Alex Francis

Flexible torsional couplings are used primarily to transmit power between rotating components in industrial power systems, including turbomachinery, while allowing for small amounts of misalignment that may otherwise lead to equipment failure. The torsional coupling lumped characteristics, such as torsional- and flexural stiffness, as well as natural frequencies of vibration are important for design of the entire power system and, therefore, must be calculated or computed with a high degree of… Show more

Flexible torsional couplings are used primarily to transmit power between rotating components in industrial power systems, including turbomachinery, while allowing for small amounts of misalignment that may otherwise lead to equipment failure. The torsional coupling lumped characteristics, such as torsional- and flexural stiffness, as well as natural frequencies of vibration are important for design of the entire power system and, therefore, must be calculated or computed with a high degree of accuracy. In this paper, we compare theoretical-, computational-, and experimental methods of characterizing torsional stiffness of a family of metallic disk type flexible couplings. We demonstrate the sensitivity of torsional stiffness to various design parameters and characterization assumptions, including boundary conditions, level of model detail, and material properties of the coupling's components. We also develop a full 3D parametric finite element model of the coupling and report on its experimental validation.

DOI: 10.1115/1.4029392 Show less

Fused Deposition Modeling (FDM) technology is a process of manufacturing three-dimensional objects, which is widely used in the rapid prototyping and additive manufacturing industries. Characterization of the mechanical properties of 3-D printed parts becomes important as the technology expands to consumer- as well to functional prototyping markets. Mechanical strength of produced parts greatly depend on several printing variables, such as (1) part orientation on the printing bed, (2) material… Show more

Fused Deposition Modeling (FDM) technology is a process of manufacturing three-dimensional objects, which is widely used in the rapid prototyping and additive manufacturing industries. Characterization of the mechanical properties of 3-D printed parts becomes important as the technology expands to consumer- as well to functional prototyping markets. Mechanical strength of produced parts greatly depend on several printing variables, such as (1) part orientation on the printing bed, (2) material selection to be used by the printer, and (3) part fill density. The fill density is a parameter which can make the final product completely solid, hollow, or anything in between. As in composite materials, the mechanical properties are affected by the density- and the direction of the filament layers. In this study, we experimentally investigate sensitivity of mechanical properties of FDM built samples to the fill density and the filament orientation. We also investigate accuracy of the developed parametric finite element model that is used to predict material properties based on print parameters. Show less

Designing battery packs for safety in automotive applications requires multiscale modeling, as macroscopic deformations due to impact cause the mechanical failure of individual cells on a sub-millimeter level. The separator material plays a critical role in this process, as the thinning or perforating of the separator can lead to thermal runaway and catastrophic failure of an entire battery pack. The electrochemical properties of various polymer separators have been extensively investigated;… Show more

Designing battery packs for safety in automotive applications requires multiscale modeling, as macroscopic deformations due to impact cause the mechanical failure of individual cells on a sub-millimeter level. The separator material plays a critical role in this process, as the thinning or perforating of the separator can lead to thermal runaway and catastrophic failure of an entire battery pack. The electrochemical properties of various polymer separators have been extensively investigated; however, the dependency of mechanical properties of these thin films on various factors, such as high temperature and strain rate, has not been sufficiently characterized. In this study, the macroscopic mechanical properties of a multilayer polymer thin film used as a battery separator are studied experimentally at various temperatures, strain rates, and solvent saturations. Due to the anisotropy of the material, material testing was conducted in two perpendicular directions (machine and transverse directions). Material samples were tested in both dry and saturated conditions at several temperatures, and it was found that temperature and strain rate have a nearly linear effect on the stress experienced by the material. Additionally, saturating the separator material in a common lithium-ion solvent had softened it and had a positive effect on its toughness. The experimental results obtained in this study can be used to develop mathematical constitutive models of the multilayer separator material for subsequent numerical simulations and design. Show less

The use of lithium-ion batteries has become increasingly popular in the automotive industry. An understanding of how these batteries will behave structurally is of great importance, however experimental testing can be expensive and time consuming. Finite Element Analysis (FEA) can deliver a reliable low cost approximation of physical testing results yet an accurate understanding of the batteries material properties must first be acquired. In this research the material properties of the… Show more

The use of lithium-ion batteries has become increasingly popular in the automotive industry. An understanding of how these batteries will behave structurally is of great importance, however experimental testing can be expensive and time consuming. Finite Element Analysis (FEA) can deliver a reliable low cost approximation of physical testing results yet an accurate understanding of the batteries material properties must first be acquired. In this research the material properties of the individual components of a lithium ion battery were explored under varying conditions of temperature, hydration, and strain rates. Tests have been conducted with a tensile tester equipped with an environmental chamber to simulate actual service conditions. The experimental data was then be compared to constitutive models capable of simulating how the materials will react under these varying conditions. The constitutive models with their optimized parameters were then imported into an FEA package to perform a dynamic analysis on the lithium-ion battery as a whole. Show less

