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- Drag reduction (2)
- Equations of state (2)
- Friction stir welding (2)
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- Velocity gradients (2)
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- Composite boom (1)
- Composite materials (1)
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- Conservation of momentum (1)
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Articles 1 - 14 of 14
Full-Text Articles in Engineering Science and Materials
Mechanics Of Pure Bending And Eccentric Buckling In High-Strain Composite Structures, Jimesh D. Bhagatji, Oleksandr G. Kravchenko, Sharanabasaweshwara Asundi
Mechanics Of Pure Bending And Eccentric Buckling In High-Strain Composite Structures, Jimesh D. Bhagatji, Oleksandr G. Kravchenko, Sharanabasaweshwara Asundi
Mechanical & Aerospace Engineering Faculty Publications
To maximize the capabilities of nano- and micro-class satellites, which are limited by their size, weight, and power, advancements in deployable mechanisms with a high deployable surface area to packaging volume ratio are necessary. Without progress in understanding the mechanics of high-strain materials and structures, the development of compact deployable mechanisms for this class of satellites would be difficult. This paper presents fabrication, experimental testing, and progressive failure modeling to study the deformation of an ultra-thin composite beam. The research study examines the deformation modes of a post-deployed boom under repetitive pure bending loads using a four-point bending setup and …
Effect Of Platelet Length And Stochastic Morphology On Flexural Behavior Of Prepreg Platelet Molded Composites, Siavash Sattar, Benjamin Beltran Laredo, Sergii G. Kravchenko, Oleksandr G. Kravchenko
Effect Of Platelet Length And Stochastic Morphology On Flexural Behavior Of Prepreg Platelet Molded Composites, Siavash Sattar, Benjamin Beltran Laredo, Sergii G. Kravchenko, Oleksandr G. Kravchenko
Mechanical & Aerospace Engineering Faculty Publications
Prepreg platelet molding compound (PPMC) can be used to create structural grade material with a heterogeneous mesoscale morphology. The present work considered various platelet lengths of the prepreg system IM7/8552 to study the effect of platelet length on the flexural behavior of PPMC composite. A progressive failure finite-element analysis was used to understand competing failure modes in PPMC with the different platelet length. The interlaminar and in-plane damage mechanisms were employed to describe complex failure modes within the mesostructure of PPMCs. Experimental results of the flexural tests of the PPMC with different platelet length sizes were used to validate the …
Elastic Properties Of The Non-Mixing Copper Donor Assisted Material In Friction Stir Welding Of Aluminum Alloys Using Nanoindentation, M. Ojha, A. H. Al-Allaq, Y. S. Mohammed, S. N. Bhukya, Z. Wu, A. A. Elmustafa
Elastic Properties Of The Non-Mixing Copper Donor Assisted Material In Friction Stir Welding Of Aluminum Alloys Using Nanoindentation, M. Ojha, A. H. Al-Allaq, Y. S. Mohammed, S. N. Bhukya, Z. Wu, A. A. Elmustafa
Mechanical & Aerospace Engineering Faculty Publications
Friction stir welding of high-strength materials such as steels is the impeded by the lack of the vast heat input needed to start the process. Contact friction is considered the most dominant source of heat generation for FSW steels which tends to cause severe wear conditions of the tool hear. To relieve the extreme wear conditions that occur on the tool heads because of FSW steels, we introduce the non-mixing Cu donor stir material to friction stir welding of aluminum alloys. The elastic properties of the Cu donor assisted friction stir welded aluminum alloys are measured using nanoindentation. The hardness …
Post-Weld Heat Treatment Effects On Microstructure, Crystal Structure, And Mechanical Properties Of Donor Stir–Assisted Friction Stir Welding Material Of Aa6061-T6 Alloy, Aiman H. Al-Allaq, Manish Ojha, Yousuf S. Mohammed, Srinivasa N. Bhukya, Zhenhua Wu, Abdelmageed A. Elmustafa
Post-Weld Heat Treatment Effects On Microstructure, Crystal Structure, And Mechanical Properties Of Donor Stir–Assisted Friction Stir Welding Material Of Aa6061-T6 Alloy, Aiman H. Al-Allaq, Manish Ojha, Yousuf S. Mohammed, Srinivasa N. Bhukya, Zhenhua Wu, Abdelmageed A. Elmustafa
Mechanical & Aerospace Engineering Faculty Publications
Friction stir welding (FSW) technology combines heat input from friction and extreme plastic deformation to produce high-quality joints in aluminum and other alloy systems. This necessitates examining the final welded joint’s mechanical and structural properties. Post-weld heat-treated AA6061-T6 alloy that resulted from the application of a Cu donor stir–assisted (CDSA) friction stir welding (FSW) material was examined for crystal structure and mechanical properties. CDSA FSW samples were tested at a constant tool rotational speed of 1400 rpm and a welding translational speed of 1 mm/s. CDSA samples of 20% and 60% thickness of the AA6061-T6 base alloy were selected to …
Comment On "Roles Of Bulk Viscosity On Rayleigh-Taylor Instability: Non-Equilibrium Thermodynamics Due To Spatio-Temporal Pressure Fronts" Phys. Fluids 28, 094102 (2016), Robert L. Ash
Mechanical & Aerospace Engineering Faculty Publications
No abstract provided.
