Michael Sutton - US grants

Computer vision measurements will be combined with analytical developments in mechanics to obtain useful "hybrid" methods for analyzing the integrity of structures ;itin-situ;ro. An accurate, three-dimensional non-contacting measurement technique which can be used to compute small motions of an object, with particular application to robots will be developed. Initial work will center on the general optics equations and on appropriate simplifications necessary for the intended applications. The improved non-contacting computer-based measurement technique will be applied to investigate the microscale motions of materials, yielding improved models of multilayer media, fracture processes, etc.

Measurement of the normal displacement of a three-dimensional body subjected to arbitrary loading or boundary displacements has been a major problem for experimentalists for the past century. Elaborate optical methods including holography and speckle interferometry are only applicable to the two dimensional problem where the specimen surface is plane. Recently, improvements in video cameras and computers (storage capacity) have led to significant advances in image analysis which can be effectively employed to record displacements. The approach is to record and store in pixel form the surface features of the specimen in its deformed and undeformed state. Intensity interpolation methods are then employed to identify small subsets on the specimen and to determine the displacement of these subsets. The method has been established for two-dimensional bodies undergoing plane deformation. The proposed program will extend these methods to three- dimensional specimens by utilizing two video cameras and stereo imaging procedures to obtain the images required for displacement determinations. Advanced methods of image correlation methods will be employed to achieve sub-pixel accuracy in the displacement measurements.

Advanced computer vision equipment will be used to improve the sensitivity in measuring in-plane displacements on the surface of structural components. Smaller displacement measurements will detect smaller flaws in a structure and will provide more accurate assessment of the parameters which control brittle fracture of structures. The equipment will also be used to measure the micromechanical deformation of grain boundaries in metals leading to a better understanding of the material parameters which control the strength of metals.

This project will study three dimensional deformation fields in the vicinity of stationary and growing cracks. A project with both analytical and experimental components will be conducted. Finite element methods will also be used to asses the role of thickness on near tip deformation fields.

The research will apply high temperature Moire interferometry and high temperature digital image correlation to obtain strain and displacement fields in the vicinity of crack tips under high temperature creep loading. THe work will include microstructural examination of damage initiation and growth to develop a better understanding of the physics, at the same time advancing analytical and numerical solutions for the near tip stress-strain fields. The ultimate aim is to develop improved methods for prediction of creep damage in materials and structures.//

A loading frame will be purchased for projects involving the use of two dimensional and three dimensional computer vision to study the surface deformation near a growing crack and a static crack, and optical measurements of strain at high temperatures near 1000oC. The research will extend strain measurement techniques to lower size scales to study deformation and fracture phenomena at the grain scale.

9512456 Sutton This Academic Research Infrastructure (Instrumentation) Award is to partially fund the development of a materials characterization facility with emphasis on testing in an aggressive environment. The long range goal of the research involved is life-prediction methodologies using mathematical models which incorporate accurate material parameters. Much existing data shows that safety throughout the lifetime of a structure is extremely sensitive to the environment, however except in very special cases there is inadequate ability to predict how safety changes as structures age. This facility will contribute to providing better experimental data in this area. ***

9500304 Sutton This Research Equipment Grant is made to partially fund the purchase of a controlled environment furnace. The furnace will be used for the long-term effort in the life assessment of superalloys at elevated temperatures. Data will also be collected on the evolution of microstructural changes under various loading and environmental conditions. ***

Development and Application of 3D Measurement Methodologies at Reduced Length Scales

Abstract
The development and application of measurement methodologies for quantitative determination of three-dimensional surface deformations on planar or curved objects with spatial resolutions extending to the nanometer scale is the focus of this research effort. A unique aspect of the research is the emphasis on both 3D metrology and also the development of methodologies applicable to generic imaging systems (e.g., SEM, optical) for identification and accurate correction of complex image distortions. Applications of the resulting methodologies will include studies of local deformation behavior in (a) nano-structured materials, (b) micro-scale tensile and bending tests of non-homogeneous materials and (c) this-film blister/bulge specimens undergoing delamination.

