Ingenieurwissenschaften und zugeordnete Tätigkeiten
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- AC weld pool support (2)
- Electron backscatter diffraction (2)
- Kikuchi pattern (2)
- Wasserstoff (2)
- Welding of aluminum (2)
- Welding of thick metal plates (2)
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Eingeladener Vortrag
- nein (5)
The determination of the fatigue life in technical alloys containing large and small defects must rely on a propagation model which accounts for short and long crack growth. Recently an analytical model which incorporates propagation in the short crack regime and plastic correction for the crack driving force has been presented by two of the authors.
This work is intended to show further validation of the model, taking into account data sets for different materials with different testing conditions.
Despite the assumptions about missing parameters, the value of which had to be taken from the literature, the predictions showed a fairly good approximation of the fatigue lives. A possible interpretation of the results in terms of multiple crack initiation and propagation at higher loads is proposed.
The one-phase methods described in Chapter 2 were shown to be able to predict casting to some extent, but could not depict segregation, sedimentation and blockage occurring during flow. On the other hand, the distinct element methods described in Chapter 3 did not take into account the presence of two phases in the system and describes concrete as distinct elements interacting through more or less complex laws. A reliable numerical model of a multiphase material behaviour shall take into account both phases (solid and liquid). From the numerical point of view, concrete flow shall be seen therefore as the free surface flow of a highly-concentrated suspension of rigid grains.
The roles of microalloying niobium, titanium and vanadium for controlling austenite grain growth, microstructure evolution and hardness were investigated at different simulated heat affected zones (HAZ) for high strength low alloy (HSLA) S690QL steel. High resolution FEG-SEM has been used to characterize fine bainitic ferrite, martensite and nanosized second phases at simulated coarse and fine grain HAZs. It was found that for Ti bearing steel (Ti/N ratio is 2) austenite grain had the slowest growth rate due to the presence of most stable TiN. The fine cuboidal particles promoted intragranular acicular ferrite (IGF) formation. Nb bearing steel exhibited relatively weaker grain growth retardation compared with titanium bearing steels and a mixed microstructure of bainite and martensite was present for all simulated HAZs. IGF existed at coarse grain HAZ of Ti+V bearing steel but it was totally replaced by bainite at fine grain HAZs. Hardness result was closely related to the morphology of bainitic ferrite, intragranular ferrite and second phases within ferrite. The microstructure and hardness results of different simulated HAZs were in good agreement with welded experimental results.
Computational Advances
(2014)
In Europe a multi-national research project was initiated entitled “Rational Production and
Improved Working Environment through Using Self-Compacting Concrete”, followed by
another project entitled “Testing SCC”, which helped spreading the benefits of SCC to a wide
range of appliers. This project was also the basis of a widely accepted European guideline
on Self compacted concrete published by the European industry association bibm,
CEMBUREAU, EFCA, EFNARC, ERMCO, which again builds the basis of the European
standards for the testing of SCC (EN 12350, Parts 8 to 12) as well as for the actual
modernisation of the European concrete standard EN 206-1.
Optical and scanning electron microscopy, as well as electron microprobe analysis and electron backscatter diffraction, have been used to study diffusion processes that occur in a diffusion pair that consistsof a single-crystal CMSX-10 nickel-base superalloy and polycrystalline nickel, at temperatures of 1050–1250°C. It has been found that, in this system, the distributions of γ-stabilizing elements (Cr, Co, W, and Re) are described by the Boltzmann solution for diffusion between two semiinfinite plates of a binary alloy. The processing of these distributions has shown that the diffusion coefficients of Cr, Co, W, and Re in the multicomponent system are close to those in binary alloys of these elements with Ni. The diffusion redistribution of the elements leads to the dissolution of the γ′ phase in the nickel-base superalloy, growth of nickel grains toward the superalloy constituent of the diffusion pair, and the formation of porosity on both sides of the migrating interface, which is determined from a crystal misorientation of the alloy single crystal and nickel grains.
Drop-out of molten material was avoided by EM pressure
Compensation of the hydrostatic pressure of up to 20 mm thick
aluminum and stainless steel (experiment and FEM)
Mitigation of the weld bead dynamics
Significant changes in the velocity distributions in the weld pool
Weld pool geometry shape changes due to Hartmann effect
Significant porosity reduction
Surface quality improvements
Drop-out of molten material was avoided by EM pressure
Compensation of the hydrostatic pressure of up to 20 mm thick
aluminum and stainless steel (experiment and FEM)
Mitigation of the weld bead dynamics
Significant changes in the velocity distributions in the weld pool
Weld pool geometry shape changes due to Hartmann effect
Significant porosity reduction
Surface quality improvements
The term „Alternative Solvents“ often refers to ionic liquids (ILs), mainly to distinguish these substances from traditional (i.e., molecular) solvents.
In applications, any „alternative“ is required to perform better than something that is proven and tested.
To bring ILs into practical use, availability and costs are the fundamental points to be addressed.
There are two ways to proceed:
▬ tailoring a molecule, implanting the expected characteristics
advantage: optimization of the targeted performance possible
risks: outcome not always foreseeable, costly and time-intensive (“trial and error“)
▬ to target on mixtures of well-characterized ILs with molecular solvents
advantage: substance characteristics are known, less costly, less time-consuming,
mixture composition another tunable parameter
risks: the same but with less impact
For the basic engineering of technical processes, knowledge of phase equilibria, particularly of
mixtures, over a broad (p,T) range is mandatory.
This contribution reports on recent experimental results from our laboratory:
▬ the solubility of CO2 in a mixture of water and [bmim][CH3SO4]
▬ the solubility of CO2 in a mixture of methanol and [bmim][PF6]