In order to prevent an accident due to leakage of a contained fluid from the joints, it is important to establish a method for the estimation of stress relaxation behavior. It is a need to evaluate the creep strain behavior of gasket by the viscoelasticity constitutive equation in order to estimate the stress relaxation behavior. Recently, the creep behavior has been evaluated by a viscoelasticity model of single axis. However, the viscoelasticity model of single axis can not evaluate the stress in direction other than the thickness direction. In the present study, the 3-D viscoelasticity theory is applied to the creep property behavior of gasket, and it is obtained the 3-D viscoelasticity constitutive equation that is capable of including the stress in directions other than the thickness direction. The obtained constitutive equation is applied to finite element (FE) model of the test equipment based on the JIS R3453 test method, the stress relaxation behavior of analysis result agrees well with test result according to JIS R3453 test method. It is shown that the stress relaxation of the bolted flange joint under actual service conditions can be estimated by FE analysis, using the creep strain behavior of gasket by the 3-D viscoelasticity theory.

View full abstract

Berms are used to control erosion and scouring by reducing the rate of surface runoff. In addition, the berms are expected to improve the stability of a slope. Regarding the standard for the gradient of excavation surfaces, which is covered by the Ordinance on Industrial Safety and Health, Japan (Articles 356 and 357), each excavation surface divided by said horizontal step, i.e., berm, can be regarded as an individual surface if the width of the step is 2m or more. This paper introduces regulations and design standards for the berm width and slope height for each institution. Then the analyses of the effect of berm width on the stability of slope and its failure mode are carried out using the Rigid-Plastic Finite Element Method.

View full abstract

Dust explosions caused by electrostatic discharges sometimes occur during the pneumatic conveyance of powders and dust collection. This paper reports a method for detecting a precursory discharge between a charged metal body and a grounded body that occurs inside a duct or a silo. For the purpose of detection, currents flowing in an earth wire were measured when electrostatic discharges occurred inside the corresponding metal duct. As a result of the experiment, it was found that it may be possible to discriminate between a corona and a spark discharge by evaluating the rise time or frequency of the currents flowing in the earth wire when electrostatic discharges occur.

View full abstract