Fatigue of Structural and Additively Manufactured Steels: Damage Assessment and Modelling Techniques

PhD thesis in Offshore technologyThe topics of damage assessment by in situ measurements before a macroscopic crack has been initiated, nonlinear damage modelling and additive manufacturing are herein discussed and researched from the perspective of the maintenance of ageing structures and mechanical equipment subjected to fatigue loading. In relation to the aforementioned topics, the thesis can be categorized into three parts, all of which are related to the maintenance of ageing structures and mechanical equipment. These are: 1) Fatigue damage monitoring prior to macroscopic crack initiation, 2) Damage modelling based on S-N curves, and 3) Mechanical properties of additively manufactured steel. 1. Fatigue damage monitoring prior to macroscopic crack initiation A conceptual framework is developed to select a method to assess small fatigue crack propagation and fatigue damage accumulation. The framework is focused on the underlying fatigue mechanism which is correlated with the measurable change for each of the identified parameters throughout the fatigue life, and how the parameter will change. The framework is based on the literature and is useful for both research and development communities, for those who are involved in structural integrity assessment. An experimental study is also performed regarding the feasibility of adopting macroscopic hardness indentations and their correlation with fatigue damage accumulation. Both Brinell and Vickers were adopted, with Brinell being found to exhibit a more continuous change, in addition to being statistically significant. 2. Damage modelling based on S-N curves A new damage function is proposed herein, based on the damage theory known as the theory of the S-N fatigue damage envelope. The work can be considered a framework to develop S-N curve-specific damage functions, as the underlying theory can be applied to any S-N curve for materials or structural details. Furthermore, the proposed damage function is compared with other recently proposed functions, including Miner’s rule, using experimental data. The proposed function generally exhibits better prediction than Miner’s rule and some of the other models. A generalized expression/function for fatigue damage was also proposed by investigating the functional forms commonly adopted in the literature. The relation of the parameters or variables of the functional form can be represented in three dimensions, resulting in it being able to be evaluated in three dimensions with experimental data, where it will result in a surface. Herein, it is also shown that two special cases of the proposed function exist, where the parameters are reduced to a single ratio, which is subsequently evaluated based on experimental data. 3. Mechanical properties of additively manufactured steel An experimental study is performed regarding the mechanical properties of additively manufactured steel printed by the technology of Bound Metal Deposition. Specimens were printed in various directions, which were subsequently tension tested to develop stress-strain curves. It was found that the printing technology would result in the final product exhibiting anisotropic behaviour correlated to a mesh of crack-like defects. The crack like defects also result in the conclusion that the printed specimens are expected to exhibit very poor fatigue capacity in comparison to their traditionally manufactured counterparts and also to exhibit anisotropic behaviour in relation to fatigue. Keywords: Fatigue damage assessment, hardness-based fatigue damage, nonlinear damage modelling, additively manufactured stee

«Lean kommuneplan» - en kvalitativ undersøkelse av implementeringen av Masterplan som verktøy for kommuneplanen

Denne oppgaven tar for seg implementeringsprosessen av en Masterplan i en kommune. Masterplanen er et Lean-verktøy som brukes for å arbeide for felles mål i hele organisasjonen, samt samle mål fra ulike planer på ett sted. Hensikten er å besvare problemstillingen: Hva kjennetegner implementeringen av Masterplan i Gjesdal kommune, hvilke utfordringer og muligheter møter man i implementeringen? Formålet er å se på hva som kjennetegner implementering av et nytt verktøy for planarbeid i kommunal sektor. Oppgavens data baserer seg på intervju med de tre hovedansvarlige for Masterplanen, samt tidligere gjennomførte intervju med 17 ledere i kommunen om holdninger til Masterplanen. Videre brukes også feltsamtaler og dokumenter fra kommunen i analysen. Den teoretiske rammen er pragmatisk institusjonalisme. Her benyttes translasjonsteori, adapsjonsteori, situasjonelt perspektiv og metaforer for å forstå implementeringen, samt faser av motstand for å klassifisere denne. Hovedfunnene er at kommunen har hentet Masterplan som idé fra Lean og Hoshin Kanri, som de har fått kjennskap til både gjennom litteratur og i kontakt med andre organisasjoner. Kommunen har oversatt idéen til en praksis som passer for kommunen. Idéen om Masterplan kom, på samme måte som Lean, fra private produksjonsbedrifter, og har dermed blitt modifisert i implementeringen til kommunen. Kommunens utfordringer med implementeringen har i hovedsak knyttet seg til tidsbruk, da kommunen må drive med deres kjernevirksomhet, det å levere tjenester til innbyggerne, samtidig som Masterplanen har blitt implementert. Videre har også implementeringen ført til andre endinger i organisasjonen.This thesis addresses the implementation process of a Master Plan in a municipality. The Master Plan is a Lean tool that is used to work for common goals throughout the organization, as well as to gather goals from different plans in one place. The thesis´ purpose is to answer the research question: What characterizes the implementation of Masterplan in Gjesdal municipality, what challenges and opportunities do they face in the implementation? The thesis looks at what characterizes the implementation of a new tool for planning in the municipal sector. The data is based on interviews with the three primary individuals responsible for the Master Plan, as well as previously conducted interviews with 17 leaders in the municipality about their views regarding the Master Plan. Furthermore, field interviews and documents from the municipality are also used in the analysis. The theoretical framework is pragmatic institutionalism. Here, translation theory, adaptation theory, situational perspective and metaphors are used to understand the implementation of the Master Plan, as well as phases of resistance to classify this. The main findings of this thesis are that the municipality has taken Master Plan as an idea from Lean and Hoshin Kanri. The municipality became aware of both through literature and through contact with other organizations. The municipality has translated the idea into a practice that suits the municipality. In the same way as Lean, the idea for Master Plan came from private production companies and has been modified in its implementation. The implementation of the Master Plan by the municipality has created both opportunities and challenges. From an opportunity perspective, the implementation has led to other changes in the organization, like possibilities to improve in other areas. As for challenges, they have mainly been related to time consumption, as the municipality must conduct its core business, providing services to the inhabitants, at the same time as the Master Plan has been implemented

