Micro- and Nano-Mechanical Behavior of Materials: Poster Session
Program Organizers: Sundeep Mukherjee, University Of North Texas; Mahmoud Baniasadi, Georgia Southern University; Meysam Haghshenas, University of Toledo
Tuesday 10:00 AM
November 3, 2020
Room: Poster Hall
Location: MS&T Virtual
Atomistic Simulations of Collisions between SiC Nanoparticles: Kevin Kayang1; Alexey Volkov1; 1University of Alabama
Interaction of SiC nanoparticles in the head-to-head and oblique collisions is studied in atomistic simulations for various nanoparticle size, geometric collision parameter, and temperature. The simulations are performed for both crystalline and amorphous nanoparticles in a broad range of nanoparticle velocities, from those that result in adhesion of nanoparticles to those that induce partial melting or fragmentation of nanoparticles. The propagation of the shock waves and phase transformations in the nanoparticles induced by high-velocity impact are studied. The impact-induced deformation of nanoparticles is compared with the deformation observed during uniaxial quasi-static compression of the same nanoparticles. The center-of-mass velocities, angular velocities, and temperatures of individual particles are obtained as functions of time and are used to calculate values of normal and tangential accommodation coefficients of the nanoparticle relative velocity. The simulation results are used to obtain maps of collision outcome on the plane of relative velocity and geometric collision parameter.
Characterization of Fatigue Damage Behavior in Unidirectional Carbon Fiber Reinforced Plastic Laminates: Akihiro Kudou1; Satoshi Kobayashi1; Toshiko Osada1; 1Tokyo Metropolitan University
In this study, tensile fatigue tests with acoustic emission (AE) measurement were performed on unidirectional carbon fiber reinforced plastic (CFRP) laminates with and without a notch. The relationship between fatigue damage and associated AE behavior were characterized. The AE waves from splitting occurrence and progress were also identified by comparing the damage behavior with and without a notch. Splitting occurred along the fiber direction from the tip of a notch in a specimen with a notch and the AE behavior reflected the splitting behavior. We discussed the AE behavior based on the experimental results about splitting behavior and the relationship between the AE and the fatigue damage behaviors in unidirectional CFRP laminate was clarified. From this relationship, it is possible to predict the damage type, size and quantity by comprehensively evaluating the frequency characteristics and each parameter of AE waves.
Cyclo[18]carbon as an Ultra-flexible Material: Siyuan Fang1; Yun Hang Hu1; 1Michigan Technological University
Cyclo[18]carbon is the first sp-hybridized carbon material being successfully synthesized and imaged. This work employed DFT calculations to reveal the mechanical properties of cyclo[18]carbon, including stretching, expanding and contracting, and demonstrated that cyclo[18]carbon is an ultra-flexible material. Furthermore, the electrical conductivity can be tuned by mechanical deformation. These unique mechanical and electronic properties enable its potential applications in molecular devices.
Diffusion Induced Abnormal Softening Behaviors in Nanocrystals: Sixue Zheng1; Xiang Wang1; Scott Mao1; 1University of Pittsburgh
Due to the high surface-to-volume ratio of nanocrystals, surface-related deformation mechanisms govern plasticity resulting in the well-known “smaller is stronger” power-law scaling in nanocrystals. As the sample size of nanowires (NWs) further went down to sub-ten nanometer, strong surface diffusion activities took place and influenced the mechanical behaviors. Here, by performing in situ high-resolution transmission electron microscopy (HRTEM) tensile testing, we revealed an inverse Hall-Petch relation in Ag NWs, while Pt NWs showed a traditional “Hall-Petch” size-dependent behavior. This difference resulted from surface atomic diffusion activities in Ag NWs, which may lower the critical stress for surface dislocation nucleation. To reveal the effect of surface diffusional creep on plastic flow, the coupled displacive-diffusive plasticity in Ag NWs and the pure displacive plasticity in Pt NWs were quantitatively investigated by analyzing the lattice stress-applied strain evolution in nanowires.
