Numerical Analysis of the Impact of Manufacturing Errors on the Structural Stiffness of Foil Bearings

2017 ◽  
Author(s):  
Aurelian Fatu ◽  
Mihai Arghir
Keyword(s):  
Standard Deviation ◽  
Mechanical Characteristics ◽  
Three Dimensional ◽  
Simplified Model ◽  
Radial Clearance ◽  
Foil Bearings ◽  
Bump Height ◽  
Manufacturing Errors ◽  
The Impact ◽  
Bearing Structure

The dynamic characteristics of foil bearings operating at high rotation speeds depend very much on the mechanical characteristics of the foil structure. For this reason, the stiffness and damping of the structure of foil bearings is a problem that is the focus of many analyses. The mechanical characteristics of the foil structure (top and bump foil) are analyzed either by using a simple approach obtained for an isolated bump modeled as a beam or with more elaborate ones taking into account the three-dimensional nature of the bumps and their mutual interactions. These two kinds of models give different foil structure stiffness, with lower values for the simplified model. However, the published experimental results of the foil bearing structure tend to validate the simplified model. The present paper explains the differences between the simplified and the elaborate models by taking into account the manufacturing errors of the foil structure. A three-dimensional model based on the non-linear theory of elasticity is developed. The model offers a unique insight into the way the bearing structure deforms when the rotor is incrementally pushed into the foil structure. Three realistic manufacturing errors, bump height, bump length and radius of the bump foil are analyzed. Bump height and length vary following a normal distribution with a given standard deviation while the radius of the bump foil is given a waviness form with an imposed peak-to-peak amplitude. Three to five cases were calculated for each kind of error. Results show that only the manufacturing errors of the bump height affect the stiffness of the foil structure by diminishing its values. Height errors of 20 μm standard deviation (4% of the average bump height and 60% of the radial clearance) may induce a 40–50% reduction of the stiffness of the foil structure, i.e. in the range of the predictions of the simplified model.

Numerical Analysis of the Impact of Manufacturing Errors on the Structural Stiffness of Foil Bearings

2017 ◽  
Vol 140 (4) ◽  
Author(s):  
Aurelian Fatu ◽  
Mihai Arghir
Keyword(s):  
Standard Deviation ◽  
Mechanical Characteristics ◽  
Three Dimensional ◽  
Simplified Model ◽  
Radial Clearance ◽  
Foil Bearings ◽  
Bump Height ◽  
Manufacturing Errors ◽  
The Impact ◽  
Bearing Structure

The dynamic characteristics of foil bearings operating at high rotation speeds depend very much on the mechanical characteristics of the foil structure. For this reason, the stiffness and damping of the structure of foil bearings are problems that are the focus of many analyses. The mechanical characteristics of the foil structure (top and bump foil) are analyzed either by using a simple approach obtained for an isolated bump modeled as a beam or with more elaborate ones taking into account the three-dimensional nature of the bumps and their mutual interactions. These two kinds of models give different foil structure stiffness, with lower values for the simplified model. However, the published experimental results of the foil bearing structure tend to validate the simplified model. The present paper explains the differences between the simplified and the elaborate models by taking into account the manufacturing errors of the foil structure. A three-dimensional model based on the nonlinear theory of elasticity is developed. The model offers a unique insight into the way the bearing structure deforms when the rotor is incrementally pushed into the foil structure. Three realistic manufacturing errors, bump height, bump length, and radius of the bump foil, are analyzed. Bump height and length vary following a normal distribution with a given standard deviation while the radius of the bump foil is given a waviness form with an imposed peak-to-peak amplitude. Three to five cases were calculated for each kind of error. Results show that only the manufacturing errors of the bump height affect the stiffness of the foil structure by diminishing its values. Height errors of 20 μm standard deviation (4% of the average bump height and 60% of the radial clearance) may induce a 40–50% reduction of the stiffness of the foil structure, i.e., in the range of the predictions of the simplified model.

