Graduation 2014

Graduation 2014 Photo Gallery

  • Graduation 2014

  • Graduation 2014

  • Graduation 2014

  • Graduation 2014

  • Graduation 2014

  • Graduation 2014

WPI’s 146th Commencement ceremony was held on the campus Quadrangle, on May 17, 2014 where 794 Bachelor of Science degrees, 381 master’s degrees, and 31 PhDs were awarded.  Students, their families and friends, trustees, and special guests were on hand to experience the messages delivered by key note speaker, Bernard Amadei, Founder of Engineers without Borders, Interim President Philip Ryan and WPI President-Elect Laurie Leshin.  During this school year, Materials Science and Engineering 4 students were awarded Doctor of Philosophy degrees and 35 students received their Master of Science degree.

PhD Graduates 2014

 Prof. Richard Sisson & Dr. Danielle Belsito
Prof. Liang & Danielle Belsito
Prof. Diana Lados & Xiang Chen

MS Graduates 2014

Georgios Antoniadis
Frank Bruton
Ziyong Chen
Yi Pan
Anbo Wang
Quiyang Wu
Liu Yang
Yuqing Zhou
Luke Bassett
Xiaoqing Cai
Yi Cui
Hayley Rose Sandgren
Hongze Wang
Xangzi Xu
Yuwei Zhai
Kan Yu (Oct)
Aaron Birt
Dongyu Chai
Jin Liu
Yichao Tang
Pak Hei Wu
Fan Yang
Ling Zhang

MS Thesis Defense

Friction Stir Processing and Welding of Wrough and Cast Aluminum Alloys: Process Optimization and Heat Transfer Modeling

Authors:
Student:  Yi Pan
Advisor:  Prof.  Diana Lados

Abstract:
Friction stir welding and processing (FSW/FSP) are solid-state techniques widely used for joining, localized microstructure/property modifications, and repair of structural components in the aerospace and automotive sectors.  Understanding their effects on the microstructure evolution and mechanical properties of the materials is critical in design for structural integrity.  In this study, four aluminum alloy systems (wrought 6061 and cast A356, 319, and A390 ) were friction stir processed using various processing parameters in both as-fabricated and pre-weld heat treated conditions. A novel 2D heat transfer model was developed to predict weld temperature distributions and their evolution during processing, which further was validated on various combinations of materials and processing conditions. The effects of processing parameters and pre-weld heat treatment on the resulting microstructures, hardness/micro-hardness, and tensile properties of the materials were systematically investigated and mechanistically correlated to morphological changes in the grain structure, characteristic phases, and strengthening precipitates. Tensile tests were performed in room temperature air both along and across the processing zones. Properties of the welds were successfully linked to the microstructural changes in the nugget that were uniquely predicted using the proposed 2D heat transfer model. Optimum processing parameter domains that provide both defect-free welds – evaluated using a new quality index – and good mechanical properties were also determined for each alloy and related to the thermal history of the process. The results of these studies will be presented and discussed, together with recommendations for design and materials/process optimization.

Micro-Fatigue Crack Growth Testing and 3D Characterization of Small Cracks in Ti-6Al-4V Made by Additive Manufacturing Using Synchrotron X-Ray Tomography

Authors:
Student:  Hayley Sandgren
Advisor:  Prof.  Diana Lados  

Abstract:
Additive manufacturing (AM) is a method of building components layer-by-layer using data from 3D models, producing near-net shapes.  By producing components in this manner, energy, cost, material waste, and component lead time are all reduced, and complex parts can be created that would otherwise require unfeasible or expensive processes.  A significant aspect to the study of additive manufactured structural components is developing a fundamental understanding of their fatigue behavior.  Fatigue behavior of a material is controlled by three types of cracks: microstructurally-small, physically-small, and long cracks.  Compared to physically-small and long cracks, microstructurally small cracks are highly impacted by material’s microstructural characteristic features so their behavior is more difficult to characterize.  Small cracks are often observed and studied using the standard replication technique.  Unfortunately, this tedious method only provides information regarding the surface, while cracks may behave differently within the material.  Alternatively, the use of powerful x-rays from a synchrotron allows performing high-resolution tomographic observations of cracks in 3D.  Tomography was used in this study to characterize and mechanistically understand the microstructurally-small fatigue crack growth behavior in Ti-6Al-4V alloys made by Laser Engineered Net Shaping (LENS).  LENS is an AM technique that demonstrated good compatibility with Ti alloys and great potential for fabrication of structural components, especially for the aerospace sector.  Tomographic results combined with optical and scanning electron microscopy enabled a complete characterization of microstructurally-small fatigue crack growth in the studied material, and provides a new basis for material/component design and optimization for fatigue resistance.

