| 1. |
- Arnell, Matilda, 1987-
(författare)
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Distribution patterns of fleshy-fruited woody plants at local and regional scales
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Fleshy-fruited woody plants share a long history with humans, providing us with food and wood material. Because of this relation, we have actively moved some of these plants across landscapes and continents. In Sweden, these species are often found in open and semi-open habitats such as forest edges, their fruits are most often dispersed by birds and their flowers are, with some exceptions, pollinated by insects. In this thesis my overall aim was to map and analyse distribution patterns of fleshy-fruited woody plants in Sweden to expand our knowledge on the mechanisms governing their distributions. First, I mapped a population of the early flowering, fleshy-fruited shrub Daphne mezereum (common mezeron, tibast) and surveyed the reproduction and fruit removal of all individuals (chapter I). My main aim was to investigate to what extent reproduction and fruit removal was affected by local distribution patterns. Secondly, I mapped local distribution patterns of fleshy-fruited woody species and analysed spatial associations between life stages and species (chapter II). My main aim was to relate these spatial associations to predictions of how bird dispersal would shape the local distribution patterns and the hypothesis that birds create ‘wild orchards’. Thirdly, I digitized historical maps and surveyed fleshy-fruited woody species along transects across landscapes (chapter III). My aim was to examine the hypothesis that these species accumulate in open and semi open habitats created by human land use. Fourthly, I estimated range filling of woody plants in Sweden at a 1 km2 resolution (chapter IV). My aim was to compare these estimates among species with different dispersal systems to understand the effect of dispersal on the occupancy of woody species at regional scales.I found the distribution patterns of these species to be affected by past and present land use, supporting the hypothesis that these plants accumulate in open habitats. Occurrences of species in this guild in todays’ forest are positively related to past human land use (chapter III) and the density of D. mezereum increases with decreasing distances to forest edges (chapter I). This accumulation may in part be explained by the positive effect of forest edges on reproduction and fruit removal (chapter I). I further found local distribution patterns of this guild and the individual species to be aggregated (chapter I and II), and spatial associations between saplings and reproductive individuals to support the ‘orchard’ hypothesis (chapter II). The aggregated pattern of fruit-bearing individuals was positively related to fruit removal whereas aggregated flowering individuals was negatively related to fruit set (chapter I). On the regional scale, I found these species to occupy climatically suitable areas, or fill their potential ranges, to a less extent that wind dispersed trees and shrubs (chapter IV), which may indicate dispersal limitation.In conclusion, the behaviour of birds and humans have shaped, and still shape the current distribution of fleshy-fruited trees and shrubs in Sweden, resulting in accumulation in open habitats and locally aggregated distribution patterns. Changing land-use practices and potential mismatches between fruit maturation and bird dispersal with a changing climate may thus result in even lower chances of these species to fill their potential ranges, due to habitat losses and dispersal limitations at local and regional scales.
