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The influence of tyre-damping properties on vehicle-oscillation parameters
ABSTRACTS 16.
E. Absi. On the Rheology of Clays. Ann/s Inst. tech. Bytim. 18,213, 1137-1145, Sept. 1965; (in French). Static and quasistatic normal stress loading experiments on suturated clay indicate a Poisson ratio very near the incompressible value of l/2. An attempt is made to relate the gross values of elastic modulus and Poisson ratio to those of the “solid skeleton” and the interstitial liquid. Both free-draining and non-draining specimens are reported. Reviewer notes that prior work by others is hinted at, but no references are given. (Appl. Mech. Rev.)
17.
18.
B. Balazsy. Reciprocal Influence of Continuous Foundation Section. MPlyipztestud. Szle 15, 7, 317-324, July 1965; (in Hungarian). Prandtl’s bearing capacity formula does not always correspond to experience gained in the field. In order to determine the reciprocal influence between nearby footings, model studies were made. Results are presented in the form of curves readily applicable for design. (Appl. Mech. Rev.). Yu. B. Belenki et al. The Influence of Tyre-Damping Properties on Vehicle-Oscillation meters. Avtom. Prom. No. 12, pp. 1618, December 1966; (in Russian).
Para-
A complete translation from the Russian is not known to exist. The multi-ply tyres with extensively developed tread patterns used on very heavy commercial vehicles have powerful damping properties. Instances are given of tyres of varying sizes having damping coefficients of 4.5-8.0, 5.0-6.0 and up to 9.0 kg xs/cm in the range of working loads and pressures. However, the damping properties of these tyres are not infrequently ignored in investigations and, to demonstrate their importance therefore, computer investigations were made of the twin-mass oscillatory system formed by the tyre and the dynamic model of a two-axle vehicle fitted with the type of tyres mentioned. The mathematical model of the tyres is shown at (a) in the figure and that of the two-axle vehicle at (b). Analysis of the oscillograms obtained revealed the following: (I) With the traversing by the vehicle of a single obstacle having a height of 10 cm and a length of I m at a speed of 43.5 km/hr, reduction of the tyre-damping coefficient from 5 to 0 kg x s/cm increases the relative, sprung- and unsprung-mass displacements and the vertical and angular accelerations of the sprung masses. Owing to the rise in speed of the relative displacements, the character of damper operation changes, the damper valve coming into operation three times on the compression stroke with a tyre-damping coefficient of 0 instead of once as with a coefficient of 0.5 kg x s/cm. Furthermore, the shape of the oscillograph traces for the sprung-mass and, particularly, the unsprung-mass displacements and velocities change abruptly. Other oscillation parameters also manifest a similar type of change. (2) The existence of a tyre-damping coefficient exerts a beneficial influence on the fundamental oscillation parameters; therefore, from the point of view of ride smoothness stability, damping within the tyre is useful. With increase in the damper-resistance coefficient, acceleration and displacement over a single bump decrease in the low-frequency-resonance range and increase in the high-frequency-resonance and higher-than-resonance-frequency ranges. However, with a succession of equally spaced bumps, acceleration decreases slightly in the highfrequency-resonance range and increases in the between- and beyond-resonance ranges. The range of influence of damping within the tyre is different from this; in the low-frequency-resonrange of influence of damping within the tyre is different from this; in the low-frequency resonance range, the influence exerted by damping within the tyre on acceleration and displacement is slight, but, at the higher frequencies, acceleration becomes substantially reduced with an increase in internal tyre damping. (3) With increase in the tyre-damping coefficient, the energy expended by virtue of high-frequency oscillation rises sharply. During the traversing of a single bump, a proportion of the tyre energy (sometimes considerable) is dissipated, the actual proportion rising with increase in the tyre-damping coefficient. In the frequency range up to 4 c/s, the tyre-damping coefficient has no material infiuence on tyre-energy dissipation. At a frequency of 15 c/s, a tyre with a damping coefficient of 3 kg x s/cm dissipates energy equivalent to 10 h.p./ton and one with a damping coefficient of 12 kg x s/cm energy equivalent to 36 h.p./ton. (M.I.R.A.). 19. G. E. Blight. Effective Stress Evaluation for Unsaturated Soils. J. Soil Mech. Fdns Div. Am. Sot. civ. Engrs 93, No. SM2, Proc. Paper 5146, March 1967, pp. 125-148. Methods are developed for evaluating effective stresses and shear strength parameters from laboratory shear, volume change and swelling pressure tests on unsaturated soil. The effective 73
E. Absi. On the Rheology of Clays. Ann/s Inst. tech. Bytim. 18,213, 1137-1145, Sept. 1965; (in French). Static and quasistatic normal stress loading experiments on suturated clay indicate a Poisson ratio very near the incompressible value of l/2. An attempt is made to relate the gross values of elastic modulus and Poisson ratio to those of the “solid skeleton” and the interstitial liquid. Both free-draining and non-draining specimens are reported. Reviewer notes that prior work by others is hinted at, but no references are given. (Appl. Mech. Rev.)
