THE EXAMINATION OF DISCONTINUITIES IN WELDS BY STEREORADIOGRAPHY

SINCE WELDS ARE RARELY DEFECT-FREE, IT IS DESIRABLE TO QUANTIFY THE EFFECTS OF DEFECTS ON THE MECHANICAL PROPERTIES OF WELDS AND TO DEVELOP A FIELD INSPECTION PROCEDURE MORE RELIABLE, MORE COMPLETE, FASTER, AND LESS COSTLY THAN THAT CURRENTLY IN USE. THIS INVESTIGATION OF THE FEASIBILITY AND PRACTICABILITY OF STEREORADIOGRAPHY WAS TO SATISFY THE LATTER OBJECTIVE. STEREORADIOGRAPHY, UNLIKE NORMAL INCIDENCE RADIOGRAPHY OR ULTRASONIC INSPECTION, PERMITS DIRECT THREE DIMENSIONAL OBSERVATION OF INTERNAL FLAWS. STEREORADIOGRAPHY ENTAILS OBTAINING AN X-RAY EXPOSURE AT TWO KNOWN POSITIONS OF THE OBJECT WITH RESPECT TO THE X-RAY TUBE AND VIEWING THE STEREO-PAIR THROUGH A STEREO-VIEWER (STEREOSCOPE). BY ACCURATELY MEASURING THE PARALLAX DIFFERENCES RESULTING FROM THE SPECIMEN (OR X-RAY TUBE) SHIFT, ONE MAY CALCULATE THE WELD FLAW'S DEPTH BELOW THE PLATE SURFACE USING PHOTOGRAMMETRIC PRINCIPLES. TO EVALUATE THIS TECHNIQUE, TEN PORES IN A DEFECTIVE WELDMENT WERE MEASURED AT THREE DIFFERENT TIMES. THE RESULTS WERE COMPARED TO DETERMINE HOW WELL AN OBSERVER COULD REPRODUCE HIS MEASUREMENTS. THE WELD WAS SECTIONED, AND THE ACTUAL PORE DEPTHS WERE MEASURED DIRECTLY. THESE RESULTS WERE COMPARED TO THE STEREORADIOGRAPHICALLY-MEASURED DEPTHS TO DETERMINE THE ACCURACY OF THE TECHNIQUE. IT WAS FOUND THAT STEREORADIOGRAPHY COULD MEASURE DEPTH BELOW A SURFACE TO WITHIN .04 INCH OF THE ACTUAL PORE DEPTH. ALSO, THE AVERAGE STEREORADIOGRAPHICALLY-MEASURED DEPTHS WERE REPRODUCIBLE WITHIN .04 INCH. IN BOTH CASES, THESE ERRORS ARE SIGNIFICANTLY SMALL FOR MANY ENGINEERING PURPOSES. STEREORADIOGRAPHY WAS FOUND TO BE FEASIBLE USING THE TECHNIQUE DEVELOPED, BUT, FOR GENERAL FIELD PRACTICAL APPLICATIONS, TOO SENSITIVE AND TOO TIME-CONSUMING IN ITS PRESENT STAGE OF DEVELOPMENT. HOWEVER, FURTHER EFFORT IN APPLYING AUTOMATED IMAGE ANALYSIS TO STEREORADIOGRAPHY MAY OVERCOME OR MINIMIZE THE LIMITATIONS. /AUTHOR/

• Supplemental Notes:
  • TECH REPT NO M-24 2 APP
• Corporate Authors:

  Construction Engineering Research Laboratory

  Army Corps of Engineers, P.O. Box 4005
  Champaign, IL  United States  61820
• Authors:
  • Carlson, K W
  • Lawrence, F V
• Publication Date: 1972-9

Media Info

• Features: Figures; References; Tables;
• Pagination: 9 p.

Subject/Index Terms

• TRT Terms: Accuracy; Defects; Feasibility analysis; Inspection; Mathematical models; Mechanical properties; Weldments; Welds
• Uncontrolled Terms: Weld defects
• Old TRIS Terms: Stereoradiography
• Subject Areas: Geotechnology; Highways; Materials;

Filing Info

• Accession Number: 00217333
• Record Type: Publication
• Files: TRIS
• Created Date: Apr 27 1974 12:00AM