Fatigue Crack Growth Analysis of Interacting Subsurface Cracks Using S-Version FEM

Author(s):  
Ayaka Suzuki ◽  
Akiyuki Takahashi ◽  
Masanori Kikuchi

Fatigue crack growth simulation using the s-version finite element method (FEM) is presented. Two subsurface cracks are aligned in the depth direction of a specimen, and is subjected to a cyclic tension-tension loading. The fatigue crack growth behavior of the cracks is directly simulated using our automatic fatigue crack growth simulation system with the s-version FEM. Along with the direct simulation, proximity rules for crack combinations and surface cracks are used in the s-version FEM simulation. The numerical results with and without the application of the proximity rules are compared to make a validation of the application of the proximity rules in the evaluation of fatigue crack growth behaviors and residual fatigue life. The results clearly illustrate that the proximity rules accelerate the fatigue crack growth rate, and provide us with a substantially conservative evaluation. Finally, the proximity rules are slightly modified for making better approximation of combining and surface cracks. It can be found that the new proximity rules are able to give a fatigue crack growth evaluation closer to the direct simulation results.

2017 ◽  
Vol 741 ◽  
pp. 82-87 ◽  
Author(s):  
Akiyuki Takahashi ◽  
Ayaka Suzuki ◽  
Masanori Kikuchi

In this paper, fatigue crack growth simulation of interacting subsurface cracks using the s-version finite element method (SFEM) is presented. In order to evaluate the accuracy and reliability of the proximity rules published by the ASME, during the fatigue crack growth simulations, the subsurface cracks are approximated to either a single elliptical crack or semi-elliptical surface crack in accordance with the proximity rules. Then, the proximity rules are slightly modified for improving the accuracy and reliability. The results of crack depth evolution calculated by the SFEM with the use of the new proximity rules suggest that the approximation to deep cracks drastically improves the accuracy of the fatigue crack growth evaluation. Thus, the approximation to deep cracks must be a promising approach for having better evaluation of fatigue crack growth of subsurface cracks.


Author(s):  
Masanori Kikuchi ◽  
Yoshitaka Wada ◽  
Chikako Ohdama

Mixed mode fatigue tests are conducted using surface cracked specimen. Slant surface cracked specimens are made where crack angle is 15°, 30°, 45° and 60°. It is shown that factory roof is made at deepest point of surface crack due to ΔKIII, and crack growth rate decreases by the factory roof. Fatigue crack growth is simulated using S-version FEM (Finite Element Method) using crack growth criteria. It is shown that conventional crack growth criteria are not available to predict fatigue crack growth with factory roof. In this study, modified criterion for the prediction of crack growth rate is proposed. By using this criterion, fatigue crack growth simulation is conducted, and results are compared with those of experiments and discussed.


2003 ◽  
Vol 2003 (0) ◽  
pp. 307-308
Author(s):  
Toshiyuki MESHII ◽  
Kenichi ISHIHARA ◽  
Katsuhiko WATANABE

2019 ◽  
Vol 11 (4) ◽  
pp. 547-555
Author(s):  
Shuji Tomaru ◽  
Akiyuki Takahashi

Purpose Since the most of structures and structural components suffers from cyclic loadings, the study on the fatigue failure due to the crack growth has a great importance. The purpose of this paper is to present a three-dimensional fatigue crack growth simulation of embedded cracks using s-version finite element method (SFEM). Using the numerical results, the validity of the fitness-for-service (FFS) code evaluation method is verified. Design/methodology/approach In this paper, three-dimensional fatigue crack propagation analysis of embedded cracks is performed using the SFEM. SFEM is a numerical analysis method in which the shape of the structure is represented by a global mesh, and cracks are modeled by local meshes independently. The independent global and local meshes are superimposed to obtain the displacement solution of the problem simultaneously. Findings The fatigue crack growth of arbitrary shape of cracks is slow compared to that of the simplified circular crack and the crack approximated based on the FFS code of the Japan Society of Mechanical Engineers (JSME). The results tell us that the FFS code of JSME can provide a conservative evaluation of the fatigue crack growth and the residual life time. Originality/value This paper presents a three-dimensional fatigue crack growth simulation of embedded cracks using SFEM. Using this method, it is possible to apply mixed mode loads to complex shaped cracks that are closer to realistic conditions.


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