Finite Element Analysis On The Stress-Deformation Features Of Gravity Cage Flotation Structures

With the development of the global economy, the increasing population and the steady improvement of living standards, the whole society is in need of the aquatic products. It is obvious that the traditional fishing industry and the shallow sea aquaculture, has been unable to meet the people’s strong demand for aquatic products. The emergence of ocean pasture product based on marine cage farming technology, provides a new approach on the alleviation of the contradiction between supply and demand of aquatic products.In the early1970s and the southeast coastal areas, we began shallow water cages farm.But in recent years, coastal marine environment has been severely damaged, resulting in decrease of farmed fish quality. Going to the deep sea has become an inevitable trend.Currently, the deep-water gravity cage is more popular.The floating frame structure is mainly responsible for the resistance to waves and currents, for providing the buoyancy of entire cage and for supporting effective farming volume of mesh system. Floating frame plays an important role in the performance of the anti-wave. Its safety and reliability will directly determine the success of farming.Therefore, this article will explore deformation characteristics, the stress distribution and ultimate bearing capacity of the floating cage frame structure under complex sea conditions.This paper includes the following sections.The first chapter is a preface, introducing the industrial background of cage aquaculture and progress in cage researchat home and abroad.In the second chapter, based on the the basic assumptions of shell theory, and geometric equations, physical equations, balance equations, the mathematical model of the deformation-stress analysis is established in orthogonal curvilinear coordinates.In the third chapter, through physical model tests, statistics of HDPE material elastic modulus has been obtained under different loading rates. We then analyze the mechanical properties of HDPE from the perspective of microscopic molecules.In the fourth chapter, material yield criterion is derived from four kinds of intensity theory as a judgment of material. Then, based on the effect of the actual destruction of farms floating frame, the local failure assumption is proposed as a judgment for structural failure. And via physical testing and finite element simulations, the effectiveness and practicality of the assumptions is examined.Based on ANSYS structural modeling platform, the fifth chapter deals with the finite element model of the simplified double-floating pipe, analyzing the deformation-stress characteristics of the floating frame in pure stream, pure waves and wave-current mixing condition.Chapter six discusses the ultimate bearing capacity of floating frame set by three kinds of anchoring form in uniform loading. Chapter seven summarizes the results of this study, and the prospect of future research directions.