scholarly journals Vibrational Study of a Helicopter Tail Rotor Blade with Different Polymer Inner Core Materials

2019 ◽  
Vol 57 (2) ◽  
pp. 169-178
Author(s):  
Andrei Daniel Voicu ◽  
Anton Hadar ◽  
Daniel Vlasceanu ◽  
Daniela Ioana Tudose
Keyword(s):  
Rotor Blade ◽  
Inner Core ◽  
Dynamic Properties ◽  
Polymeric Materials ◽  
Core Material ◽  
Structural Elements ◽  
Blade Profile ◽  
Structural Vibrations ◽  
Vibrational Study ◽  
Material Choice

Determining the dynamic properties in the frequency domain of aircraft structural elements is a very important aspect taken into account nowadays by aircraft manufacturers. One of the helicopters most exposed element to structural vibrations is the rotor blade, thus making its construction and the material choice a very important decision. Finite element methods can be used to assess the vibrational properties of such elements, in order to prove their airworthiness. The main objective of the article is to study how the use of different materials affects the structural behavior of the helicopter tail rotor blade, with regard to the frequencies at which these structures are prone to vibrate. The blade profile is the NACA0012 symmetric airfoil used on the IAR330 helicopter tail rotor blade and the main objective is to identify the best inner core material, while highlighting the importance of polymeric materials.

Materials Selection for Sandwich Pipes Under the Combined Effect of Pressure, Bending and Temperature

2007 ◽  
Author(s):  
Allan R. de Souza ◽  
Theodoro A. Netto ◽  
Ilson P. Pasqualino
Keyword(s):  
Structural Strength ◽  
Material Selection ◽  
Low Cost ◽  
Polymeric Materials ◽  
External Pressure ◽  
Core Material ◽  
Annular Layer ◽  
Oil And Natural Gas ◽  
Longitudinal Bending ◽  
Logic Approach

Recent researches point to the great potential of the sandwich pipe conception for ultra deepwater exploitation and production of oil and natural gas. Its configuration is very simple and comprises two concentric metallic pipes with a core material, polymeric or ceramic, in the annulus. The main functions of the annular layer are: to provide satisfactory thermal insulation so as to avoid the formation of wax and hydrates along the pipeline during production shutdown; to improve the overall structural strength of the system. Polypropylene and cement have been recently proposed for these applications. The reason for the choice of these materials was the low cost and the extensive availability in industry. Here a systematic material selection approach is employed in order to assess the applicability of other polymeric materials. The attributes of materials needed to meet the design specification are thoroughly studied. The list of possible materials was enlarged and the modified digital logic approach is used with the purpose to define a top group of materials for further numerical comparative study. Finite element analyses are carried out to assess the structural strength of the sandwich pipe under pure external pressure or longitudinal bending and combined external pressure and bending. Additionally, the effect of thermal gradient is included to the numerical analyses to evaluate each pre-selected material of the top group. Results indicate that other potential materials such as PEEK and polycarbonate can improve the structural performance of the sandwich pipe conception and yet meet other several design criteria.

scholarly journals 3D Printing of Solvent-Free Supramolecular Polymers

2021 ◽  
Vol 9 ◽  
Author(s):  
Harald Rupp ◽  
Wolfgang H. Binder
Keyword(s):  
3D Printing ◽  
Dynamic Properties ◽  
Polymeric Materials ◽  
Fundamental Principle ◽  
Supramolecular Polymers ◽  
Fused Deposition Modelling ◽  
Self Healing ◽  
Polymer Science ◽  
Fused Deposition ◽  
Molecular Ordering

Additive manufacturing has significantly changed polymer science and technology by engineering complex material shapes and compositions. With the advent of dynamic properties in polymeric materials as a fundamental principle to achieve, e.g., self-healing properties, the use of supramolecular chemistry as a tool for molecular ordering has become important. By adjusting molecular nanoscopic (supramolecular) bonds in polymers, rheological properties, immanent for 3D printing, can be adjusted, resulting in shape persistence and improved printing. We here review recent progress in the 3D printing of supramolecular polymers, with a focus on fused deposition modelling (FDM) to overcome some of its limitations still being present up to date and open perspectives for their application.

Cold Blade Profile Generation Methodology for Compressor Rotor Blades Using FSI Approach

2017 ◽  
Author(s):  
Kirubakaran Purushothaman ◽  
Sankar Kumar Jeyaraman ◽  
Ajay Pratap ◽  
Kishore Prasad Deshkulkarni
Keyword(s):  
Aspect Ratio ◽  
Rotor Blade ◽  
Axial Compressor ◽  
Operating Conditions ◽  
Rotor Blades ◽  
Blade Profile ◽  
Interaction Technique ◽  
Compressor Rotor ◽  
Blade Shape ◽  
Blade Geometry