Mechanical Behavior of Resilin-mimicking Materials: Annaliza Perez-Torres1; Fuqian Yang1; 1University of Kentucky
Natural resilin, an elastomeric protein found in many insects and arthropods, has gained attention due to its unique properties, such as large strain, high resilience, efficient energy storage and exceptional cyclic lifetime at a micro/nanoscale. Due to these outstanding properties, it is of great importance to produce man-made materials to mimic the properties of natural resilin for potential applications in biodevices and systems. In this work, we synthesize resilin-mimicking hydrogels from Polydimethylsiloxane (PDMS), Polyethylene glycol (PEG), and Polyacrylamide (PAAm) and study the contact deformation of the hydrogels. The contact modulus and energy dissipation during the contact deformation are characterized. We use finite element analysis to simulate the contact deformation of the hydrogels and compare numerical results with experimental data.
Mechanical Properties of Hybrid Core-shell Ceramic Nanoparticles: Kevin Kayang1; Alexey Volkov1; 1University of Alabama
Atomistic simulations of quasi-static and dynamic compression of hybrid nanoparticles (NPs) consisting of TiO2 and SiC cores and Al2O3 shells are performed to reveal the microscopic mechanisms of load transfer between cores and shells and fracture of such NPs. The individual NPs are considered as elements of porous films composed of a scaffold of NPs covered by coatings that are used to increase the mechanical integrity and durability of the NP films. These materials have the potential to transform engineering practice in areas such as the design of light-weight and multifunctional aerospace structures, as well as energy absorbing, damping, and generation. The simulations are performed for both crystalline and amorphous NPs. The effect of shells on the key mechanical properties of the NPs, such as effective elastic moduli, yield and fracture stress, and toughness, is determined by comparison of the computational results obtained for core-shell and single-materials NPs.
Processing, Characterization, and Modeling of Nano-twinned Alloys: Understanding the Role that Controlling and Tuning of Microstructure has in Dislocation-twin Interactions: Francisco Andrade Chávez1; Orcun Koray Celebi1; Huseyin Sehitoglu1; Jessica Krogstad1; 1University of Illinois at Urbana-Champaign
Nanotwinned metallic systems have the potential to warrant an optimum combination of high strength, ductility and cracking resistance. Dislocation-twin interactions are responsible for the remarkable properties they exhibit, but realizing the full potential requires greater control over the nature and distribution of nanotwins. Here we use a combination of magnetron sputtering and molecular statics simulations as a route to develop a fundamental understanding of the mechanisms necessary to achieve such control of the microstructure. This is done through the manipulation of sputtering parameters, alloy chemistry and substrate interfacial strain. The nickel-titanium alloy system is used as a model system to manipulate the SFE, and thereby the likelihood for twinning. Preliminary results confirm that twin density can be directly modified through alloy chemistry and that interfacial strain modulation is effective in controlling twin orientation. Precise microstructural control facilitated by this work, will enable future systematic experimental exploration of specific dislocation-twin interactions.
Small-Scale Mechanical Behavior of Ion-irradiated Amorphous Metals versus Multi-Principal Alloys: Maryam Sadeghilaridjani1; Vahid Hasannaeimi1; Shristy Jha1; Sundeep Mukherjee1; 1University of North Texas
The effect of ion irradiation on the mechanical properties of amorphous metals will be discussed and compared with the response of multi-principal alloys (or high entropy alloys). The changes in hardness, modulus, and strength were characterized as a function of irradiation depth using small-scale techniques such as nanoindentation and micro-pillar compression. After Ni-ion irradiation, the metallic glass showed lower hardness and yield strength. In contrast, both the high entropy alloy and 304 stainless steel showed hardening after irradiation, with the degree of hardening being significantly higher for the steel. Irradiation-induced hardening of the steel and HEA was attributed to hindrance of dislocation movement from the defects generated. Softening behavior of the metallic glass was attributed to structural changes and increase in free volume in the irradiated region while retaining a fully amorphous state.
Twinning and Detwinning in Small-sized Crystals: Xiang Wang1; Scott Mao1; 1University of Pittsburgh
Twinning is not only a basic deformation model but also can act as an effective way to improve the mechanical property of materials. However, Twinning is hardly activated in body-centered cubic (Bcc) metals under room temperature and slow strain rates. Here, by performing in situ high-resolution transmission electron microscopy (HRTEM), we found that a majority of deformation twins in Bcc metals are unstable and undergo spontaneously detwinning upon unloading, in stark contrast to those in most Fcc metals. Such unexpected instability of Bcc twins was associated with the prevalence of the inclined twin boundaries—a peculiar structure where twin boundaries are not parallel to the twinning plane, and the degree of instability is in direct proportion to the fraction of the inclined twin boundary. This work provides significant insights into the structure and stability of deformation twins in Bcc metals.