In-plane and out-of-plane shear fracture toughness of rocks

2021 ◽  
Author(s):  
Bahador Bahrami ◽  
Morteza Nejati ◽  
Majid Reza Ayatollahi ◽  
Thomas Dreisner
Keyword(s):  
Fracture Toughness ◽  
Shear Fracture ◽  
Shear Loading ◽  
Mode Ii ◽  
Mode Iii ◽  
Brazilian Disk ◽  
Plane Shear ◽  
Double Edge ◽  
Out Of Plane ◽  
Tensile Fracturing

<p><span>Rocks in the subsurface are exposed to high amount of confinement which can potentially suppress the formation or the development of tensile-based cracks and thus, give rise to shear-based fracture growth. However, measuring the shear fracture toughness of rocks have been studied less in the literature, as providing the required confinement to force the shear fracturing precede tensile fracturing is not an easy task. In the current study, two new tests namely the double-edge notched Brazilian disk (DNBD) and the axially double-edge notched Brazilian disk (ANBD) are proposed to measure the in-plane (true mode II) and the out-of-plane (true mode III) shear fracture toughness of rocks, </span><span>K</span><sub><span>IIc </span></sub><span>and </span><span>K</span><sub><span>IIIc</span></sub><span>, respectively. We use the term </span><span>true </span><span>to emphasis that not only sustains the crack shear loading, but also the type of fracturing is shear-based. Finite element method is used to study the variations of stress field around the crack tip in these tests and to prove the applicability of the tests in providing mode II and mode III loading conditions. It is argued that both tests are straightforward and have several advantages compared to the existing ones. The effectiveness of the tests is empirically corroborated by conducting some experiments on Bedretto Granite. The pulverized surface of fracture in both the tests denotes the existence of friction which indicate the shear-based nature of fracture. Finally, the measured values of </span><span>K</span><sub><span>IIc </span></sub><span>and </span><span>K</span><sub><span>IIIc </span></sub><span>for Bedretto granite are compared to each other and to the reported values of </span><span>K</span><sub><span>Ic </span></sub><span>in the literature. It is shown that </span><span>K</span><span>IIc </span><span>and </span><span>K</span><span>IIIc </span><span>values are close to each other while both are more than two times greater than </span><span>K</span><span>Ic</span><span>.</span></p>

Computational Analysis of the AFM Specimen on Mixed-Mode II and III Fracture

2010 ◽  
Vol 452-453 ◽  
pp. 173-176 ◽  
Author(s):  
Qing Fen Li ◽  
Li Zhu ◽  
Friedrich G. Buchholz ◽  
Sheng Yuan Yan
Keyword(s):  
Mixed Mode ◽  
Strain Energy Release ◽  
Shear Loading ◽  
Mode Ii ◽  
Loading Conditions ◽  
Mode Iii ◽  
Plane Shear ◽  
Loading Mode ◽  
Out Of Plane ◽  
Global Deformation

Some results of 3D finite element analyses of the all fracture modes (AFM) specimen on mixed-mode II and III fracture are presented in this paper. The computational fracture analysis is based on the calculation of separated strain energy release rates (SERRs) along the crack front by the modified virtual crack closure integral (MVCCI)-method and the commercially available FE-code ANSYS. Calculation results show that under pure in-plane shear loading (mode II), not only the mode II, but also the mode III loading conditions, are generated owing to the Poission’s ratio effects. Similarly, under pure out-of-plane shear loading (mode III), besides the mode III, the mode II loading conditions are induced due to the global deformation. Nevertheless, once in-plane and out-of-plane shear loadings are superimposed, the fracture behavior appears more complex. Further discussion is given associate with some previous study.

Asymptotic Crack-Tip Fields in Perfectly Plastic Solids Under Mixed Mode II/III Loading Conditions

2006 ◽  
Vol 129 (4) ◽  
pp. 664-669
Author(s):  
J. Pan ◽  
P.-C. Lin
Keyword(s):  
Mixed Mode ◽  
Crack Tip ◽  
Shear Loading ◽  
Mode Ii ◽  
Pure Mode ◽  
Loading Conditions ◽  
Mode Iii ◽  
Plane Shear ◽  
Crack Tip Fields ◽  
Perfectly Plastic

In this paper, governing equations and solutions for asymptotic singular and nonsingular crack-tip sectors in perfectly plastic materials are first summarized under combined in-plane and out-of-plane shear loading conditions. The crack-tip fields under mixed mode II/III loading conditions are then investigated. An assembly of crack-tip sectors is adopted with stress discontinuities along the border of the two constant stress sectors. The solutions of the crack-tip fields under pure mode II, mixed mode II/III, and nearly pure mode III loading conditions are presented. The trends of the angular variations of the mixed mode II/III crack-tip stresses agree with those of the available computational analysis and the asymptotic analysis for low strain hardening materials. The pure mode II crack-tip stresses are similar to those of Hutchinson, and the nearly pure mode III stresses are similar to those of the pure mode III crack-tip field of Rice.

