Initiation and Growth of Fatigue Cracks in and Residual Strength of the F-100 Wing

2009 ◽  
pp. 144-144-20 ◽  
Author(s):  
WD Graziano ◽  
GE Fitch
Keyword(s):  
Residual Strength ◽  
Fatigue Cracks

Modified Swift Criteria for Residual Strength of Multiple Site Damage Structure

2009 ◽  
Vol 417-418 ◽  
pp. 881-884 ◽  
Author(s):  
Jian Yu Zhang ◽  
Rui Bao ◽  
Bin Jun Fei
Keyword(s):  
Residual Strength ◽  
Yield Criterion ◽  
Fatigue Cracks ◽  
Tensile Load ◽  
Maximum Load ◽  
Alloy Sheet ◽  
Multiple Cracks ◽  
Multiple Site ◽  
Multiple Site Damage ◽  
Aluminum Panels

As more aircrafts reach or exceed their design life, it is becoming very important to research multiple cracks damage, especially the multiple site damage (MSD) in order to re-evaluate their service life and damage tolerance/durability performance. The existing of MSD may remarkably reduce the residual strength of an aerospace structural component than those with a singe lead crack. This study investigated the residual strength of aluminum alloy sheet with MSD through three types of aluminum specimens test. Aluminum panels with bare collinear constant diameter holes were chosen as specimens. After some constant amplitude tension-tension load cycles, the MSD were found in these specimens since there were multiple fatigue cracks emanating from the saw cuts of holes. The residual strength was recorded as the maximum load when every specimen was subjected to monotonically increasing tensile load until failure occurred. In different failure prediction criteria that were often used in engineering in order to evaluate the accuracy of these criteria, Swift criterion (ligament yield) criterion got more accurate prediction results than other criteria. Although Swift criterion was more accurate than some other criteria, its error was still big for some specimens. Two modified approaches were proposed in order to get more accurate and appropriate failure criterion for MSD structure.

Residual Strength Research for Aluminum Alloy Sheet with Multiple Site Damage

2007 ◽  
Vol 348-349 ◽  
pp. 489-492
Author(s):  
Jian Yu Zhang ◽  
Chuan Sheng Wang ◽  
Rui Bao ◽  
Bin Jun Fei
Keyword(s):  
Aluminum Alloy ◽  
Residual Strength ◽  
Yield Criterion ◽  
Fatigue Cracks ◽  
Alloy Sheet ◽  
Average Stress ◽  
Multiple Site ◽  
Aluminum Alloy Sheet ◽  
Stress Criterion ◽  
Multiple Site Damage

This study investigated the residual strength of aluminum alloy sheet with multiple site damage (MSD) through three types of aluminum specimens test. Aluminum panels with bare collinear constant diameter holes were chosen as specimens. And there were saw cuts at both edges of all the holes. After some constant amplitude tension-tension load cycles, the MSD were found in these specimens since there were multiple fatigue cracks emanating from the saw cuts of holes. The residual strength was recorded as the maximum load when every specimen was subjected to monotonically increasing tensile load until failure occurred. The test results were compared with predicted residual strength results by five different failure prediction criteria that were often used in engineering in order to evaluate the accuracy of these criteria. The failure criteria included: fracture criterion, net ligament loss criterion, ligament yield criterion, CTOA/CTOD criterion and average stress criterion. Ligament yield criterion (Swift criterion) and average stress criterion got more accurate prediction results than other criteria.

Formation of Persistent Slip Band in Fatigued Copper Single Crystals

1982 ◽  
Vol 40 ◽  
pp. 470-471
Author(s):  
N. Y. Jin
Keyword(s):  
Volume Fraction ◽  
Fatigue Cracks ◽  
Wall Structure ◽  
Matrix Structure ◽  
Dislocation Dipole ◽  
Slip Bands ◽  
Persistent Slip Bands ◽  
The Matrix ◽  
Hard Shell ◽  
Copper Single Crystals

Localised plastic deformation in Persistent Slip Bands(PSBs) is a characteristic feature of fatigue in many materials. The dislocation structure in the PSBs contains regularly spaced dislocation dipole walls occupying a volume fraction of around 10%. The remainder of the specimen, the inactive "matrix", contains dislocation veins at a volume fraction of 50% or more. Walls and veins are both separated by regions in which the dislocation density is lower by some orders of magnitude. Since the PSBs offer favorable sites for the initiation of fatigue cracks, the formation of the PSB wall structure is of great interest. Winter has proposed that PSBs form as the result of a transformation of the matrix structure to a regular wall structure, and that the instability occurs among the broad dipoles near the center of a vein rather than in the hard shell surounding the vein as argued by Kulmann-Wilsdorf.

The Effect of Secondary Metalworking Processes on Susceptibility of Aircraft to Catastrophic Failures and Prevention Methods

2013 ◽  
Vol 58 (4) ◽  
pp. 1207-1212
Author(s):  
E.S. Dzidowski
Keyword(s):  
Dynamic Recovery ◽  
Fatigue Cracks ◽  
Shear Bands ◽  
Adiabatic Shear ◽  
Deformation Mechanisms ◽  
Processing Maps ◽  
Adiabatic Shear Bands ◽  
Flow Localization ◽  
Catastrophic Failures ◽  
Prevention Methods

Abstract The causes of plane crashes, stemming from the subcritical growth of fatigue cracks, are examined. It is found that the crashes occurred mainly because of the negligence of the defects arising in the course of secondary metalworking processes. It is shown that it is possible to prevent such damage, i.e. voids, wedge cracks, grain boundary cracks, adiabatic shear bands and flow localization, through the use of processing maps indicating the ranges in which the above defects arise and the ranges in which safe deformation mechanisms, such as deformation in dynamic recrystallization conditions, superplasticity, globularization and dynamic recovery, occur. Thanks to the use of such maps the processes can be optimized by selecting proper deformation rates and forming temperatures.

Sign in / Sign up

Export Citation Format

Share Document