A new test method for measuring the shear strength associated with mode III delamination of paperboard is studied with the purpose of reducing the size of the test configuration. The method, which uses a split cantilever beam (SCB) specimen, measures the shear strength indirectly through the fracture resistance. The methodology is based on the double cantilever beam (DCB) specimen, used for measuring the normal delamination strength of paperboard. The study is based on finite element analyses, where cohesive elements are implemented for predicting the fracture response. An experimental evaluation of the test method was carried out in a pre-study conducted between Karlstad, Skövde and Lund University together with Tetra Pak. The experiments considered both the SCB-specimen and the standardised DCB-specimen, and for determination of the fracture behaviour the cohesive law presented by Tryding & Ristinmaa (2017) were considered. The result obtained from the experiments is used as a basis for evaluating the analyses. To model the fracture development, the relation presented by Tryding & Ristinmaa (2017) is implemented in the commercial finite element software Abaqus through a user-specified element. From the analyses of the DCB-specimen it is shown that through implementation of a specified cohesive law, it is possible to simulate mode I fracture development of paperboard in an accurate manner. The results for the DCB analyses correlate well with the experimental results. The result for the SCBspecimen shows a deviating behaviour from the experimental result by underestimating the shear strength. It is noted that the specimen is subjected to notable deformations in both the first shear direction and the normal direction, preventing pure shear loading from being obtained. Based on the analyses, it is indicated that the current test configuration does not obtain pure shear separation in mode III, and thereby underestimates the actual shear strength of the paperboard. It is also shown that reducing the specimen length with 400 mm has no significant impact on the properties related to the cohesive law. By altering the initial crack length, it is possible to further reduce the length of the specimen. However, to prevent development of unstable fracture, the length of the paperboard should exceed 300 mm. Alternating the crack length and the width of the paperboard also seems to contribute to lower displacements in the normal direction and provides a better fit with the experiments. Tryding, J. & Ristinmaa, M. (2017). Normalization of cohesive laws for quasi-brittle materials. Engineering Fracture Mechanics, 178, 333-345. doi:10.1016/j.engfracmech.2017.03.020 / En ny testmetod för att mäta skjuvstyrkan för modus III delaminering av kartong studeras i syftet att reducera testutrustningens storlek. Testmetoden, som använder sig av en delad konsolbalk (SCB), mäter skjuvstyrkan indirekt genom brottresistansen. Metodiken är baserad på det standardiserad konsolbalks testet DCB, var två balkar är sammankopplade och som används för att mäta delaminering styrkan i kartongens normala riktning. Studien baseras på analyser med finita element, var kohesiva element implementeras för att prediktera brottbeteendet. En experimentell utvärdering av testmetoden genomfördes i en förstudie mellan Karlstads, Skövdes och Lunds universitet tillsammans med Tetra Pak. Experimenten gjordes både för DCB- och SCB-testet, och för att utvärdera brottbeteendet användes de kohesiva lagarna som presenterats av Tryding & Ristinmaa (2017). De experimentella resultaten används som bas vid utvärdering av analyserna. För att modellera spricktillväxten implementeras de kohesiva lagarna i det kommersiella FEM programmet Abaqus genom ett användar specificerat element (UEL). Från analyserna av DCB-testet visas det att det är möjligt att simulera modus I sprickbildning i kartong genom implementering av en specifik kohesive lag. Simuleringarna av DCB-testet stämmer väl överens med de experimentella resultaten. Resultaten från SCB-analyserna visar däremot på ett avvikande beteende från experimenten genom att underskatta skjuvstyrkan. Det noteras i analyserna av SCB-testet att märkbara deformationer i både den första skjuvriktningen och normal riktningen uppkommer, vilket förhindrar att ren skjuvbelastning i modus III erhålls. Baserat på analysernas resultat indikeras det att den nuvarande konfiguration för SCB-testet inte ger ren skjuvbelastning i modus III och underskattar därför kartongens faktiska skjuvstyrka. Det visas också att en 400 mm reducering av SCB-geometrins längd inte har någon märkbar påverkan på de kohesiva egenskaperna. Genom att ändra den initiala spricklängden är det möjligt att ytterligare reducera SCBgeometrins längd. För att försäkra sig om att sprickas tillväxt förblir stabil bör däremot längden på kartongen överstiga 300 mm. Att minska den initiala spricklängden och bredden på kartongen verkar generellt bidra till lägre deformationer i normal riktningen och ett resultat som ligger närmare de experimentella. Tryding, J. & Ristinmaa, M. (2017). Normalization of cohesive laws for quasi-brittle materials. Engineering Fracture Mechanics, 178, 333-345. doi:10.1016/j.engfracmech.2017.03.020

