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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。

基本信息

批准号：
01560182
负责人：
SOBUE Nobuo
金额：
$ 1.41万
依托单位：
Nagoya University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1989
资助国家：
日本
起止时间：
1989 至 1990
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-01560182/
关键词：
Piezoelectric effect Wood Fracture Mechanic analysis Loading、modes

项目摘要

The object of this project was directed to fundamental research on the piezoelectric effect of wood during fracture and its application to the fracture analysis.1. A hydraulically controlled cyclic fatigue testing machine was used to measure the piezoelectric charge by combining a static mean load and small cyclic load, because the charge amplifier which is commonly used for the measurement of electronic charge does not have static sensibility. This improvement enabled the piezoelectric measurement at very high stress level until fracture load.2. The anisotropy of the piezoelectric effect was measured by using circular plate samples. The piezoelectricity in the fiber-direction loading and in the perpendicular to fiber direction loading was detected although usually they had not been clearly observed. Piezoelectric charge decreased as the frequency of the stress cycle decreased, especially the decrease below 10 Hz was remarkable, probably because of the leakage of current by humidity in the wood.3. The piezoelectric effect (piezoelectric voltage per unit stress) decreased slightly with the increase of the stress level. It decreased remarkably at fracture initiation load and increased suddenly at near ultimate stress.4. The piezoelectric effect under impact loadings (bending mode, shear mode parallel to the fiber direction, uni-axial mode parallel to the fiber-, radial-, tangntial-, and LT-45^ﾟ-directions, and cleavage mode) was examined. The piezoelectric effect was confirmed in above all loading modes. Especially in bending mode, a very complex signal was detected during the fracture process.5. However, the origin of the piezoelectric effect of wood has not been enough clarified. A representation on crystallographic and structural analysis should be done.

本课题针对木材断裂过程中的压电效应及其在断裂分析中的应用进行基础研究。针对压电电荷测量常用的电荷放大器不具有静灵敏度的问题，采用液压控制的循环疲劳试验机，结合静态平均载荷和小循环载荷对压电电荷进行测量。这一改进使压电测量能够在非常高的应力水平直到断裂载荷下进行。利用圆板试样测量了压电效应的各向异性。在纤维方向加载和垂直于纤维方向加载中，虽然通常不清楚地观察到压电性，但也检测到了压电性。压电电荷随着应力循环频率的降低而降低，特别是在10 Hz以下的降低较为显著，这可能是由于木材中的湿度泄漏电流造成的。随着应力水平的增加，压电效应（单位应力的压电电压）略有下降。在断裂起裂载荷下显著减小，在接近极限应力时突然增大。研究了冲击载荷下的压电效应（弯曲模式、平行于纤维方向的剪切模式、平行于纤维方向的单轴模式、径向模式、切向模式、LT-45^ _(_) -方向和解理模式）。在所有加载模式下均证实了压电效应。特别是在弯曲模式下，在断裂过程中检测到非常复杂的信号。然而，木材压电效应的起源一直没有得到足够的澄清。应进行晶体学和结构分析。