Research On Vibration Dynamics And Control Of Diamond Beaded Rope During Sawing Process

As the machining tool for diamond beaded saw machine, dynamic behavior of beaded rope directly effects of diamond beaded rope life and processing quality. In the process of processing, due to positioning wheel effect, the beaded rope has the corresponding bending with the change of angle of view, at the same time, diamond bead in time and space have different impact on the workpiece, and the impact is main cause the vibration of beaded rope. Diamond rope "flexible" vibration generated by machining has both advantages and disadvantages. In the process of processing, if the string diamond beaded rope high frequency and small amplitude vibration, it is helpful for cuttings discharge and reduces the processing temperature, reducing the impact of beaded cuts into the workpiece, then. Reduce the wear of beads, the bead wire processing variable sawing processing for vibration. Conversely, the wire impact force are increased, noise increased, the diamond beaded rope life reduced, can’t conducive to sawing machine. Therefore, on the basis of comprehensive domestic and foreign research, this paper proposes to study the dynamics and control of diamond beaded rope in machining process. According to the theoretical research results of the axial movement and the structure and process characteristics of the beaded-rope. Study on the dynamic behavior of wire processing from these four aspects of the wire vibration causes, the diamond wire free and forced vibration in the processing zone, the transverse vibration control of coupled vibration and the beaded rope wheel study on the dynamic behavior of beaded rope processing.The main contents are as follows:(1) Based on virtual material fractal theory and Hertz contact theory, the elastic modulus and Poisson’s ratio of the virtual materials were analyzed, the equivalent parameter model of virtual material is constructed. According to the multi-body dynamics theory, a multi wire saw machine driving system model is established. Using finite element method, the equivalent parameters of the virtual material is introduced to the finite element model of the wire saw machine. Analysis the natural vibration characteristics of the wire saw machine with the condition of considering and without considering the joint surface is carried out, the natural frequency and vibration mode of the key components are obtained. Use Adams and vibration module, analysis of the rope saw machine in the forced vibration response, the curve of displacement, velocity, acceleration and frequency, given the transverse vibration of the string bead wire incentives.(2)The transverse dynamics vibration equation of the beaded string is based on multi-body dynamics principle, using the Lagrange equation to establish the vibration mechanics model of the beaded string. Analyzed the structural parameter such as the length, linear density, tension and speed of beaded string, and then study the influence on natural frequency as they changed. On the strength of the principle of collection quality method, the affection of beaded string’s tension, velocity, quality and active site on transversal vibration inherent frequency is analyzed in detail, reveals the impact of physical parameters and structure parameters of the beaded string on free vibration and the modal shape of beaded string in different position. Build an experimental system. The experimental results verify the correctness of the transverse vibration numerical theory analysis on beaded string, the error is in range of 8%, indicating that the reliability of experimental test and theoretical analysis.(3)According to the law of volume constancy, the paper analyzes the sawing force of a single beaded and obtains the average effective cutting depth of a single beaded is in relation to the length of a string of beads, the number of the diamond grits per unit area, the cutting angle θ, the movement parameters of the beaded string and has nothing to do with the length of the work-piece. On the basis of Hamilton’s principle, the forced vibration mechanics model of beaded string is established and the transverse vibration response of beaded string under different loading is given. Based on the theory of random vibration, the power spectrum between output and input system of the beaded string, the self-spectral function of output system and the mean square value model is established, the influence of velocity, tension active site and other parameters of beaded string on the mechanism of random vibration is explored, and the power spectrum of output and input, the rule that the mean square value changes with linear velocity, tension and active site of beaded string is obtained. At the same time, based on the characteristics of green’s function of time and space, the characteristics of longitudinal vibration of beaded string is further analyzed, reveals the law that the maximum longitudinal vibration amplitude is at the cutting site of the processing zone, the minimum amplitude is at the middle of the processing zone, and the maximum effective amplitude in cutting-in site is about 30% bigger than that in cutting-out site. The experiment for analyzing the law of forced vibration characteristics is conducted under the condition of different parameters.(4)The transverse vibration mechanical model of each section of beaded string, the torsional vibration mechanics model of each wheel and the dynamic model of tension system is set up according to the Hamilton’s principle and Newton’s second law. Besides, the steady-state analytical model of coupling vibration of rope sheave is given too. Control scheme which based on the structural parameters optimization design of tension system is proposed, the influence of some structure parameters, such as the length and the rotation angle of the tension arm, on transverse vibration displacement of the beaded string is analyzed in detail. Obtained the law that with the change of structural parameters, the transverse vibration deformations of the 1,3 period of beaded string are basically consistent. Through the structural parameters optimization design, the transverse vibration of beaded string was controlled effectively, the transverse vibration deformations of the 1,3 period of beaded string decline by an average of 31.438% and 16.0% respectively. According to the principle of variable structure control, a beaded string variable structure controller is designed, the mechanics model of variable structure control is given, the inhibiting effect of the controller on the transverse vibration deformation of beaded string is explored, and improves the stability of the beaded string’s tension, in addition, the level of coupling vibration between the beaded string and the driving wheel has been restrained.Therefore, through the research on the dynamic characteristics and vibration control during the machining process of the diamond beaded string, the problem of dynamic controlling of the vibration characteristics in the flexible machining of the wire saw is broke effectively, and the basic key problem which restricts the development of wire saw’s high efficiency machining will be solved. Moreover, it has great significance on enriching and developing the "flexible" processing theory and the design theory of the "machining tools" which combines stiffness and flexibility.