A model for predicting primary creep damage in axial cracked cylinders—I. Theory

1992 ◽  
Vol 43 (4) ◽  
pp. 615-627 ◽  
Author(s):  
F.W. Brust ◽  
B.N. Leis
Keyword(s):  
Creep Damage ◽  
Primary Creep

scholarly journals Creep Damage Repair of a Nickel-Based Single Crystal Superalloy Based on Heat Treatment

Metals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 623
Author(s):  
Xiaoyan Wang ◽  
Meng Li ◽  
Yuansheng Wang ◽  
Chengjiang Zhang ◽  
Zhixun Wen
Keyword(s):  
Heat Treatment ◽  
Single Crystal ◽  
Creep Damage ◽  
Primary Creep ◽  
Single Crystal Superalloy ◽  
Secondary Creep ◽  
Creep Life ◽  
Phase Coarsening ◽  
Damage Repair ◽  
Creep Time

Taking nickel-based single crystal superalloy DD6 as the research object, different degrees of creep damage were prefabricated by creep interruption tests, and then the creep damage was repaired by the restoration heat treatment system of solid solution heat treatment and two-stage aging heat treatment. The results show that with the creep time increasing, the alloy underwent microstructure evolution including γ′ phase coarsening, N-type rafting and de-rafting. After the restoration heat treatment, the coarse rafted γ′ phase of creep damaged specimens dissolved, precipitated, grew up, and became cubic again. Except for the specimens with creep interruption of 100 h, the γ′ phase can basically achieve the same arrangement as the γ′ phase of the original sample. The comparison of the secondary creep test shows that the steady-state creep stage of the test piece after the restoration heat treatment is relatively increased, and the total creep life can reach the same level as the primary creep life. The high temperature creep properties of the tested alloy are basically recovered, and the restoration heat treatment effect is good.

Effects of Primary and Secondary Creep Formulations on API 579-1 Residual Life Evaluation

2018 ◽  
Author(s):  
Lorenzo Scano ◽  
Luca Esposito
Keyword(s):  
Constitutive Equation ◽  
Residual Life ◽  
Creep Damage ◽  
Primary Creep ◽  
Secondary Creep ◽  
Time To Rupture ◽  
Life Evaluation ◽  
Omega Method ◽  
Material Constitutive Equation ◽  
Rate Formulation

A sound material constitutive equation is crucial for the residual life evaluation of pressure components operating in the creep range. In a previous work [1], the authors investigated how a secondary creep formulation encompassing both the dislocational and the diffusional range influences the assessment of damage according to API 579-1 [2] within the whole component stress range. In the present paper the work has been extended in order to include the effects of primary creep in the constitutive equation for the ASTM A335 P22 low-alloy steel used for the manufacturing of the HRSG header whose welded details were previously investigated. The creep damage was first calculated according to API 579-1 Section 10 via inelastic, time-dependent FEA and the Larson-Miller approach (LMP) with code-defined, minimum time-to-rupture data. This led to a first reckoning of the primary creep impact in terms of API 579-1 residual life for the components under evaluation. The API 579-1 time-to-rupture was then assessed with a detailed stress analysis implementing the Omega Method and its creep strain rate formulation. The obtained results were finally compared to those previously determined through the LMP procedure and the different creep correlations (secondary and primary+secondary).

Creep ruptures of AISI 347 austenitic stainless steel foils at elevated temperature of 750 ℃

2015 ◽  
Vol 231 (6) ◽  
pp. 516-522
Author(s):  
H Osman ◽  
FM Nor ◽  
YM Hamdan ◽  
MN Tamin
Keyword(s):  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Creep Damage ◽  
Primary Creep ◽  
Second Phase ◽  
Precipitate Coarsening ◽  
Second Phase Particles ◽  
The Matrix ◽  
Dislocation Movement ◽  
Rupture Properties

The creep rupture properties of AISI 347 austenitic stainless steel foil used in compact recuperators have been evaluated at 750 ℃ in the stress range of 54–221 MPa to establish baseline behavior for its extended use. The creep curve of the foil shows that the primary creep stage is brief and creep life is dominated by tertiary creep deformation with rupture lives in the range 3–433 h. Power law relationship was obtained between the minimum creep rate and the applied stress with stress exponent value of n = 4.25. The creep damage tolerance parameter for specimen tested at 750 ℃ and 54 MPa indicates that creep fracture takes place by precipitate coarsening mechanism. Nucleation of voids mainly occurs at second-phase particles (Cr23C6 carbides). The improvement in strength is attributed to the precipitation of fine niobium carbides in the matrix which prevents dislocation movement of the microstructure.

