The Experts below are selected from a list of 480 Experts worldwide ranked by ideXlab platform

Van Asselt P.h. - One of the best experts on this subject based on the ideXlab platform.

  • Analysis of stressed membrane structures: Implementation of non-linear material behaviour in structural analysis
    2007
    Co-Authors: Van Asselt P.h.
    Abstract:

    A growing use of tensioned membrane structures requires insight and understanding of the mechanical behaviour of the structure and the membrane material. In current practise the complex material behaviour is simplified due to the uncertainties that exist around the material behaviour. Testing and modelling the membrane material may provide a more accurate tool for structural analysis. Research has been performed on PTFE coated fibreglass, a widely used architectural textile. Non-linear material properties have been identified as well as other material characteristics. Different aspects of bi-axial fabric testing have been researched. A bi-axial test protocol must provide accurate measurements that will provide insight in the non-linear stress-strain relation of PTFE coated fibreglass. Various bi-axial tests have been performed in the Stevin Lab at the Faculty of Civil Engineering, Delft University of Technology. Accurate displacements measuring devices have been designed and created to record the strains of the fabric. These tests supplied insight in the non linear material properties. Bi axial tests at preset stress ratios have been performed on six identical cruciform test samples of PTFE coated fiber glass (Verseidag B18089). Various approaches have been made to model the fabric’s stress-strain behaviour. Modelling the stress strain relation by creating a best fit surface through the experimental data did not result in a useable model. A different approach where the nonlinear stress strain relation is linearized and where Hooks Law was applied did not result in an accurate model. The best results were obtained by a non linear model based on the fibres’ geometry. This model showed good resemblance with the experimental data. The model is calibrated by three parameters, fibre diameter, fibre spacing and Young Modulus of the fibres. The material model is programmed in FORTRAN language and is linked to the general purpose finite element software Ansys. Several test cases have been analysed, based on the material model. It appears that non linear geometric behaviour combined with non linear material behaviour demands an accurate description of the Jacobian matrix for convergence purposes. The performance of the model is not yet at the level of industrial application. Calculation times exceed the reasonable for desktop application. Various recommendations have been made in order to improve the model’s performance. Additional tests on other fabric qualities may contribute to the applicability of the model. These tests must turn out whether the model can easily be adapted to other fabric qualities.Design and ConstructionCivil Engineering and Geoscience

Fikri Bin Muhamad Ismail Fikri - One of the best experts on this subject based on the ideXlab platform.

  • Computer Simulation of Hollow Buckling Cylinder Tubing by Finite Element Analysis
    2010
    Co-Authors: Fikri Bin Muhamad Ismail Fikri
    Abstract:

    The failure of a compression member has to do with the strength and stiffness of the material and the geometry (slenderness ratio) of the member. Whether a compression member is considered short, intermediate, or long depends on these factors. The buckling of hollow cylinder tubing is considered as failure due to elastic instability where the actual compressive stress at the point of failure is less than the ultimate compressive stresses that the material is capable of withstanding. For the purpose of this project few assumptions have been made which are the material element is homogeneous and isotropic, Hooks Law holds (stress linearly proportional to strain), the maximum stress the hollow cylinder can handle is equivalent to yield stress of material used which are steel and aluminum, the loads and the bending moment act in a plane passing through a principal axis of inertia of cross section and the deflection are small compared to cross sectional dimension

Sergey S. Kokarev - One of the best experts on this subject based on the ideXlab platform.

  • Gravity as a bend of 4D elastic plate
    2002
    Co-Authors: Sergey S. Kokarev
    Abstract:

    Gravity is represented as a linear theory of strong plate bend at the variational functionals level. Some estimates of elastic constant of space-time are made. Physical (elastic) sense of field lagrangians and Einstein Equations is discussed. The question about physical nature of space, time, gravity and Einstein Equations (EE) has been discussing from the earliest era of special (SR) and general (GR) relativity up to a present time. Today we have powerful mathematical means of formulation and investigation of space-time physics, while physical foundations of the theories and their relations both to observable world and to other physical topics often remain beyond the scope of attention. In my report I am going to demonstrate physical relevance of linear elasticity theory (Hooks Law) language for formulation and clarifying standard GR. Note, that difficulties of most of the attempts, that have been made in this direction, were caused by restriction to (at best) 4D elasticity([1]-[3]) — we’ll see that it totally excludes the possibility of ”embedding ” gravity into elasticity. The starting points of our consideration are two quite obvious observations: 1) We locally live in 4D Minkowski world M4; 2) In every 3D simultaneity section, which is locally isometric to 3D euclidian space E3, we deal with (approximate) Hooks Law, when investigate contact interactions properties of real mechanical bodies: σ = 2µD + λTr[D]η, (1) where σ and D — 3D stress and strain tensors, defined by expressions1

C. Naumann - One of the best experts on this subject based on the ideXlab platform.

  • Abstract
    2005
    Co-Authors: K. Salomon, G. Anton, K. Graf, J. H Össl, A. Kappes, T. Karg, U. Katz, R. Lahmann, C. Naumann
    Abstract:

    Calibration sources are an indispensable tool for all detectors. In acoustic particle detection the goal of a calibration source is to mimic neutrino signatures as expected from hadronic cascades. A simple and promising method for the emulation of neutrino signals are piezo ceramics. We will present results of measruements and simulations on these piezo ceramics. 1 The Piezoelectric Effect and Signal Propagation in Water The active element of a transducer is a piezoelectric material. When an electric field is applied to the material, the polarized molecules are distorted in the electric field. This distortion causes the material to change its dimensions. This phenomenon is known as electrostriction or inverse piezoelectric effect. In addition, a permanently-polarized material such as lead zirconate titanate (PZT) produces an electric field when the material changes dimensions as a result of an imposed mechanical force. This phenomenon is known as the piezoelectric effect. A piezoelectric material can be modeled by connecting Hooks Law for anisotropic materials to the Gauss Law for electrical displacement. This is described by tensor equations: ∂k(ciklmSlm + elikEl) = ρüi; ∂i(eilmSlm + ǫilEl) = 0 (1

K. Salomon - One of the best experts on this subject based on the ideXlab platform.

  • Abstract
    2005
    Co-Authors: K. Salomon, G. Anton, K. Graf, J. H Össl, A. Kappes, T. Karg, U. Katz, R. Lahmann, C. Naumann
    Abstract:

    Calibration sources are an indispensable tool for all detectors. In acoustic particle detection the goal of a calibration source is to mimic neutrino signatures as expected from hadronic cascades. A simple and promising method for the emulation of neutrino signals are piezo ceramics. We will present results of measruements and simulations on these piezo ceramics. 1 The Piezoelectric Effect and Signal Propagation in Water The active element of a transducer is a piezoelectric material. When an electric field is applied to the material, the polarized molecules are distorted in the electric field. This distortion causes the material to change its dimensions. This phenomenon is known as electrostriction or inverse piezoelectric effect. In addition, a permanently-polarized material such as lead zirconate titanate (PZT) produces an electric field when the material changes dimensions as a result of an imposed mechanical force. This phenomenon is known as the piezoelectric effect. A piezoelectric material can be modeled by connecting Hooks Law for anisotropic materials to the Gauss Law for electrical displacement. This is described by tensor equations: ∂k(ciklmSlm + elikEl) = ρüi; ∂i(eilmSlm + ǫilEl) = 0 (1