scholarly journals Notch-acuity effects on the fracture toughness of saline ice

1991 ◽  
Vol 15 ◽  
pp. 230-235 ◽  
Author(s):  
S.J Defranco ◽  
Y. Wei ◽  
J. P. D. Dempsey
Keyword(s):  
Fracture Toughness ◽  
Notch Root ◽  
Crack Tip ◽  
Constant Thickness ◽  
Razor Blade ◽  
Mean Values ◽  
Fracture Testing ◽  
Apparent Fracture Toughness ◽  
Band Saw ◽  
Image Position

Dynamic ocean-induced loading of ice has recently prompted interest in the fatigue strength of ice and, consequently, aspects of the fracture testing of ice need to be examined. One aspect in fracture testing, the effects of notch acuity on the apparent fracture toughness (KQ) of saline ice, was investigated in this study using four groups of single-edge notched-bend specimens with different crack-(or notch-) root radii, fabricated by four different methods; namely, drilling a small hole of two different radii at the crack tip, cutting a crack with a band saw and using a hand-held razor blade to scribe a sharp crack. For this study, tests were performed on saline ice using one crack length and orientation, constant thickness and constant temperature (−25°C). The mean values and the standard deviations of the apparent fracture toughness of the specimens with blunt notches were higher than those with sharp cracks. The results presented in a plot of fracture toughness versus where ρ is the crack-tip radius, provide a preliminary estimate of the required notch acuity for fracture-toughness testing of saline ice.

scholarly journals Notch-acuity effects on the fracture toughness of saline ice

1991 ◽  
Vol 15 ◽  
pp. 230-235 ◽  
Author(s):  
S.J Defranco ◽  
Y. Wei ◽  
J. P. D. Dempsey
Keyword(s):  
Fracture Toughness ◽  
Notch Root ◽  
Crack Tip ◽  
Constant Thickness ◽  
Razor Blade ◽  
Mean Values ◽  
Fracture Testing ◽  
Apparent Fracture Toughness ◽  
Band Saw ◽  
Image Position

Dynamic ocean-induced loading of ice has recently prompted interest in the fatigue strength of ice and, consequently, aspects of the fracture testing of ice need to be examined. One aspect in fracture testing, the effects of notch acuity on the apparent fracture toughness (KQ) of saline ice, was investigated in this study using four groups of single-edge notched-bend specimens with different crack-(or notch-) root radii, fabricated by four different methods; namely, drilling a small hole of two different radii at the crack tip, cutting a crack with a band saw and using a hand-held razor blade to scribe a sharp crack. For this study, tests were performed on saline ice using one crack length and orientation, constant thickness and constant temperature (−25°C). The mean values and the standard deviations of the apparent fracture toughness of the specimens with blunt notches were higher than those with sharp cracks. The results presented in a plot of fracture toughness versuswhere ρ is the crack-tip radius, provide a preliminary estimate of the required notch acuity for fracture-toughness testing of saline ice.

scholarly journals Crack-fabrication techniques and their effects on the fracture toughness and CTOD for fresh-water columnar ice

1991 ◽  
Vol 37 (126) ◽  
pp. 270-280 ◽  
Author(s):  
Y. Wei ◽  
S.J. DeFranco ◽  
J. P. Dempsey
Keyword(s):  
Fracture Toughness ◽  
Notch Root ◽  
Crack Tip ◽  
Mean Value ◽  
Microplastic Deformation ◽  
Unstable Fracture ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Apparent Fracture Toughness ◽  
Image Position

AbstractThe effects of notch acuity (crack-tip sharpness) on the fracture toughness of S2 ice were investigated using six groups of single-edge-notched-bend (SENB) specimens with different crack (or notch) root radii fabricated by six different methods. The mean value and standard deviations of the apparent fracture-toughness values KQ of the specimens with blunt notches were significantly higher than those of the specimens with sharp cracks. The results presented in a plot of fracture toughness versus , where p is the crack-tip radius, provide an estimate of the required notch acuity for fracture-toughness testing. The microstructural features in the immediate vicinity of the crack tip and the crack-tip geometry govern the magnitude of the apparent fracture toughness of the ice. The crack-tip-opening-displacement (CTOD) measured in this study indicates the existence of microplastic deformation in the vicinity of the crack tip at the initiation of unstable fracture.

scholarly journals Crack-fabrication techniques and their effects on the fracture toughness and CTOD for fresh-water columnar ice

