A NOVEL GENERAL FORMULATION FOR SINGULAR STRESS FIELD USING THE ES-FEM METHOD FOR THE ANALYSIS OF MIXED-MODE CRACKS

2010 ◽  
Vol 07 (01) ◽  
pp. 191-214 ◽  
Author(s):  
G. R. LIU ◽  
N. NOURBAKHSHNIA ◽  
L. CHEN ◽  
Y. W. ZHANG
Keyword(s):  
Stress Field ◽  
Unique Feature ◽  
Crack Tip ◽  
Singular Stress ◽  
Fem Method ◽  
Smoothed Finite Element Method ◽  
Singular Stress Field ◽  
Crack Tip Element ◽  
Triangular Elements ◽  
Edge Based

This paper presents a general formulation for simulating the singular stress field at the vicinity of the crack-tip for linear fracture mechanics problems, based on the edge-based smoothed finite element method (ES-FEM) settings. This novel "singular ES-FEM" makes use of the unique feature offered by the ES-FEM that only the assumed displacement values (not the derivatives) are required to compute the stiffness matrix of the discretized system. The present singular ES-FEM method uses a basic mesh of linear triangular elements and a layer of novel "five-noded crack-tip elements" sharing the crack-tip node. The five-noded crack-tip element has one additional node on each of the edges connected to the crack-tip, and the locations of the "edge-node" can be arbitrary. A number of examples are analyzed and the results demonstrate that the present singular ES-FEM is generally softer and much more accurate than the existing FEM. The stress intensity factors obtained using the singular ES-FEM are very stable for different area-integration paths designed around the crack-tip. The present singular ES-FEM is found an excellent alternative to the standard FEM for fracture problems.

OS0108 Analysis of Intensity of Singular Stress Field for Single Lap Joint Base on Crack Tip Stress Method

2013 ◽  
Vol 2013 (0) ◽  
pp. _OS0108-1_-_OS0108-3_
Author(s):  
Tatsujiro MIYAZAKI ◽  
No-Aki NODA ◽  
Takumi UCHIKOBA ◽  
Rong LI ◽  
Yoshikazu SANO
Keyword(s):  
Stress Field ◽  
Crack Tip ◽  
Lap Joint ◽  
Singular Stress ◽  
Single Lap Joint ◽  
Singular Stress Field ◽  
Crack Tip Stress

scholarly journals Two Objective and Independent Fracture Parameters for Interface Cracks

2017 ◽  
Vol 84 (4) ◽  
Author(s):  
Jia-Min Zhao ◽  
He-Ling Wang ◽  
Bin Liu
Keyword(s):  
Stress Intensity ◽  
Stress Field ◽  
Phase Angle ◽  
Crack Tip ◽  
The Other ◽  
Singular Stress ◽  
Interface Cracks ◽  
Loading Mode ◽  
Fracture Parameters ◽  
Singular Stress Field

Due to the oscillatory singular stress field around a crack tip, interface fracture has some peculiar features. This paper is focused on two of them. One can be reflected by a proposed paradox that geometrically similar structures with interface cracks under similar loadings may have different failure behaviors. The other one is that the existing fracture parameters of the oscillatory singular stress field, such as a complex stress intensity factor, exhibit some nonobjectivity because their phase angle depends on an arbitrarily chosen length. In this paper, two objective and independent fracture parameters are proposed which can fully characterize the stress field near the crack tip. One parameter represents the stress intensity with classical unit of stress intensity factors. It is interesting to find that the loading mode can be characterized by a length as the other parameter, which can properly reflect the phase of the stress oscillation with respect to the distance to the crack tip. This is quite different from other crack tip fields in which the loading mode is usually expressed by a phase angle. The corresponding failure criterion for interface cracks does not include any arbitrarily chosen quantity and, therefore, is convenient for comparing and accumulating experimental results, even existing ones. The non-self-similarity of the stress field near an interface crack tip is also interpreted, which is the major reason leading to many differences between the interfacial fracture and the fracture in homogenous materials.

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