水(地)源热泵机组运输过程中压缩机固定螺栓断裂原因分析

在模拟水(地)源热泵机组出厂运输过程中多次出现压缩机固定螺栓断裂的问题,本文通过对螺栓设计强度、材质、安装工艺、载荷分布等方面进行排查,并结合整机结构做受力仿真分析,确定机组结构设计不合理为螺栓断裂根本原因。通过改进冷凝器底部支座与机组底座的结构,进行有限元分析及运输环境振动试验,结果表明机组结构完好,未发生压缩机螺栓断裂问题,机组结构整改合格。     

电站稳压器支承裙座锚固螺栓断裂失效分析

某电站稳压器支承裙座锚固螺栓在安装一段时间后发生断裂,从力学和材料角度对该螺栓断裂原因进行了分析。对断裂螺栓进行了金相组织观察、化学成分分析、力学性能试验以及断口的宏观及微观形貌观察,发现螺栓断口附近组织异常,外部环状带晶粒粗大,硬度和抗拉强度偏低导致裂纹启裂,裂纹逐渐扩展引起螺栓整体失稳断裂;螺栓局部出现组织异常的原因为螺栓热处理过程中控温不当导致局部过热。     

钛合金高锁螺栓断裂原因分析

某飞机用钛合金高锁螺栓在装配过程中发生断裂。通过宏观分析、微观分析、金相检验、力学性能复查和装配现场调查等方法对螺栓的断裂原因进行了分析。结果表明:该钛合金高锁螺栓为单边弯曲应力造成的过载断裂,与螺栓制造质量无关。螺栓装配区域操作空间狭小,安装时扳手的转动平面易发生倾转,从而在螺栓上形成弯曲应力,建议改进装配工具。     

高加抽汽管疏水阀气动执行机构螺栓断裂原因分析

某核电厂大修期间,发现高压加热系统中疏水阀气动头与阀门本体连接的6颗内六角沉头螺栓中有5颗发生了断裂。通过分析断裂螺栓材料、力学性能、显微组织和断口等,并结合阀门实际运行信息,认为疏水阀气缸中的工作压力超过公称压力致使螺栓长期处于高的拉一拉型交变应力状态,从而引起螺栓的疲劳断裂。同时提出了防止该类螺栓在其使用过程中发生类似断裂事故的建议。     

70推土机主离合器分离杆螺栓失效分析

主离合器分离杆螺栓是一个重要安全件，使用中经常发生断裂。经过失效分析确定断裂原因是由其配件引起。提高配件的冷加工质量及改进结构，可解决分离杆螺栓的断裂问题。     

某飞控部件连接螺柱断裂分析

通过断口分析、金相检验和硬度测试查明了连接螺柱断裂失效的机理和过程,并结合有限元分析得出连接螺柱在疲劳载荷下的动响应,对失效的原因做出判断。结果发现：连接螺柱疲劳抗力不足以及飞控部件承力构件布局不合理是造成连接螺柱断裂的主要原因。最后,从工艺和结构方面有针对性地采取了改进和预防措施,避免同类失效的再次发生,达到改进产品质量、延长使用寿命、提高服役安全性和可靠性的目的。     

70推土机主离合器分离杆螺失效分析

主离合器分离杆螺栓是一个重要安全件，使用中经常发生断裂，经过失效分析确定断裂原因是由其配件引起，提高配件的冷加工质量及改进结构，可解决分离杆螺栓的断裂问题。     

柴油机用高强度螺栓断裂失效分析

某柴油机用30CrMoSi钢高强度螺栓在使用过程中发生断裂。通过化学成分分析、金相检验、断口分析、硬度测试等方法对螺栓断裂原因进行了分析。结果表明:螺栓断裂为早期疲劳断裂,螺栓螺纹根部存在加工缺陷以及螺栓材料中存在较多的非金属夹杂物是导致其疲劳断裂的主要原因。最后针对螺栓断裂原因提出了预防措施。     

