Plane strain crack toughness testing of high strength metallic materials.
01 Jan 1966-
About: The article was published on 1966-01-01. It has received 1318 citations till now. The article focuses on the topics: Fracture toughness & Crack closure.
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Book•
01 Jan 1971
TL;DR: A concise, self-contained introduction to solid polymers, the mechanics of their behavior and molecular and structural interpretations can be found in this article, which provides extended coverage of recent developments in rubber elasticity, relaxation transitions, non-linear viscoelastic behavior, anisotropic mechanical behavior, yield behavior of polymers and other fields.
Abstract: A concise, self-contained introduction to solid polymers, the mechanics of their behavior and molecular and structural interpretations. This updated edition provides extended coverage of recent developments in rubber elasticity, relaxation transitions, non-linear viscoelastic behavior, anisotropic mechanical behavior, yield behavior of polymers, breaking phenomena, and other fields.
2,335 citations
TL;DR: The tensile strength of mother-of-pearl (nacre) is of the order of 170 MPa (dry) and 140 MPa(wet), values which are best modelled assuming that pullout of the platelets is the main mode of failure as discussed by the authors.
Abstract: Mother-of-pearl (nacre) is a platelet-reinforced composite, highly filled with calcium carbonate (aragonite). The Young modulus, determined from beams of a span-to-depth ratio of no less than 15 (a necessary precaution), is of the order of 70 GPa (dry) and 60 GPa (wet), much higher than previously recorded values. These values can be derived from ‘shear-lag’ models developed for platey composites, suggesting that nacre is a near-ideal material. The tensile strength of nacre is of the order of 170 MPa (dry) and 140 MPa (wet), values which are best modelled assuming that pull-out of the platelets is the main mode of failure. In three-point bending, depending on the span-to-depth ratio and degree of hydration, the work to fracture across the platelets varies from 350 to 1240 J m -2 . In general, the effect of water is to increase the ductility of nacre and increase the toughness almost tenfold by the associated introduction of plastic work. The pull-out model is sufficient to account for the toughness of dry nacre, but accounts for only a third of the toughness of wet nacre. The additional contribution probably comes from debonding within the thin layer of matrix material. Electron microscopy reveals that the ductility of wet nacre is caused by cohesive fracture along platelet lamellae at right angles to the main crack. The matrix appears to be well bonded to the lamellae, enabling the matrix to be stretched across the delamination cracks without breaking, thereby sustaining a force across a wider crack. Such a mechanism also explains why toughness is dependent on the span-to-depth ratio of the test piece. With this last observation as a possible exception, nacre does not employ any really novel mechanisms to achieve its mechanical properties. It is simply ‘well made’. The importance of nacre to the mollusc depends both on the material and the size of the shell. Catastrophic failure will be very likely in whole, undamaged shells which behave like unnotched beams at large span-to-depth ratios. This tendency is increased by the fact that predators act as ‘soft’ machines and store strain energy which can be fed into the material very quickly once the fracture stress has been reached. It may therefore be advantageous to have a shell made of an intrinsically less tough material which is better at stopping cracks (e. g. crossed lamellar). However, nacre may still be preferred for the short, thick shells of young molluscs, as these have a low span-to-depth ratio and can make better use of ductility mechanisms.
1,123 citations
TL;DR: In this paper, a crack in a structural member introduces a local flexibility that affects its vibration response, and the crack will open and close in time depending on the rotation and vibration amplitude.
1,080 citations
Journal Article•
TL;DR: In this paper, the applicability of linear elastic fracture mechanics to concrete and similar materials is analysed by use of the Fictitious Crack Model, where the fracture zone in front of a crack is represented by a fictitious crack able to transfer stress.
