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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.
Cold cracks in welds are the result of the formation of brittle microstructure as martensite in the presence of diffusible hydrogen as well as of tensile stresses. Cold cracks occur when the combination of cold crack influence parameters (CCIP) overcomes a critical limit. In this study, critical combinations of CCIP were identified with an enhanced test procedure under welding conditions. The test is based on the physical simulation technique of heat affected zone (HAZ) and it is carried out using the test and simulation center Gleeble 3500. Thereby, laboratory special specimens are charged with hydrogen from pure hydrogen atmosphere in the initial stage of the test. Rigidly restraint specimen section is subjected to different weld temperature cycles. Through the thermal exposure, the desired microstructure of HAZ is set in the test zone of the restraint specimen section. A plastic deformation takes place owing to the prevented expansion during heating and contraction of the specimen during cooling. Consequently, compressive or tensile reactions stresses arise in the deformed zone. Cracked specimen represents a critical combination of the CCIP. The quantitative cold crack criterion separates the cold crack susceptible combinations from those non susceptible.