<p>Sammanfattning</p><p>I en pappersrulle är de yttre lagren utsatta för dragspänning. Om det finns variationer i rullens diameter i form av valkar finns det risk för att papperet förlängs irreversibelt i dessa positioner och orsaka slappa stråk. Den deformation som uppstår vid långvarig belastning av papper kallas krypning.</p><p>Uppgiften i detta arbete var, att på lab., simulera valkar genom att utsätta pappersremsor för konstant dragspänning av olika storlekar. En av frågeställningarna var om egenskapsförändringar kan påvisas när papper utsätts för konstant inspänningskraft under en längre tid. De parametrar som undersökts var töjning, kryphastighet och relaxation, även mätningar på papperets mekaniska egenskaper dragstyrka, brottöjning och dragstyvhet har utförts i detta arbete.</p><p>De papperskvalitéer som undersöktes var 71g/m2 MG-papper, 80g/m2 optisk liner och 135g/m2 liner. Inspänningskraften som papperet utsattes för motsvarade 10 %, 30 % och 50 % av dragstyrkan hos varje kvalité. Provremsor belastades under ett, fyra och sju dygn, för att sedan relaxeras.</p><p>Resultaten visar att dragstyrkan och dragstyvheten inte påverkas av att papperet varit utsatt för en inspänningskraft. Däremot blev brottöjningen mindre ju större den irreversibla förlängningen hos papperet var. Samtliga papperskvalitéer relaxerar tillbaka till ursprungslängd efter fyra dygn när belastningen var 10 %. Om belastningen däremot var 30 % och 50 % uppstod en irreversibel förlängning redan efter ett dygn. Vid belastning under sju dygn uppstod permanent förlängning hos samtliga kvalitéer och belastningar utom MG-papper 10 % som relaxerade till ursprungslängd. MG-papper är därmed den papperskvalité som står emot krypning bäst och är på så sätt minst känslig för valkar i pappersrullen.</p><p>En högre belastning ger en högre kryphastighet och större irreversibel förlängning. För att undvika uppkomsten av slappa stråk bör därför banspänningen som används vid upprullningen av papperet inte vara större än 10 % av dragstyrkan hos papperskvalitén.</p><p>Hur länge papperet är belastat påverkar också den slutliga irreversibla förlängningen. Det innebär att lagring ökar risken för att slappa stråk kommer att uppstå i efterbearbetningen.</p> / <p>Abstract</p><p>In a paper roll the outer layers are under tensile stress. If there are variations in the roll diameter there is a risk that the thicker parts of the roll will make the paper elongate more in these regions, because they will be under a higher tensile stress. This may cause baggy webs. The deformation that occurs during a long time under tensile stress is called creep.</p><p>Experiments have been performed with strips of paper that have been exposed to a constant load and constant climate (50 % RH, 23°C). The properties that have been examined are creep strain, creep rate and relaxation after creep. Studies of tensile strength, tensile stiffness and strain at break have also been made.</p><p>The paper qualities that have been examined were 71g/m2 MG-paper, 80g/m2 liner and 135g/m2 liner. The paper qualities in this study are exposed to loads that correspond to 10 %, 30 % and 50 % of their tensile strength. The paper strips were under load during 24h, four and seven days.</p><p>The results in these studies show that tensile strength and tensile stiffness remains the same after the paper has been exposed to a constant load. The strain at break, on the other hand, decreases with increasing irreversible elongation of the paper strips. All paper qualities recover to the initial length after four days under a load of 10 % of the tensile strength. If the load corresponds to 30 % or 50 % of the tensile strength a permanent elongation arose as early as after 24h. After seven days, only the MG-paper recovered to the initial length if the load corresponded to 10 % of the tensile strength. This means that MG-paper is more resistant to creep then the liner qualities. Consequently, MG-paper is the paper quality that is least sensitive to ridges.</p><p>A higher load gives a higher creep rate and larger irreversible elongation of the paper. To avoid baggy webs to arise, the load should not exceed 10 % of the paper’s tensile strength when winding the paper roll. The time under which the paper is under load also influence the final irreversible elongation. Therefore, to avoid baggy webs the paper roll shouldn’t be stored for too long.</p>

