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1.
Katsutoshi Fujiwara 《Journal of Wood Science》2002,48(4):277-282
Bandsaw roll-tensioning was theoretically analyzed by amplifying Aoyama's fundamental equations. In the analysis the accumulated amount of tension after several roll-stretching passes was expressed as the linear accumulation of the amount of tension at each roll-stretching pass. The same condition was applied for the expression of the accumulated amount of crown back. The relations between the distance from the gullet in the transverse direction of the bandsaw blade to the roll-stretching point and the distance from the gullet in the transverse direction of the bandsaw blade at which the amount of tension becomes maximum, minimum, or zero were clarified. To meet the requisites to adjust the amount of tension at an arbitrary distance in the transverse direction of the bandsaw blade or the amount of crown back, an adjusting procedure was developed. The process of bandsaw roll-tensioning can theoretically be controlled by this procedure. 相似文献
2.
3.
Ricardo O. Foschi 《Wood Science and Technology》1975,9(4):243-255
The relationship between residual stress distribution induced in bandsaw blades by cold rolling during tensioning and the transverse deflected shape obtained when the tensioned blade is bent over a given radius is studied. It is shown that the light-gap technique is not a reliable estimator of residual stresses since, while two transverse deflected shapes may be close to each other, the corresponding stress distributions may be far apart. The technique may be improved, within limits, by decreasing the tolerance with which a desired transverse deflected shape is approached during the tensioning process. A method for computing this tolerance is given. 相似文献
4.
This paper presents a method for detecting gullet cracks in a bandsaw during sawing by monitoring burst-type acoustic emission (AE) signals with large amplitude. The amplitudes of the AE signal and profile height amplitude distributions based on roughness profiles of the sawn surface were compared for the bandsaw with and without gullet cracks. The amplitudes of the AE signal increased and the sawn surface quality became worse with the increased number of gullet cracks in the bandsaw. 相似文献
5.
以湖南益阳康富南路跨线桥为实例,对其吊杆索力分别采用DASP动态采集分析系统和JMM-268索力动测仪进行测试,从而比较两种频率测量方法用于短吊杆索力测量的优劣。通过实例比较得知,DASP动态采集分析系统更适宜短吊杆索力的测量,其精度比JMM-268索力动测仪高。以弦振动理论为基础的振动频率法是桥梁健康检测中检测索力的一种常用间接方法。由于系杆拱桥的吊杆比较短,且吊杆索力受两端约束条件影响比较大,根据本例实际考虑了短粗拉索的抗弯刚度,采用边界条件为两端铰接拉索的自由振动进行分析,建立由频率识别拉索索力的近似公式。 相似文献
6.
This paper presents an on-line method for detecting damaged teeth in the bandsaw using acoustic emission (AE) signal energy. The method is based on an analysis of differences in AE energies generated by normal and damaged teeth during sawing. Because of the difference in the amount of sawing, the AE energy was low for sawing by the damaged tooth and high for sawing by the normal tooth immediately after the damaged tooth. The ratio of AE energy for two successive teeth — a normal tooth immediately following a damaged tooth — was much greater than 1, whereas the ratio of AE energy for two successive normal teeth was close to 1. The results demonstrate that the technique using the AE energy ratio for two successive teeth is effective for on-line detection of damaged bandsaw teeth.Part of this paper was presented at the 9th Annual Meeting of the Chugoku Skikoku Branch of the Japan Wood Research Society, Tottori, October 1997 相似文献
7.
In this paper, a 2-D and 3-D finite element model of roll tensioning process of circular saw blade were established by Static/General module of ABAQUS software based on finite element method. The rolling force and tensioning stress distribution of circular saw blade were calculated by these two models which were proved to be true and reliable. The effects of yield strength of circular saw blade on tensioning stress distribution and rolling force were studied. The research achievements showed that a circular saw blade made with high yield strength obtained a higher tangential compressive stress and radial compressive stress in the rolled region during roll tensioning process, which has both advantages and disadvantages for the stability of the saw blade. Besides, a circular saw blade made with high yield strength also put forward higher requirements for roll tensioning equipment because of the large rolling force during roll tensioning process. 相似文献
8.
