시멘트 혼합토의 내구성 평가법에 관한 연구

박성식,황세훈 한국지반공학회 2012 한국지반공학회논문집 Vol.28 No.11

Cemented soils have been used for subbase or base materials of roads, backfill materials of retaining walls and cofferdam. Such cemented soils can be degraded due to repeated wetting and drying or various weathering actions. Unlike rocks, a standard method was not defined for evaluating the durability of cemented soils. In this study, a slaking durability test and an ultrasound cleaner were used for developing a new durability test method for cemented soils. For durability tests, cemented sands with different cement ratios (4, 6, 8, and 12%) with cylindrical specimens were prepared and then air cured or under-water cured for three days. Three-day-cured specimens were dried for one day and then submerged for one day before testing. The weight loss after the slake durability test or ultrasonic cleaner operation for 10 or 20min was measured and used for assessing durability. When a cement ratio was 4%, the weight loss from ultrasonic cleaner test was 7-25% but that from slake durability test was as much as 30-60%. For specimens with cement ratio of more than 8%, the weight loss was less than 10% from both tests. A durability index increased with increasing a cement ratio. The durability index of under-water cured specimen was higher than that of air cured specimen. The ultrasonic cleaner test was found to be an effective tool for durability assessment of cemented sands rather than the slake durability test.

자동차용 파킹 락 기어의 내구시험과 시험 지그 개발

문현식(Hyun-Sik Mun),박성영(Sung-Young Park) 한국산학기술학회 2018 한국산학기술학회논문지 Vol.19 No.6

일반적으로 변속기 전체에 대한 내구시험을 통하여 파킹 락 기어의 내구성을 평가한다. 파킹 락 기어 부품 하나의 내구시험에 대한 시험 기준은 부재한 상황이다. 따라서 본 연구에서는 파킹 락 기어의 내구시험 기준을 자체적으로 설정하여, 내구 성능시험을 수행하였다. 파킹 락 기어의 항복응력을 구하기 위해 정적 파단 시험을 수행하였고, 항복응력의 60%를 내구시험 조건으로 설정하였다. 설정된 시험조건으로 100만회의 반복내구 성능시험을 수행하였다. 또한, 내구 성능시험을 수행하기 위하여, 전용 지그를 제작하였다. 제작된 지그가 정적 파단시험에서 파손되어, 파손된 지그에 대한 유한요소해석을 수행하고 설계를 변경하였다. 수정한 지그를 제작하여 자체적으로 설정한 시험기준으로 내구 성능시험을 수행한 결과, 파킹 락기어는 본 조건에 충족하였다. 본 연구에서 수행된 시험과 해석을 통하여 파킹 락 기어의 성능 및 내구 한계에 대한 기초 데이터를 확보하였고, 이러한 기초 데이터는 파킹 락 기어의 설계와 개발에 중요한 기초 자료로 활용될 것으로 사료된다. Generally, the durability of the parking lock gear is evaluated through an endurance test for the entire transmission but no test standard exists for the durability test of one part of a parking lock gear. Therefore, in this study, the durability test standards of the parking lock gear were determined autonomously, and the durability performance test was conducted. A static fracture test was carried out to determine the yield strength of the parking lock gear, and a durability test condition was set to 60 % of the yield strength. The durability test of 1,000,000 times was conducted under the given conditions using a dedicated test jig manufactured for the test. Because the jig fractured during the static fracture test, finite element analysis for the jig was carried out and the jig was re-designed. The modified jig was manufactured and the durability test was carried out based on the test standard of autonomously. The basic data on the performance and endurance limit of the parking lock gear were obtained using these tests and analyses, and the basic data will be used as fundamental materials for the design and the development of the parking lock gear.

항공기 전기체 내구성시험 기법 개발

설창원(Chang-Won Shul),양명석(Myung-Seog Yang),이기범(Kee-Bhum Lee),정재권(Jae-Kwon Jung),강휘원(Hui-Won Kang),이경용(Kyung-Yong Lee) 한국항공우주학회 2004 韓國航空宇宙學會誌 Vol.32 No.6

