【博士论文】弦振动理论在木工带锯条中的研究与应用

【作者】 王正

【导师】 孙友富蒋本浩

【作者基本信息】 南京林业大学, 木材科学与技术, 2008, 博士

  【摘要】 木工带锯机是木材加工行业中应用最广的设备。带锯条的受力极其复杂,锯解作业时带锯条会发生共振和晃动(抖振),这将影响锯解质量,所以对带锯条张紧力的振动特性研究尤为重要。作者在解读国内外文献的基础上,应用弦振动理论研究带锯条的振动,首先将带锯条的振动简化为弦的振动、简化为受拉伸与弯曲耦合效应的板梁振动和杆的扭转振动。应用静态和动态力学计算模型进行分析研究,主要包括理论解、有限元近似解法、随机激励谱分析。同时应用行波理论,研究带锯条的拍击和抖振现象,考虑带锯条预紧力T0(初拉力)的变化、带锯轮转动时扭矩引起的松紧边张力差△T的变化,以及带锯条转动所引起的惯性力Qn的变化三种情况,以期建立基频、动频、应变与张紧力和张紧应力的关系。研究结果表明:一,通过静态和动态计算模型理论分析,并用随机激励谱分析法验证,说明将弦振动理论应用到带锯条系统的振动研究是可行的。二,在静态下,锯条紧松边固有频率值(静频)相同;在开机空载时,锯条紧边固有频率值(动频)高于其静态时的固有频率值,松边固有频率值(动频)则小于静态时的固有频率值。三,带锯条横向摆动量的大小与锯轮转速有关,这是运行时产生的拍击和抖振造成的。四,用随机频谱分析法测量张紧带锯条振动的基频值,可用来确定带锯条的张紧力和张紧应力。五,实际的带锯条是一个有宽度和长度的长板条,除横向振动外还有扭转振动。同时带锯条的振动也应考虑面内的纵向振动,这些问题亟需进一步深入研究。总之,应用弦振动理论研究带锯条的振动,将复杂的带锯条振动简化成简单的弦振动,再考虑实际复杂因素,将经典的振动理论应用到古老的木工带锯机研究中去,这种由繁到简的过程是思维上的创新,为研制张紧力适时检测仪器和国产新一代带锯机的结构设计提供理论依据。

The Research of the Theory of String Vibration Applied in the Woodworking Band Saw Blade

 【Abstract】 Woodworking band saw is the most widely equipment used in wood processing industry. The force of Saw Blade is extremely complex when it’s working, there will be resonance and sway (quiver) on band Saw Blade, which will affect the sawed quality When the saw is in operations, so the study of vibration characteristics of its tension is particularly important. In this paper both domestic and foreign literature was unscrambled and the vibration of band Saw Blade was study on the basis of string vibration theory, The band saw was simplified into a string, with the vibration of saw Blade to be simplified to the string vibration for the first time, vibration of the tensile and bending coupling effect of plate girder structure and reverses vibration of staff. Analyze its static mechanical computing model and dynamic mechanical computing model, main including the string vibration theory, finite element approximate solution, random excitation spectroscopy experiments mutual authentication and supplement, also applied traveling wave theory of the spanking and quiver phenomenon of the band Saw Blade was studied at the same time, namely, this paper considered three things which were the changes of the band Saw Blade’s Preload(T0) (pre-pull) force when the band saw was static, the changes of tension difference (△T)between its tight-edge and the loose-edge was brought about Its torque when the band saw was running, and the inertia forces(Qn) was caused when the band saw was running, in order to establish its relationships between first frequency, travelling frequency, strain , tension and its stress.According to studies, (1) In terms of the analysis of static and dynamic computing model, and the mutual validation of random excitation spectrum analysis and dynamic spectrum analysis, the string vibration theory is applicable to the study of saw blade vibration system. (2) Statically, the tight-edge and the loose-edge of saw blade had the same natural frequency; non-loadedly, saw blade’s tight-edge natural frequency was higher than its static value, while saw blade’s loose-edge natural frequency was less than its static value; (3) The horizontal swing of band saw blade related to rotation speed of band saw wheels, which results from the spanking and quiver. (4) Measured first frequency of band saw blade vibration can be used to determine its tension and stress; (5) Actual Saw Blade is a long band with fixed width and length, there is not only horizontal vibration but also torsion vibration. At the same time, the vertical vibration of the band saw should also be considered when studying the vibration of the band saw, and these issues need further study. In conclusion, this innovative method of studying the vibration of band saw blade via string vibration theory simplified the complex band saw blade system into the string vibration, considered again its actual complex factors and applied classic vibration theory to the studies of wood working band saw machine, which will provide theoretical evidence for the further design of tension timely detection apparatus and a new generation of China-made high-quality wood working band saw machine.

 

 

 

 

 

 

 

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