Thermal shock resistance and fracture toughness during the graphitization process

“…Despite these difficulties the centrally slotted Brazilian Disc (BD) or the CBD geometry specimens have been widely used to determine mixed mode fracture toughness and mode II fracture of graphite [11,12,13,14,15]. Recently, Smith et al [16] published on the subject of the consequences of the T-stress in elastic brittle fracture.…”

Section: Introductionmentioning

confidence: 99%

“…Yamauchi et al also researched mixed mode I/II fracture toughness of graphite using both center-notched disk specimens [17] and edge-notched half disc specimens [18] for an impact fracture test method. Other researchers have studied the mode I fracture toughness of graphite and thermal shock mode I fracture toughness of graphite [12,19,20].…”

Section: Introductionmentioning

confidence: 99%

The shear fracture toughness, K, of graphite

Burchell

Erdman

2016

Carbon

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The critical shear stress intensity factor, K IIc , herein referred to as the shear fracture toughness, K IIc (MPa√m), of two grades of graphite are reported. The range of specimen volumes was selected to elucidate any specimen size effect, but smaller volume specimen tests were largely unsuccessful, shear failure did not occur between the notches as expected. This was probably due to the specimen geometry causing the shear fracture stress to exceed the compressive failure stress. In subsequent testing the specimen geometry was altered to reduce the compressive footprint and the notches (slits) made deeper to reduce the specimen's ligament length. Additionally, we added the collection of Acoustic Emission (AE) during testing to assist with the identification of the shear fracture load. The means of K IIc from large specimens for PCEA and NBG-18 are 2.26 MPa√m with an SD of 0.37 MPa√m and 2.20 MPa√m with an SD of 0.53 MPa√m, respectively. The value of K IIc for both graphite grades was similar, although the scatter was large. In this work we found the ratio of K IIc /K Ic ≈1.6.

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“…Since the strategic importance of this variable, several researchers have tried to determine the fracture toughness of polycrystalline graphite under mode I or under mixed mode tensile-shear loading conditions (e.g. Yamauchi et al, 2000Yamauchi et al, , 2001Wang & Liu, 2008;Etter et al, 2004;Yum & You, 2001;Wosu et al, 2005;Jurf & Pipes, 1982;Latella & Liu, 2006;Sato et al, 1978Sato et al, , 1981Knibbs, 1967;Allard et al, 1991;Burchell, 1996;Lomakin et al, 1975;Losty, 1962;Greenstreet, 1968;Greenstreet et al, 1969;Aliha et al, 2015a;Nemeth, 2011;Mostafavi et al, , 2013aMostafavi et al, , 2013b. Especially Awaji and Sato (1978), Li et al (1999), Yamauchi et al (2000Yamauchi et al ( , 2001, and Shi et al (2008) conducted a large number of tests to determine fracture toughness under mode I and mixed mode I+II with different cracked specimens.…”

Section: Introductionmentioning

confidence: 99%

“…Jurf and Pipes (1982) instead adopted the laser irradiation technique. Regarding thermal properties, thermal shock fracture toughness was investigated by Sato et al (1981). They considered two different types of carbon as a function of heat treatment temperature during the graphitization process.…”

Section: Introductionmentioning

confidence: 99%

Review of local strain energy density theory for the fracture assessment of V-notches under mixed mode loading

Ayatollahi¹,

Berto²,

Campagnolo³

et al. 2017

10.5267/j.esm

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The present work summarizes some recent experimental, theoretical and numerical results on brittle fracture of isostatic polycrystalline graphite. The analyses have been carried out on Vnotched samples under mixed mode (I+II), torsion and compression loading, considering various combinations of the notch tip radius, opening angle and notch tilt angle. The static strength of the considered specimens is assessed through an approach based on the strain energy density averaged over a control volume. The center of the control volume is located on the notch edge, where the principal stress reaches its maximum value. The correct orientation is obtained by a rigid rotation of the crescent-shaped volume while the size depends on the fracture toughness and the ultimate strength of the material. This methodology has been already used in the literature to analyze U-and V-shaped notches subject to mode I loading with very good results and advantages with respect to classic approaches. The results reported in this new work show, also under mixed mode loading conditions, good agreement between experimental data and theoretical predictions.

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Thermal shock resistance and fracture toughness during the graphitization process

Cited by 20 publications

References 17 publications

Effect of heat treatment temperature (HTT) on density, weight and volume of glass-like carbon (GC)

Effect of heat treatment temperature (HTT) on density, weight and volume of glass-like carbon (GC)

The shear fracture toughness, K, of graphite

Review of local strain energy density theory for the fracture assessment of V-notches under mixed mode loading

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