scholarly journals Stress Intensity Factor calculation from displacement fields

2017 ◽  
Vol 11 (41) ◽  
pp. 269-276 ◽  
Author(s):  
S. Beretta ◽  
L. Patriarca ◽  
S. Rabbolini
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Displacement Fields

The Importance of the Mode II Term on the Analysis of Angled Cracks in Unidirectional Carbon Fiber Composites

2021 ◽  
Author(s):  
Jacob Biddlecom ◽  
Garrett J. Pataky
Keyword(s):  
Stress Intensity Factor ◽  
Regression Analysis ◽  
Stress Intensity ◽  
Carbon Fiber ◽  
Intensity Factor ◽  
Fiber Composites ◽  
Shear Loading ◽  
Mode Ii ◽  
Carbon Fiber Composites ◽  
Displacement Fields

Abstract Carbon fiber reinforced polymers (CFRP) have been used in many high-performance applications where strength to weight ratio is an important characteristic. The goal of this research was to analyze the effects of Mode II, also known as shear loading, on the displacement fields surrounding a crack for unidirectional carbon fiber composites. Tensile and fatigue experiments were conducted on angled unidirectional CFRP coupled with digital image correlation (DIC) to analyze the full field displacement. Angled CFRP cracks experienced mixed mode loading which required addition insight due to the complex stresses on the fiber/matrix interface. The experimental displacement fields acquired from DIC were used as inputs for an anisotropic regression analysis to determine the mode I and mode II stress intensity factor ranges. The results from the regression analysis were used to predict the displacement fields around a crack. When comparing the experimental results with the predicted results, the inclusion of Mode II increased the agreement between predicted and experimental displacement fields around a crack tip for two different fiber orientation angles. Crack growth rate analysis and analytical stress intensity factor ranges were used to expand on the agreement of the results as well as bring to light CFRP specific fracture mechanisms that lead to disagreements.

scholarly journals A Continuum Theory of Crack Shielding in Ceramics

1987 ◽  
Vol 54 (1) ◽  
pp. 54-58 ◽  
Author(s):  
M. Ortiz
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Constitutive Model ◽  
Closed Form ◽  
Applied Stress ◽  
Continuum Theory ◽  
Displacement Fields ◽  
Stress Strain ◽  
Macroscopic Crack

A phenomenological constitutive model is proposed which aims at describing the overall effect of microfracture in ceramics. Based on this model, the asymptotic stress, strain, and displacement fields at the tip of a stationary macroscopic crack are determined in closed form. The near-tip stress-intensity factor is computed and observed to be significantly smaller than the applied stress-intensity factor even for moderate amounts of damage.

scholarly journals The transition from subsonic to supersonic cracks

2015 ◽  
Vol 373 (2038) ◽  
pp. 20140122 ◽  
Author(s):  
Chris Behn ◽  
M. Marder
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Low Frequency ◽  
Continuum Theory ◽  
Vertical Displacement ◽  
Displacement Fields ◽  
Lattice Systems ◽  
Crack Motion ◽  
Rayleigh Wave Speed

We present the full analytical solution for steady-state in-plane crack motion in a brittle triangular lattice. This allows quick numerical evaluation of solutions for very large systems, facilitating comparisons with continuum fracture theory. Cracks that propagate faster than the Rayleigh wave speed have been thought to be forbidden in the continuum theory, but clearly exist in lattice systems. Using our analytical methods, we examine in detail the motion of atoms around a crack tip as crack speed changes from subsonic to supersonic. Subsonic cracks feature displacement fields consistent with a stress intensity factor. For supersonic cracks, the stress intensity factor disappears. Subsonic cracks are characterized by small-amplitude, high-frequency oscillations in the vertical displacement of an atom along the crack line, while supersonic cracks have large-amplitude, low-frequency oscillations. Thus, while supersonic cracks are no less physical than subsonic cracks, the connection between microscopic and macroscopic behaviour must be made in a different way. This is one reason supersonic cracks in tension had been thought not to exist.

Damage accumulation near a hole under low cycle fatigue proceeding from measurements of local deformation response

2020 ◽  
Vol 86 (10) ◽  
pp. 46-55
Author(s):  
S. I. Eleonsky ◽  
Yu. G. Matvienko ◽  
V. S. Pisarev ◽  
A. V. Chernov
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Damage Accumulation ◽  
Stress Ratio ◽  
Low Cycle Fatigue ◽  
Accumulation Process ◽  
Stress Range ◽  
Cycle Fatigue ◽  
Deformation Response

A new destructive method for quantitative determination of the damage accumulation in the vicinity of a stress concentrator has been proposed and verified. Increase of damage degree in local area with a high level of the strain gradient was achieved through preliminary low-cycle pull-push loading of plane specimens with central open holes. The above procedure is performed for three programs at the same stress range (333.3 MPa) and different stress ratio values 0.33, – 0.66 and – 1.0, and vice versa for two programs at the same stress ratio – 0.33 and different stress range 333.3 and 233.3 MPa. This process offers a set of the objects to be considered with different degree of accumulated fatigue damages. The key point of the developed approach consists in the fact that plane specimens with open holes are tested under real operation conditions without a preliminary notching of the specimen initiating the fatigue crack growth. The measured parameters necessary for a quantitative description of the damage accumulation process were obtained by removing the local volume of the material in the form of a sequence of narrow notches at a constant level of external tensile stress. External load can be considered an amplifier enhancing a useful signal responsible for revealing the material damage. The notch is intended for assessing the level of fatigue damage, just as probe holes are used to release residual stress energy in the hole drilling method. Measurements of the deformation response caused by local removing of the material are carried out by electronic speckle-pattern interferometry at different stages of low-cycle fatigue. The transition from measured in-plane displacements to the values of the stress intensity factor (SIF) and the T-stress was carried out on the basis of the relations of linear fracture mechanics. It was shown that the normalized dependences of the stress intensity factor on the durability percentage for the first notch (constructed for four programs of cyclic loading with different parameters), reflect the effect of the stress ratio and stress range of the loading cycle on the rate of damage accumulation. The data were used to obtain the explicit form of the damage accumulation function that quantitatively describes damage accumulation process. The functions were constructed for different stress ratios and stress ranges.

A new type of cracks adding to Griffith–Irwin cracks

2019 ◽  
Vol 485 (2) ◽  
pp. 162-165
Author(s):  
V. A. Babeshko ◽  
O. M. Babeshko ◽  
O. V. Evdokimova
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Crack Tip ◽  
Stress Concentrations ◽  
New Type

The distinctions in the description of the conditions of cracking of materials are revealed. For Griffith–Irwin cracks, fracture is determined by the magnitude of the stress-intensity factor at the crack tip; in the case of the new type of cracks, fracture occurs due to an increase in the stress concentrations up to singular concentrations.

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