- Msepostdoc-list - ecn.purdue.edu

FW: SEMINAR NOTICE: K. Swaminathan, MS Final Exam, Thur. 11/8, 8:30 am ARMS 1028
by Stacey, Lisa A 01 Nov '12

01 Nov '12

MATERIALS SCIENCE AND ENGINEERING SEMINAR Effect of Crystallographic Orientation on Sub-critical Grain Boundary Cracking in a Nickel Based Superalloy by Kameshwaran Swaminathan Master of Science Final Examination Co-Advisors: Prof. J. Blendell and Prof. K. Trumble ABSTRACT Sub-critical intergranular crack growth is an important creep fracture mechanism in polycrystalline superalloys. The root cause of this fracture is not well understood. The role of grain orientation on the formation of sub-critical grain boundary cracks during creep of a conventionally cast nickel-based superalloy has been analyzed in this study. The crystallographic orientations of grain pairs adjacent to grain boundaries normal to the tensile axis were measured using Electron Back-Scattered Diffraction (EBSD). The difference in the Schmid factor for the {111} <112> slip system between the grains was compared to the occurrence of sub-critical grain boundary cracking. In addition, the difference in the amount of potential primary creep strain between the grains (for unconstrained state) was analyzed. The cracked grain boundaries were found to have significantly larger Schmid factor mismatch, as well as larger potential primary creep strain mismatch, than those of the uncracked grain boundaries. These larger mismatches in Schmid factor and potential primary creep strain indicate possible development of large enough stress concentration at the grain boundary sufficient to initiate sub-critical cracks. The experimental results suggest possible correlation between crystallographic orientation of the grains and sub-critical cracking at the grain boundary with a critical value for Schmid factor mismatch and potential primary creep strain mismatch in the creep tested alloy. Assumptions and limitations are considered in proposing future experiments for further refinement of the analysis. Date: Thursday, November 8, 2012 Time: 8:30 A.M. Place: ARMS 1028 PURDUE MSE [cid:image003.png@01CDB83C.F28ABEA0] Lisa Stacey Secretary/Development Assistant Purdue University School of Materials Engineering 765/494-4100

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Fwd: MSEGSA Potluck Saturday, November 10th
by Donna Bystrom 31 Oct '12

31 Oct '12

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REMINDER: Seminar Notice - C. Magadanz, Wed. 10/31, 10:30 am, HAMP 3153
by Stacey, Lisa A 30 Oct '12

30 Oct '12

Please see seminar notice below (note location outside of ARMS). MATERIALS SCIENCE AND ENGINEERING SEMINAR Effect of Machining Damage on Low Cycle Fatigue Crack Initiation Life in Drilled Holes in Udimet(r) 720 by Christine Magadanz Master of Science Final Examination Advisor: Prof. K. Trumble ABSTRACT White layer is a generic term for a light etching surface layer on metal alloys that can result under extreme deformation conditions in wear, sliding or machining. While there has been some characterization of white layer due to abusive machining, the specific effect on fatigue crack initiation life has not been well documented. This study aimed to establish a relationship between the presence of white layer due to abusive machining and fatigue crack initiation life in a wrought nickel based superalloy (Udimet(r) 720). Low cycle fatigue testing was conducted on large specimens containing through holes drilled with parameters aimed at creating holes with and without white layer. Initially, Acoustic Emission monitoring technologies were used to monitor for acoustic events associated with crack initiation, however, this technology was deemed unreliable for this testing. Instead, cycles to crack initiation was determined using striation density measurements on each fracture surface to estimate the number of cycles of crack propagation, which was subtracted from the total number of cycles for the specimen. A total of sixteen specimens were tested in this manner. The results suggested that the crack initiation lives of holes machined with good machining parameters were statistically longer than crack initiation lives of holes machined with poor machining parameters. The mean initiation life of the poorly machined specimens was a factor of approximately 2 times shorter than the mean initiation life of the well machined specimens. The holes machined with good machining parameters exhibited subsurface initiations which suggested that no anomalies affected crack initiation for these specimens. It was also shown that some of the poorly machined holes exhibited subsurface initiations rather than initiations at white layer damage. These holes had better surface finish than the poorly machined specimens that did fail at white layer. The mean initiation life of the subsurface initiation holes was 10 times longer than the mean initiation life of the holes that cracked at white layer. Lastly, no apparent correlation between white layer thickness and initiation life was demonstrated in this study. Date: Wednesday, October 31, 2012 Time: 10:30 A.M. Place: HAMP 3153 PURDUE MSE [cid:image003.png@01CDB6BC.A1A144E0] Lisa Stacey Secretary/Development Assistant Purdue University School of Materials Engineering 765/494-4100

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REMINDER: Seminar Notice - Y. Kim, Wed. 10/31, 9:30 am, HAMP 1266
by Stacey, Lisa A 30 Oct '12

30 Oct '12

Please see seminar notice below (note location outside of ARMS). MATERIALS SCIENCE AND ENGINEERING SEMINAR Chirality Control of Carbon Nanotubes by Yae ji Kim Ph.D. Prelim Exam - Part I Advisor: Prof. A. Strachan ABSTRACT Single-walled carbon nanotubes have received extensive attention because of their extraordinary mechanical and electrical properties. For electrical applications, carbon nanotubes are very attractive for use in high-performance devices since metallic carbon nanotubes can show nearly ballistic conduction. Furthermore, semiconducting carbon nanotubes have a large range of band gaps energies, including direct band gaps, which make it possible to replace silicon based transistors. To realize the carbon based electrical devices, a major need for chirality control should to be fulfilled. I propose an experimental and computational setup for studying the effect of lattice mismatch and solid crystal-CNT interaction on the growth of CNTs on bimetal catalyst surfaces. I believe that these parameters are closely related to initial nucleation of CNT structures and thus will be a key to controlling the chirality of CNTs Date: Wednesday, October 31, 2012 Time: 9:30 A.M. Place: HAMP 1266 PURDUE MSE [cid:image003.png@01CDB6BC.7F8A2840] Lisa Stacey Secretary/Development Assistant Purdue University School of Materials Engineering 765/494-4100

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FW: AAE Colloquium Announcement, Thur. Nov. 1st
by Stacey, Lisa A 30 Oct '12

30 Oct '12

Please see the attached AAE Fall 2012 Colloquium Series announcement for this Thursday, Nov. 1st.

