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Zeitschriftendaten
Format
Zeitschrift
eISSN
2083-4799
Erstveröffentlichung
23 Sep 2008
Erscheinungsweise
4 Hefte pro Jahr
Sprachen
Englisch

Suche

Volumen 18 (2018): Heft 1 (March 2018)

Zeitschriftendaten
Format
Zeitschrift
eISSN
2083-4799
Erstveröffentlichung
23 Sep 2008
Erscheinungsweise
4 Hefte pro Jahr
Sprachen
Englisch

Suche

5 Artikel
Uneingeschränkter Zugang

Variable Surface Temperature Distribution as a Criticality Indicator of the Self-Heating Effect in Composites

Online veröffentlicht: 24 Apr 2018
Seitenbereich: 5 - 12

Zusammenfassung

Abstract

Since self-heating effect may significantly intensify structural degradation, it is essential to investigate its criticality, i.e. the temperature value at which fatigue fracture is initiated. In this paper, a new and sensitive criticality indicator based on evaluation of evolution of surface temperature distribution was proposed and experimentally validated. It was shown that comparing to other measurement techniques the presented approach allows for precise evaluation of the critical value of the self-heating temperature. The properly determined critical value may be helpful both during design and operation of elements made of polymers and polymeric composite.

Schlüsselwörter

  • self-heating effect
  • surface temperature distribution
  • fatigue fracture
Uneingeschränkter Zugang

Influence of the Air-Entraining Agent in the Concrete Coating on the Reinforcement Corrosion Process in Case of Simultaneous Action of Chlorides and Frost

Online veröffentlicht: 24 Apr 2018
Seitenbereich: 13 - 19

Zusammenfassung

Abstract

The paper presents the test results to evaluate the effect of air-entraining agent addition on the intensity of reinforcement corrosion in concrete with blast-furnace slag cement in the case of simultaneous action of chloride corrosion and frost. Two groups of reinforced concrete specimens were prepared for the study. The first group of specimens included air-entraining agent addition and the other group was prepared without air-entraining agent. The blast-furnace slag cement (CEM III/A) was used for the specimens. Two parallel reinforcing rods were placed in each specimen. The specimens were subjected to 120 cycles of freezing and thawing in 3% NaCl solution to induce corrosion on the reinforcement. To determine the occurrence of the reinforcement corrosion and estimate the corrosion activity the non-destructive electrochemical galvanostatic pulse method was used. On each specimen the corrosion current density of the reinforcement was measured as well as the reinforcement stationary potential and the concrete coating resistivity, i.e. values indicating the ongoing reinforcement corrosion. Measurements were made on all specimens in two steps: before freezing and thawing cycles in 3% NaCl solution and after the cycles. The analysis of the obtained results allowed to determine differences in corrosion processes intensity on the reinforced bars in the concrete specimens depending on whether or not the air-entraining agent was added. Based on the analysis it was found that in the case of simultaneous action of chloride corrosion and frost it is advisable to use both blast-furnace slag cement and air-entraining agent. The use of only blast-furnace slag cement (although it is a chloride resistant cement), without the addition of air-entraining agent is insufficient.

Schlüsselwörter

  • reinforcement corrosion in concrete
  • influence of chlorides and frost
  • galvanostatic pulse method
  • blast-furnace slag cement
  • air-entraining agent
Uneingeschränkter Zugang

Roughness of Metal Surface After Finishing Using Ceramic Brush Tools

Online veröffentlicht: 24 Apr 2018
Seitenbereich: 20 - 27

Zusammenfassung

Abstract

The paper describes processes of metal parts edges deburring and surface of metal samples polishing with ceramic tools based on fibre aluminium oxide. It presents the construction of basic types of tools and their practical industrial applications, and evaluates the influence of machining parameters on surface roughness. An important advantage of the used tools is the possibility of deburring and machining of external flat and shaped surfaces as well as internal surfaces and even deep drilled holes. These tools can be practically used for machining all construction materials. The results of machining of selected engineering materials, such as aluminium 5052 and 2017A, Inconel 718, non-alloy steel, in various variants of machining parameters are presented. The influence of machining parameters on machined surface roughness was described.

