5 Werkstofftechnik
Filtern
Erscheinungsjahr
- 2018 (23) (entfernen)
Dokumenttyp
- Beitrag zu einem Tagungsband (23) (entfernen)
Sprache
- Englisch (23) (entfernen)
Schlagworte
- Adiabatic calorimeter (2)
- Aluminium (2)
- CCUS (2)
- Carbon steels (2)
- Coarsening (2)
- Creep (2)
- Fatigue (2)
- Inconel 686 (2)
- Martensitic steel (2)
- Phase change material (2)
- Salt eutectics (2)
- Superaustenite steel (2)
- Supercritical/dense phase CO2 (2)
- Thermal energy storage (2)
- AISI 304L (1)
- Additive Manufacturing (1)
- Additive manufacturing (1)
- Aggressive environment (1)
- Air-coupled ultrasonic testing (1)
- Airborne ultrasonic testing (1)
- Alloy 2618A (1)
- Alloy 2818A (1)
- Anisotropy (1)
- Austenitic stainless steel (1)
- CCS (1)
- CO2 corrosion (1)
- Coating (1)
- Composite (1)
- Composite structures (1)
- Composites (1)
- Concrete (1)
- Continnum damage model (1)
- Corrosion (1)
- Crystal plasticity (1)
- Cyclic loading (1)
- Damage (1)
- Degradation (1)
- Distributed fibre optic sensors (1)
- Droplet corrosion (1)
- Fatigue of sandwich shell structures (1)
- Ferritic-martensitic steels (1)
- Ferroelectret (1)
- Geothermal (1)
- High - temperature corrosion (1)
- High temperature corrosion (1)
- Hydrogen (1)
- IN718 (1)
- Impurities (1)
- Injection (1)
- Long-term behavior (1)
- Metal seal (1)
- Microstructure evolution (1)
- Neutron diffraction (1)
- Nickel based coatings (1)
- Non-destructive testing (1)
- Optical backscatter reflectometry (1)
- Optical fibre (1)
- Oxide scale (1)
- Pipeline (1)
- Polyaniline (1)
- Residual Stresses (1)
- Residual stress (1)
- Residual stresses (1)
- Rotor blade (1)
- S-phase (1)
- Scale-bridging (1)
- Selective Laser Melting (1)
- Selective laser melting (1)
- SiO2 (1)
- Simulation of concrete (1)
- Structural health monitoring (SHM) (1)
- Swept wavelength interferometry (SWI) (1)
- Temperature (1)
- Thermomechanics (1)
- ToF-SIMS (1)
- Transducers (1)
- Transmission electron microscopy (1)
- Under cyclic loading (1)
- Virtual experiments (1)
- Wind turbine (1)
- Wind turbine blades (1)
- X-ray laminography (1)
- laser cladding (1)
Organisationseinheit der BAM
- 5 Werkstofftechnik (23)
- 5.1 Mikrostruktur Design und Degradation (10)
- 5.2 Metallische Hochtemperaturwerkstoffe (7)
- 5.3 Polymere Verbundwerkstoffe (5)
- 7 Bauwerkssicherheit (5)
- 8 Zerstörungsfreie Prüfung (5)
- 5.5 Materialmodellierung (4)
- 7.6 Korrosion und Korrosionsschutz (3)
- 8.5 Röntgenbildgebung (3)
- 9 Komponentensicherheit (3)
During the energy transformation from fossil fuels to renewable energy sources, the use of hydrogen as fuel and energy storage can play a key role. This presents new challenges to industry and the scientific community alike. The storage and transport of hydrogen, which is nowadays mainly realized by austenitic stainless steels, remains problematic, which is due to the degradation of mechanical properties and the possibility of phase transformation by hydrogen diffusion and accumulation. The development of materials and technologies requires a fundamental understanding of these degradation processes. Therefore, studying the behavior of hydrogen in austenitic steel contributes to an understanding of the damage processes, which is crucial for both life assessment and safe use of components in industry and transportation. As one of the few tools that is capable of depicting the distribution of hydrogen in steels, time-of-flight secondary ion mass spectrometry was conducted after electrochemical charging. To obtain further information about the structural composition and cracking behavior, electron-backscattered diffraction and scanning electron microscopy were performed. Gathered data of chemical composition and topography were treated employing data fusion, thus creating a comprehensive portrait of hydrogen-induced effects in the austenite grade AISI 304L. Specimens were electrochemically charged with deuterium instead of hydrogen. This arises from the difficulties to distinguish between artificially charged hydrogen and traces existing in the material or the rest gas in the analysis chamber. Similar diffusion and permeation behavior, as well as solubility, allow nonetheless to draw conclusions from the experiments.
