scholarly journals Modeling Onset of Tertiary Creep for Rupture Life Prediction

2020 ◽  
Author(s):  
Nathan Beets
Keyword(s):  
Life Prediction ◽  
Rupture Life ◽  
Tertiary Creep

scholarly journals Creep-Rupture Life Prediction for 9Cr-1Mo-Nb-V Weld Metal

2015 ◽  
Vol 55 (10) ◽  
pp. 2189-2197
Author(s):  
Ayumu Miyakita ◽  
Ken Yamashita ◽  
Genichi Taniguchi ◽  
Tetsuo Suga
Keyword(s):  
Weld Metal ◽  
Life Prediction ◽  
Rupture Life ◽  
Creep Rupture

Time to Initiation of Tertiary Creep Property of Grade 91 Steels

2016 ◽  
Author(s):  
Kazuhiro Kimura ◽  
Kota Sawada
Keyword(s):  
Creep Rate ◽  
Minimum Creep Rate ◽  
Rupture Life ◽  
Creep Rupture ◽  
Tertiary Creep ◽  
Time To Initiation ◽  
Wide Range ◽  
Minimum Stress ◽  
Grade 91

Creep deformation property of Grade 91 steels was analyzed on more than 370 creep curves over a wide range of time to rupture from about 10 hours to beyond 100,000 hours, in order to evaluate time to 1% total strain, time to minimum creep rate and time to initiation of tertiary creep. Time to initiation of tertiary creep was assessed as a 0.2% offset with a slope of minimum creep rate. It is difficult to determine time to minimum creep rate precisely, which is a basis of 0.2% offset, however, it has been confirmed that time to initiation of tertiary creep is not sensitive to the time when the creep rate indicates minimum value. Life ratio of 1% total strain time against creep rupture time increases up to about 60% with increase of temperature and decrease of stress. Life ratio of time to initiation of tertiary creep also tends to increase with decrease in stress. However, change of it is in a range of 50 to 60% of creep rupture life over a wide range of creep rupture life from 10 hours to 100,000 hours, and it is not sensitive to creep test temperature. Over a range of temperatures from 500 to 600°C and up to about 200,000 hours, a temperature and time-dependent stress intensity limit, St is controlled by 67% of minimum stress to rupture. However, a difference between 67% of minimum stress to rupture and 80% of minimum stress to initiation of tertiary creep decreases with increases in temperature and time, and both values approach each other in the long-term beyond about 100,000 hours at 600°C. In the long-term beyond about 10,000 hours at 650°C, St is controlled by 80% of minimum stress to initiation of tertiary. The stable life fraction of time to initiation of tertiary creep establish a reliability of a temperature and time-dependent stress intensity limit value.

scholarly journals The rupture life prediction in cold dwell fatigue of Ti-6Al-4V based on the creep deformation

2020 ◽  
Vol 321 ◽  
pp. 11071
Author(s):  
Yutaro Ota ◽  
Tomomichi Ozaki ◽  
Keiji Kubushiro.O
Keyword(s):  
Creep Deformation ◽  
Minimum Creep Rate ◽  
Life Prediction ◽  
Dwell Time ◽  
Room Temperature ◽  
Rupture Life ◽  
Ti Alloys ◽  
Dwell Fatigue ◽  
Strain Change ◽  
Long Time

Titanium a lloys have been found that the fatigue strength of Ti alloys decreases due to cold dwell fatigue (CDF) at room temperature. Ti and Ti alloys generate creep deformation at room temperature (T/Tm = 0.15). Thus, it is considered that creep affects the reduction in fatigue life in CDF tests. This research intends to clarify the effects of long time dwell under tensile stress and rupture life prediction from the view of creep deformation in CDF characteristics of Ti-6Al-4V. Rupture cycle decreased with increase of dwell time. Additionally, lower limit of rupture life ratio “NCDF/NLCF” was defined from rupture in creep test if it was assumed that creep test was extremely long time dwell CDF test. When strain change in whole dwell time was extracted in CDF tests, strain change was like creep curves and minimum creep rate changed depending on dwell time. Minimum creep rate was calculated by the formula based on experimental results, and then rupture time was calculated by Monkman-grant relationship. All of rupture cycle predictions were in factor of 2. Therefore, rupture cycle and time can be calculated if dwell time is known in CDF tests.