On the Impact of Geometric Variability on Fan Aerodynamic Performance, Unsteady Blade Row Interaction, and Its Mechanical Characteristics

2014 ◽  
Vol 136 (9) ◽  
Author(s):  
R. Schnell ◽  
T. Lengyel-Kampmann ◽  
E. Nicke
Keyword(s):  
Boundary Layer ◽  
Standard Deviation ◽  
Mechanical Characteristics ◽  
Principal Component ◽  
Aerodynamic Performance ◽  
Pressure Amplitude ◽  
Turbulent Transition ◽  
Blade Row ◽  
The Impact ◽  
Blade Row Interaction

The focus of the present study is to assess and quantify the uncertainty in predicting the steady and unsteady aerodynamic performance as well as the major mechanical characteristics of a contrarotating turbofan, primarily due to geometric variations stemming from the manufacturing process. The basis of this study is the optically scanned blisk of the first rotor, for which geometric variations from blade to blade are considered. In a first step, selected profile sections of the first rotor were evaluated aerodynamically by applying the 2D coupled Euler/boundary-layer solver mises. Statistical properties of the relevant flow quantities were calculated firstly based on the results of the nine manufactured blades. In a second step, the geometric variations were decomposed into their corresponding eigenforms by means of principal component analysis (PCA). These modes were the basis for carrying out Monte Carlo (MC) simulations in order to analyze in detail the blade's aerodynamic response to the prescribed geometric variations. By means of 3D-computational fluid dynamics (CFD) simulations of the entire fan stage for all the nine scanned rotor 1 blade geometries, the variation of the overall stage performance parameters will be quantified. The impact of the instrumentation will be discussed, here partly doubling the standard deviation of the major performance indicators for the instrumented blades and also triggering a premature laminar/turbulent transition of the boundary layer. In terms of the unsteady blade row interaction, the standard deviation of the resulting blade pressure amplitude shall be discussed based on unsteady simulations, taking advantage of a novel harmonic balance approach. It will be shown that the major uncertainty in terms of the predicted blade pressure amplitude is in the aft part of the front rotor and results from upstream shock/blade interaction. Apart from the aerodynamic performance, an analysis of the mechanical properties in terms of Campbell characteristics and eigenfrequencies was carried out for each of the scanned blades of rotor 1, reflecting the frequency scattering of each eigenmode due to geometric variability.

scholarly journals GW46 High Voltage Isolation Switch Solid-Heat Coupling Simulation Analysis and Experimental Study

2020 ◽  
Vol 179 ◽  
pp. 01004
Author(s):  
Yuyang Song ◽  
Benxue Liu ◽  
Qinghui Wang ◽  
Peng Yuan
Keyword(s):  
Experimental Data ◽  
Experimental Study ◽  
Contact Pressure ◽  
High Voltage ◽  
Mechanical Characteristics ◽  
Simulation Analysis ◽  
Three Dimensional ◽  
Simplified Model ◽  
Clamping Force ◽  
Simulation Results

Taking the high⁃voltage disconnector of the GW46 type as research object, this research first use Solidworks to build its three-dimensional simplified model, then use ABAQUS to simulate the mechanical characteristics of the disconnector over a wide temperature range, analyzing the influence of the clamping force between the dynamic and static contacts on temperature, the contact pressure between the dynamic and static contacts of the high⁃voltage disconnector of the GW46 type increases with the ambient temperature, and the contact pressure becomes smaller. Compared simulation results with experimental data, the error is less than 5%. Analysis shows that using the ABAQUS to simulation analysis of temperature rise of the high⁃voltage disconnector of the GW46 type, it can be determined that the contact pressure between the dynamic and static contacts changes with temperature. It avoids the complexity of the traditional theoretical calculation of query parameters and tedious calculations, and provides strong reference evidence for improving the reliability of the high⁃voltage disconnector of the GW46 type.

Systematic Analysis of the Impact of Bump Height Manufacturing Errors on the Unbalance Response of a Foil Journal Bearing

2020 ◽  
Vol 143 (1) ◽  
Author(s):  
Omar Benchekroun ◽  
Mihai Arghir
Keyword(s):  
Degrees Of Freedom ◽  
Journal Bearing ◽  
Systematic Analysis ◽  
Mean Values ◽  
Bump Height ◽  
Unbalance Response ◽  
Machining Errors ◽  
Manufacturing Errors ◽  
The Mean ◽  
The Impact

Abstract The present work exhibits the numerical investigation of the bump height-manufacturing errors on the unbalance response of an aerodynamic foil journal bearing. This is the first study on the impact of manufacturing errors based on an important number of samples. A statistical analysis predicts the mean values of the characteristics and the standard errors of the mean. The paper presents the most important aspects of the numerical model that was used and the way it was implemented for the unbalance analysis of a four degrees-of-freedom rotor. It was considered that the bump height-manufacturing errors had a normal distribution (i.e., each bump had a different random height) around the design (mean) height value. The standard deviation of the bump heights (the same for all bumps) is a measure of the magnitude of the manufacturing errors. The results give a qualitative but above all quantitative overview of the impact of machining errors on some characteristics of aerodynamic foil bearings.

