Reliability-based Optimization Of Rocket Structure Based On SiPESC Platform

Engineering structure design is normally divided into three levels: safety factor method,partial safety method and reliability-based design.Safety factor method is convenient for engineers,but due to its rough measurement,safety factor method usually yield a conservative or risky design.Though the design resulted from reliability-based design optimization which uses structural reliability as design index is accurate enough for practical use,constituting a design code for RBDO is hard that it can hardly be popularized among this field.Now that partial safety factor method is able to accurately take uncertainty of engineering structure into account,constituting a design code for designers,this paper proposes an algorithm based on given reliability-based design data,aimed at seeking for the partial safety factor and construct the model for the optimization based on the acquired partial safety factor which is applied in rocket structure design.First,this paper illustrates the background and significance of the research and summarize the lately progress in related fields,proposing that the design based on the safety factor usually achieve a conservative design resulted from its inherent limitation.This paper presents uncertainty-based design based on partial safety factor and discovers the principles of the results under different dimensions of random variables,different performance functions and different target reliability.In addition,this paper compare the design result based on the mean partial safety factor method with those resulted from safety partial factor and reliability-based design,verifying the efficiency of this method.Then,this paper executes uncertainty-based design for the orthogonal stiffened cylindrical shell under moment and axial pressure with the partial safety factor method and compare the result with those based on safety factor,RBDO and conventional partial safety factor respectively.Based on the design result,this paper explicate that by properly using structural design data given target reliability and refer to the consistent partial factor as design criterion,engineers can propose the structural design which can be put into practical use.Finally,taking the lightweight design of Kagome conical shell as an example,this paper compares the design result based on safety factor,RBDO and conventional partial safety factor respectively and discovers that design based on safety factor method cannot only reach the target reliability but consume large quantities of material,that RBDO can produce a design exactly meeting the target reliability and that design based on mean partial safety factor approximately satisfies the target reliability.Besides,design based on mean partialsafety factor is superior to that based on safety factor method and conventional partial safety factor method and approximates to the design of RBDO.On another hand,regarding non-existence of a module for reliability-based optimization in the present commercial programme,this paper constructs a reliability-based optimization module for rocket structure in the SiPESC platform.By integrating CAE analysis,computer experimenting method,surrogate model method,optimization design and reliability analysis in to a single platform,this paper constitutes a module especially for reliability-based optimization design Under the circumstance that non-existence of reliability-based optimization design module in extant commercial programme.