During the frontal crash the longerons absorb most energy of all vehicles construction elements. In order to analyse the energy absorbing capabilities of longerons under axial compression loading and to evaluate the influence of longerons geometrical characteristics and materials degradation on the vehicles safety experimental investigations and numerical calculations were performed. To assess the crashworthiness of longerons the main objective was to study the behaviour of thin-walled structural elements under axial loading conditions using the Finite Element (FE) model. The numerical FE models were created using the computer code LS-DYNA. Two models of longerons were investigated with different sections shape and for each of them materials with the four different mechanical characteristics were applied. Validation of created FE model was performed according to the experimental investigation and the results were obtained of validated FE models of vehicles crash analysis [I].The results of analyses show that the value of absorbed energy by the longerons of new vehides exceeds the value of the oldest cars. The degradation of structures in the old cars has the significant influence on the absorbed energy.
This paper presents methodology for determining residual stresses originated from welding process in load bearing bridge steel structures made of square profile tubes. Simulated welding process was performed together with the selected welding sequences and due to significant thermal effect on the welding area residual stresses inside the butt weld area and around it were evaluated. The developed finite element (FE) model allows determining residual stresses of welding in any type of hollow sections butt welds.
Scientists recently focus on concrete's hardening early age and its influence to solidity of a structure. Because of complex physical-chemical processes and developed strains, stresses appear in concrete and after they exceed tensile strength of concrete-develops cracks. In practice it is noted that a structure often cracks prior to commencement of exploitation. Therefore this article analyzes the influence of stresses caused by autogenous shrinkage over solidity of structure. The importance of stresses caused by concrete shrinkage significantly increases in places where a cross-section shifts. The stress concentration area develops at these points. One of the stress concentration areas is around the formwork's transverse brace and stresses due to autogeneous shrinkage are solved. To define stresses, analytical and finite element methods are used. The stresses concentration area is calculated more precisely using the finite elements method, the results obtained are exhaustive and it allows to get a clearer picture of stresses.
This work analyses the material fracture problem due to mixed-mode: dynamic opening and in-plane shear cases. Fracture criterions are analysed and new regularities are established, that mixed-mode fracture can be determined using critical characteristics of fracture and toughness: shear modulus and Poison's ratio.Stress intensity factor dependence curves are determined due opening and in-plane shear cases with different angle of initial crack trajectory. The opening and inplane shear fracture influence ratio is set.
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