Engineering Commons^™

Advances In Additively Manufactured Titanium Alloys By Powder Bed Fusion And Directed Energy Deposition: Microstructure, Defects, And Mechanical Behavior, Hongyi Y. Ma, J. C. Wang, Peng Qin, Y. J. Liu, L. Y. Chen, L. Q. Wang, Laichang Zhang

Research outputs 2022 to 2026

Ti and its alloys have been broadly adopted across various industries owing to their outstanding properties, such as high strength-to-weight ratio, excellent fatigue performance, exceptional corrosion resistance and so on. Additive manufacturing (AM) is a complement to, rather than a replacement for, traditional manufacturing processes. It enhances flexibility in fabricating complex components and resolves machining challenges, resulting in reduced lead times for custom designs. However, owing to distinctions among various AM technologies, Ti alloys fabricated by different AM methods usually present differences in microstructure and defects, which can significantly influence the mechanical performance of built parts. Therefore, having an in-depth …

Real-Time Identification Of Oxygen Vacancy Centers In Linbo₃ And Srtio₃ During Irradiation With High Energy Particles, Miguel L. Crespillo, Joseph T. Graham, Fernando Agulló-López, Yanwen Zhang, William J. Weber

Nuclear Engineering and Radiation Science Faculty Research & Creative Works

Oxygen vacancies are known to play a central role in the optoelectronic properties of oxide perovskites. A detailed description of the exact mechanisms by which oxygen vacancies govern such properties, however, is still quite incomplete. The unambiguous identification of oxygen vacancies has been a subject of intense discussion. Interest in oxygen vacancies is not purely academic. Precise control of oxygen vacancies has potential technological benefits in optoelectronic devices. In this review paper, we focus our attention on the generation of oxygen vacancies by irradiation with high energy particles. Irradiation constitutes an efficient and reliable strategy to introduce, monitor, and characterize …

Micro-Ct Evaluation Of Defects In Ti-6al-4v Parts Fabricated By Metal Additive Manufacturing, Haijun Gong, Venkata Karthik Nadimpalli, Khalid Rafi, Thomas Starr, Brent Stucker

Department of Manufacturing Engineering Faculty Research and Publications

In this study, micro-computed tomography (CT) is utilized to detect defects of Ti-6Al-4V specimens fabricated by selective laser melting (SLM) and electron beam melting (EBM), which are two popular metal additive manufacturing methods. SLM and EBM specimens were fabricated with random defects at a specific porosity. The capability of micro-CT to evaluate inclusion defects in the SLM and EBM specimens is discussed. The porosity of EBM specimens was analyzed through image processing of CT single slices. An empirical method is also proposed to estimate the porosity of reconstructed models of the CT scan.

Geometric Effects Of Open Hollow Hydroxyapatite Microspheres Influence Bone Repair And Regeneration In Sprague Dawley Rats, Youqu Shen, M. N. Rahaman, Yongxian Liu, Yue-Wern Huang

Materials Science and Engineering Faculty Research & Creative Works

Effective regeneration of bone defects caused by trauma or chronic diseases is a significant clinical challenge. Bone deficiency is overcome using treatments that rely on bone regeneration and augmentation. While various treatments have been investigated with encouraging results, complete and predictable bone reconstruction is often difficult [1]. Synthetic bone grafts have advantages such as consistent quality, safety, and good tissue tolerance. They usually function as inert or osteoconductive implants. Encouraging results from synthetic grafts have been reported. For instance, hollow hydroxyapatite (HA) microspheres showed the ability to facilitate bone repair in rats with non-healing calvarial defects [2,3]. However, new bone …

Impact Of Pulse Length On The Accuracy Of Defect Depth Measurements In Pulse Thermography, James Pierce, Nathan B. Crane

Faculty Publications

Pulse thermography is a nondestructive testing method in which an energy pulse is applied to a surface while the surface temperature evolution is measured to detect sub surface defects and estimate their depth. This nondestructive test method was developed on the assumption of instantaneous surface heating, but recent work has shown that relatively long pulses can be used to accurately determine defect depth in polymers. This paper examines the impact of varying input pulse length on the accuracy of defect depth quantification as a function of the material properties. Simulations using both thermoplastics and metals show that measurement error is …