본 논문에서는 기체 구조건전성 기준서(MIL-HDBK-1530B) 및 기체 구조건전성 프로그램(ASIP)에 의거하여 고등 훈련기(T-50)의 구조건전성평가와 양산 결정자료 획득을 위한 전기체 내구성시험 기법 개발에 대하여 기술하였다. 전기체 부유식 시험조립 기법, 시험하중 최적화 모사 기법, 시험부가 장치 설계 기법, 시험조립 설계 및 설치 기법, 시험안전장치 설계 및 운용 기법 및 전기체 내구성시험 수행 결과를 수록하였다. 1배 수명 전기체 내구성시험을 성공적으로 수행함으로써 시험기법의 타당성을 입증하였다. This paper describes the test technique for the full-scale airframe durability test according to the military handbook(MIL-HDBK-1530) and ASIP(Aircraft Structure Integrity Program) to evaluate structural integrity and to obtain basic data for IPA(Initial Production Approval) of the Korean advanced trainer(T-50). This paper covers the full-scale airframe floating setup technique, the optimized test load simulation method, test rig design technique, test setup design and installation techniques, test safety device design and operation technique, and durability test results. As 1st life durability test was successfully performed, it was confirmed that this method is available in a full-scale airframe structural test.

대형트럭 리프 스프링 단품 다축리그 시험모드 개발과 유한요소 모델을 이용한 다축내구 해석의 연구

최정헌(JungHun Choi),유승원(Seungwon Yoo),김현남(Hyunnam Kim) 한국자동차공학회 2014 한국자동차공학회 학술대회 및 전시회 Vol.2014 No.11

The leaf spring is one of the most important parts of the vehicle because the damage of the leaf spring leads to lifethreatening accidents. In general, the most typical method of leaf spring durability test that is conducted by manufacturers of leaf spring is vertical load durability test in test lab. However, the leaf spring which has satisfied the target life of the vertical load durability test in test lab couldn"t satisfy the target life of the real vehicle durability test. Therefore, the aim of this study is to develop the Multi-axial Durability Test Mode which is consist of simple sine waves and damage the leaf spring as the same level with the real vehicle durability test in accelerated durability test road. And then, it presents the Multi-axial Fatigue Analysis Method by using Finite Element Model which is validated with the Multi-axial load test result and the Multi-axial Durability Test mode.

A Study of the Correlation between Sinusoidal Sweep and Random Vibration Durability Tests through Specimen Tests

홍창섭,양홍준,강윤식,오재윤,오택열 한국정밀공학회 2016 International Journal of Precision Engineering and Vol.17 No.12

In this paper, we study the correlation between a sinusoidal sweep durability test and a random vibration durability test through specimen tests. We compute random vibration durability test conditions having the same fatigue damage spectrum as a sinusoidal sweep durability test using the numerical analysis method. We use two kinds of specimens of different shape to perform durability tests. This paper proposes a normalization process that uses the average of the fatigue damage time caused only by a sinusoidal sweep durability test, and the average of the fatigue damage time caused only by a random vibration durability test. The normalization process makes it possible to remove the difference of fatigue life due to the difference of specimen shape. Thus, we determine one trend equation that can predict the test results of two kinds of specimen with high reliability. Through the trend equation, we can find the correlation between the fatigue life due to sinusoidal sweep vibration, and the fatigue life due to random vibration, which depends only on the specimen material and the excitation method.

수종별 목재 데크재의 내구성에 관한 연구

김경중,이원재,최철,김희진,강석구 한국가구학회 2017 한국가구학회지 Vol.28 No.2

Recently, as people’s interest in wood has increased, the use of wood as household and landscape decking materials has increased. As the deck material, imported wood such as synthetic wood, Ipe, and Malas was used in addition to the existing preserved wood, but recently deck use has been activated as part of the activation of domestic materials. As an important quality factor in the selection of such decking material, various durability along with weatherability for long - term use is required for maintenance. Generally used tropical hardwoods have excellent weatherability and durability without additional preservative treatment. However, the domestic larch is a wood species with a higher specific gravity and durability than ordinary conifers. However, it has not yet been used as a deck material due to lack of comparative studies on its characteristics. Therefore, hardness and durability of wood were measured using six specimens of Ipe, Massaranduba, Malas, Douglas-fir, Larch and Torrefied-Larch. Density Profile was used to measure the density, and Brinell hardness test and resistance test against momentary impact were carried out for the test of resistance to static load. Also, The hardness and durability of wood were measured by castor test with resistance test against dynamic load, as well as, nail down test by experiment on surface hardness and durability. As a result of the experiment, the hardness was increased in proportion to the density, and it was confirmed that the imported lumber was harder and durable than the domestic larch.

