共查询到20条相似文献,搜索用时 78 毫秒
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利用光学显微镜和扫描电镜观察新型Ni-Co基高温合金的铸态组织,采用JMatPro软件在平衡和非平衡凝固条件下对该合金进行热力学计算,研究了合金的相析出特点。结果表明:试验合金呈现枝晶形貌,偏析严重,主要组织为γ′相、η相、γ/γ′共晶组织以及MC碳化物。平衡凝固条件下,试验合金的主要析出相为γ′、η、μ、σ、碳化物以及硼化物;钛和铝含量增加导致γ′相析出量增加,析出温度升高;η相析出温度和析出量随钛含量增加呈线性增加。在非平衡凝固过程中,钛、钼元素富集在液相中,而铝、铬、钴和钨元素在液相中贫乏。 相似文献
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用SEM、TEM、EDS和ICP-AES等方法进行微观组织分析,用冲击试验机测定冲击性能,研究了LF9镍基合金经(800~1 040)℃×1 h固溶水冷处理后γ′相和η相的变化及对合金冲击性能的影响.结果表明:合金中的γ′相在高温下发生长大,原始锻态γ′相的平均尺寸约20 nm,980℃固溶时平均尺寸约120 nm,而1 020℃时γ′相完全溶解;820℃时次生析出η相沿晶界平行往外生长,在η相两侧形成贫γ′区,约980℃时析出量达到最多,约1 040℃时完全溶解;贫γ′区的微塑性区能减缓裂纹的扩展速率,改善合金的冲击性能;η相的析出数量增多和尺寸增大降低了合金的冲击性能. 相似文献
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制备了名义成分为Ni-9Ta-6Al-6W-4Co-2Cr-0.4Mo-xRe(x分别为6.2,6.8,质量分数/%)的两种单晶高温合金,研究了铼含量对合金铸态显微组织和相转变温度以及热处理态显微组织和高温持久性能的影响。结果表明:微量增加铼后,铸态合金的凝固偏析程度和γ+γ′共晶组织含量均增加,固溶过程中共晶组织快速溶解的峰值温度提高;热处理态合金中的γ′相尺寸略微减小,持久加载过程中拓扑密排相的析出量增加;铼的微量增加显著改变了铼和铬的成分分配比,增强了固溶强化效果,明显提高了合金的高温持久性能。 相似文献
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采用电导率测试、室温拉伸性能测试、扫描电镜和透射电镜分析等方法,研究了不同的均匀化处理对铝锌镁钪合金组织和性能的影响。结果表明:铸态铝锌镁钪合金为过饱和固溶体,合金元素在晶界偏析,形成了富锌、镁的非平衡共晶T相和富铁、硅、锰的杂质相;当均匀化温度为350℃,过饱和基体析出平衡相η-MgZn2;随着均匀化温度的升高,非平衡共晶T相逐渐溶入基体,电导率下降,晶内析出大量Al3(Sc,Zr)粒子,合金的热加工性能提高;470℃×12h是试验合金较适宜的均匀化制度。 相似文献
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以第四代镍基单晶高温合金DD15为基础,将其铼含量(质量分数)分别调整为5%,6%,7%制备单晶高温合金,研究了铼含量对合金凝固组织特征与元素分布的影响。结果表明:随铼含量的增加,试验合金的γ′相析出温度、溶解温度升高,固相线温度略微下降,液相线温度无明显变化;增加铼含量,合金一次枝晶间距与二次枝晶间距均增大,(γ+γ′)共晶组织含量增多,γ′相尺寸减小,体积分数降低;铼含量的增加使得合金组织中负偏析元素铼、钨、钼、铬、钴的偏析程度降低,但正偏析元素钽的偏析程度增大。 相似文献
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研究了两种典型铸态K480及DD407高温合金在870℃下经3 000 h时效过程中γ′相的稳定性,探讨γ′相的粗化机制。结果表明:K480合金和DD407合金经过长期时效后组织中均无TCP相析出,γ′相发生轻微粗化现象,合金组织稳定性良好,其中DD407合金中γ′相长大趋势大于K480合金的;随着时效时间的延长,K480合金中晶界逐渐变宽,碳化物沿晶界长大,最终连结成链状,并有成膜趋势;K480合金中γ′相长大符合二次方定律,而DD407合金的符合三次方定律;该两种合金γ′相长大方式分别为界面控制和扩散控制。 相似文献
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离心铸造的HP40和HP40-Nb合金被广泛用作制氢转化炉炉管材料,通常管壁温度可高达1000℃。通过观察HP40和HP40-Nb合金在原始铸态和高温状态下的显微组织,研究了不同Nb含量对合金共晶组织稳定性的影响。采用扫描电镜和X射线衍射仪研究了炉管材料的显微组织和相结构。研究结果表明:在碳含量0.4%左右的HP合金中,Nb含量0.210%~0.357%时主要起到固溶强化作用,共晶碳化物主要是M7C3,仅有少量的富Nb共晶MC散布在晶界上;当Nb含量0.89%~1.55%时,HP40-Nb原始铸态组织中析出了富Cr的M7C3碳化物和富Nb共晶MC。对于高温状态下的HP40-Nb合金,在晶界和枝晶间形成的富Nb共晶的MC提高了原始共晶组织的稳定性,使得炉管材料的使用温度可向高温推移。 相似文献
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Clarence W.DE SILVA 《Instrumentation》2019,(4):72-84
An engineering system may consist of several different types of components,belonging to such physical"domains"as mechanical,electrical,fluid,and thermal.It is t... 相似文献
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INTEGRAL EQUATION METHOD'S APPLICATION IN HOLE-EDGE STRESS OF COMPOSITE MATERIAL PLATE WITH DIFFERENT SHAPED HOLES 总被引:1,自引:0,他引:1
LI Cheng ZHENG Yanping 《机械工程学报(英文版)》2008,21(6):115-118
The strength of composite plate with different hole-shapes is always one of the most important but complicated issues in the application of the composite material. The holes will lead to mutations and discontinuity to the structure. So the hole-edge stress concentration is always a serious phenomenon. And the phenomenon makes the structure strength decrease very quickly to form dangerous weak points. Most partial damage begins from these weak points. According to the complex variable functions theory, the accurate boundary condition of composite plate with different hole-shapes is founded by