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- Ablation (3)
- Charring ablators (2)
- Pyrolysis gas (2)
- Rough Surface (2)
- Turbulent Flow (2)
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- Blowing Effects (1)
- Carbon Preform (1)
- Carbon fiber preforms (1)
- Charring ablator (1)
- Chemical nonequilibrium (1)
- Cyclic crack growth; Plastic dissipated energy; Crack tunneling; ABAQUS; Plasticity induced crack closure (PICC) (1)
- Flow field simulations (1)
- Flow-tube Oxidation (1)
- Heat flux (1)
- Heat transfer (1)
- Heat-shields (1)
- In situ fracture of foams; SEM; PVC foam; PES foam; Fatigue of foam (1)
- Indentation; Conical; Uniqueness; Sensitivity; Condition number (1)
- Intermetallics (1)
- LeMANS (1)
- MOPAR (1)
- Magnetic measurements (1)
- Magnetically ordered materials (1)
- Martensitic transformations (1)
- Metals and alloys (1)
- Micro-tomography (1)
- Momentum Injection (1)
- Multi-dimensional modeling (1)
- Navier-Stokes solver (1)
- Oxidation (1)
Articles 1 - 16 of 16
Full-Text Articles in Entire DC Network
On The Uniqueness And Sensitivity Of Indentation Testing Of Isotropic Materials, J. K. Phadikar, T. A. Bogetti, Anette M. Karlsson
On The Uniqueness And Sensitivity Of Indentation Testing Of Isotropic Materials, J. K. Phadikar, T. A. Bogetti, Anette M. Karlsson
Mechanical Engineering Faculty Publications
Instrumented indentation is a popular technique to extract the material properties of small scale structures. The uniqueness and sensitivity to experimental errors determine the practical usefulness of such experiments. Here, a method to identify test techniques that minimizes sensitivity to experimental erros is in indentation experiments developed. The methods are based on considering “shape functions,” which are sets of functions that describe the force–displacement relationship obtained during the indentation test. The concept of condition number is used to investigate the relative reliability of various possible dual indentation techniques. Interestingly, it was found that many dual indentation techniques can be as …
Implementation Of A Plastically Dissipated Energy Criterion For Three Dimensional Modeling Of Fatigue Crack Growth, Parag G. Nittur, Anette M. Karlsson, Leif A. Carlsson
Implementation Of A Plastically Dissipated Energy Criterion For Three Dimensional Modeling Of Fatigue Crack Growth, Parag G. Nittur, Anette M. Karlsson, Leif A. Carlsson
Mechanical Engineering Faculty Publications
Fatigue crack growth is simulated using three dimensional elastic-plastic finite element analysis. The crack extension per load cycle, da/dN, as well as crack front profile changes (crack tunneling) under cyclic loading is not specified as an input but evaluated based on a condition that relates plastically dissipated energy to a critical value. Simulation of cyclic crack propagation in a middle-crack tension M(T) specimen using this implementation captures the well established, experimentally obtained crack growth rate reduction accompanying a single overload event. The analysis predicts that the single overload also affects the crack front profile, where a tunneling crack propagates with …
Experimental Investigation Of Blowing Effects On Turbulent Flow Over A Rough Surface, Mark A. Miller, Alexandre Martin, Sean C. C. Bailey
Experimental Investigation Of Blowing Effects On Turbulent Flow Over A Rough Surface, Mark A. Miller, Alexandre Martin, Sean C. C. Bailey
Mechanical Engineering Faculty Publications
A high Reynolds number turbulent channel flow facility was used to study the combined effects of roughness and flow injection on the mean flow and turbulence characteristics. It was found that the additional momentum injection through the surface enhanced the roughness effects and for the mean flow the effect of blowing was indistinguishable from that of increased roughness. However, for the turbulence statistics, this analogy broke down in that the addition of blowing resulted in behavior which did not follow that predicted by Townsend’s hypothesis. This was observed as a reduction of outer-scaled Reynolds stress well into the outer layer. …
Conical Indentation Of A Viscoelastic Sphere, J. K. Phadikar, T. A. Bogetti, V. N. Kaliakin, Anette M. Karlsson
Conical Indentation Of A Viscoelastic Sphere, J. K. Phadikar, T. A. Bogetti, V. N. Kaliakin, Anette M. Karlsson
Mechanical Engineering Faculty Publications
