Experimental study on a noncontact method using laser displacement sensors to measure vibration stress in piping systems

This study presents a noncontact measurement method of vibration induced stress (vibration stress) using multiple laser displacement sensors and clarifies its applicability to piping vibration. In the beam structures such as piping, the stress due to bending deformation can be caused by vibration. In the presented method, the vibration displacement in the beam structures induced by the bending deformation is measured at three different locations using laser displacement sensors in a noncontact manner and the vibration stress is estimated by a simple calculation based on the beam theory. First, an applicability validation of the presented method was done by a vibration test using a cantilevered beam plate. This validation was done by comparing measurements by the presented method and the conventional method using strain gauges. Next, an experimental validation was conducted by the vibration test using a pipe specimen, and the applicability to the piping vibration was confirmed.     

Hydro-thermo-mechanical analysis on high cycle thermal fatigue induced by thermal striping in a T-junction

Turbulent mixing in a T-junction causes thermal striping which is irregular and frequent fluctuation of thermal layer. Thermal striping is a significant thermal problem because it causes unpredicted high cycle thermal fatigue and fatigue cracking in piping systems. Since this phenomenon is hardly detected by common plant instruments due to high frequency and complex mechanism, numerical approaches are indispensable for a precise evaluation. This research was carried out to define a suitable and effective numerical method for evaluating thermal stress and fatigue induced by thermal striping. A three-dimensional hydro-thermo-mechanical analysis was performed based on one-way separate analysis method to find out the characteristics of stress components and its results were compared to the results of a one-dimensional simplified analysis. It was found that the detailed three-dimensional analysis is indispensable because one-dimensional simplified analysis can overestimate or underestimate according to the assumed heat transfer coefficient and cannot estimate the considerable mean stress effects.     

Fatigue life evaluation of mechanical components using vibration fatigue analysis technique

Unit brackets attached on a cross member and subjected to random loads often fail due to self-vibration. To prevent such failures, it is necessary to understand the fatigue failure mode and to evaluate the fatigue life using test or analysis techniques. The objective of this study is to develop test specifications for components, which are applicable to predict fatigue life at the stage of initial product design, for the unit brackets by using a vibration fatigue technique. For this objective, the necessity of a fatigue analysis considering resonant effect was reviewed. Also, a series of vibration fatigue analyses were carried out by changing the acceleration’s direction and magnitude. Then, a methodology was proposed to determine the optimum vibration fatigue test specification of the component, which gives an equivalent failure mode with the vehicle test condition.     

高层供水管道系统的噪声控制研究

针对高层供水管道系统产生的噪声污染问题进行了系统的理论分析和实验研究。分析了管道系统的振动激励源及管道系统的动态特性；并根据管道系统动态特性、振动和噪声信号特点等，分析了实例中管道系统噪声产生的原因，采取了相应的改造措施，达到了降低噪声的目的。     

Substructuring including interface reduction for the efficient vibro-acoustic simulation of fluid-filled piping systems

The operation of pumps and valves leads to strong acoustic excitation in fluid-filled piping systems. Efficient substructuring and model order reduction strategies are required for the sound prediction in piping systems, and in order to reduce the sound transmission to attached components, such as the floor panel in vehicles, for example. This research presents a finite element based automatic substructuring and component mode synthesis technique, which is a combination of an extended Craig–Bampton method for fluid–structure coupled piping systems and a novel, consecutive interface reduction. Hereby, the remaining interface degrees of freedom between different substructures are further reduced using appropriate Ritz vectors. The proposed model order reduction strategy accelerates the computation of transfer functions in fluid-filled extended piping systems. In order to validate the simulation results, experimental results are obtained by a hydraulic test bench for dynamic measurements, where fluid pulsation is induced by piezo-driven transducers. The observed fluid–structure interaction phenomena correspond to the predictions by the proposed computation approach.     