This paper describes a methodology for obtaining correct blade geometry of high aspect ratio axial compressor blades during running condition taking into account of blade untwist and bending. It discusses the detailed approach for generating cold blade geometry for axial compressor rotor blades from the design blade geometry using fluid structure interaction technique. Cold blade geometry represents the rotor blade shape at rest, which under running condition deflects and takes a new operating blade shape under centrifugal and aerodynamic loads. Aerodynamic performance of compressor primarily depends on this operating rotor blade shape. At design point it is expected to have the operating blade shape same as the intended design blade geometry and a slight mismatch will result in severe performance deterioration. Starting from design blade profile, an appropriate cold blade profile is generated by applying proper lean and pre-twist calculated using this methodology. Further improvements were carried out to arrive at the cold blade profile to match the stagger of design profile at design operating conditions with lower deflection and stress for first stage rotor blade. In rear stages, thermal effects will contribute more towards blade deflection values. But due to short blade span, deflection and untwist values will be of lower values. Hence difference between cold blade and design blade profile would be small. This methodology can especially be used for front stage compressor rotor blades for which aspect ratio is higher and deflections are large.

Strengthening and Retrofitting of Motín de Oro II Bridge in Mexico

2020 ◽  
pp. 193-209
Author(s):  
Jose M. Jara ◽  
Bertha A. Olmos ◽  
Guillermo Martínez
Keyword(s):  
Material Properties ◽  
River Flow ◽  
Dynamic Properties ◽  
Flow Characteristics ◽  
Ambient Vibration ◽  
Structural Elements ◽  
Box Girder ◽  
Prone Area ◽  
Scour Protection ◽  
Ambient Vibration Measurements

This chapter presents the studies conducted to retrofit an existing bridge in a seismic prone area of Mexico. The Motín de Oro II Bridge was built in the 1970s with a continuous box girder superstructure and wall-type substructure. From the 1970s to nowadays, the design truck loads in Mexico have been substantially incremented and many bridges built in that period have required to be evaluated and, in some cases, rehabilitated and retrofitted. Firstly, the study presents the results of visual inspections of all parts of the bridge and a description of the preliminary studies conducted to determine the material properties, to evaluate the river flow characteristics and to calculate the scour depth. Secondly, the chapter discusses the initial structural analyses of the bridge subjected to the original gravitational and seismic loads and to the current loads before the intervention. These analyses allow to select the structural elements that require to be retrofitted and the best strategy to follow. Finally, the study presents results of the numerical retrofitted model and the experimental assessment of the dynamic properties based on ambient vibration measurements. Additionally, the scour protection and the general construction procedure are also described.

scholarly journals Quasi-Static Indentation Properties of Aluminium Foam-Frp Sandwich Panel

2018 ◽  
Vol 7 (3.11) ◽  
pp. 193
Author(s):  
Ummu Raihanah Hashim ◽  
Aidah Jumahat ◽  
Muhammad Fashan Md Ghazali
Keyword(s):  
Energy Absorption ◽  
Sandwich Panel ◽  
Polymeric Materials ◽  
Aluminium Foam ◽  
Core Material ◽  
Depth Of Penetration ◽  
Basalt Fibre ◽  
Reinforced Polymer ◽  
Static Indentation ◽  
Fibre Reinforced Polymer

Synthetic FRP have been used for many years in wide applications owing to their versatility and good performance. However, environmental problems caused by extensive use of polymeric materials arise mainly due to lack of landfill spaces and depletion of finite resources of fossil raw materials, such as petroleum or natural gas. Hence, materials derived from natural products are emerging as potential substitutes for petroleum-based material. The usage of natural fibre reinforced polymer (NFRP) composite have triggered considerable interest to explore the usefulness of this material. Excellent energy absorption of sandwich-structured composite made it a versatile structure used in various industries such transportation, automotive, building construction and marine. On top of that, the research data on aluminium foam as a core material in sandwich panel are limited and need to be further studied. This research is aimed to determine the quasi-static indentation properties of Basalt Fibre Reinforced Polymer/Aluminium Foam (BF-AF) sandwich panel and compare with the properties of Glass Fibre Reinforced Polymer/Aluminium Foam (GF-AF) sandwich panel. In this study, BFRP and GFRP composites with nanosilica were fabricated using vacuum bagging method. Aluminium foam was used as a core in the sandwich panel structure. The quasi-static indentation tests were performed using 10mm indenter and the specimen size was 50mm x 50mm with thickness of 3mm. The effect of aluminum foam on indentation properties were studied. The results showed that the addition of nanosilica enhanced the energy absorption, depth of penetration and damage area of the composites. The indentation properties of BF-AF were higher than those of GF-AF sandwich panel composites. Therefore, this research contributes to a new knowledge on the properties of aluminium foam-FRP composite materials