Instrumented indentation is commonly used for determining mechanical properties of a range of materials, including viscoelastic materials. However, most—if not all—studies are limited to a flat substrate being indented by various shaped indenters (e.g., conical or spherical). This work investigates the possibility of extending instrumented indentation to nonflat viscoelastic substrates. In particular, conical indentation of a sphere is investigated where a semi-analytical approach based on “the method of functional equations” has been developed to obtain the force–displacement relationship. To verify the accuracy of the proposed methodology selected numerical experiments have been performed and good agreement was obtained. Since it takes …
Coupled Flow Field Simulations Of Charring Ablators With Nonequilibrium Surface Chemistry, Hicham Alkandry, Iain D. Boyd, Alexandre Martin
Coupled Flow Field Simulations Of Charring Ablators With Nonequilibrium Surface Chemistry, Hicham Alkandry, Iain D. Boyd, Alexandre Martin
Mechanical Engineering Faculty Publications
This paper describes the coupling of a Navier-Stokes solver to a material response code to simulate nonequilibrium gas-surface interactions. The Navier-Stokes solver used in this study is LeMANS, which is a three-dimensional computational fluid dynamics code that can simulate hypersonic reacting flows including thermo-chemical nonequilibrium effects. The material response code employed in this study is MOPAR, which uses the one-dimensional control volume nite-element method to model heat conduction and pyrolysis gas behavior. This coupling is demonstrated using a test case based on the Stardust sample return capsule. Coupled simulations are performed at three different trajectory conditions. The effects of the …
A New Approach To Light-Weight Ablators Analysis: From Micro-Tomography Measurements To Statistical Analysis And Modeling, Nagi N. Mansour, Francesco Panerai, Alexandre Martin, Dilworth Y. Parkinson, Alastair A. Macdowell, Abdelmoula Haboub, Timothy A. Sandstrom, Tony Fast, Gerard L. Vignoles, Jean Lachaud
A New Approach To Light-Weight Ablators Analysis: From Micro-Tomography Measurements To Statistical Analysis And Modeling, Nagi N. Mansour, Francesco Panerai, Alexandre Martin, Dilworth Y. Parkinson, Alastair A. Macdowell, Abdelmoula Haboub, Timothy A. Sandstrom, Tony Fast, Gerard L. Vignoles, Jean Lachaud
Mechanical Engineering Faculty Publications
The morphology characteristics and ablation behavior of a highly porous carbon fiber preform are studied using a combined experimental/numerical approach. Morphological characterization of the three-dimensional structure of the material is performed by hard X-rays synchrotron micro-tomography at the Advanced Light Source of Lawrence Berkeley National Laboratory. The resulting micro-tomography voxels are used to compute geometrical properties of the carbon preform, like porosity, specific surface area and tortuosity, that are otherwise indirectly measured through experimental techniques. The reconstructed volumes are used to build a computational grid for numerical simulations of the fibers' ablation. By modeling the diffusion of oxygen through the …
Volume Averaged Modeling Of The Oxidation Of Porous Carbon Fiber Material, Alexandre Martin
Volume Averaged Modeling Of The Oxidation Of Porous Carbon Fiber Material, Alexandre Martin
Mechanical Engineering Faculty Publications
Charring ablators remain the premium choice for space exploration missions that involve atmospheric re-entry. This type of ablative material is composed of a carbon matrix, usually made of fibers, which is then impregnated with a resin. During re-entry, the high heat flux produced by convective heating causes the material to chemically react. First, the resin pyrolyzes, and is vaporized into a gas that travels through the material, and is eventually ejected at the surface. Then, as the temperature rises, the surface of the porous matrix recess through ablative processes. For re-entry conditions typical of space exploration missions, this is mainly …
Flow-Tube Oxidation Experiments On The Carbon Preform Of Pica, Francesco Panerai, Alexandre Martin, Nagi N. Mansour, Steven A. Sepka, Jean Lachaud
Flow-Tube Oxidation Experiments On The Carbon Preform Of Pica, Francesco Panerai, Alexandre Martin, Nagi N. Mansour, Steven A. Sepka, Jean Lachaud
