Abstract of Special Research Report (RR-2000)
National Institute of Occupational Safety and Health, Japan
Modeling and Servo System of the Compliant Actuator Controlled by Field-Sensitive Fluid
RR-2000-1 |
Noboru SUGIMOTO and Tsuyoshi SAITO |
: In order to develop such a practical human-symbiotic robot that works in collaboration with human-workers for heavy work, physically helps the aged and the disabled person, and gives a patient rehabilitation training, the risk reduction concerning with the excessive force, which are applied to a part of human body by the contact of the robot with its users, is the most important problem. In accordance with the procedure of ISO/CD 12100, positively utilizing of inherently safe actuators capable of limiting their force output and moving speed individually should be considered firstly as a safety measure against this problem. The utilization of the safe actuators with such limiting function, however, has been hard to introduce practically due to their difficulty with motion control and their limited choices of types. |
Application of Finite Element Analysis to Residual Stress Measurement with Hole Drilling Method
RR-2000-2 |
Takashi HONDA |
: Residual stress is the stress which exists in components and structures before application of any service or external load. It is known that residual stresses significantly influence the structural stability of components and structures. Therefore an accurate quantitative estimation of residual stresses is very important and affordable techniques for measurement of residual stresses are needed. |
Measurement of Autoignition Temperatures of Flammable Liquids Using 1 Liter Round Vessel
RR-2000-3 |
Haruhiko ITAGAKI |
: Autoignition temperatures of flammable liquids have been measured by many researchers. Many data by the ASTM method have been reported especially. However, a fire sometimes happened due to the autoignition of the flammable liquid when the flammable liquid leaked out though it was dealt with under the lower temperature than this measured data by the ASTM method. Because, autoignition temperature is not the value specific to the material, but it varies with the measuring device and the method. Actually, the data reported by a literature is often different from the data reported by another literature. Therefore, the flammable liquid may sometimes ignite under lower temperature than the measured data by the ASTM method. |
Decomposition Flame Propagation Properties of Ozone/Oxygen Mixtures
RR-2000-4 |
Takaaki MIZUTANI and Hidenori MATSUI |
: Ozone is the strong oxidizing agent which has been used for water treatment, pulp bleaching and others. Recently, along with development of ozone generator, high concentration of ozone up to 20 vol.% in oxygen has been able to be obtained. It is well known that ozone is rapidly decomposed into oxygen with flame propagation by some ignition sources. But the decomposing explosion properties and the flame propagation behaviour of high concentration ozone in a closed vessel are not sufficiently clear. It is important to clarify the decomposing property for safe handling of ozone. |
Propagation Brush Discharge Occurring on Insulating Inner-Bag Used with Anti-Static FIBC and Its Countermeasures
RR-2000-5 |
Mizuki YAMAGUMA and Tsutomu KODAMA |
: An energetic form of discharge called the propagating brush discharge (PBD) was studied in view of a hazard assessment during the operation of an anti-static flexible intermediate bulk container (FIBC) with a highly insulating inner-bag. The conditions for producing PBDs were investigated using various kinds of materials of FIBD and insulating films made of polyethyleneterephthalate. The magnitude of PBD greatly depended on the structure and the resistivity of the FIBC materials. A material having fine conductive threads for dissipating static-charges, for example, was possible to produce extremely energetic PBDs due to an ionizing process on its threads. A less conductive, dissipating rubber type, however, produced rather weak discharges. In all conditions experimented, PBDs easily exceeded the critical level above which flammable gas or vapor can be ignited. This means that any level of PBD has to be avoided in the atmosphere where flammable gas/vapor exists. Two countermeasures to prevent the PBD were tried. Pinholes on an insulating sheet mitigated the charge accumulation, and when the interval of the pinholes was 4 cm or less, PBDs were no longer observed. Giving conductivity to the surface of an insulating film was also found to be effective for the prevention of the PBD if the level of static charge was relatively small. |
Fire Spread over Metal Dust Layer
RR-2000-6 |
Masaaki YASHIMA and Toei MATSUDA |
: Light metal powders such as aluminum (Al) and magnesium (Mg) have been known as combustible powder to cause dust explosions in industries. With development of material science and manufacturing process, other fine powders of metals (Ti, Ta, Zr, Fe, alloys, etc.) are produced mainly or secondarily, then they will fall on the ground or equipment. In this condition of the powder (dust) accumulation, dust explosions or fires may occur when an ignition source is given. It has a tendency for metal powder to form dust layer rather than dust cloud before ignition. The spreading of fire over a dust layer is the primary phenomenon in dust fires. |
Effect of Air-Bag Support for Prevention of Trench Collapse in Centrifuge Tests
RR-2000-7 |
Yasuo TOYOSAWA, Noriyuki HORII, Satoshi TAMATE, Tomohiro YAMADA and Hiroaki HAJYOUTA |
: Accidents due to collapse sometimes occur in trench excavation site. The need for decreasing these accidents is currently one of major concern. Air-bag support can expect laborsaving of trench excavation. However, there are few research results about the air-bag for earth support, and its prevention mechanism for trench collapse is not fully understood. |