P-S-N선도를 이용한 진동리퍼 기어박스-생크 용접부의 피로수명 평가

오광근(Kwang Keun Oh),김재훈(JaeHoonKim),박정렬(Jung Yeol Park),양규상(GyuSangYang),박종원(JongWonPark),김성현(Sung Hyun Kim) 대한기계학회 2015 大韓機械學會論文集A Vol.39 No.12

진동리퍼은 암반의 파쇄와 리핑 작업을 동시에 하기 위해서 개발된 장비이며 기존의 암반 파쇄용 유압 브레이커와 작동 원리가 다르다. 진동리퍼의 기진력을 투스로 전달하는 기어박스-생크 용접부는 매우 중요한 부분이며 진동리퍼의 기계적 건전성의 예측이 필수적이다. 본 연구는 생크소재 및 용접재료의 변화에 따른 용접부의 피로수명 예측을 목적으로 하고 있다. 생크의 재료는 Hadox-hituf, AR 400을 사용하였고 용접금속은 CSF-71T, CSF-81T를 사용하였다. 피로시험은 응력비 R=0에서 각 재료조건에 대해서 수행하였다. P-S-N 선도는 JSME-S002 규정에 맞춰 파괴확률 10%, 50%, 90%에 대해서 나타냈으며 수명 예측 식을 도출하였다. A vibro ripper utilizes high-frequency vibration for rock fragmentation. This concept is different from those used by other existing breakers. The gearbox-shank welded joint of a vibro ripper is a very important part. Because it delivers the vibromotive force to the tooth, it is important to predict its soundness. This study was conducted to predict the fatigue life under welding conditions. The shank materials were Hardox-Hituf and AR400, and the filler metals were CSF-71T and CSF-81T. Fatigue tests were conducted under each set of conditions. P-S-N curves are presented based on the statistical testing method recommended by JSME-S002, and a comparison is made of the results under each set of conditions. The life was estimated using a P-S-N curve.

드럼세탁기 축계의 피로수명 평가

김대진(D. J. Kim),위우택(W. T. We),석창성(C. S. Seok),이근호(G. H. Lee),민제홍(J. H. Min) 한국정밀공학회 2006 한국정밀공학회 학술발표대회 논문집 Vol.2006 No.5월

To estimate the fatigue life of flange-shaft assembly, fatigue test for flange material and bending fatigue test for flange-shaft assembly were conducted. Also, finite element analysis for flange-shaft assembly was conducted. Then, we have changed the obtained P-N curve to S-N curve using the finite element analysis results which were stress values at the location of fracture. The S-N curve of flange material itself was almost consistent with that of flange-shaft assembly, so it seems that the fatigue life of flange-shaft assembly could be estimated by using S-N curve for flange material and the stress at the location of fracture calculated by finite element methods.

eVTOL 블레이드 피치 제어용 전기식 작동기의 준정적 내구해석 기반 피로수명 평가

김영철,김동협,김상우,이종환,강정현,김도형 한국항공우주학회 2023 韓國航空宇宙學會誌 Vol.51 No.5

The structural safety for the fatigue behavior of an electro-mechanical actuator for eVTOL blade pitch control was investigated. The load history of the actuator was calculated using the multi-body dynamics analysis. Furthermore, a static load analysis against the rated load was performed to determine a weak area and construct a stress spectrum for the weak area. A P-S-N curve was derived for conservative fatigue life evaluation, and a quasi-static durability analysis was performed by applying the constructed stress spectrum to the algebraic equation of the P-S-N curve. As a result, fatigue lives of over 10^7 cycles were calculated for all parts of the actuator, confirming structural safety for fatigue behavior. 본 연구에서는 eVTOL 블레이드 피치 제어용 전기식 작동기의 피로거동을 검토하였다. 다물체 동역학 해석을 통해 작동기의 하중이력을 산출하였다. 또한 정격하중에 대한 정하중 해석을 수행하여 취약 부위를 선정하고, 취약 부위의 응력 스펙트럼을 구축하였다. 이후 보수적인 피로수명 평가를 위해 P-S-N 선도를 작성하였고, 구축된 응력 스펙트럼을 P-S-N 선도의 대수방정식에 적용하여 준정적 내구 해석을 수행하였다. 해석 결과, 작동기의 모든 부품에 대해 10^7 cycles 이상의 피로수명이 산출되어 피로 거동에 대해 구조적으로 안전함을 확인하였다.

