On the morphology and substructure of martensite
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temperature, strain range, and strain rate. T h i s r e p o r t o r i g i n a t e d f r o m w o r k s p o n s o r e d b y the U.S. A t o m i c E n e r g y C o m m i s s i o n , D i v i s i o n of R e a c t o r Development and Technology, Fuels and Materials Branch, under Contract AT (40-1)- 2847.
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Fig. 3--Comparison of e x p e r i m e n t a l and e s t i m a t e d fatigue b e h a v i o r of AISI 304 s t a i n l e s s steel at 1200~ t h e two l i n e s i n F i g . 2, f o r s t r a i n r a n g e v a l u e s of 0.5 a n d 2.0 p c t , a r e b a s e d on m e a s u r e m e n t s a t a s t r a i n r a t e of 4 x 10 -3 s e c -1. If it i s d e s i r e d to e s t i m a t e t h e f a t i g u e b e h a v i o r a t a s t r a i n r a t e of 4 x 10 -4 s e c -1, t h e t i m e f o r 1 c y c l e i s c a l c u l a t e d to b e 100 a n d 25 s e c , r e s p e c t i v e l y , f o r t h e 2 a n d 0.5 p c t s t r a i n r a n g e s . F i g . 2 y i e l d s tf v a l u e s of 9.3 a n d 41.5 h r , r e s p e c t i v e l y , f o r t h e s e two s t r a i n r a n g e s . S i n c e :
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On the Morphology and Substructure of Martensite
[5]
S
and for a triangular
1. R. A. T. Dawson, W. J. Elder, G. J. Hill, and A. T. Price: Thermal and High Strain Fatigue, Proc. of an Intern. Conf. organizedby the Inst. Metalsin association with the Iron and Steel Inst. Church House, London, June, 1967, The Metalsand MetallurgyTrust, 1967, pp. 239-69. 2. A. Cobs, C. J. Hill, R. A. T. Dawson, and S. J. Watson: ibid., pp. 270-94. 3. G. J. Hill: ibid., pp. 312-27. 4. A. Coles and A. chitty: ibid., pp. 328-45. 5. C. D. Walker: Joint International Conference on Creep, Paper 24, Session 3, pp. 49-56, The Institution of MechanicalEngineers, London, 1963. 6. A. Coles and D. Skinner: J. Roy. AerorLSoc., 1965, vol. 69, pp. 53-55. 7. J. T. Berlingand J. B. Conway: paper presented at the First International Conference on Pressure VesselTechnology,Universityof Delft, Netherlands, September 1969; to be published. 8. J. F. Eckel: Proc.ASTM, 195t, vol. 51, pp. 745-56. 9. J. T. Berlingand T Slot: paper presented at ASTM Symposium on Fatigue at ElevatedTemperatures,San Francisco, California,June 24, 1968, to be published; also availableas GEMP642 report, GeneralElectric Company, Nuclear Systems Programs, Cincinnati, Ohio.
S. K. DAS A N D G. T H O M A S strain-wave
dt = 2f Ae t
form: [6]
w h e r e ~t i s t h e t o t a l s t r a i n r a t e , f i s t h e f r e q u e n c y , a n d ~xQ i s t h e t o t a l s t r a i n r a n g e , it f o l l o w s t h a t :
tfet N/ = 2aQ
[7]
T h i s e x p r e s s i o n a l l o w s c o n v e r s i o n of t h e tf v a l u e s to c y c l e s to f r a c t u r e , N f . A p p l y i n g E q . [7J-to t h e a b o v e tf d a t a it w a s f o u n d t h a t N f i s e s t i m a t e d to b e 335 a n d 5980, r e s p e c t i v e l y , a t t h e 2 . 0 a n d 0 . 5 p c t s t r a i n r a n g e s . T h e s e e s t i m a t e d v a l u e s of N f a r e p l o t t e d in
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