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Predicting thermal safety events of lithium-ion (Li-ion) batteries is significant in optimizing electrochemical systems with high thermal tolerance. The safety performances of Li-ion batteries are dictated by the thermal stability of their component materials both individually and collectively due to intricate exothermic reactions. Although the heat release of individual battery material has been thoroughly investigated, the safety hazards of inter-electrode chemical crosstalk under thermal abuse scenarios remain elusive and thus need a fundamental understanding. This study carries out a comprehensive thermal analysis of various material samples harvested from a commercial Li-ion cell using differential scanning calorimetry (DSC), complemented with full-cell accelerating rate calorimetry (ARC) and computational modeling. Reaction kinetics of electrolyte, wet cathode, wet anode and DSC-full cell samples imitating cell layered architectures are delineated to reveal substantial thermal interactions between electrodes. High-resolution kinetic parameters of reaction mechanisms are estimated using a synergy of Kissinger's method and mechanism-driven non-linear optimization strategies. A thermal abuse model is built based on the extracted kinetic parameters to simulate the cell-level thermal runaway phenomenon and compared with experimental observations, indicating how interlayer crosstalk effects significantly impact the thermal safety characteristics of Li-ion cell chemistries.

In this study, a high power infrared heater was implemented to preheat an H13 steel die used for high pressure die casting. The performance of the heating system was quantified experimentally by measuring die temperatures in various locations with embedded thermocouples. Heating time was reduced significantly by using a flat, stainless-steel reflector on one side of the heater. A numerical model was developed to simulate the infrared radiation heat transfer into the die. The model was validated against literature data and experimental results. The model was then used to evaluate different lamp configurations to obtain a more uniform heating distribution and to avoid hot spots on protruding surfaces. The validated model has proven to be useful in evaluating different lamp configurations tailored for specific die geometries or heating requirements.

A conjugate heat and mass transfer model was implemented into a commercial CFD code to analyze the convective drying of corn. The Navier–Stokes equations for drying air flow were coupled to diffusion equations for heat and moisture transport in a corn kernel during drying. Model formulation and implementation in the commercial software is discussed. Validation simulations were conducted to compare numerical results to experimental, thin-layer drying data. The model was then used to analyze drying performance for a compact, crossflow dehydrator. At low inlet air temperatures, the drying rate in the compact dehydrator matched the thin-layer drying rate. At higher temperatures, heat losses through the external walls resulted in temperature and moisture variations across the dehydrator.

In this work we present the development of a Smart Learning Factory (SLF) at Purdue University for preparing students with the skills, capabilities, and technological experiences necessary to excel in an Industry 4.0 environment. Functionally, the SLF is a replica of an actual cyber-physical production factory designed to intentionally foster collaboration between courses from multiple disciplinary areas, particularly mechanical, electrical, mechatronics, and robotics. Our objective is to reduce course silos by deliberately fusing the interconnection between courses by using SLF as the common unifying platform. Activities in design, manufacturing processes, production, production management, automation, energy, information, and communications, teamwork and collaboration are integrated using a vertical and horizontal integration framework. Unifying project activities were designed and introduced into these courses using this framework. As a result, 22 courses were integrated and a total of 26 vertical and horizontal integrated projects developed. This integration also facilitated the development of an energy credential using the SLF. Students progressing from freshman through senior year in college will better understand the interconnection of content between different courses, apply their learning to a manufacturing environment, gain a holistic perspective of the interdependent structures of the cyber-physical system, the connected enterprise, and the manufacturing ecosystem.

