DIN 35NiCrMoV125 (equivalent to AISI 4340), which is a high
strength low alloy steel (HSLA), is mainly used at military applications in the
production of gun barrels. The main aim of this study was to determine the
low cycle fatigue (LCF) behaviour and the influence of temperature on low
cycle fatigue failure properties of that steel.
Three different temperatures (room temperature, 2500C and 4000C)
were used in the experiments in order to analyze the effect of temperature.
For each temperature, five strain amplitudes (in the range of 0.2% offset
yield point to 2% strain) were applied and the duplicates of each
experiment were performed to obtain more accurate results. Strain
amplitudes and the corresponding stresses were calculated from tension
tests performed at each temperature. Strain amplitude versus fatigue life (e-
N) curves for three different temperatures predicted that fatigue life at a
given strain increases with increasing temperature. The transition lives of
those three curves were observed at 1 % strain amplitude and no significant
effect of temperature on transition lives was observed. For stress based
analysis, stress versus fatigue life (S-N) curves were drawn. These curves
pointed that fatigue strength at a given number of cycle decreases with
increasing temperature.
Fractographic analyses of the fracture surfaces were performed to
examine the effects of load and temperature on the specimens. It was
observed that the number of crack initiation sites increases with increasing
strain.
| Identifer | oai:union.ndltd.org:METU/oai:etd.lib.metu.edu.tr:http://etd.lib.metu.edu.tr/upload/1060979/index.pdf |
| Date | 01 January 2003 |
| Creators | Onem, Orkun Umur |
| Contributors | Gurbuz, Riza |
| Publisher | METU |
| Source Sets | Middle East Technical Univ. |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | text/pdf |
| Rights | To liberate the content for public access |
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