Creep crack growth simulation under transient stress fields

1988 ◽  
Vol 19 (4) ◽  
pp. 829-835 ◽  
Author(s):  
D. S. Wilkinson ◽  
S. B. Biner
Keyword(s):  
Crack Growth ◽  
Creep Crack Growth ◽  
Stress Fields ◽  
Transient Stress ◽  
Growth Simulation ◽  
Creep Crack ◽  
Crack Growth Simulation

The Linkage Between Microscopic Cavitation Damage and Macroscopic Crack Growth

2000 ◽  
Vol 122 (3) ◽  
pp. 279-282 ◽  
Author(s):  
P. R. Onck ◽  
B.-N. Nguyen ◽  
E. van der Giessen
Keyword(s):  
Crack Growth ◽  
Power Law ◽  
Scale Up ◽  
Creep Crack Growth ◽  
Stress Fields ◽  
Process Window ◽  
Macroscopic Scale ◽  
Cavitation Damage ◽  
Creep Crack ◽  
Random Nucleation

This paper is concerned with a recent microstructural approach to model creep crack growth. The model spans three different length scales, from the scale of individual cavities, through the grain scale up to the macroscopic scale of cracks in components and test specimens. In order to study the initial stages of creep crack growth, we consider a near-tip process window in which a large number of grains are represented discretely. This window is surrounded by a standard continuum. Macroscopic specimen dimensions and loading configuration are communicated to this near-tip region by applying boundary conditions in accordance with the asymptotic stress fields for power-law creeping materials. The paper presents some novel results of this type of modeling obtained using remote higher-order crack-tip fields. Specific attention is focused on the effect of random nucleation and grain deformation on nonsymmetric crack growth from either initially sharp or blunt cracks. [S0094-4289(00)00703-9]

Determination of Creep Crack Growth Threshold by Experiments under Elevated Temperature with Pre-Stressed Specimens

2014 ◽  
Vol 891-892 ◽  
pp. 371-376
Author(s):  
Hao Liu ◽  
Rui Bao ◽  
Bin Jun Fei
Keyword(s):  
Growth Rate ◽  
Crack Growth ◽  
Testing Machine ◽  
Creep Crack Growth ◽  
Compact Tension ◽  
Test Method ◽  
Stress Fields ◽  
Creep Crack ◽  
Growth Threshold

A novel test method is presented in this paper for determination of the creep crack growth threshold. In this method, a wedge is placed in the notch of a standard compact tension (CT) specimen with a pre-crack, which provides an evaluable stress fields characterized with stress intensity factor (K) at the crack tip. Then the specimen is kept in the test temperature for a certain time. The creep crack growth threshold of the material at a given temperature can be obtained by extrapolating the curves of the crack growth rate vs.Kin the double logarithmic coordinates. Since it does not need mechanical testing machine and several specimens can be tested simultaneously, the proposed method is economical in both costs and time. Tests on a nickel-based powder metallurgy superalloy FGH97 are conducted using this method at 600°C, 650°C and 750°C, which indicate its feasibility.

Estimation of Creep Crack Growth Properties Using Circumferential Notched Round Bar Specimen for 12CrWCoB Rotor Steel

2005 ◽  
Vol 297-300 ◽  
pp. 397-402
Author(s):  
Je Chang Ha ◽  
Joon Hyun Lee ◽  
Masaaki Tabuchi ◽  
A.Toshimitsu Yokobori Jr.
Keyword(s):  
Crack Growth ◽  
Axial Stress ◽  
Creep Crack Growth ◽  
Turbine Rotor ◽  
Rotor Steel ◽  
Creep Ductility ◽  
Crack Growth Behaviour ◽  
Creep Crack ◽  
Round Bar ◽  
Growth Properties

Most heat resisting materials in structural components are used under multi-axial stress conditions and under such conditions ductile materials often exhibit brittle manner and low creep ductility at elevated temperature. Creep crack initiation and growth properties are also affected by multi-axial stress and it is important to evaluate these effects when laboratory data are applied to structural components. Creep crack growth tests using circumferential notched round bar specimens are a simple method to investigate multi-axial stress effects without using complicated test facilities. Creep crack growth tests have been performed using a 12CrWCoB turbine rotor steel. In order to investigate the effects of multi-axial stress on creep crack growth properties, the tests were conducted for various notch depths at 650°C. The circumferential notched round bar specimen showed brittle crack growth behaviour under multi-axial stress conditions. Creep crack growth rate was characterized in terms of the C* parameter. A 12CrWCoB turbine rotor steel has been tested using circumferential notched round bar specimens with different multi-axiality. Circumferential notched round bar specimens show increased brittle creep crack growth behaviour due to the multi-axial stress condition. Creep crack growth properties could be predicted by allowing for the decrease of creep ductility under multi-axial conditions.

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