Asymptotic Crack-Tip Fields in Perfectly Plastic Solids Under Combined In-Plane and Out-of-Plane Shear Loading Conditions

2005 ◽  
Author(s):  
J. Pan
Keyword(s):  
Mixed Mode ◽  
Crack Tip ◽  
Shear Loading ◽  
Mode Ii ◽  
Pure Mode ◽  
Loading Conditions ◽  
Mode Iii ◽  
Plane Shear ◽  
Crack Tip Fields ◽  
Perfectly Plastic

In this paper, governing equations and solutions for asymptotic singular and non-singular crack-tip sectors in perfectly plastic materials are first summarized under combined in-plane and out-of-plane shear loading conditions. The crack-tip fields under mixed mode II/III loading conditions are then investigated. An assembly of crack-tip sectors is adopted with stress discontinuities along the border of the two constant stress sectors. The solutions of the crack-tip fields under pure mode II, mixed mode II/III, and nearly pure mode III loading conditions are presented. The trends of the angular variations of the mixed mode II/III crack-tip stresses agree with those of the available computational analysis and the asymptotic analysis for low strain hardening materials. The pure mode II crack-tip stresses are similar to those of Hutchinson and the nearly pure mode III stresses are similar to those of the pure mode III crack-tip field of Rice.

Experimental Investigation on Mode II Fracture Toughness KIIC of Concrete and Fracture Behavior

2006 ◽  
Vol 324-325 ◽  
pp. 1149-1152 ◽  
Author(s):  
Shi Lang Xu ◽  
Hong Bo Gao ◽  
Xiu Fang Zhang
Keyword(s):  
Fracture Toughness ◽  
Crack Length ◽  
Fracture Behavior ◽  
Shear Fracture ◽  
Discontinuity Point ◽  
Fracture Load ◽  
Mode Ii ◽  
Mode Ii Fracture ◽  
Double Edge ◽  
Mode Ii Fracture Toughness

Using the double-edge notched geometry proposed by Xu and Reinhardt recently, the dimension of 200 mm×200 mm×100mm concrete cube specimens, of which the crack length are 10 mm, 20 mm, 30mm, 40mm, 50mm respectively, are designed to experimentally measure mode II fracture toughness KIIC of concrete. For almost all specimens, typical shear fracture features i.e. approximately 0º initial cracking angle as well the following crack forwards propagation along the direction of ligament is phenomenally observed. This fact strongly confirms that this double-edge notched geometry is validly and capable of being utilized as a mode II fracture geometry to evaluate mode II fracture behavior. Then, from the discontinuity point of the measured load-displacement plot, the critical shear fracture load Pc is determined and the corresponding mode II fracture toughness KIIC is also calculated using the formula developed by Xu and Reinhardt. The computed results show that KIIC has no dependency on initial crack length, about 3.36MPa·m1/2 for the tested specimens.

Mixed-Mode [I/III] Fracture Simulation of Rubber

2014 ◽  
Vol 931-932 ◽  
pp. 1053-1057
Author(s):  
Kiatisak Permpipat ◽  
Petch Jearanaisilawong
Keyword(s):  
Mixed Mode ◽  
Shear Loading ◽  
Mode I ◽  
Mixed Mode Fracture ◽  
Tearing Mode ◽  
Mode Iii ◽  
Plane Shear ◽  
Finite Element Software ◽  
Fracture Simulation ◽  
Out Of Plane

The objective of this work is to develop fracture simulations of rubber undergoing a combined tensile and out-of-plane shear loading. Rubber sheets are tested under mode-I (opening mode), mode-III (tearing mode) and mixed-mode [I/II of fracture. The experiments are simulated in finite element software to evaluate the J-integral for each mode of deformation. Comparison between simulation and testing results are in good agreement. The simulations serve as test cases and evaluation tools for the development of mixed mode fracture criterion of rubber.