A pouch cell method for retesting double-sided electrodes harvested from commercial lithium-ion batteries in a 3-electrode cell arrangement has been developed. By relying on pressure from restraint plates to make tab electrical connections, this method (1) requires no welding, (2) does not require a dry room, (3) does not require precision sealing equipment inside of an inert-gas glove box, and (4) does not require removal of composite material off of one side of the electrode which may compromise the composite to be tested on the other side. Lithium chips pressed onto copper mesh serve as the reference and counter electrodes and the electrolyte used was 1.0 M LiPF6 1:1 ethylene carbonate (EC):Diethyl carbonate (DEC) v/v. Electrochemical cycling of electrodes from a commercial 3.6 Ah 18650 lithium-ion cell demonstrated cell function and showed stable capacity and potential charge/discharge profiles after two cycles for the cathode and four cycles for the anode. The areal capacity of the anode and cathode was determined to be 5.50 ± 0.31 and 5.50 ± 0.30 mAh/cm2, respectively, based on a potential range of 0.005–1.5 V versus Li/Li+ for the anode and 3.0–4.25 V versus Li/Li+ for the cathode. High frequency, 500 kHz impedance measurements of the anode and cathode cells shows a real impedance of 1.55 Ohms and 2.17 Ohms, respectively, which is similar to prior studies on pouch cells with continuous tabs of similar capacity.

Lithium-ion batteries are a proven energy storage device which continue to gain market share across a wide range of applications. However, the safety of these devices is still a major factor in many applications. In failures which result in thermal runaway, a series of chemical reactions are initiated which produce a large quantity of gas and heat. The pressure and temperature inside the battery rise sharply and may cause fire or explosion. The lithium-ion battery vent cap is a key safety device used in 18650 format cells to prevent an energetic failure of the metal casing. In this paper, the cap structure and venting parameters of three cap designs are analyzed. The venting parameters investigated were the open flow area and discharge coefficient. Open flow area through different components of the cap assembly were measured using 3D x-ray scans. A new experimental apparatus was used to measure mass flowrate and pressure ratio across the battery cap, which allowed calculation of discharge coefficient. Results indicate that discharge coefficients follow the same trend as a sharp-edged orifice, albeit at a reduced magnitude due to the more tortuous flow path. A semi-empirical model is proposed to simulate mass flow through the battery cap.

High pressure die casting (HPDC) is a highly violent process that causes significant wear on the die from chemical attacks and from repeated cycling at high pressure and temperature. In practice, HPDC dies are usually preheated by injecting aluminum into the die as warm-up shots. Although warm-up shots transfer heat into the die at a high rate, the warm-up shots are often rejected as scrap due to defects caused by the lower-than-optimal die temperature. The present work aims to develop an auxiliary heating system using an array of high-power, electric infrared lamps to preheat an HPDC die. The potential advantage of this method is a reduction in scrap material and a reduction in thermal cycles on the casting die. Experiments were conducted to quantify the heating rate for various infrared electric heater configurations. A numerical model was also developed to simulate the radiation heat transfer from the lamp array to the die. The model was validated against experiments and subsequently used to optimize the configuration of the heater. The heating system was improved by adding a small radiation shield to minimize hot spots on protruding surfaces while still maintaining a fast heating time. The validated numerical model can be used in the future to develop custom heater solutions for different die geometries.

Physics-based aging models are critical for understanding capacity degradation mechanisms in Li-ion batteries. This paper presents a technique for aging analysis of a Li-ion cell due to growth of the solid electrolyte interphase (SEI) layer driven by a solvent decomposition reaction at the electrode surface. The model employs an iterative technique based on the analytical solutions of the underlying conservation equations. The single-particle model describing Li-ion intercalation and de-intercalation processes is solved analytically using Green's function technique. The SEI formation problem is solved using the integral balance method. An iterative technique that combines these analytical solutions is shown to result in a converged result within a few iterations. The model is shown to agree well with results from past studies, as well as a numerical simulation. The capacity fade of Li-ion batteries is investigated under different operating conditions and different regimes, including both cycling and storage. The present model offers much faster computation time than numerical models for modeling the degradation of Li-ion cells. Further, the iterative technique described here may serve as a framework for semi-analytical solutions for other, more complicated problems. This work contributes towards improving the performance and reliability of electrochemical energy conversion and storage systems.

