不锈钢瓶壳缩口应力分析与强制缩口工艺的应用

不锈钢瓶壳缩口应力分析与强制缩口工艺的应用陈美贞，杨立镇，严慕容，钟城统等一、缩口工艺分析如图１６所示的不锈钢瓶壳，材料为ＩＣｒ１８ＮｉｇＴｉ，厚度为０．６毫米．若采用落料一拉伸】十拉伸２十拉伸３十缩颈ｌ十缩颈２十旋压工艺成型，不仅工序繁多，浪费材料...     

两端缩口薄壁筒形件新型组合模具结构设计

缩口薄壁筒形件是一种广泛应用的结构件,由于两端缩口工艺较为复杂,在实际加工生产中,存在加工效率不高、产品合格率低的问题。在传统圆筒件缩口工艺分析研究的基础上,提出了一套薄壁筒形件两端同时缩口的嵌套组合模具新结构。通过在实际生产中的应用,加工效率成倍增长,产品合格率大大提高,为类似的薄壁圆筒件加工工艺及模具设计提供了重要参考。     

某车型燃油箱进油管液压成型工艺研究

汽车燃油箱进油管作为汽车整个供油系统的重要组成部件,通常其沿轴向截面复杂,同时对密封性、强度和耐腐蚀性要求高,但整体成型难度很大。对于制造这种薄壁、大变形、密封性要求高的异形截面管式构件,适用管材充液成型技术进行整体成型。文中分析了进油管充液成型工艺,包括缩口、扩口预变形处理,充液成型,并重点研究了内压力对零件成型效果的影响,最终完成进油管样件的试制。     

缩口成形技术及其工艺装备

目前,缩口成形技术已不仅仅局限于加工管类零件了,它与扩口等其它工艺联袂,可替代拉伸、胀形等一些较为复杂的工艺过程,制作出空心台阶或锥体。这项工艺的发展,使得生产过程中材料损耗更少,模具成本降低,生产效率提高,因而受到了机械制造行业的普遍重视。一、缩口成形原理缩口成形是通过模具对管料或类似管料施加外力使其在变形区产生塑性变形,从而获得一定尺寸、形状制件的一种加工方法。如图1α所示,工件1在外力     

缩口扩口复合成型工艺研究与应用

针对铁路车辆罐车零件锥管缩口、扩口的成型特点,用冲压成型缩口、扩口的力学分析及变形原理进行工艺计算与研究,找出该零件废品率高的原因。通过改进工艺毛坯（钢管）的外径与壁厚尺寸,用冲压成型缩口、扩口工艺理论及图表进行论证分析,并进行试制,取得了较好的效果。     

提高托辊径向圆跳动的工艺方法

针对带式输送机关键部件托辊采用常规制造工艺普遍存在的径向圆跳动性能超标的问题，提供了系统的工艺解决方案，着重介绍了一种新型托辊辊体的缩口工艺，并对89×315托辊进行了缩口工艺分析和计算，最后设计出一种托辊辊体专用缩口成形模具及缩口专用机床，生产出的托辊质量显著提高。     

高速铣加工壁板类零件转角

高速切削加工技术是一项全新的先进制造技术,其具有高的生产效率、加工精度、表面质量和生产成本低等优点。航空制造业中主承力结构件多数为整体坯料"掏空"的整体结构件,代替传统的拼接结构。因此在对材料去除率大、加工质量要求高、加工周期长的整体结构件加工中更能体现其独特的优势。探讨适合高速切削特点高速铣削零件转角的工艺改进方案,提高零件的加工质量缩短加工周期,能优质高效地完成生产任务。     

铅黄铜零件的塑性成型工艺

HPb59-1铅黄铜是光学仪器中广泛采用的一种有色金属材料,常用的加工工艺有铸造和切削加工等方法,上述工艺方法存在着材料利用率低(30％左右)、生产效率低和铸件有砂眼气孔等缺陷。为了解决上述工艺存在的问题,江南光学仪器厂研制成功了铅黄铜零件的塑性成型工艺,该厂采用此工艺生产的生物显微镜的转动板、镜筒滑座等部分零件已大批量投入生产,制件已达到设计技术要求,技术经济效果显著。     

救生舱成型装备应用探讨

矿用可移动式救生舱批量化生产,影响其生产效率和产品质量的关键工序是救生舱壳体成型,针对壳体成型,我们研制了系列成型装备,经过生产应用,生产效率提高5-7倍,一次交验合格率提高至98%,材料利用率提高至95%以上。     

航空整体结构件的高速切削加工

针对航空整体结构件的形状复杂、壁薄、体积大等结构特性和材料去除率高、难加工、易变形的工艺特征,结合高速切削加工的技术和经济优势的特点,分析和讨论了航空整体结构件高速切削加工过程中涉及到的刀具材料、切削参数、走刀策略和装夹方式等对加工质量和加工效率产生的影响。     

