外文翻譯--竹子的機(jī)械特性（英文）

1、 Mechanical Characteristics of Bamboo Tadashi Shioya1, a and Toshikatsu Asahina1, b 1 Department of Mechanical Engineering, College of Industrial Technology, Nihon University 1-2-1 Izumicho, Narashino, Chiba 275-8575,

2、Japan atshioya@gakushikai.jp, basahina.toshikatsu@nihon-u.ac.jp Keywords: bamboo, fracture toughness, elastic modulus, attenuation, damping coefficient, inverted torsion pendulum, water concentration. Abstract. Fractu

3、re toughness, stress-strain relation and the damping characteristics of bamboo are investigated. The fracture toughness of bamboo in tearing along the longitudinal direction is measured by the use of newly devised appa

4、ratus in which the crack opening displacement is controlled in a constant velocity and a quasi-steady extension of the crack is maintained. The stress-strain relation of bamboo is examined in a reversible elastic rang

5、e using a conventional tensile test in the longitudinal direction. Repeated tensile loading tests show that the stress-strain relation has a strong non-linear hysteresis and that it converses to a steady loop. The da

6、mping of bamboo is measured by the use of inverted torsion pendulum apparatus. The specimen is taken so that damping of twisting longitudinal bar is measured. The damping coefficient of bamboo is much larger than tha

7、t of metals. The mechanical properties of bamboo are examined in terms of water concentration and fiber density in the bamboo. Introduction Bamboo is one of candidate bio-materials for structural use. The strength of

8、 the bamboo in the longitudinal direction (fiber direction) is higher than that of most other wood materials. With its lightness and strength, the bamboo has larger specific strength (strength per weight) than most m

9、etallic materials. However, there have been few researches on mechanical properties other than the elastic constants and the fracture strength of longitudinal direction or the bending direction. In this study, mechan

10、ical properties of bamboo are extensively examined using three types of experiments. First, conventional tensile test is conducted for a straight specimen of bamboo. Loading and unloading are repeated with changing t

11、he velocity to obtain the hysteresis curve. The second type of test is a quasi-steady tearing along the fiber direction to obtain the fracture toughness. The third is a free oscillation test in pure torsion obtaining

12、 the damping characteristic of bamboo. Experiment Material. The material used in the experiment of this study is mao bamboo or moso bamboo (academic name: phyllostachys edulis), most widely spread in east Asia. Since

13、 bamboo is a bio-material, its characteristics differ from specimen to specimen. In this experimental study, the position at the original material from which the specimen is taken is examined. It is found in the fol

14、lowing experiments that the difference of characteristic is small among data of the specimens taken from different height positions from the earth and the different facing direction (north, south, east and west) if th

15、e specimen is taken from the same bamboo. However, it is found that the specimen radial position and water content have some effect on the mechanical characteristics. The bamboo is a kind of composite material with c

16、ellular fibers and matrix. The fiber density of outer side is richer than that of inner side (Fig. 1). The water concentration in the specimen is controlled by aging for several days to weeks. Key Engineering Materia

17、ls Vols. 525-526 (2013) pp 609-612 Online available since 2012/Nov/12 at www.scientific.net © (2013) Trans Tech Publications, Switzerland doi:10.4028/www.scientific.net/KEM.525-526.609All rights reserved. No part of

18、 contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of TTP, www.ttp.netwhere l is the crack extension length and EI is the bending rigidity of the cracked

19、part of beam. The fracture toughness IC Kis calculated by the cantilever beam theory as bIl P EG K2 2C 2IC 1 ? ? ? ?(2) Example of the observed load-displacement is shown in Fig. 4. The crack length l is observed

20、 by a video camera. The obtained fracture toughness IC Kis also exhibited in Fig. 4. Fig. 3. Fracture Toughness Specimen Fig. 4. Load-Time Relation with Fracture Toughness Damping Tests. The inverted torsion pendul

21、um apparatus used in the experiment is shown in Fig. 5. An example of attenuation wave in free oscillation in the experiment is shown in Fig. 6. Assuming linear small range attenuation, the amplitude A in a free osci

22、llation is expressed as, ? ? ? ? ft ft A A ? ? 2 cos exp 0 ? ?, (3) where 0 A is the initial amplitude at 0 ? t , f is the frequency and ? is the damping coefficient per unit wave length time. The peak profile (ampl

23、itude) is fitted to logarithmic curve, and the damping coefficient ? is obtained by the logarithmic decay. The experiment was conducted in the frequency range from 0.13 to 0.76 Hz. The obtained damping coefficient p

24、er unit wave length is almost unchanged in this range, confirming that the damping is proportional to the strain velocity. 0 50 100 150 -0.04-0.0200.020.04Time，t，[sec]Angle of twist ，θ，[rad.]Fig. 5. Inverted Torsion Pen

25、dulum Apparatus Fig. 6. Attenuation Curve in Torsion Oscillation. The specimens are taken from several radial positions in the same bamboo bar, in order to examine the effect of fiber density. The obtained damping c