新型小径木通用平托盘力学性能理论研究

新型小径木通用平托盘是一种用森林低质资源小径木材及废弃木材为原材料制成的绿色环保型托盘,是一种应用前景广阔的托盘,但对于小径木托盘的设计理论研究还较少。本研究运用结构力学理论,建立小径木通用平托盘在均布载荷及集中载荷不同作业情况下的力学模型,进行抗弯力学性能理论分析得出小径木通用平托盘的弯曲强度与弯曲刚度条件,提出小径木通用平托盘的尺寸与托盘承载性能关系的设计模型。为新型小径木通用平托盘实现产业化推广提供理论依据。     

木托盘的发展前景及存在的问题研究

对木托盘的发展前景及存在的问题进行研究,通过分析近年我国不同材质托盘所占比重的变化、新生产托盘的数量及国外木托盘所占的比重,得出未来很长一段时间木托盘占据市场主导地位的情况不会改变的结论。针对当前木托盘制造使用、检疫处理、维修及回收利用等方面存在的主要问题,总结得出规范设计制造过程、采用热处理方法、加强废弃托盘的回收利用是实现木托盘可持续发展的主要措施。     

刨花模压托盘工艺

托盘是堆放和搬运货物的工具。用小径材、枝桠材生产刨花模压托盘代替实木托盘,以提高木材利用率。本研究用松木和杨木为原料,对生产模压托盘的关键工艺参数进行了研究。结果表明,刨花模压托盘的力学性能可达到实木托盘的性能要求。     

原木运材汽车车架弯曲及裂纹的分析

1车架纵梁弯曲及裂纹原因汽车车架弯曲、裂纹多发生在距后横梁3～4．5m的纵梁中前部位；架驶室后悬置横梁与纵梁左右两边的连接处；后钢板弹簧卷耳处；使用挂车时拖曳后横梁处。出现裂纹规律一般是从槽钢上边缘起延伸至整个下翼。产生上述现象的原因主要有两个方面。1．1产品结构与工艺方面（l）车架边梁通常是按照等强度设计的，应有足够的强度和刚度，但由于严重超载及林区运材公路质量较低，汽车上下坡频繁，其动荷系数往往超过设计值，较宽的轴矩使纵梁中部刚度减弱，强度和疲劳破坏也最易发生。（2）悬架由钢板弹簧、辅助钢板弹簧及减…     

基于ANSYS的重载纤维模塑托盘结构与性能研究

以一种新型重载纤维模塑托盘为研究对象,利用有限元分析软件对其模拟分析与结构优化。通过ProE软件对重载纤维模塑托盘进行建模,在ANSYS软件中对其整体与局部结构进行模拟分析。利用正交试验方法,设计并优化托盘结构。结果表明:正六边形面孔的面板最大应力最小,面孔的优化尺寸为面孔深度22 mm、壁厚6 mm、拔模角度2°、倒角半径6 mm。支腿的优化尺寸为拔模角度2°、厚度25 mm和倒角半径15 mm。优化的重载纤维模塑托盘在6 t均布静载荷作用下,所受到最大应力为41.86 MPa,小于重载纤维模塑材料极限应力。正六边形面孔板具有更好的承载性能;影响面孔与支腿结构单元强度的主要因素是拔模角度和厚度;优化后的重载纤维模塑托盘结构强度能够达到重载要求。     

木塑托盘力学性能测试方法研究

在众多替代木材的托盘新技术新产品中,木塑托盘以其良好的综合性能,在发达国家的物流作业中得到广泛使用。我国目前针对通用托盘的力学性能要求和检测方法比较完善,但木塑托盘因其独特的性质,现有的通用托盘检测方法并不适用.通过试制不同规格的木塑托盘,在尝试利用现有通用托盘力学性能检测方法的基础上对木塑托盘的力学性能检测方法进行了相关的研究。     

植物纤维模压平托盘的开发利用与市场化推广

论述了国内托盘市场的现状与发展趋势.植物纤维模压平托盘作为托盘市场的新产品,其是将托盘与农林废弃物相结合.对这种新型托盘的特点及利用进行了分析,并展望其产业化前景,这对指导其市场推广有一定的意义.     

蓝莓采摘车车架刚度有限元分析及弯曲扭转刚度试验

蓝莓采摘车车架与传统车架不同,U型车架没有承受主要拉应力的下横梁,对受到静止满载工况弯曲刚度、扭转工况扭曲刚度等提出更高的要求.车架结构不但承受油箱、传输带、鼓风系统和采摘人员等重力,还承受弯曲扭转变形.对蓝莓采摘车车架进行有限元刚度分析,可以初步确定整个车架的刚度情况.对车架弯曲刚度进行有限元分析,对光车架和车架结构扭转工况进行刚度分析,并且进行刚度试验.结果表明,车架在极限扭转工况,整车变形不大,刚度足够.用实验验证蓝莓采摘车车架刚度,以便更好验证整车车架扭转恶劣工况稳定性.     

酚醛树脂刨花模压托盘生产工艺

为了探究酚醛树脂刨花模压托盘的生产工艺,采用正交试验分析施胶量、热压温度和热压时间对模压托盘物理力学性能的影响。结果表明：在优化工艺参数：施胶量20%、热压温度200 ℃、热压时间10 min的条件制备的酚醛树脂模压托盘,含水率、密度、24 h吸水厚度膨胀率以及叉举抗弯性能均满足GB/T 30672—2014《模压平托盘 植物纤维类》中一次性使用模压平托盘的相关要求。     

模压托盘模具改进设计

1 模具工作原理及存在问题 模压托盘模具是模压托盘生产线中的必备装置,其主要由上下模体、封边板、脱模顶杆机构等组成.热压时,上模与下模合模形成一封闭腔,将铺于下模的物料热压成型,通过上、下顶杆脱模后,完成整个模压托盘的压制过程.每次热压可同时压制两个托盘,不同结构形式的模具可压制出不同形状的托盘.     

