Absorbed energy during compression and crushing of high strength steel sheets
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E a = 79.4 (~e:o.o~)~
9 t 2"~x 103
" t 1"9
(N) (J)
and in d y n a m i c c o m p r e s s i o n :
E a'
=
g . (aB) ~
9
t L9
(J)
E a ' / E a d e c r e a s e s with i n c r e a s i n g t e n s i l e s t r e n g t h of s t e e l sheet, and a p p r o a c h e s about 1.2 at above 400 N / m m 2.
R E C E N T L Y the d e v e l o p m e n t of safety v e h i c l e s to p r o t e c t the l i v e s of d r i v e r s and p a s s e n g e r s d u r i n g a u t o m o b i l e c o l l i s i o n s is in p r o g r e s s worldwide. F u r t h e r m o r e , in the United States, FMVSS ( F e d e r a l M o t o r Vehicle Safety Standard) is b e i n g s t r e n g t h e n e d y e a r a f t e r y e a r . Along with this, t h e r e is a t e n d e n c y for the safety s t a n d a r d s in v a r i o u s c o u n t r i e s to b e come i n c r e a s i n g l y s t r i c t . As a r e f l e c t i o n of this s i t u a t i o n , high s t r e n g t h s t e e l s h e e t s that p o s s e s s p r o p e r t i e s f a v o r a b l e for s t r e n g t h m e m b e r s a r e a l r e a d y coming into use f o r v a r i o u s p a r t s . In this type of sheet c o n s t r u c t i o n , howe v e r , the p r i n c i p a l mode of d e f o r m a t i o n is b u c k l i n g . However, not enough light has b e e n shed on the r e l a t i o n b e t w e e n the s t r e n g t h p r o p e r t i e s of the m e m b e r s and the m e c h a n i c a l p r o p e r t i e s of the s t e e l s h e e t s . In this paper, t h e r e f o r e , t e s t s t r u c t u r e s w e r e des i g n e d to s i m u l a t e the f r a m e s and m e m b e r s d u r i n g a u t o m o b i l e c o l l i s i o n s and e x p e r i m e n t s were made to d e t e r m i n e the i n f l u e n c e of m e c h a n i c a l p r o p e r t i e s on the a m o u n t of e n e r g y a b s o r b e d i n the c r u s h i n g of t h e s e t e s t s t r u c t u r e s made of h i g h - s t r e n g t h s t e e l s h e e t s . F u r t h e r , study was a l s o given to the m a x i m u m load o c c u r r i n g in the i n i t i a l stage of c r u s h i n g , that has b e e n t r e a t e d as a b u c k l i n g load. E X P E R I M E N T A L PROCEDURE T h e m e c h a n i c a l t e s t v a l u e s and t h i c k n e s s e s of the s t e e l s h e e t s that w e r e u s e d in the s t a t i c t e s t a r e shown in T a b l e I, and t h e i r s t r e s s - s t r a i n c u r v e in F i g . 1. Of them, the S a m p l e s A, C, and H w e r e u s e d a l s o in the d y n a m i c t e s t . H e r e , ay is the lower y i e l d
K. TODA is Deputy General Superintendent of the Works, H. GONDOH is General Manager of the Technical Research Office, H. TAKECHI is Manager of the Steel Materials Research Section, and M. USUDA is Assistant Managerof Steel Materials Research in Kimitsu Works, Nippon Steel Corporation, Chiba Pref., Japan. Manuscript submitted July 3, 1974. METALLURGICALTRANSACTIONS A
800 H
~s''' 200~ "
S
600
E
-~
400
"~ O z
0
I
I
I
I
I
10
20
30
40
50
60
Nominal strain (%) Fig. I--Stress-strain curves of specimens
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