基于有限元和试验模态分析的振动筛动力学参数研究

1、第35卷2007年第1期 63Mining & Processing Equipment63分选钻井振动筛是固相控制系统的重要设备,正向大型化、自动化、集成化、智能化方向发展,工作过程中的动力学问题越来越多,对动力学特性的要求也越来越高1。同时,随着非线性动力学理论、现代设计理论与方法、计算机软硬件的迅速发展以及现代测试技术向数字化、智能化方向的发展,为振动筛进行全面、系统的动力学设计和修改提供了可能2。国产钻井振动筛出现的主要问题是:筛箱易损坏、横梁和侧板断裂等。要想从根本上解决国产振动筛的上述问题,必须进行振动筛的动力学设计。从工作条件上看,振动筛除受激振器的受迫振动外,还受到固相

2、颗粒的冲击作用,受力相当复杂。在振动筛动态设计过程中,有必要对振动筛的动力学特性进行精确的分析和研究。振动筛动力学参数的确定可以通过理论和试验两种方法得到,理论方法一般采用有限元法进行几何建模、划分网格、数值求解,从而获得固有频率和主振型。试验模态分析技术是结构动力学中的一种“逆问题”分析方法(相对于有限元分析的“正问题”分析方法,以试验或实测数据为依据,采用理论和试验分析相结合的方法,应用参数估计和系统辨识的数学手段对实际结构的动力学参数进行辨识。文章首先采用有限元法分析,估计筛箱结构的振动频率和振型等有关动态特性参数,再进行试验模态分析对有限元模型进行修改,再做分析,最终达到精确确定钻井振

3、动筛的动力学参数。1筛箱动态特性的有限元分析P D Z S 型平动椭圆振动筛是由筛箱、激振器和弹簧等部件组成。采用一对齿轮强迫同步,在两齿轮轴上装有偏心块,由此产生惯性力,使得筛箱产生振动。整个筛箱由4个螺旋弹簧支撑,筛箱侧板支撑方向加有纵向加强肋板,侧板中部和安装弹簧支撑座处的外侧衬有加强板。两侧板与6根L型加强板、1根出口端圆管加强梁、2根激振器保护筒梁、2根后端梁、27根纵向加强梁、后挡板等均通过焊接联接,在两侧板外侧四个角处,还焊有弹簧支撑板。为使筛箱在工作过程中处于平动,在设计时需保证激振力的合力作用线通过筛箱的质心。筛箱的有限元网格是在Pro /Mechanica软件Structu

4、re模块中建立的。首先在Pro /Engineer软件中建立筛箱各零件的三维模型,装配并作相应的简化,然后通过A p p l i c a t i o n 菜单直接进入P r o /M e c h a n i c a 软件环境。由于筛箱零件主要以板材为主,因此在单元划分时,主要采用二维壳单元,局部结构(如加强梁、筛网抬架采用梁单元,这样既有效地减小了模型规模,又能保证计算的准确性。按照筛箱与底座固结的实际位置施加弹簧单元边界条件,这样就形成了筛箱的有限元模型,如图1所示。该模型的总结点数为640,梁单元数为110,壳单元数为论文编号:1001-3954(200701-0063-065基于有限元和

5、试验模态分析的振动筛动力学参数研究*朱维兵西华大学机械工程与自动化学院四川成都610039摘要:以P D Z S 型平动椭圆振动筛为计算实例,建立了筛箱系统动态特性分析的有限元模型,用工程分析软件Pro /Mechanica对筛箱的动态特性作分析研究,计算了筛箱的低阶固有频率、模态振型;应用试验模态分析技术,采用一点激振,多点拾振的测试方法,对整体振动筛进行了实测,获得了振动筛固有频率、阻尼比和主振型,为钻井振动筛动力学设计和动力学修改提供了参考。叙词:钻井振动筛有限元法试验模态分析固有频率*四川省制造与自动化重点实验室基金项目(SZD-Z02244。作者简介:朱维兵,1971年生,博士,副教

6、授;现从事现代机械设计方面的教学和研究工作。图1筛箱有限元网格图表1筛箱前5阶模态分析结果阶数模态频率(Hz431.28出口端纵向加强梁的弯曲振动5出口端L 型加强板的弯曲振动本栏目编辑赵斌基于有限元和试验模态分析的振动筛动力学参数研究第35卷2007年第1期 64Mining & Processing Equipment64分选504,弹簧单元数为4。利用Pro /Mechanica软件的Structure模块,建立该模型的质量矩阵M 和刚度矩阵K ,求解可得筛箱模态振型及固有频率,前五阶模态分析结果如表1所示。2振动筛试验模态分析在进行模态试验分析时,首先要确定被测物体的固定方式。

