Aeroelastic Tailoring of Helicopter Blades

2013 ◽  
Author(s):  
Donatien Cornette ◽  
Benjamin Kerdreux ◽  
Yves Gourinat ◽  
Guilhem Michon
Keyword(s):  
Dynamic Behaviour ◽  
Vertical Shear ◽  
Dynamic Loads ◽  
Modal Approach ◽  
Aeroelastic Tailoring ◽  
Helicopter Blades ◽  
Shear Modification ◽  
Elastic Couplings ◽  
The Impact ◽  
Aerodynamic Lift

The dynamic loads transmitted from the rotor to the airframe are responsible for vibrations, discomfort and alternate stress of components. A new and promising way to minimize vibration is to reduce dynamic loads at their source by performing an aeroelastic optimization of the rotor. This optimization is done thanks to couplings between the flapwise-bending motion and the torsion motion. The impact of elastic couplings (composite anisotropy) on the blade dynamic behaviour and on dynamic loads are evaluated in this paper. Firstly, analytical results, based on a purely linear modal approach, are given to understand the influence of those couplings in terms of frequency placement, aerodynamic lift load and vertical shear modification. Then, those elastic couplings are introduced on a simplified but representative blade (homogeneous beam with constant chord) and results are presented.

Aeroelastic Tailoring of Helicopter Blades

2015 ◽  
Vol 10 (6) ◽  
Author(s):  
Donatien Cornette ◽  
Benjamin Kerdreux ◽  
Guilhem Michon ◽  
Yves Gourinat
Keyword(s):  
Dynamic Behavior ◽  
Center Of Gravity ◽  
Dynamic Loads ◽  
Modal Approach ◽  
Aeroelastic Tailoring ◽  
Helicopter Blades ◽  
Analytical Results ◽  
Aeroelastic Model ◽  
Elastic Couplings ◽  
Homogeneous Beam

The dynamic loads transmitted from the rotor to the airframe are responsible for vibrations, discomfort and alternate stress on components. A new and promising way to minimize vibration is to reduce dynamic loads at their source by performing an aeroelastic optimization of the rotor. This optimization uses couplings between the flapwise-bending motion and the torsion motion. The impacts of elastic couplings (composite anisotropy) and inertial couplings (center-of-gravity offset) on blade dynamic behavior and on dynamic loads are evaluated in this paper. First, analytical results, based on a purely linear modal approach, are given to understand the influence of these couplings on blade dynamic behavior. Then, a complete nonlinear aeroelastic model of the rotor, including elastic and inertial couplings, is derived. Finally, this last model is used to improve a simplified but representative blade (homogeneous beam with constant chord) and results are presented.

Nonlinear Composite Beam Theory

1988 ◽  
Vol 55 (1) ◽  
pp. 156-163 ◽  
Author(s):  
O. A. Bauchau ◽  
C. H. Hong
Keyword(s):  
Beam Theory ◽  
Small Strain ◽  
Composite Beams ◽  
Helicopter Blades ◽  
Nonlinear Composite ◽  
Shearing Strain ◽  
Elastic Couplings ◽  
New Formulation ◽  
Aluminum Beam ◽  
The Impact

The modeling of naturally curved and twisted beams undergoing arbitrarily large displacements and rotations, but small strains, is a common problem in numerous engineering applications. This paper has three goals: (1) present a new formulation of this problem which includes transverse shearing deformations, torsional warping effects, and elastic couplings resulting from the use of composite materials, (2) show that the small strain assumption must be applied in a consistent fashion for composite beams, and (3) present some numerical results based on this new formulation to assess its accuracy, and to point out some distinguishing feature of anisotropic beam behavior. First, the predictions of the formulation will be compared with experimental results for the large deflections and rotations of an aluminum beam. Then, the distinguishing features of composite beams that are likely to impact the design of rotating blades (such as helicopter blades) will be discussed. A first type of extension-twisting coupling introduced by the warping behavior of a pretwisted beam is discussed, then, a shearing strain squared term, usually neglected in small strain analyses, is shown to introduce a coupling between axial extension and twisting behavior, that can be significant when the ratio E/G is large (E and G are Young’s and shearing moduli of the beam, respectively). Finally, the impact of inplane shearing modulus changes and torsional warping constraints on the behavior of beams exhibiting elastic couplings is investigated.

scholarly journals Bond Between Steel and Self-Compacting Concrete in Composite Tube Columns

2017 ◽  
Vol 63 (2) ◽  
pp. 131-143
Author(s):  
M. Szadkowska ◽  
E. Szmigiera
Keyword(s):  
Vertical Shear ◽  
Self Compacting Concrete ◽  
Composite Tubes ◽  
Research Results ◽  
Composite Tube ◽  
Geometric Factors ◽  
The Impact

Abstract This paper presents research results of composite tubes filled with self-compacting concrete. The impact of the selected materials and geometric factors on resistance to the vertical shear was evaluated in this study. The resistance of the tested members was compared with recommendations given in Eurocode PN-EN 1994-1-1. From the results obtained in the tests it can be deduced that more parameters should be taken into consideration when determining resistance to the vertical shear in the interface between steel and concrete than PN-EN 1994- 1-1 recommends.