Creep Properties and Damage Study of Ni-Based Alloy C276 at High Temperature

2011 ◽  
Vol 328-330 ◽  
pp. 1143-1148 ◽  
Author(s):  
Xue Ping Mao ◽  
Qi Guo ◽  
Sheng Yuan Zhang ◽  
Su Yang Hu ◽  
Dao Gang Lu ◽  
...  
Keyword(s):  
High Temperature ◽  
Stress Level ◽  
Creep Damage ◽  
Primary Creep ◽  
Type I ◽  
High Temperature Creep ◽  
Fuel Cladding ◽  
Creep Tests ◽  
Temperature Creep ◽  
Creep Characteristic

One of the two challenges about Supercritical Water-Cooled Reactor is material, especially for the fuel cladding. High temperature creep tests of Ni-based alloy C276, one of the candidate materials for the fuel cladding, were carried out at 650°C~750°C, with stress 130MPa~430MPa. The effects of temperature and stress on creep were investigated, the change laws of steady state creep rate with stress and time to rupture were analysed, and creep damage factors were separately calculated based on Kachanov’s formula and Norton’s formula. The results indicate that there exist two types of primary creep characteristics in C276: Type I creep characteristic at lower stress level and Type II at higher stress level respectively. C276 shows excellent high temperature creep resistance, and Kachanov’s damage factors D vs normalized time are basically coincident at 650°C, 700°C and 750°C. The damage obtained by Norton’s formula starts at about 40% of lifetime, and the damage factors calculated by Kachanov’s formula are relatively conservative.

A new model for characterizing primary creep damage

1992 ◽  
Vol 54 (1) ◽  
pp. 45-63 ◽  
Author(s):  
F. W. Brust ◽  
B. N. Leis
Keyword(s):  
Creep Damage ◽  
Primary Creep ◽  
New Model

TEM of grain growth and phase transformations during creep of SCS-6 silicon carbide fibers

1995 ◽  
Vol 53 ◽  
pp. 350-351
Author(s):  
L. A. Giannuzzi ◽  
C. A. Lewinsohn ◽  
C. E. Bakis ◽  
R. E. Tressler
Keyword(s):  
Silicon Carbide ◽  
Creep Rate ◽  
Vapor Deposition ◽  
Chemical Vapor ◽  
Primary Creep ◽  
Excess Carbon ◽  
Silicon Carbide Fibers ◽  
Sic Fiber ◽  
Carbon Core ◽  
Grain Width

The SCS-6 SiC fiber is a 142 μm diameter fiber consisting of four distinct regions of βSiC. These SiC regions vary in excess carbon content ranging from 10 a/o down to 5 a/o in the SiC1 through SiC3 region. The SiC4 region is stoichiometric. The SiC sub-grains in all regions grow radially outward from the carbon core of the fiber during the chemical vapor deposition processing of these fibers. In general, the sub-grain width changes from 50nm to 250nm while maintaining an aspect ratio of ~10:1 from the SiC1 through the SiC4 regions. In addition, the SiC shows a <110> texture, i.e., the {111} planes lie ±15° along the fiber axes. Previous has shown that the SCS-6 fiber (as well as the SCS-9 and the developmental SCS-50 μm fiber) undergoes primary creep (i.e., the creep rate constantly decreases as a function of time) throughout the lifetime of the creep test.

scholarly journals Microstructural evolution during high-temperature tensile creep at 1,500°C of a MoSiBTiC alloy

2020 ◽  
Vol 39 (1) ◽  
pp. 136-145 ◽  
Author(s):  
Sojiro Uemura ◽  
Shiho Yamamoto Kamata ◽  
Kyosuke Yoshimi ◽  
Sadahiro Tsurekawa
Keyword(s):  
Grain Size ◽  
Grain Boundaries ◽  
Microstructural Evolution ◽  
Grain Boundary Sliding ◽  
Primary Creep ◽  
Tensile Creep ◽  
Tertiary Creep ◽  
Continuous Dynamic Recrystallization ◽  
Continuous Dynamic ◽  
Creep Regime

AbstractMicrostructural evolution in the TiC-reinforced Mo–Si–B-based alloy during tensile creep deformation at 1,500°C and 137 MPa was investigated via scanning electron microscope-backscattered electron diffraction (SEM-EBSD) observations. The creep curve of this alloy displayed no clear steady state but was dominated by the tertiary creep regime. The grain size of the Moss phase increased in the primary creep regime. However, the grain size of the Moss phase was found to remarkably decrease to <10 µm with increasing creep strain in the tertiary creep regime. The EBSD observations revealed that the refinement of the Moss phase occurred by continuous dynamic recrystallization including the transformation of low-angle grain boundaries to high-angle grain boundaries. Accordingly, the deformation of this alloy is most likely to be governed by the grain boundary sliding and the rearrangement of Moss grains such as superplasticity in the tertiary creep regime. In addition, the refinement of the Moss grains surrounding large plate-like T2 grains caused the rotation of their surfaces parallel to the loading axis and consequently the cavitation preferentially occurred at the interphases between the end of the rotated T2 grains and the Moss grains.

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