Material Sample Removal for Life Assessment
The information required to perform a life assessment of a turbine rotor includes date of manufacture, material specification and properties, such as ASTM number and class, chemical composition, yielding strength (YS), ultimate tensile strength (UTS), modulus of elasticity (E), stress intensity factor (KIC), fracture appearance transition temperature (FATT), fatigue crack growth rate (da/dn), etc. The majority of these parameters can be researched in the available literature. However, when a deterministic analysis is required, these parameters can be measured by removing material samples from low stress areas of the rotor or from the actual area of concern making sure that the impression left after material removal does not increase the local stress concentration. A metallurgical evaluation of the removed material sample is performed to yield these material properties, to measure material hardness, to detect any material microstructural damage such as creep, etc. The material samples can be bore honing shavings, periphery filing samples, sliver samples, core samples, ring samples, or bore miniature samples.