The mechanical behavior of soft tissues such as blood vessels is complex and not completely understood. A detailed study of this behavior is important to understand the function of organs such as the heart and blood vessels, which undergo repeated changes in pressure during each heart beat. Many diseases result in changes in both mechanical behavior and microscopic structure of tissues. Thus, understanding how tissue structure, geometry, mechanical properties, and function are related may lead to advances in health care. This project focuses on measuring the structure and mechanical behavior of blood vessels, together with simpler model systems such as collagen tubes. The measured properties will be used to build mathematical models that can predict changes in tissue function resulting from disease. An important part of this work is measuring mechanical properties on the microscopic scale, since the local mechanical environment controls how tissues behave during development and after injury.

The research objectives are to (a) bring together researchers and engineers at various stages in their careers to discuss recent advances in experimental mechanics and the role that is being played by non-contacting measurement methods, including full-volume measurements (e.g., computer aided tomography), general surface motions (e.g. stereo-vision) and simulation methods integrated with experimental measurements, (b) serve as a catalyst for international collaboration and partnership in the broader area of experimental mechanics and (c) provide participants with the opportunity to view and use modern, vision-based technology to make quantitative measurements. To meet these objectives, (a) internationally recognized research scientists and engineers will serve on the organizing committee and (b) outstanding investigators in non-contacting methods will be provided partial travel support to ensure their active participation via an invited presentation.
The growth and development of digital imaging technology, coupled with extraordinary advances in computational and image processing technology, is culminating in a wide range of vision-based, non-contacting measurement methods, providing the impetus for this Workshop and Symposium. Educational efforts will include (a) broad dissemination of the time and place for the symposium via email, direct personal contact and professional society distributions (e.g., the Society for Experimental Mechanics), (b) special encouragement to young investigators to attend via small travel grants, (c) direct access to vision equipment and technology for hands-on experience, and (d) dissemination of the results from symposium in the form of proceedings (CD-ROM, print) and, for those cases where high quality papers are available, publication in archival outlets such as the Journals of Strain and Experimental Mechanics.

"This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5)."
Atherosclerotic plaque rupture is the leading cause of acute cardiovascular events such as heart attack and stroke. Many studies of atherosclerosis use mice as an animal model, since plaque structure and composition can easily be altered using genetic engineering, drugs, or diet. However, spontaneous plaque rupture is rare in atherosclerotic mice, necessitating new approaches to relate the pathology of mouse plaques to their biomechanical properties and stability against rupture. This project will apply two novel approaches to study the biomechanical behavior of mouse atherosclerotic plaques: 1. measurement of local surface strains on normal arteries and plaques under tensile loading using three-dimensional digital image correlation (3D-DIC), a non-contacting optical method; 2. direct measurement of the forces necessary to cause detachment of the plaque from the underlying vessel wall, in order to estimate plaque-artery fracture energy. A primary goal of the project is to correlate biomechanical measurements with underlying tissue structure, particularly with those features which have been clinically associated with plaque rupture in humans. An additional goal is to apply analytical methods derived from classic fracture mechanics to the problem of plaque rupture.

If successful, this research will provide new experimental tools and computational approaches to study atherosclerotic plaque rupture, with an emphasis on small animal models. Application of 3-D DIC to measure local strains on the micrometer length scale is likely to find broad utility in mechanical studies of biological tissues. The project will offer an introduction to mechanical testing and data analysis to area high school students by providing an educational/laboratory experience module for the SCienceLab outreach program developed by the USC Center for Science Education. This SCienceLab module will be the first in the program to focus on engineering concepts. The project will also help to strengthen the newly established Biomedical Engineering Program at USC.