The Effect Of Noise On The Response Of A Vertical Cantilever Beam Energy Harvester, Michael I. Friswell, Onur Bilgen, S. Faruque Ali, Grzegorz Litak, Sondipon Adhikari
The Effect Of Noise On The Response Of A Vertical Cantilever Beam Energy Harvester, Michael I. Friswell, Onur Bilgen, S. Faruque Ali, Grzegorz Litak, Sondipon Adhikari
Mechanical & Aerospace Engineering Faculty Publications
An energy harvesting concept has been proposed comprising a piezoelectric patch on a vertical cantilever beam with a tip mass. The cantilever beam is excited in the transverse direction at its base. This device is highly nonlinear with two potential wells for large tip masses, when the beam is buckled. For the pre-buckled case considered here, the stiffness is low and hence the displacement response is large, leading to multiple solutions to harmonic excitation that are exploited in the harvesting device. To maximise the energy harvested in systems with multiple solutions the higher amplitude response should be preferred. This paper …
Non-Equilibrium Pressure Control Of The Height Of A Large-Scale, Ground-Coupled, Rotating Fluid Column, R. L. Ash, I. R. Zardadhkan
Non-Equilibrium Pressure Control Of The Height Of A Large-Scale, Ground-Coupled, Rotating Fluid Column, R. L. Ash, I. R. Zardadhkan
Mechanical & Aerospace Engineering Faculty Publications
When a ground-coupled, rotating fluid column is modeled incorporating non-equilibrium pressure forces in the Navier-Stokes equations, a new exact solution results. The solution has been obtained in a similar manner to the classical equilibrium solution. Unlike the infinite-height, classical solution, the non-equilibrium pressure solution yields a ground-coupled rotating fluid column of finite height. A viscous, non-equilibrium Rankine vortex velocity distribution, developed previously, was used to demonstrate how the viscous and non-equilibrium pressure gradient forces, arising in the vicinity of the velocity gradient discontinuity that is present in the classical Rankine vortex model, effectively isolate the rotating central fluid column from …
The Influence Of Pressure Relaxation On The Structure Of An Axial Vortex, Robert L. Ash, Irfan Zardadkhan, Allan J. Zuckerwar
The Influence Of Pressure Relaxation On The Structure Of An Axial Vortex, Robert L. Ash, Irfan Zardadkhan, Allan J. Zuckerwar
Mechanical & Aerospace Engineering Faculty Publications
Governing equations including the effects of pressure relaxation have been utilized to study an incompressible, steady-state viscous axial vortex with specified far-field circulation. When sound generation is attributed to a velocity gradient tensor-pressure gradient product, the modified conservation of momentum equations that result yield an exact solution for a steady, incompressible axial vortex. The vortex velocity profile has been shown to closely approximate experimental vortex measurements in air and water over a wide range of circulation-based Reynolds numbers. The influence of temperature and humidity on the pressure relaxation coefficient in air has been examined using theoretical and empirical approaches, and …
Volume Viscosity In Fluids With Multiple Dissipative Processes, Allan J. Zuckerwar, Robert L. Ash
Volume Viscosity In Fluids With Multiple Dissipative Processes, Allan J. Zuckerwar, Robert L. Ash
Mechanical & Aerospace Engineering Faculty Publications
The variational principle of Hamilton is applied to derive the volume viscosity coefficients of a reacting fluid with multiple dissipative processes. The procedure, as in the case of a single dissipative process, yields two dissipative terms in the Navier-Stokes equation: The first is the traditional volume viscosity term, proportional to the dilatational component of the velocity; the second term is proportional to the material time derivative of the pressure gradient. Each dissipative process is assumed to be independent of the others. In a fluid comprising a single constituent with multiple relaxation processes, the relaxation times of the multiple processes are …