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| 2. |
- Lindgren, Jessica, 1971-
(författare)
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Small remnant habitats : Important structures in fragmented landscapes
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The world-wide intensification of agriculture has led to a decline in species richness due to land use change, isolation, and fragmentation of natural and semi-natural habitats in agricultural and forestry landscapes. As a consequence, there is a current landscape management focus on the importance of green infrastructure to mitigate biodiversity decline and preserve ecosystem functions e.g. pollination services and pest control. Even though intensification in agriculture has been ongoing for several hundreds of years, remnant habitats from earlier management practices may still be remaining with a surprisingly high plant richness. Preserving these habitats could help conserving plant species richness in agricultural landscapes, as well as other organisms that are dependent on plants for food and shelter.In this thesis I focus on two small remnant habitats; midfield islets and borders between managed forest and crop field in southeastern Sweden. In the past, both habitats were included in the grazing system and therefore often still have remnant population of grassland specialist species left today. I have used these two remnant habitats as model habitats to investigate the effect of landscape factors and local factors on species richness of plants, flower morphologies and plants with fleshy fruits. Additively, I analysed the effect of surrounding landscape and local openness on the functions; pollination success, biological pest control of aphids and seed predation on midfield islets.One of my studies showed that spatial distribution and size of the habitat affected plant species richness. Larger habitat size and higher connectivity between habitats increased species richness of plants in the habitats. Openness of the habitats was shown to be an important factor to increase species richness and richness of flower morphologies, both on midfield islets and in forest borders. Even though midfield islets had the highest species and morphology richness, both habitat types are needed for habitat complementary as forest borders have more plants with fleshy fruits and a higher richness of plant species that flowers in spring/early summer. It was also shown that a more complex forest border, not just with gaps in the canopy, but also with high variation in tree stem sizes increases plant species richness in the field layer. The conclusion is that by managing small remnant habitats to remain or become more semi-open and complex in their structure, would increase species richness of plants, grassland specialist species, and flower morphologies. It would also increase some ecosystem functions as seed predation and biologic pest control of aphids are more effective close to trees. If both midfield islets and forest borders would be managed to be semi-open, the area and connectivity of semi-open habitat would increase in the agricultural landscape, which may also improve pollination success as the connectivity between populations has a possibility to increase. Grassland specialist species are clearly abundant in the small remnant habitats. As the decline of semi-natural grasslands is causing a decline in grassland specialists’ species, not only plants, I recommend that small remnant habitats are included in conservation and management plans and strategies to improve habitat availability and connectivity for grassland species in agricultural landscapes.
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| 3. |
- Marteinsdóttir, Bryndís, 1980-
(författare)
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Plant community assembly in grazed grasslands
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Species assembly into local communities from the surrounding region can be caused either by species failure to reach the site (i.e. seed limitation) or to establish (i.e. establishment limitation). The aim of this thesis was to investigate plant species assembly and to determine the relative importance of different factors in that process.In a cultivated landscape in southeast Sweden, plant community assembly was studied in grazed ex-arable fields. Community assembly from the surrounding region into the local community was explored using trait-based null models and seed sowing and transplanting experiments. The influence of local environmental factors and landscape history and structure on community assembly was also studied. In addition, differences in species assembly between ex-arable fields and semi-natural grasslands were explored.Seed limitation was the strongest filter on local community assembly. Only a fraction (36%) of species in a region dispersed to a local site and adding seeds/transplants increased species establishment. Species abundance at the regional scale, species dispersal method and seed mass strongly influenced which species arrived at the local sites. Establishment limitation also affected the assembly. Of species arriving at a site 78% did establish, seedling survival was low and which species established was influenced by species interactions, local environmental conditions and stochastic events. In addition, landscape structure that determined the species richness in the regional species pool influenced the local assembly. The comparison between assembly in ex-arable fields and semi-natural grasslands indicated that the main cause of difference in species assembly between them was difference in their age.The main conclusion of this thesis is that regional processes are more important than local factors in determining plant community assembly.
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| 4. |
- Bachmann, Jörg Alexander, 1989-
(författare)
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Evolutionary consequences of dominance at the Brassicaceae self-incompatibility locus
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Self-incompatibility (SI) is a genetic mechanism that allows plants to enforce outcrossing by rejecting self-pollen and pollen from close relatives. In the Brassicaceae, SI is sporophytic and controlled by the self-incompatibility locus (S-locus). The S-locus harbors two tightly linked genes SRK and SCR, which encode the female and male SI specificity determinants, respectively. S-locus heterozygotes often only express the S-specificity of the more dominant allele, and at the pollen level such dominance relationships are mediated by small RNAs (sRNAs). The S-locus is thus an example of a locus under strong balancing selection, where dominance modifiers have evolved.In this thesis, I investigate the consequences of S-locus dominance for plant mating system evolution and allopolyploid speciation. I further investigate evolutionary conservation and sequence-level effects of dominance relationships among S-alleles. For this purpose, I used the crucifer genus Capsella as a model system.First, I demonstrated that targeted long-read sequencing results in structurally accurate assemblies of full-length S-haplotype sequences, and that indel errors in such assemblies can be corrected using short reads. Second, I investigated the genetic basis of loss of SI, the first step in the evolution of self-fertilisation, in the self-compatible (SC) Capsella orientalis. I found that loss of SI was dominant and mapped to the S-locus, where C. orientalis harbored a fixed coding frameshift deletion in SCR that is likely to lead to loss of male specificity. I further identified a sRNA-based dominance modifier that is associated with dominant suppression of recessive SCR alleles. Taken together, these results suggest that loss of SI in C. orientalis involved a dominant S-haplotype, suggesting that dominant haplotypes may be favored under conditions that select for loss of SI. Third, I show that a dominant S-haplotype may also have contributed to the shift to SC in the widespread allotetraploid Capsella bursa-pastoris. Fourth, I showed that dominance relationships at the S-locus are largely conserved between the SI outcrossing species C. grandiflora and Arabidopsis halleri which diverged ~8 Mya. I also found that dominant S-haplotypes accumulate more transposable elements than recessive S-haplotypes, in line with expected sequence-level consequences of S-locus dominance. In sum, this thesis provides new insights into the broad conservation of dominance hierarchies at the Brassicaceae S-locus, and the role of dominant S-alleles in allopolyploid speciation and plant mating system shifts.
