Papers by Author: Agnieszka Derewonko

Abstract: The objective of this work is to describe part of the selecting process of a rubber-coated fabric material model. The material is used to construct an air cushion that is a carrying element of the cassette pontoon bridge unit. During operation the air cushion is permanently in contact with a metal component, fresh water and air. Therefore various interactions, such as a contact problem, flow of medium and thermodynamics can occur. The basic material model for numerical simulation was selected based on the uniaxial tensile test. The simple method was used to describe time-dependent material properties for numerical analysis, which allows computation to take a reasonable time. In order to assess the usefulness of the selected material model the impact puncture test was modelled with the same conditions and properties as in the laboratory testing machine called Instron. Moreover, an attempt of simulating the damage process is described. The energy absorbed by the material was registered during the laboratory test which was compared with the results of numerical analysis. An acceptable compatibility of the results is noticed.

Abstract: The purpose of this paper is to describe the selection process of a rubber-like material model useful for simulation behaviour of an inflatable air cushion under multi-axial stress states. The air cushion is a part of a single segment of a pontoon bridge. The air cushion is constructed of a polyester fabric reinforced membrane such as Hypalon^®. From a numerical point of view such a composite type poses a challenge since numerical ill-conditioning can occur due to stiffness differences between rubber and fabric. Due to the analysis of the large deformation dynamic response of the structure, the LS-Dyna code is used. Since LS-Dyna contains more than two-hundred constitutive models the inverse method is used to determine parameters characterizing the material on the base of results of the experimental test.

Abstract: The paper deals with analysis of contact stress fields and relative displacements as well as inspection of fretting phenomena in the neighborhood of mating surfaces of the riveted joint subjected to cyclic loading. The study of micro-local phenomena follows the riveting process analysis. Numerical FE simulations of the upsetting process are carried out to determine the residual stress and strain fields. Nondestructive testing methods are used for validation of numerical results. The contact with friction is defined between the mating parts of the joint. The influence of the initial load and sheet material model is studied. Maximum values of relative displacements are comparatively small but surface condition is strongly affected by sliding movements during cyclic loading. Plastic strain energy is taken into account for more efficient numerical analysis of the fretting wear.