Mechanical Engineering Faculty Publications
Oxidation experiments on the carbon preform of a phenolic-impregnated carbon ablator were performed in the NASA Ames ow-tube reactor facility, at temperatures between 700 and 1300 K, under dry air gas at pressures between 103 and 104 Pa. Mass loss, volumetric recession and density changes were measured at different test conditions. An analysis of the diffusion/reaction competition within the porous material, based on the Thiele number, allowed us to identify low temperature and low pressure conditions to be dominated by in-depth volume oxidation. Experiments above 1000 K were found at transition conditions, where diffusion and reaction occur at similar scales. …
Multi-Dimensional Modeling Pyrolysis Gas Flow Inside Charring Ablators, Haoyue Weng, Alexandre Martin
Multi-Dimensional Modeling Pyrolysis Gas Flow Inside Charring Ablators, Haoyue Weng, Alexandre Martin
Mechanical Engineering Faculty Publications
Using an ablative thermal/material response code, the importance of three-dimensionality for modeling ablative test-article is addressed. In particular, the simulation of the pyrolysis gas flow inside a porous material is presented, using two different geometries. The effects of allowing the gas to flow out of the side wall are especially highlighted. Results show that the flow inside the test-article is complex, and that the 0D or 1D assumption made in most Material Response (MR) codes might not be valid for certain geometries.
Compressive Response Of Polycrystalline Nicomnga High-Temperature Meta-Magnetic Shape Memory Alloys, H. E. Karaca, A. S. Turabi, B. Basaran, A. K. Pathak, I. Dubenko, N. Ali, Y. I. Chumlyakov, P. Li
Compressive Response Of Polycrystalline Nicomnga High-Temperature Meta-Magnetic Shape Memory Alloys, H. E. Karaca, A. S. Turabi, B. Basaran, A. K. Pathak, I. Dubenko, N. Ali, Y. I. Chumlyakov, P. Li
Mechanical Engineering Faculty Publications
The effects of the addition of quaternary element, Co, to polycrystalline NiMnGa alloys on their magnetic and shape memory properties have been investigated. NiCoMnGa polycrystalline alloys have been found to demonstrate good shape memory and superelasticity behavior under compression at temperatures greater than 100 °C with about 3% transformation strain and low-temperature hysteresis. It is also possible to train the material to demonstrate a large two-way shape memory effect.
Mice Lacking Pten In Osteoblasts Have Improved Intramembranous And Late Endochondral Fracture Healing, Travis A. Burgers, Martin F. Hoffmann, Caitlyn J. Collins, Juraj Zahatnansky, Martin A. Alvarado, Michael R. Morris, Debra L. Sletsema, James J. Mason, Clifford B. Jones, Heidi L. Ploeg, Bart O. Williams
Mice Lacking Pten In Osteoblasts Have Improved Intramembranous And Late Endochondral Fracture Healing, Travis A. Burgers, Martin F. Hoffmann, Caitlyn J. Collins, Juraj Zahatnansky, Martin A. Alvarado, Michael R. Morris, Debra L. Sletsema, James J. Mason, Clifford B. Jones, Heidi L. Ploeg, Bart O. Williams
Mechanical Engineering Faculty Publications
The failure of an osseous fracture to heal (development of a non-union) is a common and debilitating clinical problem. Mice lacking the tumor suppressor Pten in osteoblasts have dramatic and progressive increases in bone volume and density throughout life. Since fracture healing is a recapitulation of bone development, we investigated the process of fracture healing in mice lacking Pten in osteoblasts (Ocn-cretg/+; Ptenflox/flox). Mid-diaphyseal femoral fractures induced in wild-type and Ocn-cretg/+; Ptenflox/flox mice were studied via micro-computed tomography (mCT) scans, biomechanical testing, histological and histomorphometric analysis, and protein expression analysis. Ocn-cretg/+; Ptenflox/flox mice had significantly stiffer and stronger intact bones …
Time-Dependent Mechanical Response Of A Composite Pfsa Membrane, Narinder S. Khattra, Zongwen Lu, Anette M. Karlsson, Michael H. Santare, F. Colin Busby, Thomas Schmiedel
Time-Dependent Mechanical Response Of A Composite Pfsa Membrane, Narinder S. Khattra, Zongwen Lu, Anette M. Karlsson, Michael H. Santare, F. Colin Busby, Thomas Schmiedel
Mechanical Engineering Faculty Publications
