Abstract
Following foreign object damage (FOD), a decision to repair components using novel additive manufacturing (AM) technologies has good potential to enable cost‐effective and efficient solutions for aircraft gas turbine engine maintenance. To implement any new technology in the gas turbine remanufacturing world, the performance of the repair must be developed and understood through careful consideration of the impact of service life‐limiting factors on the structural integrity of the component. In modern gas turbine engines, high cycle fatigue (HCF) is one of the greatest causes of component failure. However, conventional uniaxial fatigue data is inadequate in representing the predominant HCF failure mode of gas turbine components that is caused by vibration. In this study, the vibratory fatigue behavior of Ti6Al4V deposited using wire‐fed electron beam additive manufacturing (EBAM) was examined with the motivation of developing an advanced repair solution for fatigue critical cold‐section parts, such as blades and vanes, in gas turbine engine applications. High cycle fatigue data, generated using a combination of step‐testing procedure and vibration (resonance) fatigue testing, was analyzed through Dixon–Mood statistics to calculate the endurance limits and standard deviations of the EBAM and wrought Ti6Al4V materials. Also plots of stress (S) against the number of cycles to failure (N) were obtained for both materials. The average fatigue endurance limit of the EBAM Ti6Al4V was determined to be greater than the wrought counterpart. But the lower limit (95% reliability) of 426 MPa for the EBAM Ti6Al4V was lower than the value of 497 MPa determined for wrought Ti6Al4V and was attributed to the slightly higher data scatter–as reflected by the higher standard deviation–of the former material.
Highlights
In airfoil design for aeroengine gas turbines, soft- and hardbody impact is one of the greatest concerns for flight safety, especially during the takeoff and landing stages
The aviation industry has developed maintenance protocols to inspect, maintain, and refurbish/ replace blades having foreign object damage (FOD). e refurbishing scheme depends on the severity of impact and can involve only blade blending for minor damage to complex repairs, using welding and machining operations, for moderate to severe damage [4]
To consider advanced repair with additive design for structural parts subjected to high frequency vibrations, such as the rotating gas turbine engine blades, conventional uniaxial fatigue data at a R > 0 are inadequate in representing high cycle fatigue (HCF) failures caused by blade resonance conditions [11, 12]
Summary
In modern gas turbine engines, high cycle fatigue (HCF) is one of the greatest causes of component failure. Conventional uniaxial fatigue data is inadequate in representing the predominant HCF failure mode of gas turbine components that is caused by vibration. The vibratory fatigue behavior of Ti6Al4V deposited using wire-fed electron beam additive manufacturing (EBAM) was examined with the motivation of developing an advanced repair solution for fatigue critical cold-section parts, such as blades and vanes, in gas turbine engine applications. High cycle fatigue data, generated using a combination of step-testing procedure and vibration (resonance) fatigue testing, was analyzed through Dixon–Mood statistics to calculate the endurance limits and standard deviations of the EBAM and wrought Ti6Al4V materials.
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