Eigenspannungsoptimiertes Schweißen von Nahtlosrohren

Translated title of the contribution: Residual stress optimzed welding of seamless pipes

Gerhard Stix

Research output: ThesisDoctoral Thesis

Abstract

Lattice boom cranes are exposed to static and dynamic loads during use. Dynamically oscillating stresses occur due to forces of gravity during lifting and turning of loads, static stresses are resulting from the wind loads. The induced residual stresses during welding the lattice boom cranes must be particularly observed, because these stresses directly influence the stress distribution under load and thus can also affect the static and dynamic strength of lattice boom cranes. The aim of this study is to investigate the key factors for the formation of residual stresses in welding tubular k-joints and to optimize. On the one hand, the stresses are investigated by geometrical factors and on the other hand, the influence on residual stress by changing the welding sequence. The variable parameters of the investigations were the angle of the angle between the chord and the brace, chord slenderness, eccentricity and the change of the weld length. First, the weld is divided into two lying “3”, in the other sequence a continuous seam in form of a lying “8” is welded. To reduce the welding tests, a simplified 3D-FE-model was developed. This simplified model consists of two braces and one chord. Based on this model, some preliminary investigations were carried out. With the knowledge of the welding simulation, welding tests were carried out on a robot welding system. Two different diameters and wall thickness for the brace and two different wall thickness and one diameter for the chord were used for the real welds. Both welding sequences were put into practice. Metallographical investigations and validation of residual stresses by hole drilling method with strain gauges of the different welding sequences were analysed and compared in conclusion. The deformation behaviour of different weld length was examined by simulation models and real test with a hydraulic 1 MN press and a 3D surface measurement system.
Translated title of the contributionResidual stress optimzed welding of seamless pipes
Original languageGerman
QualificationDr.mont.
Supervisors/Advisors
  • Buchmayr, Bruno, Assessor A (internal)
  • Kessler, Franz, Assessor B (internal)
Publication statusPublished - 2015

Bibliographical note

embargoed until null

Keywords

  • K-joints
  • residual stresses
  • hole drilling method
  • welding simulation
  • crane engineering

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