Analyzing the Impact of X-Ray Tomography on the Reliability of Integrated Circuits

2015 ◽  
Author(s):  
Halit Dogan ◽  
Md Mahbub Alam ◽  
Navid Asadizanjani ◽  
Sina Shahbazmohamadi ◽  
Domenic Forte ◽  
...  
Keyword(s):  
Integrated Circuits ◽  
Integrated Circuit ◽  
3D Imaging ◽  
Three Dimensional ◽  
Serial Sectioning ◽  
Promising Technique ◽  
Flash Memories ◽  
X Ray ◽  
3D Information ◽  
The Impact

Abstract X-ray tomography is a promising technique that can provide micron level, internal structure, and three dimensional (3D) information of an integrated circuit (IC) component without the need for serial sectioning or decapsulation. This is especially useful for counterfeit IC detection as demonstrated by recent work. Although the components remain physically intact during tomography, the effect of radiation on the electrical functionality is not yet fully investigated. In this paper we analyze the impact of X-ray tomography on the reliability of ICs with different fabrication technologies. We perform a 3D imaging using an advanced X-ray machine on Intel flash memories, Macronix flash memories, Xilinx Spartan 3 and Spartan 6 FPGAs. Electrical functionalities are then tested in a systematic procedure after each round of tomography to estimate the impact of X-ray on Flash erase time, read margin, and program operation, and the frequencies of ring oscillators in the FPGAs. A major finding is that erase times for flash memories of older technology are significantly degraded when exposed to tomography, eventually resulting in failure. However, the flash and Xilinx FPGAs of newer technologies seem less sensitive to tomography, as only minor degradations are observed. Further, we did not identify permanent failures for any chips in the time needed to perform tomography for counterfeit detection (approximately 2 hours).

scholarly journals Numerical simulation of the impact of an integrated renovation project on the Maowei Sea hydrodynamic environment

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Cui Wang ◽  
Ling Cai ◽  
Yaojian Wu ◽  
Yurong Ouyang
Keyword(s):  
Water Exchange ◽  
Land Reclamation ◽  
Three Dimensional ◽  
Exchange Capacity ◽  
Reclamation Project ◽  
Hydrodynamic Environment ◽  
Sea Area ◽  
Water Quality Models ◽  
The Impact ◽  
Main Factor

AbstractIntegrated renovation projects are important for marine ecological environment protection. Three-dimensional hydrodynamics and water quality models are developed for the Maowei Sea to assess the hydrodynamic environment base on the MIKE3 software with high resolution meshes. The results showed that the flow velocity changed minimally after the project, decreasing by approximately 0.12 m/s in the east of the Maowei Sea area and increasing by approximately 0.01 m/s in the northeast of the Shajing Port. The decrease in tidal prism (~ 2.66 × 106 m3) was attributed to land reclamation, and accounted for just 0.86% of the pre-project level. The water exchange half-life increased by approximately 1 day, implying a slightly reduced water exchange capacity. Siltation occurred mainly in the reclamation and dredging areas, amounting to back-silting of approximately 2 cm/year. Reclamation project is the main factor causing the decrease of tidal volume and weakening the hydrodynamics in Maowei Sea. Adaptive management is necessary for such a comprehensive regulation project. According to the result, we suggest that reclamation works should strictly prohibit and dredging schemes should optimize in the subsequent regulation works.

scholarly journals Mechanical Behavior of Hydroxyapatite-Chitosan Composite: Effect of Processing Parameters