The Specific Characteristics of Shock and Blast Impacts on Construction Sites

2021 ◽  
pp. 81-88
Author(s):  
A.A. Komarov ◽  
Keyword(s):  
Dynamic Load ◽  
Static Load ◽  
Dynamic Loads ◽  
Potential Hazard ◽  
Construction Sites ◽  
Static Loads ◽  
Equivalent Static Loads ◽  
Plane Crash ◽  
Nuclear Plants ◽  
The Impact

The practices of hazardous and unique facilities’ construction imply that specific attention is paid to the issues of safety. Threats associated with crash impacts caused by moving cars or planes are considered. To ensure safety of these construction sites it is required to know the potential dynamic loads and their destructive capacity. This article considers the methodology of reducing dynamic loads associated with impacts caused by moving collapsing solids and blast loads to equivalent static loads. It is demonstrated that practically used methods of reduction of dynamic loads to static loads are based in schematization only of the positive phase of a dynamic load in a triangle forms are not always correct and true. The historical roots of this approach which is not correct nowadays are shown; such approach considered a detonation explosion as a source of dynamic load, including TNT and even a nuclear weapon. Application of the existing practices of reduction of dynamic load to static load for accidental explosions in the atmosphere that occur in deflagration mode with a significant vacuumization phase may cause crucial distortion of predicted loads for the construction sites. This circumstance may become a matter of specific importance at calculations of potential hazard of impacts and explosions in unique units — for instance, in the nuclear plants. The article considers a situation with a plane crash, the building structure load parameters generated at the impact caused by a plane impact and the following deflagration explosion of fuel vapors are determined.

scholarly journals The Specific Energy Modal Components of the Impact Dynamic Loads in a Solid

2015 ◽  
Vol 111 ◽  
pp. 556-560 ◽  
Author(s):  
Zhanna G. Mogilyuk ◽  
Mikhail S. Hlystunov ◽  
Valery I. Prokopiev
Keyword(s):  
Specific Energy ◽  
Dynamic Loads ◽  
The Impact

scholarly journals Impact Coefficient Analysis of Curved Box Girder Bridge Based on Vehicle-Bridge Coupling

2022 ◽  
Vol 2022 ◽  
pp. 1-11
Author(s):  
Fei Guo ◽  
Heng Cai ◽  
Huifang Li
Keyword(s):  
Shear Force ◽  
Primary Beam ◽  
Dynamic Loads ◽  
Box Girder ◽  
Impact Coefficient ◽  
Force Impact ◽  
Girder Bridge ◽  
The Moment ◽  
The Impact ◽  
Load Weight

In the current vehicle-bridge dynamics research studies, displacement impact coefficients are often used to replace the moment and shear force impact coefficients, and the vehicle model is also simplified as a moving-load model without considering the contribution of vehicle stiffness and damping to the system in some concerned research studies, which cannot really reflect the mechanical behavior of the structures under vehicle dynamic loads. This paper presents a vehicle-bridge coupling model for the prediction of dynamic responses and impact coefficient of the long-span curved bending beam bridge. The element stiffness matrix and mass matrix of a curved box girder bridge with 9 freedom degrees are directly deduced based on the principle of virtual work and dynamic finite element theory. The vibration equations of vehicle-bridge coupling are established by introducing vehicle mode with 7 freedom degrees. The Newmark-β method is adopted to solve vibration response of the system under vehicle dynamic loads, and the influences of flatness of bridge surface, vehicle speed, load weight, and primary beam stiffness on the impact coefficient are comprehensively discussed. The results indicate that the impact coefficient presents a nonlinear increment as the flatness of bridge surface changes from good to terrible. The vehicle-bridge coupling system resonates when the vehicle speeds reach 60 km/h and 100 km/h. The moment design value will maximally increase by 2.89%, and the shear force design value will maximally decrease by 34.9% when replacing moment and shear force impact coefficients with the displacement impact coefficient for the section internal force design. The load weight has a little influence on the impact coefficient; the displacement and moment impact coefficients are decreased with an increase in primary beam stiffness, while the shear force impact coefficient is increased with an increase in primary beam stiffness. The theoretical results presented in this paper agree well with the ANSYS results.

scholarly journals Empirical Analysis of the Impact Strength of Textile Knitted Barrier Meshes

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Zbigniew Mikołajczyk ◽  
Beata Szałek ◽  
Katarzyna Pieklak
Keyword(s):  
Measurement Data ◽  
Test Stand ◽  
Dynamic Loads ◽  
Measuring System ◽  
Electronic Measuring ◽  
Computer Data ◽  
Analysis System ◽  
Data Analysis System ◽  
Dynamic Stress Distribution ◽  
The Impact

