Stress-intensity-factor influence coefficients for surface flaws in pressure vessels
In the fracture-mechanics analysis of reactor pressure vessels, stress-intensity-factor influence coefficients are used in conjunction with superposition techniques to reduce the cost of calculating stress-intensity factors. The present study uses a finite-element code, together with a virtual crack extension technique, to obtain influence coefficients for semielliptical surface flaws in a cylinder, and particular emphasis was placed on mesh convergence (less than 1% error was sought in the results from any one mesh construction parameter). Comparison of the coefficients with those obtained by other investigators shows good agreement. Furthermore, stress-intensity factors obtained by superposition for a severe thermal-transient loading condition agree within 1% of the values calculated by a direct finite-element method. Influence coefficients were calculated for three specific axially oriented semielliptical surface flaws. The first was a 2-m-long inner-surface flaw in a nuclear reactor pressure vessel with depth-to-wall-thickness ratios between 0.2 and 0.9. The second was an inner-surface flaw in the reactor vessel with a surface-length-to-depth ratio of 6 and with depth-to-wall-thickness ratios between 0.05 and 0.2. The third was a 1-m-long flaw on the outer surface of a test vessel with depth-to-wall-thickness ratios between 0.1 and 0.9. For the reactor vessel, separate coefficients were calculated for the cladding on the inner surface and for the base-material region. This allows for an accurate accounting of the effect of thermal stresses in the cladding on the stress-intensity factor for surface flaws that extend through the cladding into the base material.
- Research Organization:
- Oak Ridge National Lab., TN (USA)
- DOE Contract Number:
- AC05-84OR21400
- OSTI ID:
- 5801635
- Report Number(s):
- NUREG/CR-3723; ORNL/CSD/TM-216; ON: TI85006633
- Country of Publication:
- United States
- Language:
- English
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