17.
18.
B. Balazsy. Reciprocal Influence of Continuous Foundation Section. MPlyipztestud. Szle 15, 7, 317-324, July 1965; (in Hungarian). Prandtl’s bearing capacity formula does not always correspond to experience gained in the field. In order to determine the reciprocal influence between nearby footings, model studies were made. Results are presented in the form of curves readily applicable for design. (Appl. Mech. Rev.). Yu. B. Belenki et al. The Influence of Tyre-Damping Properties on Vehicle-Oscillation meters. Avtom. Prom. No. 12, pp. 1618, December 1966; (in Russian).
Para-
A complete translation from the Russian is not known to exist. The multi-ply tyres with extensively developed tread patterns used on very heavy commercial vehicles have powerful damping properties. Instances are given of tyres of varying sizes having damping coefficients of 4.5-8.0, 5.0-6.0 and up to 9.0 kg xs/cm in the range of working loads and pressures. However, the damping properties of these tyres are not infrequently ignored in investigations and, to demonstrate their importance therefore, computer investigations were made of the twin-mass oscillatory system formed by the tyre and the dynamic model of a two-axle vehicle fitted with the type of tyres mentioned. The mathematical model of the tyres is shown at (a) in the figure and that of the two-axle vehicle at (b). Analysis of the oscillograms obtained revealed the following: (I) With the traversing by the vehicle of a single obstacle having a height of 10 cm and a length of I m at a speed of 43.5 km/hr, reduction of the tyre-damping coefficient from 5 to 0 kg x s/cm increases the relative, sprung- and unsprung-mass displacements and the vertical and angular accelerations of the sprung masses. Owing to the rise in speed of the relative displacements, the character of damper operation changes, the damper valve coming into operation three times on the compression stroke with a tyre-damping coefficient of 0 instead of once as with a coefficient of 0.5 kg x s/cm. Furthermore, the shape of the oscillograph traces for the sprung-mass and, particularly, the unsprung-mass displacements and velocities change abruptly. Other oscillation parameters also manifest a similar type of change. (2) The existence of a tyre-damping coefficient exerts a beneficial influence on the fundamental oscillation parameters; therefore, from the point of view of ride smoothness stability, damping within the tyre is useful. With increase in the damper-resistance coefficient, acceleration and displacement over a single bump decrease in the low-frequency-resonance range and increase in the high-frequency-resonance and higher-than-resonance-frequency ranges. However, with a succession of equally spaced bumps, acceleration decreases slightly in the highfrequency-resonance range and increases in the between- and beyond-resonance ranges. The range of influence of damping within the tyre is different from this; in the low-frequency-resonrange of influence of damping within the tyre is different from this; in the low-frequency resonance range, the influence exerted by damping within the tyre on acceleration and displacement is slight, but, at the higher frequencies, acceleration becomes substantially reduced with an increase in internal tyre damping. (3) With increase in the tyre-damping coefficient, the energy expended by virtue of high-frequency oscillation rises sharply. During the traversing of a single bump, a proportion of the tyre energy (sometimes considerable) is dissipated, the actual proportion rising with increase in the tyre-damping coefficient. In the frequency range up to 4 c/s, the tyre-damping coefficient has no material infiuence on tyre-energy dissipation. At a frequency of 15 c/s, a tyre with a damping coefficient of 3 kg x s/cm dissipates energy equivalent to 10 h.p./ton and one with a damping coefficient of 12 kg x s/cm energy equivalent to 36 h.p./ton. (M.I.R.A.). 19. G. E. Blight. Effective Stress Evaluation for Unsaturated Soils. J. Soil Mech. Fdns Div. Am. Sot. civ. Engrs 93, No. SM2, Proc. Paper 5146, March 1967, pp. 125-148. Methods are developed for evaluating effective stresses and shear strength parameters from laboratory shear, volume change and swelling pressure tests on unsaturated soil. The effective 73