scholarly journals Swelling Elastomers: Comparison of Material Models

2021 ◽  
Author(s):  
Sayyad Zahid Qamar ◽  
Maaz Akhtar ◽  
Tasneem Pervez
Keyword(s):  
Accurate Determination ◽  
Strain Energy Function ◽  
Element Model ◽  
Material Behavior ◽  
Experimental Investigations ◽  
Material Models ◽  
Sultan Qaboos University ◽  
Compressive Loads ◽  
Tension And Compression

Little data is available about the material properties and swelling response of the elsatomers used in swell packers. This information is necessary for modeling and simulation of these elastomers in different petroleum applications. An experimental setup was therefore designed and implemented at Sultan Qaboos University (SQU) to investigate the material behavior of these elastomers under tension and compression, so that these properties could be used for different simulations. Before developing a finite element model (FEM) of elastomer seal performance, it was felt that a thorough evaluation needs to be carried out to decide which of the currently available material models is most suitable for swelling elastomers. This comparison translates into the selection of the correct strain energy function for accurate determination of material coefficients. Different hyperelastic material models are compared here. Experimental investigations under tensile and compressive loads, along with their numerical analysis are presented in detail in this chapter.

scholarly journals Determination of the hyperelastic material behavior of hydrogel specimens for expandable lens implants

2019 ◽  
Vol 5 (1) ◽  
pp. 351
Author(s):  
Heiner Martin ◽  
Olga Sahmel ◽  
Thomas Eickner ◽  
Niels Grabow ◽  
Christine Kreiner ◽  
...  
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Material Properties ◽  
Element Model ◽  
Material Behavior ◽  
Hyperelastic Material ◽  
Human Lens ◽  
Experimental Investigations

Abstract Theoretical and experimental investigations were carried out for development of human lens implants made from hydrogel material. The material properties were measured and implemented in a Finite element model. Though the material is still too stiff for accommodative lenses, the theoretical and experimental foundations for the implant development were established.

A Method for Determination of Elastohydrodynamic Behavior of Line Shafting Bearings in Their Environment

2007 ◽  
Author(s):  
C. Andreau ◽  
F. Ferdi ◽  
R. Ville ◽  
M. Fillon
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Steady State ◽  
Accurate Determination ◽  
Material Behavior ◽  
Oil Film ◽  
Dynamic Coefficients ◽  
Supporting Line ◽  
Element Method

Safe operation of a rotating line shafting needs to use proper tools and methodology for an accurate determination of its static and steady state behavior in running conditions. Taking into account properly the characteristics of shaft environment is of primary importance. These characteristics are mainly bearing material behavior, oil film dynamic coefficients (stiffness and damping), flexibility and deformations of structure supporting line shafting bearings. Global non linear behavior of the entire system needs to be analyzed to get an accurate solution, as oil film dynamic coefficients depend on steady state location of shaft inside the considered bearing, which depends itself on oil film stiffness, and also on flexibility and deformations of supporting structure. Calculations of structure flexibility and deformations, as well as line shafting stiffness characteristics are performed straightforwardly using finite element method. Solving global matrix equilibrium equation needs to solve elastohydrodynamic (EHD) problem on each bearing. A specific finite element method is developed for this purpose. This method is attractive for taking into account thick and flexible bearing materials such as multi layer synthetic materials. It can also support further developments (effects of geometry defects on bearings, solving thermoelastohydrodynamic problem). The application of the method to the propulsion line shafting of a large LNGC ship (Liquid Natural Gas Carrier) is presented, the final target being the determination of the most optimum bearing offsets for operating safely the vessel in all relevant conditions.

scholarly journals Experimental investigations of very long waves reflected from the ionosphere

1936 ◽  
Vol 156 (889) ◽  
pp. 614-633 ◽  
Keyword(s):  
Interference Pattern ◽  
Accurate Determination ◽  
Long Waves ◽  
Experimental Investigations ◽  
Great Length ◽  
Interference System ◽  
Phase Variations ◽  
Characteristic Features ◽  
The Waves

