Applications of Polynomial Chaos-Based Cokriging to Aerodynamic Design Optimization Benchmark Problems

In this work, the polynomial chaos-based Cokriging (PC-Cokriging) is applied to a benchmark aerodynamic design optimization problem. The aim is to perform fast design optimization using this multifidelity metamodel. Multifidelity metamodels use information at multiple levels of fidelity to make accurate and fast predictions. Higher amount of lower fidelity data can provide important information on the trends to a limited amount of high-fidelity (HF) data. The PC-Cokriging metamodel is a multivariate version of the polynomial chaos-based Kriging (PC-Kriging) metamodel and its construction is similar to Cokriging. It combines the advantages of the interpolation-based Kriging metamodel and the regression-based polynomial chaos expansions (PCE). In the work the PC-Cokriging model is compared to other metamodels namely PCE, Kriging, PC-Kriging and Cokriging. These metamodel are first compared in terms of global accuracy, measured by root mean squared error (RMSE) and normalized RMSE (NRMSE) for different sample sets, each with an increasing number of HF samples. These metamodels are then used to find the optimum. Once the optimum design is found computational fluid dynamics (CFD) simulations are rerun and the results are compared to each other. In this study a drag reduction of 73.1 counts was achieved. The multifidelity metamodels required 19 HF samples along with 1,055 low-fidelity to converge to the optimum drag value of 129 counts, while the single fidelity models required 155 HF samples to do the same

A new analytical expression for the relationship between the Charpy impact energy and notch tip position for functionally graded steels

The effect of the distance between the notch tip and the position of the middle phase in the FGSs on the Charpy impact energy is investigated in the present paper. The results show that when the notch apex is close to the middle layer, the Charpy impact energy reaches its maximum value. This is due to the increment of the absorbed energy by plastic deformation ahead of the notch tip. On the other hand, when the notch tip is far from the middle layer, the Charpy impact energy strongly decreases. Another fundamental motivation of the present work is that for crack arrester configuration, no accurate mathematical or analytical modelling is available up to now. By considering the relationship between the Charpy impact energy and the plastic volume size, a new theoretical model has been developed to link the Charpy impact energy with the distance from the notch apex to the middle phase. This model is a simplified one and the effect of different shapes of the layers and the effect of microstructure on the mechanical properties and plastic region size will be considered in further investigation. The results of the new developed closed form expression show a sound agreement with some recent experimental results taken from the literature. \ua9 The Chinese Society for Metals and Springer-Verlag Berlin Heidelberg

Design of an element test specimen for fatigue delamination growth of a thick laminate

Following the observation of multiple delaminations growing from a tunnelling crack in the spar cap of a wind turbine rotor blade subjected to cyclic loading, an element test specimen is proposed. Design of the element test specimen to study fatigue delamination of a thick laminate is presented. Complexities inherent to a full structure e.g., curvatures, ply drops, manufacturing defects, etc. are removed to study the fatigue delamination damage mechanism. The element test specimen is made of unidirectional layers with two embedded artificial delamination cracks connected by a tunnelling crack. In this paper, analytical and numerical (2D) models are used to design the element test specimen