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A robust-based fatigue optimization method for systems subject to uncertainty
U. L. Rosa,A. M. G. de Lima,L. K. S. Gonçalves,M. H. Belonsi 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.9
A robust design method based on fatigue for stochastic problems is proposed. In most cases, fatigue analyses of structures are performed by assuming the nominal values of their parameters in a deterministic way. However, since the systems are frequently subject to parametric uncertainty and random forces simultaneously, it does not provide a representative fatigue index. Thus, it becomes essential to consider these uncertainties on the fatigue models. Here, a plate stochastic finite element is used to formulate the probabilistic Sines’ index in frequency-domain, where the random fields are discretized using Karhunen-Loève expansion with hypercube sampling as stochastic solver. To maximize fatigue performance, a robust optimization combined with a robust reduction is proposed to increase the efficiency of the method. The envelopes of stresses and the Sines’ coefficients for optimized solutions confirm the importance of considering uncertainty on fatigue models for more realistic situations.
MORPHOLOGICAL CHARACTERIZATION OF THE SURFACE OF NANOPOROUS ALUMINUM OXIDE BY AFM AND LAWS OF SCALE
L. C. DE LIMA,M. M. G. DE MACEDO,M. P. DE ALBUQUERQUE,MARCELO P. DE ALBUQUERQUE,R. A. SIM˜AO 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2009 NANO Vol.4 No.3
This article presents a morphological, chemical, and fractal dimension study of the time evolution of aluminum AC anodization in 1 M H3PO4 solution. The morphological analysis was accomplished by Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM). According to SEM, ordered porous pattern was already observed after 90 s of anodization, yet AFM revealed a different surface morphology evolution. Stripes were observed on the surface at the initial stages of anodization, developing to the formation of a complete phosphate layer at an intermediate stage and finally, to a porous structure at the steady stage. The phosphate layer was observed by AFM as well as by Auger Electron Spectroscopy (AES). Nevertheless, it could not be noticed by SEM. AFM data were quantified by fractal dimension and no significant changes in terms of fractal dimension were found in the function of the anodization time.