Geometrical analysis of thread milling—part 2: calculation of uncut chip thickness

Thread milling offers interesting possibilities for machining internal or external threads. This machining technique uses a mill with a triangular profile for metric threads and a helical interpolation strategy. Thus, the uncut chip thickness cannot be easily evaluated from a simplified approach. The present study deals with a model for calculating uncut chip thickness during internal thread milling. This step is needed to understand and model the cutting forces. The model developed uses the geometrical definitions of the mill and takes into account the milling mode and the cutting conditions. The link with the interferences between the tool and the thread is also established and corroborates a previous study. A full analytical formulation of the problem is proposed, and results from different milling settings are presented.     

非最佳量针测量螺纹的定义中径

通过最佳和非最佳2组三针测量同一螺纹的中径,实现了对螺距、牙型半角都有误的螺纹的单一中径和中径的准确测量.介绍了不需要按传统的三针测量方法复杂地修正程序来求解修正值的新方法,并对该方法进行了不确定度分析.该方法简便易行,非常适合工厂加工过程中精密螺纹工件中径的精密测量和工厂计量室对螺纹塞规周期检定中的中径测量.     

A novel internal thread defect auto-inspection system

This paper describes a novel optical thread plug gauge (OTPG) for internal thread inspection using machine vision. The OTPG is composed of a rigid industrial endoscope, a charge-coupled device camera, and a two degree-of-freedom motion control unit. A sequence of partial wall images of an internal thread are retrieved and reconstructed into a 2D unwrapped image. Then, a digital image processing and classification procedure is used to normalize, segment, and determine the quality of the internal thread. The proposed OTPG provides an orientation-free and convenient method for detecting defects such as scratches, collapses, and flaws in an internal thread.     

提高模具电火花加工切割形状精度的途径

电火花线切割是模具零件的主要加工方式。模具加工精度包括表面粗糙度、形状位置精度和尺寸精度,慢走丝线切割难以控制表面粗糙度和形状精度。影响数控电火花线切割加工精度的因素主要有偏移量、取件位置、切割路线、起点、装夹与定位及引入、切出、超切、回退程序等。通过进行合理的工艺分析,正确计算数控编程中电极丝的设计走丝轨迹,可确保模具的加工精度。通过确定穿丝孔和优化切割路线来改善切割工艺,是提高模具型腔切割质量和生产效率的一条行之有效的重要途径。     

基于应力转换的内螺纹高周疲劳强度分析方法

螺纹具有特征尺寸小、结构复杂的特点,其非线性接触的有限元分析具有很高的难度,因此机械零件强度仿真分析时螺纹通常被忽略,只根据经验对螺纹作保守设计。事实上承受循环重载的零件极容易从螺纹部位发生疲劳断裂,在设计阶段有必要进行疲劳强度校核。针对此问题,提出了一种基于应力转换的内螺纹高周疲劳强度分析方法。此方法把螺纹根部应力分解为近源应力和远源应力两部分,通过无螺纹简化模型仿真获得螺纹接触压力和摩擦力之后转换为近源应力和远源应力并叠加得到螺纹根部最大应力,最后考虑应力梯度、存活率和表面粗糙度等因素的影响系数,借助Haigh图计算各扣内螺纹的疲劳安全系数。把这种方法与带螺纹的细节模型有限元仿真和疲劳强度分析结果进行对比,所提方法的安全系数结果与细节模型的相应结果相差–7.6%;把这种方法应用于某型号缸体主轴承壁,其分析结果与疲劳试验结果相差–8.2%,证明了它的可行性。     

A Machine Vision Approach for Detecting and Inspecting Circular Parts

In this paper, we present a machine vision approach for detecting and inspecting circular parts and parts with circular arcs on the contours. The method uses the Hough transform technique and uses the directional information of a normal to the circle at each boundary point. Cubic polynomial curve fitting is used to estimate the normal, and determine the concavity of the fitted curve at each given boundary point. The proposed Hough transform method is a two-stage pro-cedure. The first stage uses a 2D accumulator array to detect circle centres. The second stage uses a 1D accumulator array to detect the radii of circles. The proposed method is robust for detecting circular parts with partial occlusion such as peripheral defects or burrs. For an image of size N × N, the storage requirements are N 2 and the time complexity is bounded by (N+m)n, where m is the number of circle centres detected in the first stage and n is the number of boundary points in the image.     

