Brittle and Ductile Creep Rupture Life Prediction of 1CrMoV Steel Notched Thick Plates

1990 ◽  
Vol 112 (3) ◽  
pp. 225-232 ◽  
Author(s):  
K. Ando ◽  
Y. Takeda ◽  
K. Takezoe
Keyword(s):  
Crack Initiation ◽  
Damage Mechanics ◽  
Notch Root ◽  
Rupture Life ◽  
Prediction Method ◽  
Creep Rupture ◽  
Material Behavior ◽  
Analytical Prediction ◽  
Crack Initiation Life ◽  
Creep Rupture Test

An analytical prediction method of brittle and ductile creep rupture life of 1CrMoV steel notched thick plate is proposed. Rupture time is evaluated as a sum of crack initiation life ti and crack growth life tp. In the case of ductile creep at high stresses, ti is evaluated by the creep deformation criteria. In addition, in the case of brittle creep at low stresses, ti is evaluated by Kachanov’s damage mechanics theory. Materials constants in Kachanov’s theory can be determined by the relatively short-term creep rupture test of notched specimen, etc., according to the present method. Creep rupture test, interrupted creep test, and micro-structural observation, have been used, which can explain the variety of material behavior, i.e., notch weakening at low stresses and notch strengthening at high stresses. In addition, in this analysis the analytically estimated creep crack initiation life corresponds to the time to creep void initiation just inside the notch root.

CDM Approach Applied to Crack Initiation and Propagation under Variable Amplitude

2016 ◽  
Vol 829 ◽  
pp. 55-60
Author(s):  
Jin Yang Chu ◽  
Jian Xing Mao
Keyword(s):  
Crack Initiation ◽  
Damage Accumulation ◽  
Damage Mechanics ◽  
Low Cycle Fatigue ◽  
Fatigue Crack Initiation ◽  
Continuum Damage Mechanics ◽  
Cycle Fatigue ◽  
Variable Amplitude ◽  
Crack Initiation Life ◽  
Initiation Stage

In this paper, the low cycle fatigue crack initiation life was regarded as a process of damage accumulation and a damage accumulation model was established based on the Continuum Damage Mechanics. By the model, we analyzed how the variable amplitude applied at the crack initiation stage influenced the low cycle fatigue life of high temperature materials. With the parameters of GQGH4169 alloy at room temperature, we determined the specific values of damage parameters by finite element method and numerical analysis method. Then, the crack initiation life predictions were carried out. The results show that using this approach can not only predict the crack initiation life of CT specimen accurately, but also reflect a definite influence of variable amplitude on the crack propagation life combining with the Paris Law, and the test costs reduced consequently.

Crack Initiation Life Model of Stiffened Plates Based on Damage Mechanics

2014 ◽  
Vol 904 ◽  
pp. 508-512
Author(s):  
Hong Wang ◽  
Ping Yang ◽  
Jun Lin Deng ◽  
Qin Dong
Keyword(s):  
Fatigue Crack ◽  
Crack Initiation ◽  
Plastic Strain ◽  
Fatigue Damage ◽  
Damage Evolution ◽  
Damage Mechanics ◽  
Low Cycle Fatigue ◽  
Fatigue Crack Initiation ◽  
Stiffened Plate ◽  
Crack Initiation Life

Based on the continuum damage mechanics theory, according to the development of the fatigue damage evolution equation, and combining the interaction coefficient of stiffener and plate, with plastic strain as the control quantity of damage evolution, the stiffened plate low cycle fatigue damage mechanics model is established, and the calculation method of the fatigue crack initiation life is obtained. This method for the initiation life of fatigue crack is divided into the life before the damage and the life of the damage evolution. The model results are compared with those of the finite element results. Conclusions show that the model can reflect the regularity of axial plastic strain evolution of stiffened plate, and can be directly used for fatigue loads analysis under the mechanism of initiation life.

