Yoshihide Fukahori

Mechanism of rubber abrasion. Part I: Abrasion pattern formation in natural rubber vulcanizate

Abstract The driving force to generate the periodic surface patterns, and thus rubber abrasion consists of two kinds of periodic motions, stick-slip oscillation and the microvibration generated during frictional slidings of rubber. The stick-slip oscillation is the driving force to propagate cracks, then abrasion patterns and the microvibration with the natural frequency of the rubber induced in the slip phase of the stick-slip oscillation is another driving force for the initiation of the cracks. Although initial cracks originate in the slip region of the rubber surface, the propagation of the cracks is strongly excited in the stick region. Accordingly, the initial size of the abrasion pattern, pattern spacing, equals the distance determined by the natural period of the rubber and the mean sliding velocity while the constant pattern spacing after the critical number of frictional slidings agrees with the distance given by the period of the stick-slip oscillation and the mean sliding velocity. Consequently, during rubber abrasion, two driving forces produce bimodal size distribution of abraded particles, small particles of the order of ten micrometres by microvibrations and large ones of the order of a few hundred micrometres by the stick-slip motions.

Mechanism of rubber abrasion: Part 2. General rule in abrasion pattern formation in rubber-like materials

Abstract The mechanism of rubber abrasion proposed in the previous paper was reconfirmed not only in unfilled and filled NR but in SBR and silicone rubber. It is an essential and general rule in rubber abrasion that the microvibration induced in the slip phase of stick-slip oscillation generates the initial abrasion patterns and the stick-slip motion propagates them to the final abrasion patterns. The initial pattern spacing agrees with the distance determined by the relation between the natural frequency of the material and the mean sliding velocity, meanwhile the final pattern spacing in the propagation reaches the distance given by the frequency of the stick-slip oscillation and the mean sliding velocity. Reinforcement by carbon blacks makes the frequencies of the both periodic motions in rubber larger, which of course gives the smaller initial and final pattern spacings in rubber abrasion. In addition, the microvibration attenuates more rapidly in more filled rubbers when it spreads over the rubber surface as a surface wave. Both phenomena have a great influence on the smaller abrasive wear of more filled rubbers.

Mechanism of rubber abrasion part 3: how is friction linked to fracture in rubber abrasion?

Abstract We propose a new concept to understand the mechanism of rubber abrasion. Friction and fracture in abrasive wear of rubber are linked theoretically and experimentally through the formation of a periodic surface pattern, the abrasion pattern, generated by two kinds of periodic motion, stick-slip oscillation and microvibration. The direct driving force for fracture, i.e. the pattern formation, is the magnitude of the mean strain produced at the surface of the rubber by the two motions. The mean strain amplitude e ∗ is governed by the friction constant μ, Youngs modulus E of the material and the normal load P, as e ∗ = μP/ES , where S is the cross-sectional area, which is correlated to the rate of abrasion loss V with the relation, V = d c(e ∗ / d n . Thus, abrasive wear of rubber is strongly dependent on fracture resistant properties of the material under repeated deformation of the mean strain amplitude e ∗ . Several questions in rubber abrasion remained unanswered are discussed according to the above concept.

The mechanics and mechanism of the carbon black reinforcement of elastomers

Abstract The author proposes a new concept, including a model and theory of the carbon black reinforcement of elastomers, based on stress analysis. Two assumptions are introduced: first, that there are very few or no chemical crosslink in the interface layer of carbon particle and matrix elastomer; and, second, that crazing or a craze-like phenomenon takes place within the interface layer. The deformable character of the interface layer depending on the magnitude of extension will realize the dramatic improvement of elastomers over a wide range of extension. At present time, although there is no direct experimental evidence to prove the assumptions, such assumptions just provide a reasonable interpretation of the carbon black reinforcement of elastomers.

Seismic isolation apparatus

A seismic isolation apparatus which has a composite multilayered member comprising a plurality of hard plates having rigidity and a plurality of soft plates having viscoelastic property which are arranged to form alternating layers between an upper flange and a lower flange; and satisfies the condition that the proper vibration to the horizontal direction of the seismic isolation apparatus which is represented by fH and obtained by the equation fH=+E,fra 1/2+EE p 2ROOT +E,rad KHM+EE wherein KH represents a spring constant of the seismic isolation apparatus to the horizontal direction, M represents mass of a structure mounted on the seismic isolation apparatus, and fH has a value in the range of: 0.1 Hz</=fH</=2 Hz when the displacement of the seismic isolation apparatus in the horizontal direction is 2 mm or less, 0.1 Hz</=fH</=0.8 Hz when the displacement of the seismic isolation apparatus in the horizontal direction is equal to 100% shearing strain, and 0.9 Hz</=fH when deformation in terms of shearing strain is relaxed by 10% from the maximum deformation in measurement of a hysteresis loop of the seismic isolation apparatus. The seismic isolation apparatus has the function of seismic isolation, prevention of shake by wind, and isolation of traffic vibration and is advantageously used for structures having a light weight, such as single family houses.

Sound damping materials

A sound damping material is disclosed, which is a composite structural body comprising honeycomb or corrugated core, plain sheet and pressure sensitive adhesive layer, a height direction of the honeycomb or corrugated core being perpendicular to a surface of a vibrating body. In this sound damping material, one pressure sensitive adhesive layer is at least existent between the honeycomb or corrugated cores or between the honeycomb or corrugated core and the plain sheet.

A large-deformation finite-element analysis for multilayer elastomeric bearings

Abstract Finite element methods are applied for multilayer elastomeric bearings under large deformation. The method is capable of handling nonlinear elasticity and incompressibility of rubber-like materials. The strain energy density function which determines elastic properties of the materials is obtained empirically through strip biaxial testing. The computation using the strain energy density function is conducted to analyze the stress and strain distribution and the performance characteristics of multilayer elastomeric bearings, which is in good agreement with the results of actual experiments.

Molecular behaviour of elastomeric materials under large deformation: 1. Re-evaluation of the Mooney-Rivlin plot

Abstract Partial derivatives of the strain energy function ∂W ∂I 1 and ∂W ∂I 2 are widely evaluated for various rubber vlucanizates under small to very large extension. The Mooney-Rivlin plot is reproduced with the plot of the original equation, σ = 2(λ − λ −2 ) ( ∂W ∂I 1 + λ −1 ∂W ∂I 2 ) , in which an inevitability for the plot to give a straight line is not found. Even if a straight line is obtained, the constants C1 and C2 differ from ∂W ∂I 1 and ∂W ∂I 2 , respectively.

Anti-seismic rubber bearing

There is provided an anti-seismic rubber bearing made up of a laminate structure formed by bonding a plurality of rigid plates having stiffness properties and a plurality of flexible plates having viscoelastic properties each other alternately, and flanges each attached to the upper and lower surfaces of the laminate structure, characterized by that the local strain is evenly distributed throughout the structure by lowering the local strain which occurs near the flanges.

GENERALIZED CONCEPT OF THE REINFORCEMENT OF ELASTOMERS. PART 1. CARBON BLACK REINFORCEMENT OF RUBBERS

Abstract The author had a detailed discussion about the new interface model and the concepts proposed by the author concerning the carbon black reinforcement of rubbers, with additional experiments...