60°圆锥管螺纹基面中径的测量及三针的选择

60°圆锥管螺纹是一种常见的管螺纹.GB12716-91规定该螺纹的螺纹代号为NPT,锥度为1:16.尺寸代号(规格)有19种.每25.4mm有27牙、18牙、14牙、11.5牙和8牙共5种.该螺纹牙型角平分线垂直螺纹轴线,距大端面或小端面距离为L处的截面为基面,螺纹在基面上的中径、大径和小径均可在标准中查知.     

圆锥螺纹中径轴切的双线测量法

圆锥螺纹的外径d、中径d_2及底径d_1,要求在距端面为L距离的基准面上进行测量。在大型工具显微镜和万能工具显微镜上,可以用影像法和轴切法进行测量,也可以利用轴切双线法、简易块规轴切双线法进行测量。对高精度的锥度螺纹中径来说,如果用专制测量刀和标准三针直径进行测量,就可以直接和中径接触测出中径尺寸了。其测量方法简单,操作方便,精度也比较高。现将轴切双线法介绍如下: 1.测量刀的制作: 仪器原带的测量刀是刃口形,而且只有5毫米宽,刻线距刃口0.3毫米,太近,影响压线。刃口和三针接触面小,磨擦力小,不稳定,操作不方便,也容易磨损。     

在正弦尺上测量曲线齿圆锥齿轮铣刀盘刀片

本文介绍一种用正弦尺测量曲线齿圆锥齿轮铣刀盘刀片齿形角及基距的方法。在刀片尾柄的中心截面上,从刀片的基面到刀片工作侧刃刀尖的距离,称为刀片的基距,在此截面上的齿形角,就是要测量的齿形角。测量装置及测试时的装置参数的计算测量装置必须保证使表头运动方向与刀片尾柄中心截面重合,指示表座,应能定向定位,调整高低后,与刀片尾柄中心截面重合的位置仍然不     

用双位法测量机床V形导轨的直线度

机床V形导轨的直线度通常是在两个相互垂直的截面上以节距法测量:在垂直于水平面的截面上,用各种水平仪进行测量;在水平截面上,用各种自准直光学量仪进行测量.因一般中小企业没有自准直光学量仪,故本文介绍一种用平尺和指示表以双位法测量水平面上的直线度的方法.本方法的优点是在测量中可进行连续观测,避免了节距测量法之测得值不连续的缺陷.     

三坐标测量机测头半径对测量数据的影响及其消除方法

分析了三坐标测量机测头半径对测量数据的影响,对由三坐标测量机在复杂曲面上测得的点,每一截面的测量点用大挠度三次样条连接,而各截面间采用基样条函数连接,组成基样条函数和大挠度三次样条曲线的混合曲面,在此基础上推导出测量点所形成的曲面及其法向等距面的数学模型,从而消除测头半径的影响。     

60°圆锥管螺纹基面中径的测量及最佳三针直径的选择

60°圆锥管螺纹是一种常见的管螺纹。ＧＢ1 2 71 6 -91规定该螺纹的螺纹代号为ＮＰＴ。锥度为 1∶1 6。尺寸代号 (规格 )有 1 1 6 ,1 8,1 4,3 8,1 2 ,3 4,1 ,1 ,1 ,2 ,2 ,3,3 ,4,5 ,6 ,8,1 0和 1 2共十九种。每 2 5 4ｍｍ有 2 7牙 ,1 8开 ,1 4牙 ,1 1 5牙和 8牙共五种。该螺纹牙型角平分线垂直螺纹轴线。距大端面或小端面距离为Ｌ处的截面为基面。螺纹在基面上的中径、大径和小径可在标准中查知。本文介绍用标准楔形块、斜铁、三针在立式光学计上测量基面中径的方法。1　测量所需器具夹角为工件锥角 φ ,小头尺寸为经精确测出…     

