The Effects of Accelerated Stress Conditions on Electromigration Failure Kinetics and Void Morphology

1996 ◽  
Vol 428 ◽  
Author(s):  
S. Bauguess ◽  
L. H. Liu ◽  
M. L. Dreyer ◽  
M. Griswold ◽  
E. Hurley
Keyword(s):  
Current Density ◽  
Integrated Circuit ◽  
Failure Criteria ◽  
Open Circuit ◽  
Operating Conditions ◽  
Stress Conditions ◽  
Diffusional Flux ◽  
Accelerated Life ◽  
Wide Range ◽  
The Relationship

AbstractAccelerated life testing has long been used to measure the electromigration reliability of integrated circuit (IC) metallization systems. In order to establish or verify electromigration design rules for IC products the measured data is extrapolated over a wide range of operating conditions using phenomenological models. These models assume that the components of the diffusional flux, thermal stress and resulting void morphology are independent of test/operating condition. In this paper, electromigration void morphology and failure criteria are studied over a range of stress conditions and microstructures for non-layered AlCu and AlCuSi metallurgies. The failure criteria, defined as the average change in conductor resistance prior to an open circuit condition, was strongly dependent on test current density. Moreover, the nature of the relationship between failure criteria and current density was governed by the linewidth (W) relative to the median grain size (D50). This dependence can be explained qualitatively in terms of the Blech Effect.

Current Distribution in a Polymer Electrolyte Membrane Fuel Cell Under Flooding Conditions

2009 ◽  
Author(s):  
A. Jamekhorshid ◽  
G. Karimi ◽  
X. Li
Keyword(s):  
Fuel Cell ◽  
Polymer Electrolyte ◽  
Current Distribution ◽  
Current Density ◽  
Polymer Electrolyte Membrane ◽  
Operating Conditions ◽  
Average Current Density ◽  
Electrolyte Membrane ◽  
Wide Range ◽  
Average Current

Non-uniform current distribution in polymer electrolyte membrane fuel cells results in local over-heating, accelerated ageing, and lower power output than expected. This issue is very critical when fuel cell experiences water flooding. In this work, the performance of a PEM fuel cell is investigated under cathode flooding conditions. A partially flooded GDL model is proposed to study local current density distributions along flow fields over a wide range of cell operating conditions. The model results show as cathode inlet humidity and/or cell pressure increase the average current density for the unflooded portions of the cell increases but the system becomes more sensitive to flooding. Operating the cell at higher temperatures would lead to higher average current densities and the chance of system being flooded is reduced. In addition, higher cathode stoichiometries prevent system flooding but the average current density remains almost constant.

The Effects of Non-Flatness on the Performance of Slippers in Axial Piston Pumps

1983 ◽  
Vol 197 (4) ◽  
pp. 239-247 ◽  
Author(s):  
C J Hooke ◽  
Y P Kakoullis
Keyword(s):  
Film Thickness ◽  
Operating Conditions ◽  
Successful Operation ◽  
Small Deviations ◽  
Axial Piston Pumps ◽  
Satisfactory Performance ◽  
Wide Range ◽  
Minimum Film Thickness ◽  
Axial Piston ◽  
The Relationship

All previous analyses of slippers in axial piston pumps have assumed that the slipper running surface was perfectly flat and have all failed to explain the satisfactory performance of these bearings. It has been suggested, however, that slippers in axial piston pumps may depend, for their successful operation, on the small deviations from a perfect flat of the slipper surface. This paper examines the relationship between such a non-flatness and the minimum film thickness produced under steady operating conditions. It is shown that a very wide range of slipper non-flatnesses can lead to satisfactory slipper performance and that the minimum film thickness predicted is remarkably insensitive to the actual amount of deviation from flat.

