scholarly journals Brittle fracture of rock under combined tensile and compressive loading conditions

2017 ◽  
Vol 54 (1) ◽  
pp. 88-101 ◽  
Author(s):  
S.B. Tang ◽  
C.Y. Bao ◽  
H.Y. Liu
Keyword(s):  
Friction Coefficient ◽  
Brittle Fracture ◽  
Crack Initiation ◽  
Crack Extension ◽  
Shear Crack ◽  
Pressure Coefficient ◽  
Compressive Loading ◽  
Confining Pressure ◽  
Loading Conditions ◽  
Stress Criterion

The brittle fracture of rock with an angled crack under combined tensile and compressive loading conditions is studied using linear elastic fracture mechanics (LEFM). The modified maximum tangential stress criterion (MTSC) and the maximum shear stress criterion (MSSC) are used to check crack initiations in the tensile and shear modes, respectively. The effects of the friction coefficient of the crack surfaces and the nonsingular stresses (T stresses) on the crack initiation are studied for the cases of both low and high compressive confining pressure coefficients. The T stresses include those both parallel (Tx) and perpendicular (Ty) to the crack plane. The type of crack initiation under the combined tensile and compressive loading conditions is found to remain tensile dominated when the compressive confining pressure coefficient is small. However, shear crack extension becomes possible with the compressive confining pressure coefficient and friction coefficient increasing if the crack orientation angle is small. Moreover, the high compressive confining pressure and substantial friction are found to increase the possibility of shear crack extension. The theoretical predictions presented in this study move one step forward than the available analytical solutions for the angled crack subjected to general biaxial load and agree well with those from experimental tests.

scholarly journals Моделирование динамического старта трещины на основе перидинамической численной модели и критерия инкубационного времени

2021 ◽  
Vol 91 (3) ◽  
pp. 435
Author(s):  
М.О. Игнатьев ◽  
Ю.В. Петров ◽  
Н.А. Казаринов
Keyword(s):  
Experimental Data ◽  
Brittle Fracture ◽  
Crack Initiation ◽  
Polymer Material ◽  
High Speed ◽  
Numerical Scheme ◽  
Glassy Polymer ◽  
Fracture Model ◽  
Loading Conditions ◽  
Dynamic Brittle Fracture

The problems of dynamic brittle fracture under the high-speed loading conditions were investigated. A new numerical scheme based on the peridynamic approach and a structural-time fracture model is used to predict the crack initiation in the specimens of glassy polymer material. Comparison of numerical results with experimental data is presented

Producing Mechanism and Distribution Laws of Remote Cracks for Geotechnical Engineering Structure

2011 ◽  
Vol 50-51 ◽  
pp. 869-874
Author(s):  
Hou Quan Zhang ◽  
Xing Gen Huang ◽  
Li Bing Xue ◽  
Yan Feng Zhang
Keyword(s):  
Shear Crack ◽  
Process Analysis ◽  
Geotechnical Engineering ◽  
Failure Process ◽  
Pressure Coefficient ◽  
Confining Pressure ◽  
Necessary Condition ◽  
Engineering Structure ◽  
Rock Failure Process ◽  
Distribution Laws

The purpose of this paper is to investigate producing mechanism and distribution laws of remote cracks for geotechnical engineering structure. The fracture modes of geotechnical material containing a hole with different lateral confining pressure coefficients of 0, 0.05, 0.1, 0.15, 0.25, 0.33, 0.75 and 1 were numerically simulated using RFPA2D (rock failure process analysis) code. The results indicate that under a certain confining pressure, three types of cracks, i.e., primary crack, remote crack and shear crack, can be observed simultaneously in the same sample. When the lateral pressure coefficient is satisfied that 0<k<0.33, the remote cracks in en echelon forms occur in the remote region from the hole. The minimum distance of remote crack from the hole boundary is more than 0.5r (“r” denotes the radius of hole). Remote cracks are resulted by the connection of many micro vertical tensile cracks. The distribution laws of remote cracks are followed by the modulus r (i=1, 2, 3, 4). A primary tensile crack is one necessary condition for the occurrence of remote cracks for circular geotechnical engineering structure.

scholarly journals Numerical Simulation of Crack Initiation and Growth in PBX High Explosive Subject to Compression

