【作者】 陆春月；

【导师】 寇子明；

【作者基本信息】 太原理工大学 ， 机械工程， 2013， 博士

【摘要】 砌块成型机是生产砌块的关键设备,其振动密实成型技术决定了砌块质量的高低。我国生产的砌块存在密实度低的问题,导致抗压强度普遍较低,耐久性差。欧美等国的砌块成型技术先进,振动频率可达60Hz-85Hz,台振机加速度达到10g以上,模振机加速度可达20g左右,我国以台振机为主,频率在50Hz-65Hz,加速度一般不超过10g。与欧美等国相比,我国成型机振动系统频率低,加速度小,是导致密实度不高的主要原因。研究和开发具有自主知识产权的能够生产高强砌块的成型机,对打破国外高端成型机的技术垄断,提高我国砌块成型机技术力量具有重要意义。现有的振动密实大多采用偏心式惯性振动,受自身结构的制约,其振动频率很难再提高。本文提出利用液压激振作为振动输出源,结合分段非线性弹性力的振动系统来解决低频、小加速度问题。主要研究内容与结论如下：(1)分析混凝土密实成型影响因素,确定合理的振动参数,以此为设计依据,在分析了几种振动形式的基础上,提出了以两段不对称弹簧组成非线性力的双质体液压高频垂直定向振动系统。研究开发了转轴式高频激振器,并构建了整个液压调频激振系统。(2)分析激振器-液压缸组成的振动系统激振机理,针对系统参数时变性强的特点,建立基于瞬变流原理的带旋转流体液压振动系统的动力学模型,用有限差分法求得系统的动态特性。由仿真结果得,该液压激振系统的频率和振幅可控可调,在相同的系统压力下,输出激振力比直流液压振动系统大；外负载一定时,对物料加压工况下,振动系统输出激振力随之增大,有利于振动密实。(3)通过实验测定了弹性元件的载荷-变形曲线,得到了弹性力变化的滞回曲线,拟合了分段多项式的函数表达式。对成型机振动系统受力分析与运动过程分析,建立了具有五段非线性力的带双向间隙的双质体非线性振动模型,并用等价线性化法求得系统一次近似解,可得本文设计的振动系统从结构上保证了振动能量集中作用于模箱而不耗散于系统其他元件；用龙格-库塔法得到系统的数值模拟结果表明,频率70Hz-90Hz系统加速度可达15g以上,且产生混沌振动,实现以确定频率输入获得宽频响应,以低频激励获得高频谐响,大大提高混凝土颗粒的均匀性与密实度。(4)研制实验样机,搭建模箱工作模态测试系统,通过定阶得到系统模态参数。搭建振动参数采集系统并测取相关参数,分析频率、压力对系统振幅与加速度的影响规律。结合模态参数,实验结果表明砌块成型机在双频(70Hz,80Hz)激励下能产生多种共振同时存在的混沌振动,实现节能宽频振动密实,当在外激频率60Hz-90Hz范围内,系统振动加速度最大峰值达到甚至超过20g,指标超过国标的规定,与仿真结果一致,表明了本文所提出的非线性液压振动系统的正确性与合理性。(5)以实验所得输入输出数据为依据,采用支持向量机建立成型机实际振动系统整体实验模型。采用中值滤波和卷积滤波处理实验中的异常数据并进行数据光滑。利用5折交叉验证法确定支持向量机核函数最优参数,获得基于离散数据的实验模型；提出改进网格寻优方法并结合交叉验证法搜索核函数最优参数,获得基于时间序列的振动系统实验模型,以实验数据验证了两种模型响应预测的准确性,该实验模型是对理论模型的补充和完善。综上所述,本文的研究工作为开发能够生产高密实度砌块的成型机提供了理论支撑,对振动利用工程的发展以及建筑砌块行业的节能减排具有重要意义。更多还原

