A Study of the Effect of Geometry Changes on the Structural Stiffness of a Composite D-Spar

2010 ◽  
Author(s):  
Swaroop B. Visweswaraiah ◽  
Damiano Pasini ◽  
Larry Lessard
Keyword(s):  
Cross Section ◽  
Beam Theory ◽  
Leading Edge ◽  
Structural Stiffness ◽  
Cross Sectional ◽  
Composite Blade ◽  
The Matrix ◽  
Coupling Parameters ◽  
Laminate Theory ◽  
The Impact

The paper examines the impact of varying two geometric cross-section parameters of an advance composite D-spar on its structural stiffness. For a given blade topology, the orientation of the D-spar web with respect to the beam axis and the distance of the D-spar web from the leading edge of the blade have been selected here as the variables of study, as they govern the elastic properties of the composite cross-section. A code has been developed to calculate the matrix terms of the Euler-Bernoulli cross-sectional stiffness utilizing the closed form expressions of the structural properties formulated by assuming both Thin-Walled composite Beam theory (TWB) and Classical Laminate Theory. The code has been validated through the Variational Asymptotic Beam Sectional analysis (VABS) for the cross-sectional stiffness matrix. Two cases have been studied for a quasi-isotropic laminate D-spar. The first is for a symmetric airfoil, whereas the second is for an unsymmetrical airfoil. The variation of the stiffness parameters for the quasi-isotropic D-spar including the coupling parameters has been visualized into parametric maps. The paper also examines the impact that these geometric variables have on the stiffness-to-mass ratio to show that along with the ply orientations they play a major role in the aeroelastic tailoring and structural optimization of a composite blade.

A Beam Theory for Large Global Rotation, Moderate Local Rotation, and Small Strain

1988 ◽  
Vol 55 (1) ◽  
pp. 179-184 ◽  
Author(s):  
D. A. Danielson ◽  
D. H. Hodges
Keyword(s):  
Cross Section ◽  
Variational Principles ◽  
Beam Theory ◽  
Small Strain ◽  
General Context ◽  
Equilibrium Equations ◽  
Cross Sectional ◽  
Local Rotation ◽  
Material Points

Kinematical relations are derived to account for the finite cross-sectional warping occurring in a beam undergoing large deflections and rotations due to deformation. The total rotation at any point in the beam is represented as a large global rotation of the reference triad (a frame which moves nominally with the reference cross section material points), a small rotation that is constant over the cross section and is due to shear, and a local rotation whose magnitude may be small to moderate and which varies over a given cross section. Appropriate variational principles, equilibrium equations, boundary conditions, and constitutive laws are obtained. Two versions are offered: an intrinsic theory without reference to displacements, and an explicit theory with global rotation characterized by a Rodrigues vector. Most of the formulas herein have been published, but we reproduce them here in a new concise notation and a more general context. As an example, the theory is shown to predict behavior that agrees with published theoretical and experimental results for extension and torsion of a pretwisted strip. The example also helps to clarify the role of local rotation in the kinematics.

scholarly journals Evaluation of Flow Resistance Models Based on Field Experiments in a Partly Vegetated Reclamation Channel

Geosciences ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 47 ◽  
Author(s):  
Giuseppe Francesco Cesare Lama ◽  
Alessandro Errico ◽  
Simona Francalanci ◽  
Luca Solari ◽  
Federico Preti ◽  
...  
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Flow Resistance ◽  
Field Experiments ◽  
Common Reed ◽  
Cross Sectional ◽  
Riparian Plants ◽  
Water Level Measurements ◽  
The Impact ◽  
Resistance Coefficients