Sammanfattning I en pappersrulle är de yttre lagren utsatta för dragspänning. Om det finns variationer i rullens diameter i form av valkar finns det risk för att papperet förlängs irreversibelt i dessa positioner och orsaka slappa stråk. Den deformation som uppstår vid långvarig belastning av papper kallas krypning. Uppgiften i detta arbete var, att på lab., simulera valkar genom att utsätta pappersremsor för konstant dragspänning av olika storlekar. En av frågeställningarna var om egenskapsförändringar kan påvisas när papper utsätts för konstant inspänningskraft under en längre tid. De parametrar som undersökts var töjning, kryphastighet och relaxation, även mätningar på papperets mekaniska egenskaper dragstyrka, brottöjning och dragstyvhet har utförts i detta arbete. De papperskvalitéer som undersöktes var 71g/m2 MG-papper, 80g/m2 optisk liner och 135g/m2 liner. Inspänningskraften som papperet utsattes för motsvarade 10 %, 30 % och 50 % av dragstyrkan hos varje kvalité. Provremsor belastades under ett, fyra och sju dygn, för att sedan relaxeras. Resultaten visar att dragstyrkan och dragstyvheten inte påverkas av att papperet varit utsatt för en inspänningskraft. Däremot blev brottöjningen mindre ju större den irreversibla förlängningen hos papperet var. Samtliga papperskvalitéer relaxerar tillbaka till ursprungslängd efter fyra dygn när belastningen var 10 %. Om belastningen däremot var 30 % och 50 % uppstod en irreversibel förlängning redan efter ett dygn. Vid belastning under sju dygn uppstod permanent förlängning hos samtliga kvalitéer och belastningar utom MG-papper 10 % som relaxerade till ursprungslängd. MG-papper är därmed den papperskvalité som står emot krypning bäst och är på så sätt minst känslig för valkar i pappersrullen. En högre belastning ger en högre kryphastighet och större irreversibel förlängning. För att undvika uppkomsten av slappa stråk bör därför banspänningen som används vid upprullningen av papperet inte vara större än 10 % av dragstyrkan hos papperskvalitén. Hur länge papperet är belastat påverkar också den slutliga irreversibla förlängningen. Det innebär att lagring ökar risken för att slappa stråk kommer att uppstå i efterbearbetningen. / Abstract In a paper roll the outer layers are under tensile stress. If there are variations in the roll diameter there is a risk that the thicker parts of the roll will make the paper elongate more in these regions, because they will be under a higher tensile stress. This may cause baggy webs. The deformation that occurs during a long time under tensile stress is called creep. Experiments have been performed with strips of paper that have been exposed to a constant load and constant climate (50 % RH, 23°C). The properties that have been examined are creep strain, creep rate and relaxation after creep. Studies of tensile strength, tensile stiffness and strain at break have also been made. The paper qualities that have been examined were 71g/m2 MG-paper, 80g/m2 liner and 135g/m2 liner. The paper qualities in this study are exposed to loads that correspond to 10 %, 30 % and 50 % of their tensile strength. The paper strips were under load during 24h, four and seven days. The results in these studies show that tensile strength and tensile stiffness remains the same after the paper has been exposed to a constant load. The strain at break, on the other hand, decreases with increasing irreversible elongation of the paper strips. All paper qualities recover to the initial length after four days under a load of 10 % of the tensile strength. If the load corresponds to 30 % or 50 % of the tensile strength a permanent elongation arose as early as after 24h. After seven days, only the MG-paper recovered to the initial length if the load corresponded to 10 % of the tensile strength. This means that MG-paper is more resistant to creep then the liner qualities. Consequently, MG-paper is the paper quality that is least sensitive to ridges. A higher load gives a higher creep rate and larger irreversible elongation of the paper. To avoid baggy webs to arise, the load should not exceed 10 % of the paper’s tensile strength when winding the paper roll. The time under which the paper is under load also influence the final irreversible elongation. Therefore, to avoid baggy webs the paper roll shouldn’t be stored for too long.