7、固定方式一般有两种:一种是按照其实际工作状况的方式约束,二是悬吊式。由于本次试验对象是中型平动椭圆振动筛,由底座、支撑弹簧、筛箱、激振器及其它配套装置组成。模态试验可在实际工作状态、电机停转的空载状态下进行。考虑到钻井振动筛在激振器激励下运动的振动频率范围。一般认为3,靠近激振源激振频率的模态对结构振动影响较大,远离激振源激振频率的模态对结构振动影响较小。因此,试验频段的上限一定要大于激振频率。结合前面筛箱结构的有限元分析结果,选取试验频段为激振器激振频率附近的1530Hz的频段(激振器激振频率=22.33Hz。筛箱是一个由若干型材和板材构成的组合结构,因此存在着筛箱总体振动和筛箱局部结构的振

8、动问题。为了提高测试精度,防止漏掉振型,激振点和测点的选择应考虑4:(1激振点的激振要避开各阶模态的节点和节线,以免遗漏模态;(2应能够提供足够的能量,把需要频段中的模态全部激发出来,使各测试的信号有良好的信噪比。为此,参考前面有限元分析的结果在筛箱上布置146个测点,共438个自由度。激励信号可采用随机信号、脉冲信号等,在本次试验中根据现场条件,采用单点激振、锤击脉冲信号法,测试分析系统框图,如图2所示。用橡皮锤敲击筛箱中部激发筛箱总体振动,用磁电式速度传感器在146个测点处拾振。试验采用力锤(含力传感器激励,磁电式速度传感器进行响应测量;用电荷放大器对速度传感器输出的电信号进行放大;由于信

9、号中混有电压波动及其它环境噪声等原因造成的高频干扰,故采用低通滤波器进行滤波。动态数据采集系统采用D a t a Physics公司16通道Signalcalcmobilyzerdynamic signalanalyzer440,模态分析软件采用Signalstar。数据采集的参数设置为:对每一通道,采用低通抗混滤波,根据采样定理选取采样频率为2500Hz,采样数据长度为16384点,激励和响应窗函数分别采用力窗和响应窗。进行数据处理时,首先需要确定触发系统。脉冲信号采用信号触发,即当有一脉冲信号过来时,才进行一次触发平均。为减少随机误差,应进行多次平均。考虑到筛箱结构的阻尼较小,频响函数的半

10、功率带较窄,故应尽量提高频率分辨率。针对现场振动筛实际运行情况,对振动筛进行了1530Hz频率范围模态参数抽取,通过模态分析计算可得到振动筛的模态参数:固有频率、主振型和阻尼比,表2列出了模态分析结果,各阶振型如图3。可见,有限元法和试验模态分析的结果是吻合的,因此可以确定试验结果真实可靠。模态分析共得到3阶模态参数,对于不同的固有频率,相应主振型的振动描述如下:第一阶主振型为侧板的一阶弯曲振动,第二阶主振型为侧板的二阶弯曲振动,第三阶主振型为出口端纵向加强梁的弯曲振动。由于所得3阶弹性模态都在激振频率(22.33Hz附近,容易引起筛箱侧板的共振,故需对其结构进行适当修改,使其模态频率远离激振

11、频率。另外,连接试验振动筛两侧的圆管加强梁刚度过低,所以振动筛动态设计中要予以重点考虑,以防止类似现场中广泛存在的侧板断裂故障发生。图2测试分析系统框图表2筛箱模态分析结果阶数模态频率(Hz模态阻尼比(%118.453.56224.32.563图3基于有限元和试验模态分析的振动筛动力学参数研究(下转第65页第35卷2007年第1期 65Mining & Processing Equipment65分选湘潭钢铁集团公司于2000年在生产系统改造过程中,安装了5台CCJ/A系列除尘器,在使用过程中,由于除尘器一直很难保证处于稳定良好的运行状态,并存在噪声大的问题。为了彻底解决这些问题,特参

