scholarly journals A Numerical Simulation of Effects of Softening and Heterogeneity on the Stress Intensity Factor of Quasi-Brittle Material

2014 ◽  
Vol 6 ◽  
pp. 586472 ◽  
Author(s):  
Tielin Chen ◽  
Chao Li ◽  
Dingli Zhang
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Brittle Material ◽  
Fracture Behavior ◽  
Brittle Materials ◽  
Numerical Approach ◽  
Crack Initiation And Propagation ◽  
Nonlinear Fracture ◽  
Initiation And Propagation

A numerical approach to simulate the crack initiation and propagation process of the nonlinear fracture behavior of the quasi-brittle materials under tensile loading is presented. The nonlinear fracture of Mode I of quasi-brittle material is analyzed by considering the effects of microscopic softening rate and heterogeneity. The results show that the softening rate and the heterogeneity of quasi-brittle material affect the values of stress intensity factor K I. The softening index affects merely the size of the plastic zones while the heterogeneity causes the more sophisticated response of quasi-brittle materials.

Stress Intensity Factors of a Crack on the Interface of Adhesive and Adherents

2010 ◽  
Vol 452-453 ◽  
pp. 249-252
Author(s):  
Yu Zhang ◽  
Naoaki Noda ◽  
Xin Lan ◽  
Kentarou Takaisi
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Stress Intensity Factors ◽  
Crack Initiation And Propagation ◽  
Intensity Factors ◽  
Singular Stress ◽  
Materials Properties ◽  
Initiation And Propagation ◽  
Different Thickness

Adhesive joints are widely used as the joints with the same or different adherents, such as in engineering and electric devices. However, because of mismatch of different materials properties, failures due to crack initiation and propagation are often observed on the interface between adhesive and adherents. Therefore, it is important to analyze stress intensity factor of crack on the interface. In this paper, the effect of material combination of adhesive and adherents on stress intensity factor and effect of the thickness of adhesive on stress intensity factor are discussed. A useful method to calculate the stress intensity factor of interface crack is presented with focusing on the stresses at the crack tip calculated by finite element method. The stress intensity factors are indicated in charts under different thickness of adhesive . It is found that the intensity of singular stress first increases with increasing , then decreases from about , and keeps constant from about , when is the width of adhesive. These results are helpful to design dimensions of devices and choose appropriate materials when adhesives are used inside of them.

Research on Fracture Behavior of a Cracked Film-Substrate Medium

2006 ◽  
Vol 324-325 ◽  
pp. 903-906
Author(s):  
Bao Liang Liu ◽  
Xian Shun Bi
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Boundary Element Method ◽  
Intensity Factor ◽  
Boundary Element ◽  
Fracture Behavior ◽  
Thickness Ratio ◽  
Film Substrate ◽  
Substrate Medium ◽  
Element Method

This study gives the problem of a crack in the film oriented perpendicular to the film-substrate interface with the crack tip terminating at the interface. Based on Beuth’s theory, three-dimensional model is simplified to plane strain problems, which obtains fracture mechanisms of a cracked film-substrate medium by applying the boundary element method(BEM). The method aptly resolves the problem involving stress concentration and, further, that this study develops the multi-region boundary element method and applies it to evaluate the cracked film-substrate medium. It shows that the stress intensity factor is affected by the different elastic mismatches and the thickness ratio of the film and the substrate. These results indicate: 1) The stress intensity factor has remarkable increased with the decrease of the thickness ratio of the film and the substrate. The effect of the fracture behavior of film is negligible when the thickness ratio of the film and the substrate is above 10, therefore, it is treated as thin film; 2) The stress intensity factor will decrease with the increase of α ( −1 pα p +1) for β = 0 and β =α / 4 , where α and β are called Dundurs parameters. What’s more, this paper studies the special condition of the film-substrate medium, which is the analysis of the fracture of the absence of any elastic mismatch between the film and the substrate, i.e.α=β=0, and revision of the formula of Xia and Hutchinson is put forward for the stress intensity factor of the deep crack problems by comparing to the former conclusions of Y.Murakami.