농용트랙터 신뢰성 평가 시험규격 개발

심기중(Kijoong Sim),조원용(Wonyong Cho  ),이영준(Youngjun Lee) 한국자동차공학회 2011 한국자동차공학회 지부 학술대회 논문집 Vol.2011 No.9

In this paper, we studied the reliability test specification development for agricultural tractor using mowing the lawn. To develop the reliability test specification, firstly, we investigated the usage and working conditions of tractor duty mode, weight, working velocity and transmission steps and so on. Usage of tractor is acquired through the investigation of user and working conditions are acquired by the measuring data of the working load. Secondly, we made the test specification of performance, durability using analysis of acquisition data. Developed test specifications were categorized the lab. test and field test, performance and durability. We tested the agricultural tractor performance, durability using developed 62 type test code. We described the test specification development process and test results.

승강장 안전발판 시스템의 내구성 평가

박민흥(Min Heung Park),곽희만(Hee Man Kwak),김민호(Min Ho Kim) 한국신뢰성학회 2016 신뢰성응용연구 Vol.16 No.2

Purpose: The purpose of this study is to evaluate durability of platform safety step system in railway. Method: We performed finite element analysis & durability analysis of platform safety step system with VPD (Virtual Product Development) techniques and examined the durability standard & qualification life through the rig test during no failure test time in reliability qualification test. We continued to test 1 million cycles in KRS (Korea Railway Standard) for system’s robust design performance. Result: FEM analysis results are 14.9MPa & 14.7MPa of pin-joint, pivot and durability analysis result is above 1 million cycles. we calculated theoretically no failure test time 855,000 cycles and through the 1 million cycles durability rig test in KRS standard we confirmed product quality. Conclusion: This platform safety step system was designed very safe in terms of a mechanical strength & durability.

Load-Carrying Performance and Hydrostatic Tests of Encapsulated Anchor Systems for Unbonded Post-Tensioning Single-Strands

Ah Sir Cho,Thomas H.-K. Kang 한국콘크리트학회 2018 International Journal of Concrete Structures and M Vol.12 No.2

ACI 318-14 and 423.7-14 require the use of encapsulation system for an unbonded single-strand tendon for the purpose of corrosion protection and enhanced durability. In this study, load-carrying performance and hydrostatic tests were conducted for a newly developed, unbonded post-tensioning (PT) anchor with encapsulation, following the guidelines put forth in KCI-PS101 and ACI 423.7-14. The static load and fatigue tests as part of this study were used to evaluate the anchorage system behavior under static and cyclic loads, respectively. The hydrostatic test was used to demonstrate that the encapsulation system withstood at least 9.3 kPa of water pressure in a 24 h period according to ACI 423.7-14, and thus has been proven to promote the durability of unbonded PT single-strand tendons. Additionally, the push-in and jacking tests were used to assess the compressive and tensile strengths of the anchor as used in the field. Although these tests were not performed to failure for safety reasons, the anchor endured at least 1.18 and 1.02 times the nominal ultimate strength of a strand in each test, respectively. The authors’ previous load transfer tests were also reported in this paper, showing that test specimens with only two horizontal backup bars were capable of resisting at least 1.7 times the nominal ultimate strength of a strand. Based on the favorable results from the loadcarrying performance and hydrostatic tests, the developed encapsulated anchor systems are being applied in actual practice as an economically feasible option in Korean PT industry and are expected to improve the corrosion resistance and durability of posttensioned structures.

Performance Evaluation of a Driving Power Transmission System for 50 kW Narrow Tractors

