ULTIMATE LIGHTWEIGHT DESIGN BASED ON SHAKEDOWN STRENGTH AND ITS APPLICATION ON DESIGNING A MANNED AIRTIGHT MODULE

Structural lightweight optimization design is classically per- formed according to the elastic limit rule, which leads to an unacceptable structure weight or strength redundant to an ex- tent. Shakedown theory is implemented in the present study to assess the load-bearing capacity of the structure. Within the shakedown load limit, failure forms of ratcheting, incremental collapse and alternate plasticity will be avoided. Moreover, the full potential of a material can be utilized by following the shake- down limit framework. Therefore, under this framework, by sac- rificing some abundant loading bearing capacity, an extremely lightweight design of the structure can be reached. The current research presents a mathematical and algorithmic framework for producing extreme lightweight designs of structures that exhibit constrained shakedown loading capacity, which is an innovative means to the lightweight design and makes the optimal structure design in a relatively practical way. The hybrid genetic algorith- m is introduced to obtain a more accurate global solution. The accuracy and effectiveness of the proposed numerical optimiza- tion method are validated and demonstrated by a classical prob- lem and subsequently adopted in optimal parameter design of the connecting structure to be used in a manned airtight module. In the end, the research suggests an optimal result for both load capacity and lightweight design for the manned airtight module. And an ultimate lightweight design is given by sacrificing redun- dant load capacity. This study confirmed that the hybrid genetic algorithm is an effective means for determining the optimal pa- rameter in accordance with the shakedown constraints. In addi- tion, the results of this study support the idea that shakedown analysis should be used in the optimization design of airtight modules instead of using the traditional elastic limit rule. As the load capacity evaluates by shakedown analysis would be more factual. Moreover, this study highlights the design performance enhancements attributed to allowing redundant shakedown load capacity to exchange an ultimate reduction of material.