Page 426 - Practical Design Ships and Floating Structures

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thickness on local contraction values are made with other technical parameters kept fixed.

1 ) Fitting curve between the maximum local contraction lengths and the maximum longitudinal
deformation of the whole plate. The local maximum contraction in relation to the maximum
longitudinal deformation of each experimental plate of certain thickness is derived from the data of the
experimental plates processed. The relation curve between the maximum local contraction and the
maximum longitudinal deformation of plates of this thickness is obtained with the help of spline
function. Similarly, a group of curves of plates of different thickness can be obtained.

2) Thickness correcting factors. According to the above fitting curves. correcting factors k.,, are
defined as:

where suffix i is the number of experimental plates, and suffix 10 and 20 are the normal thickness of
the experimental plates respectively. And the theoretical value of real ship plates is defined without
suffix.

5 OPTIMUM DESIGN OF TECHNICAL PAREMETERS IN LINE HEAT FORMING

5.1 Optimum theorem and its characteristic

The method adopted in this paper is the mixed integer one, which combines the simple method and
rotation coordinate methods and has the following characteristics:

1) Discrete or continuous optimal solutions can be obtained.
2) It can be used for continuous or discrete variables, or both of them.
3) Searching times are decreased greatly, because only the calculation of the discrete variables at
nodes is necessary.

5.2 Optimal models

Given as the optimum solution is the optimal result x*, which satisfies

.fi = (x*) = min.fi(x)

and meets the constraining conditions

where x, n and m are design variables (technical parameters), the number of objective functions and
the number of constraints respectively.