锯链与链轮啮合的几何条件及节距偏差的影响

根据新型锯链的结构特点，参考链传动的几何条件，推导出一套锯链与链轮啮合传动的几何条件基本公式。这套公式涉及了等节距锯链和不等节距锯链两种情况，还涉及星形驱动链轮、轮辋式驱动链轮和星形导向链轮三种链轮。     

链锯链轮设计计算理论的研究

为了满足链锯的链速向高速方向发展，锯链的节距应变小。现有国内外有关链轮的设计计算理论只适用于锯链节距为１５ｍｍ或１５ｍｍ以上的锯链与链轮的正确啮合与链轮设计。而节距ｔ≤１０．２６ｍｍ的链轮设计应用现有的链轮设计计算理论进行设计有很大的局限性。通过对国内外不同节距锯链结构，外形尺寸以及锯链与轮链啮合实际状态的比较、分析，研究出锯链与链轮的正确啮合的理论，并建立了一整套较完善的链轮设计计算理论。依据本     

轮圈式链轮设计理论的研究

本文提出链锯链轮与锯链正确啮合条件的新理论。对于小节距型号的链锯锯链确定了不同的几何参数作为原始数据 ,并在正确啮合条件下建立了一套适用于不同形式小节距锯链的轮圈式链轮设计理论公式。     

锯链链轴强化技术的研究

链锯是伐木、造材的主要工具。锯链作为链锯的切削工具,工作状况较恶劣。而我国目前制造的锯链,质量偏低,有的甚至几天就报废。主要表现有:①各组成件,在制造和使用过程中常产生微裂纹,在交变载荷作用上断裂;②所用的材料含碳、硫、磷量过多,产生低温脆断;③切齿磨损快,切削速度过低;④由于链轴磨损过快,使锯链节距变长,破坏了锯链与驱动轮的正确啮合,加速锯链和链轮的磨损,经常产生掉链。因此锯链材料的选择和强化,是当前提高锯链质量的关键课题。现本文仅就其中链轴的材     

减少油锯链轮齿面磨损的方法

在油锯使用过程中,经常发现链轮齿面严重磨损,其主要原因之一,是由于油锯手不注意正确使用和调整。延长链轮与锯链使用寿命,提高油锯工作效率,以下办法是可行的: 1.使用油锯时,禁止新锯链与磨损了的链轮,或者节距拉长、磨损的旧锯链与新链轮装配使用。最好是一只新链轮搭配2～4条新锯链,经常轮换使用,使     

拨梁式链条输送机的设计

一般的链条输送机系采用链和链轮啮合的方式传送动力。由于链条和链轮之间易磨损,使链条节距增大较快,破坏了啮合特性,容易发生脱链、产生冲击,降低链轮轮齿及链条强度,使用寿命缩短。     

锯链连接片偏磨原因的受力分析及解决途径的研究

通过对国内外万能锯链负荷工作时的受力分析,发现现有万能锯链的切齿组件的设计几何参数不尽合理。因而,造成正压合力集中,促使连接片偏磨,缩短了锯链寿命。同时,偏磨后的切齿组件切削功能恶化,影响了链锯机械性能的发挥。为此,重新设计了切齿组件,使正压合力趋向多点均匀分布。经生产、台架试验证明,新型锯链的使用寿命,是国产锯链的2倍左右,是斯蒂尔锯链的1.5倍;切削效率比国产锯链提高35—116.7％,比奥利根锯链提高3—4％。同时,切齿组件在整个生产过程中,始终保持着良好的切削状态和原设计的主要几何参数。证明“正压合力多点均匀分布”的设计理论是克服连接片偏磨的可靠途径。     

M_3L_2—950型电锯改进的研究

吉林省永吉县旺起林场将 M_3L_2—950型电锯进行了改进。本文主要论述了改进电锯的结构和性能;改进电锯的测定和台架试验以及初步分析和结论。它的发展有助于各地林业贮木场和林场造材电锯的技术革新和新技术的推广。改进电锯将15mm 节距直齿式锯链换成节距刨刀式锯链。为此电锯的锯木和传动机构也相应做了改动。经测定,改进电锯的锯截效率提高2—3倍。     

JL10—60型锯链链轴高频感应加热淬火自动送料装置

ＪＬ１０－６０型锯链链轴高频感应加热淬火自动送料装置富裕林札厂孔德生，盛华君，郑克学１研制送料装置的意义ＪＬ１０－６０型锯链（节距１０．２６ｍｍ）是安装在油锯、电锯上进行树木采伐和造材用的链式刀具。锯链由切齿链片、传动链片和连接片通过链轴铆接成环形链...     

