Material relation to assess the crashworthiness of ship structures

A ship collision accident can result in severe environmental damage and loss of life. Therefore the non-linear finite element method with shell elements is used to assess the crashworthiness of ship steel structures through collision simulations. However, a non-linear finite element-based benchmark revealed inconsistencies and inaccuracies in the results of collision analysis using current material relations and failure criteria. To overcome these problems in this thesis, the steel material's true strain and stress relation is derived in a novel way from tensile experiments until failure on the basis of optical measurements. The novel material relation is obtained until failure with respect to the strain reference length. Furthermore, this material relation, including failure, can be varied to accommodate different finite element sizes. By this means good correspondence in numerical results for the simulation of tensile and plate specimens and complex topologies under indentation loading is achieved for different mesh sizes ranging from 0.88 mm to 140 mm. It is shown that the choice of a constant strain failure criterion suffices for thin steel ship structures. Furthermore, a procedure to optimise a conventional ship side structure for crashworthiness in the conceptual design stage is presented. This procedure extends the assessment procedure for structural arrangements from Germanischer Lloyd. The energy absorbed until inner plate rupture during a right-angle ship collision is used as an optimisation objective. This procedure exploits the novel element length-dependent strain and stress relation, including failure. A particle swarm algorithm is used to identify the crashworthy conceptual design. By this means a crashworthy conceptual ship side structure is obtained, which can absorb significantly more energy than the initial rules-based concept with a reasonable weight increase

Influence of weld stiffness on buckling strength of laser-welded web-core sandwich plates

This paper investigates the influence of weld rotation stiffness on the global bifurcation buckling strength of laser-welded web-core sandwich plates. The study is carried out using two methods, the first is the equivalent single-layer theory approach solved analytically for simply supported plates and numerically for clamped plates. First-order shear deformation theory is used. The second method is the three-dimensional model of a sandwich plate solved with finite element method. Both approaches consider the weld through its rotation stiffness. The weld rotation stiffness affects the transverse shear stiffness. Plates are loaded in the web plate direction. Four different cross-sections are considered. Weld stiffness is taken from experimental results presented in the literature. The results show a maximum of 24% decrease in buckling strength. The strength was affected more in plates with high reduction of transverse shear stiffness and high bending stiffness. Furthermore, clamped plates were influenced more than simply supported. The intersection between buckling modes shifted towards higher aspect ratios, in the maximum case by 24%. The results show the importance of considering the deforming weld in buckling analysis.Peer reviewe

Ultimate strength of corroded web-core sandwich beams

The corrosive marine environment is a threat to the ultimate strength of steel sandwich structures. Therefore, ultimate strength experiments were carried out in three-point bending for beams with different corrosion exposure times, i.e. one and two years. Standard laser-welded web-core sandwich beams are studied and different corrosion protection systems considered. The beams experienced general corrosion. The thickness reduction in unprotected plates and laser welds is around the typical 0.1 mm/year. This led to an ultimate strength reduction of 10% and 17% for beams with exposure times of one and two years, respectively. The experimental ultimate strength is in agreement with finite element simulations. The ultimate strength was maintained for the beams protected with coating or closed-cell polyurethane (PU) foam.Peer reviewe

Continuous Monitoring of Software Services: Design and Application of the Kieker Framework

In addition to studying the construction and evolution of software services, the software engineering discipline needs to address the operation of continuously running software services. A requirement for its robust operation are means for effective monitoring of software runtime behavior. In contrast to profiling for construction activities, monitoring of operational services should only impose a small performance overhead. Furthermore, instrumentation should be non-intrusive to the business logic, as far as possible. We present the Kieker framework for monitoring software runtime behavior, e.g., internal performance or (distributed) trace data. The flexible architecture allows to replace or add framework components, including monitoring probes, analysis components, and monitoring record types shared by logging and analysis. As a non-intrusive instrumentation technique, Kieker currently employs, but is not restricted to, aspect-oriented programming. An extensive lab study evaluates and quantifies the low overhead caused by the framework components. Qualitative evaluations provided by industrial case studies demonstrate the practicality of the approach with a telecommunication customer self service and a digital photo submission service. Kieker is available as open-source software, where both the academic and industrial partners contribute to the code. Our experiment data is publicly available, allowing interested researchers to repeat and extend our lab experiments

