Static Structural Optimization Research Articles

On design sensitivities in the structural analysis and optimization of flexible multibody systems

The structural analysis and optimization of flexible multibody systems become more and more popular due to the ability to efficiently compute gradients using sophisticated approaches such as the adjoint variable method and the adoption of powerful methods from static structural optimization. To drive the improvement of the optimization process, this work addresses the computation of design sensitivities for multibody systems with arbitrarily parameterized rigid and flexible bodies that are modeled using the floating frame of reference formulation. It is shown that it is useful to augment the body describing standard input data files by their design derivatives. In this way, a clear separation can be achieved between the body modeling and parameterization and the system simulation and analysis.

Adjoint-Based High-Fidelity Structural Optimization of Wind-Turbine Blade for Load Stress Minimization

A high-fidelity multidisciplinary modeling and optimization capability is employed for optimization of structural properties of the 13 m Scaled Wind Farm Technology Facility wind-turbine blade of Sandia National Laboratories. This involves coupling a Reynolds-averaged Navier–Stokes fluid dynamics solver with a structural finite element solver. The exact sensitivities of performance objectives are obtained using the discrete adjoint method. For each of several load cases, the composite fiber angles throughout the internal structure of the blade are optimized to minimize a scalar stress parameter that correlates with the accumulation of fatigue damage. Three main types of loads regularly experienced by a wind-turbine blade are identified: aerodynamic loads, centrifugal loads, and gravitational loads. Static structural optimization is performed with the blade under centrifugal and aerodynamic loads, and dynamic optimization with the blade under gravitational loads. Then, static and dynamic optimizations are performed again with all combined loads present. A 18–60% reduction in the driving stress for fatigue is seen in after optimization.

Non-linear dynamic response structural optimization for frontal-impact and side-impact crash tests

Vehicle crash optimization is a representative non-linear dynamic response structural optimization that utilizes highly non-linear vehicle crash analysis in the time domain. In the automobile industries, crash optimization is employed to enhance the crashworthiness characteristics. The equivalent-static-loads method has been developed for such non-linear dynamic response structural optimization. The equivalent static loads are the static loads that generate the same displacement field in linear static analysis as those of non-linear dynamic analysis at a certain time step, and the equivalent static loads are imposed as external loads in linear static structural optimization. In this research, the conventional equivalent-static-loads method is expanded to the crash management system with regard to the frontal-impact test and a full-scale vehicle for a side-impact crash test. Crash analysis frequently considers unsupported systems which do not have boundary conditions and where adjacent structures do not penetrate owing to contact. Since the equivalent-static-loads method uses linear static response structural optimization, boundary conditions are required, and the impenetrability condition cannot be directly considered. To overcome the difficulties, a problem without boundary conditions is solved by using the inertia relief method. Thus, relative displacements with respect to a certain reference point are used in linear static response optimization. The impenetrability condition in non-linear analysis is transformed to the impenetrability constraints in linear static response optimization.

Stability of Ge12C48 and Ge20C40 heterofullerenes: A first principles molecular dynamics study

By using first-principles molecular dynamics, we address the issue of structural stability for the C60−mGem family of doped heterofullerenes through a set of calculations targeting C48Ge12 and C40Ge20. Three kinds of theoretical tools are employed: (a) static structural optimization, (b) a bonding analysis based on localized orbitals (Wannier wavefunctions and centers) and (c) first-principles molecular dynamics at finite temperature. This latter tool allows concluding that the segregated form of C40Ge20 is less stable than its Si-based counterpart. However, the non-segregated forms of C40Ge20 and C40Si20 have comparable stabilities at finite temperatures.