As a new use of bamboo, bamboo cubes may be useful as a shot-blast material for surface treatments. However, a suitable processing
technique for bamboo cubes has not been established. In this study, to obtain basic knowledge regarding the processing technology
for bamboo cubes, we installed shearing blades (upper and lower blades) in a universal testing machine to test cross-sectional
shearing of bamboo. The shearing force generated in this shearing was composed of a vertical component (F
v), a forward component (F
f), and a side component (F
s). This shearing force (F
v, F
f, and F
s) and the machining accuracy were investigated under various processing conditions. The shearing force became larger as the
thickness of bamboo increased. In particular, F
v showed a tendency to increase rapidly. Changes in the shear angle of the upper blade had a remarkable influence on F
v. This result suggests that the shearing force could be greatly decreased by adjusting the shear angle. The shearing force
within bamboo of 3mm in thickness was almost unaffected by the blade angle, and the change of shearing force with increasing
clearance was almost indiscernible. It was clearly demonstrated that a large number of bamboo cubes could be made when the
shear angle was large and cross-sectional shearing was performed from the bark side. However, a consequence of a large shear
angle is that burr area increases.
Part of this article was presented at the 53rd Annual Meeting of the Japan Wood Research Society, Fukuoka, March 2003 相似文献
9.
Summary A model for the isothermal transport of bound water through the cell wall of wood is developed, based on the assumption that the driving force for moisture movement is the gradient of spreading pressure , as first proposed by Babbitt (1950). This pressure is a surface phenomenon, derivable from the surface sorption theory of Dent (1977), a modification of the BET sorption theory. The force resisting moisture transport is assumed to be inversely proportional to moisture content and directly proportional to the equivalent viscosity of the sorbed water, calculated to be orders of magnitude larger than that of free water. The coefficients normally used to describe isothermal moisture transport in wood are derived from the model, and their predicted behavior as functions of the relative vapor pressure h of the cell wall are described graphically. An attempt is made to calculate a quantitative magnitude for the diffusion coefficient D, based on an assumed relationship between viscosity and the activation energy for water diffusion. 相似文献
10.
为了实现快速修枝,结合桉树的通直度较其他林木高的特点,设计一种以两个対置分布的驱动轮作为攀爬驱动机构,从而使自身可以沿着树干直接往上爬升的爬树修枝机。该爬树修枝机主要由攀爬装置和修枝装置组成。对攀爬装置进行动力学分析,确定了驱动轮与树干之间的摩擦系数和攀爬装置夹紧力所要满足的关系式;根据滑切切割可降低切割阻力的原理,对修枝装置的切割刀片进行了设计,在综合考虑爬树修枝机的结构布置和总体质量的前提下,为减少修枝装置的切割阻力,确定其定刀片的倾角为10°,动刀片的倾角为12°;在桉树活立木和以圆形钢管作为模拟树干的试验装置上分别进行爬树修枝机的攀爬性能和修枝性能测试,结果表明:在攀爬装置所用的电动推杆推力为600 N的条件下,本研究所设计的爬树修枝机能够顺利攀爬桉树活立木,树干未见损伤,具有较好的攀爬性能,打滑率仅为10.03%,爬树修枝机能够切断直径10 mm以下的桉树枝条。结合爬树修枝机的结构参数和试验条件进行计算和分析可知,此时爬树修枝机的加速度为2.88 m/s2,最大爬升速度为2.97 m/s,修枝过程中所消耗的功率为603.10 W,而切断直径更大的枝条并且避免动刀片与树干之间产生作用力,则需要进一步增加攀爬装置的电动推杆的推力,推力至少为1 573 N,在此推力下,爬树修枝机消耗的功率为1 585.73 W。 相似文献
11.
