Effects of measurement techniques on the experimental characterization of crack tip opening angle-Δa resistance curves
- 86 Downloads
One of the most promising approaches to characterizing the stable tearing process for lower constraint configurations in metallic materials has been indicated to be the crack tip opening angle (CTOA) criterion. In this paper we examine the effect of measurement distance selection and the impact of measurement procedures/analysis on the experimental CTOA-Δa resistance curve behavior of a Ti-6Al-4V and an Al5083 alloy. A new, systematic procedure for carrying out the experimental, surface CTOA measurement process has been used, which has uncovered artifacts of measurement distance selection that have not been presented prior to this study. By studying the CTOA-Δa behavior using a rigidly defined and consistent method, it is apparent that the measurement distance behind the crack tip at which angles are measured has a direct impact on the shape of the early transitional behavior of the CTOA-Δa behavior as well as the critical, experimental CTOA values produced.
Key WordsStable tearing fracture crack tip opening angle CTOA Ti-6Al-4V Al5083
critical, experimental crack tip opening angle
compact tension specimen
crack length after pre-cracking
maximum to minimum load ration for fatigue pre-cracking
crack length extension beyondai
crack tip opening angle measurement distance behind the crack tip
Unable to display preview. Download preview PDF.
- 2.Newman, J.C. Jr. andJames, M.A., “A Review of the CTOA/CTOD Fracture Criterion—Why It Works!,” AIAA,1324,1042–1051 (2001).Google Scholar
- 3.ASTM Standard E1290-99, “Standard Test Method for Crack Tip Opening Displacement (CTOD) Fracture Toughness Measurement,” Annual Book of ASTM Standards, 3.01 (2002).Google Scholar
- 4.Dawicke, D.S., Sutton, M.A., Newman, J.C. Jr. andBigelow, C.A., “Measurement and Analysis of Critical CTOA for an Aluminum Alloy Sheet,”NASA TM 109024, NASA Langley Research Center.Hampton, VA, September (1993).Google Scholar
- 5.ASTM Standard E399-83, “Standard Test Method for Plane-Strain Fracture Toughness of Metallic Materials,” Annual Book of ASTM Standards, 3.01 (1993).Google Scholar
- 6.Dawicke, D.S., Piascik, R.S., and Newman, J.C. Jr, “Analysis of Stable Tearing in a Thick Aluminum Alloy,” Fatigue and Fracture Mechanics, Vol. 28, ASTM STP 1321, J.H. Underwood, B.D. Macdonald, and M.R. Mitchell, editors, ASTM (1997).Google Scholar