Continued improvements in combustion processes, introduction of biofuels, decreasing fuel consumption and increasing specific power will inevitably lead to an increase of the combustion pressure, which can be accompanied with a temperature increase. This will increase the loading on many components and drives the development of materials more resistant to the harsh conditions close to the engine. The cylinder head is one of the components that will be affected by the increased loads. Therefore, thermomechancial loads (TMF) originating from the cyclic temperature variations from the heating up and cooling down cycles of the engine and the high cycle fatigue load (HCF) emanating from the repeated combustion pressure pulses may cause failure of the component. Today, most cylinder heads for heavy trucks are cast in either lamellar graphite iron (LGI) or compacted graphite iron (CGI). In both cases, the graphite particles are embedded in a pearlitic matrix. A possible improvement of the endurance life of the component is to add silicon to the composition. Silicon promotes the formation of ferrite and the hypotheis is that the more ductile ferritic matrix enclosing the graphite particles will improve the resistance to macro crack initiation and propagation and thus the life of the component. The purpose of this master thesis is to investigate the effect of a ferritic matrix as well as other added alloying elements such as molybdenum and nickel on the high cycle fatigue properties of CGI. The HCF properties of three ferritic alloys with different amounts of molybdenum and four pearlitic alloys with additions of molybden or nickel were compared at a fatigue life of 2 miljon cycles and a stress ratio of R=0.1. The results show that the silicon alloyed ferritic base material, without molybdenum, had a fatigue strength that on average was about 10 % higher than the corresponding pearlitic base alloy without alloying elements. Adding 0.25 wt % molybdenum improved the fatigue strength for both the pearlitic and the ferritic alloy with about 5-10 %. Further, for the pearlitic materials, molybdenum also improved the static mechanical properties while no such effect was seen for the alloys with a ferritic matrix. It was also found that nickel did not alter the HCF or the static properties significantly on the materials with pearlitic matrix.

The development of the commercial 5G network with high-frequency mmWave requires tighter base station grid, which increases the demand for smaller and more unobtrusive products. One way to connect materials of different properties and keeping the product size small is to use adhesive joints instead of screw joints. The thesis project is about understanding the material behaviour of adhesive joint and determining the material model. Adhesive joints can be described as a highly temperature-dependent material, including both hyperelastic and viscoelastic material behaviours. A relaxation test was carried out to evaluate the joint behaviour and its temperature dependence. The results showed that the Neo Hookean material model and the Generalized Maxwell model can be used to describe the basic joint properties. Additionally, the adhesive joint exhibited a softening behaviour under cyclic loading, in which the softening in the first load cycle was captured by the Mullins effect. A cyclic loading test was carried out to evaluate the joint damage. The results showed that when the joint thickness was equal to the applied displacement, no visible joint damage will occur. However, if the joint thickness is less than the applied displacement, total joint failure can be captured by small reaction force and discontinuities in the force-displacement curve. / Utvecklingen av den kommersiella 5G-nätverk med högfrekvent signaler sätter krav för en tätare basstationsnät, vilket i sin tur behöver mindre och mer diskreta produkter. Ett sätt att combinera material med olika egenskaper och samtidigt försöka minimera produktsstorleken är att ersätta skruvförband med limförband. Detta masterexamensarbete handlar om att undersöka materialbeteende hos limfog och att bestämma dess materialmodell. Limfogd kan beskrivas som ett temperaturberoende material med både hyperelastiskt och viscoelastiskt materialbeteende. En relaxationstest genomfördes för att utvärdera limfogens beteende och dess temperaturberoende egenskaper. Testresultaten visade att Neo Hookean och Generalized Maxwell material modellen kan användas för att beskriva de grundläggande materialegenskaperna hos limfogen. Under cyklisk last initierades skadan i limfog där materialets styvhet minskades med antal ökade lastcykel. Minskningen av styvheten vid den första lastcykel kan beskrivas med Mullins effekt. När limfogens tjocklek är lika med den applicerade förskjutning, visades ingen synlig skada. Däremot om tjockleken är mindre än den applicerade förskjutning, kan total brott i limfogen identifieras med små reaktionskraft och diskontinuitet i kraftförskjutningskurvan.