索网式和双联式缆索起重机的设计计算都十分困难 ,主要是因为过去的索道索系比较简单 ,以致现行的索道设计计算体系 ,都只计算悬挂缆索在均匀重力场的作用下 ,承受垂直载荷时的受力状态。双联式和索网式缆索起重机的出现 ,首次提出了悬挂缆索的斜向集中载荷和索网结构承重时的受力分析问题。文中对索网式缆索起重机的计算 ,实际上是对悬挂缆索的斜向集中载荷和索网结构承重时的受力分析 ;而且这种分析 ,同样适用于双联式缆索起重机的设计计算 ,并为今后发展更为复杂的索道索系的设计计算提供了新的理论依据 相似文献
12.
The experimental results of orthogonal cutting of maple and the modeling of the cutting mechanics are presented. The tool cutting forces were measured for different feed rates. A set of equations relating the tangential and feed forces to the tool edge width and feed rate (chip thickness) to calculate the chip and edge cutting force coefficients was developed. Then the chip force and edge force coefficients were calculated from experimentally obtained cutting forces and were plotted in a polar-coordinate system with respect to the fiber orientation of the maple disk. The polar-coordinate presentation of the cutting force results and the calculated cutting force coefficients provides an excellent visual appreciation of the relation between the cutting forces and the wood fiber orientation. Chips were also collected from various sectors of the wood disk. This analysis further identified the effects of fiber orientation and cutting forces on the types of chip formed and hence the cutting mechanics involved. By applying the calculated cutting coefficients for each tool orientation (in respect to the grain) it is possible to predict the feed and tangential forces for any feed rates. There is good agreement between the predicted and measured cutting forces. 相似文献
13.
对木质材料切削中比较特殊的一类切削方式———无屑切削的切削机理及切削力进行了理论上的研究,并在单板切条试验机上进行试验验证。研究证明,楔型刀锯进行木质材料无屑切削时,其切削力受木材的树种、切削方向、锯片尺寸、角度参数及切削用量的影响较大。 相似文献
14.
根据漾濞县2006年森林资源二类调查中的核桃专项调查资料,概述了漾濞县核桃资源面积、产量、株数、分布情况及其资源特点,采用理论结合实际的方法,对全县核桃资料价值量进行全面估算结果,林木价值量为11.674 5亿元,林地价值量为6.307 8亿元,合计17.982 3亿元. 相似文献
15.
分析了微米木纤维模压制品螺纹连接的受力,提出了其力学分析的基本假设,建立了螺纹牙的力学模型,推导了螺纹牙受力分布函数,对螺纹牙受力分布曲线进行了数学描述,提出了微米木纤维模压制品螺纹牙受力分布的百分比。应用本文提出的理论,可以根据微米木纤维模压制品的刚度和螺纹的几何参数定量计算螺纹牙受力分布,进而计算其螺纹连接的强度,为微米木纤维模压制品螺纹连接的强度计算提供了重要的理论依据。 相似文献
16.
Summary This paper investigates a method for slicing thick pieces of wood across the grain using a sharp steel knife, and it demonstrates the effectiveness of the knife slicing process at an experimental level. In order to highlight the key parameters facilitating or hindering the thick slicing process, several factors affecting the cutting forces and the cut surface quality have been studied; the blade geometry, the effect of friction, the cutting speed, the boundary load constraints and the wood moisture content. The results indicate that a large proportion of the cutting force may be related to the wedging action of the blade in the wood. Therefore, significant reductions in the cutting energy can be achieved by optimising the blade shape. A simple homogeneous strain model has been developed which quantifies the cutting forces in terms of the blade angle and the blade surface friction. The results from this theoretical model are compared with the experimental findings and discussed in relation to methods for improving the cutting technique.This work was funded by the Foundation for Research Science and Technology. This support is gratefully acknowledged 相似文献
17.
利用三维坐标仪 ,对一空间叶片进行了定位测量 ,计算出各截面的主要参数 ,根据叶片的受力特点 ,对叶片进行强度校核 ,并对结果进行了理论分析 相似文献
18.
