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- Coal (2)
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- Atom-probe tomography (1)
- Char (1)
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- Degradation function; Porosity; Damage; Ductile fracture; Strain-rate dependence (1)
- Direct quadrature method of moments (DQMoM) (1)
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- Multicomponent droplet vaporization (1)
- Nickel alloys (1)
- PDF method (1)
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Articles 1 - 10 of 10
Full-Text Articles in Engineering
Experimental And Modeling Study Of Compressive Creep In 3d-Woven Ni-Based Superalloys, Hoon-Hwe Cho, Dinc Erdeniz, Keith W. Sharp, David C. Dunand
Experimental And Modeling Study Of Compressive Creep In 3d-Woven Ni-Based Superalloys, Hoon-Hwe Cho, Dinc Erdeniz, Keith W. Sharp, David C. Dunand
Mechanical Engineering Faculty Research and Publications
Micro-architectured Ni-based superalloy structures, with Ni-20Cr-3Ti-2Al (wt.%) composition and γ/γ′-microstructure, are created by a multi-step process: (i) non-crimp orthogonal 3D-weaving of ductile, 202 μm diameter Ni-20%Cr wires, (ii) gas-phase alloying with Al and Ti, (iii) simultaneous transient-liquid phase (TLP) bonding between wires and homogenization within wires via interdiffusion, (iv) solutionizing to create a single-phase solid solution, and (v) aging to precipitate the γ′ phase. The creep behavior of these 3D-woven γ/γ′ nickel-based superalloys is studied under uniaxial compression via experiments at 825 °C and via finite element (FE) analysis, using a 3D model of the woven structures obtained …
Pore-Resolving Simulation Of Char Particle Gasification Using Micro-Ct, Greg Hingwah Fong, Scott Jorgensen, Simcha L. Singer
Pore-Resolving Simulation Of Char Particle Gasification Using Micro-Ct, Greg Hingwah Fong, Scott Jorgensen, Simcha L. Singer
Mechanical Engineering Faculty Research and Publications
Understanding the interaction between transport, reaction and morphology at the scale of individual char particles is important for optimizing solid fuel gasification and combustion processes. However, most particle-scale models treat porous char particles as an effective porous continuum, even though the presence of large, irregular macropores, voids and fractures render such upscaled treatments mathematically invalid, and the models non-predictive. A new modeling framework is therefore proposed to elucidate the impact of morphology on char particle gasification and combustion. A pore-resolving, transient, three-dimensional simulation for gasification of a realistic coal char particle is developed based on X-ray micro-computed tomography (micro-CT). The …
Effects Of Nb And Ta Additions On The Strength And Coarsening Resistance Of Precipitation-Strengthened Al-Zr-Sc-Er-Si Alloys, Dinc Erdeniz, Anthony De Luca, David N. Seidman, David C. Dunand
Effects Of Nb And Ta Additions On The Strength And Coarsening Resistance Of Precipitation-Strengthened Al-Zr-Sc-Er-Si Alloys, Dinc Erdeniz, Anthony De Luca, David N. Seidman, David C. Dunand
Mechanical Engineering Faculty Research and Publications
A dilute Al-0.07Zr-0.02Sc-0.005Er-0.06Si (at.%) alloy was microalloyed with 0.08 at.% Nb or Ta. Atom-probe tomography reveals that, upon aging, Nb and Ta partition to the coherent L12-Al3(Zr,Sc,Er) nanoprecipitates (with average concentrations of 0.2 and 0.08 at.%, respectively), with both segregating at the matrix/nanoprecipitate heterophase interface. This is consistent with the Nb- and Ta-modified alloys exhibiting, as compared to the unmodified alloy: (i) higher peak microhardness, from a higher nanoprecipitate volume fraction and/or latticeparameter mismatch; and (ii) improved aging resistance, from slower nanoprecipitate coarsening due to the small diffusivities of niobium and tantalum in aluminum. Analogous results …
Soot And Spectral Radiation Modeling For High-Pressure Turbulent Spray Flames, Sebastian Ferreyro Fernandez, C. Paul, A. Sircar, A. Imren, D. C. Haworth, Somesh Roy, Michael F. Modest
Soot And Spectral Radiation Modeling For High-Pressure Turbulent Spray Flames, Sebastian Ferreyro Fernandez, C. Paul, A. Sircar, A. Imren, D. C. Haworth, Somesh Roy, Michael F. Modest
Mechanical Engineering Faculty Research and Publications
A transported probability density function (PDF) method and a photon Monte Carlo/line-by-line (PMC/LBL) spectral model are exercised to generate physical insight into soot processes and spectral radiation characteristics in transient high-pressure turbulent n-dodecane spray flames, under conditions that are relevant for compression-ignition piston engines. PDF model results are compared with experimental measurements and with results from a locally well-stirred reactor (WSR) model that neglects unresolved turbulent fluctuations in composition and temperature. Computed total soot mass and soot spatial distributions are highly sensitive to the modeling of unresolved turbulent fluctuations. To achieve reasonable agreement between model and experiment and to capture …
Geometric Construction-Based Realization Of Spatial Elastic Behaviors In Parallel And Serial Manipulators, Shuguang Huang, Joseph M. Schimmels
Geometric Construction-Based Realization Of Spatial Elastic Behaviors In Parallel And Serial Manipulators, Shuguang Huang, Joseph M. Schimmels
Mechanical Engineering Faculty Research and Publications
