Question

Q2 (a) Explain in detail the terms Ductile and Brittle fracture. Include in your answer sketches, examples, stages (6 marks) and microstructures expected. Explain using sketches and equations the terms Stress Concentration at the tip of a pore and Plane Strain Fracture Toughness. (b) 7 marks) A polymer that contains internal flaws 1 mm in length fails at a stress of 25 MPa. Determine the plane strain fracture toughness of the polymer. Comment on your answer. (c) 7 marks

Answer 1

Ductile and Brittle Fracture: A fracture is the saturation of the material in the two or more application by the application of stress. When no deformation takes place before fracture then it is called as Brittle fracture. Brittle fracture involves small energy absorption and occurs at high speeds, it will continue even loading is discontinued. In crystalline , fracture occur by change as the result of tensile stress acting normal to crystallographic planes with no loading. In normal to the applied tension . Ductile fracture or tulture describe ultimate failure of ductile materials loaded in tension. Instead of checking the batential pulls apart, generally leaving a rough surface. There is a slow propogation and an absorption of large fracture are: void fracture , the basic steps inductile fracture are: void fracture , void anlescence (check fracture) crack propogation and failure, Example: - colour , aluminium and steel