conformal mapping method to settle the boundary condition problem of complex hole-shapes. Composite plate with commonly hole-shapes in engineering is studied by several complex variable stress fimction. The boundary integral equations are founded based on exact boundary conditions. Then the exact hole-edge stress analytic solution of composite plate with rectangle holes and wing manholes is resolved. Both of offset axis loadings and its influences on the stress concentration coefficient of the hole-edge are discussed. And comparisons of different loads along various offset axis on the hole-edge stress distribution of orthotropic plate with rectangle hole or wing manhole are made. It can be concluded that hole-edge with continuous variable curvatures might help to decrease the stress concentration coefficient; and smaller angle of outer load and fiber can decrease the stress peak value. 相似文献
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30 keV Ga+ focused ion beam induced secondary electron (iSE) imaging was used to determine the relative contrast between several materials. The iSE signal compared from C, Si, Al, Ti, Cr, Ni, Cu, Mo, Ag, and W metal layers does not decrease with an increase in target atomic number Z2, and shows a non-monotonic relationship between contrast and Z2. The non-monotonic relationship is attributed to periodic fluctuations of the stopping power and sputter yield inherent to the ion–solid interactions. In addition, material contrast from electron-induced secondary electron (eSE) and backscattered electron (BSE) images using scanning electron microscopy (SEM) also shows non-monotonic contrast as a function of Z2, following the periodic behavior of the stopping power for electron–solid interactions. A comparison of the iSE and eSE results shows similar relative contrast between the metal layers, and not complementary contrast as conventionally understood. These similarities in the contrast behavior can be attributed to similarities in the periodic and non-monotonic function defined by incident particle–solid interaction theory. 相似文献
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This paper proposes a novel grading method of apples,in an automated grading device that uses convolutional neural networks to extract the size,color,texture,an... 相似文献
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分布动态载荷识别的抗噪处理 总被引:2,自引:2,他引:0
针对正交多项式频域法在用多种响应对矩形薄板进行载荷识别中抗噪性较差的问题,综合运用平均法、矩阵预处理和奇异值截断法等方法对之进行改善,并引入空间映射的思想,将该方法的应用范围拓展为复杂的模型.利用仿真算例,证实了该方法具有较好的抗噪性. 相似文献
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针对工程实践中环网通讯相关问题的处理缺乏理论基础及国产化安全级DCS平台的开发缺乏成熟经验借鉴问题,对基于MELTAC-N平台核电厂安全级DCS环网的软硬件实现进行了研究。提出了安全级DCS环网双环网冗余设计、光切换开关设计等硬件设计方法,以及以RPR协议为基础,采用全数据收发策略的软件设计方法。在CPR1000安全级DCS平台上对安全级DCS环网的可靠性及实时性进行了评价,并进行了容错能力、响应时间及响应时间稳定性测试验证实验。结果表明,基于MELTAC-N平台安全级DCS环网软硬件设计具有较好的容错能力及响应时间稳定性。 相似文献
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The fraction defective of semi-finished products is predicted to optimize the process of relay production lines, by which production quality and productivity ar... 相似文献
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The use of hand gestures can be the most intuitive human-machine interaction medium.The early approaches for hand gesture recognition used device-based methods.... 相似文献
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J. A. Williams 《Lubrication Science》1997,3(3):267-306
