Cyclic crack opening displacement behavior during high-amplitude block loading
✍ Scribed by T. Yeh; L.H. Burck
- Publisher
- Elsevier Science
- Year
- 1979
- Tongue
- English
- Weight
- 765 KB
- Volume
- 12
- Category
- Article
- ISSN
- 0013-7944
No coin nor oath required. For personal study only.
✦ Synopsis
Load-crack opening displacement hysteresis behavior was monitored for fifty cycles of highamplitude loading which followed fatigue pre-cracking at low stress intensity factor levels. The material studied was quenched and tempered (400°C) AISI 4140 steel which showed pronounced cyclic softening. Despite this softening behavior, cycle-tecycle decreases in load-COD hysteresis were observed during the initial cycles of high-amplitude loading. Steady state @ad-COD hysteresis behavior was attained by fifty loading cycles in each case and the fifty-cycle hysteresis loop widths agreed well with those for continuously cycled (non-precracked) samples for equivalent loading conditions. The cydes during which the load-COD hysteresis decreased most dramatically represented fatigue crack growth distances equal to approximately 30% of the calculated plane strain monotonic plastic zone size. Greater percentage reductions in load-COD hysteresis were observed for lower stress intensity factor ranges. The observed behavior was in general agreement with that predicted by finite element fatigue crack closure models in the literature.
In addition, the level of prior loading was found to have a pronounced effect on subsequently measured fracture toughness values for this material.