Recent Advances On Carrier And Exciton Self-Trapping In Strontium Titanate: Understanding The Luminescence Emissions, Miguel L. Crespillo, Joseph T. Graham, Fernando Agullo-Lopez, Yanwen Zhang, William J. Weber

Nuclear Engineering and Radiation Science Faculty Research & Creative Works

An up-to-date review on recent results for self-trapping of free electrons and holes, as well as excitons, in strontium titanate (STO), which gives rise to small polarons and self-trapped excitons (STEs) is presented. Special attention is paid to the role of carrier and exciton self-trapping on the luminescence emissions under a variety of excitation sources with special emphasis on experiments with laser pulses and energetic ion-beams. In spite of the extensive research effort, a definitive identification of such localized states, as well as a suitable understanding of their operative light emission mechanisms, has remained lacking or controversial. However, promising advances …

Metamorphic Robustness Testing: Exposing Hidden Defects In Citation Statistics And Journal Impact Factors, Zhi Q. Zhou, T.H. Tse, Matt Witheridge

Faculty of Engineering and Information Sciences - Papers: Part B

We propose a robustness testing approach for software systems that process large amounts of data. Our method usesmetamorphic relations to check software output for erroneous input in the absence of a tangible test oracle. We use this technique to testtwo major citation database systems: Scopus and the Web of Science. We report a surprising finding that the inclusion of hyphensin paper titles impedes citation counts, and that this is a result of the lack of robustness of the citation database systems in handlinghyphenated paper titles. Our results are valid for the entire literature as well as for individual fields such …

Current-Driven Production Of Vortex-Antivortex Pairs In Planar Josephson Junction Arrays And Phase Cracks In Long-Range Order, Francisco Estellés-Duart, Miguel Ortuño, Andrés M. Somoza, Valerii M. Vinokur, Alex Gurevich

Physics Faculty Publications

Proliferation of topological defects like vortices and dislocations plays a key role in the physics of systems with long-range order, particularly, superconductivity and superfluidity in thin films, plasticity of solids, and melting of atomic monolayers. Topological defects are characterized by their topological charge reflecting fundamental symmetries and conservation laws of the system. Conservation of topological charge manifests itself in extreme stability of static topological defects because destruction of a single defect requires overcoming a huge energy barrier proportional to the system size. However, the stability of driven topological defects remains largely unexplored. Here we address this issue and investigate numerically …

Optical-Fiber-Based Smart Concrete Thermal Integrity Profiling: An Example Of Concrete Shaft, Ruoyu Zhong, Ruichang Guo, Wen Deng

Civil, Architectural and Environmental Engineering Faculty Research & Creative Works

Concrete is currently the most widely used construction material in the world. The integrity of concrete during the pouring process could greatly affect its engineering performance. Taking advantage of heat production during the concrete curing process, we propose an optical-fiber-based thermal integrity profiling (TIP) method which can provide a comprehensive and accurate evaluation of the integrity of concrete immediately after its pouring. In this paper, we use concrete shaft as an example to conduct TIP by using the optical fiber as a temperature sensor which can obtain high spatial resolution temperature data. Our method is compared with current thermal infrared …

Development Of Pre-Repair Machining Strategies For Laser-Aided Metallic Component Remanufacturing, Xinchang Zhang, Wenyuan Cui, Leon Hill, Wei Li, Frank W. Liou

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Remanufacturing worn metallic components can prolong the service life of parts that need frequent replacement but are extremely costly to manufacture, such as aircraft titanium components, casting dies. Additive manufacturing (AM) technology enables the repair of such valuable components by depositing filler materials at the worn area layer by layer to regenerate the missing geometry. In general, damaged parts would be inspected and pre-machined prior to material deposition to remove oil, residue, oxidized layers or defects located in inaccessible regions. Therefore, the motivation of this paper is to introduce pre-repair machining strategies for removing contaminated materials from damaged components and …

The Role Of Ceramic And Glass Science Research In Meeting Societal Challenges: Report From An Nsf-Sponsored Workshop, Katherine T. Faber, Tewodros Asefa, Monika Backhaus-Ricoult, Richard K. Brow, Julie Y. Chan, Shen Dillon, William Fahrenholtz, For Full List Of Authors, See Publisher's Website.

