螺纹紧固件工程应用研究

螺纹紧固件在工业生产中应用广泛,螺距、旋合长度、拧紧力矩是正确选用螺纹紧固件、提高螺纹紧固件连接可靠性的关键参数。对螺纹紧固件的螺距、旋合长度进行了介绍,对拧紧力矩进行了计算,并对扳手的选用进行了分析。     

压水堆堆内构件异种材料螺纹联接件在热循环载荷下的疲劳试验分析研究

压水堆电厂的反应堆堆内构件中的螺纹联接件与一般联接件不同,在高温、辐照环境中工作,除承受机械载荷外,还承受由于水流以及地震等引起的动态载荷。而在寿命期内反复的冷-热-冷循环,会使异种材料联接件产生交变循环热应力,甚至会使预紧力松弛,因此预紧力合适与否将直接影响联接件联接的可靠性。对通过模拟实际联接结构的联接件进行热循环试验和分析,研究热循环载荷对预紧力和联接结构的影响。     

Tensile behaviour of threaded steel fasteners at elevated rates of strain

The tensile behaviour of threaded steel fasteners was studied experimentally at elevated rates of strain. Two testing techniques were used to perform the tests at strain-rates in the range from 10⁻³ to 1.9×10³ s⁻¹. The tests at low and medium strain-rates were performed in a servo-hydraulic testing machine, while tests at high strain-rates were achieved using a split-Hopkinson tension bar. All tests were carried out using a purpose-made fixture to ensure uniform test conditions, and to control the location at which failure by thread shearing could occur. The material tests and the threaded assembly tests showed approximately the same trend of an increased strength with increasing strain-rate. Owing to the strength ratio between the purpose-made fixture and the threaded fastener, two of three possible failure modes occurred during the performed tests, i.e. bolt breaking and bolt thread stripping. The length of the thread engagement, the grip length and the strain-rate had an influence on the failure mode. In addition, these parameters had varying effect on the strength and ductility of the threaded assembly. A modification of the Alexander [4] model was proposed, to predict the maximum load and mode of failure of threaded steel fasteners at high strain-rates. The modified model was in good agreement with the experimental results.     

弹上设备螺纹联接在温度循环载荷下的分析研究

弹上设备螺纹联接结构承受温度循环载荷作用时,由于螺纹紧固件和联接体材料特性不同,会产生交变循环热应力,影响螺纹联接的可靠性。利用有限元方法分析螺纹联接结构在温度循环载荷作用下的力学行为,对不同材料的螺纹紧固件和联接体进行分析,得到应力、接触压力和残余预紧力的变化情况,为工程设计提供了可靠的依据。     

Bearing Friction Torque in Bolted Joints

Formulas are developed for calculation of the effective radius of the bearing friction forces on the rotating contact surface in threaded fasteners. These formulas provide a more accurate estimation of the underhead bearing friction torque component in threaded fastener applications. This enhances the reliability, safety, and quality of bolted assemblies, especially in critical applications. It is well known that the torque-tension correlation in threaded fasteners, and the resulting joint clamping force, is highly sensitive to friction torque components: under the turning head and between threads. This analysis focuses on the bearing friction torque component under the turning head of a threaded fastener. Furthermore, it analyzes the error contained in the current practice when an approximate value, equal to the mean contact surface radius, is used instead of the actual bearing radius. New formulas for the bearing friction radius are developed for a mathematical model of a bolted joint using four different scenarios of the contact pressure distribution under the rotating fastener head or nut. The effect of the radially varying sliding speed over the rotating contact surface is analyzed and compared with a constant-friction-coefficient scenario. Numerical results and error analysis are presented in terms of a single nondimensional variable, namely, the radii ratio between the outside and the inside bearing area.     

由振动引起的螺栓连接预紧力松脱的数学模型

引入一种数学模型以研究螺纹连接在横向振动作用下引起的松脱.此横向振动激励会引起螺纹接触面间的滑动以及螺栓头与支撑表面之间的滑动.式中包括剪切力、支撑力以及螺纹摩擦阻力矩,它们均与振动速度相关,当所施加横向振动激励足够大时,螺纹连接会出现松脱现象.本文研究了螺栓预紧力、支撑力及螺纹摩擦系数、横向振动激励以及螺栓头下部弯矩...     

