Regression Study on Variables Affecting Vibration Fatigue Behavior of Additive Manufactured Titanium 6Al-4V

Abstract

This discovery type experiment was intended to inspect the vibration fatigue behavior of Laser Powder Bed Fusion (LPBF) Titanium (Ti) 6Al-4V hybrid bending specimens as a function of four parameters: stress amplitude; build type; geometric variation; and surface roughness. These specimens were additively manufactured (AM) with relatively limited disclosure of process parameters but underwent post-fusion treatments of solution heat treatment (SHT), aging, and hot isostatic pressing (HIP), all critical processes to ensure granular uniformity and consistent material strength. Also, specimens were built three distinct ways to assess the effect of build orientation and size. The aerospace industry’s interest in using AM parts to improve performance of small scale gas turbine engines was the motivation of this study. Based on the test results in this investigation, the assumption that the material properties of LPBF parts are the same as conventionally made components presents the risk of unacceptably unpredictable fracture behavior, which can quickly lead to disastrous events in turbine engines. The experiment was intended to improve understanding of the effects of stress amplitude; build type; geometric variation; and surface roughness on vibration fatigue to better predict behavior.