Considering Corrosion And Reliability Of Structural Topology Optimization Design

With the rapid development of advanced industry, reliability has become a crucialattribute of systems and equipments. Engineers always expect that structures not onlypossess lightweight design but also can meet the performance and reliabilityrequirements over its entire lifetime. The lightweight design has many advantages, likereducing material use, eliminating energy consumption which are all significant toenvironmental protection and sustainability of the modern industry. However,uncertainties are inevitable in industry practices and appear in various ways, such asgeometry of structures, material properties, and external loads, etc. Structures designedin the deterministic manner may not achieve the required reliability due to the existingof various uncertainties. In addition, even though many brand new systems and deviceshave a very high reliability initially, they may fail before the anticipated lifetime inharsh condition due to the corrosion which gradually weakens the strength of structures.To overcome the aforementioned issues, there is, therefore, an urgent need fordeveloping a new structural topology optimization method to take into account ofcorrosion phenomenon and design structures with a high reliability over the entiremission time.Reliability-based topology optimization (RBTO) which combines designautomation with reliability analysis and topology optimization has been extensivelystudied in the past decades. To the best of our knowledge, very limited work thatconsiders corrosion issue in structural topology optimization has been reported. The aimof this thesis is to advance the state of the art of topology optimization by developing aset of new algorithms and models that can handle the corrosion problem in structuraltopology optimization so that the designed structures are able to meet the reliabilityrequirement over the entire mission time. The primary research contributions andinnovative outcomes are summarized as follows:(1) Development of a topology optimization platform based upon ANSYS andMATLAB. The developed platform provides an efficient way to solve the topology optimization problems which aims at minimizing the mass of structures undercompliance constraints. Solid isotropic material with penalization (SIMP) model,variable density topology optimization method, and method of moving asymptotes(MMA) are included in this platform to solve topology optimization problem. Agraphical user interface (GUI) is developed in MATLAB to make the topologyoptimization user-friendly to be used by engineers. Several numerical examples aredemonstrated by this platform to illustrate its effectiveness in terms of solving thetopology optimization problems.(2) Development of a new corrosion model that fits topology optimization and isable to mimic the corrosion phenomenon in engineering practices. In this model, analgorithm is put forth to find elements on the surface of structures, and corrosion rate isused to quantify how much depth the structure will corrode per unit time. Corrosioncoefficient is introduced to characterize the reduction rate of material density within anelement. By using the corrosion calculation model, corrosion phenomena of structurescan be modeled, and the topology of structures being corroded for a certain period oftime can be generated.(3) Study of the RBTO based on the proposed corrosion model. First orderreliability method (FORM) is employed to seek the most probable point (MPP).Sequential optimization and reliability assessment (SORA) is used to solve the proposedRBTO problem. By using this method, the lightest structure that suffers corrosion butalso satisfies reliability requirement over its mission time can be designed.