need help for the questions

1. In the discussion for fatigue up to this point we have talked about the damaging effect of the number of cycles of loading but we have not discussed about frequency (i.e. how often these loading cycles occur). Which class of materials do you think might be sensitive to the frequency of loading? Provide two physical mechanisms that may affect fatigue life (at least indirectly).

2. According to an old report from the Battelle Memorial Institute on “Prevention of failure of metals under repeated load” (1941), nitriding is a method to enhance the notch sensitivity of steels and improves fatigue performance – discuss briefly.

3. Provide a first order discussion of the effect of grain size on fatigue performance of metallic materials

4. Fit the constants of Paris’ law for 7075-T6 aluminum (Figure below). Find the number of cycles required for a crack to grow from 1 mm to 1 cm in 7075-T6 for a stress amplitude of 10 MPa. Assume shape factor of 1.

5. Bent shafts and axles are often straightened by cold-bending in a press. Discuss the implications on future fatigue life.

6. According to an old report from the Batelle Memorial Institute on “Prevention of failure of metals under repeated load” (1941), nitriding is a method to enhance the notch sensitivity of steels and improves fatigue performance – discuss briefly.