This paper addresses the realization of spatial elastic behavior with a parallel or a serial manipulator. Necessary and sufficient conditions for a manipulator (either parallel or serial) to realize a specific elastic behavior are presented and interpreted in terms of the manipulator geometry. These conditions completely decouple the requirements on component elastic properties from the requirements on mechanism kinematics. New construction-based synthesis procedures for spatial elastic behaviors are developed. With these synthesis procedures, one can select each elastic component of a parallel (or serial) mechanism based on the geometry of a restricted space of allowable candidates. With each elastic component …
An Efficient Coal Pyrolysis Model For Detailed Tar Species Vaporization, Jianqing Li, Simcha L. Singer
An Efficient Coal Pyrolysis Model For Detailed Tar Species Vaporization, Jianqing Li, Simcha L. Singer
Mechanical Engineering Faculty Research and Publications
An accurate and computationally efficient model for the vaporization of many tar species during coal particle pyrolysis has been developed. Like previous models, the molecular fragments generated by thermal decomposition are partitioned into liquid metaplast, which remains in the particle, and vapor, which escapes as tar, using a vapor-liquid equilibrium(VLE) sub-model. Multicomponent VLE is formulated as a rate-based process, which results in an ordinary differential equation (ODE) for every species. To reduce the computational expense of solving many ODEs, the model treats tar and metaplast species as a continuous distribution of molecular weight. To improve upon the accuracy of …
Mechanical Behavior Of Three-Dimensional Braided Nickel-Based Superalloys Synthesized Via Pack Cementation, Nicolas Lippitz, Dinc Erdeniz, Keith W. Sharp, David C. Dunand
Mechanical Behavior Of Three-Dimensional Braided Nickel-Based Superalloys Synthesized Via Pack Cementation, Nicolas Lippitz, Dinc Erdeniz, Keith W. Sharp, David C. Dunand
Mechanical Engineering Faculty Research and Publications
Braided tubes of Ni-based superalloys are fabricated via three-dimensional (3-D) braiding of ductile Ni-20Cr (wt pct) wires followed by post-textile gas-phase alloying with Al and Ti to create, after homogenization and aging, γ/γ′ strengthened lightweight, porous structures. Tensile tests reveal an increase in strength by 100 MPa compared to as-braided Ni-20Cr (wt pct). An interrupted tensile test, combined with X-ray tomographic scans between each step, sheds light on the failure behavior of the braided superalloy tubes.
Modeling Multicomponent Fuel Droplet Vaporization With Finite Liquid Diffusivity Using Coupled Algebraic-Dqmom With Delumping, Alanna Y. Cooney, Simcha L. Singer
Modeling Multicomponent Fuel Droplet Vaporization With Finite Liquid Diffusivity Using Coupled Algebraic-Dqmom With Delumping, Alanna Y. Cooney, Simcha L. Singer
Mechanical Engineering Faculty Research and Publications
Multicomponent fuel droplet vaporization models for use in combustion CFD codes often prioritize computational efficiency over model complexity. This leads to oversimplifying assumptions such as single component droplets or infinite liquid diffusivity. The previously developed Direct Quadrature Method of Moments (DQMoM) with delumping model demonstrated a computationally efficient and accurate approach to solve for every discrete species in a well-mixed vaporizing multicomponent droplet. To expand the method to less restrictive cases, a new solution technique is presented called the Coupled Algebraic-Direct Quadrature Method of Moments (CA-DQMoM). In contrast to previous moment methods for droplet vaporization, CA-DQMoM solves for the evolution …
A Degradation Function Consistent With Cocks–Ashby Porosity Kinetics, John A. Moore
A Degradation Function Consistent With Cocks–Ashby Porosity Kinetics, John A. Moore
Mechanical Engineering Faculty Research and Publications
The load carrying capacity of ductile materials degrades as a function of porosity, stress state and strain-rate. The effect of these variables on porosity kinetics is captured by the Cocks–Ashby model; however, the Cocks–Ashby model does not account for material degradation directly. This work uses a yield criteria to form a degradation function that is consistent with Cocks–Ashby porosity kinetics and is a function of porosity, stress state and strain-rate dependence. Approximations of this degradation function for pure hydrostatic stress states are also explored.
Experimental Validation Of An Unscented Kalman Filter For Estimating Transient Engine Exhaust Composition With Fourier Transform Infrared Spectroscopy, David Wilson, Casey Allen
Experimental Validation Of An Unscented Kalman Filter For Estimating Transient Engine Exhaust Composition With Fourier Transform Infrared Spectroscopy, David Wilson, Casey Allen
Mechanical Engineering Faculty Research and Publications
Fourier transform infrared (FTIR) spectroscopy is a prevalent technique for measuring the comprehensive chemical composition of engine emissions. However, its applicability to transient emissions is limited due to recirculation of exhaust from past engine cycles within a FTIR gas cell and nonstationarity of the infrared beam intensity. An unscented Kalman filter is developed to overcome these limitations and obtain accurate, time-resolved estimations of engine exhaust composition from FTIR measurements. Residence time distribution within the FTIR gas cell is modeled using the well-mixed assumption, while the Fourier transform of an interferogram generated from a linearly evolving, uniformly broadened absorption line is …