Research And Optimization Of Side Structure With Mechanical Properties Of Blast-resistance

With the rapid development of defense-related science and technology,the strength and accuracy of a variety of surface warfare weapons are greatlyimproved, as well as the means to combat. Consequently, the risk constantlyincreases that a serving vessel suffers from underwater explosion. In order tomake an effective protection against attack from underwater weapons,ensuring that the vessel can still maintain vitality after the attack, continuingto explore innovative structures, countries all over the world are activelyengaged in researches of theory and experience on mechanism of underwaterexplosion and structural response under underwater explosion and theory ofblast-resistance and optimization design.Side structure presents very complex and non-linear dynamic responsein a quite short period of time, which is a strongly non-linear mechanicalproblem. It’s extremely hard to get analytical solutions through amathematical model for this kind of problems. Meanwhile, the experimentstudy is also limited and cannot be widely used because of funding issues andthe uncertainty of the experiment. In this context, this thesis uses numericalsimulation method to explore the structural response and optimization underunderwater explosion. The study mainly includes a few parts: the study ofcharacteristics of explosive load, the study of dynamic responses of differentside structure designs, the optimization of each design and the differences ofblast-resistance between them.Firstly, this thesis gives a brief introduction of explosive detonationtheory. According to the explosive detonation theory, this thesis simulates theexplosion loads on side structures using semi-theoretical semi-empirical formula proposed by Cole. This part provides a theoretical basis for thefollowing computing of structure responses.On this basis, the thesis uses non-linear finite element solver to simulatethe dynamic responses of a simplified model. The simulation result shows thedynamic responses, such as acceleration, velocity, displacement of thestructure, and also the level of energy absorption and specific energyabsorption. Besides, from the perspective of the blast-resistance of structure,this thesis proposes three structural designs. The dynamic responsesmentioned above are analyzed and compared for each design.The dynamic response is closely related to the design parameters. Eitherthe thickness arrangement of shell elements or the shape of the structure is ofgreat influence to the mechanical properties. DOE (design of experiment) isintroduced to explore the relationship among the variables. Intelligentoptimization algorithms are used to optimize the size and shape to get theoptimal solution which satisfies the constraints. Also, the concept ofapproximate model is introduced in the optimization process, which is usedto replace the finite element analysis with little computational cost.In the end, this thesis presents a practical example which is morecomplex. A detailed three cabin model of vessel is established automaticallyin ABAQUS by using PYTHON and parametric modeling techniques. Thentake the thickness and shape of side structure as design parameter. Runmulti-objective and single-objective optimization for thickness and shapeoptimization respectively. Finally, the optimal solution is obtained.