Betriebsverhalten höchstfester Aluminiumschrauben in thermisch belasteten Magnesiumkomponenten

Translated title of the contribution: Operating behaviour of high-strength aluminium bolts in thermally loaded magnesium components

Gerhard Franz Gerstmayr

Research output: ThesisDoctoral Thesis

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Abstract

The goal of this research project is the determination of the performance properties of high-strength self-tapping aluminium bolts in thermally loaded magnesium materials. Relevant aspects like the clamping load retention in the bolted joint as well as the corrosion resistance of the used materials are evaluated. The creep behaviour of the used magnesium alloys AZ91 and AE44 as well as of the aluminium bolt Taptite2000 EN AW 7075 in different heat treatment and final machining conditions is decisive for the clamping load retention. In a further step, the relaxation behaviour of the bolted joint at elevated temperatures between 120 °C and 150 °C is investigated in order to quantify the influence of essential parameters like core hole size and thermal stability of the magnesium and aluminium alloys. As numerous components are subjected to cyclic mechanical loadings in service, the influence of superimposed service loadings on the progress of clamping load is investigated in addition. Tests on prototype transfer gearboxes allow an evaluation of the relaxation behaviour of a real component. The here investigated bolted joint consists of different materials. As a consequence, the galvanic corrosion behaviour has to be taken into account. In addition, the susceptibility to stress corrosion cracking of the 7xxx aluminium alloys has to be considered. By means of exposure tests in a salt spray chamber, the galvanic corrosion behaviour of steel and aluminium bolts with different corrosion protection systems in the magnesium alloy AZ91 is investigated. The stress corrosion cracking behaviour of the high-strength aluminium bolt EN AW 7075 in variable nut materials is part of the investigations in order to identify the rate determining corrosion mechanism of stress corrosion cracking in aluminium alloys. A simulation model, which depicts the process of thread forming, the generation of clamping load during tightening and the drop in clamping load at elevated temperatures shall improve the understanding of the bolted joint's behaviour. This model is evaluated by comparison of simulation results with experimental test results of static tightening and relaxation tests.
Translated title of the contributionOperating behaviour of high-strength aluminium bolts in thermally loaded magnesium components
Original languageGerman
QualificationDr.mont.
Supervisors/Advisors
  • Antrekowitsch, Helmut, Assessor B (internal)
  • Eichlseder, Wilfried, Assessor A (internal)
Publication statusPublished - 2010

Bibliographical note

embargoed until 13-01-2015

Keywords

  • Magnesium Aluminium Corrosion Bolts Self-tapping Creep Relaxation Bolted joint thermal load

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