摘要
本文研究对象是机械振打器除灰设备中实现能量传递作用的活塞杆。工作情况下,振打器的活塞杆经常容易被打断。由于以上原因,在研究活塞杆破坏原因时可以从断裂力学的方向着手分析。活塞杆的受力分析是基于弹性力学和冲击动力学的,文中深入阐述了弹性力学和冲击动力学问题所涉及的理论知识。活塞杆的应力分析可以通过ANSYS/LS-DYNA有限元软件来进行模拟,找出活塞杆应力较大部位,然后搭建试验台,测试危险部位的应变。
在利用此软件分析活塞杆的应力时,活塞杆的冲击作用载荷是一种脉冲载荷,为了使分析的问题能够具体量化,选用作用周期为0.05s的三角形脉冲载荷,载荷的最大值发生在0.025s。从减小活塞杆应力的角度考虑,分别计算了不同圆角半径、不同台阶厚度下的活塞杆的应力分布情况。通过计算得出圆角半径取为5mm能够很好的满足要求,台阶厚度为3mm时,活塞杆的应力分布较理想。由于活塞杆有截面变化,应力波在传递过程中会产生拉应力,导致活塞杆的断裂发生在台阶的顶端。此外,对于活塞杆来说,它发生疲劳破坏的部位往往也是应力发生集中的部位,文中通过Z方向的应力云图和Von mises云图得出活塞杆台阶的圆角处和活塞杆的底端(既有压应力,又有拉应力)都是危险截面。此外,通过查阅相关文献,对承受冲击的活塞杆材料的选择也略有介绍。
运用现代测试技术对活塞杆进行了试验研究,在冲击动力学相关知识的基础上,按照实验系统的需求,介绍了具体的试验台搭建过程,并完成了试验台的安装。为了降低成本同时又能达到实验目的,本文以虚拟仪器技术基本知识为参考,在以前的冲击力测试系统实验基础上加入了应变花和计算机等硬件。为了使采集到的数据转化为需要的数据,通过LabVIEW软件设计了采集数据和处理分析数据的程序。然后把数值模拟计算的数据与试验得出的结果进行对比分析。发现计算出的结果与试验结果相符,从试验上证明了数值模拟是可靠的。
In the paper, the piston rod that is the role of energy transfer in mechanical rapping-off-ash device is investigated. In the case of work, it is easy to be interrupted for the piston rod. To solve this problem, we use fracture mechanics to study fracture mechanism of the piston rod. Stress Analysis of the piston rod is based on the dynamics of elasticity and impact, This paper describes the theoretical knowledge of impact and elasticity which are involved in depth.The stress on the piston rod is simulated basing on ANSYS/LS-DYNA and the strain on the dangerous parts of piston rod is tested by test.
The stress of the piston rod is analyzed baseing on ANSYS/LS-DYNA, in order to simplifying the process of problem analysis, force of the impact on the piston rod is taken as the form of triangular pulse load, whose time is lasting 0.05s, and it can get the maximum load in 0.025s. From the perspective of the stress, simulating the stress distribution under the various fillet radius and the different thickness of the the piston rod step.By calculating,it is good enough for requirements when the fillet radius is 5mm and the thickness of step is 3mm. Because of cross-section changes,tensile stress will be produce in the transmission process of stress wave,tensile stress makes the piston rod of the fracture occur at the top of the steps. In addition, the location of stress concentration is broken easily, the analysis reaches that chamfering position and the the bottom of the piston rod are dangerous section through Z-direction stress cloud and the Von mises stress cloud .In addition, though searching related information, selecting the piston rod materials that should be absorb impact is also a slight introduction.
We did some experiments on the piston rod with modern test technique.Combining with the basic knowledge of impact dynamics and the requirements of system, a detailed designing scheme of testing bed was presented and finally brought the test bed a forming assembly. The virtual instrumental technique has been adop ted, the testing system of impact signal constituted by hardwares of sensor, data collection card and computer was constructed, thus realized an optimized combination of functional requirements and economic cost. The programs of data processing and analysis system were designed at the LabVIEW platform and realized the transformation from indirect data into the direct data. Finally a comparison on the test result of this system with the computer simulation was given out. The identical between the finite element analysis results and the experiment results indicates that the finite element analysis is right.
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