scholarly journals Prediction of Crack Propagation Rate and Stress Intensity Factor of Fatigue and Welded Specimen with a Two-Dimensional Finite Element Method

2020 ◽  
Vol 834 ◽  
pp. 012008
Author(s):  
Y. O. Busari ◽  
A. Ariri ◽  
Y. H. P. Manurung ◽  
D. Sebayang ◽  
M. Leitner ◽  
...  
Keyword(s):  
Finite Element Method ◽  
Stress Intensity Factor ◽  
Finite Element ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Crack Propagation ◽  
Crack Propagation Rate ◽  
Propagation Rate ◽  
Two Dimensional ◽  
Dimensional Finite Element

Crack-Propagation Rate in 7075-T6 Plates Under Cyclic Tensile and Transverse Shear Loadings

1969 ◽  
Vol 91 (4) ◽  
pp. 764-769 ◽  
Author(s):  
Soushiro Iida ◽  
A. S. Kobayashi
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Crack Propagation ◽  
Sliding Mode ◽  
Crack Propagation Rate ◽  
Propagation Rate ◽  
Opening Mode ◽  
Direct Stiffness ◽  
Maximum Opening

Crack-propagation rate in 7075-T6 tension plates was determined for central cracks initially oriented in 45, 60, and 90 deg, to the width direction of the tension plates which were loaded cyclically. Opening and sliding mode of stress-intensity factors, K1 and K2, were determined by the method of direct stiffness for curved cracks generated from these initially slanted cracks. Crack-propagation rates, Δa/ΔN, were then plotted against the maximum opening mode of stress-intensity factor, K1, in the presence of sliding mode of stress-intensity factor, K2. Comparison between the corresponding crack-propagation rate in control specimens without K2 showed that the propagation rate is definitely increased in the presence of K2.

Experimental Determination of the Crack Tip Stress Intensity Factor in Integrally Stiffened Panels

2016 ◽  
Vol 1135 ◽  
pp. 112-127
Author(s):  
Carlos E. Chaves ◽  
Caio Magno de Assunção
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Crack Propagation ◽  
Crack Propagation Rate ◽  
Propagation Rate ◽  
Experimental Information ◽  
Image Correlation ◽  
Manufacturing Cost ◽  
Stiffened Panels

Integral structures offer large benefits in terms of manufacturing cost, but suffer from a lower degree of fail safety when compared to built-up structures. In order to achieve an improvement on the fatigue crack propagation (FCP), crack containment features (also known as crenellations) have been used on these structures. The source of the FCP improvement is the stress intensity factor (K) modification due to the geometry change. In the current study, an analysis about means of estimating K from the experimental information, and also to verify the K behavior while the crack propagates was performed. The study tested two AA 7475 panels, one with crenellations and another without. As the crack propagates, the K values were estimated in two forms, based on the crack propagation rate and by using a digital image correlation (DIC) system, coupled with strain gages. Based on DIC system, it was possible to evaluate the K estimation, the singularity dominated zone size and the K increase, as long as the crack propagated, for both test specimens. A comparison between the two methods was also made, and finally the use of a DIC system as a tool for estimating the K parameter was discussed.

Analysis of Crack Propagation in Fixed-Free Single-Walled Carbon Nanotube Under Tensile Loading Using XFEM

2010 ◽  
Vol 1 (4) ◽  
Author(s):  
Anand Y. Joshi ◽  
Satish C. Sharma ◽  
S. P. Harsha
Keyword(s):  
Finite Element Method ◽  
Carbon Nanotubes ◽  
Stress Intensity Factor ◽  
Finite Element ◽  
Carbon Nanotube ◽  
Stress Intensity ◽  
Fracture Mechanics ◽  
Intensity Factor ◽  
Crack Propagation ◽  
Tensile Loading

