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Open access

Henryk Olszewski, Wiktoria Wojnicz and Edmund Wittbrodt

Abstract

An original method of skeletal system modelling is presented in detail. Using DICOM images obtained from CT and PET tests, shell models of nine bones were created (humerus, radius, ulna, scapula, clavicle, femur, tibia, fibula, pelvis). Two methods of bone behaviour are also proposed, the first method treating the bone as a solid structure and the second method treating the bone as a complex porous structure. The behaviour of model parts is numerically examined by using the finite element method

Open access

Veronika Valašková, Daniel Papán and Marián Drusa

Abstract

Blasting operations are one of the fundamental parts of daily civil engineering. Drilling and blasting still remain the only possible ways of tunnelling in very adverse geological conditions. However, this method is a source of various disadvantages, the main one being tremors propagating through the geological environment which not only affect buildings, but also disturb the comfort of living in the vicinity of the source. Designing this procedure is mostly done using standardized empirical relations. This article shows the possibility of using a FEM technique in predicting blast effects. This approach is demonstrated in a simple case study on the impact of blasting operations on steel pipes.

Open access

T. Jankowiak and T. Łodygowski

Abstract

The paper considers the failure study of concrete structures loaded by the pressure wave due to detonation of an explosive material. In the paper two numerical methods are used and their efficiency and accuracy are compared. There are the Smoothed Particle Hydrodynamics (SPH) and the Finite Element Method (FEM). The numerical examples take into account the dynamic behaviour of concrete slab or a structure composed of two concrete slabs subjected to the blast impact coming from one side. The influence of reinforcement in the slab (1, 2 or 3 layers) is also presented and compared with a pure concrete one. The influence of mesh density for FEM and the influence of important parameters in SPH like a smoothing length or a particle distance on the quality of the results are discussed in the paper

Open access

M. Drusa and J. Vlcek

Abstract

In the case of realized geotechnical monitoring (GTM) of reinforced retaining wall in difficult geological conditions is demonstrated the important role at realisation of transport infrastructures, which are often realized in insufficient quality due to inappropriate geotechnical parameters from survey works or not fitted well design of structure at certain conditions. This can result in large deformations of structure, or losing stability or structure life-time is very limited and remediation work is complicated and expensive. There was built on the modernized railway line Bratislava – Trenčín, closed to Zlatovce, overpass and connected road embankments on the route of first class I/61. Structure was designed as a bridge over the railway track before the northern portal of the railway tunnel Turecký vrch was open. A part of the embankment and overpass was a retaining wall reinforced by geosynthetics. The results of the geotechnical monitoring of this wall were afterwards simulated using finite element method (FEM) and results of this comparison are the scope of this article.

Open access

T. Pała and I. Dzioba

Abstract

The paper presents the results of two butt welded joints by conventional method. The welding process was performed using a variety of linear welding energy. The studies included experimental and computational part. In experimental studies determined the distribution of hardness and mechanical properties of the individual analyzed sections of welded joints. The data obtained were intended to determine the extent of zones in the welded joints that have certain strength characteristics. Also conducted uniaxial tensile tests of welded joints with the registration of displacement fields on the surface of specimens by means of Aramis video-system what the final result are images of strain fields map on the surface of welded joints. The resulting strain values were compared with the results of numerical computations FEM.

Open access

Jędrzej Żywicki, Paweł Dymarski, Ewelina Ciba and Czesław Dymarski

Abstract

The article presents the calculation and design stages of the TLP platform serving as a supporting construction of a 6 MW offshore wind turbine. This platform is designed to anchor at sea at a depth of 60 m. The authors presented the method of parameterization and optimization of the hull geometry. For the two selected geometry variants, the load and motion calculations of the platform subjected to wind, wave and current under 50-year storm conditions were performed. The maximum load on the structure was determined in these extreme storm conditions. For these loads, the MES calculation of the designed platform was performed for the selected variant. Authors have presented a method for calculating maximum wind, wave and current stresses on the structure during the worst storm in the past 50 years. For these loads the MES endurance calculations of the designed platform were made. Based on the results of these calculations, the required structural changes and recalculations have been made in succession to the structural design of the platform, which meets the design requirements and has the required ad hoc strength. The article contains stress analysis in „difficult“ nodes of constructions and discusses ways of solving their problems. The work is part of the WIND-TU-PLA project from the NCBR Research Agreement (Agreement No. MARTECII / 1/2014).

