Blair London

The Mechanical and Thick Section Bending Behavior of Friction Stir Processed Aluminum Plate

D. Hilbert et al. — Thu, 26 Aug 2010 17:40:57 PDT

Friction stir processing (FSP) 2519-T87 aluminum plate results in enhanced ductility, 25% strain at fracture. However, the yield strength in the FSP zone drops to 175 MPa from ~400 MPa. Actively cooling the plate during FSP increases the yield strength to 185 MPa and decreases ductility to 20% strain at fracture. Thick bending of a plate of the alloy was demonstrated after the surface was subjected to FSP.

Use of Friction Stir Processing and Friction Stir Welding For Nitinol Medical Devices

Blair London et al. — Thu, 26 Aug 2010 17:40:57 PDT

Metallic materials may be joined utilizing a friction stir processing technique. The friction stir processing technique utilizes a shaped, rotating tool to move material from one side of the joint to be welded to the other without liquefying the base material.

Peak Stir Zone Temperatures during Friction Stir Processing

Sprinivasan Swaminathan et al. — Thu, 26 Aug 2010 17:40:56 PDT

The stir zone (SZ) temperature cycle was measured during the friction stir processing (FSP) of NiAl bronze plates. The FSP was conducted using a tool design with a smooth concave shoulder and a 12.7-mm step-spiral pin. Temperature sensing was accomplished using sheathed thermocouples embedded in the tool path within the plates, while simultaneous optical pyrometry measurements of surface temperatures were also obtained. Peak SZ temperatures were 990 ⁰Cto 1015 ⁰C (0.90 to 0.97 TMelt) and were not affected by preheating to 400⁰C, although the dwell time above 900 ⁰C was increased by the preheating. Thermocouple data suggested little variation in peak temperature across the SZ, although thermocouples initially located on the advancing sides and at the centerlines of the tool traverses were displaced to the retreating sides, precluding direct assessment of the temperature variation across the SZ. Microstructure-based estimates of local peak SZ temperatures have been made on these and on other similarly processed materials. Altogether, the peak-temperature determinations from these different measurement techniques are in close agreement.

Investigation of Subcritical Fatigue Crack Growth in Gamma Titanium Aluminides

Blair London — Thu, 26 Aug 2010 17:40:55 PDT

Our titanium aluminide alloy was readily heat treated to a fully lamellar state by holding at 1345C for 1.5 hours and furnace cooling resulting in a grain size of 330 muon m. The yield stress, ultimate stress, and total elongation were 315MPa, 465MPa, and 0.46% respectively. The fully lamellar microstructure shows significant work hardening. No long cracks initiated at R=0.1 and variation max=300MPa with up to 1.4 million cycles.

Heat Treatment of Gamma Titanium Aluminide Alloys

Thomas J. Kelly et al. — Thu, 26 Aug 2010 17:40:55 PDT

A gamma titanium aluminide alloy article, is prepared using a piece of a gamma titanium aluminide alloy having a composition capable of forming alpha, alpha-2, and gamma phases. The alpha transus temperature of the gamma titanium aluminide alloy piece is determined. The gamma titanium aluminide alloy piece is consolidated by hot isostatic pressing at a temperature of from about 50 F. to about 250 F. below the alpha transus temperature and at a pressure of from about 10,000 to about 30,000 pounds per square inch, for a duration of from about 1 to about 20 hours. The piece is heat treated at a temperature of from about 5 F. to about 300 F. below the alpha transus temperature for a time sufficient to refine the microstructure and generate a microstructure comprising from about 10 to about 90 volume percent gamma phase. The step of heat treating is conducted at a temperature of from about 45 F. to about 200 F. above the temperature of the step of hot isostatic pressing.

Evidence of Heterogeneous Substructure Development During Primary Creep of Ti-6Al-2Sn-4Zr-2Mo

R. W. Hayes et al. — Thu, 26 Aug 2010 17:40:55 PDT

No Abstract.

Steady-State Creep Deformation of Investment Cast Near-Gamma Titanium Aluminide

D. A. Wheeler et al. — Thu, 26 Aug 2010 17:40:54 PDT

No Abstract.

