Browsar Mekanik och maritima vetenskaper (M2) // Mechanics and Maritime Sciences (M2) efter Titel
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- Post1D Modeling and Simulations of Soot Oxidation in Diesel Particulate Filters and Monoliths using GT-POWER(2016) Lerdmaleewong, Chanin; Luong, Staffan; Chalmers tekniska högskola / Institutionen för tillämpad mekanik; Chalmers University of Technology / Department of Applied MechanicsDiesel particulate filter (DPF) is part of the exhaust aftertreatment system for diesel engines. The DPF’s main function is to trap particulate matter (soot) from the exhaust stream. The trapped soot is removed by regeneration of the filter. The regeneration process involves soot oxidation via oxygen and nitrogen dioxide. Simulations on kinetics and pressure drop are widely used in the assessment of the DPF. In this work detailed kinetic models of soot oxidation (by oxygen) were investigated and implemented in a flow-through monolith model and also in a DPF model using GT-POWER. The detailed kinetic models and data origins from previously published data. The DPF model consists of a number of interrelated sub-models soot oxidation by NO2 , NO oxidation and pressure drop. These sub-models were developed by using semi-steady state and transient engine data on a catalyzed DPF. Kinetics and pressure drop analysis were found to be the key in finding parameters for the models. The implementation of these models into GT-POWER required some special techniques due to rigid built-in model structure. The detailed kinetics was adequate to predict the low temperature experiment, in general, the detailed kinetic model was able to reduce the residual by approximately 25% compared to global kinetics model.
- Post1D Simulation Modeling for an Exhaust Aftertreatment System SCR Calibration Modeling in GT-SUITE(2021) Ramanjaneyalu, Puneeth; Chalmers tekniska högskola / Institutionen för mekanik och maritima vetenskaper; Sjöblom, Jonas; Sjöblom, Jonas; Yitbarek, ZemichaelThe Euro legislative regulations are imposed successively to hold back toxic elements that are harmful to the environment. Carbon monoxide (CO), hydrocarbons (HC) and nitric oxide (NOx) are the major toxic elements that cause serious health hazards for the living species. From many research works, selective catalytic reduction (SCR) is the most promising technology to address NOx. The objective of this project is to develop a surface reaction mechanism model, reaction rate calibration for SCR catalyst and validation. Firstly, building the SCR catalyst and surface reaction mechanism model in GTSUITE. The reaction rate calibration or characterization is performed for six reaction rate expressions with 18 unknown parameters by applying physical properties of the catalyst for example diameter and area of the catalyst. Furthermore, the digital laboratory Simulink black-box is utilized to produce the target reaction rate curves for all chemical reactions to calibrate the parameters then to compare with simulated GT-model results. Finally, validation for steady state or urea stairs, US, conditions and transient driving cycle conditions against WHTC (world harmonized transient driving cycles) for the Euro V regulations using tail pipe, engine-out emissions, mass flow rate and temperature traces experiments data. Overall, chemical kinetics modeling for SCR catalyst in GT-SUITE was successfully implemented and have reasonable results for urea stair cases, but the outcome can be further improved for transient cycles by extract information from 3D CFD to 1D in the future. Inevitably, simulations analysis is the best possible way to validate the results in quick time with low cost and it is a key factor during the development process.
- Post1D Transient Simulation of Heavy Duty Truck Cooling system – HDEP 16 DST, Euro 6(2012) Raghavan, Ganesh; Chalmers tekniska högskola / Institutionen för tillämpad mekanik; Chalmers University of Technology / Department of Applied MechanicsIn future and also in the present time, with the focus on minimizing environmental impacts, the truck industry faces a big technological challenge in terms of meeting statutory emission legislations and also on satisfying the ever increasing demand of customers in terms of minimizing the fuel consumption. There are other challenges in terms of having a short development time and reducing the overall development cost. All the above stated challenges requires measures in terms of how computer simulations can be used to better represent a system, how different concepts can be tested, how the overall system can be tested in particular system working environment which ultimately will give a short development time with minimum cost. This thesis work basically answers the above questions in a holistic manner by considering how the truck cooling system be modeled using different CFD tools like AMESim and GT Cool to understand how different performance parameters of a cooling system vary for a steady and transient driving cycle. In this thesis work, the cooling system model has been developed for an ongoing project in Volvo Powertrain AB. The model has been developed for 16L DST, 750 Hp, Euro 6 heavy duty truck engine with other auxiliary components like, air compressor, transmission oil cooler, cab heater, urea heater to mention a few. The model has been developed such that it can run on both steady and transient cycles by changing few elements in terms of how the input is given to the model. One of the aims of this thesis work was to evaluate the two tools mentioned above in terms of workability, implementability and reliability. Results in terms of pressure drop, mass flow rate, heat transfer rate, thermostat valve fluctuation etc. have been compared for above mentioned tools. It is pointed out that since the model has been developed for an ongoing project, the validation of the model by performing actual tests couldn’t be performed because of the unavailability of the engine. In the end certain conclusions have been drawn out in terms of cooling system performance and how effective the tools were in simulating the cooling system.
