• 한국철도학회논문집
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• 제15권3호
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• pp.266-271
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• 2012

본 연구는 빠르게 대중화 되어가는 철도의 주행안전성과 승차감 개선을 목적으로 수행하였다. 가스압접을 실시하는 장대레일의 강도 안전성을 확보하기 위하여 인장시험과 회전굽힘시험을 실시했다. 실험을 통하여 가스 압접부의 인장강도를 결정하는 요소는 가해진 압력보다 업셋길이의 변화에 기인하며, 업셋길이가 늘어남에 따라서 취성파괴에서 연성파괴가 발생하는 것을 관찰했다. 파단면의 조직검사를 통해 그 면에 존재하는 취성파면의 유무에 따라서 강도 안전성을 용이하게 평가할 수 있었다. 회전굽힘시험 결과 업셋길이 25mm에서 373MPa의 우수한 피로한도가 나타났으며, 무한수명을 얻을 수 있었다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2008년도 추계학술대회논문집
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• pp.226-229
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• 2008

To investigate an in-pile behavior of the newly developed DUO fuel pellet, the irradiation test will be carried out in the domestic test reactor. Irradiation test capsule for the HANARO reactor, which is a specially designed equipment used for material, irradiation and creep test, must satisfy the operational requirement on the hydraulic characteristics and structural integrity. In this study, a pressure drop, a flow-induced vibration and a short-term endurance test for the newly developed non-instrumented test capsule were carried out using FIVPET as a out-pile evaluation test. The test results show that the new test rig satisfy the HANARO operational requirement with sufficient margin.

• 한국지반공학회논문집
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• 제21권6호
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• pp.127-135
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• 2005

부산점토에 대한 변형률 속도 의존적인 압밀특성을 분석하기 위해 다양한 변형률 속도의 일정 변형률(CRS) 압밀시험과 하중제어 압밀시험을 수행하였다. 부산점토에 대한 실내시험 결과에서 선행압밀하중은 압밀과정 동안에 유발되는 변형률 속도에 의존적이고 선행압밀하중에 대해 정규화시킨 압밀곡선은 유일하다는 것을 알 수 있었다. CRS 시험에서 얻어진 압밀계수 및 투수계수는 정규압밀영역에서 변형률 속도에 관계없이 일정한 값에 수렴함을 알 수 있었다. 또한 하중제어 압밀시험을 통해서 전응력이 일정한 상태에서 간극수압이 증가하는 Mandel-Cryer 효과를 볼 수 있었다. 그리고 장시간의 하중제어 압밀시험을 통해 선행압밀하중 부근에서 흙 구조의 붕괴로 인하여 급격한 간극수압의 증가현상이 관찰되었다.

• 한국가스학회지
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• 제17권3호
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• pp.20-26
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• 2013

본 연구에서는 수압파열시험 장비를 이용하여 Type3 복합용기의 설계 파열압력에 관한 실증연구를 수행하였다. 고압가스를 저장할 수 있는 6.8L급 사용압 31MPa Type3 복합용기에 대한 유한요소 설계해석을 통하여 파열압을 예측하였고 해석의 정확성을 확인하기 위하여 수압파열시험을 3회 실시하였다. 파열시험설비는 수압으로 최대 400MPa까지 가압이 가능한 장비를 활용하였다. 해석으로 예측된 소형 복합용기의 설계 파열압과 실제 파열시험 결과를 비교한 결과, 값의 차이는 4% 이내로 나타났다. 이를 통하여 해석기법의 신뢰성을 확인하였으며, 본 실증에서 검증된 해석기법을 복합용기의 안전성 확보를 위한 국내인증 및 제품검사에 적용할 예정이다.

• 국제물리치료학회지
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• 제11권2호
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• pp.2042-2051
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• 2020

Background: Many trials have been conducted the methods and types of intervention of form rollers, but no research has been done yet that mixes the methods and types of intervention. Objectives: To analyze the effects of myofascial release on the improvement of range of motion (ROM), flexibility, pain pressure threshold, and balance. Design: Randomized controlled trial. Methods: All subjects measured ROM, flexibility, pressure pain threshold, and dynamic balance by pre-test. After pre-test, subjects were randomized that static-vibration foam rolling group (n=12), dynamic-vibration foam rolling group (n=12), general foam rolling group (n=12). For the intervention, 3 sets of 90 seconds were applied to each group, and rest time was set to 60 seconds between sets. In the post-test and follow-up test after 10 minutes, all three groups were measured the ROM, flexibility, pressure pain threshold, and dynamic balance. Results: The results of comparing ROM, flexibility, pressure pain thresholds, dynamic balance ability appeared higher significant difference in the pre-post-10 minutes follow up test in comparison between time in the intragroup (P<.001). As a result of comparing the change of pre-post-10 minutes follow up, static vibration foam rolling showed higher significant difference compared to control groups (P<.001). Conclusion: Through this study, when foam rolling is applied within the same intervention time, static foam rolling can be expected to have a better effect than the existing dynamic foam rolling as well as vibration foam roller can expect better effect than general foam rolling.

