July 2018 - Msepostdoc-list

Seminar Notice for Jung-Ting Tsai's MS Final Exam. Seminar, Monday, July 16, at 2:00, in IMI 102; Exam same day at 3:00, in IMI 102. "Integrated Structural Monitoring of Composite Materials via Distributed Optical Sensor"
by Son, Rosemary E 09 Jul '18

09 Jul '18

Please consider attending the following: MATERIALS ENGINEERING SEMINAR "Integrated Structural Monitoring of Composite Materials via Distributed Optical Sensor" By Jung-Ting Tsai Purdue MSE MS Final Exam Advisor: Professor Jan-Anders Mansson ABSTRACT Measuring the strain history in pre-impregnated thermoset composites during the curing process provides valuable data for manufacturing specification development, quality control, diagnostics of dimensional stability, and validation of cure models. Unlike traditional Fiber-Bragg Grating-based methods, the Distributed Optical Sensors (DOS) provide information along the entire optical fiber distance (optical path length) of the sensor embedded in the laminate for strain measurement. This study's unique contribution to the field is the coupling of the optical sensor monitoring of composite cure strain with models of the cure kinetics, viscosity, and glass transition temperature of the thermoset matrix. Coupling the strain measurements to the material models facilitates coherent comparisons between strain sensor output and thermoset material behavior during the cure process rather than making suppositions of material behavior based on the strain measurement alone. In this research, two laminate types were manufactured with an embedded optical sensor from IM7/5320-1 prepreg tape; a [0]20 Unidirectional (UD) laminate and a 50/40/10 (%0°/%±45°/%90°) Structural Laminate (SL) with the optical sensor routed along three different ply interfaces including [0/0], [45/90], and the [0/45]. The internal residual strain developed during each stage of the thermal cure cycle is examined, including after cooling. Results show that the local strain has variable magnitude, which depends on the ply configuration. The laminate micro-structure was also investigated by optical microscopy for selected cross-sections to provide the resin pocket geometry created by different optical sensor placements in the laminates. Lastly, a Micromechanics-Base approach was used to calculate the chemical shrinkage and the residual strain in the UD laminate during curing and compared with the measured results from the DOS to further validate the strain measurements. The Classical Laminate Plate Theory (CLPT) was used to calculate the residual strain in the SL after curing and compared with the measured results from the optical sensor. A continuous DOS was embedded inside the SL and attached to the surface of a coupon, along with traditional Strain Gauges (SG) and the Digital Image Correlation (DIC). The results from the SG and the DIC were compared to the results from the DOS. Tensile and bending tests were performed on a notched composite laminate coupon with embedded DOS. Tensile test results show that the SG and the DIC reading match closely with the results from the DOS at the far region of the notch. Near the notch, the DOS was able to monitor the strain concentration during tensile and bending tests without malfunctioning the system. Finite element analysis was performed to obtain the theoretical distribution of axial strains along the inspection lines corresponding to the locations of the physical DOS segments to compare the theoretical and experimental strains. As the results indicate, the DOS readings agree well with the theoretical results. The strain measurements from the DOS overcome some of the limitations from the SG and the DIC. Therefore, it was demonstrated that a DOS system can deliver reliable and robust continuous monitoring of mechanical strains in a composite laminate. Keywords: optical sensors, distributed strain, out-of-autoclave prepreg, cure behavior, residual/ internal strain, composite materials, digital image correlation, strain gauge, and non-destructive testing Date: Monday, July 16, 2018 Time:2:00 P.M. Place: IMI 102

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Seminar Notice for Cheng-Eun Kim's Ph.D. Final. Seminar, Wednesday, July 11, at 9:00, in ARMS 1028; Exam same day at 10:00, in ARMS 2326. " Atomistic Simulations and Microscopic Experiments: to Understand Nanoscale Composition Control
by Son, Rosemary E 09 Jul '18

