Monday  |  Salon 9  |  10:00 AM–10:20 AM

#16001, Thermomechanical Behavior of Additively Manufactured Metals studied using Digital Image Correlation

Following the wide-spread development of polymer-based additive manufacturing (AM), Laser Powered Bed Fusion (L-PBF) techniques have evolved considerably in recent years for the fabrication of additively manufactured metals. Consequently, additively manufactured metals are increasingly being considered as structural components in a number of industries, including the aerospace and nuclear industries, often in applications involving combined mechanical and thermal loads over a wide range of time scales. Thus, there is a growing need to study the fracture and fatigue behavior of L-PBF AM metals when subjected to elevated temperatures.
In this work, L-PBF samples fabricated from nickel-based (Inconel 625) and titanium-based (Ti-6Al-4V) alloys are subjected to combined mechanical and thermal loading. Uniaxial tensile experiments are performed on different sample geometries to study cyclic material plasticity at the macroscale and the microscale. By applying appropriate speckle patterns at two length scales, we use multiscale stereo Digital Image Correlation (stereo-DIC) to measure the plastic strain fields developed. Following previous studies at room temperature the cyclic plasticity experiments are performed at high temperatures (up to 1,000°C) to investigate the materials’ thermomechanical fatigue behavior and to allow for comparison of the results and conclusions about the influence of temperature. Following isothermal cyclic plasticity experiments we then investigate fatigue life (through S/N curve measurements) and fatigue crack growth (through da/dN measurements) in these materials under combined thermal and mechanical loading. Special emphasis is placed on the interpretation of experimental in the presence of residual stresses caused by thermal processing history of AM components. Such residual stresses can affect damage nucleation and growth and consequently fatigue life. Of particular interest in the fatigue experiments is the influence of residual stresses on crack growth rates of the different AM metals at high temperatures.

Elisabeth Funck   University of Illinois at Urbana-Champaign
John Lambros   University of Illinois at Urbana-Champaign
Eann Patterson   University of Liverpool