scholarly journals Propagation Speed of Dynamic Mode-I Cracks in Self-Compacting Steel Fiber-Reinforced Concrete

Materials ◽  
2020 ◽  
Vol 13 (18) ◽  
pp. 4053 ◽  
Author(s):  
Kaiming Pan ◽  
Rena C. Yu ◽  
Xiaoxin Zhang ◽  
Gonzalo Ruiz ◽  
Zhimin Wu
Keyword(s):  
Crack Propagation ◽  
Testing Machine ◽  
Propagation Speed ◽  
Fiber Reinforced Concrete ◽  
Cohesive Crack ◽  
Image Correlation ◽  
Dynamic Mode ◽  
Mode I ◽  
Strain Gages ◽  
Loading Rates

The objective of this study is to measure the crack propagation speed in three types of self-compacting concrete reinforced with steel fibers loaded under four different loading rates. Central-notched prismatic beams with two types of fibers (13 mm and 30 mm in length), three fiber volume ratios, 0.51%, 0.77% and 1.23%, were fabricated. Four strain gages were glued on one side of the specimen notch to measure the crack propagation velocity, a fifth one at the notch tip to estimate the strain rates upon the initiation of a cohesive crack and the stress-free crack. A servo-hydraulic testing machine and a drop-weight impact device were employed to conduct three-point bending tests at four loading-point displacement rates, the former to perform tests at 2.2 μm/s, 22 mm/s and the latter for those at 1.77 m/s, 2.66 m/s, respectively. With lower fiber contents, smooth mode-I cracks were formed, the crack speed reached the order of 1 mm/s and 20 m/s. However, crack velocities up to 1417 m/s were obtained for the concrete with high content of fibers under impact loading. This value is fairly close to the theoretically predicted terminal crack velocity of 1600–1700 m/s. Numerical simulations based on cohesive theories of fracture and preliminary results based on the technique of Digital Image Correlation are also presented to complement those obtained from the strain gages. In addition, the toughness indices are calculated under all four loading rates. Strain hardening (softening) behavior accounting from the initiation of the first crack is observed for all three types of concrete at low (high) loading rates. Significant enhancement in the energy absorption capacity is observed with increased fiber content.

scholarly journals Propagation Speed of Dynamic Mode-I Cracks in Self-compacting Steel Fiber-reinforced Concrete

2020 ◽  
Author(s):  
Kaiming Pan ◽  
Rena C. Yu ◽  
Xiaoxin Zhang ◽  
Gonzalo Ruiz ◽  
Zhimin Wu
Keyword(s):  
Crack Propagation ◽  
Testing Machine ◽  
Propagation Speed ◽  
Fiber Reinforced Concrete ◽  
Cohesive Crack ◽  
Image Correlation ◽  
Dynamic Mode ◽  
Mode I ◽  
Strain Gages ◽  
Loading Rates

The objective of this study is to measure the crack propagation speed in three types of self-compacting concrete reinforced with steel fibers loaded under four different loading rates. Central-notched prismatic beams with two types of fibers (13 mm and 30 mm in length), three fiber volume ratios, 0.51%, 0.77% and 1.23%, were fabricated. Four strain gages were glued on one side of the specimen notch to measure the crack propagation velocity, a fifth one at the notch tip to estimate the strain rates upon the initiation of a cohesive crack and the stress-free crack. A servo-hydraulic testing machine and a drop-weight impact device were employed to conduct three-point bending tests at four loading-point displacement rates, the former to perform tests at 2.2 μm/s, 22 mm/s and the latter for those at 1.77 m/s, 2.66 m/s, respectively. With lower fiber contents, smooth mode-I cracks were formed, the crack speed reached the order of 1 mm/s and 20 m/s. However, crack velocities up to 1417 m/s were obtained for the concrete with high content of fibers under impact loading. This value is fairly close to the theoretically predicted terminal crack velocity of 1600–1700 m/s. Numerical simulations based on cohesive theories of fracture and preliminary results based on the technique of Digital Image Correlation are also presented to complement those obtained from the strain gages. In addition, the toughness indices are calculated under all four loading rates. Strain hardening (softening) behavior accounting from the initiation of the first crack is observed for all three types of concrete at low (high) loading rates. Significant enhancement in the energy absorption capacity is observed with increased fiber content.