Abrasive wear has long been recognised as one of the most potentially serious tribological problems facing the operators of many types of plant and machinery; several industrial surveys have indicated that wear by abrasion can be responsible for more than 50% of unscheduled machine and plant stoppages. Locating the operating point of a tribological contact in an appropriate operational ‚map’︁ can provide a useful guide to the likely nature and origins of the surface degradation experienced in use, though care must be exercised in choosing the most suitable parameters for the axes of the plot. Laboratory testing of materials and simulations of machine contacts are carried out for a number of purposes; at one level for the very practical aims of ranking candidate materials or surface hardening treatments in order of their wear resistance, or in an attempt to predict wear lives under field conditions. More fundamentally, tests may be aimed at elucidating the essential physical mechanisms of surface damage and loss, with the longer term aim of building an analytical and predictive model of the wear process itself. In many cases, component surface damage is brought about by the ingress of hard, particulate matter into machine bearing or sealing clearances. These may be running dry although, more usually, a lubricant or service fluid is present at the interface. A number of standardised wear test geometries and procedures have been established for both two- and three-body wear situations, and these are briefly described. Although abrasive wear is often modelled as following an ‚Archard’︁ equation (i.e. a linear increase in material loss with both load and time, and an inverse dependence on specimen hardness) both industrial experience and laboratory tests of particularly lubricated contacts show that this is not always the case: increasing the hardness differential in an abrasively contaminated lubricated pair may not always reduce the rate of damage to the harder surface. 相似文献
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CHEN Sunyi 《机械工程学报(英文版)》2007,20(6):13-17
A graph as the new engineering method for estimate the safety of bulging deformation of coke tower is proposed. Through stresses analysis of circumferential weld of coke tower and comparing the stresses produced by pressure with heat stress of steady state, residual stress, bending stress produced by both itself weight and wind loads, it showed that the stresses produced by pressure on the angle distortion are the main factor of equivalent stress of the combined stress. After comparing four kinds of stress controlling conditions, the relation to stress with depth of angular distortion, grade of curvature of angular distortion and half of region of angular distortion has been inferred. Graph of deformation allowable value of coke tower for different condition by angular distortion and half of region of angular distortion has been plotted. The five steps for its engineering use have been explained. The lighter the grade of curvature is, the larger of bulge allowance, may be, and the bigger of depth of angular distortion may pose too. For the coke tower with a popular structure of Dg 5 400 mm×28 mm, the result by graph is nearly more than the result of two formulas formed by other research, the error is less than 7.0%. But, the graph can be easily applied to different size of angular distortion. 相似文献