Experimental research of rectilinear translational vibrations of a screen box excited by a ball balancer

The vibrations of the screen box excited by the ball balancer are experimentally investigated. The stand of the screen and two-frequency vibration exciter in the form of the ball balancer has been created for this purpose. The elastic supports of the box allow it to perform three principal vibrational motions corresponding to three resonant speeds of the shaft rotation: vertical rectilinear, angular oscillatory around one of two transverse central axes of the box. During the adjustment of the stand, it has been defined that the ball balancer excites almost ideal two-frequency vibrations of the screen box. The slow frequency corresponds to the rotational speed of the balls centers around the longitudinal axle of the shaft, and the fast one corresponds to the rotational speed of the shaft with the unbalanced mass attached to it. The two-frequency mode arises in a broad range of parameters and its general characteristics can be changed by changing: the mass of the balls and unbalanced mass; angular velocity of the shaft rotation. It is experimentally defined that the balls get stuck at the lowest resonance frequency, thus exciting the first form of the box vibrations. As a result, the box makes almost pure translational rectilinear vibrations and there are no angular components. In this regard, there is no need to impose additional kinematic constraints on the box motions. On the assumption that the box makes two-frequency vibrations, in the software package for statistical analysis Statistica, the coefficients in the relevant law have been picked up. At the same time, it has been defined that: – the process of determination of the coefficients values is stable (robust), the coefficients practically do not vary with the time interval of measurement of the law of the box motion; – the amplitude of the slow vibrations is directly proportional to the total mass of the balls; – the amplitude of the fast vibrations is directly proportional to the unbalanced mass. The discrepancy between the laws of motion obtained experimentally and with the statistical analysis methods is less than 1 %.