Abstract: A calculation model (the Fictitious Crack Model), based on fracture mechanics and the finite element method, 1s presented. In the model the fracture zone in front of a crack is represented by a fictitious crack that 1s able to transfer stress. The stress transferring capability of the fictitious crack normally decreases when the crack width increases. The applicability of linear elastic fracture mechanics to concrete and similar materials is analysed by use of the Fictitious Crack Model. It" Is found that linear elastic fracture mechanics 1s too dependent on, among other things, specimen dimensions to be useful as a fracture approach, unless the dimensions, for concrete structures, are in order of meters. The usefulness of the J-integral, the COD-approach and the R-curve analysis is also found to be very limited where cementitious materials are concerned. The complete tensile stress-strain curve is introduced as a fracture mechanical parameter. The curve can be approximatively determined if the tensile strength, the Young's modius and the fracture energy are known. Su1table~lest methods Tor determining" TRise~~/'Voerties are presented and test results are reported for a number of concrete qua! » a. A new tyr * very stiff tensile testing machine Is presented by which it is possible to carry r . itable tensile tests on concrete. The complete tensile stress-strain curves h •«• feen determined for a number of concrete qualities. The thesi' overs a complete system for analysing crack propagation in concrete as it Include* -ealistic material model, a functional calculation model and methods for determiv" «/ the material properties necessary for the calculations. Therefore this work oi r t to be of use as a base for further studies of the fracture process of concrete < i similar materials.
897 citations
Cites background from "Plane strain crack toughness testin..."
...where f(a/d) for a three-point bend test is (Brown and Srawley, 1967): f(a/d) = 1....
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TL;DR: In this article, a technical review of fracture toughness testing, evaluation and standardization for metallic materials in terms of the linear elastic fracture mechanics as well as the elastic-plastic fracture mechanics is given.
594 citations
References
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658 citations
186 citations
01 Jan 1965
TL;DR: In this article, a boundary value collocation procedure was used in conjunction with the Williams stress function to determine values of the stress-intensity factor K for single edge cracks of various depths in specimens subjected to pure bending.
Abstract: : A boundary-value-collocation procedure was used in conjunction with the Williams stress function to determine values of the stress-intensity factor K for single edge cracks of various depths in specimens subjected to pure bending. The results are of use in connection with K(sub Ic) fracture toughness tests, which utilize rectangular-section crack-notch beam specimens loaded in four-point bending, and are in good agreement with published results derived from experimental compliance measurements. The results are expressed in convenient, compact form in terms of the dimensionless quantity Y(exp 2)=K(exp 2)B(exp 2)W(exp 3)/M(exp 2), which is a function of relative crack depth a/W only, where B and W are the specimen width and thickness and M is the applied bending moment. On the assumption that the condition for a valid K(sub Ic) test is that the maximum nominal stress at the crack tip should not exceed the yield strength of the material, the K(sub Ic) measurement capacity of bend specimens was estimate as a function of a/W. The measurement capacity is proportional to the yield strength and to the square root of the specimen depth, and it is greatest for a/W in the range 0.2 to 0.3. Values of K for single-edge-notch specimens subjected to combined bending and tension were obtained by superposition of the present results and those of earlier work for specimens loaded in uniform tension. These values are of interest in connection with the use of single-edge-notch specimens that are off-center pin-loaded in tension. It is shown that the K(sub Ic) measurement capacity of such specimens is not very sensitive to the eccentricity of loading.
145 citations
TL;DR: In this paper, an approximate stress intensity factor for an embedded elliptical crack in a plate which is subjected to uniaxial tension in the direction perpendicular to the crack surface is derived.
Abstract: An approximate stress intensity factor is derived for an embedded elliptical crack in a plate which is subjected to uniaxial tension in the direction perpendicular to the crack surface. The major axis of an eccentrically located elliptical crack is assumed to be parallel with the two plate surfaces. The approximate stress intensity factors on the minor axis of the elliptical crack are then determined as αBσ√a√π where a is a correction factor due to the curvature of the ellipse and 6 is a correction factor due to the eccentricity of the crack in the wall.
28 citations