FATIGUE LIFE AND CRACK PROPAGATION UNDER RANDOM AND PROGRAMMED LOAD SEQUENCES

1965 ◽  
pp. 403-428 ◽  
Author(s):  
J. SCHIJVE
Keyword(s):  
Fatigue Life ◽  
Crack Propagation

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.

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.

Experimental and theoretical fatigue-crack propagation lives of variously notched plates

1974 ◽  
Vol 9 (2) ◽  
pp. 61-66 ◽  
Author(s):  
R A Smith ◽  
K Jerram ◽  
K J Miller
Keyword(s):  
Fatigue Life ◽  
Crack Propagation ◽  
Finite Element Analyses ◽  
Intensity Factors ◽  
Complex Profile ◽  
Propagation Law ◽  
Theoretical Predictions ◽  
Life Predictions ◽  
Theoretical Results

The fatigue lives of variously notched plates have been determined theoretically and experimentally. Theoretical predictions of fatigue lives involved the determination of stress-intensity factors from finite-element analyses. By invoking a crack propagation law, fatigue-life predictions were made for four specimens. Fatigue experiments were conducted on four notched plates subjected to end load plus bending. Comparison with theoretical results shows that the experimental lives were greater by factors of 1.30 to 1.54. These results are most satisfactory since (1) a safe prediction of fatigue life has been made for a complex profile subjected to non-simple loading conditions, and (2) a theoretical elastic analysis has sufficed for a situation involving plastic strains.

Study on the Influence of Crack Growth Behavior on Fatigue Life in Simulated Reactor Coolant Environment of Different Temperature

2020 ◽  
Author(s):  
Tatsuru Misawa ◽  
Takanori Kitada ◽  
Takao Nakamura
Keyword(s):  
High Temperature ◽  
Fatigue Life ◽  
Crack Propagation ◽  
Crack Growth ◽  
Crack Propagation Rate ◽  
Propagation Rate ◽  
Growth Behavior ◽  
Crack Growth Behavior ◽  
Reactor Coolant ◽  
Different Temperatures

Abstract It has been clarified that the fatigue life is decreased in the fatigue test of high-temperature and high-pressure water that simulates PWR reactor coolant environment compared to that in the atmosphere. Temperature, strain rates, dissolved oxygen concentration, etc. affect the decrease of fatigue life. The influence of crack growth behavior on the fatigue life of Type 316 austenitic stainless steel [1] in simulated PWR reactor coolant environment of different temperatures was investigated in this study. Fatigue tests were conducted under different temperatures (200°C and 325°C) in a simulated PWR reactor coolant environment with interrupting, and cracks generated on the specimen surface were observed with two-step replica method. From the results of observation, the influence of crack growth behavior in different temperatures on the fatigue life was clarified. As a result, it was confirmed that the decrease of the fatigue life due to high temperature is mainly caused by the acceleration of crack propagation rate in the depth direction by the increase of crack coalescence frequency due to the increase of crack initiation number and crack propagation rate in the length direction.

Effect of Micro Structure on Fatigue Characteristics of Lead Free Solder Joints

2011 ◽  
Author(s):  
Takahiro Akutsu ◽  
Qiang Yu
Keyword(s):  
Grain Size ◽  
Fatigue Crack ◽  
Fatigue Life ◽  
Solder Joint ◽  
Crack Propagation ◽  
Solder Joints ◽  
Lead Free ◽  
Lead Free Solder ◽  
Micro Structure ◽  
Free Solder

This paper presents the influence of the micro structure on the crack propagation in lead free solder joint. The author’s group have studied the Manson-Coffin’s law for lead free solder joint by using the isothermal fatigue test and FEM analytical approaches to establish the practicable evaluation of thermal fatigue life of solder joints, for example, for the Sn-Cu-Ni solder, because this solder is attracted from the aspect of the decrease of solder leach in the flow process and material cost. However, even if the same loading is given to the solder joints of BGA test piece, there was a large dispersion in the fatigue life. Even though the effect of the shape difference has been considered, the range of the dispersion could not been explained sufficiently. In the study, the fatigue crack propagation modes in the solder joints were investigated, and an internal fatigue crack mode and an interfacial fatigue crack mode were confirmed. And the tendency of a shorter on fatigue life in the interfacial fatigue mode was confirmed. To clarify the mechanism of these fatigue crack modes, the crystal grain size in the solder joints was investigated before the fatigue test and also after the test. Furthermore, the verification of the mechanism using FEM models considering the crystal grain size was carried out. First of all, each element in FEM models matching to the average crystal grain size was made. Second, the inelastic strain ranges in each FEM models were studied. As a result, it was shown that the influence of the crude density of the crystal grain to the fatigue crack progress can be evaluated. In addition, the micro structure of the solder joint of large-scale electronic devices is observed, and FEM model was made based on the observation result. As a result, it was shown that the influence of the directionality with the crystal grain to the fatigue crack progress can be evaluated.

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