NTK300型风电机组主轴疲劳断裂失效分析

随着风电机组服役时间的逐年增长,早期投产的风电机组陆续出现主轴的疲劳断裂事故。本文结合国内某风电场的NTK300风电机组主轴断裂问题,对断裂主轴进行宏观和微观断口分析,结果表明:风电机组主轴在额定工况载荷作用下,虽工作应力水平较低,应力集中不明显,但长期服役后仍可能发生疲劳断裂。同时,通过有限元分析发现,额定工况载荷作用下的主轴在断裂位置处应力分布相对集中。通过主轴高周疲劳断面SEM图片的对比发现,主轴在断裂位置的轴向截面应力分布梯度与某一时刻疲劳裂纹萌生和扩张的方向基本一致。     

某无人机用涡喷发动机主轴疲劳寿命计算

涡喷发动机主轴所承受载荷十分复杂,扭矩、轴向力、离心载荷和陀螺力矩等载荷共同作用于主轴,在高温区还承受热负荷。在这些交变载荷共同作用下,疲劳断裂失效是其主要失效模式。根据无人机的任务剖面,编制该无人机用涡喷发动机主轴的疲劳载荷谱;并用工程估算方法得到该涡喷发动机主轴的S-N曲线,基于ANSYS建立有限元模型并进行疲劳寿命分析,给出了该涡喷发动机主轴的寿命。     

摩擦焊机主轴断裂失效分析

对中国某型号摩擦焊机主轴断裂失效事故展开实例研究。对断裂主轴的化学成分、金相组织等进行分析,结果表明:主轴断口形貌具有明显的贝纹扩展特征,断面总体上属于低公称应力和偏载应力集中状况下的旋转弯曲疲劳断裂。     

电梯主轴断裂失效分析

对电梯主轴在使用过程中发生的断裂进行了失效分析.结果表明:电梯主轴由于热处理工艺不当,使得显微组织中存在上贝氏体和硬度偏低,从而在电梯多次启动和停止过程中,主轴因受到交变载荷而于应力集中最为严重、承载面积最小的键槽转角处发生扭转疲劳断裂.     

水厂循环泵主轴断裂失效分析

针对离心循环水泵主轴断裂，校核了断裂处轴径和疲劳强度安全系数，对断口进行了宏观形貌、金相、SEM、能谱及强度分析，并对主轴材料进行了化学成分分析，及硬度、拉伸、冲击性能试验。分析结果表明，主轴断裂主要是由于疲劳断裂原因造成，并提出了相应的防护措施。     

电梯减速器输出轴的疲劳断裂分析

为了找到某型号电梯减速器输出轴突然断裂的原因,通过试验方法得到主轴的化学性能、机械性能和材料性能,进行应力、疲劳强度和疲劳寿命的理论计算。并运用有限元方法对不同曲率半径的键槽进行疲劳分析,和理论的疲劳计算结果相比较,得出断裂的原因是键槽上的低曲率半径引起的高缺口效应。分析结果表明,主轴键槽拐角高应力随着键槽拐角曲率半径增大而减小,疲劳寿命随之延长。     

矿用提升绞车主轴断裂原因分析与预防措施

针对矿用提升绞车在频繁的矿井工作过程中主轴极易出现断裂造成安全事故的问题,对提升绞车的核心部位主轴进行了受力分析,找出了断裂的主要原因——疲劳断裂,并针对这一情况提出了6条预防措施,以确保提升绞车的安全使用和矿井的高效运行。     

柴油机球铁曲轴断裂失效分析

柴油机氮化球铁曲轴在服役过程中发生了断裂,断裂发生在第一曲拐与第二主轴颈之间的曲柄处。对其失效原因进行了分析,结果表明：裂纹起始于第一曲拐右下圆角根部,并在弯曲载荷作用下扩展,最终导致弯曲疲劳断裂;曲轴材料的基体组织、化学成分及力学性能均符合技术要求,渗氮层过浅是曲轴发生疲劳断裂的主要原因。     

5kW离网小型风力发电机主轴的疲劳分析

以处于试制阶段的新型5 kW离网小型风力发电机主轴为研究对象,对该主轴进行了两种工作位置下的极限载荷分析.在确认分析结果正确后找出了该主轴上可能发生疲劳破坏的两个危险点,并得出这两个点的应力变化规律,通过有限元软件ANSYS求出这两个危险点在发生疲劳破坏前应力循环的次数,验证了该主轴能满足设计疲劳寿命.     