This study presents a methodology for improving the efficiency of Baptist and Stone and Shen models in predicting the global water flow resistance of a reclamation channel partly vegetated by rigid and emergent riparian plants. The results of the two resistance models are compared with the measurements collected during an experimental campaign conducted in a reclamation channel colonized by Common reed (Phragmites australis (Cav.) Trin. ex Steud.). Experimental vegetative Chézy’s flow resistance coefficients have been retrieved from the analysis of instantaneous flow velocity measurements, acquired by means of a downlooking 3-component acoustic Doppler velocimeter (ADV) located at the channel upstream cross section, and by water level measurements obtained through four piezometers distributed along the reclamation channel. The main morphometrical vegetation features (i.e., stem diameters and heights, and bed surface density) have been measured at six cross sections of the vegetated reclamation channel. Following the theoretical assumptions of the divided channel method (DCM), three sub-sections have been delineated in the reference cross section to represent the impact of the partial vegetation cover on the cross sectional variability of the flow field, as observed with the ADV measurements. The global vegetative Chézy’s flow resistance coefficients have been then computed by combining each resistance model with four different composite cross section methods, respectively suggested by Colebatch, Horton, Pavlovskii, and Yen. The comparative analysis between the modeled and the experimental vegetative Chézy’s coefficients has been performed by computing the relative prediction error (εr, expressed in %) under two flow rate regimes. Stone and Shen model combined with the Horton composite cross section method provides vegetative Chézy’s coefficients with the lowest εr.

Sandwich Beam Analysis

1972 ◽  
Vol 39 (3) ◽  
pp. 773-778 ◽  
Author(s):  
D. Krajcinovic
Keyword(s):  
Cross Section ◽  
Static Load ◽  
Sandwich Beam ◽  
Beam Theory ◽  
Simple Algebra ◽  
Sandwich Beams ◽  
Consistent Theory ◽  
Entire Cross Section ◽  
Cross Sectional ◽  
Beam Analysis

A consistent theory of sandwich beams subjected to static load is presented. The theory is developed under the assumption that the Bernoulli’s hypothesis is valid for each lamina independently but not for the entire cross section as a whole. It is shown that the generalized displacement may be chosen in such a way that the set of equations governing the motions for which the beam remains straight on one, and a set of equations describing bending and shear types of motions on the other hand are independent. Furthermore, after some simple algebra, separate equations for each generalized displacement are derived. The normal stress is given in the from which is familiar from strength of materials with two additional terms embodying the influence of the cross-sectional distortion (deviation from classical beam theory).

The cross-section of Johannesburg Securities Exchange listed equity returns (1994-2011)

2015 ◽  
Vol 32 (4) ◽  
pp. 422-444 ◽  
Author(s):  
Jakobus Daniel Van Heerden ◽  
Paul Van Rensburg
Keyword(s):  
Cross Section ◽  
Equity Returns ◽  
Research Approach ◽  
Momentum Effect ◽  
Cross Sectional ◽  
Data Set ◽  
Content Type ◽  
Specific Factors ◽  
The Cross ◽  
The Impact

Purpose – The aim of this study is to examine the impact of technical and fundamental (referred to as firm-specific) factors on the cross-sectional variation in equity returns on the Johannesburg Securities Exchange (JSE). Design/methodology/approach – To reach the objective, the study follows an empirical research approach. Cross-sectional regression analyses, factor-portfolio analyses and multifactor analyses are performed using 50 firm-specific factors for listed shares over three sample periods during 1994 to 2011. Findings – The results suggest that a strong value and momentum effect is present and robust on the JSE, while a size effect is present but varies over time. Multifactor analyses show that value and momentum factors are collectively significant in explaining the cross-section of returns. The results imply that the JSE is either not an efficient market or that current market risk models are incorrectly specified. Practical implications – The findings of the study offers practical application possibilities to investment analysts and portfolio managers. Originality/value – To the authors’ knowledge, this is the first study to use such a comprehensive data set for the specific analyses on the JSE over such a long period. All previously identified statistical biases are addressed in this study. Different approaches are applied to compare results and test for robustness for the first time.