홍순중,하종규,김용주,Shaha Nur Kabir,서영우,정선옥 한국농업기계학회 2018 바이오시스템공학 Vol.43 No.1

Purpose: The development of compact tractors that can be used in dry fields, greenhouses, and orchards for pest control, weeding, transportation, and harvesting is necessary. The development and performance evaluation of power transmission units are very important when it comes to tractor development. This study evaluates the performance of a driving power transmission unit of a 50 kW multi-purpose narrow tractor. Methods: The performance of the transmission and forward-reverse clutch, which are the main components of the driving power transmission unit of multi-purpose narrow tractors, was evaluated herein. The transmission performance was evaluated in terms of power transmission efficiency, noise, and axle load, while the forward-reverse clutch performance was evaluated in terms of durability. The transmission’s power transmission efficiency accounts for the measurement of transmission losses, which occur in the transmission’s gear, bearing, and oil seal. The motor’s power was input in the transmission’s input shaft. The rotational speed and torque were measured in the final output shaft. The noise was measured at each speed level after installing a microphone on the left, right, and upper sides. The axle load test was performed through a continuous equilibrium load test, in which a constant load was continuously applied. The forward-reverse clutch performance was calculated using the engine torque to axle torque ratio with the assembled engine and transmission. Results: The loss of power in the transmission efficiency test of the driving power unit was 6.0-9.7 kW based on all gear steps. This loss of horsepower was equal to 11-18% of the input power (52 kW). The transmission efficiency of the driving power unit was 81.5-89.0%. The noise of the driving power unit was 50-57 dB at 800 rpm, 70-77 dB at 1600 rpm, and 76-83 dB at 2400 rpm. The axle load test verified that the input torque and axle revolutions were constant. The results of the forward-reverse clutch performance test revealed that hydraulic pressure and torque changes were stably maintained when moving forward or backward, and its operation met the hydraulic design standards. Conclusions: When comprehensively examined, these research results were similar to the main driving power transmission systems from USA and Japan in terms of performance. Based on these results, tractor prototypes are expected to be created and supplied to farmhouses after going through sufficient in-situ adaptability tests.Purpose: The development of compact tractors that can be used in dry fields, greenhouses, and orchards for pest control, weeding, transportation, and harvesting is necessary. The development and performance evaluation of power transmission units are very important when it comes to tractor development. This study evaluates the performance of a driving power transmission unit of a 50 kW multi-purpose narrow tractor. Methods: The performance of the transmission and forward-reverse clutch, which are the main components of the driving power transmission unit of multi-purpose narrow tractors, was evaluated herein. The transmission performance was evaluated in terms of power transmission efficiency, noise, and axle load, while the forward-reverse clutch performance was evaluated in terms of durability. The transmission’s power transmission efficiency accounts for the measurement of transmission losses, which occur in the transmission’s gear, bearing, and oil seal. The motor’s power was input in the transmission’s input shaft. The rotational speed and torque were measured in the final output shaft. The noise was measured at each speed level after installing a microphone on the left, right, and upper sides. The axle load test was performed through a continuous equilibrium load test, in which a constant load was continuously applied. The forward-reverse clutch performance was calculated using the engine torque to axle torque ratio with the assembled engine and tra... Purpose: The development of compact tractors that can be used in dry fields, greenhouses, and orchards for pest control, weeding, transportation, and harvesting is necessary. The development and performance evaluation of power transmission units are very important when it comes to tractor development. This study evaluates the performance of a driving power transmission unit of a 50 kW multi-purpose narrow tractor. Methods: The performance of the transmission and forward-reverse clutch, which are the main components of the driving power transmission unit of multi-purpose narrow tractors, was evaluated herein. The transmission performance was evaluated in terms of power transmission efficiency, noise, and axle load, while the forward-reverse clutch performance was evaluated in terms of durability. The transmission’s power transmission efficiency accounts for the measurement of transmission losses, which occur in the transmission’s gear, bearing, and oil seal. The motor’s power was input in the transmission’s input shaft. The rotational speed and torque were measured in the final output shaft. The noise was measured at each speed level after installing a microphone on the left, right, and upper sides. The axle load test was performed through a continuous equilibrium load test, in which a constant load was continuously applied. The forward-reverse clutch performance was calculated using the engine torque to axle torque ratio with the assembled engine and transmission. Results: The loss of power in the transmission efficiency test of the driving power unit was 6.0-9.7 kW based on all gear steps. This loss of horsepower was equal to 11-18% of the input power (52 kW). The transmission efficiency of the driving power unit was 81.5-89.0%. The noise of the driving power unit was 50-57 dB at 800 rpm, 70-77 dB at 1600 rpm, and 76-83 dB at 2400 rpm. The axle load test verified that the input torque and axle revolutions were constant. The results of the forward-reverse clutch performance test revealed that hydraulic pressure and torque changes were stably maintained when moving forward or backward, and its operation met the hydraulic design standards. Conclusions: When comprehensively examined, these research results were similar to the main driving power transmission systems from USA and Japan in terms of performance. Based on these results, tractor prototypes are expected to be created and supplied to farmhouses after going through sufficient in-situ adaptability tests.