Fracture mechanics analysis of the crack development in structural timbers under high temperature drying

高温干燥结构木材裂纹扩展的断裂力学分析

基本信息

  • 批准号:
    14560132
  • 负责人:
  • 金额:
    $ 2.18万
  • 依托单位:
  • 依托单位国家:
    日本
  • 项目类别:
    Grant-in-Aid for Scientific Research (C)
  • 财政年份:
    2002
  • 资助国家:
    日本
  • 起止时间:
    2002 至 2003
  • 项目状态:
    已结题

项目摘要

Following four subjects were studied:(1)development of fracture mechanics test which can simulate mechanical behavior of wood under high temperature drying, (2)characteristics of crack propagation in actual kiln drying, (3)improvement of non-destructive measurement of inner moisture distribution during drying, and (4)fracture mechanics analysis of crack development mechanism.1.A specially designed apparatus which induced a stress in a wood sample during high temperature drying between 100 and 120°C was made. The sample was immersed in silicon oil and dried. The apparatus was composed of a glass cell and a load cell which was durable at high temperature and humidity. Fracture toughness was 0.8MN/m^<3/2> and 0.18MN/m^<3/2>, respectively for environmental and high temperature. A large decrease of stress occurred during crack extension through a late wood zone under environmental drying condition. However, a slight decrease occurred at high temperature drying.2.From the observations of the … More fracture mechanics test in the glass cell and actual high temperature. kiln drying, the following crack development process was shown. At the beginning stage of drying, micro cracks occur in a late wood zone. Then it extends to both early wood zones and finally grows to a visible check. Slightly shifted cracks on a radial line extended to a zigzag "Inazuma ware".3.A measuring method of moisture gradient in wood during drying was examined by evaluating the change of electric capacitance at high frequency range. An electrode was scanned around a cross section of a specimen. The moisture gradient in a wood was well estimated. Temperature dependence of capacity is required to be clarified in future application at conventional kiln drying.4.Mechanical condition around a crack tip in wood can be shown by a mechanical compliance model having a viscoelastic compliance element. The increase of temperature induces large decrease of the fracture toughness. This means that the increase of creep at high moisture and temperature conditions decreases a stress induced during actual high temperature kiln drying. This mechanism can explain the restraint of surface check occurrences at high temperature drying. Crack arrest occurs by increase of crack propagation resistance. "Why inner checks are apt to occur in high temperature drying?" is next problem to be solved. Less
本论文主要研究了以下四个方面的内容:(1)模拟木材高温干燥力学行为的断裂力学试验方法的开发;(2)实际窑干过程中裂纹扩展的特性;(3)干燥过程中木材内部水分分布的无损测量方法的改进;(4)裂纹扩展机理的断裂力学分析。将样品浸入硅油中并干燥。该装置由玻璃传感器和耐高温高湿的测力传感器组成。室温和高温下的断裂韧性分别为0.8MN/m^<3/2>和0.18MN/m^<3/2>。在环境干燥条件下,裂纹扩展过程中,应力大幅度降低。然而,在高温干燥时略有下降。 ...更多信息 在玻璃池和实际高温下进行断裂力学试验。窑干燥后,显示了以下裂纹发展过程。在干燥初期,木材后期区域出现微裂纹。然后,它延伸到两个早期的木材区,最后增长到一个可见的检查。径向线上的微位移裂纹延伸成锯齿形的“Inazuma器皿”。3.通过测量高频电容的变化,研究了木材干燥过程中水分梯度的测量方法。电极在样本的横截面周围扫描。很好地估计了木材中的水分梯度。在今后的应用中,需要澄清传统窑干燥时容量与温度的关系。4.木材裂纹尖端附近的力学状态可以通过具有粘弹性柔度单元的力学柔度模型来表示。温度的升高导致断裂韧性的大幅度下降。这意味着在高湿度和温度条件下蠕变的增加降低了在实际高温窑干燥期间引起的应力。这一机理可以解释高温干燥对表面裂纹的抑制作用。裂纹止裂是通过增加裂纹扩展阻力来实现的。“为什么在高温干燥中容易发生内部裂纹?“是下一个需要解决的问题。少

项目成果

期刊论文数量(6)
专著数量(0)
科研奖励数量(0)
会议论文数量(0)
专利数量(0)
Nobuo Sobue, Mayuko Yokotsuka: "Estimation of moisture gradient in timbers by capacity measurement in RF range while scaning electrodes"Conference proceedings of 5th International Conference on Electromagnetic Wave Interaction with Water and Moist Substan
Nobuo Sobue、Mayuko Yokotsuka:“通过扫描电极时射频范围内的容量测量来估计木材中的水分梯度”第五届电磁波与水和潮湿物质相互作用国际会议的会议记录
  • DOI:
  • 发表时间:
  • 期刊:
  • 影响因子:
    0
  • 作者:
  • 通讯作者:
Nobuo Sobue, Mayuko Yokotsuka: "Estimation of moisture gradient in timbers by capacity measurement in RF range while scanning electrodes"Conference proceedings of 5th International Conference on Electromagnetic Wave Interaction with Water and Moist Substa
Nobuo Sobue、Mayuko Yokotsuka:“通过扫描电极时射频范围内的容量测量来估计木材中的水分梯度”第五届电磁波与水和潮湿物质相互作用国际会议的会议记录
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  • 发表时间:
  • 期刊:
  • 影响因子:
    0
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SOBUE Nobuo其他文献