Cold Stretching 압력용기용 ASS304 소재의 극저온 인장 및 피로거동

최훈석(Hoon Seok Choi),김재훈(Jae Hoon Kim),나성현(Seong Hyun Na),이윤형(Youn Hyung Lee),김성훈(Sung Hun Kim),김영균(Young Kyun Kim),김기동(Ki Dong Kim) 대한기계학회 2016 大韓機械學會論文集A Vol.40 No.5

ASS304 소재로 제작된 cold stretching 압력용기는 극저온 액화천연가스의 운반 및 저장에 이용된다. Cold stretching 압력용기는 특정 수압을 이용하여 허용응력까지 기존의 압력용기를 신장시킴으로써 재료에 상당량의 소성변형이 나타난다. 이 경우, ASS304 소재의 특성에 따라 소성변형 후 항복강도가 증가하며, 신장량에 따라 두께가 감소한다. 따라서 강도 및 무게측면에서 기존의 압력용기 대비 높은 효율을 나타낸다. 본 연구에서는 ASME 코드에 의거하여 제작된 소형 cold stretching 압력용기에서 직접 채취한 시편을 이용하여 극저온 인장 및 피로특성을 평가하였다. 또한 저온피로시험으로부터 획득한 S-N 선도를 통계적으로 접근하여 P-S-N 선도를 작성하였으며, SEM 을 이용하여 파단면을 분석하였다. Cold stretching(CS) pressure vessels from ASS304 (austenitic stainless steel 304) are used for the transportation and storage of liquefied natural gas(LNG). CS pressure vessels are manufactured by pressurizing the finished vessels to a specific pressure to produce the required stress σk. After CS, there is some degree of plastic deformation. Therefore, CS vessels have a higher strength and lighter weight compared to conventional vessels. In this study, we investigate the tensile and fatigue behavior of ASS304 sampled by CS pressure vessels in accordance with the ASME code at cryogenic temperature. From the fatigue test results, we show S-N curves using a statistical method recommended by JSEM-S002. We carried out the fractography of fractured specimens using scanning electron microscopy (SEM).

회주철의 미세구조와 인장거동 분석 및 확률론적 피로수명평가

성용현(Yong Hyeon Sung),한승욱(Seung-Wook Han),최낙삼(Nak-Sam Choi) 대한기계학회 2017 大韓機械學會論文集A Vol.41 No.8

보통회주철(GC300)에 Cr, Mo, Cu 첨가제를 넣어 고급 회주철(HCI350)을 제작하고, 미세 조직과 기계적 물성치, 피로강도의 변화를 연구하였다. 주철을 환봉형과 평판형 주물로 제작하였으며, 이들을 절단 및 연마하여 나이탈 수용액으로 에칭한 후 미세조직의 면적비율을 측정하였다. 첨가물에 의해 편상 흑연결정(flake graphite)의 크기가 감소하고 고밀 펄라이트 함량이 증가하여 인장강도, 피로강도의 향상이 확인되었다. 피로시험 결과 획득한 피로수명 데이터를 바탕으로 최우추정법이 적용된 2모수 와이블 분포를 이용하여 확률-응력-수명 곡선을 산출하였다. 확률-응력-수명곡선 산출 결과 HCI350은 GC300에 비해 피로강도는 크게 개선되었고 수명데이터의 분산성은 낮아졌으나, 피로응력완화에 따른 피로수명의 증가가 크게 나타났다. 산출된 확률-응력-수명 곡선을 이용하여 요구수명 사이클 수에 대한 허용응력 값을 정량적으로 제시함으로써 신뢰성 수명설계에 위한 기초자료를 제시하였다. High-grade gray cast iron (HCI350) was prepared by adding Cr, Mo and Cu to the gray cast iron (GC300). Their microstructure, mechanical properties and fatigue strength were studied. Cast iron was made from round bar and plate-type castings, and was cut and polished to measure the percentage of each microstructure. The size of flake graphite decreased due to additives, while the structure of high density pearlite increased in volume percentage improving the tensile strength and fatigue strength. Based on the fatigue life data obtained from the fatigue test results, the probability - stress - life (P-S-N) curve was calculated using the 2-parameter Weibull distribution to which the maximum likelihood method was applied. The P-S-N curve showed that the fatigue strength of HCI350 was significantly improved and the dispersion of life data was lower than that of GC300. However, the fatigue life according to fatigue stress alleviation increased further. Data for reliability life design was presented by quantitatively showing the allowable stress value for the required life cycle number using the calculated P-S-N curve.

