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Paper itaec-2003-18:
Fracture behavior of welded steel bridge components

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Mahmoud K M

Fracture behavior of welded steel bridge components

Abstract: This paper presents the investigation of fracture behavior of welded steel bridge components. The interaction between a macroscopic crack and continuously distributed microscopic damage in a power-law hardening material is studied by accounting for void accumulation in the vicinity of the crack-tip. The damage is assumed to be concentrated to a small circular zone centered at the crack-tip, where growth and coalescence of microvoids are invoked. A component, loaded in Mode-I under plane strain condition, is considered. The deformation theory of plasticity is employed to obtain the stress, strain and displacement fields ahead of the tip of the crack, where a damage variable, D, is introduced to describe the mechanical effect of distributed microscopic damage. Only isotropic damage is considered in this paper. For monotonic loading, the external applied stress for small-scale and large-scale yielding solutions is found to be proportional to a0 -1/ (n+1), where a0 is half the initial crack length and n is the strain-hardening exponent of the material. This reduces to Griffith's classical result for elastic material. For fatigue crack propagation under small-scale yielding, the effects of initial crack size, final crack size and the cyclic stress level on the service life of welded steel bridge components are assessed and found to be in good agreement with Paris power-law for fatigue crack growth.

Keywords: fracture behavior, bridge components, damage mechanics, microvoids, Mode-I, HRR singularity


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