Remaining Life Prediction of Ethylene Cracking Tubes Under Carburizing and Creep Joint Action

2015 ◽  
Author(s):  
Luowei Cao ◽  
Chenyang Du ◽  
Shanshan Shao ◽  
Guoshan Xie
Keyword(s):  
Prediction Model ◽  
Oxide Layer ◽  
Transition Layer ◽  
Life Prediction ◽  
Rupture Life ◽  
Base Material ◽  
Stress Rupture ◽  
Remaining Life ◽  
Carburized Layer ◽  
Life Prediction Model

Remaining life prediction model of ethylene cracking tubes (ECT) suffered joint damage of carburizing and creep have been set up in this study. Materials employed in this work were cut from Cr35Ni45-type radiation section of ECT. Layered structure, including oxide layer, carburized layer and carburizing transition layer, have been found from inside to outside of the tubes in scanning electron microscopy (SEM) images. However, no abrupt transition occurs between carburized layer and the base material. Both carburizing related layers caused the damage of the tubes, together with oxide layer. In order to facilitate the life prediction accuracy, carburizing transition layer was considered as a part of the damage layer. The remaining life of ECT was investigated by review of the microstructure and stress-rupture tests. Stress-rupture tests have been finished to obtained the rupture life of the tubes at 1000°C, 1040°C, 1080°C and 1125°C under six loading stresses (10MPa, 15MPa, 17MPa, 20MPa, 25MPa and 30MPa, respectively). In the results of stress-rupture tests, the combination of testing temperature at 1040°C and loading stress with 15MPa got the highest rupture life of 830h. Finally, a modified Larson-Miller remaining life prediction model of ECT, considering the comprehensive effect of carburizing and creep damage, has been established.

Remnant Life Prediction of Service-Exposed 12Cr1MoV Superheater Tube in Power Plant

2013 ◽  
Vol 791-793 ◽  
pp. 382-385
Author(s):  
Xin Wei Zhu ◽  
Hong Hui Cheng ◽  
Mei Hua Shen ◽  
Jin Ping Pan
Keyword(s):  
High Temperature ◽  
Tensile Test ◽  
Life Prediction ◽  
Rupture Life ◽  
Tensile Creep ◽  
Working Temperature ◽  
Working Stress ◽  
Superheater Tube ◽  
High Temperature Tensile ◽  
The Relationship

Tensile test at ambient temperature, tensile test at high temperature and high temperature tensile creep test were carried out before remnant life prediction. According to the high temperature tensile creep test data, the relationship between working stress, working temperature and rupture life was obtained by MATLAB surface fitting tool. In order to obtain the temperature field and stress field of the superheater tube, ANSYS software was used. Then, the remnant life of the superheater tube was predicted by the extrapolating method and the relationship between working stress, working temperature and rupture life.

scholarly journals Numerical Prediction of Creep Rupture Life of Ex-Service and As-Received Grade 91 Steel at 873 K

2021 ◽  
Vol 18 (3) ◽  
pp. 8845-8858
Author(s):  
IMAM UL FERDOUS ◽  
NASRUL AZUAN ALANG ◽  
Juliawati Alias ◽  
Suraya Mohd Nadzir
Keyword(s):  
Finite Element ◽  
Stress State ◽  
Creep Strain ◽  
Life Prediction ◽  
Rupture Life ◽  
Creep Rupture ◽  
Rupture Time ◽  
Damage State ◽  
Grade 91 ◽  
Grade 91 Steel

Infallible creep rupture life prediction of high  temperature steel needs long hours of robust  testing over a domain of stress and temperature. A substantial amount of effort has been made to  develop alternative methods to reduce the time  and cost of testing. This study presents a finite  element analysis coupled with a ductility based  damage model to predict creep rupture time  under the influence of multiaxial stress state of  ex-service and as-received Grade 91 steel at 873 K. Three notched bar samples with different  acuity ratios of 2.28, 3.0 and 4.56 are modelled in commercial Finite Element (FE) software,  ABAQUS v6.14 in order to induce different stress  state levels at notch throat area and investigate  its effect on rupture time. The strain-based  ductility exhaustion damage approach is  employed to quantify the damage state. The  multiaxial ductility of the material that is  required to determine the damage state is  estimated using triaxiality-ductility Cock and  Ashby relation. Further reduction of the ductility  due to the different creep mechanisms over a  short and long time is also accounted for in the  prediction. To simulate the different material conditions: ex-service and as-received material,  different creep coefficients (A) have been  assigned in the numerical modelling. In the case  of ex-service material, using mean best fit data  of minimum creep strain rate gives a good life  prediction, while for new material, the lower  bound creep coefficient should be employed to  yield a comparable result with experimental  data. It is also notable that ex-service material  deforms faster than as-received material at the  same stress level. Moreover, higher acuity  provokes damage to concentrate on the small  area around the notch, which initiates higher  rupture life expectancy. It also found out that,  the stress triaxiality and the equivalent creep  strain influence the location of damage initiation  around the notch area.

scholarly journals Research on Creep Rupture Life Prediction for 2.25Cr-1Mo-V Weld Metal

2012 ◽  
Vol 30 (3) ◽  
pp. 228-237 ◽  
Author(s):  
Tetsuo SUGA ◽  
Takeshi NAKAGAWA ◽  
Ayumu MIYAKITA ◽  
Ken YAMASHITA ◽  
Mikihiro SAKATA
Keyword(s):  
Weld Metal ◽  
Life Prediction ◽  
Rupture Life ◽  
Creep Rupture
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