Fragments from explosive device have been and still are a great threat, but has now changed into terrorist attacks involving IED (Improvised Explosive Devise) rather than hostile forces. This master thesis will show the effects on concrete plates (50 mm depth) impacted by different projectiles, which should replicate fragments hitting buildings. The projectiles used were the 8 mm sphere, the 6 mm sphere, the 8 mm cylinder (RCC) and the FSP (fragment simulating projectile). The thesis was made at request from FOI (Swedish Research Defiance Agency) at Grindsjön and it contains both experiments made there and numerical simulations. The experiments were conducted at Grindsjön, the projectile were fired in velocities between 800 m/s and 1600 m/s. The 8 mm and RCC obtains higher penetration depth at lower velocity, while the FSP, due to its soft material, will need much higher velocity. Full penetration was obtained at 1510 m/s for the 6 mm sphere, 1310 m/s for the 8 mm sphere and 950 m/s for the RCC. The simulations were made in LS-DYNA using a meshfree solver (SPH) and the results shows that the RCC creates a bigger initial elastic wave, which will make the concrete block crack more, but it will also make the projectile lose more kinetic energy resulting in lower penetration depth in the concrete. The spherical projectiles have higher penetration depth, but it gives smaller elastic waves resulting in less cracking of the concrete. The simulations overestimate the penetration depth for the non-flat projectiles while giving good agreements for the flat projectiles, also the damage pattern are consistent with the experiments. An actual fragment from a grenade was obtained and simulated showing that all of the projectile except the RCC shows good agreements and therefore the RCC should not be used in simulating fragments.

It has a long been known that many, if not all, diseases are associated with changes in the mechanical properties of cells. Although these changes in tissue mechanics have been believed to be a conseguence of the disease, recent data show that alterations of these mechanical properties have potent eect to many cellular functions. Thus, there is no reason to believe that altered cellular mechanics could be a cause of the disease, rather than its consequence. A complete understanding of cell mechanics and how the latter one depends on the presence of a disease is therefore necessary in order to develop methods of early diagnosis. In this master thesis we report the preliminary results of cell mechanical response of broblasts obtained simulating AFM (Atomic Force Microscopy) with COMSOL 4.1. Specically, we tried to nd out what is the relationship that coexists between the reaction force of a broblast when urged by this type of technique. A subsequent process of reverse engineering led to a simply analytical model for the quantication of the mechanical properties of this type of cell. The second part of this work aims to improve the understading of the mechanotrasduction mechanism of cells. The second model, indeed, reports the results of soft concact and adhesion of a broblast with a polyacrylamide substrate. Finally, we built up a numerical model that combines the assumptios of the rst and the second one.

In this thesis the influence of the drying pressure on interfibre bond strength was investigated. Five different drying pressures, 0.7, 2.9, 4.5, 6.7, and 15 kPa, were applied during the preparation of fiber-fiber cross test pieces. The nominal overlap area of each fibre-fibre cross was measured in a transmission light microscope. A tensile tester was used to record the loaddeformation behavior of each fiber-fiber cross. The final results of the interfibre bond strength were defined by both the overlap area and the maximum force of each bond. The results showed that the influence of drying pressure to the average strength were very weak, although a maximum could be seen at 2.9 kPa of drying pressure. Moreover, the results suggested the overall trend of decreasing strengths at very high drying pressures. Finally, a statistical significance study of the results was presented. In addition, the influences of fiber type (spring wood vs. summer wood) and press type (steel vs. steel or steel vs. rubber) on interfibre bond strength were also discussed.

When a tipper trailer empties the load it carries, a torque occurs if the trailer stands on uneven ground. To withstand this torque, and prevent the trailer to roll over, the chassis‟ torsional stiffness must be high enough. The stiffness is highly dependent of the geometry of the chassis structure. When analysing different geometries the pre-processing of the finite element (FE)-model is time consuming. The first part in this master thesis was to assess what element type to use for this type of load case. It was necessary to simplify the FE-model as much as possible for the second part of the thesis. A comparison of modelling the chassis with beam elements instead of shell elements was performed. It was concluded that resultant beam elements should be used when analysing the torsional stiffness of the chassis. In the second part of this master thesis a program was developed to automate the FE-modelling of the chassis, this to be able to compare several chassis structures in a short amount of time. The program generates a FE-model of the desired chassis structure depending on parameters given from the user. The program produces a text file, containing information about the FE-model, which can be read and viewed in a LS-DYNA compatible pre-processor.

