Give one approach to imposing a compressive surface stress o

Give one approach to imposing a compressive surface stress on metal surface? After imposing this compressive surface stress on metal surface, which property can be improved? (Circle the correct answer) What phenomenon we will observe at the crack tip during crack propagation due to plastic deformation? Will this phenomenon make crack propagation? (Circle the correct answer) faster; slower What are the crystal structures for austenite and a-Ferrite. respectively? a- ferrite: Austenite: SC; FCC; BCC; HCP Estimate the theoretical fracture stress of a brittle material if it is known that fracture occurs by the propagation of an elliptically shaped surface crack of length 0.4 mm that has a tip radius of curvature of 0.004 mm when a stress of 1000 MPa is applied.

Solution

3. Fatigue life

4. When there is plastic deformation at the crack tip (as occurs most often in metals) the energy to propagate the crack may increase by several orders of magnitude as the work related to plastic deformation may be much larger than the surface energy.

a) faster