Download or read book The Effects of Slip Character and Crack Closure on the Growth of Small Fatigue Cracks in Titanium aluminium Alloys written by James M. Larsen and published by . This book was released on 1990 with total page 286 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book The Effects of Slip Character and Crack Closure on the Growth of Small Fatigue Cracks in Titanium aluminium Alloys written by James M. Larsen and published by . This book was released on 1990 with total page 261 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Effects of Slip Character and Crack Closure on the Growth of Small Fatigue Cracks in Titanium aluminum Alloys written by James Milligan Larsen and published by . This book was released on 1987 with total page 261 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Crack Closure Effects on the Growth of Small Surface Cracks in Titanium Aluminum Alloys written by JM. Larsen and published by . This book was released on 1988 with total page 19 pages. Available in PDF, EPUB and Kindle. Book excerpt: Among other factors, the reported failure of linear elastic fracture mechanics to correlate the growth rates of large and very small fatigue cracks has been attributed to microstructural and crack closure effects. These two factors have been examined in experiments on three titanium-rich Ti-Al alloys, which display significant differences in plastic slip character ranging from homogeneous wavy slip to extremely heterogeneous planar slip. The variation in slip character has a dramatic effect on the level of roughness induced crack closure, which in turn, strongly influences the growth rate behavior of large fatigue cracks. In the present project the behavior of small fatigue surface cracks in these materials was investigated using two specialized experimental techniques. A computer-controlled photomicroscopic system was employed to monitor surface crack length directly, and an automated laser interferometric technique was used independently to determine crack length and to measure the development of crack closure. Although slip character has a strong influence on the propagation of large cracks, the present findings indicate that there is a minimal effect of slip character on the growth of small fatigue cracks. Direct crack opening displacement measurements indicate that this is largely because of a transient development of crack closure in the small cracks. For the materials tested, the crack depth required to fully develop crack closure ranged from 5 to 13 times the mean distance between grain boundaries. Above this crack size, data from small surface cracks and large cracks in C(T) specimens were well consolidated by the linear-elastic parameter ?K.

Download or read book Mechanics of Fatigue Crack Closure written by Wolf Elber and published by ASTM International. This book was released on 1988 with total page 671 pages. Available in PDF, EPUB and Kindle. Book excerpt:

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Download or read book Small crack Test Methods written by James M. Larsen and published by ASTM International. This book was released on 1992 with total page 228 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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

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Download or read book Effects of Closure on the Fatigue Crack Growth of Small Surface Cracks in a High Strength Titanium Alloy written by Jira, JR. and published by . This book was released on 1988 with total page 19 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.