Open access

Mariusz Żółtowski, Bogdan Żółtowski and Leonel Castaneda

Abstract

This paper presents a methodology to evaluate the technical state of a Francis turbine by shaft rotor dynamic simulation. There are several rotor dynamic criteria that define the technical state of a turbo-machine. To feed the shaft rotor dynamic model this delivers the required information to accomplish the technical assessment. The numerical rotor dynamic model uses as input, the field forces obtained by the fluid-solid interaction analysis undertaken over the blades of the runner.

The rotor dynamic numerical simulations allow to determinate the record-in-time of the displacements of any point along the shaft. This information is relevant for diagnosis tasks, because it is possible to decompose it spectrally and to estimate the severity of the vibrations. Comparing the results of the numerical model against those obtained from machines that operates under normal conditions, it is possible to determinate the technical state of the turbo-machine. This allows studying the stability of the turbine working on several operation ranges.

A Francis turbine is a very complex machine that involves many physical phenomena of different nature. In this way, the hydraulic input forces needed by the rotor dynamic model should not be assumed but calculated directly from the fluid interaction over the turbine structure.

Open access

Bartłomiej Żyliński

Finite element local analysis of wave slamming on offshore structure

Offshore platforms are exposed to waves slamming event. Waves hitting the columns with a high velocity are in many cases the design criteria for column structure. This paper focuses on the analysis of wave slamming on floating platform column. Significant for wave slamming pressure is load history, which is usually based on model test. Wave slamming loads were defined on all four walls of column to assess the worst place. For south wall of column three positions exposed to slamming loads between elevation 21.000 (SWL) and elevation 35.500 were checked. Dynamic analysis has been performed with nonlinear FEM program ABAQUS/explicit. The steel was modeled as an elastic-plastic material with isotropic hardening.

Open access

W. Barnat

Abstract

This paper presents experimental and numerical studies on influence of an incidence angle of the shock wave on a steel plate. The problem of interaction between the wave front and a barrier is important from the point of view of protection the crew of armored vehicles. One way of remedying the harmful effects of impacts of the shock wave is the reflection wave of the barrier set at an angle to the face of the wave. The article presents the numerical and experimental approach to the subject. The numerical part presents four models in which the plate was set at angles 0◦, 15◦, 30◦, 45◦. In each case, the plate was loaded by a wave formed after the explosion 2 kg of TNT. In the experimental part the results are presented from an experiment in which the wave was formed from 2 kg TNT detonation at a distance of 0.4 m in parallel to the steel plate.

Open access

Björn Riemer and Kay Hameyer

Abstract

This paper presents a methodology for the calculation of the flux distribution in power transformer cores considering nonlinear material, with reduced computational effort. The calculation is based on a weak coupled multi-harmonic approach. The methodology can be applied to 2D and 3D Finite Element models. The decrease of the computational effort for the proposed approach is >90% compared to a time-stepping method at comparable accuracy. Furthermore, the approach offers a possibility for parallelisation to reduce the overall simulation time. The speed up of the parallelised simulations is nearly linear. The methodology is applied to a single-phase and a three-phase power transformer. Exemplary, the flux distribution for a capacitive load case is determined and the differences in the flux distribution obtained by a 2D and 3D FE model are pointed out. Deviations are significant, due to the fact, that the 2D FE model underestimates the stray fluxes. It is shown, that a 3D FE model of the transformer is required, if the nonlinearity of the core material has to be taken into account.