Metal Fatigue Failures in Aerospace

Metal component fatigue failures continue to account for a number of in-service disruptions in aerospace and ground transportation, as seen on the runway in Las Vegas this month.  Disruptions typically cause emergency situations requiring immediate action which lead to delays or serious conditions for flight crew and passengers, something fatal.  Many failures are preventable with proper inspection methods but not all.  In fact, inspection and maintenance time could be significantly reduced with the addition of surface fatigue enhancements such as laser peening (LSP) for deep surface improvements.  Fatigue failures take place in engines as well as in structural or fuselage components.  Fan blades and fan discs are susceptible to high cycle fatigue, fretting fatigue, or foreign object damage, or galling, which all lead to failure mechanisms such as cracks and resulting crack propagation.  Aerospace jet engine blades and fan discs experience significant forces which mechanical design and redesign often fail to permanently address.
Laser peening is specifically capable of preventing the occurrence of these failures, most of which are associated with the introduction and propagation of cracks.  The deep compressive residual stresses imparted by laser peening, significantly reduce or eliminate crack introduction or propagation.  Why?  Fatigue life and fatigue strength improvements are proportional to the magnitude and depth of the induced compressive residual stresses remaining in a component; laser peening imparts compressive residual stresses up to 8 mm deep (10-20 times deeper than conventional shot peening), thereby imparting significant increases in component service lifetime.
Click here to see the National Transportation Safety Board Aviation Accident Reports for more information on fatigue failures.