Residual stresses in roller-expanded steam generator tube transitions. Final report
- Pennsylvania State Univ., University Park, PA (US). Materials Research Lab.
The residual stresses induced by roller expansion were studied in two overexpanded and two underexpanded Inconel Alloy 600, 3/4 inch O.D. tubes. Each pair were intended to be duplicates and were expanded using procedures similar to those applied in nuclear power plant installations wherein the steam generator tubing is expanded into a hole in the tube sheet. The stresses were measured using a combination of strain gage and stress relief and X-ray diffraction (XRD) with most being performed by XRD. Over 1,000 measurements were repeated at least three times on each tube sample. Both hoop and axial direction stresses were measured along transverses through the expanded zone of the tubes on the outside diameter (O.D.) and inside diameter (I.D.) surfaces. Also, subsurface measurements were performed on the inside diameters. The profiles of the XRD obtained residual stress distributions agreed reasonably well with previously published results, but the magnitudes were much higher. The profiles and magnitudes of the stresses, when compared with in-service and stress-corrosion tests, confirmed the correlation between cracking and residual stresses due to roller expansion. Comparison of the residual stress patterns in the overexpanded (340 MPa hoop and 245 MPa axial) and underexpanded (436 MPa hoop and 508 MPa axial) tubes confirmed the greater susceptibility of the latter for stress corrosion cracking.
- Research Organization:
- Electric Power Research Inst., Palo Alto, CA (United States); Pennsylvania State Univ., University Park, PA (United States). Materials Research Lab.
- Sponsoring Organization:
- Electric Power Research Inst., Palo Alto, CA (United States)
- OSTI ID:
- 10163377
- Report Number(s):
- EPRI-TR--102355; ON: UN93014711
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
220200
36 MATERIALS SCIENCE
360105
COMPONENTS AND ACCESSORIES
CORROSION AND EROSION
CRACK PROPAGATION
EXPANSION
EXPERIMENTAL DATA
INCONEL 600
NUCLEAR POWER PLANTS
PRESSURE DEPENDENCE
RESIDUAL STRESSES
STEAM GENERATORS
STRAIN GAGES
STRESS CORROSION
TUBES
VERY HIGH PRESSURE
X-RAY DIFFRACTION