Finite Element Fracture Mechanics Study of Pre-Northridge Connections

2006 ◽  
Vol 324-325 ◽  
pp. 1007-1010 ◽  
Author(s):  
Hong Bo Liu ◽  
Chang Hai Zhai ◽  
Yong Song Shao ◽  
Li Li Xie
Keyword(s):  
Stress Intensity Factor ◽  
Finite Element ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Fracture Behavior ◽  
Integral Approach ◽  
J Integral ◽  
Finite Element Analyses ◽  
Element Analysis ◽  
Weld Root

The objective was to quantify the variation of stress intensity factor to weld root flaw sizes in steel frame connections. Finite-element analyses were used to study fracture toughness in welded beam-column connections. Investigations of fracture behavior mainly focused on the standard pre-Northridge connection geometry. Finite element analysis was performed using the ANSYS computer program. Stress intensity factor was calculated through a J-integral approach. Results show that stress intensity factor is not uniform and is largest in the middle of beam flange. Stress intensity factor increases nearly linear with the increase of flaw size. Backing bars have little effect on weld fractures.

scholarly journals Hole Defects Affect the Dynamic Fracture Behavior of Nearby Running Cracks

2018 ◽  
Vol 2018 ◽  
pp. 1-8 ◽  
Author(s):  
R. S. Yang ◽  
C. X. Ding ◽  
L. Y. Yang ◽  
P. Xu ◽  
C. Chen
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Dynamic Fracture ◽  
Fracture Behavior ◽  
Dynamic Stress ◽  
Crack Path ◽  
Dynamic Stress Intensity Factor ◽  
Experimental System ◽  
Intersection Area

Effects of defects on the dynamic fracture behavior of engineering materials cannot be neglected. Using the experimental system of digital laser dynamic caustics, the effects of defects on the dynamic fracture behavior of nearby running cracks are studied. When running cracks propagate near to defects, the crack path deflects toward the defect; the degree of deflection is greater for larger defect diameters. When the running crack propagates away from the defect, the degree of deflection gradually reduces and the original crack path is restored. The intersection between the caustic spot and the defect is the direct cause of the running crack deflection; the intersection area determines the degree of deflection. In addition, the defect locally inhibits the dynamic stress intensity factor of running cracks when they propagate toward the defect and locally promotes the dynamic stress intensity factor of running cracks when they propagate away from the defect.

CONNECTION BETWIN FRACTAL DIMENSION OF THE CONCRETE FRACTURE SURFACE AND MECHANICS OF DESTRUCTION CHARACTERISTICS

2020 ◽  
Vol 91 (5) ◽  
pp. 46-58
Author(s):  
G.I. SHAPIRO ◽  
Keyword(s):  
Stress Intensity Factor ◽  
Fractal Dimension ◽  
Stress Intensity ◽  
Fracture Mechanics ◽  
Intensity Factor ◽  
Fracture Surface ◽  
Aggregate Size ◽  
Concrete Fracture ◽  
Nonlinear Fracture Mechanics ◽  
Nonlinear Fracture

As it was found previously, the concrete fracture surface formed from tensile force is described by fractal geometry methods. It is shown thatthe fractal dimension value is related to the tensile stress gradient φ_i, to the aggregate size and, as shown earlier, does not depend on the strength of concrete. Moreover, the fractal dimension depends on the size of the sample only until its size reaches a value to which linear fracture mechanics is applicable. The stress intensity factor is related to the fractal dimension, and both characteristics are related to the aggregate size. A connection for the critical stress intensity factor K_Ic^f(l,φ_i) characterizing the crack resistance of the material in nonlinear fracture mechanics with the crack size l and the specimenis proposed. The stress intensity factor for a fractal crack K_Ic^f(l,φ_i) can be used to calculate structures using nonlinear fracture mechanics.