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| 5. |
- Dahlgren, Johan Petter, 1978-
(författare)
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Linking plant population dynamics to the local environment and forest succession
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Linking environmental variation to population dynamics is necessary to understand and predict how the environment influences species abundances and distributions. I used demographic, environmental and trait data of forest herbs to study effects of spatial variation in environmental factors on populations as well as environmental change in terms of effects of forest succession on field layer plants. The results show that abundances of field layer species during forest succession are correlated with their functional traits; species with high specific leaf area increased more in abundance. I also found that soil nutrients affect vegetative and flowering phenology of the forest herb Actaea spicata. The effect of nutrients shows that a wider range of environmental factors than usually assumed can influence plant phenology. Moreover, local environmental factors affected also the demography of A. spicata through effects on vital rates. An abiotic factor, soil potassium affecting individual growth rate, was more important for population growth rate than seed predation, the most conspicuous biotic interaction in this system. Density independent changes in soil potassium during forest succession, and to a lesser extent plant population size dependent seed predation, were predicted to alter population growth rate, and thereby the abundance, of A. spicata over time. Because these environmental factors had effects on population projections, they can potentially influence the occupancy pattern of this species along successional gradients. I conclude that including deterministic, as opposed to stochastic, environmental change in demographic models enables assessments of the effects of processes such as succession, altered land-use, and climate change on population dynamics. Models explicitly incorporating environmental factors are useful for studying population dynamics in a realistic context, and to guide management of threatened species in changing environments.
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| 6. |
- Forslund, Helena, 1978-
(författare)
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Herbivory, phenotypic variation, and reproductive barriers in fucoids
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Along the shores of the Northern hemisphere Fucus (Phaeophyceae) species are a prominent presence, providing substrate, shelter, and food for many species. Fucus evanescens, a non-indigenous species (NIS) in Sweden, and F. radicans, a recently described species that so far has only been found inside the species poor Baltic Sea, are the focus of this thesis.Interactions with enemies (e.g. predators, herbivores, parasites) have been shown to play a role in the success of NIS. The low consumption of Fucus evanescens by the generalist gastropod Littorina littorea in Sweden was found to depend on high levels of chemical defense in the introduced population, not the failure of the herbivore to recognize F. evanescens as suitable food.A survey of the relative abundance of F. radicans and F. vesiculosus and the most common associated fauna along the Swedish Bothnian Sea coast showed that F. radicans and F. vesiculosus are equally abundant throughout the range of F. radicans. The most common associated fauna were found to be more abundant on F. radicans compared to F. vesiculosus. In Sweden, where F. radicans had lower levels of defense chemicals than F. vesiculosus, F. radicans was grazed more than F. vesiculosus in bioassays. This could, together with other factors, influence the range of F. radicans.Fucus radicans and F. vesiculosus are closely related, recently separated, and growing sympatrically, therefore, possible reproductive barriers between F. radicans and F. vesiculosus were studied. In Estonia F. radicans and F. vesiculosus reproduces at different times of the year. No such clear reproductive barrier was found between the two species in Sweden where they reproduce at the same time and fertilization success and germling survival were the same for hybrids as for F. vesiculosus.Since the high clonality of F. radicans means that the gentic diversity in F. radicans populations is low I investigated how genetic diversity translates to phenotypic diversity in nine traits. Phlorotannin levels, recovery after desiccation, and recovery after freezing showed inherited variation, while the other six traits showed no variation related to genetic diversity. Phenotypic variation in populations of F. radicans will be higher in populations with higher genetic diversity and this might be beneficial to the community.