A closed system of a liquid metal jet loop operating in vacuum is modelled and investigated using a commercial 1D simulation tool. Possible methods to approximate a free-falling jet in vacuum to capture the behavior of the system in 1D is investigated. As the characteristics of the jet loop system is captured, the influence of different components on the system pressure and the jet nozzle flow rate is investigated further. The effects of the volume of the accumulator, the frictional forces within the check valves are inspected in isolation and the effect of an increased volume of alloy in the system is considered when system failure occurs due to check valve stiction. Several simulation tools are tested, and the simulations are ultimately performed using Simcenter AMESim 2019.2. The performance of the pump with respect to flow rate at different pressure levels are validated with measurement data acquired from the pump supplier as the Covid-19 virus limits the possibility to perform measurements in the lab. Ultimately, possible improvements of the system are suggested, and the conclusion is that a slightly larger accumulator volume would benefit the system, and that a larger volume of alloy would not prevent failure due to stiction forces in the inlet check valve. It is also confirmed that the check valves have major effects on the pressure and flow rate in the system.

The main objective of the work presented in this Licentiate of Engineering thesis is to investigate and model the fatigue crack propagation behaviour of the nickel-based superalloy Inconel 792, with special attention to the industrial lifing of high-temperature components. In-phase (IP) crack propagation tests have been performed at different temperatures and loading regimes, including extended hold times. The observations from these tests have been the basis for establishing several hypotheses to describe the crack growth behaviour, which progressively have been verified experimentally and numerically. Most prominently, it has been observed that crack closure has a substantial impact on crack growth and can explain, to a large degree, the crack growth behaviour for this material under the conditions studied. This phenomenon has been observed experimentally and modelled numerically to extend further the precision of the methodology. / Huvudsyftet med arbetet som presenteras i denna licentiat avhandling är att undersöka och modellera utmattnings sprickväxtbeteendet hos den nickelbaserade superlegeringen Inconel 792, med särskild uppmärksamhet riktad mot liuslängsdmodellering av högtemperaturkomponenter i en industriell kontext. I-fas (IP) sprickväxtprov har utförts vid olika temperaturer och belastningsregimer, inklusive hålltider. Observationerna från dessa tester har legat till grund för hypoteser för att förklara spricktillväxtbeteende, vilka successivt har verifierats experimentellt och numeriskt. Mest framträdande har det observerats att sprickslutning har en väsentlig inverkan på sprickväxten, och kan i stor utsträckning förklara sprickväxten för detta material under studerade förhållanden. Detta fenomen har observerats experimentellt och modellerats numeriskt för att förbättra metodens precision. / <p>Ytterligare forskningsfinansiär: Siemens Energy through "Turbines for Future Energy Systems" (Turbiner forframtidens energisystem), Grant No.44100-1</p>

