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Despite very rapid development of science in the recent years, the issues occurring in the electric arc have not been fully recognized. The main reason for this situation is the complexity of phenomena which occur in the arc as well as very high temperatures. The paper presents results of numerical calculations of phenomena which occur in the welding arc. The CFD Fluent package was used for modelling the following phenomena in the electric arc: melting, solidifying, generation of heat and multiphase flows. The 3D Model of a 50x30x6 metal plate cutaway padded with the use of the GMA method with a wire of 1.2 mm diameter was developed. The paper focuses on presenting the distribution of temperatures in time, the process of melting and later solidifying of the material, as well as the transport of the material from the arc to the padding weld. It also shows the initial verification of the model by comparing the results with a picture recorded by 1000 frames/second fast camera. [ABSTRACT FROM AUTHOR]

In the paper the values of the Q-stress determined for various elastic-plastic materials for single edge notched plates in tension (SEN(T)) presented. Used in the paper specimens, are the basic structural elements, which can be used to idealizing real construction, based on FITNET procedure. The influence of the yield strength, the work-hardening exponent and the crack length on the Q-parameter was tested. The numerical results were approximated by the closed form formulas. All obtained results may be a handy catalogue of the J-Q curves, which may be useful in engineering practice. [ABSTRACT FROM AUTHOR]

The paper focuses on hot rolled and fast cooled dual phase (DP) steel strips for automotive application. The analysis carried out in this work includes many tests and experiments such as: dilatometric and plastometric tests, Gleeble simulations of hot rolling process, simulation of strip cooling after rolling and hot rolling of DP steel samples in laboratory conditions. The main part of the paper contains the results of experimental rolling of DP steel samples in laboratory conditions. Especially, the influence of cooling rate on phase volume fraction and some mechanical properties of DP strips have been analysed. The realized hot rolling with controlled cooling of DP samples in laboratory conditions allowed for obtaining diversified steel microstructure and thus wide range of mechanical properties. The results of the analysis carried out in this work provide the useful data for the designing of thermo-mechanical rolling of DP steel strips. [ABSTRACT FROM AUTHOR]

The paper presents examples of fatigue stress fractures of quarry equipment drive shafts. In order to determine the real cause of this damage, we have performed a detailed analysis of the problem The paper presents the experimental data, numerical analysis and metallographic examination. [ABSTRACT FROM AUTHOR]

A numerical method, being a combination of the vortex method and the boundary element method, is used here to predict the two-dimensional flow field in the vicinity of an underflow vertical lift gate. In practice, tunnel-type flat-bottomed lift gates experience strong hydrodynamic loading, due to vortex detachment from the gate bottom edge, and near-wake velocity fluctuations. This paper presents a stream function, and velocity and vorticity distributions for two gate gaps. The vortex detachment mechanism is described and the vortex shedding frequency, expressed as a Strouhal number, is presented. The predicted velocity and vorticity fields are then used to calculate the pressure distribution on the gate surface by the boundary element method. The time histories of the lift and drag coefficients are presented. The proposed numerical method has been validated by the measurements of the downpull coefficient for the flow around the lift gate. [ABSTRACT FROM AUTHOR]

The paper presents the results of tests, numerical analyses and theoretical analyses of reinforced concrete beams loaded with a torsional moment as well as a shearing force and a bending moment, carried out in the Research Laboratory of the Institute of Building Engineering at Wrocław University of Technology. The research focused on the load capacity and stiffness of such elements. Beams angular (in the shape of the inverted letter L) and rectangular in cross section were investigated. The tests were carried out in two series. In the first test series the elements were loaded with solely a torsional moment. In the second test series the beams were subjected to the combined load of a torsional moment, a shearing force and a bending moment. The behaviour of the beams with the different cross sectional shapes was compared. The experimental results and the ones yielded by numerical analyses were compared with theoretical and standard results. [ABSTRACT FROM AUTHOR]

