共查询到20条相似文献,搜索用时 93 毫秒
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利用SRV试验机模拟重型车辆发动机电镀Cr活塞环/缸套摩擦副的工作状态,测试了不同条件下摩擦副的摩擦因数和磨损量.采用扫描电镜(SEM)、能谱仪(EDS)分析了磨痕形貌和表面化学成分,研究了电镀Cr活塞环的磨损机制.结果表明,随载荷的增加,摩擦副的摩擦因数减小,总失重量增加.随滑动频率的增加,摩擦副的摩擦因数减小,总失重量先减小后增加,滑动频率为20 Hz时,总失重量达到最小值.随温度的升高,摩擦副的摩擦因数增大,总失重量增加.活塞环和缸套的磨损机理以磨粒磨损为主,在高载荷,高频率或高温条件下,活塞环的磨损机理转变为磨粒磨损和黏着磨损. 相似文献
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气相氧化法制备氧化锌的结晶形貌 总被引:10,自引:3,他引:7
研究了锌蒸气高温气相氧化条件对氧化锌结晶形貌的影响结果.结果表明:气相氧化法制备的氧化锌有无定形、颗粒状、单针状、四针状、多针状等5种典型的结晶形貌;这些结晶形貌与原料锌粉的粒度及表面状态没有直接联系,但都强烈地依赖于锌蒸气氧化时的物理化学环境;在不同的氧分压下,锌蒸气具有不同的氧化行为,由此导致了不同形貌的氧化锌结晶;通过改变制备条件可以有效地调控氧化锌的结晶形貌. 相似文献
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SINCE NiTi alloy is one of the promising candidatesfor sensors and actuators due to its excellentmechanical properties[1-9].Nickel-titanium shapememory thin film is expected to become one of thepromising materials for microdevice applications[1-14],which demonstrates advantages of low cost,fastresponse,and large output energy density.In thisresearch,we will focus on microfabrication andperformance of annealed nickel-titanium shapememory thin film with preferred structures for micro-device ap… 相似文献
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Raja Kountanya Ibrahim Al-Zkeri Taylan Altan 《Journal of Materials Processing Technology》2009,209(11):5068-5076
Understanding chip formation mechanisms in hard turning is an important area of research. In this study, experiments with varying cutting conditions and tool edge geometry were performed concurrently with finite element simulations. The aim was to investigate how the two mechanisms reported in literature namely—surface shear-cracking (SCH) and catastrophic thermoplastic instability (CTI) contribute to overall chip geometry and machining forces. By varying tool edge geometry and cutting conditions predominance of one over another is discussed. The calculation prescribed by Recht [Recht, R., 1964. Catastrophic thermoplastic shear. J. Appl. Mech. 31, 189–193] for representative cutting conditions resulted in a small critical cutting speed of 0.034 m/min indicating CTI was operative in the range of cutting conditions tested. FEM simulations were conducted on a subset of experimental conditions. Chip geometry and forces were compared between experiments and simulations. The experimental results indicated that SCH predominated in a majority of conditions. However, formation of saw-tooth chips in the FEM simulations established the occurrence of CTI also. Specifically, the edge radius did not alter chip geometry parameters. However, machining forces decreased with cutting speed and chip formation frequency increased linearly with cutting speed. A more negative rake angle also increased the chip pitch. The findings also indicate that only an intrinsic length scale governs saw-tooth chip formation in hard turning. 相似文献
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Numerical simulation technology was applied for optimizing the casting design and conditions in large cast iron castings for marine engine. By the simulation of mold filling and solidification sequences the problems of the previous casting conditions were analyzed and marked improvements for large cylinder liner parts were derived from these results. Especially the amount and positions of chills were optimized to increase the mechanical properties and to minimize the shrinkage and microporosity in the castings. Ultrasonic testing, penetration testing and mechanical property testing were carried out for the parts with the modified casting conditions. It showed that no defects in the castings were found and the productivity could be distinctly increased. The mechanical properties satisfied also the specification demanded. 相似文献
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采用扫描电镜、原子力显微镜和表而粗糙度测量仪对具有不同表面状态的690TT合金表面形貌进行了表征与比较。采用零电荷电位测量、动电位扫描和电化学快慢扫描等方法对不同的690TT合金的腐蚀行为进行了比较。结果表明,与机械抛光样品相比较,打磨样品表面起伏较严重,拥有更大的表面粗糙度值;在相同的腐蚀环境中,打磨样品比机械抛光样品表现出更大的腐蚀速度和更高的应力腐蚀开裂敏感性。分析认为,单纯的表面较大粗糙度和残余应变均能够促进690TT合金的腐蚀。实验中打磨690TT样品表现出的较高腐蚀速度和应力腐蚀开裂敏感性是由其较大的表面粗糙度和表面残余应变综合影响结果。 相似文献