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.

Deformation and Failure of Pre-Notched Thin Metal Plates Subjected to Confined Blast Loading

2015 ◽  
Vol 782 ◽  
pp. 49-58
Author(s):  
Han Liu ◽  
Peng Wan Chen ◽  
Bao Qiao Guo ◽  
Shao Long Zhang ◽  
Hai Bo Liu ◽  
...  
Keyword(s):  
High Speed ◽  
Dynamic Deformation ◽  
Blast Loading ◽  
Thin Metal ◽  
Image Correlation ◽  
Deformation And Failure ◽  
Full Field ◽  
3D Digital Image Correlation ◽  
Metal Plates ◽  
Dic Technique

In this paper, the dynamic deformation and rupture of pre-notched thin metal plates subjected to confined blast loading were investigated. The thin copper plates with cross-shape pre-notch were clamped on the end of a confined cylinder vessel by a cover flange. An explosive charge with a mass of 4g was detonated in the vessel center to generate blast load acting on the metal plates. The images of metal plates were recorded by two high-speed cameras. The displacement and strain fields during the deformation and rupture process were measured by using 3D digital image correlation (3D DIC). The effects of pre-notches on the dynamic deformation and rupture of thin metal plates were analyzed. The microstructure of fracture surface was examined The 3D DIC technique is proven to be an effective method to conduct dynamic full-field deformation measurement.

Application of 3D image correlation for full-field transient plate deformation measurements during blast loading

2009 ◽  
Vol 36 (6) ◽  
pp. 862-874 ◽  
Author(s):  
Vikrant Tiwari ◽  
Michael A. Sutton ◽  
S.R. McNeill ◽  
Shaowen Xu ◽  
Xiaomin Deng ◽  
...  
Keyword(s):  
Blast Loading ◽  
Image Correlation ◽  
3D Image ◽  
Full Field ◽  
Plate Deformation ◽  
Deformation Measurements

Study of Mode I-II Mixed Crack Propagation in Electrofusion Joint of Polyethylene Pipe

2018 ◽  
Author(s):  
Yue Zhang ◽  
Jianfeng Shi ◽  
Jinyang Zheng
Keyword(s):  
Finite Element ◽  
Crack Propagation ◽  
Strain Distribution ◽  
Axial Stress ◽  
Propagation Direction ◽  
Image Correlation ◽  
J Integral ◽  
Full Field ◽  
Crack Propagation Direction ◽  
Finite Element Numerical Simulation

Electrofusion joint plays an important role in connecting polyethylene (PE) pipe. In our previous study, penetrating crack failure through the fitting with an angle of about 70° was observed, and axial stress was found to be an important factor in the crack propagation. In this paper, experiments were carried out to study the crack propagation phenomena of the electrofusion joint of PE pipe. Digital Image Correlation (DIC) method was used to measure the displacement on specimen’s surface, as well as full-field strain distribution, based on which the J-integral of the crack tip was calculated. Besides, a finite element numerical simulation was conducted, and its accuracy was verified by experimental J-integral value. Through combination of experimental observations and finite element method, the phenomenon that the angle between crack propagation direction and tube axial is about 70° is detailed analysed. By comparison and analysis of the testing results, critical J-integral value during crack propagation is determined. Furthermore, critical J-integral value of crack propagation in electrofusion joint is predicted.

scholarly journals An Experimental Study of Ductile Failure Under Multi-Axial Loading

2014 ◽  
Author(s):  
Wei-Yang Lu ◽  
Helena Jin
Keyword(s):  
Constitutive Models ◽  
Stress Triaxiality ◽  
Ductile Failure ◽  
Axial Loading ◽  
Image Correlation ◽  
Experimental Investigations ◽  
Full Field ◽  
Basic Set ◽  
Ductile Behavior ◽  
Tubular Specimens

Recent experimental investigations show that most models are not able to capture the ductile behavior of metal alloys in the entire triaxiality range, especially at low triaxiality. Modelers are moving beyond stress triaxiality as the dominant indicator of material failure and developing constitutive models that incorporate shear into the evolution of the failure model. Available data that cover low triaxiality range are rare and a series of critical experiments is needed. Here, experiments of smooth thin as well as notched tubular specimens of Al6061-T651 under combined tension-torsion loading were conducted. This provides a very basic set of data for phenomenological models. A full-field deformation technique, digital image correlation (DIC), was applied to these tests to allow measurement of the field deformation, including the notched area. The microstructural features of the tested specimens were characterized to better understand the different failure mechanisms which led to ductility variation in the aluminum alloy.

The Effect of the Loading Rate on the Full-Field Strain Distribution on the Surface on the Intervertebral Discs

2020 ◽  
Vol 143 (1) ◽  
Author(s):  
Ruspi Maria Luisa ◽  
Cristofolini Luca
Keyword(s):  
Strain Distribution ◽  
Loading Rate ◽  
Statistical Significance ◽  
Intervertebral Discs ◽  
Image Correlation ◽  
Field Strain ◽  
Strain Rates ◽  
Rate Dependency ◽  
Full Field ◽  
Loading Rates

Abstract Contrasting results are reported when the spine is tested at different strain rates. Tissue specimens from the ligaments or the intervertebral discs (IVD, including annulus fibrosus and nucleus pulposus) exhibit higher stiffness and lower dissipation at high strain rates. Counterintuitively, when spine segments are tested at high rates, the hysteresis area and loop width increase. It is unclear how the load is shared between the different structures at different loading rates. The hypotheses of this study were: (i) As the IVD stiffens at higher loading rates, the strain distribution around the disc would be different depending on the loading rate; (ii) Preconditioning attenuates the strain-rate dependency of the IVD, thus making differences in strain distribution smaller at the different rates. Six segments of three vertebrae (L4–L6) were extracted from porcine spines and tested in presso-flexion at different loading rates (reaching full load in 0.67, 6.7, and 67 s). The full-field strain maps were measured using digital image correlation on the surface of the IVDs from lateral. The posterior-to-anterior trends of the strain were computed in detail for each IVD, and compared between loading rates. The values and the direction of principal strain on the surface of the IVDs, vertebrae, and endplates remained unchanged at different rates. In the transition zone between IVD and vertebra, only slight differences due to the loading rate appeared but with no statistical significance. These findings will allow better understanding of the rate-dependent behavior and failure of the IVD.

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 Full-Field Strain Characterizations and Fracture Process of Rock Blasting Using a Small-Scale Double-Hole Bench Model

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Jun Yang ◽  
Xin Liu ◽  
Zhenyang Xu ◽  
Hongliang Tang ◽  
Qi Yu
Keyword(s):  
Digital Image Correlation ◽  
Crack Propagation ◽  
Digital Image ◽  
Fracture Process ◽  
Image Correlation ◽  
Field Strain ◽  
Small Scale ◽  
Rock Blasting ◽  
Full Field ◽  
Bench Model

A small-scale double-hole bench model is designed with granite to study the fracture mechanism of rock blasting. By combining high-speed camera and digital image correlation, the full-field strain characterization and fracture process of the specimen bevel surface are investigated. The preliminary test results show that the strain concentration zone corresponds to the crack propagation location, and digital image correlation can well detect the crack propagation. In addition, through observing the crack propagation pattern on the specimen bevel surface, it can be seen that the fracture of the specimen is caused by the dominant horizontal crack and the dominant vertical crack, and the generation of the dominant horizontal crack takes precedence over that of the dominant vertical. Finally, the measurements of two-dimensional digital image correlation and three-dimensional digital image correlation are discussed.

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.

Sign in / Sign up

Export Citation Format

Share Document