Lithium batteries have a tendency to fail violently under adverse conditions leading to the rapid venting of gas. Overcharge, thermal heating, and a combination of the two conditions are applied here to investigate the gas venting process. A test chamber has been constructed with data recordings including chamber pressure and temperature, battery voltage, current, and surface temperature as functions of time throughout the charging and failure processes. High-speed imaging and schlieren flow visualization are used to visualize the gas venting process. A direct comparison between lithium iron phosphate based K2 26650 and lithium nickel manganese cobalt oxide LG 18650 cells is made through a test series of the three failure methods. Failure under thermal, overcharge, and thermal-overcharge conditions are generally similar in terms of the gas venting process, but are observed to have increasingly energetic failures. The thermal-overcharge abuse condition demonstrates an ability to reconnect via internal short circuit even after an initial electrical failure seen as the refusal to accept charge. This reconnection is associated with a secondary, more energetic failure which can produce weak shock pressure waves.

The current interrupt device (CID) and vent mechanism in the cap of 18650 lithium-ion cells decrease thermal runaway risks by electrically isolating the cell upon internal pressure increase and relieving internal pressure before case rupture, respectively. Geometry analysis, CID- and vent-activation pressure measurement, and finite element analysis mechanical simulation of the vent mechanism were performed for MTI and LG MJ1 18650 caps. The MTI cap used a spot-weld and the LG MJ1 cap used a notch-groove connection for the CID. The vent-activation mechanism was a notch-grooved disk for both caps. The CID-activation pressures were 1.058 ± 0.053 and 1.293 ± 0.119 MPa at ambient temperature and 0.920 ± 0.076 and 1.066 ± 0.068 MPa at 100°C for the MTI and LG MJ1 caps, respectively. The vent-activation pressures were 2.308 ± 0.196 and 2.202 ± 0.083 MPa at ambient temperature and 1.919 ± 0.132 and 1.866 ± 0.084 MPa at 100°C for the MTI and LG MJ1 caps, respectively. Mechanical simulations predicted vent-activation pressures in agreement with experiments and showed decrease maximum stress sensitivity to applied pressure near the vent-activation pressure, consistent with observed sample-to-sample vent-activation pressure variation. Mechanical simulation also predicted vent-activation pressures of 0.448 and 0.400 MPa for the MTI and LG MJ1 caps, respectively, at 300°C.

A coupled, thermal and gas generation/venting model has been developed for simulating the onset and evolution of thermal runaway in 18650 format Li-ion battery cells. The model simulates heat and gas generation during external heating of an electrically isolated cell that results in thermal runaway. Gas generation within the cell leads to pressure build up until the point at which the vent mechanism opens and relieves the internal pressure. Compressible flow of gases is modeled through the vent cap as a function of pressure ratio across the vent. The energy balance of the battery cell includes: heat generated from decomposition reactions and electrical short, external heat transfer to the surroundings, heat absorbed with vaporization and melting processes, as well as the energy loss as material is vented from the cell. The model was able to capture features of the temperature evolution of the battery cell well and generate detailed information about the progression of thermal runaway. The model was exercised to simulate time-to-venting and time-to-thermal-runaway for various changes in cell design parameters such as: amount of free liquid electrolyte, external convection coefficient, and electrolyte evaporation rate after vent opening.

Measurement and modeling of thermal phenomena in Li-ion cells is a critical research challenge that directly affects both performance and safety. Even though the operation of a Li-ion cell is in most cases a transient phenomenon, most available thermal models for Li-ion cells predict only steady-state temperature fields. This paper presents the derivation, experimental validation and application of an analytical model to predict the transient temperature field in a cylindrical Li-ion cell in response to time-varying heat generation within the cell. The derivation is based on Laplace transformation of governing energy equations, and accounts for anisotropic thermal conduction within the cell. Model predictions are in excellent agreement with experimental measurements on a thermal test cell. The effects of various thermophysical properties and parameters on transient thermal characteristics of the cell are analyzed. The effect of pulse width and cooling time for pulsed operation is quantified. The thermal response to multiple cycles of discharge and charge is computed, and cell-level trade-offs for this process are identified. The results presented in this paper may help understand thermal phenomena in Li-ion cells, and may contribute towards thermal design and optimization tools for energy conversion and storage systems based on Li-ion cells.