The Effects of Membrane Thickness on the Performance and Impedance of the Direct Methanol Fuel Cell

2010 ◽  
Vol 224 (10) ◽  
pp. 2211-2221 ◽  
Author(s):  
S H Seo ◽  
C S Lee
Keyword(s):  
Fuel Cell ◽  
Current Density ◽  
Direct Methanol Fuel Cell ◽  
Impedance Measurement ◽  
Open Circuit ◽  
Operating Conditions ◽  
Membrane Thickness ◽  
Ohmic Loss ◽  
Direct Methanol ◽  
Methanol Fuel Cell

The purpose of this work is to investigate the effect of membrane thickness on direct methanol fuel cell (DMFC) performance and impedance under various operating conditions including operating temperature, methanol concentration, cathode flowrate, and cathode backpressure. The experiments were conducted by using three membranes of NRE-212 (50.8 m), N-115 (127 m), and N-117 (183 m) loading Pt—Ru (4 mg/cm<sup>2</sup>) and Pt-black (4 mg/cm<sup>2</sup>) at the anode and the cathode, respectively. The DMFC performance was analysed in terms of a polarization curve expressed by measuring voltage and current density and power—current density. In order to analyse performance losses such as activation loss and ohmic loss, the real and imaginary components of impedance were measured by AC impedance measurement system at various frequencies. Also, the crossover current at the open circuit was measured by using humidified nitrogen at the cathode and power supply. It was shown that DMFC performance was improved by the reduction of resistance for proton transport at the thinner membrane under the same test conditions. The comparison of open circuit voltage shows that using of a thicker membrane results in a larger value than that of using a thin membrane due to the decrease in methanol crossover.

Effects of Stator Flow Distortion on Rotating Blade Endurance: Part 2—Stress Analysis and Failure Criteria

2012 ◽  
Author(s):  
Harold Simmons ◽  
Vishwas Iyengar ◽  
Timothy C. Allison
Keyword(s):  
Structural Response ◽  
Failure Criteria ◽  
Load Flow ◽  
Operating Conditions ◽  
Flow Distortion ◽  
Blade Vibration ◽  
Rotating Blades ◽  
Rotating Blade ◽  
Wide Range ◽  
Major Factors

Blade vibrations, with the possibility of failure, is one of the major factors controlling the reliability of compressors and turbines. The prospects of encountering high alternating stress environments in blades make efficient turbomachine operation a very challenging task. In many cases the compressor or turbine functions through a wide range of load, flow, temperature, and speed which affect blade vibration, thus the stress environment continuously changes as the operating conditions changes. Any flow disturbance upstream of the rotating blades and some disturbances downstream will produce repetitive wake pulses that excite the blades. Resonance occurs with any coincidence of repetitive pulses with structural natural frequencies of rotating blades or impellers resulting in substantial amplification of alternating stresses. Most OEM design practices control vibratory stresses by avoiding resonance with expected stator sources; those excitations that cannot be avoided are designed with sufficient endurance to prevent failure. Thus three aspects of rotor/ blade design affect reliability: 1) aerodynamic excitation level and frequency, 2) structural response and resonance margins, and 3) selection and control of materials, coatings and their fabrication process to withstand the service environment. The main objective of this study is to develop a mathematical model to simulate the stresses in the rotating blade row that evaluates all three aspects of design to assess long term endurance. This is a two part paper on high cycle fatigue (HCF) failure analysis procedure of rotating blades and impellers. Part 1 [1] discusses aerodynamic excitation caused by stator vane and its role in generation of blade vibration. Here comprehensive computational fluid dynamics (CFD) is used to get a better understanding of the stator-rotor flow interactions at different operating conditions. The results of the aerodynamic simulations are order related excitation spectrum that can be applied to the stress/pulsation relationship defined in this part of the paper. This paper, Part 2, discusses an empirical dynamic stress model developed by impulse testing, assessing material endurance strength, and evaluation of criteria for failure by HCF.

