Industri- och materialvetenskap (IMS) // Industrial and Materials Science (IMS)

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A method for characterization of elastic in-plane material properties of continuous fiber reinforced polymer tubes
(2020) Bredenberg, Tobias; Borenius, John; Chalmers tekniska högskola / Institutionen för industri- och materialvetenskap; Blinzler, Brina; Fagerström, Martin
As fiber reinforced polymers are becoming commonplace in more and more industries every year, the need for accurate engineering tools connected to these materials arises. In several industries tubular composites are a staple, however the manufacturing methods used for tubular laminated composites do not transfer well into making test coupons for traditional material testing. This creates the need for a method where material properties can be derived from testing of tubular specimen. This thesis therefore aims to create a method for characterizing the elastic in-plane material properties of a tubular fiber reinforced composite. The method uses physical tests of two specific lay ups in order to isolate and derive the in-plane material properties one by one. The results of this thesis shows that the material properties derived from the test data is within close proximity of other material systems using the same fibers, which suggests that a promising first step has been taken. However, there is a need for validation in order to finalize the accuracy of the model. Furthermore a number of practical suggestions are made to reduce error sources for future testing.
A Post-Processing Automation Tool for Finite Element Analysis on Airplane Fuselage
(2024) Wennersten, Jacob; Chalmers tekniska högskola / Institutionen för industri- och materialvetenskap; Chalmers University of Technology / Department of Industrial and Materials Science; Larsson, Fredrik; Pouya , Shahbabai; Auth, Kim Louisa
The work in this project revolves around investigating how automation can be used to improve the post-processing efficiency and quality when analyzing and sizing an airplane structure. The project is carried out at Heart Aerospace, based in Gothenburg, Sweden who is currently working on the design of an electric 30-seater regional aircraft for short travel called the ES-30, whose main engines are powered by batteries. A program called ”H-ADAPT” (Heart Aerospace Design Analysis & Post-processing Tool), which serves as a tool with a graphical user interface, was created and used to perform the necessary analytical strength and stability analysis for the stringers and skins of the airplane fuselage. The program imports the large data files generated in the finite element analysis and summarize the different load cases, checks margin of safety and suggests optimized geometries for the elements. The user can edit the geometrical and material parameters of the elements, save and load the progress, as well as export the results to an Excel table for documentation. Validation of the analytical solutions is performed through hand-calculations, as well as comparison against a finite element analysis, for certain elements. Unfortunately, the global finite element model lacked some geometrical information, and the user must manually give this input to the program for every element. This disrupts the automation and is time-consuming, which was one of the main purposes of the program to optimize. However, in the future if the geometrical information has been added, the program provides useful analysis and an easy-to-use graphical user interface to help with the sizing of the elements. It was also created in such a way that more complex analysis can be added, as well as more parts of the airplane.
Advancing in vitro models for high-throughput 3D bioprinting
(2024) Moliner Carrillo, Laia; Chalmers tekniska högskola / Institutionen för industri- och materialvetenskap; Chalmers University of Technology / Department of Industrial and Materials Science; Klement, Uta; Godoy, Paulo
Three-dimensional in vitro models have been proposed as a solution to reduce the high failure rates in clinical trials. Even so, there is a clear lack of techniques capable of creating these cell culture models in a straightforward, cost-effective, and rapid manner, enabling researchers and companies to perform large-scale screenings. One promising candidate to address this need is three-dimensional bioprinting, a technology that can generate viable constructs using biomaterials, cells, and biological molecules. In this context, CELLINK has developed the BIO CELLX biodispenser, which combines liquid dispensing and bioprinting in a highly automated system, significantly reducing human intervention. Despite its potential, it remains uncertain whether this technology can effectively accelerate the laborious processes currently associated with preclinical stages. This study evaluates the key factors necessary for the implementation of BIO CELLX as a high-throughput bioprinter and explores workflow optimizations that could enhance both the dispensing process and the resulting outcomes. The workflow has been validated for new software release and hardware modifications to achieve full functionality, demonstrating high droplet accuracy and uniform mixing. Results indicate that increasing the number of mixing cycles does not negatively impact cell viability; on the contrary, it enhances homogeneous cell density and overall cell viability. Additionally, the performed experiments suggest that the usage of nozzles with larger diameters, along with adapted dispensing parameters, can improve droplet centralization. This project provides an in-depth analysis, highlighting crucial elements required to achieve a precise and efficient three-dimensional bioprinter.