Because of the properties of the material (concrete), computer simulations in the field of reinforced concrete structures are pose a challenge. As opposed to steel, concrete when subjected to compression exhibits nonlinearity right from the start. Moreover, it much quicker undergoes degradation under tension. All this poses difficulties for numerical analyses. Parameters needed to correctly model concrete under compound stress are described in this paper. The parameters are illustrated using the Concrete Damaged Plasticity model included in the ABAQUS software. [ABSTRACT FROM AUTHOR]

Although the extended finite element method (XFEM) allows for modelling arbitrary discontinuities, its low order elements often means that frequent improvements on accuracy are required. The generalized finite element method (GFEM), the extension of the conventional FEM, improves the approximation accuracy of the FEM by introducing generalized degrees of freedom and re-interpolating nodal degrees of freedom. This paper enhances the implementation of the XFEM for stress analysis around cracks by coupling the GFEM and XFEM. The generalized node shape functions are used in a cluster of nodes around the cracks, and the conventional finite element shape functions are adopted at nodes outside the cracks, thereby reducing costs and improving the accuracy of stresses in the vicinity of the cracks. Several numerical examples show that the proposed approach generates higher accuracy for stress intensity factor computations at affordable costs. [ABSTRACT FROM AUTHOR]

In bridge engineering the following forms of structure geometry representation are typically applied: non-dimensional models preferred in the Bridge Management Systems and one-dimensional (1D), two-dimensional (2D) or three-dimensional (3D) models used in structural analysis. Classification proposed in this paper is more precise and takes into account both the type of model elements and the size of space used for model creation. Proposed taxonomy of the geometrical models and presented notation of the distinguished classes enable consistent and uniform classification as well as objective comparison of all models which can be applied in bridge engineering, both in the Bridge Management Systems and in structural analysis of bridges. [ABSTRACT FROM AUTHOR]

Development of the rheological model of copper based alloys, accounting for the state of the solid solution prior to deformation, is the objective of the paper. Two alloys are considered, Cu-1%Cr and Cu-0.7%Cr-1%Si-2%Ni. Plastometric tests were performed at various temperatures and various strain rates. Different preheating conditions before the tests were applied aimed at investigation of the effect of the initial microstructure on the flow stress. Three different rheological models for the investigated alloys were developed using inverse analysis of the tests results. Accuracy of the inverse analysis for various models was compared and the best model was selected. This model allowed comparison of the flow stress for various preheating schedules at different temperatures and strain rates, including also those which were not applied in the plastometric tests. Developed models were implemented into the finite element code FORGE based on the Norton-Hoff visco-plastic flow rule and simulations of forging of the alloys were performed. [ABSTRACT FROM AUTHOR]

This paper presents the determination of virtual micro-forming limit diagrams from two types of numerical simulations based on the finite element method: one with modelling of the full tool for micro-deep drawing and a thin blank with geometric imperfections, based on a defined roughness; and a second called "reduced simulation" where different deformation paths were simulated with appropriate boundary conditions by introducing the same type of geometric imperfections on aluminium 1050A (99.5%). A new test for detecting the onset of necking, called the "change of slope" criterion has been defined. Several methods based on histograms to represent the distributions of major and minor strains, have been used to determine the strain at the onset of necking. The numerical micro-forming limit diagrams (MFLD) were then compared to one obtained experimentally. [ABSTRACT FROM AUTHOR]

Hardmetals belong to the materials hardly wettable by liquid brazing alloys, so they should not be brazed without removing the surface layer after sintering. In the paper, mechanical and chemical methods of preparing a hardmetal surface for brazing are discussed. Special attention is paid to the electrolytic etching method that gives very good energetic properties to surfaces of hardly wettable materials. Electrolytic etching of hardmetals consists in anodic dissolution of tungsten carbide grains in water solution of alkaline metal hydroxides. The α phase (WC) is removed from surfaces of carbide preforms, leaving the much better wettable β phase (Co-W-C). Cobalt does not show amphoteric properties, so it does not dissolve in bases. With regard to brazing, besides significant development of the surface, an especially profitable feature of this method is isolating the metallic cobalt phase, which allows easier wetting by brazing alloys. On the grounds of surface roughness measurements, parameters of electrolytic etching were determined to remove WC grains from surfaces of carbide performs and to obtain much higher Co fraction on the brazed surface. The presented results are based on measurements of wetting angles on B40 hardmetal surfaces, isolated α and β phases and C45 steel, as well as on EDX cobalt analysis on hardmetal surfaces. [ABSTRACT FROM AUTHOR]