09 Jul '18

Please consider attending the following: MATERIALS ENGINEERING SEMINAR "Atomistic Simulations and Microscopic Experiments: To Understand Nanoscale Composition Control" By Chang-Eun Kim Purdue MSE Ph.D. Final Exam Advisor: Professor David F. Bahr ABSTRACT In this dissertation, the possibility of using the quantum mechanics calculation in combination with experimental result is explored, in order to explain experimentally observed phenomena in materials science problems. A series of published works in this theory-experiment combinatory approach will be introduced. The topics include the phase stability of Sb2O4, surface instability of MgB2, the interplay of diffusion and mechanical strengthening effect in multilayer, and latest findings of the syntheses of metallic nano-foams. The theory-experiment combinatory approach has proven to be useful in various materials science problems. The phase transformation trajectory of the Sb2O4 polymorphs, the surface reconstruction pathways of MgB2(0001), and diffusion kinetics of Cr-Cu dilute alloy system are calculated by the density functional theory coupled with the nudged elastic band method. Finally, the syntheses of Cu and Cu-Ni alloy nano-foams are reported, detailing their microstructure and morphology characterized by electron microscopies. The potential application of the theory-experiment combinatory approaches in the nano-foam synthesis is further discussed toward better understanding of the structure-property relations of the metallic nano-foams. Date: Wednesday, July 11, 2018 Time: 9:00 A.M. Place: ARMS 1028

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MSE Guest Speaker Jairo Diaz Friday, July 13, 2018 ARMS 1021, Coffee/Snacks, 10:30am / Seminar, 11:00am
by Coar, Stacey L 09 Jul '18

09 Jul '18

[cid:image003.jpg@01D41760.0933DC80] Stacey Stacey Coar Secretary/Development Assistant School of Materials Engineering Purdue University Neil Armstrong Hall of Engineering 701 West Stadium Ave. Room 2300 West Lafayette, IN 47907 765-494-4100 scoar(a)purdue.edu<mailto:scoar@purdue.edu>

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Seminar Notice for Kara Luitjohan's Ph.D. Final. Seminar Monday, July 16, at 2:00, in ARMS 1028; Exam same day at 3:00, in ARMS 2326. "Boron Segregation and its Effects in Advanced High Strength Steels"
by Son, Rosemary E 09 Jul '18

09 Jul '18

Please consider attending the following: MATERIALS ENGINEERING “Boron Segregation and its Effects in Advanced High Strength Steels” By Kara E. Luitjohan Purdue MSE Ph.D. Final Exam Advisors: Professor David R. Johnson and Professor Volkan Ortalan ABSTRACT There is a current push in the automotive industry to increase the fuel economy of passenger vehicles. One method to achieve this goal is through the use of advanced high strength steels (AHSS). Included under the umbrella of AHSS are alloys containing small amounts of boron, 0.002 - 0.005 wt% B. This addition of boron leads to difficulties during commercial production, specifically via continuous casting. The casting difficulties are predicted to stem from a metatectic reaction, δ → γ + L, occurring in the iron-boron binary system. Depending on which thermodynamic database is utilized, this reaction is predicted to occur at different boron levels. To experimentally investigate the predicted metatectic reaction, levitation zone melting is used to control the boron segregation in two simple Fe-B binary alloys, and confocal scanning laser microscopy allows for in-situ observation of local microstructural changes as temperature is varied. Based on the experimental results, the metatectic reaction occurs over a broader range of compositions than predicted with the reaction occurring from 0.0025 to ∼0.06 wt% B. The experimental technique successfully applied to the binary system is then used to investigate how the addition of carbon and other solute elements affect the metatectic reaction and subsequent solidification. When carbon is added to the Fe-B system, levitation zone melting results in a δ-bcc to γ-fcc peritectic jump as steady-state growth conditions are reached with respect to carbon segregation. Boron remains in solution until the last zone to solidify. Although the boron content throughout the ingot remains below 5 ppm B, it has an impact on the microstructure as bainite forms where proeutectoid ferrite and pearlite are predicted base on the carbon composition. When other solute elements are added in three different boron-containing commercial steels, the controlled solidification conditions of levitation zone melting are not enough to prevent the formation of a low melting temperature boron-rich phase throughout the directionally solidified ingots. These ingots display a peritectic jump, similar to the ternary case, followed by a breakdown of the planar solidification front leading to the formation of boron-rich intercellular liquid. During dendritic solidification, as seen in continuous casting, boron-rich inter-dendritic liquid can be predicted to form which will result in a low melting boron-rich phase that could be the source of the casting defects. Date: Monday, July 16, 2018 Time: 2:00 P.M. Place: ARMS 1028