An investigation into the predictability of membrane durability in Proton-exchange membrane fuel cells
(2023) Lindqvist, Justus; Chalmers tekniska högskola / Institutionen för industri- och materialvetenskap; Chalmers University of Technology / Department of Industrial and Materials Science; Ekh, Magnus; Toth, Gabor
This work addresses the issue of lifetime of the proton exchange membrane, one of the vital components of Proton exchange membrane fuel cells, with a focus on its mechanical and fatigue response under typical operating conditions. Although the durability of a complete system can only be defined by investigating each of its constituent materials and components, both separately and in combina tion, the polymer membrane that acts as a gas separator and a solid electrolyte is at the heart of a fuel cell’s performance. The mechanical stability of this membrane is the most pressing issue for efficient commercialization of Hydrogen fuel cells, and a large hindrance for achieving longer lifetimes of hydrogen fuel cells is the lack of understanding of its degradation and eventual failure during operation. To properly evaluate this one needs to a.) determine the in-situ mechanical stresses that develop in the membrane, and b.) to evaluate the effect of the mechanical stress response on the membrane fatigue life. Both of which will be covered in this thesis.
An Investigation of Finite Element Models of Roller Bearings
(2021) Rahani, Ramin; Chalmers tekniska högskola / Institutionen för industri- och materialvetenskap; Larsson, Fredrik; Norberg, Sven; Koch, Jonas
Increasing demands on the design of transmissions for heavy trucks include higher loads, longer lifetime and reduction of noise. To design gearboxes with aid of the finite element method it is important to obtain precise force transfer and thus accurate stress distribution close to a roller bearing seat. Therefore, stable and numerically accurate bearing models are necessary. The purpose of the thesis is to accurately describe the local or average behavior of roller bearings and to present finite element results of the required detail level close to the bearings. It entails calibration of bearing models with results from commercial bearing analysis tools. The objectives are to find improved ways to model the change from contact to play between the rollers and the rings, study stiffness of different bearing distribution models, investigate mesh-sensitivity and implement axial stiffness in the bearing models. The Abaqus finite element software is used to predict the behavior of roller bearings. The analysis includes modelling of bearings and execution of load steps. Matlab scripts are used to post-process the bearing models and evaluate them with bearing analysis tools. The commercial software Shaft and Bearing Analysis (SABR) is used to create bearing reference models. An optimization process is implemented with Matlab to automate the convergence process of SABR. The developed model with GAP-elements agrees with the reference model in the same way as the model using nonlinear springs. Bearing models with different distribution loads show increasing deformation as the ring thickness increases. For bearings of extreme sizes, it is found that small rollers are slightly more flexible and large rollers a bit stiffer. The mesh study demonstrates that the relative size difference between adjacent elements does not affect the stiffness. When the spring spacing is equal to or smaller than the element size, the bearing stiffness is not affected by the spring spacing or the element size. The deflection of the bearings is influenced by the axial play. Axial stiffness should be high and does not give a large contribution to the total deflection. The results from the Abaqus bearing models provide good accuracy to model pure radial, pure axial and a combination of radial and axial loads along with bearing misalignments.