The paper concerns the numerical homogenization of non-homogeneous linear-elastic materials by using the fast multipole boundary element method (FMBEM). Application of the FMBEM allows for the analysis of structures with larger number of degrees of freedom (DOF) in comparison to the conventional collocation BEM, which has at least the quadratic complexity. The FMBEM is convenient in the numerical homogenization by modelling of complex representative volume elements. In this article two examples of homogenization are presented. The first one concerns a porous material, and the second one -- a composite material. The obtained results are in good agreement with analytical, semi-empirical and empirical models, and also with numerical results presented by other authors. [ABSTRACT FROM AUTHOR]

In this paper a numerical estimation of hydrodynamic torque converter model is discussed. During the estimation it was assumed that the flow through in working area contains multiple flow streams. A contribution of each individual flow stream in transferring torque was assumed based on a pre-selected torque function. Model estimation relied upon proper equation and function parameter selection that provided minimization of the modelling error. Statistical factors were selected for accuracy evaluation of the modelled torque function. In this case torque functions were converted to diverging series, where values of fundamental statistical factors were calculated. Based on tests and numerical calculations for a pre-selected hydrodynamic torque converter it was concluded that there is a relation between modelling accuracy and values of some of the statistical factors. Application of statistical factors drastically simplified numerical calculations during modelling estimation. [ABSTRACT FROM AUTHOR]

In the paper, special emphasis was put on the structural stiffness of car elements described by crashworthiness parameters. We showed how the structure parameters described by crashworthiness indicators can be calculated for various structures. The effect of crashworthiness parameters of different constructions and profiles on the relationship between the energy absorption and the maximum collision force is given. One- and multi-layer, empty and filled with different-density plastic foam elements were described. The behaviour of different elements and the effect of plastic foam density on the crashworthiness parameters were analyzed. [ABSTRACT FROM AUTHOR]

This paper presents the results of an investigation of the grinding wheel wear in a peripheral surface grinding process. During this investigation varying geometrical parameters of an active grinding wheel surface have been measured and the components of the grinding force and acoustic emission signal have been recorded. On the basis of these output quantities an analysis has been conducted of an acoustic emission descriptor's practicability, i.e. a root-mean-square (RMS) value, to characterize the cutting abilities of a grinding wheel in the time progress of its work. This article also presents a new energy coefficient, which determines the rate of grinding wheel wear in the form of a RMS value of acoustic emission signal falling on a contact surface of a grinding wheel. Moreover, the article presents some examples of a correlation between the root-mean-square value of acoustic emission signal and the surface roughness of a workpiece, which shows that the parameters of acoustic emission signal can be a useful tool to monitor the surface roughness during the grinding process. [ABSTRACT FROM AUTHOR]

The paper describes the girders of bridges made of steel beams connected in a flexible way with a concrete deck slab. There are analyzed internal forces and displacements versus the changes in the connection degree that are due to variable cyclic loads occurring in bridges. The analysis of the problem is based on a classical parameter characterizing the connection flexibility Cz and supplied with the coefficients μ and β defined by authors. They allow the connection degree of a combined girder to be estimated. There are analyzed two solutions to the problem of partial interaction in composite steel and concrete girder: a linear one based on the solution of analytical form (differential equations) and a non-linear one based on mechanics of clearances. The latter solution accurately shows the work of connectors in bridge spans. The analysis is illustrated by numerical examples of a real composite bridge. The attention is focused on the diagrams showing various shapes of curves representing the coefficients μ and β. [ABSTRACT FROM AUTHOR]