Examensarbetet handlar om utmattning av skruvar och har genomförts på Scania CV. Skruvar används på Scania för att till exempel sätta samman olika delar i ett lastbilschassi. Det är därmed viktigt att skruvarna håller för den belastningen som de utsätts för. Axiell utmattningsprovning av skruvar är standardiserad och välbeprövad medan publicerade testdata för böjutmattningsprovning nästan är obefintliga. Inom vissa utvecklingssammanhang antas skruvar hålla för högre ingenjörsspänningar i böjbelastning än i ren dragbelastning eftersom utmattningsprovning av provstavar har påvisat denna skillnad. I detta examensarbete har en helt ny provuppställning tagits fram för att genomföra böjutmattningsprovning både vid utmattningsgränsen och för kortare livslängd. Resultat i utmattningshållfasthet jämfördes sedan med resultat från axiell utmattningsprovning som även genomfördes i arbetet. Olika modeller för att beskriva spänningstillståndet i skruven togs fram med hjälp av teoretiska lösningar och FEM-modeller. Resultaten visar att skruvarna som är testade håller för 65-80 % högre ingenjörsspänningar i böjbelastning än i axiell belastning. Skillnaden i utmattningshållfasthet på grund av olika lastfall kan förklaras med olika teorier, till exempel gradientinverkan eller volymsinverkan. Här undersöktes utifall volymsinverkan kan förklara skillnaden i livslängd mellan de olika lastfallen med hjälp av weakest link teorin och resultaten visar att det så är fallet. / The master thesis concerns fatigue strength of screws and has been carried out at Scania CV. Screws are used at Scania in different types of joints in heavy vehicle chassis. It is therefore of importance that these screws are able to withstand the loads they are subjected to. Axial fatigue strength testing is well established and standardized while no test data for bending fatigue strength is published. In some development processes, screws are assumed to have higher fatigue strength when subjected to bending than in axial loading since notched laboratory specimen have shown this behavior. During this thesis work, a completely new experimental setup for fatigue strength due to bending load is proposed. Fatigue testing is performed with this setup for screws both at the endurance limit and shorter fatigue life. The fatigue strength results are thereafter compared to the results from fatigue testing using axial loading, which is also performed during this work. Different models, theoretical and using FEM, have been developed in order to describe the stress state in the screws tested. The results show a 65-80 % higher fatigue strength for screws subjected to bending compared to axial loading using an engineering stress measure. The difference in fatigue strength for different load types can be explained by different theories, for example the gradient effect or the stressed volume effect. Here, the stressed volume effect is investigated and the results obtained by using weakest link theory show that the difference can be explained by the volume effect.

In order to prevent the occurrence of cracks in paper packages, the in-plane mechanical behavior for the full paperboard needs to be investigated. Further, it is of importance to understand also the in-plane behavior of the plies that build up the paperboard. In order to characterize the crack growth behavior, a normalized stress-widening model was developed, based on the minimum fracture energy, according to Tryding (2014). The model depends on the tensile strength, _t, and the maximum slope after peak stress in short-span tensile tests, Nmax. In this Master's thesis, it was investigated if the normalized stress-widening model is a true master curve, which describes the crack growth in full paperboards, and in their plies, respectively. To verify if the model is a true master curve, six paperboards from three di_erent suppliers were investigated. From short-span tensile tests, the properties needed for the stress-widening model were obtained. The results indicate that the normalized stress-widening model is a true master curve, which also is valid for unloading. Furthermore, a linear relation between _t and Nmax was obtained, which means that the model might be reduced to be dependent of the tensile strength, _t, and a constant that will be de_ned empirically by the linear relation between _t and Nmax. All three-ply boards were based on sandwich construction theory, which was supported by the results, were two paperboards, Paperboard A and Paperboard C had signi_cantly larger tensile strength, in comparison to their density, than Paperboard D and Paperboard E, which indicates that Paperboard A and Paperboard C have better material distribution than Paperboard D and Paperboard E. From the thesis, it can be concluded that, by performing short-span tensile tests, it is possible to normalize the post-peak stress behavior for paperboards into a master curve. Since all paperboards that have been investigated follow the master curve, it can be concluded that the fracture behavior can be characterized by the three parameters that a_ect the model, i.e. the tensile strength, _t, the maximum slope after peak stress, Nmax, and the tensile sti_ness, E.

