A simple projection moiré system to measure displacements of aircraft structures

2007 ◽  
Vol 42 (6) ◽  
pp. 477-495 ◽  
Author(s):  
U Galietti ◽  
K Genovese ◽  
L Lamberti ◽  
D Posa
Keyword(s):  
Analytical Model ◽  
Large Scale ◽  
Industrial Applications ◽  
Processing Method ◽  
Simple Analytical Model ◽  
Aerodynamic Loads ◽  
Out Of Plane ◽  
Plane Displacement ◽  
Good Agreement ◽  
Projection Moire

This work presents a simple projection moiré system (PMS) to measure displacements of large-scale aeronautical components. The system includes standard optics, uses a standard fringe-processing method, and relies on a simple analytical model to recover topographic information. An extensive calibration campaign, based on design of experiments, is conducted in order to find the best analytical model for retrieving the out-of-plane displacement field from the moiré pattern and to find the optimal combination of parameters involved in the measurement system. In order to check the suitability of the present PMS device for practical industrial applications, distortions induced by aerodynamic loads on a landing-light glazing of an Airbus A340 are measured. Experimental results are in good agreement with other measurements carried out independently.

Failure of a Thermal Barrier System Due to a Cyclic Displacement Instability in the Thermally grown Oxide

2000 ◽  
Vol 645 ◽  
Author(s):  
Daniel R. Mumm ◽  
Anthony G. Evans
Keyword(s):  
Bond Coat ◽  
Large Scale ◽  
Thermal Exposure ◽  
Thermally Grown Oxide ◽  
Thermal Barrier ◽  
Oxide Interface ◽  
Barrier Coating ◽  
Out Of Plane ◽  
Plane Displacement ◽  
Thermally Grown

ABSTRACTThe mechanism controlling the cyclic failure of a commercial thermal barrier system has been investigated. The system comprises an electron-beam physical vapor deposited (EB-PVD) yttria-stabilized zirconia thermal barrier coating (TBC), deposited on a (Ni Pt) Al bond coating. The thermally grown oxide (TGO) layer that forms between the TBC and bond coat at high temperature is unstable with respect to out of plane displacement, provided initial perturbations are present. With cyclic thermal exposure, the TGO displaces into the bond coat at periodic interfacial sites. The out-of-plane displacements induce strains above the TGO, normal to the interface, that cause cracking. The cracks nucleate either within the TBC layer or at the TBC/TGO interface, and extend laterally until they coalesce with cracks from other sites and coating failure occurs by large scale buckling. The TGO displacements are accommodated by visco-plastic deformation of the underlying bond coat, and are driven by a lateral component of the growth strain in the TGO. The susceptibility of the TGO to out-of-plane displacement depends critically upon the initial morphology of the metal/oxide interface. The observed material responses are compared with predictions of a ‘ratcheting’ model.

Warpage Measurement Using Projection Moire´ System and Two Automatic Image Segmentation Algorithms

2007 ◽  
Author(s):  
Wei Tan ◽  
I. Charles Ume
Keyword(s):  
Image Segmentation ◽  
Electronic Packages ◽  
Printed Wiring Board ◽  
Segmentation Algorithms ◽  
Out Of Plane ◽  
Cte Mismatch ◽  
Image Models ◽  
Wiring Board ◽  
Plane Displacement ◽  
Projection Moire

Out-of-plane displacement (warpage) has been a major reliability concern for board-level electronic packaging. Printed wiring board (PWB) and component warpage results from CTE mismatch among the materials that make up the PWB assembly (PWBA). Warpage occurring during surface-mount assembly reflow processes and normal operations may lead to serious reliability problems. In this paper, a projection moire´ warpage measurement system and two types of automatic image segmentation algorithms were presented. In order to use the projection moire´ technique to separately determine the warpage of a PWB and assembled electronic packages in a PWBA, two image segmentation algorithms based on mask image models and active contour models (snakes) were developed. They were used to detect package locations in a PWBA displacement image generated by the projection moire´ system. The performances of the mask image and snake approaches based on their resolutions, processing rates, and measurement efficiencies were evaluated in this research. Real-time composite Hermite surface models were constructed to estimate the PWB warpage values underneath the electronic packages. The above automatic image segmentation algorithms were integrated with the projection moire´ system to accurately evaluate the warpage of PWBs and assembled chip packages individually.

A Simple Analytical Model to Simulate Oblique Ballistic Impact onto Fabric

2011 ◽  
Vol 110-116 ◽  
pp. 3453-3458
Author(s):  
Mohamad Ali Akbari ◽  
Golam Hosein Liaghat ◽  
Hadi Sabouri
Keyword(s):  
Experimental Data ◽  
Analytical Model ◽  
Ballistic Impact ◽  
Experimental Results ◽  
Simple Analytical Model ◽  
Good Agreement

A simple analytical model for oblique ballistic impact of projectiles into fabrics are presented. This model is extension of Chocron-Benloulo penetration model. Results are compared with experimental data. There is good agreement between analytical and experimental results.

scholarly journals Natural Smoldering of Cigarettes

2003 ◽  
Author(s):  
Fernando de Souza Costa
Keyword(s):  
Boundary Layer ◽  
Analytical Model ◽  
Heat Losses ◽  
Algebraic Equations ◽  
Simple Analytical Model ◽  
Influence Coefficients ◽  
Linear Algebraic Equations ◽  
Char Oxidation ◽  
Diffusive Processes ◽  
Good Agreement

The smoldering of cigarettes without drawing is described by a simple analytical model. A burning cigarette is assumed to be divided in 4 zones: unburned tobacco, dry tobacco, char and ash, separated by infinitesimally thin fronts of drying, pyrolysis and char oxidation. Circumferential heat losses and the convective-diffusive processes in the boundary layer are considered. A set of non-linear algebraic equations is solved to determine smoldering rates, drying lengths and pyrolysis lengths and to obtain the profiles of temperature. The influence coefficients of several parameters on smolder characteristics are calculated. Theoretical burn rates have shown a good agreement to experiments.