The Effect of Cross-sectional Geometry on ZT Enhancement in Rough Silicon Nanostructures

2010 ◽  
Vol 1267 ◽  
Author(s):  
Jyothi Swaroop Sadhu ◽  
Marc G Ghossoub ◽  
Sanjiv Sinha
Keyword(s):  
Thermal Conductivity ◽  
Boundary Condition ◽  
Cross Section ◽  
Silicon Nanowires ◽  
Silicon Nanostructures ◽  
Dramatic Reduction ◽  
Cross Sectional ◽  
The Wire ◽  
Phonon Localization ◽  
The Impact

AbstractThe dramatic reduction in the thermal conductivity of rough silicon nanowires is due to phonon localization in the wire resulting from multiple scattering of phonons from the rough walls. We report the dependence of thermal conductivity of the nanowires as a function of the surface roughness and the diameter of the wire by modeling the nanowire as a waveguide. In addition, we estimate the impact of boundary condition, dimensionality and cross section of rough wire on the thermal conductivity. This theoretical model gives insights for tailoring thermal conductivity and enhancing the ZT of silicon to 1 for its use in thermoelectrics

Impact Behavior of Biaxially Compressed Wood

2011 ◽  
Vol 673 ◽  
pp. 247-252
Author(s):  
Minoru Yamashita ◽  
Noriyuki Sawada ◽  
Toshio Hattori
Keyword(s):  
Cross Section ◽  
Wood Specimen ◽  
Japanese Cedar ◽  
Surface Strain ◽  
Bending Test ◽  
Impact Behavior ◽  
Biaxial Compression ◽  
Cross Sectional ◽  
The Impact ◽  
Compressed Wood

The wood bar with square cross-section was biaxially compressed with respect to the cross-sectional plane and the impact 4-point bending test was performed using the compressed wood. The wood material used was sap wood of Sugi, which is a kind of Japanese cedar. The biaxial compression apparatus which enabled to prevent the gap generation between the material and the tool was used. The fixation of wood specimen was also processed. The bar length was 100 mm and the edge length in cross-section was 15 ~ 25 mm. In the 4-point bending test, the distance between the supports and the stress points were 80 mm and 40 mm. The stress points were impacted by a light-weight drop-hammer with 3.0 kg mass. The impact velocity was 2 m/s. The surface strain was measured by a strain gage. When the Young’s modulus was estimated by assuming a linear elastic property, it attained about 32 GPa, which was more than 4 times of the uncompressed wood. The stress – strain hysteresis loop was more remarkable under the impact condition. It was found that the compressed wood provided not only a high rigidity, but also a good property in dissipation of vibration energy.

scholarly journals The Vibration of Tubular Beam Conveying Fluid with Variable Cross Section

2020 ◽  
Vol 65 (1) ◽  
pp. 56-62
Author(s):  
Mohamed Gaith
Keyword(s):  
Flow Velocity ◽  
Cross Section ◽  
Natural Frequencies ◽  
Variable Cross Section ◽  
System Stability ◽  
Variable Cross ◽  
Cross Sectional ◽  
Critical Flow Velocity ◽  
Constant Flow Rate ◽  
The Impact

The dynamics and stability of flow induced vibration of flow conveying in pipes particularly in case of high velocity flow may lead to severe damage. Predicting the circular natural frequencies and critical fluid velocities is an important tool in design and prevent system failures. In this study transverse dynamic response of simply supported pipe with variable tubular cross sectional area carrying fluid with a constant flow rate is investigated. Euler Bernoulli's beam theory is used to model the pipe. Hamilton's principle will be used to produce the governing equation of motion for the system. The resulting partial differential equation is solved using Galerkin's technique. The impact of the flow velocity and non-uniform variable cross section on the natural frequencies of the system, critical flow velocity and system stability is presented.

scholarly journals NUMERICAL SIMULATION OF THE BROKEN ROCK MASS TRANSPORTATION IN A ROTATING PIPELINE

2021 ◽  
Vol 2 (4) ◽  
pp. 141-150
Author(s):  
Guil Nam Khan ◽  
Evgeny P. Rusin
Keyword(s):  
Cross Section ◽  
Bulk Material ◽  
Longitudinal Axis ◽  
Pneumatic Conveying ◽  
Discrete Elements ◽  
Cross Sectional ◽  
Horizontal Pipe ◽  
Angular Velocities ◽  
The Cross ◽  
The Impact

