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131.
MoSi2-based intermetallics containing different volume fractions of MoB or Mo5Si3 were fabricated by hot-pressing MoSi2, MoB, and Mo5Si3 powders in vacuum. Both classes of alloys contained approximately 5 vol.% of dispersed silica phase. Additions of MoB or Mo5Si3 caused the average grain size to decrease. The decrease in the grain size was typically accompanied by an increase in flexure strength, a decrease in the room temperature fracture toughness, and a decrease in the hot strength (compressive creep strength) measured around 1200 °C, except when the Mo5Si3 effectively became the major phase. Oxidation measurements on the two classes of alloys were carried out in air. Both classes of alloys were protected from oxidation by an in-situ adherent scale that formed on exposure to high temperature. The scale, although not analyzed in detail, is commonly recognized in MoSi2 containing materials as consisting mostly of SiO2. The MoB containing materials showed an increase in the scale thickness and the cyclic oxidation rate at 1400 °C when compared with pure MoSi2. However, in contrast with the pure MoSi2 material, oxidation at 1400 °C began with a weight loss followed by a weight gain and the formation of the protective silica layer. The Mo5Si3 containing materials experienced substantial initial weight losses followed by regions of small weight changes. Overall, the MoB and Mo5Si3 additions to MoSi2 tended to be detrimental for the mechanical and oxidative properties. 相似文献
132.
133.
H.P. Stüwe 《Advanced Engineering Materials》2003,5(5):291-295
The concept of equivalent plastic strain is discussed. Definitions may be based on kinematic arguments (like change of geometry) or on equivalence of plastic work. Complications arise when strain is accumulated in increments with variable strain path. 相似文献
134.
135.
隧道受震破壞調查分析與修復管理案例 总被引:1,自引:0,他引:1
就隧道震後之災損模式進行統計與災損原因研判,並利用數值分析方法研判安全性,就結構加固等改善措施之設計考量作詳細說明;另由於隧道結構物的損壞範圍大,且修復經費受限,必須藉由定期檢测進行長期維護管理,以防範意外發生。於此,利用Vidco-GIS自動化影像地理资訊系統之e化新技術,以動態及靜態影像紀錄隧道災損狀況,同時亦整合建置前期設計、施工圖及定期維護等資料,相關成果以資料庫方式纳入日常維護管理,以有限人力有效率地進行維護管理紀錄並随時掌握現況供作決策之明確參考。 相似文献
136.
Backlash is one of the most important non-linearities that limit the performance of speed and position control in industrial, robotics, automotive, automation and other applications. The control of systems with backlash has been the subject of study since the 1940s. This survey reveals that surprisingly few control innovations have been presented since the early path breaking papers that introduced the describing function analysis of systems with backlash. Promising developments are however taking place using adaptive and non-linear control strategies. 相似文献
137.
Allen Daniel N.; Strauss Gregory P.; Kemtes Karen A.; Goldstein Gerald 《Canadian Metallurgical Quarterly》2007,21(6):713
Hemispheric involvement in reasoning abilities has been debated for some time, and it remains unclear whether the right hemisphere's involvement in problem solving is modality specific or dependent on the type of spatial reasoning required. In the current study, 2 types of nonverbal reasoning abilities were examined, spatial reasoning and proportional reasoning, in 109 patients with cerebrovascular disease that was confined to either the right or the left hemisphere or was diffuse in nature. Results indicated that no lateralizing effects were present based on type of spatial reasoning. Findings are consistent with the suggestion that higher order cognitive processes involved in nonverbal abstraction and problem solving are not strongly lateralized to the right hemisphere but rather are more generally distributed throughout the cortex. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
138.
本文采用流动模拟实验方法,以渗透率损害率为评价气层损害的定量标准,对以川东石炭系为主的完井液损害程度及滤失深度进行了试验研究,并对地层损害进行了预测。 相似文献
139.
包行方 《石油化工设备技术》1996,17(1):5-8
充分利用了带主焊缝的役后试板,在国内首次开展回火脆化、氢介质下断裂韧性与疲劳扩展的研究,结果表明,加氢反应器焊缝有明显的脆化表现。同时,核查了反应器开停车升温速度和降温速度规定,以及确定了裂纹允许尺寸的参考数据,为今后安全运行提供了充分的依据。 相似文献
140.
This paper focuses on the microscopic damage and progressive failure of a composite reinforced by plain-weave glass cloth under tensile fatigue loading. The fatigue process was divided into three stages like that of multi-directional laminates. It was found that the internal damage at each stage (matrix cracks, debonds in the weft, successive debonds in the warp and ‘metadelaminations’ between warps and wefts) occurred near the cross-over point of the fabric. The modulus decay mechanism was explained by considering the progression of this internal damage. From the end of the first stage to the beginning of the middle stage, a characteristic damage state (CDS) (called a ‘meta-CDS’) was observed. It was found that woven composites have a unit area of damage accumulation (called a ‘unit cell’) and the damage of each unit cell and its distribution control the total fatigue damage of the material. 相似文献