The mission of the Materials at Extremes Research Group (MERG) is to develop a tier 1 research group capable of transformative research in the area of mechanics of materials. This goal includes all subclasses of materials from metals and ceramics to composites and multifunctional materials. As traditional materials are exposed to more exotic boundary conditions and composite materials are designed to incorporate hybrid mechanical behavior, the need to characterize and model the mechanical response of materials has dramatically increased. Whether the need is to model the behavior of a traditional material at unstudied extremes or characterize the fundamental deformation and fracture mechanisms of a candidate composite material system, the MERG team has the expertise and capability to conduct meaningful scientific discovery. An emphasis is placed on rigorous quantitative research that incorporates experimental, theoretical, and numerical techniques towards solving issues of structural integrity. This approach will lead to wide acceptance of our findings and allow rapid adoption of our techniques in academia, government, and industry.

In pursuit of these goals, considerable effort must be expended to:
  • Expand the UTEP’s capability to conduct experimental research that replicate the extreme boundary conditions experienced by modern materials. Emphasis will be placed on measuring the volumetric deformation and microstructural evolution towards the development of novel theory.

  • Construct theoretical models that capture the key phenomena (at appropriate time- and length-scales) that enable modeling the constitutive response, damage evolution, and life at a high fidelity.

  • Design numerical tools to facilitate the rapid implementation of theory into academia, government, and industry.

The PI’s vision is to export professional scholars who are guided by ethics, driven to produce quality research and publications, and capable of public discourse on scientific findings. The students in this group will be highly sought-after upon graduation. In my eyes, the success of my students reflects upon my performance as an advisor.

Research Initiatives

Real-Time Mechanical State Tool for the Predictive Maintenance of Turbomachinery

Funded by the Air Force Research Lab

The reliability of turbomachinery is of great concern to aircraft turbomachinery design and health management engineers. There is a desire to move from “schedule/unscheduled” maintenance towards a “predictive” maintenance paradigm. Ideally, the next generation of turbomachinery will be installed with lick-and-stick or embedded sensors to capture the thermomechanical history from installation to death. This real-time, highly sampled, “Big Data”, can be exploited to enable a real-time predictive maintence paradigm. This paradigm can be achieved with the development of Mechanical State models. The research objectives (ROs) of this proposal are to (RO1) develop a physically realistic mechanical model capable of modeling standard and emergent phenomena; (RO2) generate a high-fidelity and statistically-significant database of standard and nonstandard test data for both the calibration and post-audit validation of the model; and (RO3) develop, implement, and post-audit validate the prediction tool against “service history” experiments.

Partnership for Research and Education Consortium in Ceramics and Polymers

Funded by the US Department of Energy - National Nuclear Security Agency

The overall goal of this Partnership for Research and Education Consortium in Ceramics and Polymers (PRE-CCAP) is to establish a sustainable pipeline of highly trained next generation workforce and community of technical peers for DOE/NNSA’s core mission. The PRE-CCAP will focus on providing opportunities for minority student research internships, research skills training, intellectual collaboration between Minority Serving Institutions (MSI) and DOE laboratories, and to increase visibility of NNSA related scientific activities. The project objectives are to: 1) Build a sustainable pipeline in STEM discipline, 2) Provide intellectual collaboration between MSIs and NNSA labs, and 3) Increase visibility for long term recruitment pipeline development. The proposed activities will include: K12 outreach, new courses, seminar/workshops, student internship, student research training, joint MSI-NNSA labs projects, annual meetings, student co-advising, NNSA lab presence at MSIs’ career fair, and website and social media exposure. The PRE-CCAP brings together 3 MSIs and 2 DOE/NNSA national laboratories: The University of Texas at El Paso (UTEP, a Hispanic Serving Institution), Florida International University(FIU, a Hispanic Serving Institution), Tennessee State University (TSU, an HBCU), Los Alamos National Lab (LANL), Kansas City National Security Campus (KCNSC).