- Post3-D object tracking through the use of a single camera and the motion of a driverless car(2021) Ovnell, Andreas; Chalmers tekniska högskola / Institutionen för mekanik och maritima vetenskaper; Benderius, Ola; Benderius, OlaThere has been a very large increase in interest and development of partially or fully driverless cars in recent years. For these driverless cars to function, they need to be able to navigate to their destination while avoiding nearby objects. This can be done using simultaneous localisation and mapping (SLAM). SLAM is the task of simultaneously creating a map of the surrounding objects while keeping track of the car’s position within this map. This thesis will look into the feasibility of using a single camera attached on a driverless car to perform SLAM on cones detected by the real-time object detection system You only look once (YOLO). Three different methods were tested. All of these require a calibrated camera that is capable of determining horizontal and vertical angles from the pixel positions. The first ‘triangulation’ method uses that the distance travelled and rotation between two frames is known. The second ‘plane projection’ method is an optimisation problem which consists of finding the variables which result in lowest error, and through this determine the cone distances and car speed. The map of the surrounding cones is moved according to the estimated velocity and rotation of the car such that the car is always placed at the origin, allowing for use of multiple detections to improve accuracy. The third ‘distance from cone height’ method works by using the size of the cone detections in order to determine the approximate distance of each cone, use this to determine the approximate angle of the camera and then use the median angle to make the final distance estimates. The triangulation method was shown to be completely unsuitable for mono-camera use. The plane projection method was shown to be unreliable, likely due to a relatively small number of visible cones and a too large noise amplitude of detections from YOLO. The distance from cone height method was shown to be the best out of the tested methods, as it was simple, fast and quite reliable. However, this method still had an error approximately 1.4 times larger than what is advertised by commercial stereo camera systems.
- Post3D modelling of plane-strain fracture toughness tests using ansys wokbench(2020) Wester, Filip; Gunnarsson, Eric; Chalmers tekniska högskola / Institutionen för mekanik och maritima vetenskaper; Ekberg, AndersThis thesis shows the possibilities of modeling and recreating the fracture toughness test E399 using available test data. It also adds to the conclusion that for a excessive amount of plasticity the 95% secant can not be used to derive KIC as the crack has not propagated at that point. Further it has been shown that for limited amount of plasticity the J-integral can be used to calculate the linear elastic stress intensity factor. The thesis also discusses the validity of adding friction between the specimen and the pin to increase the stiffness in the simulation to match the test data and compare this approach to other methods. Finally, ways of using FE modelling to get information from invalid tests are discussed.
- Post3D thermal modeling of a battery cell on a test jig fixture using CFD(2023) Daneshvari, Reza; Chalmers tekniska högskola / Institutionen för mekanik och maritima vetenskaper; Chalmers University of Technology / Department of Mechanics and Maritime Sciences; Sebben, Simone; Andersson, Ingemar; Arvani, Maedeh; Ramesh Babu, AnandhThe thermal conditioning of battery cells plays a crucial role in ensuring their safety and maximizing the driving range of electric vehicles. To gain a comprehensive understanding of battery cell performance under various conditions, testing is conducted within controlled chambers that replicate real-world scenarios. While battery packs and modules can function independently during testing, individual cells require mechanical support. This is where the jig comes into play, serving as a robust support structure that enables current conduction and facilitates effective liquidbased thermal conditioning. The objective is to achieve optimal cell climatization and maintain it at a suitable temperature. In order to comprehend the thermal properties of the jig when exposed to the heat generated by the battery cell, Computational Fluid Dynamics (CFD) simulations are employed. These simulations provide insights into the underlying physics of the phenomena and aid in the identification of potential enhancements for the jig design or testing conditions to prevent cell damage. The model can be adjusted to simulate different temperature scenarios, allowing for a comprehensive evaluation of the jig’s response under varying conditions.
