Tatsuro Muro

Tractive performance of a driven rigid wheel on soft ground based on the analysis of soil-wheel interaction

Abstract A new analytical method has been presented to predict the tractive performance of a rigid wheel running on soft ground. The resultant stress of the normal stress and the shear resistance applied around the peripherical contact part of the rigid wheel should be calculated by use of the dynamic pressure-sinkage curve measured from the plate loading and unloading test, considering the rolling locus of the wheel in the direction of the external resultant force of the effective driving force and the axle load. The effective driving force could be calculated as the difference of the driving force, i.e. the integration of shear resistance and the locomotion resistance calculated from the total amount of sinkage. As a result, the analytical relations between the driving force, the effective driving force and the slip ratio, the amount of sinkage and the slip ratio, the amount of eccentricity of resultant force and the slip ratio, and the entry angle, the exit angle and the slip ratio could be verified experimentally.

Tractive performance of a bulldozer running on weak ground

Abstract To determine the tractive performance of a bulldozer running on weak ground in the driven state, the relations between driving force, drawbar pull, sinkage, eccentricity and slip ratio have been analysed together with each energy balance; effective input energy, sinkage deformation energy, slippage energy and drawbar pull energy. It is considered that the thrust is developed not only on the main straight part of the bottom track belt but also on parts of the front idler and rear sprocket, and the compaction resistance is calculated from the amount of slip sinkage. For a given vehicle and soil properties, it is determined that the drawbar pull increases directly with the slip ratio and reaches about 70% of the maximum driving force. The compaction resistance reaches about 13% of the maximum driving force. The sinkage of the rear sprocket, the eccentricity, and the trim angle increase with the increment of slip ratio due to the slip sinkage. These analytical results have been verified experimentally. After determining the optimum slip ratio to obtain a maximum effective tractive power, it is found that a larger optimum drawbar pull at optimum contact pressure could be obtained for a smaller eccentricity of vehicle center of gravity and a larger track length-width ratio under the same contact area.

Effects of a roller and a tracked vehicle on the compaction of a high lifted decomposed granite sandy soil

The aim of this research was to innovate a new compaction machinery by comparing experimentally the effects of a two-axle, two wheel road roller and a tracked vehicle on the compaction of a decomposed granite sandy soil with a high spreading lift. By measuring the amount of sinkage of the terrain surface, the dry density distribution versus depth using a cone penetrometer, the normal earth pressure distribution versus depth using a stress state transducer (SST), the effects of the road roller and the tracked vehicle on the increment of the soil dry density were considered theoretically. It was observed that the tracked vehicle showed a larger amount of sinkage and a larger dry density distribution versus depth than the roller. The ratio of shear stress to normal stress was still large enough at the deep stratum, so that an optimal shear strain was developed on the whole range of the high lifted stratum and it increased the soil compaction density due to the dilatancy effect.

Optimum track belt tension and height of application forces of a bulldozer running on weak terrain

Abstract The productivity of a flexible tracked bulldozer running on weak terrain varies remarkably with the flexibility of the track belt and the height of application of effective drawbar pull or pushing force. The land locomotion resistance due to the sinkage of the rear sprocket of the bulldozer severely affects the tractive performance. Here, several relations between the track belt tension, the height of application forces, the driving force and the effective drawbar pull or pushing force, the amount of sinkages of the front idler and rear sprocket, the tractive power efficiency, and the slip ratio have been analysed for the given vehicle dimensions of a 150 kN weight bulldozer running on a silty loam terrain by means of a rigorous simulation programme. As a result, it is revealed that the effective drawbar pull and the tractive power efficiency increase remarkably with the increase of track tension. Also, to obtain the maximum efficiency, the optimum height of application of effective optimum drawbar pull and pushing force is about 0, −40 and −80 cm, and the eccentricity of the vehicle center of gravity is −0.05, 0.00 and 0.05, respectively.

Comparison between centrifugal and vertical vibro-compaction of high-lifted decomposed weathered granite sandy soil using a tracked vehicle

The aim of this research was to develop a new vibro-compaction machine by comparing experimentally and theoretically the effects of a tracked vehicle of total weight 9.8 kN mounted with a centrifugal or vertical oscillator on a high lifted decomposed weathered granite sandy soil. By measuring the amount of sinkage of the terrain surface, the dry density distribution with depth, the normal earth pressure distribution with depth, and the vertical and horizontal acceleration distribution with depth, the compacting effect of centrifugal and vertical vibro-tracked vehicles on the increment of dry density in a deep soil stratum were compared for a frequency of about 54 Hz. It was observed that the centrifugal vibro-tracked vehicle showed a 25% increase in the final amount of sinkage and a 11.3% increase in the maximum dry density of compacted soil compared to the vertical vibro-tracked vehicle. We believe that the centrifugal vibro-tracked vehicle can be shown from the analysis of the stress and acceleration propagation to be a better compaction machine at a high frequency of oscillation for a high lifted soil stratum when compared to conventional vertical vibro-tracked vehicles.

