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ME 215 – Engineering Materials I

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

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  1. ME 215 – Engineering Materials I Chapter 7 Brittle Fracture and ImpactProperties Mechanical Engineering University of Gaziantep Dr. Oğuzhan YILMAZ Assistant Professor

  2. 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.

  3. 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

  4. Introduction

  5. Introduction

  6. Introduction Load-time history for an instrumented Charpy test (Dieter, 1988)

  7. origin of fracture radiating markings Figure 1 Brittle Fracture

  8. direction of crack propagation direction of crack initiation Figure 2 Brittle Fracture

  9. Impact Properties

  10. Impact Properties

  11. Impact Properties

  12. Impact Properties

  13. Impact Properties

  14. E : Young’s modulus, MPa ρ : mass density, kg/mm3 e : plastic strain corresponding to Vx Impact Velocity

  15. Figure 3 Specimen Shape

  16. Figure 4 U = m * g * (h0 – h1) Impact Testing (Pendulum Type)

  17. Figure 5 Figure 6 Charpy and Izod Type Impact Tests Charpy Izod

  18. ductile fracture brittle fracture Impact Fracture

  19. Factors Affecting Impact Properties

  20. Factors Affecting Impact Properties

  21. Fig. 7 Factors Affecting Impact Properties

  22. Figure 8 Factors Affecting Impact Properties

  23. Factors Affecting Impact Properties

  24. Factors Affecting Impact Properties Effect of specimen orientation of Charpy transition-temperature curves (Dieter, 1988)

  25. Ductile-to-Brittle Transition (Embrittlement)

  26. Figure 9 Alternative Impact Tests

  27. Figure 10 Figure 11 Alternative Impact Tests

  28. Impact Testing of Plastics

  29. Impact Testing of Plastics

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