This Master’s Thesis was conducted during spring 2014. An experimental and numerical investigation was conducted on the austenitic 316L stainless steel. The main focus of the study was the investigation of ratcheting effects. Experimentally, the main focus was the two-rod test, which had not been conducted previously. The two-rod test resembles a structure and a load case where ratcheting effects may be produced, although being less complicated than structures used in prior studies. Furthermore, the stress state in the structure is uniaxial. Other tests were also performed to characterize the material. Based on results from uniaxial tensile tests and fully reversed strain cycling of 316L, four material models were calibrated. The four material models were  Bi-linear kinematic hardening model  Multilinear kinematic hardening model (Mróz)  Armstrong-Frederick non-linear kinematic hardening model  Chaboche non-linear kinematic hardening model with three superimposed back-stress     tensors. The two-rod test was then numerically simulated with different material models. The results from the FE simulations were then compared to the test results obtained from the two-rod tests. The goal, apart from investigating the ratcheting effects in 316L steel, was to evaluate the material models’ ability to reproduce the two-rod test results. The results from the comparison suggest that the bi-linear and the multilinear material model agreed with the test results to a larger extent than the Armstrong-Frederick and Chaboche model. The two non-linear hardening material models predicted in most cases a constant ratcheting rate which did not agree with the test results. Even though the predictions of the two-rod tests with the bilinear and the multilinear models generally was better than predictions with the two non-linear hardening material models, the bilinear and the multilinear models predicted plastic shakedown in certain cases which was not observed in the tests. The employment of an isotropic part in the non-linear kinematic hardening material models might have improved the simulations’ agreement to experimental results. The setup for the two-rod test proved robust and reliable. The results suggest that structural ratcheting effects dominate the two-rod test results. Furthermore, the comparison between simulations and the two-rod tests suggest that a more advanced material model does not necessarily yield in a better prediction. / Det här examensarbetet utfördes under våren 2014. En experimentell och numerisk undersökning genomfördes på det austenitiska rostfria stålet 316L. Huvudområdet för studien var att undersöka fenomenet ratcheting (progressiv plastisk deformation). Experimentellt var huvudfokus på det så kallade tvåstångstestet, vilket tidigare inte hade utförts. Tvåstångstestet utgör en struktur och ett lastfall vari ratcheting kan skapas, samtidigt som strukturen är mer renodlad än de som undersökts i tidigare studier för samma ändamål. Dessutom är spänningstillståndet enaxligt i strukturen. Utöver tvåstångsprovning gjordes även ytterligare provning för att karaktärisera materialet. Utgående från resultat från enaxligt dragprov och fullt reverserad töjningsstyrd cykling anpassades fyra materialmodeller efter materialet. Dessa fyra materialmodeller var  Bi-linjär kinematiskt hårdnande modell  Multilinjär kinematiskt hårdnande modell (Mróz)  Armstrong-Frederick icke-linjärt kinematiskt hårdnande modell  Chaboche icke-linjärt kinematiskt hårdnande modell med tre superponerade back stress-    tensorer. En FEM-modell över tvåstångsprovet användes för att simulera de olika materialmodellernas respons. Resultaten från dessa jämfördes sedan med resultaten från tvåstångsprovningen. Målet, bortsett från att karaktärisera ratchetingeffekterna i 316L-stålet, var att utvärdera materialmodellernas förmåga att återskapa resultaten från tvåstångsprovningen. Resultaten från jämförelsen mellan simuleringarna och tvåstångsprovningen pekar på att den bi-linjära och den multilinjära materialmodellen förmår återskapa provresultaten bättre än Armstrong-Frederick-modellen och Chaboche-modellen. De två sistnämnda materialmodellerna predikterade i de flesta fall konstant ratchetinghastighet, vilket inte överensstämde med provresultaten från tvåstångsprovningen. Även om predikteringen av tvåstångsprovningen med den bi-linjära och multilinjära materialmodellen överlag var bättre än för de icke-linjärt hårdnande materialmodellerna predikterade den bi-linjära och multilinjära materialmodellen i vissa fall plastisk shakedown, vilket inte sågs i provresultaten. Införandet av isotropt hårdnande i de icke-linjärt kinematiskt hårdnande materialmodellerna kan ha förbättrat simuleringarnas överensstämmande med provresultaten då materialet visar på omfattande plastiskt hårdnande, både i monotont dragprov såväl som cykliskt hårdnande. Metoden som utvecklades för tvåstångsprovningen visade sig robust och pålitlig. En slutsats som kan dras är att effekter från materialratcheting förmodligen är små i jämförelse med effekter från strukturratcheting i tvåstångsprovningen. Dessutom kan från jämförelsen mellan simuleringarna och tvåstångsprovningen sägas att en mer avancerad materialmodell inte nödvändigtvis resulterar i en prediktering som överensstämmer bättre med provningen.