DESCRIPTION (provided by applicant): The remarkable information processing capacity of neurons in the mammalian brain stems from the dense network of synaptic connections they receive and the ability of these synapses to change with experience. However, the constellation of synaptic changes thought to underlie learning and memory ("Hebbian" plasticity) can also produce instability of activity within neural circuits, leading to a potential host of debilitating outcomes ranging from mental retardation to epilepsy. Work over the last decade has suggested that "homeostatic" forms of synaptic plasticity can promote long-term stability within neuronal networks by offsetting potentially destabilizing levels of synaptic activity through compensatory increases or decreases in synaptic strength. While this idea has generated wide interest in the field, we still lack a clear picture of how these compensatory changes are implemented at synapses and how they work in concert with Hebbian synaptic modifications. Recent work has challenged the picture provided by initial accounts that homeostatic compensation at central synapses as an intrinsically slow and cell-wide form of plasticity. We now propose the hypothesis that homeostatic synaptic plasticity is not defined by a unitary global process, but rather describes a family of compensatory mechanisms, a subset of which interact locally at synapses with processes important for information storage. This hypothesis will be tested in three specific aims, by examining: whether unique features of synaptic/neuronal activity drive distinct forms of synaptic compensation (Aim 1);whether compartmentalized biochemical processing in neurons mediates distinct aspects of homeostatic plasticity (Aim 2);and whether local mechanisms of homeostatic compensation interact with Hebbian synaptic plasticity at the same set of synaptic inputs (Aim 3). Since this project centers around a class of processes that are fundamental to basic neuron function, its implications are likely to broad, informing aspects of neuron signaling, development, and the devastating neurological disorders that have been linked with homeostatic plasticity, such as epilepsy. This project will also inform many basic science issues related to our understanding of learning and memory, such as the role of localized protein synthesis and degradation in synaptic plasticity and how such Hebbian synaptic modifications can endure in the face of compensatory mechanisms that would otherwise reverse them. PUBLIC HEALTH RELEVANCE: Our ability to learn and remember is thought to involve specific changes in the network of synaptic connections in the brain;however, synaptic changes thought to underlie learning and memory can also produce instability of activity within neural circuits, leading to a host of debilitating outcomes ranging from mental retardation to epilepsy. Work over the last decade has suggested that a different class of synaptic modification - homeostatic synaptic plasticity - promotes compensatory changes in the strength of synapses to offset destabilizing levels of activity within neuronal networks and recent evidence has linked altered regulation of homeostatic plasticity with neurological dysfunction. However, the traditional viewpoint has been that these homeostatic mechanisms act on the neuron as a whole, rather than at the level of individual synapses, and therefore do not interact with mechanisms important for learning and memory storage. Recent evidence has challenged this view prompting us to propose and test the hypothesis that neurons are not limited to a single global compensation mechanism to promote network stability, but can rather draw from a family of mechanistically-distinct processes, some of which act locally at synapses and can interact with mechanisms important for information processing and storage.

The research objective of this award is to advance our understanding of mechanical failure mechanisms in arterial tissue, focusing on atherosclerotic plaque failure. Arterial tissue failure leads to several life-threatening clinical conditions, including atherosclerotic plaque rupture and aortic dissection. Arterial tissue has structural similarities to fiber-reinforced composite materials used for engineering and manufacturing applications. In this project, theoretical and analytical approaches developed to describe failure of reinforced composites will be extended to interpret the results of experimental studies of plaque failure in atherosclerotic mice, which develop plaques comparable to those seen in humans. The research will combine experimental studies of the structure and biochemistry of the interface between tissue layers in atherosclerotic mouse arteries with development of theoretical and computational models of delamination mechanisms at both macroscopic and microscopic length scales. The models will be used to simulate controlled peeling/delamination experiments on atherosclerotic mouse arteries using both cohesive zone and micromechanical approaches. The validated models will then be used to predict those conditions that result in arterial tissue failure.

