Session: 18-07: Failure Prediction and Life Asssessment II

Submission Number: 179185

Validating Residual Stress Effects on Laser Wire DED Fatigue Data With the Walker Model 

Laser Wire Directed Energy Deposition (DED) is an additive manufacturing (AM) process that benefits the critical aerospace and defense industry due to the process having high material deposition, reduced material waste, and negligible outgassing toxicity. Due to the high demand for sustainability in important defense systems, laser wire DED has been sought after as a viable repair option. Despite the benefits and the demand for laser wire DED, the AM process still has challenges that need to be overcome. A significant challenge is residual stress from high temperature gradients during the build. This challenge has recently been addressed with a unique air-cooling grinding process, which eliminates high residual stresses by hundreds of MPa. Using the hole drill method as a measuring tool, both the air cooling and the normal flooding cooling processes for grinding result in parts with lower residual stress for stainless steel 316L than the untreated counterpart. These findings on residual stress also support fatigue results, where both the air and flood cooling processes produced specimens with longer life at the same stress amplitude. To further verify the results of the residual stress measurements, the Walker Equation mean stress model was used to calculate an equivalent stress amplitude for fatigue life. Furthermore, this work presents a viable demonstration for approximating residual stress using Walker’s Equation. The comparisons in this work validate the presence and accuracy of residual stress while showing promise for future assessment of residual stress from fatigue data variation.

Presenting Author: Onome Scott-Emuakpor Hyphen Innovations

Presenting Author Biography: Dr. Scott-Emuakpor is the Founder and CEO of Hyphen Innovations, a spin out company from an Air Force Program. Dr. Scott-Emuakpor has +20 years of R&D experience focused on material testing, design improvement, vibration mitigation, and additive manufacturing of aerospace parts.

Authors:

Harshith Vadrevu Hyphen Innovations
Onome Scott-Emuakpor Hyphen Innovations
Philip Johnson Hyphen Innovations
Troy Krizak Hyphen Innovations
Manigandan Kannan Hyphen Innovations