- Post3D-skrivare till sjöss - En studie om möjligheten att använda additiv tillverkning ombord på fartyg(2013) Karlsen, Rikard; Stubbe, Paul; Chalmers tekniska högskola / Institutionen för sjöfart och marin teknik; Chalmers University of Technology / Department of Shipping and Marine TechnologyThis bachelor thesis examines and discusses the possibility of using 3D printers onboard sea going vessels. The study explores additive manufacturing where objects are built up by materials in a layer by layer principle. The basis for this work is a literature study and interviews conducted with experts in businesses and faculty in the field. This paper describes the concept of additive manufacturing (AM) and the benefits the technology provides compared to traditional manufacturing. The project shows the applications currently available in AM and potentials and problems in the field. The various techniques of AM is presented and also an examination of how the design is implemented through digital modeling. The study shows that for smaller side project, an extrusion based AM machine for plastic could be a valued tool for a committed crew. The thesis also shows that it is possible to produce spare parts onboard, but an AM system onboard is not considered to be a realistic solution regarding replacing the spare parts inventory or the crafting of tools. The thesis shows that the advantage of an AM system today is that it can offer increased availability by manufacturing parts that makes the organization less dependent on delivered parts during port visits. Moreover, it is possible that work with AM technology can be positive for ingenuity and problem solving.
- Post7DCT Transmission efficiency optimization: Design and simulation of oil traps that reduce the churning los(2020) Forsström, Birk; Minar, Matus; Chalmers tekniska högskola / Institutionen för mekanik och maritima vetenskaper; Andersson, Sven B; Johansson, RobertThe automotive industry is undergoing a big change when switching from building combustion engine cars to electric powered cars. With the big limitation of range that comes with using battery to store energy there is an even greater need in finding ways to improve the efficiency. Together with CEVT (China Europe Vehicle Technology), this master’s thesis purpose is to make an improvement of the gearbox that lower the torque that is required to rotate it. To verify the results a prototype is built with materials available in the company’s workshop and investigated if it can withstand a test in a testing rig. With the use of CFD-analysis (Computational Fluid Dynamics) the lubricant of the gears is investigated through a simulation of a benchmark. The aim was to find areas where reduction of churning losses can be made with the use of a new part that is created in CAD (Computer Aided Design). Inspiration for these improvements is found in previous studies made by employees at CEVT and at rival companies. The process of creating a new part is iterative and performed with rough simulations before a comprehensive simulation is made that can be compared with the benchmark. Through the benchmark simulation it was concluded that the differential gear stands for most of the churning losses along with the output shaft above it. A new part was created that protects the top shaft from being hit by incoming oil transported by the differential, it also collects the oil in two containers for further redistribution. These changes resulted in a decrease in drag torque generated by the oil of 16.3% at 50km/h and a trend of larger reduction at higher speeds. For a prototype build, experimental tests were conducted on the ABS-plastic available at the company. It was concluded that the plastic would withstand the heat and oil inside of the gearbox and afterwards a prototype was built for future testing. In the end of the study it was concluded that oil can be collected in the upper regions of the gearbox by taking care of the splash from gears. This along with protecting gears from splash that hit them in the opposite direction of speed can reduce the churning losses by around 16%. With this knowledge a future work would be to investigate how to distribute this oil from these regions to where it is needed. By doing so, future development of gearboxes can be made around how oil is being transported by gears to benefit from these possibilities.
