Ultrasonic fatigue testing of thin-walled stainless steel tubes
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Ultrasonic Fatigue Testing of ThinWalled Stainless Steel Tubes B R I G I T T E WEISS AND ROLAND S T I C K L E R F A T I G U E t e s t i n g at u l t r a s o n i c f r e q u e n c i e s has been shown to be a c o n v e n i e n t and e a s y m e t h o d 1-3 to inv e s t i g a t e the m i c r o s t r u c t u r a l c h a n g e s in a v a r i e t y of m a t e r i a l s and to obtain i n f o r m a t i o n on the fatigue b e h a v i o r o v e r a wide r a n g e of t e s t i n g c y c l e s . F o r e x a m p l e , it would take m o r e than 1.5 y e a r s in the usual l a b o r a t o r y fatigue t e s t e q u i p m e n t , o p e r a t i n g at 200 Hz, to a c c u m u l a t e 101~ t e s t c y c l e s , while only a p p r o x i m a t e l y 140 h r of t e s t i n g a r e r e q u i r e d to obtain the s a m e n u m b e r of c y c l e s in an u l t r a s o n i c t e s t i n g d e v i c e o p e r a t e d at 20,000 Hz. BRIGITTE WEISS and ROLAND STICKLER are Senior Research Engineer and Manager, respectively, Physical Metallurgy, Westinghouse Research Laboratory, Pittsburgh, Pc. Manuscript submitted August 4, 1969. METALLURGICALTRANSACTIONS
H o w e v e r , only a s m a l l n u m b e r of i n v e s t i g a t i o n s of the application of u l t r a s o n i c fatigue t e s t i n g to e n g i n e e r ing m a t e r i a l s have b e e n r e p o r t e d . 2'4 This l i m i t e d app l i c a t i o n m a y be due in p a r t to the u n c e r t a i n t y in the c o r r e l a t i o n b e t w e e n high and low f r e q u e n c y t e s t data and in p a r t to the r e q u i r e d c r i t i c a l s p e c i m e n d i m e n s i o n s , e . g . , thin w i r e s and r o d s o r s h e e t s p e c i m e n s . On the o t h e r hand, c o n v e n t i o n a l c o m p r e s s i o n - t e n s i o n fatigue t e s t i n g of such s a m p l e g e o m e t r i e s , e s p e c i a l l y in t h i n - w a l l e d tubes, p o s e s c o n s i d e r a b l e e x p e r i m e n t a l d i f f i c u l t i e s in r e s p e c t to s a m p l e m o u n t i n g , a l i g n m e n t , and the p r e v e n t i o n of b u c k l i n g or bending. It was the p u r p o s e of the p r e s e n t e x p e r i m e n t s to d e t e r m i n e the a p p l i c a b i l i t y of u l t r a s o n i c t e s t i n g e q u i p m e n t to the study of fatigue p r o p e r t i e s and fatigue d a m a g e in t h i n - w a l l e d 316 s t a i n l e s s s t e e l tubing such a s u s e d a s cladding m a t e r i a l f o r n u c l e a r r e a c t o r s . U l t r a s o n i c T e s t E q u i p m e n t and Method of E v a l u a t i o n . The e q u i p m e n t used for t h e s e e x p e r i m e n t s c o n s i s t e d of an u l t r a s o n i c f r e q u e n c y g e n e r a t o r (500 w output) which s e r v e s as the power supply for an a i r - c o o l e d u l t r a s o n i c c e r a m i c t r a n s d u c e r ( " c o n v e r t e r " ) . * The *The experimentshavebeen madepossibleby Mr. S. Jacke of Branson Sonic Power Co., Danbury, Conn., who provideda suitable test facility,and Mr. A. E. Harris, who assistedin cond
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