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Journal Details
Format
Journal
eISSN
2083-4799
ISSN
1730-2439
First Published
23 Sep 2008
Publication timeframe
4 times per year
Languages
English

Search

Volume 11 (2011): Issue 4 (December 2011)

Journal Details
Format
Journal
eISSN
2083-4799
ISSN
1730-2439
First Published
23 Sep 2008
Publication timeframe
4 times per year
Languages
English

Search

4 Articles
Open Access

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

Published Online: 03 Jan 2012
Page range: 5 - 10

Abstract

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.

Keywords

  • turbine blade
  • FEM
  • erosion
  • normal modes
Open Access

The effect of compositional changes on the crystallisation behaviour and mechnical properties of Li2O-CaO-SiO2-Al2O3

Published Online: 03 Jan 2012
Page range: 11 - 21

Abstract

The effect of compositional changes on the crystallisation behaviour and mechnical properties of Li<sub>2</sub>O-CaO-SiO<sub>2</sub>-Al<sub>2</sub>O<sub>3</sub>

The crystallisation characteristics of glasses based on the Li2O-CaO-SiO2-Al2O3(LCSA) system containing TiO2, ZrO2 has been investigated by differential thermal analysis (DTA), X-ray diffraction analysis (XRD), and scanning electron microscopy (SEM). The partial replacement of Li2O, CaO and SiO2 by TiO2, ZrO2 in the studied glass-ceramics led to the development of different crystalline phase assemblages, including lithium calcium silicates, wollastonite, β-eucryptite and β-spodumene using various heat-treatment processes. The rod-like growth morphology was observed by SEM for glass free of TiO2. In this glass, ZrO2 reduced mobility of boundary at sintering temperature, 1000°C and relatively density was 77%. The most sinterability observed in sample containing TiO2 and free of ZrO2 at sintering temperature, 1000°C and relatively density was 84%.

Keywords

  • LiO-CaO-SiO-AlO
  • crystallisation
  • TiO
  • ZrO
  • glass-ceramic
Open Access

Surface roughness and diametral consistency of holes drilled into DDGS/phenolic resin blends

Published Online: 03 Jan 2012
Page range: 22 - 34

Abstract

Surface roughness and diametral consistency of holes drilled into DDGS/phenolic resin blends

In this study, corn-based distillers dried grains with solubles (DDGS) has been utilized as a filler and blended with phenolic resin. The blends were compression molded into rectangular test specimens, into which holes have been machined using a standard 9.52 mm (3/8 in) diameter, two-fluted twist drill. A series of tests was then conducted to examine the effects of DDGS content, cutting speed, and feed rate upon the surface finish (roughness) of the interior hole slot, as well as the consistency of the drilled hole diameter. DDGS content was 0, 25, 50, and 75%, by weight. Cutting speed was 17, 30, and 46 m/min (55, 100, and 150 ft/min). Feed rate was 0.025, 0.152, and 0.279 mm/rev (0.001, 0.006, and 0.011 in/rev). Results indicate that as the DDGS content increased, roughness exhibited a weak but statistically significant decrease. When the cutting speed increased, roughness increased slightly. However, when feed rate increased, roughness increased at a greater rate than that due to cutting speed. In terms of diametral consistency, the effect of adding DDGS resulted in holes with diameters less than the nominal drill size. As cutting speed increased, the holes tended to be oversized. Based on the cutting speed and feed rate levels used, optimal machining conditions which would reduce roughness occurred for 75% DDGS, cutting speed of 17 m/min (55 ft/min), and feed rate of 0.025 mm/rev (0.001 in/rev). However, to maintain consistent hole diameter, optimal conditions were found to be 40% DDGS, 30 m/min (100 ft/min), and 0.152 mm/rev (0.006 in/rev) and would produce a drilled hole with a diameter of 9.52 mm (0.375 in). As the use of biofillers in plastic composites evolves, it will become increasingly important to examine the machinability of these novel materials.

Keywords

  • biofiller
  • bioplastics
  • composites
  • machinability
  • drilling
Open Access

Corrosion resistance examinations of Ti6Al4V alloy with the use of potentiodynamic method in ringer's and artificial saliva solutions

Published Online: 03 Jan 2012
Page range: 35 - 42

Abstract

Corrosion resistance examinations of Ti6Al4V alloy with the use of potentiodynamic method in ringer's and artificial saliva solutions

The research results of corrosion resistance of the Ti6Al4V alloy in the simulated body fluids (SBF) are presented. The polished specimens have shown better corrosion resistance than grinded surfaces in both liquids. The artificial saliva has revealed more aggressive test solution than Ringer's solution. The pitting tendency has been observed in Ringer's solution for grinded specimens.

