Further studies on dynamic crack branching

Kobayashi, A. S.; Kang, Bruce S.; Barker, Donald E.

doi:10.1007/bf02330060

Cited by 38 publications

(19 citation statements)

References 11 publications

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“…The dependence 7(V) takes place only in the regime of controlled fracture for dT/dV > 0; in this case, the dependences 7(u) and 7(V) are similar (they differ only in the scale on the velocity axis). The results agree with the data of [10,23], but only qualitatively agree with the data of [17]. The appreciable increase in 7 at V > 100 m/sec and Kla at v > 104 sec -1 is caused by the local heating of the material at the crack tip due to transition to adiabatic conditions and "unfreezing" of the SHV relaxation process.…”

Section: P(t) = Ese(t)supporting

confidence: 79%

Determination of fracture toughness and fracture energy of brittle materials under impact wedging

Eremenko¹,

Novikov²,

Синицын³

et al. 1996

J Appl Mech Tech Phys

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539.375 1. Test Procedure. Modern fracture mechanics is characterized by an advanced mathematical apparatus and a high level of experimental facilities [1]. The available theoretical and experimental methods allow one to determine criterion parameters for various types of loading. Standard methods of determination of fracture toughness Klc in statics, Kid in dynamics, and the dynamic stress intensity factor (SIF) in crack growth KD or arrest Kla have been developed [2, 3].In high-speed loading for a characteristic loading time of (1-5) 9 10 -3 sec and smaller using standard loading schemes, difficulties arise which are due to dynamic effects.We used stress-wave loading of a specimeu by the Hopkinson split bar (HSB) method to determine the fracture toughness and fracture energy of brittle materials under high-speed loading.Hopkinson proposed to determine stresses in a shock-wave pulse propagating in a bar under explosive loading from the rebound velocity of a measuring bar which is butt-joined with a loading bar [4]. The fracture stresses of brittle materials under tension are considerably lower than those under compression, and a spall forms in bars under intense pulse loading. Khanukaev [5] determined critical spalling stresses in rocks (granite, marble, etc.) from the velocity of the part spalled from the bar, using the Hopkinson method.Ivanov [6] reported determination of fracture energy in spalling experiments using the integral energy criterion. Kol'skii improved the Hopkinson method. He proposed to measure the wave velocities of transmitted pulses and to compute stresses and strains in a specimen placed between two bars using measured parameters of incident, reflected, and transmitted pulses [7]. Later, the HSB method led to many applications in various types of uniaxial dynamic loading experiments, including determination of fracture toughness.Novikov [8] reported experiments on determination of the dynamic fracture toughness of hard alloys loaded by the HSB method. Specimens in the form of disks (tablets) with a through central cut loaded in the diametric direction were tested.An original procedure for determining the fracture toughness of steels and alloys was proposed by Kostin et al. [9]. A bar having a ringed cut with a sharp (fatigue) crack in the base of the cut is subjected to shock-wave loading. As a specimen, the part of the bar neighboring the cut is studied. According to the HSB method, the stresses and forces P in the section of the crack and also the strains 6 due to its opening are determined and a quasi-static P -6 diagram is constructed and analyzed by the standard method. The dynamic fracture toughness Kid and the fracture energy Gc are determined from the P -~ diagram. In the case of plastic materials, the calculation is performed using the J-integral.The growth rate of SIF iswhere r, is the characteristic time of increase in load from zero to a load that corresponds to a critical state. The attainable loading rate for steels is of the order of 10 6 (MPa 9 m 1/2) sec -1. This is app...

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Section: P(t) = Ese(t)supporting

confidence: 79%

Determination of fracture toughness and fracture energy of brittle materials under impact wedging

Eremenko¹,

Novikov²,

Синицын³

et al. 1996

J Appl Mech Tech Phys

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“…This concept was applied to dynamic crack curving by Ramulu and Kobayashi [8]. In accordance with previous findings, Ramulu et al [9] observed that successful branching always took place at a constant value of K I , which was therefore cited as a necessary condition for branching to occur. Under these conditions, multiple off-axis secondary cracks were generated and the dynamic curving criterion provided a sufficient condition for these secondary cracks to kink simultaneously.…”

Section: Introductionmentioning

confidence: 55%

“…Earlier work by Kalthoff [10] pointed out that attraction or repulsion between the two branches is controlled by the ratio K II /K I . Ramulu et al [9] observed that the photoelastic patterns of running branched cracks initially showed strong mixed mode effects but the mode II effect weakened as the cracks propagated, and eventually approached K II = 0.…”

Section: Introductionmentioning

confidence: 99%

Dynamic crack bifurcation in PMMA

Murphy

Ali

2006

Engineering Fracture Mechanics

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Publication informationEngineering Fracture Mechanics, 73 (16): 2569-2587Publisher Elsevier Item record/more information http://hdl.handle.net/10197/4908 Publisher's statementThis is the author's version of a work that was accepted for publication in Engineering Fracture Mechanics. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Engineering Fracture Mechanics (73, 16, (2006) AbstractAn investigation of the branching characteristics of small PMMA single edge notched tensile (SENT) specimens is presented. The influence of notch depth and specimen thickness was examined and it was found that branching only occurred for thicker specimens and very short notch depths. The location at which successful branching occurred was very consistent for a given notch depth. Subsequently, however, a statistical variation of branching patterns was observed. A series of simulations was then performed to provide further insight into these tests and in particular to examine the evolution of the fracture process region ahead of the running crack. A finite volume / cohesive zone formulation was used to model micro-crack nucleation and dynamic interaction in the process zone. The cohesive strength and fracture resistance were estimated from unnotched tensile tests and the application of LEFM to the notch test data. Even though a very simple criterion was used to govern the insertion and subsequent behaviour of the cohesive surfaces in the model, many of the experimental observations were reproduced, including high frequency oscillations in crack velocity, the substantial increase in the fracture surface area due to the formation of subsurface microcracks, and location at which successful branching took place.

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“…Crack branching in brittle materials has been a subject of theoretical [1][2][3][4] and experimental [5][6][7][8][9][10][11][12][13][14][15][16][17][18] studies. In particular, a criterion which controls the initiation of crack branching has drawn the attention of many researchers.…”

Section: Introductionmentioning

confidence: 99%

“…Hence different propositions have been proposed as to the role of the high crack velocity. Several researchers suggested that Kd should play a dominating role while high crack velocity should be a necessary but not a sufficient condition for the branching [6][7][8][9]14]. Recently a review of crack branching has been given by Ramulu and Kobayashi [18].…”

Section: Introductionmentioning

confidence: 99%

Branching of a fast crack in polymers

Arakawa

Toko

1991

Int J Fract

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Crack branching in Araldite D and Homalite-911 was studied using a modified Cranz-Schardin type high speed camera which provided simultaneously taken shadow patterns and specimen-focussed images. Fracture parameters including crack velocity ~i, stress intensity factor Kd and specific crack extension resistance R* were measured in the course of crack propagation. No definite critical values could be determined with one of those fracture parameters for the onset of crack branching. Instead, the product R*/t, i.e., energy per unit crack width per unit time, was found to have a critical value for the branching.

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Further studies on dynamic crack branching

Cited by 38 publications

References 11 publications

Determination of fracture toughness and fracture energy of brittle materials under impact wedging

Determination of fracture toughness and fracture energy of brittle materials under impact wedging

Dynamic crack bifurcation in PMMA

Branching of a fast crack in polymers

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