Recent developments in the field of thermally induced waves and vibrations

Tile steadily rising costs of labor and raw materials and of workers\" safety necessitates consideration of kerr losses and noise along with measures of improved production, cutting accuracy, and surface quality. Reduction of kerf losses can be achieved by using thinner saws as long as blade stability can be maintained through blade design and on-line control. The current status of saw vibration control research is reviewed here. The topics include vibration reduction and control through saw design and membrane stress modification, feedback vibration control, and methods for reduction of aerodynamically excited vibration noise.

Principal developments in thin circular saw vibration and control research

A review report on principal developments in thin circular saw vibration and control research

Estimation of nonconservative aerodynamic pressure leading to flutter of spinning disks

On the detection of natural frequencies and mode shapes of submerged rotating disk-like structures from the casing

Membrane stresses alter the dynamic behavior and stability of circular-disk elements, such as circular saws and grinding wheels, by shifting the disk's natural frequency spectrum. Such shifts are directly related to variation in the critical rotation speed at which standing-wave-resonance instability occurs. Negative critical-speed variations reduce the disk stability, and positive critical-speed variations increase stability.

Control of circular-disk stability with membrane stresses

A modal testing method permitting identification of the natural frequencies, the number of nodal diameters and wave motions in a rotating disk is presented in this paper. This method is applicable at arbitrary rotation speed without requiring a priori information about the vibration modes of the stationary disk. The influence of disk rotation speed on the prediction of mode shapes with this method is shown, and experimental predictions of modal parameters are presented for both axisymmetric and asymmetric disks.

Mode identification of a rotating disk

A number of studies has shown that natural frequencies and, accordingly, the minimum critical speed for the formation of a standing wave in thin, rotating, circular disks can be beneficially altered by purposely induced initial membrane stresses. The possibility of controlling natural frequencies by induced thermal membrane stresses, rather than initial stresses, has received some previous theoretical attention and is experimentally examined here for a stationary, constant-thickness, centrally clamped, circular disk. The primary advantages of thermal membrane stresses are manifested in the inherent flexibility in adjustment of the thermal as opposed to the initial stresses. Increases in the minimum critical speed, which is proportional here to the zero nodal circle—two nodal-diameter natural frequency, of 20 percent were determined with moderate heating. This can be considered a relatively small critical-speed increase when compared with variations expected in many common rotating disk environments. A thermal model, which utilizes as input the peripheral disk heat flux and the controlled disk temperature at some known radius, is shown to predict the temperature distribution and natural frequencies with reasonable accuracy. The applicability of this model enhances the potential practicality of the induced thermal-membrane-stress method of natural frequency and/or critical speed control.

C. D. Mote

Papers

Control of circular-disk stability with membrane stresses

Mode identification of a rotating disk

Thermally induced natural-frequency variations in a thin disk