RIASSUNTO
ABSTRACT
The ship hull plate inevitably adopts non-developable surface fabricated by integrating mechanical bending with subsequent thermal forming. This paper primarily proposes a geometric flattening process to determine initial planar configuration based on area equivalent principle and investigates simplified nonlinear kinetic analysis to calculate required strain distribution. Then heating path can be distributed perpendicular to the direction of principal strain. These indicate that the proposed process can effectively establish initial planar geometric shape and determine principal strain distribution to plan heating path, therefore reduce dependence on manual experience of technician.
INTRODUCTION
Substantial engineering structures, especially in the ship yard, invariably apply developable and non-developable surfaces to meet the mechanical and hydrodynamics performance requirement. The non-developable surface generally cannot be fabricated at one time from planar shape and need to integrate mechanical bending with thermal forming to generate compound curvature configuration. Consequently, it is indispensable to determine initial planar configuration. But the flattening process may result in different planar configuration along with the adopted method. Meanwhile, after obtaining the planar shape, in order to determine the heating path, the strain distribution need to be investigated by means of carrying out nonlinear kinetic analysis from flattened configuration to desired surface.
Many researchers have done some contributions to these domains. Phillip and Aspragathos (1997) dealt with the approximate design of planar unfolding for doubly curved surface to obtain planar shape with certain gap and overlap. The method adopted geodesic method and Gaussian curvature to investigate the generation of plane pattern. Liang and Bin (2004) put forward development algorithm using the triangle mesh subdivision and demonstrated two kinds of development methods consisting of unconstrained and constrained flattening model. Then they minimized the strain energy required to form spatial shape from planar shape and compared with the initial configuration. But the process needed to figure out the superposition or gap which might lead to larger amount of calculation.