- Email: [email protected]
Analysis and simulation of dynamical vehicle-terrain interaction
84
ABSTRACTS solved before an entirely satisfactory theory can be developed. A fully comprehensive bibliography is appended. Author promises follow-up article to include conclusions. (Appl. Mech. Rev., Nov. 1969.)
27.
D. Sehuring and M. R. Belsdorf. Analysis and simulation of dynamical vehicle-terrain interaction. 209 pp. (May 1969). The reported study is part of a broad research program designed to acquire off-road mobility knowledge: develop analysis, prediction, and decision methodologies; and organize knowledge and methods to facilitate use by military planners, vehicle designers and field personnel concerned with off-road mobility. This particular study was concerned with the development of generalized vehicle-terrain mathematical models of wheeled and tracked vehicles running in hard and soft soil. The computer simulation phase of work was carried to the point of mechanizing 3-degree-of-freedom and 5-degree-of-freedom models in real time on the analog computer. (U.S. Gov. Res. Dev. Rep., 25.9.69, AD-690841.)
28.
N . B . Shankar. Plastic properties of certain clays. Soil Mech. Fndn Engng, 6 (3), 339-348 (July 1968). This is an interesting experimental study seeking new paths for improving the determination technique of soil consistency (plasticity) limits. Since they were introduced in 1911 by Atterberg, these limits have been considered as strictly conventional and empirical; they are still generally used because they cannot yet be replaced by any better parameters. The study compares the standard Casagrande method with the penetrometric one, shear strength of soil being determined at the same time by vane tests. Penetration seems to be more reliable, as liquid limit determined by this method corresponds to an almost constant shear strength value. Author brings out a proposal in this respect. He also declares that the presently used method for plastic limit has to be modified. The study confirms the advantages of the new grooving tool proposed by Hovanyi (Geotechnique, 8, 78-79, 1958). The results concerning temperature influence on plasticity limit values are also interesting. (Appl. Mech. Rev., Nov. 1969.)
30.
EI-Sohby, A. Mohamed. Elastic behaviour of sand. J. Soil Mech. Fndns Div., ASCE, 95, 13931409 (Nov. 1969). The total deformation of a mass of sand subjected to a constant stress ratio is divided into an elastic component due to the elastic deformations of the individual particles, and a sliding component due to the relative movements between the particles. The elastic deformations under these stress conditions are separated from the total deformations and correlated to the applied stresses. A theoretical treatment of the elastic behavior of a mass of sand under different stress systems is presented, and an attempt is made to explain the relation between the simple contact properties of two spheres, and the actual behavior of a mass of sand particles. Tests that bear out the predicted elastic behavior are also described, and methods to determine the elastic constants for a certain type of sand at a particular porosity are also given. Furthermore, the significance of these elastic constants is discussed. In addition, the effect of the properties of the sand on the elastic behavior is considered. (Authors' summary.)
31.
W . H . Tang and K. Hoeg. Two-dimensional analysis of stress and strain in soils, report 5, planestrain loading of a strain-hardening soil. U.S. Army Eng. Waterways Experiment Station, Report 5 (Mar. 1968). Idealized stress-strain relationships for a strain-hardening soil are formulated and discussed. The normality rule during plastic flow is assumed to be valid and forms the basis for the stress increment-strain increment relations. The method was applied to a flexible 5 ft wide strip footing resting on frictional material with aunit weight of 119 lb/cu ft. To perform the numerical computations, the soil continuum was replaced by a lumped parameter model. If plastic volume change of the soil element takes place during virgin loading, the element is work-hardened. Upon subsequent reloading, no plastic straining will occur until a stress state is reached, bringing the stress up to the previous yield surface. Analysis of the strip footing statically loaded to 35.8 psi indicated that a failure pattern was developing. Decrease in settlement was proportional to the increase in elastic modulus. Because of the inertia of the assumed 2-ft-thick concrete footing, the ratio of peak, response to peak applied footing pressure during impulse loads is about I .35 and occurs after 45 msec. As friction angle and cohesion are increased, displacements are increased, indicating an inadequacy in the present formulation of strain-hardening behavior. (J. Soil Mech. Fndns Div., Nov. 69.)
