Key Engineering Materials Vols. 326-328

Abstract: In this study, the creep rupture tests of STS304 stainless steels were investigated at three different elevated temperatures of 600
, 650
and 700
under the constant creep stresses. Creep rupture characteristics such as creep stress, creep rupture time, steady state creep rate and so on were evaluated. The behaviors of creep rate curve and initial strain are compared at three different elevated temperatures. The stress exponent (n) at 600
, 650
and 700
based on steady state creep rate showed 22.5, 20.6 and 11.4 respectively. By increasing the temperature, the stress exponent is decreased. At the temperature of 700
, the lowest stress exponents are shown and this behavior is also observed in the case of stress exponent based on rupture time. The creep life prediction by LMP method is presented and the equation of this result is as follows: T(logtr+20)=-0.005152-14.56+24126.

Abstract: This paper presents the results of the Minimum Commitment Method (MCM) applied to predict the creep rupture life of type 316LN SS. Constant A, and the function of P(T) and G(σ) being used in the MCM equation were determined. To determine a proper value of the constant A, a focal point method and a trial and error one were adopted, respectively. It was found to be A=-0.02~-0.05 for type 316LN SS. Each prediction curve with the A values were presented up to 106 hours and compared to the experimental data at each temperature. Using the short-term creep rupture data for under 2,000 hours, a long-time rupture reaching up to 106 hours was predicted by the MCM.

Abstract: This study was conducted to evaluate the applicability of photocatalytic metal membrane system for the treatment of humic acid and heavy metals in aqueous solution. The catalysts, TiO2 powder P25 Degussa and metal membrane with 0.5 μm nominal pore size were used for experiments. Removal efficiency of humic acid and heavy metals increased with the increase of TiO2 dosage, however decreased over 0.3 g/L of TiO2 dosage. The addition of H2O2 as an oxidation reagent had a positive effect for the removal rate of humic acid and heavy metals. Metal membrane with stainless steel seemed to be quite stable to UV light with oxidation reagent in long-term operational periods over 6 months. Moreover, TiO2 particles can be effectively separated from the treated water by membrane rejection and the permeation flux was also enhanced by the combination of photocatalytic reaction.

Abstract: In this study, numerical analysis to develop optimal dust collector having an axial inlet cyclone was performed for the 3 dimensional flow field with a control volume including gases and particles. We applied FVM(Finite Volume Method) for calculating the flow distribution and the pressure drop into the control volume using a commercial code FLUENT. The k-ε turbulence model was used to obtain the analytical results and the major parameters were the geometrical dimension of helical guide vanes, the inner diameter and length of cylindrical part. Particle trajectory calculations were performed for the particle sizes of 5~75㎛ corresponding to KS A 0090. Finally we found out and recommended one dust collector that showed appreciable performance improvement. The experiment for confirming the numerical results was conducted by KS R 1041. From the numerical analysis and the experimental test, it was seen that the specified collector recommended in this study had dust collecting rate of about 99.91% and the pressure drop of 23.9mbar, and was more effective than old one that had been conventionally used in real work field.

Abstract: For the designed and manufactured compound CVT that can improve the characteristics of efficiencies and power ratios, realize backward and forward motion including geared neutral without an auxiliary device, various experimental studies have been performed to verify their design validation and theoretical performance analysis. Various comparisons between the theoretical and the experimental results have verified that they can improve the efficiency and speed ratio when compared with the case power circulation mode mechanism and power split mechanism mode are used individually.

Abstract: In the recent years, the studies on the mechanical behaviors of various materials subjected to biaxial loading have been worked since they are more complicated and intrinsically different from those under the simple uniaxial condition. The cruciform specimen without any slots has been commonly used for the goal so far. We prepare improved biaxial specimen with slots and make sure its validity by means of finite element analysis and photoelastic experiment. Even though the equal load biaxiality was applied to the specimens, as the results, we found that the stress biaxiality ratios in central region of specimen differ according to the position from the center of them, the specimen with slots in the arms is more effective to make state stress uniform than the specimen without slot.

Abstract: The reflective photoelastic experiment can be used more effectively than the transparent of photoelastic experimental method in industrial fields. Therefore the reflective photoelastic experimental hybrid method for the fracture mechanics of isotropic material was developed in this research. Using the reflective photoelastic experimental hybrid method we can obtain stress intensity factors and separate stress components from only the isochromatic fringe patterns. The errors between the experimental values and theoretical values for stress intensity factors are less than 10%. It was verified that the reflective photoelastic experimental hybrid method is very useful for the static plane fracture problems, for the stress intensity factors and for the stress components at the vicinity of the crack-tip in isotropic materials.

Abstract: Small snubber of hydrogen compressor do duty as buffer pulsation of compressed hydrogen. Snubber is a kind of internal pressure vessel and design optimum of snubber very important problem. In this paper, we will estimation results of elastic finite element structural analysis using the commercial program such as ANSYS for comparison to the limits in ASME Code Sec. Ⅷ that are related to membrane and bending stresses. In case of membrane stress in a circular cylindrical due to internal pressure or to distributed live loads. Bending stress in the central portion of flat head due to pressure. In addition, We will propose optimum design value of snubber for hydrogen compressor.

Abstract: In this paper, we present a newly designed flexible optical fiber force sensors which use fiber Bragg gratings and diaphragm and bridge type transducer, to detect a distributed normal force and which is the first step toward realizing a tactile sensor using optical fiber sensors (FBG). The transducer is designed such that it is not affected by chirping and light loss to enhance the performance of the sensors. We also present the design and fabrication process and experimental verification of the prototype sensors.

Abstract: This article presents a new approach to measure the fluid velocity using the flow-induced vibration of a microcantilever. The gas flow sensor was fabricated using the microfabrication technology and mounted on a printed circuit board for experimental evaluation. For signal processing, a Wheastone bridge circuit was prepared. The experimental measurement of the fluid velocity was performed in the wind tunnel. The flow-induced vibration of the microcantilever was firstly visualized. Based on the power spectrum analysis, the vibrating frequency was constant at 1.173 kHz, independently of the inlet velocity. It is completely different from the conventional flow-induced vibration proportional to the inlet velocity. The peak-to-peak voltage outputs corresponding to the air velocities of 3, 4, 5 and 6 m/s were measured.