新能源客车电容支架安装螺栓的断裂原因分析

某新能源客车上的电容支架固定螺栓发生批量断裂。通过对断裂螺栓进行宏观观察、力学性能测试、金相检验、化学成分分析等,分析了其断裂原因。结果表明:螺栓的断裂为双向弯曲疲劳断裂;发生断裂的主要原因是电容支架与车架连接结构设计不当,导致结构松动,使螺栓受到弯曲交变应力作用;次要原因是螺纹表面脱碳,降低了螺栓的疲劳强度。     

高压容器用螺栓断裂失效分析

某高压设备进行水压试验前准备,在拧紧螺栓过程中有一螺栓发生断裂,通过对断裂螺栓进行化学成分分析、力学性能试验、金相检验以及断口分析,找出了螺栓的断裂原因。结果表明:由于螺栓原材料在切除冒口时切除量不够,使螺栓中存在较多的夹杂物,夹杂物容易导致应力集中并萌生微裂纹,在螺栓后续加工过程中受到力(拉拔应力和热处理内应力)作用时,裂纹不断扩展并形成空洞,从而导致螺栓在拧紧过程中施加较小的外力就发生了断裂。     

Failure analysis of a pressure vessel bolt in a nuclear fuel fretting wear simulator

This paper presents a failure analysis on a pressure vessel bolt of a fretting wear simulator. After 500 h tests, in an upper pressure vessel of a fretting wear simulator, one bolt among eight was fractured near the bolt neck regions. The fracture surface was examined by using a scanning electron microscope (SEM) to determine the failure initiation and failure mode. The result indicates that the fracture surface shows intergranular fracture features. Based on the mechanical property data of a bolt material, it is concluded that the exerted stress on the bolt applied by an internal pressure of the pressure vessel has a negligible effect on the major failure causes. In order to verify the mechanical properties of the fractured bolt, tensile test has been performed and its result was compared with material specification. As a result, it is thought that both excess heat treatment during the surface hardening procedure and loose parts in the thread hole have significant effects on the pressure vessel bolt failure. In this paper, the reasons for this failure were discussed by using metallographic studies of the failure surface, mechanical tests with the failed bolt and the stress distribution of the contact regions with considering loose parts by using FE analysis.     

普通螺母及自锁螺母对螺栓标定特征曲线的影响

采用纵波法并使用自制的内螺纹夹具,分别选择普通螺母和自锁螺母来标定螺栓,通过不同的拧紧策略和标定方法,分析普通螺母和自锁螺母标定螺栓特征曲线的差异。结果表明:采用普通螺母和自锁螺母标定螺栓因方法不同会获得不同的标定特征曲线,自锁螺母的锁紧扭矩使螺栓温度升高导致超声波声时差增加,因此获得的标定特征曲线会平行右移。     

汽轮机高压外缸结合面双头螺栓断裂分析

某电厂汽轮机高压外缸结合面双头20Cr1Mo1VTiB钢螺栓在安装时发生断裂,通过断口分析、化学成分分析、金相检验以及力学性能测试等方法对螺栓的断裂原因进行了分析。结果表明:该螺栓钢存在严重的显微组织缺陷,力学性能指标不符合技术条件要求,减弱了螺栓的承载能力,螺纹处的应力集中效应会加剧螺栓的缺口敏感性,导致螺栓在安装时于螺纹处发生脆性断裂。     

非线性间隙杆单元的特性及其迭代算法

螺栓与栓孔之间间隙引起的非弹性变形是栓接结构产生挠度的一个重要原因.该文根据有限元的基本方法,建立了有间隙拉压杆单元,能够模拟有间隙栓接结构的力学行为,并准确计算出连接节点处间隙引起的结构的非弹性变形,并针对间隙单元的特点提出了基于剩余荷载系数增量理论的迭代求解方法.该文提出的计算方法为贵州省正安县桑坝大桥施工过程中拱...     

