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- 저자 : Dong-Cherng Wen (검색결과 4 건)
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Improvement of Slurry Erosion Resistance of Martensite/Ferrite Duplex Stainless Steel by Hot Rolling
Dong-Cherng Wen 대한금속·재료학회 2010 METALS AND MATERIALS International Vol.16 No.1
Test samples of martensite/ferrite duplex stainless steels (M/Fss) were prepared using thermal-mechanical processes and their slurry erosion behaviors were systematically studied. Test results show that hot rolling is an attractive process for improving erosion resistance. This improvement is more evident at higher impinging angles and larger reduction ratios. The thermal-mechanical-treated samples exhibit higher slurry erosion resistance for all impinging angles compared to that obtained by conventional quenching treatment without rolling. The variation tendency of the erosion rate versus the impinging angle for samples rolled with different degrees of reduction is similar in that the erosion rate initially increases and then decreases as the impinging angles increase from 15° to 90°, reaching a maximum at approximately 30°. After impingement erosion, the surface morphologies of the samples exhibit many long furrows and ridges at a low impinging angle of 30°. At a high impinging angle of 90°, the samples exhibit a worn surface with abundant overlapping and irregular concavities. The surface hardness of the samples after impingement erosion increases as the impinging angles and reduction ratios increase due to the enhanced effects of both work hardening and the formation of straininduced martensite.
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Dong-Cherng Wen 대한금속·재료학회 2009 METALS AND MATERIALS International Vol.15 No.3
A duplex structure of δ-ferrite and lath martensite with interlath retained austenite film is developed in this study by modifying the alloy addition. The presence of δ-ferrite can further strengthen the grain refinement of austenite during hot rolling. As a result, the amount of retained austenite is enhanced. Tempered martensite embrittlement occurs due to the decomposition of retained austenite, and grain refinement can in fact ameliorate the tempered martensite embrittlement by delaying the onset of the embrittlement to a higher temperature. The combined effect of uniform and small grains as well as a large amount of retained austenite provides a further increase in the mechanical properties. After identical tempering treatments, all mechanical properties measured in the as-rolled condition were found to be higher than those of direct quenching without rolling. After hot rolling, the increase in the hardness and tensile strength was not accompanied by a drop in the ductility and toughness. A duplex structure of δ-ferrite and lath martensite with interlath retained austenite film is developed in this study by modifying the alloy addition. The presence of δ-ferrite can further strengthen the grain refinement of austenite during hot rolling. As a result, the amount of retained austenite is enhanced. Tempered martensite embrittlement occurs due to the decomposition of retained austenite, and grain refinement can in fact ameliorate the tempered martensite embrittlement by delaying the onset of the embrittlement to a higher temperature. The combined effect of uniform and small grains as well as a large amount of retained austenite provides a further increase in the mechanical properties. After identical tempering treatments, all mechanical properties measured in the as-rolled condition were found to be higher than those of direct quenching without rolling. After hot rolling, the increase in the hardness and tensile strength was not accompanied by a drop in the ductility and toughness.
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SMC Reliable Design for T-S Model-Based Systems
Yew-Wen Liang,Sheng-Dong Xu,Der-Cherng Liaw,Cheng-Chang Chen,Li-Wei Ting 제어로봇시스템학회 2009 제어로봇시스템학회 국제학술대회 논문집 Vol.2009 No.8
This paper studies the robust reliable control issues based on the Takagi-Sugeno (T-S) fuzzy system modeling method and the sliding mode control (SMC) technique. The combined scheme is shown to have the merits of both approaches. It not only alleviates the on-line computational burden by using the T-S fuzzy system model to approximate the original nonlinear one (since most of the system parameters of the T-S model can be computed off-line) but it also preserves the advantages of rapid response and robustness of the SMC schemes. Moreover, the combined scheme does not require on-line computation of any nonlinear term of the original dynamics and the increase in the partition number of the region of premise variables does not create extra on-line computational burdens for the scheme. Under the design, the control mission can continue safely without prompt external support even when the susceptible actuators fail to operate. The proposed analytical results are also applied to the attitude control of a spacecraft. Simulation results demonstrate the benefits of the proposed scheme.
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of Midcourse Guidance Laws via a Combination of Fuzzy and SMC Approaches
Yew-Wen Liang,Chun-Hone Chen,Der-Cherng Liaw,Shih-Tse Chang,Sheng-Dong Xu 제어·로봇·시스템학회 2010 International Journal of Control, Automation, and Vol.8 No.2
Issues regarding the design of midcourse guidance laws for antimissiles are addressed. The antimissile is expected to be guided to a place with a desired direction, where a ballistic missile is predicted to pass in the reverse direction, so that the target can be easily found and locked for terminal interception. The predicted location and direction of a ballistic missile may vary with time, due to information update using a trajectory prediction algorithm. To fulfill the guidance performance, the guidance laws are designed by combining the Takagi-Sugeno (T-S) fuzzy approach and the Sliding Mode Control (SMC) technique. Under the designed guidance law, it is shown that the antimissile is able to be efficiently guided to a specified location and direction, even when the existence of uncertainties and disturbances.
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