While Lithium-ion batteries have the potential to serve as an excellent means of energy storage, they suffer from several operational safety concerns. Temperature excursion beyond a specified limit for a Lithium-ion battery triggers a sequence of decomposition and release, which can preclude thermal runaway events and catastrophic failure. To optimize liquid or air-based convective cooling approaches, it is important to accurately model the thermal response of Lithium-ion cells to convective cooling, particularly in high-rate discharge applications where significant heat generation is expected. This paper presents closed-form analytical solutions for the steady-state temperature profile in a convectively cooled cylindrical Lithium-ion cell. These models account for the strongly anisotropic thermal conductivity of cylindrical Lithium-ion batteries due to the spirally wound electrode assembly. Model results are in excellent agreement with experimentally measured temperature rise in a thermal test cell. Results indicate that improvements in radial thermal conductivity and axial convective heat transfer coefficient may result in significant peak temperature reduction. Battery sizing optimization using the analytical model is discussed, indicating the dependence of thermal performance of the cell on its size and aspect ratio. Results presented in this paper may aid in accurate thermal design and thermal management of Lithium-ion batteries.

Cylindrical Li-ion cells have demonstrated among the highest power density of all Li-ion cell types and typically employ a spiral electrode assembly. This spiral assembly is expected to cause large anisotropy in thermal conductance between the radial and axial directions due to the large number of interfaces between electrode and electrolyte layers in the radial conduction path, which are absent in the axial direction. This paper describes a novel experimental technique to measure the anisotropic thermal conductivity and heat capacity of Li-ion cells using adiabatic unsteady heating. Analytical modeling of the method is presented and is shown to agree well with finite-element simulation models. Experimental measurements indicate that radial thermal conductivity is two orders of magnitude lower than axial thermal conductivity for cylindrical 26650 and 18650 LiFePO 4 cells. Due to the strong influence of temperature on cell performance and behavior, accounting for this strong anisotropy is critical when modeling battery behavior and designing battery cooling systems. This work improves the understanding of thermal transport in Li-ion cells, and presents a simple method for measuring anisotropic thermal transport properties in cylindrical cells.

The transient source measurement technique is a nonintrusive, nondestructive method of measuring the thermal properties of a given sample. The transient source technique has been implemented using a wide variety of sensor shapes or configurations. The modern transient plane source (TPS) sensor is a spiral-shaped sensor element which evolved from transient line and transient hot strip (THS) source techniques. Commercially available sensors employ a flat interface that works well when test samples have a smooth, flat surface. The present work provides the basis for a new, cylindrical strip (CS) sensor configuration to be applied to cylindrical surfaces. Specifically, this work uses parameter estimation theory to compare the performance of CS sensor configurations with a variety of existing flat sensor geometries, including TPS and THS. A single-parameter model for identifying thermal conductivity and a two-parameter model for identifying both thermal conductivity as well as volumetric heat capacity are considered. Results indicate that thermal property measurements may be carried out with greater measurement sensitivity using the CS sensor configuration than similar configurations for flat geometries. In addition, this paper shows how the CS sensor may be modified to adjust the characteristic time scale of the experiment, if needed.

