Fundamental Research on the Development of the Fracture Analysis of Wood Using the Piezoelectric Effect.

Research Project

Project/Area Number	01560182
Research Category	Grant-in-Aid for General Scientific Research (C)
Allocation Type	Single-year Grants
Research Field	林産学
Research Institution	Nagoya University
Principal Investigator	SOBUE Nobuo Nagoya Univ., Faculty of Agriculture, Josyu., 農学部, 助手 (50023495)
Co-Investigator(Kenkyū-buntansha)	SASAKI Yasutosi Nagoya Univ., Fac. Agriculture, Josyu., 農学部, 助手 (90154004) TSUZUKI Kazuo Nagoya Univ., Fac. Agriculture, Assoc. Prof., 農学部, 助教授 (60023438) TAKEMURA Tomio Nagoya Univ., Fac. Agriculture, Professor, 農学部, 教授 (90014919) HIRAI Nobuyuki Shizuoka Univ., Fac. Agriculture, Professor, 農学部, 教授 (70023439)
Project Period (FY)	1989 – 1990
Project Status	Completed (Fiscal Year 1990)
Budget Amount *help	¥2,200,000 (Direct Cost: ¥2,200,000) Fiscal Year 1990: ¥900,000 (Direct Cost: ¥900,000) Fiscal Year 1989: ¥1,300,000 (Direct Cost: ¥1,300,000)
Keywords	Piezoelectric effect / Wood / Fracture / Mechanic analysis / Loading、modes
Research Abstract	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.