New Specimen Design for Studying the Growth of Small Fatigue Cracks with Surface Acoustic Waves

Blair London — Thu, 26 Aug 2010 17:40:54 PDT

The study of small surface fatigue cracks in AISI 4140 quenched and tempered steel by a nondestructive surface acoustic wave technique is summarized. A novel cantilevered bending, plate-type fatigue specimen is described that is compatible with the acoustic method. Small cracks are initiated from a 25-μm deep surface pit produced by an electrospark machine. The importance of studying these

Work in Progress: The Five Basic “Positions” of Engineering

Blair London et al. — Thu, 26 Aug 2010 17:40:53 PDT

Classical ballet technique relies on mastery of the five basic positions of the feet. Every movement in classical ballet goes through one or more of these positions. The positions are practiced in class, used in choreography, and become second nature in performance on stage. Engineering may have a similar context. These engineering “positions” are not just the foundational coursework leading up to an engineering degree such as mathematics, chemistry, or physics. Rather, the positions are aspects of engineering that a practicing engineer routinely does to successfully perform as engineers. The engineering positions discussed are: question, analyze, team, write, and speak. We believe these positions need to be included and practiced in engineering classes because they are the essence of engineering practice and performance.

Work in Progress – Classical Ballet Structure and Practice Applied to Engineering Class Sessions

Blair London et al. — Thu, 26 Aug 2010 17:40:53 PDT

Classical ballet classes have a universal structure that fosters active in-class learning. This structure creates a safe environment for students to try, fail, be corrected, and succeed. Engineering classes lack a common structure; most learning in engineering occurs outside of class. Engineering classes could move toward adopting a similar structure to ballet to improve in-class learning and mirror engineering culture and practice. The paper describes aspects of ballet class structure and practices that work and how these can apply to engineering classes. A new engineering class session structure is presented following the ballet model where engineering students are motivated to participate and learn during the class.

The Ballet Model in Engineering Classes – What Works, What Doesn't, and What's New

Blair London et al. — Thu, 26 Aug 2010 17:40:52 PDT

Six different engineering courses were taught using aspects of the classical ballet instruction model in organization, teaching methods, and learning strategies. There was a strong focus on performance. The courses spanned sophomore to senior levels. Some aspects of the ballet model worked well: setting rules for the Sacred Space for learning, the beginning activity (“stretch”), the overall organization of the class session, communicating the known ideal, including historical background, and using demonstrations. Some aspects did not work (thus far): exams are not yet performances on stage, little practice or rehearsal occurs, little competition between students occurs, asking students questions in class is uncomfortable, and many students do not want to be in class. New ideas presented include “casting” for exams and highlighting the role of repetition in learning. It was deemed worthwhile to apply the performing arts model to foster increased learning during engineering class.

On the Creep Deformation of a Cast Near Gamma TiAl Alloy Ti-48Al-1Nb

R. W. Hayes et al. — Thu, 26 Aug 2010 17:40:52 PDT

The steady-state creep deformation behavior of a cast two phase gamma TiAl alloy having the composition Ti---48Al---1Nb (at.%) has been studied. Tension creep tests using the stress increment technique (θθ2θ3) were conducted over the temperature range of 704–850°C at constant initial applied stress level of 103.4–241.3 MPa. The activation energy for creep over the temperature and stress regime of this study varied 317.5 kJ/mol (137.8 MPa) up to 341.0 kJ/mol (206.8 MPa) with an average value of 326.4 kJ/mol. This is well within the range of values previously measured for gamma TiAl alloys where creep controlled by volume diffusion has been suggested as rate controlling. The stress exponents meaured were 5.0 at 704°C, 4.9 at 750°C, 4.7 at 800°C and 4.46 at 850°C. Using the activation energy of 326.4 kJ/mol, the temperature compensated steady-state creep rate was plotted against long stress with all temperatures collapsing onto a single line having a slope equal to 4.95. Using conventional creep analysis, this value of the stress exponent can be taken as suggestive of dislocation climb controlled power law creep as the operative deformation mechanism within the stress and temperature regime of the present study. The boundary separating the lamellar grains in two phase gamma TiAl alloys having the duplex microstructure may be a very important aspect of this microstructure with respect to creep deformation resistance. The interlocking γ/α2 laths making up these boundaries are expected to be very resistant to grain boundary sliding which may contribute to creep deformation in the dislocation creep regime. Finally, some previous observations along with a comparison of the creep behavior of the Ti---48Al---1Nb alloy to that of a Tiz.sbnd;50.3Al binary have been discussed in terms of the pre-exponential constant A in the power law creep equation. TiAl alloys having similar stress and temperature dependencies but differing steady-state strain rates over comparable stress-temperature regimes may be rationalized on the basis of differing power law creep constants which may reflect differences in stacking fault energies.

