A Dislocation Migration Approach to Mode II Fracture Initiation and Propagation under Cyclic Loading

2010 ◽  
Author(s):  
A. Karami ◽  
J. Szymanski ◽  
Jane W. Z. Lu ◽  
Andrew Y. T. Leung ◽  
Vai Pan Iu ◽  
...  
Keyword(s):  
Cyclic Loading ◽  
Fracture Initiation ◽  
Mode Ii ◽  
Mode Ii Fracture ◽  
Initiation And Propagation

scholarly journals Development of a test method to investigate mode II fracture and dissection of arteries

2020 ◽  
Author(s):  
Brian FitzGibbon ◽  
Patrick McGarry
Keyword(s):  
Crack Initiation ◽  
Test Method ◽  
Ring Test ◽  
Mode Ii ◽  
High Shear ◽  
Crack Initiation And Propagation ◽  
Mode Ii Fracture ◽  
Initiation And Propagation ◽  
Mode Ii Crack ◽  
Arterial Tissue

The current study presents the development and implementation of a bespoke experimental technique to generate and characterise mode II crack initiation and propagation in arterial tissue. The current study begins with a demonstration that lap-shear testing of arterial tissue results in mixed mode fracture, rather than mode II. We perform a detailed computational design of a bespoke experimental method (which we refer to as a shear fracture ring test (SFRT)) to robustly and repeatably generate mode II crack initiation and propagation in arteries. This method is based on generating a localised region of high shear adjacent to a cylindrical loading bar. Placement of a radial notch in this region of high shear stress is predicted to result in a kinking of the crack during a mode II initiation and propagation of the crack over a long distance in the circumferential (c)-direction along the circumferential-axial (c-a) plane. Fabrication and experimental implementation of the SFRT on excised ovine aorta specimens confirms that the bespoke test method results in pure mode II initiation and propagation. We demonstrate that the mode II fracture strength along the c-a plane is eight times higher than the corresponding mode I strength determined from a standard peel test. We also calibrate the mode II fracture energy based on our measurement of crack propagation rates. The mechanisms of fracture uncovered in the current study, along with our quantification of mode II fracture properties have significant implications for current understanding of the biomechanical conditions underlying aortic dissection.

scholarly journals Peridynamic Simulation to Fracture Mechanism of CBN Grain in the Honing Wheel Dressing Process

Micromachines ◽  
2021 ◽  
Vol 12 (10) ◽  
pp. 1186
Author(s):  
Fuwei Wang ◽  
Yuanlong Chen ◽  
Yang Gao ◽  
Yuan Liang ◽  
Jie Su ◽  
...  
Keyword(s):  
Fracture Mechanism ◽  
Fracture Initiation ◽  
Grinding Wheel ◽  
Mode I ◽  
Mode Ii ◽  
Damage Initiation ◽  
Bond Rotation ◽  
Fracture Evolution ◽  
Initiation And Propagation ◽  
Progressive Fracture

Regularly dressing of CBN honing wheel is an effective way to keep its sharpness and correct geometry during honing process. This study aims to understand the fracture mechanism of single CBN grain in the dressing process of honing wheel. The honing wheel dressing process was simplified into the dressing process of grinding wheel, and the bond-based Peridynamic method considering bond rotation effect was developed to investigate the progressive fracture evolution, stress characteristics, and fracture modes of CBN grains in this process. It was found that fracture evolution of CBN grains mainly underwent four stages: elastic deformation, damage initiation, crack formation, and macro fracture. In addition, the fracture initiation and propagation were mainly determined by the tensile and shear stress, where the former led to mode I fractures and the latter led to mode II fractures. The propagation of mode I fractures was stable while the propagation of mode II fracture was unstable. The results show that the Peridynamic approach has great potential to predict the fracture mechanism of CBN grain in the dressing process of honing and grinding wheels.

scholarly journals Environmental effects on mode II fracture toughness of unidirectional E-glass/vinyl ester laminated composites

2021 ◽  
Vol 28 (1) ◽  
pp. 382-393
Author(s):  
Mazaher Salamt-Talab ◽  
Fatemeh Delzendehrooy ◽  
Alireza Akhavan-Safar ◽  
Mahdi Safari ◽  
Hossein Bahrami-Manesh ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Sulfuric Acid ◽  
Vinyl Ester ◽  
Cohesive Zone Model ◽  
Flexural Modulus ◽  
Mode Ii ◽  
Zone Model ◽  
Sharp Drop ◽  
Mode Ii Fracture ◽  
Mode Ii Fracture Toughness

Abstract In this article, mode II fracture toughness ( G IIc {G}_{\text{IIc}} ) of unidirectional E-glass/vinyl ester composites subjected to sulfuric acid aging is studied at two different temperatures (25 and 90°C). Specimens were manufactured using the hand lay-up method with the [ 0 ] 20 {{[}0]}_{20} stacking sequence. To study the effects of environmental conditions, samples were exposed to 30 wt% sulfuric acid at room temperature (25°C) for 0, 1, 2, 4, and 8 weeks. Some samples were also placed in the same solution but at 90°C and for 3, 6, 9, and 12 days to determine the interlaminar fracture toughness at different aging conditions. Fracture tests were conducted using end notched flexure (ENF) specimens according to ASTM D7905. The results obtained at 25°C showed that mode II fracture toughness increases for the first 2 weeks of aging and then it decreases for the last 8 weeks. It was also found that the flexural modulus changes with the same trend. Based on the results of the specimens aged at 90°C, a sharp drop in fracture toughness and flexural modulus with a significant decrease in maximum load have been observed due to the aging. Finite element simulations were performed using the cohesive zone model (CZM) to predict the global response of the tested beams.

scholarly journals Displacement Rate Effects on the Mode II Shear Delamination Behavior of Carbon Fiber/Epoxy Composites

Polymers ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1881
Author(s):  
Kean Ong Low ◽  
Mahzan Johar ◽  
Haris Ahmad Israr ◽  
Khong Wui Gan ◽  
Seyed Saeid Rahimian Koloor ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Peak Load ◽  
Epoxy Composites ◽  
Displacement Rate ◽  
Interface Debonding ◽  
Mode Ii ◽  
Scanning Electron Micrographs ◽  
Unstable Crack ◽  
Mode Ii Fracture ◽  
Mode Ii Fracture Toughness

This paper studies the influence of displacement rate on mode II delamination of unidirectional carbon/epoxy composites. End-notched flexure test is performed at displacement rates of 1, 10, 100 and 500 mm/min. Experimental results reveal that the mode II fracture toughness GIIC increases with the displacement, with a maximum increment of 45% at 100 mm/min. In addition, scanning electron micrographs depict that fiber/matrix interface debonding is the major damage mechanism at 1 mm/min. At higher speeds, significant matrix-dominated shear cusps are observed contributing to higher GIIC. Besides, it is demonstrated that the proposed rate-dependent model is able to fit the experimental data from the current study and the open literature generally well. The mode II fracture toughness measured from the experiment or deduced from the proposed model can be used in the cohesive element model to predict failure. Good agreement is found between the experimental and numerical results, with a maximum difference of 10%. The numerical analyses indicate crack jump occurs suddenly after the peak load is attained, which leads to the unstable crack propagation seen in the experiment.

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