用专用表夹测量蜗杆轴向齿距

在蜗杆诸多参数的测量中 ,蜗杆的轴向齿距是其主要参数之一。蜗杆的轴向齿距是指在蜗杆的轴向截面上相邻同名齿形间的距离。蜗杆的轴向齿距偏差是指在蜗杆轴向截面上实际齿距Ｐ实 与公称齿距Ｐ之最大差值。通常情况下 ,小尺寸蜗杆轴向齿距的测量 ,一般在万能工具显微镜上用影象法和测量刀法进行 ,但对于模数小螺旋角大的蜗杆 ,可采用自制的专用表夹把杆杠千分表装夹在万能工具显微镜立柱的物镜下面 ,通过移动横向滑台而进行测量。自制的专用表夹如图 1所示。图 1图 2其具体操作方法如下 :1 首先把专用表夹安装在万能工具显微镜的物镜上 ,用…     

关于三槽丝锥测量方法的改进

三槽丝锥中径的测量,有些专业书籍中介绍了用三槽丝锥检查仪的测量方法和在万能工具显微镜上配用光学分度头的测量方法。然而,前者需要配备专用的三槽丝锥检查仪和成套的校准件,后者在测量中会出现三槽分度不均或不准带来的补偿麻烦。本人认为用三针法测量螺纹单一中径的原理可应用于此。其设想的测量方法为：将丝锥装夹在万能工具显微镜两顶针间,用丝锥手柄的光杆部分测得丝锥的转动中心坐标值,然后在校准部分的起点位置处找到牙凸等于１／２基本螺距的瞄准点,此瞄准点的横向坐标值与丝锥中心坐标值之差即为１／２单一中径尺寸。１．…     

测高仪在检测动叶锁紧块螺纹中径的应用

尾气透平动叶锁紧块,总体结构为不规则四面体,其中径受被测件结构限制不能在万能工具显微镜或测长仪等测量设备上直接测量.本文介绍动叶锁紧块螺纹中径在测高仪上可实现高精度、快速测量的方法,与常规测量方法相比,简便易行.     

NPT锥螺纹中径的一种测试方法及其测量不确定度评定

一、测量原理及方法 锥螺纹的中径是指在给定基面上．沿垂直于轴线方向量得的平均圆锥的直径：平均圆锥是由截割锥螺纹牙凸和牙凹宽度相等的锥体母线所形成的假想圆锥。传统上对锥螺纹中径的测量方法也比较多。主要有影像法、三针法、正弦规法、组合测量法等。     

Fatigue crack propagation into the residual stress field along and perpendicular to laser beam butt‐weld in aluminium alloy AA6056

Laser beam butt welds in Al‐alloys are very narrow and are accompanied by steep residual stress gradients. In such a case, how the initial crack orientation and the distance of the notch tip relative to the weld affect fatigue crack propagation has not been investigated. Therefore, this investigation was undertaken with two different crack orientations: along the mid‐weld and perpendicular to the weld. Fatigue crack propagation ‘along the mid‐weld’ was found to be faster in middle crack tension specimens than in compact tension specimens. For the crack orientation ‘perpendicular to the weld’, the relative distance between the notch tip and the weld was varied using compact tension specimens to generate either tensile or compressive residual stresses near the notch tip. When tensile residual stresses were generated near the notch tip, fatigue crack propagation was found to be faster than that in the base material, irrespective of the difference in the initial residual stress level and whether the crack propagated along the mid‐weld or perpendicular to the weld. In contrast, when compressive weld residual stresses were generated near the notch tip, fatigue crack arrest, slow crack propagation, multiple crack branching and out of plane deviation occurred. The results are discussed by considering the superposition principle and possible practical implications are mentioned.     