scholarly journals Thermal Behaviour of a Cylindrical Li-Ion Battery

2021 ◽  
Vol 65 (2-4) ◽  
pp. 218-223
Author(s):  
Luca Giammichele ◽  
Valerio D’Alessandro ◽  
Matteo Falone ◽  
Renato Ricci
Keyword(s):  
Surface Temperature ◽  
Heat Generation ◽  
Lithium Iron Phosphate ◽  
Iron Phosphate ◽  
Open Circuit ◽  
Operating Conditions ◽  
Battery Cell ◽  
Cell Potential ◽  
Discharge Rates ◽  
Wide Range

This paper presents an experimental evaluation of thermal and electrical performances of a 26650 cylindrical Lithium Iron Phosphate/graphite battery cell. Thermal management of Lithium batteries is a fundamental issue of electric mobility, where batteries are subjected to severe operating conditions. Therefore, battery heat generation is a very important characteristic to be studied. In this work cell performances were assessed during battery discharge at ambient temperature over a wide range of discharge rates. The cell surface temperature was measured both with thermocouples and infrared thermography. Furthermore, also the open circuit potential and entropic heat coefficient were experimentally measured. Based on this experimental data, a simplified battery thermal model was used to evaluate the battery heat generation. The results show a substantial increase of battery surface temperature especially at high discharge rates. During discharge, the heat generated is greater at low battery state of charge due to the sudden decrease of cell potential. The contributions to heat generation are also carefully evaluated.

scholarly journals Dancing with Bubbles: Deterministic versus Probabilistic Bubble Models in Dense Phase Sand Fluidized Beds for Biomass Gasification

Processes ◽  
2021 ◽  
Vol 9 (7) ◽  
pp. 1092
Author(s):  
Nicolas Torres Brauer ◽  
Hugo de Lasa
Keyword(s):  
Bubble Dynamics ◽  
Probabilistic Approach ◽  
Operating Conditions ◽  
Bubble Flow ◽  
Rise Velocity ◽  
Type B ◽  
Dense Phase ◽  
Bubble Rise Velocity ◽  
Wide Range ◽  
The Relationship

This study addresses the need to model bubble flow in a fluidized bed using a probabilistic approach, which includes intrinsic bubble flow randomness. It is shown that the proposed probabilistic predictive model (PPM) overcomes the limitations of deterministic correlations, commonly used to describe bubble dynamics in high-density (above 2000 kg/m3) sand-beds of Type B particles of the Geldart classification. It is proven that a PPM can describe the relationship between bubble axial chord and bubble rise velocity using minimum and maximum behavioral bands. This probabilistic model, which applies to a wide range of operating conditions, as shown in the present study, can be considered applicable to single bubbles injected at incipient fluidization, as well as to bubbly beds with and without loaded biomass pellets.

Comparison of Deterministic and Linear Cosine Spatial Filtering of Transmission Electron Micrographs

1972 ◽  
Vol 30 ◽  
pp. 596-597
Author(s):  
David A. Ansley
Keyword(s):  
Spherical Aberration ◽  
Focal Length ◽  
Chromatic Aberration ◽  
Spatial Filter ◽  
Operating Conditions ◽  
Objective Lens ◽  
List Type ◽  
Spatial Filters ◽  
Transmission Electron ◽  
Wide Range

The coherence of the electron flux of a transmission electron microscope (TEM) limits the direct application of deconvolution techniques which have been used successfully on unmanned spacecraft programs. The theory assumes noncoherent illumination. Deconvolution of a TEM micrograph will, therefore, in general produce spurious detail rather than improved resolution.A primary goal of our research is to study the performance of several types of linear spatial filters as a function of specimen contrast, phase, and coherence. We have, therefore, developed a one-dimensional analysis and plotting program to simulate a wide 'range of operating conditions of the TEM, including adjustment of the:(1) Specimen amplitude, phase, and separation(2) Illumination wavelength, half-angle, and tilt(3) Objective lens focal length and aperture width(4) Spherical aberration, defocus, and chromatic aberration focus shift(5) Detector gamma, additive, and multiplicative noise constants(6) Type of spatial filter: linear cosine, linear sine, or deterministic