基于FANUC系统B类宏程序的内外螺纹的数控铣削加工

数控机床使用丝锥攻丝、板牙套扣等常规方法虽可进行内外螺纹加工,但是一种规格的丝锥或板牙只能加工一种规格的螺纹,一般只能加工单线螺纹,多线螺纹几乎无法加工。论文利用FANUC数控系统G02/G03螺旋插补和B类宏程序功能,通过M37×Ph5P2.5实例,对刀、计算后编制宏程序,完成了内外螺纹的数控铣削加工,此加工方法不受螺纹直径、螺距大小、旋向、线数、工件复杂程度的影响,螺纹刀具品种也可以变少,适用性较强。     

考虑反向螺旋的双螺杆磨浆机挤压建模

轴向力和功耗是双螺杆磨浆机设计的重要参数,目前尚无理论计算方法。根据实验观察和分析,固体料塞是影响双螺杆磨浆机轴向力和功耗的主要因素。料塞一般出现在双螺杆磨浆机反向螺旋和正、反向螺旋的结合区域。考虑反向螺旋中料塞的作用,根据力平衡原理建立了反向螺旋料塞的剪切模型和流动模型,根据该模型可以求解双螺杆磨浆机螺杆扭矩、功耗、轴向力和流率。与实验测量结果相比,当反向螺旋扣数、反向螺旋狭槽宽度变化时,理论计算和测量结果有较好的一致性。该研究对双螺杆磨浆机的优化设计具有重要的意义。     

双点火间隙等离子流火花塞的设计及其特征长度的研究

根据火花塞点火放电过程中三个阶段等离子流能量的变化,通过改变火花塞电极结构,增大带电粒子的动量进而提高火花塞点火性能。设计了双点火间隙电极结构的等离子流火花塞,该火花塞工作时两个间隙同时点火形成双火核,等离子流能量增大,火焰传播速度快,点火能量及起动性增强。放电测量结果为,当特征长度L＋=10mm,电极间隙h=1.0mm时,点火电压为19000V,最大峰值电流为200A,点火能量为103mJ。     

新型石油套管螺纹检查台的设计

根据平面四连杆机构原理设计了新型石油套管螺纹检查台。该检查台可借助钢管重力使套管从一个检查工位自动移送至下一检查工位 ,实现对石油套管管端螺纹的连续检测。     

Electromagnetic superposed forming of large-scale one-dimensional curved AA2524-T3 sheet specimen

This study proposes a methodology for helical mill-grinding of tiny internal threads made of hard brittle materials such as SiCp/Al composites. The methodology uses the helical mill-grinding method incorporating with a diamond form-grinding wheel. A mathematical model is established to predict thread form errors and provide a rational range of wheel parameters, such as variation of tool profile angle Δα and ratio of the wheel diameter to the thread major diameter η. Based on the methodology, a grinding wheel is developed for processing the M2 internal threads in a validation experiment. The study demonstrates that an M2 internal thread made of the SiCp/Al composite of 45% SiC volume fraction is successfully machined in 5 min with pitch error <0.08% and angle error <0.3%. The thread profile on the pitch diameter is within the axial equivalent tolerance zone (0–0.016 mm), which indicates that the thread precision reaches the H4 level.     

基于主成分分析的BP神经网络内螺纹冷挤压成形质量预测

根据冷挤压内螺纹成形中径、螺距、牙型半角和牙高率等来综合评定内螺纹的成形质量等级,并基于BP神经网络对其进行预测。在BP神经网络预测模型数据前处理过程中,采用主成分分析方法以提取影响内螺纹冷挤压成形质量的主要因素,消除各影响因素之间的线性相关性。试验结果表明,与传统的BP神经网络相比,采用该方法的BP神经网络模型,简化了网络结构,提高了收敛速度及预测精度,能准确实现内螺纹成形质量等级的预测,从而为内螺纹质量的检测提供了一条新途径。     

三爪自定心卡盘盘丝平衡计算及分析

本文研究了三爪自定心卡盘盘丝平面螺纹的质径积与平面螺纹的起止点的相位之间的关系，找到了使盘丝质径积获得极小值的一般规律，以及该极小值的大小和相位。为盘丝的合理设计提供依据     

Glycoproteins and skin-core structure in Nephila clavipes spider silk observed by light and electron microscopy

Microscopical imaging of natural, unstressed draglines or of untreated bulk samples showed two types or threads with diameters of either approximately 1-2 microm or 4-5 microm, which could be identified as products of the minor or major ampullate glands. The threads had a circular profile in serial cross sections and are surrounded by a thin outer layer of a different material within the section. Such fibrillar configurations were also found in untreated threads or in the same serial sections of transmission electron microscopy (TEM) samples by means of the special technique of laser scanning microscopy. In TEM slides, numerous cavities with the same circular profile were detectable, and the length of these cavities is variable from 40-300 nm. The threads are oriented parallel and twisted around themselves to construct a double thread. In the interface between the two single threads, bridge-like structures are prominent. The single untreated thread consists of cylindrical fibers with a diameter of approximately 1-1.5 microm. Apparently more than eight fibers are within a thread and each fiber is composed of a great number of fibrils with a diameter of about 150 nm. The surface of threads is coated with a characteristic layer approximately 150-250 nm thick that contains glycoproteins. These were demonstrated for the first time by labeling with concanavalin A lectin-gold complex and are dependent on the diameter and length of the thread. The same substances could also be detected inside the single thread. The skin can be removed completely or partially by mechanical treatment, or by washing with phosphate-buffered saline or trypsin.     