The continuum and micromechanical modeling approaches developed in mouse studies can be readily modified to understand tissue failure processes in human diseases. The proposed effort has potential to positively impact patient management, while guiding the development of successful interventions. The models developed will also be applicable for analyzing failure of non-biological composite materials having similar structure and material properties. The insight gained into mechanisms of arterial tissue adhesion and failure is expected to prove useful to the biomedical device industry, for example in the development of improved biomimetic surgical adhesives. The educational and outreach aspects of the project include undergraduate training in biomechanics, outreach to high school teachers in STEM subjects through Project Lead the Way, and strengthening the new Biomedical Engineering Program at the University of South Carolina.

The research objective of this award is to simulate and measure the formation of acoustic solitons in two-dimensional granular waveguides. The PIs will design and fabricate hexagonally packed granular lattices "defined as granular phononic crystals" contained in a narrow channel. The PIs will unveil unique soliton formation and transmission mechanisms in the assembled granular architectures. The fundamental understanding of soliton propagation will enable a new class of waveguides that can filter, delay, and redirect acoustic solitons in a controllable and efficient manner. The PIs will achieve this research goal by developing an advanced discrete element model (DEM) and a novel digital image correlation (DIC) technique. Based on molecular dynamics techniques, the DEM will simulate the propagation of solitons under the full consideration of axial and rotational dynamics of tightly packed, frictional particles. The PIs will verify the numerical simulation results by the DIC techniques that measure extremely small particle displacements at high sampling rates.

From the viewpoint of physics, the findings in this study will contribute to the advancement of nonlinear mechanics of granular media based on the Lagrangian description of particle dynamics. With a view towards potential engineering applications, the fabricated solitonic waveguide can open a new paradigm in mechanical wave filtering, acoustic imaging, and nondestructive evaluation by leveraging an added degree of freedom in controlling mechanical waves. Besides contributing to science and engineering, the research activities will also have a broader impact on educating students. The PIs will recruit and train underrepresented students via student services and programs at the University of South Carolina (USC). The knowledge and product obtained from this work will be integrated into the new graduate program in aerospace engineering at USC.

This grant provides funding for the development of the friction extrusion process and associated equipment to enable direct production of high-value materials (such as titanium wires) from low-cost precursors (such as powders or machining chips) with reduced energy consumption. Friction extrusion die and process chamber design will be studied. Experiments and numerical simulations will be carried out to develop an in-depth understanding of the scientific principles and physical mechanisms operating in the friction extrusion process. Friction extrusion experiments will be carried out to gain a physical understanding of the process and equipment, such as the effect of extrusion die and chamber design on power consumption and quality of the produced wire. Computational models will be created to simulate the extrusion process in order to investigate issues (e.g. full-field material flow pattern and thermal history) not approachable experimentally. Validation and visualization experiments will be designed and performed to provide measurements of material position, velocity and temperature for validating simulation model predictions, so that computational models can be utilized reliably for process design and optimization purposes.

If successful, the results of this research can be used to enable the design, optimization and utilization of the friction extrusion process for the energy-efficient production of high-value materials from low-cost precursors and for recycling machining wastes (chips). The friction extrusion process has the potential to greatly reduce energy requirements for the production of titanium wire feedstock by eliminating costly vacuum melting and billet casting. Wires produced from this process could be used as feedstock for additive manufacturing processes or as filler wires for niche welding applications.

There is a continuing demand in the United States for sustainable and hazard-resilient but highly affordable low-rise buildings for households and businesses. The goal of this research project is to investigate the feasibility of high-quality reinforced earth masonry (REM) for seismic resistant low-rise buildings. This goal will be achieved by transforming sustainable and locally appropriate but brittle unfired earth masonry into a stronger and more ductile system by using non-biodegradable recycled plastic fibers combined with internal steel reinforcement. This research will investigate REM as a low-cost option for low-rise industrial buildings and sheds, with a vision of fostering the development of small plants and warehouses by reducing construction and maintenance costs, thus promoting economic development.

