UBC Theses and Dissertations
Supercritical speed response of circular saws Yang, Longxiang
This study investigates the dynamics of circular saws at supercritical speeds. A classical governing equation of a circular saw subjected to transverse and membrane forces is derived in both body-fixed and space-fixed coordinate systems. The transverse loads are generalized as spring, damping and out of plane cutting forces, and the membrane loads include rotational, thermal and in-plane cutting forces. Galerkin's Method is used to study the natural and forced response of a saw blade, and the effects of spring and damping on the stability at supercritical speed are discussed. An idling experiment is conducted to comprehend the fundamental behavior of circular saws at supercritical speed. The natural frequency, the steady state response, the flexibility and the runout variation of the circular saws are measured. The nonlinear vibration of the thin blade is observed. The effects of a spring-damper system and heating on the stability of a circular saw are investigated. A cutting test is conducted to find out the dominant parameters of supercritical speed cutting. At first, the prehminary experiments of the standard blade are conducted. Then, tip side cutting marks are discussed, and finally, the phenomenon of unstable cuttings are presented. The general solution of a rotating string subject to an elastic constraint is developed. Based on this, the discrepancy between theoretical and experimental stability results is analysed for a guided rotating disk.