There is currently no standardized method for testing dentures made of dental ceramic materials. This creates problems for comparisons between studies concerning strength in materials and geometry. The geometry of the maxillary first premolar was used for the analysis. The modeled crown has two underlying layers, a thin cement layer closest to the crown that attaches the crown to dentin. Simplifications are made so that dentin geometry is modeled in CAD as a cuboid and the cement layer above follow its geometry. For the actual analysis, a FE-analysis has been made of different loading positions and areas to clearly show how important it is to be consistent in the selection of these. The load has been placed on two surfaces with 150 N each to resemble a real occlusal maximum load. The standard area used in other analysis was set to be 5.5 mm2 on each cusp. A comparative analysis has been made of various ceramic materials to see what impact it has on the cement layer strength. Similarly the cement material properties were modified to see how it affects the ceramic crowns strength. In real applications, one usually tries to achieve as thin cement layer as possible but here the analysis is of how much influence the cement layer thickness has on the overall crown strength. Two cylindrically shaped simplified models were created to see how much the anatomical geometry effects on the maximum stresses. One was modeled with a flat top and the other with an angled top. The load placement and the magnitude of its area turned out to be very important for the resulting maximum stresses. Surface area ranged from 0.07 - 26 mm2, and the resulting von Mises stresses for these ranged from 1120 to 34 MPa. Generally speaking, varying cement materials available on the market does not give huge impact on ceramic bearing stress. Panavia F 2.0 was found to be the strongest cementing layer that caused the highest failure load of the existing materials on the market. Super Bond B&D gave the lowest failure load. However, you could see that it was a bit more important to be careful for the crown material. The made up ceramic materials (Hypothetical Ceramic and Experimental Ceramic) proved to cause relatively close stresses for the cement to fail. It was also clear that a thicker cement layer reduces the expected failure load and the structure becomes weaker. The simplified models seemed to give a substantial exaggeration of strength. The expected failure load was nearly twice as large for these (slightly lower for the angled model) than for the anatomical model. When comparing with the test data from another study it proved that it does not match with the simulations. In the study different cementing materials had been tested and Super Bond B&D turned out to be the strongest material. With this in hand it can be said that a stable test setup with consistently identical geometries is necessary in order to evaluate these kinds of structures. / Idag finns ingen standardiserad provninvgsmetod för tandproteser gjorda i odontologiska keramikmaterial. Det skapar problem vid jämförelser mellan studier som rör hållfasthet med avseende på material och geometri. I det här examensarbetet har en geometri från övre käkbenets första premolar analyserats. Den modellerade kronan har två underliggande lager, ett tunt cementlager närmast kronan som fäster kronan till dentin. Förenklingar är gjorda så att dentinets geometri modellerats i CAD som ett rätblock och cementlagret ovan följer dess geometri. Vid själva analysen har man gjort FE-analys av olika lastpositioner och areor för att tydligt visa hur viktigt det är att vara konsekvent vid valet av dessa. Lasten har lagts på två ytor med 150 N på vardera kusp för att likna ett verkligt betts högsta lastkraft. Som standardfall att använda för andra analyser valdes en area på 5.5 mm2 på vardera kusp. En jämförande analys har gjorts av olika ceramiska material för att se vilken inverkan det har på cementlagrets hållfasthet. På samma sätt ändrades cement materialets egenskaper för att se hur det inverkar på kermaikkronans hållfasthet. I verkliga applikationer försöker man oftast nå ett så tunnt cementlager som möjligt, här har en analys gjorts av hur stor inverkan på hållfastheten som cementlagret har. Två cylindriskt formade förenklade modeller skapades för att se den anatomiska geometrins inverkan på spänningsbilden. En modellerades med platt topp och den andra med vinklad topp. Lastens placering och arean den är utbredd på visade sig vara väldigt viktigt för de resulterande maximala spänningarna. Ytans area varierade mellan 0.07 – 26 mm2 och resulterande von Mises spänningarna för dessa varierade 1120 – 34 MPa. Generellt sett hade olika cementmaterial som finns på marknaden inte jättestor inverkan på keramiklagrets spänningsbild. Panavia F 2.0 visade sig ändå vara det starkaste cementeringslagret som orsakade högst brottlast av de befintliga materialen på marknaden. Superbond B&D gav lägst resultat. Däremot kunde man se att det var lite viktigare att vara noggrann med kronans materialval. De påhittade keramikmaterialens (Hypothetical Ceramic och Experimental Ceramic) spänningar visade sig komma realtivt nära cementlagrets brottgräns. Det visade sig också tydligt att för ett tjockare cement lager minskar den förväntade brottlasten och strukturen blir svagare. De förenklade modellerna tycktes ge en kraftig överdrift i hållfasthet. Den förväntade brottlasten var nästan dubbelt så stor för dessa (något lägre för den vinklade modellen) än för den anatomiska modellen. Vid jämförelse med testdata från en annan studie visade de sig inte stämma överens med simuleringarna särskilt bra. Man hade testat olika cementeringsmaterial och där visade sig Superbond B&D vara det starkaste materialet. Utifrån det kan man säga att en stabil provningsuppställning med konsekvent identiska geometrier är nödvändigt för att kunna valuera sådana här strukturer.