Cold Spraying as a Repair Method for Crankshaft Journals
(2023) Blomgren , Matilda; Gunnarsson, Stefán; Chalmers tekniska högskola / Institutionen för industri- och materialvetenskap; Chalmers University of Technology / Department of Industrial and Materials Science; Persson, Christer; Persson, Christer; Sritharan, Venkatesh; Höckefors, Malin
In this study, the feasibility of repairing crankshaft journals with cold spraying was investigated. It was researched through a systematic literature study, and contact with cold spraying companies, with the main focus on the parameters affecting the coating properties; surface hardness and adhesive strength, machinability of the cold sprayed coating, and limitations to the shape and size of repair. The most critical factor affecting the deposit hardness and adhesive strength is the impact velocity. The size and shape of the repair are limited by both the cold spraying process capacity and the crankshaft design. The design elements limiting shape and size are the critical zones; radiuses, oil holes, and the lower part of the pin journals. Machining the cold sprayed coating is possible, however, it can be problematic due to the critical zones and simultaneous machining of two materials. The cold spraying companies, which differ by the pressure system they specialize in, have recommended materials for the repair, only the recommendation from the high pressure cold spraying company can fully meet the design requirements. For low-pressure cold spraying, three feedstock materials have been recommended, Ni/Zn, Al/Zn, and Cu/Zn composites. For high-pressure cold spraying, two feedstock materials have been recommended, a tungsten carbide with nickel and cobalt, and a tungsten carbide with stainless steel. The latter can be further developed to meet the crankshaft requirements. The recommended materials must comply with Volvo’s list of substances. The recommended feedstock materials include substances on the lists. The materials shall therefore be assessed if allowed to be used, if not it must be considered if other feedstock materials are available, or if the material open for development can be optimized with the lists in mind. A detailed recommended plan of testing is presented with the purpose of defining the unknown parameters of the coatings; compatibility and strength, and to verify that the coating meets all journal requirements.
Coupled Multi-Physical Processes in Structural Battery Composites
(2023) Dahlberg, Clara; Chalmers tekniska högskola / Institutionen för industri- och materialvetenskap; Chalmers University of Technology / Department of Industrial and Materials Science; Asp, Leif; Xu, Johanna
This thesis examines the change in open cell potential when a structural battery, at a constant state of charge, is exposed to a tensile load. A structural battery full-cell was manufactured. It was electrochemical cycled before being clamped into a tensile machine. In the tensile machine, a potentiostat was connected to the cell which measured the Open Circuit Potential (OCP) while the cell was exposed to a varying tensile load. Two of the three cells used during the experiment were fully delithiated and the third was fully lithiated. The coupling factor was also calculated to gain an understanding of how the cell was affected by different states of charge and different loads. The results show that when the load increases, the cell potential decreases, but when the load decreases, the potential increases. This response is immediate for all three cells and the response of the potential is not strain rate dependent. The state of charge shows that a fully lithiated cell has a lower coupling factor than a fully delithiated cell. This is in accordance with previous experiments in the open literature performed on the half-cell as the cell shows a similar behavior, but the coupling factor is higher for the delithiated cell than for the lithiated cell. The conclusion that can be drawn after performed experiments is that the model used works to validate and investigate the behavior of the coupling factor in the full-cell under different states of charge and varying tensile loads.
Creating an algorithm for hard landing detection using aircraft flight data
(2023) Gunnarsson, Jacob; Angervall, Fredrik; Chalmers tekniska högskola / Institutionen för industri- och materialvetenskap; Chalmers University of Technology / Department of Industrial and Materials Science; Ekh , Magnus; Cetin, Fatih; Scott, Alan
Aircraft hard landings can cause damage to a landing gear or aircraft frame which in turn can cause a critical failure. As such, methods to detect hard landings have been created in different ways, for example, based on a pilot’s judgment or adding various sensors to a landing gear. The aim of the thesis is to identify existing hard landing detection methods and compare them in order to find a suitable concept to further evaluate in regards to application in a commercial aircraft. The literature review of current hard landing detection methods and interviews with aerospace engineers showed that using flight data parameters was a promising concept. A load predicting algorithm was created and tested in order to evaluate the concept. To make the algorithm, a CAD model of an arbitrary main landing gear (MLG) was first built for implementation in a multi-body dynamic model. This was then used to create a database of landing gear responses for different drop test simulations. Through sweeps over relevant parameters, longitudinal and normal tire forces were obtained for a spread of drop tests. The database was then used in the algorithm, based on an interpolation scheme, to give tire longitudinal and normal forces as an output at three critical instances. The outputs could in the future be used to decide whether a hard landing has occurred or not by comparing them to limits. It became evident that a good database is necessary for the algorithm to provide proper force estimations. The algorithm was accurate for an assumed runway friction. However, for a lower friction, the estimated forces were inaccurate. An alternative method using the angular velocity of the wheel to estimate the longitudinal force independent of friction was tested. While simplifications were made, it was shown that the method gave better estimations for low friction. Using aircraft flight parameters for detecting hard landings was proved to be a concept with potential. For implementation in commercial use however, several points were identified as requirements for it to be a reliable method with high fidelity and functionality.
