Additive Manufacturing Fatigue and Fracture V: Processing-Structure-Property Investigations and Application to Qualification: Titanium and Steel
Sponsored by: TMS Structural Materials Division, TMS: Additive Manufacturing Committee, TMS: Mechanical Behavior of Materials Committee
Program Organizers: Nik Hrabe, National Institute of Standards and Technology; John Lewandowski, Case Western Reserve University; Nima Shamsaei, Auburn University; Mohsen Seifi, ASTM International/Case Western Reserve University; Steve Daniewicz, University of Alabama
Monday 2:00 PM
March 15, 2021
Room: RM 2
Location: TMS2021 Virtual
Session Chair: John Lewandowski, Case Western Reserve University
2:00 PM Invited
Strain Accumulation during Fatigue and Fracture of Additively Manufactured Ti6Al4V: Experiments and Simulations: Raymundo Muro-Barrios1; Raeann VanSickle1; Huck Beng Chew1; John Lambros1; 1University of Illinois
Additively manufactured (AM) Ti6Al4V alloys often exhibit void imperfections from their manufacturing process, adding to the background porosity typically responsible for failure in conventional metals, resulting in a two-scale porosity. Driven by the unique microstructure of the AM material these dual-scale voids begin to grow under loading in the vicinity of a crack, leading to eventual crack advance. Here, the accumulation of strains in the AM microstructure is experimentally studied using a combination of high-resolution digital image correlation, optical microscopy, and electron backscatter diffraction (EBSD). On the simulation side, a cracked elasto-plastic material seeded with void distributions representing the two void size scales observed experimentally is modelled using Gurson-type elements. A comparison with experiments is then made for the predicted vs. measured crack paths and strain fields. The numerical simulations, being 3D, also allow us to explore the interaction of the dual-scale voids in the sample interior.
2:30 PM
Effect of Defects on Stress State Dependent Fracture of Additively Manufactured Metals: Allison Beese1; 1Pennsylvania State University
Additive manufacturing of metals often produces components that contain internal pores. For eventual qualification and certification, the impact of these internal defects on the failure properties and eventual performance of the material must be understood. This presentation will detail a combined experimental-computational approach for identifying the impact of internal defects on the fracture behavior of additively manufactured metals. In particular, the fracture behavior was experimentally investigated under a range of stress states and with a range of internal pore sizes to determine how the stress state dependent ductility was impacted with increasing pore size. Fracture models used to capture and predict this behavior will be presented.
2:50 PM
Structure-property Relationships to Explain the Elasto-plastic Anisotropy of Additively Manufactured Metal Alloys: Hunter Macdonald1; Jishnu Battacharyya1; Md Shamsujjoha1; Sean Agnew1; 1University of Virginia
AM 316L stainless steel produced using manufacturer recommended laser powder bed fusion processing parameters is used as a medium to investigate the sources of mechanical anisotropy. Crystallographic orientation distribution (ODF or texture) measurements were made using both electron backscattered diffraction (EBSD) and X-ray diffraction (pole figures). The elastic properties are predicted using the measured ODF, estimates of the single crystal elastic constants, and homogenization theory. The results agree well with experiment elastic property assessments using ultrasonic pulse-echo velocity measurements and resonant ultrasound spectroscopy (RUS). Similarly, the plastic properties (yield, hardening rates, and thermal activation parameters) were assessed using tension, compression, and stress relaxation tests performed along various directions. The results of these tests and associated crystal plasticity modeling suggest that more than texture is required to explain the observed plastic anisotropy, and the role of residual stress is considered. The developed understanding paves the way to better prediction of failure.
3:10 PM Invited
Design of Fatigue Resistant Additive Manufactured Austenitic Stainless Steels: Jonathan Pegues1; Seungjong Lee2; Theron Rodgers1; David Siaz1; Shaun Whetten1; Andrew Kustas1; Michael Roach3; Nima Shamsaei2; 1Sandia National Laboratories; 2Auburn University; 3University of Mississippi Medical Center
The unpredictable fatigue behavior of additive manufactured (AM) materials has limited their widespread adoption for use in fatigue critical applications. To overcome this challenge, models capable of predicting microstructure and fatigue performance of AM materials under a variety of processing and loading conditions are necessary. This talk reviews some recent work in establishing the process-structure-property relationships of AM austenitic stainless steels as they relate to fatigue resistance. The deformation behavior and failure mechanisms associated with the surface and microstructural characteristics are considered to estimate fatigue performance under various loading conditions. In addition, a computational method to predict the microstructures resulting from different processing conditions is explored and compared with experimental observations. These results are discussed in the context of leveraging additive manufacturing to produce site specific microstructures/properties and improving confidence of AM parts in fatigue critical applications.SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525
3:40 PM
Progressive Amplitude Fatigue Performance of Additively Manufactured Stainless Steel Superalloy: Sanna Siddiqui1; Krystal Rivera1; Isha Ruiz-Candelario1; Ali Gordon2; 1Florida Polytechnic University; 2University of Central Florida
Advances in aerospace component manufacturing design are being achieved through the additive manufacturing (AM) technology. Variations in cyclic loads (i.e., variable amplitude fatigue) is a common phenomenon experienced by aerospace components during in-service use, hence the need for AM components to withstand fatigue failure under these conditions. This study has performed progressive strain amplitude fatigue tests at increasing strain ranges with the intent to capture the cyclic stress-strain curve, fatigue failure life, hardening/softening response, and fracture response of as-built direct metal laser sintered (DMLS) Stainless Steel GP1. Preliminary results indicate fatigue failure in specimens prior to reaching strain ranges where plasticity effects become more pronounced. Also evident is variation in cyclic softening/hardening response to stabilization at elastic versus plastic strain ranges. Scanning electron microscopy was used to identify the precursors for fatigue crack initiation and propagation under progressive amplitude fatigue loading.