废旧机床主轴剩余寿命评估模型

如何准确评估废旧主轴的剩余寿命是其可再制造性评估的关键.基于此,针对废旧主轴的疲劳断裂失效现状,综合考虑裂纹闭合效应,加入裂纹拓展有效因子,提出一种基于非线性连续疲劳损伤模型的主轴剩余寿命评估模型.为提高主轴S-N曲线的拟合精度,疲劳试件是通过原废旧主轴的轴身经线切割加工而成,将主轴谐响应分析获得的六级最大应力,作为拉压疲劳试验的循环应力,从而获得接近实际主轴的S-N曲线.对于主轴剩余寿命评估模型参数求解问题,把试验得到的数据和参数通过非线性拟合中的最小二乘法,构建关于应力和寿命的S-N曲线,采用Python的方法来求解该模型中的参数使主轴的剩余寿命评估模型更具有准确性,来保证预测评估主轴剩余寿命结果的准确性.以某机床集团的CAK5085型数控车床的主轴为例,对其进行剩余寿命评估.通过试验的数据和模型的计算结果进行对比,验证修正后模型的准确性、可行性.     

高速喷漆涡轮转子轴疲劳寿命分析

通过对高速喷漆涡轮转子轴质量等效,将涡轮系统复杂振动转化为简单的单自由度振动问题。在此基础上,论述了等幅应力下有限疲劳寿命分析方法,推算出高速喷漆涡轮转子轴有限疲劳寿命,分析了该转子轴直径、悬臂长、振动幅值及偏心距对疲劳寿命的影响规律。为转子轴的维修和制造奠定基础。     

HSK主轴／刀柄联接锥面的疲劳寿命分析与计算

在分析HSK主轴／刀柄联接锥面疲劳失效的各影响因素的基础上,利用有限元软件NX Nastran中的疲劳分析和计算功能,针对HSK 63E型刀柄在主轴锥孔内反复拉紧和松开的工况进行了疲劳强度和疲劳安全因子的计算,仿真过程和计算结果可以为设计新型HSK刀柄的结构优化、选材和热处理工艺提供理论参考。     

Research on the spindle deflecting reliability of the wellbore trajectory control tool based on Palmgren-Miner

Wellbore trajectory control tool is a sort of point-the-bit drilling tool to achieve the steering function while drilling. In complex conditions, the spindle bears the acting force of the bit pressure, the torque, the force of biasing mechanism and so on. So the force is very complex. Basing on the early research of our group, the further research of spindle deflecting reliability of prototype has been carried out. Based on the contact analysis between the tool spindle and the inner eccentric ring, the variation law of contact stress between the inner ring of the eccentric mechanism and the spindle is studied. Based on Palmgren-Miner and the fatigue life experiment of the spindle material, the cumulative damage calculation model of the spindle is established, and the fatigue life of spindle is solved. The result shows that the deflecting reliability of the spindle can be guaranteed.

     

Residual stress fluctuates periodically via the workpiece rotation phase during low frequency vibration cutting

The turning process is a standard machining process employed in diverse sectors. However, it produces long continuous chips that can affect the efficiency of the process, accelerate the tooling's wear, or damage the machined surface. As a solution, low frequency vibration cutting synchronizing with the spindle rotation has recently been developed as a new machining method in turning operation. It applies vibrations in the tool feed direction and can synchronously control the applied vibrations and the spindle rotation. It can also effectively divide the long continuous chips generated by the turning process and has the potential to reduce thermo-mechanical load on the tool by periodically enabling the tool to leave the workpiece due to the vibrations. Low frequency vibration cutting, the cutting characteristics of which differ from those of conventional turning, induces residual stresses in the machined surface; however, the properties of these stresses have not yet been studied. Residual stress can have both beneficial and negative effects on the fatigue life of products. While compressive residual stress increases the fatigue life of the product, tensile residual stress facilitates the growth of fine cracks on the product's surface and reduces fatigue life. Therefore, it is important to understand the characteristics of the residual stress developed on a machined surface. In this study, an annealed 0.45% C steel bar was machined via straight turning of the vibration cutting process synchronizing with the spindle rotation, and the residual stress on the finished surface was measured. Particular focus was placed on analyzing the effects of the spindle phase on the characteristics of the residual stress inside the machined surface, especially the effects of the number of vibrations per spindle rotation, D, which is a unique parameter defining the vibration condition. Our results revealed that the residual stress varied depending on the position of the finished surface owing to the change in feed with the spindle phase during the process. Furthermore, D was observed to heavily influence the distribution of the residual stress on the finished surface. By means of adjusting its value, the residual stress value could either fluctuate periodically according to the phase of the workpiece or not fluctuate.     