Critical plane approach to low cycle thermal fatigue of welds in exhaust manifolds
(2018) Alm, Jakob; Chalmers tekniska högskola / Institutionen för industri- och materialvetenskap; Chalmers University of Technology / Department of Industrial and Materials Science
Components in internal combustion engines are often subjected to temperature cycling that lead to low-cycle fatigue due to thermal expansion and contraction. Furthermore, these thermal loads may be multiaxial and non-proportional in nature which means that traditional fatigue evaluation methods are not sufficient. Welds constitute another complication since they are often more sensitive to fatigue damage than the base material. This is in large part due to the notch effect associated with the boundaries of the weld in addition to the presence of tensile residual stresses near the weld. At Volvo Cars, there is an interest in developing a new methodology for numerically evaluating the low cycle fatigue life of welds during thermal cycling. Methods that can account for non-proportional loading are of particular interest. One of the most prevalent methods for non-proportional multiaxial fatigue evaluation is the critical plane approach. Evaluating weld fatigue also requires treatment of the weld geometry to resolve the stress-strain gradients in the vicinity of the weld. This thesis explores the possibility of combining the critical plane approach with common weld modelling techniques to accurately model low cycle thermal fatigue. The Smith-Watson-Topper model using the maximum normal stress to the critical plane was chosen as the critical plane fatigue model and compared to a traditional strain-based fatigue evaluation methodology. Welds were modelled with shell elements, solid elements and with the effective notch method. Weld residual stresses were accounted for by considering them as a tensile mean stress combined with a mean stress correction. To assess and compare the methods, a welded exhaust manifold subjected to low cycle thermal fatigue was evaluated by using Finite Element Analysis (FEA). It was shown that both the critical plane approach and traditional strain-based fatigue evaluation offered a conservative fatigue life estimate compared to available experimental values. It was also shown that modelling the weld with shell elements resulted in fatigue life estimates within the margin of error for the experimental values. Using the effective notch method gave the lowest fatigue life estimate but the fatigue failure location was predicted to be the weld toe which corresponded with known failure locations from experimental testing. Mean stress effects were shown to have a negligible impact at the considered fatigue lives. It is important to note that further numerical and experimental validation is needed before deploying the methodology in an industrial setting.
Deep material networks for lead-free solder alloys
(2023) Juhlin Onbeck, Gustav; Chalmers tekniska högskola / Institutionen för industri- och materialvetenskap; Chalmers University of Technology / Department of Industrial and Materials Science; Larsson, Fredrik; Ruoshan Luo
In this report the Deep Material Network (DMN) method is applied to a microstructural model for SAC-305, SnAgCu with 3 weight percent silver and 0.5 weight percent copper, generated by a phase field simulation for spinodal decomposition. The DMN method homog enizes a heterogeneous microstructure for multiscale simulation purposes. Five microstruc tures from the phase-field simulations were generated, and for each micro structure a data set describing the homogenized elastic parameters was calculated. The data sets were generated using finite element simulations for each morphology. The DMN method is modified to use individual weights for each node and a bias, the modifications improved the accuracy of the network and brings the method more inline with conventional neural network structures. The new DMN method was evaluated on data sets for each of the individual microstructures and on combinations of multiple microstructure data sets. DMNs trained on data sets of multiple microstructures resulted in a much greater error than DMNs trained on individual data sets. The DMNs trained on a single microstructure reached a relative error of 2.5 - 3 %, whereas a DMN trained on a multi-microstructure set could at best reach an error of 11.5 %.