A Study on the Fracture Behavior of Magnesium and Aluminium Alloy under Dynamic Biaxial Stress

2005 ◽  
Vol 297-300 ◽  
pp. 1579-1584
Author(s):  
Do Yeon Hwang ◽  
Akira Shimamoto ◽  
Ryo Kubota
Keyword(s):  
Fracture Toughness ◽  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Magnesium Alloy ◽  
Intensity Factor ◽  
High Speed ◽  
Fracture Behavior ◽  
Biaxial Stress ◽  
Caustic Method ◽  
Magnesium Alloy Az31b

In this study, the dynamic behaviors of cracks under dynamic biaxial stress are investigated. We conduct dynamic loading fracture experiments on the aluminum (2024-T3) and the magnesium alloy (AZ31B-O) under equitable biaxial stress with a hydraulic high-speed biaxial experimental machine. The processed specimens are cruciform with a crack. Different kinds of cracks are defined by their crack angles. We analyze the results by the caustic method. We obtained the stress intensity factor and the fracture toughness value in the neighborhood of the crack tip under dynamic biaxial stress. We analyzed the obtained data, and then, we compared results.

Fracture Analysis for Attaching Fiber Reinforced Composite on V-Notch Wedge Structure

2017 ◽  
Vol 909 ◽  
pp. 133-142
Author(s):  
Teng Hui Chen
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Critical Stress ◽  
High Stress ◽  
Brittle Materials ◽  
Critical Stress Intensity Factor ◽  
Fiber Reinforced ◽  
Engineering Structures ◽  
Wedge Structure

Sharp V-notches with various angles often appear in engineering structures. When being loaded, the high stress at the apex could result in crack propagation on the structure and further fracture. For this reason, safety evaluation should be emphasized for products or engineering structures with such geometric characteristics. Sharp V-notches are regarded as wedge structures that the above situations seriously and often appear on brittle materials. Regarding the stress intensity factor K of the driving force for wedge structure failure, Chen, Dunn, and Seweryn, with numerical analysis for the fracture experiment, explained that the critical stress intensity factor Kc for single isotropic material fracture could be the intensity failure specification for wedge structures. Nevertheless, V-notched brittle materials are likely to receive great stress over the surface elastic energy of the structure when being loaded, causing brittle failure at the apex. When the high-strength and light-weight composite material is attached to reinforce the surface of brittle materials, the energy is reinforced to enhance the critical stress intensity factor of the overall structure, aiming to improve the failure of brittle materials resulted from stress singularity. This paper therefore tends to discuss the effects of the composite attachment, layer, and fiber reinforced direction on the critical stress intensity factor when the structure is being fractured.

Fracture behavior of periodically bonded interface of piezoelectric bi-material under compressive–shear loading

2019 ◽  
Vol 24 (10) ◽  
pp. 3216-3230 ◽  
Author(s):  
S Kozinov ◽  
A Sheveleva ◽  
V Loboda
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Fracture Behavior ◽  
Compressive Loading ◽  
Closed Form Solution ◽  
Industrial Applications ◽  
Shear Loading ◽  
Form Solution ◽  
Applied Loading

A closed-form solution is constructed for a bi-material consisting of two piezoelectric (or piezoelectric and dielectric) half-planes, which are periodically bonded along the interface and can partially contact along the initially unbonded parts. Under compressive loading, the size of the frictionless contact zone is usually quite large; in some cases the interface is completely closed. Such a situation is frequently observed in industrial applications. Since the periodic bonding of two different materials is extremely widespread, it is very important to study the influence of the mutual material properties of the composite and the applied loading on the size and shape of the opened regions, as well as the stress intensity factor at the bonding points. To formulate the problem, the electromechanical factors are presented through piecewise analytic functions, so that the problem in question is reduced to the combined periodic Dirichlet–Riemann problem, which is solved exactly. The obtained solution provides explicit formulas for the mechanical stresses and displacements along the interface and allows one to find the dependence of the contact zones and the stress intensity factor on the ratio of the bonded parts of the interface to the period for the different values of applied loading and materials.

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