scholarly journals Effect of Holes on Dynamic Crack Propagation under Impact Loading

2020 ◽  
Vol 10 (3) ◽  
pp. 1122
Author(s):  
Fei Wang ◽  
Meng Wang
Keyword(s):  
Crack Propagation ◽  
Impact Loading ◽  
Split Hopkinson Pressure Bar ◽  
Numerical Models ◽  
Failure Criteria ◽  
Maximum Tensile Stress ◽  
Dynamic Crack Propagation ◽  
Dynamic Crack ◽  
Hopkinson Pressure Bar ◽  
Cracked Structures

In civil, geotechnical, and mining engineering, the investigation of the holes’ effect on dynamic crack propagation is essential because it can be used to predict possible fracture and protect cracked structures being further damaged. In this paper, a specimen made from polymethyl methacrylate (PMMA) with a pre-crack and two holes was proposed, and the Split-Hopkinson pressure bar was employed to investigate the effect of holes on dynamic crack propagation under impact loading. Notably, the locations of the holes were well designed with different two-hole spacing (12 mm, 16 mm, and 20 mm) and crack-hole distance (15 mm, 30 mm, and 45 mm). Crack propagation gauges were applied to monitor the fracturing time and crack extending velocity. The interaction characteristic between the crack and two holes was studied numerically using the AUTODYN code. In the numerical models, the failure criteria of maximum tensile stress and softening damage were employed for brittle material. The crack path, the propagating velocity, the particle velocity vector, and the stress state between the holes were analyzed. The calculation results indicate that compressive stresses between the two holes induced by the deformation of the holes play a crucial role in confining the vertical crack propagation. Both experimental and numerical results demonstrate that the holes have a suppressing action on the moving crack; as the two-hole spacing decreases, the suppressing action intensifies.

scholarly journals Dynamic Crack Propagation and Fracture Behavior of Pre-cracked Specimens under Impact Loading by Split Hopkinson Pressure Bar

2019 ◽  
Vol 2019 ◽  
pp. 1-11 ◽  
Author(s):  
Shijun Zhao ◽  
Qing Zhang
Keyword(s):  
Crack Propagation ◽  
Impact Loading ◽  
Split Hopkinson Pressure Bar ◽  
Dynamic Crack Propagation ◽  
Dynamic Crack ◽  
Hopkinson Pressure Bar ◽  
Brazilian Disk ◽  
Split Hopkinson ◽  
Pressure Bar ◽  
Cracked Specimens

Deformation and fracture of brittle materials, especially crack propagation, have drawn wide attention in recent years. But dynamic crack propagation under impact loading was not well understood. In this paper, we experimentally tested Brazilian disk (BD) fine sandstone specimens containing pre-cracks under cyclic impact loading by the Φ 74 mm diameter split Hopkinson pressure bar (SHPB) test device. The pre-cracked specimens were named central straight through crack flattened Brazilian disk (CSCFBD). By using the low air-pressure loading conditions (0.1 MPa, equal to the impact velocity of 3.76 m/s), a series of dynamic impact tests were detected successfully, and the effects of pre-cracks on dynamic properties were analyzed. Experimental results show that the multiple cracks mostly initiate at/or near the pre-crack tips and then propagate in different paths and directions varying by inclination angles, leading to the ultimate failure. Compared to static or quasi-static loading, dynamic crack propagation and fracture behavior are obviously different. Furthermore, we characterized the crack propagation paths, directions, and fracture patterns and discussed the influences of the pre-cracks during the breakage process. We concluded that the results obtained are significant in investigating the failure mechanism and mechanical properties of brittle materials under impact loading.

scholarly journals Rock Dynamic Crack Propagation under Different Loading Rates Using Improved Single Cleavage Semi-Circle Specimen

2019 ◽  
Vol 9 (22) ◽  
pp. 4944
Author(s):  
Fei Wang ◽  
Meng Wang ◽  
Mohaddeseh Mousavi Nezhad ◽  
Hao Qiu ◽  
Peng Ying ◽  
...  
Keyword(s):  
Crack Propagation ◽  
Split Hopkinson Pressure Bar ◽  
Dynamic Stress Intensity Factor ◽  
Crack Arrest ◽  
Dynamic Crack Propagation ◽  
Dynamic Crack ◽  
Hopkinson Pressure Bar ◽  
Tight Sandstone ◽  
Crack Propagation Velocity ◽  
Loading Rates

The objective of this paper is to investigate the complete process of dynamic crack propagation in brittle materials under different loading rates. By using Improved Single Cleavage Semi-Circle (ISCSC) specimens and Split Hopkinson Pressure Bar equipment, experiments were conducted, with the fracture phenomenon and crack propagation of tight sandstone investigated. Meanwhile, the process of crack propagation behaviour was simulated. Moreover, with the experimental–numerical method, the crack propagation dynamic stress intensity factor (DSIF) was also calculated. Then, the crack propagation toughness of tight sandstone under different loading rates was investigated and illustrated elaborately. Investigation results demonstrate that ISCSC specimens can achieve the crack arrest position unchanged, and the numerical simulation could effectively deduce the actual crack propagation, as their results were well matched. During crack propagation, the crack propagation DSIF in the whole process increases with the rising loading rate, and so does the crack propagation velocity. Several significant dynamic material parameters of tight sandstone are also given, for engineering reference.

