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On 14 August 2018, the Morandi bridge in Genoa Italy collapsed, which caused 43 people to die and great losses. Here I am not going to talk about why it collapsed. But I want to say what we can do to prevent this kind of tragedy from happening. Any structures are like us, if we are sick, we go to doctors. But if structures are sick, how could we know?
Yes, through structural health monitoring-SHM! SHM is process of implementing damage detection strategy, which is like a doctor giving us indication of the structure health status. However, the SHM is not like our health insurance which can be free. Some structure owners may be hesitated on investing large money before they see the VALUE.
Although it is proved that SHM is beneficial, the existing literature doesn’t tell them: when to do the monitoring? How often to do that? Which SHM techniques to choose? After monitoring, what action to take? There are so many decisions needed to be made, that’s why here comes my research, which can help to answer all these questions by breaking the wall of value of monitoring information!
So how do we do that? Here we introduce a decision tree. A Decision tree is a decision support tool that uses a tree-like graph or model to describe decisions and their possible outcomes, including how likely it will happen, how severe the consequences will be. Based on the probabilities and their respective costs and benefits, the value of every decision can be quantified.
Based on the decision trees, different SHM strategies can be compared and the optimal strategy will be the one with highest value. After Knowing the value of SHM, we can improve the decision basis for design, operation and life-cycle integrity management of structures to reduce the risk, reduce the cost and extend service life benefits.
So that everyone in society can benefit from a safer and more reliable environment!
Currently, mandatory requirements and recommendations for the detection of irregularities in laser beam welded joints are based on classic micrographs as set out in the standard ISO 13919-1:2019. Compared to classic micrographs, computed tomography enables a non-destructive, three-dimensional and material-independent mode of operation, which delivers much more profound results. Even in building material testing, methods with limited informative value can be checked and supplemented by CT examinations.
The development of standards that include simulation models is often based on heuristics that include experimental data that is used to calibrate and validate the simulation models. However, these data and the corresponding calibration procedures are usually not part of the publicly accessible documentation making it very difficult to identify gaps in the current standard or extend it to new innovative solutions. The poster shows an adapted procedure that integrates the complete process into a database and a workflow to be published alongside the standard.
Maritime exposure poses particular challenges for corrosion
protection in plant construction. In addition to the right choice
of materials, special design features that can have an impact
on corrosion resistance must also be taken into account to
ensure long-lasting corrosion protection. In practice, structural
crevice arrangements are unavoidable, and therefore the
crevice corrosion resistances of stainless steels are of
particular importance. These and other influences are being
investigated in this joint project.
In the maritime context of offshore operation, corrosion, in combination with the materials used, poses a particular challenge to ensure safe operation over long indefinite periods and to minimise susceptibility to failure. Until today, only a few corrosion protection systems have proven themselves for the interaction of efficiency, installation, and maintenance in the offshore sector. In addition, available corrosion test methods sometimes have major deficits about conclusions of the durability. Therefore, there is more research and development needed.
The flagship project H2Mare of the Federal Ministry of Education and Research aims to enable the production of green hydrogen and PtX products at high seas. Research is being driven forward by the partners in four individual projects, where BAM is involved in two.
In PtX-Wind, major kinds of corrosion attacks at offshore constructions are characterized and investigated, and suitable corrosion protection measures determined. In TransferWind, attention focusses on transferring scientific results into standardization.
This poster at the H2Mare Conference 2023 presents an overview of the investigation methods and contribution of the department “Corrosion and Corrosion Protection”.
Corrosion testing in a laboratory container: Corrosion testing with artificial seawater and sediment
(2022)
Electricity generation by offshore wind turbine generators (WTG) is an important pillar of the energy transition. Corrosion processes on WTGs pose a particular challenge with regard to safe operation over longer periods of time due to the highly corrosive conditions in the offshore area. BAM is therefore conducting research to ensure a safe operation of the turbines over their intended service life to protect people and the environment.
In a joint research project, different corrosion-relevant areas of a WTG foundation structure were specifically simulated in test basins within a laboratory container. The aim of the work was, on the one hand, the gravimetric and electrochemical determination of corrosion rates in the different areas of an WTG that are relevant for cathodic corrosion protection (CCP): Underwater and sediment zone as well as the transition area between these two zones. Also, targeted tests were carried out under CCP. In addition, investigations regarding calcareous deposition during CCP were carried out on idealized specimens under laboratory conditions to better assess its influence on the protection process. The investigations were carried out in a laboratory container with different basins, which were filled with sand as sediment and artificial seawater according to ISO 15711and connected via a closed water circuit.
