About

Our nationally recognized faculty, researchers and professional staff are dedicated to excellence in research, education, innovation and service. Learn more about the individuals who make up the Department of Mechanical Engineering by visiting their profiles.

Research topics

• Composite material
• Materials science
• Computer Science
• Mechanics
• Chemical engineering
• Physics
• Nanotechnology
• Geology
• Engineering
• Optics
• Mechanical engineering

Selected publications

• Electrical Conductivities of Conductors, Semiconductors, and Their Mixtures at Elevated Temperatures

  Advanced Engineering Materials · 2026-02-28 · 1 citations

  articleOpen accessSenior authorCorresponding

  Modernization efforts across the energy and industrial sectors are driving developments in engineered materials with tailored electrical properties suitable for operation in demanding thermal environments. The nominal electrical properties of common material classes, including metals, semiconductors, and insulators, are well‐known and routinely measured by researchers in materials science, geophysics, engineering, and physics. Despite decades of study, a persistent conductivity gap exists between metals and semiconductors at elevated temperatures. In this article, experimental data from the literature are reviewed to provide the first summary of the electrical properties of metals, semiconductors, and some insulators under direct‐current conditions at elevated temperatures, further highlighting the existing conductivity gap between these material classes. To bridge this gap, metal‐ceramic irregular metamaterials (MCiM) are proposed as novel engineered composites containing high‐ and low‐conductivity granular materials identified from the literature. The bulk electrical conductivity that emerges from the MCiM as a function of material constituents, relative volume fraction, and temperature is modeled with an effective medium approximation. MCiM mixtures composed of Cu/Cu 2 O, Cu/MgO, and Ni/Cu 2 O are predicted to span the conductivity gap between and S/m. In comparison to current materials exhibiting a negative temperature coefficient of resistivity, MCiM offers a low‐cost alternative for high‐temperature applications where tailored electrical properties are required. Opportunities for future research focusing on characterizing the temperature‐dependent conductivities of commercially available metal and ceramic powders to experimentally validate the MCiM concept are discussed.

  PublisherDOI

• Modeled effects of density gradients on resonance signatures of pressed powder compacts

  The Journal of the Acoustical Society of America · 2025-10-01

  article

  Plastic deformation of powder during compaction can cause heterogeneities within the resulting tablet, with models such as the Drucker-Prager Cap (DPC) popular for simulating this process in powder metallurgy and pharmaceuticals. For materials that cannot be homogenized via sintering, persistent density gradients can affect the resulting performance of the tablets but be challenging to quantify in production environments. Prior studies have demonstrated the ability to resolve linear grading with resonant ultrasound spectroscopy (RUS). Here we present work to link 2-D density variations in compressed powder compacts to their resulting modal response characteristics. Using a DPC model calibrated against real-world pressing data, we simulated compaction and relaxation in compacted powders, capturing verticaland radial stress and density gradients arising from plasticity and die-wall friction, with larger-volume tablets exhibiting greater bulk density contrasts. Using the resulting volume distributions, we assess the impacts on the ability of RUS to resolve heterogeneities, highlighting details such as gradient symmetry and mode matching. These results underscore the sensitivity of resonance to subtle density nonuniformities and support the development of RUS-based inspection protocols for detecting process-induced inhomogeneities in compacted powders.

  PublisherDOI

• Interaction of grain morphology and intergranular friction on grain packing

  Soft Matter · 2025-01-01 · 1 citations

  articleOpen accessSenior author

  The bulk density of loosely packed grains is determined by grain morphology and the intergranular friction coefficient. Creating simulated grain packings with realistic packing densities is the first step in performing predictions of granular material behavior at higher compaction stresses. Our novel approach performs jamming simulations at near-zero pressure where the surface properties are decoupled from the elastic properties to explore the interaction between grain morphology and intergranular friction. We use bonded particle model (BPM) grain representations with different subparticle resolutions to vary their morphological properties. Our investigation uses both regular- and irregular-shaped BPM grains to develop a relationship between grain morphology, intergranular friction, and the jamming limit that applies to simulated and physical grains. The relationship prescribes a friction coefficient for use in simulations of grain packing that considers the effect of morphology.