ABSTRACTS solved before an entirely satisfactory theory can be developed. A fully comprehensive bibliography is appended. Author promises follow-up article to include conclusions. (Appl. Mech. Rev., Nov. 1969.)
27.
D. Sehuring and M. R. Belsdorf. Analysis and simulation of dynamical vehicle-terrain interaction. 209 pp. (May 1969). The reported study is part of a broad research program designed to acquire off-road mobility knowledge: develop analysis, prediction, and decision methodologies; and organize knowledge and methods to facilitate use by military planners, vehicle designers and field personnel concerned with off-road mobility. This particular study was concerned with the development of generalized vehicle-terrain mathematical models of wheeled and tracked vehicles running in hard and soft soil. The computer simulation phase of work was carried to the point of mechanizing 3-degree-of-freedom and 5-degree-of-freedom models in real time on the analog computer. (U.S. Gov. Res. Dev. Rep., 25.9.69, AD-690841.)
28.
N . B . Shankar. Plastic properties of certain clays. Soil Mech. Fndn Engng, 6 (3), 339-348 (July 1968). This is an interesting experimental study seeking new paths for improving the determination technique of soil consistency (plasticity) limits. Since they were introduced in 1911 by Atterberg, these limits have been considered as strictly conventional and empirical; they are still generally used because they cannot yet be replaced by any better parameters. The study compares the standard Casagrande method with the penetrometric one, shear strength of soil being determined at the same time by vane tests. Penetration seems to be more reliable, as liquid limit determined by this method corresponds to an almost constant shear strength value. Author brings out a proposal in this respect. He also declares that the presently used method for plastic limit has to be modified. The study confirms the advantages of the new grooving tool proposed by Hovanyi (Geotechnique, 8, 78-79, 1958). The results concerning temperature influence on plasticity limit values are also interesting. (Appl. Mech. Rev., Nov. 1969.)
30.
EI-Sohby, A. Mohamed. Elastic behaviour of sand. J. Soil Mech. Fndns Div., ASCE, 95, 13931409 (Nov. 1969). The total deformation of a mass of sand subjected to a constant stress ratio is divided into an elastic component due to the elastic deformations of the individual particles, and a sliding component due to the relative movements between the particles. The elastic deformations under these stress conditions are separated from the total deformations and correlated to the applied stresses. A theoretical treatment of the elastic behavior of a mass of sand under different stress systems is presented, and an attempt is made to explain the relation between the simple contact properties of two spheres, and the actual behavior of a mass of sand particles. Tests that bear out the predicted elastic behavior are also described, and methods to determine the elastic constants for a certain type of sand at a particular porosity are also given. Furthermore, the significance of these elastic constants is discussed. In addition, the effect of the properties of the sand on the elastic behavior is considered. (Authors' summary.)
31.
W . H . Tang and K. Hoeg. Two-dimensional analysis of stress and strain in soils, report 5, planestrain loading of a strain-hardening soil. U.S. Army Eng. Waterways Experiment Station, Report 5 (Mar. 1968). Idealized stress-strain relationships for a strain-hardening soil are formulated and discussed. The normality rule during plastic flow is assumed to be valid and forms the basis for the stress increment-strain increment relations. The method was applied to a flexible 5 ft wide strip footing resting on frictional material with aunit weight of 119 lb/cu ft. To perform the numerical computations, the soil continuum was replaced by a lumped parameter model. If plastic volume change of the soil element takes place during virgin loading, the element is work-hardened. Upon subsequent reloading, no plastic straining will occur until a stress state is reached, bringing the stress up to the previous yield surface. Analysis of the strip footing statically loaded to 35.8 psi indicated that a failure pattern was developing. Decrease in settlement was proportional to the increase in elastic modulus. Because of the inertia of the assumed 2-ft-thick concrete footing, the ratio of peak, response to peak applied footing pressure during impulse loads is about I .35 and occurs after 45 msec. As friction angle and cohesion are increased, displacements are increased, indicating an inadequacy in the present formulation of strain-hardening behavior. (J. Soil Mech. Fndns Div., Nov. 69.)