共查询到19条相似文献，搜索用时 93 毫秒
1.
2.
对带式输送机落料点常见缓冲装置的特点进行了分析，针对现有缓冲装置的问题，设计出一种无间隙快速更换缓冲块的曲线缓冲床。 相似文献
3.
4.
提出一种用于起重机的新型缓冲元件：弹簧-橡胶复合缓冲元件.利用珠海三思计量仪器有限公司生产的高性能智能电子万能实验机,对不同缓冲元件的性能进行测试.结果表明：弹簧-橡胶复合缓冲元件集成了弹簧与橡胶用于缓冲材料的优点,较弹簧缓冲元件大幅度提高了最大缓冲力和缓冲容量;虽然弹簧-橡胶复合缓冲元的缓冲效率低于弹簧缓冲元件的缓冲效率,但其衰减系数却远远大于弹簧缓冲元件;弹簧-橡胶复合缓冲元件的衰减系数略高于橡胶缓冲元件的衰减系数.综合考虑最大缓冲力及缓冲容量,弹簧-橡胶复合缓冲元件的缓冲性能优于弹簧缓冲元件;橡胶种类和厚度是影响弹簧-橡胶复合缓冲元件缓冲性能的两个主要因素. 相似文献
5.
6.
7.
8.
【目的】植物纤维多孔材料的制备通常采用热分解型化学发泡剂,研究碳酸氢铵(NH4HCO3)、碳酸氢钠(NaHCO3)、偶氮二甲酰胺/碳酸氢钠(AC/NaHCO3)以及AC/NaHCO3不同复配比例对植物纤维多孔材料的泡孔结构及缓冲性能的影响。【方法】以漂白针叶木浆为主要原料,添加NH4HCO3、NaHCO3、AC/NaHCO3 3种不同的发泡剂,以及AC/NaHCO3不同复配比例条件下,采用微波成型工艺制备植物纤维多孔材料。利用Image Pro Plus 6.0软件对植物纤维多孔材料泡孔的显微图像进行处理分析,得到孔隙率、孔径大小及泡孔分布等参数;通过静态压缩测试分析材料力学性能和单位体积变形能。【结果】对比3种发泡剂试样,AC/NaHCO3复配发泡剂制备的植物纤维多孔材料具有较高的孔隙率且泡孔分布较均匀,得到最小缓冲系数为4.93,具有良好的缓冲特性;对比AC/NaHCO3 3种不同配比的试样,得出比例为2∶1... 相似文献
9.
《林业科学》2017,(5)
【目的】借助适当的泡孔参数表征手段,探究纤维多孔缓冲包装材料的泡孔参数(孔隙率和孔径大小及分布)与其力学性能的关系,为制备出性能优良的纤维多孔缓冲包装材料提供理论依据,为进一步研究和揭示纤维多孔缓冲包装材料的发泡机制提供参考,以推动绿色环保缓冲包装材料的发展。【方法】以木粉和废瓦楞纸浆为主要原料,同时添加发泡剂等辅料,采用热压成型方式制备出具有不同孔隙结构的发泡材料,使用Image Pro Plus 6.0图像处理软件对材料的显微图像进行处理与分析,得出不同材料的泡孔结构参数,即孔隙率和孔径大小及分布,通过静态压缩性能测试及4次压缩回弹测试得到材料的应力-应变曲线、缓冲系数-应力曲线、4次压缩平均回弹率曲线和单位体积变形能曲线,对材料泡孔结构参数与其力学性能的关系进行分析。【结果】不同的泡孔参数与材料力学性能有着不同的关系,其中孔隙率与材料力学性能的关系为:孔隙率越大,材料的应力-应变曲线越平缓,最小缓冲系数越小,单位体积变形能越小;随着孔隙率的增大,材料的平均回弹率先升高后降低。孔径大小及分布与材料力学性能的关系为:大泡孔所占面积百分比越大,材料同一应变条件下对应的应力值越小,最小缓冲系数越小;大泡孔所占面积百分比越小,即孔径分布越均匀,材料的平均回弹率越高,单位体积变形能越大。【结论】通过适当的泡孔参数表征手段及试验和统计方法,对纤维多孔缓冲包装材料微观泡孔结构参数(孔隙率和孔径大小及分布)进行表征,将宏观与微观相结合,获得其与不同孔隙结构材料力学性能间重要的理论关系,对于继续深入研究纤维多孔缓冲包装材料微观结构、优化泡孔形貌及均匀性甚至后续生产制备均具有重要的指导意义。 相似文献
10.