Bacillus mycoides phages and their satellites

1984 ◽  
Vol 30 (5) ◽  
pp. 691-698 ◽  
Author(s):  
Anna S. Tikhonenko ◽  
Nina N. Belyaeva ◽  
Anna F. Kretova
Keyword(s):  
Inner Core ◽  
Structural Elements ◽  
Small Particles ◽  
Electron Microscopic ◽  
Bacillus Mycoides ◽  
Specific Antibodies ◽  
Helper Phage ◽  
Electron Microscopic Technique ◽  
Large Particles ◽  
The Relationship

The relationship between large and small particles of phages No. 1M and H17 reproducing simultaneously in one and the same bacterial cell of Bacillus mycoides was studied by the immune electron microscopic technique. The large particles of phages No. 1M and H17 were morphologically identical with phage No. 1 of B. mycoides, whereas only the tails of small particles of phages No. 1M and H17 were morphologically identical with the tail of phage No. 1. Antigens were identified in phages No. 1, No. 1M, and H17 using specific antibodies against phage No. 1, containing only large phage particles, and specific antibodies against phage H17 small heads. It was shown that (i) all structural elements of large particles and tails of small particles of phage No. 1M were antigenically identical with those of phage No. 1; (ii) all structural elements of small and large particles of phage H17, except the inner core of the tail, were antigenically different from phage No. 1; and (iii) the small heads of phages No. 1M and H17 were antigenically identical. Particles of phage No. 1 are morphologically and antigenically identical with the large particles of phage No. 1M and are antigenically different from the large particles of phage H17. Since the tails of small and large particles are antigenically identical in each phage pair (No. 1M and H17), this suggests that in both cases, the genome of a small defective phage codes for the synthesis of head proteins only, whereas its tail is borrowed from the corresponding helper phage. The small phage may therefore be considered as a satellite of the large phage which depends on a helper partner for production of complete particles and whose tail proteins are identical with those of the helper phage.

FEM Analysis of Cylindrical Structural Elements under Local Shock Loading

2014 ◽  
Vol 566 ◽  
pp. 499-504 ◽  
Author(s):  
Leopold Kruszka ◽  
Yu.S. Vorobiov ◽  
N.Yu. Ovcharova
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Strain State ◽  
Shock Loading ◽  
Dynamic Properties ◽  
Fem Analysis ◽  
Finite Deformations ◽  
High Rate ◽  
Structural Elements ◽  
Stress Strain

High rate deformations of structures cylindrical elements are considered 3D formulation. Elastic-plastic finite deformations and dynamic properties of material take into account. The problem become geometrically and physically nonlinear and finite element method is used. The numerical analyses of dynamics stress-strain state of real structures elements is executed.

Blades Forced Vibration Under Aero-Elastic Excitation Modeled by Van der Pol

2017 ◽  
Vol 27 (11) ◽  
pp. 1750166 ◽  
Author(s):  
Ladislav Pust ◽  
Ludek Pesek
Keyword(s):  
Rotor Blade ◽  
Analytical Approach ◽  
Nonlinear Models ◽  
Dynamic Properties ◽  
Deformation Wave ◽  
Response Curves ◽  
Van Der Pol ◽  
External Forces ◽  
Real Type

This paper employs a new analytical approach to model the influence of aerodynamic excitation on the dynamics of a bladed cascade at the flutter state. The flutter is an aero-elastic phenomenon that is linked to the interaction of the flow and the traveling deformation wave in the cascade when only the damping of the cascade changes. As a case study the dynamic properties of the five-blade-bunch excited by the running harmonic external forces and aerodynamic self-excited forces are investigated. This blade-bunch is linked in the shroud by means of the viscous-elastic damping elements. The external running excitation depends on the ratio of stator and rotor blade numbers and corresponds to the real type of excitation in the steam turbine. The aerodynamic self-excited forces are modeled by two types of Van der Pol nonlinear models. The influence of the interaction of both types of self-excitation with the external running excitation is investigated on the response curves.

scholarly journals Civil engineering materials

2021 ◽  
Vol 3 (2) ◽  
pp. 154-172
Author(s):  
Furkan Findik ◽  
Fehim Findik
Keyword(s):  
Civil Engineering ◽  
Construction Materials ◽  
Structural Elements ◽  
Structural Members ◽  
Structural Form ◽  
Bituminous Materials ◽  
Number Of Factors ◽  
Material Choice ◽  
Properties Of Materials ◽  
Materials Used

For any construction project to prove satisfactory, it is essential to understand the properties of materials during both the design and construction phases. It is crucial to consider the economic viability and sociological and environmental impact of a project. During this initial design phase, possible alternative locations and a preliminary assessment of suitable construction materials are taken into account. The decision of which structural form and material choice is most appropriate depends on a number of factors including cost, physical properties, durability and availability of materials. Buildings can contain wood, metals, concrete, bituminous materials, polymers, and bricks and blocks. Some of these can only be used in non-structural elements, while others can be used alone or in combination with structural elements. The actual materials used in the structural members will depend on both the structural form and other factors mentioned earlier. In this study, various materials such as metal, timber, concrete floor and polymer used in civil engineering were examined, the properties and usage areas of these materials were examined.

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