Session: IMECE Undergraduate Research and Design Exposition

Paper Number: 121210

121210 - Tensile and Fatigue Behavior of Additively Manufactured Ti-6al-4v Alloy 

Laser powder bed fusion processed Ti-6Al-4V is investigated to continue improving the aerospace industry. To mechanically characterize Ti-6Al-4V, tensile and fatigue tests were performed in ANSYS Workbench 2022 R2 using two dog bone models created in SolidWorks 2022. One dog bone is a custom, small-scale specimen proportional to the flat dog bone standard while the other is an ASTM E8M round specimen. Mesh was generated to adequately characterize the deformation of the specimens for the computer simulations. The boundary conditions applied to the specimens include a fixed support on the grip's face perpendicular to the plane consisting of the specimen's length and a tensile force on the opposing perpendicular grip face. All tests were performed using structural analysis at room temperature. Firstly, the tensile tests were simulated to show the von-Mises stress, total deformation, and total strain for each specimen. The results of the tests were applied to Microsoft Excel to create stress-strain curves for each specimen. The provided stress-strain graphs made in Excel from the ANSYS data characterize the ductility, strength, elastic recovery, and yielding behavior of the titanium alloy. The average yield strength was found to be 1128 MPa, and the Young’s Modulus was calculated to be 107 GPa. Both are valid because they correspond well with researched data on the topic. It was found that deformation increases along the specimens' length from the fixed support to the applied force. No deformation occurs at the fixed end, and highest deformation was at the end with the applied force. Stress and strain are both lowest on the grips specifically at the corners opposing the boundary conditions for each specimen. Stress and strain are highest at the fillets of each specimen and fluctuate nearly the same throughout the specimens. The second part of the project characterizes the fatigue mechanics of the material. Computer simulated tests were performed to find biaxial indication, fatigue life, fatigue factor of safety, and fatigue sensitivity. An S-N curve was created to present the behavior of Ti-6Al-4V under alternating stress. This data was inputted into the engineering database on ANSYS Workbench 2022 R2. For both specimens, the fatigue tests were run at a constant amplitude load ratio of 0.1 and the Goodman theory was chosen for the mean stress theory. The safety factor tests indicate that the gauge center, specifically near the fillets, will fail before the design life is reached. Biaxial indication shows that all specimens have mostly uniaxial stress. The fatigue life tests support the preliminary research that the grips would sustain infinite life, and the gauge center near the fillets would fail first. Fatigue sensitivity tests present that as the load history increases, the available life cycles decrease. The ANSYS Workbench program allows for sufficient mechanical characterization of Ti-6Al-4V while still being cost effective. It is well known that Ti-6Al-4V is versatile with very useful mechanical properties. As additive manufacturing is becoming an integral part of aerospace technology, Ti-6Al-4V is a prime candidate for research because it is compatible with laser power bed fusion which can make complex, customized, thin, and light-weight parts. The future of this project is to perform a mesh sensitivity test and to compare mesh shapes to get more accurate results. Further considerations to be analyzed with Ti-6Al-4V are print orientation of the parts, defects that can occur while printing, and the correlation between the complexity of geometry on the properties of the part. 

Presenting Author: Ciara Morse The University of New Orleans

Presenting Author Biography: Ciara Morse is an undergraduate student in mechanical engineering in her senior year enrolled at The University of New Orleans with a 3.6 GPA. Ciara has been the chair of ASME-UNO for three semesters and plans on graduating with a total of two and a half years dedicated to leading the club. She has been to one of the Student Leadership Weekends for the young leaders of ASME’s student chapters and has even raised one-thousand dollars for one of ASME-UNO's events. Aside from leading the student chapter, Ciara has had two year-long research projects. One was funded by the National Science Foundation while the other was funded by LaSPACE. Her research has been the mechanical characterization, via tensile and fatigue tests, of different materials used in additive manufacturing. In her free time, she volunteers annually at the Special Olympics and works for her father that is an independent contractor.

Authors:

Ciara Morse The University of New Orleans
Uttam Chakravarty The University of New Orleans