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Institute
Verzugsberechnung einer komplexen Struktur mittels eines analytisch-numerischen Hybridmodells
(2010)
Thermomechanische Simulation geschweißter Mischverbindungen aus Aluminium- und Stahlwerkstoffen
(2011)
The paper presents a numerical and experimental approach for the quantification of the thermo-mechanical properties in multi-pass weld’s heat affected zone (HAZ) of low alloy steel “S355J2+N”. First, the characteristic temperature cycles for multi-pass welds were identified by FE temperature field simulations of welding. Based on the identified temperature cycles, the microstructure in the HAZ has been physically simulated with the simulation and testing system Gleeble 3500 to investigate the influence of multi thermal exposure on the thermo-mechanical properties. Thus, the thermo-mechanical material properties including thermal strain and temperature dependent stress strain behaviour as function of peak temperatures and cooling rates have been determined. These material properties were used to calibrate a developed model for numerical prediction of the material properties of multi-pass weld HAZ.
Thermal shock behavior of ceramics plays a decisive role in their broad industrial applications. For
enhanced understanding of damage and failure mechanism under thermal shock loading, in the present
work, a combination of experimental testing and numerical simulation methods has been used. The
thermal shock behavior of the alumina (99.7%) disk samples has been investigated by using a plasma
test stand: the bottom of the ceramic disks were locally heated in the center by plasma beam; during the
heat treatment the temperature distribution at the top of the sample was recorded with a thermographic
system. To characterize the thermal shock resistance, a thermomechanical simulation was subsequently
carried out. It calculates the temperature and stress distribution within the ceramic disks. The
calculated critical thermal tension stresses are reported, which led to the failure of the ceramic disks
under thermal shock loading. The effect of the sample thickness on the temperature and stress
distribution is presented. Compared with the experimental results the simulated results show excellent
agreement. As conclusion, it is possible to determine the thermal shock behavior of ceramic materials by
the combination of experimental testing and numerical simulation.
Die vorliegende Arbeit stellt das von Professor Michailov vorgeschlagene Spitzentemperatur-Austenitisierungs-
Abkühlzeit-Modell für die thermomechanische Schweißsimulation unter Berücksichtigung der Gefügeumwandlungen vor. Das Modell erfasst die für die Gefügeausbildung maßgebenden Temperaturzyklen durch seine drei so genannten STAAZ-Parameter: Spitzentemperatur, Austenitisierungs- und Abkühlzeit. Die Korrelation dieser Temperaturzyklusparameter mit den thermomechanischen gefügeabhängigen Werkstoffeigenschaften erfolgt auf Grundlage einer empirischen Datenbasis. Mit der vorgenommenen Erweiterung zu Mehrmalig-(M-)STAAZ lässt sich das aus einem vorgelagerten Temperaturzyklus entstandene Zwischengefüge berücksichtigen.
The work deals with the elastic-plastic thermo-mechanical deformation process after spot heating of large thin plates. It promotes a new theoretical model of the process. The main target is to clarify the kinetics of the plastic strain formation during thermal straightening and to explore the main interactions. For this purpose, a simplified mechanical problem is formulated and applied. As a result, definite thermo-mechanical relations between temperature, initial strain, and accumulated plastic strain are obtained. Finally, a verification study is presented and discussed. The results contribute to extending the knowledge about the process and to establishing a theoretical background for development of applied analytical or analytical-numerical approaches for practical use in the designing and planning phases in welding production. An application to a particular case is described in an accompanying paper (part 2).