2018 ◽  
Vol 183 ◽  
pp. 01019
Author(s):  
Huang Xicheng ◽  
Li Shangkun ◽  
Qiang Wei ◽  
Chen Gang ◽  
Tian Rong ◽  
...  
Keyword(s):  
Crack Initiation ◽  
Structural Integrity ◽  
High Explosive ◽  
Compressive Loading ◽  
Confining Pressure ◽  
Complex Stress ◽  
Flow Rule ◽  
Brittle Solids ◽  
High Confining Pressure ◽  
Stress States

PBX solid high explosive exhibits brittle behaviour in uniaxial tension, quasi-brittle in uniaxial compression, and ductile when subject to high confining pressure. Tension cracking is the primary failure mode of PBX quasi-brittle solid, which is the main effect leading to overall failure of structural integrity. One characteristics of brittle or quasi-brittle solids, such as PBXs, is that when subject to overall compressive loading, the tensile cracks can still initiate inside the material due to existence of imperfection within the materials. In present study the extended finite element method is applied to analyze the cracking failure mechanism in the PBX 9502 platelike specimen with cavity subjected to overall compression. The nonlinear constitutive behaviours and failure of PBX under complex stress states were described by means of stress state dependent strength surface, non-associated flow rule and cohesive model the nonlinear behaviors of PBXs, including failure. Analysis indicates the tensile stress around the cavity arises in the specimen although loaded by overall compression, and this local tensile condition leads to cracking initiation. The comparison between simulation results and the experimental data published by LANL[Liu C, Thompson D G. Crack initiation and growth in PBX 9502 high explosive subject to compression. Journal of Applied Mechanics, 2014, 81(10):212-213] shows that they are in agreement with each other on some aspects of crack behaviours, including overall development of crack history and inflexion, crack initiation moment, crack initial speed, etc.

scholarly journals Study on mechanical behavior and damage process of concrete with initial damage under eccentric load

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Ge Lina ◽  
Yi Fu ◽  
Zhou Junxia ◽  
Du Changbo
Keyword(s):  
Crack Initiation ◽  
Shear Crack ◽  
Peak Stress ◽  
Confining Pressure ◽  
Type I ◽  
Uniform Load ◽  
Eccentric Load ◽  
Initiation Point ◽  
Initial Damage ◽  
Damage Process

AbstractIn order to analyze the influence of eccentric load on mechanical properties and damage process of concrete with initial damage, the eccentric load compression tests of concrete under different confining pressures were carried out with the help of PFC particle flow program. The results show that: the eccentric load does not change the relationship between peak stress, crack initiation stress and confining pressure of concrete under uniform load, but decrease the value of them. The peak stress increasing coefficient under uniform load is higher than that under eccentric load, and the peak stress increasing coefficient increases in a linear function with the confining pressure, and the increasing rate is approximately the same. Under uniaxial compression of eccentric load, a type I shear crack approximately parallel to the loading direction is formed, while under biaxial compression, a bending type shear crack with the lower tip of the initial crack as the inflection point is formed. The number of microcracks in concrete under uniform load and eccentric load can be divided into three stages: the calm period at the initial loading stage, the pre-peak expansion period from crack initiation point to peak point, and the rapid increase period after the peak.

Brittle Fracture Analysis of a Dissimilar Metal Weld

2013 ◽  
Author(s):  
A. Blouin ◽  
S. Chapuliot ◽  
S. Marie ◽  
J. M. Bergheau ◽  
C. Niclaeys
Keyword(s):  
Brittle Fracture ◽  
Weld Joint ◽  
Threshold Stress ◽  
Base Alloy ◽  
Welding Process ◽  
Loading Conditions ◽  
Brittle To Ductile Transition ◽  
Dissimilar Metal ◽  
Dissimilar Metal Weld ◽  
Metal Weld

One important part of the integrity demonstration of large ferritic components is based on the demonstration that they could never undergo brittle fracture. Connections between a ferritic component and an austenitic piping (Dissimilar Metal Weld — DMW) have to respect these rules, in particular the Heat Affected Zone (HAZ) created by the welding process and which encounters a brittle-to-ductile transition. Within that frame, the case considered in this article is a Ni base alloy narrow gap weld joint between a ferritic pipe (A533 steel) and an austenitic pipe (316L stainless steel). The aim of the present study is to show that in the same loading conditions, the weld joint is less sensitive to the brittle fracture than the surrounding ferritic part of the component. That is to say that the demonstration should be focused on the ferritic base metal which is the weakest material. The bases of this study rely on a stress-based criterion developed by Chapuliot et al., using a threshold stress (σth) below which the cleavage cannot occur. This threshold stress can be used to define the brittle crack occurrence probability, which means it is possible to determine the highest loading conditions without any brittle fracture risk.

