Hideyuki Otaki

An index of the tensile strength of brittle particles

The elementary comminution event can be regarded as a single particle subject to a stress field where the breakage of particle occurs through contact with other particles or with the grinding media, or with the solid walls of the mill. Although the particle is loaded predominantly in compression or impact, substantial tensile stresses are induced within the particle. These tensile stresses are responsible for splitting failure of the particle. In this paper, the state of stress in a spherical particle due to two diametrically opposed forces is analyzed theoretically. A simple equation for the state of stress at the center of the particle is obtained. An analysis of the distribution of stresses along the z-axis due to distributed pressures and concentrated forces, and on diametrically horizontal plane due to concentrated forces, shows that it is reasonable to propose the tensile stress at the center of the particle at the point of failure as an index of the tensile strength of the particle. As the state of stress along the z-axis in an irregular specimen tends to be similar to that in a spherical particle compressed diametrically with the same force, this index of the tensile strength has some validity for irregular particles as well. This index of strength reflects the influences of Poissons ratio, and of the radius of region where the distributed pressures act.

Motion analysis of a tumbling ball mill based on non-linear optimization

Non-linear optimization, a technique of numerical analysis, is applied to motion analysis of ball media in a tumbling ball mill. The basic principles of optimization are explained. The motion equations of ball media are established. The point of maximum energy is computed, and this maximum energy is 2.34% greater than the energy at the point of maximum falling height. The distribution graph of media collision energy shows that this is a multi-limit problem. We propose to define the total potential energy of charge as the accumulation of energy of all dropping points. Optimization of the parameters related to the total potential energy demonstrates that the point of maximum total potential energy does not depend on the mill size. The operation parameters are optimized with the total collision energy of the ball media per unit time as the objective function. The total collision energy of the ball media per unit time under the optimal operation parameters is increased significantly.

Implementation of collinear collisions of particles for comminution

Abstract In order to achieve collinear collision of particles and to obtain a high impact velocity by a mechanical method, a prototype dual cone impact mill was designed and built. This dual cone impact mill mainly consists of two cone disks with the same geometrical dimensions, and the same rotational speeds rotating in opposite directions. There are no grinding media in the dual cone impact mill. The mechanism of particle motion on the inner surface of a cone disk is analyzed, and we obtain an equation of particle velocity that takes friction into account. It appears that theoretically, the normal impact velocity between two colliding particles can reach up to 6 1 2 times the circumferential velocity of the cone disk. The dependence of the comminution effect on two parameters, cone disk speed and air flow rate, was experimentally investigated. The results obtained from grinding quartz and cement clinker indicate that this prototype mill can be used for grinding materials of Mohs hardness up to of 6–7, while achieving mean particle sizes of 10 μm.

Driving of an Actuator Using Muscular Voltage.

It is difficult to drive an actuator using muscular voltage measured by the conventional method, which is based on medical treatment and is not intended to elucidate the movement of an arm. In this paper, we propose a suitable measuring method to elucidate the movement by changing the position of an electrode. We also propose two evaluation values calculated from measured voltage to represent the movement of an arm. Using a fuzzy method based on these values, we can represent the movement of an arm fairly well. We applied this fuzzy method to driving an arm-type actuator, which can reproduce the movement of an arm.

Building of Window based on Object-Model.

With the increasing application of large-scale and complicated systems in practical use, there is a need to develop systems on engineering work stations (EWS), in consideration of memory and speed of processing. However, it is very difficult to develop an application program with a graphical user interface (GUI) on an EWS. The authors have built a model of GUI based on the concept of object-model, and developed a function to create a source code of GUI by using this model. In this paper, knowledge representation of the model, the method for creating a source code of GUI by means of the model, and the method for controlling communication between the application and GUI are described.

Managing System of Knowledge Base in Machining.

It is possible to incorporate a system which manages a knowledge base into an expert system. Because, by using this system, we can rebuild knowledge bases which have no logical contradictions with knowledge of experts and phenomena which we experience daily. However, it is difficult to build beyond systems in the machining field due to the existence of many kinds of knowledge, if we want to achieve rebuilding of the knowledge bases using current representation language. Thus, we developed a truth maintenance system for knowledge bases by using a new predicate-logic representation language. This paper describes how to manage knowledge bases and how to treat the functions in a truth maintenance system using this system when contradictions occur in the practical machining problem.

Measurement of the thermal distribution of a machine device using a charge-coupled device camera.

For the purpose of estimating the thermal condition of machine devices, we investigate a new method of measuring temperature using an encapsulated liquid crystal (ECL) film and a charge-coupled device (CCD) camera. When an ECL film is placed in direct contact with subjects, it exhibits some colors accompanying temperature change. But even if these colors are obtained, it is difficult to judge values for temperature or extension of isothermal line with the naked eye because of optical noise. In solving the above problems, we investigate a new photogaraphical recording method of intensifying colors using a CCD camera and graphical processing with a personal computer. The availability of this method is confirmed by analyzing heat conduction in the plate.

Hybrid type transfer mechanism. (2nd Report).

We described in the previous report a new transfer mechanism which has two motors; one is the main motor for conveying materials and the other is an auxiliary motor for controlling tensile force and chain slack. But, when we use generally conveying system it can be foreseen that vibration often occures by the outer load and the performances decrease. So to decrease the vibration, we investigate the controlling method to hold constant the tensile force of chain and improve the efficiency. In this report, we use modern control theory for the hybrid type transfer mechanism and discuss the performance of controlling system.

Hybrid type transfer mechanism.

are driven by a motor, and the driven sprocket is controlled by a brake to give a moderate tensile force. However, it is difficult to adequately control the tensile force, because the brake has a tendency to influence the torque and revolution of the driving motor. We then developed a new driving system which has two motors ; one is the main motor for conveying materials and the other is an auxiliary motor which is used to control tensile force and chain slack without influencing torque and revolution of the main motor. In this report, we describe the performance of this system.

Lubrication properties of nylon mixed with lubricants.

Plastics are used widely as sliding parts. In order to investigate the effect of the varied lubricants mixed in the nylon rollers, experimental equipment was designed and manufactured. In the experiment on the friction of the nylon roller, a nylon roller was rotated contacting with a steel roller in the same direction. From the results of the experiments, it was clarified that the lubrication properties, the friction characteristic and the wear resistance differ with each lubricant mixed in the roller, and the limit for use as the sliding parts could be obtained.