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Off-road mobility research
Journal of Terramechanics, 1970, Vol. 7, No. 1, pp. 79 to 85. Pergamon Press Printed in Great Britain.
ABSTRACTS 1.
L. Barden, A. J. Khayatt and A. Wightman. Elastic and slip components of the deformation of sand. Can. GeotechnicalJ. 6, 227 (Aug. 1969). The significance of a separation into elastic and slip components is considered for the case of particulate material. Tests on sand, including a variety of stress paths in a triaxial and a plane strain apparatus, indicate that for a majority of first-loading paths the total strains are closely given by the slip strains alone. The stress dilatancy theory is seen to provide a simple and accurate flow rule for predicting the slip strains. (Authors' summary.)
2.
L. Barden, A. O. Madedor and G. R. Sides. Volume change characteristics of unsaturated clay. Soil Mech. and Fndns Div., A.S.C.E., 95, 33-51 (Jan. 1969). The engineering properties of a partly saturated soil are governed by the parameters of structure (including void ratio) and degree of saturation. Article describes the results of careful experiments arriving at interesting correlations between stress-path and compressibility and between suction pressure and collapse; it discusses the mechanism of collapse of unsaturated clay. Tests are carried out with samples of "West-water" and "Derwent" clays ranging from 1 0 ~ to 5 0 ~ raw clay content of the illite-type. (Appl. Mech. Rev., Nov. 1969).
3.
G . E . Bartlett and J. N. Deutschman. Off-road mobility research, Volume 1. 164 pp. (Nov. 1968). A summary of research and engineering studies conducted on a long-range program of offroad mobility research is presented. These studies, some of which are only partially completed, are directed at providing technical knowledge which is required to match off-road vehicles with military mobility requirements. A hybrid computer model is described which will permit predicting vehicle dynamics performance of simulated vehicles traversing a broad spectrum of offroad situations. A critique of existing soil trafficability theories is made, based on a review of the literature which treats the comparison of vehicle performance prediction with experimental results. Analytical and experimental studies of the velocity field and soil fabric in clay soil exposed to dynamic loads are summarized. A general method is discussed for processing mobility related environmental information and for mapping vehicle performance by computer methods. A concept is introduced for testing vehicles in relation to the total environment in order to define the vehicle performance envelope. Also a method is introduced for displaying potential vehicle performance in selected geographic areas and for producing "testable" specifications for off-road vehicles. Engineering studies of an off-road driving simulator for synthesizing dynamic visual displays and vehicle motion in the laboratory are reviewed. (U.S. Gov. Res. Dev. Rep,, 10.9.69, AD-690169.)
4.
G . E . Bartlett and J. N. Deutsehman. Off-road mobility research, Volume 2. 165 pp. (Nov. 1968). Contents: Vehicle dynamics model formulation: Tabulated summaries of vehicle trafficability data; Full-scale test and evaluation practice study discussions of conclusions and recommendations; Water balance in S.E. Asia; Statistical distribution of soil moisture; Geometric and soil characteristics of streams; Instrumentation for measurements within soil; lnterparticle force calculation for clay; Soil fabric studies; Visibility study--plans for field testing; Auxiliary displays for improving off-road mobility; Design for vehicle motion simulation. (U.S. Gov. Res. Dev. Rep., 10.9.69, AD-690170.)
5.
M . L . Carter. Integrating penetrometer provides average soil strength. Agric. Engng, 618 (Oct. 1969). A force transducer, an operational amplifier and a d.c. signal generator are the main components of this instrument. The force to move the penetrometer cone through the soil is sensed by a proving ring with electric resistance strain gauges. The strain gauge bridge excitation is supplied by a d.c. generator mechanically connected so that the output voltage E1 is proportional to the rate of penetrometer probe insertion dx/dt. 79
ABSTRACTS 1.
L. Barden, A. J. Khayatt and A. Wightman. Elastic and slip components of the deformation of sand. Can. GeotechnicalJ. 6, 227 (Aug. 1969). The significance of a separation into elastic and slip components is considered for the case of particulate material. Tests on sand, including a variety of stress paths in a triaxial and a plane strain apparatus, indicate that for a majority of first-loading paths the total strains are closely given by the slip strains alone. The stress dilatancy theory is seen to provide a simple and accurate flow rule for predicting the slip strains. (Authors' summary.)
2.
L. Barden, A. O. Madedor and G. R. Sides. Volume change characteristics of unsaturated clay. Soil Mech. and Fndns Div., A.S.C.E., 95, 33-51 (Jan. 1969). The engineering properties of a partly saturated soil are governed by the parameters of structure (including void ratio) and degree of saturation. Article describes the results of careful experiments arriving at interesting correlations between stress-path and compressibility and between suction pressure and collapse; it discusses the mechanism of collapse of unsaturated clay. Tests are carried out with samples of "West-water" and "Derwent" clays ranging from 1 0 ~ to 5 0 ~ raw clay content of the illite-type. (Appl. Mech. Rev., Nov. 1969).
3.
G . E . Bartlett and J. N. Deutschman. Off-road mobility research, Volume 1. 164 pp. (Nov. 1968). A summary of research and engineering studies conducted on a long-range program of offroad mobility research is presented. These studies, some of which are only partially completed, are directed at providing technical knowledge which is required to match off-road vehicles with military mobility requirements. A hybrid computer model is described which will permit predicting vehicle dynamics performance of simulated vehicles traversing a broad spectrum of offroad situations. A critique of existing soil trafficability theories is made, based on a review of the literature which treats the comparison of vehicle performance prediction with experimental results. Analytical and experimental studies of the velocity field and soil fabric in clay soil exposed to dynamic loads are summarized. A general method is discussed for processing mobility related environmental information and for mapping vehicle performance by computer methods. A concept is introduced for testing vehicles in relation to the total environment in order to define the vehicle performance envelope. Also a method is introduced for displaying potential vehicle performance in selected geographic areas and for producing "testable" specifications for off-road vehicles. Engineering studies of an off-road driving simulator for synthesizing dynamic visual displays and vehicle motion in the laboratory are reviewed. (U.S. Gov. Res. Dev. Rep,, 10.9.69, AD-690169.)
4.
G . E . Bartlett and J. N. Deutsehman. Off-road mobility research, Volume 2. 165 pp. (Nov. 1968). Contents: Vehicle dynamics model formulation: Tabulated summaries of vehicle trafficability data; Full-scale test and evaluation practice study discussions of conclusions and recommendations; Water balance in S.E. Asia; Statistical distribution of soil moisture; Geometric and soil characteristics of streams; Instrumentation for measurements within soil; lnterparticle force calculation for clay; Soil fabric studies; Visibility study--plans for field testing; Auxiliary displays for improving off-road mobility; Design for vehicle motion simulation. (U.S. Gov. Res. Dev. Rep., 10.9.69, AD-690170.)
5.
M . L . Carter. Integrating penetrometer provides average soil strength. Agric. Engng, 618 (Oct. 1969). A force transducer, an operational amplifier and a d.c. signal generator are the main components of this instrument. The force to move the penetrometer cone through the soil is sensed by a proving ring with electric resistance strain gauges. The strain gauge bridge excitation is supplied by a d.c. generator mechanically connected so that the output voltage E1 is proportional to the rate of penetrometer probe insertion dx/dt. 79