The aim of this scientific work is the analysis of the LCF process in carbon steel welded joints. Strain-controlled fatigue tests were performed on ASTM A 516 J7 Grade 70 steel and welded joints made of the same steel. The experimental results allowed the comparison of LCF behavior of the welded joints to that of the base metal. This paper presents an analysis of the low-cycle fatigue (LCF) process during fatigue testing of welded steel joints by thermographic investigations. Infrared thermography has been applied in the past to investigate high-cycle fatigue (HCF) of metals and welded joints, and it has been found that the thermal pattern of the specimen surface during HCF tests is characterized by three phases with a stabilized temperature. A similar thermal pattern was observed in the LCF tests. The thermal increments during the LCF life were correlated to the hysteresis loops derived from the traditional procedure and the experimental results confirm that there is a correlation between the stable hysteresis loops and the stabilized temperature. Moreover, the LCF behavior of welded joints was compared to that of the base material. Fatigue constants (K', n') and LCF curves for welded joints and carbon steel specimens were determined from the strain-controlled fatigue tests. They are useful parameters in predicting fatigue life of components and welded details made from the same steel and subjected to any random service loading. Further experiments are planned to investigate the failure surface and crack initiation and propagation through microscope evaluation of the specimen at cycle intervals and in order to correlate the detected temperature increment deltaT to crack initiation and propagation during low-cycle fatigue tests.
Using infrared thermography in low-cycle fatigue studies of welded joints
Welding Journal, New York ; 89 , 9 ; 195s-200s
2010
6 Seiten, 13 Bilder, 5 Tabellen, 15 Quellen
Aufsatz (Zeitschrift)
Englisch
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