The mechanical response of a composite fuel cell membrane, made from layers of reinforced and unreinforced PFSA material, is investigated via both experimental and numerical means. First, the time-dependent mechanical properties for the reinforced layers are measured for a range of environmental and loading conditions. A three-network, viscoelastic-plastic constitutive model is developed to characterize the mechanical response of this reinforced membrane material. This constitutive model is then used in finite element simulations of a fuel cell unit (consisting of composite membrane, electrodes, gas diffusion layer and bipolar plates) where the effect of relative humidity (RH) cycling on the stress response …
In Situ Analysis Of Fatigue Crack Propagation In Polymer Foams, Elio E. Saenza, Leif A. Carlsson, Anette M. Karlsson
In Situ Analysis Of Fatigue Crack Propagation In Polymer Foams, Elio E. Saenza, Leif A. Carlsson, Anette M. Karlsson
Mechanical Engineering Faculty Publications
This paper presents an in situ SEM experimental study on cyclic crack propagation in closed-cell polymer foams. The microscopic failure mechanisms in precracked PVC and PES specimens of 60 and 90 kg/m3 densities were examined under low-cycle fatigue loading. In the PVC foam, crack propagation occurred incrementally by successive failure of cell boundaries in front of the crack tip. The crack occasionally jumped to cell boundaries above or below the main crack resulting in non-self similar growth. Crack propagation in the PES foam occurred incrementally by extensive plastic tearing and subsequent tensile failure of the cell edge in front …
Comparison Of Models For Mixture Transport Properties For Numerical Simulations Of Ablative Heat-Shields, Hicham Alkandry, Iain D. Boyd, Alexandre Martin
Comparison Of Models For Mixture Transport Properties For Numerical Simulations Of Ablative Heat-Shields, Hicham Alkandry, Iain D. Boyd, Alexandre Martin
Mechanical Engineering Faculty Publications
The goal of this study is to evaluate the effects of different models for calculating the mixture transport properties on flowfield predictions of ablative heat-shields. The Stardust sample return capsule at four different trajectory conditions is used as a test case for this study. In the first part of the study, the results predicted using Wilke's mixing rule with species viscosities calculated using Blottner's curve fits and species thermal conductivities determined using Eucken's relation are compared to the results obtained using Gupta's mixing rule with collision cross-section (CCS) data. The Wilke/Blottner/Eucken model overpredicts the heat transfer to the surface relative …
Investigation Of Turbulent Structure Modification By Momentum Injection Into Turbulent Flow Over A Rough Surface, Mark A. Miller, Huaibao Zhang, Alexandre Martin, Sean C. C. Bailey
Investigation Of Turbulent Structure Modification By Momentum Injection Into Turbulent Flow Over A Rough Surface, Mark A. Miller, Huaibao Zhang, Alexandre Martin, Sean C. C. Bailey
Mechanical Engineering Faculty Publications
Utilizing a turbulent channel flow facility, experiments were performed to determine the modifications made to the temporal and spatial structure of turbulence over a sinusoidally rough surface due to momentum injection through the surface. As expected, when compared to the smooth-walled conditions, it was found that the surface roughness increased wall shear stress, decreased the turbulence energy content near the wall, and shifted that energy content to wavelengths on the order of the roughness elements. The addition of momentum injection was found to produce further modifications analogous to increasing the roughness height by increasing the wall shear stress and further …
Modeling Of Chemical Nonequilibrium Effects In A Charring Ablator, Alexandre Martin
Modeling Of Chemical Nonequilibrium Effects In A Charring Ablator, Alexandre Martin
Mechanical Engineering Faculty Publications
Charring ablators remain the premium choice for space exploration missions that involve atmospheric re-entry. These type of ablative material are composed of a carbon matrix, usually made of fibers, which is then impregnated with a resin. During re-entry, the high heat flux produced by convective heating causes the material to chemically react. First, the resin pyrolyzes, and is vaporized into a gas that travels through the material, and is eventually ejected at the surface. Since the composition of the gas at the surface greatly affects the heat flux, and therefore the surface temperature, it is thus important to be able …