1991 ◽  
Vol 37 (126) ◽  
pp. 270-280 ◽  
Author(s):  
Y. Wei ◽  
S.J. DeFranco ◽  
J. P. Dempsey
Keyword(s):  
Fracture Toughness ◽  
Notch Root ◽  
Crack Tip ◽  
Mean Value ◽  
Microplastic Deformation ◽  
Unstable Fracture ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Apparent Fracture Toughness ◽  
Image Position

Abstract The effects of notch acuity (crack-tip sharpness) on the fracture toughness of S2 ice were investigated using six groups of single-edge-notched-bend (SENB) specimens with different crack (or notch) root radii fabricated by six different methods. The mean value and standard deviations of the apparent fracture-toughness values K Q of the specimens with blunt notches were significantly higher than those of the specimens with sharp cracks. The results presented in a plot of fracture toughness versus , where p is the crack-tip radius, provide an estimate of the required notch acuity for fracture-toughness testing. The microstructural features in the immediate vicinity of the crack tip and the crack-tip geometry govern the magnitude of the apparent fracture toughness of the ice. The crack-tip-opening-displacement (CTOD) measured in this study indicates the existence of microplastic deformation in the vicinity of the crack tip at the initiation of unstable fracture.

The Effects of Crack Growth History on Fracture Toughness

2019 ◽  
Author(s):  
M. A. Probert ◽  
H. E. Coules ◽  
C. E. Truman ◽  
M. Hofmann
Keyword(s):  
Fracture Toughness ◽  
Finite Element ◽  
Crack Growth ◽  
Parametric Study ◽  
Finite Element Modelling ◽  
Crack Tip ◽  
High Yield ◽  
Element Modelling ◽  
History Effects ◽  
Apparent Fracture Toughness

Abstract The introduction of cracks into loaded versus unloaded components has a significant effect on the apparent fracture toughness within finite element modelling. The history effects of crack introduction can be beneficial to defect assessment procedures that do not consider prior plasticity specifically from crack introduction. It is assumed that as strain energy is released due to plastic deformation during crack formation a reduction in the energy available for crack propagation under fracture conditions is experienced. This can be characterized by the formation of a plastic wake behind the crack tip and leads to significant increases in load at critical J and other crack growth parameters for modelling situations. However experimental evidence validating this apparent fracture toughness increase are needed. A beneficial increase in apparent fracture toughness can prolong the life of components that might be taken out of service prematurely if history effects are not considered. This paper discusses a series of experimental and modelling approaches that have been taken to assess the magnitude of the benefit in increase of apparent fracture toughness by the manipulation of crack introduction history effects. An initial parametric study of material properties on the effect of introducing cracks into loaded and unloaded components indicates that most benefit be derived from high hardness, high yield materials such as Aluminum 7000 series alloys. Further work has been carried out with experimental C(T) specimens of Aluminum Alloy 7475 T7351. Cracks were introduced by fatigue into the samples. One set of specimens was fatigued with a low mean load and the other with a high mean load, this was achieved by keeping a consistent ΔKI between specimens and changing the load ratio one set of specimens. Fracture test results indicate that the influence of prior plasticity on fracture initiation is much subtler in experimental trials than in the finite element model. Crack growth resistance curves and neutron diffraction results measuring the residual stress created ahead of the crack tip by this method are be discussed and contrasted with the parametric study and finite element modelling of the two different crack introduction scenarios.

Fracture Mechanics Study on the Effects of Various Notch Radii by Using FE Analysis

2015 ◽  
Author(s):  
Zalikha Murni Abdul Hamid ◽  
Keun-Hyung Bae ◽  
Gyo-Geun Youn ◽  
Dae-Young Lee ◽  
Yun-Jae Kim ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Fracture Mechanics ◽  
Fracture Strain ◽  
Notch Root ◽  
Damage Model ◽  
Fe Analysis ◽  
Experiment Data ◽  
Apparent Fracture Toughness ◽  
Notch Root Radius ◽  
Plane Strain Deformation

This paper predicts the effects of notch root radius on the ductile fracture behavior of the structure through evaluation based on fracture mechanics concept. To understand the effects of notch radii on structure, FE analysis of J-integral for plane strain deformation fields with various size of notches were predicted. The fracture toughness of the specimens with various notch radii were determined by stress modified fracture strain damage model FE simulation that was established based on notched bar tensile test data. The simulated results were validated by comparison with the experiment data. Findings show that the value of apparent fracture toughness increases with the increase in the notch radii. Therefore, indicates the increase in the resistance to the crack propagation. Similar trend can be shown for both C(T) and M(T) specimen. Thus, shows that the proposed method can be used to obtain effects of various notch radii.