Schlüsselwörter

  • cutting tools
  • brush ceramic tools
  • deburring
Uneingeschränkter Zugang

Synthesis, Characterization and Their Antimicrobial Activities of Boron Oxide/Poly(Acrylic Acid) Nanocomposites: Thermal and Antimicrobial Properties

Online veröffentlicht: 24 Apr 2018
Seitenbereich: 28 - 36

Zusammenfassung

Abstract

Boron oxide (B2O3)/Poly(acrylic acid) (PAA) nanocomposites were synthesized by solution intercalation method, and characterized by Fourier transform infrared spectroscopy (FTIR-ATR), transmission electron microscopy (TEM), X-ray diffraction and thermogravimetric analysis (DTA/TG). The effect of boron oxide amount on the thermal stability of nanocomposites was investigated. Moreover, the antimicrobial activities of them were also determined by the serial dilution method against E. coli and S. aureus. XRD analysis showed that boron oxide was homogenously dispersed in polymer matrix; FTIR-ATR that there was interaction between PAA and boron oxide; and TEM that boron oxide particles had spherical structure, and dispersed in nano size in polymer matrix; DTA/TG that the thermal stability of polymers increased with the adding of boron oxide into polymer matrix, and changed the decomposition mechanism of PAA. B2O3/PAA nanocomposites exhibited higher decomposition temperature. The decomposition mechanisms of PAA and its nanocomposites occurred through three decomposition steps; dehydration, decarboxylation and chain scission. B2O3/PAA nanocomposites showed greater antimicrobial activity with increasing B2O3 amount.

Schlüsselwörter

  • Boron oxide
  • poly(acrylic acid)
  • thermal stability
  • nanocomposite
  • antimicrobial activity
Uneingeschränkter Zugang

Structure and Properties of Welded Joints of 7CrMoVTiB10-10 (T24) Steel

Online veröffentlicht: 24 Apr 2018
Seitenbereich: 37 - 47

Zusammenfassung

Abstract

Gas Tungsten Arc butt welded joints of tubes of 7CrMoVTiB10-10 made using bainitic-martensitic P 24-IG filler metal were found to be susceptible to root cracking. This was avoided by using the CMS-IG filler metal and austenitic EPRI P87 filler metal. Detailed coefficient of thermal expansion analysis for both filler metals was performed. Unfortunately, CMS-IG filler metal is characterized by a lower creep rupture strength than P 24-IG. For this reason, the joints were produced by the 141 method with using two filler metals: P 24- IG and EPRI P87. All the welded joints was characterized by the B quality level. Macrostructural, microstructural and hardness data for both welded joints are presented. The standard requirement, < 350 HV10, was marginally not met and was achieved through post weld heat treatment.

Schlüsselwörter

  • 7CrMoVTiB10-10 steel
  • welded joint
  • root cracking
5 Artikel
Uneingeschränkter Zugang

Variable Surface Temperature Distribution as a Criticality Indicator of the Self-Heating Effect in Composites

Online veröffentlicht: 24 Apr 2018
Seitenbereich: 5 - 12

Zusammenfassung

Abstract

Since self-heating effect may significantly intensify structural degradation, it is essential to investigate its criticality, i.e. the temperature value at which fatigue fracture is initiated. In this paper, a new and sensitive criticality indicator based on evaluation of evolution of surface temperature distribution was proposed and experimentally validated. It was shown that comparing to other measurement techniques the presented approach allows for precise evaluation of the critical value of the self-heating temperature. The properly determined critical value may be helpful both during design and operation of elements made of polymers and polymeric composite.

Schlüsselwörter

  • self-heating effect
  • surface temperature distribution
  • fatigue fracture
Uneingeschränkter Zugang

Influence of the Air-Entraining Agent in the Concrete Coating on the Reinforcement Corrosion Process in Case of Simultaneous Action of Chlorides and Frost

Online veröffentlicht: 24 Apr 2018
Seitenbereich: 13 - 19

Zusammenfassung

Abstract

The paper presents the test results to evaluate the effect of air-entraining agent addition on the intensity of reinforcement corrosion in concrete with blast-furnace slag cement in the case of simultaneous action of chloride corrosion and frost. Two groups of reinforced concrete specimens were prepared for the study. The first group of specimens included air-entraining agent addition and the other group was prepared without air-entraining agent. The blast-furnace slag cement (CEM III/A) was used for the specimens. Two parallel reinforcing rods were placed in each specimen. The specimens were subjected to 120 cycles of freezing and thawing in 3% NaCl solution to induce corrosion on the reinforcement. To determine the occurrence of the reinforcement corrosion and estimate the corrosion activity the non-destructive electrochemical galvanostatic pulse method was used. On each specimen the corrosion current density of the reinforcement was measured as well as the reinforcement stationary potential and the concrete coating resistivity, i.e. values indicating the ongoing reinforcement corrosion. Measurements were made on all specimens in two steps: before freezing and thawing cycles in 3% NaCl solution and after the cycles. The analysis of the obtained results allowed to determine differences in corrosion processes intensity on the reinforced bars in the concrete specimens depending on whether or not the air-entraining agent was added. Based on the analysis it was found that in the case of simultaneous action of chloride corrosion and frost it is advisable to use both blast-furnace slag cement and air-entraining agent. The use of only blast-furnace slag cement (although it is a chloride resistant cement), without the addition of air-entraining agent is insufficient.