Dynamic Crack Propagation and Arrest in PWR Pressure Vessel Steel: Interpretation of Experiment With the X-FEM Method

2007 ◽  
Author(s):  
B. Prabel ◽  
S. Marie ◽  
A. Combescure
Keyword(s):  
Finite Element ◽  
Crack Propagation ◽  
Strain Rate ◽  
Thermal Shock ◽  
Crack Growth ◽  
Split Hopkinson Pressure Bar ◽  
Dynamic Crack Propagation ◽  
Dynamic Crack ◽  
Pressure Vessel Steel ◽  
Vessel Steel

In the frame of analysis of the pressure thermal shock in a PWR RVP and the associated R&D activities, some developments are performed at CEA on the dynamic brittle propagation and crack arrest. This paper presents a PhD work on the modeling of the dynamic brittle crack growth. For the analyses, an important experimental work is performed on different geometries using a French RPV ferritic steel: Compact Tension specimens with different thickness, isothermal rings under compression with different positions of the initial defect to study a mixed mode configuration, and a ring submitted to thermal shock. The first part of this paper details the test conditions and main results. To propose an accurate interpretation of the crack growth, a viscous-elastic-plastic dynamic model is used. The strain rate influence is taken into account based on Cowper-Symond’s law (characterization was made from Split Hopkinson Pressure Bar tests). To model the crack propagation in the Finite Element calculation, eXtended Finite Element Method (X-FEM) is used. The implementation of these specific elements in the CEA F.E. software CAST3M is described in the second part of this paper. This numerical technique avoids re-meshing, because the crack progress is directly incorporated in the degrees of freedom of the elements crossed by the crack. The last part of this paper compares the F.E. predictions to the experimental measurements using different criteria. In particular, we focused on a RKR (Ritchie-Knott-Rice) like criterion using a critical principal stress in the front of the crack tip during the dynamic crack extension. Critical stress is found to depend on crack speed, or equivalently on strain rate. Good results are reported concerning predictive simulations.

scholarly journals Dynamic crack propagation: quasistatic and impact loading

2016 ◽  
Vol 2 ◽  
pp. 389-394 ◽  
Author(s):  
Yuri Petrov ◽  
Nikita Kazarinov ◽  
Vladimir Bratov
Keyword(s):  
Crack Propagation ◽  
Impact Loading ◽  
Dynamic Crack Propagation ◽  
Dynamic Crack

scholarly journals FRACTAL CHARACTERISTICS OF CRACK PROPAGATION IN COAL UNDER IMPACT LOADING

Fractals ◽  
2018 ◽  
Vol 26 (02) ◽  
pp. 1840014 ◽  
Author(s):  
YIXIN ZHAO ◽  
SHUANG GONG ◽  
CHENGGUO ZHANG ◽  
ZHENNAN ZHANG ◽  
YAODONG JIANG
Keyword(s):  
Fractal Dimension ◽  
Crack Propagation ◽  
Impact Loading ◽  
Crack Velocity ◽  
High Speed ◽  
Split Hopkinson Pressure Bar ◽  
Hopkinson Pressure Bar ◽  
Bedding Angle ◽  
Fractal Characteristics ◽  
Pressure Bar

This paper studied the fractal characteristics of crack propagation in coal containing beddings under impact loading condition. Split Hopkinson pressure bar (SHPB) system was applied to determine the prepared notched semi-circular bending specimens. The high-speed camera was used to record the propagation characteristics of cracks. The image processing method and fractal dimension calculation software are combined to further analyze the effects of bedding and loading rate on the fractal characteristics of crack propagation in coal. The experimental results presented that the presence of bedding has a remarkable impact on the crack propagation. The crack velocity of coal samples with [Formula: see text] bedding angle is of the maximum, however, the crack velocity of samples with [Formula: see text] bedding angle is of the minimum. Bedding angles also have obvious influence on the fractal dimension of cracking path, the bedding angle of [Formula: see text] being the largest, and those of [Formula: see text] and [Formula: see text] having the intermediate values, while those of [Formula: see text] and [Formula: see text] being the smallest. Several points of instantaneous fractal crack velocity are close to the Rayleigh wave velocity ([Formula: see text]). The crack velocities of coal specimens with bedding angles of [Formula: see text], [Formula: see text] and [Formula: see text] are prone to the high value.

Dynamic Crack Propagation Behavior of the Mg-Li Alloys under High-Speed Impact Loading

2005 ◽  
Vol 488-489 ◽  
pp. 717-720 ◽  
Author(s):  
Gui Ying Sha ◽  
Yong Bo Xu ◽  
En Hou Han
Keyword(s):  
Crack Propagation ◽  
High Speed ◽  
Loading Rate ◽  
High Loading ◽  
Dynamic Crack Propagation ◽  
Dynamic Crack ◽  
Hopkinson Pressure Bar ◽  
Propagation Behavior ◽  
High Loading Rate ◽  
Crack Propagation Behavior

The dynamic experiments for the Mg-Li alloys with single phase structure were carried out using the Hopkinson pressure bar. The dynamic crack propagation behavior and fracture mechanism of the alloys were investigated. The results show that the dynamic crack propagation is a deceleration process for the Mg-Li alloys under high loading rate. The fastest crack propagation velocity for Mg-3.3Li alloy is m/s 37 . 1253 , and 935.36m/s for Mg-14Li alloy. Observations of the fracture by SEM reveal that the dynamic fracture surface for Mg-3.3Li alloy mainly appears to be brittle fracture along grain boundaries. Whereas, the Mg-14Li alloy is ductile fracture mode under high loading rate. The main reason for these may be the transformation of hcp→bcc structure and the precipitation of the MgLi2Al and AlLi, as increase of Li in Mg-Li alloy.

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