In this experimental investigation, the tensile creep behavior of commercial-purity molybdenum sheet at temperatures between 1300°C and 1700°C is critically evaluated, based upon experimental creep testing and microstructural characterizations. The high-temperature properties of molybdenum are of interest because there are many applications in which molybdenum and molybdenum alloys are used at elevated temperatures. Understanding of the creep mechanisms and the constitutive relations between stress and strain at elevated temperatures is needed in order to determine if molybdenum is an appropriate choice for a given high-temperature design application and to accurately predict its creep life. The creep behavior of two commercially-available grades of molybdenum was determined using short-term creep tests (1/2 to 14 hours) at slow to moderate true-strain rates of 10⁻⁶ to 10⁻⁴ s⁻¹ and temperatures between 1300°C and 1700°C. High-temperature, uniaxial tensile testing was used to produce data defining the relationship between tensile creep strain-rate and steady-state flow stress at four temperatures: 1340°C, 1440°C, 1540°C, 1640°C. Microstructural changes that occurred during creep testing were evaluated and compared to changes resulting from elevated temperature exposure alone. Mechanisms for dynamic abnormal grain growth that occurred during creep testing and the causes of the microstructural changes that occurred as a function of temperature are discussed. / text

Earthquakes form by sudden brittle failure of rock mostly as shear ruptures along a rupture plane. Beside this, mechanisms other than pure shearing have been observed for some earthquakes mainly in volcanic areas. Possible explanations include complex rupture geometries and tensile earthquakes. Tensile earthquakes occur by opening or closure of cracks during rupturing. They are likely to be often connected with fluids that cause pressure changes in the pore space of rocks leading to earthquake triggering. Tensile components have been reported for swarm earthquakes in West Bohemia in 2000. The aim and subject of this work is an assessment and the accurate determination of such tensile components for earthquakes in anisotropic media. Currently used standard techniques for the retrieval of earthquake source mechanisms assume isotropic rock properties. By means of moment tensors, equivalent forces acting at the source are used to explain the radiated wavefield. Conversely, seismic anisotropy, i.e. directional dependence of elastic properties, has been observed in the earth's crust and mantle such as in West Bohemia. In comparison to isotropy, anisotropy causes modifications in wave amplitudes and shear-wave splitting. In this work, effects of seismic anisotropy on true or apparent tensile source components of earthquakes are investigated. In addition, earthquake source parameters are determined considering anisotropy. It is shown that moment tensors and radiation patterns due to shear sources in anisotropic media may be similar to those of tensile sources in isotropic media. In contrast, similarities between tensile earthquakes in anisotropic rocks and shear sources in isotropic media may exist. As a consequence, the interpretation of tensile source components is ambiguous. The effects that are due to anisotropy depend on the orientation of the earthquake source and the degree of anisotropy. The moment of an earthquake is also influenced by anisotropy. The orientation of fault planes can be reliably determined even if isotropy instead of anisotropy is assumed and if the spectra of the compressional waves are used. Greater difficulties may arise when the spectra of split shear waves are additionally included. Retrieved moment tensors show systematic artefacts. Observed tensile source components determined for events in West Bohemia in 1997 can only partly be attributed to the effects of moderate anisotropy. Furthermore, moment tensors determined earlier for earthquakes induced at the German Continental Deep Drilling Program (KTB), Bavaria, were reinterpreted under assumptions of anisotropic rock properties near the borehole. The events can be consistently identified as shear sources, although their moment tensors comprise tensile components that are considered to be apparent. These results emphasise the necessity to consider anisotropy to uniquely determine tensile source parameters. Therefore, a new inversion algorithm has been developed, tested, and successfully applied to 112 