【作者】 王毅；

【导师】 曹平祥；

【作者基本信息】 南京林业大学 ， 木材科学与技术， 2005， 硕士

【摘要】 随着对竹类资源利用的日益增加,特别是竹材人造板的广泛应用,竹材机械加工中的各种现象已引起广泛关注。竹材的切削加工是其中至关重要的一个环节,在竹材的切削中,常会遇到和木材切削不同的问题。对竹材切削原理的研究已是竹材加工利用领域急需开展的一项任务。　本文运用压电测力技术测量竹材切削过程中的切削力,采用CCD 摄像技术拍摄切削过程,然后分析切削力和切削区变形以及切屑形成之间的关系。　选用炭化和本色两种竹材并分别制作了专门的竹节部和节间材试件,对竹材的纵向、　横向及端向(每个方向又分为径向和弦向两个不同切削方向)等三个主要切削方向的切削过程分组加以研究。在每个小组内,运用正交试验设计方法安排试验,研究了在不同切削厚度、含水率和刀具前角下切削竹材的切削力和切屑形成情况。　纵向切削和横向切削都能形成三种切屑类型,而端向切削只能形成二种切屑类型。　采用准平衡悬臂梁的力学模型,提出了在上述三个方向进行切削时各类切屑形成的机理及判据,得出了形成各类型切屑的条件。　在试验条件相同的情况下,对竹节部和节间材切削,会形成相同类型的切屑,即其切屑形成机理相同。但由于竹节部维管束排列方向的特殊性,在某些情况下,竹节部的切削力、切屑形态以及加工表面质量都和节间材有所差异。　炭化竹材力学性能较本色竹材有一定降低,导致炭化竹材的切削力要较本色竹材略小,加工表面质量略有降低,但切削炭化竹材和本色竹材形成的切屑类型是一致的。　竹材的大部分力学性能在径向和弦向差异并不大,其它试验条件相同时,在这两个方向上切削形成的切屑类型是一致的,切削力差异也不显著。　在竹材的纵向、横向及端向切削试验中,切削厚度对切削力的影响都是同样显著的,切削力随着切削厚度增加而增大;在竹材的纵向、横向及端向切削试验中,竹材含水率对切削力的影响也都是同样显著的,当竹材含水率从绝干增加到平衡含水率时,切削力随含水率的增加而增大,而从平衡含水率增加到饱和含水率时,切削力则随含水率的增加而减小。在竹材的纵向、横向及端向切削试验中,刀具前角对切削力的影响都不显著。更多还原

【Abstract】 Nowadays, with the increasing utilizations of bamboo resources, especially in the means of bamboo composites, the phenomena in machining bamboo are paid more and more attention, in which bamboo cutting is one of the most important parts. Some new problems appear in bamboo cutting, and they are often different from what are met in wood cutting. Therefore it is urgently needed to develop research on the fundamentals of bamboo cutting. In this paper, piezoelectric pressure indicators are applied to measure the cutting forces in bamboo cutting, and the cutting processes are recorded using CCD camera. Then the relation between cutting forces, chip deformation and chip types are analyzed. Test specimens in the nodal zone and the internodal zone are made from both carbonized bamboo and normal bamboo. Experiments are arranged in groups according to the three different cutting directions: 90-0,0-90,90-90(in each direction, experiments are further developed in two different grain directions: tangential and radial direction). In each group, Orthogonal Latin Spare table is used to arrange the experiments, so that the influences of the factors of cutting depth, moisture content of bamboo and rake angle of knife on the chip formation could be studied. In 90-0 and 0-90 cutting, three different chip types can be gained respectively, however, in 90-90 cutting only two chip types can be gained. To explain the principle of the chip formation in the above 3 cutting directions, the model of quasi-equilibrium beam is adopted. The fundamentals of chip formation in the 3 cutting directions are developed to estimate what type of chip will be formed given cutting forces measured in the cutting process. With the same cutting parameters, same chip types can be gained in either the nodal zone or the internodal zone. In other words, the principles of chip formation are entirely the same in these two different zones. However, as the result of the particularity of the arrangement of vascular bundle in the nodal zone, in some cases, the cutting forces, chip form and the quality of the machined surface would be different from the internodal zone. After carbonization, some mechanical properties of bamboo would be weakened, however, this does not influence the chip formation of the treated bamboo. The cutting forces in cutting the carbonized bamboo would be less than cutting the normal one, and the surface quality would become worse in some degree. Most of the mechanical properties of bamboo are almost the same in tangential and radial direction, same chip types can be gained in these two different cutting directions, and there are also no differences in the cutting forces between the two different directions. In the cutting experiments in the 3 different cutting directions (90-0,0-90 and 90-90), cutting depth has the same evident influence on the cutting forces, and the cutting forces will increase with the increase of cutting depth. In the cutting experiments in these 3 different cutting directions, moisture content of bamboo also has the same evident influence on the cutting forces, the cutting forces will increase when the moisture content increase from absolutely dry to equilibrium moisture content, however, cutting forces will decrease when the moisture content increase from equilibrium moisture content to saturated moisture content. In the cutting experiments in the 3 different cutting directions, rake angle of knife does not have notable influence on the cutting forces.更多还原