Effects Of Closure On The Fatigue Crack Growth Of Small Surface Cracks In A High Strength Titanium Alloy
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| Author | : Jira, JR. |
| Publisher | : |
| Total Pages | : 19 |
| Release | : 1988 |
| Genre | : Crack closure |
| ISBN | : |
Fatigue crack growth experiments were conducted on surface flaws in a high-strength titanium alloy. Surface crack lengths in the range 50-?m to 8 mm were investigated under both increasing and decreasing ?K conditions. Crack length and closure loads were determined from load-displacement data obtained with the aid of a laser interferometric displacement gage, which has resolution capability at 0.01 ?m. Stress ratios of 0.1, 0.5, and -1.0 and net-section stress levels from 0.2 to 0.9 of yield stress were utilized. The applied stress intensity factor range, ?K, correlated crack-growth-rate data for R = 0.1 and R = -1, but all R = 0.5 data fell along a separate band. The effective stress intensity factor range ?Keff determined from closure data, consolidated most of the data into a single band, but some small-crack data fell outside the band. Fracture surface roughness and plasticity were concluded to be the primary features contributing to crack closure.
| Author | : James M. Larsen |
| Publisher | : |
| Total Pages | : 286 |
| Release | : 1990 |
| Genre | : Aluminum alloys |
| ISBN | : |
An investigation was performed to study the effects of slip character and crack closure on the propagation of small fatigue cracks in titanium- aluminum alloys. The materials examined were solution-treated Ti-4Al and Ti-8Al, as well as aged Ti-8Al. The propagation of naturally initiated surface cracks of depths as small as 25 micrometers was compared with the behavior of large through-thickness cracks. An extensometer was used to monitor crack closure throughout the large crack tests, and the closure behavior of the small cracks was measured using a computerized laser interferometric displacement gage having a displacement resolution of 0.01 micrometer. The measurements of crack closure were used to compute an effective stress intensity factor range. In all three alloys and for all test conditions, which included a range of stress levels and stress ratios, small cracks propagated faster than large cracks subjected to an equivalent Delta K, and the small cracks propagated under conditions that were significantly below the large-crack threshold, Delta K(th). Although the character and distribution of slip in Ti-Al alloys may have a dramatic influence on fatigue crack initiation and on the propagation of large cracks, this effect was minimal for small cracks.
| Author | : Wolf Elber |
| Publisher | : ASTM International |
| Total Pages | : 671 |
| Release | : 1988 |
| Genre | : Fracture mechanics |
| ISBN | : 0803109962 |
| Author | : |
| Publisher | : |
| Total Pages | : 702 |
| Release | : 1995 |
| Genre | : Aeronautics |
| ISBN | : |
| Author | : James M. Larsen |
| Publisher | : ASTM International |
| Total Pages | : 228 |
| Release | : 1992 |
| Genre | : Elasticity |
| ISBN | : 0803114699 |
Reviews the most recent methods for testing small cracks in a variety of materials, providing detailed quantitative information on necessary procedures for data acquisition. Emphasizes the characterization of small, three-dimensional fatigue cracks, initiated either naturally or artificially. The ei
| Author | : National Aeronautics and Space Administration (NASA) |
| Publisher | : Createspace Independent Publishing Platform |
| Total Pages | : 32 |
| Release | : 2018-07-13 |
| Genre | : |
| ISBN | : 9781722867089 |
The corrosion fatigue crack growth characteristics of small surface and corner cracks in aluminum alloy 2024 is established. The damaging effect of salt water on the early stages of small crack growth is characterized by crack initiation at constituent particle pits, intergranular microcracking for a less than 100 micrometers, and transgranular small crack growth for a micrometer. In aqueous 1 percent NaCl and at a constant anodic potential of -700 mV(sub SCE), small cracks exhibit a factor of three increase in fatigue crack growth rates compared to laboratory air. Small cracks exhibit accelerated corrosion fatigue crack growth rates at low levels of delta-K (less than 1 MPa square root of m) below long crack delta-K (sub th). When exposed to Paris regime levels of crack tip stress intensity, small corrosion fatigue cracks exhibit growth rates similar to that observed for long cracks. Results suggest that crack closure effects influence the corrosion fatigue crack growth rates of small cracks (a less than or equal to 100 micrometers). This is evidenced by similar small and long crack growth behavior at various levels of R. Contrary to the corrosion fatigue characteristics of small cracks in high strength steels, no pronounced chemical crack length effect is observed for Al by 2024 exposed to salt water. Piascik, Robert S. and Willard, Scott A. Langley Research Center RTOP 538-02-10-01...
| Author | : Walter G. Reuter |
| Publisher | : ASTM International |
| Total Pages | : 428 |
| Release | : 1990 |
| Genre | : Fracture mechanics |
| ISBN | : 080311284X |
From the symposium (on title) held in Sparks, Nevada, April 1988. Twenty-two peer-reviewed papers are divided into sections on models and experiments (monotonic loading), and fatigue crack growth. Areas addressed include the differences in constraint for 2-D through-thickness cracks and 3-D surface
| Author | : K.S. Ravichandran |
| Publisher | : Elsevier |
| Total Pages | : 511 |
| Release | : 1999-09-30 |
| Genre | : Technology & Engineering |
| ISBN | : 0080569706 |
This book contains the fully peer-reviewed papers presented at the Third Engineering Foundation Conference on Small Fatigue Cracks, held under the chairmanship of K.S. Ravichandran and Y. Murakami during December 6-11, 1998, at the Turtle Bay Hilton, Oahu, Hawaii. This book presents a state-of-the-art description of the mechanics, mechanisms and applications of small fatigue cracks by most of the world's leading experts in this field. Topics ranging from the mechanisms of crack initiation, small crack behavior in metallic, intermetallic, ceramic and composite materials, experimental measurement, mechanistic and theoretical models, to the role of small cracks in fretting fatigue and the application of small crack results to the aging aircraft and high-cycle fatigue problems, are covered.
| Author | : James M. Larsen |
| Publisher | : |
| Total Pages | : 261 |
| Release | : 1990 |
| Genre | : |
| ISBN | : |
| Author | : Stephen W. Smith |
| Publisher | : |
| Total Pages | : 34 |
| Release | : 2001 |
| Genre | : |
| ISBN | : |