Design methods for high thermal efficiency load bearing inserts used in composite sandwich structures
(2019) Pandey, Jivatsha; Chalmers tekniska högskola / Institutionen för industri- och materialvetenskap; Chalmers University of Technology / Department of Industrial and Materials Science
Composite sandwich panels with foam cores are gaining importance in the automotive industries due to their lightweight design. The panels are subjected to localized loads with the help of inserts. These load carrying inserts cause an adverse effect such as stress development, thermal losses etc., in the panels. In this thesis, a special engineering design is considered to help improve the stresses developed in the core and reduces the thermal losses in the sandwich panel. The panel is assumed to be perfectly bonded to transfer the loads. Thin face sheets with different materials such as aluminum, carbon fibre (CF) and glass fibre (GF) along with different thick foam core material such as extruded polystyrene (XPS), Polyethylene terephthalate (PET) and Polyvinyl chloride (PVC) are investigated. An analytical model to calculate the thermal conductivity across the sandwich panel with insert is developed using Fourier heat transfer law. An FE model of the sandwich panel with insert is also developed to analyze the strength and heat flux for different geometry within the panel. Finally, an optimization toolbox is developed based on the constraints and objective.
Detecting falls and poses in image silhouettes
(2011) Schräder, Niklas; Chalmers tekniska högskola / Institutionen för material- och tillverkningsteknik; Chalmers University of Technology / Department of Materials and Manufacturing Technology
About one third of all people aged 65 and above will accidentally fall during one year. A fall can have severe consequences,such as fractures, and a fallen person might need assistance at getting up again. A lot of research has been dedicated into the development of automatic fall detection methods during the recent years. These automatic methods are created to detect falls so an alarm can be raised and help can come. In this thesis, a part of a fall detection system for a household robot aimed at helping the elderly is developed. The system is able to classify human pose from a silhouette in an image. By associating the pose “lying down” with a fallen person, the system can be used for fall detection. The algorithm is based on an image analysis feature called shape contexts. These shape contexts describe distributions of edge points by binning them into polar histograms. Altough the dataset used for training contains falls in many difficult angles, the algorithm classifies falls correctly for 97 % of a set of unseen images.
Development of a Recommendation Tool Identifying Environmental Sustainability Potential of Additive Manufacturing
(2023) Karlsson, Emma; Simonsen, Alexandra; Chalmers tekniska högskola / Institutionen för industri- och materialvetenskap; Chalmers University of Technology / Department of Industrial and Materials Science; Despeisse, Mélanie; Hryha, Eduard
This master’s thesis aims to support Volvo Penta in reaching their sustainability goals by exploring the environmental sustainability advantages of metal additive manufacturing (AM). This is achieved by creating a recommendation tool, which intends to identify the environmental sustainability potential of AM for components. The project methodology consisted of three phases: exploration study, development of the recommendation tool, and testing and evaluation. During the first phase, AM knowledge was obtained through a literature review and interviews. In the second phase, the structure, criteria, scoring and recommendations of the recommendation tool were developed. In the last phase, the usability and performance of the recom mendation tool were tested. The main result from the exploration study was the environmental sustainability advantages of AM identified for the product life cycle phases. Five component categories were created to capture these advantages, namely design and function, customisation or small series, material reduction, manufacturing process, and supply chain. The final recommendation tool consisted of three parts, one for briefly describing the components, one for eliminating non feasible components and one for evaluating the components. The elimination was based on requirements connected to AM buildability for binder jetting and powder bed fusion, while the evaluation criteria were based on the identified sustainability advantages divided into the component categories. The result of the recommendation tool is a mean score for each component category and corresponding recommendations. The usability test indicated that engineering judgement based criteria depend highly on the users’ perception and experience of AM and the component. The evaluation indicates a strong correlation between AM expert opinions and the recommendation tool results
Development of modelling and homogenisation procedures for stochastic tape-based discontinuous composites
(2022) Sjöberg, Jacob; Haglund Nilsson, Olle; Chalmers tekniska högskola / Institutionen för industri- och materialvetenskap; Fagerström, Martin; Fagerström, Martin