CNZ1─5B型多用途木材干燥窑

本文介绍新设计的ＣＮＺ１－５Ｂ型多用途木材干燥窑及其用于干燥立木地板、竹材地板、阻燃胶合板、曲木家具坯件、鞋楦、卫生筷和纸浆托盘等的工艺要点     

A novel method for the reinforcement of harp soundboard

The effects of a carbon fiber-reinforced plastic (CFRP) overlay on the wooden soundboard of a harp were compared to those of conventional veneer reinforcement with respect to the vibrational properties and bending strength. CFRP reinforcement has a minimal effect on the vibrational properties of the soundboard in its width direction, whereas conventional veneer reinforcement significantly reduces the acoustic conversion efficiency of the soundboard. The CFRP-reinforced soundboard also has sufficient bending strength in its longitudinal direction. These results indicate that CFRP is a promising material for the reinforcement of the wooden soundboards of harps to minimize the reduction of the sound amplitude.     

Effects of density profile of MDF on stiffness and strength of nailed joints

Nail-head pull-through, lateral nail resistance, and single shear nailed joint tests were conducted on medium density fiberboard (MDF) with different density profiles, and the relations between the results of these tests and the density profiles of MDF were investigated. The maximum load of nail-head pull-through and the maximum load of nailed joints were little affected by the density profile. However, the ultimate strength of lateral nail resistance, the stiffness, and the yield strength of nailed joints were affected by the density profile of MDF and showed high values when the surface layer of the MDF had high density. It is known that bending performance is also influenced by density profile. Therefore, the stiffness and the yield strength of nailed joints were compared with the bending performance of MDF. The stiffness of nailed joints was positively correlated with the modulus of elasticity (MOE); in the case of CN65 nails, the initial stiffness of joints changed little in response to changes in MOE. The yield strength of nailed joints had a high positive correlation with the modulus of rupture (MOR). The stiffness and the yield strength of nailed joints showed linear relationships with MOE and MOR, respectively.     

Crack influence on load-bearing capacity of glued laminated timber using extended finite element modelling

Abstract

Most of the cracks are caused by changes in temperature and relative humidity which lead to shrinkage and swelling of the wood and thereby induce stresses in the structure. How these cracks influence the strength of the wooden structure, especially the shear strength, is not well understood. However, it is reasonable to expect that cracks have an impact on the shear strength as they preferably run along the beams in the direction of grain and bond lines. The purpose of this study was to investigate the load-bearing capacity of cracked glulam beams and to find a model that could predict the failure load of the beams due to the cracks. Three-point bending tests were used on glulam beams of different sizes with pre-manufactured cracks. An orthotropic elastic model and extended finite element method was used to model the behaviour of the cracked beams and to estimate the load-bearing capacity. The conclusions were validated by numerical simulations of the mechanical behaviour of three-point bending of glulam beams with different crack locations. The crack initiation load was recorded as the failure load and compared to the experimental failure load. The results of the compaction simulations agree well with the experimental results.     

Prediction of bending stiffness and moment carrying capacity of sugi cross-laminated timber

Cross-laminated timber (CLT) panels consist of several layers of lumber stacked crosswise and glued together on their faces. Prototype sugi CLT floor panels were manufactured and bending tests were carried out under the different parameters of lumber modulus of elasticity (MOE), number of layers, thickness of lumber and thickness of CLT panels. On the basis of above tests, bending stiffness and moment carrying capacity were predicted by Monte Carlo method. MOE of lumber was measured by using grading machine and tensile strength of lumber was assumed to be 60 % of bending strength based on the obtained bending test. Bending stiffness EI of CLT panels could be estimated by adopting composite theory and equivalent section area. Experimental moment carrying capacity showed 12 % higher value than the calculated moment carrying capacity by average lumber failure method, and also showed 45 % higher value than the calculated moment carrying capacity by minimum lumber failure method due to the reinforcement of the outer layer by the neighboring cross layer.     

秸秆刨花板性能分析

对普通木质刨花板、麦秸刨花板及稻草刨花板进行了密度、含水率、吸水厚度膨胀率、静曲强度和弹性模量、内结合强度、表面结合强度及握钉力的测试,结果表明,麦秸刨花板在强度方面不及木质刨花板,稻草刨花板在抗弯性能上也无法满足要求,两种秸秆板的握钉力都较差。产生上述差距的关键原因是板坯的密度,另外,与原料形态、加工工艺、机械设备等也有关系。     

Median-based regression methods in wood science applications

Summary Regression analyses using the traditional, mean-based, least squares (LS) and the median-based, least absolute deviations method (LAD) were performed on twenty-five sets of bending strength and stiffness data. Comparisons of regression models were made to determine the effect of mathematical technique. In all cases, model coefficients demonstrated some degree of sensitivity to regression method. In cases where the residual data appeared to approximate a normal distribution, the models produced fairly similar results. However, the LS technique was found to be highly influenced by even a single extreme residual value. LAD regression proved to be far more stable in the presence of extreme residual values due to its more rational distance function.This material is based upon work supported by the Cooperative State Research Service, U.S. Department of Agriculture, under Agreement No. 90-37291-5748     

林木穴盘精密播种机的选型设计

穴盘精密播种机的种类及形式较多,当前发展的主流是气吸式播种。分析比较了各播种原理和形式的优缺点,结合林木穴盘育苗的应用,对林木穴盘精密播种机选型进行研究,对排种器的结构形式提出改进并给出结构设计方案。