scholarly journals Pitch damping identification in high speed regimes with a free-to-tumble rig

2020 ◽  
Vol 12 (4) ◽  
pp. 261-265
Author(s):  
Catalin PIRVU ◽  
Mihai Victor PRICOP ◽  
Jean-Philippe PRÉAUD ◽  
Louis WALPOT
Keyword(s):  
Experimental Data ◽  
Wind Tunnel ◽  
Dynamic Stability ◽  
Curve Fitting ◽  
High Speed ◽  
Oscillatory Behavior ◽  
Damping Coefficient ◽  
Test Conditions ◽  
Nonlinear Dynamic Stability ◽  
Pitch Damping

Many re-entry bodies, even if they are debris or not, have nonlinear dynamic stability characteristics that produce oscillations in flight. The free-to-tumble techniques can be used to extract damping coefficient of specific body for planetary entry. The curve fitting approach is used to predict oscillatory behavior and the damping coefficient for the various test conditions of the wind tunnel obtained after the experimental data. The analysis presented provides an overview of the free-to-tumble test techniques and illustrates the effects of dynamic stability of the inter-stage tronconical system. It is proposed that these test techniques and curve fitting solution be refined in the future to better define the dynamic stability curves for the re-entry bodies.

Laboratory Measurement of Tire Flatspot3

2009 ◽  
Vol 37 (4) ◽  
pp. 279-301 ◽  
Author(s):  
N. K. Mani ◽  
M. A. Berzins ◽  
J. L. Turner
Keyword(s):  
Experimental Data ◽  
Laboratory Test ◽  
High Speed ◽  
Test Procedure ◽  
Mechanistic Explanation ◽  
Special Care ◽  
Laboratory Measurement ◽  
Test Conditions

Abstract Tires flatspot when they remain loaded without rolling for a period of time. The magnitude of this flatspot and the speed with which it recovers due to subsequent rolling are influenced by the temperature and load histories. Experience indicates that controlled measurement in the laboratory is the best way to measure the flatspot characteristics of tires. However, the laboratory test procedure must be based on the flatspot and recovery conditions the tire experiences in the field for the measurements to truly represent tire performance. Processing of the experimental data to compute the initial flatspot and its decay due to rolling also requires special care since the flatspot decays from the first revolution of the tire after flatspot. Effects of flatspot on a tire can be measured in many ways using low or high speed uniformity measurements or by measuring the radial runout of the tire. This paper will address the issues involved in flatspot measurement of tires and also present mechanistic explanation of the influence of test conditions on flatspot.

Estimating ink mileage of dry toners in electrophotography

TAPPI Journal ◽  
2013 ◽  
Vol 12 (3) ◽  
pp. 9-14
Author(s):  
RENMEI XU ◽  
CELESTE M. CALKINS
Keyword(s):  
Experimental Data ◽  
Curve Fitting ◽  
Graphite Furnace ◽  
Atomic Absorption Spectrometer ◽  
Density Region ◽  
Coated Papers ◽  
Graphite Furnace Atomic Absorption ◽  
S Model ◽  
Better Than ◽  
Film Weight

This work investigates the ink mileage of dry toners in electrophotography (EP). Four different substrates were printed on a dry-toner color production Xerox iGen3 EP press. The print layout contained patches with different cyan, magenta, yellow, and black tonal values from 10% to 100%. Toner amounts on cyan patches were measured using an analytical method. Printed patches and unprinted paper samples, as well as dry toners, were dissolved in concentrated nitric acid. The copper concentrations in the dissolved solutions were analyzed by a Zeeman graphite furnace atomic absorption spectrometer. Analytical results were calculated to determine the toner amounts on paper for different tonal values. Their corresponding reflection densities were also measured. All data were plotted with OriginPro® 8 software, and four mathematical models were used for curve fitting. It was found that the C-S model fitted the experimental data of the two uncoated papers better than the other three models. None of the four models fitted the experimental data of the two coated papers, while the linear model was found to fit the data well. Linear fitting was the best in the practical density region for the two coated papers. Ink mileage curves obtained from curve fitting were used to estimate how much ink was required to achieve a target density for each paper; hence, the ink mileage was calculated. The highest ink mileage was 3.39 times the lowest ink mileage. The rougher the paper surface, the higher the requirement for ink film weight, and the lower ink mileage. No correlation was found between ink mileage and paper porosity.

Formation of Standing Waves in Radial Tires

1984 ◽  
Vol 12 (1) ◽  
pp. 44-63 ◽  
Author(s):  
Y. D. Kwon ◽  
D. C. Prevorsek
Keyword(s):  
High Speed ◽  
Critical Speed ◽  
Unit Length ◽  
Standing Waves ◽  
Rolling Resistance ◽  
Damping Coefficient ◽  
Circular Membrane ◽  
Critical Speeds ◽  
Steel Cord ◽  
The Individual

Abstract Radial tires for automobiles were subjected to high speed rolling under load on a testing wheel to determine the critical speeds at which standing waves started to form. Tires of different makes had significantly different critical speeds. The damping coefficient and mass per unit length of the tire wall were measured and a correlation between these properties and the observed critical speed of standing wave formation was sought through use of a circular membrane model. As expected from the model, desirably high critical speed calls for a high damping coefficient and a low mass per unit length of the tire wall. The damping coefficient is particularly important. Surprisingly, those tire walls that were reinforced with steel cord had higher damping coefficients than did those reinforced with polymeric cord. Although the individual steel filaments are elastic, the interfilament friction is higher in the steel cords than in the polymeric cords. A steel-reinforced tire wall also has a higher density per unit length. The damping coefficient is directly related to the mechanical loss in cyclic deformation and, hence, to the rolling resistance of a tire. The study shows that, in principle, it is more difficult to design a tire that is both fuel-efficient and free from standing waves when steel cord is used than when polymeric cords are used.

scholarly journals Polyconvex hyperelastic modeling of rubberlike materials

2021 ◽  
Vol 43 (7) ◽  
Author(s):  
Cyprian Suchocki ◽  
Stanisław Jemioło
Keyword(s):  
Experimental Data ◽  
Power Law ◽  
Curve Fitting ◽  
Constitutive Relations ◽  
Data Sets ◽  
Power Law Model ◽  
Stored Energy ◽  
Data Approximation ◽  
Exponential Power ◽  
Hyperelastic Models

AbstractIn this work a number of selected, isotropic, invariant-based hyperelastic models are analyzed. The considered constitutive relations of hyperelasticity include the model by Gent (G) and its extension, the so-called generalized Gent model (GG), the exponential-power law model (Exp-PL) and the power law model (PL). The material parameters of the models under study have been identified for eight different experimental data sets. As it has been demonstrated, the much celebrated Gent’s model does not always allow to obtain an acceptable quality of the experimental data approximation. Furthermore, it is observed that the best curve fitting quality is usually achieved when the experimentally derived conditions that were proposed by Rivlin and Saunders are fulfilled. However, it is shown that the conditions by Rivlin and Saunders are in a contradiction with the mathematical requirements of stored energy polyconvexity. A polyconvex stored energy function is assumed in order to ensure the existence of solutions to a properly defined boundary value problem and to avoid non-physical material response. It is found that in the case of the analyzed hyperelastic models the application of polyconvexity conditions leads to only a slight decrease in the curve fitting quality. When the energy polyconvexity is assumed, the best experimental data approximation is usually obtained for the PL model. Among the non-polyconvex hyperelastic models, the best curve fitting results are most frequently achieved for the GG model. However, it is shown that both the G and the GG models are problematic due to the presence of the locking effect.

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