Fig. 5-a: Meshes of a Fillet Weld Joint
Fig. 5-b: Meshes of a V Butt Weld Joint
Fig. 6 : Optimization scheme
3. OPTIMIZATION PROCEDURE
The optimization procedure in Fig.6 is proposed to help shipbuilders in choosing the parameters of design and fabrication to get optimum thin stiffened panels regarding the minimum structural weight and high productivity without the corrective measures of post-welding assembly.
3.1 Step 1 : Choosing Main Parameters
Beforehand, the shipbuilders have to choose the variable parameters distinguished by "i" and "j" indices for design and fabrication parameters such as length Ai, width Bi, thickness Ti and for arc-welding process such as tension Uj, intensity Ij and welding speed Sj.
Previously are also fixed some invariable parameters such as the type of stiffener (HP, T beam girder,…) and the type of weld joints (single weld or multipass-weld, discontinuous, alternate or simultaneous, etc…).
3.2 Step 2 : Building up 3D FE Models (i, j)
It is seen that for one value of i and of j, only one model is built up: 3D model (i, j) = [Ai, Bi, Ti, Uj, Ij, Sj]
In such a form, if any of these parameters has more than one value, a great number of 3D models will be needed.
It is noted that for fabrication parameters, the Constructor-Engineer can not use some heat input energy neither less than the minimum value nor greater than the maximum value in order to ensure the best quality of his weld joints. Therefore, the welding parameters (Uj, Ij, Sj) must be chosen so that the linear heat input energy stays inside these two limits (these values are determined by the welding laboratory of every shipyard) :
