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ME 215 – Engineering Materials I. Chapter 7 Brittle Fracture and Impact Properties. Mechanical Engineering University of Gaziantep. Dr. Oğuzhan YILMAZ Assistant Professor. Introduction. A great deal of attention was directed to the brittle failure of welded ships and tankers .
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ME 215 – Engineering Materials I Chapter 7 Brittle Fracture and ImpactProperties Mechanical Engineering University of Gaziantep Dr. Oğuzhan YILMAZ Assistant Professor
Introduction A great deal of attention was directed to the brittle failure of welded ships and tankers. Failures occured during winter months and when the are in heavy seas and anchored at dock. This fact focussed on that normally ductile mild steel can become brittle under certain conditions. Therefore, researches aimed to understand the mechanism of brittle fracture and fracture in general. While the brittle failure of ships concentrated great attention to brittle failure in mild steel. Brittle failures in tanks, pressure vessels, pipelines, and bridges have been noticed.
Introduction • Three basics factors contribute to a brittle-cleavage type of fracture: • triaxial state of stress • Low temperature • High strain rate or rapid rate of loading
Introduction Load-time history for an instrumented Charpy test (Dieter, 1988)
origin of fracture radiating markings Figure 1 Brittle Fracture
direction of crack propagation direction of crack initiation Figure 2 Brittle Fracture
E : Young’s modulus, MPa ρ : mass density, kg/mm3 e : plastic strain corresponding to Vx Impact Velocity
Figure 3 Specimen Shape
Figure 4 U = m * g * (h0 – h1) Impact Testing (Pendulum Type)
Figure 5 Figure 6 Charpy and Izod Type Impact Tests Charpy Izod
ductile fracture brittle fracture Impact Fracture
Fig. 7 Factors Affecting Impact Properties
Figure 8 Factors Affecting Impact Properties
Factors Affecting Impact Properties Effect of specimen orientation of Charpy transition-temperature curves (Dieter, 1988)
Figure 9 Alternative Impact Tests
Figure 10 Figure 11 Alternative Impact Tests