12、考有关资料,组织相关人员,进行分析和讨论,并根据我矿的实际情况对CCJ /A系列冲激式除尘器进行改造。改造后基本保证除尘器的运行率为98%以上,保证了操作岗位粉尘基本消除;且原来的噪声大、不方便操作和维护等问题都得到有效解决。1基本参数、结构及原理CCT /J系列除尘器基本参数,见表1。CCJ /A系列除尘器其原理(见图1是通过水流相对运动激起水花与除尘器利用压差吸引过来的粉尘碰撞而结合,从而达到除尘的目的。2CCJ /A 系列除尘器系统故障原因分析分析、讨论表明现有除尘系统的不足之处:论文编号:1001-3954(200701-0065-066提高CCJ/ A 系列冲激式除尘器稳定性和效率的

13、措施肖文志1廖洪刚2邓奕11湘潭湖南工程学院数理系湖南湘潭4111042湘潭钢铁集团公司湘乡白云石矿摘要:结合冲激式除尘器和泡沫式除尘器的工作原理,以较低成本对冲激式除尘器进行改造,降低除尘器的运行成本和提高除尘器的运行效率。叙词:冲激式泡沫式粉尘改造表1型号耗水量(m 3/h充水容积电机功率数量溢流蒸发排灰水(m 3(kW(台CCJ /A-144942012001.2304CCJ /A-157560017003711.进水管道2.室13.上叶片4.室25.通气管6.溢流管7.溢流箱8.水池9.储水箱10.下叶片图1CCJ /A 系列除尘器工作原理图(上接第64页3结论(1先利用Pro /Me

14、chanica软件进行有限元分析可以减少模态试验的预试验时间,能较为准确地选定激励点和测试点。(2通过试验模态分析,得到了试验振动筛的动力学参数:固有频率、主振型和阻尼比。与有限元法分析结果一致,因此结果是可靠和真实的。同时详细分析了各阶主振型的振动形态,为振动筛的动力学设计和动力学修改提供了依据。(3由于所得3阶弹性模态都在激振频率附近,容易引起筛箱侧板的共振,故需对其结构进行适当修改,使其模态频率远离激振频率。另外,试验振动筛连接两侧板的圆管加强梁刚度过低,这可能是振动筛侧板易断裂的一个重要原因,在动态设计中要予以重点考虑,同时对防止现场广泛存在的侧板断裂故障提供了借鉴意义。(4通过有限元

15、法和试验模态分析技术获得振动筛的动态特性参数,进行振动筛动态特性参数的修改,从而进行振动筛的优化设计,为解决钻井振动筛现场存在的问题提供了强有力的理论支持。参考文献1茹军,胡钦峰,张明洪.钻井液振动筛整机动态检测中的若干问题.石油矿场机械,2003(32傅志方.振动模态分析与参数辨识.北京:机械工业出版社,1990.3张传涛,闫国兴,张明洪.MN-1型三电机自同步振动筛试验模态分析.矿山机械,2005(73刘建文.直线振动筛筛框模态分析和故障诊断研究.矿山机械,2004(7(收稿日期:2006-07-25(修改稿日期:2006-11-03d c d c d c d c d c d c d c

16、d c d c d c d c d c d c d c d c d c d c d c d c d c d c d c d c d c d c d c d c d c d c d c 提高CCJ /A 系列冲激式除尘器稳定性和效率的措施【Descriptors】Hierarchical fuzzy control Decouple Ball mill Pow-dering systemStudy to the Foundry of High Manganese Steel Liner with Copper Alloy Mould.NIU XianMing et al.(22-24 in or

17、der to get the high manganese steel liner without heat treatment, the paper analyses the heat transmission process between the liner and the copper alloy mould, calculates the density of the heat current conducted from the alloy mould, designs the structure of the copper alloy mould and the distribu

18、tion of the cooling water groove. The employment result shows that the copper alloy mould processes the advantage of long lifespan and low cost. 【Descriptors】Liner Cal-culation for the heat transmission Design to the structure of the cop-per alloy mouldDevelopment and Optimization of the Grinding Me

19、dia System. .XIAO QingFei et al.(28-31 The paper puts forward the grinding media system and analyses the existed problem, introduces the studying development about the for-eign and domestic grinding media system and gets several pieces of conclusion, which shows that the in China the suitable fillin