This paper is an account of experiments which have been carried out to determine the characteristic features (amplitude, height of reflexion, and polarization) of waves of very great length (18·8 km) reflected from the ionosphere at fairly small angles of incidence. The transmission characteristics of long waves have previously been studied by Holling-worth, Naismith, and Namba. In Hollingworth's pioneer experiment measurement were made on the space characteristics of the interference pattern produced at the ground by the superposition of the direct and the downcoming wave. the observations were made within the range 300-1000 bin from the sender, during the daytime, and one minimum and one maximum of the interference pattern were located. With the large distances to be covered the measurements extended over three months, and it was necessary to assume constancy of the conditions from day to day. The result demonstrate the presence of the interference system in a very beautiful manner, but cannot be used for an accurate determination of the height of reflexion at any one time. In §2 of the present paper we describe experiments, of the same type as Holling-worth's, carried out at shorter distances (70-140 km). The advantage of using shorter transmission distances are twofold. Firstly, it is possible to make sufficient measurements in the course of a single day (or night) to determine the reflexion height and the reflexion coefficient for a single day (or night), and, secondly, the information derived applies to the conditions of nearly vertical incidence, and so is more directly comparable with the detailed information which is now available concerning short waves. In the papers mentioned above muck attention has been given to the observation and explanation of the effects observed near sunset. It is pointed out that if the resultant signal strength on a single aerial system is alone observed, it is impossible to decide whether the changes are due to changes of amplitude, phase, or polarization of the downcoming wave. Assuming that the sunset variations are due entirely to phase variations, Hollingworth first deduced a change of reflexion height from 75 km to 90 km during sunset, but later believed that the variations were almost entirely explained by a rotation of the plane of polarization of the wave, and that the change of reflexion height was only about 2 km. Naismith states that no sunset variations are observable at short distances (100 km) from the sender, and suggests that at vertical incidence the waves are reflected from a higher level which does not exhibit changes at sunset.

A Study of the Dynamic Behavior of Elastomeric Materials Using Finite Elements

1996 ◽  
Vol 118 (4) ◽  
pp. 503-508 ◽  
Author(s):  
G. E. Vallee ◽  
Arun Shukla
Keyword(s):  
Finite Element ◽  
Dynamic Behavior ◽  
Split Hopkinson Pressure Bar ◽  
Material Model ◽  
Element Model ◽  
Material Behavior ◽  
Hopkinson Pressure Bar ◽  
Material Models ◽  
Finite Element Program ◽  
Elastomeric Materials

A numerical method is described for determining a dynamic finite element material model for elastomeric materials loaded primarily in compression. The method employs data obtained using the Split Hopkinson Pressure Bar (SHPB) technique to define a molecular constitutive model for elastomers. The molecular theory is then used to predict dynamic material behavior in several additional deformation modes used by the ABAQUS/Explicit (Hibbitt, Karlsson, and Sorenson, 1993a) commercial finite element program to define hyperelastic material behavior. The resulting dynamic material models are used to create a finite element model of the SHPB system, yielding insights into both the accuracy of the material models and the SHPB technique itself when used to determine the dynamic behavior of elastomeric materials. Impact loading of larger elastomeric specimens whose size prohibits examination by the SHPB technique are examined and compared to the results of dynamic load-deflection experiments to further verify the dynamic material models.

Study on Deflection Performance of Radial Tire by Finite Element Method

2011 ◽  
Vol 42 (11) ◽  
pp. 30-35
Author(s):  
Gang Cheng ◽  
Guoqun Zhao ◽  
Yanjin Guan ◽  
Zhonglei Wang
Keyword(s):  
Finite Element ◽  
Nonlinear Boundary ◽  
Accurate Determination ◽  
Element Model ◽  
Nonlinear Boundary Conditions ◽  
Contact Friction ◽  
Radial Tire ◽  
The Road ◽  
Contact Stress Distribution

In order to improve vehicle safety, the accurate determination of the tire's loading behaviour is necessary in the domain of vehicle dynamics. The interaction between the tire and the surface of the road must be understood thoroughly. A 3D finite element model of the tire-road has been built by using MARC software according to the actual construction of the 195/60R14 radial tire. The rebar model of the radial tire is employed to simulate the complex multilayer cord-rubber composites and directly define the cord directions varying with their positions. The geometric nonlinearity due to large deformation, material nonlinearity and the nonlinear boundary conditions from tire–rim contact and tire–road contact are also considered. The relationships between load and the tire deflection, the tire deformation, the contact stress distribution and the distribution of the contact friction force are discussed.

An Isoparametric Four-Node Beam Element for the Analysis of Planar Robot Manipulators

1993 ◽  
Author(s):  
Ahmad A. Smaili ◽  
Muhammad Sannah
Keyword(s):  
High Speed ◽  
Structural Characteristics ◽  
Accurate Determination ◽  
Element Model ◽  
Beam Element ◽  
Body Motion ◽  
Nonlinear Transient ◽  
Rigid Joints ◽  
Derivatives Of

Abstract Accurate determination of the dynamic response of high speed flexible manipulators requires that the dynamic model incorporates the influence of joint compliances, in addition to faithfully representing the physical characteristics of the links. A finite element model is herein presented for this purpose. The model is based on a 4-node isoparametric Timoshenko beam element to model the structural characteristics of the links including the effects of shear deformation and rotary inertia. It also includes the influence of the rigid body motion and the time derivatives of the elastic deformations of the manipulator on the characteristic matrices of the system, and accounts for the inertia of the drive units and payload and the damping of externally applied dampers. Quasistatic analysis, modal analysis, and linear and nonlinear vibrational responses of a 3-R planar manipulator are determined by solving the appropriate equations of equilibrium. The results of the analysis revealed that the compliance of the joints have a considerable influence on the manipulator response which is manifested by considerable increase in endpoint deflections and substantial decrease in fundamental natural frequency. Nonlinear transient response exhibited a behavior that differs drastically from that obtained when rigid joints are assumed.

