1. Wave motion in infinite inhomogeneous waveguidesIgor Špacapan, Miroslav Premrov, 2003, original scientific article Abstract: The analysis of wave motion in infinite homogeneous waveguides, having a complicated cross-section and/or an irregular inclusion, is a rather difficult task for the majority of available methods, especially when striving for accurate results. In contrast, this presented procedure performed in the frequency domain, is simple to apply. It yields correct results because the radiation conditions are considerably accurately satisfied, and it offers a clear parametric insight into wave motion. This procedure uses the FE modelling of an analysed section of the waveguide. It is based on the decomposition of wave motion, distinguishing propagating and non-propagating wavemodes by solving the eigenvalue problem. The presented examples demonstrate the effectiveness of this procedure, whilst a comparison between computed and analytical results demonstrates its accuracy.
Keywords: waves, wavemodes, waveguides, inhomogeneity, finite element method, parametric analysis, radiation conditions, eigenvalue problem, frequency domain
Published in DKUM: 01.06.2012; Views: 2340; Downloads: 65
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2. Crack tip shielding or anti-shielding due to smooth and discontinuous material inhomogeneitiesN.K. Simha, Franz Dieter Fischer, Otmar Kolednik, Jožef Predan, G.X. Shan, 2005, original scientific article Abstract: This paper describes a theoretical model and related computational methods forexamining the influence of inhomogeneous material properties on the crack driving force in elastic and elastic-plastic materials. Following the configurational forces approach, the crack tip shielding or anti-shielding dueto smooth (e.g. graded layer) and discontinuous (e.g. bimaterial interface)distributions in material properties are derived. Computational post-processing methods are described to evaluate these inhomogeneity effects.The utility of the theoretical model and computational methods is demonstrated by examining a bimaterial interface perpendicular to a crack in elastic and elastic-plastic compact tension specimens.
Keywords: fracture mechanics, fracture toughness, composite materials, layered material, inhomogeneity, cracks, finite element method, elastic bimaterials
Published in DKUM: 01.06.2012; Views: 2697; Downloads: 91
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3. On the local variation of the crack driving force in a double mismatched weldJožef Predan, Nenad Gubeljak, Otmar Kolednik, 2007, original scientific article Abstract: A material inhomogeneity in the direction of crack extension causes a difference between the near-tip crack driving force, Jtip, and the nominally applied far-field crack driving force, Jfar. This difference can be quantified by a material inhomogeneity term, Cinh, which is evaluated by a post-processing procedure to a conventional finite element stress analysis. The magnitude of the material inhomogeneity term is evaluated for cracks in an inhomogeneous welded joint made of a high-strength low-alloy steel. Both a crack proceeding from the under-matched (UM) to the over-matched (OM) and from the OM to the UM weld metal are treated. The effects of the inhomogeneity of the different material parameters (modulus of elasticity, yield strength, and strain hardening exponent) on Cinh and Jtip are systematically studied. The results demonstrate that the material inhomogeneity term is primarily influenced by the inhomogeneity of the yield strength. A crack growing towards an OM/UM interface experiences an accelerated crack growth rate or a pop-in, an UM/OM interface leads to a reduced crack growth rate or a crack arrest. The application of global assessment methods of the mismatch effect which are included in the Engineering Treatment Model (ETM) or in the Structural Integrity Assessment Procedures for European Industry (SINTAP) is discussed.
Keywords: crack driving force, material inhomogeneity, mismatched weld, interface, J-integral, finite element modeling
Published in DKUM: 31.05.2012; Views: 1754; Downloads: 88
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