Effects of Shot-Peening and Stress Ratio on the Fatigue Crack Propagation of AL 7475-T7351 Specimens

• Published in: Applied sciences 2018-03, Vol.8 (3), p.375
• Main Authors: Ferreira, Natália, Antunes, Pedro, Ferreira, José, D. M. Costa, José, Capela, Carlos
• Format: Article
• Language: English
• Subjects: aeronautical aluminum alloys; Aerospace engineering; Aerospace materials; Aircraft; Alloys; Aluminum alloys; Compressive properties; Corrosion resistance; Crack closure; Crack initiation; Crack propagation; Damage assessment; Damage tolerance; Design engineering; fatigue crack propagation; Fatigue cracks; Fracture mechanics; Free surfaces; Growth rate; Lasers; Load; Mechanical engineering; Metal fatigue; overloads; Paris law; Propagation; Residual stress; shot peening; Strain hardening; Stress concentration; Stress distribution; Stress propagation; Stress ratio; Tensile stress; Test methods; Thickness; Yield stress
• ISSN: 2076-3417; 2076-3417
• DOI: 10.3390/app8030375

The approach to engineering design based on the assumption that flaws can exist in any structure and cracks propagate in service, is commonly used in aerospace engineering. [...]the prediction of crack growth rates based on the application of fracture mechanics theory is an important aspect of a structural damage tolerant assessment. According to the material manufacturer, the ultimate tensile stress and yield stress are σUTS = 490 MPa and σYS = 414 MPa, respectively. In the present study, specimens were machined from the same thickness bars, so there is no microstructure change between 4 and 8 mm thickness specimens. [...]the effect of thickness is only caused by changes in stress distribution along cross section and consequent variation on crack closure level [31]. According to the diffraction peak breadth profiles, the thickness layer affected by all surface treatments is circa 200 µm. The average value of the compressive residual stresses occurring trough a layer below the free surface with a 150 µm depth is about 200 MPa.