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.

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>

Analysis of Experimental and Calculated Values of Shear Broken Cement Paste

2017 ◽  
Vol 1144 ◽  
pp. 40-47
Author(s):  
Barbora Mužíková ◽  
Pavel Padevět ◽  
Petr Bittnar ◽  
Jakub Antoš
Keyword(s):  
Critical Stress ◽  
Infinite Plate ◽  
Critical Factor ◽  
Measured Data ◽  
Image Correlation ◽  
Mode Ii ◽  
Notched Specimen ◽  
The Real ◽  
Double Edge ◽  
Real Test

This paper is focused on testing in mode II. In this article there is presented the double-edge notched specimen based on the theory of the infinite plate to determine the critical factor KII. There are three approaches to this testing here. Firstly, the real test documented by photos and measured data to determine the value of the critical stress intensity was carried out. Secondly, the real test evaluated by the digital image correlation and finally the numerical model in Adina was made. The success of the testing was lower than has been expected (only 24 %). All three prescriptions were used for all 55 specimens. The highest value of KII is reached with the prescription without fly ash.

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.

Shear fracture (Mode II) toughness measurement of anisotropic rock

2021 ◽  
pp. 103043
Author(s):  
Dongliang Sun ◽  
Qiuhua Rao ◽  
Shanyong Wang ◽  
Qingqing Shen ◽  
Wei Yi
Keyword(s):  
Fracture Mode ◽  
Shear Fracture ◽  
Mode Ii ◽  
Anisotropic Rock ◽  
Toughness Measurement

scholarly journals Mode I and Mode II Delamination of Flax/Epoxy Composite Laminate

2018 ◽  
Vol 202 ◽  
pp. 01002
Author(s):  
Thamilarasu S. Rajendran ◽  
Mahzan Johar ◽  
Shukur Abu Hassan ◽  
King Jye Wong
Keyword(s):  
Fracture Toughness ◽  
Composite Laminates ◽  
Epoxy Composite ◽  
Shear Fracture ◽  
Natural Fibres ◽  
Fracture Mechanisms ◽  
Mode I ◽  
Mode Ii ◽  
Scanning Electron Micrographs ◽  
Experimental Calibration

In recent decades, natural fibres are getting their attention as reinforcement in composite materials. This is because natural fibres are environmental friendly. However, delamination is commonly recognised as one of the earliest failures in composite laminates. The objective of the present work is to investigate mode I and mode II delamination behaviour of flax fabrics reinforced epoxy composite. The delamination characterisation was carried out using double cantilever beam (DCB) and three point end notched flexure (ENF) tests. The fracture toughness were calculated using experimental calibration method (ECM). Results showed that the average fracture toughness was 485 N/m and 962 N/m, respectively. Finally, through scanning electron micrographs, it was observed that the ply/ply debonding and fibre/matrix debonding were the major fracture mechanisms in DCB specimen. As for ENF specimen, shear fracture dominated the energy dissipation process.

Shear fracture (Mode II) of brittle rock

2003 ◽  
Vol 40 (3) ◽  
pp. 355-375 ◽  
Author(s):  
Qiuhua Rao ◽  
Zongqi Sun ◽  
O. Stephansson ◽  
Chunlin Li ◽  
B. Stillborg
Keyword(s):  
Fracture Mode ◽  
Shear Fracture ◽  
Brittle Rock ◽  
Mode Ii

Fracture characterization and modeling of Gyroid filled 3D printed PLA structures

2021 ◽  
Vol 63 (5) ◽  
pp. 397-401
Author(s):  
Ahmet Refah Torun ◽  
Ali Sinan Dike ◽  
Ege Can Yıldız ◽  
İsmail Sağlam ◽  
Naghdali Choupani
Keyword(s):  
Fracture Toughness ◽  
Shear Fracture ◽  
Industrial Applications ◽  
Shear Mode ◽  
Mode I ◽  
Mode Ii ◽  
Mixed Mode Fracture ◽  
Pure Mode ◽  
Two Dimensional ◽  
3D Printed

Abstract Polylactic acid (PLA) is a commonly used biodegradable material in medical and increasingly in industrial applications. These materials are often exposed to various flaws and faults due to working and production conditions, and increasing the demand for PLA for various applications requires a full understanding of its fracture behavior. In addition to ABS, PLA is a widely used polymeric material in 3D printing. The gyroid type of filling is advantageous for overcoming the relatively higher brittleness of PLA in comparison with conventional thermoplastic polymers. In this study, the effects of various filling ratios on the fracture toughness of 3D printed PLA samples with gyroid pattern were investigated numerically and experimentally for pure mode I, combined mode I/II, and pure mode II. Two-dimensional finite element modeling was created, and the two-dimensional functions of stress intensity coefficients were extracted in loading mode I, mode I/II, and mode II at varied filling ratios of the gyroid PLA samples. Mixed-mode fracture tests for 3D printed PLA samples with a gyroid pattern at various filling ratios were performed by using a specially developed fracture testing fixture. The results showed that the amount of fracture toughness of the samples under study in tensile mode was much higher than those values in shear mode. Also, as the percentages of the filling ratios in the samples increased, both tensile and shear fracture toughness improved.

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