An Accelerated Creep Testing (ACT) Program for Advanced Creep Resistant Alloys for High Temperature Fossil Energy (FE) Applications

Funded by the US Department of Energy - National Energy Technology Laboratory

Of primary concern to the FE materials scientist is the rapid experimental screening of the long-term creep behavior of candidate materials. These candidate materials must be manufactured and subjected to physical experiments to gather the empirical evidence necessary for material qualification for long-term creep. The time-to-material-qualification is high when using conventional creep tests. Accelerated creep testing (ACT) is a well-established method to reduce the time-for-material-qualification; however, none of the existing ACTs provide rapid and detailed information concerning long term creep deformation and rupture behavior. The proposed research seeks to address these challenges by developing an accelerate creep testing program for metallic materials using two new ACTs: the stepped isothermal method (SIM) and the stepped isostress method (SSM). These ACTs are capable of recording over a short period of “real” time, the long-term multistage creep deformation to rupture of materials. Recent experiments on polymers show the remarkable capacity to accelerate from 20 to 107 hrs. The Research Objective (RO) of this project is to vet, improve, and test the feasibility of these ACTs for metallic materials. These overarching goals will be achieved by the following technical approach. A database of long-term creep data for surrogate materials P91 steel and IN718 nickel-based superalloy will be collected. Pre-ACT experiments will be performed to establish the baseline properties of the material, evaluate a reference-calibration approach for the ACTs, and develop creep deformation mechanisms map. The framework of the ACTs will be scrutinized and mathematical rules and constraints posed to establish the systematic repeatability of time acceleration. A targeted test matrix of ACTs will be executed to probe the limits of time acceleration. A post-audit validation where ACT tests are compared to the experimental database will be used to determine the extent that the ACTs are independent of systematic errors and calibration bias. Finally, a comprehensive ASTM style “Test Standard - An Accelerated Creep Testing Program for New Material Qualification” will be written that includes geometry, test parameters, regression software, and recommendations for the retrofit of existing creep frames. The result of this project, a new test standard for ACT, will benefit the FE material scientist. While, existing ACTs such as the master curve method and the stress relaxation test have the ability to accelerate the collection of creep information, their ability to provide efficient and rapid indications of the long-term creep behavior of materials is limited. The classic master curve method requires the careful selection of an appropriate time-temperature parameter, stress-parameter function, interpolation/extrapolation range, and does not predict the multistage creep deformation. The stress relaxation test requires advanced equipment and numerical integration schemes and does not provide the multistage creep deformation and rupture data. The ACTs SIM and SSM will enable the collection of multistage creep deformation and rupture of extremely long-lived (106 hr) metallic materials in less than 24 hr. The software for ACT will be made available to the public. By making this software available publically, the FE material scientist will be able to rapidly experimental screen new candidate materials. This project has the potential to reduce the time to implementation of new creep resistant alloys from decades to months.

A Guideline for the Assessment of Uniaxial Creep and Creep-Fatigue Data and Models

Funded by the US Department of Energy - National Energy Technology Laboratory

Of primary concern to Advanced-UltraSupercritical fossil energy component designers is a determination of which constitutive models are the “best”, capable of accurately reproducing the normal and complex loading phenomena expected in components subjected to creep and creep-fatigue; as well as what experimental datasets are proper or “best” to use for fitting the constitutive parameters. In addition, the inherent uncertainty in experiments and the repeatability and stability of extrapolations (for long lived FE components) is a major concern. The first research objective (RO1) is to develop an aggregated database of creep and creep-fatigue validation data from existing datasets for P91 steel and 316 stainless steel. An extensive database of creep, stress relaxation, monotonic tensile, fatigue, and creep-fatigue experimental data will be collected. A systematic assessment of the uncertainty and integrity of the datasets will be conducted using pivot tables, characteristic curves, and quantitative measures of goodness to evaluate the extent that the test information (variables of material- and equipment/test-related uncertainty) influence the statistical dispersion of the data. This procedure could be replicated for other materials of interest. The second research objective is to employ the RO1 database to benchmark existing creep and creep-fatigue models in a variety of finite element models. RO2 will involve the investigation into the data fitting and parameter extraction using both analytical as well as a novel multi-objective optimization approach (MACHO). At this point, judgments on the sensitivity and criticality of the parameters for the different constitutive models will be presented. User defined material routines will be written and employed in blind post-audit validation tests where the models will be blindly compared to a database of complex load experiments to evaluate the models’ ability to predict the complex phenomena observed in real components. Next, the model performance will be evaluated with respect to experiment uncertainty. The repeatability and stability of extrapolations using the models will be tested across boundary conditions and regimes. Finally, the models will be assigned letter grades (A,B,C,D,F) for each loading condition, phenomena, and regime of interest. Using the guidelines resulting from RO1 and RO2, a component designer will be able to easily select the best constitutive model(s) and experimental datasets for an intended design.

