人工林间伐集材索道研究

对间伐集材索道工程设计中的索系选择、索道布线、设计计算、机械装备的选型与配置以及安装拆转技术进行系统研究;将缆索起重机许用荷重设计法和钢管桅杆支架技术应用到林业索道工程中,提出闭式牵引索快速安装和拆转的余长免接法技术,设计出JP双(单)轮增力跑车,以及与JS2-0.8自行式绞盘机组合配套的Ⅱ13型优化索系。     

索道承载索的定比图算法及平面曲线束水平间距定比关系的探讨

本文根据平面曲线在一定条件下所形成的曲线束中,曲线间水平间距的定比关系,建立了曲线定比图算法。用这种方法计算索道承载索的最大容许荷重,比用索道承载索的无量纲容许荷重表节省用表量96%。并可以避开大量繁琐的理论计算,获得同样精确的计算结果。对其他工程的设计计算和科学实验数据的预测和检验,亦将具有较大的实用价值。     

支点钢索倾角θ在实际生产中几点新应用

文章依据承载索张紧度的一般检验法“倾角法”原理,提出的两种参数(无荷索上支点拉力T_(02),有荷索上支点拉力T_2)从而测定:①无荷重索的上支点拉力;②单荷重时上支点拉力;③鞍座吊索的拉力。     

介绍一种集材架空索道主索张力补正系数计算新公式

<正> 集材架空索道承载索在张力计算、侧型设计中,为了使计算结果更为科学、更符合实际,都必须引入钢索无荷重中央挠度系数的补正系数。目前,计算补正系数有两种公式。     

单个集中静载荷悬链线张力计算方法的研究

本文用将荷重化为等效链长的方法,导出单个集中静载荷悬链线的两个精确公式:水平张力同荷重位置的关系式和上支点的张力计算公式。并以上述公式为基础,用解非线性方程组的牛顿法,编出一个精确计算设计张力的电算程序。较好地解决了林业架空索道设计法关于单个集中静载荷悬链线设计张力的计算问题。     

Ⅲ72增力松紧式索道提升重量的研究

Ⅲ７２增力松紧式索道利用双索承载原理，采用小规格钢索做承载－起重索。额定钢索拉力产生的提升力用于提升重量，提升的重量随索长增加而减少，随负荷与下支点距离增大而减少。提升重受钢索拉力限制，并使索道有较大的中央挠度。当以跨中央负荷为设计荷重时，运营中钢索有产生超拉力的可能，为此提出制动力矩调整方法，并进行设计方法的探讨。     

架空索张力简略计算法

从1961年开始施行的安装索道主要负责人制度,成了科学地指导木材运输现场的开端.到目前为止,取得这种资格活跃在生产中的人们在全国已有相当的数量. 可是既使对承载索设计较为精通熟练的人计算起来也需要相当的时间,到现在所发表的各种各样的计算方式,由于均采用抛物线的理论,虽说比较容易理解,但是对于现场工作人员而言,仍是个难题. 从这种情况出发,笔者早就推荐应用“许用载荷表”的计算方法.这项提案在1977年被采纳后,自同年开始也可用下面叙述的通过“许用载荷表”计算张力的计算法.     

承载索挠度的测算公式

索道挠度通常使用手水准仪进行野外测量,以确定集材索道的载重量。Sessions(1976)和Binkley,Sessiohs研究出分两步计算的方法。这种方法对测绘索道几何图形很有作用。图1:为计算荷重需要而测量的承载索中央挠度     

索道钢索过载警报器

目前,测定承载索安装拉力有倾角法和振动波法两种.倾角法就是现场测定承载索抛物线上、下两支点处切线与水平线夹角来计算安装拉力;振动波法是根据振动学原理来测定承载索的安装拉力.这两种方法都需在架设起来的承载索支点处测量或敲击多次,才能测定出设计安装拉力.这样,对归楞、装车的高支架索道,     

钢索张紧度测定仪

为贯彻落实英明领袖华主席抓纲治国伟大战略决策,加速林业机械化发展的步伐,今年成立了三结合的索道革新试验小组,试制成钢索张紧度测定仪。经生产实践检验,它制作简单,使用方便,精度可满足生产的要求,有利于及时掌握索道承载索的张紧度。钢索张紧度测定仪是用普通测角手水准仪改装而成,如图1。原理是用倾角法测定钢索无荷重时的中央挠度系数S,然后得出索道承载索的张紧度。索道设计时,S值的大小根据索道类型、跨距、地形和钢索情况确定。林用索道通常取S=0.03-0.05。用倾角法测定S值的公式是:     

牛顿迭代法悬索线形与拉力的研究

从悬链线的标准线形出发 ,推导悬索无荷线形及拉力的计算式 ;通过建立状态协调方程 ,导出有荷水平拉力与有荷挠度的关系 ,运用牛顿迭代的数值解法求解悬索有荷线形与拉力。     

钢丝绳弹性模量的研究

钢丝绳是不少机械的重要组成部分。钢丝绳属挠性体,负荷时不可避免出现弹性伸长,其关键参数弹性模量的取值问题关系到机械设计的精度与安全性。架空索道、缆索起重机等承载索挠度比较大的设备,弹性伸长更是不可忽视。通过综合考虑挠度引起弹性模量和弹性伸长引起弹性模量推导出等效弹性模量。     