Proceedings of the International Conference on Electromagnetic Wave Interaction with Water and Moist Substance (ISEMA) 2009
2009 年电磁波与水和潮湿物质相互作用国际会议 (ISEMA) 论文集
  • DOI:
  • 发表时间:
    2009
  • 期刊:
  • 影响因子:
    0
  • 作者:
    吉永秀一郎;阪田匡司;酒井武;森貞 和仁;Morisada K.;吉永 秀一郎;吉永秀一郎;森貞和仁;吉永秀一郎;SOBUE Nobuo
  • 通讯作者:
    SOBUE Nobuo
Monitoring of individual moisture content of piled timbers during drying by impedance tomography method
阻抗断层扫描法监测干燥过程中堆放木材的个体含水量
  • DOI:
  • 发表时间:
    2009
  • 期刊:
  • 影响因子:
    0
  • 作者:
    吉永秀一郎;阪田匡司;酒井武;森貞 和仁;Morisada K.;吉永 秀一郎;吉永秀一郎;森貞和仁;吉永秀一郎;SOBUE Nobuo;Nobuo Sobue
  • 通讯作者:
    Nobuo Sobue

SOBUE Nobuo的其他文献

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{{ truncateString('SOBUE Nobuo', 18)}}的其他基金

Development of high frequency CT monitoring of moisture contents of individual timbers piled in kiln
窑内堆放木材含水率高频CT监测技术的发展
  • 批准号:
    19580185
  • 财政年份:
    2007
  • 资助金额:
    $ 2.18万
  • 项目类别:
    Grant-in-Aid for Scientific Research (C)
Identification of defects of wood by using wave analysis of tap tone and application to machine stress rating of lumber
利用敲击声波分析识别木材缺陷及其在木材机械应力评级中的应用
  • 批准号:
    12660148
  • 财政年份:
    2000
  • 资助金额:
    $ 2.18万
  • 项目类别:
    Grant-in-Aid for Scientific Research (C)
Fracture mechanics approach on evaluation of residual strength of structural timbers having a crack which emanates in moisture non-steady state condition
潮湿非稳态条件下裂纹结构木材残余强度评价的断裂力学方法
  • 批准号:
    10660160
  • 财政年份:
    1998
  • 资助金额:
    $ 2.18万
  • 项目类别:
    Grant-in-Aid for Scientific Research (C)
REUSE OF RUBBER WASTE OF AUTOMOBILES AS WOOD-RUBBER COMPOSITE MATERIALS FROM THE VIEWPOINT OF LOCAL RECYCLE OF INDUSTRY WASTE.
从工业废物本地化回收的角度看汽车橡胶废料作为木橡胶复合材料的再利用。
  • 批准号:
    08660201
  • 财政年份:
    1996
  • 资助金额:
    $ 2.18万
  • 项目类别:
    Grant-in-Aid for Scientific Research (C)
DEVELOPMENT OF THE FUNCTIONS FOR AUTOMATED DENSITY CORRECTION AND MOISTURE GRADIENT MEASUREMENT OF HIGH FREQUENCY MOISTURE METER
高频水分计自动密度校正和水分梯度测量功能的开发
  • 批准号:
    07556040
  • 财政年份:
    1995
  • 资助金额:
    $ 2.18万
  • 项目类别:
    Grant-in-Aid for Scientific Research (B)
Improvement of electrical properties of wood by combination with ceramics
与陶瓷结合改善木材的电性能
  • 批准号:
    04660182
  • 财政年份:
    1992
  • 资助金额:
    $ 2.18万
  • 项目类别:
    Grant-in-Aid for General Scientific Research (C)
Development of Dynamic Portable Graders for Structural Lumber Using Tapping Method
攻丝法动态便携式结构材平地机的研制
  • 批准号:
    01860021
  • 财政年份:
    1989
  • 资助金额:
    $ 2.18万
  • 项目类别:
    Grant-in-Aid for Developmental Scientific Research (B).
Fundamental Research on the Development of the Fracture Analysis of Wood Using the Piezoelectric Effect.
利用压电效应进行木材断裂分析的基础研究。
  • 批准号:
    01560182
  • 财政年份:
    1989
  • 资助金额:
    $ 2.18万
  • 项目类别:
    Grant-in-Aid for General Scientific Research (C)
Analysis of fracture mechanism of bolted joints and nail joints in LVL
LVL中螺栓接头和钉接头断裂机理分析
  • 批准号:
    62560174
  • 财政年份:
    1987
  • 资助金额:
    $ 2.18万
  • 项目类别:
    Grant-in-Aid for General Scientific Research (C)

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2D/3D modeling of concrete weight coating to understand its performance including crack development
对混凝土重量涂层进行 2D/3D 建模,以了解其性能,包括裂纹发展
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