Session: 04-08-01: Dynamics and Control of Aerospace Structures

Paper Number: 72043

Start Time: Monday, 06:20 PM

72043 - Tensile and Fatigue Response of the Laser Powder-Bed Fused Ti-6al-4v Alloy at High Temperature Conditions 

As an effective and flexible Additive manufacturing (AM) process, laser powder-bed fusion (L-PBF) can fabricate ultra-light-weight yet high-energy-density solid state parts vastly suitable for aerospace, automotive, electro-mechanical, and biomedical applications. The widespread industrial applications of L-PBF process demand for an extensive investigation on the tailored properties of the high-strength alloys, because the scanning strategy, powder metallurgy, remelting, and heat dissipation of the L-PBF process have significant effects on the microstructure, strength, hardness, endurance, and fatigue life of the alloy. While producing components by the L-PBF process, a comprehensive understanding of the material and mechanical behavior is required to optimize the process parameters effectively and predict the reliability of the finished parts. A robust study on the tensile and fatigue behavior of the L-PBF processed part ranging from room temperature to high temperature can facilitate the characterization and application of this material at extreme thermal conditions. Therefore, the purpose of this study is to investigate the thermal and mechanical properties of L-PBF processed specimens at room and elevated temperatures while varying the loading conditions. The study covers finite element (FE) modeling of the tensile and fatigue behavior of the L-PBF processed Ti-6Al-4V specimens and corresponding experimental validation at room and high temperatures. The L-PBF processed specimen used for the study is a heat-treated and post-machined dog-bone structure similar to the standard ASTM sub-size flat specimen. The FE modeling for the fatigue analyses is conducted for a load ratio of R = 0.1 and by applying fully-reversed and zero-based cyclic loads at different frequencies. The high-temperature test condition is obtained by adjusting the convective heat transfer coefficient of air surrounding the specimen. Results for the von Mises stress, strain, total deformation, fatigue life, the factor of safety, and fatigue limit are obtained from the FE model at room and elevated temperatures. The numerical results show that the fatigue life decreases as the load increases. It is also found that the strength and fatigue life decrease as the temperature increases due to the development of thermal stress. The performance of the L-PBF processed specimens is also compared to the conventionally manufactured Ti-6Al-4V parts under the same magnitude of load and temperature to outline the differences in strength and fatigue resistance properties. The validation of the FE model is performed by comparing the numerical results with the experimental results under the similar operating conditions. Results for tensile strength, elongation, thermal stress, and fatigue life of the Ti-6Al-4V build-part obtained at different temperatures provide a detailed understanding of the thermal, metallurgical, and mechanical properties of this alloy. The overall study also provides a guide to investigate high-temperature mechanical properties of other functional materials used in the L-PBF process.

Presenting Author: M. Shafiqur Rahman University of New Orleans

Authors:

M. Shafiqur Rahman University of New Orleans
Mohammad Khairul Habib Pulok University of New Orleans
Uttam K. Chakravarty University of New Orleans