• Journal of the Korean Institute of Gas
• /
• v.14 no.6
• /
• pp.51-56
• /
• 2010

Records of accidents for buried pipeline across the river were gathered and causes were analysed. The results are intended to be utilized as basic data for determining a reasonable criteria for the depth of buried city gas pipeline crossing the river. Accident of river-crossing buried pipeline was mainly caused by flood. Sometimes corrosion was detected at the failed location of the pipe. In order to determine reasonable and efficient depth of burial of the pipeline, hydraulic evaluation of the river and structural analysis of the pipeline are necessary. Published data for the buried natural gas pipeline incidents were also investigated and summarized. Main causes of buried natural gas pipeline incidents were external interference and corrosion. However, the two main causes of incidents showed significant difference in the proportion of the entire incident, depending on burial environment.

• Journal of Welding and Joining
• /
• v.7 no.3
• /
• pp.19-27
• /
• 1989

Both the SS41 steel and the M.E.F(martensite encapsulated islands of frrite) dual phase steel made of SS41 steel by heat treatment were welded by friction welding, and then manufactured machinemade Vnotch standard Charpy impact specimens and precracked with a fatigue system at BM(base metal), HAZ(heat affected zone) and WZ(weld interface Zone). The impact test of them was performed with an instrumented impact test machine at a number of temperatures in constant loading velocity and the dynamic fracture characteristics were studied on bases of the absorbed energy, dynamic fracture toughness and fractography from the test. The results obtained are as follows; At the room temperature, the absorbed energy is HAZ.geq.WZ.geq.BM in case of the M.E.F. dual phase steel: BM.geq.HAZ.geq.WZ in case of the SS41 steel, HAZ.geq.BM.geq.WZ at the low temperature. The absorbed energy is decreased markedly with the temperature lowering; it is highly dependent on the temperature. The dynamic fracture toughness of the M.E.F. dual phase steel is HAZ.geq.WZ.geq.BM at the room temperature; BM.geq.WZ.geq.HAZ below-60.deg. C. Therefore the reliability of friction welding is uncertain at the low temperature(below-60.deg. C). The dynamic fracture toughness of the SS41 steel; HZA.geq.WZ.geq.BM at overall temperature region. The flaw formed by rotational upsetting pressure was shown y SEM; in this region. The absorbed energy per unit area and dynamic fracture toughness were low relative to other region.

• Tunnel and Underground Space
• /
• v.32 no.6
• /
• pp.558-567
• /
• 2022

The evolution of temperature and thermal stress in a granite specimen is studied via heating experiment in the context of a high-level radioactive waste repository. A heating condition based on the decay-induced heat is applied to a cubic granite specimen to measure the temperature and stress distributions and their evolution over time. The temperature increases quickly due to heat conduction along the heated surfaces, but a significant amount of thermal energy is also lost through other surfaces due to air convection and conduction into the loading machine. A three-dimensional finite element-based model is used to numerically reproduce the experiment, and the thermo-mechanical coupling behavior and modeling conditions are validated with the comparison to the experimental results. The most crucial factors influencing the heating experiment are analyzed and summarized in this paper for future works.

• The Journal of Korean Academy of Prosthodontics
• /
• v.48 no.2
• /
• pp.111-121
• /
• 2010

Purpose: This 3D-FEA study was performed to investigate the influence of marginal bone loss pattern around the implant to the stress distribution. Material and methods: From the right second premolar to the right second molar of the mandible was modeled according to the CT data of a dentate patient. Teeth were removed and an implant ($\Phi\;4.0{\times}10.0mm$) was placed in the first molar area. Twelve bone models were created; Studied bone loss conditions were horizontal bone loss and vertical bone loss, assumed bone loss patterns during biologic width formation, and pathologic vertical bone loss with or without cortification. Axial, buccolingual, and oblique force was applied independently to the center of the implant crown. The Maximum von Mises stress value and stress contour was observed and von Mises stresses at the measuring points were recorded. Results: The stress distribution patterns were similar in the non-resorption and horizontal resorption models, but differed from those in the vertical resorption models. Models assuming biologic width formation showed altered stress distribution, and weak bone to implant at the implant neck area seams accelerates stress generation. In case of vertical bone resorption, contact of cortical bone to the implant may positively affect the stress distribution.