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Seminar Reminder for Sam Reeve's Ph.D. Final Exam. Seminar Tuesday, July 10, 2018 at 8:30 a.m., in ARMS 1028; Exam same day at 9:30 a.m., in ARMS 2326. "Materials Design with Molecular Dynamics: Novel Properties in Martensitic Alloys through Free Energy
by Son, Rosemary E 09 Jul '18

09 Jul '18

Please consider attending the following: MATERIALS ENGINEERING SEMINAR "Materials Design with Molecular Dynamics: Novel Properties in Martensitic Alloys through Free Energy Landscape Engineering" By Samuel T. Reeve Purdue MSE Ph.D. Final Exam Advisor: Professor Alejandro Strachan ABSTRACT Novel properties in martensitic alloys are predicted using molecular dynamics (MD) simulations, the uncertainty from input models in MD is explored and quantified, and new data infrastructure for MD is developed. New properties are developed through free energy landscape engineering (FELE), where coherent, epitaxial integration of two materials at the nanoscale can result in metamaterials with fundamentally different behavior. Free energy as a function of strain is calculated using MD simulations and analytically combined to predict potential new properties for a Ni 63% - Al 37% martensitic alloy combined with B2 NiAl, shown to be an ideal candidate for modifying the martensitic landscape. Direct MD simulations show the landscape predictions hold, producing large reduction in thermal hysteresis while retaining transformation strain, second order martensitic transformations, and both tunable and ultra-low stiffness. These properties are shown for structures including nanolaminates, nanowires, and nanoprecipitates. The uncertainty in these results is described, including atomic level variability, cycle variability, and the interatomic model; the model uncertainty is most significant, but only generally approximated through similar results with a second, independent interatomic potential. Beginning from simpler models, functional uncertainty quantification (FunUQ) is developed to directly address the errors between multiple interatomic models. Functional derivatives describe the sensitivity to local changes to the input function and a computationally feasible calculation method for MD simulations is derived. Together with the discrepancy between two models, the functional error between models can be calculated. These capabilities are shown for relatively simple MD models, structures, and properties, with extension to more complex systems and properties. Challenges are addressed, with primary attention to cases where the discrepancy between input functions is large. Improvements for community use of MD simulations is finally presented through use of the nanoHUB online collaboration and cloud computing platform to improve a growing materials data infrastructure (MDI). Tools which introduce unfamiliar users to MD simulations are shown first. Next, connections with existing atomistic MDI are described including databases for interatomic models, structures, tests, and properties. Tools to document and improve MD workflows with Jupyter notebooks are then demonstrated, connecting all of these tools and resources. To conclude, future possibilities and challenges with FELE are considered, extension of FunUQ to complex interatomic models and applicability to other materials modeling is examined, and new directions in atomistic MDI are discussed. Date: Tuesday, July 10, 2018 Time: 8:30 A.M. Place: ARMS 1028

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Reminder: Today MSE Speaker Nathan Levkulich Friday, July 6, 2018 ARMS 1021, Coffee/Snacks, 10:30am Seminar, 11:00am
by Coar, Stacey L 06 Jul '18

06 Jul '18

[cid:image001.jpg@01D41506.6ACCF0F0] Stacey Stacey Coar Secretary/Development Assistant School of Materials Engineering Purdue University Neil Armstrong Hall of Engineering 701 West Stadium Ave. Room 2300 West Lafayette, IN 47907 765-494-4100 scoar(a)purdue.edu<mailto:scoar@purdue.edu>

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Tomorrow: MSE Speaker Nathan Levkulich Friday, July 6, 2018 ARMS 1021, Coffee/Snacks, 10:30am Seminar, 11:00am
by Coar, Stacey L 05 Jul '18

05 Jul '18

[cid:image001.jpg@01D41437.1A00E4D0] Stacey Stacey Coar Secretary/Development Assistant School of Materials Engineering Purdue University Neil Armstrong Hall of Engineering 701 West Stadium Ave. Room 2300 West Lafayette, IN 47907 765-494-4100 scoar(a)purdue.edu<mailto:scoar@purdue.edu>

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