Conventional laminated composites have, due to their high stiffness- and strength-to-weight ratios, shown to be a viable alternative to metals in applications where lightweight structures are of essence. However, the current reach of conventional laminated composites is limited to certain industries and high-end products as a result of their high manufacturing cost. As a way to reduce cost while maintaining high performance, stochastic tape-based discontinuous composites (STBDCs) have emerged, offering a middle ground between the easy manufacturing of short fibre composites and high performance of continuous fibres composites. The irregular mesostructure and high interest from industries have increased the demand for efficient and predictive models (analytical and numerical) describing the mechanical response of this class of material. As a response to the increased interest, this project aimed to develop a method to predict the elastic properties of STBDCs, based on the mesostructural configuration and constituent properties (impregnated tapes and pure matrix). To replicate the complex material structure, a modular MATLAB code was developed as the core of the project. The MATLAB code takes the tape and plate dimensions, material properties, voxel resolution, etc, as inputs, then builds the material layer-by-layer by placing tapes at random positions and angles until the desired plate thickness has been reached. The developed algorithm allows tapes to form around each other (drape) to replicate the compression part of the real manufacturing process. The outputs of the code are, among other visualisations, a 3D-image of the material structure and Abaqus input files for the coming analysis. Based on the generated material structures, smaller statistical volume elements (SVEs) were extracted and used for the analysis. Nearly 400 SVEs of different dimensions from different samples were extracted and analysed to have a large enough sample size to account for the variability of the material. Computational homogenisation was used to determine the volume averaged in-plane elastic parameters. The homogenisation process was carried out by applying periodic boundary conditions (PBCs) to the SVEs using the Abaqus plug-in EasyPBC. The computational homogenisation was initially focused on a full 3D-model but as a subsequent step, the full 3D-model was reduced to a 2D-model by an intermediate analytical homogenisation process using classical laminate theory. A full 3D- and reduced 2D-model were generated for each SVE sample to allow a comparative analysis. Finally, experimental data of manufactured STBDCs plates was used as a comparison to verify the results of the numerical model. The study found that the voxel-based 3D-model and the developed methodology can be used to accurately evaluate the elastic properties of STBDCs. More specifically, the generated material samples and methodology used provided reliable results for all studied SVE dimensions, converging to elastic properties within one standard deviation compared to experimental tests. Furthermore, the reduced 2D-model showed a similar accuracy compared to the 3D-model while also requiring significantly less computational power, indicating that this is a reasonable simplification to make. It should be noted that the developed model is not a perfect representation of reality, simplifications had to be made to stay within the limitations of the project. As a consequence, the fibre volume fraction (FVF) of experimental data could not be reached, making the model slightly under-predict the elastic properties. With further improvements to raise the FVF, the data indicates that the model would produce more accurate results compared to experimental tests, thus being a reliable source material for future industrial use.
Development Process of Topology Optimized Casted Components
(2018) Kåmark, Nadine; Chalmers tekniska högskola / Institutionen för industri- och materialvetenskap; Chalmers University of Technology / Department of Industrial and Materials Science
Both weight optimization and casting as a manufacturing method is widely used in the industry today. Topology optimization, as a weight optimization approach, is used to design lighter and more competitive components. Meanwhile, casting is a time and cost-efficient manufacturing method with the capacity to create complex shapes. Today, castability is not taken into account until the end of the development process. When the design is adjusted to become feasible to cast, mass is added which does not necessarily contribute to improve the structural strength. Thus, the structure is no longer optimized. Casting simulations assist in evaluating castability, but generally require animations and pictures to be analyzed manually. At Volvo Cars and within the Re-OPTIC project founded via LIGHTer, there is an interest in finding methods to evaluate castability in the early phase of the development process. The purpose of this thesis is therefore to find a way of evaluating castability numerically, in order to be able to compare design concepts in the early phase of the development process. A process where optimization results can be casting-simulated, without manually realizing the design using CAD, is also presented in this thesis. Furthermore, the topology optimization manufacturing constraints member size control and draw direction are evaluated from a weight perspective, as well as a discretization improvement tool and the usage of two design spaces. This thesis is only considering the casting solidification process. The topology optimization work is carried out in the commercial software OptiStruct. The casting simulations is obtained using the commercial software Click2Cast.