锯链张力的计算

锯链张力包括安装张力、离心张力、制造误差引起的附加张力、热张力、惯性动张力和驱动张力。静止时锯链不脱离导致导轨面的临界张力与导板轮廓线曲率半径和锯链质量线密度成正比。无缓冲器导板的安装张力应包括离心张力,数值较大;而有缓冲器导板的安装张力应不包括离心张力,数值较小。锯链的驱动张力是驱动力与切削阻力及摩擦阻力相对抗而产生的,在不同位置其大小不等。锯链的最大张力发生在驱动链轮啮入点附近,其数值相当大。文章给出了各种张力的计算公式。     

LQ-18型锯链切削性能试验台研制

评定锯链的切削性能包括切削阻力、锯切功率、锯切效率以及锯链运转的平稳性等指标。这些指标的测定依赖于可靠的锯链切削性能试验装置。本文在现有LQ—11型锯链切削试验台的基础上,分析总结经验．结合计算机技术、测试技术,设计出性能更加完善的LQ-18型锯链切削性能试验台。该试验台采用了进给速度及链轮轴无级调速的运动形式,能够同时测量三向切削力、驱动链轮轴转矩、转速及进给速度,并且由计算机组成的测试系统直接测量、显示计算测试数据,生成测试报告,提高测量精度及测试效率。该专用锯切试验台结构先进,测试范围宽,测定精度高,重复性好。     

Duration of load revisited

A duration of load study representing 13 years of testing was recently terminated. Preliminary results have been published over the years. This paper represents the final account of the study, which was focused on the influence of moisture content on time to failure for structural timber subjected to bending under constant load conditions. Two constant moisture conditions (MC = 11 and 20%) and one condition of varying moisture (MC between 11 and 20%) were applied. A total of 816 Norway spruce boards of dimensions 44 × 95 × 1,800 mm³ were included. Eight groups of non-destructively matched samples were formed. Four groups were subjected to short-term strength tests, and four groups were subjected to long-term tests. Creep and time to failure were monitored. Time to failure as a function of stress level was established and the reliability of stress level assessment was discussed. A significant mechanosorptive effect was demonstrated both in terms of increased creep and shortening of time to failure. The test results were employed for the calibration of four existing duration of load models. The effect of long-term loading was expressed as the stress level SL₅₀ to cause failure after 50 years of loading. SL₅₀ was found to be of the order 0.60 for MC = 11%, 0.50 for MC = 20% and 0.44 for MC varying between 11 and 20%. The test results revealed no evidence of a threshold stress level. A reliability based calibration of load-duration factors was performed using probabilistic models of loads and of the short-term and long-term strengths. For permanent and imposed library loads, reliability-based estimation of the load duration factor gave almost the same results as direct, deterministic calibration.     

基于车辙等效的轴载换算关系研究

车辙作为高速公路路面主要病害之一,在我国现行公路沥青路面设计规范中没有纳入车辙指标。目前在国内许多科研机构和学者都在致力于车辙形成机理及车辙预测等方面的研究工作,足尺加速加载试验在公路工程领域是科研费用最昂贵,结果可靠性较接近实际路面状况。通过对野外三种路面结构的加速加载试验,利用车辙等效的关系确定出不同路面结构对应的合理轴载换算指数。将加速加载试验成果与室内车辙试验进行对照,证实室外加速加载试验得出的轴载换算指数与室内试验结果之间的差异。     

Wood material features and technical defects that affect yield in a finger joint production process

