Open Access. Powered by Scholars. Published by Universities.®

Mechanical Engineering Commons

Open Access. Powered by Scholars. Published by Universities.®

Articles 1 - 12 of 12

Full-Text Articles in Mechanical Engineering

Overcoming Fatigue Through Compression For Advanced Elastocaloric Cooling, Huilong Hou, Jun Cui, Suxin Qian, David Catalini, Yunho Hwang, Reinhard Radermacher, Ichiro Takeuchi Apr 2018

Overcoming Fatigue Through Compression For Advanced Elastocaloric Cooling, Huilong Hou, Jun Cui, Suxin Qian, David Catalini, Yunho Hwang, Reinhard Radermacher, Ichiro Takeuchi

Ames Laboratory Accepted Manuscripts

Elastocaloric materials exhibit extraordinary cooling potential, but the repetition of cyclic mechanical loadings during long-term operation of cooling systems requires the refrigerant material to have long fatigue life. This article reviews the fundamental cause of fatigue from aspects of initiation and propagation of fatigue cracks in shape-memory alloys (SMAs) that are used as elastocaloric materials, and highlights recent advances in using compression to overcome fatigue by curtailing the generation of surfaces associated with crack propagation. Compression is identified as a key means to extend fatigue lifetime in engineering design of elastocaloric cooling drive mechanisms. We summarize the state-of-the-art performance of ...


Synergistic Effects Of Processing And Nanofiber Reinforcement On The Mechanical And Ferroelectric Performance Of Geopolymer Matrix Composites, Akm S. Rahman, Muhammad E. Hossain, Donald W. Radford Jun 2017

Synergistic Effects Of Processing And Nanofiber Reinforcement On The Mechanical And Ferroelectric Performance Of Geopolymer Matrix Composites, Akm S. Rahman, Muhammad E. Hossain, Donald W. Radford

Publications and Research

tThis study involved the evaluation of mechanical and ferroelectric properties of a new classof nanofiller infused inorganic polymer (geopolymer, GP). To evaluate the mechanical per-formance, compressive strength and fracture resistance of neat and nanofillers infused GPwere studied at various treatment temperatures. It was found that, addition of 5 vol% alu-mina nanofiber (ANF), increased compressive strength and modulus by over 30% and 60%,respectively, while it increased fracture toughness (KIC) by over 60% compared to the baselinespecimens. Simultaneously, ferroelectric properties were investigated at various treatmenttemperatures (250◦C, 650◦C and 870◦C). Remarkably, higher ferroelectric hysteresis wasobserved with the GP treated ...


Temperature Filed Numerical Simulation Of Laser Welding For Ta15 Titanium Alloy By Coupling Thermal And Phase Transformation, Wenmin Ou, Yanhong Wei, Xiaohong Zhan, Gaoyang Mi Oct 2016

Temperature Filed Numerical Simulation Of Laser Welding For Ta15 Titanium Alloy By Coupling Thermal And Phase Transformation, Wenmin Ou, Yanhong Wei, Xiaohong Zhan, Gaoyang Mi

The 8th International Conference on Physical and Numerical Simulation of Materials Processing

No abstract provided.


Bi2O3-Y2O3-Ceo2 Solid Solution Oxide-Ion Electrolyte, Kevin Huang, Man Feng, John Goodenough Feb 2015

Bi2O3-Y2O3-Ceo2 Solid Solution Oxide-Ion Electrolyte, Kevin Huang, Man Feng, John Goodenough

Kevin Huang

No abstract provided.


The Mechanism Governing Cutting Of Hard Materials With Hybrid Laser/Waterjet System Through Controlled Fracture, Zhuoru Wu Jan 2015

The Mechanism Governing Cutting Of Hard Materials With Hybrid Laser/Waterjet System Through Controlled Fracture, Zhuoru Wu

Graduate Theses and Dissertations

Ceramics are generally difficult to machine due to their inherent natures of high hardness and low toughness. The present dissertation investigated the mechanism governing cutting of hard ceramic materials with a novel hybrid CO2-Laser/Waterjet (LWJ) system through controlled fracture propagation. It has been proved that the hybrid machining method is more efficient and is capable of providing high quality cutting that overcomes the major drawbacks with current machining techniques including EDM and Nd:YAG laser. The LWJ method implements a high power laser heating followed by low pressure waterjet quenching which subsequently dictates fracture initiation and propagation along the ...


A Study To Evaluate Non-Uniform Phase Maps In Shape Memory Alloys Using Finite Element Method, Naren Motte Jan 2015

A Study To Evaluate Non-Uniform Phase Maps In Shape Memory Alloys Using Finite Element Method, Naren Motte

Theses and Dissertations

The unique thermo-mechanical behavior of Shape Memory Alloys (SMAs), such as their ability to recover the original shape upon heating or being able to tolerate large deformations without undergoing plastic transformations, makes them a good choice for actuators.

This work studies their application in the aerospace and defense industries where SMA components can serve as release mechanisms for gates of enclosures that have to be deployed remotely. This work provides a novel approach in evaluating the stress and heat induced change of phase in a SMA, in terms of the transformation strain tensor. In particular, the FEA tool

ANSYS has ...