基于UG的内螺纹瓶盖注塑模设计

UG MoldWizard是UG系统的一个独立的智能化设计注射模具的模块,它运用知识嵌入的基本理念,按照注射模具设计过程的一般顺序来实现模具设计的整个过程.在本次内螺纹瓶盖的设计中,充分体现UG在注塑模设计中的高效和快捷.通过对内螺纹瓶盖工艺分析,巧妙地采用镶块成型内螺纹和项出塑件,从而简化模具结构.并对模架、浇注系统...     

Flow direction characteristics in the vicinity of the spark plug in an S. I. Engine

The flame speed may be decomposed into the burning speed and the flame transport speed. The flame transport speed is affected considerably by the flow direction, variation rate of flow direction, and flow speed in the combustion chamber. Especially, the flow direction and the variation rate of flow direction at the spark plug location during the ignition period have an important effect on the ignition process and the early flame propagation process. We measured the flow direction component and the variation rate of flow direction with a hot wire probe at the spark plug location. It was shown that the representative flow direction of ignition period is the right-vertical direction of crank shaft and it was used to investigate the variation rate of flow direction.     

汽车零部件无损检测技术

无损检测技术是一种在不破坏受检对象的前提下测定、评价物体内部或表层物理和机械性能及各类缺陷和其他技术参数的综合性检测技术.其应用范围随着科学与生产的发展日趋广泛. 在汽车制造行业中无损检测的应用十分广泛.许多汽车零部件,如制动鼓、制动盘、轴颈、转向节等关键的安全件,如果零部件表面出现细微裂纹,或者内部有缺陷,在长期交变应力的作用下,裂纹会从外表逐渐向内发展,或者由内向外延伸,进而产生安全隐患.因此,上述零部件在生产制造过程中,必须经过一系列的无损检测.常用的汽车零部件无损检测有射线检测、超声检测、电磁涡流检测、磁粉检测和渗透检测,亦称五大探伤方法.     

Experimental study of fine center electrode spark plug in bi-fuel engines

In the present work, the erosion of platinum fine center electrode spark plugs and conventional nickel plugs are investigated in a gasoline and natural gas bi-fuel engine. The effect of electrode erosion is evaluated by comparing the required ignition voltage and cold start ability of the different plug designs. After durability tests, platinum fine center electrode plug had insignificant electrode erosion and negligible gap growth; whereas the nickel plug had notable erosion and gap growth. There was no detectable side sparking for fine center electrode plugs. In terms of performance, the required ignition voltage of fine center electrode plug was lower than conventional spark plug. Also, results of a cold start test demonstrated that the starting time of the engine with fine electrode plugs was lower than conventional spark plugs. The surface of electrodes was studied by the scanning electron microscope and the energy dispersive X-ray spectroscopy techniques. Cracking and peeling was observed on the surface of the nickel conventional electrodes, but not on the surface of the platinum fine electrodes. These tests show that platinum fine center electrodes could be suitable for gasoline/natural gas bi-fuel engines to meet long lifetime demand.     

Duplex positioning method for increasing the fatigue life of threaded connections under eccentric loading

A new method, duplex positioning method DPM, to increase the fatigue lifetime of the threaded connection under eccentric loading is presented. When DPM is applied, the most damaged stud regions periodically are removed from risky positions by a change of the stud’s and nut’s mutual position in the axial direction alongside with a change of the stud’s position in respect to bending plane. The mathematical model for DPM enables us to predict its efficiency. To simulate the fatigue strength of the stud the following was used: Patterson’s and Kenny’s thread deflection factors, solutions for the distributions of the axial load and bending moment along the threads, Neuber’s method for the stress concentration factors in multiplier notches, Heywood’s formulas for the stress due to the thread flank loading and for the combined stresses, as well as the results of the photoelastic analysis of the araldite models under eccentric loading.

     

基于55°密封管螺纹的锥螺纹数控加工研究

通过对我国管螺纹现行标准、作用、工艺及功能特点的详细介绍,探讨了以数控加工的方式进行55°密封管螺纹的圆锥外螺纹的加工思路、工艺参数选择及程序编制。通过对55°密封管螺纹的数控加工工艺的研究发现,数控加工管螺纹不但可以提高加工精度及加工效率,而且在切削过程中选择适当的切削用量,可以较好地保证加工质量。