• Geomechanics and Engineering
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• 제18권3호
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• pp.291-298
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• 2019

In order to study the mechanical properties of rock salt, triaxial compression tests under different temperatures and confining pressure are carried out on rock salt specimens, the influence of temperature and confining pressure on the mechanical properties of rock salt was studied. The results show that the temperature has a deteriorative effect on the mechanical properties of rock salt. With the increase of temperature, the peak stress of rock salt decreases visibly; the plastic deformation characteristics become much obvious; the internal friction angle increases; while the cohesion strength decreases. With the increase of confining pressure, the peak stress and peak strain of rock salt will increase under the same temperature. Based on the test data, the Duncan-Chang constitutive model was modified, and the modified Duncan-Chang rock salt constitutive model considering the effect of temperature and confining pressure was established. The stress-strain curve calculated by the modified model was compared with the stress-strain curve obtained from the test. The close match between the test results and the model prediction suggests that the modified Duncan-Chang constitutive model is accurate in describing the behavior of rock slat under different confining pressure and temperature conditions.

• 한국분무공학회지
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• 제16권4호
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• pp.201-209
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• 2011

Optimum engine performance is obtained when the spray characteristics is well matched to the geometry of a combustion chamber. Among many parameters governing the combustion performance in internal combustion engine, fuel supply characteristics and atomization are important performance factors. Therefore, spray characteristics of high pressure multi-hole injector has been studied experimentally. An experimental test system has been made to operate high pressure injection system and to visualize spray behavior. Spray visualization has been performed to analyze spray formation, spray cone angle, bent angle and penetration length. Spray interaction with piston has been analyzed with various injector installation angle, injection pressure and ambient pressure. Test results show that penetration length is greatly influenced by the injection pressure. Penetration length is decreased as ambient pressure increased. Spray cone angle is increased as injection pressure and ambient pressure increased. However, bent angle is not influenced by the change of injection pressure and ambient pressure. Spray cone angle distribution map is plotted using the experimental data. Fuel movement around the spark-plug has been enforced as increasing injector installation angle.

• 한국지반공학회논문집
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• 제19권2호
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• pp.217-225
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• 2003

지반보강 그라우팅은 대상지반의 공학적 특성 및 사용 목적에 따라 주입재 종류, 주입압력, 주입량 등을 적절히 선택해야 효율적이고 경제성 있는 시공이 될 수 있다. 특히, 압력 그라우팅 공법을 견고한 암반층이 아닌 일반 토사층에 적용시 압력이 높은 경우 수압파쇄에 의한 주입재 이탈 등의 문제가 발생하기 쉬우므로 현장조건에 알맞는 주입압력을 미리 설정하는 것이 필요하다. 이 연구는 느슨 내지 중밀 정도의 쇄석과 모래를 이용한 실험실 모형시험을 통하여 적정 주입압과 주입방법을 밝히기 위해 수행되었다. 최적 주입압, 주입량 그리고 주입시간을 조사하기 위해 실험과정에서 주입조건을 변화시켰다. 시험결과로부터 쇄석 및 모래지반에서 압력그라우팅의 최적 주입압은3~4kg/$cm^2$ 임을 알 수 있었다.

• 한국농공학회지
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• 제30권3호
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• pp.38-50
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• 1988

carried out to present a rheology model which is able to treat time-dependent properties of clay. The results were summarized as follow ; 1. The slope (a(e1)) of deviator stress in strain rate test was independent on axial strain, and pore water pressure was decreased with increment of strain rate. 2. The pore water pressure in a stress relaxation condition was not changed when the strain rate before stress relaxation was 0.05%/min., but it was increased with increment of time when the strain rate before stress relaxation was 0.2%/min 3. The greater the stress condition (q/qmax) and the strain rate before creep test became, the greater the increment rate of axial strain in creep test became. 4. SEKIGUCHI's constitutive equation was slightly overpredicted while empirical equation proposed in the study was well coincided with measured values. 5. The constitutive equation induced by a strain function could be dealed with a behavior of the pore water pressure increased with increment of elapsed time after primary consolidation.

• 한국해양공학회지
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• 제30권2호
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• pp.100-108
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• 2016

A high-pressure ball valve was developed, and both the structural strength and sealing performance were assessed based on a nonlinear finite element analysis. Different parts were modeled with solid elements and assembled, taking into account both contact and sliding effects. Three different loading scenarios were analyzed, including a high-pressure closure test and fire and shell test conditions. The structural safety of each part was checked under each loading condition, and the sealing performance was also investigated to validate the performance of the valve.