A Microstructure Evolution, Static and Dynamic Properties, and Damage Mechanisms in Ti-6Al-4V Manufactured by Additive Manufacturing

Authors:
Student:  Yuwei  Zhai
Advisor:  Prof.  Diana Lados  

Abstract:
Additive manufacturing (AM) refers to an advanced technology used for the layer-by-layer fabrication of three-dimensional near-net-shaped functional components directly from computer models, using unit materials.  The fundamentals and working principle offer AM several advantages compared with traditional processes such as subtractive machining, casting, forging, and powder metallurgy.  These include superior design and geometrical flexibility, innovative multi-material fabrication, reduced tooling and fixturing, shorter cycle time for design and manufacturing, instant local production at a global scale, and material, energy, and cost efficiency.  Laser Engineered Net Shaping (LENS) is a powder-based AM technique that is able to fabricate fully-dense and defect-free metallic components, and is especially compatible with Ti alloys.  This makes LENS a promising technique for critical applications, especially in the aerospace field.  However, applying LENS to structural aerospace components requires the optimization of the processing conditions, as well as a fundamental understanding of the microstructure evolution and static and dynamic properties of the LENS-fabricated materials.  In this study, Ti-6Al-4V parts were produced using two LENS fabrication conditions in order to determine the effects of processing parameters on microstructure, hardness, and tensile properties of the material.  In addition, long and microstructurally-small room temperature fatigue crack growth tests were also performed using two stress ratios, R = 0.1 and 0.8, to establish the crack growth mechanisms at various stages and in various orientations with respect to the layer deposition direction.  The effects of post-LENS heat treatment on microstructure and properties of the alloy were also investigated.  These results will be systematically presented and discussed, together with guidelines for material and process design and optimization for fatigue-critical applications.

PhD Dissertations

Application of Computational Thermodynamic and Solidification Kinetics to Cold Sprayable Powder Alloy Design

Authors:
Student:  Danielle Belsito
Advisor:  Prof. Richard D. Sisson, Jr.  

Abstract:
Military aircraft that require high maneuverability, durability, ballistic protection, reparability, and energy efficiency require structural alloys with low density, high toughness, and high strength. Also, repairs to these aircraft demand a production process that has the flexibility to be relatively in-situ with the same high-performance output.  Materials produced by the cold spray process, a thermo-mechanical powder consolidation technique, meet many of the requirements.

In accordance with President Obama’s 2011 Materials Genome Initiative, the focus of this effort is to design customized aluminum alloy powders which exploit the unique behavior and properties of the materials created by the cold spray process. Analytical and computational models are used to customize microchemistry, thermal conditioning, and solidification behavior by predicting equilibrium and non-equilibrium microstructure and resulting materials properties and performance. Thermodynamic, kinetic, and solidification models are used, including commercial software packages Thermo-Calc, Pandat™, and JMatPro®, and TC-PRISMA.

A Novel Methodology for Evaluating Hot Compressive Dwell Effects on Fatigue Crack Growth and Optimizing Materials' Microstructures for High Temperature Applications

Authors:
Student:  Xiang Chen
Advisor:  Prof. Diana Lados  

Abstract:
It has been reported that the number of motor vehicles has reached 256 million in the U.S. in 2008.  The engine is the “soul of a vehicle”, and the costs of replacing a malfunctioning engine can easily reach $2,000.  Thus, two important questions arise: 1. How long can an engine last? and 2. How can an engine do better?  This research is aimed to answer both questions.  Regarding the first question, a novel quantitative physics-based model was developed to predict the life of an engine in actual operating conditions.  Every engine experiences in service periodic Hot Compressive Dwell (HCD) conditions of creep-fatigue.  In HCD, tensile residual stresses build up under compressive loading, accelerating crack initiation and crack propagation in engine components such as the combustion chamber wall.  This phenomenon significantly shortens the service life of an engine, and its effects have been largely ignored in previous studies.  The proposed model takes into account these effects by adding residual stress contributions to the elastic and plastic response of the material to predict fatigue crack growth under HCD conditions.  In contrast with the few existing complex models, this approach is using the simple and well-recognized Paris Law for fatigue crack growth.  To understand and quantify these effects a common automotive engine material, 319 cast Al alloy, was investigated at both room and elevated (250°C) temperatures.  Significant crack acceleration due to compressive dwell was observed at elevated temperature, and the new model was successfully able to predict this behavior.  Regarding the second question, comprehensive SEM and TEM studies were performed to understand creep-fatigue effects at the microstructural scale of the studied alloy, and recommendations will be given for improved microstructures for high temperature applications in the transportation sector.  In addition to performance advantages, this work is expected to contribute to better design and lighter materials for use in high temperature structural applications that will reduce fuel consumption and carbon emissions, and bring important environmental benefits.

