V. Sabelkin
Air Force Institute of Technology
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Publication
Featured researches published by V. Sabelkin.
Journal of Tribology-transactions of The Asme | 2007
V. Sabelkin; S. Mall
The contact interaction between a rough cylindrical body (i.e., with asperities) and a deformable smooth flat was investigated using the finite-element analysis. Analysis included both elastic-plastic deformation and friction. Further, the effects of several parameters of rough surface on the evolution of the contact area with increasing contact load were investigated. These were radius, number, constraint, and placement of asperities. Contact area of rough surface is smaller than its counterpart of smooth surface, and this decrease depends on number, radius, constraint, and placement of asperities. The elastic material behavior results in considerably smaller contact area than that from elastic-plastic material behavior. The evolution of contact area with increasing contact load is of the complex nature with elastic-plastic material deformation since the yielded region widens and/or deepens with increasing load depending on number, radius, and constraint of asperities. The effect of constraint on the asperity depends upon its nature (i.e., from either sides or one side) and radius of the asperity. The effects of these several parameters on the contact area versus applied load relationships are expressed in the graphical form as well as in terms of equations wherever possible.
Journal of Composite Materials | 2016
V. Sabelkin; S. Mall; Ts Cook; Jacob Fish
A ceramic–matrix composite, consisting of five-harness satin Hi-Nicalon fiber in silicon carbide matrix prepared by slurry melt infiltration method, was characterized for tension–tension fatigue and creep behaviors under the combustion and laboratory environments at 1205℃. There was about 100 times reduction in fatigue life under the combustion environment in comparison to the laboratory environment. There was about 50 times reduction in the creep life under the combustion environment in comparison to the laboratory environment. The combustion caused more embrittlement in the tested CMC than the laboratory environment, and it was more in fatigue than creep under the combustion environment only.
Smart Structures and Materials 2006: Sensors and Smart Structures Technologies for Civil, Mechanical, and Aerospace Systems | 2006
Yeoheung Yun; Vesselin Shanov; Swathi Balaji; Yi Tu; Sergey Yarmolenko; Sudhir Neralla; Jag Sankar; S. Mall; Jay Lee; Larry W. Burggraf; Guangming Li; V. Sabelkin; Mark J. Schulz
This paper describes progress in development of a sensor-actuator-nanoskin material based on multi-wall carbon nanotube arrays. This material can have individual sensing, actuation, or reinforcement properties, or the material may have combined multi-functional properties. The sensing and actuation properties are based on the theoretical telescoping property of multi-wall carbon nanotubes. The sensing property has been demonstrated in the literature. The actuation property is modeled in this paper but not demonstrated. Work is described that later may verify the actuation. Nanoskin samples are also fabricated and tested for mechanical, hydrophobicity, and capillarity properties. Overall, synthesis of dense arrays of long multi-wall carbon nanotubes is opening the door for the development of novel sensors, actuators, and multifunctional smart materials.
Journal of Materials Engineering and Performance | 2016
V. Sabelkin; H.E. Misak; V.Y. Perel; S. Mall
Corrosion-pit-to-crack transition behaviors of three aluminum alloys using two pit configurations were investigated under ambient and saltwater environments. Fatigue stress ranges for crack initiation from a through-pit were less than that from a corner-pit in both environments in all three materials, while stress intensity factor ranges showed the opposite trend. Further, stress ranges or stress intensity factor ranges for crack initiation were less in saltwater than that in ambient environment for both pit configurations. Fatigue damage mechanisms in a test environment were similar for both pit configurations in all three materials. An empirical relationship is proposed to estimate pit-to-crack transition fatigue cycles.
Journal of Composite Materials | 2017
Abhendra K. Singh; V. Sabelkin; S. Mall
Tension–tension fatigue tests in a combustion environment were performed on double-edge notched oxide/oxide ceramic matrix composite specimens. The composite, designated as N720/A, constituted woven 0°/90° Nextel™720 fibers in alumina matrix. Monotonic tensile and cyclic loads at a frequency of 1 Hz and a stress ratio of 0.05 were applied on the specimens in a combustion environment. The maximum specimen temperature due to combustion flame impingement in the notch region was 1250 ± 50℃. A stiffness reduction of less than 10% evaluated for the run-out specimens showed the harsh combustion environment had a minimal effect on specimen degradation. The residual strength was evaluated to be ∼75%–85% the strength of non-fatigued (virgin) double-edge notch specimens in room temperature. The monotonic tensile strength and the fatigue limit for 90,000 cycles (run-out) were found to be ∼40 MPa less in the combustion environment when compared to published results for 1200℃ laboratory air environment. The damage mechanisms were also the same in the two environments. Finite element analyses showed that the reduction in strength and fatigue limit in the combustion environment (as compared to the laboratory air environment) was due to the presence of thermal gradient stresses because of non-uniform specimen temperature distribution.
Advances in Applied Ceramics | 2018
Abhendra K. Singh; V. Sabelkin; S. Mall
ABSTRACT Creep-rupture tests were performed in the combustion environment on double-edge notch and centre hole oxide/oxide ceramic matrix composite specimens. The specimens were exposed to the maximum temperature of 1250 ± 50°C in the notch region where the combustion flame directly impinged. Specimens were loaded to the desired creep load levels and the loads were sustained till either the specimens ruptured or a run-out time of 25 h was achieved. Optical and scanning electron microscopes were used to characterise specimen damage. The test results were compared to its counterparts in 1200°C (isothermal) laboratory air environment. At a given creep life, the applied creep stress for both the notch types was generally lower in the combustion environment than the laboratory air environment. Finite element simulations attributed lower applied creep stress in the combustion environment to the presence of thermal gradient stresses, which were not present in the isothermal laboratory air environment.
Composite Structures | 2007
V. Sabelkin; S. Mall; M.A. Hansen; R.M. Vandawaker; M. Derriso
Carbon | 2013
H.E. Misak; V. Sabelkin; S. Mall; Paul E. Kladitis
Carbon | 2012
V. Sabelkin; Heath Edward Misak; S. Mall; Ramazan Asmatulu; Paul E. Kladitis
Composite Structures | 2015
Sina Askarinejad; Nima Rahbar; V. Sabelkin; S. Mall