To clarify the inducing mechanism of kerf deviation caused by unsymmetrical set of the handsaw, we hypothesized that the moment
on the bottom edge of the saw blade, which is generated by the unsymmetrical set on handsaw teeth, bends the saw blade and
this deformation should be one factor of the kerf deviation. To verify this hypothesis, the bend of a saw blade was examined
by experiment and by calculation. In the experiments, a model tooth was attached to an actual handsaw. In the calculations,
a saw model with a rectangular prism as the model tooth was analyzed by the finite element method. Loads were applied on the
model tooth or the rectangular prism. From both the experiments and the calculations, the following results were obtained:
(1) the deformation of the handsaw was caused by the unsymmetrical set in the length direction and the height direction of
the saw blade; (2) the deformation and the inclination of the blade was larger at the front part of the saw than at the butt
part; and (3) comparing the saw handle fixing conditions, the kerf deviation in the sawing line was supposed to be larger
in the free handle condition and that kerf deviation in the depth direction was larger in the fixed handle condition. Based
on the above results, it is apparent that one of the kerf deviation mechanisms originated from unsymmetrical set on the saw
teeth.
Part of this report was presented at the 54th Annual Meeting of the Japan Wood Research Society, Sapporo, Japan, August 2004. 相似文献
19.
This study aims to clarify the effect of density of riparian vegetation on effective tractive force for various bedload transport conditions. Hydraulic model experiments were performed using a straight channel, and the methods used to calculate the effective tractive force necessary for estimating bedload transport rate in channels with riparian vegetation were studied. An apparatus was developed to directly measure the effective tractive force in a channel with riparian vegetation. Applying the apparatus in a hydraulic experiment allowed accurate direct measurement of effective tractive force, formerly estimated indirectly. Based on the experimental results, the effect of the density of vegetation on the effective tractive force was examined. Then the methods for estimating effective tractive force and bedload transport rate were studied. As a result of the experiment, it was found that the coefficient of velocity U/U* and the ratio of coefficient of velocity (U/U*)/(U/U*) are negatively correlated with the density of vegetation. A very high negative correlation was also obtained between recession coefficient of effective tractive force ( = effective tractive force of a flow with riparian vegetation/effective tractive force of a flow with no riparian vegetation) and the density of vegetation. The friction factor of the channel bed f was positively correlated with the density of vegetation. Methods were presented for accurately estimating effective tractive force using equations including the relationships of the density of vegetation to the coefficient of velocity, the ratio of the coefficient of velocity, and the recession coefficient of effective tractive force. Using the estimated effective tractive force and an existing bedload equation enabled very accurate calculation of bedload transport rate in flows through riparian vegetation. The methods presented in this study have potential to be developed as a tool that can provide guidance in the planning and designing of riparian vegetation that are intended for the prevention and mitigation of floods and resultant sediment transportation. 相似文献
20.
A. Krilov 《Wood Science and Technology》1976,10(3):199-208
Summary Examination of the bandsaw teeth (1) untreated, (2) swaged and (3) treated by thermal high-frequency surface hardening method has shown that their average microhardness is 473 DPN (<46 Rc), 502 DPN (<49 Rc) and 836 DPN (>62 Rc) respectively.Scanning electron microscopy revealed that no significant change occurred within the crystalline microstructure of untreated and swaged specimens. The high-frequency treated specimen, however, has shown a definite structural modification of a very finely grained martensitic type, extending from the apex for a distance of 0.24 mm.The relationship between DPN microhardness distribution throughout the bandsaw steel and the range of H.F. impulse times from 24/50 to 36/50 of a second was also investigated, and depth of the hardened zone determined.The optimal H.F. impulse time length corresponding to the optimal tooth hardness appears to lie between 32 and 33/50 of a second. Operating with 32/50 impulse time on a conventional 2.41 mm thick SANDVIK bandsaw with 0.73 mm side swage, it was found that the average hardness of a H.F. treated tooth apex is about 905 DPN (>64 Rc) to a depth of 415 m and in practical terms approaches the estimated optimum for high-speed cutting. 相似文献