Assessment of the fracture process zone in rocks using digital image correlation technique: The role of mode-mixity, size, geometry and material

2019 ◽  
Vol 29 (4) ◽  
pp. 646-666 ◽  
Author(s):  
M Moazzami ◽  
MR Ayatollahi ◽  
A Akhavan-Safar
Keyword(s):  
Digital Image Correlation ◽  
Fracture Process ◽  
Fracture Process Zone ◽  
Process Zone ◽  
Specimen Size ◽  
Image Correlation ◽  
Mode I ◽  
Mode Ii ◽  
Mode Mixity ◽  
Zone Length

This paper presents an experimental research on the length and shape of the fracture process zone of rocks under mode I, mixed mode (I + II) and mode II loading conditions for different geometries of cracked specimens made of two types of rocks, using the digital image correlation approach. Single edge notch bending (SENB) and semi-circular bend specimens are the two geometries considered. In order to investigate the effect of the specimen size on the fracture process zone length, rocks with three different sizes are produced and tested. To investigate the effect of the mode mixity on the fracture process zone length of marble and sandstone, the specimens are tested under different modes of loading. According to the experimental results, it is found that the fracture process zone length changes with mode ratio, specimen size, geometry and the material properties. The fracture process zone length increases when the mode of loading moves from mode I to mode II. Experimental results also show that fracture process zone becomes longer for specimens with larger sizes. The fracture process zone is also affected by the specimen geometry.

scholarly journals Mixed-Mode I-II Fracture Process Zone Characteristic of the Four-Point Shearing Concrete Beam

Materials ◽  
2020 ◽  
Vol 13 (14) ◽  
pp. 3203
Author(s):  
Guodong Li ◽  
Zhengyi Ren ◽  
Jiangjiang Yu
Keyword(s):  
Specific Surface ◽  
Mixed Mode ◽  
Fracture Process ◽  
Fracture Process Zone ◽  
Concrete Beam ◽  
Coarse Aggregate ◽  
Process Zone ◽  
Image Correlation ◽  
Mode I ◽  
Surface Areas

The size of the fracture process zone (FPZ) has significance for studying the fracture mechanism and fracture characteristics of concrete. This paper presents the method of assessing the FPZ of Mixed-Mode I-II for quasi-static four-point shearing concrete beams with pre-notched by Lagrangian strain profiles from digital image correlation (DIC). Additionally, it explores the influences of volume rates of the coarse aggregate of 0%, 28%, 48%, and 68%, and the specific surface areas of 0.12 m2/kg, 0.15 m2/kg, and 0.26 m2/kg on the size of the FPZ. It shows that the size of FPZ in four-point shearing concrete beam can be characterized by the displacement field and strain field using DIC. The size of FPZ conforms to linear positive correlation with the volume rate of coarse aggregate, and linear negative correlation with the specific surface area of coarse aggregate. It presents that the crack initiation of the four-point shearing beam with the pre notch is dominated by mode I load, and the propagation and fracture of Mixed-Mode I-II cracks are caused by the combined effect of Mode I and Mode II loading.

scholarly journals Crack Propagation and Fracture Process Zone (FPZ) of Wood in the Longitudinal Direction Determined Using Digital Image Correlation (DIC) Technique

2019 ◽  
Vol 11 (13) ◽  
pp. 1562 ◽  
Author(s):  
Ying Yu ◽  
Weihang Zeng ◽  
Wen Liu ◽  
He Zhang ◽  
Xiaohong Wang
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
Strain Field ◽  
Fracture Process ◽  
Fracture Process Zone ◽  
Process Zone ◽  
Longitudinal Direction ◽  
Image Correlation ◽  
Elastic Crack ◽  
Dic Technique

As a state-of-the-art method, the digital image correlation (DIC) technique is used to capture the fracture properties of wood along the longitudinal direction, such as the crack propagation, the strain field, and the fracture process zone (FPZ). Single-edge notched (SEN) specimens made of Douglas fir (Pseudotsuga menziesii) from Canada with different notch-to-depth ratios are tested by three-point-bending (3-p-b) experiment. The crack mouth opening displacements (CMOD) measured by the clip gauge and DIC technique agree well with each other, verifying the applicability of the DIC technique. Then, the quasi-brittle fracture process of wood is analyzed by combing the load-CMOD curve and the strain field in front of the preformed crack. Additionally, the equivalent elastic crack length is calculated using the linear superposition hypothesis. The comparison between the FPZ evolution and the equivalent elastic crack shows that specimens with higher notch-to-depth ratios have better cohesive effect and higher cracking resistance.

The Influence of the Chosen Type of Form Lubricator in the Form for Cement Paste with Fly Ash on the Fracture Process Zone

2017 ◽  
Vol 731 ◽  
pp. 92-97
Author(s):  
Barbora Mužíková ◽  
Pavel Padevět
Keyword(s):  
Fly Ash ◽  
Crack Growth ◽  
Cement Paste ◽  
Fracture Process ◽  
Fracture Process Zone ◽  
Process Zone ◽  
The Other ◽  
Mode Ii ◽  
Air Bubbles ◽  
The Real

This paper is focused on the cracks growth in mode II of specimens made of cement paste with fly ash. Three prescriptions were made for testing in mode II, during the making air bubbles arose at the bottom of the specimen that were lubricated with oil. These little caverns can have an influence on the growth of the cracks in the fracture process zone. On the other side, specimens that were lubricated with a wax, no caverns were observed. There are complex mechanisms of crack growth in the fracture process zone, cavern or inertial elements have a fundamental effect on the success of the real tests in mode II. Specimens lubricated with wax have a 50 % higher successful running of the test than those, whose forms were lubricated with the oil.

scholarly journals Study on the Fracture Process Zone near the Mode I Dynamic Crack Tip

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Chenmeng Ji ◽  
Chengzhi Qi
Keyword(s):  
Approximate Method ◽  
Fracture Process ◽  
Fracture Process Zone ◽  
Process Zone ◽  
Crack Problem ◽  
Crack Tip ◽  
Complex Stress ◽  
Mode I ◽  
Dynamic Crack ◽  
Stress Function Method

Evaluation of the shape and size of the fracture process zone near the mode I dynamic crack tip is still a problem unsolved completely at present. The research on the relationship between the fracture process zone and crack velocity near the mode I dynamic crack tip is quite limited, and some researchers have also developed experimental methods or numerical methods. In this research, based on the theory of elastodynamics and the complex stress function method, an approximate method for solving the mode I dynamic crack problem was proposed. The fracture process zone near the mode I dynamic crack tip was analyzed. The results showed that the areas of the fracture process zone determined based on the approximate method are nearly the same as the results obtained based on the well-known stress fields. The approximate method could provide a good reference for determining the fracture process zone near the mode I dynamic crack tip since no analytic methods had been found for evaluating the fracture process zone near the dynamic crack tip to the authors’ knowledge.

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