Fatigue-Crack Propagation Behavior of Incoloy 800 at Elevated Temperatures

Linear-elastic fracture mechanics techniques were used to characterize the fatigue-crack propagation behavior of Incoloy 800 in an air environment over the temperature range 75 to 1200 deg F (24 to 649 deg F). Crack growth rates were measured over the range 5×10−7 to 5×10−5 in./cycle. Material Grades 1 and 2 were found to exhibit essentially the same behavior over this range. In general, crack growth rates increased with increasing test temperature, although the increases were less then previously noted for austenitic stainless steels. This difference is probably related to the superior oxidation resistance of Incoloy 800.

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Effect of Biaxial Static Loads on Fatigue Crack Propagation Behavior under Cyclic Tensile and Torsional Loading

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.321-323.720 ◽

2006 ◽

Vol 321-323 ◽

pp. 720-723

Author(s):

Yong Hak Huh ◽

Philip Park ◽

Dong Jin Kim ◽

Jun Hyub Park

Keyword(s):

Fatigue Crack ◽

Crack Propagation ◽

Fatigue Crack Propagation ◽

Growth Rates ◽

Biaxial Loading ◽

Torsional Loading ◽

Static Loads ◽

Fatigue Crack Propagation Behavior ◽

Propagation Behavior ◽

Crack Propagation Behavior

Fatigue crack propagation behavior under cyclic tensile or torsional loading with biaxial static loads has been investigated. Two different biaxial loading systems, i.e. cyclic tensile loading with static torsional load and cyclic torsional loading with static tensile load, were employed to thin-walled tubular specimens. The crack propagation was measured by two crack gages mounted near the notch and crack opening level was measured by unloading compliance method. The directions of the fatigue crack propagated under respective biaxial loading conditions were examined and the growth rates were evaluated by using several cyclic parameters, including equivalent stress intensity factor range, Keff, crack tip opening displacement range, CTD, minimum strain energy density factor range, Smin. Furthermore, the growth rates were evaluated by effective cyclic parameters considering crack closure. It was found that the biaxial static stress superimposed on the cyclic tensile or torsional loading tests has no influence on the propagation directions of the cracks. Furthermore, it was shown that the fatigue crack growth rates under biaixial faigue loading were well expressed by using the cyclic fatigue parameters, Keq,eff, CTDeff, Smin,eff considering crack closure effect.

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Influence of Geometry and Test Method on Fatigue Crack Propagation Behavior of a Ni-Base Jet Engine Alloy

Volume 7A: Structures and Dynamics ◽

10.1115/gt2015-42772 ◽

2015 ◽

Cited By ~ 1

Author(s):

Youri N. Lenets ◽

Alonso Peralta ◽

Ross Miller ◽

James Neumann

Keyword(s):

Fatigue Crack ◽

Crack Propagation ◽

Crack Growth ◽

Fatigue Crack Propagation ◽

Ion Beam ◽

Test Method ◽

Jet Engine ◽

Fatigue Crack Propagation Behavior ◽

Propagation Behavior ◽

Crack Propagation Behavior

The majority of fatigue crack growth tests worldwide makes use of the compact tension (CT) specimens that are not necessarily representative of cracks developing under service conditions in highly stressed components of a jet engine. Over the years other geometries have been designed to facilitate a study of relatively small, semi- or quarter-elliptically shaped surface flaws subjected to high tensile and compressive stresses. Despite an extensive use by the aerospace community, practical aspects of testing and data analysis relevant to the complex surface- or corner-flawed geometries are not regulated by a commonly accepted set of rules. Two types of test specimens — CT and surface-crack tension (SCT) — were machined from a forged and heat treated Inconel 718. For both geometries the crack orientation and propagation direction with respect to the original forging were the same. The CT specimens were tested in accordance with the ASTM Standard E647 as well as using an alternative compression pre-cracking procedure. After correct application of the compression pre-cracking to the CT geometry both approaches had yielded reasonably consistent results. At high ΔK values both studied geometries also produced similar results, however, as the ΔK values decreased, a trend towards slower crack growth rates in the SCT specimens became evident. In order to address a so-called small-crack effect, several SCT specimens received much smaller crack starter notches produced by the focused ion beam (FIB) technology. The results of the present study highlight the importance of the appropriate material properties for accurate and reliable service life prediction of the critical aerospace propulsion hardware with particular emphasis on the influence of specimen/crack geometry and test method on the fatigue crack propagation behavior of jet engine alloys.

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Three-Dimensional Characterization of Fatigue Crack Propagation Behavior in an Aluminum Alloy Using High Resolution X-Ray Microtomography

Materials Science Forum ◽

10.4028/www.scientific.net/msf.638-642.378 ◽

2010 ◽

Vol 638-642 ◽

pp. 378-383 ◽

Cited By ~ 3

Author(s):

Hui Zhang ◽

Peng Cheng Qu ◽

Yuuji Sakaguchi ◽

Hiroyuki Toda ◽

Masakazu Kobayashi ◽

...

Keyword(s):

Aluminum Alloy ◽

Fatigue Crack ◽

Crack Propagation ◽

Crack Growth ◽

Fatigue Crack Propagation ◽

Three Dimensional ◽

X Ray ◽

Fatigue Crack Propagation Behavior ◽

Propagation Behavior ◽

Crack Propagation Behavior

Synchrotron X-ray microtomography was used to investigate the three-dimensional fatigue crack propagation behavior of an aluminum alloy. Local crack growth rates along specimen thickness were calculated. Crack observation revealed that crack propagation was retarded in three regions where there exist overlapping crack segments. Crack growth retardation was found to occur in these crack overlapping regions due to stress shielding. Observation of crack propagation process indicated that one of the overlapping crack segments initiated from the twisted crack. Crack tip opening displacement was measured and it was found that crack opening was larger in single planar crack region than that in crack overlapping region.

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