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G.J. Reddy, R.S. Raju, J.A. Rao and R.S.R. Gorla

Abstract

An unsteady magnetohydromagnetic natural convection on the Couette flow of electrically conducting water at 4°C (Pr = 11.40) in a rotating system has been considered. A Finite Element Method (FEM) was employed to find the numerical solutions of the dimensionless governing coupled boundary layer partial differential equations. The primary velocity, secondary velocity and temperature of water at 4°C as well as shear stresses and rate of heat transfer have been obtained for both ramped temperature and isothermal plates. The results are independent of the mesh (grid) size and the present numerical solutions through the Finite Element Method (FEM) are in good agreement with the existing analytical solutions by the Laplace Transform Technique (LTT). These are shown in tabular and graphical forms.

Open access

Ondřej Bílek, Imrich Lukovics, David Sámek and Jana Knedlová

Abstract

Residual stresses lower the utility value of plastic parts. Determination of the induced stresses can help deal with them. Measurements are time-consuming and expensive. A new approach to measuring residual stresses, such as indentation measurement, can lead to the simple determination of residual stresses. The paper shows the relationship between the condition of injection moulding, the subsequent residual stress, and hardness through thickness. The computer model displays the field and magnitude of residual stress in the samples. The model results are then compared to measured parameters after indentation and the magnitude of residual stress determined by the standard hole drilling method.

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

J. Bartnicki, J. Tomczak and Z. Pater

Abstract

This paper presents results of numerical calculations for the rolling process by means of three tools of stepped shafts from aluminum alloy 7075. Forming with the usage of tools with three different wedge spreading angles underwent analysis. In the paper, the obtained distributions of stresses, strains and Cockcroft-Latham damage criterion were given. Moreover, the influence of the wedge spreading angle on shape faults presence in the obtained product was determined. At the same time, the force parameters, which play a crucial role in the designed experiment, were analyzed.

Open access

J. Tomczak, Z. Pater and J. Bartnicki

Abstract

This paper presents results of theoretical and experimental research on skew rolling process of balls with diameter ;30 mm in multiple helical tools. Numerical analysis of the process was conducted basing on finite element method (FEM), using the commercial software Simufact Forming in version 10.0. Simulations were made in the three-dimensional state of strain with consideration of complex thermal analysis, due to which progression of the products shape was determined. Distributions of strains and temperatures as well as the process force parameters were also determined. The results of numerical calculations were experimentally verified in laboratory conditions. The obtained results confirmed the possibility of semi-finished products of balls type manufacturing by means of rolling in multiple helical impressions.

Open access

J. Piwnik and K. Mogielnicki

Abstract

The main aim of the paper is an evaluation of the real impact of a container surface roughness on metal plastic flow in the forward microextrusion process. For the purposes of experiment a specially designed and constructed by authors toolkit was used. Analyzed material was an annealed aluminium wire with 1,7 mm in diameter, with a stress-strain curve defined. Toolkit contains two experimental models of containers and rectangular dies with the same dimensions, differing only in the containers roughness degree. In order to determine the degree of the containers top layers asperities a roughness profiles with using laser microscope were made for each. Punch pressures have been calculated while forward extruding. In the next step the deflection of parallel lines marked at the samples longitudinal sections were analyzed. The extruded samples were submitted to the microhardness testing. Numerical analyses of analogous microextrusion processes have been also conducted. Container surface roughness was modelled as a rigid triangular wave with a zero friction factor at the interface m =0. Punch pressures and shapes of extruded samples flow nets were determined. Conducted investigations revealed the possibility of receiving products with different mechanical properties obtained by the container roughness assorting.

Open access

P. Lacki, J. Adamus, W. Więckowski and J. Winowiecka

Abstract

Despite substantial demand for drawn parts made of high-strength sheet metal (including titanium alloys) observed in the modern industry, particularly automotive and aviation, their application remains insignificant. This results from the fact that such sheet metal shows poor plasticity and its cold-forming is almost impossible. Low drawability makes it impossible to obtain even such simple shapes as spherical cups. The authors of this study developed circular sheet-metal blanks with cutouts on their perimeter. The blanks allow for cold forming of spherical cups from Ti6Al4V titanium alloy sheet metal using conventional rigid tools. The cutouts proposed in the study affect plastic strain distribution, which in turn leads to an increase in forming depth by about 30%. The numerical analysis, performed using the PamStamp 2G System software based on finite element method, was verified experimentally.

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

Łukasz Gołuński and Bolesław Augustyniak

Modeling by finite element methods of impact of erosion on frequency of normal modes of l-0 blade

After some time of exploitation steam turbine rotors blades in energetic industry they are being eroded and also their frequency of normal modes is changed. Those changes can cause to unwanted shift of blades normal mode frequencies. It is necessary to find quick method of rating changes of frequency in connection of mass loss due erosion. The evaluation of this dependence was made by finite element modeling method using HyperWorks 8.0 software. Geometrical model of blade L-0 with mass of 22 kg and length of 74 cm was used. There were calculated frequencies of the first five modes in function of mass loss along the leading blade edge (up to mass loss of 1,2%). Small losses of weight (around 0,2%) cause similar changes in values (around 0,2%) for all modes but with different types of frequency change (decrease or increase). The frequency decreases for all modes except mode the 3rd. For bigger mass loss an monotonic decrease of frequency was observed in 1st, 2nd, 5th mode and maximum (around +1,5 %) for 3rd mode and minimum (- 0,5%) for 4th mode. For maximum mass loss (1,2%) maximal decrease of frequency was observed in 2nd mode around -2%. Results of this modeling can be used to estimate changes of frequencies caused by erosion in exploited blades when their mass loss is known.

Open access

A. Jasik

Abstract

The paper presents the results of numerical calculations of temperature and thermal stress distribution in thermal barrier coatings deposited by thermal spraying process on the nickel based superalloy. An assumption was made to apply conventional zirconium oxide modified with yttrium oxide (8YSZ) and apply pyrochlore type material with formula La2Zr2O7. The bond coat was made of NiCoCrAlY. Analysis of the distribution of temperature and stresses in ceramic coatings of different thicknesses was performed in the function of bond-coat thickness and the type of ceramic insulation layer. It was revealed that the thickness of NiCrAlY bond-coat has not significant influence on the stress distribution, but there is relatively strong effect on temperature level. The most important factor influenced on stress distribution in TBC system is related with type and properties of ceramic insulation layer.