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.

Determination of Stress Intensity Factors for an Interfacial Crack in a Bi-Material by Digital Photoelasticity

2004 ◽  
Vol 1-2 ◽  
pp. 139-146
Author(s):  
M. Ravichandran ◽  
K. Ramesh
Keyword(s):  
Stress Intensity ◽  
Stress Field ◽  
Stress Intensity Factors ◽  
Interfacial Crack ◽  
Intensity Factors ◽  
Singular Stress ◽  
Singular Stress Field ◽  
Digital Photoelasticity ◽  
Least Squares Approach

The main sources of error in the determination of stress intensity factors (SIFs) for an interface crack in a bi-material by conventional photoelasticity are the measurement of the positional co-ordinates of the data point and the fringe order. In the present work, use of two digital photoelasticity methods for collecting these data is discussed. SIFs are evaluated using constant radius method and a least squares approach based on the singular stress field equation. The need for developing a multi-parameter stress field solution for evaluating SIF is highlighted.

An improved boundary element formulation for calculating stress intensity factors: Application to aerospace structures

1987 ◽  
Vol 22 (4) ◽  
pp. 203-207 ◽  
Author(s):  
M H Aliabadi ◽  
D P Rooke ◽  
D J Cartwright
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Boundary Element ◽  
Stress Intensity Factors ◽  
Crack Tip ◽  
Stress Fields ◽  
Element Formulation ◽  
Intensity Factors ◽  
Singular Stress ◽  
Singular Stress Field

In order to compute stress intensity factors accurately, the standard boundary element method is modified to take explicit account of the singularity in the stresses at a crack-tip. The known expansion terms of the crack tip displacement and stress fields are subtracted to remove the numerical difficulties associated with the representation of a singular stress field at the crack-tip. Hence the accuracy of calculation is much improved, without appreciably increasing the amount of computation involved. Furthermore, the stress intensity factor is directly obtained as a part of a solution and no extrapolations are required. The improved formulation is applied to a configuration, which is representative of a part of the wing in a civil transport aeroplane. This configuration consists of a pair of circular cut-outs (supply ports) near to which smaller holes exist; these small holes are particularly susceptible to cracking.

scholarly journals Crack Paralleling an Interface Between Dissimilar Materials

1987 ◽  
Vol 54 (4) ◽  
pp. 828-832 ◽  
Author(s):  
J. W. Hutchinson ◽  
M. E. Mear ◽  
J. R. Rice
Keyword(s):  
Stress Intensity ◽  
Interface Crack ◽  
Stress Intensity Factors ◽  
Dissimilar Materials ◽  
Complex Stress ◽  
External Loading ◽  
Universal Relation ◽  
Intensity Factors ◽  
Elastic Solids ◽  
Complex Stress Intensity Factor

A crack paralleling a bonded plane interface between two dissimilar isotropic elastic solids is considered. When the distance of the crack from the interface is small compared to the crack length itself and to other length scales characterizing the geometry, a simple universal relation exists between the Mode I and Mode II stress intensity factors and the complex stress intensity factor associated with the corresponding problem for the crack lying on the interface. In other words, if the influence of external loading and geometry on the interface crack is known, then this information can immediately be used to generate the stress intensity factors for the sub-interface crack. Conditions for cracks to propagate near and parallel to, but not along, an interface are derived.

Determination of the Stress Intensity Factors for Axisymmetric Cylindrical Interface Crack by an Eigenvalue Method

2009 ◽  
Author(s):  
Lin Weng ◽  
Zengliang Gao ◽  
Xiaogui Wang
Keyword(s):  
Finite Element ◽  
Stress Intensity ◽  
Interface Crack ◽  
Stress Intensity Factors ◽  
Stress Singularity ◽  
Intensity Factors ◽  
Singular Stress ◽  
Cylindrical Interface ◽  
Eigenvalue Method ◽  
Fiber Matrix

An eigenvalue method was proposed to study the stress intensity factors associated with the oscillating stress singularity for the axisymmetric cylindrical interface crack of the fiber/matrix composites. The fiber is a transversely isotropic material and the matrix is isotropic. Based on the fundamental equations of the spacial axisymmetric problem and the assumption of first-order approximation of the singular stress field, the discrete characteristic equation was derived using the displacement functions in the form of separated variables and the technique of meshless method. The eigenvalue is relative to the order of stress singularity, and the associated eigenvector is with respect to the displacement angular variations. The stress angular variations were derived by introducing the displacement angular variations into the constitutive relations. A finite element fiber/matrix model was used to verify the validation of the proposed eigenvalue method. The numerical results of the order of stress singularity and normalized stress angular variations are in good agreement with those obtained by the eigenvalue method. Based on the order of stress singularity and stress angular variations obtained by the eigenvalue method, as well as the numerical singular stress fields obtained by the finite element method (FEM), the stress intensity factors were determined successfully with the linear extropolation method.

Evolution of Tenacity in Mixed Mode Fracture – Volumetric Approach

2020 ◽  
Vol 22 (4) ◽  
pp. 931-938
Author(s):  
O. Zebri ◽  
H. El Minor ◽  
A. Bendarma
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Stress Intensity Factors ◽  
Mixed Mode ◽  
Local Stress ◽  
Critical Stress Intensity Factor ◽  
Mixed Mode Fracture ◽  
Intensity Factors ◽  
Singular Stress

AbstractIn fracture mechanics most interest is focused on stress intensity factors, which describe the singular stress field ahead of a crack tip and govern fracture of a specimen when a critical stress intensity factor is reached. In this paper, stress intensity factors which represents fracture toughness of material, caused by a notch in a volumetric approach has been examined, taking into account the specific conditions of loading by examining various U-notched circular ring specimens, with various geometries and boundary conditions, under a mixed mode I+II. The bend specimens are computed by finite element method (FEM) and the local stress distribution was calculated by the Abaqus/CAE. The results are assessed to determine the evolution of the stress intensity factor of different notches and loading distances from the root of notch. This study shows that the tenacity is not intrinsic to the material for all different geometries notches.

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