【作者】 白继平；

【导师】 阮健；

【作者基本信息】 浙江工业大学 ， 机械电子工程， 2013， 博士

【摘要】 疲劳试验机是测试试件材料力学性能和预测试件疲劳寿命极限的标准设备,随着工业生产的飞速发展,对构件材料的疲劳试验要求越来越高,如高速铁路机车组件,某些构件的疲劳寿命要求达到107周次,甚至要超过1010周次,这些都给疲劳试验机带来了新的挑战。疲劳试验机是一种高耗能试验机,性能好坏直接影响材料疲劳试验的周期,决定了疲劳试验的效率。采用2D高频转阀控制液压缸的液压疲劳试验方案,有效地突破了传统伺服阀对液压疲劳试验机造成的频宽“瓶颈”限制,大幅提高了电液疲劳试验机的工作频率,可以拓宽电液疲劳试验机的应用领域。2D高频转阀是利用单个阀芯的旋转和轴向滑动的双自由度设计而成的,阀芯的高速旋转可以实现阀口的高频“通断”,进而可以实现对液压缸实现高频控制,阀芯轴向滑动可以调节阀口面积波形的幅值,改变液压缸敏感腔流量的大小,进而控制活塞杆输出载荷力的幅值。但是,随着2D高频转阀控制液压缸疲劳试验系统工作频率的提高,存在活塞杆输出载荷力幅值严重衰减的问题。本文提出2D高频转阀控制液压缸的谐振式疲劳试验方案,研究疲劳试验机的变谐振频率控制理论和谐振工况下的变幅控制理论,及活塞杆输出载荷力的偏置控制理论。疲劳试验机谐振工况下,试件吸收的能量几乎完全释放,所以可以保证高频、高效疲劳试验。论文的主要工作和成果如下：1、对2D高频转阀控制液压缸疲劳试验系统的工作原理进行了研究。建立了三通2D高频转阀的数学模型；建立了三通2D高频转阀控制单出杆液压缸疲劳试验系统的数学模型；建立了四通2D高频转阀的数学模型；建立了四通2D高频转阀控制双出杆液压缸疲劳试验系统的数学模型；研究了液压动力机构谐振工况的工作过程。2、对2D高频转阀结构进行了优化研究。仿真模拟了2D高频转阀阀腔流场；研究了阀芯结构几何形状对阀芯轴向液动力的影响;研究了阀芯台肩沟槽数对阀芯受到的液动力矩及轴向液动力的影响；研究了2D高频转阀阀口的气穴现象。3、对2D高频转阀控制液压缸疲劳试验系统进行了仿真研究。建立了2D高频转阀控制单出杆液压缸疲劳试验系统仿真模型：建立了2D高频转阀控制双出杆液压缸疲劳试验系统仿真模型；研究了2D高频转阀控制液压缸疲劳试验系统的谐振工况,包括阻尼特性研究、偏置量控制研究、变幅控制研究和变频控制研究。4、对2D高频转阀控制液压缸疲劳试验系统的谐振机理进行了研究。研究了2D高频转阀控制单出杆液压缸和双出杆液压缸的谐振机理,并发现2D高频转阀与液压缸之间连接管路的容积对系统变谐振频率控制有较大影响,当管路体积系数超过50%时,活塞杆初始位置变化对系统固有频率变化的影响较小；另外,相同系统参数情况下,管路体积系数对双出杆液压缸疲劳试验系统固有频率影响较大。5、搭建了2D高频转阀控制单出杆液压缸疲劳试验机和2D高频转阀控制双出杆液压缸疲劳试验机。试验研究了单出杆液压缸试验机,选取活塞杆初始位置在5mm、10mm、40mm、45mm、95mm和145mm时进行载荷力扫频试验,测得谐振频率分别是922Hz、870Hz、845Hz、768Hz、742Hz和718Hz,并测取了初始位置在10mm、40mm、95mm和145mm时系统流量；通过2D高频转阀阀口轴向开度来控制载荷力幅值,并选取活塞杆初始位置为5mm、10mm、40mm、95mm和145mm时进行载荷力幅值扫频测试。试验研究了双出杆液压缸试验机,选取活塞杆初始位置在2mm、3mm、6.5mm、10mm、13.5mm、16mm和18mm时进行载荷力扫频试验,测得谐振频率分别是1011Hz、998Hz、979Hz、949Hz、973Hz、992Hz和1005Hz,并测取了活塞杆初始位置在2mm、3mm、16mm和18mm时系统流量;选取活塞杆初始位置为2mm、3mm、10mm、13.5mm和18mm,进行谐振工况载荷力变幅值控制测试；选取活塞杆初始位置为3mm时,对活塞杆输出载荷力进行偏置控制研究。更多还原