The aorta is the largest artery in the mammal and it’s rather distensible due to its high degree of elasticity. It has a heterogeneous structure, where some of the key elements are the proteins collagen and elastin; which are essential for the mechanical properties of the aortic tissue. This thesis investigates the influence of elastase and collagenase on mechanical properties of porcine aorta. This was achieved by developing an appropriate biaxial tensile test method; which closely represents the in vivo conditions of the aortic tissue. To investigate the influence of collagen and elastin some samples were exposed to the enzymes collagenase and elastase to chemically manipulate a decomposition of the proteins in tissue. The exposed samples were tested in the developed biaxial test method and compared to native (untreated) samples. The wall samples exposed to enzymes were exposed for a varied time period of 1h, 3h and 6h. All experimental data from the mechanical tests were also used to identify model parameters of three different constitutive functions (Fung, HGO and Ogden), trying to define the differences in the results depending on type of enzyme exposure and exposure time. The results of the study show that collagenase exposed samples tends to be less distensible compared to the native samples in the circumferential direction. The longitudinal direction showed no differences between native and exposed samples, probably due to that the collagen fibers lay in the circumferential direction. The elastase exposed tissue samples tended to be more distensible than the native samples, especially for the circumferential direction. However, the results from the biaxial tests are complex and difficult to analyse. Further on additional test are necessary to achieve a deeper understanding of the results. The constitutive model results show that the anisotropic models (Fung and HGO) describe the experimental data more accurate than the isotropic model (Ogden), possibly due to that biological material is most often anisotropic. The parameter identification is not conclusive due to varied results and additional tests are desirable to reach a more statistical accuracy.

Replikprovning är en oförstörande provningsmetod som ofta tillämpas på komponenter i högtemperaturanläggningar i syfte att studera utveckling av krypskador. Metoden går ut på att man i fält tar en kopia, benämnd replik, av stålets ytliga mikrostruktur genom att lägga en plastfilm eller gummimassa på en noggrant preparerad yta. Genom att studera mikrostrukturen i mikroskop kan man på ett tidigt stadium upptäcka krypskador i form av kaviteter, håligheter, i korngränserna och därigenom göra en bedömning av skadans omfattning. DEKRA Industrial AB är ett företag inom teknisk provning och besiktning som använder sig av replikprovning. Då replikprovning inte är en ackrediterad metod, finns inga standarder att förhålla sig till vid utförandet av provningen. Samtliga provare på DEKRA bör följa samma riktlinjer, så att både provning och bedömning utförs på ett enhetligt sätt inom företaget. Därför har procedurbeskrivning, instruktioner för provtagning och utvärderingsdirektiv utvecklats i detta exjobb. Från litteraturen känd modell för beräkning av tiden till krypbrott har tillämpats på replikprovning. Därigenom införes ett nytt tankesätt kring utvärdering av replikerna och bedömning av tidsintervall för uppföljande provning. Rapporten redogör för provningsprocedurens alla steg samt hur replikerna utvärderas och hur inspektionsintervall bedömes. Hur replikerna tillämpas på krypmodellen beskrivs också i rapporten. / Replica testing is a non destructive testing method often applied to parts in high temperature plants, in order to study creep damage growth. The method involves taking a copy, called replica, of the microstructure by applying a plastic film or a rubber paste on a carefully prepared test surface. By studiyng the microstructure in microscope creep damage can be detected, in the form of cavities in the grain boundaries, in an early stage. DEKRA Industrial AB is an inspection company performing non destructive testing such as replica testing. Since replica testing is not an officially recognized method there are no standards that relate to the performance of the test. Both testing and evaluation should be carried out in a uniform manner within the company. Therefore instructions for the method were developed in this thesis. A model for the prediction of time to creep rupture, according to litterature, was applied to the replica test results, thereby introducing a new way of thinking concerning the evaluation of the replica and the assessment of inspection intervals. This report describes the method of replica testing, its evaluation and the determination of inspection intervals as well as the application of the creep model to replica testing.