钛合金单面螺纹抽钉内螺纹热攻丝

钛合金单面螺纹抽钉的内螺纹加工一直是个难题,纵锥经常扭断。这里在分析了紧固件热攻丝机理的基础上,对热攻丝新工艺进行了初步的试验研究,得出热攻丝可降低切削力和提高螺纹精度。     

Manufacturing and use of novel sensoric fasteners for monitoring forming processes

This paper presents sensoric fasteners which are produced by metal forming. Sensoric fasteners enable the monitoring of pretensioning forces and operating loads in mechanical connections between components. For the gathering of combined force and torque sensor signals in individual spatial directions the sensor unit has to provide the capability to transmit loads in all directions of space. The elementary sensors are integrated into the metallic fasteners structure during manufacture. This results in an assembly of supporting structure and sensor which shows a highly reproductive and sensitive interaction between its mechanical and electrical properties. In order to evaluate this interaction calibration measurements are carried out.With the help of examinations of both stationary and transient running manufacturing processes it can be shown, that the new fasteners provide the mechanical connection between tools and machine as well as the possibility to monitor operating loads. The latter allows monitoring and analysis of process forces acting within the mechanical connections.     

数控铣床加工端面螺纹的方法

利用数控铣床的宏程序功能与端面螺纹的阿基米德螺旋线特性来加工端面螺纹,具有工艺设计简单,程序编制简单,经济性好的特点;通过对端面螺纹加工的工艺分析和宏程序编制方法的详细论述,介绍了端面螺纹在数控铣床上的加工过程。     

A machine vision system for the detection of missing fasteners on steel stampings

A machine vision system that has been developed for the detection of missing fasteners on steel stampings is described. The system has been tested using images generated by a commercial machine vision system installed on an assembly line for the production of automotive cross-car beams. This particular application was considered to be challenging due to variations in the operating conditions, such as the lighting, together with the fact that the appearance of the fasteners could change depending upon their angle relative to the camera. A neuro-fuzzy image classification algorithm was developed and tested against a threshold-based classification algorithm. Results indicate that both algorithms perform well when optimized, but the neuro-fuzzy algorithm was found to degrade in a less abrupt fashion when the input data deviated from the trained data. A graphical user interface (GUI) was designed to enable implementation on the assembly line. The developed system is adaptable to other machine vision-based automated inspection applications.     

超长、大管径精密螺纹套管专用数控套车机床研究

介绍了一种用于管长12 m、管径φ200～550 mm的多头、变螺距精密螺纹套管加工的专用数控套车机床的工作原理、基本组成.重点分析了该机床数控径向切削进给的实现方法,以及多刀同时切削多头螺纹的技术实现,给出了工程应用实例.     

薄壁深腔小径螺纹的数控加工研究

常规生产中的小径螺纹加工时丝锥特别容易断裂,经常造成昂贵工件的报废.针对该问题,以某汽车电路防护盖薄壁深腔小径螺纹的加工为例,阐述了在数控加工中心机床上加工薄壁深腔工件小径螺纹的加工策略.从工艺角度进行了具体分析,设计了必要的支撑夹具,并采用浮动攻丝夹头装夹挤压丝锥进行攻丝,避免了非正常的丝锥断裂或螺纹烂牙.     

万向支架微小螺纹副自动装配系统

针对万向支架微小螺纹副装配自动化程度低、一致性差的问题,研制了一套自动装配系统,并对装配过程中的微小螺纹零件中心位置提取方法和多个微小螺纹副之间的装调策略进行了研究.首先,提出了一种改进的清晰度评价函数,并基于该函数实现了机器视觉装置的自动聚焦.然后,针对螺轴以及内环螺纹孔的端面特征不对称问题,提出了变聚焦位置分区域图...     