While flow across long tube bundles is considered classical data, pin-fin arrays made up of short tubes have become a growing topic of interest for use in cooling gas turbine airfoils. Data from the literature indicate that decreasing streamwise spacing increases heat transfer in pin-fin arrays; however, the specific mechanism that causes increased heat transfer coefficients remains unknown. The present work makes use of time-resolved PIV to quantify the effects of streamwise spacing on the turbulent near wake throughout various pin-fin array spacings. Specifically, proper orthogonal decomposition was used to separate the (quasi-) periodic motion from vortex shedding and the random motion from turbulent eddies. Reynolds number flow conditions of 3.0 × 103 and 2.0 × 104, based on pin-fin diameter and velocity at the minimum flow area, were considered. Streamwise spacing was varied from 3.46 pin diameters to 1.73 pin diameters while the pin-fin height-to-diameter ratio was unity and the spanwise spacing was held constant at two diameters. Results indicated that (quasi-) periodic motions were attenuated at closer streamwise spacings while the level of random motions was not strongly dependent on pin-fin spacing. This trend was observed at both Reynolds number conditions considered. Because closer spacings exhibit higher heat transfer levels, the present results imply that periodic motions may not contribute to heat transfer, although further experimentation is required.

Staggered arrays of short cylinders, known as pin–fins, are commonly used as a heat exchange method in many applications such as cooling electronic equipment and cooling the trailing edge of gas turbine airfoils. This study investigates the near wake flow as it develops through arrays of staggered pin fins. The height-to-diameter ratio was unity while the transverse spacing was kept constant at two cylinder diameters. The streamwise spacing was varied between 3.46 and 1.73 cylinder diameters. For each geometric arrangement, experiments were conducted at Reynolds numbers of 3.0e3 and 2.0e4 based on cylinder diameter and velocity through the minimum flow area of the array. Time-resolved flowfield measurements provided insight into the dependence of row position, Reynolds number, and streamwise spacing. Decreasing streamwise spacing resulted in increased Strouhal number as the near wake length scales were confined. In the first row of the bundle, low Reynolds number flows were mainly shear-layer-driven while high Reynolds number flows were dominated by periodic vortex shedding. The level of velocity fluctuations increased for cases having stronger vortex shedding. The effect of streamwise spacing was most apparent in the reduction of velocity fluctuations in the wake when the spacing between rows was reduced from 2.60 diameters to 2.16 diameters.

Arrays of variably-spaced pin fins are used as a conventional means to conduct and convect heat from internal turbine surfaces. The most common pin shape for this purpose is a circular cylinder. Literature has shown that beyond the first few rows of pin fins, the heat transfer augmentation in the array levels off and slightly decreases. This paper provides experimental results from two studies seeking to understand the effects of gaps in pin spacing (row removals) and alternative pin geometries placed in these gaps. The alternative pin geometries included large cylindrical pins and oblong pins with different aspect ratios. Results from the row removal study at high Reynolds number showed that when rows four through eight were removed, the flow returned to a fully-developed channel flow in the gap between pin rows. When larger alternative geometries replaced the fourth row, heat transfer increased further downstream into the array.Copyright © 2014 by ASME

In much of the public literature on pin-fin heat transfer, Nusselt number is presented as a function of Reynolds number using a power-law correlation. Power-law correlations typically have an accuracy of 20% while the experimental uncertainty of such measurements is typically between 5% and 10%. Additionally, the use of power-law correlations may require many sets of empirical constants to fully characterize heat transfer for different geometrical arrangements. In the present work, artificial neural networks were used to predict heat transfer as a function of streamwise spacing, spanwise spacing, pin-fin height, Reynolds number, and row position. When predicting experimental heat transfer data, the neural network was able to predict 73% of array-averaged heat transfer data to within 10% accuracy while published power-law correlations predicted 48% of the data to within 10% accuracy. Similarly, the neural network predicted 81% of row-averaged data to within 10% accuracy while 52% of the data was predicted to within 10% accuracy using power-law correlations. The present work shows that first-order heat transfer predictions may be simplified by using a single neural network model rather than combining or interpolating between power-law correlations. Furthermore, the neural network may be expanded to include additional pin-fin features of interest such as fillets, duct rotation, pin shape, pin inclination angle, and more making neural networks expandable and adaptable models for predicting pin-fin heat transfer.Copyright © 2013 by ASME