Drag force control of flow over wavy cylinders at low reynolds number

Three-dimensional numerical simulations on the laminar flow around a circular cylinder with different diameter along the spanwise leading to a type of sinusoidal waviness, named wavy cylinder are performed at low Reynolds number. A series of wavy cylinders with different combinations of spanwise wavelength and wave amplitude are conducted at a Reynolds number of 100. The optimal range of wavelength and the effect of wave amplitude are obtained. The results show that the 3-D free shear layers from the cylinder are more difficult to roll up to vortex and hence the wake formation lengths of some typical wavy cylinders are larger than that of the circular cylinder and in some cases the free shear layers even do not roll up into vortex behind the cylinder. The mean drag coefficients of the typical wavy cylinders are less than that of a corresponding circular cylinder with the same mean diameter; also the fluctuating lift coefficients are reduced. The reduction of mean drag coefficient and fluctuating lift coefficient of wavy cylinder increases with the value of wavy amplitude. Furthermore, a typical wavy cylinder model at Re=150 is also simulated and found that the control of flow induced vibration by modifing the spanwise wavelength of cylinder has a relationship with the variation of Reynolds number.     

Aerodynamic performance evaluation of basic airfoils for an agricultural unmanned helicopter using wind tunnel test and CFD simulation

There is growing interest in unmanned aerial pesticide application, which is a new farming paradigm aimed at reducing labor and improving production stability. To alleviate the difficulties being experienced by operators and pilots, researchers are focusing on the lack of lift and are trying to enhance lift by improving rotor airfoil. In this study, with the objective of enhancing the rotor performance of agricultural unmanned helicopters, the performance of basic airfoils was evaluated in a wind tunnel and via computational fluid dynamics simulation. The lift and power characteristics of rotor blades were also evaluated. As airfoil design steps to improve the lift of unmanned helicopter, the characteristics of lift, drag, and power were analyzed via wind tunnel tests for the 400 mm section models of two airfoils, specifically a thick airfoil (V1505A) with blunt nose and a thin airfoil (V2008B) with drooping nose. The V1505A airfoil is appropriate for the inboard region, which requires stable aerodynamics at a high angle of attack. On the other hand, the V2008B airfoil is ideal for the outboard region of the rotor because it has a relatively high dynamic efficiency. Therefore, it is expected that a transitional airfoil blade with a negative twist angle can solve the problems of unmanned aerial pesticide application.

     

串列三圆柱绕流的时均压力分布与气动力

运用刚性模型测压风洞试验方法对单圆柱、不同间距串列双圆柱和串列三圆柱绕流的时均压力分布与气动力进行了研究。首先,进行单圆柱模型和不同间距串列双圆柱模型的绕流试验,试验的雷诺数为3.4×104;其次,通过与单圆柱进行对比,讨论了气动干扰对串列三圆柱时均压力分布与时均阻力的影响规律;最后,通过与串列双圆柱进行对比,讨论了圆柱的数量对干扰规律的影响。试验结果发现,串列三圆柱的绕流存在两个完全不同的流态,其切换的临界间距(L/D)cr在3.5～4.0之间,两个流态下的时均压力分布与时均阻力存在明显的差异。本研究可对实际工程中串列圆柱结构的风荷载取值提供参考。     

Optimum nose shape of a front-rear symmetric train for the reduction of the total aerodynamic drag

For a high-speed train, the same power car is used as the first car and as the last car in a reverse direction simultaneously. Therefore, the previously optimized nose shape, considering only the first car position, is not well adopted in the last car position of a front-rear symmetric train in view of the aerodynamic drag. The three-dimensional nose shape optimization of a front-rear symmetric train is conducted to minimize the total aerodynamic drag of the entire train using CFD. The 3-D nose model is constructed by the vehicle modeling function with the optimized area distribution to minimize the micro-pressure wave. It is revealed that the total aerodynamic drag of the optimum shape for the entire train is reduced by 23.0% when compared to that of the conventionally optimized shape only for the first car of the symmetric train.     

全缠绕复合气瓶ANSYS参数化结构分析

复合材料气瓶逐渐取代钢制气瓶并得到广泛应用.介绍全缠绕复合气瓶的ANSYS参数化设计过程,并使用ANSYS提供的APDL参数设计语言编制复合气瓶及其内衬铝胆的建模和分析程序,借助于VC 开发出友好的可视化用户界面,通过在设计的对话框中修改复合气瓶相应的设计参数而实现系列产品的设计与分析,从而形成复合气瓶专用的有限元分析软件.     

A numerical study on fluid flow around two side-by-side rectangular cylinders with different arrangements

This study numerically examines the flow around a pair of parallel rectangular cylinders placed perpendicular to the direction of the flow using the immersed boundary method at a fixed Reynolds number of 100. A total of eight spacing ratios between 0.1 and 2 are considered in the two arrangements of the cylinders. The two cylinders are arrayed in inline and a staggered arrangement. The pattern of the wake of the two cylinders depends on their arrangements and spacing. The results, show four flow regimes: (i) A single bluff-body regime, (ii) an asymmetric wake regime, (iii) a transition regime, and (iv) a coupled street regime. All flow regimes appear in the case of the inline arrangement. In the case of the staggered arrangement, only the three flow regimes other than the coupled street flow regime are shown. The flow characteristics depend on the flow regime, including the flow structure, drag force, lift force, and frequency. We analyzed the flow characteristics by comparing the flow regimes, vortex shapes, drag and lift coefficients, and Strouhal numbers, which depended on the arrangement. The results of the drag, lift, and Strouhal numbers depend on the interaction of the jet that forms between the cylinders and the adjacent wakes near the cylinder. Therefore, the flow characteristics are sensitive to the arrangement and the distance between the cylinders.