earthquakes that occurred during the most recent intense swarm episode in West Bohemia in 2000 at the German-Czech border. Their source mechanisms have been retrieved using isotropic and anisotropic velocity models. Determined local magnitudes are in the range between 1.6 and 3.2. Fault-plane solutions are similar to each other and characterised by left-lateral faulting on steeply dipping, roughly North-South oriented rupture planes. Their dip angles decrease above a depth of about 8.4km. Tensile source components indicating positive volume changes are found for more than 60% of the considered earthquakes. Their size depends on source time and location. They are significant at the beginning of the swarm and at depths below 8.4km but they decrease in importance later in the course of the swarm. Determined principle stress axes include P axes striking Northeast and Taxes striking Southeast. They resemble those found earlier in Central Europe. However, depth-dependence in plunge is observed. Plunge angles of the P axes decrease gradually from 50° towards shallow angles with increasing depth. In contrast, the plunge angles of the T axes change rapidly from about 8° above a depth of 8.4km to 21° below this depth. By this thesis, spatial and temporal variations in tensile source components and stress conditions have been reported for the first time for swarm earthquakes in West Bohemia in 2000. They also persist, when anisotropy is assumed and can be explained by intrusion of fluids into the opened cracks during tensile faulting. / Erdbeben entstehen durch plötzlichen Sprödbruch des Gesteins, meist als Scherbruch entlang einer Bruchfläche. Daneben werden für einige Beben v.a. in vulkanischen Gebieten auch Mechanismen beobachtet, die scheinbar vom Modell des Scherbruches abweichen. Ursachen dafür beinhalten komplexe Bruchgeometrien und tensile Erdbeben. Bei tensilen Erdbeben kommt es während des Bruchs zum Öffnen oder Schließen der Bruchfläche und damit zu Volumenänderungen. Erdbeben mit tensilen Anteilen stehen wahrscheinlich oft im Zusammenhang mit Fluiden, welche zur Durckänderung im Porenraum von Gesteinen und damit zum Auslösen des Bebens führen. Sie wurden auch im Vogtland während eines Erdbebenschwarms im Jahr 1997 beobachtet. Die Beurteilung und sichere Bestimmung tensiler Anteile von Erdbeben sind Ziel und Gegenstand dieser Arbeit. Bei Standardverfahren zur Bestimmung von Erdbebenmechanismen werden isotrope Gesteinseigenschaften angenommen. Momententensoren beschreiben dabei Kräfte, die das abgestrahlte Wellenfeld erklären. Allerdings wird seismische Anisotropie, d.h. Richtungsabhängigkeit elastischer Eigenschaften, in der Erdkruste und im Mantel wie z.B. im Vogtland beobachtet. Anisotropie bewirkt im Vergleich zu isotropen Medien Veränderungen der Wellenamplituden und -polariserungen sowie das Aufspalten von Scherwellen. In der vorliegenden Arbeit werden daher der Einfluss seismischer Anisotropie auf wahre oder scheinbar auftretende tensile Quellanteile untersucht und Erdbebenmechanismen unter Berücksichtigung seismischer Anisotropie bestimmt. Es wird gezeigt, dass Momententensoren und Abstrahlmuster von Scherbrüchen in anisotropen Medien denen von tensilen Brüchen in isotropen Medien ähneln können. Umgekehrt treten Ähnlichkeiten tensiler Beben in anisotropen Gesteinen mit Scherbrüchen in isotropen Medien auf. Damit existieren Mehrdeutigkeiten beobachteter tensiler Quellanteile. Die Effekte von Anisotropie hängen von der Orientierung des Bruches und vom Grad der Anisotropie ab. Außerdem beeinflusst Anisotropie das Moment eines Bebens. Herdflächenorientierungen können auch dann verlässlich bestimmt werden, wenn man Isotropie statt Anisotropie annimmt und die Spektren von Kompressionswellen verwendet. Bei Hinzunahme der Spektren von Scherwellen können Uneindeutigkeiten auftreten. Abgeleitete Momententensoren zeigen systematische Artefakte. Beobachtungen tensiler Quellanteile von Beben im Vogtland im Jahr 1997 können nicht allein durch moderate Anisotropie erklärt werden. Weiterhin wurden früher bestimmte Momententensoren induzierter Beben nahe der Kontinentalen Tiefbohrung, Bayern, unter Annahme anisotroper Parameter reinterpretiert. Die Beben werden einheitlich als Scherbrüche charakterisiert, obwohl deren Momententensoren tensile Bestandteile enthalten, die als scheinbar angesehen werden. Die Resultate unterstreichen die Notwendigkeit, seismische Anisotropie zu berücksichtigen, um tensile Komponenten von Erdbeben eindeutig zu bestimmen. Ein