上海光源储存环不锈钢真空室

铝合金和不锈钢都适合制造上海光源储存环的真空室,但各有特色,从而导致不同的加工和成本问题.实质上,不锈钢真空室可以看作是铝合金真空室的一个"内核".上海光源最终采用了不锈钢真空室,其主要理由是加工铝合金真空室时要用数控床切削掉约一半的材料,而加工壁薄不锈钢真空室几乎没有材料的损失.因此,经费大量节省和加工周期大大缩短.但结构复杂的薄壁不锈钢真空室的尺寸精度要做到和机加工铝合金真空室相当,难度极大.在研制了多个样机后,终于解决了成形片尺寸公差和焊接变形等难题,定型了工艺和工装,真空室的尺寸公差得到了控制.长度约3m的每段真空室的平面度和直线度的公差都小于1mm.真空室经900℃真空退火后,焊缝处的导磁率从2.5下降到1.02.真空预调试后真空室内达到5×10 -9Pa的极限真空.400m真空室现场安装后的位置公差都小于2mm.     

SSRF电子储存环铝合金超高真空室研制

上海光源3.5GeV电子储存环超高真空室采用铝合金材料,经数控加工后焊接而成,其结构复杂,精度要求高.在预制研究中成功地完成了一段6 m长典型真空室的设计、制造与调试.该真空室的平面度达到0.23 mm,横向偏移量1.4mm,内表面单位面积出气率4.1×10-10 Pa·m/s.在研制中暴露出结构设计和加工工艺等方面的多种问题,并找到了妥善解决的方法,为工程批量生产准备了条件.     

SSRF电子储存环真空室材料电子激发解吸的实验研究

用电子激发方法对ＳＳＲＦ储存环初步选定的真空室材料的动态出气特性进行了实验研究，得到了主要解吸气体成分的电子激发解吸系数与电子入射累积剂量的关系，对真空室材料经不同表面处理后的电子激发解吸特性进行了比较，初步确定了该真空室的表面处理工艺，为ＳＳＲＦ储存环超高真空系统的建立提供了一定的实验依据。     

水轮机主轴加工工艺技术

在水轮机组中,各种型号上的主轴是最关键的部件,其加工误差及尺寸精度历来是水轮机加工中一个难题,特别是大型内法兰结构的主轴加工,难度大,形位公差及粗糙度等要求高。必需采取一定工艺措效才能满足加工要求,本文针对我们在生产中遇到问题及解决方法进行论述。     

SSRF电子储存环真空室材料电子激发解吸的实验研究

用电子激发方法对SSRF储存环初步选定的真空室材料的动态出气特性进行了实验研究 ,得到了主要解吸气体成分的电子激发解吸系数与电子入射累积剂量的关系 ,对真空室材料经不同表面处理后的电子激发解吸特性进行了比较 ,初步确定了该真空室的表面处理工艺 ,为SSRF储存环超高真空系统的建立提供了一定的实验依据     

薄壁铝合金衬套类零件的加工方法

随着发动机的发展要求,迫切需要材料节省、紧凑结构、轻质量等特点的部件,在汽车等行业中,薄壁铝合金衬套类零件成为最优选择。但因为其力学性能差、自由状态下变形量大,在加工中受力状态和自由状态下应变量相差较大,迫使验收标准往往以自由状态下的形位公差和尺寸公差为检查标准。因此如何提高产品的加工精度成为急需解决的问题。     

安装座加工工艺及研究

由我中心所承制的某机型安装座零件，其精度要求高，壁薄，加工时较难保证零件的尺寸及形位公差的要求。     

电机动环机械加工工艺设计

动环是油冷电机中常用的零件,安装在电机轴上,其工作面与电机静环滑动配合起到机械密封油的作用。本文详细论述了电机动环机械加工工艺设计,通过完整的工艺过程,加工后的电机动环,经检测零件的尺寸精度以及形位公差都能够达零件设计要求。     

基于光谱共焦的在线集成表面粗糙度测量方法

为了提高加工检测效率,实现尺寸形位公差与微观轮廓的同平台测量,提出一种基于光谱共焦位移传感器在现场坐标测量平台上集成表面粗糙度测量的方法。搭建实验测量系统且在LabVIEW平台上开发系统的硬件通讯控制模块,并配套了高斯轮廓滤波处理及表面粗糙度的评价环境,建立了非接触的表面粗糙度测量能力。对标准台阶、表面粗糙度标准样块和曲面轮廓样品进行了测量,实验结果表明:该测量系统具有较高的测量精度和重复性,粗糙度参数Ra的测量重复性为0.0026μm,在优化零件检测流程和提高整体检测效率等方面具有一定的应用前景。     

