Linear elastic fracture mechanics:
Linear elastic fracture mechanics:
Brittle solids fracture because the applied stress is amplified by minute cracks (of order 1 Mmin size) which occur naturally as a result of fabrication, solidification, fatigue.
These cracks are termed Griffith cracks.
Wide sheet of thickness B consider an elliptical through thickness crack in an elastic sheet subject to a stress ( ? ) in the y – direction causes a stress distribution a long ox1.
Wide or infinite width sheet means W >> 2a or w/a= ?
?m = maximum stress ; ? = applied stress; ?2 is amplified from ? to ?2 at both tips of the crack where ?2 falls to ? as x1 increases ( x1 distance from the crack ).
The Maximum Stress Amplification at the crack tip:
MSA = ?_2/?=(1+ 2a/b) for central crack
For a circle (a = b) ? MSA = 3
For a thin crack ( a/b=500 );MSA ? 103
For low applied stress, the stress at the crack tip approach the theoretical strength of the solid ( inter atomic bonds reach to their breaking point ).
These conditions occur only in materials that is unable to relieve the stress concentration by plastic flow or other mechanisms of crack blunting such as diamod and ceramics
المادة المعروضة اعلاه هي مدخل الى المحاضرة المرفوعة بواسطة استاذ(ة) المادة . وقد تبدو لك غير متكاملة . حيث يضع استاذ المادة في بعض الاحيان فقط الجزء الاول من المحاضرة من اجل الاطلاع على ما ستقوم بتحميله لاحقا . في نظام التعليم الالكتروني نوفر هذه الخدمة لكي نبقيك على اطلاع حول محتوى الملف الذي ستقوم بتحميله .
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