20、g rate of the media, precise size of the steel ball, accurate loading and adding approach for the steel ball, suitable shape of the media and reasonable material are the optimal selection in the grinding media system.【Descriptors】Grinding media system Filling rate Fine grinding media Accurate loadin

21、g and adding approach for the steel ball Study to the Material and Quality of the Hammerhead of the Ham-mer Crusher.YIN JinGuang(32-33 The paper introduces the process for studying the material and quality of the hammerhead of the hammer crusher. According to the kinetic analysis to the hammerhead a

22、nd the energy condition for crushing, it deduces the calculation formula of the hammerhead quality, which offers the theoretic reference for determining the hammerhead quality. In addition, the high-chrome manganese tungsten alloy is selected as the material of the hammerhead, which has good anti-ab

23、rasion properties, strong toughness properties and long lifespan, is a perfect material for the hammerhead. 【Descriptors】 Hammer crusher High-chrome manganese tungsten alloy Quality of the hammerhead Discussion of the Build-Up Welding Repair Technique Applied to the Roller Surface of Roller Press.SH

24、I LiYan et al.(34-35 The paper briefly introduces the roller press about its working prin-ciple and basic structure, discusses and studies the build-up welding repair technique applied to the roller surface, and puts forward the matter need to attention in the employment course. 【Descriptors】Build-u

25、p welding repair Roller press Application and discussion Realization of Variable Frequency Control to the Vibration Mill with the Communication between OMRON PLC and the Upper-Position Processor.SU Dan et al.(43-45 The paper offers the approach to design the program for realizing the communication b

26、etween OMRON programmable controller and the upper-position processor by VC+6.0, and provides the approach to realize the communication between the computer and the PLC with RS232 tandem communication port. The scheme has been success-fully applied to the variable frequency control to the vibration

27、mill.【Descriptors】Upper-position processor PLC Tandem communi-cation Vibration millInnovating the Grinding Technique to Improve the Product Quality.ZOU JunPun et al.(59-61 According to the properties and characteristic of the cement output from the vertical kiln and current grinding technique status

28、, the paper suggests that on condition that the inner quality of the chamotte is ensured, the barrel mill with big ratio of the length to the diameter is guaranteed, pretreatment to the material before grinding and the in-novation to the greatly fine grinding technique are applied to improvethe fine

29、 grinding degree, proportion of each grade and particle shape, thus, the product quality could increase. 【Descriptors】Grinding technique Pretreatment Fine grinding degree Product quality the Analysis to the Finite Element and Testing Mode. .ZHU WeiBing(63-65 The PDZS type translation elliptical vibr

30、ation screen serving as the calculation example, the paper establishes the finite element model for analyzing the dynamic characteristic of the screen box system, makes the analytical study to the dynamic characteristic of the screen box with the engineering analysis software Pro / Mechanica, calcul

31、ates the low-order natural frequency and modal vibration shapes of the screen box. In addition, applying the testing modal analysis technique and the testing approach that is the vibration is excited at one point and picked up at multi-point, it makes actual measurement to the whole vibration screen

32、, thus gets the natural frequency, damping ratio and main vibration type of the vibration screen, which offers the reference for the dynamic design and the dynamic improvement to the drilling vibration screen. 【Descriptors】Drilling Vibration screen Finite element approach Modal analysis Natural freq

33、uency Measurement to Improve the Stability and Efficiency of CCJ/A Serial Swashing Dust Catcher.XIAO WenZhi et al.(65-66 Combining the working principle of the swashing dust catcher and that of the foamy one, the paper innovates the swashing dust catcher with low cost, so as to decrease the operatio

34、n cost of the dust catcher and increase the operation efficiency. 【Descriptors】Swashing Foamy Dust InnovationOptimization to the Simulation of the Movement of the ZRBF Vi-bration Screen Surface with Matlab. .FANG ZhiHua et al.(67-70 According to the movement differential equation for the vibration s

35、ystem of three freedom of ZRBF vibration screen, the paper applies the powerful and perfect common numerical analysis, matrix algo-rithm and drawing function of Matlab to makes the simulative analysis to the movement track on the screen surface, which could help to select the suitable exciting point

36、 and exciting force so as to makes the optimization design, meanwhile, it offers the convenient and efficient computer optimization approach for actual engineering application.【Descriptors】Matlab simulation ZRBF vibration screen Movement of screen surfaceDomestic Current Study Status and Prospect of the Automatic Medi-cine Feeding System of the Concentrator for the C