- PostA booklet for the mandatory Crowd and Crisis Management course – according to the STCW ’95 Convention(2010) Magnusson, Tobias; Lewenhaupt, Ian; Chalmers tekniska högskola / Institutionen för sjöfart och marin teknik; Chalmers University of Technology / Department of Shipping and Marine TechnologyProblem: Only compendiums are used in the CCM courses. There is a lot of literature on crisis management and human behaviour, but the authors did not find any book combining these two subjects. Existing literature is either too extensive or not fully relevant for seafarers. Purpose: The purpose of this master thesis is to study theories related to crowd and crisis management and discuss them with course providers, course participants, authorities and specialists in the area. Further, the purpose is also, to use the result of the above mentioned study as a launch pad to start a writing process towards a booklet in Swedish on crowd and crisis management for seafarers. Completion of the writing process is outside the aim of this essay. The aim is that the booklet later on can be useful for students and seagoing personnel. Method: Interviews, literature studies and case studies. Results: The mandatory requirements for the Crowd and Crisis Management course are found in the Swedish Transport Agency (STA) TSFS 2010:20 Annex 18. In Sweden course providers have to be authorized by STA. At the time for this research there were six providers approved by STA. Through literature studies relevant theories in crisis management were found: Diffusion of innovations and emergency preparedness, The Situational Leadership model, the Fundamental Interpersonal Relations Orientation model, Wilfred Bion’s theories on group dynamics, Geert Hofstede’s Cultural Dimensions and Recognition-primed decisions (RPD). The interviews showed that most of the course providers discussed situational leadership in their courses in one way or another. Course participants asked for more education in leadership and clear authoritative leadership, some of the interviewees asked for military inspired leadership training. There were also a demand for communication theories and theories on human behaviours. When the course providers were asked what they think a book about CCM shall include, they answered: stress and crisis reactions, International Safety Management (ISM) for preparedness, mental preparedness, reaction during an accident, awareness for group dynamics, human behaviour, communication and procedures for tactical thinking during stress. The views of the providers are thus more or less the same as the course curriculum provided by the Swedish Transport Agency.
- PostA case study about complete battery implementation onboard tugs(2018) Höckersten, Andreas; Nilsson, Adam; Chalmers tekniska högskola / Institutionen för mekanik och maritima vetenskaper; Chalmers University of Technology / Department of Mechanics and Maritime SciencesNew regulations are presented as a reaction to the shipping industry`s contribution to the global warming and emission of other pollutants. New sustainable solutions to energy production onboard ships are therefore needed. Battery power have been presented as one of the solution to lower dangerous emissions from burning fossil fuels in combustion engines. Fully electric cars powered by stored energy in batteries already exists and can be seen as an emission free solution. However, the concept is not common within the shipping industry, even if there is a rising interest in the subject. This paper is presenting that vessels with a fixed route such as ferries have showed the biggest interest in adapting this concept with battery. However, hybrid systems are more common in the shipping industry but could act as an important first step when going from diesel to battery. The purpose of this thesis is to investigate the environmental and economic benefits and disadvantages of converting a hybrid tugboat to a fully electric vessel, how much the local society, close to where the vessel operates have to gain on this retrofitting to a fully electric propulsion line and what the difference in cost between the hybrid propulsion line and the fully electric. The results are achieved with help of scientific literature and calculations with information from the company that owns the vessel we are investigating for this case study. The results of converting a hybrid vessel to a fully electric vessel with a battery energy storage system onboard shows that the benefits for the local area where the ship is operating, regarding costs for health issues related to harmful emissions of NOx (Nitrogen Oxides), SOx (Sulphur Oxides), PM (Particular Matter) and VOC (Volatile Organic Compound), are high. Considering the results when calculating the global effects on CO2 (Carbon dioxide) emissions, the same benefits with the energy system change is not as great since the result show a very little difference, depending in which country the electricity is produced in. Regarding the production of the li-ion (Lithium-Ion) batteries, the calculations are showing that only a fraction of the total CO2 emissions from the battery are coming from the production.
- PostA case study about Covid-19’s effects on liner shipping - The impact of the Covid-19 pandemic on outbound and inbound flows between Sweden and China(2021) Olsson, Sten; Yang, Richard; Chalmers tekniska högskola / Institutionen för mekanik och maritima vetenskaper; Larsson, Martin; Ringsberg, HenrikNo one expected the virus Covid-19 to affect the whole world. Most countries initiated lockdowns, quarantine and restrictions. E.g., China shut down their exports. However, Sweden adapted another strategy, instead of proceeding to lockdowns they relied on social distancing. Furthermore, the strategy benefited the Swedish economy and shipping lines operating in Sweden. Delimitations as routes, vessels, industry, type of study, time span and unit carrier were included. A literature study was conducted to form a theoretical basis for the thesis’ research questions. Additionally, a qualitative case study was conducted. The case study is based on semi-structured interviews and internal documents. This thesis attempts to examine three research questions, all based on the novel Covid-19 virus. ● How was the Covid-19 impact compared to other historical crises in terms of inbound and outbound flows? ● How has the Covid-19 pandemic affected the inbound and outbound flows of containers for shipping lines between China and Sweden, comparing the first and second half of 2020? ● How has the pandemic and its side effects affected the relationship between shipping lines and their customers? Regarding the first research question, the thesis came to the conclusion that there was not much similarity from historical events alike Covid-19. SARS occurred 2003 and only spread in East Asia. The differences in virus structure and geographical spread, as well as the lack of published or documented studies made conclusions of similar pandemics uninterpretable. Compared to the financial crisis, Covid-19 had few similarities. E.g., economic decline. However, the financial crisis took years for the global economy to recover from. Whereas, Covid-19 only took months. Regarding the second research question, it was obvious from the case study that the Swedish import was declining in the first half but recovered and surged in the second half. The Swedish export was steady the whole year. Finally, the case study found that the sudden increase in demand for transport exceeded the available containers. which bottlenecked shipping lines and the cargo owners’ supply chains. Despite this, the cargo owners and other customers of shipping lines were overall understanding of the disruptions caused by the pandemic.