Pin fin arrays are most commonly used to promote convective cooling within the internal passages of gas turbine airfoils. Contributing to the heat transfer are the surfaces of the channel walls as well as the pin itself. Generally the pin fin cross-section is circular; however, certain applications benefit from using other shapes such as oblong pin fins. The current study focuses on characterizing the heat transfer distribution on the surface of oblong pin fins with a particular focus on pin spacing effects. Comparisons were made with circular cylindrical pin fins, where both oblong and circular cylindrical pins had a height-to-diameter ratio of unity, with both streamwise and spanwise spacing varying between two and three diameters. To determine the effect of relative pin placement, measurements were taken in the first of a single row and in the third row of a multi-row array. Results showed that area-averaged heat transfer on the pin surface was between 30 and 35 percent lower for oblong pins in comparison to cylindrical. While heat transfer on the circular cylindrical pin experienced one minimum prior to boundary layer separation, heat transfer on the oblong pin-fins experienced two minimums, where one is located before the boundary layer transitions to a turbulent boundary layer and the other prior to separation at the trailing edge.Copyright © 2013 by ASME

Pin fin arrays are commonly used to cool the trailing edge of gas turbine airfoils. While the majority of pin fin research focuses on uniformly-spaced arrays, the goal of the present work was to determine if non-uniform spacing in the streamwise direction could be utilized to maintain high heat transfer while simultaneously extending the array footprint. The uniqueness of the work lies in the basis for selecting the non-uniform spacing pattern. The non-uniform arrangement was chosen to exploit previously published row-by-row heat transfer development where the initial rows showed little variation with streamwise spacing. As such, a non-uniform array was considered where the initial rows had spacing of 3.46 diameters and the inner rows gradually decreased to a final spacing of 1.73 diameters. Three seven-row arrays were considered having constant streamwise spacing of 2.16, 2.60, and 3.03 pin fin diameters. All configurations had constant spanwise spacing of two diameters and constant pin height of one diameter. Three Reynolds numbers of 3.0e3, 1.0e4, and 2.0e4 were considered based on pin fin diameter and minimum area velocity. At high Reynolds numbers, heat transfer and pressure drop measurements were in agreement for the nonuniform array and for a closely spaced array having 2.16 diameter streamwise spacing. While array performance was similar, the non-uniform array covered 16.8% more streamwise distance than the closely spaced array. At low Reynolds numbers, however, the non-uniform array was outperformed by the closely spaced array.Copyright © 2013 by ASME

Pin-fin channels are commonly used for cooling the trailing edges in turbine blades and vanes. While many studies have investigated heat transfer performance of pin-fin channels, few studies have investigated pin-fin flowfields. The present study compares the time-dependent near wake flow and the time-mean surface heat transfer for varying pin-fin configurations at a Reynolds number of 2.0e4. Pin-fin aspect ratio showed little influence on pin-surface heat transfer coefficients when increasing H/D from 1.0 to 2.0. Changes in streamwise and spanwise spacing, however, were found to significantly impact the behavior of the near wake flow and local heat transfer coefficients. Decreasing spanwise spacing from S/D = 3.0 to 1.5 in a single pin-fin row was found to suppress downstream vortex shedding and create biased, asymmetric wakes. Local heat transfer coefficients on the trailing side of the pin-fin reflected that vortex shedding, observed for spanwise spacings S/D ≥ 2.0, was beneficial for heat transfer on the pin-surface. Similarly, decreasing streamwise spacing from X/D = 3.03 to 2.16 was found to suppress vortex shedding in the first row of a seven row array. For those cases that support vortex shedding, X/D ≥ 2.60, pin-fin heat transfer increased on the trailing side but array heat transfer in downstream rows decreased.Copyright © 2012 by ASME