Materials Science and Engineering Faculty Research & Creative Works

Under the sponsorship of the U.S. National Science Foundation, a workshop on emerging research opportunities in ceramic and glass science was held in September 2016. Reported here are proceedings of the workshop. The report details eight challenges identified through workshop discussions: Ceramic processing: Programmable design and assembly; The defect genome: Understanding, characterizing, and predicting defects across time and length scales; Functionalizing defects for unprecedented properties; Ceramic flatlands: Defining structure-property relations in free-standing, supported, and confined two-dimensional ceramics; Ceramics in the extreme: Discovery and design strategies; Ceramics in the extreme: Behavior of multimaterial systems; Understanding and exploiting glasses and melts under …

Nondestructive Evaluation Of Steel Bridges: Methods And Applications, Theodore Hopwood Ii, Christopher Goff, Jared Fairchild, Sudhir Palle

Kentucky Transportation Center Research Report

Nondestructive evaluation (NDE) methods can be used to assess in-service steel bridges for problematic conditions caused by factors such as design, manufacturing, fabrication, and the service effects of traffic and corrosion. This report discusses typical NDE test methods used on bridges, including penetrant testing, magnetic particle testing, eddy current testing, ultrasonic testing (including phased array testing), radiography, and acoustic emission testing. NDE operations such as flaw location, characterization, and sizing are covered as well. Results of a national survey of departments of transportation’s (DOTs) use of NDE are presented. A simple procedure for using NDE to address DOT bridge concerns …

Influence Of An Electric Field On Grain Growth And Sintering In Strontium Titanate, Wolfgang Rheinheimer, Fabian Lemke, Michael Hoffman

Electric Field Assisted Sintering and Related Phenomena Far From Equilibrium

Within the last five years considerable efforts were done in investigating electric field assisted sintering (flash sintering). However the experiments are hard to control: shrinkage occurs within seconds and the local temperature is undefined due to joule heating. Therefore the present study removes these two parameters by investigating grain growth under electric field in the no-current-case for strontium titanate.

The impact of an electric field on grain growth in strontium titanate is investigated between 1350°C and 1550°C for fields of up to 50V/mm. To prevent joule heating by a current flowing through the material insulating Al2O3 plates separate the electrodes …

Vacancy-Type Defects Study On Ultra-Fine Grained Aluminium Processed By Severe Plastic Deformation, Li-Jun Su, C Lu, Guanyu Deng, A Kiet Tieu, L C. Zhang, P Guagliardo, S N. Samarin, J F. Williams

Faculty of Engineering and Information Sciences - Papers: Part A

Vacancy-type defects play an important role in the metal materials deformed by severe plastic deformation (SPD). The present work use positron annihilation lifetime spectroscopy (PALS) to test the vacancy-type defects in aluminium alloys processed by equal channel angular pressing (ECAP) and accumulative roll bonding (ARB). ECAP at room temperature and cryogenic temperature was conducted to AA1050 and ARB with 200 C preheating was conducted to AA1050 and AA6061 to produce laminated AA1050 sheets, AA6061 sheets and AA1050/AA6061 composites. High fraction of vacancy-type defects were detected in all the deformed samples. Vacancies associated with dislocations and bulk mono-vacancies have been identified …

Defects Induced Ferromagnetism In Plasma-Enabled Graphene Nanopetals, Zengji Yue, Donghan Seo, Kostya Ostrikov, Xiaolin Wang

Faculty of Engineering and Information Sciences - Papers: Part A

Ferromagnetism in graphene is fascinating, but it is still a big challenge for practical applications due to the weak magnetization. In order to enhance the magnetization, here, we design plasma-enabled graphene nanopetals with ultra-long defective edges of up to 105 m/g, ultra-dense lattice vacancies, and hydrogen chemisorptions. The designed graphene nanopetals display robust ferromagnetism with large saturation magnetization of up to 2 emu/g at 5 K and 1.2 emu/g at room temperatures. This work identifies the plasma-enabled graphene nanopetals as a promising candidate for graphene-based magnetic devices. 2014 AIP Publishing LLC.

