THE INFLUENCE OF LOADING VARIABLES ON ENVIRONMENT-ENHANCED FATIGUE CRACK GROWTH IN HIGH STRENGTH STEELS

An experimental program was carried out to further determine the range of applicability of the superposition model, proposed by Wei and Landes, for estimating the effects of cyclic loading variables and chemical environment on fatigue crack growth. AISI 4340 steel, tempered at 200 deg F and 500 deg F, and RQ360A steel were used in this investigation. The influences of frequency, stress ratio, and cyclic-load waveform were examined. The results showed that the superposition model provides correct estimates of the trend and the order of magnitude for the influences of these variables within the applicable range provided that steady-state crack growth data are used. Data on the AISI 4340 steel suggest the presence of some synergistic effect of fatigue and environmental attack. Modification of this model will be needed to incorporate this effect and to improve the accuracy of predictions. Environment can affect fatigue-crack growth at K levels below the K level for stress corrosion cracking. Data obtined on the RQ360A steel indicate that the environmental effect can depend on frequency and cyclic-load waveform. These results are in agreement with published results on highly alloyed steels. Further basic studies will be needed to clarify these effects and to develop viable prediction procedures. Nonsteady-state crack growth in fatigue was observed. This state of carck growth would occur at the start of testing and following test interruptions. This phenomenon must be recongnized, and be taken into consideration in data acquisition and subsequent utilization. /Author/

• Availability:
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• Corporate Authors:

  American Society for Testing and Materials (ASTM)

  100 Barr Harbor Drive, P.O. Box C700
  West Conshohocken, PA  United States  19428-2957
• Authors:
  • Miller, G A
  • Hydak, S J
  • Wei, R P
• Publication Date: 1973-11

Media Info

• Features: Appendices; Figures; References; Tables;
• Pagination: p. 524-531
• Serial:
  • Journal of Testing and Evaluation
  • Volume: 1
  • Issue Number: 6
  • Publisher: American Society for Testing and Materials (ASTM)
  • ISSN: 0090-3973
  • EISSN: 1945-7553
  • Serial URL: https://www.astm.org/DIGITAL_LIBRARY/JOURNALS/TESTEVAL/index.html

Subject/Index Terms

• TRT Terms: Accuracy; Alloy steel; Environmental impacts; Fatigue (Mechanics); Forecasting; Fracture mechanics; Frequency (Electromagnetism); High strength steel; Mathematical models; Repeated loads; Stress ratio; Waveform analysis
• Uncontrolled Terms: Models
• Old TRIS Terms: Waveform
• Subject Areas: Bridges and other structures; Environment; Highways;

Filing Info

• Accession Number: 00264611
• Record Type: Publication
• Files: TRIS
• Created Date: Jan 29 1975 12:00AM