In order to characterise the material and damage behaviour of additively manufactured polyamide 12 (PA12) under quasi-static load and to implement it in a numerical model, experiments under quasi-static load as well as microstructural investigations were carried out. Selective laser sintering (SLS) was used as the manufacturing process. For the classification of the material behaviour, quasi-static cyclic tests with holding times as well as tensile tests were performed. X-ray refraction and computed tomography (CT) were...

This research aims to study the fastening rotation behavior of cold-formed steel screw connections by experimental testing and analytical modelling. Both the experimental test and finite element results showed the failure modes of tilting and bearing failure. The rotation failure mode of the screw connection was studied by an analytical method using a spring model with screw-plate stiffness which included the bending and shear stiffness of the screw and the bearing stiffness of the screw...

A monitoring system for fatigue crack propagation was developed using a non-contact acoustic emission (AE) monitoring system. The AE signals generated during the plane bending fatigue test were first monitored. The AE generation rate increased after approximately 0.5 of the fatigue life ratio. The maximum amplitude of the AE signals increased with a tendency similar to that of the crack propagation. The sensor sensitivities for the flat and arced surfaces were then compared. The sensitivity...

The paper presents the results of experimental tests and numerical simulations related with the strength differential effect. Tensile and compression tests on 2CrMoV low-alloy steel are performed to evaluate the magnitude of the yield stress difference in tension and compression. The strength differential parameter is then used in the formula for equivalent stress proposed by Burzynski. The material effort calculated using Burzynski and Huber-Mises-Hencky hypotheses was compared for different start-stop cycles. Analytical notch stress-strain correction...

This article focuses on the performance study and frequency response analysis with the state space model of a linearized two stage two spool non-conventional electrohydraulic servovalve from a set of nonlinear state equations. The performance of this valve depends on many valve geometries and fluid parameters. This non-conventional electrohydraulic servovalve is controlled by a pressure controlled pilot, which generates a differential pressure between the upper and lower chambers of two spools. This differential pressure acts...

The research presented in the paper deals with the improvement of firemen protective clothing. The proposed modification of the special textile PROTON is based on the application of TiSi(N) nanocomposite reflective layer, which improves the thermal resistance of the coated material. The second improvement deals with the implementation of auxetic textile into the protective clothing structure. Such material is characterized with the very good blast wave resistance. In the paper both phenomena were studied. The...

Thermal processes in domain of thin metal film subjected to an ultrashort laser pulse are considered. A mathematical description of the process discussed is based on the system of four equations. Two of them describe the electrons and lattice temperature, while third and fourth equations represent the generalized Fourier law, it means the dependencies between the electrons (lattice) heat flux and the electrons (lattice) temperature gradient. In the generalized Fourier law the heat fluxes are...

In this paper, we investigate the problem of the dynamic behaviour of a double-beam system with intermediate elastic restraints subjected to a moving point force. Problem is solved by replacing this type of structure with two single-span beams loaded with a given moving force and redundant forces representing reactions in the intermediate restraints. Redundant forces are obtained by solving Volterra integral equations of the second order which are compatibility equations corresponding to each redundant. Solutions...

Virtual additive manufacturing (AM) is one of the new directions of research that is necessary to improve AM technology. Abaqus/SIMULIA software allows to simulate the whole process using user subroutines to expand solver capabilities. Two of the most important subroutines are UepActivationVol and UMATHT. The UepActivationVol is related to an activation of elements in accordance with the defined path of the process. The second one the UMATHT is used to implement and combine thermal and...