- Author
-
Early, J. G.
- Title
- Ambient-and Elevated-Temperature Mechanical Properties of AAR M128-69-B Steel Plate Samples Taken from Fire Tested Insulated Tank Car Rax 202. Report No 8. Failure Analysis Report.
- Coporate
- National Bureau of Standards, Gaithersburg, MD
- Sponsor
- Department of Transportation, Washington, DC
- Report
-
NBSIR 75-725
May 1975
59 p.
- Distribution
- LIMITED DISTRIBUTION Available from National Technical Information Services
- Keywords
-
steels
- Abstract
- Studies were undertaken at NBS to measure the elevated-temperature mechanical properties and to determine the elevated-temperature fracture behavior of selected AAR M128-B steel plates taken from tank car RAX 202. A secondary effort was to measure the ambient-temperature mechanical properties to determine if the requirements of specification AAR M128-B-69 were satisfied. Three plate samples were selected for this study. The NBS results of check chemical analyses, hardness surveys, thickness measurements, macroscopic observations, and metallographic analyses of these plate samples had been previously reported. Results of ambient-temperature tensile tests showed that all three plate samples met the strength and ductility requirements of specification AAR M128-B-69. Results of hot-tensile tests showed a continuous decrease in strength properties and an increase in tensile ductility in the temperature range from 1100 F to 1250 F. Analysis of stress-rupture data for all three plate samples indicated that a single straight line represented the data at reach test temperature. In the temperature and stress range investigated, a decrease in the initial stress of approximately 20 to 30 percent resulted in a twelvefold increase in rupture life. A comparison of the results of the metallographic analyses of hot-tensile and representative stress-rupture specimens in this study with the previously reported results on the initial rupture site in the failed shell course indicated the presence of an identical fracture mode. These results confirm the previously reported finding that the initial rupture of tank car RAX 202 was a stress-rupture crack. A comparison of hot tensile and stress-rupture results between specimens from tank car RAX 201 and specimens from tank car RAX 202 showed substantial disagreement.