Analysis of roller-induced residual stresses in bandsaw plates and their effects on plate vibration and stability.

摘要

Bandsaws are used extensively in nearly every phase of wood machining and are indispensable cutting tools in forest products industry. In recent years, increasing attention has been devoted to the bandsaw plate vibration and stability to improve the cutting performance. However, an indispensable bandsaw plate pre-stressing procedure, known as "roll-tensioning", still remains mysterious and empirical. Although proper roll-tensioning has proved directly related to efficient cutting, a quantitative or even qualitative understanding of how roll-tensioning improves the cutting efficiency is not available.;Among many factors, lack of knowledge of residual stresses induced in the roll-tensioning process is the most important single issue. Without knowledge of the residual stresses in the bandsaw plate, analytical investigation of the effects of roll-tensioning is impossible or at least unreliable.;This research focuses on the mechanism of generation of residual stress by rolling and then establishes the quantitative relationship between the roll-tensioning process variables and the resulting effects on bandsaw cutting performances in terms of bandsaw plate vibration, lateral cutting stability and walking stability. The major contribution of this research is as follows.;First, the plastic flow of the material in the roller/plate contact zone during rolling is investigated on bandsaw plate for the first time. The unveiled stress-inducing mechanism and the residual stress distribution thus discovered provide a solid base for further analytical investigation of the effects of roll-tensioning on bandsawing.;Second, this research provides a mathematical model for predicting the effects of roll-tensioning on bandsaw plate vibration and stability. The quantitative relationship between the roll-tensioning process variables and the bandsaw plate stiffnesses and lateral buckling loads thus developed agrees well with experimental measurements. Phenomena commonly observed in practice such as plate buckling by excessive roll-tensioning and de-tensioning are clarified.;Third, the light-gap method, commonly used to measure the amount of roll-tensioning, is theoretically validated. Although, the light-gap can not be a reliable measure of the residual stress in the bandsaw plate, it can be a measure of bandsaw plate lateral buckling loads and walking stability if measured correctly.