The technical objectives of this research are the following: (1) to engineer, prototype, and verify an affordable and high-quality REM system for seismic resistant low-rise buildings, and (2) to formulate, verify and implement a new numerical model to accurately and efficiently predict the structural response of REM walls. The hypotheses are:v(1) engineering of earth blocks and mortar stabilized with nine percent or less cement, and reinforced with one percent or less volume fraction of recycled plastic fibers, combined with internal steel reinforcement, will change the strength and ductility of REM, making it suitable for seismic resistant buildings, and (2) computationally efficient numerical models based on newly developed nonlinear macroelements (MEs), whose kinematics are described by the smallest possible number of degrees of freedom, will enable the accurate prediction of the response of REM structures subject to static and dynamic loads. This research will be conducted in three phases. First, selected prototype block-mortar combinations (unreinforced, fiber reinforced, and fiber reinforced with grouted steel bars) will be characterized through load testing of materials and assemblages. A candidate reinforced system will be selected for the second phase. Three-dimensional (3D) digital image correlation (3D-DIC) will be used to measure full-field deformation maps and inform the development of numerical models. The resulting constitutive models for materials, mortar joints, and REM assemblages will serve to formulate detailed finite element (FE) models. Second, performance data will be obtained through large-scale testing and 3D-DIC monitoring of REM walls subject to quasi-static cyclic loading. The results will inform the formulation and validation of new structural ME models and their FE code implementation. Third and final, ME-based FE models of the large-scale specimens will be developed based on the comparison between numerical and experimental results. The resulting first-generation ME models will be used for a preliminary estimate of seismic design coefficients and factors to establish feasibility. In addition, a preliminary quantification of sustainability-related parameters and construction cost for representative REM materials and buildings will be performed to provide a basis for comparison with alternative systems, for example, light-framed wood, as well as life-cycle cost analysis.

Abstract: A severe health burden imposed by many neuropsychiatric and neurological diseases can be linked to limitations in, or disruption of, molecular pathways which guide development, maintenance or plasticity of synaptic connections. Importantly, as many neural circuits are persistently active the individual synaptic connections must undergo continuous and coordinated homeostatic changes to counteract continual synaptic strengthening/weakening and development of network instability. Thus, developing a functional map of sites of activity- dependent dynamic coordination of the molecules and signaling pathways that define the process is central to enabling an understanding of many CNS diseases. The work proposed is uniquely important as it will elucidate novel and yet potent molecular signaling pathways that mediate accurate and reproducible activity-dependent adaptations in synaptic efficacy. Specifically, investigations focus on understanding how post-synaptic sensing of activity via the mTORC1/BDNF signaling pathway mediates increased presynaptic neurotransmitter release during reduced excitatory input to the post-synaptic element. Investigations will test the hypothesis that tomosyn-1 is a central presynaptic target of mTORC1/BDNF/TrkB receptor signaling and that trans-synaptic adjustments in presynaptic neurotransmitter release via this signaling pathway occur via UPS regulation of tomosyn-1 protein levels. We will also define specific sites within the secretory pathway by which tomosyn exerts control over presynaptic neurotransmitter release. Commonality of this trans-synaptic mechanism will also involve comprehensive evaluation at Mossy fiber/CA3 and at CA3/CA1 synapses of hippocampal brain slices, as these circuits are known to exhibit strikingly divergent synaptic plasticity. In addition, we will characterize the E3 ligase responsible for UPS regulation of tomosyn, determine if the E3 ligase activity is sensitive to mTORC1/BDNF/TrkB signaling and if ubiqutination of tomosyn by the E3 ligase regulates tomosyn protein levels and neurotransmitter release. The investigations employ state of the art optical imaging of vesicle cycling, genetic models targeting protein/signaling function, optogenetic control of neuronal excitability and analysis of synaptic function in cultures of hippocampal neurons and hippocampal slices. Biochemical assays will quantify and establish activity dependent control on tomosyn protein via the UPS. This information will significantly advance understanding on mechanisms by which activity- dependent changes in post-synaptic mTORC1 activity coordinate spatial and temporal adjustments in presynaptic neurotransmitter release.