Question

You are a failure analysis engineer who must certify the integrity of an engineering component. Your component manufacturer has informed you that the plane strain fracture toughness of the component is measured to be as high as 140 ???√? and certifies that the surface cracks observed in the components are not bigger than 0.01 mm. During service, this component is to be continuously cycled at 3000 revolutions per minute between compressive and tensile stresses of 350 MPa. Assume that ? = 1.12 for all possible surface cracks. Materials constants are ? = 3.4 and ? = 2 × 10^−15 .

(a) You have access to three non-destructive testing techniques as shown in the table below. By calculating the critical crack length required to cause fracture, determine if any of the three techniques can be used to detect the crack before the fracture of the component.

Technique	Smallest detectable crack (mm)
X-ray radiography	0.50
γ-ray radiography	0.2
Ultrasonic inspection	0.13

(b) If you are to remove the component as soon as the crack length reaches 55% of the critical crack length to cause fracture, determine how many useful hours of the life of this component remains.

Answer 1