- PostA CFD Analysis and Aerodynamic Comparison of Two Silver Arrows(2013) Ejresjö, Fredrik; Kange, Björn; Kjellström, David; Lindbäck, Mathias; Lundell, Stefan; Mybeck, Markus; Chalmers tekniska högskola / Institutionen för tillämpad mekanik; Chalmers University of Technology / Department of Applied MechanicsDuring 1933 to 1939 the sport of racing was completely dominated by the German manufactures Auto Union (known today as Audi) and Mercedes-Benz. With their superior race cars (named Silver Arrows after their shining bodies and blistering acceleration) the German racing teams were victorious in most of the Grand-Prix races during this period. The cutting edge technologies in these cars remain a source of inspiration for new Mercedes-Benz and Audi cars to this day. The body shape of the Silver Arrows reveal that a great deal of time was spent optimizing the cars from an aerodynamic point of view, with the purpose of minimizing flow resistance. However, the term “downforce”, which is central to design of modern race cars, was relatively unknown. Compared to the modern use of powerful computers, the possibility of making flow calculations was also very limited at the time. In this project, two Silver Arrows (Auto Union Type C and Mercedes-Benz W25) have been analyzed from an aerodynamic point of view with the main purpose of calculating lift and drag force. No CADdata was available for the cars which is why they have been modeled from scratch. Two CMC-models of the cars, scaled 1:18 were used as a baseline. These were laser scanned at Volvo Cars. Curves for both cars have been extracted from the scanned data. With the profile curves as support, the bodies of the cars were modeled in CATIA V5 and from separate measurements the details of the cars were modeled. The final CAD-models were transferred to ANSA where initial surface meshes were generated. In STAR CCM+ high quality CFD-compatible surface meshes were generated. Volume meshes were then constructed and used in the simulations. The simulations were run with the boundary conditions rotating wheels and a moving ground at 80km/h. Pitch and yaw angels were set to 0⁰. The results of the simulation were analyzed and visualized using the post processing tools in STAR CCM+. The results of the simulations show that the Silver Arrows have good basic shapes from an aerodynamic perspective, but their design also include several drag-producing features and details. Both cars have little to no downforce, which was expected due to the lack of knowledge about the phenomenon at the time. Overall, the group is content with the result of the project and considers the objectives to be fulfilled. However, because of the emphasis on the pre processing, some planned parts needed to be excluded from the project. Originally, CFD-simulations were supposed to be performed in two different velocities. Also, wind tunnel testing of the CMC-models was to be carried out, and the obtained results were to be compared with the simulations. These parts would have contributed to a more thorough analysis of the Silver Arrows, why the project group recommends further tests and simulations.
