Parameter study of chain trenching machines of Underwater Construction Robots via analytical model
Analytical model by considering the kinematics, dynamics, and energetics of the trenching machine is adopted and proposed to design an underwater chain trenching machine at UCRC-KIOST. In this paper, parameter study and sensitivity analysis is conducted to show how the variations of operational and geometric parameters, as well as cutting tools and material condition affect the forces, moment, weight, and power components. The study sheds some important insights about how the trenching machine behaves and thus the information from this study can be used to design a trenching machine for the required working condition. The parameter study shows that minimum weight requirement for self-propelled vehicle is increased during operation at steep bar angle, and to keep the traction of the vehicle getting worst, it is recommended to cut the trench at low bar angle and make sure the cutting tool is still sharp. The results also show that traverse speed, cutting depth, uniaxial compressive strength, and trench width are the most sensitive parameters affecting the power and angular speed. On the other hand, weight of the vehicle, nose radius, bar length, and pivot point location does not affect the total chain power at all.
Study on the Design of an Underwater Chain Trencher via a Genetic Algorithm
In this study, a genetic algorithm (GA) with an analytic model is adopted to conduct multi-objective optimization for design of an underwater chain trencher. The optimization problem is defined as minimizing a product of the chain power and weight subject to the uniaxial compressive strength, coefficient of traction, bar length (L), nose radius (R) and ratio of the chipping depth over the spacing (l/S), of which the ranges are determined based on the specifications of commercial trenchers satisfying established performance requirements and previous parametric studies. It is found that an optimal design of the GA was obtained with L and l/S close to their low bound and R far from its low bound while that of a simple parametric analysis was acquired with the three parameters close to their low bounds. Moreover, in the most severe soft rock and traction conditions, the power and weight in the optimal design obtained by the GA are turn to be within the feasible ranges of targeted commercial trenchers.
Effect of cutter pick rake angle on the failure pattern of high-strength rocks
Abstract One aspect of cutter pick application, namely, cutting of high-strength rocks at low and negative rake angles is examined, and the validity of Evans' cutting theory which is based on the assumption of tensile failure is discussed. It is shown theoretically that at low and negative rake angles, rock failure is most likely to take place as a result of compressive stresses created by the geometry of the cutting pick, rather than tensile stresses. The findings of some available laboratory experiments are also shown to be in agreement with the theoretical suggestions made in this work.