Effect of Tool-Part Interaction in Composite Manufacturing Simulations
(2024) Tzanetou, Afroditi; Chalmers tekniska högskola / Institutionen för industri- och materialvetenskap; Chalmers University of Technology / Department of Industrial and Materials Science; Fagerström, Martin; Sibin, Saseendran
Carbon Fiber Reinforced Polymers (CFRP) are widely used across multiple industries, especially in aerospace due to their lightweight and superior specific stiffness and strength. Despite their advantages, their mechanical properties are significantly influenced by the manufacturing process, since factors as the curing process and tool-part interactions are critical in the development of defects like shape distortions. Examining the critical parameters of CFRP manufacturing process with a focus on of tool-part interaction, the main goal of this master thesis is the development of validated methods for Finite Element (FE) models to investigate the process-induced distortions and predict the tool effect on the processing. In the frame of this project, L-shaped CFRP components are manufactured and FE models are built-up in LS-DYNA simulating the curing and demolding process of the composites so as to predict the resulting shape distortions in terms of spring-in and warpage. The FE simulations are validated using measurements from the manufactured components, and the numerical results are analysed aiming to assess the impact of tool-part interaction on process-induced distortions. The goal is to determine whether this interaction significantly influences the distortions, justifying its consideration in future studies. The results of this master thesis indicate the importance of selecting a high-fidelity material model in numerical simulations, since linear material models poorly predict spring-in and warpage when compared to experimental results. Using a simplified composite constituent model, the FE simulation is inadequate for capturing the tool effect and the tool-part contact simulation becomes ineffective. Implementation of more efficient methods to numerically measure spring-in and warpage are recommended to enhance the FE validation process. Additionally, experimental results suggest that titanium tools induce more significant deviations from the flat composite surface than steel tools, while asymmetric laminates exhibit considerably higher warpage than quasi-isotropic and unidirectional ones. Based on these findings, a re-evaluation of the assumptions made in this study is also suggested, so as the FE simulations developed in this work can be recognised as a precise tool for accurate spring-in and warpage prediction.
Environmentally assisted fatigue in LWR - Development of a calculation tool
(2021) Skoglund, Annelie; Chalmers tekniska högskola / Institutionen för industri- och materialvetenskap; Josefson, Lennart; Magnusson, Robert
The ASME Boiler and Pressure Vessel Code [1] provide rules for the design and construction of class 1 nuclear power plant components. Current design of fatigue curves is based primarily on straincontrolled fatigue tests of small polished samples at room temperature in air but recent data from the USA and Japan demonstrate that the light water reactor (LWR) coolant has significant effects on the fatigue resistance of materials. The Nuclear Regularity Commission (NRC) has written a report, NUREG/CR-6909 [2] that reviews and quantifies these effects on fatigue life of typical reactor materials and proposes a method for establishing reference curves and environmental fatigue correction factors for evaluating fatigue life. The purpose of this project is to use the proposed influence in fatigue life, due to the environmental parameters, such as temperature, rate of strain, dissolved-oxygen and amount of sulphide in the LWR coolant environment, according to the NRC report [2] to calculate the environmental fatigue correction factor. If the fatigue correction factor becomes larger than 1, the fatigue usage factor will decrease. The fatigue usage factor is the number of cycles of a certain load divided by the total number of allowable cycles of the same load. In other words, if the fatigue correction factor is larger than 1, for example 2, the number of allowable cycles will decrease to half of the previous number of allowable cycles, i.e., the fatigue life of the specimen will decrease. The research is performed using the software ANSYS Mechanical Workbench [3] and PIPESTRESS [4]. In ANSYS an axisymmetric 2-dimensional model of a pipe is constructed. The load set is one single thermal transient which will, together with convection at surfaces cause a temperature distribution over time over the whole domain. This temperature distribution in turn will cause strains in the material. The strain rates and the temperature changes are then used to calculate the fatigue correction factor. The report contains the results of the fatigue corrections factors calculated for a single common thermal transient with different ramp times of the temperature load. The load is applied on a straight pipe with different thicknesses of a common reactor material. The results from ANSYS and PIPESTRESS are then compared. When studying a temperature decrease of the coolant from 290℃ to 20℃ it can clearly be seen that the fatigue correction factor increases when the thickness of the pipe increases in both PIPESTRESS and ANSYS but the values are always slightly lower in ANSYS. The result differs between the software when studying the ramping time dependence. In PIPESTRESS the worst scenario appears for the thicker pipes when the temperature is down to 20℃ in 10 seconds while 1 second is worse for the two thinner ones. In ANSYS on the other hand the worst case is 1 second ramping time no matter thickness except for 60 mm when 10 seconds is worse.