Optimizing integrated reference cases in the OCTAVIUS project

Adding a carbon capture plant to a power plant reduces the efficiency of said power plant. In order to keep this drop in efficiency as small as possible, several optimisation studies are performed in the OCTAVIUS project. Based on the work of the European Benchmarking Task Force-EBTF within the CESAR, CAESAR, and DECARBit projects, two reference power plants are modelled in Ebsilon®Professional. The first is an 800 MWe coal case, the second a 430 MWe natural gas combined cycle (NGCC) case. For each power plant two separate capture plants are considered: one using 30 wt% MEA as solvent system, the other with CESAR1, a mixture of AMP and PZ as solvent system. This results in four different reference cases which are optimized by varying different process parameters and evaluating process modifications. In a second step, the integration of the capture plant into the power plant is evaluated. This is important especially for the coal fired power plant, where integration of waste heat from the capture plant or the CO2 compressor intercoolers can lead to a significant increase in overall efficiency. The configuration of intercoolers for the CO2 compressor is adapted to achieve the highest overall efficiency. For the natural gas combined cycle plant, integration is not that beneficial, since there is no heat sink available in the water steam cycle. In the end, the cost of electricity and cost of CO2 avoided is calculated for all four cases. While the CESAR1 solvent system in a conventional absorber-stripper scheme is less costly (almost 17%) than the MEA solvent system in a process with Lean Vapour Compression for the coal cases, the result is the opposite for the two NGCC cases though the difference is not substantial

Current status and future operational models for transit shipping along the Northern Sea Route

Author's accepted version (post-print).Available from 09/05/2020.acceptedVersio

Safety Considerations of Hydrogen Application in Shipping in Comparison to LNG

Shipping accounts for about 3% of global CO2 emissions. In order to achieve the target set by the Paris Agreement, IMO introduced their GHG strategy. This strategy envisages 50% emission reduction from international shipping by 2050, compared with 2008. This target cannot be fulfilled if conventional fuels are used. Amongst others, hydrogen is considered to be one of the strong candidates as a zero-emissions fuel. Yet, concerns around the safety of its storage and usage have been formulated and need to be addressed. Safety, in this article, is defined as the control of recognized hazards to achieve an acceptable level of risk. This article aims to propose a new way of comparing two systems with regard to their safety. Since safety cannot be directly measured, fuzzy set theory is used to compare linguistic terms such as safer. This method is proposed to be used during the alternative design approach. This approach is necessary for deviations from IMO rules, for example, when hydrogen should be used in shipping. Additionally, the properties of hydrogen that can pose a hazard, such as its wide flammability range, are identified

Case Study on the Heat Pump Integration for Enhanced Efficiency in Battery-Electric Short-Sea Ferries

This case study investigates the potential of incorporating water heat pumps into onboard thermal systems to utilize low-temperature waste heat for onboard heating and enhance the efficiency and economics of all-electric battery-driven ferries. We analysed a hybrid-driven roll-on/roll-off passenger ferry operating in the Baltic Sea, gathering data on vessel operation, power, and heat provision in low-temperature cycles. We integrated real-time measurement data, energy flow analysis, and thermodynamic calculations to draw conclusions for a potential battery retrofit scenario featuring an all-electric operation and a battery system capacity of 10 MWh. Our results indicate that the integration of heat pumps in battery-electric mode can cover more than 50 % of the onboard nominal heat capacity of HVAC systems, with a seasonal coefficient of performance (SCOP) of 3.5 during the heating season. The overall electric energy demand of the vessel during the 6-month heating period is reduced by approximately 8 % compared with direct-electric heating