We consider an "infinite" plate under cyclic loading characterized by: R=1(=a)=100MPanominalstress The fatigue properties of the material ( R=1, smooth samples) are listed in the table below D=170MPa-endurancelimit The plate contains a circular hole with radius r=5mm, acting as stress raiser with a stress concentration coefficient Kt=3. We have: K1=1.12(a)1/2Kic=90MPam1/2Kth=10MPam1/2(Kthth-thresholdoflongcrackpropagation) 1. What is the expected crack length ac at failure? 2. Plot the Kitagawa diagram for the material of the plate (use the log-log sheet provided). What is the critical crack length ath for which propagation and subsequent failure are possible under applied nominal stress of 100MPa, if no notch is present? 3. Describe successive steps of fatigue damage of the notched plate (r=5mm) under (=a)=100MPa and plot the "crack trajectory" on the Kitagawa diagram. Consider now a plate containing a circular hole with radius r=1mm(Kt and all other data remain unchanged). 4. How (if at all) will the reduction of the hole radius from 5 to 1mm influence the fatigue life of the plate? NF(1)>NF(5)NF(1)=NF(5)NF(1)