Influence of deformation history on the yield locus and stress-strain behavior of aluminum and copper
- PDF / 437,833 Bytes
- 5 Pages / 612 x 792 pts (letter) Page_size
- 55 Downloads / 217 Views
1~. ECENT e x p e r i m e n t a l and t h e o r e t i c a l c o n t r i b u t i o n s to the u n d e r s t a n d i n g of the p l a s t i c d e f o r m a t i o n of m e t a l s subjected to c o m p l e x s t r e s s e s have b e e n r e v i e w e d by Lin I and P a u l . 2 E x p e r i m e n t a l e v i d e n c e on the effect of p r e v i o u s p l a s t i c d e f o r m a t i o n upon s u b s e q u e n t d e f o r m a t i o n is s c a r c e and c o n f l i c t i v e . I n f o r m a t i o n about changes in the s i z e , p o s i t i o n , and shape of yield loci with p l a s t i c d e f o r m a t i o n is p a r t i c u l a r l y c o n t r a d i c t o r y . 3 Yield loci can u n d e r g o v a r i o u s c o m b i n a t i o n s of e x p a n s i o n , t r a n s l a t i o n , and d i s t o r t i o n depending upon the m a t e r i a l , the type of p r e v i o u s d e f o r m a t i o n , and the d e f i n i t i o n of yielding chosen to specify the yield locus. In c o m m e r c i a l l y pure a l u m i n u m and OFHC copper 3'4 the yield loci following p r e s t r a i n s of l e s s than 0.01 w e r e found to be i s o t r o p i c if the p l a s t i c s t r a i n used to define yielding was g r e a t e r than 2 • 10 -3 and a n i s o tropic if it was l e s s . In the p r e s e n t study we c o n s i d e r a) the path d e p e n d ence of p l a s t i c d e f o r m a t i o n , b) the effects of p r e s t r a i n ing on yield loci and s t r e s s - s t r a i n b e h a v i o r , and c) the p o s s i b l e e x i s t e n c e of a l i m i t e d h i s t o r y dependence as suggested by M i a s t k o w s k i . s E X P E R I M E N T A L INVESTIGATION A p p a r a t u s and S p e c i m e n s C o m b i n e d s t r e s s t e s t s w e r e conducted on the axial t e n s i o n - i n t e r n a l p r e s s u r e t e s t i n g m a c h i n e as d e s c r i b e d in Refs. 3 and 6. Axial loads w e r e applied to t u b u l a r t e s t s p e c i m e n s by an I n s t r o n T e s t i n g Machine through t e s t i n g f i x t u r e s d e s i g n e d to a c c o m m o d a t e s i m u l t a n e o u s a x i a l loading and i n t e r n a l p r e s s u r i z a t i o n and to m i n i m i z e b e n d i n g effects. I n t e r n a l p r e s s u r i z a t i o n was achieved by a s p e c i a l l y d e s i g n e d h y d r a u l i c p r e s s u r e g e n e r a t o r .3 The t h i n - w a l l e d t u b u l a r test s p e c i m e n s w e r e m a chined from round b a r stock to the d i m e n s i o n s shown in Fig. 1, following p r o c e d u r e s to avoid r e s i d u a l S. S. HECKER, formerly with the Los Alamos Scientific Laboratory, Los Alamos, N. M., is now Senior Research Metallurgist, General Motors Research Laboratories, Warren, Mich. 48090. Manuscript submitted February 7, 1972. METALLURGICAL TRANSACTIONS
s t r e s s e s and p r o v i d e r e p r o d u c i b l e m e c h a n i c a l p r o p e r t i e s . 7 The wall t h i c k n e s s m e a s u r e d at 30 points along the t e s t s e c t i o n was found to v a r y by l e s s than 0.0003 in. for each s p e c i
Data Loading...
