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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Investigating Moisture Gradient-Induced Warpage of Veneers

Strong, Kerrigan Ann 02 September 2021 (has links)
Flatness of wood composite panels, such as Laminated Veneer Lumber, is often difficult to control during the manufacturing process. Out-of-plane deformation, or warpage, of wood veneers caused by changes in moisture content affects the ability to press flat panels. To understand wood panel warpage, experimental methods are developed to create and measure moisture-induced deformation of wood veneers on five species of various thicknesses. Three moisture induction methods are investigated and evaluated to determine the increase in moisture content. Experiments are developed to produce moisture gradients of two concentrations in the veneers to examine the effect on warpage behavior. Additionally, the surface area of applied moisture and veneer thickness is also investigated. Three-dimensional scanning technology is used to measure warpage of veneers. A procedure using a structured-light scanner is developed to analyze the surface curvatures to observe the effect of moisture-induced warpage. After moisture-induction treatment of the veneer, surface deformation data is measured using the scanner and the data is converted into a 3D solid body model that is used for curvature comb analysis. The results show that curvature comb analysis can be used to analyze the geometry of moisture-induce warpage. The method can be used to analyze the effect of moisture gradient variables on warpage behavior including concentration, veneer thickness, and surface area. The experimental methods developed can be used by future researchers to validate theoretical warpage prediction models. / Master of Science / Flatness of wood composite panels, such as Laminated Veneer Lumber, is often difficult to control during the manufacturing process. Warpage of wood veneers is caused by changes in moisture content affecting manufacturers' ability to press flat panels. To understand wood panel warpage, experimental methods are developed to create and measure moisture-induced warpage of wood veneers on five species of various thicknesses. Three moisture induction methods are investigated and evaluated to determine the increase in moisture content. Experiments are developed to produce moisture gradients of two concentrations in the veneers to examine the effect on warpage behavior. Additionally, the surface area of applied moisture and veneer thickness is also investigated. Three-dimensional scanning technology is used to measure warpage of veneers. A procedure is developed to analyze the surface curvatures to observe the effect of moisture-induced warpage. After moisture-induction treatment of the veneer, surface deformation data is measured and converted into a 3D solid body model that is used to analyze curvature. The results show that moisture induction methods used to induce warpage can experience different geometries to analyze a veneer's curvature. The methods can be used to analyze warpage behavior of veneers by future researchers to validate warpage prediction model.
2

Deformationsmätning och uppdatering av geodetiskt nätverk i Mårtsbo provfält

Erlandsson, Axel, Frelin, Alexander January 2019 (has links)
Geodetiska provfält är viktiga för att geodetiska instrument kan kontrolleras och kalibreras. Exempelvis så kan en längdbas användas för att kontrollera nollpunktsfelet hos en Electronic Distance Measuement. Provfältets höga noggrannhet möjliggör även att detaljpunkterna exempelvis kan användas för att kontrollera noggrannheten vid utsättning eller inmätning. Att hålla provfältets koordinater uppdaterade är viktigt för att bibehålla den höga noggrannheten. Tidigare forskning visar att kända punkter kan vara bra för att kontrollera GNSS-antenner innan de sätts i bruk. Precisionen av mätningar var något man valde att utveckla på Statens Institution för Byggnadsforskning i Gävle på 70-talet (Statens Institut för Byggnadsforskning, 1984). Byggforskningen byggde ett provfält i Mårtsbo där punkter mättes in som sedan redovisats i en koordinatlista. Till en början användes provfältet för att kontrollera olika instrument och mätmetoder, men nu har det stått orört under en längre tid. Denna studie görs för att ta reda på om punkterna i området har rört sig något sen 1977 då fältet upprättades och därigenom avgöra om punkterna måste tilldelas nya koordinater innan användningen av fältet återupptas.   Innan mätning kontrollerades och kalibrerades instrumenten som skulle användas. För att koppla stomnätet till SWEREF 99 16 30 och RH 2000 gjordes en statisk GNSS-mätning på de två mest öppna punkterna i nätet. Vinklar och avstånd mellan punkterna erhölls genom att använda satsmätning med multistation. För att få med alla detaljpunkter gjordes en koordinattransformation med hjälp av de gamla koordinaterna och de nya som mätts in. I efterarbetet bearbetades GNSS-mätningarna i programvaran Leica Geo Office. Satsmätningarna behandlades i programvaran SBG Geo och där gjordes två nätutjämningar, en med lokala koordinater och en med koordinater i  SWEREF 99 16 30 och RH 2000. Slutligen transformerades resterande koordinater från det lokala systemet till SWEREF 99 16 30 och RH 2000 i  programvaran Gtrans. Baserat på resultatet har signifikant deformation uppstått på flera av punkterna. De största förändringarna som skett är i plan 2,2 mm i P5 och i höjd 1,7 mm i P7. Noggrannheten som uppnåtts i denna studie är inte lika bra som tidigare, men ändå tillräckligt för att använda fältet. / Geodetic test fields are important because they allow geodetic instruments to be tested and calibrated. For example, the baseline can be used when checking the zero-point error in an Electronic Distance Measurement. The high accuracy of the test field will also make it possible to use the detail points for checking the accuracy of the measurements when surveying. Keeping the coordinates of the field updated is important to maintain the high accuracy of the points. Previous research shows that known points were used to check GNSS-antennas before commercial use. The precision of measurements was something that the Swedish Institute of Constructional Science chose to develop even further in the late 1970s. A geodetic test field was constructed in Mårtsbo where points were established and presented in a coordinate list. The field was at first used to control different measuring equipment and methods, but in later years it has not been used at all. The aim of this study is to re-measure and update the coordinates of the test field. For this study, the instruments was controlled and calibrated before any measurements. To link to the well-established points with known coordinates in the control network static GNSS-measurements were performed on the two points located in the most open areas and positioned in SWEREF 99 16 30 and RH 2000. The angles and distances between the points were given by using rounds of measurements. To get coordinates for every detail point a coordinate transformation was used with the measured points as control points. During the post-processing of the GNSS-data the Leica Geo Office software was used to compute the coordinates. The rounds of measurements with multistation were processed in the software SBG Geo and network adjustments with both old and new coordinates were carried out. Finally, the rest of the coordinates were transformed into the new coordinate system which was done in the software Gtrans.. The result shows that significant local deformation has occurred on several points. The largest of deformation in plane is 2,2 mm in P5 and in height is 1,7 mm in P7. The uncertainties of the measured points are a bit higher in this study compared to earlier one, but they are still good enough to be use in this test field.
3