Synthesis, Processing and Applications of Carbonaceous Nanomaterials

Authors:
Student:  Yuqin Yao
Advisor:  Prof. Jianyu Liang      

Abstract:
Carbon is one of the most abundant non-metal elements in the world. The unique arrangement of electrons enables diverse properties and applications of carbon. Long before the discovery of C60 in 1985, which is now considered a milestone in the vibrant field of carbon nanotechnology, carbon has been a vital part of human history. It has been a key enabling material in many fields including aerospace, transportation, energy storage, electric devices, infrared sensors, etc. The report of fullerene triggered a feverish surge of interest and effort in the study of nanostructured carbon. Along with the discovery of carbon nanotubes (CNTs) and graphene nanosheets (GNS), the nanocarbon family has been extensively studied. However, controlled production of carbon nanomaterials with low cost and high efficiency and incorporation of nanocarbon to maximize their contribution in advanced applications still faces a lot of technical difficulties.

The objective of this work is to study and optimize processes to synthesize multiwall carbon nanotubes (MWCNTs) and GNS, and to apply GNS in nano-composite anode materials for Lithium ion batteries (LIBs). Therefore, in this thesis, there are three main parts: (1) development of the post-processing method to obtain free-standing CNT arrays by the template-assisted chemical vapor deposition (CVD) method; (2) development of a synthesis protocol to obtain GNS by oxidation of natural graphite flakes and reduction of the resulted graphene oxides; and (3) fabrication of TiO2/GNS in core-shell structure by a static electric assembling method to improve anode performance for LIB applications.

Metal Recovery via Automated Sortation

Authors:
Student:  Hao Yu
Advisor:  Prof. Diran Apelian

Abstract:
Each year, millions of tons of nonferrous metals are discarded in US. These metals are wasted due to the lack of proper recovery methods. Recent developments in spectroscopic technology have enabled us to identify the waste composition in real time. This opens the door for high-speed automated metal sortation and recovery, especially for the recovery of high value precious metals, such as Ti, Ni, Co, Mo and Ta.  

Automated sortation system includes three main phases: (i) feeding of material, (ii) composition identification and (iii) physical separation. For precious metals, because of low volume and industry fragmentation, high strength metals exist in the form of chips, usually smaller than 10 mm, therefore it is extremely difficult to introduce metals chips individually onto the sorting system.  

At CR3, we have invented and developed a novel feeding mechanism to provide single layer feeding of small metal chips. A lab-scale prototype was built and proven to be feasible, scalable and reliable. A model was developed to predict the output of feeding variables based on initial input parameters. An operation window of the process was also defined for various metal chip resources. These will be presented, reviewed, and discussed.

 
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PhD Graduates

Unable to Attend Commencement
Yuqin Yao (Feb)
Hao Yu

Attended Commencement
Danielle Belsito (Feb)
Xiang Chen

Masters Graduates

Unable to Attend Commencement
Qihao Guo
Meinan He (Oct)
Wenhuan Li (Oct)
Yun Lu (Oct)
Michael Scanlon (Feb)
Mohan Su (Oct)
Shu Su (Feb)
Kun Wang (Oct)
Di Wu (Oct)
Yuan Xie (Oct)
Xiaomeng Xu (Oct)
Kan Yu (Oct)
Xiang Zhou (Oct) 

Attended Commencement
Georgios Antoniadis
Luke Bassett
Aaron Birt
Frank Bruton
Xiaoqing Cai
Dongyu Chai
Ziyong Chen (Feb)
Yi Cui
Jin Liu
Yi Pan
Hayley Rose Sandgren
Yichao Tang
Anbo Wang
Hongze Wang
Pak Hei Wu
Quiyang Wu
Xangzi Xu (Feb)
Fan Yang (Feb)
Liu Yang
Yuwei Zhai
Ling Zhang
Yuqing Zhou