Your company designed a structure that includes analuminum plate for which you specified routine inspectionafter every 50,000 loading cycles. The NDT procedure thatis employed by the operator of the structure possesses aresolution limit of 1 mm. Through a mix-up, the inspectionteam calibrated their instrument to yield a crack resolutionlimit of 1 cm. No crack was found on this occasion, butunstable fracture took place following 34,945 additionalloading cycles in association with the development of anedge crack, oriented normal to the major stress direction.Injuries to clients of the operator resulted from the failure.The operator is being sued, but is trying to pass the blameonto your design team. Are there grounds for a lawsuitagainst you for improper design and inspection specifications, or against the operator based on improper inspectionprocedures? The key stress level fluctuates between 50 and100 MPa. The properties of the alloy are:KIC = 30 MPa √m , σys = 550 Mpa, E = 70 GPa, and thecrack growth rate relation is given by da/dN = 5 x 10-35ΔK4, with da/dN and ΔK being given in units of m/cycle andPa\/m, respectively.
Your company designed a structure that includes an
aluminum plate for which you specified routine inspection
after every 50,000 loading cycles. The NDT procedure that
is employed by the operator of the structure possesses a
resolution limit of 1 mm. Through a mix-up, the inspection
team calibrated their instrument to yield a crack resolution
limit of 1 cm. No crack was found on this occasion, but
unstable fracture took place following 34,945 additional
loading cycles in association with the development of an
edge crack, oriented normal to the major stress direction.
Injuries to clients of the operator resulted from the failure.
The operator is being sued, but is trying to pass the blame
onto your design team. Are there grounds for a lawsuit
against you for improper design and inspection specifications, or against the operator based on improper inspection
procedures? The key stress level fluctuates between 50 and
100 MPa. The properties of the alloy are:
KIC = 30 MPa √m , σys = 550 Mpa, E = 70 GPa, and the
crack growth rate relation is given by da/dN = 5 x 10-35
ΔK4, with da/dN and ΔK being given in units of m/cycle and
Pa\/m, respectively.
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