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赵步青 《机械工人(热加工)》2004,(7):17-19
正常的高速钢断口呈无光泽的细陶瓷状,淬火过热的断口较粗糙,当奥氏体晶粒非正常长大到毫米级时,钢变得极脆,易产生穿晶解理断裂,其断口因晶粒取向不同而呈现亮暗相间、鱼鳞似的组织,称“鳞状断口”,又称萘状断口,简称萘断口(因为与萘的闪光相似)。 相似文献
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《机械工程材料》2015,(10)
采用热压烧结方法分别制备了Al2O3-TiCN复合陶瓷(AT)及掺杂MgO-Y2O3复合助剂的Al2O3-TiCN复合陶瓷(ATMY);研究了烧结温度和MgO-Y2O3复合助剂对复合陶瓷相对密度、显微组织及力学性能的影响。结果表明:当烧结温度在1 400~1 600℃时,AT和ATMY的相对密度均在97.3%以上;当烧结温度不超过1 500℃时,利用第二相TiCN可有效抑制Al2O3晶粒长大,AT和ATMY的显微组织、断裂韧度均无明显差异;当烧结温度超过1 500℃时,TiCN不能有效地抑制Al2O3晶粒长大,导致AT显微组织粗化,在1 600℃烧结的AT的断裂韧度为4.5 MPa·m1/2;掺杂了MgO-Y2O3复合助剂后可与TiCN协同抑制Al2O3晶粒长大,在1 600℃烧结的ATMY的显微组织细小均匀,断裂韧度可达5.1 MPa·m1/2。 相似文献
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In a recent paper, the Ritz method with simple algebraic polynomials as trial functions was used to obtain an eigenvalue equation for the free vibration of a class of homogeneous solids with cavities. The method presented is here extended to the study of a class of non-homogeneous solids, in which each solid is composed of a number of isotropic layers with different material properties. The Cartesian coordinate system is used to describe the geometry of the solid which is modelled by means of a segment bounded by the yz, zx and xy orthogonal coordinate planes and by two curved surfaces which are defined by fairly general polynomial expressions in the coordinates x, y and z. The surface representing the interface between two material layers in the solid is also described by a polynomial expression in the coordinates x, y and z. In order to demonstrate the accuracy of the approach, natural frequencies are given for both a two- and three-layered spherical shell and for a homogeneous hollow cylinder, as computed using the present approach, and are compared with those obtained using an exact solution. Results are then given for a number of two- and three-layered cylinders and, to demonstrate the versatility of the approach, natural frequencies are given for a five-layered cantilevered beam with a central circular hole as well as for a number of composite solids of more general shape. 相似文献
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通过分析膨胀套在实际使用产生滑移受阻现象、卡死现象原因的实质,并在分析产生问题原因的基础上提出了改进措施即:增加导向机构。 相似文献
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设计了磨粉机快辊轴承座的加工工艺和具体的工装夹具.利用卧式加工中心加工磨粉机快辊轴承座,辅以能够高效快速夹紧的夹具,既可以保证加工精度,又能够提高加工效率. 相似文献
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本文以某些积算和双笔记录仪产品为例说明由于仪表功能设计的不合理或选型不当,影响了仪表的正常使用,制造厂和用户应关注这类问题。 相似文献
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一种涡旋压缩机径向随变机构的设计 总被引:1,自引:0,他引:1
详细介绍了运用随变原理设计的一种新型径向密封机构的结构特点,工作原理及主要参数的确定方法,该机构可补偿由于涡旋体加工精度不高而造成的功率损失,适用于涡旋压缩机的批量生产。 相似文献
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Modern methods of implementation of the rule of positive gradient of mechanical properties are considered; this rule was formulated by I.V. Kragelskii and its application serves to minimize the friction and wear of solids. The given methods include the application of coatings with the method of finishing antifricton abrasion-free treatment; application of new metal-cladding lubricating materials; and creation of a nanostructural state of the surface iron nitride layer by nitriding steel with a positive gradient of hardness normal to the surface. 相似文献
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V. P. Dragunov E. G. Kostsov 《Optoelectronics, Instrumentation and Data Processing》2009,45(3):234-242
Specific features of operation of one- and two-capacitor microelectromechanical converters (MEMC) of energy of mechanical microscopic vibrations into electric energy with a modulated electrode-gap magnitude and with allowance for the mutual influence of electrical and elastic forces are analyzed, and the characteristics of these two devices are compared. The main factors restricting the increase in MEMC power are demonstrated to be the effects of “collapsing” and the condition of conservation of positive rigidity of the system. Expressions for estimating the limiting MEMC parameters are derived. The possibility of electrical energy generation in the presence of “real“ sources of wide-spectrum microscopic vibrations is considered. 相似文献