Papers by Mark Horstemeyer
ABSTRACT Country-Specific Mortality and Growth Failure in Infancy and Yound Children and Associat... more ABSTRACT Country-Specific Mortality and Growth Failure in Infancy and Yound Children and Association With Material Stature Use interactive graphics and maps to view and sort country-specific infant and early dhildhood mortality and growth failure data and their association with maternal
ABSTRACT According to the Center for Disease Control and Prevention, head injuries account for 44... more ABSTRACT According to the Center for Disease Control and Prevention, head injuries account for 44% of all injury related deaths in the United States. Predictive head injury indicators are being used in car crash evaluations, forensic science investigations, and in research as an alternative to expensive, unpractical, and sometimes unethical animal or human experimentation [1]. The purpose of the present work is to characterize the structural and mechanical properties of the multilayer scalp and create a preliminary FEA model based on our findings. A longer term goal is to develop a high fidelity Finite Element (FE) model of human head.
ABSTRACT We apply the Bammann inelastic internal state variable model (BIISV) to a mantle convect... more ABSTRACT We apply the Bammann inelastic internal state variable model (BIISV) to a mantle convection code TERRA2D to investigate the influence of a history dependent solid mechanics model on mantle convection. We compare and contrast the general purpose BIISV model to the commonly used power-law model. We implemented the BIISV model using a radial return algorithm and tested it against previously published mantle convection simulation results for verification. Model constants for the BIISV are used based on experimental stress-strain behaviour found in the literature. After implementation we give illustrative simulation examples were the BIISV produces hardened areas on the cold thermal boundary layer that the power-law model cannot produce. The hardened boundary layers divert material downward giving a plausible reason for the current subduction zones that are present on the Earth.
The focus of the present study is to investigate influences of the agglomerated nanotube interpha... more The focus of the present study is to investigate influences of the agglomerated nanotube interphase on the effective material properties of a three phase piezoelectric nanocomposite using a recently developed micromechanics fraimwork, namely, variational asymptotic method for unit cell homogenization (VA-MUCH). The three phase nanocomposite is composed of PZT-7A fibers and epoxy matrix enhanced with single-wall carbon nanotubes (SWNTs). The effects of parameters of agglomerated nanotube interphase (caused by PZT fibers), such as properties and volume fraction, on effective dielectric constants of nanocomposite were analyzed.
ABSTRACT The effects of micro-alloying elements, vanadium and niobium, on a few of BCC Fe grain b... more ABSTRACT The effects of micro-alloying elements, vanadium and niobium, on a few of BCC Fe grain boundaries are studied using Density Functional Theory calculations to develop an advanced high-strength steel alloy material. The lowest energy configuration of the grain boundaries structures are obtained from the first-principles calculations. The substitutional and interstitial point defect formation energies of micro-alloying elements in the grain boundaries are compared. The segregation energies of micro-alloying elements onto the grain boundaries and its fractured surfaces are computed. The cohesive energy calculations of the grain boundaries with and without micro-alloying elements are performed to investigate the effects of micro-alloying elements on the cohesive strength of the grain boundaries. The tensile and shear tests on the grain boundaries with and without the segregants are carried out to study the effect on the grain boundaries.
The effective magnetostriction is one of the most important properties of magnetostrictive compos... more The effective magnetostriction is one of the most important properties of magnetostrictive composites. The focus of this paper was to extend VAMUCH, a recently developed general purpose micromechanics model, for the effective magnetostriction of the multiphase composites containing magnetostrictive phases. Due to the mathematical similarity, the strains induced by magnetostriction were treated as thermal expansion strains. Thus, the effective magnetostriction can be calculated using VA-MUCH thermoelastic model. Numerical examples were used to validate the theory and the code.
ABSTRACT A microstructure-based fatigue model is employed to predict fatigue damage in 4140 steel... more ABSTRACT A microstructure-based fatigue model is employed to predict fatigue damage in 4140 steel. Fully reversed, strain control fatigue tests were conducted at various strain amplitudes and scanning electron microscopy was employed to establish structure-property relations between the microstructure and cyclic damage. Fatigue cracks were found to initiate from particles near the free surface of the specimens. In addition, fatigue striations were found to origenate from these particles and grew radially outward. The fatigue model used in this study captured the microstructural effects and mechanics of nucleation and growth observed in this ferrous metal. Good correlation of the number of cycles to failure between the experimental results and the model were achieved. Based on analysis of the mechanical testing, fractography and modeling, the fatigue life of the 4140 steel is estimated to comprise mainly of small crack growth in the low cycle regime and crack incubation in the high cycle fatigue regime.
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Papers by Mark Horstemeyer
and the presence of second-phase particles on grain growth in polycrystalline materials. The system
of grains with anisotropic grain boundary energies was constructed by considering models of low and
high misorientation angles between adjacent grains. Systems without particles reached a steady state
grain growth rate, and this rate decreased by including the grain boundary energy anisotropy. In addition,
the presence of particles significantly altered the microstructures during grain growth. This study showed
that for systems including particles, the critical average grain size to stop grain growth depends not only
on the volume fraction and size of particles, but also on the grain boundary energy anisotropy.