- PostA CFD Investigation of Sailing Yacht Transom Sterns(2014) Allroth, Jens; Wu, Ting-Hua; Chalmers tekniska högskola / Institutionen för sjöfart och marin teknik; Chalmers University of Technology / Department of Shipping and Marine TechnologyThe objective of this thesis was to investigate whether the hydrodynamic performance of the wide, box-shaped transoms that have become very popular on modern performance cruisers is better than the performance of the more conventional, less wide, rounder transoms. The investigation of the hydrodynamic performance was evaluated with the aid of computational fluid dynamics using the Reynolds Average Navier-Stokes (RANS) viscous solver SHIPFLOW 5.0 with Volume of Fluids method surface capturing (VOF). First part of the study was to conduct verification of the software using the Least Square Root method. Second part was to make a validation of the software where Computational Fluid Dynamics (CFD) results were compared to experimental data from towing tank tests of Delft Systematic Yacht Hull Series (DSYHS) hulls. In the third part an average modern performance cruiser was designed to later be used as a base line for a systematic transom geometry variation study. Twelve hulls were created with varying transom size and shape. Each hull was tested in four conditions; upright and heeled condition at Froude numbers 0.35 and 0.60. Finally the results from the CFD computations were used to set up a simple upwind-downwind race to distinguish which hull that had the best overall performance. In the upwind-downwind race the round transoms performed best for the three fastest transom sizes. The fastest hull around the course has an immersed transom ratio (At/Ax) of 0.16 and it is 1.9 % faster with round transom than with boxy. The study has led to better understanding of the relation between hydrostatic and hydrodynamic resistance at high Froude numbers where the gain from a big immersed transom area is larger than the loss from increased transom resistance. Also, the influence on wave resistance from the curvature of the water and buttock lines has been clearly illustrated. For low Froude numbers, where the transom is wetted, the effect from viscous pressure resistance, base drag, has been pinpointed.
- PostA CFD Investigation of SailingYacht Forebodies in Head Seas(2015) Kostalas, Konstantinos; Pluto, Adam; Chalmers tekniska högskola / Institutionen för sjöfart och marin teknik; Chalmers University of Technology / Department of Shipping and Marine TechnologyThe objective of this thesis is to investigate the hydrodynamic performance of a modern 41 feet sailing yacht by comparing the performance values acquired from simulations for different forebody geometry designs on the yacht. The particulars such as length, beam, displacement and prismatic coefficient are kept as similar as possible for all hulls. The resistance of the different designs are tested in flat water and in tests with waves. The set up for the waves is made with data taken from Svenska Björn; which is a caisson lighthouse in the Baltic Sea. The wave lengths tested in this study includes lengths of 12.5m, 25m and 34.5m and the yachts are run in straight head sea. The encounter frequency for the 25m wave matches the natural pitch frequency of the yachts. To evaluate realistic upwind condition, for cruising and racing, tests with a heel angle of 20o are additionally performed. All hulls are tested at Froude number 0.35 in the conditions described in the previous paragraph. This investigation is made with the aid of CFD using Unsteady Reynolds Averaged Navier-Stokes (U-RANS) equations integrated in the solvers provided in Star CCM+ software. Also, Volume of Fluids method for surface capturing is used. At the start of the study a verification of the software is made with the use of Least Square Root method. Then, a validation of the CFD results from the software is done by a comparison with data from towing tank tests from Delft Systematic Yachts Hull Series hull. In total three hulls are tested with a systematic forebody geometry variation of shape. The main result of this study is a better understanding of how the forebody design of a sailing yacht affects the performance. The study is done at high Froude number, where the gain from having a sharp and pointed entry angle and then diving into the water is larger than having volumes in the lower part of the bow. Having a tumblehome design that prevents the yacht from diving into waves gives calmer motions but higher resistance. However it is important to conclude that the drag, pitch and heave for all yachts are close and a definite winner hull is difficult to name because some of the three yachts are better than the other in certain conditions. Nevertheless, the best design overall is the hull with sharp entry angle and flare.
