Volume 14, Issue 10 (1-2015)                   Modares Mechanical Engineering 2015, 14(10): 50-58 | Back to browse issues page

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Ghajar R, Alizadeh J. Mixed mode two dimensional weight functions for the subsurface elliptical cracks under normal loadings. Modares Mechanical Engineering 2015; 14 (10) :50-58
URL: http://mme.modares.ac.ir/article-15-10025-en.html
Abstract:   (5038 Views)
Elliptical subsurface cracks are one of the probable types of cracks that occur in engineering structures. Due to the non-symmetrical geometry with respect to the crack surface, coupling of the fracture modes occurs in an elliptical subsurface crack and so, the crack under normal loading will experience all fracture modes. Mode III caused by the coupling effect under normal loading is negligible whereas mode II is significant. In this paper, mixed mode two dimensional weight functions of the elliptical subsurface cracks parallel to the surface are derived for aspect ratios of αlpha=0.2, 0.4, 0.6, 0.8, 1.0 and ratios of crack depth to crack length of Betta=0.05, 0.06, 0.08, 0.1, 0.14, 0.2, 0.3, 0.5, 1.0. Mixed mode stress intensity factors under uniform normal loading are used as reference stress intensity factors. By curve fitting on the calculated weight functions coefficients, the derived weight functions are able to be used for any αlpha and Betta. To verify the weight functions, the stress intensity factors of all points of the crack front are calculated under linear, elliptic paraboloid and trigonometric paraboloid stress distributions and compared to the finite element results. Comparison of the results shows high accuracy with mean relative error less than 7%. Using derived weight functions, mixed mode stress intensity factors of the subsurface elliptical crack can be determined for any αlpha and Betta and under any normal stress distributions.
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Article Type: Research Article | Subject: Creep, Fatigue & Failure
Received: 2014/06/17 | Accepted: 2014/09/12 | Published: 2014/09/24

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