Dynamic Behavior of Materials IX: Dynamic Loading of Additive Manufactured Materials
Sponsored by: TMS Structural Materials Division, TMS: Mechanical Behavior of Materials Committee
Program Organizers: Eric Brown, Los Alamos National Laboratory; Saryu Fensin, Los Alamos National Laboratory; George Gray, Los Alamos National Laboratory; Marc Meyers, University of California, San Diego; Neil Bourne, University of Manchester; Avinash Dongare, University of Connecticut; Benjamin Morrow, Los Alamos National Laboratory; Cyril Williams, US Army Research Laboratory
Monday 8:30 AM
February 28, 2022
Room: 304D
Location: Anaheim Convention Center
Session Chair: Eric Brown, Los Alamos National Laboratory; Arezoo Zare, Washington State University; Mukul Kumar, Lawrence Livermore National Laboratory
8:30 AM
Triaxiality-dependence of Dynamic Failure in Additively Manufactured Steel: Jack Borg1; Bernard Gaskey2; Parth Garud3; Peter Sable4; 1Marquette University; 2University of Dayton Research Institute; 3Georgia Institute of Technology; 4Air Force Research Laboratory
Significant progress has been made characterizing the low-rate uniaxial mechanical properties of additively manufactured metals, but much less literature exists on the dynamic properties in more complex stress states. Here, we focus on 17-4PH stainless steel, comparing tension and coupled tension-shear of as-printed additively manufactured material to a wrought and machined baseline. We use a progression of split-Hopkinson pressure bar, Taylor anvil, and high velocity plate impact to characterize the failure of the material in dynamic loading conditions across several orders of magnitude of strain rates, and to compare the progression of failure properties under differing triaxiality states. Cohesively paired simulations for each experiment were conducted using Johnson-Cook constitutive models in ANSYS and CTH for the dynamic-high rate and high velocity impact experiments respectively. Results facilitate parameterization and validation of material models necessary for engineering design of additively manufactured structural parts for complex dynamic loads. APPROVED FOR PUBLIC RELEASE. #AFRL-2021-2219
8:50 AM
Additive Manufacturing and Intermediate-rate Mechanical Response of High Performance Steel: Bernard Gaskey1; Nick Hopkins2; Richard Harris3; Philip Flater3; 1University of Dayton Research Institute; 2Integrated Solutions for Systems; 3Air Force Research Lab Munitions Directorate
Additive manufacturing (AM) promises to revolutionize engineering design by enabling geometries and structures that that were previously impossible to produce. However, much of the current literature on metal AM is concentrated on a select few alloys. Due to the dynamic thermal environment during printing, AM parts often require heat treatment to optimize their microstructure or mechanical performance. We address both of these current shortcomings by focusing on a high-performance, low alloy martensitic steel in the as-printed condition. We show that with optimized manufacturing process parameters, it is possible to print a microstructurally complex alloy with mechanical performance approaching wrought material without the traditional multistep heat treatment process. Split-Hopkinson pressure bar measurements show that the excellent as-printed properties are retained under dynamic loading conditions, making this type of 3D printed steel a candidate for many new structural applications with combined quasi-static and dynamic loads. APPROVED FOR PUBLIC RELEASE. #AFRL-2021-1951
9:10 AM
Design of Damage Resistance Materials Using Additive Manufacturing: Saryu Fensin1; David Jones1; George Gray1; Carl Trujillo1; Daniel Martinez1; Ankur Agrawal1; Dan Thoma1; 1Los Alamos National Laboratory
In this work, selective laser melting with varying laser power, laser speed, hatch spacing and layer thickness is used to manufacture more than 200 samples of 316 L stainless steel. Properties that can be rapidly measured such as density and hardness are used as initial parameters to rapidly down-select 9 samples out of the initial 200 samples. These 9 samples are then characterized and their mechanical response under uniaxial stress and strain conditions measured. Specifically, spall recovery experiments are performed on these 9 samples to determine if any relationships exist between the dynamic strength of the material and the processing parameters. Our work shows that there exists a critical laser power and hatch spacing that does indeed lead to optimum spall strength. The results from these dynamic experiments that open avenues for material design using AM will be discussed in this talk.
9:30 AM
Tailorable Shock and Fragmentation Behaviors of Additively Manufactured Interpenetrating Composites: Spencer Taylor1; Bernard Gaskey2; Zachary Cordero1; 1Massachusetts Institute of Technology; 2Air Force Research Lab
PrintCasting is a recently developed hybrid additive manufacturing process that can be used to form architectured composites, where constituents are patterned in a periodic array with a characteristic length scale on the order of several hundred microns. We can utilize this fine architectural control offered by PrintCasting to fabricate munitions casings with tailorable interpenetrating mesostructures, allowing precisely controlled shock dynamics and fragmentation behavior. In this study, we examine the effect of mesostructure on the dynamic behavior of PrintCast composites of steel and aluminum with interpenetrating BCC and TPMS mesostructures. Plate impact experiments reveal the relationship between composite geometry and bulk shock behavior. Fragmentation tests with high-rate imaging and pressure sensing are used to compare conventional monolithic and PrintCast munitions casings. These experiments together demonstrate the ability to tailor the dynamic behavior of composites through PrintCasting.