Understanding Practical Limits To Heavy Truck Drag Reduction, Drew Landman, Richard Wood, Whitney Seay, John Bledsoe
Understanding Practical Limits To Heavy Truck Drag Reduction, Drew Landman, Richard Wood, Whitney Seay, John Bledsoe
Mechanical & Aerospace Engineering Faculty Publications
A heavy truck wind tunnel test program is currently underway at the Langley Full Scale Tunnel (LFST). Seven passive drag reducing device configurations have been evaluated on a heavy truck model with the objective of understanding the practical limits to drag reduction achievable on a modern tractor trailer through add-on devices. The configurations tested include side skirts of varying length, a full gap seal, and tapered rear panels. All configurations were evaluated over a nominal 15 degree yaw sweep to establish wind averaged drag coefficients over a broad speed range using SAE J1252. The tests were conducted by first quantifying …
Response To "Comment On Variational Approach To The Volume Viscosity Of Fluids" [Phys. Fluids 18, 109101 (2006)], Allen J. Zuckerwar, Robert L. Ash
Response To "Comment On Variational Approach To The Volume Viscosity Of Fluids" [Phys. Fluids 18, 109101 (2006)], Allen J. Zuckerwar, Robert L. Ash
Mechanical & Aerospace Engineering Faculty Publications
We respond to the Comment of Markus Scholle and therewith revise our material entropy constraint to account for the production of entropy. (c) 2006 American Institute of Physics.
Variational Approach To The Volume Viscosity Of Fluids, Allan J. Zuckerwar, Robert L. Ash
Variational Approach To The Volume Viscosity Of Fluids, Allan J. Zuckerwar, Robert L. Ash
Mechanical & Aerospace Engineering Faculty Publications
The variational principle of Hamilton is applied to develop an analytical formulation to describe the volume viscosity in fluids. The procedure described here differs from those used in the past in that a dissipative process is represented by the chemical affinity and progress variable (sometimes called "order parameter") of a reacting species. These state variables appear in the variational integral in two places: first, in the expression for the internal energy, and second, in a subsidiary condition accounting for the conservation of the reacting species. As a result of the variational procedure, two dissipative terms appear in the Navier-Stokes equation. …
An Apparatus For Measuring The Thermal Conductivity Of Cast Insulation Materials, Christine A. Wilkins, Robert L. Ash
An Apparatus For Measuring The Thermal Conductivity Of Cast Insulation Materials, Christine A. Wilkins, Robert L. Ash
Mechanical & Aerospace Engineering Faculty Publications
A steady-state apparatus has been developed for measuring the thermal conductivity of cast materials. The design has employed a novel thermal symmetry arrangement which can permit total electrical isolation of the test material from its surroundings. © 1980 American Institute of Physics
Effect Of Compliant Wall Motion On Turbulent Boundary Layers, Dennis M. Bushness, Jerry N. Hefner, Robert L. Ash
Effect Of Compliant Wall Motion On Turbulent Boundary Layers, Dennis M. Bushness, Jerry N. Hefner, Robert L. Ash
Mechanical & Aerospace Engineering Faculty Publications
A critical analysis of available compliant wall data which indicated drag reduction under turbulent boundary layers is presented. Detailed structural dynamic calculations suggest that the surfaces responded in a resonant, rather than a compliant, manner. Alternate explanations are given for drag reductions observed in two classes of experiments: (1) flexible pipe flows and (2) water-backed membranes in air. Analysis indicates that the wall motion for the remaining data is typified by short wavelengths in agreement with the requirements of a possible compliant wall drag reduction mechanism recently suggested by Langley. Copyright © 1977 American Institute of Physics.