Abdominal aortic aneurysms (AAA) occurs due to local enlargement of the abdominal aorta and affects about 1-2 % of the elderly Swedish population. At admission, AAA patients receive a Computed Tomography-Angiography (CT-A) scanning, and later they are followed-up by 2D ultrasound examinations. There is a need to know if an adequate geometry can be constructed from the baseline CT-A scan and follow-up 2D ultrasounds. To test our hypothesis only CT-A images have been used from six patients and hypothetical ultrasound cross-sections (HUCS) were extracted from the follow-up CT-A scans. The baseline AAA surface was expanded in a mechanical model by applying pressure inside of it until it reached the HUCS. The obtained morphed geometries were then compared with the CT-A-based geometries. The discrepancy between them were calculated by distance measurements. Also, the rupture risk indicators volumes and stresses were compared. Finally, a sensitivity analysis studied the effect of HUCS positioning on the volumes and stresses. The results show that an adequate geometry can be constructed by the investigated concept of morphing. The average distances between the morphed and CT-A-based geometries are 2-4 mm. The average volume difference for the six patients are between 3.8-16.2 %. The wall stress for the morphed and CT-A-based geometries are close only for the first follow-up. / Bukaortaaneurysm (AAA) uppstår på grund av lokal förstoring av bukaortan och drabbar 1-2 % av den äldre svenska befolkningen. Vid antagning får bukaortaaneurysm-patienterna en datortomografscanning (CT-A) och senare påföljs av 2D ultraljudsscanningar. Det finns ett behov att veta om en adekvat geometri kan konstrueras från datortomografiscanningen och 2D ultraljudsbilderna. För att testa vår hypotes har endast datortomografibilder från sex patienter använts med hypotetiska ultraljudstvärsnitt (HUCS) tagna från CT-A uppföljningarna. AAA-ytan vid baslinjen expanderades i en strukturmekanisk modell genom inre övertryck tills den nådde de hypotetiska ultraljudstvärsnitten. Därefter jämfördes de morfade geometrierna med de CT-A-baserade geometrierna. Geometriavvikelsen mellan de beräknades genom avståndsmätningar. Även, rupturriskindikatorerna volymer och spänningar jämfördes. Slutligen, genom en känslighetsanalys undersöktes effekten av positioneringen av hypotetiska ultraljudstvärsnitten på volymerna och spänningarna. Resultaten visar att en adekvat geometri kan konstrueras genom den undersökta koncepten av morfning. De genomsnittliga avstånden mellan de morfade och CT-A-baserade geometrierna är 2-4 mm. Genomsnittliga volymskillnaderna för de sex patienterna är mellan 3.8-16.2 %. Väggspänningarna för de morfade och CT-A-baserade geometrierna är nära enbart för den första uppföljningen.

Cleavage fracture is one of the most severe failure modes in low alloy ferritic steel structures and the fracture toughness is strongly dependent on the size of the specimen, crack depth and temperature. This thesis investigates how the fracture toughness is affected under conditions that relates to size and constraint effects through a fracture mechanical experiment test series. Furthermore, modeling the experiment with a non-local weakest link model to investigate the importance of the stress measure and how the model parameters can be determined for yielding the best result. The experiment is divided into two sets of testing, a pre-test series to determine an appropriate testing temperature for the main test series. The second set consists of four groups with different sizes and crack depth with 12 specimens in each group. The testing temperature was determined to be -155 ◦C. For the large sized test specimen with a shallow crack, the master curve fails to accurately predict the probability of failure by overestimating the fracture toughness. This is not the case for the small test specimens which indicates that the size effects exceeds the low constraint effects for larger sized test specimens and development of the master curve method is needed. When evaluating the stress state in front of the crack tip in the non-local weakest link model, the results yields the least residual error was obtained when using a large sized specimen with high constraint together with a small sized specimen with low constraint for prediction of the probability of failure.

The objective of this thesis has been to investigate the effect a liquid shim has on the bearing strength of a composite bolted joint. The shim is necessary to close gaps that occur during the assembly of the joints, preventing the structural parts from being fastened correctly. The shim however increases the load eccentricity of the joint and will have a negative effect on the joint strength, but the significance of this weakening is not well understood.This thesis primarily focuses on a parametric finite element study on the effect the liquid shim has on the bearing of both a homogenised carbon fibre/epoxy model and a fully detailed laminate model based upon the same material. Parameters studied were the plate and shim thicknesses, lateral support, number of fasteners, bolt pre-tension and bolt diameter and the relative strength decreases were documented.A literature study was also conducted to consider previous results concering the strength change due to the inclusion of a shim. It was found that the results show a large spread dependent on material system, geometry and assumptions regarding numerical behaviour. The finite element simulation was compared with the results from these studies, showing fairly good agreement.The analysis conducted has shown that there is a major increase in stress and strain on the bearing surface because of the shim. Moreover, it is shown that this strength reduction is dependent on both model and parameters studied, which necessitates experimental testing in order to verify which is the more applicable for future methodology.