Crack Growth by Dimensional Reduction Methods

2012 ◽  
Vol 525-526 ◽  
pp. 17-20
Author(s):  
P.H. Wen ◽  
M.H. Aliabadi
Keyword(s):  
Crack Growth ◽  
Dimensional Reduction ◽  
Crack Extension ◽  
Initial Growth ◽  
Stress Criterion ◽  
The Maximum Principle ◽  
Reduction Methods ◽  
Small Increments ◽  
Crack Growth Path ◽  
Crack Paths

This paper presents a new fatigue crack growth prediction by using the dimensional reduction methods including the dual boundary element method (DBEM) and element-free Galerkin method (EFGM) for two dimensional elastostatic problems. One crack extension segment, i.e. a segment of arc, is introduced to model crack growth path. Based on the maximum principle stress criterion, this new prediction procedure ensures that the crack growth is smooth everywhere except the initial growth and the stress intensity factor of mode II is zero for each crack extension. It is found that the analyses of crack paths using coarse/large size of crack extension are in excellent agreement with analyses of the crack paths by the tangential method with very small increments of crack extension.

scholarly journals Verification of Brittle Fracture Criteria for Bimaterial Structures

2014 ◽  
Vol 8 (1) ◽  
pp. 44-48
Author(s):  
Grzegorz Mieczkowski ◽  
Krzysztof Molski
Keyword(s):  
Experimental Data ◽  
Composite Materials ◽  
Cyclic Loading ◽  
Brittle Fracture ◽  
Axial Loading ◽  
Loading Conditions ◽  
Fracture Criteria ◽  
Interfacial Cracks ◽  
Theoretical Results ◽  
Brittle Fracture Criteria

Abstract The increasing application of composite materials in the construction of machines causes strong need for modelling and evaluating their strength. There are many well known hypotheses used for homogeneous materials subjected to monotone and cyclic loading conditions, which have been verified experimentally by various authors. These hypotheses should be verified also for composite materials. This paper provides experimental and theoretical results of such verifications for bimaterial structures with interfacial cracks. Three well known fracture hypotheses of: Griffith, McClintock and Novozhilov were chosen. The theoretical critical load values arising from each hypotheses were compared with the experimental data including uni and multi-axial loading conditions. All tests were carried out with using specially prepared specimens of steel and PMMA.

The Analysis of the Stress Field and Crack of Rock under the Blast Loading

2010 ◽  
Vol 168-170 ◽  
pp. 1252-1255
Author(s):  
Zhong Guo Zhang ◽  
Ya Dong Bian ◽  
Bin Gao
Keyword(s):  
Stress Field ◽  
Crack Initiation ◽  
Crack Extension ◽  
Crack Tip ◽  
Blast Loading ◽  
Crack Arrest ◽  
The Stability ◽  
Crack Tip Stress

The crack tip stress field of rock is analyzed under blast loading, and the crack arrest criterion, the conditions of rock crack initiation and crack extension are presented in this paper. The study will help the design of maintaining the stability of stope drift active workings.

scholarly journals Brittle Fracture Theory Describes the Onset of Frictional Motion

2019 ◽  
Vol 10 (1) ◽  
pp. 253-273 ◽  
Author(s):  
Ilya Svetlizky ◽  
Elsa Bayart ◽  
Jay Fineberg
Keyword(s):  
Friction Coefficient ◽  
Brittle Fracture ◽  
Static Friction ◽  
Quantitative Agreement ◽  
Interface Fracture ◽  
Earthquake Dynamics ◽  
Rupture Dynamics ◽  
Static Friction Coefficient ◽  
Fracture Theory ◽  
Macroscopic Motion

Contacting bodies subjected to sufficiently large applied shear will undergo frictional sliding. The onset of this motion is mediated by dynamically propagating fronts, akin to earthquakes, that rupture the discrete contacts that form the interface separating the bodies. Macroscopic motion commences only after these ruptures have traversed the entire interface. Comparison of measured rupture dynamics with the detailed predictions of fracture mechanics reveals that the propagation dynamics, dissipative properties, radiation, and arrest of these “laboratory earthquakes” are in excellent quantitative agreement with the predictions of the theory of brittle fracture. Thus, interface fracture replaces the idea of a characteristic static friction coefficient as a description of the onset of friction. This fracture-based description of friction additionally provides a fundamental description of earthquake dynamics and arrest.

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