07/28/17: Wanting & Carmine gave oral presentations at SES2017

 Track III: Impact and High Strain Rate Deformation
Symposium III-A: Particle Impact Based Manufacturing Processes

Temperature-dependent Laser-induced Projectile Impact Test of Aluminum 6061 Microspheres for Cold Spray Additive Manufacturing

C. Taglienti* | W. Xie | V. K. Champagne | A. Nardi | S. Müftü | J-H. Lee

Abstract: Cold spray is a unique additive manufacturing process, where a large number of ductile metal microparticles are deposited to create new surface coatings or free-standing structures. The metallic particles are accelerated through a gas stream, reaching velocities of over 1 km/s. At the range of velocities, the particles experience high-strain-rate microscopic ballistic collisions to a target substrate, resulting in extreme plastic deformation of the particles. Though this cold spray technique has been in use for decades, the extreme material science behind the deformation of the particles has not been well understood due to the experimental difficulties arising from the spatial (~ µm) and temporal scales (~10 ns) of the extreme events.In this study, using a recently developed method, the advanced laser induced projectile impact test (α-LIPIT), the dynamic behavior of the microparticles during the collision can be precisely observed. We observed single aluminum 6061 particles, approximately 20 μm in diameter, impact and rebound off of the rigid target surface at a range of impact speeds and several different temperatures from a room temperature to 300°C. As we employ a sapphire target surface with sufficient rigidity over the ductile microparticles, all plastic deformation takes place within the impacting particle. From observation of the collision, we extract characteristics information on the dynamic response of the particles and the relationship the response has with various parameters (e.g. surrounding temperature, particle diameter, and impact velocity). By providing highly-controlled single particle impacts results, we will be able to calibrate and improve computational simulations. This, in turn, can provide insight into the underlying material science behind the cold spray process.


Track III: Impact and High Strain Rate Deformation
Symposium III-B: Dynamic Mechanical Behaviors of Materials

Anti-ballistic Performance of Carbon Nanotube Fibers in Comparison with Kevlar KM2 and Nylon Fiber Filaments

W. Xie* | R. Headrick | L. Taylor | M. Pasquali | J-H. Lee

Abstract: Lightweight and flexible body armor is generally based on ballistic fabrics, made from high-strength filament fibers like Kevlar. A variety of numerical models have been developed to predict the ballistic performance of the fabrics, in which mechanical properties of a single fiber and a single filament at high strain rates is crucial. However, experimental studies of single filaments were mostly within the quasi-static regime, while only a few investigated filaments’ high-strain-rate response by ballistic impacts with millimeter-size projectiles. Thus, real-time energy dissipation of the projectiles originating from the mechanical interaction with a single fiber was unknown, due to the extremely large mass of the projectiles compared to the single filaments.Advanced laser induced projectile test (a-LIPIT) system was introduced to perform a transverse impact of a single micro-projectile on a fiber. One single fiber (~10 mm in dia.) was suspended in air with a fiber holder. As a micro-projectile, a single glass sphere (~ 30 mm in dia.) was accelerated to approximately 500 m/s using high-power laser ablation. Light pulses, generated by a femtosecond oscillator were used to take ultra-high-speed optical images (maximum 40 million frames per second). Using the optical images, accurate kinetic information of the impacting micro-projectiles and the responding fiber was recorded.