Teruaki Ono

Study on Young's Modulus and Internal Friction of Wood in Relation to the Evaluation of Wood for Musical Instruments

Youngs modulus E and internal friction Q-1 in longitudinal (L) direction and specific gravity γ were measured for numerous specimens of 25 softwood species. There was a high correlation between Q-1/(E/γ) and E/γ, and the suitability of wood for musical instruments can be evaluated by using the value of E/γ. Furthermore, effects of grain angle in the longitudinal-radial plane on Youngs modulus and internal friction of wood were investigated. From these results, it is concluded that the value of internal friction as well as Youngs modulus of wood is determined in large part by microfibril angle in the S2 layer of tracheid against the L direction.

Anisotropy of Dynamic Young's Modulus and Internal Friction in Wood

The dynamic Youngs modulus E and the internal friction Q-1 in three principal directions were measured from the longitudinal vibration in several species of softwood and hardwood. The modulus E in the radial (R) and tangential (T) directions was much lower than that in the longitudinal (L) direction regardless of the wood species, and the order of magnitude was El Er > Et, whereas the friction Q-1 showed exactly the opposite tendency, i.e., Ql-1 Qr-1 < Qt-1. An investigation of the relationship between the values showed that the internal friction could be expressed by an exponential equation of the specific Youngs modulus E/γ regardless of the direction and wood species, and that the exponent in three principal directions was slightly lower than that in the L direction. Furthermore, the differences in the values (E and Q-1) and exponents between directions were considered from the structural aspect, and it was found that the causes were the same and could be explained well by the difference in the structural factors.

Aluminum titanate-tetragonal zirconia composite with low thermal expansion and high strength simultaneously

Abstract Aluminium titanate was strengthened by alloying with 3 mol% yttria stabilized zirconia to attain a small expansion coefficient of 2 × 10 −6 and a high strength of 100 MPa, simultaneously. Long milling and optimization of the composition of the alloy to an equal weight of the component oxides and also of the firing temperature at 1400 °C were important for the purpose. In the optimal conditions, aluminum titanate grains of 3 μm was surrounded by zirconia matrix of ca. 0.3 μm grains containing zirconium titanate where would be a balance between the tension in the matrix and the expansion force of aluminum titanate grains. Formation of zirconium titanate was important for the strengthening to decrease the lowering of the strength brought about by the unstabilization of PSZ.

Internal friction, crack length of fracture origin and fracture surface energy in alumina-zirconia composites

Two series of alumina-zirconia composites, i.e. alumina-unstabilized zirconia and alumina-partially stabilized zirconia with 3 mol % Y2O3, with different zirconia content were slip casted and fired at 1550°C for 3 h. Elastic constant, bending strength and fracture toughness were measured. Internal friction was determined to follow the formation of cracks, nondestructively, which could be one of the fracture origins. The crack length of the fracture origin and the fracture surface energy were calculated by applying Griffiths fracture theory. Microstructures of the fracture surfaces were observed using a scanning electron microscope. For the unstabilized zirconia system, the increase in the internal friction of the order from 10−4 to 10−3 was a guide to find the formation of cracks which lead to the fracture. The increase in the cracks becoming a fracture origin lead to the increase inKlc and also to the apparent increase in the fracture surface energy. For the partially stabilized zirconia system, the increase in the fracture surface energy with an increase in zirconia content, keeping low internal frictions of the order of 10−4, indicates the intrinsic strengthening of the grain boundaries in comparison to the unstabilized zirconia system. Internal friction is the most suitable nondestructive physical quantity to find the microcracks which leads to the fracture.

Composition Dependence of Internal Friction in Al2O3–3Y–ZrO2 Composites

An apparatus was developed for measuring internal friction automatically with high accuracy at high temperatures. The composition dependence of the internal friction in an Al2O3–3Y–ZrO2 system was investigated at room temperature using it. The results showed that no cracks were produced in the 3Y–ZrO2 contents less than 40%, and that an energy absorption peak existed at about 20% 3Y–ZrO2 content.

Composition dependence of dynamic Young’s modulus and internal friction in Al2 O3 ‐3Y‐ZrO2 composites

The specific dynamic Young’s modulus E’/ρ and the internal friction Q−1 of Al2 O3 ‐3Y‐ZrO2 composites with different 3Y‐ZrO2 content were investigated. With the increase of 3Y‐ZrO2 content, the E’/ρ decreased linearly showing a large inflection point at about 20% and a small one at 65%, and the Q−1 reached a peak at 17% and a trough at 40%, and increased showing a shoulder at about 70%. The specific loss modulus E‘/ρ calculated from E’/ρ and Q−1 showed the peaks at 17% and 65%. The E‘/ρ peaks corresponded with the E’/ρ inflection points in composition. As a result, it was estimated that they were due to the tetragonal to monoclinic transformation of ZrO2 phase, and that the increase of internal friction at above 40% was not due to the crack formation and the ZrO2 phase transformation, but due to the flexural deformation caused by shearing force.

Development of a carbon‐fiber‐reinforced composite for guitar soundboards: Investigation of bracing effect by experiment and simulation

A carbon‐fiber‐reinforced polyurethane foam composite whose physical and acoustic properties closely resemble those of wood for stringed‐instrument soundboards was developed. A guitar with such a composite‐made soundboard produced an almost identical tone to that produced with a wooden soundboard. The procurement of wood for soundboards, however, has not yet become very difficult. To accelerate the production and use of guitars with composite soundboards, it is necessary to create an attractive guitar that has characteristic and unique tones that cannot be realized on a wooden soundboard, making use of composite characteristics of design freedom. Wooden top boards, soundboards, have bracing that has traditionally and experientially been glued; however, the effects of bracing have never been clarified. In this study, the bracing effect on the frequency response and vibration mode in a guitar top board was investigated using experimentation and simulation. From the results obtained, a composite‐made soundbo...