Effect of Graphene Addition on Crack Propagation Resistance in Glass Fibre Reinforced Polymer Matrix Composite

2018 ◽  
Author(s):  
G. V. Vigneshwaran ◽  
S. Balasivanandha Prabu ◽  
R. Paskaramoorthy
Keyword(s):  
Fracture Toughness ◽  
Crack Propagation ◽  
Fiber Surface ◽  
Dip Coating ◽  
Image Correlation ◽  
Mode I ◽  
Molding Process ◽  
Mode I Fracture ◽  
Crack Propagation Resistance ◽  
Mode I Fracture Toughness

The effect of graphene nanoplatelets (GNPs) on enhancing the interlaminar fracture toughness of glass fiber/epoxy composites was investigated. The GnPs were physically deposited on the fiber surface by the dip coating technique. The composites were fabricated by hand layup technique followed by the compression molding process. Mode-I fracture test was conducted on the composite specimens. Crack propagation was studied by the digital image correlation (DIC) technique. Mode-I fracture toughness for composites loaded with 0.5 wt.% GnPs showed improvement by an average of 60% when compared to the pristine composites. It is concluded that the addition of GnPs produces a strong fiber/matrix interface bonding which effectively limits the crack propagation.

The cellular level mode I fracture behaviour of spruce and birch in the RT crack propagation system

Holzforschung ◽  
2016 ◽  
Vol 70 (2) ◽  
pp. 157-165 ◽  
Author(s):  
Pekka Tukiainen ◽  
Mark Hughes
Keyword(s):  
Crack Propagation ◽  
Fracture Behaviour ◽  
Crack Tip ◽  
Cellular Level ◽  
Image Correlation ◽  
Environmental Scanning ◽  
Mode I ◽  
Microscopic Structure ◽  
Pure Mode ◽  
Displacement Fields

Abstract The effect of the microscopic structure and the moisture content (MC) of wood on its fracture behaviour has been investigated. Green and air-dried spruce (Picea abies [L.] Karst.) and birch (Betula pendula Roth.) wood were subjected to pure mode I loading in the radial- tangential (RT) crack propagation system. Tests were carried out in situ in an environmental scanning electron microscope to observe crack propagation at the cellular level. Crack-tip displacement fields were computed by digital image correlation, and crack propagation was observed from the images captured during testing. Both the MC and the microscopic structure were found to affect the fracture process. In the air-dried birch and spruce, only microcracking caused large displacements ahead of the crack-tip. In spruce, the microcracking zone was larger than in birch. In green birch and spruce, microcracking was less evident than in the air-dried specimens, and in some cases, there were notable deformations in a few cells ahead of the crack-tip before crack extension. Microcracking is considered to be the main toughening mechanism in spruce and birch in the RT crack propagation system.

scholarly journals Experimental Investigations on Crack Propagation Characteristics of Granite Rectangle Plate with a Crack (GRPC) under Different Blast Loading Rates

2020 ◽  
Vol 2020 ◽  
pp. 1-18
Author(s):  
Xin Liu ◽  
Jun Yang ◽  
Zhenyang Xu ◽  
Lianjun Guo ◽  
Hongliang Tang
Keyword(s):  
Crack Propagation ◽  
Crack Width ◽  
Crack Velocity ◽  
Axial Strain ◽  
Blast Loading ◽  
Image Correlation ◽  
Experimental Investigations ◽  
Full Field ◽  
Loading Rates ◽  
Average Crack

The experimental system of 3D digital image correlation (3D-DIC) is set up to eliminate a certain extent of out-of-plane motion for accurate measuring the full-field strain field during crack propagation, and the effect of blast loading rates of fracture behavior of granite rectangle plate with a crack (GRPC) is investigated. The experimental results indicated that the maximum values of the strain concentration zone do not fully represent the crack tip during the whole process of crack propagation. The axial strain threshold value tip (ASTVT) plotting with lines and coordinate contours corresponding with the actual crack at the shooting area can be used to describe the position of the crack. The axial strain 1.3% is more practical to obtain crack velocity and average crack velocity, and the average crack velocity decreases as the blast loading rates increase. Through observing the relationship between crack width and time, it can be found that there are three stages, and the crack width increases as the blast loading rates increase.

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