Lifetime aspects including fatigue failure of concrete structures were traditionally only of minor importance. Because of the growing interest in maxing out the capacities of concrete, its fatigue failure under compression has become an issue. A variety of interacting phenomena such as e.g. loss of prestress, degradation due to chemical reactions or creep and shrinkage influence the fatigue resistance. Failure due to cyclic loads is generally not instantaneous, but characterized by a steady damage accumulation. Therefore, a reliable numerical model to predict the performance of concrete over its lifetime is required, which accurately captures order effects and full three-dimensional stress states.
Many constitutive models for concrete are currently available, which are applicable for specific loading regimes, different time scales and different resolution scales.
However, a key limitation of those models is that they generally do not address issues related to fatigue on a structural level. Very few models can be found in the literature that reproduce deterioration of concrete under repeated loading-unloading cycles. This is due to the computational effort necessary to explicitly resolve every cycle which exceeds the currently available computational resources. The limitation can only be overcome by the application of multiscale methods in time.
The objective of the paper is the development of numerical methods for the simulation of concrete under fatigue loading using temporal multiscale methods.
First, a continuum damage model for concrete is developed with a focus on fatigue under compressive stresses [1]. This includes the possibility to model stress redistributions and capture size effects. In contrast to cycle based approaches, where damage is accumulated based on the number of full stress cycles, a strain based approach is developed that can capture cyclic degradation under variable loading cycles including different amplitudes and loading frequencies. The model is designed to represent failure under static loading as a particular case of fatigue failure after a single loading cycle. As a consequence, most of the material parameters can be deduced from static tests. Only a limit set of additional constitutive parameters is required to accurately describe the evolution under fatigue loading. Another advantage of the proposed model is the possibility to directly incorporate other multi-physics effects such as creep and shrinkage or thermal loading on the constitutive level.
Second, a multiscale approach in time is presented to enable structural computations of fatigue failure with a reduced computational effort. The damage rate within the short time scale corresponding to a single cycle is computed based on a Fourier based approach [2]. This evolution equation is then solved on the long time scale using different implicit and explicit time integration schemes. Their performance and some limitations for specific loading regimes is discussed.
Finally, the developed methods will be validated and compared to experimental data.
[1] Vitaliy Kindrachuk, Marc Thiele, Jörg F. Unger. Constitutive modeling of creep-fatigue interaction for normal strength concrete under compression, International Journal of Fatigue, 78:81-94, 2015
[2] Vitaliy Kindrachuk, Jörg F. Unger. A Fourier transformation-based temporal integration scheme for viscoplastic solids subjected to fatigue deterioration, International Journal of Fatigue, 100:215-228, 2017
A continuum damage model for concrete is developed with a focus on fatigue under compressive stresses. This includes the possibility to model stress redistributions and capture size effects. In contrast to cycle based approaches, where damage is accumulated based on the number of full stress cycles, a strain based approach is developed that can capture cyclic degradation under variable loading cycles including different amplitudes and loading frequencies. The model is designed to represent failure under static loading as a particular case of fatigue failure after a single loading cycle. As a consequence, most of the material parameters can be deduced from statictests. Only a limit set of additional constitutive parameters is required to accurately describe the evolution under fatigue loading. Another advantage of the proposed model is the possibility to directly incorporate other multi-physics effects such as creep and shrinkage or thermal loading on the constitutive level. A multiscale approach in time is presented to enable structural computations of fatigue failure with a reduced computational effort. The damage rate within the short time scale corresponding to a single cycle is computed based on a Fourier based approach. This evolution equation is then solved on the long time scale using different implicit and explicit time integration schemes. Their performance and some limitations for specific loading regimes is discussed.