No abstract

Structural optimization for reinforcing the anti-vibration characteristics of the generators in the engine room of a ship is presented. To improve the vibration characteristics of the structures, topology optimization methods can be effective because they can optimize the fundamental characteristics of the structure with their ability to change the topology of the target structure. Topology optimization is used to improve the characteristics of the anti-vibration reinforcement of the generators in the engine room. First, an experimentally observed vibration phenomenon is simulated using the finite element method for frequency response problems. Next, the objective function used in topology optimization is set as the dynamic work done by the load based on the energy equilibrium of the structural vibration. The optimization problem is then constructed by adding the volume constraint. Finally, based on finite element analysis and the optimization problem, topology optimization is performed on several vibration cases to improve their performance and reduce weight.

Cooling structures require sufficient thermal conductivity. However, structure with thermal conducting could suffer high temperature, and thermal deformation could become serious. Thus, designing structures suppressing thermal deformation is an important task for designing cooling structures. Structural characteristics like stiffness and thermal conductivity are affected by structural shape. Thus, we intend to design structure with sufficient thermal conductivity, small thermal deformation, and light weight. Since these design factors have a trade off relationship, this research aims to develop design method achieving these characteristics with high levels. Structural optimization methods are able to be utilized designing structure satisfying contradicting design factors. Topology optimization (TO) is one of the most flexible optimization methodology. Thus, TO is selected as structural optimization in this research. Since we intend to design structures have sufficient thermal conductivity and minimum thermal deformation, the target of optimization is maximization of stiffness for thermal stress and thermal conductivity is introduced as a constraint. As criteria of stiffness and thermal conductivity, the structural compliance and thermal compliance are used. The structural optimization is implemented using solid isotropic material with penalization (SIMP) method of TO. Design variables are updated by sequential linear programming (SLP) in the early stage. In the latter stage, phase field method is applied to update design variables. To clarify the validity and the utility of the proposed methodology, some numerical examples are studied. Through these numerical examples, optimal shapes with high thermal conductivity and high stiffness for thermal deformation are clarified.

No abstract

The non-destructive testing for detecting structural damage at the earliest possible stage is significant in the safe and long life operation of large marine structure such as ships. In the non-destructive testing, the variation in structural characteristics from the original one to the damaged one is used to identify the damage. Vibration characteristic is one of the most popular criteria used for it due to its sensitivity for the structural damage. In this paper, a damage identification method used in non-destructive testing is proposed based on topology optimization focusing on the difference of eigenfrequency between the original structure and the damaged one. Eigenfrequency analysis of a structure is considered. A minimization of the least squared error between the eigenfrequency of the damaged structure and the target eigenfrequency is set as an objective function. An optimization algorithm is constructed based on the topology optimization and the method of moving asymptotes (MMA). The validity and the usefulness of the proposed method is confirmed by several numerical examples.