Effect of Internal Defects on the Fatigue Behavior of Additive Manufactured Metal Components: A Comparison between...

Area of Science:

• Materials Science
• Mechanical Engineering
• Aerospace Engineering

Background:

• Widespread application of Additive Manufacturing (AM) in the aircraft industry necessitates detailed Fatigue and Damage Tolerance (F&DT) characterization for critical components.
• Metal AM processes, like Laser Powder Bed Fusion (LPBF), inherently introduce internal defects that significantly degrade fatigue properties.

Purpose of the Study:

• To characterize the F&DT behavior of Ti6Al4V and Inconel 718 produced by LPBF, focusing on the impact of artificial defects.
• To develop a simplified stress-life-defect size model based on fracture mechanics to predict critical defect sizes.
• To validate the model using experimental fatigue test results and fracture surface analysis.

Main Methods:

• Production of Ti6Al4V and Inconel 718 coupons with controlled, artificial defects using Laser Powder Bed Fusion (LPBF).
• Conducting fatigue tests to assess the F&DT behavior of the manufactured coupons.
• Fracture mechanics analysis and fracture surface examination to understand defect influence and validate a predictive model.

Main Results:

• Observed differing defect sensitivity between Ti6Al4V and Inconel 718, with Inconel exhibiting greater defect tolerance.
• Devised a simplified stress-life-defect size model validated by experimental data and fracture analysis.
• The model's predictions align with experimental fatigue test results, confirming its utility.

Conclusions:

• Inconel 718 demonstrates superior defect tolerance compared to Ti6Al4V in LPBF-processed components.
• The developed fracture mechanics-based model provides a method for predicting critical defect sizes.
• The proposed approach can inform tailored Non-Destructive Testing (NDT) strategies for AM aerospace components.