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Residual strain measurement of piezoelectric multilayers by spiral structure
박준협,Young-Ryun Oh,Hyun-Suk Nam,김윤재,Tae-Hyun Kim,김희연 대한기계학회 2012 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.26 No.7
A new structure is described to measure the residual strain of thin film of piezoelectric multi-layers. The spiral shaped structure consists of the four fixed-guided beams. Piezoelectric multilayers consisting of SiOx/Pt/PZT/Pt on SiNx substrate are used to evaluate the suggested structure. Finite element analysis predicts that the out-of-plane displacement of the spiral structure by residual stress depends linearly on the beam length, but there is little difference depending on the beam width. PZT is prepared by sol-gel method and multilayered spiral structures are released by microfabrication technique. Sensitivity analysis of the spiral structure with various layer stack shows that the high displacement of piezoelectric multilayers can be decreased by the application of SiOx layer with compressive stress over the piezoelectric multilayers.
박준협,김기주 한국정밀공학회 2013 International Journal of Precision Engineering and Vol.14 No.8
Increasing the fuel economy has been an inevitable issue for the development of new cars, and one of the important measures to improve the fuel economy is to decrease the vehicle weight. In this study, savings in weight using lightweight materials such as aluminum alloy can lead to increase fuel economy and reduction in air pollution. In order to obtain this goal, the researches about lighter and stronger link components have been studied without sacrificing safety. Aluminum alloy material has a weak point compared to the steel material in strength for life cycle. In this study, in order to design a lighter and more reliable chassis component using aluminum material as compared with existing steel chassis components, a new camber link shape was suggested by adding vertical ribs to an existing I-beam type link and to investigate how each design parameter makes an effect on the reliability and component weight. The computer aided engineering (CAE) was performed with 9 design parameters and 2 levels. Through the analysis of variance, 3 parameters which were the most influential one on weight were selected. Through these results, the weight of the aluminum camber link was 59% that of the steel link. The stiffness of the optimized aluminum camber link under all loads was more than 100% that of the steel link.
박준협,송지호,Park, Jun-Hyeop,Song, Ji-Ho 대한기계학회 2001 大韓機械學會論文集A Vol.25 No.2
An integrated fatigue strength assessment system was computerized. The system developed consists of 9 modules: user interface, cycle counting, load history construction, data searching, fatigue properties estimation, fatigue data analysis, true stress and strain analysis, expert system for crack initiation life prediction, fatigue crack initiation and propagation life prediction. Fatigue strength database also was included in this system. The fatigue expert system helps a beginner to predict a fatigue crack initiation life in fatigue strength assessment. The expert system module in this system is developed on the personal computer by using C language and UNiK, an expert system developing tool. To evaluate the system, the results of test under variable loading of SAE and failure data from a field were analyzed. The evaluation show that the system provided fatigue life prediction within 3-scatter band and gave reasonable predictions. To get more accurate predictions of fatigue life without fatigue properties, we recommend utilizing the system along with the fatigue strength database.