Effects of Spiker® Needle Peening on Residual Stress and Fatigue Performance in Aerospace FOD-Safe Repairs

Needle peening is increasingly used in aerospace repair applications to improve fatigue performance through the introduction of beneficial compressive residual stresses. Needle peening can be used to peen critical components directly on the aircraft while ensuring no foreign object damage (FOD) to contaminate the structure. The technology incorporates real-time monitoring of individual needles, standoff distance control, interchangeable peening heads, and data recording for process traceability and reporting.

This paper presents the evaluation of the Spiker® needle peening tool and its effects on residual stress distribution and fatigue performance for representative aerospace materials.

Experimental data was generated through two distinct testing programs. The first program focused on fighter aircraft structural applications and was conducted using 7050-T7451 aluminum coupons. The second program focused on aero-engine applications using Ti-6Al-4V titanium and DA718 nickel-based superalloy coupons. Residual stress distributions were characterized using X-ray diffraction and, in a few cases using the hole drilling method. Fatigue testing included uniaxial spectrum fatigue loading for the aluminum specimens and cyclic bending fatigue for the titanium and Inconel specimens.

The results demonstrate the ability of needle peening to generate favorable compressive residual stresses and significantly improve fatigue performance across the three material types investigated.