A. Derewońko

CARBON-EPOXY COMPOSITE FATIGUE STRENGTH - EXPERIMENT AND FEM NUMERICAL ESTIMATION

The development of composite materials characterized by the constant amelioration of their mechanical properties (stiffness and strength) has widened their application for structural elements, mainly in aeronautical, naval and automobile industries. The possibility of tailoring the composite’s properties appropriately to the applied load (by changing the direction of the fibre alignment and applying a corresponding matrix) results in the growing importance of the design process. The paper presents a numerical technique of determining the fatigue strength of the laminated carbon–epoxy composite. The experimental investigations were carried out to determine the complete set of the stiffness characteristics E ij , G ij , �� ij , the strength characteristics �1 i,n , �0 i,n . and the S-N fatigue curves. The static and fatigue numerical calculations were carried out for the material anisotropic model of the particular composite layers. Eight-node 3D finite elements with the composite’s properties were used to develop the specimen’s numerical model. The contact problem between the composite layers enabling the reflection of a mutual interaction was taken into account. The numerical investigation also included the state of effort analysis and the fatigue life assessment of the composite. The assessment of the composite’s fatigue life was performed using the MSC.Fatigue code. The verification of models and numerical analysis was carried out for composite specimens made of the CE 8201-24545/120 prepreg. The experimental verification confirmed that the places of the lowest fatigue life, found out in numerical analysis, are located in the area of the gauge part.

Analysis of Microslips and Friction in the Riveted Joints

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.

Thermal-mechanical coupled simulation

Optimal design of engineering structures and technological processes requires taking into account various factors affecting the state of strain and stresses in the structure. Coupled thermo-mechanical analysis enables, among others, determination of undesirable changes in a body shape resulting from the implementation method of the initiallyboundary conditions, for example, time-varying load and physical properties of the material depending on the temperature. They are also used to determine residual stresses remaining after manufacturing to prevent revalued stiffness and rigidity of the designed construction. In this study, coupled thermo-mechanical analysis illustrated by metal machining operation is presented. The commercial code MSC.Marc has been used to develop a coupled thermomechanical finite element model of plane-stress orthogonal metal cutting operations. Metal cutting is one of the most important and common manufacturing processes in the car industry. A thermal mechanical transient analysis is performed to convert mechanical work into heat by plastic deformation of the workpiece material and friction during metal machining operation. The finite element mesh distortion, due to large deformations, requires a remesh technique. The influence of parameters of the 2D and 3D finite element mesh adaptation on plastic deformation and temperature generated in the cutting processing is considered.

Pneumatic air object application in design of water crossing

The results of numerical analysis of the decomposing process of a single pneumatic cassette pontoon bridge as a temporary roadway are presented in the paper. The cassette pontoon bridge is an innovative solution designed for quick assembly of the construction on water. The repeatability of a single module, facility of transportation and operation mean that it can be used in many applications: crossings for military vehicles (e.g. tanks or wheeled vehicles lightarmoured), replacement crossing for trucks (e.g. delivering materials for the construction of the permanent bridge), ribbons replacing flooded roads and footbridges on suddenly increased watercourses. The main problem in our consideration is single cassette pontoon stability at the moment of filling the pontoon. The numerical investigations presented in the present paper aimed at testing the influence of the load on the process of filling the single cassette pontoon. To perform the analyses, LS-DYNA software, in which the dynamic equations of motion are solved using an explicit time integration method, was used. The paper presents initial verification of the initial conditions influence on the process of filling the single cassette pontoon. An important factor considered in the work is a strong influence of an unbalanced load distribution on the surface of the cassette capacity on the process of filling the pontoon.