Pb Thin Films On Si(111): Local Density Of States And Defects, Stefan Eilers, Yi Du, S X. Dou

Australian Institute for Innovative Materials - Papers

Local density of states and atomic structure of the stripped incommensurate phase, the √3 x√7 phase and the 1 x 1 phase of a monolayer of Pb on Si(111) are characterized by scanning tunneling microscopy and spectroscopy. The dI/dV-images reveal congruent local density of states structures for the stripped incommensurate and the √3 x√ phase but suggest a hexagonal lattice of the local density of states for the 1x1 phase while the atomic structure consists of one more atom in the center of each hexagon. Vacancy defects and impurities show a depletion of local density of states for the stripped …

Neutron Irradiation Effects On Domain Wall Mobility And Reversibility In Lead Zirconate Titanate Thin Films, Joseph T. Graham, Geoff L. Brennecka, Paulo Ferreira, Leo Small, David Duquette, Christopher Apblett, Sheldon Landsberger, Jon F. Ihlefeld

Nuclear Engineering and Radiation Science Faculty Research & Creative Works

The effects of neutron-induced damage on the ferroelectric properties of thin film lead zirconate titanate (PZT) were investigated. Two sets of PbZr_0.52Ti_0.48O₃ films of varying initial quality were irradiated in a research nuclear reactor up to a maximum 1 MeV equivalent neutron fluence of (5.16± 0.03) x 10¹⁵ cm^-2. Changes in domain wall mobility and reversibility were characterized by polarization-electric field measurements, Rayleigh analysis, and analysis of first order reversal curves (FORC). With increasing fluence, extrinsic contributions to the small-signal permittivity diminished. Additionally, redistribution of irreversible hysterons towards higher coercive fields was …

Reaction Method Control Of Impurity Scattering In C-Doped Mgb2: Proving The Role Of Defects Besides C Substitution Level, S K. Chen, K Y. Tan, A S. Halim, X Xu, K S. B De Silva, W K. Yeoh, S X. Dou, A Kursumovic, J L. Macmanus-Driscoll

Australian Institute for Innovative Materials - Papers

In this study, Si and C were incorporated into polycrystalline MgB2 via in situ reaction of Mg and B with either SiC or with separate Si and C (Si+C). The electrical transport and magnetic properties of the two series of samples were compared. The corrected resistivity at 40K, pA(40K), is higher for the SiC reacted samples regardless of carbon (C) substitution level, indicating larger intragrain scattering because of the simultaneous reaction between Mg and SiC and carbon substitution during the formation of MgB2. In addition, because of the cleaner reaction route for the SiC reacted samples, the calculated active area …

Occurrence Of Surface Defects On Strips During Hot Rolling Process By Fem, Hai-Liang Yu, Kiet Tieu, Cheng Lu, Guan-Yu Deng, Xiang-Hua Liu

Faculty of Engineering and Information Sciences - Papers: Part A

During a hot rolling process, surface defects on strips can severely affect the quality of the rolled product, particularly for two conditions: (1) there are initial defects on continuous casting slabs that propagate and/or are inherited from those on the surface of rolled steels from upstream rolling processes; and (2) there are no initial defects on continuous casting slabs, and they consequently appear on the surface of rolled steels due to improper rolling technologies. In this paper, the authors present a new 3D finite element model coupled with constrained node failure to understand better the initiation and growth of surface …

Simulation Of Defects In Micro-Deep Drawing Of An Aluminium Alloy Foil, Syamsul Hadi, Hai-Liang Yu, Kiet Tieu, Cheng Lu