daher neu entwickelter Inversionsalgorithmus wurde getestet und erfolgreich auf 112 Erdbeben der letzten intensiven Schwarmepisode im Jahr 2000 im Vogtland an der deutsch-tschechischen Grenze angewandt. Die Herdparameter wurden unter Verwendung isotroper und anisotroper Geschwindigkeitsmodelle ermittelt. Die Beben zeigen Lokalmagnituden zwischen 1,6 und 3,2. Sie weisen zueinander ähnliche Herdflächenlösungen mit linkslateralem Versatz auf steil einfallenden, etwa Nord-Süd orientierten Bruchflächen auf. Die Fallwinkel nehmen oberhalb 8,4km Tiefe ab. Für über 60% der betrachteten Erdbeben werden tensile Quellanteile mit Volumenvergrößerung beobachtet. Die tensilen Komponenten zeigen Abhängigkeiten von Herdzeit und -ort. Sie sind zu Beginn des Schwarms sowie in Tiefen unterhalb 8,4km besonders signifikant und nehmen später an Bedeutung ab. Abgeleitete Hauptspannungsachsen enthalten P Achsen mit nordwestlicher und T Achsen mit südwestlicher Streichrichtung. Sie ähneln denen in Mitteleuropa. Es werden tiefenabhängige Fallwinkel beobachtet. Die Änderungen erfolgen für die P Achsen graduell von 50° hin zu flacheren Fallwinkeln bei tieferen Beben. Sie erfolgen jedoch abrupt für die T Achsen von etwa 8° oberhalb einer Tiefe von etwa 8,4km zu 21° einfallend unterhalb dessen. Mit dieser Arbeit werden erstmals zeitliche und räumliche Veränderungen tensiler Quellanteile und Spannungszustände im Vogtland für Erdbeben im Jahr 2000 beobachtet. Diese haben auch dann Bestand, wenn seismische Anisotropie berücksichtigt wird. Sie können durch Fluide erklärt werden, die in die Bruchflächen eindringen.

This thesis focuses on the description of 3D printing technologies using the FDM method, which uses deposition of molten thermoplastics and their subsequent cooling and solidification layer by layer. This unique structure then shows a strong anisotropy of mechanical properties and, as a result, their testing and print settings are very important. Tensile testing of plastic materials, including indicators of mechanical properties, are described in this thesis according to ČSN EN ISO standard. The practical part presents the concept of a device capable of performing these tests. The block diagram indicates the functional elements and the connections among them. Tensile strength test is described together with results processing. Necessary product documentation is also included.

Polysaccharides are now popularly used in paper technology since they are able to improve mechanical properties of the paper. Xylan and pectin are two natural polymers that have a wide range of applications nowadays. These two polysaccharides can be used in their native forms as well as derivatives. In this study, xylan and pectin were modified to obtain cationic derivatives before adding into the paper for enhancement. The work was motivated by the fact that xylan and pectin share the same negative surface properties as cellulose. This leads to a slight repulsion effect between them once they are close. Their cationic derivatives, therefore, are believed to strengthen the paper due to electrostatic interactions between two oppositely charged objects beside hydrogen bonds. To fulfil the purposes, oat spelt xylan and apple pectin were chemically modified using different modification methods, including oxidation, amidation, and a combination of these two methods. A quantitative method to determine the adsorbed amount and relative retention capacity of xylan onto paper using high performance liquid chromatography was also developed. The results show that oat spelt and apple pectin, as well as their modified derivatives, can improve the paper mechanical properties. The oat spelt xylan significantly enhances the tensile strength, however, this contribution has a saturation level in correlation with the relative retention capacity of the xylan onto cellulose. The best retention capacity is achieved when 5% of xylan is added. This finding provides a practical approach to the application of xylan as a paper additive in consideration of economic issues. Although the application of apple pectin and its amidated derivatives in paper is rather rare, some interesting points have been discovered in this work. Among the apple pectin samples used, only the ones with low degree of esterification give a slight enhancement in tensile index at 5% dosage. The results also suggest that the dosage of the pectin added into the paper should not exceed 5% due to its viscous property at high concentrations.