Shear Fracture – Testing Mode II and Determining Fracture Toughness

2016 ◽  
Vol 825 ◽  
pp. 35-40
Author(s):  
Barbora Mužíková
Keyword(s):  
Fracture Toughness ◽  
Cement Paste ◽  
Fracture Mode ◽  
Shear Fracture ◽  
Infinite Plate ◽  
Critical Factor ◽  
Mode Ii ◽  
Fracture Testing ◽  
Double Edge ◽  
Testing Mode

The best way how to test fracture mode II and determinate the critical factor KII of cement paste beams is investigated. Several methods are presented and the test based on a theory of the double-edge notched infinite plate is described in detail and will be carry out.

scholarly journals Analysis of Elastic Medium with Nonconcentric Two Circular Inclusions under Out-of-Plane Shear Loading.

1998 ◽  
Vol 64 (618) ◽  
pp. 438-444 ◽  
Author(s):  
Kenichi HIRASHIMA ◽  
Shigerou NAKANE ◽  
Mutsumi MIYAGAWA ◽  
Shinji KIKUCHI
Keyword(s):  
Elastic Medium ◽  
Shear Loading ◽  
Plane Shear ◽  
Out Of Plane

scholarly journals Graphene fatigue through van der Waals interactions

2020 ◽  
Vol 6 (42) ◽  
pp. eabb1335
Author(s):  
Teng Cui ◽  
Kevin Yip ◽  
Aly Hassan ◽  
Guorui Wang ◽  
Xingjian Liu ◽  
...  
Keyword(s):  
Cyclic Loading ◽  
Flexible Electronics ◽  
Shear Fracture ◽  
Van Der Waals ◽  
Van Der Waals Interactions ◽  
Pristine Graphene ◽  
Plane Shear ◽  
Dynamic Reliability ◽  
Polymer Interface ◽  
Out Of Plane

Graphene is often in contact with other materials through weak van der Waals (vdW) interactions. Of particular interest is the graphene-polymer interface, which is constantly subjected to dynamic loading in applications, including flexible electronics and multifunctional coatings. Through in situ cyclic loading, we directly observed interfacial fatigue propagation at the graphene-polymer interface, which was revealed to satisfy a modified Paris’ law. Furthermore, cyclic loading through vdW contact was able to cause fatigue fracture of even pristine graphene through a combined in-plane shear and out-of-plane tear mechanism. Shear fracture was found to mainly initiate at the fold junctions induced by cyclic loading and propagate parallel to the loading direction. Fracture mechanics analysis was conducted to explain the kinetics of an exotic self-tearing behavior of graphene during cyclic loading. This work offers mechanistic insights into the dynamic reliability of graphene and graphene-polymer interface, which could facilitate the durable design of graphene-based structures.

Experimental and theoretical investigation of mixed mode I/III brittle fracture of U-notched polystyrene components

2017 ◽  
Vol 53 (1) ◽  
pp. 15-25 ◽  
Author(s):  
A.R. Torabi ◽  
Behnam Saboori
Keyword(s):  
Brittle Fracture ◽  
Mixed Mode ◽  
General Purpose ◽  
Shear Loading ◽  
Mode I ◽  
Mean Stress ◽  
Plane Shear ◽  
Out Of Plane ◽  
Notch Tip ◽  
Stress Criteria

Brittle fracture of components made of the general-purpose polystyrene and weakened by an edge U-notch under combined tension/out-of-plane shear loading conditions (mixed mode I/III) has not been studied yet experimentally or theoretically. In this research, a recently developed loading fixture is employed for experimentally investigating the fracture of U-notched general-purpose polystyrene samples with various notch tip radii of 0.5, 1, 2 and 4 mm when they are subjected to different combinations of tension/out-of-plane shear. The samples are fabricated with four different notch tip radii with the purpose of assessing the influence of this geometrical parameter. The experimental values of fracture load and out-of-plane fracture angle are theoretically predicted by the two stress-based criteria of point stress and mean stress lately extended to general loading case of mixed mode I/II/III. It is shown that both the point stress and mean stress criteria provide acceptable predictions to fracture behavior of U-notched general-purpose polystyrene specimens. The critical distances needed for the point stress and mean stress criteria are determined based on the experimental results of the U-notched samples tested under pure mode I loading. No meaningful difference is found between the fracture loads and fracture initiation angles predicted by the point stress and mean stress criteria. It is also observed that as the mode III contribution in the applied mixed mode I/III loading increases, a larger total external load is needed for the fracture of U-notched general-purpose polystyrene specimens to occur.

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