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Framework for Deriving Computational Interface Methods for Contact, Fracture, and Material Joining

We seek to derive rather than derived mathematical formulations for interface problems in materials and structures. The formulations provide the basis for implementing software within finite element analysis software codes for solving challenging transient, nonlinear, sharp, and unstable problems that are not easily solved with current methods or software.

We derive methods through a rigorous mathematical approach. Current methods are designed with numerical tuning parameters that are artificial, not part of the underlying physics but are needed to get computational results, like paying a fee to the middleman to get into the show that you really want to see. Rather, we derive methods with enhanced stability and in which all parameters have a derived value that do not need to be adjusted by the user. This way, the user focuses on capturing the physics of reality and less time adjusting the knob on the radio to get a clear sound. Read more ab out individual projects below.

Current Projects

Predictive Fatigue Behavior of Structural Materials Through Computationally Informed Textural and Microstructural Influences

Illustrations of Polymer-Matrix Composites.
Metals are composed of many grains, and fatigue cracks tend to form in some of these grains and their boundaries, but not others. A method for predicting fatigue does not exist yet because there are fundamental knowledge gaps.

Typical computational models of microstructures involve many finite elements, provide enormous data, and take time to run. We are targeting the micron to mm scale—called the mesoscale—which is the length scale over which grains interact with their neighbors. Targeting this length scale is the most efficient to address questions about fatigue because it provides only the necessary data. We have derived a computational framework that targets this length scale.

Applications: Aluminum alloys are common in aircraft fuselage and turbine components, some automotive parts, naval ships, and windows and building components. Of course, it is also used in aluminum cans and baking foil, however fatigue is mostly a problem in systems with repeated cyclic loading, like turbines, cars, computer cases (heat up, cool down), and machinery. This computational framework can be used to gain knowledge about aluminum fatigue by predicting cracks, giving us insight for designing against fatigue. This will lead to microstructures and alloys that have 50% or 100% longer fatigue life, so parts can run longer before cracks happen.

Read more about the project on ResearchGate.

Frictional Response of Bolted Metallic Surfaces

Model of Friction Response.
We developed a multiscale modeling framework for characterization and prediction of vibration and dissipation in bolted joints. The framework incorporates physics-based models of friction from asperity-asperity (small bumps) on surfaces at microscale into the macroscale friction coefficient of the surface, accounting for pressure and degradation effects.

Applications: This framework helps improve the performance of products, like your car, with dissimilar metals joined together. If you have ever heard or felt a rattle in your car while driving on the highway, you recognize that controlling the behavior of joints is important for maintaining comfortable and safe performance. Without lubrication, the teeth in gears can wear down, and applying the right amount of friction is important to bring vehicles using disc brakes to a safe stop.

Vibration, noise, and heat are useful energy lost to dissipation that otherwise could be performing mechanical work. The framework increases understanding in how joints dissipate energy and generate heat, leading to reduced energy loss. This is good for climate change and reduces the cost of components, increases their longevity, and makes more efficient use of limited resources.

Read more about the project on ResearchGate.

Interface Integrity and Debonding in Polymer-Matrix Composites

Composite materials are increasingly being used in aircraft, hypersonic rockets and space vehicles, cars and trucks, and structures due to their excellent mechanical properties such as high strength-to-weight ratio and directionally-dependent stiffness. However, defects in these materials tend to occur at the interfacial bonds, either between the fiber and matrix at the micro-scale or between the lamina at the mesoscale. In this project, we develop an approach to numerically predict the onset of cracking in these composite materials.

Applications: Because composites are engineered materials, the manufacturer chooses the weave pattern and the ratio of fiber and matrix. Fibers provide the strength and stiffness but have to be connected through the matrix, therefore it’s best to align fibers in the direction that maximum loads are going to be applied.

The software simulates failure in composites, which will help manufacturers optimize microstructures for load applications, arrange fibers in preferred directions, and connect low length scale material strength/toughness to the structural load at which the composite component would fail.

Read more about the project on ResearchGate.

Past Projects

Discontinuous Element Insertion Program (DEIP)

DEIP is a MATLAB/OCTAVE toolbox for inserting zero-thickness elements into a continuous finite element mesh in two and three dimensions. These elements are used for intrinsic cohesive zone modeling and for the Discontinuous Galerkin method in order to model a variety of evolving interfaces and discontinuities in materials (cracks, grain boundaries, bedding planes, etc.). The algorithm is topology based and is suitable for complex, unstructured meshes.

Applications: This open source software is a tool for rendering the computational geometry of just about any interface problem. DEIP can be adapted to fit many needs. Our team has used it for cracking in composites, periodic microstructure representative volume elements, grain boundary sliding and cavitation in steel alloys in pressure vessels of power plants for studying creep life, for ductile cracks in aluminum, and many of the projects listed on this website.

Read more about the project on ResearchGate.