高等级公路用“坐标法”定线和放样的应用

采用“坐标法”定线和放样与传统方法相比较,具有灵活、方便、准确的特点。能节省很多工作量和时间。本文介绍的方法在设计测量中有较高的使用价值。     

载货汽车的平顺性预测

行驶平顺性是现代高速、高效汽车的一个重要性能，其评价指标主要有加速度加权均方根值和加速度均方值以及疲劳－降低工效界限、舒适性降低界限和人体对振动的吸收功率等几种．优化和预测相结合，不仅可以显著提高汽车的平顺性、缩短设计周期、提高设计质量，而且可以缩进实验时间，大大减少产品的开发成本．以某载货汽车为例，建立其力学和数学模型，对其平顺性评价进行了计算机预测，并就其结果进行了比较、分析和总结．     

Tests for outdoor window profiles: 90° mortise tenon corner joints strength assessment

The research focuses on the assessment of the performances of glued laminated wood corner joints for outdoor window profiles applications, proposing a methodology to appreciate the strength of 90° tenon mortise corner joints. The rationale relies on the potential damage (i.e. breaking of the frame) that can be caused by poor glueing processes and/or typology of adhesives. There is a number of standards for assessment of wood-adhesive bonds for outdoor windows; however, there is a lack of specific standards related to glueing assessment for outdoor wood frames, which can take into account all the factors influencing the glueing quality. The proposed methodology was tested on red oak window profiles. A commercially available polyvinyl acetate-based adhesive was used for corner joints. Bending strength of 90° tenon mortise corner joints was measured and compared with maximum admissible loads on the frame to limit its deformations within admissible ranges. The test results show that the 90° tenon mortise corner joints strength exceeds the admissible load to preserve the functionality of the frame. In order to appreciate the influence of conditioning processes on adhesion, shear strength tests of the flatwise glued joint samples (bond lines of lamellae) were carried out after different conditioning processes.     

木榫旋转焊接节点剪切试验研究与理论分析

为研究无胶层合木梁中旋转焊接木榫的抗剪性能,选用山毛榉木榫旋转焊接SPF(spruce-pine-fir)层板,制备20个单榫焊接节点试件开展双剪试验,获得其破坏模式及荷载-位移曲线.试件的破坏模式为木榫受剪出现类双铰破坏,同时开孔附近基材受木榫挤压破坏.试件的平均峰值位移为4.460 mm,平均峰值荷载为6.127 ...     

Fatigue and creep in chipboard

Summary Matched samples of chipboard were loaded in four-point bending under either a 7 hours loaded/17 hours unloaded cycle, a 17 hours loaded/7 hours unloaded cycle, or constant load in order to asses the effect of cyclic loading on creep deformation. Tests were carried out at three humidity levels (30, 45 and 90% RH) and at three stress levels (30, 45, and 60% of the short term strength). The creep rate of samples under constant load was greater than under cyclic load, with the 7 hours loaded/17 hours unloaded samples giving the lowest creep rate. Analysis of the data on an accumulated time-under-load basis showed that the law of superposition did not apply to the 7 hours loaded/17 hours unloaded samples at the 30% and 45% stress levels, with these samples giving lower deflection than for the other loading conditions. The 17 hours loaded/7 hours unloaded samples also did not appear to obey the law of superposition, although the difference between them and the constantly loaded samples was slight. Considerable scatter in data accumulated at the 60% stress level did not allow any differences in the superposition analysis of cyclic and constant loaded samples to become apparent. Increasing the stress level applied to samples produced an almost linear increase in relative creep for all loading regimes. The 7 hours loaded/17 hours unloaded samples gave consistently lower relative creep values at all levels of stressing, but particularly at the 30 and 45% stress levels. Increasing the relative humidity from 30% to 65% RH had an almost negligible effect on relative creep of all samples, but increasing the humidity to 90% RH caused a marked increase in relative creep.     

大跨度偏压隧道双侧壁导坑法施工方案的优化及效果分析

以京珠复线长（沙）湘（潭）高速公路邓家湾隧道为依托，通过数值计算对双侧壁导坑法原设计方案和优化方案进行对比，确定了最优方案应用于施工。现场施工与监测显示，该方案确保了隧道施工安全，加快了施工进度，因而是合理可行的。施工方案的优化，完善了双侧壁导坑法施工工艺，可为类似大跨偏压隧道的施工提供参考。     

Fracture analysis of perpendicular to grain loaded dowel-type connections using a 3D cohesive zone model

The strength and fracture behavior of dowel-type connections with stiff dowels loaded perpendicular to grain was studied by nonlinear 3D finite element (FE)-analysis. A cohesive zone model was used to model the perpendicular to grain fracture of the wood, i.e., failure by wood splitting along the grain. The influence of load eccentricity and dowel-to-loaded-edge distance was studied for a plate type of geometry loaded in tension and for a simply supported beam loaded in bending. The strength found from the FE-analysis is compared to strength from experimental tests with centric loading, showing overall good agreement. Numerical results for centric loading are further compared to strength predictions according to the linear elastic fracture mechanics (LEFM)-based design criterion present in Eurocode 5 (EN 1995-1-1:2004). The comparison showed good agreement regarding the relative influence of connection geometry, but the design criterion appears, however, to yield unconservative strength predictions. The results of the FE-analyses regarding dowel load eccentricity showed that such loading conditions may yield significantly lower strengths compared to centric loading. An approximate engineering method to account for the strength reduction due to load eccentricity is, furthermore, presented.