随机振动环境下结构的疲劳失效分析

讨论了随机振动响应的统计特性分析、结构响应的动应力与常规疲劳载荷的关 系,如何将结构响应动应力等价为常规的静力疲劳载荷,利用Ｓ－Ｎ曲线和名义应 力法对结构寿命的估算方法等。完成了用功率谱密度表示的随机振动载荷作用下悬 臂板结构的响应分析以及疲劳寿命估计。     

Ultrasonic testing to measure the stress statement of steel parts

This paper presents an efficient method for stress measurement propagation. Pulse-echo method are used as stress measurement method on railway wheels. Hard service conditions and brake failures can lead to dangerous stress on the railway wheels. Stress measurements so important for wheels. Especially wheel expose to severe drag braking conditions in freight service. Residual stresses can significantly reduce the engineering properties and fatigue life of materials such as railway components. The paper presents results of stress state investigation of ER7 steel. Finally, the article briefly discusses how to adopt the pulse-echo method to railway wheels. Reducing cost of residual stress measurement investigated.

     

基于LMS Test．1ab的压缩机管道振动测试与分析

提出了应用LMS Test．1ab进行往复压缩机管道振动测试的新方法，利用LMS Test．1ab数据采集、分析软件及相关硬件，搭建了往复压缩机管道振动测试系统，对管道系统的固有频率进行了测试，并对测试结果进行了验证，从而证实了本系统的准确性与实用性。     

滚珠丝杠进给系统滚动结合部径向动态特性参数辨识

针对滚珠丝杠进给系统滚动结合部径向动态特性参数难以确定的问题,提出了一种进给系统在整机状态下滚动结合部径向动态特性参数辨识方法。该方法将丝杠简化为欧拉-伯努利梁,以建立在简谐激振力作用下丝杠轴向上各截面的径向振动方程;设计实验以测量丝杠上测量点的径向振动位移,结合丝杠径向振动方程所计算的理论值建立优化目标函数,基于人工鱼群算法优化识别出滚动结合部的径向刚度及径向阻尼参数。以自行研制的滚珠丝杠进给实验台为研究对象,采用该方法对其导轨副、两端轴承组及滚珠丝杠副滚动结合部的径向刚度与径向阻尼参数进行识别。实验结果表明：以该方法辨识的结合部的参数所计算的丝杠上测量点的径向振动位移与实验测试值之间的误差在3.0%以内,验证了该方法的正确性和有效性。     

Similitude study of an in-service industrial piping system under high flow induced vibration

Flow induced vibration problem of an in-service duplex stainless steel piping system was investigated in previous research. The investigation required multiple sets of site measurement results at the offshore gas processing platform which raises the concerns of safety and its practicality. A lab scale of the mentioned piping system is preferable to study the flow induced vibration problem at different operating conditions to better understand the dynamic behaviour of this piping system. In addition, most of the dimensional analyses were performed either solely on structure or fluid system. System with flow induced vibration problem has never been attempted and thus it is important to perform similitude study of the piping system prior to fabrication of the lab scale model. Buckingham Pi theorem was applied and the similitude was verified by computational mechanics both qualitatively and quantitatively. The calculated non-dimensional variables of a scaled piping system in describing the flow characteristics which contribute to the structure deformation give similar scale factor, flow pattern and flow induced dynamic deformation and stress in this fluid-structure interacted piping system indicating that geometric, kinematic and dynamics similarity are achieved.     

Damage prevention design of the branch pipe under pressure pulsation transmitted from main steam header

Vibration has severely increased at the branch pipe of the main steam header since the beginning of commercial operation of nuclear power plants. Intense broadband disturbance flow at a discontinuous region such as elbows, valves or headers generates an acoustical pulsation which is propagated through the piping system. The pulsation becomes the source of low frequency vibration at the piping system. If it coincides with the natural frequency of the pipe system, excessive vibration results. High-level vibration due to the pressure pulsation related to high dynamic stress, and ultimately, to failure probability fatally affects the reliability and confidence of the plant piping system. This paper discusses steady-state high vibrations appearing in the branch piping system due to the effect of acoustical pulsations transmitted from the large main steam header by broadband turbulence in a 700 MW power plant. The excitation sources and response of the piping system are investigated by using on-site measurements and analytical approaches. Energy absorbing restraints with additional stiffness and damping factor were designed and installed to reduce vibration damage.     

