Numerical investigation on nonlinear contact coupling during ship launching process by an array of airbags

Abstract

Ship launching by an array of airbags is a novel approach widely used in Chinese shipyards and also in other countries. Previous studies on a material constitutive model of ship-launching airbags highlighted that loaded airbags suffering nonlinear deformation due to the contact during launching process while their bearing forces may induce hull deformation, which is a complex nonlinear contact coupling problem. This study presents an iterative approach for numerically simulating the coupling effect between the loaded airbag array and the ship hull during slippery in three steps. Firstly, an effective launching simulation program known as “Simulation Program for Ship Launching by Airbags (SPSLAs)” is developed based on airbag hyperelastic constitutive model for predicting the real-time forces and moments acting on the hull bottom structures under certain working height of airbags at the whole launching process. Secondly, the array of airbags with the real-size are built by a finite element (FE) software to investigate dynamic response of airbag array. Finally, the results are transferred to the FE model of the hull to evaluate the global and local structural stress responses. Additionally, this methodology was applied to analyze the launching practice of a bulk carrier with the deadweight of 57,000 tons for validation.