ISSN:
1460-2695
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Abstract— The crack tip cyclic heat generation rate, fatigue crack growth rate, and the crack closure stress were measured in a β-annealed Ti-6Al-4V for R ratios of -0.1, 0.1 and 0.2. The R= -0.1 and 0.1 cases exhibited macroscopic crack closure and the R = 0.2 case exhibited no macroscopic crack closure as measured by strain gage techniques. There was a transition in the slope of the da/dN vs ΔK curve for the closure cases and no transition for the no-closure case. The crack tip heat generation rate above the transition for the closure cases was an order of magnitude greater than for the no-closure case. Also the crack tip heat generation rate below the transition was greater for the closure cases than for the no-closure case. The transition in the heat generation rate and the crack growth rate was attributed to a transition from static frictional locking of shear branch cracks to sliding of the branch crack surfaces. Below the transition the crack faces are locked open creating a large roughness-induced closure component. When the branch cracks are allowed to undergo reverse shear, the amount of roughness-induced closure markedly decreases and the fracture surface becomes less tortuous. The relative sliding generates the increased heat.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1460-2695.1988.tb01171.x
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