The Problem of Identifying and Modeling the Relationship between Monetary Factor and Inflation in the Russian Economy

2008 ◽  
pp. 61-76
Author(s):  
A. Porshakov ◽  
A. Ponomarenko
Keyword(s):  
Money Supply ◽  
Money Demand ◽  
Russian Economy ◽  
Long Run ◽  
Complex Approach ◽  
Wide Range ◽  
Long Time ◽  
The Relationship ◽  
Supply Side Factors

The role of monetary factor in generating inflationary processes in Russia has stimulated various debates in social and scientific circles for a relatively long time. The authors show that identification of the specificity of relationship between money and inflation requires a complex approach based on statistical modeling and involving a wide range of indicators relevant for the price changes in the economy. As a result a model of inflation for Russia implying the decomposition of inflation dynamics into demand-side and supply-side factors is suggested. The main conclusion drawn is that during the recent years the volume of inflationary pressures in the Russian economy has been determined by the deviation of money supply from money demand, rather than by money supply alone. At the same time, monetary factor has a long-run spread over time impact on inflation.

Structure and properties of compact articles from high-alloyed iron powder with adding of boron nitride

2020 ◽  
pp. 39-48
Author(s):  
B. O. Bolshakov ◽  
◽  
R. F. Galiakbarov ◽  
A. M. Smyslov ◽  
◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Boron Nitride ◽  
Grain Boundary ◽  
Bending Strength ◽  
Physical And Mechanical Properties ◽  
Operating Conditions ◽  
Structure And Properties ◽  
Steam Turbines ◽  
Friction Forces ◽  
Wide Range

The results of the research of structure and properties of a composite compact from 13 Cr – 2 Мо and BN powders depending on the concentration of boron nitride are provided. It is shown that adding boron nitride in an amount of more than 2% by weight of the charge mixture leads to the formation of extended grain boundary porosity and finely dispersed BN layers in the structure, which provides a high level of wearing properties of the material. The effect of boron nitride concentration on physical and mechanical properties is determined. It was found that the introduction of a small amount of BN (up to 2 % by weight) into the compacts leads to an increase in plasticity, bending strength, and toughness by reducing the friction forces between the metal powder particles during pressing and a more complete grain boundary diffusion process during sintering. The formation of a regulated structure-phase composition of powder compacts of 13 Cr – 2 Mо – BN when the content of boron nitride changes in them allows us to provide the specified physical and mechanical properties in a wide range. The obtained results of studies of the physical and mechanical characteristics of the developed material allow us to reasonably choose the necessary composition of the powder compact for sealing structures of the flow part of steam turbines, depending on their operating conditions.

A pilot web former designed to study retention-formation relationships

2010 ◽  
Vol 25 (2) ◽  
pp. 185-194
Author(s):  
Anna Svedberg ◽  
Tom Lindström
Keyword(s):  
Pilot Scale ◽  
Operating Conditions ◽  
Montmorillonite Clay ◽  
Speed Ratio ◽  
Good Reproducibility ◽  
Total Solids ◽  
Retention Aids ◽  
Solids Content ◽  
Relationship Of ◽  
The Relationship

Abstract A pilot-scale fourdrinier former has been developed for the purpose of investigating the relationship between retention and paper formation (features, retention aids, dosage points, etc.). The main objective of this publication was to present the R-F (Retention and formation)-machine and demonstrate some of its fields of applications. For a fine paper stock (90% hardwood and 10% softwood) with addition of 25% filler (based on total solids content), the relationship between retention and formation was investigated for a microparticulate retention aid (cationic polyacrylamide together with anionic montmorillonite clay). The retention-formation relationship of the retention aid system was investigated after choosing standardized machine operating conditions (e.g. the jet-to-wire speed ratio). As expected, the formation was impaired when the retention was increased. Since good reproducibility was attained, the R-F (Retention and formation)-machine was found to be a useful tool for studying the relationship between retention and paper formation.

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