surface residual stresses in the heat affected zone are highly 

 compressive, about 100 ksi for the as-welded specimen, and are 

 fairly uniform along the weld for the three azimuthal directions. 

 The two stress relieved specimens contain much lower comoressive 

 stresses, about one third the magnitude of the as-welded. These 

 results are in good agreement with those of DiGiacomo3, although, 

 in that work, the weld was of a different type. It shows the 

 existence of a steep stress gradient at the surface layer, changing 

 from compression to tension through shallow depths. A complete 

 study of the state of residual stresses in three directions 

 (triaxial stresses) would entail the combination of X-ray diffrac- 

 tion and layer removal techniques. 



Residual stress values obtained from the surface of the cir- 

 cular weld are listed in Table 2, These stresses are moderately 

 compressive in both of the directions studied. The surface of the 

 weld was electropolished prior to the X-ray stress analysis to a 

 depth of 0.003 inch to rid the weld surface of scale and contami- 

 nations. Inevitably, this operation removed base metal which may 

 have had much higher compressive stresses than that obtained from 

 the imderlying surface exposed after the removal. This may 

 account for the low compressive stresses obtained from the circu- 

 lar weld. 



The X-ray diffraction method is also applicable to titainiura 

 alloys, provided that modifications are made in the technique to 

 satisfy more stringent requirements. 



CONCLUSIONS 



Based on the results of this investigation it may be concluded 

 that residual stresses at the surface of welds and adjacent base 

 metal of tee and circular fillet HY-I3O/I5O weldments are highly 

 compressive, and that a stress-relief heat treatment reduces the 

 residusil stresses by a factor of three. 



FUTURE WORK 



Stress gradients in the direction normal to the surface of 

 additional high strength steel weldments will be studied. The 

 study will require the removal of thin metal layers by the electro- 

 polishing technique and the determination of the residual stresses 

 by X-ray diffraction at the surface exposed by each removal. 



ACKNOWLEDGMENT 



The work reported herein was accomplished under the overall 



3. Ibid. 



300 