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| 7. |
- Larsén, Eva, 1980-
(författare)
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Phylogeny and macroevolution in Isoetes (Isoetales)
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis has focused on the evolutionary history of Isoetes (Isoetales, Lycopsida), its phylogeny, megaspore morphology and evolutionary path through deep time. With a broadened sampling of species to include more of the worldwide diversity of the genus compared to previous work an unexpected sister to the rest of the genus was found. Isoetes wormaldii Sim is a critically endangered species from the southeastern Cape region in South Africa, which grows in ponds and slow-moving streams. There are only a few, small populations, and they are very sensitive to habitat changes. The rest of Isoetes is divided into five major clades, which show complex and not readily understandable biogeographic patterns, and by which processes the species came to live in their current locations in the world is often a conundrum. The age of the extant Isoetes is intriguing as it could potentially explain some of the baffling geographic distributions. Analyses based on whole chloroplast genomes and nuclear cistrons found that the choice of clock model and which genome dataset the dating analysis is based on matter greatly when trying to date the genus as the results were highly inconsistent. The solution to the dating analysis woes might be dependent on finding new bases, e.g., fossil evidence, for age calibrations which would require the morphology of Isoetes to be better understood. Our study of megaspore morphology found substantial differences among species of Isoetes in both ornamentation and surface texture/structure. While no major clade within the genus could be unambiguously defined by their spore morphology there are some characteristics of smaller clades and patterns of ornamentation and surface texture across the phylogeny. Our tentative hypothesis is that a pustulate megaspore ornamentation and a cobwebby texture are ancestral features in the megaspore of Isoetes.
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| 8. |
- Lindgren, Åsa, 1973-
(författare)
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Effects of herbivory on arctic and alpine vegetation
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The distribution of plant species and functional traits in alpine and arctic environments are determined by abiotic conditions, but also by biotic interactions. In this thesis, I investigate interactions among plants and herbivory effects on plant community composition and plant functional traits in three different regions: Swedish Lapland, Beringia (USA/Russia) and Finnmark (Norway). Reindeer grazing was found to be extensive in southern Lapland and had limited effects on plant community composition and seedling germination. However, reindeer presence was found to influence plant functional traits, particularly in the subalpine birch forest. Tall herbs were lower and had lower SLA when reindeer were present, while small herbs showed an opposite pattern. The contrasting effects on the two herb groups are probably explained by a competitive release for small herbs when the tall herbs are suppressed by reindeer. Rodents had the largest relative impact on plant community composition in southern Lapland and this is consistent with the study from Finnmark, where rodents heavily affected dwarf shrubs on predator-free islands. With no predators present, vole densities increased profoundly and almost depleted some dwarf shrub species. These results support the idea that small mammals in arctic and alpine tundra are controlled by predators (i.e. top-down). However, a decrease in the nutritional quality in a sedge after defoliation gives support for the idea that small mammals are regulated by plant quality (i.e. bottom-up). In Beringia, small and large herbivores differed in the relation to plant community composition, since large herbivores were related to species richness and small herbivores were related to plant abundance. Plant functional traits were related only to large herbivores and standing crop of vascular plants.