Thermomechanical Fatigue Behavior of a Directionally Solidified Ni-Base Superalloy

2005 ◽  
Vol 127 (3) ◽  
pp. 325-336 ◽  
Author(s):  
M. M. Shenoy ◽  
A. P. Gordon ◽  
D. L. McDowell ◽  
R. W. Neu
Keyword(s):  
Crack Initiation ◽  
Fatigue Behavior ◽  
Fatigue Tests ◽  
Material Behavior ◽  
Directionally Solidified ◽  
Creep Tests ◽  
Physically Based ◽  
Estimation Scheme ◽  
Crack Initiation Life ◽  
Base Superalloy

A continuum crystal plasticity model is used to simulate the material behavior of a directionally solidified Ni-base superalloy, DS GTD-111, in the longitudinal and transverse orientations. Isothermal uniaxial fatigue tests with hold times and creep tests are conducted at temperatures ranging from room temperature (RT) to 1038°C to characterize the deformation response. The constitutive model is implemented as a User MATerial subroutine (UMAT) in ABAQUS (2003, Hibbitt, Karlsson, and Sorensen, Inc., Providence, RI, v6.3) and a parameter estimation scheme is developed to obtain the material constants. Both in-phase and out-of-phase thermo-mechanical fatigue tests are conducted. A physically based model is developed for correlating crack initiation life based on the experimental life data and predictions are made using the crack initiation model.

Notch Root Displacement (NRD) Approach to Predict Crack Initiation Life of Notched Specimen in High-Temperature Multiaxial Low Cycle Fatigue

1990 ◽  
Vol 112 (4) ◽  
pp. 429-434 ◽  
Author(s):  
Hiroshi Umeda ◽  
Masao Sakane ◽  
Masateru Ohmani
Keyword(s):  
High Temperature ◽  
Crack Initiation ◽  
Low Cycle Fatigue ◽  
Notch Root ◽  
Three Dimensional ◽  
Fem Analysis ◽  
Cycle Fatigue ◽  
Notched Specimen ◽  
Crack Initiation Life ◽  
Three Dimensional Finite Element

This paper describes the notch root displacement (NRD) approach to assess the crack initiation life of notched specimens in high-temperature multiaxial low cycle fatigue. Two and three-dimensional finite element method (FEM) analyses were made to estimate the local displacement at the notch root in tension, torsion, and combined tension/torsion. From the FEM analysis, a simple equation which expresses the intensity of the notch root displacement was derived and it was applied to the experimental data. The equation well correlates the crack initiation life of the notched specimen in high-temperature multiaxial low cycle fatigue.

A Study on the Creep Rupture Life Estimation of Internally Pressurized Welded Pipe Joints

2006 ◽  
Author(s):  
Tetsuo Teramae
Keyword(s):  
Crack Growth ◽  
Welded Joint ◽  
Rupture Life ◽  
Creep Rupture ◽  
Coarse Grained ◽  
Experimental Result ◽  
Fine Grained ◽  
Pipe Joints ◽  
Creep Rupture Test ◽  
Welded Pipe

A study had been conducted to establish the precise method estimating the creep rupture life of welded steam pipe joints used for thermal power plants. Firstly, basic creep data of 2.25CrlMo low alloy steel, such as rupture time, minimum creep strain rate, and creep crack growth rate, had been obtained on mother material, fine-grained heat affected zone (HAZ), coarse-grained HAZ, and weld metal. Secondly, internally pressurized creep rupture test had been conducted on the pipe specimens of mother material, seam welded joint and girth welded joint. Whereas girth welded pipe joints showed longer lives than those of mother material pipes, seam welded pipe joints showed shorter rupture lives. To clarify the effect of fine-grained HAZ on the rupture life of the seam welded pipe joint, an analytical study had been performed taking the difference of creep deformation between fine-grained HAZ and mother material into account. The analytical creep rupture life had agreed quite well with experimental one. Finally, internally pressurized creep rupture test had been conducted on the specimens of the seam welded pipe joints with a semi-elliptical notch introduced along the outer HAZ of weld line. Creep rupture life of these specimens was calculated as the sum of crack incubation time and crack growth time. It was shown that the calculated creep rupture life had agreed quite well with the experimental result.

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