张玉民 《林业机械与木工设备》1997,25(11):35-35,22
Ｊ－５０拖拉机缓冲装置后支架损坏的原因分析（１６５０２３）大兴安岭新林技工学校张玉民Ｊ－５０拖拉机是我国林业生产的专用拖拉机。在生产作业中，由于行走系统的严重磨损和驾驶维修不当，易造成行走系中的缓冲装置反支架不同程度的损坏（折断、裂纹、变形），影响木... 相似文献
11.
软木伸缩缝填料用作水电站钢蜗壳垫层材料的探讨 总被引：1，自引：0，他引：1
就软木伸缩缝填料用作水电站钢蜗壳垫层材料进行探讨,分析其作用和效果;介绍软木的特性以及软木伸缩缝填料的生产工艺;并对几种常用的垫层材料进行试验对比分析.试验结果表明,软木伸缩缝填料适合作大、中型水电站钢蜗壳外包垫层的材料. 相似文献
12.
X-ray diffraction is a well-established method for the determination of the mean microfibril angle (MFA). When the sample is a slice of wood variations in the fibre orientation, the shape of the cells, and the measurement geometry affect the intensity curve. A general form for diffraction conditions in terms of angles describing the fibre orientation and the shape of the cell was derived. Intensity curves were calculated by using Monte Carlo method and compared with experimental ones. Both peak fitting and variance methods were used for determining the mean MFA from the intensity curves. Norway spruce was used as an example. Results indicate that deviations in the fibre orientation, the spiral grain, do not affect the mean MFA considerably when using the symmetrical transmission geometry. When using the perpendicular transmission geometry large deviations in spiral grain or tips tend to increase the MFA determined with the variance method and decrease the MFA determined with the fitting method. The shape of the cell should be considered when using the reflection 200 and the fitting method. The variance method is insensitive to the shape of the cell. 相似文献
13.
《Southern Forests》2013,75(2):115-120
This study was conducted to develop a height–age growth model and site index curves for site quality evaluation of old secondary-growth stands of Pinus kesiya in the northern Philippines. The Chapman-Richards growth function was used in the guide curve method to generate anamorphic site index curves for this species. In order to evaluate the developed model, coefficient of determination (R 2 ), root mean square error (RMSE), bias (ē), absolute mean difference (AMD) and mean percent bias (MPB) were used as statistical criteria. The Chapman-Richards model explained about 96.84% of the total variation of the dominant height. The value of ē was ?0.004 m, AMD was 2.566 m, MPB was 3.88% and RMSE was 3.331. The site index curves developed as a result of this study are significant for forest managers in predicting the growth patterns and classification of site productivities for Pinus kesiya stands. 相似文献
14.
单因素实验设计在缓冲包装材料制备中的应用 总被引：2，自引：0，他引：2
采用单因素实验设计方案确定配方中各组分用量,在已确定木质剩余物缓冲包装材料原料配方的基础上,通过单因素实验分别单独考察不同组分用量、配比等对材料表观性能的影响,实验结果表明,木纤维含量在32-36 g,淀粉/PVA复配胶黏剂的比例在1∶1和3∶1之间,发泡剂在3-7 g,丙三醇含量在10-20 ml及滑石粉为5 g时材料的表面质量得到显著改善,分层、发泡程度及弹性均较适宜,得出木质剩余物缓冲包装材料的最佳原料配方范围为：木纤维32 g、34 g和36 g,淀粉/PVA比例1∶1、2∶1和3∶1,发泡剂3 g、5 g和7 g,丙三醇10 ml、15 ml和20 ml,滑石粉5 g,为制备具有良好的生物可降解性与环境协调性的木质剩余物纤维发泡缓冲包装材料奠定基础。 相似文献
15.