Heating by friction in the geared contacts degrades the lubrication performance of a planetary gear system, which depends directly on temperature. In wind turbine gearboxes adequate lubrication ensures reliable operation. In this study, in situ cooling was used to continuously remove heat from a Planetary Gear System (PGS). Highly conductive copper coils surrounded a stationary ring gear of the PGS to circulate coolant. SAE 90 grade gear oil lubricant was used with water as the coolant… Show more

Heating by friction in the geared contacts degrades the lubrication performance of a planetary gear system, which depends directly on temperature. In wind turbine gearboxes adequate lubrication ensures reliable operation. In this study, in situ cooling was used to continuously remove heat from a Planetary Gear System (PGS). Highly conductive copper coils surrounded a stationary ring gear of the PGS to circulate coolant. SAE 90 grade gear oil lubricant was used with water as the coolant. Block-on-ring (BOR) tests were also done to obtain friction characteristics at the test speeds used in the uncooled and cooled tests. So far, preliminary test data show that the temperature of an uncooled PGS increases with rotational speed, while continuous cooling produces very low operational temperature, necessary for preserving low friction coefficients at elevated speeds. The BOR tests also show that the oil and outer ring temperature as well as BOR coefficient of friction increase with rotational speed.

Paper No. IJTC2011-61209 Show less

Pin-on-disk tests were performed to investigate the superlubricity of graphene oxide (GO) coatings. Stainless steel pins (with round and flat ends) were coated with GO and ran against stainless steel disks and lubricated with SAE 75-90 motor oil.
The experimental results indicate that graphene oxide performs similarly (with round- and/or flat-end pins) with or without oil, in all cases exhibiting excellent (i.e., low) coefficient of friction. Compared
to non-graphene coated specimen… Show more

Pin-on-disk tests were performed to investigate the superlubricity of graphene oxide (GO) coatings. Stainless steel pins (with round and flat ends) were coated with GO and ran against stainless steel disks and lubricated with SAE 75-90 motor oil.
The experimental results indicate that graphene oxide performs similarly (with round- and/or flat-end pins) with or without oil, in all cases exhibiting excellent (i.e., low) coefficient of friction. Compared
to non-graphene coated specimen, the lubrication characteristics of GO-coated specimens were superior.

Paper No. IJTC2011-61207
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The spate of technological advancements in turbine engines, fuel cell
-powered automobiles, and power plants has necessitated a need for
advanced rolling element bearings (REBs). In fact, a growing
consensus among tribologists is that lubricating rolling element
bearings with powders is a viable option under extreme loads, speed
and harsh temperature conditions. Since the REBs operate primarily
in the mixed/boundary lubrication regime , they are potential
candidates for… Show more

The spate of technological advancements in turbine engines, fuel cell
-powered automobiles, and power plants has necessitated a need for
advanced rolling element bearings (REBs). In fact, a growing
consensus among tribologists is that lubricating rolling element
bearings with powders is a viable option under extreme loads, speed
and harsh temperature conditions. Since the REBs operate primarily
in the mixed/boundary lubrication regime , they are potential
candidates for powder lubrication.
In this study, a prototype radial ball bearing (RBB) lubricated in situ
by pelletized powder lubricants is studied. In the powder-lubricated
RBB, alternate conventional rolling elements have been replaced
with encapsulated spring-loaded lubricant pellets. By depositing a
thin film of powder lubricant on the inner and outer races, the REB is
lubricated under extreme speed and load condition adequately. The
candidate lubricants used are pelletized MoS2, WS2, and H3BO3
powders. The lubricant pellets are characterized using a multiplex
powder tribometer. The tests are carried out using an in-house
bearing testing rig.
It is hoped that the promising results from this study will offer the
necessary proof-of-performance (PoP) needed to assure a wholesale
adaptation by beneficiary industries such as the automotive and
aerospace industries who are reluctant to adopt powder/solid
lubrication technologies. Show less

In this study a novel in situ rolling element bearing (REB) lubricant cooling system is developed that provides a continuous cooling of the bearing outer race. In the design the stationary outer race is expanded to accommodate a cooling coil for the continuous cooling of the lubricant and the outer race. Water is used as the coolant While Amsoil 75W-90 Severe Gear® oil is used as a lubricant. Heat generated during the test run is removed by the coolant flowing through the cooling coil. The… Show more

In this study a novel in situ rolling element bearing (REB) lubricant cooling system is developed that provides a continuous cooling of the bearing outer race. In the design the stationary outer race is expanded to accommodate a cooling coil for the continuous cooling of the lubricant and the outer race. Water is used as the coolant While Amsoil 75W-90 Severe Gear® oil is used as a lubricant. Heat generated during the test run is removed by the coolant flowing through the cooling coil. The tribological effects at the speeds of the cooling test were evaluated using block-on-ring tribometer tests. Results from the experiments indicate that in the absence of cooling the temperature of the bearing outer race rises while cooling dramatically lowers the temperature. Also, the coefficient of friction increases with increasing speed. As such, in situ cooling that leads to reduced operational temperature minimizes lubricant degradation that can result from uncontrolled frictional heating. Show less