FE Modelling of Steel Blind Rivets for Strength, Fatigue and Crash Applications
(2018) Rydman, Siri; Chalmers tekniska högskola / Institutionen för industri- och materialvetenskap; Chalmers University of Technology / Department of Industrial and Materials Science
FEM the Wood Revolution In-depth FE-analysis of a wood-glue-steel joint in a wind turbine tower
(2019) Borglund Aspler, Emil; Jern, Linnéa; Chalmers tekniska högskola / Institutionen för industri- och materialvetenskap; Chalmers University of Technology / Department of Industrial and Materials Science
Modvion is a company that develop 150m tall wind turbine towers made out of modules of Engineered Wood Products (EWP), specifically Laminated Veneer Lumber (LVL). One of the big challenges in their design is the joining of the modules, which is the focus of this thesis. The joint design was given from the beginning along with physical test data from tensile tests performed at Research Institutes of Sweden (RISE). In this thesis a Finite Element (FE)-model of the joint was created, with the aim to replicate the response obtained from the physical tensile tests using simulations. The main goal was to use the FE-model in order to describe the inner mechanics of the joint. The joining of two LVL panels is made with Loctite CR 421 Purbond and a perforated steel plate. The joint and its materials are studied using physical testing and the commercial softwares ANSA as pre-processor, Abaqus Unified FEA as solver, and META as postprocessor. The material parameters for the wood given by data sheets provided by the manufacturer are compared to physical test data. Remaining material parameters and simulation parameters are calibrated through material validation and parameter studies. Finally a small study was performed on whether the joint can be improved by making modifications to the perforated steel plate. The effects of these modifications were studied in order to find the critical areas of the joint. The obtained results show that the number of holes in the steel plate are critical for the performance of the joint when it comes to its tensile strength. This is because the holes enables the glue to create adhesive anchors that facilitates the stress transfer from the glue to the steel. Since the steel plate is the component of the joint that can withstand the highest amount of loading, the efficiency of the stress transfer is crucial in order to prevent the glue from breaking entirely at relatively small loads, which would result in a lower ultimate tensile strength of the joint. Although, some insecurities remains in the implementation of the FE-model, the results in this thesis can be used as a foundation for future research on this topic.
Finite Element Model Calibration with Digital Image Correlation
(2018) Bergbom, Lotta; Chalmers tekniska högskola / Institutionen för industri- och materialvetenskap; Chalmers University of Technology / Department of Industrial and Materials Science
Finite Element (FE) models are widely used to predict the mechanical behaviour of materials and components when subjected to different loads. In the industry, this is a valuable way to reduce the number of physical experiments and, thereby, costs when developing new products. With many actors trying to become more material efficient, new materials with sometimes complex structures are employed or the limits of how much the material is loaded are pushed. As a consequence of this, the need for adequate and accurate material models in the FE modelling increases. Digital Image Correlation(DIC) is a non-contact measurement technique used to measure displacements and strains locally on a surface in space and time. The goal of this thesis is to use DIC data to calibrate some typical material models used in FE modelling. The value and potential of the proposed calibration method is evaluated. The work is performed in collaboration with Research Institutes of Sweden AB (RISE) who has extensive experience with physical experiments, modelling and DIC. As there already existed test results from tensile tests made of steel, these were used when developing the calibration method. For later applications more complicated material models are of interest but for concept testing, the choice of material model is less important and therefore the relatively simple linear isotropic elasticity and von Mises plasticity with linear hardening are chosen. The work was mainly divided into two parts. The first part consisted of examining the experimental data obtained from DIC as a means for pre-processing and analysis of the data quality. The second part of the work was concentrated on constructing FE models whose results could be compared to the available experimental data and to calibrate the material models by using an optimising method. In order to assess the calibration method and how it is affected by different prerequisites, different case studies were carried out. The aim of the case studies was to investigate how different assumptions of the material model and of the FE modelling affected the results and thereby also giving an indication of the calibration method’s robustness. This thesis therefore provides an idea of how this calibration method could work and what potential it has by showing some of the potential pitfalls to avoid when developing the method further. Since the developed method is material model independent, more advanced materials and models could be evaluated in the future.

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Browsar Industri- och materialvetenskap (IMS) // Industrial and Materials Science (IMS) efter Program "Applied mechanics (MPAME), MSc"

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