A SIMPLE ANALYTICAL MODEL FOR EVALUATION OF PENETRATION DEPTH AND RESISTANT STRENGTH OF CONCRETE TARGETS

2013 ◽  
Vol 13 (03) ◽  
pp. 1250061 ◽  
Author(s):  
A. RAMACHANDRA MURTHY ◽  
G. S. PALANI ◽  
NAGESH R. IYER
Keyword(s):  
Penetration Depth ◽  
Analytical Model ◽  
Cavity Expansion ◽  
Strength Parameter ◽  
Spherically Symmetric ◽  
Simple Analytical Model ◽  
Depth Of Penetration ◽  
Projectile Velocity ◽  
Symmetric Cavity ◽  
Good Agreement

This paper presents a simple analytical model for evaluation of penetration depth and resistant strength of concrete target. The model is based on the assumption that the deformation and failure of the projectile are negligible. Normal impact is assumed in the model. It is also assumed that the penetration is steady state within the time step, the momentum balance equation can be integrated, resulting in an explicit expression for the pressure at the target interface. The expressions for spherically symmetric cavity expansion for a material with locked hydrostatic stress and constant shear strength have been developed. The constants for failure criterion are derived based on Mohr–Coulomb and Tresca-limit yield line theories. Final depth of penetration has been derived using the results of spherically symmetric cavity expansion analysis, relating the radial stress at the cavity surface to cavity expansion velocity and Newton’s second law of motion. Target resistant strength parameter is expressed as a function of penetration depth, projectile velocity, nose performance coefficient, target density, mass of projectile, and radius of the projectile. The expressions for velocity, acceleration and displacement at any instant of time have been deduced based on total depth of penetration and target resistant strength. To validate the methodologies, numerical studies have been conducted and observed that the penetration depth and target resistant strength obtained in the present study are in good agreement with the corresponding experimental values reported in the literature. It is also observed that the time history of penetration depth and projectile velocity are in good agreement with the corresponding literature values.

An experimental study on the mixed-mode crack tip deformation fields in polymethyl methacrylate

2003 ◽  
Vol 38 (4) ◽  
pp. 313-328 ◽  
Author(s):  
P-F Luo ◽  
F. C Huang
Keyword(s):  
Polymethyl Methacrylate ◽  
Plane Stress ◽  
Mixed Mode ◽  
Plane Deformation ◽  
Crack Tip ◽  
Specimen Thickness ◽  
Mixed Mode Crack ◽  
Out Of Plane ◽  
Plane Displacement ◽  
Good Agreement

Stereo vision was used to measure the full three-dimensional deformation field around the crack tip region of a compact tension shear (CTS) specimen made of polymethyl methacrylate (PMMA) subjected to mixed-mode (I/II) loading. The stress intensity factors (SIF), K1 and KII, were then estimated using both measured in-plane and out-of-plane deformation fields. The KI and KII values determined from in-plane displacements are in very good agreement with those determined from out-of-plane displacement. The far-field J integral values computed using the line integral are compared with those evaluated using the measured KI and KII values. The extent of the region near a mixed-mode crack tip where the plane stress solutions can reasonably predict the in-plane and out-of-plane displacements was investigated. Experimental results indicate that the solution of the out-of-plane displacement derived on the basis of the plane stress condition does not provide a good approximation to the experimental data for distances from the crack tip within half the specimen thickness. However, there is good agreement between the in-plane displacement measurements and the computed results, even for r/h < 0.5.

A Model for the Pull-In Parameters of Magnetostatic Actuators with Fringing Effect

2013 ◽  
Vol 432 ◽  
pp. 229-234
Author(s):  
Yu Ming Fang ◽  
Jun Jian Qie
Keyword(s):  
Analytical Model ◽  
Simple Analytical Model ◽  
The Past ◽  
Wide Range ◽  
Mems Actuators ◽  
Fringing Field ◽  
Simulation Results ◽  
Fringing Field Effect ◽  
Gap Spacing ◽  
Good Agreement

Predicting Pull-In parameters is crucial in the design of MEMS actuators. In the past, the Pull-In parameters of magnetostatic actuators with the fringing field effect are often estimated using finite element method (FEM). However, FEM is cumbersome, time consuming and non-transparent, which is not convenient for the design optimization. Usually, there are a simple analytical model without leakage reluctance and a detailed analytical model with leakage reluctance respectively. This paper used the two models to derive the Pull-In model of magnetostatic actuators respectively. The accuracy of the two Pull-In models is examined by comparing their results with the FEM results. Simulation results show that the Pull-In model without leakage reluctance is unsuitable to predict Pull-In parameters. The Pull-In model with leakage reluctance has shown a good agreement with the FEM results for a wide range of gap spacing.

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