木材复式弯曲成形方法分析

在分析以前木材复式弯曲成形方法的基础上,提出了木材数控复式弯曲方法,解决了小曲率和无固定旋转中心弯曲构件的弯曲成形问题,并分析了复式弯曲方式对木材密度等方面的影响,在利用钢带弯曲的基础上完善了木材弯曲工艺,为家具和门窗上应用的复杂曲线形状弯曲构件提供新的加工方法,对于木材加工企业新的木质弯曲件产品开发利用提供了新的思路和解决方案。     

木材加工双摆角铣头主壳体的有限元模态分析

本文应用SolidWorks对双摆角铣头的主壳体进行了三维实体建模,利用COSMOSWorks对其进行模态分析,计算出主壳体前几阶模态的固有振动频率、振型模态及合位移。对进一步了解双摆角铣头的振动特性和优化其结构设计,避免共振现象的发生提供了设计参考。     

基于现场总线的切梗丝机控制系统设计

采用控制层现场总线Profibus-DP和设备层现场总线As-i构成了切梗丝机2层网络控制系统,实现了数字化分散控制;使用WinAC Slot 412作为系统的主控制器,完成了PLC控制程序和人机界面的设计.运行结果表明：切梗丝机整体配合精密可靠,在线停机时间几乎为0,维护量降低了95%以上,梗丝厚度等各项指标均达到了设计要求.     

裂纹对木梁承压与抗弯强度的影响

设计了裂纹木梁的承压与抗弯性能试验,研究了裂纹对木梁强度的影响.结果表明:裂纹对横纹承压强度的影响较小,对抗弯强度影响较大;在承压面为50mm×50mm时木材自身的变异性影响较小;试件长度≥150mm时,局部长度承压值趋于稳定;上下表层横向裂纹使抗弯强度降低近一半.     

基于Solidworks的包馅机械成型刀盘的仿真分析

针对包馅机械的成型刀盘在设计和校核过程中计算复杂的问题,利用Solidworks Motion和Solidworks Simulation结合使用,分析了成型刀具在一个工作循环中的力矩与速度以及各瞬时应力与变形的变化。     

利用织物实际弯曲形态测试其弯曲性质的算法

介绍了织物弯曲理论和测试方法的研究现状,提出了一种利用织物在自重作用下的实际弯曲形态间接测试织物弯曲性质的测试方法。详细叙述了该方法的测试原理,在此基础上利用数学多项式回归和微积分方法对实际弯曲形态曲线上的信息进行计算处理,提出了织物在自重作用下的弯矩与曲率、弯曲刚度与曲率关系的算法。利用此方法对织物进行测试,取得了很好的结果,与KES方法测试得到的弯曲刚度值对比,获得了很好的相关性验证。     

The influence of compression failure on the bending, impact bending and tensile strength of spruce wood and the evaluation of non-destructive methods for early detection

Bending strength (MOR) and bending Young’s modulus (MOE) according to DIN 52186 and MOE calculated on the basis of eigenfrequency and sound velocity were tested on small clear wood specimens of Norway spruce wood with and without compression failure. One group of specimens was climatised in a normal climate of 20°C and 65% relative humidity, while the other group was stored for one month under water before testing. The MOR of specimens with compression failure decreased about 20% on average (normal climate and wet) compared with the specimens without compression failure. The MOE of the specimens with compression failure was reduced only minimally compared with the specimens without compression failure stored in a normal climate, but very distinct differences (more then 30%) were found under wet conditions. The MOE of the specimens with compression failure calculated on the basis of eigenfrequency and sound velocity were not reduced or only minimally compared with the specimens without compression failure. It is therefore not possible to detect compression failure and to determine reduction in MOR using eigenfrequency or sound velocity. In addition, impact bending (DIN 52189), tensile strength and tensile MOE (DIN 52188) were tested on small clear wood specimens of Norway spruce wood with and without compression failure. The specimens with compression failure revealed an average reduction in impact strength of about 40% and an average reduction in tensile strength of about 20% compared with the specimens without compression failure, whereas tensile MOE of the specimens with compression failure was not reduced compared with the specimens without compression failure. The detection of compression failure by computer tomography (CT) was tested on Norway spruce wood boards 10 cm in thickness, and detection by optical scanner was tested on planed Norway spruce wood boards. CT recognised large compression failures easily, whereas the scanner was not able to detect them.     

Relation on microscopic compression creases and crack of wood under static cyclic bending load

The relationship between microscopic compression failure lines and crack-nucleation is reported. Static and reversed cyclic bending load was applied to the specimens made from wood of Agathis species (Agathis sp.). The maximum subjected load was ±450～650 kgf/cm². The observation of the microscopic compression failure line and cracks nucleated at the root of the specimen was made every half cycle of load. The microscopic compression creases nucleate at the tip of the notch on the one side face of the specimen in the compression cycle. The length of the microscopic compression creases shortened in the tension cycle. This is because the microscopic compression creases are stretched parallel to the cell axis. In the next compression cycle, the microscopic compression, creases appear again. After repeating these processes several times and when the shape of the microscopic compression creases has not yet recovered to its original shape a large part of the microscopic compression creases change into cracks. In other word, the cracks nucleate. Mostly, the tip of the microscopic compression creases preceeds the tip of the cracks. The microscopic compression creases and the cracks propagate by steps, and after repeating these processes several times failure of the specimen occurs. The cracks nucleate in the compression cycle and sometimes in the tension cycle too. The cracks follow microscopic compression creases. The microscopic compression creases and the cracks run at nearly right angles to the cell axis.