• The Journal of Korean Academy of Prosthodontics
• /
• v.45 no.2
• /
• pp.240-249
• /
• 2007

Statement of problem: A phenomenon of screw-loosening in implant abutment is frequently occurred in a single and multiple implant restoration. Purpose: This study was performed to evaluate an effect of abutment material on screw-loosening before and after a cyclic loading. In a single-tooth implant, different materials of abutment, Type III Gold alloy and Zirconium composite$(ZrO_2/Al_2O_3)$ were used. Material and method: The Gold alloy(Type III) and Zirconium composite$(ZrO_2/Al_2O_3)$ were used to make a superstructure of implant, the one of types of UCLA, Each group was constituted of 5 sample with a 30-degree offset angulated loading platform. The external hexagonal fixture was rigidly hel d in a special holding zig to ensure solid fixation without rotation during the tightening and a cyclic loading. A Titanium-alloy screw was used to connect and controlled to be tighten in 20Ncm torque by a digital torque gauge. A 20 times of consecutive closing/opening cycle were performed to evaluate the immediate torque loss. In 5 sample of each material group, an initial opening torque was recorded during 3 closing/opening cycle, then 2Hz, 200N, 1,000,000 cyclic loadings were performed, then a opening torque was evaluated. Result & Conclusion: 1. In this limited study, titanium alloy screw tightened in 20Ncm, a cold-welding phenomen on was not observed during the 20 times of closing/opening cycle(p=0.11, p=0.18). 2. In titanium alloy abutment screw, repeated opening and closing of the screw caused to progressive decrease of opening torque(p=0.014). 3. The difference in preload of screw between gold alloy abutment and ceramic$(ZrO_2/Al_2O_3)$ abutment was not significant(p=0.78). 4. The difference in torque loss of screw between gold alloy abutment and ceramic$(ZrO_2/Al_2O_3)$ abutment was not significant after 2Hz,200N, 1,000,000 cyclic loading(p=0.92). 5. In titanium alloy abutment screw tightened by 20Ncm, the screw loosening was not significant on each group after 2Hz, 200Ncm, 1,000,000 cyclic loading(p=0.59).

• Archives of design research
• /
• v.15 no.4
• /
• pp.263-274
• /
• 2002

This study aims to analyze the image of long-span structures. For the intention, it analyzes the relationship between images and physical attributions of elements such as materials, stresses, configurations, compositions and shapes of structures. The image of structures can represent following 5 factors; friendly-unfriendly, strong-weak, dynamic-calm, superior-inferior, and regular-irregular. The friendly-unfriendly in the image of structure mostly determines on a finished material and partly with a structural shape. The strong-weak in the image of structure determines on configuration of the structural members. The dynamic-calm in the image of structure determines on the structural shape. Hence the structure has dynamic forms when it seems to be open and sharp, namely when it receives the flow of forces in the structural shape, and it has a (-) gauss curved rate or an diagonal appearance. The superior-inferior in the image of structure determines on composition of structural elements. The structure seems to be superior is contributed not simply to support load but positively to create design as a tectonic element. From now on, this study can provide the useful information on the long-span structure design through the more appropriate analysis of the image.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.5 no.3
• /
• pp.65-71
• /
• 2001

