by

DOI: 10.1007/s10704-005-4397-6
Print publication date: 9/1/2005
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DOI: 10.1007/s10704-005-4396-7
Print publication date: 9/1/2005
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by Lazzarin, P.; Berto, F.

Dealing with sharp V-shaped notches, some recent papers have discussed the possibility of using the strain energy averaged over an ad hoc control volume to predict the static strength of material with a brittle or quasi-brittle behavior as well as the fatigue behavior of welded joints. This approach is applied here to components weakened by cracks and blunt V-shaped notches. As a result, Kitagawa and Atzori’s diagrams reported in the literature to summarise fatigue limit of cracked and notched components are immediately derived, leading to a natural transition between the Linear Elastic Fracture Mechanics and the Linear Notch Mechanics.

DOI: 10.1007/s10704-005-4393-x
Print publication date: 9/1/2005
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by An, Deukman; Cho, Yongjoo; Son, Inho

We investigate the dependence of stress intensity factors on elastic constants in two dimensional elastic isotropic bodies, using Bueckner’s weight function theory. This dependence is described in terms of Poisson’s ratio. The dependence on Poisson’s ratio shows up when the resultant tractions on each of the contours separately is non-zero in multiply connected bodies. As an example, we calculate mode I stress intensity factor KI for a crack under concentrated loading applied at one of crack faces.

DOI: 10.1007/s10704-005-4392-y
Print publication date: 9/1/2005
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by Korsunsky, Alexander M.; Nguyen, Giang D.; Houlsby, Guy T.

We consider the non-local damage plasticity modelling of the essential work of rupture (EWR), i.e. the specific energy required to cause failure within a specimen, resulting in its separation into two parts. The more usual concept of essential work of fracture (EWF) is a measure of the specific energy, per unit cross sectional area, consumed during the propagation of cracks across a series of double edge-notched tensile (DENT) specimens. Recently, a novel framework has been proposed allowing the determination of a related quantity, the essential work of necking and tearing from a single tensile test on an unnotched dogbone specimen of ductile metal. Simultaneous multiple gauge length extensometry forms a crucial component of the experimental approach, and allows capture of such phenomena as strain localisation, post-critical deformation behaviour, damage non-locality, elastic snap-back, and size effects. In this study the rupture test is simulated using a non-local damage-plasticity model using finite elements. The results are interpreted in terms of essential and non-essential work of rupture.

DOI: 10.1007/s10704-005-4391-z
Print publication date: 9/1/2005
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by Dini, Daniele; Nowell, David; Korsunsky, Alexander M.

Components subject to fretting experience a peculiar combination of loading conditions, where contact and classical fatigue interact intricately to produce failure. As a consequence, the prediction of fretting fatigue limit curves poses a challenge, in part due to the large number of parameters governing the phenomenon. This poses an obstacle to formulating efficient predictive approaches.We demonstrate that these difficulties can be overcome successfully by means of a combination of experimental and computational approaches. Our analysis relies on various experimental data from Hertzian and ’flat and rounded’ contact pad specimens and different calculation procedures developed previously, which resulted in fretting threshold curves for specific loading conditions. The derivation of such thresholds is however rather lengthy, so that for the purposes of formulating design rules a more efficient ’master curve’ approach is proposed.This paper presents comprehensive results on the application of an efficient and concise functional description of the fretting fatigue threshold curves based on the use of a ’multi-scaling power law’. The predictions encompass all of the results obtained for different loading conditions by the stress-based approach and by short crack arrest methodology.

DOI: 10.1007/s10704-005-4390-0
Print publication date: 9/1/2005
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by Gitman, Inna M.; Askes, Harm; Aifantis, Elias C.

Two homogenisation schemes (first-order or local, and second-order or non-local) are employed in this paper. In case second-order homogenisation is applied, it turns out that elastic behaviour at the micro-scale implies the appearance of second-order space and time derivatives of macroscopic strain in an otherwise elastic constitutive equation for the macroscopic stress. The coefficients of the second-order terms scale with the size of the Representative Volume Element (RVE) employed in the homogenisation scheme.

DOI: 10.1007/s10704-005-4389-6
Print publication date: 9/1/2005
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by Lira-Vergara, E.; Rubio-Gonzalez, C.

The elastodynamic response of an infinite non-homogeneous orthotropic material with an interfacial finite crack under distributed normal and shear impact loads is examined. Solution for the stress intensity factor history around the crack tips is found. Laplace and Fourier transforms are employed to solve the equations of motion leading to a Fredholm integral equation on the Laplace transform domain. The dynamic stress intensity factor history can be computed by numerical Laplace transform inversion of the solution of the Fredholm equation. Numerical values of the dynamic stress intensity factor history for some materials are obtained. Interfacial cracks between two different materials and between two pieces of the same material but different fiber orientation are considered. Bimaterial formulation of a crack problem is shown to converge to the mono-material formulation, derived independently, in the limiting case when both materials are the same.

DOI: 10.1007/s10704-005-4292-1
Print publication date: 9/1/2005
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by Carpinteri, Alberto; Paggi, Marco

The problem of multi-material junctions composed of angularly nonhomogeneous elastic wedges in plane elasticity is addressed. For this new type of grading the governing equation for the Airy stress function is derived and, by applying the eigenfunction expansion method, a fourth-order ODE with nonconstant coefficients for the eigenequation is obtained. The solution to this ODE permits the formulation of an eigenvalue problem similar to that valid for material junctions between homogenous different materials. It is mathematically demonstrated that the angular grading influences the order of the stress-singularity. The potentials of the use of this new class of materials in joining technology are carefully investigated and some illustrative examples are deeply discussed. Comparisons with the corresponding results obtained from homogeneous materials are made.

DOI: 10.1007/s10704-005-4087-4
Print publication date: 9/1/2005
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by Porwal, Pankaj K.; Phoenix, S. Leigh

An analytical model is developed to study various ‘system effects’ during impact of a flat-faced, cylindrical projectile into a flexible, multi-layered target with no bonding between layers. Each thin layer is assumed to have in-plane, isotropic, elastic mechanical properties. The model allows variation of the mechanical properties from layer to layer as well as the spacings between the layers in order to study their combined effects on the ballistic performance of the system. In particular, we consider such performance measures as the V50 limit velocity, the number of layers penetrated when impacting below this limit, and the residual projectile velocity after complete penetration above this limit. The V50 performance of the target is found to degrade progressively as the spacings between layers are increased relative to the sum of layer thicknesses without spacing. A second finding is that for a given set of layers with differing mechanical properties, both the V50 and the residual velocity depend on the order of layer placement. A third finding is that among systems with identical layers of a given in-plane tensile strength, the V50 velocity increases with increasing strain-to-failure of the layers. However the relative magnitude of this increase diminishes with increasing target-to-projectile areal density ratio. The model builds on the authors’ previous analysis for impact into a single elastic membrane and the results have important design implications for armor design especially for hybrid material configurations.

DOI: 10.1007/s10704-005-3993-9
Print publication date: 9/1/2005
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