  PublisherOA PDFDOI

• The role of randomly packed particles on macroscopic elastic bonded grain properties

  Computational Particle Mechanics · 2024-01-17 · 2 citations

  articleSenior author
  PublisherDOI

• Intermediate Strain Rate Behavior of a Polymer-Particle Composite with High Solids Loading

  Conference proceedings of the Society for Experimental Mechanics · 2024-01-01

  book-chapterSenior author
  PublisherDOI

• The Role of Pressure-Dependent Viscoplasticity and Volumetric Dilatation in Energetic Materials at Intermediate Strain Rates

  2023-07-19 · 1 citations

  book-chapter

  The mechanical behavior of energetic aggregate materials (polymer bonded explosives, propellants, etc.) at low to intermediate strain rates is a complex function of the material constituents, manufacturing methods, and microstructure morphology. Shear-induced volumetric dilatation, similar to the characteristic behavior of granular materials and soils, can play a key role to open up porosity in the microstructure, particularly when the material is under some degree of confinement. We present a continuum modelling approach that accounts for this phenomena via a pressure-dependent viscoplastic extension to the classical ViscoSCRAM [1] constitutive model and use it to study the role of shear-induced dilatation in confined and unconfined material at a variety of strain rates. Modeling results are compared with intermediate strain rate Split Hopkinson Pressure Bar experiments and show good agreement between predicted and measured stresses.

  PublisherDOI

• The Effect of Particle System on Quasistatic Compression Behavior and Damage Accumulation of High Solids Loading Polymer-Particle Composites

  Applied Composite Materials · 2023-10-09 · 1 citations

  articleSenior author
  PublisherDOI

• The Role of Pressure-Dependent Viscoplasticity and Volumetric Dilatation in Energetic Materials at Intermediate Strain Rates

  2023-07-19

  book-chapterOpen access

  The mechanical behavior of energetic aggregate materials (polymer bonded explosives, propellants, etc.) at low to intermediate strain rates is a complex function of the material constituents, manufacturing methods, and microstructure morphology. Shear-induced volumetric dilatation, similar to the characteristic behavior of granular materials and soils, can play a key role to open up porosity in the microstructure, particularly when the material is under some degree of confinement. We present a continuum modelling approach that accounts for this phenomena via a pressure-dependent viscoplastic extension to the classical ViscoSCRAM [1] constitutive model and use it to study the role of shear-induced dilatation in confined and unconfined material at a variety of strain rates. Modeling results are compared with intermediate strain rate Split Hopkinson Pressure Bar experiments and show good agreement between predicted and measured stresses.

  PublisherOA PDFDOI

• The role of pressure-dependent viscoplasticity and volumetric dilatation in energetic materials at intermediate strain rates.

  2022-06-01

  articleOpen access

  Abstract not provided.

  PublisherOA PDFDOI

• Mesostructure Evolution During Powder Compression: Micro-CT Experiments and Particle-Based Simulations

  Conference proceedings of the Society for Experimental Mechanics · 2022-01-01 · 2 citations

  book-chapterOpen access1st authorCorresponding
  PublisherOA PDFDOI

Frequent coauthors

• J. E. Shepherd

  California Institute of Technology

  19 shared

• Wayne M. Trott

  Sandia National Laboratories

  10 shared

• Michael S. Oliver

  10 shared

• Scott I. Jackson

  Mitchell Institute

  10 shared

• Frank Beckwith

  Sandia National Laboratories

  8 shared

• Ki Tae Wolf

  Sandia National Laboratories

  8 shared

• Mark Luke

  Texas A&M University

  8 shared

• Kevin Long

  Sandia National Laboratories

  8 shared

Awards & honors

• SPOT Award for Leadership, Sandia National Laboratories (201…
• Employee Recognition Award, Sandia National Laboratories (20…
• Outstanding Women at Sandia National Laboratories (2009)