The nuclear power plant(NPP) should be shut down for inspection and tests prior to a return to power if the earthquake exceeds the operating basis earthquake(OBE). The OBE at the plant is considered to have been exceeded if the computed cumulative absolute velocity(CAV) from the earthquake record is greater than 0.16g-sec. However, the CAV criterion should be determined considering the seismic and structural characteristics of the plant. An experimental study using shaking table is conducted in this study to evaluate intensity of CAV criterion. Appropriate level of CAV is evaluated based on the test results using the developed seismic damage indicator(SDI) model. The model consists of stacked acrylic cylinders and is developed to behave consistently for each directional seismic load. The result of the experimental study in dicates that the CAV criterion of 0.16g-sec is conservative enough to be applied to Korean NPPs since the CAV value of the seismic input motion of the Korean standard NPPs ranges from 0.3 to 0.5 g-sec. The developed SDI is expected to be useful not only in easily determining OBE exceedance but also in evaluating earthquake damage quantitatively to provide guidelines for better post-shutdown inspection and test.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 1996.10a
• /
• pp.351-356
• /
• 1996

\ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner \ulcorner\ulcorner\ulcorner \ulcorner\ulcorner \ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner \ulcorner\ulcorner \ulcorner\ulcorner \ulcorner\ulcorner \ulcorner\ulcorner\ulcorner \ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner \ulcorner\ulcorner \ulcorner\ulcorner. \ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner \ulcorner\ulcorner \ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner \ulcorner\ulcorner. \ulcorner\ulcorner \ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner \ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner \ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner. \ulcorner\ulcorner \ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner \ulcorner \ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner \ulcorner\ulcorner \ulcorner\ulcorner \ulcorner \ulcorner\ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner. \ulcorner\ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner \ulcorner\ulcorner\ulcorner \ulcorner\ulcorner \ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner, \ulcorner\ulcorner \ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner\ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner BBA(Building Block Approach)\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner \ulcorner\ulcorner \ulcorner\ulcorner. \ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner. \ulcorner \ulcorner\ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner\ulcorner\ulcorner\ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner \ulcorner\ulcorner \ulcorner \ulcorner \ulcorner\ulcorner \ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner.

• Journal of Energy Engineering
• /
• v.28 no.3
• /
• pp.1-9
• /
• 2019

A major stress determining the remaining life of the tube in feedwater heater of fossil fuel power plant is hoop stress by the internal pressure. However, thermal stress due to temperature difference across the wall thickness also contributed to reduce the remaining life of the tube. Therefore, thermal loading must be considered even though the contribution of internal pressure loading to the stresses of the tube was known to be much higher than that of the thermal loading. In this study, thermal stress of the tubes in the de-superheating zone was estimated, which was generated due to the temperature difference across the tube thickness. Analytic equations were shown for determining the hoop stress and the radial stress of the tube with uniform thinning and for the temperature across the tube thickness. Accuracy and effectiveness of the analytic equations for the stresses were verified by comparing the results obtained by the analytic equations with those obtained from finite element analysis. Using finite element analysis, the stresses for eccentric thinning were also determined. The effect of heat transfer coefficient on thermal stress was investigated using series of finite element analyses with various values of heat transfer coefficient for both inner and outer surface of the tube. It was shown that the effect of heat transfer coefficient at outer surface was larger than that of heat transfer coefficient at inner surface on the thermal stress of the tube. Also, the hoop stress was larger than the radial stress for both cases of uniformly and eccentrically thinned tubes when the thermal loading was only considered without internal pressure loading.

• Journal of Korea Society of Industrial Information Systems
• /
• v.25 no.6
• /
• pp.47-54
• /
• 2020

The acupressure is a treatment that applies pressure to certain parts of the body and has been mainly used for pain relief in the field of oriental medicine. However, the treatment effect is often different depending on the practitioner's ability, experience, and physical strength, so standardized acupressure is needed. In this regard, the equipment is being released, but this is mainly a rolling massage method, which reduces energy concentration and poses a risk of injury. Therefore, in this study, a device that provides vertical acupressure based on variable bogie (wheel truck) was implemented. As a result of experimenting with load and body pressure distribution and desirability to validate the device's bearing pressure, the acupressure rod held up to 150kg, the body pressure ratio was measured lower than the body pressure ratio of the comparison item in section 0%