Abstract

Purpose:

The purpose of the study is to develop a model that will facilitate the choice of maintenance strategy within the Swedish pulp and paper industry. Without compromising system availability, the model aims to reduce inventory holding costs.

Methodology:

At first, a literary research was conducted to create a holistic view over the chosen topic, in time it developed into a literature framework. Secondly, a case study was conducted in order to obtain empirical data. The data were obtained through interviews and archival records. The literature framework and the empirical data were then cross-analyzed with each other.

Findings:

In this thesis, a model has been developed based on previously applied and accepted methods. The methods have been identified and described in order to provide a strategy in which the inventory levels- and value could be lowered. The findings indicate that the organization must seek to assign ABC-classified and VED-analyzed components different maintenance actions in order to reduce the total cost.

Theoretical contribution:

This thesis contributes to a methodology development regarding spare parts management. It aims to add knowledge to the existing gap regarding spare parts order point and batch size. The thesis provides a procedure in which systems including critical and expensive components are evaluated in order to assign them the appropriate maintenance.

Practical relevance:

The model has only been exemplified by using a system position from Stora Enso Skutskär, the numerical values are examples. The model must be tested with real values and the risk analysis must be carried out with a group of employees with great insight regarding the selected component and system position.

Limitations:

This thesis is delimited to spare parts management and inventory management. The study only involves one Swedish organization, whereas the organization and its spare parts management illustrates the complexity concerning spares. The model will not be verified as the focus is to highlight the research gap and to develop the model.

Syftet med detta arbete är att prova limträbalkars tvärkraftskapacitet genom olika utformning av förstärkningar med träribbor. En litteraturstudie är genomförd för att kartlägga tidigare forskning inom området. Det finns ett antal provade förstärkningsmetoder för limträ, dock endast ett fåtal som behandlar tvärkraftskapacitet.

Detta arbete är en vidareutveckling av ett tidigare examensarbete av Ahlskog och Ross (2015). Deras studie bygger på en metod där sadelbalkar i limträ förstärkts mot tvärkraftsbrott genom att förstärkningsribbor limmats på utsidan av tvärsnittet i vinkel mot fiberriktningen med trälim av typen PVAc.

Fem olika provserier har testats med avseende på limträs tvärkraftskapacitet. För att få ett statistiskt underlag innehöll varje provserie åtta provbitar. En serie var oförstärkt, två provserier förstärktes med pålimmade träribbor och två serier förstärktes med infrästa träribbor. Förstärkningsribborna vinklades för att ta drag- eller tryckkraft inom de olika förstärkningsmetoderna.

Förstärkningarnas kapacitet mot tvärkraftsbrott testades med drag- och tryckprovmaskin där deformation samt tryckkraft registrerades. Insamlade mätvärden behandlades genom en statistisk analys och normalfördelningskurvor ritades för hela mätmängden utifrån antagandet att provresultaten var normalfördelade. Metoden med pålimmade träribbor jämfördes med metoden med infrästa träribbor. Förstärkning med träribbor utsatta för dragkrafter jämfördes med förstärkning med träribbor utsatta för tryckkrafter. Samtliga förstärkta provserier jämfördes med den oförstärkta provserien.

Arbetet resulterade i en ökning av tvärkraftskapaciteten med 16% av medelvärdet för provserien med infrästa träribbor utsatta för tryckkraft. Det har även konstaterats att det karakteristiska värdet för tvärkraftskapaciteten ökade med 14% i provserien med pålimmade träribbor som utsatts för dragkraft.

I slutet av detta arbete presenteras förslag på framtida studier.

The objective of this report is to derive an analytical and numerical USC model for thermal analysis. These models are meant to calculate USC temperature variation across the USC duct as well as the fluid temperature along the USC. The main purpose of the analytical model is to attain a detailed steady state tool for USC (as in this report) design and dimensioning. The numerical model is meant to calculate the time dependant USC thermal performance as well as being a benchmark for the analytical model.

Annealing procedures for hot-wire sensors of platinum and platinum-plated tungsten have been investigated experimentally. It was discovered that the two investigated sensor metals behave quite differently during the annealing process, but for both types annealing may improve long-term stability considerably. Measured drift of sensors both without and with prior annealing is presented. Suggestions for suitable annealing temperatures and times are given. 