有限元方法数值模拟往复压缩机管路的振动

建立了往复压缩机管道振动的数学模型,提出了恰当的边界条件。利用有限元分析软件CAE—SAR对往复压缩机级间管道的振动模型进行求解,获得了管道系统的振动模态和振幅的计算结果。应用这种方法对7M50—305／314型氮氢气压缩机陕西管道振动进行了计算分析,并对其各个弯头位置的振幅进行了实际的测量。测量结果证实了理论分析中所建模型及其边界条件的合理性。     

A separation of experimental study on coatings failure signal responses under rolling contact

The objective of present study is to address the signal responses of the acoustic emission (AE), vibration and torque in rolling contact fatigue (RCF) tests of the coatings. The Fe-Cr alloy coatings were deposited using plasma spraying technique. The AE, vibration and torque sensors were assembled to detect the coating failures during the RCF tests, respectively. The results show the signal responses of the vibration and torque accurately indicate the RCF failures of the coatings, but based on the coating losses. The AE signals can sensitively monitor fatigue fractures prior to the formation of the final failure.     

含多条裂纹梁的模态与振动疲劳寿命分析

基于Paris公式,提出了一种含多条裂纹梁疲劳寿命预估的方法。在模态分析中,基于传递矩阵方法,利用无质量的弯曲弹簧等效裂纹,提出一种求解含有多条裂纹梁固有振型的方法,分析裂纹数目、裂纹位置、裂纹深度对裂纹梁固有频率的影响。在振动疲劳分析中,研究了在简谐激励作用下裂纹数目对裂纹尖端应力强度因子的影响。通过Paris疲劳裂纹扩展方程和同步分析法,考虑裂纹梁振动与裂纹扩展的相互作用,分析了裂纹数目和裂纹位置对裂纹梁疲劳寿命的影响。结果表明,裂纹数量、裂纹位置和深度对梁的模态参数和疲劳寿命有重要影响。     

多轴应力响应下结构振动疲劳寿命预估的时域方法研究

应用Von Mises应力准则将多轴应力响应等效合成为单轴应力,给出了基于功率谱输入和时域输入的多轴应力响应振动疲劳寿命预估方法,时域输入法的求解过程没有丢失应力分量相位的相互信息,较功率谱输入法更完备。针对激励载荷是以功率谱密度函数形式表达的,提出了Monte-Carlo伪随机历程模拟将激励功率谱转换到时域激励中,再通过时域输入法进行寿命预估的求解思路,保证了等效合成的Von Mises应力的相位信息具有实际的物理意义,可指导多轴应力响应下结构振动疲劳寿命的精确预估以及声疲劳试验研究。     

基于阻尼减振技术的热电厂减温减压器管道研究

为解决抚顺某热电厂减温减压器减温水管道振动严重的问题,将阻尼减振技术应用到管道减振中。开展了对减温水管道系统振动频率和速度的现场测量及其图纸资料的搜集,运用有限元分析软件Sap2000建立了管道有限元模型,进行了模态和力学分析,掌握了减温水管道的振动特性,并且对管道进行了阻尼减振模拟仿真,建立了管道振动特性与阻尼减振技术之间的关系。依据模拟仿真的数据结果,提出了解决管道振动的最佳方案。该方案运用阻尼减振技术,在不停机、未改变管道原有结构布置的情况下,在管道的适当位置安装了阻尼器,实现了工程项目的减振改造。实际改造结果表明,安装了阻尼器的管道振动速度达到了管道振动安全标准的要求,能够保证机组长周期、稳定运行。     

