Crack deflection in the nonlinear zone of ultra-high-strength steel fatigue crack growth curve

ABSTRACT

The fatigue crack growth rate (FCGR) of 10Ni5CrMoV steel under variable load ratios was investigated. The microscopic observations of growth direction and microstructural analysis were conducted by means of electron backscatter diffraction and transmission electron microscopy. The results showed that FCGR of 10CrNi5MoV steel increased with the increasing load ratio in the mid-growth rate regime; however, it did not completely conform to the Paris Formula. A nonlinear zone existed in the logarithmic coordinate system of the FCGR curve and was unaffected by load ratio. The main impact factors for the appearance of the nonlinear zone were grain size and the size of the plastic zone surrounded fatigue cracks. In the nonlinear zone of the FCGR curve, an apparent crack deflection phenomenon occurred.

KEYWORDS:

• 10Ni5CrMoV steel
• fatigue crack growth
• nonlinear zone
• plastic zone
• crack deflection

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The author (Kaiming Wu) gratefully acknowledges the financial support from the Major Technology Innovation of Hubei Province [grant number 2016AAA022].