Small-Specimen Brittle-Fracture Toughness Testing

Andrews, WR; Kumar, Vineet; Little, MM

doi:10.1520/stp28819s

Cited by 13 publications

(4 citation statements)

References 8 publications

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“…On the lower shelf and in the transition region, where cleavage and quasi-cleavage are the micromechanisms responsible for fracture, the difference between the critical SIF values for specimens of different sizes and with cracks of different lengths is primarily determined by a statistical factor in accordance with Weibull's weak-link hypothesis [17][18][19][20]. Though large enough in the section where the cracks are situated, the specimens used here are 15 to 20 times smaller than the forging from which they were fabricated.…”

Section: Fracture Toughness Temperature Dependencementioning

confidence: 99%

The Influence of Plastic Prestraining on Brittle Fracture Resistance of Metallic Materials With Cracks

Pokrovsky¹,

Troshchenko²,

Kopcmsky³

et al. 1995

Fatigue Fract Eng Mat Struct

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The purpose of the present work was to study the influence of different regimes of overloading of pressure vessel steels in different states which correspond to the steel properties at the beginning of a reactor operation and at different degrees of embrittlement (simulated by heat treatment). The experiments were performed on 25, 50 and 150 mm thick specimens with short and long cracks of various shape in the temperature range from 293 to 623 K corresponding to the service temperature range of those steels.The following factors were investigated contribution of different effects (residual stresses, strain hardening, crack tip blunting) into the enhancement of the brittle fracture resistance of steels after warm prestressing, stability of the positive warm prestressing effect during subsequent exposure of the steels to different service loading conditions; size effect on optimal regimes of thermo-mechanical prestressing and on the brittle fracture resistance characteristics of the steels studied after warm-prestressing. An approach is proposed to predict the increase in the brittle fracture resistance of steels with cracks after warm prestressing. NOMENCLATURE a = crack length or small semi-axis of a semi-elliptical surface crack Aa =crack increment B, W, S = 3PB specimen thickness, width and length, respectively c = large semi-axis of a semi-elliptical surface crack E = Young's modulus JI, =critical J-integral at the crack growth onset (ASTM standard E813) K = stress intensity factor K,c =critical stress intensity factor under plane strain conditions K , =critical stress intensity factor (non-plane strain condition) determined at crack growth onset by KCV =impact fracture energy determined by testing V-notched specimens with a 0.25 mm notch tip HB = hardness the 5% secant method (GOST 25.506-85, ASTM standard E616-82) radius (GOST 9454-60, type IV) K, = critical stress intensity factor after warm prestressing K h = stress intensity factor during holding under load K,, = critical stress intensity factor defined via JLc value K , = critical stress intensity factor determined by the 5% secant method n = strain hardening coefficient AN = number of cycles P = load rp = plastic zone size T = temperature & = temperature of holding under load V = crack faces displacement along the load Line 6 = crack tip opening displacement Kr = K,/Kc!T,) K,, =maximum stress intensity factor in a cycle 73 1 132 V. V. POKROVSKY et at. ai = critical crack tip opening displacement 6, =longitudinal critical strain v = Poisson's ratio u, = ultimate tensile strength uy = yield stress $ =transverse critical strain S , , = residual crack tip opening displacement at unloading after warm prestressing

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Section: Fracture Toughness Temperature Dependencementioning

confidence: 99%

The Influence of Plastic Prestraining on Brittle Fracture Resistance of Metallic Materials With Cracks

Pokrovsky¹,

Troshchenko²,

Kopcmsky³

et al. 1995

Fatigue Fract Eng Mat Struct

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“…[8][9][10][11][12][13][14]. As discussed by Mertde, 2 this variability can be traced to physical effects, such as difference in size and geometD, of test specimens, and to the existence of scatter due to material variability.…”

Section: Fracture-toughness Correlation Parametersmentioning

confidence: 99%

An investigation of crack-tip stress field criteria of predicting cleavage-crack initiation

Keeney-Walker¹,

Bass²,

Landes³

1991

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“…However, variations in loading conditions and in specimen geometries are known to produce considerable differences I- [4][5][6][7][8][9][10][11][12][13][14][15]. These parameters, when successfully determined, provide useful guidance for material ranking and for design against fracture.…”

Section: Introductionmentioning

confidence: 99%

“…Accordingly, the CL theory derives the rate of crack propagation (da/dt) as [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]17] da flW~…”

Section: Introductionmentioning

confidence: 99%

The specific enthalpy of fracture for beta Ti-15-3 alloy

1992

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Fatigue crack propagation (FCP) experiments were conducted on beta Ti-15-3 alloy under various loading conditions to examine the constancy of the specific enthalpy for fracture, advanced by the Crack Layer (CL) theory as a material parameter characteristic of its intrinsic toughness. The energy release rate and the irreversible work were determined from load-displacement curves during crack propagation. Microscopic and diffraction analyses were conducted to identify the damage mechanisms ahead of the crack tip. A damage zone whose geometry exhibited plane strain character at the initial stage of crack propagation was observed optically. The damage zone transformed into plane stress configuration when the crack reached half its critical length. Damage mechanisms involved slip lines and microcracking which is believed to ensue from intense accumulation of slip processes. The magnitude of microcracking became more weighty as the crack moved deeper into plane stress dominance. The damage preceding crack advance was quantitatively assessed as the 'crack resistance moment' which is the volume of transformed material per unit crack extension. Application of the CL theory to the data generated under a wide range of applied stress levels gave rise to a constant value of the specific enthalpy of fracture, 20 MJ/m 3. This value is in close agreement with the specific energy of slip lines computed from microstructural considerations.

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Small-Specimen Brittle-Fracture Toughness Testing

Cited by 13 publications

References 8 publications

The Influence of Plastic Prestraining on Brittle Fracture Resistance of Metallic Materials With Cracks

The Influence of Plastic Prestraining on Brittle Fracture Resistance of Metallic Materials With Cracks

An investigation of crack-tip stress field criteria of predicting cleavage-crack initiation

The specific enthalpy of fracture for beta Ti-15-3 alloy

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