9:50 AM Break
10:05 AM
Evaluation of the Effectiveness of Additive Friction Stir Deposition for Ballistic Repair of Aluminum Alloy 7075: George Stubblefield1; Malcolm Williams1; Zack Tew1; Russell Rowe1; Craig Mason2; James Jordon1; Paul Allison1; Mark Barkey1; 1University of Alabama; 2Pacific Northwest National Laboratory
In this work, Additive Friction Stir Deposition (AFSD) was employed for ballistic repair of AA7075-T6511 plates. After ballistic penetration with 7.62x51 FMJ rounds, the AA7075-T6511 plates were repaired using AFSD with AA7075 as the filler material feedstock. The repaired plates were shot with the same 7.62x51 FMJ rounds, and the damage characteristics and initial vs residual velocities were compared against the original plates. AFSD successfully repaired the damaged original plates, without any obvious defects such as large cracks or pores. Although the surface looked pristine other than milling marks, the damage characteristics of the repaired plates were significantly different than the original plates. The increase of spalling and petalling with the repaired material can be attributed to the thermomechanical processing of AFSD, which would alter the original T6511 temper. Despite the damage discrepancy, the repaired plates performed similarly to the original plates with respect to initial vs residual velocity.
10:25 AM
Spall Failure of ECAE-processed Mg-6Al via Laser-driven Micro-flyer Impact Experiments: Christopher Dimarco1; Debjoy Mallick2; Chengyun Miao1; David Gibbins1; Jenna Krynicki1; Nathaniel Davenport1; Laszlo Kecskes1; Tim Weihs1; K.T. Ramesh1; 1Johns Hopkins University; 2US Army CCDC Army Research Laboratory
Magnesium alloys have been proven to achieve a high specific strength when processed via traditional strengthening mechanisms. This makes them prime candidates for protection-based applications. However, they suffer from low failure strains, which translates to poor dynamic performance. To the spall strength, recent dynamic impact experiments on rolled Mg-9Al examined the effects of a strong basal texture, large grains, and high aspect ratio lath precipitates on the spall strength. Herein, we examine a similar binary alloy system (Mg-6Al), but with a lower aluminum content and processed via Equal Channel Angular Extrusion (ECAE). The resulting microstructure consists of a reduced grain size, finer and more equiaxed precipitates, and a larger dislocation density. These experiments utilize laser-driven micro-flyer techniques that facilitates high-throughput capabilities (i.e. meaningful statistics). We show the results of the spall strength as a function of material strain rate and loading direction and compare them with Mg-9Al results.
10:45 AM
Deformation Mechanisms and Shock Loading Responses of a Tribology-grade NiTiHf Alloy: Tyler Knapp1; Aaron Stebner1; 1Georgia Institute of Technology
Small Hf additions to tribology-grade nickel-rich NiTi alloys improve processability of the alloys by reducing sensitivity to cooling rate after solid solution annealing and precipitate hardening heat treatments. Such alloys have shown improved denting resistance and rolling contact fatigue performances. Here, we report upon a first look at their dynamic compressive performances when subjected to impacts from projectiles moving at 150-600 m/s. Characterization of the microstructure before and after shock loading using a combination of scanning and transmission electron microscopy techniques reveals that samples subjected to the higher impact velocities had lower levels of cracking that correlated with dissolution of strengthening nanoprecipitates within plastic deformation bands, whereas samples subjected to lower impact velocities showed plastic deformation bands that contained the strengthening nanoprecipitates. This outcome indicates that precipitates will dissolve under sufficiently high loading, increasing Ni content and causing a superelastic response with a higher spall strength.
11:05 AM
Delamination Propagation in Laminate Carbon Fiber-epoxy Composites: Lilly Schroer1; Mohammad Hamza Kirmani1; 1Georgia Institute of Technology
Carbon fiber-epoxy laminate composites’ high strength, relatively low weight, and mechanical properties retention at high temperatures are advantageous for high performance applications – e.g., military and commercial aerospace structures. A composite’s strength is attributed to its transverse properties, interlaminar shear strength, and fracture toughness; however, a critical factor controlling strength under dynamic loading is the material’s tendency to delaminate. Bending, compression, and tensile loading can lead to interlaminar damage, i.e., delaminations, or the splitting apart of two fiber-rich laminate layers – reducing the composite’s bending stiffness. Delaminations are one of the most common failure modes in a laminate structure. Therefore, it is important to explore what initiates this phenomenon: structure, matrix cracking, interlaminar shear, temperature change, and interfacial adhesion between fiber and matrix. Further, the impact on the material’s mechanical properties and what toughening mechanisms can be employed to reduce this failure mode and create a stronger material.
11:25 AM
Mitigating Spall Fracture of Ductile Materials by Introducing Porosity: Edwin Chiu1; Ankit Srivastava1; 1TAMU Material Science Department
A material when subjected to shock/impact loading conditions can undergo spall fracture, when the compressive waves reflect off interfaces and free surfaces as tensile waves. Experiments have shown that in ductile materials, spall fracture is induced by the growth of pre-existing pores and/or nucleation and growth of new pores. However, porosity in ductile materials also introduces plastic compressibility that may lead to energy absorption and thus mitigate spall fracture. Following this, we investigate the role of initial porosity and nucleation of new pores on the spall fracture of porous ductile materials subjected to flyer plate impact loading conditions using finite element analysis. Our results show that porosity in ductile materials under certain circumstances can indeed mitigate spall fracture by attenuating stress waves. In this presentation we will focus on the results correlating impact velocity, initial porosity, and nucleation of new pores on the propensity of spall fracture of ductile materials.