Abstract

A cost efficient process is the goal of all production, and each manufacturing step affects the material utilization and cost efficiency. There is high diversity in the inherent features of wood, and manufacturing steps must be able to handle this. The overall objective was to study the potential and problems in manufacturing production processes in terms of material utilization efficiency. The production of finger jointed bed sides was chosen as a study case, where the chain of production units are the sawmill, finger joint plant and furniture plant. This article describes the impact of raw material and wood defects that could affect the total yield. A total of 177 logs of three types were tested: butt, intermediate and fresh knot logs. The test material quality was detected and measured through all steps in the manufacturing chain. The results show differences between log types in down-grade causes, reject volume and final yield. Also, the test material showed high levels of defective components with process-related defects, which suggested the need for technical improvement in the manufacturing process. The intermediate log group showed the overall best result.     

以手扶拖拉机为主机的JS3-2绞盘机研制

论述手扶拖拉机改制绞盘机的技术关键,对绞盘机进行总体动力学分析,提出真实反映绞盘机功率的计算法,即按最不利工作条件计算起重提升功率和重车上行功率,择其大者并有一定过载能力的计算方法,以此作为JS3-2绞盘机主机——手扶拖拉机选型的依据。介绍JS3-2绞盘机整机构造、工作原理及其主要技术参数,并进行性能分析,阐述其在生产中的应用。实践证明:JS3-2绞盘机具有合理的功率匹配、优越的性能、人性化的操作,在木材采运、路桥和水利电力工程等领域得到广泛应用。     

Long-term experiments with end-cracked wooden beams

Summary The duration of load effect for the fracture thoughness in mode II loading (forward shearing mode) has experimentally been determined for wood. The end-cracked beam specimens used were exposed to a constant load which corresponds to a nominal load level between 60 and 85% of the short-term capacity. The relative humidity was kept constant at 65% for two experimental series and changed cyclically between 40 and 90% for six experimental series. The length of a whole cycle was two weeks. In contrast to constant humidity conditions the time to failure was drastically reduced. For an end-cracked spruce beam loaded to 75% of its short-term capacity the lifetime was reduced from 2.5 months to 4 days.     

Investigation of the maximum front to back load in the chairs made from curved and modified poplar wood

The aim of this research was to build a chair resistant to force from front to back. To achieve this goal, poplar wood was treated with heat and steam, and then curved at an angle of 90°. Curved frame was used for manufacturing chairs. In this study, three different designs of chairs were used. Control sample is a chair of custom type. The first design was a chair with a curved frame forming the structure back down to bottom (one-piece type) and the second design with two curved parts (two-piece type). Front to back load tests were conducted by mechanical universal testing machine in accordance with DIN EN 1729-2 standard. For each design, the test was repeated three times. The results of the experiment showed that differences between the designs were significant. The full type chairs were broken at the load about 1725 N, but the partial type chairs at about 1421 N. For the top to bottom load test, the full type chairs were broken at about 1052 N, other chairs were more resistant. In general, by introducing a design using the curved frame made of treated poplar, the resistance of chairs is improved.     

太浦河大桥静载试验研究

吴江市苏同黎太浦河大桥主桥上部结构为三跨预应力混凝土变截面连续箱梁。本文详细介绍太浦河大桥静载试验设计方案,包括：测试截面的选择、加载车型、重量以及加载工况、荷载效率系数的确定等。通过静载试验来确定主梁控制截面在试验荷载下的应变（应力）,主梁控制截面在试验荷载作用下的最大挠度,主梁在偏载作用下的影响系数以及梁体裂缝的开展情况等数据。由试验得出本桥在试验荷载作用下各测试截面的应力、挠度校验系数均小于1.0,表明该桥的承载能力满足正常使用的要求;各测试截面的相对残余应变和相对残余变位均小于20%,说明结构处于弹性工作状态。在该桥静载试验过程中完全按照既定的试验方案进行,通过静载试验得出该桥质量良好,安全可靠。     

竹木碎料板生产工艺的研究

采用正交试验法对竹木碎料板的生产工艺条件与产品质量的关系进行试验研究，通过对试验结果的分析，提出了生产竹木碎料板应达到的生产工艺条件。