アスファルトの粘弾性と破壊限界 : 分散型のレオロジー

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Viscoelastic properties of asphalts were measured under a constant load by a cone and plate viscometer. Viscosity coefficients and delayed elastic compliances at a steady state were obtained from the creep and recovery curves at various temperatures (Fig. 1, Fig. 2). Asphalts break down when the rate of deformation reaches the critical value v_B, below which the deformation is viscous. It is assumed that brittle fracture occurs when the elastic energy stored exceeds the energy of cohesion (Fig. 3, Fig. 4). From a simple Maxwell model the following relation was derived ; t_B≦1.15τ^^- at v_B (1) where t_B is the time of fracture at the critical condition and τ^^- is the mean relaxation time. τ^^- can be expressed as τ^^-=η/G (2) where η is the viscosity coefficient and G is the instantaneous elastic modulus. Eq. (2) was derived from the generalized Maxwell model at a constant rate of deformation. t_B was measured experimentally at various temperatures and τ^^- was evaluated from Eq. (2). It was found that Eq. (1) was satisfied qualitatively, but discrepancy appeared at low temperatures and in the case of asphalts rich in asphaltenes (Table 4). In mechanical models, as shown in the foregoing descriptions, stresses are supposed to be uniform and strains small. It was found, however, by means of high speed photography, that a crack started locally and intermittently and propagated in the direction perpendicular to the direction of extension. The rate of crack propagation decreased rapidly and the mean rate was 1〜5 m/sec, being quite small in comparison with the case of brittle fracture of steel, glasses and plastics.
社団法人日本材料学会の論文
1961-05-15

アスファルトの粘弾性と破壊限界 : 分散型のレオロジー

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