A New Evaluation Method to Calculate Crack Initiation Limit with Modified Crack Aspect Ratios in Notched Specimen of Carbon Steels

2014 ◽  
Vol 563 ◽  
pp. 80-84 ◽  
Author(s):  
Takahiro Matsueda
Keyword(s):  
Aspect Ratio ◽  
Crack Initiation ◽  
Evaluation Method ◽  
Notch Root ◽  
Fatigue Crack Initiation ◽  
Carbon Steels ◽  
Notched Specimen ◽  
Aspect Ratios ◽  
Key Factor ◽  
Initiation Stress

Aspect ratio is a key factor to calculate stress intensity factor (SIF) K using fracture mechanics. While cracks are approximated to be semi-circle or semi-ellipse for simply evaluation, their shapes are changed by stress concentration source. In this study, a new method to modify aspect ratio of a crack at a notch root is proposed. Modified aspect ratio in this method succeeded to decrease prediction error of fatigue crack initiation stress, σw1 which was calculated using experimental value.

Effects of Grain Size on Crack Aspect Ratio and Crack Initiation Limit in Notched Specimen of Austenitic Stainless Steel (JIS SUS304)

2014 ◽  
Vol 620 ◽  
pp. 438-442 ◽  
Author(s):  
Takahiro Matsueda
Keyword(s):  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Aspect Ratio ◽  
Crack Initiation ◽  
Fatigue Crack Initiation ◽  
Simple Calculation ◽  
New Method ◽  
Notched Specimen ◽  
Key Factor ◽  
Initiation Stress

Aspect ratio is a key factor to calculate stress intensity factor (SIF) K using fracture mechanics. Cracks are approximated to be semi-circle or semi-ellipse in simple calculation, however, their empirical shapes are changed by stress concentration. In this study, in order to calculate K simply and precisely, a new method to predict fatigue crack initiation stress, σw1 of austenitic stainless steel with modified aspect ratio is discussed. The new method succeeded to predict σw1 within 20% error from empirical values using average austenite grain sizes.

Distribution of Aspect Ratio of Fatigue Crack at Notch Root Depending on Crack Initiation Point of Annealed Steel, JIS S45C

2017 ◽  
Vol 893 ◽  
pp. 240-244 ◽  
Author(s):  
Takahiro Matsueda ◽  
Masayuki Ishida ◽  
Koshiro Mizobe
Keyword(s):  
Stress Concentration ◽  
Aspect Ratio ◽  
Crack Initiation ◽  
Notch Root ◽  
Strength Prediction ◽  
Key Factors ◽  
Civil Structures ◽  
Initiation Point ◽  
Crack Shape ◽  
The Relationship

Aspect ratio of crack is one of key factors of fatigue strength prediction in engineering design and civil structures using fracture mechanics. Their empirical shapes are changed by stress concentration. However, it was not clear how stress concentration affects empirical results including crack shape and size. In this study, in order to investigate the relationship between stress concentration and crack geometry, the aspect ratio of cracks at notch root was observed and discussed. We succeeded to capture two important relationships which are between stress concentration and crack shape, and between crack initiation point at notch root and crack shape, respectively.

Stress-Intensity Factor for a Short Edge-Notched Specimen Subjected to Three-Point Loading

1967 ◽  
Vol 89 (1) ◽  
pp. 7-12 ◽  
Author(s):  
H. T. Akao ◽  
A. S. Kobayashi
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Aspect Ratio ◽  
Intensity Factor ◽  
Numerical Technique ◽  
Bending Moment ◽  
Mapping Function ◽  
Notched Specimen ◽  
Short Edge ◽  
Aspect Ratios

Stress-intensity factors for a short edge-notched specimen with an aspect ratio of appoximately 2.7:1 and subjected to three-point loading were obtained by using Bowie’s numerical technique of expanding a mapping function. Numerical relations between the mapping function, aspect ratios, and crack depths of different specimens as well as numerical difficulty in convergence of the procedure are discussed. The results are compared with the nondimensionalized experimental results obtained by Kies, et al., for a larger aspect ratio of 8:1. The proportionality factor between bending moment and stress-intensity factor was approximately 10 percent lower than the corresponding factor for Kies’ specimen and is in substantial agreement with Gross’ results.

Field Effects in Fatigue Crack Initiation: Long Life Fatigue Strength

1991 ◽  
Vol 113 (2) ◽  
pp. 188-194 ◽  
Author(s):  
S. D. Sheppard
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Fatigue Crack ◽  
Crack Initiation ◽  
Notch Root ◽  
Fatigue Crack Initiation ◽  
Stress Fields ◽  
Complex Geometries ◽  
The Finite Element Method ◽  
Long Life

This work is focused on explaining observed fatigue crack initiation behavior in notched members in terms of the stress state in a finite volume at the notch root. In principle, this is no different than the work of several other researchers. What is different is the manner in which the stress fields were predicted; namely using the finite element method. By using this approach, no approximations were necessary as to the form of the stress field at the notch root. This implies that this approach is extendable to complex geometries and to the finite life regime where plastic flow is expected at the notch root.

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