Fracture resistance curves of Norway spruce were evaluated over a range of crosshead speeds between 0.05 and 200 mm/min using compact tension specimens. The fracture resistance curves were determined via J-integral K R versus Δa (crack extension) using hybrid experimental–finite element method with stepwise quasi-static and transient dynamic analysis. Coupling experiments and high-speed camera with a rate of 0.5–135 frames/s capture enabled determination of crack kinetics and velocities. Digital image correlation method was employed to evaluate strain distribution maps of the fracture process zone. Deformation measurements suggested strong strain localization and significant influence of the loading rate. The most distinct strain map was evaluated for the loading rate of 200 mm/min, suggesting inertial effects. Rising fracture resistance develops for smaller crack lengths (0.15–0.20 a/w) for all loading rates, with an increase of up to 20–50% compared to initiation values. Fracture resistance R-curves were evaluated for single individual specimens as well as for averaged load–deformation responses, which hide strong localisations in single responses. Influence of deformation rate on the shape and magnitude of fracture resistance curves is significant. Inertial effects in transient dynamic response give rise to twofold higher fracture resistance of softwoods compared to quasi-static resistance. 相似文献
16.
We conducted three-point bending tests by changing the condition at the loading point and then examined the influence of the loading point on the test data. Yellow poplar (Liriodendron tulipfera L.) was used for the tests. First, using loading noses with various radii, static bending tests were conducted by varying the depth/span ratios. Deflections were measured from the displacement of the cross head and at the point against the loading nose: Young's and shear moduli were obtained from the modified Timoshenko's bending equation proposed in a previous paper. Then a similar testing procedure was undertaken by inserting cushion sheets of Teflon between the specimen and the nose. After the measuring these moduli, bending strengths were measured using the loading noses and cushion sheets. The following results were obtained: (1) When the deflection was measured from the displacement of the cross head, the radius of the loading nose had an influence on the additional deflection when the depth/span ratio was high, causing the dependence of the shear modulus on the radius. In contrast, the radius had little influence on the measurement of Young's modulus. By placing cushion sheets between the nose and the specimen, the effect of the radius was moderated. When the deflection was measured at the point against the loading nose, the radius of the nose had little influence on the additional deflection; hence the loading nose had little influence when obtaining Young's and shear moduli. This tendency was commonly observed regardless of whether the cushion sheets were in place. (2) When the specimen had a high depth/span ratio, the bending strength increased with the increase in the radius of the loading nose. However, the influence of the radius was small when the specimen had a low depth/span ratio. There was no significant effect of the cushion sheets used here on the measurement of bending strength.Part of this paper was presented at the 48th annual meeting of the Japan Wood Research Society, Shizuoka, April 1998 相似文献
17.
N. Monts T. Gauquelin W. Badri V. Bertaudire El H. Zaoui 《Forest Ecology and Management》2000,130(1-3):37-46
Current techniques for calculation of biomass in agroforestry require felling of many trees. Such methods are not well suited to the natural environment, especially if the environment is subject to anthropic degradation and if the wood supply to local populations is at stake. The method we describe here was used in a socioeconomic and ecological study of the biomass of a thuriferous juniper woodland (Juniperus thurifera L.) in the High Central Atlas mountains (Morocco). This computerized method reconstructs the different component volumes of a tree from two orthogonal-view photographs. Then, using the volume and the density of each component, it estimates the biomass of the tree. Regression curves were established between dendrometric parameters for 102 trees (tree height × crown projection area) and their estimated biomass by this computer method. A second-order polynomial equation gave the best regressions with a high coefficient of determination (R2 = 0.96). To validate the method, the biomass of seven trees (cut in a previous study) was compared with those obtained from our regression equations, while in a second study, the biomass of three trees, estimated from photographs using the computer program, was compared with values obtained after felling and weighing the same trees.
The results show that the method is reliable with a mean error percentage varying between 2.5 and 7.5 per tree. For young trees, the accuracy of the biomass could be improved, for example, by using a tree morphology classification. 相似文献
18.
根据多年的公路测设经验，利用虚交基线结合切线支距法和弦支距法测量原理，总结出一种公路平曲线测设的高效方法－虚交基线支距法。章介绍了虚交基线支距法的计算方法与测设方法。尤其在树木茂密的林区与房屋密集的村镇使用虚交基线支距法测设公路平曲线，既可减轻劳动强度，又可节省时间，提高工作效率；而且测设精度高，不存在误差累计。 相似文献
19.
林区公路工程建设是林业生产中一项十分重要的工作。根据本人多年实践经验,总结出了用可编程序计数器对林区公路工程勘测设计中平曲线(圆曲线、复曲线、回头曲线等)测设参数进行编程计算的方法。在野外勘测设计中,只需输入平曲线半径、转向角或弧长、弦长等数据,就能快速、准确地计算出圆曲线及细部测设参数,不仅提高了工作效率,而且提高了设计质量和设计水平。 相似文献