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Scientific Events

Scientific Events

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6th International Symposium on Computational Mechanics of Polycrystals, CMCn 2018

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6th International Symposium on Computational Mechanics of Polycrystals, CMCn 2018 and DAMASK User Meeting

CMCn2018 The Max-Planck-Institut für Eisenforschung in Düsseldorf is organizing the 6th International Symposium on Computational Mechanics of Polycrystals and we would like to invite you and your research colleagues to participate in this event. This symposium is part of a biannual series of symposia that originated with the establishment of the first joint research group formed between the Max Planck Society and the Fraunhofer Society and investigating Computational Mechanics of Polycrystals. This year the symposium is again combined with the DAMASK User Meeting. DAMASK is the multi-physics simulation software developed at MPIE. The symposium will take place on September 17th and 18th, 2018 in the Max-Planck-Institut für Eisenforschung at Max-Planck-Straße 1, 40237 Düsseldorf, Germany. The DAMASK User Meeting will be held on the following day, September 19th at the same location. If you and your colleagues would like to attend this event, then please register before July 15th 2018. We emphasize that registration is mandatory and that there are limited places only. Many thanks, we hope to see you in Düsseldorf! [more]

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Thermoelectric energy conversion - From waste heat to sustainable energy

Thermoelectric materials can convert waste heat into electricity, which is of significant technological and environmental interest. In my talk I will give a short introduction into the field of thermoelectrics including the measurement of the thermoelectric properties of bulk materials at low and elevated temperatures. I will introduce a selection of general concepts, which allow to improve and optimize thermoelectric materials and I will briefly talk about a selection of new directions in the field, where some of them (will) heavily rely on and benefit from the fields of metallurgy and atom probe tomography (e.g. phase boundary mapping and antiphase boundaries as a new route towards low thermal conductivities). [more]

Use of computational and physical simulation on arc welding heat affected zone microstructure evolution studies

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Use of computational and physical simulation on arc welding heat affected zone microstructure evolution studies

The heat affected zone (HAZ) is most commonly the critical part of welding joint and the comprehension of the thermal cycle it suffers during welding and its effects on the final microstructure is fundamental to predict and reduce the properties degradation on that zone. The traditional approach to study the HAZ involves several welding tests varying the principal parameters (voltage, current and welding speed) with subsequent mechanical testing. These welding trials could be very time, material and cost demanding; could not replicate the plant/field true welding conditions (need for small scale/plant no available for research tests) and still may not provide a profound insight on the mechanisms in play as the thermal history would not be evaluated. In this context, it is very interesting to use simulation techniques that have evolve significantly in the last two decades to optimize the research effort. In one side, we have the material computational simulation development, with the use of finite element methods and double ellipsoid heat source model to describe the process (thermometallurgic – mechanical coupling) and methods like CALPHAD, Phase Field and Cellular Automata to describe the microstructure evolution in details. One the other side, there are equipment (Gleeble) capable of applying very rapid and controlled thermo-mechanical cycles (acquired in the computational simulation) to a sample, so to produce physical simulated specimen that represents the HAZ region of interest, enabling more detailed characterization and some mechanical testing in isolated microstructures. This permits some validation of the computational simulation too. Seizing these techniques potential, LNTSold have been developing a series of studies in welding simulation to characterize the HAZ of different steels for oil and gas industry applications. For the X100M API 5L steel pipe, it was simulated on FEA software (Sysweld) the welding process of the pipe (SAW) and the field pipeline assembly (GMAW). The main concern for this steel is the toughness reduction it may be subject to in the HAZ, with possible formation of local brittle zones due to the evolution of very sensible constituents as the martensita-austenite (MA) constituent. From the bibliography reference, the two HAZ critical regions are the coarse grain region and the intercritically re-heated coarse grain region, so it was studied the thermal cycle of these regions with heat input variation in the FEA software. The thermal cycle was then reproduced in Gleeble samples to produce specimens for microscopy (focus on the MA constituent morphology and quantity analysis) and for Charpy impact test, to assess the toughness losses. The results indicate that the MA morphology depends very much on the peak temperature and that its quantity does not seem to control directly the impact resistance. For an AISI 4130 steel connector, it was performed a study with FEA software (Sysweld) and CALPHAD software (JMatPro) of the coarse grain HAZ region of the last welding passes, focusing in the hardness prediction and considering the post-weld heat treatment. A simulated CCT diagram and an experimental one were developed to include phase and hardness prediction in the FEA modelling. Then some heat treatment conditions (temperature x time) were evaluated using CALPHAD, trying to optimize the production time. All welding and the best heat treatment conditions were physically reproduced in Gleeble. The simulated CCT showed initially a good correlation with the experimental one, but the FEA hardness prediction was more precise using the experimental CCT. It was possible to achieve the hardness requirements and even increase the impact resistance with a faster heat treatment with close relation to simulation results. Finally, the welding of a 9% Ni steel pipe with Ni 625 alloy filler metal was also simulated in the FEA software and the different HAZ regions reproduced in Gleeble with dilatometry analysis to study the reversion and retention of austenite, which plays an important role in this steel tenacity. The goal it is also to isolate the microstructure and study its hydrogen embrittlement susceptibility. [more]

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Quantification and simulation of slip transfer across grain boundaries in near-cube oriented aluminum and meso-scale elastic strain heterogeneity in titanium

Heterogeneous deformation in metallic polycrystals arises from several factors, including anisotropy in elastic properties and plastic slip. The ability to accurately simulate heterogeneous deformation requires physically based models of slip that includes grain boundary properties, as grain boundaries are usually barriers to slip. As slip transfer across boundaries occurs in some boundaries, grain boundary properties have been installed in a dislocation density based crystal plasticity model to enable slip transfer, and used to examine idealized bicrystal tensile samples. This code will be used to simulate deformation of annealed pure aluminum foil multicrystal experiments, in order to examine thresholds for slip transfer. An analysis of slip transfer events indicates that for near-cube oriented grains, the threshold is higher than observed in hexagonal materials, and potential reasons for this will be discussed. Secondly, as computational simulations of polycrystals normally assume a zero-stress initial condition, this assumption is questionable in non-cubic metals where the coefficient of thermal expansion (CTE) is anisotropic. To assess the effect of the anisotropic CTE on initial stress states, two pure titanium samples with different textures were examined using in-situ high energy x-ray diffraction microscopy to measure the evolution of the internal stresses in each grain during heating and cooling. These data show a significant change in expansion rates in the <a> and <c> directions at about 700 C. A simulation of this experiment shows good agreement with experimentally measured data, indicating that it is possible to start a simulation with a good estimate of the internal stress state arising from the anisotropic CTE. This work was supported by grants from US DOE/BES and the Community of Madrid [more]

MPIE Colloquium

MPIE Colloquium

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Heterogeneous Catalysis: Not Always Supported Metallic Nanoparticles

[more]

Gordon Research Conference “Thin Film and Small Scale Mechanical Behavior”

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Gordon Research Conference “Thin Film and Small Scale Mechanical Behavior”

 
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