基于航空导管无扩口连接的旋转弯曲疲劳试验机研制

为了准确测验出航空导管无扩口连接处的旋转弯曲疲劳寿命,基于航空部有关标准,在参考目前国内外其他类型旋转弯曲疲劳试验机的基础上,设计了一套包含同步带传动机构、主轴机构、挠度调节机构、尾座管端固定机构及计数机构在内完整的一套设备系统。该设备能同时对带内压的六根航空无扩口连接导管进行不同挠度值的旋转弯曲疲劳试验,大大增大了试验效率,为国内同类产品的设计起到了一个引领作用。     

Driving shaft fatigue optimization design of Ω type profile twin-screw pumps

Under changeable pumped medium and working environment, the twin-screw pump is prone to be broken by fatigue failures. A structure optimization design model and method of the driving shaft are presented based on response surface methodology and finite element analysis. In this model, the shaft diameter, chamfering degree and the shaft extension of the power end are selected as optimization variables, the limit values of the variables and maximal normal deformation of the spindle are considered as the constraint conditions, and the minimization of the equivalent alternating stress on the dangerous shaft section is taken as the optimization objective so as to improve the shaft fatigue reliability. The optimization results of a case show that the equivalent alternating stress on the dangerous spindle section reduces by 26.2 %, and the maximal normal deformation decreases by 25.2 % compared with the original design. In addition, the infinite life reliability and fatigue safety factors both meet the design requirements.     

1400型压裂泵动力端花键轴断裂失效分析

针对1400型压裂泵动力端花键轴断裂的实际情况,开展了材料组份分析、机械性能测试与金相显微分析。初步确定了花键轴的断裂是疲劳断裂,裂纹源在花键齿根底部过渡圆角曲率半径最小的表面部位。对于花键轴的改进设计具有参考意义。     

驱水机技术改造及其分析

随着生产条件的变化,早前进口的一台JB-400×1000型驱水机出现严重的振动,其6213型主轴承完全散架、瘫痪。针对驱水机6213主轴承只散架、瘫痪而并无明显磨损、疲劳的破坏特点,详细研究轴承破坏的主要原因,从提高轴承支承结构刚性和降低主轴弯曲变形出发,重点解决主轴支承刚度差、轴承附加载荷大的问题,仔细分析对比了各种技改方案,以仅更改套管一个尺寸的简单措施,取得了轴承使用寿命延长数倍的改造效果,保证了生产正常运行。     

Development and application of VPG simulation technique based on equivalent virtual road profile

A Virtual Proving Ground (VPG) is a vehicle simulation environment used for evaluating durability of the suspension elements. Among the components that comprise the VPG system, the tire model with its complex nonlinear characteristics has most significant impact on the credibility of the estimated durability. This research proposes a method for generating an equivalent road profile as a way to compensate for the limits involved in modeling details of the tire characteristics. The method first identifies the frequency response function from the road heights to the spindle forces, which would contain rich information on the tire’s effect on the vehicle dynamics. Then it back-calculates a road profile using this model and the spindle force measurement. Finally the solution is updated iteratively until it yields the spindle forces close to their measured values. Using the proposed method, an equivalent road profile was successfully generated from a spindle force measurement collected from a physical durability test. In order to investigate validity of the proposed method, durability analysis was performed for a suspension component — a lower control arm. From the preliminary VPG simulation results, it was confirmed that the estimated fatigue life agreed well with the estimation based upon the force measurement.     

超声滚压工艺对TC4钛合金表面残余应力的影响

钛合金关节轴承是航空发动机的重要部件之一,但由于其润滑条件较差,极易产生磨损从而导致失效事故。采用超声滚压工艺对钛合金试件表面进行强化试验,以有效增强试件表面耐磨性能和抗疲劳特性,并着重研究静压力、滚压次数和主轴转速等超声滚压强化工艺参数对钛合金表面残余压应力与剪切应力的影响规律。试验结果与理论分析结果表明,残余压应力随着静压力、滚压次数和主轴转速的提高而增大,剪切应力随着静压力、滚压次数和主轴转速的提高而总体减小;滚压后试件表面可获得-2 000～-500 MPa的残余压应力和-600～-300 MPa的剪切应力。超声滚压技术可以有效提高钛合金材料表面的残余压应力,并有效降低表面的剪切应力。