Reference no: EM131069764

A disgruntled employee in an engineering company is intent on destroying a large steel plate used in a valuable engineering component. One evening, after the normal working hours, he cuts a very sharp notch in the edge of the plate. He orients the sharp flaw normal to the direction in which tensile stresses are applied to the plate, with the hope that the flaw would eventually result in catastrophic fracture of the plate. As he is committing the crime, a bystander telephones the plant foreman at the foreman's home. The fore-man, who leaves his home two minutes after the notification is received, travels to the scene of crime on his bicycle at an average speed of 15 km/hr. Would he have reached the plant in time to shut off the equipment before the plate fractures catastrophically? Here are some useful data for your analysis:

(i) The plate is cyclically loaded uniformly from 5 to 85 kN at a frequency of 75 Hz.

(ii) The plate is 18 cm wide and 0.5 cm thick,

(iii) The yield strength of the steel is 1250 MPa and the plane strain fracture tough ness is 48 MPa

(iv) The flaw introduced by the employee is 1 cm in length, through the thickness of the plate,

(v) The bystander, who notified the foreman, reported to the police, by phone, that, in his judgement, the crack in the plate was propagating at a velocity proportional to the crack tip opening displacement corresponding to the peak load of each cycle,

(vi) Post-failure fractographic examination revealed the presence of fatigue striations with a mean spacing of 2.5xlO~4 mm where the crack was 2.5 mm long,

(vii) The distance from the foreman's home to the factory is 5 km.

(viii) The time interval between the two phone calls was 10 minutes. State all your assumptions clearly