Extending the visco-frictional branched modeling of filled rubbers to include coupling effects between rate and amplitude dependence

The traditional way to capture rate and amplitude dependence of filled rubbers is by a branched model containing elastic, viscous, and frictional branches, leading to a decoupling of the rate and amplitude dependence. In order to capture the experimentally observed phenomena with a steeper increasing dynamic modulus with frequency, for small amplitudes, a model by Besseling (1958) is revisited. In it‘s general form several stress fractions are added and each fraction has elastic, viscous, and frictional contributions in series. In this work the potential of Bessling‘s constitutive model is investigated by extending the traditional three branches by a forth branch from this model to account for the coupling effects. The stress calculation algorithms and behavior of one-dimensional models are compared to harmonic experiments in double shear. A simple eight parameter model is studied and shown roughly to give the desired behavior, although no fitting routine has been implemented

Extending the overlay method in order to capture the variation due to amplitude in the frequency dependence of the dynamic stiffness and loss during cyclic loading of elastomers

The current work focus on the overlay method proposed by Austrell concerning frequency dependence of the dynamic modulus and loss angle that is known to increase more with frequency for small amplitudes than for large amplitudes. The original version of the overlay method yields no difference in frequency dependence with respect to different load amplitudes. However, if the elements in the viscoelastic layer of the finite element model are given different stiffness and loss properties depending on the loading amplitude level, frequency dependence is shown to be more accurate compared to experiments. The commercial finite element program Ansys is used to model an industrial metal rubber part using two layers of elements. One layer is a hyper viscoelastic layer and the other layer uses an elasto-plastic model with a multi-linear kinematic hardening rule. The model, being intended for stationary cyclic loading, shows good agreement with measurements on the harmonically loaded industrial rubber part

Vibrations analysis in high-tech facility : A swedish light synchrotron

MAX-lab is a national laboratory operated jointly by the Swedish Research Council and Lund University. As of today, the MAX project consists of three facilities, (three storage rings): MAX-I, MAX-II, MAX-III and one electron pre-accelerator called MAX-Injector. A new storage ring is needed at the benefit of material science, such as nanotechnology. MAX-IV will be 100 times more efficient than existing synchrotron radiation facilities. MAX-IV will consist of a main source that will be a 3-GeV ring with state-of-the-art low emittance for the production of soft and hard x-rays as well as an expansion into the free electron laser field. The second source, the Linac injector, will provide short pulses to a short pulse facility. It will be built as an underground tunnel next to the main ring. The main objective of the present work is to study vibrations at the foundation of the light synchrotron subjected to different excitations and analyze the influence of the surrounding vibration sources on the MAX-IV Lab's underground tunnel. Since MAX-IV will be used for high precision measurements, it will be asked to have very strict technical conditions where only very low vibration levels will be allowed. The aim is to establish realistic finite element models that predict vibrations in the foundation and in the Linac with high accuracy. To achieve this purpose it will be necessary to model loads, materials, etc. with different assumptions, in order to prove the fulfillment of the needed requirements. The vibrations are analyzed by the finite element method in both transient and steady state solutions. The ring model contains the concrete floor structure, the concrete structure of the beam containment and the soil up to a depth of about 10m and extending to the nearby roads, while Linac's model has the tunnel itself, the soil (up to 10 m deep also) and the crossing bridge over it