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Seminar Notice, Prof. J. Garritano, Fri. 11/2, 3:30 pm, ARMS 1010
by Stacey, Lisa A 26 Oct '12

26 Oct '12

Please see attached seminar notice for next Friday afternoon. Thank you, Lisa Stacey Secretary/Development Assistant Purdue University School of Materials Engineering 765/494-4100

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Benefits Enrollment Guide
by Stacey, Lisa A 26 Oct '12

26 Oct '12

MSE Dept., Your 2013 Benefits Enrollment Guides arrived today via campus mail. Open enrollment ends Nov. 16th so I wanted to let you know they're here in case you'd like to be considering your options. Lisa Stacey Secretary/Development Assistant Purdue University School of Materials Engineering 765/494-4100

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FW: Reminder: Peter G. Winchell Lecture Series Seminar, S. Harris, Fri. 10/26, 3:30 ARMS 1010 (reception to follow)
by Stacey, Lisa A 25 Oct '12

25 Oct '12

Please try to join us tomorrow for Dr. Stephen Harris, Visiting Scientist, Lawrence Berkeley National Laboratory, lecture at 3:30 w/ reception to follow. Thanks, Lisa Stacey Secretary/Development Assistant Purdue University School of Materials Engineering 765/494-4100

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FW: Seminar Notice - Y. Kim, Wed. 10/31, 9:30 am, HAMP 1266
by Stacey, Lisa A 25 Oct '12

25 Oct '12

Please see seminar notice below (note location outside of ARMS). MATERIALS SCIENCE AND ENGINEERING SEMINAR Chirality Control of Carbon Nanotubes by Yae ji Kim Ph.D. Prelim Exam - Part I Advisor: Prof. A. Strachan ABSTRACT Single-walled carbon nanotubes have received extensive attention because of their extraordinary mechanical and electrical properties. For electrical applications, carbon nanotubes are very attractive for use in high-performance devices since metallic carbon nanotubes can show nearly ballistic conduction. Furthermore, semiconducting carbon nanotubes have a large range of band gaps energies, including direct band gaps, which make it possible to replace silicon based transistors. To realize the carbon based electrical devices, a major need for chirality control should to be fulfilled. I propose an experimental and computational setup for studying the effect of lattice mismatch and solid crystal-CNT interaction on the growth of CNTs on bimetal catalyst surfaces. I believe that these parameters are closely related to initial nucleation of CNT structures and thus will be a key to controlling the chirality of CNTs Date: Wednesday, October 31, 2012 Time: 9:30 A.M. Place: HAMP 1266 PURDUE MSE [cid:image003.png@01CDB2A0.CA2D2480] Lisa Stacey Secretary/Development Assistant Purdue University School of Materials Engineering 765/494-4100

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FW: Seminar Notice - C. Magadanz, Wed. 10/31, 10:30 am, HAMP 3153
by Stacey, Lisa A 25 Oct '12

25 Oct '12

Please see seminar notice below (note location outside of ARMS). MATERIALS SCIENCE AND ENGINEERING SEMINAR Effect of Machining Damage on Low Cycle Fatigue Crack Initiation Life in Drilled Holes in Udimet(r) 720 by Christine Magadanz Master of Science Final Examination Advisor: Prof. K. Trumble ABSTRACT White layer is a generic term for a light etching surface layer on metal alloys that can result under extreme deformation conditions in wear, sliding or machining. While there has been some characterization of white layer due to abusive machining, the specific effect on fatigue crack initiation life has not been well documented. This study aimed to establish a relationship between the presence of white layer due to abusive machining and fatigue crack initiation life in a wrought nickel based superalloy (Udimet(r) 720). Low cycle fatigue testing was conducted on large specimens containing through holes drilled with parameters aimed at creating holes with and without white layer. Initially, Acoustic Emission monitoring technologies were used to monitor for acoustic events associated with crack initiation, however, this technology was deemed unreliable for this testing. Instead, cycles to crack initiation was determined using striation density measurements on each fracture surface to estimate the number of cycles of crack propagation, which was subtracted from the total number of cycles for the specimen. A total of sixteen specimens were tested in this manner. The results suggested that the crack initiation lives of holes machined with good machining parameters were statistically longer than crack initiation lives of holes machined with poor machining parameters. The mean initiation life of the poorly machined specimens was a factor of approximately 2 times shorter than the mean initiation life of the well machined specimens. The holes machined with good machining parameters exhibited subsurface initiations which suggested that no anomalies affected crack initiation for these specimens. It was also shown that some of the poorly machined holes exhibited subsurface initiations rather than initiations at white layer damage. These holes had better surface finish than the poorly machined specimens that did fail at white layer. The mean initiation life of the subsurface initiation holes was 10 times longer than the mean initiation life of the holes that cracked at white layer. Lastly, no apparent correlation between white layer thickness and initiation life was demonstrated in this study. Date: Wednesday, October 31, 2012 Time: 10:30 A.M. Place: HAMP 3153 PURDUE MSE [cid:image003.png@01CDB2A0.580CFC90] Lisa Stacey Secretary/Development Assistant Purdue University School of Materials Engineering 765/494-4100

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