﻿ 应力波在原木中传播理论的研究
 林业科学  2005, Vol. 41 Issue (5): 132-138 PDF
0

#### 文章信息

Yang Xuechun, Wang Lihai.

Study on the Propagation Theories of Stress Wave in Log

Scientia Silvae Sinicae, 2005, 41(5): 132-138.

### 作者相关文章

Study on the Propagation Theories of Stress Wave in Log
Yang Xuechun, Wang Lihai
Northeast Forestry University Harbin 150040
Abstract: By dynamics analysis of microunit, the mathematical models of propagation of stress wave along the axis-direction of a log were founded. The displacement equation, velocity equation, stress equation and strain equation were established by using the method of separation of variables. After this, the relations of displacement velocity, stress and strain at both sides of interface were presented according to the reflection and transmission principles of stress wave. On the basis of this, the transmission equations of displacement, velocity, stress and strain of stress wave alone the diameter-direction or string-direction of a log were founded as the propagation direction is vertical on the interface. The results of analysis and experiments showed that the propagation of stress wave in a log was affected by not only the wood physical properties but also the shocking force strength, shocking area, shocking direction and response time to shockings. All these equations will be theoretical references for testing log properties by using stress wave method.
Key words: stress wave    log    propagation theories    method of separation of variables

1 原木轴向的应力波传播理论

 图 1 水平方向微小单元的力学分析 Fig. 1 Forces analysis of wood microunit along horizontal direction

 (1)

 图 2 垂直方向微小单元的力学分析 Fig. 2 Forces analysis of wood microunit along vertical direction

 (2)

1.1 水平方向应力波传播理论

1) 杨学春.2004.基于应力波原木内部腐朽检测理论及试验的研究.东北林业大学博士学位论文

1) 如果F0T0不是关于x的函数, 得位移方程、速度方程、应变方程和应力方程分别为:

2) 如果F0是关于x的函数, 得位移方程、速度方程、应变方程和应力方程分别为:

1.2 垂直方向应力波传播理论

 (3)

2 原木径向和弦向应力波传播理论

2.1 传播方向与界面垂直的反射和透射

 图 3 传播方向与界面垂直的反射和透射 Fig. 3 Reflection and transmission as the propagation direction is vertical on the interface

, 则

 (4)

1) 当α=1时, 即界面两侧的波阻抗相等。这时, 应力波在界面两侧传播时, 不存在反射情况。原木轴向中的应力波传播情况属于这一种类型。

2) 当α>1时, 即界面右侧的波阻抗大于左侧的波阻抗, 透射波从应力幅值上强于入射波, 也就是说应力波从软的材料传入硬的材料。

3) 当α < 1时, 即界面右侧的波阻抗小于左侧的波阻抗, 透射波从应力幅值上弱于入射波, 也就是说应力波从硬的材料传入软的材料。

2.2 传播方向与界面不垂直的反射和透射

 图 4 传播方向与界面不垂直的反射和透射 Fig. 4 Reflection and transmission as the propagation direction is not vertical on the interface

 (5)

2.3 原木径向和弦向的应力波传播理论

 图 5 原木径向或弦向试件的等份分解 Fig. 5 Equals decomposition of diameter-direction and string-direction log sample

1) 杨学春.2004.基于应力波原木内部腐朽检测理论及试验的研究.东北林业大学博士学位论文

 (6)

 (7)

3 应力波检测原木内部腐朽的试验

1) 杨学春.2004.基于应力波原木内部腐朽检测理论及试验的研究.东北林业大学博士学位论文

4 结束语

 陈载永, 陈合进. 1997. 应力波检测木材纵向接合之弹性係数. 林产工业, (1): 8-21. 陈载永, 叶政翰. 1996. 树种对三种非破坏性测定仪检测木材弹性係数之影响. 林产工业, (2): 285-294. 陈载永, 钟建有. 1995. 应力波非破坏测定法——检测六种实木之静曲弹性係数. 林产工业, (3): 363-372. 孟瑞华, 胡勤龙, 刘毅. 2000. 应力波时间仪的研制和应用. 南京化工大学学报, (6): 55-57. DOI:10.3969/j.issn.1671-7627.2000.06.014 名波直道, 中村昇, 有马孝礼, 等.1992.応力波によゐ立木质测定(第1报)——测定方法と応力波の伝播经路.木材学会誌, 38(8): 739-746 王礼立. 1985. 应力波基础. 北京: 国防工业出版社. 王志同, 曹志强, 袁卫国. 1995. 用应力波非破损检测技术检测中密度纤维板弹性模量的研究. 木材工业, 9(5): 17-21. 吴斌, 韩强, 李沈. 2001. 结构中的应力波. 北京: 科学出版社. 杨学春, 王立海. 2002. 应力波技术在木材性质检测中的研究进展. 森林工程, (6): 11-12. DOI:10.3969/j.issn.1001-005X.2002.06.006 Koichi Y, Othman S, Rokiah H. 1998. Nondestructive detection of heart rot of acacia mangium trees in malaysial.Forest Products Journal, (3): 83-86 Kristin C S, David E K, Kent A M, et al. 1995. Stress wave techniques for determining quality of dimensional lumber from switch ties. Note FPL-RN-0265, Forest Products Laboratory, 12. Kristin C S, Daniel L S, Robert J R, et al. 1996. Nondestructive methods for detecting defects in softwood logs. Res Pap FPL-RP-546, Forest Products Laboratory, 13. Lee J, Kim K, Bae M.2003.Patterns of resistographs for evaluating deteriorated structural wood members.Journal of the Korean Wood Science and Technology, 31(6): 45-54 Robert J R, Kent A M, David W G, et al. 1997A. Relationship between log and lumber modulus of elasticity. Forest Products Journal, 47(2): 89-92. Robert J R, Michael A R, Kristin C S.1996.Determining in-place modulus of elasticity of stress-liminated timber decks using NDE.National Conference on Wood Transportation Structures, Madison, USA, 23-25 October, 277-282 Robert J R, Roy F P, John W F, et al. 2001. Relationship between stress wave transmission time and compressive properties of timbers removed from service. Note FPL-RN-280, Forest Products Laboratory, 4. Robert J R, Roy F P, Norbert V, et al. 1999. Inspection of timber bridges using stress wave timing nondestructive evaluation tools. Pap FPL-GTR-114, Forest Products Laboratory, 15. Robert J R, James C W, Anton Tenwolde. 1994. Identifying bacterially infected oak by stress wave nondestructive evaluation. Res Pap FPL-RP-512.Forest Products Laboratory, 6. Ross R J, Yang V W, Illman B L, et al. 2003. Relationship between stress wave transmission time and bending strength of deteriorated oriented strandboard. Forest Products Journal, 53(3): 33-35. Wang X, Robert J R, James A M, et al. 2001. Several nondestructive evaluation techniques for assessing stiffness and MOE of small-diameter logs. Res Pap FPL-RP-600, Forest Products Laboratory, 12.