Für die Ermittlung der Ermüdungsfunktion sowie der E-Modul-Funktion sind in den europäischen Normen verschiedene Versuchsarten vorgesehen. In Deutschland werden bisher der Einaxiale Zugschwellversuch und der Spaltzugschwellversuch angewandt. Diese vergleichsweise einfachen Versuche können das Ermüdungsverhalten eines Asphaltgemisches in situ nur mit Einschränkungen (z.B. hinsichtlich des vorherrschenden Spannungszustandes) wiedergeben. Der Triaxialversuch mit Zug-/Druckschwellbelastung kann zur realitätsnahen Untersuchung des Ermüdungsverhaltens (Ermüdungsfunktion in Verbindung mit der E-Modul-Funktion) angewandt werden, da neben der frei wählbaren Zugbeanspruchung zusätzlich beliebige Druckbeanspruchungen normal zur Zugspannung auf den Probekörper aufgegeben werden können. Aufgrund der aufwändigen Versuchsdurchführung findet der Versuch bisher nur in der Forschung Anwendung. Die für die Dissertation ausgewerteten Daten umfassen die Ergebnisse von Einaxialen Zugschwellversuchen, Spaltzugschwellversuchen und Triaxialversuchen mit Zug-/Druckschwellbelastung an insgesamt sechs verschiedenen Asphaltgemischen. Die Einflüsse aus dem Hohlraumgehalt, der Belastungsfrequenz sowie der Mischgutart und -sorte auf das Ermüdungsverhalten konnten herausgearbeitet werden. Weiterhin gelang aus den Ergebnissen aller Versuchsarten die Aufstellung von Ermüdungsflächenfunktionen in Abhängigkeit von Dehnungsanteilen infolge verschiedener Spannungskomponenten (mehraxialer Spannungszustand) unter Berücksichtigung der in den Probekörpern der verschiedenen Ermüdungsversuche auftretenden Spannungskombinationen Zug- zu Druckspannung. Die Gültigkeit der ermittelten Ermüdungsflächenfunktion für andere, über die in den angewendeten Versuchsarten hinausgehende Spannungskombinationen muss mit Hilfe geeigneter (noch zu entwickelnder) Versuche überprüft werden.

No description available.

No description available.

This thesis investigates the challenges and opportunities of recycling PA6-GF30, a glass-filled polyamide, to address the pressing environmental concerns surrounding polymer waste. Through a collaboration between Thule Group and Jönköping University, it aims to understand how the properties of recycled materials evolve over time and reprocessing cycles, proposing practical methods for their utilization in sustainable manufacturing practices. Thule Group's commitment to reducing emissions entails transitioning to sustainable materials, particularly through increased use of recycled engineering materials like PA6-GF30, to lower the carbon footprint of products, emphasizing the importance of maintaining product quality and safety while exploring the effects of recycled materials on mechanical properties. Through producing and testing post-industrial and post-consumer samples added to virgin PA6-GF30 with varying ratios, comparison with the commercially available polymers was conducted. In total, 15 different mixtures of pellets of different quantity and quality of recycled composites were investigated with tensile test and impact test, moreover the fibers of some batches were filtrated from the matrix and the fiber aspect ratio was examined with the help of an optical microscope. Results illustrated that recycled polymers generally showed more mechanical property degradation as the ratio of recycled polymers were increased. Furthermore, adding the same amount of post-consumer regrinds as opposed to post-industrial was more detrimental to the overall mechanical performance. Post-industrial composite regrinds performed 11,3% worse in UTS, meanwhile post-consumer regrinds dropped by 25,5% in the same characteristic when the samples made of 100% recycled materials were compared to the virgin composite.  The reason behind this phenomenon was investigated and supported by microscopy. One of them is the natural aging of the material that operates through chain scission, that slowly makes that polymer stiffer and weaker. The other and more dominant reason is the damage taken by the fibers, that create numerous stress concentration sites at fiber ends, within the structure, ultimately damaging the fiber-matrix interface.