A photoelastic and numeric study of the stress field in the vicinity of two interacting cracks: Stress intensity factors, T-stresses and higher order terms

2020 ◽  
Author(s):  
Vadim S. Dolgikh ◽  
Larisa V. Stepanova
Keyword(s):  
Stress Intensity ◽  
Stress Field ◽  
Stress Intensity Factors ◽  
Higher Order ◽  
Intensity Factors ◽  
Higher Order Terms

scholarly journals The asymptotic structure of transient elastodynamic fields at the tip of a stationary crack

1994 ◽  
Vol 446 (1926) ◽  
pp. 1-13 ◽  
Keyword(s):  
Stress Intensity ◽  
Dynamic Loading ◽  
Stress Intensity Factors ◽  
Higher Order ◽  
Transient Effects ◽  
Intensity Factors ◽  
Stationary Crack ◽  
Asymptotic Structure ◽  
Higher Order Terms ◽  
Correction Terms

The asymptotic structure of the transient elastodynamic near-tip fields around a stationary crack is investigated for all three fracture modes. The transient fields are obtained as the sum of their quasi-static counterparts and corresponding transient correction terms, in terms of variable-separable expansions. By allowing the coefficients of terms in the quasi-static expansion to deviate from their quasi-static restrictions, the correction terms are shown to be the particular solutions of a set of first order (for mixed mode I and II) or second order (for mode III) ordinary differential equations with constant coefficients and non-homogeneous terms involving only sine and cosine functions of the independent variable. It is found that the transient effects of dynamic loading on the near-tip fields are to alter the universal angular variations of the quasi-static field quantities for the fifth and higher order terms in their variable-separable expansions; thus the first four terms in the expansions have the same angular variations under both quasi-static and dynamic loading conditions. This seems to suggest that transient effects on the crack-tip fields are in general less severe for a stationary crack than for a propagating crack where only the first two terms in the expansions hold the same angular variations under both steady-state and transient crack growth conditions. Furthermore, the transient higher order terms for a stationary crack do not depend on the time-rate of the stress intensity factors; in fact, they only relate to the even order time-derivatives of the instantaneous values of the coefficients of the terms in the quasi-static expansions. This is also in contrast with the case of transient crack propagation where the time rates of the dynamic stress intensity factors play important roles in the higher order transient terms. Explicit expressions for the transient near-tip stress and displacement fields are provided.

The Dynamic Three-Parameter Method for Determination of Stress-Intensity Factors From Dynamic Isochromatic Crack-Tip Stress Patterns

1980 ◽  
Vol 47 (4) ◽  
pp. 795-800 ◽  
Author(s):  
H. P. Rossmanith
Keyword(s):  
Stress Intensity ◽  
Stress Intensity Factors ◽  
Correction Term ◽  
Crack Tip ◽  
Higher Order ◽  
Parameter Method ◽  
Intensity Factors ◽  
Higher Order Terms ◽  
Stress Patterns

Correction methods for the determination of dynamic stress-intensity factors from isochromatic crack-tip stress patterns are developed within the framework of a Westergaard-type stress-function analysis where higher-order terms of the series expansions of the stress functions are retained. The addition σox to the extensional stress σx, is regarded as a first correction term, and the far-field correction term which is proportional to r1/2 is referred to as the β-correction. The β-term represents effects that are due to particular loading systems and situations including finite specimen boundaries. The associated method to determine K can be termed a three-parameter method since it contains K, α, and β as parameters. The correction methods, i.e., velocity correction and higher-order term corrections, permit modification of the “static” crack velocity versus stress-intensity factor (c-K) relationship by correcting the static K for the influence of crack speed and higher-order terms. The results show that both corrections assist the interpretation of current photoelastic c-K-data even though the crack speeds do not exceed one third of the shear wave speed.

Use of automated photoelasticity to determine stress intensity factors of bimaterial joints

2005 ◽  
Vol 40 (8) ◽  
pp. 785-800 ◽  
Author(s):  
B Zuccarello ◽  
S Ferrante
Keyword(s):  
Stress Intensity ◽  
Stress Field ◽  
Stress Intensity Factors ◽  
External Loading ◽  
Intensity Factors ◽  
Singular Stress ◽  
Full Field ◽  
Basic Law ◽  
Singular Stress Field ◽  
Element Approach

A new systematic experimental procedure has been developed to obtain the stress intensity factors governing the singular stress field that occurs near the intersection between the interface and free edges of bimaterial joints. A preliminary theoretical study of the singular stress field is carried out by the well-known Airy stress function method. The obtained stress laws are properly combined with the basic law of photoelasticity in order to define a procedure that permits the zone dominated by the singularity to be located and the stress intensity factors (SIFs) to be computed on the basis of full field data provided from automated photoelasticity. In particular, a systematic error analysis is used to determine the model zone where the experimental data have to be collected in order to obtain accurate SIF evaluation. As an example, the proposed method is applied to determine the SIFs of various aluminium/ PSM-1 specimens under different external loading conditions using Fourier transform photoelasticity. The experimental results have been compared to those obtained by an independent procedure, based on a boundary element approach, in order to validate the accuracy of the proposed procedure.

Effects of the Length of Carbon Nanotube (CNT) in CNT Reinforced Composites

2006 ◽  
Vol 324-325 ◽  
pp. 855-858
Author(s):  
Q. Wang ◽  
X. F. Sun ◽  
Kimihiro Ozaki
Keyword(s):  
Fracture Toughness ◽  
Carbon Nanotube ◽  
Stress Intensity ◽  
Stress Field ◽  
Stress Intensity Factors ◽  
Reinforced Composites ◽  
Intensity Factors ◽  
Singular Stress ◽  
Singular Stress Field

In this paper, the strength of the singular stress field near the ends of the CNTs in composites was analyzed to clarify the effects of the CNT length on stress filed in the CNT reinforced composites when studying the fracture toughness. The singular stress field was separated into two types of singularities, symmetric and skew-symmetric, near the ends of CNTs according to the deformation and loading types. The stress intensity factors of the singular stress field were calculated for these two types of singularities. The effects of the CNT length in CNT reinforced composites on these stress intensity factors were investigated.

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