【作者】 贺孝梅；

【导师】 刘初升；

【作者基本信息】 中国矿业大学 ， 机械设计及理论， 2009， 博士

【摘要】 随着煤炭能源需求的增长,煤炭行业迫切需要处理能力大的振动筛进行筛分作业,同时筛分机械大型化可以减少振动筛的数量,降低设备费用,带来较好的经济效益。但是振动筛的大型化将引起筛体结构强度和刚度不足,严重影响振动筛的使用寿命。目前静强度加运动学分析的传统设计,大多是采用经验数据和安全系数的设计计算方法,不能准确揭示出结构内部动态应力分布状况,因此不能保证产品结构的设计合理性,直接影响产品的使用性能与寿命。所以研究和制造大型振动筛,提升设计水平,提高振动筛的运行可靠性已成为一项重要的研究课题。本论文以新设计的超静定网梁结构大型振动筛为研究对象,利用有限元分析法和先进的振动测试手段,将动态设计法应用于大型振动筛的设计中,提高了振动筛的可靠性。根据等厚筛分原理,提出了3种筛分效率较高的新型筛分结构。运用机械系统动力学原理建立了前2种振动筛结构较准确的动力学方程;应用多自由度系统振动理论,对振动筛进行了运动分析,计算了筛面上特殊点的振幅、运动速度、抛掷指数等工艺参数,研究了各自的筛分特性;分析了香蕉筛的结构特点和筛分特性,指出了3中筛分结构各自的适用范围。对超静定结构的特性和该结构应用于振动筛设计的可行性进行了分析,大型振动筛设计中,在香蕉筛基础上,采用了由管群通过跨中的静定板与两根激振器梁的耦联构成的超静定网梁结构。给出了振动筛的主要技术参数,确定了结构关键部件技术,并对振动筛进行了动力学参数的设计计算。进一步分析了大型超静定网梁结构振动筛的动力学特性,研究了振动筛的结构强度和可靠性。给出了提高有限元模型计算精度及稳定性的方法,建立了合理的振动筛有限元计算模型。对螺栓连接,给出了适合的简化方法。应用有限元分析法对振动筛局部重要结构及整体结构进行了固有特性分析。分析结果为结构的动力学修改提供依据,为实验模态分析的测点布置提供参考。同时运用有限元分析法对振动筛进行动力响应分析,获得了工作频率下整体及局部结构的动应力和动应变。分析结果验证了超静定网梁结构的优良特性,为振动筛的结构修改提供参考。同时采用先进的测试手段对振动筛进行了振动测试。通过对实体样机进行模态测试实验,获得了结构的模态参数。实验结果验证了有限元分析的正确性,并用于指导振动筛局部结构的修改和修正有限元计算模型。在以上工作的基础上,应用灵敏度分析法对振动筛结构进行动力学修改。根据拉格朗日乘子构造法则,用实验模态频率和振型构造目标函数对有限元模型进行修正,给出了适用于有限元模型修正的质量矩阵和刚度矩阵。基于有限元分析和实验模态分析的结果,应用特征灵敏度分析法对振动筛的进料端、出料端及侧板结构进行修改,使其动力学参数更加合理,提高了大型振动筛的刚度和结构稳定性。为了解决大型振动筛工作过程中侧板动应力过高易损坏的问题,对振动筛进行了结构优化设计。首先基于多频约束,对振动筛侧板的加强筋尺寸及侧板质量进行了优化,给出了适合多频约束的优化准则,并将解析灵敏度计算程序嵌入到优化分析程序中。其次,应用增广拉格朗日乘子法,编写出收敛速度快、求解精度高的程序,得到了加强筋在振动筛侧板上的最优布置,达到了以最少筋板数目满足较低应力的要求。结构优化后增加了振动筛的刚度,降低了变形,提高了结构的可靠性。该大型振动筛投入生产后,运行稳定,使用效果良好。空载运转实验检测结果表明:整机性能达到了设计所要求的工艺技术指标。更多还原