Growth of InAs quantum dots on GaAs nanowires by metal organic chemical vapor deposition

InAs quantum dots (QDs) are grown epitaxially on Au-catalyst-grown GaAs nanowires (NWs) by metal organic chemical vapor deposition (MOCVD). These QDs are about 10-30 nm in diameter and several nanometers high, formed on the {112} side facets of the GaAs NWs. The QDs are very dense at the base of the NW and gradually sparser toward the top until disappearing at a distance of about 2 μm from the base. It can be concluded that these QDs are formed by adatom diffusion from the substrate as well as the sidewalls of the NWs. The critical diameter of the GaAs NW that is enough to form InAs QDs is between 120 and 160 nm according to incomplete statistics. We also find that these QDs exhibit zinc blende (ZB) structure that is consistent with that of the GaAs NW and their edges are faceted along particular surfaces. This hybrid structure may pave the way for the development of future nanowire-based optoelectronic devices.     

Mixing of gas in the space between the plates of a rectifying column

This paper gives the results of an experimental investigation of the degree of mixing of the gas passing through the separating space between the plates of a rectifying column in relation to its velocity in the free section of the column, the column diameter, and the distance between the plates.     

玻纤增强尼龙6的断裂研究

通过对不同玻纤含量的玻纤增强尼龙复合材料(GFPA)的性能及断口形貌的研究,得出GFPA的宏观力学性能的变化可由断面形貌特征来定量表征。拉伸强度随拉伸断口断面平坦区面积与断面总面积之比AP/A0的变小而提高,Izod缺口冲击强度随GFPA的断面粗糙度参数RS的提高而线性提高。断面形貌的变化与玻纤在基体树脂中的应力集中作用及对裂纹扩展的阻碍作用有关。     

Optimal deployment of multiple passive sensors in the sense of minimum concentration ellipse

In the sense of minimum concentration ellipse, the optimal deployment of multiple passive sensors in bearing-only location system is studied in terms of cut angle. It is found that the optimum cut angle depends only on l, the ratio of the distance between target and the baseline of the two sensors to the baseline length. When l is greater than 0.5, the optimum cut angle can be obtained if the deployment of the target and the two passive sensors is an isosceles triangle with the baseline length as its base side. When l is less than 0.5, the optimum cut angle can be obtained if the target and the two passive sensors are located on the circle with the baseline length as its diameter, that is, the deployment of the target and the two passive sensors being a right triangle. When l equals 0.5, the optimum cut angle can be obtained if the target and the two passive sensors are deployed on an isosceles right triangle. The global minimum value of concentration ellipse can be asymptotically reached by decreasing the ratio l to zero based on these properties of the optimum cut angle.     

磨料水射流对脆性材料的冲蚀研究

磨料水射流技术作为一种特种加工技术，具有无刀具接触、无热影响区和加工范围广等优势，在众多领域得到应用。为了探究磨料水射流对脆性材料的冲蚀效果，构建和设计了磨料水射流外流场冲蚀仿真模型与磨料水射流冲蚀实验。以30 mm×50 mm的喷嘴外流场域为计算域，建立磨料水射流冲蚀仿真模型，并分析射流冲蚀过程中压力分布、水与磨料的速度分布及它们在射流中心线上的衰减规律。通过对氧化铝陶瓷材料的冲蚀实验，分析工艺参数对冲蚀孔径的影响，并结合仿真结果对比分析了射流束宽度与冲蚀孔径的关系。结果表明：水的速度随着喷嘴距离的增大而减小且分布范围变宽，射流宽度呈线性增大，磨料速度随喷嘴距离的增大而减小且分布范围基本不变；射流中心线上水的速度与磨料速度呈三段式衰减，水的第1段速度衰减段长度比磨料的长，但水的第2段速度衰减段长度比磨料的短；射流束能量的有效利用部分逐渐减小，但在15~25 mm的靶距范围内其有效利用部分较稳定，为40%；冲蚀孔径随喷嘴距离增大呈线性增大。研究结果为磨料水射流切割、铣削及抛光加工的参数选择提供实验依据，同时为磨料水射流加工过程仿真提供参考。     

