Fracture-toughness tests and displacement and crack-stability analyses of tungsten round bend specimens

Underwood, J. H.; Baratta, Francis I.; Zalinka, J. J.

doi:10.1007/bf02325993

Cited by 8 publications

(9 citation statements)

References 9 publications

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“…The three-dimensional mesh generation and the J-integral finite element calculations [19] were carried out using ABAQUS [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]]. An applied load of 100 N, elastic modulus of 350 GPa, and a Poisson's ratio of 0.23 were used in all 3-D FEA.…”

Section: Methodsmentioning

confidence: 99%

“…The K~ values obtained from the FEA were extended from e' = 0 to e' = 1 by utilizing either (14) or (16) and (17). The results are fitted to an inverse fourth order polynomial function and an exponential function for cases 1 (Eqns.…”

Section: Non-dimensionalizing K Imentioning

confidence: 99%

“…The results are fitted to an inverse fourth order polynomial function and an exponential function for cases 1 (Eqns. (13), (14), and (17)) and 2 (Eqns. (15), (16), and (17)) respectively.…”

Section: Non-dimensionalizing K Imentioning

confidence: 99%

“…Studies in the area of crack stability [10][11][12][13][14] have shown that the round bar tested in three point bending is more stable than the corresponding rectangular beam geometry [14]. This is especially significant for ceramic specimens as their stiffness often exceeds that of the testing machine leading to unstable tests.…”

Section: Introductionmentioning

confidence: 99%

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Stress intensity factor calculation for a modified round bend bar by 3-D finite element analysis

1993

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Stress intensity factors were calculated for a modified round bend bar (MRBB) using 3-D finite element analysis. The results were compared with published solutions for a rectangular and round bend bars. The stress intensity values for the MRBB are between those for the two other geometries as expected. The stress intensity solutions were non-dimensionalized utilizing limit solution for short and long cracks.

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Section: Methodsmentioning

confidence: 99%

Section: Non-dimensionalizing K Imentioning

confidence: 99%

“…The results are fitted to an inverse fourth order polynomial function and an exponential function for cases 1 (Eqns. (13), (14), and (17)) and 2 (Eqns. (15), (16), and (17)) respectively.…”

Section: Non-dimensionalizing K Imentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Stress intensity factor calculation for a modified round bend bar by 3-D finite element analysis

1993

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“…Therefore, any slight change in K~ as a function of crack length can cause considerable variation in compliance and the resulting calculation of stability. Because compliance was not accurately known, this mathematical process was applied to the straight-fronted edge crack in a three-point loaded round bend bar, [2][3][4]. In these works the stress intensity factors (SIF) presented by [5] were employed to obtain stability factors for the round bar configuration.…”

mentioning

confidence: 99%

Stability revisited for a straight-fronted edge crack in a three-point loaded round bend bar

Baratta¹

1993

Int J Fract

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Stable crack extension is difficult to realize for very brittle materials in many loading geometries for which the crack extends into an increasing stress intensity field. Stable crack extension is necessary for fracture experiments that need to be well controlled, such as in the determination of: fracture toughness, R-curve data and fatigue crack growth data. The prediction of stability is necessary in the guidance of such experiments. Theoretical calculation of the stability parameter includes: the knowledge of specimen compliance, the second derivative and the squaring of the first derivative of compliance with respect to the crack area, see (1). If the compliance is not accurately known, then it must be attained through the integral of strain energy (G) and its squared relationship with stress intensity (K~) and Young's modulus of elasticity (E), [1]. Therefore, any slight change in K~ as a function of crack length can cause considerable variation in compliance and the resulting calculation of stability. Because compliance was not accurately known, this mathematical process was applied to the straight-fronted edge crack in a three-point loaded round bend bar, [2][3][4]. In these works the stress intensity factors (SIF) presented by [5] were employed to obtain stability factors for the round bar configuration. Reference [5] was the best available at that time; the SIF's were estimated for a three-point loaded beam of several span-to-diameter ratios (S/D) based on the experimental work by [6] and the constant moment beam results using a finite element analysis by Daoud and Cartwright [7]. Therefore, the stability results given in [2-4] await further improvement either by employing a more accurate description of K~ or a direct determination of compliance. Now the latter case can be realized for the straight-fronted edge crack in a three-point loaded round bend bar by not having to utilize the integral of strain energy release rate to obtain compliance, but by directly employing the most accurate to date wide range compliance results of [8]. This is the path taken for the round beam, shown in Fig. 1, and in the approach that follows.The basis for general stability analyses are well presented elsewhere, see [9][10][11]. Therefore, these analyses are not repeated here. However, some comments are appropriate: The general stability equation used here, which was taken from [10], presumes that an idealized testing system is utilized, which infers that constant crosshead displacement is employed, and that rigid body motion occurs between the crosshead of the testing machine and the point of load application to the specimen; i.e., the deflection of the load cell is ignored. Most experimenters choose 'stroke control' during testing because it is a convenient option when using a closed loop hydraulic testing machine. Such a testing system is designed so that a transducer senses the displacement of the specimen, which is then fed Int Journ of Fracture 62 (1993)

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Stress intensity factor and load-line displacement expressions for the round bar bend specimen

Underwood

1993

Int J Fract

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Fracture-toughness tests and displacement and crack-stability analyses of tungsten round bend specimens

Cited by 8 publications

References 9 publications

Stress intensity factor calculation for a modified round bend bar by 3-D finite element analysis

Stress intensity factor calculation for a modified round bend bar by 3-D finite element analysis

Stability revisited for a straight-fronted edge crack in a three-point loaded round bend bar

Stress intensity factor and load-line displacement expressions for the round bar bend specimen

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