• Title/Summary/Keyword: Manson-Coffin 관계식

Search Result 4, Processing Time 0.019 seconds

Comparison and Evaluation of Low-Cycle Fatigue Life Prediction Methods Using Cu-Cr Alloy Developed for Rocket Engines (로켓엔진용 구리크롬 합금의 저주기 피로수명 예측방법 비교 및 평가)

  • Jongchan Park;Jae-Hoon Kim;Keum-Oh Lee
    • Journal of the Korean Society of Propulsion Engineers
    • /
    • v.26 no.5
    • /
    • pp.1-10
    • /
    • 2022
  • For Cu-Cr alloy developed for rocket engines, estimated fatigue lives were calculated using various fatigue life prediction methods and compared with fatigue life acquired from low-cycle fatigue tests. The utilized methods for fatigue life prediction are as follows: Coffin-Manson relation, plastic/total strain energy density relations, Smith-Watson-Topper relation, Tomkins relation, and Jahed-Varvani relation. As results of estimation of fatigue lives, it satisfied within scatter band two compared to the test fatigue lives in all methods. The quantitative calculation of the deviation of predicted fatigue lives gives that the total strain energy density relation presents the best result.

Life Prediction of Low Cycle Fatigue for Ni-base Superalloy GTD111 DS at Elevated Temperature (Ni기 초내열합금 GTD111 DS의 고온 저주기 피로수명 예측)

  • Kim, Jin Yeol;Yoon, Dong Hyun;Kim, Jae Hoon;Bae, Si Yeon;Chang, Sung Yong;Chang, Sung Ho
    • Transactions of the Korean Society of Mechanical Engineers A
    • /
    • v.41 no.8
    • /
    • pp.765-770
    • /
    • 2017
  • GTD111 DS of nickel base superalloy has been used for gas turbine blades. In this study, low cycle fatigue test was conducted on the GTD111 DS alloy by setting conditions similar to the real operating environment. The low cycle fatigue tests were conducted at room temperature, $760^{\circ}C$, $870^{\circ}C$, and various strain amplitudes. Test results showed that fatigue life decreased with increasing total strain amplitude. Cyclic hardening response was observed at room temperature and $760^{\circ}C$; however, tests conducted at $870^{\circ}C$ showed cyclic softening response. Stress relaxation was observed at $870^{\circ}C$ because creep effects occurred from holding time. A relationship between fatigue life and total strain range was obtained from the Coffin-Manson method. The fratography using a SEM was carried out at the crack initiation and propagation regions.

A Study of Low Cycle Fatigue Properties in CR60,SM50Q Steel and the Weldments (CR60강, SM58Q강과 그 용접부의 저사이클 피로특성)

  • 김창주;염태동;유인석;위창욱
    • Journal of Welding and Joining
    • /
    • v.12 no.1
    • /
    • pp.73-79
    • /
    • 1994
  • Low cycle fatigue test was performed by companion specimens method to compare the properties of cyclic strain for the weldments of controlled rolling steel CR60 and welding structural steel SM58Q. And the result does not showed any difference of low cycle fatigue life between weldments. Especially, the values of coefficient of cyclic plastic strain $C_{p}$ and exponent of cyclic plastic strain $K_{p}$ of heat affected zones of CR60 steel and SM58Q steel were same. And $C_{p}$ and $K_{p}$ of CR60 steel were equal to the values of weld it means a good combination between the base metal, the heat affected zone and the weld of CR60 steel.eel.eel.

  • PDF

A Study on the Fatigue Fracture Behavior in Butt Welded Joints of Steel Structures (강구조물(鋼構造物) 맞대기 용접연결부(鎔接連結部)의 피로파괴거동(疲勞破壞擧動)에 관한 연구(硏究))

  • Park, Je Seon;Chung, Yeong Wha;Kim, Jeong Tae
    • KSCE Journal of Civil and Environmental Engineering Research
    • /
    • v.6 no.3
    • /
    • pp.53-62
    • /
    • 1986
  • For the research on the fatigue fracture behavior in the welded joints of steel structures, base metal specimens and welded ones were selected, and the direct fatigue tests were carried out. Thereafter, fatigue-life (S-N) curves, plastic strain-number of cycles (${\varepsilon}_p$-N) curve, the extrapolated fatigue-life (${\varepsilon}_p$-$N_c$) curve, and da/dN-${\Delta}K$ curves were plotted. By these results the followings were obtained. It was shown that the ratio of fatigue strength at $2{\times}10^6$ cycles of the welded specimen to that of the base metal one was 0.6, and that 0.72 for the base metal and 0.65 for the welded one were the ratio of fatigue strength at $2{\times}10^6$ cycles to yielding stress. The S-N curve for the welded specimen was separated into two sections, the low gradient section and the steep section. As this result, it was shown that the more stress became to reduce, the more the reduction of fatigue strength became to be great. It was shown that fatigue strength at $2{\times}10^6$ cycles from this case was about 83 % of that from the S-N curve plotted with one section. It was thought that the reason was that weld flaw acted greatly on the fatigue strength within the low stress range. It was shown that at the instart of crack initiation plastic strain increased abrupt1y in the case of the welded specimen more than the case of the base metal specimen, and increased abruptly in the upper stress range in both cases. It was shown that the experimental constant ${\alpha}$, 0.42, in the base metal nearly accorded with Manson-Coffin's result, but this made a great difference with the case in the welded specimen. It was thought that it was due to the abrupt change of plastic strain and the influence of weld flaw.

  • PDF