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| 9. |
- Lundström, Sofie, 1971-
(författare)
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Hälsa, levnadsvanor och erfarenheter av förändring av levnadsvanor hos personer med psykossjukdom – hälsofrämjande aspekter inom psykiatrisk omvårdnad
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Bakgrund: Personer med psykossjukdom har ofta sämre fysisk hälsa jämfört med befolkningen i övrigt, delvis relaterat till ohälsosamma levnadsvanor såsom låg fysisk aktivitet, ohälsosam kost, tobaksbruk och riskfull alkoholkonsumtion. Trots att hälsofrämjande insatser har framhållits som betydelsefullt för att minska ojämlikheten i hälsa har inte det hälsofrämjande arbetet fått en given plats inom psykiatrisk vård. Ökad kunskap behövs dels om vilka levnadsvanor som påverkar hälsan, dels om vilka aspekter som påverkar möjligheten till förändring av levnadsvanor för personer med psykossjukdom.Syfte: Det övergripande syftet med avhandlingen var att utforska hälsorelaterade levnadsvanor och upplevd hälsa, samt erfarenheter av förändring av levnadsvanor och främjande aspekter för förändring, hos personer med psykossjukdom.Metod: Avhandlingen består av fyra delstudier. Delstudie I var en kvantitativ tvärsnittsstudie med syftet att kartlägga hälsorelaterade levnadsvanor och upplevd hälsa hos personer med psykossjukdom samt att undersöka könsskillnader och skillnader utifrån känsla av sammanhang (SOC). Data samlades in från personer med psykossjukdom som deltog i en hälsofrämjande levnadvaneintervention (n = 65). Beskrivande och jämförande analyser genomfördes på data, insamlad före interventionens start för att kartlägga självskattad hälsa, livskvalitet, BMI och levnadsvanor. För delstudie II som hade en kvalitativ design genomfördes narrativa intervjuer med personer med psykossjukdom som deltagit i en hälsofrämjande levnadsvaneintervention (n = 10). Syftet var att belysa innebörden av den levda erfarenheten av förändring av levnadsvanor hos personer med psykossjukdom. En fenomenologisk hermeneutisk metod användes för att analysera intervjutexterna. Deltagare i delstudie III bestod av sjuksköterskor som arbetade på olika psykiatriska öppenvårdsmottagningar (n = 15). Semistrukturerade intervjuer genomfördes för att beskriva deras erfarenheter av aspekter som främjar fysisk hälsa och stödjer hälsosamma levnadsvanor för personer med psykossjukdom. Intervjutexterna analyserades med kvalitativ innehållsanalys. Delstudie IV var en kvantitativ uppföljningsstudie och bestod av insamlad data från personer med psykossjukdom som deltagit i en hälsofrämjande levnadsvaneintervention (n = 54). Data, som bestod av självskattningar, kliniska mått och blodprover, samlades in före interventionens start, efter 12 månader och efter 24 månader. Flernivåanalys användes som metod för att undersöka hälsorelaterade förändringar efter deltagande i en hälsofrämjande levnadsvaneintervention.Resultat: Resultatet i delstudie I visade att personer med psykossjukdom hade högre BMI, lägre självskattad hälsa och livskvalitet, var mer stillasittande och rökte mer jämfört med befolkningen i övrigt. Personer med stark SOC skattade sin livskvalitet bättre och rökte mindre jämfört med de med svag SOC. Kvinnor konsumerade mer frukt och grönsaker än män. I delstudie II beskrevs innebörden av levnadsvaneförändringar, av personer med psykossjukdom: som en kamp med inre och yttre begränsningar, att det var något som måste göras på egen hand men tillsammans med andra och att längtan efter ett liv i harmoni kan motivera till förändringar. I resultatet av delstudie III framhöll sjuksköterskor aspekter som kan främja hälsa och hälsosamma levnadsvanor för personer med psykossjukdom. Sjuksköterskornas erfarenheter var: att ha ett hälsofrämjande fokus i varje möte, att stödja med varje persons förutsättningar i åtanke och att ta ansvar för hälsofrämjande insatser på varje nivå inom organisationen. Resultatet i delstudie IV visade en positiv förändring av fysisk aktivitet. Förändringen var associerad med antal tillfällen personen hade deltagit i hälsogrupp. Förändring av självskattad hälsa var positivt associerad med känslan av sammanhang. Således kan det antas att hälsofrämjande insatser som genomförs i grupp kan förbättra fysisk aktivitet, och att känslan av sammanhang bör stärkas för en bättre upplevd hälsa hos personer med psykossjukdom. Konklusion: Det finns såväl individuella aspekter som relationella, organisatoriska och samhälleliga aspekter som påverkar möjligheten till förändring av levnadsvanor. Inre