A comparison of the dislocation structures at small strains in copper deformed in tension and in torsion
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M. DONER and H. CHANG are Research Associates; and H. CONRAD is Professor and Chairman, Metallurgical Engineering and Materials Science Department, Univeristy of Kentucky, Lexington, Ky. 40506. Manuscript submitted July 2, 1973. METALLURGICAL TRANSACTIONS
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C o n s t a n t d i s p l a c e m e n t r a t e t e n s i o n and t o r s i o n t e s t s w e r e p e r f o r m e d on OFHC c o p p e r m a c h i n e d f r o m 3 / 4 in. d i a m r o d s o b t a i n e d f r o m K e l c o M e t a l P r o d u c t s Co. The OFHC c o p p e r was i d e n t i f i e d b y the m a n u f a c t u r e r a s h a r d d r a w n t e m p e r C o p p e r A l l o y i01 and had a c h e m i c a l content of 99.99+ p e t c o p p e r . The t e n s i o n t e s t s w e r e c o n d u c t e d on s t a n d a r d ASTM 2.0 in. (5.08 cm) gage length, s o l i d , c y l i n d r i c a l s p e c i m e n s using a 20,000 Ibs. (9000 kg) c a p a c i t y I n s t r o n T e s t i n g Machine with a c r o s s - h e a d s p e e d of 0.025 c m / m i n giving an a x i a l s t r a i n r a t e of 0.84 • 10 "4 s e e -x. The d i s p l a c e m e n t s w e r e m e a s u r e d c o n t i n u o u s l y with an I n s t r o n s t r a i n gage e x t e n s o m e t e r of ~ l 0 -4 c m s e n s i t i v i t y a t t a c h e d d i r e c t l y to the gage length of the s p e c imen. The t o r s i o n t e s t s w e r e c o n d u c t e d in a c o m b i n e d t o r s i o n - a x i a l l o a d i n g m a c h i n e b u i l t to o u r s p e c i f i c a t i o n s b y G i l m o r e I n d u s t r i e s , which is c a p a b l e of p e r f o r m i n g e i t h e r c o n s t a n t s t r a i n r a t e o r consta:~t l o a d i n g r a t e a x i a l loading, t o r s i o n , o r c o m b i n e d a x i a l l o a d i n g - t o r s i o n t e s t s . A d e s c r i p t i o n of the s y s t e m is given e l s e w h e r e , x4-.8 The t o r s i o n t e s t s w e r e c o n d u c t e d at the r a t e of 1.02 • 10 -3 r a d i a n s s e c -~, which r e s u l t e d in a s h e a r s t r a i n r a t e of 1.45 • 10 ~ see-*, while m a i n t a i n ing a z e r o a x i a l l o a d on the s p e c i m e n . The a n g l e of t w i s t was m e a s u r e d to within * 0.001 r a d i a n s b y an RVDT mounted on the r o t a r y shaft; the r e s i s t i n g t o r q u e was m e a s u r e d b y two 100 l b s . c a p a c i t y t e n s i o n - c o m p r e s s i o n l o a d c e l l s . The output data, r e c o r d e d b y a Model 1508A Honeywell V i s i c o r d e r , c o n s i s t e d of a n g l e of t w i s t , t o r q u e , a x i a l l o a d and c r o s s h e a d d i s p l a c e m e n t versus time. The t u b u l a r t e s t s p e c i m e n s w e r e m a c h i n e d f r o m the r o u n d b a r s t o c k to the d i m e n s i o n s shown in Fig. l(a). A s c h e m a t i c of the g r i p a s s e m b l y is given in Fig. l(b). A wall t h i c k n e s s (t) to m e a n d i a m e t e r (Din) r a t i o of 0.085 was s e l e c t e d a f t e r p r e l i m i n a r y t e s t s i n d i c a t e d that the use of s m a l l e r t/Drn r a
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