Schlüsselwörter

  • reinforcement corrosion in concrete
  • influence of chlorides and frost
  • galvanostatic pulse method
  • blast-furnace slag cement
  • air-entraining agent
Uneingeschränkter Zugang

Roughness of Metal Surface After Finishing Using Ceramic Brush Tools

Online veröffentlicht: 24 Apr 2018
Seitenbereich: 20 - 27

Zusammenfassung

Abstract

The paper describes processes of metal parts edges deburring and surface of metal samples polishing with ceramic tools based on fibre aluminium oxide. It presents the construction of basic types of tools and their practical industrial applications, and evaluates the influence of machining parameters on surface roughness. An important advantage of the used tools is the possibility of deburring and machining of external flat and shaped surfaces as well as internal surfaces and even deep drilled holes. These tools can be practically used for machining all construction materials. The results of machining of selected engineering materials, such as aluminium 5052 and 2017A, Inconel 718, non-alloy steel, in various variants of machining parameters are presented. The influence of machining parameters on machined surface roughness was described.

Schlüsselwörter

  • cutting tools
  • brush ceramic tools
  • deburring
Uneingeschränkter Zugang

Synthesis, Characterization and Their Antimicrobial Activities of Boron Oxide/Poly(Acrylic Acid) Nanocomposites: Thermal and Antimicrobial Properties

Online veröffentlicht: 24 Apr 2018
Seitenbereich: 28 - 36

Zusammenfassung

Abstract

Boron oxide (B2O3)/Poly(acrylic acid) (PAA) nanocomposites were synthesized by solution intercalation method, and characterized by Fourier transform infrared spectroscopy (FTIR-ATR), transmission electron microscopy (TEM), X-ray diffraction and thermogravimetric analysis (DTA/TG). The effect of boron oxide amount on the thermal stability of nanocomposites was investigated. Moreover, the antimicrobial activities of them were also determined by the serial dilution method against E. coli and S. aureus. XRD analysis showed that boron oxide was homogenously dispersed in polymer matrix; FTIR-ATR that there was interaction between PAA and boron oxide; and TEM that boron oxide particles had spherical structure, and dispersed in nano size in polymer matrix; DTA/TG that the thermal stability of polymers increased with the adding of boron oxide into polymer matrix, and changed the decomposition mechanism of PAA. B2O3/PAA nanocomposites exhibited higher decomposition temperature. The decomposition mechanisms of PAA and its nanocomposites occurred through three decomposition steps; dehydration, decarboxylation and chain scission. B2O3/PAA nanocomposites showed greater antimicrobial activity with increasing B2O3 amount.

Schlüsselwörter

  • Boron oxide
  • poly(acrylic acid)
  • thermal stability
  • nanocomposite
  • antimicrobial activity
Uneingeschränkter Zugang

Structure and Properties of Welded Joints of 7CrMoVTiB10-10 (T24) Steel

Online veröffentlicht: 24 Apr 2018
Seitenbereich: 37 - 47

Zusammenfassung

Abstract

Gas Tungsten Arc butt welded joints of tubes of 7CrMoVTiB10-10 made using bainitic-martensitic P 24-IG filler metal were found to be susceptible to root cracking. This was avoided by using the CMS-IG filler metal and austenitic EPRI P87 filler metal. Detailed coefficient of thermal expansion analysis for both filler metals was performed. Unfortunately, CMS-IG filler metal is characterized by a lower creep rupture strength than P 24-IG. For this reason, the joints were produced by the 141 method with using two filler metals: P 24- IG and EPRI P87. All the welded joints was characterized by the B quality level. Macrostructural, microstructural and hardness data for both welded joints are presented. The standard requirement, < 350 HV10, was marginally not met and was achieved through post weld heat treatment.

Schlüsselwörter

  • 7CrMoVTiB10-10 steel
  • welded joint
  • root cracking

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