• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2005년도 추계학술대회 논문집
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• pp.243-246
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• 2005

A tube hydroformability testing system was designed and manufactured to observe the forming steps and to provide arbitrary combination of internal pressure and axial feed. The forming limit diagram of an aluminum tube was obtained from the free bulge test and the T-shape forming test using this system, giving the criteria for predicting failure in the hydroforming process. The hydroformability of aluminum tube according to different conditions of a prebending process was discussed, based on the finite element analysis and the forming limit test. The effects of 2D and 3D prebending on the tube hydroforming process of an automotive failing arm were evaluated and compared with each other.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.1367-1372
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• 2008

A plate type supporting structure of a tube bundle in axial flow generates a certain band of a high frequency periodic excitation of a vortex shedding and/or a flow separation due to sharp edge of the plate thickness and a severe pressure drop due to a cross-sectional area of the supports. With a design consideration of the low vibration and a small flow resistance, the analysis method is uniquely confined to an experimental approach because a complex geometry of a cylindrical tube bundle and/or physical phenomena related to the fluid-structure interaction of tube bundle in a flow impede a theoretical or a numerical approach. A 5x5 cylindrical tube bundle with 5 supports which were discretely located along the bundle's axis was tested in the FIVPET hydraulic test loop for a design evaluation and an analysis perspectives. A high frequency flow-induced vibration of the supporting structures of the cylindrical tube bundle was measured at a outer surface of a supporting structure through a transparent flow housing by the laser dopper vibrometer. Pressure drop in-between three measurement distances was measured by the differential pressure transmitter. High frequency vibration and pressure drop fairly depends on the geometric design of supporting structure. So, these two parameters would be used as a qualitative design variables for design evaluation and analysis.

• Steel and Composite Structures
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• 제46권4호
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• pp.539-551
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• 2023

In order to study the fire resistance of castellated composite beams with ortho-hexagonal holes and different beam-end restraints, temperature rise tests with constant load were conducted on full-scale castellated composite beams with ortho-hexagonal holes and hinge or rigid joint constraints to investigate the temperature distribution, displacement changes and failure patterns of castellated composite beams with two different beam-end constraints during the whole course of fire. The results show that (1) During the fire, the axial pressure and horizontal expansion deformation generated in the rigid joint constrained composite beam were larger than those in the hinge joint constrained castellated composite beam, and their maximum horizontal expansion displacements were 30.2 mm and 17.8 mm, respectively. (2) After the fire, the cracks on the slab surface of the castellated composite beam with rigid joint constraint were more complicated than hinge restraint, and the failure more serious; the lower flange and web at the ends of the castellated steal beams with hinge and rigid joint constraint produced serious local buckling, and the angles of the ortho-hexagonal holes at the support cracked; the welds at both ends of the castellated composite beam with rigid joint constraint cracked. (3) Based on the simplified calculation method of solid-web composite beam, considering the effect of holes on the web, this paper calculated the axial force and displacement of the beam-end constrained castellated composite beams under fire. The calculation results agreed well with the test results.

• 비파괴검사학회지
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• 제9권1호
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• pp.48-55
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• 1989

It is desirable to develop the effective NDT techniques to evaluate the strength of composite structures. In this study several of acoustic NDT techniques were applied to investigate useful parameters for evaluating the filament wound GFRP structures and following results were obtained. 1. Propagation velocity of stress wave to axial direction in the filament wound GFRP pipe depends on the effective modulus along the propagation direction and source location was parcticable from the a measured velocities. 2. By the application of acoustic emission techniques to GFRP pipe during hydraulic test, it was proven to be possible to detect the damage initiating pressure which could be evaluated nondestructively through the measuring of stress wave energy factor(SWEF). 3. The final failure pressure of GFRP was greatly influenced in the presence of pass through defects, and void-like defects were more dangerous than the laminar type defects.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2006년도 춘계학술대회 논문집
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• pp.269-272
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• 2006

The hydroforming processing is a relatively new technology in comparison with conventional stamping process. The hydroforming processing makes torsion beam in rear suspension of automobile. The durability of torsion beam is very important characteristic that operate in an automobile. In order to optimize the hydroforming process and satisfy the durability, the hydroforming simulation which could control an axial compression and high internal pressure with computer simulation has to be operated. This paper is about an optimum design to improve the kinematic and compliance characteristics of a torsion-beam of suspension system. The result from finite element analysis shows that the forming and the durability are optimized. If there is effect of First pressure in hydroforming processing that gap is in the die tool, the prototype of tube is not satisfied on the durability test.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2004년도 제22회 춘계학술대회논문집
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• pp.125-130
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• 2004

Experimental study on combustion characteristics of double swirl coaxial injectors has been conducted for the assessment of critical injector design parameters. A reusable, unielement thrust chamber has been fabricated with a water-cooled copper nozzle. Two principle design parameters, a swirl angle and a recess length, have been investigated through hot firing tests for the understanding of their effects on high pressure combustion. Clearly, both parameters considerably affect the combustion efficiency, dynamics and hydraulic characteristics of an injector. Internal mixing of propellants in a recess region increases combustion efficiency along with the increase of a pressure drop required for flowing the same amount of mass flow rates. It is concluded that pressure buildup due to flame can be released by the increase of LOx flow axial momentum or the reduction of a recess length. Dynamic pressure measurements of the thrust chamber show varied dynamic behaviors depending on injector configurations.

