• Nuclear Engineering and Technology
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• v.48 no.6
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• pp.1376-1386
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• 2016

This study investigated the loading rate effect on the fracture resistance under cyclic loading conditions to understand clearly the fracture behavior of piping materials under seismic conditions. J-R fracture toughness tests were conducted under monotonic and cyclic loading conditions at various displacement rates at room temperature and the operating temperature of nuclear power plants (i.e., $316^{\circ}C$). SA508 Gr.1a low-alloy steel and SA312 TP316 stainless steel piping materials were used for the tests. The fracture resistance under a reversible cyclic load was considerably lower than that under monotonic load regardless of test temperature, material, and loading rate. Under both cyclic and monotonic loading conditions, the fracture behavior of SA312 TP316 stainless steel was independent of the loading rate at both room temperature and $316^{\circ}C$. For SA508 Gr.1a lowalloy steel, the loading rate effect on the fracture behavior was appreciable at $316^{\circ}C$ under cyclic and monotonic loading conditions. However, the loading rate effect diminished when the cyclic load ratio of the load (R) was -1. Thus, it was recognized that the fracture behavior of piping materials, including seismic loading characteristics, can be evaluated when tested under a cyclic load of R = -1 at a quasistatic loading rate.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.642-647
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• 2007

Determination of loading conditions for tube hydroforming(THF) process that implies an amount of the increment in axial feeding and internal pressure for each step is one of the most important constituents at the process design level. On account of the fact that those design factors mentioned above are imposed simultaneously during the process, suitable loading conditions are required to obtain robust products without any failure such as buckling, necking, bursting and so on. In which, especially, bursting is well known as the most frequently occurred failure in general THF process. In this study, therefore, determination of the loading condition based on the adaptive method was carried out to obtain safe loading paths. In addition, forming limit curves are applied to evaluate the derived loading conditions by using the simulation results. Consequently, it is found that described method in this study for THF process design is useful and has a feasibility.

• Journal of the Korean Society of Marine Environment & Safety
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• v.4 no.2
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• pp.43-52
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• 1998

Generally, the navigational safety of a ship under various loading conditions is evaluated by a loading manual. However, the loading manual handles only statical factors such as weight and buoyancy of ship without including any wave conditions. Practically ship's safety is much concerned with the occurrences on the rough sea as propeller racing, rolling, deck wetness, vertical acceleration, lateral acceleration, slamming and so on. The purpose of this paper is to present a synthetic and practical evaluation method of navigational safety using the integrated seakeeping performance index(ISPI) under loading conditions of ship in seaways. The method is calculated by means of the ISPI by measuring only vertical acceleration. Judgement of dangerousness is carried out for four lading conditions : homogeneous full loaded, half loaded, heavy ballast loaded, and normal ballast loaded conditions. In developing the practical evaluation system of navigational safety, it is useful to solve the difficulties in measuring factors by sensors. And by applying the evaluation diagrames, navigators are able to avoid dangerousness by keeping away of the danger encountering angle of wave direction which the diagram shows.

• Journal of Navigation and Port Research
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• v.46 no.2
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• pp.73-81
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• 2022

Currently, shipping by sea is becoming common because of the low price and the safety of goods. The ship is designed as a larger vessel to meet the need of this development. In the design stage, the investigation of hydrodynamic forces acting on the ship hull is very important in predicting the ship's maneuverability. Given that the ship docks at various ports for loading or discharging goods, the ship usually operates in various loading conditions, depending on the site condition and other various factors. Hence, it is necessary to investigate the effect of the loading condition on the hydrodynamic forces acting on the ship, to most accurately determine the maneuverability of the ship. In this study, an experiment of Korea Autonomous Surface Ship (KASS) was conducted at the towing tank of Changwon National University to measure the hydrodynamic forces acting on the KASS. The loading condition considered in this experiment is determined based on the draft, which was decreased by 5% for each loading condition. The smallest draft is 85% of the design draft. The static test as Oblique Towing Test (OTT), Circular Motion Test (CMT), Circular Motion Test with Drift (CMTD) is performed in the various loading conditions. First, the hydrodynamic forces in the Oblique Towing test (OTT) are compared with the result of other institutes. Second, the hydrodynamic forces in various drift angle, yaw rate and loading conditions are measured. Finally, the influence of the loading conditions on the hydrodynamic coefficient is discussed.

• Journal of the Korea Furniture Society
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• v.18 no.4
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• pp.287-295
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• 2007

To obtain a design data for box beams used as headers in light-frame timber construction, $2{\times}6\;(38{\times}140mm),\;2{\times}8\;(38{\times}184mm),\;2{\times}10\;(38{\times}235mm)\;and\;2{\times}12\;(38{\times}286mm)$ members were built as box beam specimens for bending tests. The allowable bending stresses for box beams were obtained through bending tests of these specimens, and span tables were calculated for various loading conditions based on the allowable bending stresses obtained. The allowable bending stresses were determined as the bending stresses at 10mm deflection of specimens from the results of bending tests of box beam specimens. Span tables for box beams were obtained assuming five loading conditions for headers used in exterior walls and two loading conditions for headers used in interior walls. Among these 7 loading conditions, 5 loading conditions applied to headers in exterior walls included the dead loads, the live loads and the snow loads and 2 loading conditions applied to headers in interior walls included the dead loads and the live loads.