Capillary electrophoresis coupled with electrochemiluminescence detection using porous etched joint

A new setup to couple capillary electrophoresis (CE) with electrochemiluminescence (ECL) detection is described in which the electrical connection of CE is achieved through a porous section at a distance of 7 mm from the CE capillary outlet. Because the porous capillary wall allowed the CE current to pass through and there was no electric field gradient beyond that section, the influence of CE high-voltage field on the ECL procedure was eliminated. The porous section formed by etching the capillary with hydrofluoric acid after only one side of the circumference of 2-3 mm of polyimide coating of the capillary was removed, while keeping the polyimide coating on the other part to protect the capillary from HF etching makes the capillary joint much more robust since only a part of the circumference of it is etched. A standard three-electrode configuration was used in experiments with Pt wire as a counter electrode, Ag/AgCl as a reference electrode, and a 300-microm diameter Pt disk as a working electrode. Compared with CE-ECL conventional decoupler designs, the present setup with a porous joint has no added dead volume created. Moreover, the dead volume can be increasingly decreased by shortening the distance ( approximately 100 microm) between the working electrode and the end of the separation capillary. The versatility in choice of capillaries and separation buffers within this design is the main advantage over the use of small i.d. capillary and low conductivity buffer in some CE-ECL systems. The performance of this setup is illustrated by the analyses of tripropylamine and proline.     

设置剪切型消能装置钢柱脚抗震性能的参数分析

为研究设置剪切型消能装置钢柱脚的抗震性能,该文采用有限元分析软件ABAQUS对9个柱脚节点模型进行参数分析.首先将试验与有限元计算进行对比分析,验证有限元模型的准确性.利用有效的柱脚节点模型研究了剪切型消能装置截面面积、宽厚比及钢柱轴压比对其抗震性能(承载能力、初始刚度、耗能能力、自复位能力)的影响.研究表明:柱脚的承...     

Hardening distortions of serial produced crown wheels

The hardening distortions of serial produced crown wheels are studied with respect to gear runout, inner diameter and back‐face tilt. The data analysed originates from a production data base from ordinary production as well as from directed experiments carried out in production, resulting in a large set of data. Strong influences are found for steel plants, position of material in ingots and stacking levels on hardening trays. It could be concluded that rectangular strands have a detrimental effect on gear runout, which, however, can be strongly decreased by disabling the magnetic stirring during casting. Furthermore, the inner diameter after quenching is influenced by the stacking level on the hardening tray when free‐hardening or when using a segmented central expander during press quenching. This influence is attributed to variations in hardening temperature. When press quenching using a fixed mandrel, the effect of stacking level disappears. Moreover, it is found that the back‐face tilt strongly depends on the position in the ingot as well as on the stacking level on the hardening tray.     

Molecular surface sampling and chemical imaging using proximal probe thermal desorption/secondary ionization mass spectrometry

Proximal probe thermal desorption/secondary ionization mass spectrometry was studied and applied to molecular surface sampling and chemical imaging using printed patterns on photopaper as test substrates. With the use of a circular cross section proximal probe with a tip diameter of 50 μm and fixed temperature (350 °C), the influence of probe-to-surface distance, lane scan spacing, and surface scan speed on signal quality and spatial resolution were studied and optimized. As a compromise between signal amplitude, signal reproducibility, and data acquisition time, a surface scan speed of 100 μm/s, probe-to-paper surface distance of 5 μm, and lane spacing of 10 μm were used for imaging. Under those conditions the proximal probe thermal desorption/secondary ionization mass spectrometry method was able to achieve a spatial resolution of about 50 μm as determined by the ability to distinguish surface patterns of known dimensions that were printed on the paper substrate. It is expected that spatial resolution and chemical image quality could be further improved by using probes of smaller cross section size and by incorporating a means to maintain a fixed optimal probe-to-surface distance real time, continuously adapting to the changing topography of the surface during a lane scan.