- PostA combined numerical and statistical approach to crack propagation modeling and prediction of crack propagation rates(2012) Rembeck, Martin; Sjöblom, Anders; Chalmers tekniska högskola / Institutionen för tillämpad mekanik; Chalmers University of Technology / Department of Applied Mechanics
- PostA comparative study on the modeling of matrix cracking in fiber-reinforced polymer laminates under transverse compression - XFEM versus a smeared crack approach(2016) Pourbahaaddini, Ershad; Simonsson, Philip; Chalmers tekniska högskola / Institutionen för tillämpad mekanik; Chalmers University of Technology / Department of Applied MechanicsAs the number of applications for fiber-reinforced polymers (FRP) is growing, the importance of understanding the failure behavior of this material is rising. This is merely conceivable by developing precise computational material models, which saves time, material, and energy. In general, the polymer matrix is the constitute with the lowest strength against failure in a FRP; hence the matrix requires additional attention especially under transverse compression where it is considered as the principal load carrying component of the FRP. In the present work, a comparative study on the modeling of matrix cracking in FRP laminates under transverse compression is carried out. To do so, an eXtended Finite Element Method (XFEM) approach is developed for discrete crack modeling, and the conventionally used smeared crack approach is applied via an existing Abaqus/Explicit implementation for continuum crack modeling. The comparison of the results illustrates that despite different kinematics behind the models, they both successfully predict a near identical material degradation and energy dissipation in the material response, but with differing predictions when considering frictional tractions and the predicted maximum stress levels. XFEM is established to be mesh-objective and the smeared crack method predicts the material response optimally when the mesh discretization is one element per ply with reduced integration excluding non-linear geometry effects. Moreover, the wedge effect described by geometrical deformation is distinctly represented as cracks are studied explicitly in XFEM, which provides the possibility of further study for inter-laminar effects such as delamination, crack propagation and crack migration. Key words: XFEM, smeared crack model, progressive damage analysis, transverse compression, friction, fiber-reinforced polymer
- PostA comparison of elastic mooring systems for floating wave energy converters(2020) Chen, Ho-Ann; Chalmers tekniska högskola / Institutionen för mekanik och maritima vetenskaper; Ringsberg, Jonas; Ringsberg, JonasWave energy is a widespread and abundant source of renewable energy, yet the technology of harnessing energy from waves is still in the pre-commercial stage. One of the key challenges in the development of wave energy converters (WEC) technology is to ensure the long-term performance and reliability of the mooring system, which must be designed to survice under cyclic loading, not fail due to fatigue, at a commercially competitive cost. This thesis takes WaveEL, a heaving point-absorbing WEC developed by Waves4Power, as the reference case to investigate the performance of WEC systems with different elastic mooring systems in regards to fatigue life and power absorption. As the electricity production of the heaving point-absorber WEC relies on the cyclic heave motion of the WEC device, the long-term deployment of the WEC systems under irregular ocean loads poses high fatigue damage on the mooring lines. The snap loads that act on the mooring lines also decrease the mechanical life of the mooring system. Studies have shown that by adding tether components to the mooring system, the fatigue life of the system can be increased, thus making the WEC systems more commercially feasible. A tether component is a mechanical system that reduces the responding force range and absorb the snap loads in mooring lines. It is this thesis’ objective to develop numerical models to represent tether components, and to evaluate its impact on the WEC performance by integrating the elastic tether component into the mooring system. This thesis investigates two mooring configurations: a 3-leg mooring system with floating buoys between the WEC device and the anchor to decreases the stress loading on the mooring lines, and a 2-leg mooring system with a deeper design water depth so that the system can benefit from the elasticity of the mooring lines. Comparisons are made between the two original mooring configurations and the same mooring setup with the tether component implemented. Coupled hydrodynamic-structural simulations are carried out with different mooring configurations under operational loads. The heave motions of the WEC device and the force response in the mooring lines under operation conditions are obtained from the simulation results and used to calculate the fatigue life of the mooring system and the absorbed power of the WEC system. It was found that the tether component greatly improves the fatigue life of the mooring system, whilst not negatively affecting the power absorption.
- PostA comparison of finite element formulations for analysis of the converting process of packaging materials(2015) Lindberg, Susanna; Sandvik, Patrik; Chalmers tekniska högskola / Institutionen för tillämpad mekanik; Chalmers University of Technology / Department of Applied Mechanics
- PostA Comparison of Leisure Craft Emissions(2022) Börjesson, Joel; Larsson, Sebastian; Chalmers tekniska högskola / Institutionen för mekanik och maritima vetenskaper; Eliasson Ljungklint, Johan; Isaksson, MatsThis thesis is evaluating if SCR’s (Selective Catalytic Reduction) and DPF’s (Diesel Particulate Filter) are valuable options for leisure boats in the Swedish leisure boat fleet, since the current regulations regarding emissions are lean compared with the road traffic regulations. This is done by calculating the cost for NOx and PM2.5 in Sweden, then calculating over how many diesel engines there are in the Swedish leisure boat fleet times the cost of a SCR and a DPF. The result was that SCR’s and DPF’s are more expensive than the emissions.
- PostA Computational Approach to Include the Effects of Elevated Temperatures in Finite Element Simulations(2010) Brommesson, Rebecka; Ipsen, Nils; Chalmers tekniska högskola / Institutionen för tillämpad mekanik; Chalmers University of Technology / Department of Applied Mechanics