Thermal effect during plastic deformation
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Fig. 3 - - R e p r e s e n t a t i v e s t r u c t u r e s of LRO f l - b r a s s a f t e r 0.052 s h e a r s t r a i n at cr = 1300 psi and 300~ (a) Subgrain f o r m a tion with s u b g r a i n size ranging f r o m ~3 to ~25/~. (b) Details of subboundary s t r u c t u r e . (c) Mobile dislocations in subg r a i n s and details of subboundary s t r u c ture. (d) More complex dislocation a r r a n g e m e n t in subgrains. (e) Screw dislocations in s u b g r a i n and low-energy V and Z zig-zags.
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1. N. Brown and M. Herman: AIME Trans., 1956, vol. 206, p. 604. 2. N. Brown and D. R. Lenton: ActaMeL, 1969, vol. 17, p. 669. 3. A. Gittins and R. C. Gifldns: ActaMet., 1968, vol. 16, p. 81. 4. A. B. Kuper, D. Lazarus,J. R. Manning,and C. T. Tomizuka: Phys. Rev., 1956, vol. 204, p. 1536. 5. P. A. Flinn: Trans. TMS-A1ME, 1960, vol. 218, p. 154.
6. D. McLeanand K. F. Hale: StrucmralProcesses in Creep, p. 19, Iron and Steel Institute, London, 1961. 7. G. W. Ardley and A. H. Cottretl: Proc. RoyalSoc., 1953, vol. A219, p. 328. 8. A. K. Head: Phys. Stat. Solidi., 1967,vol. 19, p. 185. 9. A. K. Head, M. H. Loretto, and P. Humble: Phys. Stat. Solidi., 1967, vol. 20, p. 521.
Thermal Effect During Plastic Deformation
a u t h o r s d i d n o t c o n s i d e r t h a t a s i g n i f i c a n t p o r t i o n of the applied mechanical energy is dispersed in the stress field around the dislocation and hence not contributing to the thermal effect in the slip plane. Furthermore, they did not take into account the simult a n e o u s f l o w of h e a t i n t o a n d o u t of t h e s l i p p l a n e s a s successive dislocation sweep through the planes. T h e i r f o r m u l a t i o n i s p r o n e to o v e r e s t i m a t e t h e t e m perature increase in the slip plane. The present note p r o p o s e s to r e m e d y t h e s e d i f f i c u l t i e s a n d h e n c e to g i v e a n i m p r o v e d a p p r o x i m a t i o n of t h e s l i p p l a n e t e m perature. A s s u m i n g t h e c o r e e n e r g y Eo a s a b o u t 15 p c t of t h e e l a s t i c s t r a i n e n e r g y E1 f o r b o t h t h e e d g e a n d s c r e w dislocation at all velocities, and further postulating o n l y 15 p c t of t h e e x c e s s s t r a i n e n e r g y , 0.15(E1 - Eo), a n d a l l t h e k i n e t i c e n e r g y E2 a s d i s p e r s e d i n the s l i p p l a n e , t h e f r a c t i o n of the a p p l i e d m e c h a n i c a l w o r k d i s p e r s e d i n the s l i p p l a n e i s e s t i m a t e d a s ,
HARISH D. M E R C H A N T
INSOFARa s
the plastic deformation takes place by t h e s t r e s s i n d u c e d d i s p l a c e m e n t of d i s l o c a t i o n s , p a r t of the d i s p e r s e d t h e r m a l e n e r g y m a y b e r e g a r d e d a s l o c a l i z e d in t h e s e p l a n e s . T h e d i s l o c a t i o n s m a y b e considered as the moving internal heat sources which a r e c o n f i n e d to s p e c i f i c s l i p p l a n e s . T h e r e h a s b e e n s o m e c i r c u m s t a n t i a l e v i d e n c e 1-4 w h i
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