【Abstract】 Concrete block machine is a key equipment of producing blocks. Its vibration compaction molding technology determines the quality of concrete blocks. Blocks produced in China have low compactness, which can lead to problembs of low compressive strength and poor durability. The block molding technology is advanced in Europe and America. The vibration frequency can be range up to60Hz-85Hz, the acceleration of table-shaking molding machine exceeds lOg and the one of mould-shaking molding machine reaches about20g. The table-shaking molding machine is the major type of block machine in our country, whose vibration frequency is in the range of50Hz to65Hz and acceleration is within10g. Compared with Europe and the United States, the vibration system of molding machine in China with low frequency and acceleration is the main cause of low compactness.There fore, it is significant to research and develop block machines in producing high strength blocks with independent intellectual property rights to break the monopoly of foreign technology. Eccentric inertia vibration is applied to most existing vibration compacting, whose frequency is hard to be improved because of restrictions of its own structure. In order to overcome the problems of low vibration frequency and acceleration, a vibration system combined hydraulic exciting as vibration source with piecewise nonlinear elastic force is presented in this dissertation.The main work can be summarized as follows:(1) The affecting factors of compacting molding of concrete is analyzed and the matching relationship among vibration parameters of compaction is determined, which will be as design basis of vibration system. After analyzing several kinds of vibration modes, a high-frequency hydraulic vertical vibration system composed of double plastid and two segment asymmetric nonlinear springs is put forward. A high frequency rotary vibration generator is studied and developed. An entire hydraulic vibration frequency modulation system is established.(2) The exciting mechanism of the hydraulic vibration system composed of the excitor and hydraulic cylinde is analysised. According to the characteristics of strong time-variant of the system parameters, a dynamic model with rotating flow of the hydraulic vibration system is established on the principle of transient flow. Dynamic characteristic of the system is obtained by finite difference method. The hydraulic vibration frequency and amplitude can be controlled and adjusted. When the system pressure is the same, it has characteristics that its output force is stronger than that of DC hydraulic vibration system, and the output force increases with the applied pressure to the material in the die box when the external load is in the reasonable range. These are very beneficial for compacting vibration.(3) The elastic force hysteresis loop is got through experimental determination of load-deformation curves of the clastic component. The expression of piecewise polynomial function is fitted from the hysteresis loop. Force analysis and motion process analysis of the machine vibration system are carried out. Then, a double masses nonlinear vibration model is established. Meanwhile it has five sections nonlinear force and biphasic gaps. The first approximate solution is obtained by applying the method of equivalent linearization. It achieves the impact that vibration energy focuses on die box, but not dissipate to other components in the system from a centralized structure. The numerical simulation results got from Runge-Kutta method shows that the system vibration accelerations can reach more than15g when the frequency is70Hz-90Hz. At the same time the system is led into chaotic vibration to realize that broadband response can be obtained from certainty frequency, while high frequency harmonic response can be obtained from low frequency excitation. All of these can greatly improve the uniformity and compaction of the concrete.(4) The operational modal testing system of die box is built on the experimental prototype. The system modal parameters are obtained through the method of lumping order determination after using peak selection method to exclude the advantages frequency. An acquisition system is built to collect the associated vibration parameters of the system. The rules how frequency and pressure influence the amplitude and acceleration are gained. Combined with the modal parameters, it also can be discovered from the experimental results that the block machine can produce a chaotic vibration with multiple resonances coexist under dual-band excitation (70Hz,80Hz). Under the chaotic vibration the energy saving compaction with broadband vibration can be achieved. When the external excitation frequency in the range of60Hz to90Hz, the maximum peak of the system’s vibration acceleration will meet or even exceed20g, which has been exceeded the national standard requirements. Obviously, there can draw a conclusion that the block making machine having this vibration system will achieve a better performance and there also indicates the correctness and rationality of the nonlinear hydraulic vibration system proposed in this dissertation.(5) An experimental model for machine’s vibration system is set up based on support vector machine (SVM) with input and output data of the experimental prototype. The experimental abnormal data is processed by using the methods of median filtering and convolution filtering. The optimal parameters of the kernel function in SVM are obtained by5-fold cross-validation method to establish an experimental model with discrete data. A secondary grid search technique in combination with cross-validation method is proposed to optimal parameters of kernel function, and then a time series experimental model of vibration system is established. The response prediction’s accuracy of two models is verified through the experimental data. It is shown that the experimental models can be a supplement for the theoretical one.In conclusion, the research work provides theoretical support for developing molding machine with the capacity of producing high compactness blocks, as well as has great significance for the development of the vibration utilization project and energy saving in building blocks industry.更多还原