Keywords

  • Ti6Al4V alloy
  • corrosion resistance
  • potentiodynamic methods
  • Ringer's liquid
  • artificial saliva
4 Articles
Open Access

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

Published Online: 03 Jan 2012
Page range: 5 - 10

Abstract

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.

Keywords

  • turbine blade
  • FEM
  • erosion
  • normal modes
Open Access

The effect of compositional changes on the crystallisation behaviour and mechnical properties of Li2O-CaO-SiO2-Al2O3

Published Online: 03 Jan 2012
Page range: 11 - 21

Abstract

The effect of compositional changes on the crystallisation behaviour and mechnical properties of Li<sub>2</sub>O-CaO-SiO<sub>2</sub>-Al<sub>2</sub>O<sub>3</sub>

The crystallisation characteristics of glasses based on the Li2O-CaO-SiO2-Al2O3(LCSA) system containing TiO2, ZrO2 has been investigated by differential thermal analysis (DTA), X-ray diffraction analysis (XRD), and scanning electron microscopy (SEM). The partial replacement of Li2O, CaO and SiO2 by TiO2, ZrO2 in the studied glass-ceramics led to the development of different crystalline phase assemblages, including lithium calcium silicates, wollastonite, β-eucryptite and β-spodumene using various heat-treatment processes. The rod-like growth morphology was observed by SEM for glass free of TiO2. In this glass, ZrO2 reduced mobility of boundary at sintering temperature, 1000°C and relatively density was 77%. The most sinterability observed in sample containing TiO2 and free of ZrO2 at sintering temperature, 1000°C and relatively density was 84%.

Keywords

  • LiO-CaO-SiO-AlO
  • crystallisation
  • TiO
  • ZrO
  • glass-ceramic
Open Access

Surface roughness and diametral consistency of holes drilled into DDGS/phenolic resin blends

Published Online: 03 Jan 2012
Page range: 22 - 34

Abstract

Surface roughness and diametral consistency of holes drilled into DDGS/phenolic resin blends

In this study, corn-based distillers dried grains with solubles (DDGS) has been utilized as a filler and blended with phenolic resin. The blends were compression molded into rectangular test specimens, into which holes have been machined using a standard 9.52 mm (3/8 in) diameter, two-fluted twist drill. A series of tests was then conducted to examine the effects of DDGS content, cutting speed, and feed rate upon the surface finish (roughness) of the interior hole slot, as well as the consistency of the drilled hole diameter. DDGS content was 0, 25, 50, and 75%, by weight. Cutting speed was 17, 30, and 46 m/min (55, 100, and 150 ft/min). Feed rate was 0.025, 0.152, and 0.279 mm/rev (0.001, 0.006, and 0.011 in/rev). Results indicate that as the DDGS content increased, roughness exhibited a weak but statistically significant decrease. When the cutting speed increased, roughness increased slightly. However, when feed rate increased, roughness increased at a greater rate than that due to cutting speed. In terms of diametral consistency, the effect of adding DDGS resulted in holes with diameters less than the nominal drill size. As cutting speed increased, the holes tended to be oversized. Based on the cutting speed and feed rate levels used, optimal machining conditions which would reduce roughness occurred for 75% DDGS, cutting speed of 17 m/min (55 ft/min), and feed rate of 0.025 mm/rev (0.001 in/rev). However, to maintain consistent hole diameter, optimal conditions were found to be 40% DDGS, 30 m/min (100 ft/min), and 0.152 mm/rev (0.006 in/rev) and would produce a drilled hole with a diameter of 9.52 mm (0.375 in). As the use of biofillers in plastic composites evolves, it will become increasingly important to examine the machinability of these novel materials.

Keywords

  • biofiller
  • bioplastics
  • composites
  • machinability
  • drilling
Open Access

Corrosion resistance examinations of Ti6Al4V alloy with the use of potentiodynamic method in ringer's and artificial saliva solutions

Published Online: 03 Jan 2012
Page range: 35 - 42

Abstract

Corrosion resistance examinations of Ti6Al4V alloy with the use of potentiodynamic method in ringer's and artificial saliva solutions

The research results of corrosion resistance of the Ti6Al4V alloy in the simulated body fluids (SBF) are presented. The polished specimens have shown better corrosion resistance than grinded surfaces in both liquids. The artificial saliva has revealed more aggressive test solution than Ringer's solution. The pitting tendency has been observed in Ringer's solution for grinded specimens.

Keywords

  • Ti6Al4V alloy
  • corrosion resistance
  • potentiodynamic methods
  • Ringer's liquid
  • artificial saliva

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