Characteristics of fatigue-crack resistance of aluminum alloys in combined modes of failure under biaxial loading

1994 ◽  
Vol 26 (3) ◽  
pp. 187-193 ◽  
Author(s):  
V. N. Shlyannikov
Keyword(s):  
Fatigue Crack ◽  
Aluminum Alloys ◽  
Crack Resistance ◽  
Biaxial Loading ◽  
Modes Of Failure

A Simple Algorithm to Eliminate Ambiguities in EBSD Orientation Map Visualization and Analyses: Application to Fatigue Crack-Tips/Wakes in Aluminum Alloys

2010 ◽  
Vol 16 (6) ◽  
pp. 831-841 ◽  
Author(s):  
Vipul K. Gupta ◽  
Sean R. Agnew
Keyword(s):  
Fatigue Crack ◽  
Aluminum Alloys ◽  
Direct Determination ◽  
Simple Algorithm ◽  
Electron Backscattered Diffraction ◽  
Lattice Curvature ◽  
Orientation Data ◽  
Orientation Map ◽  
Crack Tips ◽  
Map Visualization

AbstractA simple algorithm is developed and implemented to eliminate ambiguities, in both statistical analyses of orientation data (e.g., orientation averaging) and electron backscattered diffraction (EBSD) orientation map visualization, caused by symmetrically equivalent orientations and the wrap-around or umklapp effect. Using crystal symmetry operators and the lowest Euclidian-distance criterion, the orientation of each pixel within a grain is redefined. An advantage of this approach is demonstrated for direct determination of the representative orientation of a grain within an EBSD map by mean, median, or quaternion-based averaging methods that can be further used within analyses or visualization of misorientation or geometrically necessary dislocation (GND) density. If one also considers the lattice curvature tensor, five components of the dislocation density tensor—corresponding to a part of the GND content—may be inferred. The methodology developed is illustrated using EBSD orientation data obtained from the fatigue crack-tips/wakes in aerospace aluminum alloys 2024-T351 and 7050-T7451.

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

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.

scholarly journals Small Fatigue Crack Growth Mechanisms and Interfacial Stability in Cold-Spray 6061 Aluminum Alloys and Coatings

2018 ◽  
Vol 49 (12) ◽  
pp. 6509-6520 ◽  
Author(s):  
Anastasios G. Gavras ◽  
Diana A. Lados ◽  
Victor K. Champagne ◽  
Robert J. Warren ◽  
Dileep Singh
Keyword(s):  
Fatigue Crack ◽  
Aluminum Alloys ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Cold Spray ◽  
Interfacial Stability ◽  
Growth Mechanisms ◽  
Small Fatigue Crack

The Influence of Biaxial Mean Stresses on the Failure of Tubes by Fatigue

1961 ◽  
Vol 12 (1) ◽  
pp. 1-33 ◽  
Author(s):  
H. L. Cox ◽  
N. B. Owen
Keyword(s):  
Fatigue Crack ◽  
Mild Steel ◽  
Test Piece ◽  
Fatigue Cracks ◽  
Small Diameter ◽  
Axial Direction ◽  
Gas Pressure ◽  
Modes Of Failure ◽  
Explosive Failure ◽  
Bending Stresses

SummaryThin-walled tubes, in. in diameter, of three hard aluminium alloys and of mild steel have been tested in fatigue under three systems of alternating stresses while subjected to biaxial mean tensions imposed by means of internal pressure. In fatigue under direct or bending stresses the hoop tension in the walls of the aluminium alloy tubes did not seriously reduce the fatigue endurance, but it did markedly affect the mode and rate of crack propagation; cracks initially transverse to the tube axis tended to develop very rapidly in the axial direction. This tendency was present under both fluid and gas pressure, and under gas pressure the cracks propagated so fast that the test piece was often blown to pieces before the gas pressure fell by leakage through the cracks. The gradual taper in wall thickness along the fillets joining the test section to the enlarged ends offered no barrier to propagation of the axial cracks and the whole test piece, including its enlarged ends, was often shattered. Propagation of the axial cracks was preventible by sufficiently reducing the fillet radius, or by a ring glued on. Under alternating torsion, both endurance and mode of failure were affected by internal gas pressure. The initial fatigue crack, either circumferential or axial, often extended over a length comparable with the diameter of the tube, except under low ranges of shear stress when the crack length was sometimes very short. At each end the cracks forked in a characteristic manner and under moderate gas pressure the portions of tHe wall between the prongs of the fork were blown outwards. Under high pressure explosive failure and fragmentation often occurred. Mild steel under alternating torsion with internal gas pressure exhibited the same modes of failure, and two or more fatigue cracks were often formed simultaneously. Under high hoop tension, cracks propagated rapidly and one test piece, after two million cycles endurance, failed by exploding. However, no mild steel test piece was fragmented. A tentative explanation is offered of the reason why, in tubes of small diameter, rather short fatigue cracks may be expected to lead to fast fracture under the static loading. Attention is drawn to the inference that the initial fatigue crack itself must develop very quickly to considerable length.

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