Pin-fin arrays are commonly used as compact heat exchangers for cooling the trailing edge of gas turbine airfoils. While much research has been devoted to the heat transfer characteristics of various pin-fin configurations, little work has been done to investigate the flowfield in pin-fin arrays. Such information may allow for further optimization of pin-fin configurations. A new pin-fin facility at large scale has been constructed to allow optical access for the use of non-intrusive measurement techniques such as laser Doppler velocimetry and time-resolved, digital particle image velocimetry. Using these techniques, the flow through a single row of pin-fins having a height-to-diameter ratio of 2 and span-to-diameter ratio of 2.5 was investigated. Results show that the length of the wake region decreases with increasing Reynolds number. At higher Reynolds numbers, Karman vortices developed closer to the pin-fins than for single, infinitely long cylinders. Transverse fluctuations correlated well with endwall heat transfer indicating that the Karman vortices play a key role in energy transport.Copyright © 2011 by ASME

Current turbine airfoils must operate at extreme temperatures, which are continuously driven higher by the demand for high output engines. Internal cooling plays a key role in the longevity of gas turbine airfoils. Ribbed channels are commonly used to increase heat transfer by generating turbulence and to provide a greater convective surface area. Because of the increasing complexity in airfoil design and manufacturing, a methodology is needed to accurately measure the convection coefficient of a rib with a complex shape. Previous studies that have measured the contribution to convective heat transfer from the rib itself have used simple rib geometries. This paper presents a new methodology to measure convective heat transfer coefficients on complex ribbed surfaces. The new method was applied to a relatively simple shape so that comparisons could be made with a commonly accepted method for heat transfer measurements. A numerical analysis was performed to reduce experimental uncertainty and to verify the lumped model approximation used in the new methodology. Experimental measurements were taken in a closed-loop channel using fully rounded, discontinuous, skewed ribs oriented 45° to the flow. The channel aspect ratio was 1.7:1 and the ratio of rib height to hydraulic diameter was 0.075. Heat transfer augmentation levels relative to a smooth channel were measured to be between 4.7 and 3 for Reynolds numbers ranging from 10,000 to 100,000.Copyright © 2008 by ASME

The response of a magneto-rheological (MR) damper is often characterized by a force-velocity response plot from a sinusoidal input. These plots are created in a shock dynamometer in which one end of the damper is attached to a load frame and the other end is moved in a sine wave with a given peak velocity and frequency. The peak damper force from a series of sine wave tests of varying peak velocity is measured and plotted as discrete data points versus the relative velocity across the damper. This is a standard procedure for characterizing passive shock absorbers in the automotive industry. The validity of this characterization relies on the assumption that the damper is dominantly a velocity-dependent device. However, it is well-known that the internal dynamics of the damper depend not only on the velocity of the input, but also the frequency of the excitation. Therefore both velocity and frequency should be considered as independent parameters to achieve a more complete characterization of a MR damper's response under sinusoidal excitation. This paper investigates the dependence of the force response to both peak velocity and frequency, for several different MR dampers from a wide variety of applications. By treating the velocity and frequency as two independent parameters, a complete characterization of the damper's response under sinusoidal excitation can be characterized. After investigating how damper force varies with both peak velocity and frequency, efficient test procedures are recommended for future MR damper characterizations.Copyright © 2006 by ASME

Lithium Iron Phosphate (LFP) batteries present many challenges for accurate behavioral modeling during charge and discharge processes, as the two-phase interactions between cathode particles create multiple stable, degenerate distributions of lithium across the electrode. These degenerate distributions can cause the battery’s equilibrium open circuit potential (VOC) and equivalent series resistance (ESR) to vary at a given temperature and state of charge (SOC) depending on recent history, such as if the battery was most recently charged or discharged, a phenomenon known as hysteresis. A behavioral two-capacitor model was developed that incorporates temperature-dependent hysteresis between charge and discharge (affecting both VOC and ESR) and mimics temperature-dependent and SOC-dependent kinetics and impedance. The model includes a coupled finite volume thermal transport model with heat generation calculated due to a combination of Ohmic heating and entropic heating. The model was validated against high C-rate cyclic charge and discharge, as well as intermittent discharge and charge profiles at temperatures ranging from zero to 50°C. It is seen that for temperatures near 0°C, new physics come into play during recharge and that VOC hysteresis between charge and discharge increases as temperature decreases.