A review of fatigue damage detection and measurement techniques

A vast amount of research has been carried out towards the goal of quantifying changes related to the fatigue damaging process in materials throughout the fatigue life. However, no recommended practice has been developed for the experimental measurement of fatigue damage before a macroscopic crack has been initiated. Therefore, this paper reviews the existing fatigue damage detection and measurement techniques on the basis of both momentum within the research field and their being considered non-destructive. The techniques are separated into two categories, namely, fatigue crack monitoring and fatigue damage monitoring. The parameters of these techniques, which quantify the physical and mechanical changes of the materials during the fatigue life, were critically reviewed in regard to the mechanism behind the change, limitations, shortcomings, etc. The acoustic emission, hardness, ultrasonic, magnetic and potential drop methods are applicable for in-situ measurements while positron annihilation and X-ray diffraction are more suitable for laboratory assessments. Even though all the revived methods are applicable for metals, acoustic emissions, X-ray diffraction, ultrasonic, strain-based and thermometric methods are also suitable for composites. The reliability, advantages, weaknesses, case/material dependency and applicability of each method are compared and tabulated for making a framework for choosing suitable technique for fatigue crack or damage detection of material or components.publishedVersio

Psychodynamic Diagnostic Manual - En kunnskapsoppsummering

I denne masteroppgaven har det blitt foretatt et integrative review for å finne ut hvordan og hva den psykodynamiske diagnosemanualen PDM tilfører til den allerede eksisterende nosologi. Gjennom søk i tre ulike databaser har det blitt samlet opp kunnskap, rangert evidens og inndelt i nye former. Oppsummeringen av kunnskapen gir oss ny innsikt i søken etter svaret på oppgavens problemstilling. Samtidig tilbyr den valgte metoden et overblikk over eksisterende kunnskap på området. Et stort antall av søkeresultatene var evidens basert på spesialist-uttalelser eller bok-anmeldelser, de var i hovedtrekk positive til PDM. Mange av dem sier noe om, og beskriver, det eksisterende gapet mellom den deskriptive klarhet og presisjon som de tradisjonelle diagnosesystem representerer - og den personsentrerte, nyanserte og sofistikerte kunnskapen teorien representerer. PDM-systemet er ment som et supplement for å tette dette gapet, og tilføye tradisjonell diagnostikk en mer nyansert og rikere beskrivelse av mennesker. I undersøkelsen som er gjort her har man identifisert noen sentrale temaer som evidensen gjengir som et svar på hva PDM-2 tilbyr. Det er funnet at PDM tilbyr ny innsikt i diagnostiske dimensjoner, noe som flere påpeker som svært berikende for diagnostikken og behandlingsplanlegging. Særlig PDM´s M-akse trekkes frem som et nyttig supplement til allerede eksisterende nosologi. Andre påpeker at PDM/PDC tilbyr nye hypoteser og gir andre diagnostiske vurderinger og resultater ny mening. Validitet og reliabiliteten av PDC er et gjennomgangstema spesielt for de kvantitative funnene – Det er funnet god validitet og reliabilitet. Det betyr at PDM fungerer som et supplement til de mest kjente diagnosesystem, og at den i tillegg tilføyer noe nytt til diagnostikken. Funnene i denne undersøkelsen er hovedsakelig oppløftende på vegne av PDM-systemets fremtid. Det finnes stort potensial for PDM, og hva den kan tilby. Mer forskning og erfaring trenges for å finne ut mer om manualens anbefalte kombinasjoner mellom PDC, intervjutyper, intervjuguider, teoretiske tilnærminger, og mye mer.In this master´s thesis, an intergrative review has been performed to find out how and in what way the Psychodynamic Diagnostic Manual (PDM) adds to the already existing nosology. Knowlege has been captured through extensive searches in three different databases. Evidence has been ranked and rearranged into new forms. The review of knowledge gives us new insight into the quest of searching after the answer of this master´s thesis issues. At the same time, the selected method for this thesis, is offering us an updated overview of existing evidence for the use of the PDM. A high amount of the search results were evidence based on opinions of specialists or book-reviews, and they were mainly positive towards the PDM. Many of them describe the gap between the descriptive clarity and presicion that the traditional diangosis-systems are representing – and the individual person based, nuanced and sophisticated knowledge that the theory is representing. The PDM-system is meant to be a supplement, to fill this gap, and to add a more nuanced and richer description of people to the traditional diagnosis-systems. This study has been successfull in identifying some important themes which the evidence is giving us as an answer to what the PDM offers. The results from this review show that the PDM is offering a new insight into diagnostic dimensions, and is somthing that several studys are pointing out as very enriching for both diagnosing and treatment planning. Especially the PDM´s M-axis are identifyed as a useful tool in supplement to the already existing nosolgy. Others are pointing out that the PDM/PDC offers new hypothesis, and gives other diagnostic assesments and results a new meaning. Validity and reliability of the PDC are also a recurring theme, especially for the quantitative findings – there is found good validity and reliability. This means that the PDM is working as a supplement to the most known diagnostic systems, and that it in addition adds something new to the diagnostics. The findings in this study, are mainly uplifting on the behalf of PDM´s future. There´s a great potential for PDM and what it kan offer. More reasearch is needed to find out more about this manual´s recommended combinations between the PDC, interviewstyles, interviewguides, theoretical approaches, and much more