Cultivating Graduate Students: Techniques to Inspire Effective Research

David Braun et al. — Tue, 17 Mar 2009 10:19:02 PDT

Each year, U.S. institutions grant well over 10,000 bachelor's degrees in science and engineering. However, only a small fraction of those students pursue graduate study. Many who do often experience great difficulty partly due to a lack of preparation for research: the nature of research is inherently foreign to those who are accustomed to studying course material and demonstrating their mastery of it by passing an exam. Carefully involving undergraduates in research can be an effective means for inspiring students to pursue graduate study. We have found that one can create a positive research experience for the student by implementing simple techniques. In this presentation, we present these practical techniques which include: Defining a manageable undergraduate research project; marketing the project to undergraduates; enabling effective record keeping in laboratory notebooks; focusing and directing research through efficient experimental designs. Along with these techniques, we will present examples-taken mainly from our Polymer Electronics Laboratory. We will also present the inherent pitfalls associated with these techniques.

Travelogue from the Materials World: A First Week Laboratory Activity

Katherine C. Chen et al. — Mon, 10 Nov 2008 15:09:35 PST

A fun, yet educational, laboratory activity was developed for the first week of an introductory Materials Engineering laboratory in order to set the stage for the rest of the quarter. The class is broken up into 8 teams, and each team performs a different experiment during each lab period. The teams then rotate lab experiments each week in a round robin manner, and thus teamwork is an important component of the class. In order to quickly promote team bonding the very first week, each team goes on a materials scavenger hunt together. A variety of materials-related items are to be found around the campus, and various questions must be answered for each item. In addition, each scavenger hunt item is photographed with a Polaroid I-zone camera that produces sticker pictures. While the students work together, they are also being exposed to several materials engineering concepts (many of which will be covered in the lab). The students realize the impact of materials in their daily lives and in the world around them through this activity. The relatively inexpensive lab activity can be easily modified to suit the needs of different instructors. The assignment, procedures, and assessment of the lab activity will be discussed.

Work in Progress: Crossing the Engineering Border into Art and Society with a Materials Selection for the Life Cycle Course

Katherine C. Chen et al. — Mon, 10 Nov 2008 15:09:31 PST

A new course in materials engineering has been developed to incorporate industrial design and sustainability principles. Many current engineering tasks require the ability to comprehend and consider the complicated interplay of technology with the environment and society. Thus the changing skill set required of future engineers is being reflected in the changes with our courses. We are stepping beyond the traditional boundaries of engineering courses to present a more holistic approach to problem solving. The use of materials and processing techniques is applied to product design, and thus involves consideration of the end user and the end of product life. Green engineering and cradle to cradle design principles are also introduced in the course. Outcomes for this class include students being able to employ systems thinking, to formulate creative design solutions, and to select the appropriate materials and processing for minimal environmental impact.

Converting Traditional Materials Labs to Project-based Learning Experiences: Aiding Students' Development of Higher-order Cognitive Skills

Linda Vanasupa et al. — Mon, 10 Nov 2008 15:09:28 PST

Against a backdrop of compelling societal needs, graduates in science and engineering now must master their disciplines and demonstrate a sophisticated level of cognitive, affective and social development. This has lead a number of national and international commissions on science and engineering to urge educators to re-think the way in which STEM disciplines are taught. We have chosen to "repackage" a traditional undergraduate materials engineering curriculum in a form designed to promote the development of higher-order cognitive skills like self-directed learning and design. Classic metallurgy experiments have been converted to project-based learning experiences where students are put in the role of "designers" of problem solutions and faculty play the role of coaches. These include: designing, prototyping and marketing of a cast metal object; systems designing, building and testing of a fiber optic spectrometer; product improvement of a prosthetic device; evaluation of oxidation process for production; design and evaluation of a heat treatment process for roller bearings; and materials characterization of an everyday product. Projects were designed to leverage known relationships within the educational psychology literature that enable deeper learning. Evaluation of 36 juniors in a project-based learning course (i.e., the test cohort) against a quasi-control group in traditional engineering courses showed that the test cohort scored significantly higher on two motivation scales shown to be critical components in self-directed learning (p<0.001). The test cohort also reported a significantly higher use of peers as learning resources than the quasi-control group. Their motivation scores also correlate highly with self-reported comfort with several aspects of design, implying that their motivation contributes significantly to students' ability to effectively engage in the design process. In this paper, we present examples of the materials engineering projects that were designed and implemented, and the design features that enable them to promote the development of sophisticated cognitive functioning.