styrka, en positiv självbild och positiva erfarenheter är individuella aspekter som tillsammans med relationella aspekter såsom stöd och att få ingå i en gemenskap, kan främja förändringar hos personer med psykossjukdom. På en organisatorisk och samhällelig nivå är samverkan, ansvarsfördelning samt kunskap och kompetens viktiga ingredienser för att främja det hälsofrämjande arbetet inom psykiatrisk vård. Det hälsofrämjande arbetet bör, tillsammans med insatser såsom utbildning och praktiskt stöd, fokusera på insatser som kan öka personens känsla av sammanhang och stärka resurser. Sjuksköterskan inom psykiatrisk vård har en nyckelposition för att utveckla den hälsofrämjande omvårdnaden, där fysisk och psykisk hälsa integreras, och där personens egen förmåga till förändring främjas. Ett salutogent och personcentrerat förhållningssätt, kan bidra till en hälsofrämjande omvårdnad, men för att kunna utveckla det hälsofrämjande arbetet inom psykiatrisk vård behöver individuella, relationella samt organisatoriska och samhälleliga aspekter beaktas. Således behöver det i samverkan tas ett gemensamt ansvar för hälsa och hälsosamma levnadsvanor, och organisatoriska strukturer behöver utvecklas för att möjliggöra en personcentrerad vård och för att utveckla de hälsofrämjande insatserna för personer med psykossjukdom.
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| 10. |
- Noury, Pourya, 1984-
(författare)
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On failure of high strength steel bridge roller bearings
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis is concerned with failure analysis of high strength steel bridge roller bearings.Paper Adescribes how the commonly used Hertz formulas for contact stresses underestimate the actual stresses in practice due to temperature differences, misalignments and other construction-related conditions. In this paper, finite element analyses of bridge roller bearings were carried out to investigate the accuracy of the traditional roller bearing design rules in view of issues such as girder deformability, misalignment imperfections and material nonlinearity. The results first indicated that roller bearings develop contact stress concentrations at the outer edges of the rollers. Second, it was shown that the contact stresses are very sensitive to misalignment imperfections between the bridge girder and the abutment. Third, it was shown that the roller bearings develop inelastic deformation at relatively low loads in relation to the design load.In Paper B, the finite element method was employed to gain an understanding of the behaviour of a cracked bridge roller bearing in service. The cracked roller was considered as a two-dimensional edge-cracked disk subjected to a diametrical compressive line load. The crack parameters, stress intensity factor Mode I, KI and Mode II ,KII were calculated for the relevant load configuration and angle of disk rotation. The calculated data for KIwere also used to check the accuracy of approximate stress intensity factor solutions reported earlier for Mode I. For plain Mode I loading very good agreement was found between the obtained results and data presented in Schindler and Morf (1994).Paper Cis aimed at finding the likely failure mechanism of a bridge roller bearing made of high strength martensitic stainless steel. Spectroscopy and finite element stress analysis of the roller indicated that an initial radial surface crack, found at an end face of the roller and close to the contact region, was induced by stress corrosion cracking (SCC). The initial crack subsequently changed shape and increased in size under growth through fatigue and finally formed a quarter-circle radial crack centred on the end face corner of the roller. Numerically computed stress intensity factors for the final crack showed that crack loading was predominantly in Mode II. For a crack size as observed on the fracture surface, the maximum service load, as specified by the manufacturer, enhanced by a certain roller bearing misalignment effect, was sufficient for failure through fracture.InPaper D, after a brief summary of the history of high strength stainless steel bearings, the paper reviews service experience of failed bearings in Sweden and elsewhere. Accompanying finite element analyses were performed in order to gain better insight into the likely failure mechanism. Finally, thiscomprehensive review leads to a conclusion that identifies the causes of the failures occurred and makes some recommendations.
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