04Cr13Ni5Mo横焊堆焊工艺

04Cr13Ni5Mo马氏体不锈钢耐蚀性能良好,常被用作制造水轮机过流部件材料。为了延长水轮机过流部件的使用寿命,常采用堆焊的方法进行修复。由于没有正确的参数指导,实际修复过程中常出现裂纹。为了降低裂纹倾向,改变预热温度,研究横焊堆焊接头硬度和金相组织的变化规律。结果表明:厚板04Cr13Ni5Mo不锈钢不预热时有一定淬硬倾向,焊前需要进行预热。预热温度越高,焊接接头淬硬倾向有所降低。不同预热温度下的焊缝区域组织均为低碳马氏体和少量铁素体,热影响区为低碳马氏体。     

自行火炮协调器液压-控制系统故障仿真研究

在Pro/E中建立自行火炮协调器的三维模型,将模型简化后导入Recur Dyn软件中建立虚拟样机模型并结合实验数据进行校核,验证样机的正确性。通过设置液压系统和驱动电机故障参数,对模型进行动力学仿真分析,通过故障仿真结果与正常仿真值的对比得出液压-控制系统在不同故障参数下对仿真结果的影响,为协调器液压-控制系统故障检测和维修提供一定的参考。     

发动机叶片截面型线拟合算法比较

由于发动机叶片型面复杂且参数繁多,通常需对叶片各个截面进行检测,即把对叶片型面的检测转化为曲线测量,针对这一难题,研究了叶片截面型线的拟合算法。三次样条插值、Bezier曲线拟合、三次B样条曲线拟合是曲线造型具有代表性的三种方法,对比这三种方法的优缺点来确定适合叶片截面型线拟合的算法,并通过实例,利用三坐标测量机得到14组叶片截面型线的离散数据点,通过MATLAB编写程序来验证截面型线的拟合算法。根据三种方法理论上的优缺点和实验结果的图形显示对比可知,三次B样条曲线拟合的结果最为理想,该结论为叶片型面检测提供了依据。     

液力变矩器涡轮的辊铆工艺

针对涡轮辊铆工艺方面的问题,在涡轮的结构组成、特点、国内外设备现状以及现有加工方法的基础上,采用理论分析法和试验法确定涡轮的辊铆工艺路线和工作流程,从而进行工装设计并实现工艺动作。根据液力变矩器辊铆机的工艺动作要求,对给定涡轮产品的技术性能进行研究,分析涡轮辊铆的弯曲、滚压过程,选定液力变矩器辊铆机的辊铆头的转速与下降速度,便于后续对辊铆机控制系统的设计和滚压出合格的涡轮产品。     

折线刃球头铣刀刀片的磨削方法

球头立铣刀刀刃曲线形状直接影响其切削性能和制造工艺,直线刃球头铣刀刀片易于刃磨,但切削性能差;螺旋刃切削性能好,但刃磨难度大,加工成本较高。分段直线刃搭接的折线刃球头铣刀刀片,既改善了直线刃的切削性能,又可在周边磨床上高效磨削,实现低成本制造。     

基于弹流理论的风电主轴承润滑状态分析

基于Hertz接触理论,对联合载荷作用下滚子-滚道进行接触分析,同时基于弹流润滑理论,建立风电主轴承润滑状态理论分析模型;以某型兆瓦级风电主轴承为例,采用该模型研究其极限工况下滚子-滚道接触载荷和接触应力分布、最大受载滚子沿素线方向的接触应力和接触载荷分布以及滚子-滚道接触处平均速度,并分析其在极限载荷工况下的润滑状态。结果表明:由于滚子端部应力集中,油膜沿素线呈现两端薄、中部厚特征;滚子-滚道沿素线油膜厚度与接触表面粗糙度处于同一数量级,接触表面质量对润滑状态有重要影响;改善轴承的润滑状态可从轴承结构、润滑参数及加工质量等方面入手。     

Analyzing the surface layer after WEDM depending on the parameters of a machine for the 16MnCr5 steel

The efficient wire electric discharge machining (WEDM) technology is a trade-off between the cutting speed and the resulting surface quality. A typical morphology of a surface machined using WEDM contains a large number of craters caused by the electric sparks generated in the cutting process. The paper analyzes the influence of the cutting speed on the quantitative and qualitative evaluation of the craters formed on the surface of a workpiece made of the 16MnCr5 steel. Applying metallography to cross-section microscopic slides, diffusion subsurface damages were studied caused by the cutting. The diffusion processes taking place between the electrode and the material machined were studied using a local point EDX microanalysis applied both to the machined surfaces and to the cross sections. A detailed study was also carried out of the brass electrode to measure its wear rate caused by the cutting process as well as its degradation in terms of the quality of its morphology and the chemical composition of surface.     

汽轮机叶片锻模自动化设计系统研究

分析了汽轮机叶片锻模设计过程,通过总结和提炼企业现有的设计经验与技术,形成专家知识。综合运用UG表达法及UG二次开发工具UG/Open Menu Script、UG/Open Grip及VC++6.0等,开发了此自动设计系统。从锻模设计流程中进行工作分解,分模块进行设计,采用人机交互方式,避免了繁琐的手工绘制与重复劳动即可实现汽轮机叶片锻模的设计,提高了设计人员工作效率,缩短产品开发周期。     

小型垂直轴风力发电机的气动噪声数值模拟与试验验证

为了降低小型垂直轴风力发电机的气动噪声,对其噪声产生机理进行了分析。首先,在瞬态计算时运用大涡模拟(LES)模型对在一定工况下的三维风轮周围的流场进行分析;其次,在声学计算时运用FW-H方程对风轮产生的气动噪声进行分析并得出频谱;最后,通过实例验证了该方法能有效预测其气动噪声。结果表明:小型垂直轴风力发电机的气动噪声主要是涡流噪声;监测点的噪声值随着离风轮旋转轴半径的增加而减小,且在垂直于叶轮旋转轴的平面上具有指向性。小型垂直轴风力发电机的气动噪声分析为其进一步低噪声优化提供了依据。     

Influence of surface treatments on topography and bond strength of densely-sintered zirconium-oxide ceramic

The aim of this study was to evaluate the effect of surface treatments on the roughness and bond strength of dental materials containing MDP to zirconium oxide ceramic. Forty square-shaped zirconium-oxide ceramic blocks (Lava Zirconia, 3M-ESPE) were treated as follows: (CT) polished only; (SB) sandblasting (110 µm aluminum oxide particles) or (SC) silica coating (110 µm particles). Roughness of treated surface was measured using a profilometer (Ra) and by atomic force microscope (AFM). Two resin luting agents were used after silane application: self-adhesive (Rely X U200, 3M-ESPE) and dual cure (Rely X Ultimate, 3M-ESPE). The samples were submitted to microshear bond strength test. The failure analysis was performed. Data were submitted to ANOVA and Tukey test (α=0.05). Bond strength results ranged from 20.44 (CT+Ultimate) to 34.37 MPa (SC+U200) after 24 h and from 12.03 (CT+Ultimate) to 27.44 MPa (SC+U200) after 12 months of storage with SC statistically superior to the other treatments. Mean values of roughness varied from 0.07 (CT) to 0.85 µm (SC). The both resin luting agents showed similar results to all surface treatment groups. Silica coating provided the best treatment of the ceramic surface.