Statisk deformationsmätning med fotobaserad skanning : Utförd med icke-professionella digitalkameror

Jonsson, Anna, Eriksson, Pernilla January 2019 (has links)
Till följd av den utveckling som skett hos digitalkameror och programvaror för bildbehandling de senaste åren har intresset för fotobaserad skanning (FBS) vuxit. I denna studie utvärderades FBS som ett alternativ till terrester laserskanning (TLS) för statisk deformationsmätning och relaterade till kavitationsskador på vattenturbinkolvar där volym och maxdjup mäts. En stor del av syftet var att det skulle göras med simpla förutsättningar så att metoden blir enkel att utföra och tillämpbar framförallt i industrimiljöer. Simulerade deformationer skapades på en bräda i trä med en plan omgivande yta och på en boll i kork för att också undersöka en välvd yta. Fotograferingen utfördes med icke-professionella kameror, en digitalkamera och en smartphonekamera. Objekten som undersöktes hade en matt textur, bilderna togs med stor övertäckning (80–100%) och ljusförhållandena var goda för att undvika skuggning och blänk i bilderna. Det som utvärderades i studien var hur många kodade markörer som bör användas som konnektionspunkter för att förbättra bildmatchningen, optimalt antal skalstockar för skalsättning och vilken kameramodell och självkalibreringsmodell som gav den lägsta mätosäkerheten. Bildmatchningen och skapandet av 3D modellerna utfördes i programvaran Agisoft Photoscan. Analysen av modellerna utfördes i programvarorna 3DReshaper och CloudCompare. Resultaten utvärderades mot en skannad referensmodell framtagen med en ROMER Absolute Arm som har möjlighet att uppvisa mätosäkerheter på hundradels mm och kunde därmed anses som “sant” värde i denna studie. Resultatet visade att de kodade markörerna inte var nödvändiga som konnektionspunkter för bildmatchningen. Det visade även att oavsett kamera, självkalibreringsmodell och antal skalstockar (4, 3 & 2) låg alla modeller under den tillåtna avvikelsen i volym och maxdjup som normen för kavitationsskador på vattenturbinkolvar föreskriver (IEC 60609-1, från Swedish Standards Institute). Normen anger att mätosäkerheten på metoden som används inte får överskrida ±15% från det sanna värdet. Den här metoden har här visat sig vara tillämpbar och kan ersätta TLS för dokumentation och avgjutning för uppmätning av statiska deformationer när kraven på en relativ mätosäkerhet är ±5% av det sanna värdet. / As a result of the development of digital cameras and image processing software in recent years, the interest in close-range photogrammetry (CRP) has grown. In this study, CRP was evaluated as an alternative method to terrestrial laser scanning (TLS) for static deformation measurements and it was related to cavitation damage on water turbine pistons where the volume and maximum depth is measured. A large part of the purpose of the study was that it should be done with simple conditions so that the method will be easy to carry out and applies especially in industrial environments. Simulated deformations were created on a wooden board with a flat surrounding surface, and on a ball made of cork. The shooting was done with non-professional cameras, a digital camera and a smartphone camera. The objects that was examined had a matte texture, the images were taken with a large overlap (80–100%) and the lighting conditions were good enough to avoid shading and glare in the pictures. What was evaluated in the study was how many coded markers that should be used to improve image alignment, what the optimal number of scale bars for scaling the model is, and which camera model and self-calibration model that gave the lowest measurement uncertainty. The alignment of the images and creation of the 3D-models of the deformations were performed in the software Agisoft Photoscan. The analysis of the models was performed in the softwares 3DReshaper and CloudCompare. The results were evaluated against a scanned reference model developed with a ROMER Absolute Arm which has the ability to display measurement uncertainties on hundreds of millimetres and could thus be considered as a “true” value in this study. The result showed that the coded markers were not necessary in the image alignment procedure. It also showed that, regardless of which camera, self- calibration model and number of scale bars (4, 3 & 2), all the models created were below the permitted deviation in volume and maximum depth as the standard for cavitation damage on water turbine pistons (IEC 60609-1, from the Swedish Standards Institute) prescribes. The standard states that the measurement uncertainty of the method used must not exceed ±15% from the true value. This method has been found to be applicable and can replace TLS for documentation and volume measurement with a temporary filler for static deformations when the requirements for a relative measurement uncertainty are ±5% from the true value.

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