Does the Biaxial Loading Affect the Apparent Fracture Toughness (Kc)?

2019 ◽  
Author(s):  
Chentong Chen ◽  
Hanbin Xiao ◽  
Yuh J. Chao ◽  
Poh-Sang Lam
Keyword(s):  
Fracture Toughness ◽  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Test Data ◽  
Biaxial Loading ◽  
Stress Component ◽  
Crack Tip ◽  
Apparent Fracture Toughness ◽  
Biaxial Load

Abstract From linear elastic fracture mechanics (LEFM), it is well accepted that only the singular stress near the crack tip contributes to the fracture event through the crack tip stress intensity factor K. In the biaxial loading, the stress component that adds to the T-stress at the crack tip, affects only the second term in the Williams’ series solution around the crack tip. Therefore, it is generally believed that biaxial load does not change the apparent fracture toughness or the critical stress intensity factor (Kc). This paper revisited several specimen geometries under biaxial loading with finite element method. The sources of discrepancy between the theory and the test data were identified. It was found that the ideal biaxial loading would not be achieved for typical fracture specimens with finite geometry. Comparison to available test data shows that, while the biaxial load could affect the apparent fracture toughness, the contribution is relatively small.

Does the Biaxial Loading Affect the Apparent Fracture Toughness (KC)?

2020 ◽  
Vol 142 (3) ◽  
Author(s):  
Chentong Chen ◽  
Hanbin Xiao ◽  
Yuh J. Chao ◽  
Poh-Sang Lam
Keyword(s):  
Fracture Toughness ◽  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Test Data ◽  
Biaxial Loading ◽  
Stress Component ◽  
Crack Tip ◽  
Apparent Fracture Toughness ◽  
Biaxial Load

Abstract From linear elastic fracture mechanics (LEFM), it is well accepted that only the singular stress near the crack tip contributes to the fracture event through the crack tip stress intensity factor K. In the biaxial loading, the stress component that adds to the T-stress at the crack tip, affects only the second term in the Williams' series solution around the crack tip. Therefore, it is generally believed that biaxial load does not change the apparent fracture toughness or the critical stress intensity factor (Kc). This paper revisited several specimen geometries under biaxial loading with finite element method. The sources of discrepancy between the theory and the test data were identified. It was found that the ideal biaxial loading would not be achieved for typical fracture specimens with finite geometry. Comparison to available test data shows that, while the biaxial load could affect the apparent fracture toughness, the contribution is relatively small.

Residual Stress and Constraint Effects on Fracture in the Transition Temperature Regime

2008 ◽  
Author(s):  
K. S. Lee ◽  
A. H. Sherry ◽  
M. R. Goldthorpe
Keyword(s):  
Fracture Toughness ◽  
Residual Stress ◽  
Residual Stresses ◽  
Numerical Study ◽  
Notch Root ◽  
Crack Tip ◽  
Pressure Vessel Steel ◽  
Vessel Steel ◽  
Low Constraint ◽  
Crack Tip Constraint

This paper presents the results of a combined experimental and numerical study aimed at quantifying the influence of self-balancing residual stresses on the fracture toughness constraint benefit of a ferritic pressure vessel steel tested in the cleavage fracture regime. Tests were performed on standard and pre-compressed, high constraint, compact-tension (CT) and low constraint, single-edge-notched tension (SENT) specimens at a temperature close to the Master Curve reference temperature T0. Pre-compression is undertaken prior to pre-cracking to establish a residual stress across the uncracked ligament, which is highly tensile at the pre-crack notch root and balanced by compressive stresses further ahead of the notch. The pre-crack is subsequently introduced into material ahead of the notch, within the tensile residual stress region, specimen by electro-discharge machining and fatigue. The tests demonstrate an influence of tensile residual stresses on the apparent fracture toughness properties for both CT and SENT specimens. The tests on low constraint specimens illustrate the constraint benefit on cleavage toughness for this material, and the influence of residual stresses in reducing this benefit. The paper shows how the observed behaviour can be quantified through using two parameter fracture mechanics. Here, the J-integral is determined by taking full account of the influence of preloading on the crack driving force. Both the elastic-T-stress and the elastic-plastic Q-stress are calculated and demonstrated as constraint indexing parameters. The results demonstrate a reduction in constraint benefit for cracks located within highly bending residual stress fields. Thus, when exploring any possible benefit in fracture toughness due to crack tip constraint, it is critical that the combined influence of the primary and secondary stresses on crack tip constraint be taken fully into account.

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