Abstract of Special Research Report (RR-99)
National Institute of Occupational Safety and Health, Japan
Survey on Improving Occupational Environments in the Rapidly Aging Society Part 2 --Conditions of Care Work in Xursing Homes and the Prospects for Elderly Care Workers--
RR-99-1 |
Hisao NAGATA and Sunyoung LEE |
: Physically handicapped, dementia and bedridden elderly people are estimated to account for 2.8 million in 2000 and then 5.2 million in 2025. In the rapidly aging society, it is necessary to facilitate the participation of elderly people in activities of our society by integrating them with other generations. In order to survey the conditions of care work in nursing homes for elderly people and to examine the possibilities of future elderly care work, mail questionnaires were sent to 2000 nursing homes in March, 1999. Managers of the care workers in 969 nursing homes completed questionnaires. The response rate was 48.5%. |
Ignition Characteristics of Zirconium Dust
RR-99-2 |
Toei MATSUDA and Masaaki YASHIMA |
: Zirconium metal dust is pyrophoric, highly combustible in its dry state, and has a great affinity for oxygen at elevated temperatures. The wide use of zirconium has been found in industry and the most important use of the material is in nuclear reactors for cladding fuel rods. It has been considered that fire and explosion risks of zircaloy (98 wt.% Zr) may be expected when cutting nuclear fuel rods in a reprocessing plant. |
Ignition and Explosion Characteristics of Tantalum Dust
RR-99-3 |
Toei MATSUDA and Mizuki YAMAGUMA |
: Elemental tantalum powder is mainly used for a material of a compact high performance capacitor called the tantalum electrolytic capacitor. As the miniaturization of electronic devices, such as cellular phones, has progressed remarkably, the demand for tantalum has rapidly increased in recent years. In the spring of 1997 a manufacturer of tantalum powder experienced a tantalum dust deflagration in its bag filter dust-collecting device which resulted in a fatal accident, in which one worker was killed and the other seriously wounded. |
Analysis and Experimental Study on Labor Accidents Related to Communication in Construction Work
RR-99-4 |
Yoshiyuki EGAWA, Takahiro NAKAMURA, Takuro SHOJI, Kiyoshi FUKAYA, Shigeo HANAYASU and Yoshimi SUZUKI |
: The causes of accidents in construction work were investigated based on the labor accident reports. As the result, about 10% of them were responsible for communication errors between workers. By the analysis on the accidents caused by communication errors, it was cleared that they were classified into six models having three factors of time, place and purpose. From the examination of these three factors in the cooperation work in which two workers were injured or nearly injured 80% of accidents were occupied in three models of six ones. One model of them was experimentally verified. This model was that purpose was different and both time and place were same. In the experiment, an assembly work of some parts was performed by two teams which consisted of two members, respectively. During the work, "error" was defined to occur when the team members entered one of the restricted areas at the same time. As the result of the experimental data analysis, four error patterns were observed. The number of errors of one pattern was more than that of the others. This pattern was that a member entered the restricted area before the other left. Communication was effective when two members' position was face to face each other. However, communication was ineffective when their position was back to face. A lot of errors occurred at this position of two members. |
The Effect of Heat Conduction on the Stress Measurement of the Sheet Specimen by Means of Thermoelastic Effect
RR-99-5 |
Takashi HONDA, Tetsuya SASAKI and Teruhito OHTSUKA |
: The local stresses and strains near notches or cracks are very important for fracture analyses of cyclically loaded structure components. Thus, a number of experimental methods such as a photo-elasticity method and numerical methods such as a finite element analysis have been developed to evaluate stresses and strains near notches or cracks. Among those methods, an infrared stress analysis technique is relatively a new stress analysis technique based on the measurement of infrared radiation emitted from the surface of a body. However, when this technique was used to evaluate the stress concentration factors for several kinds of notches in sheet specimens and to estimate stress intensity factors for compact tension and center cracked tension specimens, the determined values tended to be somewhat lower than those of other comparable numerical or theoretical values, and the error increased in proportion to those values. Thus, in this study, the effect of heat conduction in a body of sheet specimens under cyclic loading was investigated by a finite differential analysis to examine the source of the error, and the results were compared with experimental results. |
Influence of SO2 Gas on Insulation Failure of Wiring Board Caused by Electrochemical Migration
RR-99-6 |
Tatsuo MOTOYAMA and Kenji ICHIKAWA |
: With progress of science and technology, highly compacted electronic equipments with high density wiring having multi-functions and high quality have been developed. And according to the change of the using environment, electronic equipments have become easy to receive the adverse effect from environments involving dew condensation or pollutant. SOx in the environment is increasing due to automotive exhaust gases and acid rain, etc., while SOx that discharged from factories is decreasing. Increase of SOx is one of the main causes of insulation troubles of electronic equipments which may affect the control system in systematized facility. Consequently this insulation trouble causes the malfunction of the equipment, and may cause the danger to workers. The purpose of this study is to prevent insulation trouble caused by the electrochemical migration under the SO2 gas environment. Experiments are carried out to clarify 1) the effect of SO2 gas on the generation of migration, and 2) the generation mechanism of migration under the SO2 gas environment. |
Thermomechanical and Isothermal Fatigue Behaivor of Stainless Steel Type 316 Weldments
RR-99-7 |
Etsuji YOSHIHISA, Takashi HONDA and S.G.S.RAMAN |
