THREE-DIMENSIONAL PHOTOELASTIC INVESTIGATION OF SIMULATED WELD DISCONTINUITIES

A REVIEW WAS MADE OF PREVIOUS INVESTIGATIONS INTO THE PROBLEM OF THE NOTCH-SENSITIVITY OF METALS IN FATIGUE. A HYPOTHESIS FOR THE PREDICTION OF THE FATIGUE BEHAVIOR OF WELDED CONNECTIONS WITH DISCONTINUITIES WAS DEVELOPED. THIS HYPOTHESIS SUGGESTS THAT THE PARAMETER BEST DEFINING THE NOTCH-SENSITIVITY OF A MATERIAL SUBJECTED TO FATIGUE LOADINGS IS A CHARACTERISTIC VOLUME OF MATERIAL AROUND THE NOTCH TIP OVER WHICH THE STRESS CONCENTRATION CAN BE AVERAGED. THE REDUCTION IN FATIGUE STRENGTH OF A MEMBER DUE TO THE PRESENCE OF A FLAW IS - ACCORDING TO THE HYPOTHESIS - DETERMINED BY THE AVERAGE ELASTIC ENERGY CONCENTRATION INDUCED BY THE FLAW OVER THE APPROPRIATE VOLUME. IN ORDER TO EVALUATE THE APPLICABILITY OF THE ENERGY CONCENTRATION HYPOTHESIS, TWO SETS OF INFORMATION WERE SOUGHT: FIRST, A SUITABLE SERIES OF FATIGUE TESTS, WHICH INVOLVED A SUFFICIENT NUMBER OF TEST SPECIMENS CONTAINING A FLAW TYPE, THE SEVERITY OF WHICH COULD BE DEFINED AND VARIED IN A RELATIVELY SIMPLE MANNER, AND SECONDLY, DETERMINATIONS OF THE ELASTIC ENERGY CONCENTRATION INDUCED BY THE SELECTED FLAWS. A LITERATURE SEARCH PRODUCED REPORTS OF AN INVESTIGATION IN WHICH A SUBSTANTIAL NUMBER OF TEST SPECIMENS, CONTAINING PARTIAL PENETRATION BUTT-WELDS OF VARYING DIMENSIONS, HAD BEEN SUBJECTED TO REPEATED LOADINGS. DUE TO THE AVAILABILITY OF THIS TEST INFORMATION AND THE RELATIVE EASE WITH WHICH THE LACK OF PENETRATION FLAWS COULD BE USED IN THE CURRENT STUDY, THIS FLAW TYPE WAS ADOPTED FOR THE ANALYSIS OF FATIGUE BEHAVIOR IN RELATION TO FLAW SEVERITY. SEVERAL FLAW GEOMETRIES WERE THEN SIMULATED IN THREE-DIMENSIONAL EPOXY MODELS AND THE STRESS DISTRIBUTIONS INDUCED BY THE FLAWS AND THE LOADING DETERMINED USING PHOTOELASTIC TECHNIQUES. THE CORRELATION OF THE PHOTOELASTIC INFORMATION WITH THE DATA OBTAINED FROM THE FATIGUE TESTS INDICATES THAT THE ENERGY DISTRIBUTIONS ARE SENSITIVE TO VARIATIONS IN FLAW SEVERITY. FOR THE PARTIAL PENETRATION BUTT-WELDS INVESTIGATED, THE PROPOSED HYPOTHESIS PROVED TO BE WELL-SUITED FOR DETERMINING THE FATIGUE STRENGTH REDUCTION CAUSED BY THE PRESENCE OF THE FLAW. IN ORDER TO FURTHER TEST THE ENERGY CONCENTRATION HYPOTHESIS, IT WAS APPLIED TO A NOTCHED MEMBER RADICALLY DIFFERENT FROM THE PARTIAL PENETRATION BUTT-WELD: A TENSION STRIP WITH A CENTRALLY LOCATED HOLE. IT WAS FOUND THAT, IN THIS CASE ALSO, THE PROPOSED HYPOTHESIS IS WELL SUITED FOR PREDICTING THE FATIGUE BEHAVIOR OF THE MEMBER. A DETAILED DESCRIPTION OF ALL PHASES OF THE PHOTOELASTIC PROCEDURE IS PRESENTED ALONG WITH THE DEFINITION AND APPLICATIONS OF THE PROPOSED ENERGY CONCENTRATION HYPOTHESIS. /AUTHOR/

• Corporate Authors:

  University of Illinois, Urbana-Champaign

  Urbana, IL  United States  61801

  Illinois Department of Transportation

  Division of Highways, 2300 South Dirksen Parkway
  Springfield, IL  United States  62764

  Bureau of Public Roads /US

  400 7th Street, SW
  Washington, DC  United States  20590
• Authors:
  • Ottsen, H
  • Munse, W H
• Publication Date: 1970-8

Subject/Index Terms

• TRT Terms: Accelerated tests; Butt welds; Defects; Deformation curve; Fatigue (Mechanics); Fatigue tests; Hypothesis testing; Joints; Mathematical models; Metals; Notching (Cutting); Photoelasticity; Repeated loads; Reviews; Simulation; Strength of materials; Welds
• Uncontrolled Terms: Hypothesis; Models; Notch sensitivity; Welded joints
• Old TRIS Terms: Photoelastic method
• Subject Areas: Data and Information Technology; Geotechnology; Highways; Materials;

Filing Info

• Accession Number: 00215933
• Record Type: Publication
• Source Agency: Bureau of Public Roads /US
• Report/Paper Numbers: Ihr-64
• Files: TRIS
• Created Date: Sep 28 1970 12:00AM