Faculty of Engineering and Information Sciences - Papers: Part A

Micro-forming refers to the application of conventional forming processes to manufacture products from ultra-thin sheet materials. While attempting to meet the increasing demand for cost-effective manufacturing of micro-formed components, it is very important to reduce the defects in the products. In this paper, we report a number of Finite Element (FE) simulations of the micro-deep drawing process with various sample thicknesses and eccentric distances. The simulations indicated that when the sample thickness is nearly equal to the gap between the plunger and the die, the sample is likely to develop fractures at the bottom corner. When the sample thickness is …

Carbon Fiber Reinforced Carbon Foams For Repair And Reconstruction Of Bone Defects, Brock Holston Marrs, Rodney Andrews, Larry Cunningham Jr.

Center for Applied Energy Research Faculty Patents

The present invention relates to a tissue scaffold and a method of preparing a tissue scaffold for implantation. The tissue scaffold includes a body having a graphite foam core. At least a first portion of the external surface of that graphite foam core is covered by a composite material to provide additional mechanical strength to the scaffold.

Study Of Vacancy-Type Defects By Positron Annihilation In Ultrafine-Grained Aluminum Severely Deformed At Room And Cryogenic Temperatures, L H. Su, Cheng Lu, Lizi He, L C. Zhang, P Guagliardo, A K. Tieu, S N. Samarin, J F. Williams, H J. Li

Faculty of Engineering - Papers (Archive)

"Commercial-purity aluminum was processed by equal-channel angular pressing (ECAP) at room temperature (RT-ECAP) and cryogenic temperature (CT-ECAP) with liquid nitrogen cooling between two successive passes.It was found that the RT-ECAPed samples showed equiaxed microstructure after 4 and 8 ECAP passes, while the CT-ECAPed samples displayed slightly elongated microstructure and slightly smaller grain size.Moreover, the CT-ECAPed samples had higher hardness values than the RT-ECAPed samples subjected to the same amount of deformation.Positron annihilation lifetime spectroscopy (PALS) was used to investigate the evolution of vacancy-type defects during the ECAP deformation process.The results showed that three types of defects existed in the ECAPed …

Solidification And The Δ/Γ Phase Transformation Of Steels In Relation To Casting Defects, Suk Chun Moon, Rian Dippenaar, Sang-Hyeon Lee

Faculty of Engineering and Information Sciences - Papers: Part A

Many advanced steels fall within the peritectic composition range, which are notoriously difficult to cast due to cracking and breakout problems in the continuous casting process especially at high casting speeds. In this study an attempt was made to obtain practical understanding of the solidification and the δ→γ phase transformation of various commercial steels using high-temperature laser-scanning confocal microscopy. Under rapid cooling conditions the transformation morphology showed a massive-type of transition rather than a classical diffusion-controlled transformation.

Anisotrophic Currents And Flux Jumps In High-Tc Superconducting Films With Self-Organized Arrays Of Planar Defects, V Yurchenko, A.J Qviller, P.B Mozhaeva, J.E Mozhaeva, J.B Hansen, C Jacobsen, I.M Kotelyanskii, Alexey V. Pan, T H. Johansen

Faculty of Engineering - Papers (Archive)

Regular arrays of planar defects with a period of a few nanometers can be introduced in superconducting YBa₂Cu₃O_7-δ (YBCO) thin films by depositing them on vicinal (also called miscut or tilted) substrates. This results in the anisotropy of critical currents flowing in the plane of the film. We present results of real-time magneto-optical imaging (MOI) of magnetic flux distribution and dynamics in a series of YBCO thin films deposited on NdGaO₃ substrates with different miscut angles θ. MOI allows reconstructing the current flow profiles. From the angle formed between domains with different …

Characterization Of Nanometer Scale Compositionally Inhomogeneous Algan Active Regions On Bulk Aln Substrates, A. V. Sampath, G. A. Garrett, E. D. Readinger, R. W. Enck, H. Shen, M. Wraback, J. R. Grandusky, L. J. Schowalter