【Abstract】 Fatigue testing machine is the standard equipment used to measure the mechanical properties of the specimen material and to detect the fatigue life limit. With the rapid development of industrial production, requirements for fatigue test of specimen material are continuously increased. In the cases of high-speed railway locomotive components and spacecraft parts, the requirements for fatigue life need to be as high as107cycles or even more than1010cycles, which poses new challenges for the fatigue testing. Fatigue testing machine is a kind of tester with high energy consumption, the performance of which largely determines the testing cycle and ultimately impact the testing efficiency. The solution of2D high-frequency rotary valve controlled hydraulic cylinder effectively overcomes the bandwidth bottleneck in traditional servo valves, significantly increases the working frequency of fatigue testing, thus broadening the application range of electro-hydraulic fatigue testing machines.2D high-frequency rotary valve is a kind of rotary valve which is designed by taking advantage of the dual freedom of spool movement, where the rotational movement of spool changes periodically the co-ordination relationship between spool notches and sleeve windows, thus achieving the periodic on-offs of valve ports and then ensuring the periodic vibration of piston rod in the valve-controlled cylinder. The axial sliding movement of the spool could adjust the waveform amplitude of valve ports area, control the flow rate to the chamber of the hydraulic cylinder and then adjust the waveform amplitude of the load force output. However, with the increase of operating frequency of the2D high-frequency rotary valve controlled hydraulic cylinder, waveform amplitude attenuation of load force output occurs. In this dissertation, the solution of2D high-frequency rotary valve controlled hydraulic cylinder in resonant fatigue testing is presented. The approaches to alter the resonant frequency of the system, to control the waveform amplitude of the load force output in resonant condition and to realize the bias-control load force output are studied. In resonant operating conditions, the specimen almost completely release the energy absorbed, which satisfies the requirements of high frequency and high efficiency in fatigue testing. The main work and findings of this study are as follows:1. The principle of2D high-frequency rotary valve controlled hydraulic cylinder is studied. The mathematical models, including three-port2D high-frequency rotary valve, three-port2D high-frequency rotary valve controlled asymmetric cylinder, four-port2D high-frequency rotary valve and four-port2D high-frequency rotary valve controlled symmetric cylinder are established. The operating process of hydraulic power mechanism is studied in resonant working conditions.2. The structure of2D high-frequency rotary valve is optimized. The flow field in the valve chamber is simulated. The impact of spool structural geometry on the axial flow force is examined. The relationship between the groove numbers on the spool shoulder and the flow moment and the axial flow force impacted on the spool is studied. Cavitation phenomena in valve ports of2D high-frequency rotary valve are studied.3. The investigation to the dynamic characteristics of2D high-frequency rotary valve controlled hydraulic cylinder in resonant working condition is simulated. Simulation model of2D high-frequency rotary valve controlled asymmetric cylinder is established. Simulation model of2D high-frequency rotary valve controlled symmetric cylinder is established. Resonant working conditions of2D high-frequency rotary valve controlled cylinder (including asymmetric cylinder and symmetric cylinder) are studied, such as damping characteristics, bias-control of the load force output, amplitude control of the load force waveform and alteration of the resonant frequency of the system.4. Resonant mechanism of the fatigue test rig is analyzed. The fatigue test rig is divided into2D high-frequency controlled asymmetric cylinder test rig and2D high-frequency controlled symmetric cylinder test rig. The investigation results show that the pipeline volume between2D high-frequency rotary valve and hydraulic cylinder has a greater impact on the alternation control of the test rig resonant frequency than other factors. When the pipeline volumetric coefficient is more than50%, the initial position of piston rod has little influence on the alternation of the natural frequency of the system. Moreover, the natural frequency alternation of the fatigue test rig composed of the symmetric cylinder is more sensitive to the value of the pipeline volumetric coefficient.5. Both2D high-frequency rotary valve controlled asymmetric cylinder fatigue test rig and2D high-frequency rotary valve controlled symmetric cylinder fatigue test rig are established. For the fatigue test rig constructed by asymmetric cylinder, sweep frequency tests of the load force output, respectively selecting the initial position of the piston rod at5mm,10mm,40mm,45mm,95mm and145mm, are carried out, and resonant frequencies measured respectively are922Hz,870Hz,845Hz,768Hz,742Hz and718Hz. Meanwhile, the flow rate of the system is measured when the initial position of the piston rod is at10mm,40mm,95mm and145mm. The load force amplitude alternation is achieved by changing the axial valve port opening of2D high-frequency rotary valve, and the sweep frequency of the waveform amplitude of the load force output is carried out when the initial position of the piston rod is respectively at5mm,10mm,40mm,95mm and145mm. For the fatigue test rig constructed by the symmetric cylinder, sweep frequency tests of the load force output, respectively selecting the initial position of the piston rod at2mm,3mm,6.5mm,10mm,13.5mm,16mm and18mm, are carried out, and resonant frequencies measured respectively are1011Hz,998Hz,979Hz,949Hz,973Hz,992Hz and1005Hz. Meanwhile, the flow rate of the system is measured when the initial position of the piston rod is at10mm,40mm,95mm and145mm. The sweep frequency of the waveform amplitude of the load force output is carried out when the initial position of the piston rod is respectively at2mm,3mm,10mm,13.5mm and18mm. The bias-control load force output of the piston rod is carried out when the initial position of the piston rod is at3mm.更多还原