Fatigue Life and Short Crack Propagation of Turbine Rotor Steels under Variable Strain Loading

2009 ◽  
pp. 972-972-12
Author(s):  
Mori T ◽  
Toyoda H ◽  
Ohta S
Keyword(s):  
Fatigue Life ◽  
Crack Propagation ◽  
Turbine Rotor ◽  
Short Crack

The Initial Life and Short Crack Propagation Life for Low Carbon Steel Based on Dislocation Method

2018 ◽  
Vol 1145 ◽  
pp. 1-7
Author(s):  
Yuan Long Yang ◽  
Qing Chun Meng ◽  
Wei Ping Hu
Keyword(s):  
Fatigue Life ◽  
Carbon Steel ◽  
Crack Propagation ◽  
Low Carbon Steel ◽  
Short Crack ◽  
Low Carbon ◽  
Grain Sizes ◽  
Steel Material ◽  
The Relationship ◽  
Good Agreement

In the paper, the relationship between the grain size and fatigue life are studied. To specify the initial and short crack propagation life of low carbon steel material, three methods are used in the simulation. At first, the K. Tanaka’s model is introduced to calculate the fatigue life of a grain. Then, the Voronoi Diagram is used to generate the microstructure of grains. At last, a criteria to specify the short crack is proposed. Based on these methods, the numerical simulation is conducted. With the help of the process, the grain sizes are generated randomly in order to specify how grain sizes effect fatigue life. The computational results are in good agreement with the experimental data. The results show that the randomness of fatigue life is closely related to the randomness of grain sizes.

Short Crack Propagation Law and Fatigue Life Prediction Method for Structural Alloy Steel

2011 ◽  
Vol 197-198 ◽  
pp. 1400-1405
Author(s):  
Zan Zhi Wang
Keyword(s):  
Fatigue Life ◽  
Crack Initiation ◽  
Crack Propagation ◽  
Life Prediction ◽  
Prediction Method ◽  
Short Crack ◽  
Fatigue Life Prediction ◽  
Structural Alloy ◽  
Propagation Law ◽  
Alloy Steels

35CrMo and 42CrMo are the two main structural alloy steels in China, and are widely used in making important structural components subjected to heavy loads. In order to search after their fatigue properties under cyclic loads, 33 specimens were tested, under different stress level and different stress ratio from each other, to observe their crack initiation lives and the failure lives, together with the growing short crack lengths at various cycles. All tests were conducted using the MTS 810-22 material testing system. Based on the results from the tests, the relationships between the maximum stress range at crack tip and the number of cycles prior to crack initiation were determined, and in the meanwhile, the small crack propagation laws and the threshold stresses for fatigue crack initiation were obtained. In the end, the fatigue life prediction method for the two structural alloy steels was carried out.

scholarly journals Fatigue Crack Growth Analysis with Extended Finite Element for 3D Linear Elastic Material

Metals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 397
Author(s):  
Yahya Ali Fageehi
Keyword(s):  
Finite Element ◽  
Fatigue Crack ◽  
Fatigue Life ◽  
Crack Propagation ◽  
Crack Growth ◽  
Mixed Mode ◽  
Propagation Path ◽  
Loading Conditions ◽  
Extended Finite Element ◽  
Linear Elastic

This paper presents computational modeling of a crack growth path under mixed-mode loadings in linear elastic materials and investigates the influence of a hole on both fatigue crack propagation and fatigue life when subjected to constant amplitude loading conditions. Though the crack propagation is inevitable, the simulation specified the crack propagation path such that the critical structure domain was not exceeded. ANSYS Mechanical APDL 19.2 was introduced with the aid of a new feature in ANSYS: Smart Crack growth technology. It predicts the propagation direction and subsequent fatigue life for structural components using the extended finite element method (XFEM). The Paris law model was used to evaluate the mixed-mode fatigue life for both a modified four-point bending beam and a cracked plate with three holes under the linear elastic fracture mechanics (LEFM) assumption. Precise estimates of the stress intensity factors (SIFs), the trajectory of crack growth, and the fatigue life by an incremental crack propagation analysis were recorded. The findings of this analysis are confirmed in published works in terms of crack propagation trajectories under mixed-mode loading conditions.

Fatigue Behavior of Circumferentially Notched Round Bars of Austenitic Stainless Steel Under Torsional and Axial Loads

2010 ◽  
Author(s):  
Masao Itatani ◽  
Keisuke Tanaka ◽  
Isao Ohkawa ◽  
Takehisa Yamada ◽  
Toshiyuki Saito
Keyword(s):  
Fatigue Life ◽  
Stress Concentration ◽  
Crack Initiation ◽  
Crack Propagation ◽  
Fatigue Behavior ◽  
Fatigue Crack Initiation ◽  
Static Tension ◽  
Cyclic Torsion ◽  
Cyclic Tension ◽  
Crack Initiation Life

Fatigue tests of smooth and notched round bars of austenitic stainless steels SUS316NG and SUS316L were conducted under cyclic tension and cyclic torsion with and without static tension. Fatigue strength under fully reversed (R=−1) cyclic tension once increased with increasing stress concentration factor up to Kt=1.5, but it decreased from Kt=1.5 to 2.5. Fatigue life increased with increasing stress concentration under pure cyclic torsion, while it decreased with increasing stress concentration under cyclic torsion with static tension. From the measurement of fatigue crack initiation and propagation lives using electric potential drop method, it was found that the crack initiation life decreased with increasing stress concentration and the crack propagation life increased with increasing stress concentration under pure cyclic torsion. Under cyclic torsion with static tension, the crack initiation life also decreased with increasing stress concentration but the crack propagation life decreased or not changed with increasing stress concentration then the total fatigue life of sharper notched specimen decreased. It was also found that the fatigue life of smooth specimen under cyclic torsion with static tension was longer than that under pure cyclic torsion. This behavior could be explained based on the cyclic strain hardening under non-proportional loading and the difference in crack path with and without static tension.

Investigation to the Effects of Grain Misorientation on the Performance of Short Cracks

2007 ◽  
Vol 353-358 ◽  
pp. 1165-1168
Author(s):  
Yan Hai Xu ◽  
Hao Li ◽  
Li Guo
Keyword(s):  
Grain Boundary ◽  
Crack Propagation ◽  
Geometric Parameters ◽  
Short Crack ◽  
Short Cracks ◽  
Grain Orientations ◽  
Grain Misorientation

The influences of crystallographic and geometric parameters such as grain misorientation on the performance of short cracks are illustrated based on FEM in this paper. Firstly, the microstructure is simulated to account for the effects of grain misorientation on the performance of short cracks and the short cracks are initiated within the microstructure for the further investigation. The influence of grain misorientation is demonstrated by the change of neighboring grain orientations with an initiated short crack from 0° to 180°. The effects of the grain boundary on the short crack with the crack arrested or retarded are described by the crack propagation until it approached the grain boundary. The results will give more useful information such as crack arrested and retardation to the further research on the characteristics and evolution of short cracks.

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