The Foundation Series on Corrosion: Integrating Science, Math, Engineering & Technology in a Lab Setting

Linda Vanasupa et al. — Mon, 10 Nov 2008 15:09:24 PST

We have developed a laboratory module focusing on the subject of corrosion. The module itself is designed to be completed in one three-hour session. It consists of three parts: I. The Impact of Corrosion Media, II. The Impact of Corroding Materials, III. The Impact of Anode/Cathode Sizes. Our objectives in developing this module were to address the need for clear bridges between math, science and technology in the engineering curriculum and to provide a means of faculty development primarily at community colleges. As a result, it was designed to allow the engineering student to experience the synergy of science, math and engineering technology in a laboratory setting. Recent findings in learning theory research were used in the design of the module to reach students of diverse learning styles. Our targeted audience is sophomore engineering majors at community colleges and institutions without Materials Science and Engineering programs. In this paper we will present the module, its goals, objectives and performance criteria, and the preliminary results of its implementation.

Curricula to Educate the 2020 MSE Engineering Professional: Simple But Powerful Changes in the Way that MSE is Taught

Linda Vanasupa et al. — Mon, 10 Nov 2008 15:09:21 PST

National leaders in science and technology sectors speak in unison as they call for engineers who are not only technically competent in their fields, but who possess the abilities to communicate well, to work on teams, to apply systems thinking, to operate in the global business environment, to design within a greater set of constraints (environmental, health and safety, sustainability, economic, societal, political, manufacturability, and ethical). In short, our challenge is to educate an engineering professional who is far more sophisticated than the engineer of the 20^th century. Additionally, challenges brought on by the overuse of natural resources put a special responsibility on materials science and engineering (MSE) faculty, whose role it is to assist in shaping the MSE profession. How can faculty deliver relevant curricula for the MSE engineering professional in an already crowded curriculum? Certainly curricular content must be up-to-date. However, a number of the goals can be met through changing the way in which the curriculum is delivered. In particular, we have emphasized mastery at the lower levels to increase retention, and implemented a number of learning “best practices”. Our preliminary results are promising: within one year, we were able to reverse a five-year trend in declining enrollment; we have just finished our fourth consecutive year of 100% on-time completions of senior projects; students exhibit a shift in mindset towards a greater awareness of their professional responsibility to serve humanity. In this paper, we will provide a survey of the techniques that we have used along with some preliminary results from our program.

Infusing the Materials Engineering Curriculum with Sustainability Principles

Katherine C. Chen et al. — Mon, 10 Nov 2008 15:09:17 PST

In order to better prepare our students for the complex, global world outside the confines of the university, we have been making concerted efforts to incorporate sustainability principles (i.e., balance of economics, society, and environment) within the materials engineering curriculum at California Polytechnic (Cal Poly) State University. Many future engineering tasks will require the understanding of complicated interplays of technology with the environment and society. In addition, energy demands and dwindling natural resources have emerged as significant challenges for scientists and engineers. The materials engineer has great opportunity to help devise sustainable solutions through appropriate materials selection and processing, and our faculty has been trying to convey such ideas and skills to our students.

Many different sustainability activities and assignments have been woven into several of our materials engineering courses. Some activities are to promote awareness and to give motivation for our students to use their engineering skills for the betterment of society and the planet. Pertinent articles from popular media sources have been used as the basis for reflection exercises and to stimulate student discussions. A freshmen design course has been developed to highlight sustainability through service learning. In addition, we have used software tools (CES Eco-selector) to quantitatively assess the environmental impact due to particular materials selection and processing techniques. Several different pedagogical techniques have been employed for these different activities.