A quantitative approach to inner shell losses

1978 ◽  
Vol 36 (1) ◽  
pp. 526-527 ◽  
Author(s):  
R.D. Leapman ◽  
P. Rez ◽  
D.F. Mayers
Keyword(s):  
Energy Transfer ◽  
Cross Section ◽  
Cross Sections ◽  
Accurate Determination ◽  
Background Intensity ◽  
Core Excitation ◽  
Quantitative Basis ◽  
Cross Section Differential ◽  
Bound Electrons

Microanalysis by EELS has been developing rapidly and though the general form of the spectrum is now understood there is a need to put the technique on a more quantitative basis (1,2). Certain aspects important for microanalysis include: (i) accurate determination of the partial cross sections, σx(α,ΔE) for core excitation when scattering lies inside collection angle a and energy range ΔE above the edge, (ii) behavior of the background intensity due to excitation of less strongly bound electrons, necessary for extrapolation beneath the signal of interest, (iii) departures from the simple hydrogenic K-edge seen in L and M losses, effecting σx and complicating microanalysis. Such problems might be approached empirically but here we describe how computation can elucidate the spectrum shape.The inelastic cross section differential with respect to energy transfer E and momentum transfer q for electrons of energy E0 and velocity v can be written as

Fast calibration of CBED patterns for quantitative analysis

1993 ◽  
Vol 51 ◽  
pp. 674-675
Author(s):  
M.A. Gribelyuk ◽  
M. Rühle
Keyword(s):  
Reciprocal Lattice ◽  
Accurate Determination ◽  
Incident Beam ◽  
Crystal Thickness ◽  
Structure Model ◽  
Beam Direction ◽  
Transmitted Beam ◽  
Reciprocal Vector ◽  
On Line

A new method is suggested for the accurate determination of the incident beam direction K, crystal thickness t and the coordinates of the basic reciprocal lattice vectors V1 and V2 (Fig. 1) of the ZOLZ plans in pixels of the digitized 2-D CBED pattern. For a given structure model and some estimated values Vest and Kest of some point O in the CBED pattern a set of line scans AkBk is chosen so that all the scans are located within CBED disks.The points on line scans AkBk are conjugate to those on A0B0 since they are shifted by the reciprocal vector gk with respect to each other. As many conjugate scans are considered as CBED disks fall into the energy filtered region of the experimental pattern. Electron intensities of the transmitted beam I0 and diffracted beams Igk for all points on conjugate scans are found as a function of crystal thickness t on the basis of the full dynamical calculation.

Computer-Assisted High-Re Solution TEM

1990 ◽  
Vol 48 (1) ◽  
pp. 162-163
Author(s):  
F.A. Ponce ◽  
H. Hikashi
Keyword(s):  
Signal To Noise Ratio ◽  
Accurate Determination ◽  
Computer Software ◽  
Video Camera ◽  
Image Contrast ◽  
Objective Lens ◽  
Computer Assisted ◽  
Optical Parameters ◽  
Astigmatism Correction

The determination of the atomic positions from HRTEM micrographs is only possible if the optical parameters are known to a certain accuracy, and reliable through-focus series are available to match the experimental images with calculated images of possible atomic models. The main limitation in interpreting images at the atomic level is the knowledge of the optical parameters such as beam alignment, astigmatism correction and defocus value. Under ordinary conditions, the uncertainty in these values is sufficiently large to prevent the accurate determination of the atomic positions. Therefore, in order to achieve the resolution power of the microscope (under 0.2nm) it is necessary to take extraordinary measures. The use of on line computers has been proposed [e.g.: 2-5] and used with certain amount of success.We have built a system that can perform operations in the range of one frame stored and analyzed per second. A schematic diagram of the system is shown in figure 1. A JEOL 4000EX microscope equipped with an external computer interface is directly linked to a SUN-3 computer. All electrical parameters in the microscope can be changed via this interface by the use of a set of commands. The image is received from a video camera. A commercial image processor improves the signal-to-noise ratio by recursively averaging with a time constant, usually set at 0.25 sec. The computer software is based on a multi-window system and is entirely mouse-driven. All operations can be performed by clicking the mouse on the appropiate windows and buttons. This capability leads to extreme friendliness, ease of operation, and high operator speeds. Image analysis can be done in various ways. Here, we have measured the image contrast and used it to optimize certain parameters. The system is designed to have instant access to: (a) x- and y- alignment coils, (b) x- and y- astigmatism correction coils, and (c) objective lens current. The algorithm is shown in figure 2. Figure 3 shows an example taken from a thin CdTe crystal. The image contrast is displayed for changing objective lens current (defocus value). The display is calibrated in angstroms. Images are stored on the disk and are accessible by clicking the data points in the graph. Some of the frame-store images are displayed in Fig. 4.

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