Musikkens innflytelse på språket

I forskingsprosjektet eg har eg tatt føre meg problemstillinga: «Korleis kan bruk av musikk påverka språk/språkutviklinga til barna i barnehagen» Det og sjå på korleis andre barnehagar jobbar og tenkar om musikk som eit verktøy til språkutvikling er noko eg syntes har vært spennande. Musikken, rim og regler er noko me er innom kvar dag i barnehagen og det og tenka meir over kva effekt det har for språket er spennande. Det har blitt brukt kvalitativ forsking ved hjelp av intervjuar for å finna ut om kva informantane tenkte om musikk og språk. Eg har så brukt funnen frå intervjua for å drøfta med problemstillinga og teori. I avslutninga har eg trekt fram dei viktigaste momenta frå forskingsprosjektet mitt og litt av eigne tankar og kva er sitt igjen med etter dette forskingsprosjektet

Technology to accelerate pangenomic scanning for unknown point mutations in exonic sequences: cycling temperature capillary electrophoresis (CTCE)

<p>Abstract</p> <p>Background</p> <p>Rapid means to discover and enumerate unknown mutations in the exons of human genes on a pangenomic scale are needed to discover the genes carrying inherited risk for common diseases or the genes in which somatic mutations are required for clonal diseases such as atherosclerosis and cancers. The method of constant denaturing capillary electrophoresis (CDCE) permitted sensitive detection and enumeration of unknown point mutations but labor-intensive optimization procedures for each exonic sequence made it impractical for application at a pangenomic scale.</p> <p>Results</p> <p>A variant denaturing capillary electrophoresis protocol, cycling temperature capillary electrophoresis (CTCE), has eliminated the need for the laboratory optimization of separation conditions for each target sequence. Here are reported the separation of wild type mutant homoduplexes from wild type/mutant heteroduplexes for 27 randomly chosen target sequences without any laboratory optimization steps. Calculation of the equilibrium melting map of each target sequence attached to a high melting domain (clamp) was sufficient to design the analyte sequence and predict the expected degree of resolution.</p> <p>Conclusion</p> <p>CTCE provides practical means for economical pangenomic detection and enumeration of point mutations in large-scale human case/control cohort studies. We estimate that the combined reagent, instrumentation and labor costs for scanning the ~250,000 exons and splice sites of the ~25,000 human protein-coding genes using automated CTCE instruments in 100 case cohorts of 10,000 individuals each are now less than U.S. $500 million, less than U.S.$500 per person.</p

Tension testing of additively manufactured specimens of 17-4 PH processed by Bound Metal Deposition

In contrast to the traditional ways of subtractive manufacturing, additive manufacturing (AM), also known as 3D printing, adapts computer-aided design to iteratively build the component or part layer by layer. The technology has recently gained a high momentum, both within academia, but also within the industrial sector. However, it is common that parts produced by AM will have more defects than parts produced by traditional methods. The objective of this paper is to investigate a new method of additive manufacturing, namely the bound metal deposition method (BMD). This method seemed promising from the perspective that the metal is not iteratively being melted, similar to such as welding. In fact, the part is first printed, then washed, for then to be sintered. Consequently, avoiding the complex thermal histories/cycles. It was found that the material will exhibit anisotropic behaviour, and have a mesh of crack like defects, related to the printing orientation.publishedVersio

Journal Staff

The aluminum–zinc-vacancy (Al Zn −V Zn ) complex is identified as one of the dominant defects in Al-containing n -type ZnO after electron irradiation at room temperature with energies above 0.8 MeV. The complex is energetically favorable over the isolated V Zn , binding more than 90% of the stable V Zn ’s generated by the irradiation. It acts as a deep acceptor with the (0/− ) energy level located at approximately 1 eV above the valence band. Such a complex is concluded to be a defect of crucial and general importance that limits the n -type doping efficiency by complex formation with donors, thereby literally removing the donors, as well as by charge compensation