here the objective is to find initial plate templates (also called blanks) for which the minimum strain has to be applied so that the desired shape is generated.

The strain field distributions thus have a significant effect on plate forming using line heating process. Depending on this, the line heating parameters (heat input, torch speed, heating pattern, etc) are decided. The blank size and the strain energy required to develop the desired compound curved surface fully depends on strain field distribution. The objective is to obtain minimum strain configurations so that least amount of raw material is used and at the same time the work required to produce the desired surface is also minimized.

In the present work a GA based optimized strain field distribution approach has been applied such that the strain energy as well as the material required for blank generation is minimised.

The strain distributions as obtained using GA for a pillow shaped surface are shown in Fig.1.

Fig.1_1.JPG

Fig.1 Strain distributions along u-direction

 

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Presentation: Oral at E-MRS Fall Meeting 2007, Symposium G, by Nisith R. Mandal
See On-line Journal of E-MRS Fall Meeting 2007

Submitted: 2007-03-16 08:23
Revised:   2009-06-07 00:44