12 research outputs found
Design of functionally graded compliant mechanisms using topology optimization
This research applies topology optimization to create feasible functionally graded complaint mechanism designs with the aim of improving structural performance compared to traditional homogeneous compliant mechanism designs. Structural performance is assessed with respect to mechanical/geometric advantage and stress distributions. A novel modified solid isotropic material with penalization (SIMP) method is adopted for representing local element material properties in FGM structures. The method of moving asymptotes (MMA) is used in conjunction with adjoint sensitivity analysis to find the optimal distribution of material properties. Functionally graded materials (FGMs) have material properties that vary based on spatial position. Here, FGMs are implemented using two different resource constraints \textendash \ one on the mechanism's volume and the other on the integral of the Young's modulus distribution throughout the design domain. Two sets of results are presented \textendash \ polymeric and metallic designs. Geometric non-linear analysis based on the Neo-Hookean model for hyperelastic materials is used to solve the mechanics problem for polymeric designs, whereas analysis of metallic materials is solved using conventional linear finite element analysis (FEA). Tensile tests are performed to obtain the material properties used in the analysis. To ensure an accurate representation when using linear FEA, metallic designs are subject to stress constraints. A novel method of stress-based design for FGM structures is presented where local yield strength is a function of local Young's modulus. Results suggest that FGMs can achieve the desired improvements in structural performance for certain designs and can also have a favorable effect on the von Mises stress distribution
Coupled aeroelastic shape and topology optimization of wings
This paper presents a method for simultaneous optimization of the outer shape
and internal topology of aircraft wings, with the objective of minimizing drag
subject to lift and compliance constraints for multiple load cases. The physics
are evaluated by the means of a source-doublet panel method for the aerodynamic
response and linear elastic finite elements for the structural response, which
are one way coupled. At each design iteration a mapping procedure is applied to
map the current wing shape and corresponding pressure loads to the unfitted
finite element mesh covering the design domain. Wings of small fixed-wing
airplanes both, with and without a stiffening strut, are optimized. The
resulting wings show internal topologies with struts and wall-truss
combinations, depending on the design freedom of the shape optimization. The
lift distributions of the optimized wings show patterns similar to the ones
obtained when performing optimization of wing shapes with constraints on the
bending moment at the root