Bending stiness is one of the most important mechanical properties in paperboard making,giving rigidity to panels and boxes. This property is currently only possible to measure bydestructive measure o the production line. The current quality control method is decient byassuming a non-realistic consistency of the paperboard properties along the machine direction.The objective of this thesis is to predict the thickness and bending stiness of the nal boardsfrom process data.Two modelling approaches are used: the rst model calculates the bending stiness from acalculated thickness, while the other one uses the measured baseboard thickness. Both modelsuse common inputs such as material properties and grammage measurement. The grammage istaken from the online baseboard measurement. The material properties come from laboratorymeasurements and assumptions. It is assumed that the density ratio between the outer andmiddle plies is constant for all product lines, at all times. The TSI of each ply is dened fromtensile testing experiments and nominal bending stiness. It is also assumed that the coatingdoes not contribute to bending stiness. The two models use equations based on laminatetheory assuming orthotropic layers and neglecting the interlaminar shear forces. The modelsuse data of two dierent natures: i.e. laboratory data and online data. Laboratory data is usedas a comparative to evaluate the models' performance of calculated values from online data.The results show various levels of prediction accuracy for dierent paperboard grades. Theaverage thickness predictions are all underestimations within a 5% error while the bendingstiness estimations vary much more from product to product; varying from 9% underestimationto 32% overestimation. The bending stiness prediction for CD is consistently higher thanfor MD for both models. Most product lines have better results with the calculated thickness,approach 1. The calculated thickness is always underestimated and bending stiness is overestimated,hence the better results with the rst approach.The most important conclusion from the models' results is the spread of laboratory measurements,when compared to the predicted values. The large variation most likely comes fromproduction, implying inconsistencies in the manufacturing process that are not accounted forby the models. These modelling approaches have failed to capture the production variationsbecause of the lack of input parameters.

It is only a matter of time before components working in high temperature environments fail due to creep. Design for creep is therefore of vital importance to maximize the lifetime of components and reduce costs that may arise from maintenance and replacement of components. This thesis aims to use metallographical methods and finite element modeling to assess creep damage in a hydrogen reformer. The decommissioned reformer, made of Fe-Ni-Cr alloys, was investigated thoroughly via replica testing, hardness measurements as well as finite element modeling of the welds. An extended literature review was performed to gain a better understanding of creep in Fe-Ni-Cr alloys, welds and the modeling of creep generally. The microstructures of samples from the reformer were analyzed and mapped out in terms of creep damage which were then compared to a creep analysis of the welds with a simulation time of 100 000 h. The FE results yielded high stresses and creep strains with a maximum of 0.95% in the boundaries of the welds which gave realistic representations of strain distributions when compared to the metallographical results. Hardness measurement indicated that a relatively narrow zone with altered mechanical properties is present along the weld boundaries. This area, called the heat affected zone, was found to be most affected by creep with microcracks reaching maximum lengths of 2 mm. The creep strains obtained from simulation did not fall in line with the observed creep damage, it was thus concluded that a material model that considers tertiary creep would yield a more realistic representation in FEM for Fe-Ni-Cr alloys. / Det är bara en tidsfråga innan komponenter som arbetar i högtemperaturförhållanden misslyckas pga kryp. Att designa med avseende på kryp är därmed viktigt för att maximera livslängden och reducera kostnader som kan komma från underhåll och från utbyte av komponenter. I detta examensarbete används metallografiska metoder och finita element modellering för att bedöma krypskador i en vätgasreformer. Vätgasreformern, som är tillverkad i Fe-Ni-Cr legeringar, togs ur drift och undersöktes metallografiskt med hjälp av replikprovning och hårdhetsprovning samt med finita element modellering av svetsar. En djupgående litteraturstudie utfördes för att öka förståelsen av kryp, specifikt i Fe-Ni-Cr legeringar och även modellering av kryp generellt. Mikrostrukturen från utvalda provbitar undersöktes och krypskador kartläggdes för att sedan jämföra med en krypanalys av svetsarna där 100 000 timmars kryp simulerades. Krypanalysen resulterade i höga spänningar och kryptöjningar upp till maximalt 0.95% i svetsgränserna vilket gav realistiska representationer av töjningsdistributionen jämfört med metallografiska resultaten. Hårdhetsmätningar indikerade att ett smalt område med förändrade mekaniska egenskaper fanns utmed svetsgränserna. Detta område, den värmepåverkade zonen, var mest utsatt för krypskador med mikrosprickor uppemåt 2 mm i längd. Kryptöjningar som erhölls från simuleringen gav inte en tillräckligt bra uppskattning av kryptöjningarna – de krypskador som observerades motsvarar lokalt högre töjning. Slutsatsen är att en materialmodell som tar hänsyn till tertiärkryp skulle i det här fallet ge en mer realistisk representation i FEM för Fe-Ni-Cr legeringar.