基于特征识别的紧固件快速装配方法研究

为了提高紧固件的装配效率,文中提出了一种基于特征识别的紧固件快速装配方法。首先提取零件上所有孔特征,进而在部件中提取所有装配孔特征;然后通过装配知识推理自动匹配得到紧固件的组合模式;提出一种更简便的装配特征定义方式,实现了紧固件的快速自动装配。最后,建立了紧固件快速装配流程,并以某部件为例演示了紧固件的快速装配,验证了方法的有效性。     

一种热控制器紧固件连接的安全分析与校验研究

以大型航天探测器AMS-02热控制系统结构测试件的连接为例,研究了航天器紧固件连接的安全校验方法。简化了热控制系统的有限元模型,通过大型有限元分析软件NASTRAN分析了施加在各连接紧固件上的轴向力和合成力。根据NASA提供的校验准则,计算得到了各类连接的安全裕度值。对于部分安全裕度值小于零的连接处,应更换强度更大的紧固件并重新进行安全校验,为航天器的最终设计提供了依据。     

钛合金紧固件在机械加工中存在的问题及措施

钛合金紧固件在机械生产加工当中使用范围广泛,构件的精准度和强度很高,各方面综合性能优越,能够运用到机械加工当中的各个领域,是一种加工生产的好材料。在钛合金紧固件使用的时候,也存在一定缺陷,这些缺陷直接影响了产品使用过程当中加工的质量,使加工存在一定的问题。本文从钛合金紧固件在机械加工当中存在问题及其改进措施进行探讨分析。     

[轮轨磨耗及预测]地铁直线轨道钢轨波磨影响参数研究

基于车辆轨道耦合动力学模型和钢轨材料摩擦磨损计算模型,分析了不同轨道结构参数和车辆运营速度对地铁直线轨道钢轨波磨发生和发展的影响。结果发现,对于不同的变量参数,轮轨接触斑内摩擦功率随时间的变化都具有一定的波动性,且摩擦功率整体波动幅度较为均匀。同时,摩擦功率1/3倍频程图分析结果表明,摩擦功率的特征频率主要集中在中低频范围。在主要特征频率处,扣件纵向刚度、纵向阻尼、横向阻尼和垂向阻尼对钢轨波磨的影响较小,扣件横向刚度、垂向刚度、扣件间距、轮轨摩擦因数和车辆运行速度对钢轨波磨的影响较大。扣件垂向刚度和扣件间距的变化会导致摩擦功率的特征频率发生偏移,主要特征频率从80 Hz偏移至100 Hz,从而导致对应波长的钢轨波磨,说明扣件垂向刚度和扣件间距对特定频率处钢轨波磨的产生和发展具有重要的影响。其余变量的增大并未导致摩擦功率的特征频率发生改变,表明其余变量不影响钢轨波磨的特征频率。     

落地车床螺纹加工装置设计

对传统落地车床尾座进行改造,将机床主轴的运动通过尾座顶尖传出,经过变速机构和挂轮机构,将运动传递到刀架,实现对螺纹加工内联系传动链的建立和传动比的调整。在解决多线螺纹加工上,利用了圆周单齿啮合离合器等机构,实现多线螺纹的圆周分线。该装置能很好地解决分体式落地车床螺纹加工困难的问题,运动传递准确,结构较为简单,实用价值大。     

石油套管特殊螺纹接头的密封设计

利用有限元技术和全尺寸试验相结合的方法,研究了石油套管特殊螺纹接头密封设计的方法。给出了设计石油套管特殊螺纹接头时,既能保证其密封性,又不至于发生粘结损坏的条件。最后利用数控机床加工出了这种接头,并进行了全尺寸评价试验,结果显示该接头的密封性能达到了设计目标,表明确定的特殊螺纹密封设计的方法是可行的。     

汽车紧固件常见问题及预防措施的研究

汽车紧固件作为串联汽车关键零部件的基础件,其质量的好坏对整车性能和安全性有着直接的影响.文中根据紧固件在装车前、装车时和装车使用后常见问题的统计分析结果,对紧固件故障类型和原因进行了分类.重点讨论了紧固件因混料问题、疲劳断裂、热处理问题、表面处理问题及过载断裂而产生的失效模式,并结合几种典型失效案例,详细分析了这些问题...