《公差原则》国标在精度设计中的应用

在机械零件的精度设计中,《公差原则》标准的应用是比较复杂的问题。 公差原则,是指在应用尺寸公差及形位公差时所应遵循的原则。它分为独立原则及相关原则二种。独立原则——图纸上标注的尺寸公差与形位公差相互无关,在检测时用普通计量器具分别对尺寸形位误差进行测量,其标注如图1所示。相关原则——图纸上标注的尺寸公差与形     

Surface integrity and removal mechanism in grinding sapphire wafers with novel vitrified bond diamond plates

In order to improve machining efficiency of sapphire wafer machining using the conventional loose abrasive process, fixed-abrasive diamond plates are investigated in this study for sapphire wafer grinding. Four vitrified bond diamond plates of different grain sizes (40?µm, 20?µm, 7?µm, and 2.5?µm) are developed and evaluated for grinding performance including surface roughness, surface topography, surface and subsurface damage, and material removal rate (MRR) of sapphire wafers. The material removal mechanisms, wafer surface finish, and quality of the diamond plates are also compared and discussed. The experiment results demonstrate that the surface material is removed in brittle mode when sapphire wafers are ground by the diamond plates with a grain size of 40?µm and 20?µm, and in ductile mode when that are ground by the diamond plates of grain sizes of 7?µm and 2.5?µm. The highest MRR value of 145.7?µm/min is acquired with the diamond plate with an abrasive size of 40?µm and the lowest surface roughness values of 3.5?nm in Ra is achieved with the 2.5?µm size.     

液体磁性磨具小孔光整加工材料去除机理及实验

针对小孔内壁光整加工技术的难题,本文提出一种新型精密研磨孔光整加工技术,以磁致相变理论为指导,从微观角度阐述了液体磁性磨具研磨孔光整加工的材料去除机理.采用"双刃圆半径"模型进行单个磨料颗粒切削模型研究,得出小孔光整加工的材料去除率数学表达式.通过实验验证了磨料粒度、入口压力、电流强度等因素对材料去除率以及表面粗糙度的影响,实验结果表明:在合适的范围内,增大磨料颗粒直径、入口压力以及电流强度有利于提高材料的去除率和表面质量.而当磨粒直径、入口压力以及电流强度选取过大时,虽然能获得较高的材料去除率,但是最终获得的表面粗糙度值并不理想.该研究为通孔零件内壁表面精密光整加工提供了有益参考.     

航空发动机叶片粗糙度测量方法研究

航空发动机叶片表面弯扭大，加工过程中难以保证表面粗糙度一致。针对现阶段粗糙度测量方法在测量叶片时缺少测量位置和方向的定义，导致测得的粗糙度值无法判定叶片粗糙度合格性的问题，开展了叶片粗糙度测量方法研究。基于叶片实测截面数据，利用坐标测量机上搭载的粗糙度测头，通过对不同类型的叶片进行多位置多方向的粗糙度测量实验，分析不同位置、不同方向的粗糙度测量结果差异，得到了叶片粗糙度测量方法。本方法将叶片粗糙度与叶片型面相关联，解决了叶片粗糙度的测量位置和测量方向缺乏规范的问题。研究结果对准确、有效、规范地评估叶片表面质量的合格性具有重要意义。     

Machinability of titanium alloy through electric discharge machining

Titanium alloy (Ti-6Al-4V), being considered as hard-to-machine material, offers many challenges especially during conventional machining. Electric discharge machining could be a good option if it offers a good match between material removal rate and surface finish of the machined feature. The issue of appropriate selection of electrode material for good machining of Ti-6Al-4V is not yet comprehensively explored which is the core focus of this study. Moreover, the effect of pulse time ratio is thoroughly examined which is not specifically studied before. Discharge current and pulse time ratio are considered as the input variables, whereas the material removal rate and surface roughness are selected as performance measures of machinability. Copper, aluminum, brass and graphite are employed to evaluate the machining behavior. Experimental results revealed that aluminum electrode provides the lowest surface roughness, whereas the maximum material removal rate is achieved using graphite electrode. However, graphite electrode can offer high material removal rate with low surface roughness by initially employing negative tool polarity for rough machining and then positive tool polarity for fine machining.     

