scholarly journals Study on the Fracture Behavior of Cracks Emanating from Tunnel Spandrel under Blasting Loads by Using TMCSC Specimens

2019 ◽  
Vol 2019 ◽  
pp. 1-13
Author(s):  
Bang Liu ◽  
Zheming Zhu ◽  
Ruifeng Liu ◽  
Lei Zhou ◽  
Duanying Wan
Keyword(s):  
Crack Initiation ◽  
Crack Propagation ◽  
Fracture Behavior ◽  
Propagation Speed ◽  
Propagation Path ◽  
Propagation Time ◽  
Dynamic Stress Intensity Factors ◽  
Inclination Angles ◽  
Crack Propagation Speed ◽  
Radial Cracks

Radial cracks may exist around tunnel edge, and these cracks may propagate and weaken tunnel stability under nearby blasting operations. In order to study the blast-induced fracture behavior of radial cracks emanating from a tunnel spandrel, a tunnel model containing a spandrel crack (TMCSC) with different inclination angles was proposed in this paper. Crack propagation gauges (CPGs) and strain gauges were used in the experiments to measure crack initiation moment and propagation time. Finite difference models were established by using AUTODYN code to simulate crack propagation behavior and propagation path. ABAQUS code was used to calculate dynamic stress intensity factors (SIFs). The results show that (1) crack inclination angles affect crack initiation angles and crack propagation lengths significantly; (2) critical SIFs of both mode I and mode II decrease gradually with the increase of the crack propagation speed; (3) the dynamic energy release rates vary during crack propagation; and (4) there are “crack arrest points” on the crack propagation paths in which the crack propagation speed is very small.

scholarly journals Crack propagation speed in ceramic during quenching

2018 ◽  
Vol 38 (7) ◽  
pp. 2879-2885 ◽  
Author(s):  
Yingfeng Shao ◽  
Boyang Liu ◽  
Xiaohuan Wang ◽  
Long Li ◽  
Jiachen Wei ◽  
...  
Keyword(s):  
Crack Propagation ◽  
Propagation Speed ◽  
Crack Propagation Speed

Effect of Contact between the Crack Faces on Crack Propagation

2013 ◽  
Vol 577-578 ◽  
pp. 61-64 ◽  
Author(s):  
Guido Dhondt
Keyword(s):  
Crack Propagation ◽  
Propagation Speed ◽  
Crack Propagation Rate ◽  
Propagation Rate ◽  
Contact Conditions ◽  
Contact Formulation ◽  
Positive Mode ◽  
Crack Propagation Speed ◽  
Crack Faces ◽  
Realistic Prediction

In mixed-mode crack propagation the crack faces frequently touch each other. The ensuing friction is expected to decrease the crack propagation speed. This effect is usually not taken into account, however, a realistic prediction of this effect may increase the calculated life and consequently increase the length of the inspection intervals. In this paper, penalty contact conditions are introduced in between the crack faces of the automatically generated mesh in a cyclic crack propagation. Special attention is given to the contact formulation and the area in which contact is defined. It is shown that the resulting crack propagation rate is significantly reduced by the introduction of friction provided that positive Mode-I is not significantly involved.

scholarly journals Analysis of Crack Propagation Path on the Anisotropic Bi-Material Rock

2010 ◽  
Vol 2010 ◽  
pp. 1-22
Author(s):  
Chao-Shi Chen ◽  
Chia-Huei Tu ◽  
Chen-Cheng Yang
Keyword(s):  
Integral Equation ◽  
Crack Initiation ◽  
Crack Propagation ◽  
Domain Boundary ◽  
Interfacial Crack ◽  
Crack Tip ◽  
Boundary Integral ◽  
Propagation Path ◽  
Disk Specimen ◽  
Fortran Code

This paper presents a single-domain boundary element method (SDBEM) for linear elastic fracture mechanics analysis in the 2D anisotropic bimaterial. In this formulation, the displacement integral equation is collocated on the uncracked boundary only, and the traction integral equation is collocated on one side of the crack surface only. The complete fundamental solution (Green's function) for anisotropic bi-materials was also derived and implemented into the boundary integral formulation so the discretization along the interface can be avoided except for the interfacial crack part. A special crack-tip element was introduced to capture exactly the crack-tip behavior. A computer program with the FORTRAN code has been developed to effectively calculate the stress intensity factors, crack initiation angle, and propagation path of an anisotropic bi-material. This SDBEM program has been verified having a good accuracy with the previous researches. In addition, a rock of type (1)/(2) disk specimen with a central crack was made to conduct the Brazilian test under diametrical loading. The result shows that the numerical analysis can predict relatively well the direction of crack initiation and the path of crack propagation.

scholarly journals A Numerical Study on the Crack Development Behavior of Rock-Like Material Containing Two Intersecting Flaws

Mathematics ◽  
2019 ◽  
Vol 7 (12) ◽  
pp. 1223 ◽  
Author(s):  
Bing Dai ◽  
Ying Chen ◽  
Guoyan Zhao ◽  
Weizhang Liang ◽  
Hao Wu
Keyword(s):  
Crack Initiation ◽  
Crack Propagation ◽  
Numerical Simulations ◽  
Inclination Angle ◽  
Numerical Study ◽  
Peak Stress ◽  
Crack Coalescence ◽  
Intersection Angle ◽  
Crack Behavior ◽  
Inclination Angles