     

两种串列方柱气动性能的试验研究

针对两种布置形式（水平布置和对角布置）的串列双方柱,通过同步测压风洞试验,在雷诺数为Re = 8.0×104、间距比为P/B = 1.75 ~ 5.00（其中P为方柱中心间距、B为方柱边长）条件下,得到了两种布置形式串列双方柱的表面风压,重点研究了对角串列双方柱的气动力、风压分布、Strouhal数等气动性能随方柱间距的变化规律,并与水平串列双方柱进行比较。水平串列双方柱的气动力在P/B = 3.00 ~ 3.50时会发生跳跃现象,下游方柱的平均阻力由负值突变为正值,而对角下游方柱平均阻力系数则均为负值。结果表明：当P/B<3.00时,对角串列双方柱的平均和脉动气动力系数、最大平均负压强度和脉动风压系数均大于水平串列双方柱,而当P/B > 3.00时则情况相反;对角串列双方柱的Strouhal数明显小于相同间距下的水平串列双方柱,且在P/B <3.00时对角串列双方柱的升力功率谱出现了多个峰值。     

Computation of aeolian tones from twin-cylinders using immersed surface dipole sources

Efficient numerical method is developed for the prediction of aerodynamic noise generation and propagation in low Mach number flows such as aeolian tone noise. The proposed numerical method is based on acoustic/viscous splitting techniques of which acoustic solvers use simplified linearised Euler equations, full linearised Euler equations and nonlinear perturbation equations as acoustic governing equations. All of acoustic equations are forced with immersed surface dipole model which is developed for the efficient computation of aerodynamic noise generation and propagation in low Mach number flows in which dipole source, originating from unsteady pressure fluctuation on a solid surface, is known to be more efficient than quadrupole sources. Multi-scale overset grid technique is also utilized to resolve the complex geometries. Initially, aeolian tone from single cylinder is considered to examine the effects that the immersed surface dipole models combined with the different acoustic governing equations have on the overall accuracy of the method. Then, the current numerical method is applied to the simulation of the aeolian tones from twin cylinders aligned perpendicularly to the mean flow and separated 3 diameters between their centers. In this configuration, symmetric vortices are shed from twin cylinders, which leads to the anti-phase of the lift dipoles and the in-phase of the drag dipoles. Due to these phase differences, the directivity of the fluctuating pressure from the lift dipoles shows the comparable magnitude with that from the drag dipoles at 10 diameters apart from the origin. However, the directivity at 100 diameters shows that the lift-dipole originated noise has larger magnitude than, but still comparable to, that of the drag-dipole one. Comparison of the numerical results with and without mean flow effects on the acoustic wave emphasizes the effects of the sheared background flows around the cylinders on the propagating acoustic waves, which is not generally considered by the classic acoustic analogy methods. Through the comparison of the results using the immersed surface dipole models with those using point sources, it is demonstrated that the current methods can allow for the complex interactions between the acoustic wave and the solid wall and the effects of the mean flow on the acoustic waves.     

Application of Immersed Boundary Method for flow over stationary and oscillating cylinders

IBM (Immersed Boundary Method) with feedback momentum forcing was applied to stationary and moving bodies. The capability of IBM to treat the obstacle surfaces, especially with moving effect has been tested for two dimensional problems. Stationary and oscillating cylinders were simulated by using IBM based on finite volume method with Cartesian coordinates. For oscillating cylinder, lateral and vertical motions are considered, respectively. Present results such as time histories of drag and lift coefficients for both stationary and oscillating cases are in good agreement with previous numerical and experimental results. Also, the instantaneous wake patterns of oscillating cylinder with different oscillating frequency ratios well represented those of previous researches. More feasibility study for IBM has been carried out to two oscillating cylinders. Drag and lift coefficients are presented for two cylinders oscillating sinusoidally with phase difference of 180°.     

Reliability analysis of process-induced cracks in rotary swaged shell nose part

The rotary swaging process is a cold working process used to reduce the diameter, produce a taper or add point to a round workpiece. For the preform design of a swaged shell nose part by a rotary swaging process, finite element simulation and experimental verification have been carried out to obtain a shell body nose of desired quality. Reliability analysis for the occurrence of process-induced cracks is performed by fault tree analysis. The various process parameters such as initial nose thickness, feed distance and reduction diameter are applied for the fault tree in order to obtain the desired target dimensions. Through simulation, the effects of initial nose thickness on the swaged shapes are analyzed. With fault tree analysis, the risk of process-induced cracks was predicted by finite element simulation and the crack occurrence was verified by swaging experiment. The results show that a swaged shell nose part having higher reliability can be successfully produced by rotary swaging process.