Fracture Mechanics-Based Quantitative Matching of Forensic Evidence Fragments

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2021-01-01
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Thompson, Geoffrey
Dawood, Bishoy
Yu, Tianyu
Lograsso, Barbara
Vanderkolk, John
Maitra, Ranjan
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Bastawros, Ashraf
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Meeker, William
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Maitra, Ranjan
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Aerospace Engineering

The Department of Aerospace Engineering seeks to instruct the design, analysis, testing, and operation of vehicles which operate in air, water, or space, including studies of aerodynamics, structure mechanics, propulsion, and the like.

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The Department of Aerospace Engineering was organized as the Department of Aeronautical Engineering in 1942. Its name was changed to the Department of Aerospace Engineering in 1961. In 1990, the department absorbed the Department of Engineering Science and Mechanics and became the Department of Aerospace Engineering and Engineering Mechanics. In 2003 the name was changed back to the Department of Aerospace Engineering.

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Ames National Laboratory

Ames National Laboratory is a government-owned, contractor-operated national laboratory of the U.S. Department of Energy (DOE), operated by and located on the campus of Iowa State University in Ames, Iowa.

For more than 70 years, the Ames National Laboratory has successfully partnered with Iowa State University, and is unique among the 17 DOE laboratories in that it is physically located on the campus of a major research university. Many of the scientists and administrators at the Laboratory also hold faculty positions at the University and the Laboratory has access to both undergraduate and graduate student talent.

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Mechanical Engineering
The Department of Mechanical Engineering at Iowa State University is where innovation thrives and the impossible is made possible. This is where your passion for problem-solving and hands-on learning can make a real difference in our world. Whether you’re helping improve the environment, creating safer automobiles, or advancing medical technologies, and athletic performance, the Department of Mechanical Engineering gives you the tools and talent to blaze your own trail to an amazing career.
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Materials Science and Engineering

The Department of Materials Science and Engineering teaches the composition, microstructure, and processing of materials as well as their properties, uses, and performance. These fields of research utilize technologies in metals, ceramics, polymers, composites, and electronic materials.

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The Department of Materials Science and Engineering was formed in 1975 from the merger of the Department of Ceramics Engineering and the Department of Metallurgical Engineering.

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Abstract

Fractured metal fragments with rough and irregular surfaces are often found at crime scenes. Current forensic practice visually inspects the complex jagged trajectory of fractured surfaces to recognize a ``match'' using comparative microscopy and physical pattern analysis. We developed a novel computational framework, utilizing the basic concepts of fracture mechanics and statistical analysis to provide quantitative match analysis for match probability and error rates. The framework employs the statistics of fracture surfaces to become non-self-affine with unique roughness characteristics at relevant microscopic length scale, dictated by the intrinsic material resistance to fracture and its microstructure. At such a scale, which was found to be greater than two grain-size or micro-feature-size, we establish that the material intrinsic properties, microstructure, and exposure history to external forces on an evidence fragment have the premise of uniqueness, which quantitatively describes the microscopic features on the fracture surface for forensic comparisons. The methodology utilizes 3D spectral analysis of overlapping topological images of the fracture surface and classifies specimens with very high accuracy using statistical learning. Cross correlations of image-pairs in two frequency ranges are used to develop matrix variate statistical models for the distributions among matching and non-matching pairs of images, and provides a decision rule for identifying matches and determining error rates. A set of thirty eight different fracture surfaces of steel articles were correctly classified. The framework lays the foundations for forensic applications with quantitative statistical comparison across a broad range of fractured materials with diverse textures and mechanical properties.

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This is a pre-print of the article Thompson, Geoffrey Z., Bishoy Dawood, Tianyu Yu, Barbara K. Lograsso, John D. Vanderkolk, Ranjan Maitra, William Q. Meeker, and Ashraf F. Bastawros. "Fracture Mechanics-Based Quantitative Matching of Forensic Evidence Fragments." arXiv preprint arXiv:2106.04809 (2021). Posted with permission.

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Fri Jan 01 00:00:00 UTC 2021
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