随机载荷下燃油泵托架疲劳寿命仿真分析

针对一类含橡胶减振垫燃油泵托架出现疲劳断裂的现象,研究利用数值仿真技术预测结构疲劳寿命的方法。应用有限元法和随机振动理论计算结构随机振动响应的各种统计参数,采用Miner累积损伤理论预测疲劳寿命。重点讨论了有限元模型中系统阻尼和橡胶垫刚度等关键参数的确定方法,并利用优化技术实现有限元模型修正的自动化。计算结果表明动态随机激励环境下存在严重的局部应力集中是造成托架损坏的主要原因。仿真结果和随机振动试验结果吻合,证明利用数值仿真技术预测此类产品的疲劳寿命是可行的。     

Annoyance rate evaluation method on ride comfort of vehicle suspension system

The existing researches of the evaluation method of ride comfort of vehicle mainly focus on the level of human feelings to vibration. The level of human feelings to vibration is influenced by many factors, however, the ride comfort according to the common principle of probability and statistics and simple binary logic is tmable to reflect these uncertainties. The random fuzzy evaluation model from people subjective response to vibration is adopted in the paper, these uncertainties are analyzed from the angle of psychological physics. Discussing the traditional evaluation of ride comfort during vehicle vibration, a fuzzily random evaluation model on the basis of annoyance rate is proposed for the human body＇s subjective response to vibration, with relevant fuzzy membership function and probability distribution given. A half-car four degrees of freedom suspension vibration model is described, subject to irregular excitations from the road surface, with the aid of software Matlab/Simulink. A new kind of evaluation method for ride comfort of vehicles is proposed in the paper, i.e., the annoyance rate evaluation method. The genetic algorithm and neural network control theory are used to control the system. Simulation results are obtained, such as the comparison of comfort reaction to vibration environments between before and after control, relationship of annoyance rate to vibration frequency and weighted acceleration, based on ISO 2631 / 1 （1982）, ISO 2631-1 （1997） and annoyance rate evaluation method, respectively. Simulated assessment results indicate that the proposed active suspension systems prove to be effective in the vibration isolation of the suspension system, and the subjective response of human being can be promoted from very uncomfortable to a little uncomfortable. Furthermore, the novel evaluation method based on annoyance rate can further estimate quantitatively the number of passengers who feel discomfort due to vibration. A new analysis method of vehicle comfort is presented.     

高耸塔器风致疲劳寿命时域分析

针对沿海多风地区高耸塔器可能因长期风致振动导致的疲劳问题,以随机风致应力响应的时程模拟、风速风向联合分布模型、雨流法以及Miner疲劳累积损伤理论为基础,提出了基于时域法的高耸塔器风致疲劳寿命数值计算方法,并针对某一典型高耸塔器进行了相关分析。结果表明：长时间的空塔工况可能导致该塔器严重的疲劳损伤甚至失效,而操作工况下的风致疲劳寿命一般可以满足设计年限要求;横风向共振是引起该塔器空塔工况风致疲劳的决定性因素,而强风造成的顺风向振动是导致其操作工况下疲劳损伤的主要原因;该塔器空塔和操作工况下的疲劳分布曲线分别呈多峰型和单峰型,可见顺风向的疲劳损伤比横风向更为集中。     

挖掘机工作装置疲劳寿命分析

针对挖掘机工作装置的疲劳破坏问题,进行了基于实测载荷历程的疲劳寿命估算,为其在服役期间的安全检查和维修决策提供依据.通过应变测量得到该工作装置薄弱部位的载荷历程,对其进行雨流计数统计,推导并确定出结构的S-N曲线,结合名义应力法理论估算出该工作装置各测点的疲劳寿命,实现了对结构进行疲劳预测分析的目的,该方法可为同类机械的疲劳寿命预测提供一定的参考依据.