Experimental considerations for steady state edge excavation under a constant cutting depth for a mortar specimen using a disk cutter bit

This paper aims to investigate experimentally steady state excavation performance under a constant cutting depth, especially the specific cutting energy of a disk cutter bit in the free edge part of a mortar specimen. Here, the tangential, lateral and normal forces acting on a disk cutter bit having three tip angles and the amount of debris were measured for several cutting spaces and cutting depths. As a result, it was observed that the specific cutting energy, i.e. the ratio of the excavation power of the disk cutter bit to the amount of debris, showed a minimum value of the ratio of cutting space to cutting depth of five, at which ratio the most efficient excavation could be attained.

An optimal method for the design of a robotic tracked vehicle to operate over fresh concrete under steering motion

The objective of this paper is to find an optimal method for the design of tracked base travel systems for special purpose vehicles and robotic machines that may be required to steer over a light bonded terrain composed of fresh concrete. For the case of a vehicle traveling on a weak fresh concrete during construction, the paper presents detailed comparative studies of the steering performances of a small model tracked test vehicle with alternative amount of steering ratio for various concrete slump values. For these studies a detailed simulation analytical method has been developed. From this work it is proven, in comparison to experiment, that the simulation analytical method is useful for predicting various steering performances of a test tracked vehicle running upon soft fresh concrete of various consistencies.

Numerical analysis to predict turning characteristics of rigid suspension tracked vehicle

Numerical analysis was developed to calculate the steering properties of a rigid suspension tracked vehicle turning on soft terrain. The developed numerical analysis is based on a method to solve a set of non-linear equations. To verify the numerical analysis, an experiment on a model-tracked vehicle turning with a steering ratio of 1.6 on a loose sandy terrain was carried out. The comparison between measured and calculated values shows that the numerical analysis can predict sinkage, slip ratios and turning radius within an error amount of 15%.

Comparison of the traffic performance of a two-axle four wheel drive (4WD), rear wheel drive (RWD), and front wheel drive (FWD) vehicle on loose sandy sloped terrain

Abstract The traffic performances during driving and braking of a 5.88 kN weight wheeled vehicle with two-axle four wheel drive, rear wheel drive, and front wheel drive running up and down a loose sandy sloped terrain were compared by means of a simulation. For the given dimensions of the vehicle and the given terrain-wheel system constants, the relationship between the effective tractive and braking effort of the vehicle, the amount of sinkage of the front and rear wheels, the total amount of sinkage of the vehicle, and the slip ratio were calculated to estimate the optimum height of force of application and the optimum eccentricity of the center of gravity of the vehicle. It was observed that, during driving action, the maximum effective tractive effort of the four wheel drive vehicle (4WD) was larger than that of the rear wheel drive vehicle (RWD), which in turn was greater than that of the front wheel drive vehicle (FWD). During the braking action, the effective braking effort at skid -20% of the four wheel vehicle (4WB) was larger than that of the front wheel brake vehicle (FWB), in turn greater than that of the rear wheel brake vehicle (RWB), when the two-axle four wheel vehicle is moving up or down the loose sandy sloped terrain. The maximum terrain slope angle up which the two-axle wheeled vehicle is able to move during driving action was found to be about 0.067π rad for the 4WD vehicle, about 0.031π rad for the RWD vehicle, and about 0.017π rad for the FWD vehicle. The effective braking effort at skid-20% of 4WB, FWB and RWB was found to decrease with slope angle.

Tractive performance and compaction effect of a road roller running on a weak sandy soil

Abstract This study aims to investigate the tractive performance of a two-axle, two-wheel vehicle with rear-wheel drive or brake and the compaction of a decomposed granite soil. The effects of traction or braking, the change of sinkage, the slip ratio of the front and rear roller, and the number of passes of the road roller were studied. A number of tests were conducted and the experimental data were compared with the theoretical analysis results. It was observed that the amount of sinkage on the front and rear roller took the minimum value when the front roller was in the unpowered rolling state and the slip ratio of the rear roller was almost zero. When the absolute value of the slip ratio of rear roller increased, the amount of sinkage on the front and rear rollers, the absolute value of the driven or braking force of the rear roller and the absolute value of effective tractive or braking effort of the road roller increased. When the front roller was in the unpowered rolling state and the rear roller was in the braking state at −5% skid, the compaction density of the soil was at a maximum.