Characterisation of Contact Pressure Distribution in Bolted Joints

Abstract: The quantification of contact area and pressure distribution in a bolted joint is essential information, as it determines the integrity of the coupling. Current bolted joint design standards are based on analytical solutions of the pressure distribution, which, because of the inherent assumptions, frequently do not accurately represent the real conditions in a joint. This study uses a non‐intrusive ultrasonic technique to quantify the contact pressure distribution in a bolted connection. The advantage of this experimental technique is that the effect of actual contact conditions can be determined. An ultrasonic wave is focused onto the clamped interface, and the reflected sound signal recorded. In areas where the contact pressure is high, most of the ultrasound is transmitted, and the reflected sound signal is weak. Whereas, when the contact pressure is low, the vast majority of the ultrasound is reflected back. A parallel experimental calibration is then used to find the relationship between the reflected sound signal and contact pressure. In this way, the pressure distribution in a clamped interface is determined for a series of different bolt torques. Two different interfaces were investigated: the first consisted of two ground surfaces clamped together, and the second a turned profile pressed against a ground surface. The effect of a washer underneath the bolt head was also considered. The turned profile was found to cause the contact to spread; there was also a certain degree of fragmentation leading to higher peak pressures than in the ground interface case. With a washer positioned under the bolt head for the turned case, the clamping performance of the bolt was improved. Good agreement was found when comparing the ultrasonic measurements with previous studies, with respect to the spread of the contact pressure distribution. However, in this study, the peak contact pressure was found to occur away from the edge of the bolt hole, and to be influenced by the edge of the bolt head.     

几何参数对拉伸试验的影响

分析了拉伸试验过程中出现的异常断裂情况,用非线性有限元分析系统Deform-3D软件模拟拉伸试验过程,研究了在各种几何参数变化和与夹具装配中出现尺寸偏差时试样上的应力分布情况及出现失效破坏的位置,其结果可用于材料试样的几何参数设计以及进一步的夹具优化设计。     

单向纤维复合材料的偏轴实验方法开发与评价(英文)

This study presents an integrated method suitable for off-axis tension and compression testing in unidirectional composites,and its application to the testing of in-plane shear characterization.A new rotating-grip test fixture,incorporating the attractive features of the existing pinned-end fixture and hydraulic wedge grips,has been developed.The proposed gripping system consists of two sets of jaw faces,each with a pair of self-aligning bearings that allows for loading in the axial and radial directions.Fi...     

基于四连杆结构的兼容型气囊式夹具

目的解决夹具在抓取圆柱桶时产生的桶体变形、桶外观破坏及夹具不能兼容不同桶型的问题。方法设计一种气囊式夹具,通过四连杆结构保证爪体始终垂直,通过气缸调整爪体间距。结果四连杆结构节省了夹具的空间,调整气缸保证了夹具工作时对不同圆柱桶的兼容性,气囊避免了圆柱桶的的外形受到破坏,双行程抓取气缸降低了设计和制造成本,同时能够使夹具适应具有锥度和翻边的圆柱桶。结论该夹具经实际应用,工作可靠,运转良好,具有推广价值。     

弱刚性机匣橡胶减振柔性夹具研究

薄壁机匣的径向刚度低,在加工过程中易出现颤振,影响工件表面加工质量和加工效率。因此,设计了一种橡胶减振柔性夹具,其可大面积地支撑工件内壁,从而提高工件的加工刚度。建立了工件?夹具系统等效动力学模型,通过机匣铣削实验验证了模型的准确性。对比分析了橡胶减振柔性夹具与传统夹具的减振性能,研究了铣削力加载频率、压板压力、T形压板压力和推动块压力对工件?夹具系统的振动影响。结果表明：工件在采用减振夹具工况下加速度有效值相较于采用传统夹具减小了43.33%;采用橡胶减振柔性夹具后,工件可以避开400~900 Hz范围内剧烈振动的频率区间,振动幅度大大减小;随着压板压力的增大,工件加速度有效值先减小后增大;针对不同高度工件,应采用不同的压板压力,以减小加工过程中工件的振动;在实际加工中,T形压板压力应超过3.56 MPa,推动块压力应超过0.26 MPa,即液压缸推力超过20 kN。研究结果对橡胶减振柔性夹具的现场应用具有重要的指导意义。     

卡环式扭矩测试系统在抽油机上的应用

由于抽油机输出轴的不可拆卸性,目前对于其功率的测试还没有合适手段,本文介绍的方法是采用卡环式扭矩测试系统来实现对抽油机功率的测试,介绍了抽油机的工作原理、卡环式传感器的结构、测试系统的软硬件结构以及此方法的应用领域.