Computer simulation of the round notched tension test of cox and low
- PDF / 293,902 Bytes
- 3 Pages / 613 x 788.28 pts Page_size
- 38 Downloads / 135 Views
Computer Simulation of the Round Notched Tension Test of Cox and Low B. MORAN AND D. M. NORRIS, J r . We c a l c u l a t e d the s t r e s s and s t r a i n s t a t e in a c i r c u m f e r e n t i a l l y notched t e n s i l e b a r with an OD (/9) t en t i m e s the r o o t r a d i u s (Ro). We found that the l o c a t i o n of the m a x i m u m p r i n c i p a l s t r e s s and m e a n s t r e s s shifts f r o m n e a r the notch t o w a r d the a x i s of s y m m e t r y as the s p e c i m e n is s t r a i n e d . T h e e q u i v a l e n t p l a s t i c s t r a i n is a l w a y s m a x i m u m at the notch r o o t . When In (Ao/A) r e a c h e d 0.18, the v a l u e at f r a c t u r e , we found that on a x i s , the e q u i v a l e n t p l a s t i c s t r a i n is 0.07 and the m a x i m u m p r i n c i p a l s t r e s s G~, is 1.97 t i m e s the y i e l d s t r e s s (Iio = 1.3 GPa). The i n i t i a l and c u r r e n t n e c k a r e a s a r e A o and A, r e s p e c t i v e l y . T h i s c o m p u t e r s i m u l a t i o n was m o t i v a t e d by a p a p e r by Cox and Low on the f a i l u r e of b l u n t - n o t c h e d , r o u n d - t e n s i l e s p e c i m e n s . ~ T h e y chose the p a r t i c u l a r g e o m e t r y of the m i l d l y notched o r p r e n e e k e d s p e c i m en b a s e d on the p r e v i o u s w o r k of Dana, A u l and Sachs 2 to a s s u r e f r a c t u r e initiation in " t h e c e n t e r of the s p e c i m e n and to c l o s e l y m a t c h the s t r e s s and s t r a i n s t a t e s found in the s m o o t h , round s p e c i m e n s . " T h e y d e t e c t e d f r a c t u r e i n i t i a t i o n on the axis of s y m m e t r y by s e c t i o n i n g and i n s p e c t i n g s p e c i m e n s f r o m tension tests interrupted before complete separation occurred, O u r e a r l i e r c a l c u l a t i o n s on round notched t e n s i o n b a r s of A5 3 3 B - 1 s t e e l , with notch r o o t r a d i u s - t o d i a m e t e r r a t i o s of Ro/D = 0.02 and 0.01, showed the m a x i m u m s t r e s s at f a i l u r e o c c u r r e d t w o - n o t c h r o o t r a d i i below the s u r f a c e and the m a x i m u m s t r a i n o cc u r r e d at the notch r o o t (see N o r r i s et al3). T h i s s t a t e of s t r e s s at f a i l u r e is c o m p l e t e l y d i f f e r e n t f r o m that found in highly n e c k e d s m o o t h t e n s i o n s p e c i m e n s w h e r e m a x i m u m s t r e s s and s t r a i n o c c u r on a x i s (see N o r r i s et al4). O u r notched s p e c i m e n e x p e r i m e n t s showed f a i l u r e s t a r t e d at the notch r o o t at, o r s l i g h t l y b e f o r e , m a x i m u m load. T h i s r e s u l t d i f f e r e d f r o m that of Cox and Low who used a n o t c h r a d i u s r a t i o Ro/D of 0.1. We s i m u l a t e d the Cox and Low notched e x p e r i ment to d e t e r m i n e the s t r e s s and s t r a i n s t a t e at f a i l u r e in a m i l d l y notched s p e c i m e n and u n d e r s t a n d t h e i r e x p e r i m e n t a l r e s u l t s . I
Data Loading...