【Abstract】 The vibrating screen with high processing capacity is urgently needed in coal industry with the increasing demand of coal energy sources. Meanwhile, the maximization of screening machines can reduce the needed number of vibrating screenings and low the cost of equipments and thus brings a good economic benefit. But the maximization of vibrating screens will lead to the deficiency of structural stiffness and strength and affect service life. Now the traditional design methods, concerning static strength and kinematics analysis, are still in use and most of the products are designed through adopting empirical data and safety factor to calculate design parameters. This method can not reveal dynamic stress state of internal structure and make the design reasonable which affects service performance and life of products. Thus it is an important research subject to design large vibrating screenings, raise the design level and improve working reliability and service life of vibrating screenings.A new designed large vibrating screen with hyperstatic net-beam structure was studied in this dissertation. The author applied finite element method (FEM) and advanced vibration test method to design the large vibrating screen. The result shows that the reliability of the vibrating screen is increased.Three new types vibrating screens with high screening efficiency were proposed based on the principle of screening process with constant bed thickness. Accurate vibration mechanical models of two screens were built according to their structural features, using dynamics principle of mechanical system. With vibration theory of multi-freedom system applied, the author analyzed motion characteristic of the vibrating screens. Screening technological parameters including amplitude, velocity, throwing index of some specific points on the screen surface were calculated and their screening characteristic were studied.Structure features and screening characteristic of banana vibrating screen and their applicability were analyzed.The features of hyperstatic structure and the feasibility of the structure which was applied in the design of large vibrating screen were analyzed. A large vibrating screen was designed based on the banana structure, adopting hyperstatic net-beam structure which is composed of static plates, exciting beams and crossbeams. Main technical parameters, critical components and the dynamic parameters of the vibrating screen were established.The dynamic characteristic of banana vibrating screen was analyzed and the structural strength and reliability was studied. The method of improving calculation accuracy of the finite element model was given. A proper finite element model of the vibrating screen was set up and an adaptive method was showed for the simplification of the bolts. The FEM was used to solve natural characteristic of local important structure and integral structure of the vibrating screen. The results offer a basis for the dynamic modification of the structure and provide a reference for the test points’arrangement of the modal experiment. The author made a dynamic response analysis of the vibrating screen, applying the FEM. The dynamic stress and strain of the integral and local structure at the working frequency were obtained. The results show a better performance of the hyperstatic net-beam structure and find out structure defect of the vibrating screen.The vibration test on the vibrating screen’s prototype was accomplished, applying advanced test experimental technology. The modal parameters of the vibrating screen were gained by means of the modal experiment test. The results reveal the effectiveness of the finite element analysis and point out the weakness part of the vibrating screen.The sensitivity analysis method was used to modify the structure of vibrating screen.The paper used experimental modal frenquency and vibration modes to construct goal function according to the lagrangian multiplier method. The mass update matrix and stiffness update matrix which is applicable to the finite element model were given. The sensitivity analysis method was applied to modify local structural parametres of the vibrating screen based on the results of FEM and experimental modal analysis which made the dynamic parameters more reasonable and improved the structural stiffness and stability of the large vibrating screen.In order to solve the problem of high dynamic stress which led to the damage of the large vibrating screen, the author made a structural optimization of the vibrating screen. The size of reinforcing ribs and the mass of the side plate were optimized based on several frequency constraints. An applicable optimization criterion was given and the algorithmic method of analytical sensitivity was embedded in the program. The author complied a program with high convergence rapidity and solving accuracy, applying augumented lagrangian multiplier method, to confirm the best position of reinforcing ribs on the side plate and obtain lower dynamic stress with the least number of reinforcing ribs. The optimal results show that the structural stiffness of the side plate is improved and the deformation is decreased and thus the structural reliability is enchanced. The vibrating screen was stable and reliable when it was used in production. The test results of no-load running experiment show that the performance of the vibrating screen accord with the design requirements well.更多还原