Minerals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 213
Author(s):  
Hamid Ait Said ◽  
Hassan Noukrati ◽  
Hicham Ben Youcef ◽  
Ayoub Bayoussef ◽  
Hassane Oudadesse ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Compressive Strength ◽  
Mechanical Strength ◽  
Bone Repair ◽  
Mechanical Stability ◽  
Three Dimensional ◽  
Processing Parameters ◽  
Composite Effect ◽  
Solid Liquid ◽  
The Impact

Three-dimensional hydroxyapatite-chitosan (HA-CS) composites were formulated via solid-liquid technic and freeze-drying. The prepared composites had an apatitic nature, which was demonstrated by X-ray diffraction and Infrared spectroscopy analyses. The impact of the solid/liquid (S/L) ratio and the content and the molecular weight of the polymer on the composite mechanical strength was investigated. An increase in the S/L ratio from 0.5 to 1 resulted in an increase in the compressive strength for HA-CSL (CS low molecular weight: CSL) from 0.08 ± 0.02 to 1.95 ± 0.39 MPa and from 0.3 ± 0.06 to 2.40 ± 0.51 MPa for the HA-CSM (CS medium molecular weight: CSM). Moreover, the increase in the amount (1 to 5 wt%) and the molecular weight of the polymer increased the mechanical strength of the composite. The highest compressive strength value (up to 2.40 ± 0.51 MPa) was obtained for HA-CSM (5 wt% of CS) formulated at an S/L of 1. The dissolution tests of the HA-CS composites confirmed their cohesion and mechanical stability in an aqueous solution. Both polymer and apatite are assumed to work together, giving the synergism needed to make effective cylindrical composites, and could serve as a promising candidate for bone repair in the orthopedic field.

scholarly journals Quantification of Measurement and Model Effects in Monopile Foundation Scour Protection Experiments

2021 ◽  
Vol 9 (6) ◽  
pp. 585
Author(s):  
Minghao Wu ◽  
Leen De Vos ◽  
Carlos Emilio Arboleda Chavez ◽  
Vasiliki Stratigaki ◽  
Maximilian Streicher ◽  
...  
Keyword(s):  
Standard Deviation ◽  
Flow Field ◽  
Three Dimensional ◽  
Small Scale ◽  
Maximum Wave Height ◽  
Chaotic Flow ◽  
The Mean ◽  
Scour Protection ◽  
Damage Number ◽  
Measurement Effects

The present work introduces an analysis of the measurement and model effects that exist in monopile scour protection experiments with repeated small scale tests. The damage erosion is calculated using the three dimensional global damage number S3D and subarea damage number S3D,i. Results show that the standard deviation of the global damage number σ(S3D)=0.257 and is approximately 20% of the mean S3D, and the standard deviation of the subarea damage number σ(S3D,i)=0.42 which can be up to 33% of the mean S3D. The irreproducible maximum wave height, chaotic flow field and non-repeatable armour layer construction are regarded as the main reasons for the occurrence of strong model effects. The measurement effects are limited to σ(S3D)=0.039 and σ(S3D,i)=0.083, which are minor compared to the model effects.

scholarly journals Simulation Tests of a Cow Milking Machine—Analysis of Design Parameters

Processes ◽  
2021 ◽  
Vol 9 (8) ◽  
pp. 1358
Author(s):  
Ewa Golisz ◽  
Adam Kupczyk ◽  
Maria Majkowska ◽  
Jędrzej Trajer
Keyword(s):  
Mathematical Model ◽  
Simplified Model ◽  
Design Parameters ◽  
Degree Polynomial ◽  
Fourth Degree ◽  
Local Loss ◽  
Linear Drag ◽  
Milking Machine ◽  
Machine Analysis ◽  
The Impact

The objective of this paper was to create a mathematical model of vacuum drops in a form that enables the testing of the impact of design parameters of a milking cluster on the values of vacuum drops in the claw. Simulation tests of the milking cluster were conducted, with the use of a simplified model of vacuum drops in the form of a fourth-degree polynomial. Sensitivity analysis and a simulation of a model with a simplified structure of vacuum drops in the claw were carried out. As a result, the impact of the milking machine’s design parameters on the milking process could be analysed. The results showed that a change in the local loss and linear drag coefficient in the long milk duct will have a lower impact on vacuum drops if a smaller flux of inlet air, a higher head of the air/liquid mix, and a higher diameter of the long milk tube are used.

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