Regarding the great importance of fast cooling in steel industry for the production processes, a deep understanding of heat transfer and fluid dynamics must be held. A steel plate is heated up until a maximum temperature of 700 ⁰ C to be the n cooled down seconds later by a configuration of multi ple impinging water jets. Different flow rates are used simultaneously by different adjacent jets to perform quenching over the sample, so different hardness is obtained in the material over a small area . Temperature drop in time i s measured and monitored by embedded thermocouples and LabVIEW program. To achieve greater understanding of the quenching performance with different flow rates , several parameters are selected to be varied in order to achieve the best working conditions. Jet diameter takes values between 4 and 10 mm, initial temperature of quenching varies from 400 to 700 ⁰ C , subcooling temperature is tested for 65 and 75 K, and jet velocity varies between 1.9 and 3.9 m/s. The result of total number of 9 expe riments shown that v ariation of jet diam eter does not influence substantially on the cooling rate if flow rate is kept constant. High initial quenching temperature (600 - 700 ⁰ C ) led to slightly higher cooling rate in the stagnation region of water jets. The peak value of heat transfer rate in the upwash flow zone was more highlighted for initial quenching temperature 600 ⁰ C and below it. High er values of subcooling and jet velocity produce better cooling rates. The result shown higher jet velocity at one column of water jets changes position of upw ash flow slightly toward the adjacent column of jets with lower jet velocity. In general, the result shown that all the studied parameters did not have negative effect on obtaining various cooling rates over the steel plate.

Lösullsisolering gjord av hampfiber varken tillverkas eller säljs som en kommersiell produkt i Sverige idag. Möjligheterna är emellertid goda att på olika sätt få igång en inhemsk lokal produktion. Beredning av fibrerna med tornadoteknik kan vara ett sätt att åstadkomma ett utgångsmaterial lämpligt för bl a lösull. Försök visar att lösullsprodukter av hampfiber går att åstadkomma med egenskaper som är likvärdiga de hos träbaserad cellulosaisolering.

Sammanfattning

Syftet var att undersöka hur människor upplever källsorteringpå ett personligt och allmänt plan och utifrånresultatet arbeta fram en förbättrad källsorteringsproduktför dagens hushåll. Medan målsättningen var attpresentera en kunskapsgrund om hur framtida källsorteringsprodukterbör designas för samarbetspartnernHammarplast Consumer AB.Från den inledande enkätundersökning identifieradesflertalet problemområden som angreps genom designmetodikoch diverse analysmetoder. Inledningsvis undersöker och ifrågasätter arbetet placeringenav källsorteringen i hemmet och vilken rollkökets historiska utveckling spelat för hushållens avfallshantering.Man frågar sig även om hur vida en nykällsorteringsprodukt bör anpassas efter bostäder medspecifika byggnadsår, eller inte och vilka avfallsmängderdet svenska hushållet ska hantera i dagsläget. Genomgåendeför projektet är att olika resonemang till stordel förs och förklaras genom illustrationer, foton ochandra grafiska element och slutligen resulterar i ett genomarbetatkoncept.Avslutningsvis förs en diskussion över filosofin kringmaterialval vid produktutveckling och vilka materialsom är bäst lämpade för det genererade konceptet ur ettekonomiskt, produktionstekniskt och miljömässigt perspektiv.

In accelerated testing, material specimens are exposed to completely artificial environments, where exposure to individual degradation agents is enhanced. In contrast, field-testing exposes specimens to multiple degradation agents. When performing a semi-natural test, the influence of a selected degradation agent may be increased while the specimen is still situated in its natural environment. Moisture is such an agent. In an experimental set-up for evaluating long-term optical performance of an building integrated Unglazed Solar Collector, a sub-task was to increase Time of Wetness (TOW) for several collector specimens for two reasons: to “simulate” an active cooling of the component as is the case for solar collectors; and to assess the role of TOW on optical degradation of the solar collector. Specimen cooling and increase in TOW was achieved by utilisation of a Direct-Air Peltier Element. TOW was estimated through measurements with WETCORR sensors (monitoring surface temperatures and moisture) and climate parameters (temperature and relative humidity) at site. At this particular test site in Gävle, Sweden, TOW was more than doubled in comparison to non-cooled surfaces. The Peltier Element proved to be inexpensive and flexible for this purpose.

High-speed machining of thin-walled structures is widely used in the aeronautical industry. Higher spindle speed and machining feed rate, combined with a greater depth of cut, increases the removal rate and with it, productivity. The combination of higher spindle speed and depth of cut makes instabilities (chatter) a far more significant concern. Chatter causes reduced surface quality and accelerated tool wear. Since chatter is so prevalent, traditional cutting parameters and processes are frequently rendered ineffective and inaccurate. For the machine tool to reach its full utility, the chatter vibrations must be identified and avoided. In order to avoid chatter and implement optimum cutting parameters, the machine tool including all components and the work piece must be dynamically mapped to identify vibration characteristics. The aim of the presented work is to develop a model for the prediction of stability limits as a function of process parameters. The model consists of experimentally measured vibration properties of the spindle-tool, and finite element calculations of the work piece in (three) different stages of the process. Commercial software packages used for integration into the model prove to accomplish demands for functionality and performance. A reference geometry that is typical for an aircraft detail is used for evaluation of the prediction methodology. In order to validate the model, the stability limits predicted by the use of numerical simulation are compared with the results based on the experimental work.