Novel Method to Characterize and Model the Multiaxial Constitutive and Damage Response of Energetic Materials

Funded by the Sandia Laboratory

This study aims to create a scientific breakthrough in the ability to predict the mechanical behavior of energetic materials through the design of a new multiaxial testing method using three dimensional (3D) digital image correlation (DIC) and the development of a novel continuum damage mechanics (CDM) based constitutive model for the volumetric and deviatoric response of energetic materials. Traditional methods to elucidate the volumetric and deviatoric response of energetic materials require the use of complex load frame configurations which apply hydrostatic pressure and uniaxial loads independently. This new method will utilize a variation of the Bridgman notched specimen method and through 3D optical strain measurements elucidate the multiaxial constitutive and damage behavior through comparison to the analytical (skeletal stress) or elastic finite element (FE) solution. This work will be extended to deal with effects of strain rate (0.001 to 1 s-1) and temperature (ambient to 75°C). The primary challenge of this effort is transforming the Bridgman method that was originally developed for metals under tension towards energetic materials under compression. An outcome of this novel characterization method is the development of a CDM-based constitutive model for the prediction of the “batch-to-batch” mechanical behavior of energetic materials. This model will be used to simulate the service conditions of mock plastic bonded explosive (PBX) material including uniaxial and multiaxial states of static and dynamic loading. This work is in collaboration with the University of Texas at El Paso.

Quantifying Thermomechanical Fatigue of Hot Mix Asphalt: A Feasibility Study

Funded by the Southern Plains Transportation Center

The objective of this proposal is to study HMA materials subject to thermomechanical fatigue to better understand how the stress, deformation, and microstructure evolve through space and time. Under thermomechanical fatigue conditions, HMAs exhibit a complex interaction of fracture mechanisms: including branching, secondary crack propagation, healing, thermal fracture, etc. Boundary conditions play a significant role in these phenomena. To achieve this goal, the following activities will be carried out: (1) conduction of experiments with indirect tension (IDT), semicircular bending (SCB), and overlay tester (OT) specimens along with three-dimensional digital image correlation (3D-DIC) at several temperatures to comprehensively observe the thermomechanical fracture and fatigue of typical HMA; (2) characterization of the meso- to macro-structural evolution using several nondestructive cumulative damage and destructive microscopy techniques; (3) characterization of 3D microstructural deformation using nano-indentation and X-ray microtomography (μCT) ; and (4) development of a multiscale stochastic damage model that focuses on the micro to macro length scales to study the mechanical responses of HMA subject to thermomechanical fatigue. This effort will produce a provisional standard test method for the fracture and fatigue of HMAs subjected to thermomechanical conditions. As reflected in the attached letter of support from TxDOT, this type of research is need so that appropriate specifications can be developed.

A Unified Viscoplasticity Constitutive, Damage, and Life Prediction Model for Thermomechanical Fatigue Based on Continuum Damage Mechanics

Stochastic Continuum Damage Mechanics Model for the Prediction of Initial/Current Damage Distribution

MACHO: MAterial Constant Heuristic Optimizer