• Ocean Systems Engineering
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• v.12 no.1
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• pp.23-38
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• 2022

In this paper, a pitch-type wave energy converter (WEC-rotor) is investigated in irregular wave conditions for the real sea testing at the west coast of Jeju Island, South Korea. The present research builds on and extends our previous work on regular waves to irregular waves. The hydrodynamic characteristics of the WEC-rotor are assessed by establishing a quasi-two-dimensional numerical wave tank using computational fluid dynamics by solving the Reynolds-averaged Navier-Stokes equation. The numerical solution is validated with physical experiments, and the comparison shows good agreement. Furthermore, the hydrodynamic performance of the WEC-rotor is explored by investigating the effect of the power take-off (PTO) loading torque by one-way and two-way systems, the wave height, the wave period, operational and high sea wave conditions. Irrespective of the sea wave conditions, the absorbed power is quadratic in nature with the one-way and two-way PTO loading systems. The power absorption increases with the wave height, and the increment is rapid and mild in the two-way and one-way PTO loading torques, respectively. The pitch response amplitude operator increases as the wave period increases until the maximum value and then decreases. For a fixed PTO loading, the power and efficiency are higher in the two-way PTO loading system than in the one-way PTO loading system at different wave periods.

• Journal of the Korea Concrete Institute
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• v.16 no.1 s.79
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• pp.88-93
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• 2004

The objective of this study was to investigate applicability of epoxy injection method to cracked RC beams and structural behavior of repaired RC beams considering pre-loading conditions. For this purpose, five test beams were fabricated under two experimental variables. The main variables of this experimental study were pre-loading conditions and repair methods. The two pre-loading conditions were selected as $70\%$ and $90\%$ of nominal strength and the repair methods were to repair the cracked RC beams under free loading after crack and sustained loading. The comparative study was executed to evaluate effects of pre-loading conditions on the structural behavior of the cracked RC beams after crack-repair. The strains of reinforcement and concrete and deflections of beams at each loading step were measured and evaluated. As the results of this study, repair methods have much influence on structural behavior of epoxy injected RC beams and epoxy injection method for cracks of RC structures is appeared to be efficient.

• Journal of Mechanical Science and Technology
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• v.17 no.6
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• pp.787-795
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• 2003

Mechanical properties of the materials used for transportations and industrial machinery under high strain rate loading conditions such as seismic loading are required to provide appropriate safety assessment to these mechanical structures. The Split Hopkinson Pressure Bar (SHPB) technique with a special experimental apparatus can be used to obtain the material behavior under high strain rate loading conditions. In this paper, dynamic deformation behaviors of the aluminum alloys such as A12024-T4, A1606 IT-6 and A17075-T6 under both high strain rate compressive and tensile loading conditions are determined using the SHPB technique.

• Geomechanics and Engineering
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• v.10 no.6
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• pp.775-791
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• 2016

The indirect tensile strengths (ITSs) of different cemented paste backfill mixes with different curing times were determined by considering crack initiation and fracture toughness concepts under different loading conditions of steel loading arcs with various contact angles, flat platens and the standard Brazilian test jaw. Because contact area of the ITS test discs developes rapidly and varies in accordance with the deformability, ITSs of curing materials were not found convenient to determine under the loading apparatus with indefinite contact angle. ITS values increasing with an increase in contact angle can be measured to be excessively high because of the high contact angles resulted from the deformable characteristics of the soft paste backfill materials. As a result of the change of deformation characteristics with the change of curing time, discs have different contact conditions causing an important disadvantage to reflect the strength change due to the curing reactions. In addition to the experimental study, finite element analyses were performed on several types of disc models under various loading conditions. As a result, a comparison between all loading conditions was made to determine the best ITSs of the cemented paste backfill materials. Both experimental and numerical analyses concluded that loading arcs with definite contact angles gives better results than those obtained with the other loading apparatus without a definite contact angle. Loading arcs with the contact angle of $15^{\circ}$ was found the most convenient loading apparatus for the typical cemented paste backfill materials, although it should be used carefully considering the failure cracks for a valid test.

• Structural Engineering and Mechanics
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• v.17 no.5
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• pp.627-639
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• 2004

The objective of this research was to evaluate the performance of metal-plate-connected truss joints subjected to cyclic loading conditions that simulated seismic events in the lives of the joints. We also investigated the duration of load factor for these joints. We tested tension splice joints and heel joints from a standard 9.2-m Fink truss constructed from $38-{\times}89-mm$ Douglas-fir lumber: 10 tension splice joints for static condition and for each of 6 cyclic loading conditions (70 joints total) and 10 heel joints for static condition and for each of 3 cyclic loading conditions (40 joints total). We evaluated results by comparing the strengths of the control group (static) with those of the cyclic loading groups. None of the cyclic loading conditions showed any strength degradation; however, there was significant stiffness degradation for both types of joint. The results of this research show that the current duration of load factor of 1.6 for earthquake loading is adequate for these joints.