RESIDUAL STRESS IN HIGH STRENGTH STEEL WELDMENTS 

 APPLICATION OP X-RAY DIFFRACTION TECHNIQUE 



Gixillo DiGlacomo 

 Research Physicist 



Irving Canner 

 Physicist 



Joseph R. Crisci 

 Physical Metallurgist 



Naval Applied Science Laboratory 



Flushing and Washington Avenues 



Brooklyn, New York II25I 



ABSTRACT 



Residusil stresses develop in weldments during fabrication. 

 Their presence may be detrimental to the fatigue life and strength 

 of the structures during service. In the past few years, the need 

 for residual stress measurements by nondestructive means has 

 paralleled the need for material of higher strength and durability. 

 On the basis of the works published in the literature, the only 

 proven nondestructive method for stress analysis is X-ray diffrac- 

 tion; however, it has not had appreciable application in actual 

 structures and weldments. This paper deals with the determination 

 of residual stresses in the weld and/or heat affected zone of high 

 strength steel weldments by the X-ray diffraction method. The 

 study included tee and butt weldments, tested in the as-welded and 

 stress relieved conditions. The residual stresses were measured 

 in the directions parsillel and transverse to the weld, on the 

 surface and two mils below the surface following electropolishing. 

 Both film and diffractometer techniques were utilized in the 

 investigation. Results show that residual stresses at the surface 

 of both weldments studied are generally compressive in both 

 directions. The as-welded specimens show residual stresses as 

 high as the yield strength, while the residual stresses in the 

 stress relieved specimens are reduced by more than 50^. 



INTRODUCTION 



Structurgil materials such as steel and titanium alloys must 

 possess high strength and fatigue life if they are to endure ocean 

 environment. The higher the strength and fatigue requirements, 

 however, the greater the need to ascertain the integrity of the 

 structure during fabrication and in service by nondestructive 

 methods. X-ray diffraction is one method which is used to deter- 

 mine residuauL stresses in metal structures nondestructively. 



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