Self-diffusion data of metals and stable electronic configuration model
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AVERAGE GRAINSIZE NOTCHED SMOOTH
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4V s i n d i c a t e a r e a s o n a b l e c o r r e l a t i o n b e t w e e n t e n s i l e s t r e n g t h and f a t i g u e s t r e n g t h . Since t e n s i l e s t r e n g t h cannot be u s e d a s a c o n s i s t e n t i n d i c a t i o n of f at i g u e s t r e n g t h in T i - 6 A 1 - 4 V , m i c r o s t r u c t u r e c o n t r o l s such a s g r a i n s i z e m a y p r o v e to be n e c e s s a r y q u al i t y a s s u r a n c e r e q u i r e m e n t s for obtaining r e p e a t a b l e fatigue s t r e n g t h . It is t h e r e f o r e i m p o r t a n t to f u r t h e r s u b s t a n t i a t e and quantify the o b s e r v e d e f f e c t of g r a i n s i z e on fatigue s t r e n g t h r e p o r t e d h e r e i n .
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FATIG~JE STRENGTH AT IO a C~fCLES ~,+-Ksi) AT 45 KSI STEADY STRESS
Fig. 1--Relationship between c~ grain size and crack initiation fatigue strength.
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1. R. W. Karry and T. J. Dolan:Amer. Soc. Testing Mater. Proc., 1953, vol. 53, p. 789. 2. N. G. Turner and W. T. Roberts: Tran~ TMS-AIME, 1968,vol. 242, p. 1223. 3.MetalsHandbook, vol. 1, p. 130, Amer.Soc. Met., Novelty,Ohio, 1962. 4. G. Sinesand J. L. Waisman:Metal Fatigue, p. 26, MaplePressCo.,York, Pa., 1959, 5. L. J. Bartlo:Fatigue at High Temperature, STP 459, pp. 144-54, Amer.Soc. TestingMater.,Philadelphia,Pa., 1969.
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Self-Diffusion Data of Metals and Stable Electronic Configuration Model G. S. UPADHYAYA
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MEAN FATIGUE STRENGTH AT 108 CYCLES ( -+ Ksi ) AT 45 Ksi STEADY STRESS FOR
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Fig. 2--Relationshipbetween ultimate tensile strength and crack initiationfatigue strength.
were made by a random intercept method for each sample. The range of measured values and the mean value obtained are shown in Fig. 1. Similar results on the effect of grain size on fatigue strength have been previously observed in steel alloys ~ and in commercially pure titanium2 and although other variables were present in our tests such as the basic chemistry and percentage primary or, the present evidence indicates processing methods which result in finer ot grain sizes should be further investigated to improve the fatigue strength of titanium components. Fig. 2 presents a comparison of the ultimate tensile strength of these materials to the smooth specimen fatigue strengths. Althoughthe fatigue strength tends to increase with tensile strength, the percentage increase in fatigue strength is abnormally higher than the corresponding increase in tensile strength. For instance, although there was only a 17 pct difference in tensile strength, greater tha
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