• Geomechanics and Engineering
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• 제28권3호
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• pp.265-281
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• 2022

A set of slurry shield test system capable of cutter cutting and slurry automatic circulation is used to investigate the deformation characteristics, the evolution characteristics of support resistance and the distribution and evolution process of earth pressure during excavating and collapsing of slurry shield tunneling in circular-gravel layer. The influence of cover-span ratio on surface subsidence, support resistance and failure mode of excavation face is also discussed. Three-dimensional numerical calculations are performed to verify the reliability of the test results. The results show that, with the decrease of the supporting force of the excavation face, the surface subsidence goes through four stages: insensitivity, slow growth, rapid growth and stability. The influence of shield excavation on the axial earth pressure of the front soil is greater than that of the vertical earth pressure. When the support resistance of the excavation face decreases to the critical value, the soil in front of the excavation face collapses. The shape of the collapse is similar to that of a bucket. The ultimate support resistance increase with the increase of the cover-span ratio, however, the angle between the bottom of the collapsed body and the direction of the tunnel excavation axis when the excavation face is damaged increase first and then becomes stable. The surface settlement value and the range of settlement trough decrease with the increase of cover-span ratio. The numerical results are basically consistent with the model test results.

• Journal of Chest Surgery
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• 제54권3호
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• pp.186-190
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• 2021

Background: Pre-lifting of the sternum marked a major turning point in pectus excavatum repair. The author developed the crane technique in 2002 and successfully applied it to more than 2,000 cases using sternal wire stitching. However, blind sternal suturing limited the use of the wire-stitch crane. We propose a novel screw for sternal lifting as a new tool for the crane technique. Methods: We developed a screw system strong enough to withstand the pressure needed for sternum lifting. The screw was designed to have a broader thread to hold the bony tissue securely. The screw's sustaining power was tested using the torsion, driving torque, and axial pull-out tests in a polyurethane block and ex-vivo porcine sternum. Results: The screws were easily driven into the sternum, and the head of the screw was connectable to the table-mounted retractor. In the torsion test, the 2° offset torsional yield was 4.53 N·m (reference value, 1 N·m). In the polyurethane block driving torque test, the maximum torque was 0.98 N·m (reference value, 0.70 N·m). The axial pull-out test was 446 N (reference value, 100 N). The maximum pull-out resistance in the ex-vivo porcine sternum model was 1,516 N. Conclusion: The screw crane was strong enough to sustain the chest wall weight to be lifted. Thus, the screws could effectively replace the sternal wire stitching in crane pre-lifting of the sternum. We expect that application of the screw-crane will be easy and that it will improve the safety and success rate of pectus repair surgery.

• 한국유체기계학회 논문집
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• 제4권1호
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• pp.30-37
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• 2001

The experimental study on the effect of axial clearance between the tip of impeller blades and stationary shroud has been performed. The investigated compressor, which is a part of a small auxiliary power unit engine, consists of a curved inlet, a centrifugal impeller, a channel diffuser and a plenum chamber. It was designed for a total pressure ratio of 4.3 and an efficiency of $77\%$ at design speed of 60,000 rpm. The experiments are carried out in an open-loop centrifugal compressor test rig driven by a turbine. For the four different clearance ratios Cr(clearance/impeller tip width) of 6.25, 10.93, 15.60 and 20.30 percent, the overall performance data are obtained at $97\%,\;90\%$ and $80\%$ of the design speed. The results show the overall pressure ratio decrease of $7.7\%$ and the efficiency loss of $8.7\%$ across the variation of clearance ratio near the design speed. It also indicates that the influence of tip clearance became weaker as the flow rate is reduced and the stable operating range is not significantly influenced by the change of clearance ratio.

• Structural Engineering and Mechanics
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• 제73권5호
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• pp.599-612
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• 2020

A combination of a gravity wall and an anchor beam is widely used to support the high soil deposit on rock mass. In this study, two groups of shaking table test were performed to investigate the responses of such combined retaining structure, where the rock masses were shaped with a flat surface and a curved surface, respectively. Meanwhile, the dynamic numerical analysis was carried out for a comparison or an extensive study. The results were studied and compared between the combined retaining structures with different shaped rock masses with regard to the acceleration response, the earth pressure response, and the axial anchor force. The acceleration response is not significantly influenced by the surface shape of rock mass. The earth pressure response on the combined retaining structure with a flat rock surface is more intensive than the one with a curved rock surface. The anchor force is significantly enlarged by seismic excitation with a main earthquake-induced increment at the first intensive pulse of Wenchuan motion. The value of anchor force in the combined retaining structure with a flat rock surface is generally larger than the one with a curved rock surface. Generally, the combined retaining structure with a curved rock surface presents a better seismic performance.