Avancerad sökning

Visar resultat 1 - 5 av 8 avhandlingar som matchar ovanstående sökkriterier.

  1. 1. Behaviour of pretensioned bolts in friction connections : towards the use of higher strength steels in wind towers

    Författare :Christine Heistermann; Carlos Rebelo; Luleå tekniska universitet; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Steel Structures; Stålbyggnad; Centrumbildning - Centrum för högpresterande stål CHS ; Centre - Centre for High Performance Steel CHS ;

    Sammanfattning : During recent years wind energy has established as an alternative to commonenergy sources. To advance its competitiveness, the costs for the constructionof a wind tower have to be reduced. One possible option is the use of frictiongrip joints instead of flange connections to join various tower segments in atubular steel tower. LÄS MER

  3. 2. Microstructure analysis of wear and fatigue in austempered high-Si steels

    Författare :Alejandro Leiro; Johan Ahlström; Luleå tekniska universitet; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Materialteknik; Engineering Materials; Konstruktionsmaterial; Engineering Materials; Centrumbildning - Centrum för högpresterande stål CHS ; Centre - Centre for High Performance Steel CHS ;

    Sammanfattning : Research on austempering of high-Si steels has increased over the last years due to their attractive combination of strength and toughness. The presence of over 1.5% of silicon prevents the precipitation of cementite during austempering and the resulting microstructure consists of bainitic ferrite and retained austenite. LÄS MER

  4. 3. Wear and fatigue properties of isothermally treated high-Si steels

    Författare :Alejandro Leiro; Peter Hedström; Luleå tekniska universitet; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Materialteknik; Engineering Materials; Centrumbildning - Centrum för högpresterande stål CHS ; Centre - Centre for High Performance Steel CHS ;

    Sammanfattning : In recent years steels containing Si contents of 1,5% or more have been isothermally transformed in order to obtain a microstructure consisting of bainitic ferrite laths and retained austenite. The refined microstructure and presence of retained austenite has allowed the manufacture of steels with high tensile strength and considerable elongation. LÄS MER

  5. 4. High temperature galling : influencing parameters and mechanisms

    Författare :Leonardo Pelcastre; Jens Bergström; Luleå tekniska universitet; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Maskinelement; Machine Elements; Centrumbildning - Centrum för högpresterande stål CHS ; Centre - Centre for High Performance Steel CHS ;

    Sammanfattning : Damage of forming tools at elevated temperatures is a major problem in metal forming processes such as hot stamping. Of special importance is the occurrence of adhesion and gross material transfer from the work-piece to the tool surface, a phenomenon known as galling. LÄS MER

  7. 5. Hot forming tribology : galling of tools and associated problems

    Författare :Leonardo Pelcastre; Ewald Badisch; Luleå tekniska universitet; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Maskinelement; Machine Elements; Centrumbildning - Centrum för högpresterande stål CHS ; Centre - Centre for High Performance Steel CHS ;

    Sammanfattning : In recent years, the use of ultra high-strength steels (UHSS) as structural reinforcements and in energy-absorbing systems in automobiles has increased rapidly; mainly in view of their favourable strength to weight ratios. However, due to their high strength, the formability of UHSS is poor, thus complex-shaped UHSS components are invariably produced through hot-metal forming processes. LÄS MER