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从索道驱动电机安装的实际结构出发,建立了驱动电机底板的力学结构模型,提出应针对底板螺栓的不同位置来分析其荷载。 相似文献
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采用有限元法对端盖连接螺栓的螺纹连接结构进行分析计算,得到螺栓预紧力与疲劳寿命之间的关系曲线并确定了螺栓最佳预紧力。对螺纹根部出现应力应变集中的区域进行疲劳寿命预测,给出了提高螺栓疲劳强度和使用寿命的措施。 相似文献
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南方林区地形复杂,山高坡陡,索道是集运木材的重要方式之一。在使用架空索道承运较长的木材时,常常采用两个载重跑车共同支承木捆。这样,当索道线路发生平面偏转时,处在转折处或其前后的门形支架必须比直线段的同类支架具有较大的宽度,否则会出现木捆与支架立柱互相干扰,影响木捆的通过性能和立柱的稳定性。因 相似文献
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支架是集材索道系统的重要组件,用以承托钢索,保证索道有足够的净空高度。但传统的南方人工林集材作业中多数采用活立木作为索道支架,活立木受其生长位置限制,难以保证最优集材路线,不适应现代小规模木材采集需求,为解决人工林索道集材中难以寻找合适的活立木作支架问题,研究设计出一种分段组合加绷索固定的可移动装配式钢管支架。通过力学和仿真分析,对承索方式、不同分段比例及绷索固定位置进行了优化。当分段位置于杆件的0.59L处时,效果最好,抗压能力是没有分段时的1.7倍。支架采用索鞍托索,使支架受力由传统的以承受弯矩为主变成以承受压力为主,改善了支架的受力条件。同时支架中间设置绷索固定后,增加了支架的约束条件,减小了支架的柔度,支架的临界载荷比无绷索固定的支架提高3倍以上。支架设计成分段可拆,降低了单个支架部件的重量,单个部件最大不超过50kg,便于在林区转移安装;支架采用标准镀锌管制造,取材方便,成本低廉,有利于降低索道系统成本。经试验及生产验证,可移动装配式林业索道支架转移、架设方便,使用安全可靠,特别适合山地林区择伐与小规模皆伐集材需要,对在人工林集材作业中推广小型索道集材,减小集材作业对生态环境的影响具有重要的意义。 相似文献
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架空索道转弯结构及其应用问题的探讨 总被引:5,自引:2,他引:3
本文在此介绍又一种造价更为低兼,但对目前研究新型架空索道转弯结构很有参考价值的林用无支架绷拉鞍座转弯集运材索道的转弯结构,供共同探讨。 相似文献
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文内介绍了中密度纤维板设备安装过程中干燥机旋风分离器支架的施工方法,对同类或近似的设备安装具有一定的参考价值。 相似文献
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Ali Awaludin Watanachai Smittakorn Takuro Hirai Toshiro Hayashikawa 《Journal of Wood Science》2007,53(3):204-210
Empirical equations to determine the bearing strength have been proposed by many researchers and design standards. Because
these equations have been developed mainly based on test results of softwood species, it is a matter of great importance (to
ASEAN structural engineers) to verify the applicability of these equations for tropical hardwood species, which are commonly
used in many ASEAN countries. In this study, wood specimens of Shorea obtusa (a tropical hardwood species) were used and the bearing test under full-hole confi guration was carried out for fi ve different
loading angles to the grain. The bearing stress-embedment curve obtained from the test was approximated by a linear elastic-plastic
diagram indicating the initial and fi nal stiffness of the curve. Testing showed that the average bearing strength parallel
to the grain was 7.25% lower than the prediction given in Eurocode 5. The bearing strength perpendicular to the grain evaluated
based on bearing load at initial cracking was substantially different from any predictions given by previous studies or design
standards. It was also found that the bearing strength and initial stiffness from the bearing stress-embedment curve for loading
at intermediate angles to the grain could be satisfactorily predicted with Hankinson’s formula. 相似文献
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P. Schlotzhauer P. A. Nelis S. Bollmus A. Gellerich H. Militz W. Seim 《Wood material science & engineering》2017,12(3):149-157
The total hardwood timber stock of German forests is fast growing. The lack of knowledge concerning test standards, product standards and sorting criteria makes it difficult to expand the processing and marketing of hardwoods into the field of construction usage. Strength and stiffness data derived from small, defect-free specimens do mostly exist, but in order to be able to insert hardwoods into building applications, data derived from real size specimens is needed. Subsequently, the results of these two different specimen categories need to be correlated and the so-called size effect needs to be quantified and qualified. This paper aims to analyze the size effect of defect-free compression, bending and tensile specimens for the six European hardwood species maple (Acer spp.), birch (Betula pendula), beech (Fagus sylvatica), ash (Fraxinus excelsior), oak (Quercus spp.) and lime (Tilia spp.). They are tested exclusively parallel to grain. Regarding the compression strength for maple, birch and ash, the specimen dimensions did not influence the compression strength value. For beech, oak and lime, it was observed that compression strength increased as the specimen volume was increased. The bending strength of all species decreased as the specimen dimensions increased. Concerning the tensile strength, a clear statement on whether dimensions influence the tensile strength value is not possible. Further research with adjusted specimen sizes, specimen shapes and machine set-ups is needed. Regarding the compression and bending MOE, in most cases, the dimensions did not influence the MOE values. In tensile testing, MOE values differed significantly for the different specimen sizes. Whether these differences were due to slightly different test set-ups in the different sizes or a true size effect could not be answered conclusively. 相似文献
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依照JJF 1059.1-2012《测量不确定度评价与表示》的方法,对浸渍纸层压木地板内结合强度测量试验中影响其测量结果不确定度进行了分析和评定。结果表明:浸渍纸层压木地板内结合强度为:σ=(1.04±0.01)MPa,其中扩展不确定度的包含因子k=2,置信概率p=95%。 相似文献
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本文对高层建筑疏散楼梯在设计中的一些错误提出了自己的观点及解决办法;阐述了疏散楼梯在设计中的重要性,必须引起设计者的足够重视。 相似文献
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针对高层建筑和低层裙房基础设计中常遇到的方案选择、高层主楼与低层裙房基础沉降差异处理等问题,提出了设计要求和实施的技术措施。 相似文献