Effect of Crystallographic Anisotropy on Micro EDM Process

In this paper, experiments are conducted by machining from different crystallographic orientations of monocrystalline silicon, and the effects of crystallographic orientation on the micro electrical discharge machining (EDM) process are discussed. The results demonstrate that the machining speed and surface roughness are varied when crystallographic orientation changes. The surface roughness is seen to vary by as much as twofold with crystallographic orientation, while the ratio between the maximum and minimum values of material removal rate is 1.76. The unique material removal mechanism of micro EDM enhances the effects of crystal anisotropy on micro electrical discharge machining process.     

Characteristics of array holes with large aspect ratio in aluminum-based cast alloy

Array holes were obtained by machining methods or nontraditional machining methods, and casting process was rarely used in the preparation of array holes. In this experiment, stainless steel thin rods coated with alcohol group graphite paint were chosen as cores to prepare array holes on aluminum-based cast alloys, and the roughness and roundness of holes were analyzed. The results show that array holes cast with 2?mm pitch of holes, 0.54?mm diameters, and large aspect ratio of 100 were obtained. The roundness and roughness of holes were influenced by consumption of carbon element from surface of hole core and wettability between molten metal and hole core surface; the lower roughness and the better roundness could be acquired under these experimental conditions. And roughness of holes (R_a) was about 6.3?µm, which is close to that obtained by machining, and the value of hole shape factor (K, characterizing the roundness of the hole) was above 0.7; the shape of the hole approached a circular shape.     

Experimental investigation on carbon steel micro-rod machining by LS-WEDT

This article proposed for the first time the method of the low-speed wire electrical discharge turning (LS-WEDT) combined with the multiple cutting strategy to fabricate carbon steel micro-rods. First, the rotating apparatus submerged in working fluid is designed and manufactured to enable the low-speed wire electrical discharge machine to generate cylindrical geometries. Besides, material removal rate, surface roughness, and machining precision of the micro-rod manufactured by the LS-WEDT are, respectively, investigated. Moreover, the surface microstructure and surface chemical reaction of micro-rods are characterized using scanning electron microscopy and energy-dispersive spectroscopy analysis. Experimental results display that the micro-rod of 70?µm diameter and 1000?µm length can be successfully fabricated. More importantly, the mean absolute diameter deviation of the micro-rod fabricated by LS-WEDT is 0.65?µm and the surface roughness is 0.53?µm, which identified the high machining precision and good surface quality of the micro-rod.     

面向精密加工的仿真技术研究及应用

详细阐述了计算机仿真技术在精密加工领域中应用的两个方面——加工过程动态仿真和加工过程物理特性仿真;建立了微细电火花加工仿真系统,实现微细电火花放电通道仿真,建立并分析了电火花加工的热学模型,分析了表面粗糙度与工艺参数的关系。系统在实际中得到验证,加工出微三维结构。通过电火花仿真系统,说明计算机仿真技术在精密加工研究方面的可行性和优越性。     

Role of machining defects and residual stress on the AISI 304 fatigue crack nucleation

Machining defects as rebuilt material and dislodgement were often induced by cutting of difficult to machining AISI 304 stainless steel. Their density increases with a decreasing of cutting speed. The effect of these defects on surface topography and residual stress was evaluated by roughness and X‐ray diffraction measurements coupled with numerical simulation. The role of the rebuilt material on the distribution of fatigue crack nucleation sites was investigated by scanning electron microscope examination of post fatigue samples loaded at different imposed strain amplitudes. The association of machining defects and fatigue crack nucleation sites was attributed to the contribution of additional tensile residual stresses induced by rebuilt material rather than local stress concentration. Moreover, the fatigue crack coalescence is promoted by increasing the rebuilt material density. When the machining defect density increases from 5 to 60 particles/mm², the fatigue life decreases from ?22% to ?65% with respect to the electropolished surface.     

Machinability of Zirconia Ceramics in Ultrasonic Drilling

Zirconia is a typical hard and brittle ceramic material, while its fracture toughness is several times higher than alumina. The use of this advanced ceramic is growing. Machining is often required for quality control of the ceramic component. However, extremely high hardness causes serious problems in conventional machining. Nontraditional ultrasonic machining offers an advantageous alternative. The present work investigates the machinability of zirconia ceramics using ultrasonic drilling. The material removal rate, hole clearance, surface roughness, and tool wear are studied by varying static load and amplitude. The material is removed at several cubic millimeters per minute with 0.5 micrometers average surface roughness. Optimal machining conditions was established with the above performance indices.