AbstractThe assumptions of instrumental methodology for measuring dynamic loads of knitted barrier meshes were defined. A test stand was built, original in terms of both mechanical construction and electronic measuring system, connected to a computer data analysis system. Maximum values of dynamic forces in the mesh fastening strings were determined. The correctness of the strain gauges construction and measurement data transmission systems was confirmed. Tests of multidirectional resistance to dynamic loads in the mesh fastening strings were carried out. The experiment involved dropping a ball with a mass of 5 kg and a diameter of 10 cm, from a height of 1 m and 2 m onto the mesh surface. The potential impact energy equaled Ep1 = 49.05 J and Ep2 = 98.1 J. The tests showed that the highest force values were observed for meshes with square-shaped a-jour structure, and for mesh with diamond-shaped a-jour geometry the force values were lower. A symmetrical forces distribution was observed in all the strings. The highest forces were recorded in the middle strings and the lowest in the outer ones. The conducted tests confirmed the correctness of the adopted constructional solutions of test stand for identification of dynamic stress distribution in mesh fastening strings. The developed method is a useful verification tool for numerical analysis of mechanical properties of barrier meshes.

Numerical Analysis on the Response of Deck Plates Laterally Impacted by a Rectangular Indenter

2018 ◽  
Author(s):  
Ling Zhu ◽  
Junying Gao ◽  
Yinggang Li
Keyword(s):  
Permanent Deformation ◽  
Dynamic Loads ◽  
Parametric Studies ◽  
Ice Floes ◽  
Maximum Impact Force ◽  
Impact Energies ◽  
The Impact ◽  
Deformation Modes ◽  
Theoretical Procedure ◽  
Good Agreement

Ship deck plates are often subjected to localized dynamic loads, such as the loads of landing helicopter or impacts of ice floes. In order to investigate the dynamic response of ship plates subjected to such dynamic loads, a series of numerical simulations are performed on ship plates with different thicknesses. Parametric studies are performed on the impact response of plates, including the thickness of the plates, mass and impact velocity of the rectangular indenter. The maximum permanent deflections of the plates are obtained during the simulation. The relation between maximum force and permanent deflection is obtained and the deformation modes are analyzed. A theoretical procedure is developed to predict the deformation of plates with different initial impact energies, and a good agreement between the theoretical and numerical results is obtained. It has also been observed that the thickness of plates has little effect on the dimensionless maximum permanent deformation and dimensionless maximum impact force.

Research of Properties of Austenitic Steels

2021 ◽  
Vol 887 ◽  
pp. 242-246
Author(s):  
A.A. Peregudov ◽  
S.A. Vologzhanina ◽  
A.F. Igolkin
Keyword(s):  
Low Temperatures ◽  
Far East ◽  
Austenitic Steels ◽  
Dynamic Loads ◽  
Complex State ◽  
Corrosion Resistant ◽  
The Far East ◽  
Static And Dynamic Loads ◽  
The Impact ◽  
Strength And Ductility

Active development of the territories of Siberia and the Far East requires the use of materials that are able to work under the combined influence of low temperatures and a complex state. When operating equipment parts at low temperatures, it is necessary to take into account the impact of static and dynamic loads, as well as the influence of an external aggressive environment. The paper studies corrosion-resistant cold-resistant metastable austenitic steels, which are widely used for manufacturing parts of low-temperature equipment. Tests were performed to assess the strength and ductility characteristics of smooth samples and samples with annular notches for static stretching in the temperature range from 293 to 77 K.

scholarly journals Fibre Orientation Effects on High Strain Rate of Carbon/Epoxy Composites

2007 ◽  
Vol 16 (1) ◽  
pp. 096369350701600
Author(s):  
J. F. Ferrero ◽  
I. Tawk ◽  
S. Rivallant ◽  
J. J. Barrau ◽  
M. Sudre
Keyword(s):  
Dynamic Behaviour ◽  
High Strain ◽  
Epoxy Composite ◽  
Fibre Orientation ◽  
Dynamic Loads ◽  
Impact Modelling ◽  
Split Hopkinson ◽  
Laminated Structures ◽  
Cracked Specimens ◽  
Properties Of Composites

Specific mechanical properties of composites make them particularly attractive. Dynamic loads are of prime interest for their applications. Laminated structures’ impact modelling implies prior material dynamic characterisation. This study suggests an analysis of split Hopkinson bar compression testing on T300/914 carbon/epoxy composite material. First, the effect of fibre orientation and stratification on compression dynamic behaviour is studied. Results show a high non-linearity for +/-45° laminates testing. This non-linearity is not observed when the laminates are reinforced with 0° and 90° plies. Analytical modelling is in agreement with the experimental results. Secondly, experiments are performed on pre-cracked specimens to show the influence of cracking on dynamic behaviour.

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