Fracture mechanics at the nanoscale level is a very complex phenomenon, whereas the macroscale fracture mechanics approach can be employed for nanoscale to simulate the effect of fracture in single-walled carbon nanotubes (SWCNTs). In this study, an extended finite element method is used to simulate crack propagation in carbon nanotubes. The concept of the model is based on the assumption that carbon nanotubes, when loaded, behave like space frame structures. The nanostructure is analyzed using the finite element method, and the modified Morse interatomic potential is used to simulate the nonlinear force field of the C–C bonds. The model has been applied to single-walled zigzag, armchair, and chiral nanotubes subjected to axial tension. The contour integral method is used for the calculation of the J-integral and stress intensity factors (SIFs) at various crack locations and dimensions of nanotubes under tensile loading. A comparative study of results shows the behavior of cracks in carbon nanotubes. It is observed that for the smaller length of nanotube, as the diameter increased, the stress intensity factor is linearly varied while for the longer nanotube, the variation in stress intensity factor is nonlinear. It is also observed that as the crack is oriented closer to the loading end, the stress intensity factor shows higher sensitivity to smaller lengths, which indicates more chances for crack propagation and carbon nanotube breakage. The SIF is found to vary nonlinearly with the diameter of the SWCNT. Also, it is found that the predicted crack evolution, failure stresses, and failure strains of the nanotubes correlate very well with molecular mechanics simulations from literature.

scholarly journals Prediction of Fatigue Crack Growth in Metallic Specimens under Constant Amplitude Loading Using Virtual Crack Closure and Forman Model

Metals ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 977
Author(s):  
Sanjin Krscanski ◽  
Josip Brnic
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Crack Propagation ◽  
Crack Closure ◽  
Crack Propagation Rate ◽  
Propagation Rate ◽  
Stress Intensity Factor Range ◽  
Small Scale ◽  
Plastic Dissipation

This paper considers the applicability of virtual crack closure technique (VCCT) for calculation of stress intensity factor range for crack propagation in standard metal specimen geometries with sharp through thickness cracks. To determine crack propagation rate and fatigue lifetime of a dynamically loaded metallic specimen, in addition to VCCT, standard Forman model was used. Values of stress intensity factor (SIF) ranges ΔK for various crack lengths were calculated by VCCT and used in conjunction with material parameters available from several research papers. VCCT was chosen as a method of choice for the calculation of stress intensity factor of a crack as it is simple and relatively straightforward to implement. It is relatively easy for implementation on top of any finite element (FE) code and it does not require the use of any special finite elements. It is usually utilized for fracture analysis of brittle materials when plastic dissipation is negligible, i.e., plastic dissipation belongs to small-scale yielding due to low load on a structural element. Obtained results showed that the application of VCCT yields good results. Results for crack propagation rate and total lifetime for three test cases were compared to available experimental data and showed satisfactory correlation.

Application of Extended Finite Element Method (XFEM) to Stress Intensity Factor Calculations

2015 ◽  
Author(s):  
Do-Jun Shim ◽  
Mohammed Uddin ◽  
Sureshkumar Kalyanam ◽  
Frederick Brust ◽  
Bruce Young
Keyword(s):  
Finite Element Method ◽  
Stress Intensity Factor ◽  
Finite Element ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Degrees Of Freedom ◽  
Extended Finite Element Method ◽  
Partition Of Unity ◽  
Extended Finite Element ◽  
Element Method

The extended finite element method (XFEM) is an extension of the conventional finite element method based on the concept of partition of unity. In this method, the presence of a crack is ensured by the special enriched functions in conjunction with additional degrees of freedom. This approach also removes the requirement for explicitly defining the crack front or specifying the virtual crack extension direction when evaluating the contour integral. In this paper, stress intensity factors (SIF) for various crack types in plates and pipes were calculated using the XFEM embedded in ABAQUS. These results were compared against handbook solutions, results from conventional finite element method, and results obtained from finite element alternating method (FEAM). Based on these results, applicability of the ABAQUS XFEM to stress intensity factor calculations was investigated. Discussions are provided on the advantages and limitations of the XFEM.

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