A ceramic part is used under a complete reverse cyclic stress with a stress amplitude (S) of 250 MPa. The yield strength and fracture toughness of materials is 550 MPa and 12.5 MPa*sqrt(m), respectively. Y is 1.4. What is the critical surface crack length?

Given your understanding of what initiates and controls failure in materials, which of the following will increase the failure strength or lifetime of a test piece or component and why? a. Decreasing the difference between the maximum and minimum stress values, as this effects the stress concentration factor b. Decreasing the temperature below the brittle-ductile transition temperature, to make it harder C. Polishing to reduce surface defects Od. Increasing its volume, to give a larger cross sectional area Oe. Increasing the grain size so there are less grain boundaries to initiate failure

2. The Goodman diagram relates oa and om for fatigue failure after a specific number of cycles Nf, where da is the cyclic stress amplitude, and om the mean stress. For a steel specimen it is found that oa oa (0). [1- (om/OTS)] where Ors is the metal's tensile stress (375MPa), and oa (0)~0.450TS is the 107 cycle fatigue limit at zero mean stress. Assuming the specimen is cycled repeatedly between 0 stress and a peak stress, what is the maximum peak stress if failure in < 107 cycles is to be avoided? Ans: 233 MPa

6. Derive the resolved shear stress(RSS) equation for dislocation at an arbitrary plane at angle (e) with horizontal under nominal axial tensile stress(o) and plot the variation of Schmidt factor with