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Fatigue and Fracture Mechanics - shaped discs if diameter 2...

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Yeditepe University Department of Mechanical Engineering 1 ME 444 Fatigue & Fracture Mechanics Fall’09 Instructor: Asst.Prof. Fethi Okyar Room: A709 Phone: x1464 Email: [email protected] Assignment #1 Due Date: Oct.5, 2009 Questions 1. A cylindrical pressure vessel is rolled from flat steel plate 10 mm thick, and the edges are welded together to produce a longitudinal welded seam. Calculate the stress intensity factor K at a hoop stress of 130 MN m - 2 for two types of possible weld defects: (a) a crack running along the whole length of the weld, and extending from the inner surface of the vessel to a depth of 5.5 mm; (b) a through-thickness crack of length 2 a = 40 mm. 2. Two wooden beams are butt-jointed using an epoxy adhesive as shown in the figure. The adhesive was stirred before application, entraining air bubbles which, under pressure in forming the joint, deform to flat, penny-
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Unformatted text preview: shaped discs if diameter 2 a = 2 mm. If the beam has dimensions shown, and the force required to debond the joint is F = 80 kN. Assume K = σ √ πa for disc-shaped bubbles. 3. The fuselage of a passanger aircraft can be considered to be an internally pressurized thin walled tube of diameter 7 m and wall thickness of 3 mm. It is made from aluminum alloy plate with a fracture toughness K c of 1000 MN m-3 / 2 . At cruising altitude, the internal gauge pressure is 0.06 MN m-2 . Multiple fatigue cracks initiated at a horizontal row of rivet holes, and linked to form a single long axial through thickness crack in the fuselage. Estimate the critical length at which this crack will run, resulting in the break-up of the fuselage....
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