US Army Research

The optical and structural properties of AlGaN active regions containing nanoscale compositional inhomogeneities (NCI) grown on low dislocation density bulk AlN substrates are reported. These substrates are found to improve the internal quantum efficiency and structural quality of NCI-AlGaN active regions for high Al content alloys, as well as the interfaces of the NCI with the surrounding wider bandgap matrix, as manifested in the absence of any significant long decay component of the low temperature radiative lifetime, which is well characterized by a single exponential photoluminescence decay with a 330 ps time constant. However, room temperature results indicate that non-radiative …

A Bist Approach For Configurable Nanofabric Arrays, Mandar V. Joshi, Waleed K. Al-Assadi

Electrical and Computer Engineering Faculty Research & Creative Works

This work proposes a Built-in Self Test (BIST) approach to test crossbars for a defined set of faults. The BIST can classify the different programmable elements in the crossbars as non-defective or defective with a certain fault type. The logic synthesis can then configure the crossbar by avoiding these defective elements.

Applying Six Sigma Methodology To The Admissions Process In Higher Education, Alok Verma

Engineering Technology Faculty Publications

Time and quality are two important metrics for improving a company's production and profit performance. Six Sigma is one of the most powerful continuous improvement tools that have been used to improve the quality of products and business processes. Six Sigma methodology provides the techniques and tools to improve the capability and reduce the number of defects in any process. It was originally developed by Motorola to systematically improve processes by eliminating defects. Although, originally developed for manufacturing processes, the tool has been effectively applied to improve business processes also. Evaluation of applications for admission in higher education is often …

Defect-Tolerant Gate Macro Mapping & Placement In Clock-Free Nanowire Crossbar Architecture, Ravi Bonam, Yong-Bin Kim, Minsu Choi

Electrical and Computer Engineering Faculty Research & Creative Works

Recently, we proposed a new clock-free nanowire crossbar architecture based on a delayinsensitive paradigm called Null Convention Logic (NCL). The proposed architecture has simple periodic structure that is suitable for non-deterministic nanoscale assembly and does not require a clock distribution network - so it is intrinsically free from timing-related failure modes. Even though the proposed architecture offers improved manufacturability, it is still not free from defects. This paper elaborates on the different programming techniques to map a given threshold gate macro on a random PGMB (Programmable Gate Macro Block) with predefined dimension. Defect-Aware and Defect Unaware approaches have been considered …

Inherited Redundancy And Configurability Utilization For Repairing Nanowire Crossbars With Clustered Defects, Yadunandana Yellambalase, Minsu Choi, Yong-Bin Kim

Electrical and Computer Engineering Faculty Research & Creative Works

With the recent development of nanoscale materials and assembly techniques, it is envisioned to build high-density reconfigurable systems which have never been achieved by the photolithography. Various reconfigurable architectures have been proposed based on nanowire crossbar structure as the primitive building block. Unfortunately, high-density systems consisting of nanometer-scale elements are likely to have many imperfections and variations; thus, defect-tolerance is considered as one of the most exigent challenges. In this paper, we evaluate three different logic mapping algorithms with defect avoidance to circumvent clustered defective crosspoints in nanowire reconfigurable crossbar architectures. The effectiveness of inherited redundancy and configurability utilization is …

Cost-Driven Repair Of A Nanowire Crossbar Architecture, Yadunandana Yellambalase, Shanrui Zhang, Minsu Choi, Nohpill Park, Fabrizio Lombardi

Electrical and Computer Engineering Faculty Research & Creative Works

The recent development of nanoscale materials and assembly techniques has resulting in the manufacturing of high-density computational systems. These systems consist of nanometer-scale elements and are likely to have many manufacturing imperfections (defects); thus, defect-tolerance is considered as one of the most some algorithms for repairing defective crosspoints in a nanoscale crossbar architecture; furthermore we estimate the efficiency and cost-effectiveness of each algorithm. Also, for a given design and manufacturing environment, we propose a cost-driven method to find a balanced solution by which figures of merit such as area, repair time and reconfiguration cost can be taken into account. Probabilistic …