STS304강의 순수 및 외팔보형 굽힘피로에 대한 파괴확률특성

노성국,정순억 경상대학교 해양산업연구소 2002 해양산업연구소보 Vol.15 No.-

Big accidents of flyings, vessel, subways, gas equipments, buildings and bridge happens frenquently. Therefore many people are suffering harm of property. The destruction cause of macaine components is almost accused by fatigue. This study is test for STS304 specimen by using pure and cantilever bending state. Rounded specimen and notched specimen including fracture surface investigation was comparatively experimented, fatigue life according to degree of surface finishing was examined. Fatigue fracture probability of notched canilever specimens were predicted by P-S-N curve, median rank and Weibull distribution. And at the relation with the rotational speed and stress the fatigue life of the test specimen was higher than low speed at high speed.

서브프레임의 피로특성 평가

김유석(Youseok Kim),정효동(Hyodong Jung),박유정(Youjeong Park),권성진(Seongjin Kwon),김영석(Youngsuk Kim) 한국자동차공학회 2017 한국자동차공학회 부문종합 학술대회 Vol.2017 No.5

확률밀도함수를 이용한 상수도 실 배관의 피로수명 특성 평가

최정훈(Jung-Hun Choi),구재민(Jae-Mean Koo),석창성(Chang-Sung Seok),송원근(Weon-Keyu Song) 대한기계학회 2008 大韓機械學會論文集A Vol.32 No.9

The fatigue characteristics of a material or a structure are generally derived from fatigue tests of standard specimens. However, test results of standard specimens are different from those of real structures or components. Therefore, to calculate more accurate fatigue life, the geometrical effect and surface condition must be considered by comparing test results of standard specimens with those of real structures or components. Thus the object of this paper is to evaluate the fatigue characteristics of a real waterwork pipe. Also, to evaluate fatigue characteristic based on life distribution, the statistical fatigue characteristics were analyzed by the normal distribution and related data of P-S-N curve.

Bonding and debonding behavior of FRP sheets under fatigue loading

Iwashita, Kentaro,Wu, Zhishen,Ishikawa, Takashi,Hamaguchi, Yasumasa,Suzuki, Toshio The Korean Society for Composite Materials 2007 Advanced composite materials Vol.16 No.1

The purpose of this study is to improve the examining and understanding of the bonding behavior of Fiber Reinforced Polymer (FRP) sheets bonded to concrete blocks and steel plates under fatigue loading. First, a series of experimental investigations is summarized in the paper. The fatigue behavior of bonding surface between FRP sheets and concrete is finally characterized by the conducted P-S-N diagram representing the relationship among the probability of FRP debonding (P), the bond stress amplitudes (S), and the number of cycles (N) at debonding on a semi-logarithmic scale. The different debonding modes for various fracturing surface are also investigated and evaluated.

피로특성평가를 위한 데이터베이스 구축

김철수(Chul-Su KIM),권혁선(Hyuk-Sun KWON),조상수(Sang-Soo CHO),김정규(Jung-Kyu KIM) 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.3

In this study, in order to perform more efficiently safety design and integrity assessment of structural members, the relational database system on the fatigue strength of steels was constructed. Fatigue strength database contained 343 S-N curves for 39 kinds of the steels and was developed using MS-SQL 2000. Furthermore, the application program for reliability analysis was developed to consider variation of applied stress and fatigue strength. This program consists of 5 modules: search condition, evaluation of P-S-N curve, probabilistic characteristics of fatigue strength and applied stress history, and reliability analysis with strength-stress interference model.