The poster at EURCORR 2022 provides an overview of the investigations and the most important results. It will be evaluated, if a simulation of offshore corrosion conditions is possible to a certain extent in an idealized system with artificial seawater and sediment.
We examine the behavior of reinforced concrete components subjected to impact induced loading conditions which might be caused by vessels collisions such as aircraft fuel tanks The concrete plates were impact damaged at TU Dresden and shipped to BAM At BAM laminar tomography as the imaging method is used to determine and quantify the damage state An automatic crack detection method based on template matching is applied to find the cracks and we aim to develop a new method using machine learning Algorithms In addition numerical models are developed to understand the experiment and to predict the damage structures based on failure mechanisms.
Our approach includes the preparation of blends of preferably liquid-crystalline polyesters with Lignin, but also the synthesis of new polyesters with Lignin-related monomer units.
While most studies employ pulped Lignin directly, we first purified the Kraft Lignin by fractionation, followed by chemical modification of the terminal OH groups. Acetylation results in the reduction of glass transition temperatures (Tg) below 200°C, improved processability in the melt with complete melting of the Lignin sample, and higher thermostability.
These Lignin fractions were melt-mixed in a mini-twin-screw extruder with polyesters. The chemical structure of the polyesters was systematically varied between poly(ethylene terephthalate), (PET); poly(ethylene terephthalate-co-oxybenzoate), (PET/HBA); liquid crystalline polyesters with fully aromatic structure; and polyesters with Lignin-related monomers like ferulic and vanillic acid). The polymer influence on the blending behavior with Lignin was examined. SEM revealed phase-separated blends with partial compatibilization of the phases indicated by the shift of Tg’s. The influence of the polyester and the Lignin on decomposition and combustion was accessed by thermogravimetry (TGA), TGA-FTIR and pyrolysis-combustion flow calorimetry (PCFC) and compared to the decomposition of polyesters. The main focus was to achieve melt-spinnable blends for fibres with improved flame retardancy or as precursors for carbon fibers. Blends of Lignin fractions with the aromatic-aliphatic polyesters (here preferably PET/HBA) were successfully spun into fibers with lab-scale melt-spinning equipment. X-ray measurements revealed orientation of the fibers with Lignin. The E-moduli raised with increasing purity of the Lignin fractions (e.g., by removal of reducing sugars).
The structure of the polymer matrix determines the decomposition and combustion behavior of the blends with Lignin. Incorporation of aliphatic subunits reduces the amount of remaining char formed in TGA and PCFC from about 40-45 wt% for fully aromatic polyesters to 18-25 wt% for semiaromatic polyesters (at almost comparable carbon content in the polymer), while the maximum temperature of combustion decreased from 480-530°C for the former to 410-465°C for the latter. Lignin fractionation and acetylation yields samples with high char content (36 wt%) and extremely low heat release capacity (80-90 kJ/gK) with combustion maximum temperature at 405°C. Lignin/ PET/HBA blends combine the low HRC with intermediate char and offer interesting opportunities for polyester fibers with improved flame retardancy without adding P-containing FRs.
The flame retardancy behavior was explored by limiting oxygen index measurements on injection-molded parts and fibers.
Determination of the corrosion product layer resistance on zinc samples by using gel electrolytes
(2022)
Crash barriers, railings, lamp posts, waste glass containers - these are just a few of the many examples of galvanized surfaces. They withstand wind and weather for decades, which is possible thanks to a protective layer made of corrosion products. When designing the atmospheric durability of galvanized components, a linear corrosion loss is assumed. In the past 30 years, however, the surrounding atmosphere has changed a lot. Due to the restriction of sulfur exhaust air, acid rain completely disappeared in Europe and Germany, which has a direct influence on the type and protective effect of the corrosion products. Under the influence of current atmospheric conditions, zinc layers are significantly more resistant and no longer show any linear corrosion loss. The established test methods cannot correctly map this change in neither short-term nor long-term tests and thus provide incorrect results. In order to solve this problem, a new measurement method was developed at BAM that can assess the protective effect of the formed surface layers in a minimally invasive manner without damaging the sample and in short test times. For this new method, gel electrolytes are used and the so-called corrosion product layer resistance RL, which is made up of various surface resistances, is measured electrochemically. As a single measurement, the surface layer resistance can provide information about the existing corrosion protection, while time-dependent measurements assess the stability of the layer. Thus, it is possible again to evaluate the corrosion protection layer. Furthermore, this method can also be used for field measurements on real components.