: In any installation, welded joints are of major concern as they are frequently the sites of localized damage. Type 316 stainless steels and their welds are commonly used for structural components designed to operate at elevated temperatures. Under these operating conditions, component life may be limited by various damage mechanisms such as fatigue, creep and oxidation. When stainless steel welds are exposed to elevated temperature, the δ-ferrite, which is introduced to reduce hot cracking and microfissuring, gets transformed to carbides and various intermetallic phases like brittle σ phase. This transformation shows to decrease ductility when high stress are applied at elevated temperature. In isothermal fatigue, an extensive transformation of δ-ferrite to σ phase was reported to be responsible for reduction in fatigue life. It was observed with a number of materials that the most conservative fatigue life may not be under isothermal fatigue test condition but thermomechanical fatigue (TMF) where combined cycles of both temperature and mechanical strain are applied. Though there are several studies on the isothermal fatigue of 316 stainless steel weldments, to the authors' knowledge there is not any work reported on the TMF behavior. In this study the TMF (inphase) behavior of type 316 stainless steel weldments with temperature range 573-973K was studied using cylindrical specimens machined from base metal, weld metal and weld joint and a comparison was made with isothermal fatigue behavior at 973K. The progress of δ-ferrite transformation in weld metal was examined at different levels of life and the effects on the fatigue behavior were also discussed. In all joint specimens, fatigue failure occurred in the weld metal region. The lives of the weld metal and joint specimens were nearly equal and were always inferior to those of base metal specimens. In base metal specimens, the effect of strain rate on isothermal fatigue life was not very much significant. Though TMF lives were always a little shorter than the isothermal fatigue lives in base metal, the difference was small at the same mechanical strain range and similar strain rate. This may be due to that fracture mode in both loading was similar-a mixed type. On the other hand, a drastic reduction in life was noticed in weld metal and joint specimens under TMF in comparison with isothermal fatigue. This was attributed to the additional damage due to many independent subsurface cracks at σ phase boundaries and linkage of these cracks with the surface crack leading to rapid crack propagation, δ-ferrite in weld metal rapidly transformed to σ phase in both isothermal fatigue and TMF tests. Difference of the stress amplitudes between both tests was considered to have caused the difference of fatigue lives. |
Survey on Organizational Safety Policy and Activity in Construction Industry
RR-99-8 |
Takuro SHOJI, Yoshimi SUZUKI, Takahiro NAKAMURA, Yoshiyuki EGAWA, Kiyoshi FUKAYA, Shigeo HANAYASU, Mitsuhiro KOJIMA, Ayako HIROSE, Naoko HASEGAWA and Ken-ichi TAKANO |
: Recently much attention has been paid to the human factor approach considering worker's psychological state and organizational factor, as well as development of new technology or improvement of working environment, in order to decrease labor accident rate further. The purpose of this study is to clarify the effect of organizational safety policy and activities on safety attitude and behavior of workers, by making use of information through questionnaire on the safety activities and systems of the several companies and by analyzing the relationship between these safety activities and safety attitude of workers. Self-rating questionnaire was developed for this study and delivered to the staffs of the safety and health division of 49 companies, 300 personnel who were working at construction sites in general contractors and 300 foremen of subordinate companies. The response rate of questionnaire obtained was about 82 %. |
Spectroscopic Measurements of a Spark Ignition in Methane-Oxygen Mixture
RR-99-9 |
Atsushi OHSAWA and Keiichi ISHIKAWA |
: Spark ignition process was investigated by using spectroscopic techniques. The stoichimetric methane and oxygen mixture (33.3 kPa) was used. Optical emission spectroscopy was used to determine the species produced by discharge and combustion. Time variations of their optical emission spectra and timeresolved imaging of light emission were used for investigating the spark ignition. To measure the spatiotemporal evolution of OH radicals, 2 D-laser induced fluorescence (LIF) method was used. |
Hydrolytic Rate of Acid Anhydrides in Heterogeneous Reaction
RR-99-10 |
Yasuhiro FUJIMOTO |
: The Reaction Calorimeter RC 1 has been used to evaluate reaction hazards in laboratories under the batch process conditions-reaction temperature, type of reaction, etc. For the better result of evaluation, the conditions for evaluation are usually attempted to be the same as ones in actual chemical plants as well as possible. But all of the reaction conditions in actual plants may not be safe and available for laboratory evaluation. Some reactions may bring explosions or burnings easily, and may be too toxic to protect normally. In such cases, less hazardous model reactions are useful if their physical and chemical characteristics are roughly similar to the actual reactions. Results using the model need not to show the actual magnitude of reaction hazard, but need to show the trend of the hazard, that is, the evaluation result using one model reaction will be useful for a variety of reactions. |
Decomposition Explosion Properties of Ethylene Oxide under High Temperature and Pressure
RR-99-11 |
Takaaki MIZUTANI and Hidenori MATSUI |
: Ethylene oxide (EO) is one of the important materials in chemical industries. There are many literatures on decomposition explosion properties of EO. However the knowledge of decomposition explosion limits and ignition energies under high temperature and high pressure have not been well known. |
Failure Mechanism of Tie-Rod Anchored Sheet Pile Wall in Centrifuge Tests
RR-99-12 |
Yasuo TOYOSAWA, Noriyuki HORII, Satoshi TAMATE and H.G.B.ALLERSMA |
: Accidents due to collapse sometimes occur in excavation site. The need for decreasing these accidents is currently one of major concern. It is difficult to find out the causes of accident, because of the disturbance of site during the rescue and the collapse itself. To find out the scenario of an accident is very important to retrieve the information involved. |