Surface Engineering For Phase Change Heat Transfer: A Review, Daniel Attinger, Amy R. Betz, Thomas M. Schutzuis, Ranjan Ganguly, Arindam Das, Chang-Jin Kim, Constantine M. Megaridis Nov 2014

Surface Engineering For Phase Change Heat Transfer: A Review, Daniel Attinger, Amy R. Betz, Thomas M. Schutzuis, Ranjan Ganguly, Arindam Das, Chang-Jin Kim, Constantine M. Megaridis

Mechanical Engineering Publications

Owing to advances in micro- and nanofabrication methods over the last two decades, the degree of sophistication with which solid surfaces can be engineered today has caused a resurgence of interest in the topic of engineering surfaces for phase change heat transfer. This review aims at bridging the gap between the material sciences and heat transfer communities. It makes the argument that optimum surfaces need to address the specificities of phase change heat transfer in the way that a key matches its lock. This calls for the design and fabrication of adaptive surfaces with multiscale textures and non-uniform wettability.

Among ...


Surface Modification Of Aluminum Alloys By Plasma Electrolytic Oxidation, Vahid Dehnavi Aug 2014

Surface Modification Of Aluminum Alloys By Plasma Electrolytic Oxidation, Vahid Dehnavi

Electronic Thesis and Dissertation Repository

Plasma Electrolytic Oxidation (PEO) is a surface treatment for the production of ceramic oxide coatings with great properties, such as high wear and corrosion resistance, on metal substrates, particularly aluminum and magnesium alloys. Formation of PEO coatings involves complex processes and mechanisms that are difficult to study. Currently, the PEO process is in a transition phase from research to commercial application, with a primary focus on the corrosion and wear protection of light alloys, and has recently generated interest as a promising surface treatment for biomedical applications.

To justify the industrial application of PEO, a more systematic and in-depth study ...


The Mechanism Governing Cutting Of Polycrystalline Cubic Boron Nitride (Pcbn) Tool Blanks With Phase Transformation Induced Fracture, Zhuoru Wu Jan 2013

The Mechanism Governing Cutting Of Polycrystalline Cubic Boron Nitride (Pcbn) Tool Blanks With Phase Transformation Induced Fracture, Zhuoru Wu

Graduate Theses and Dissertations

The thesis presents a combined experimental and computational investigation of a novel thermochemical material removal mechanism for cutting of polycrystalline cubic boron nitride (PCBN) substrates through controlled crack propagation. The CO2-Laser/Waterjet machining system developed by the Iowa State University's Laboratory for Lasers, MEMS, and Nanotechnology was utilized to achieve specimen cutting. It has been proved that the hybrid machining method is more efficiency and able to provide high quality cutting that overcomes the major drawbacks with current EDM and Nd:YAG laser machining techniques. The LWJ method implemented a high power laser heating followed by low pressure waterjet ...


Phase Field Approach For Melting Of Aluminum Nanoparticles, Kamran Samani Jan 2013

Phase Field Approach For Melting Of Aluminum Nanoparticles, Kamran Samani

Graduate Theses and Dissertations

Aluminum nanoparticles are of interest due to the variety of their applications, including additives for plastics and powder metallurgy. They can also enhance the burning rate of propellants. Metallic particles in traditional thermites are in the micron size range. When the particle diameter reduces to the nanometer range, their reactivity increases by several orders of magnitude. Thus flame rates of 0.9-1 km/s can be reached, while for micron size thermites they are on the order of centimeters or meters per second. Ignition delay time also decreases by up to three orders of magnitude.

The two main continuum methods ...


Microstructural Evaluation In Friction Stir Welded High Strength Low Alloy Steels, Majid Abbasi Gharacheh Nov 2011

Microstructural Evaluation In Friction Stir Welded High Strength Low Alloy Steels, Majid Abbasi Gharacheh

Theses and Dissertations

Understanding microstructural evolution in Friction Stir Welding (FSW) of steels is essential in order to understand and optimize the process. Ferritic steels undergo an allotropic phase transformation. This makes microstructural evolution study very challenging. An approach based on Electron Backscattered Diffraction (EBSD) and phase transformation orientation relationships is introduced to reconstruct pre-transformed grain structure and texture. Reconstructed pre-transformed and post-transformed grain structures and textures were investigated in order to understand microstructural evolution. Texture results show that there is evidence of shear deformation as well as recrystallization in the reconstructed prior austenite. Room temperature ferrite exhibits well-defined shear deformation texture components ...


Fem Modeling Of Induction Hardening Processes In Steel, J. Yuan, J. Kang, Yiming Rong, Richard D. Sisson Jr. Oct 2003

Fem Modeling Of Induction Hardening Processes In Steel, J. Yuan, J. Kang, Yiming Rong, Richard D. Sisson Jr.

Mechanical Engineering Faculty Publications

A modeling system for analyzing the integrated induction hardening processes was developed based on a general-purpose finite element program, with the capability to analyze the whole process from electromagnetic-induced thermal heating to final hardening. A coupled electromagnetic-thermal model was applied to study the induction heating process, which includes consideration of nonlinear material characteristics on temperature. Also, arrangement of AC current density distribution was conducted to simulate practical induction coil structure and magnetic concentrator effects to achieve desired heating patterns for later quenching and hardening analysis. Quenching analysis can provide cooling curve at any location in a heat-treated workpiece based on ...