Prediction of crack initiation angle in brittle structures containing inclined cracks

2021 ◽  
Vol 56 (6) ◽  
pp. 1066-1075
Author(s):  
O. Demir
Keyword(s):  
Crack Initiation ◽  
Crack Initiation Angle ◽  
Inclined Cracks

scholarly journals Investigation on the Crack Initiation of V-Shaped Notch Tip in Precision Cropping

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
Lijun Zhang ◽  
Shengdun Zhao ◽  
Zhenwei Wang
Keyword(s):  
Crack Initiation ◽  
Equivalent Stress ◽  
Initiation Time ◽  
Initiation Point ◽  
Change Rate ◽  
Crack Initiation Angle ◽  
Notch Tip ◽  
Crack Initiation Life ◽  
Microscopic Measurement ◽  
Displacement Extrapolation Method

The crack initiation of V-shaped notch tip has a very important influence on the cross-section quality and the cropping time for every segment of metal bar in course of low stress precision cropping. By the finite element method, the influence of machining precision of V-shaped notch bottom corner on the crack initiation location is analyzed and it is pointed out that the crack initiation point locates in the place at the maximal equivalent stress change rate on V-shaped notch surface. The judgment criterion of the crack initiation direction is presented and the corresponding crack initiation angle can be calculated by means of the displacement extrapolation method. The factual crack initiation angle of the metal bar has been measured by using the microscopic measurement system. The formula of the crack initiation life of V-shaped notch tip is built, which mainly includes the stress concentration factor of V-shaped notch, the tensile properties of metal material, and the cyclic loading conditions. The experimental results show that the obtained theoretical analyses about the crack initiation location, the crack initiation direction, and the crack initiation time in this paper are correct. It is also shown that the crack initiation time accounts for about 80% of the cropping time for every segment of the metal bar.

The Area Fracture Criterion of Iso-εθ Line for Mixed Mode Crack

2012 ◽  
Vol 193-194 ◽  
pp. 708-711
Author(s):  
Si Li Chen ◽  
Tao Yu ◽  
Jian Jun Shi ◽  
Jie Huang ◽  
Kai He Dong
Keyword(s):  
Crack Initiation ◽  
Mixed Mode ◽  
Fracture Criterion ◽  
Shape Change ◽  
Crack Tip ◽  
Fracture Line ◽  
Mixed Mode Crack ◽  
Engineering Significance ◽  
Crack Initiation Angle ◽  
Predicted Values

In practice, the crack in some engineering materials is often compound crack. Therefore, it is important engineering significance to study on fracture problem. Based on the shape change energy near crack tip portion, the area fracture criterion of Iso-εθ line for compound crack was proposed. A crack initiation angle formula and the fracture criterion were established. The results showed that the theoretical predicted values and the measured values are consistent. The compound crack fracture line area of fracture criterion was established.Tthe formulas are easy to be derived and convenient to apply.

Numerical Simulation of Deflection Fracturing with Finite Element Method Considering Crack Initiation Angle

2013 ◽  
Vol 712-715 ◽  
pp. 1027-1031
Author(s):  
Zhen Yu Liu ◽  
Ping Ping Zhang ◽  
Hu Zhen Wang ◽  
Xiang Rong Zhu
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Crack Initiation ◽  
Working Condition ◽  
Oil Production ◽  
Oil Well ◽  
Two Phase ◽  
Crack Initiation Angle ◽  
Object Of Study ◽  
Element Method

Aimed at deflection fracturing by oriented perforation, a two-dimensional, non-steady and two-phase Finite Element Method (FEM) is established. Taking a battery of wells in the inverted nine-spot rhombus pattern as object of study, it is reported that law of different crack initiation angle (CIA) affecting deflection fracturing. In the respect of daily oil production and cumulative oil production, the dual fracture with different CIA is more than straight fracture. So it is feasible to use deflection fracturing of oriented perforation to increase the production of the special low permeability oilfield. In contrast to dual fractures with different fracturing initiation angles, we can see that the wider CIA, the higher cumulative oil production. So we can draw such a conclusion that when deflection fracturing is implemented, angle should be increased if the working condition is permitted so as to increase the production of oil well.

Predictions of fracture load, crack initiation angle, and trajectory for V-notched Brazilian disk specimens under mixed mode I/II loading with negative mode I contributions

2017 ◽  
Vol 27 (8) ◽  
pp. 1173-1191 ◽  
Author(s):  
Bahador Bahrami ◽  
Majid R Ayatollahi ◽  
AR Torabi
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Crack Initiation ◽  
Extended Finite Element Method ◽  
Fracture Load ◽  
Shear Loading ◽  
Mode I ◽  
Extended Finite Element ◽  
Brazilian Disk ◽  
Crack Initiation Angle

In this paper, first the fracture load, the crack initiation angle and the crack trajectory are experimentally measured for the round-tip V-notched Brazilian disk specimen made of polymethyl-methacrylate under compressive-shear loading. Then, the fracture load and the crack initiation angle are predicted by using the extended finite element method on the basis of the linear cohesive crack criterion. The fracture trajectory of the round-tip V-notched Brazilian disk specimens is also estimated by means of the extended finite element method and the incremental methods. Both the experimental observations and the theoretical fracture models indicate that although the notch bisector line is under compressive-shear loading, one half of the notch border still sustains tensile stresses and fracture takes place from this half. A very good agreement is shown to exist between the theoretical predictions and the experimental results for various notch opening angles and different notch radii.

Study of Crack Initiation and Propagation in Rock under Coupled Static and Dynamic Loads

2011 ◽  
Vol 99-100 ◽  
pp. 687-691
Author(s):  
Zhi Zhen Zhang ◽  
Feng Gao ◽  
Yang Cui ◽  
Xiao Ji Shang
Keyword(s):  
Numerical Simulation ◽  
Crack Initiation ◽  
Dynamic Loads ◽  
Crack Initiation And Propagation ◽  
Propagation Behavior ◽  
Initiation And Propagation ◽  
Expansion Angle ◽  
Static And Dynamic Loads ◽  
Crack Initiation Angle ◽  
Set Up

In order to research the crack initiation and propagation behavior in rock mass under coupled static and dynamic loads, the crack initiation angle and expansion angle formulas are set up by use of the fracture mechanics theory, then numerical simulation of crack propagation are conducted using software RFPA. The results show that: the crack always extend toward the dynamic stress direction; the bigger of the crack dip, the smaller of the crack initiation angle and the more difficulty of the crack initiation and propagation, meanwhile the less influence to the damage of rock. What’s more, when the crack dip is small, theoretical value and numerical simulation value of initiation angle will be have good uniformity.

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