It is quite often that rocks contain intersecting cracks. Therefore, crack behavior cannot be completely studied by only considering several isolated, single flaws. To investigate the crack behavior of rock or rock-like material containing intersecting flaws under uniaxial loading, numerical simulations were carried out using parallel bonded-particle models containing two intersecting flaws with different inclination angles (varying β) and different intersection angles (varying αα). The crack propagation processes are analyzed and two typical patterns of linkage are observed between two intersecting flaws: (1) One-tip-linkage that contains three subtypes: Coalescence position near the tip; coalescence position at the flaw, but far away from the tip; coalescence position outside the flaw at a certain distance from the tip; and (2) two-tip-linkage with two subtypes: Straight linkage and arc linkage. The geometries of flaws influence the coalescence type. Moreover, the effects of intersection angle α and inclination angle β on the peak stress, the stress of crack initiation, and the stress of crack coalescence are also investigated in detail.

scholarly journals Arctic Linepipe With High Resistance to Crack Propagation and HIC

1996 ◽  
Author(s):  
Gregorio R. Murtagian ◽  
Guillermo L. Fitzsimons ◽  
Juan C. González ◽  
Irina S. Kotova ◽  
Nikoli I. Anenkov
Keyword(s):  
Crack Propagation ◽  
Large Diameter ◽  
Propagation Speed ◽  
Unstable Crack ◽  
Computer Data ◽  
Computer Data Acquisition ◽  
Hydrogen Induced Cracking ◽  
Crack Propagation Speed ◽  
Linepipe Steels ◽  
Work Done

Linepipe steels for sour, arctic and offshore applications, form a class of material by themselves. These linepipes are originated in the need to fulfill several special characteristics like adequacy for induction bending, toughness requirement at very low temperature to prevent a unstable crack propagation, and hydrogen induced cracking resistance. These kind of linepipes are produced through clean steel practice, resulting in a low residuals content and a low non metallic inclusions rating. It is also very important to get a fine and uniform microstructure to guarantee good performance under sour environments, arctic and offshore conditions. In the present paper, a practical test to assess fitness for service of special linepipes is presented. Two linepipes with diameters between 219 and 273 mm and Diameter/thickness (D/t) ratios from 10 to 20, intended for arctic service were studied. While linepipe of both large Diameter and D/t (above 50), have been studied, there has been very little work done for diameters below 420 mm and D/t ratios in the range of 10–20. Full scale burst tests at −40°C and −60°C were carried out under controlled conditions. Actual crack propagation speed during burst tests at temperatures below −60°C, was tracked through an oscilloscope-computer data acquisition system. Weldability and hydrogen induced cracking performances were also studied.

Development of a Pipe Rupture

1988 ◽  
Vol 110 (4) ◽  
pp. 451-456
Author(s):  
T. R. Best
Keyword(s):  
Experimental Data ◽  
Steady State ◽  
Crack Propagation ◽  
Liquid Water ◽  
Propagation Speed ◽  
Pipe Failure ◽  
Subcooled Liquid ◽  
Reaction Forces ◽  
Crack Propagation Speed

An approach to the problem of predicting reaction forces that can occur during pipe failure is provided. Use is made of experimental data measuring crack propagation speed to determine the pipe rupture forces. The results of this paper are for pipelines carrying subcooled liquid water, but may be applied to other fluids. The reaction forces during pipe failure are compared with steady-state values.

Reduced-thickness CVN testing to represent slant failure of pipelines

2013 ◽  
Vol 4 (1) ◽  
Author(s):  
Jeroen Van Wittenberghe ◽  
Philippe Thibaux ◽  
Patrick Goes
Keyword(s):  
Crack Initiation ◽  
Crack Propagation ◽  
Propagation Speed ◽  
High Strength ◽  
Dissipated Energy ◽  
Specimen Thickness ◽  
Absorbed Energy ◽  
Element Analysis ◽  
The Difference ◽  
Energy Dissipated

To avoid longitudinal ductile crack propagation along a gas pipeline, the Batelle Two Curve method is used during pipeline design. This method states that a running crack will be arrested if the gas decompression velocity exceeds the crack propagation speed at the internal gas pressure. The crack propagation curve is scaled by impact energy values obtained through Charpy V-Notch (CVN) testing. However, for high-strength steel grades this scaling leads to unconservative predictions, because the experiment does not sufficiently represent the pipeline failure mode. The CVN specimen exhibits mainly mode I failure, without significant shear lips, while real failure is a combined mode often described as slant failure. In the present study, instrumented CVN tests are carried out on samples with different thickness reduction levels. To get a better insight in the crack initiation and propagation behaviour, the CVN test is simulated by finite element analysis. The dissipated energy and resulting fracture surfaces can be successfully represented. It is observed that slant failure is promoted by reducing the specimen thickness. In addition, the specific absorbed energy is decreased. However, most of the difference of absorbed energy is in crack initiation. This means that the fraction of the total energy dissipated in crack propagation is increased for reduced thickness specimens, making it a possible tool to assess the resistance of a material to crack propagation, provided that brittle fracture is avoided.

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