The impact of the angular velocity of a horizontal pipe rotating around its longitudinal axis and the shape of its cross-section on the efficiency of pneumatic conveying of bulk material in it has been numerically investigated by the discrete elements method. The maximum number of non-contact particles, that is, particles being not in contact with other material particles and with the pipe, in the cross section of the pipe during one its revolution, is assumed the condition for effective pneumatic conveying. A method for searching for non-contact particles is proposed, which makes it possible to calculate their number at fixed pipe position angles during its rotation. For various cross-sectional shapes, the optimal angular velocities are determined at which the average number of non-contact particles in the cross-section is maximum. The results of the study can be used to increase the productivity of the removal of products of destruction when drilling horizontal boreholes in rocks and soils.

scholarly journals Natural plant stems modelling in a three-point bending test

2019 ◽  
Vol 252 ◽  
pp. 07001
Author(s):  
Bartosz Kawecki ◽  
Jerzy Podgórski ◽  
Aleksandra Głowacka
Keyword(s):  
Numerical Modelling ◽  
Cross Section ◽  
Beam Theory ◽  
Bending Test ◽  
Basic Material ◽  
Cross Sectional ◽  
Natural Plant ◽  
Cosine Series ◽  
Three Point Bending ◽  
Miscanthus Giganteus

The paper presents an approach to natural plant stems numerical modelling in a three-point bending test. Introduced subject was connected with elaborating more efficient systems for harvesting energetic plants. There were modelled, and laboratory tested two types of stems – sida hermaphrodita and miscanthus giganteus. Course of proceedings for obtaining natural cross-sectional dimensions with graphical data processing was described in detail. Basing on dozens of stems slices from random parts of plants, three different cross-section approximations were proposed and computationally implemented – a circular pipe, an elliptical pipe (symmetrical cross-section) and a sine-cosine series pipe (asymmetrical cross-section). Analytical formulas for calculating a cross-sectional area and moments of inertia for each approximation were given. Basic material parameters as an elastic modulus and yielding stress was obtained from simply supported beam theory and laboratory force – the deflexion relation. FEM models were created in Simulia Abaqus software using C3D20R elements. Preliminary approach to modelling damage with perfect plasticity was done basing on several samples bended to failure in laboratory tests. Conclusions for future work with numerical modelling natural plant stems were drawn.

scholarly journals Effect of Congestion on Flow Field of Vented Natural Gas Explosion in a Kitchen

2021 ◽  
Vol 2021 ◽  
pp. 1-22
Author(s):  
Lei Pang ◽  
Qianran Hu ◽  
Mengjie Jin ◽  
Kai Yang
Keyword(s):  
Natural Gas ◽  
Flow Field ◽  
Cross Section ◽  
Large Scale ◽  
Flame Structure ◽  
Small Scale ◽  
Gas Explosion ◽  
Cross Sectional ◽  
Surrounding Areas ◽  
The Impact

The process of gas explosion venting in a typical Chinese civil kitchen was investigated using computational fluid dynamics technology, focusing on the impact of the scale and cross-sectional characteristics of congestion, such as common furniture and electrical appliances, on the explosion flow-field parameters. An asymmetrical distribution of congestion will cause the uneven combustion of explosion flames in the kitchen. The flame will initially spread on one side of the room and then accelerate toward the surrounding areas, thereby increasing the risk of indoor gas explosion. The typical indoor overpressure change process can be divided into five stages, among which Stage V is found to be related to pseudoclosed combustion. Large-scale congestion has an obstructive effect on the explosion flow field, but it changes under certain conditions, while small-scale congestion only acts as a promoter. The flat congestion cross section helps maintain the stability of the flame structure, whereas the continuous and abrupt change of the congestion cross section can induce strong turbulent combustion. The research results provide a theoretical basis for the prevention and control of natural gas explosion hazards in civil kitchens from the perspective of congestion scale and cross-sectional mutation.

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