Technische Universität Bergakademie Freiberg: Qucosa
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Cerchar abrasivity test – laboratory testing and numerical simulation
Get PDFAbrasivity is a characteristic property of rocks. Rock abrasivity has influence on tool wear, energy consumption and construction time and is therefore an important parameter in rock engineering. Over the years, a number of testing methods have been developed to define and quantify the abrasive potential of rocks. Due to simple design and convenient handling, Cerchar abrasivity test and its index, Cerchar abrasivity index, are most commonly used to assess the rock abrasivity.
Besides the abrasivity index, various parameters can be derived from the Cerchar test thanks to the development of a special designed testing device. Diverse parameters like scratching force, applied work and specific energy can be used to estimate the cutting efficiency. Moreover, a new composite parameter named Cerchar abrasion ratio is proposed, which considers both, the wear on the stylus tip and the material removal on the rock surface and can be regarded as an indicator to evaluate the cutting effectivity.
Since the development of Cerchar abrasivity test, major attentions are focused on the abrasion of the stylus, but minor attentions are paid to investigate the mechanical behavior of rocks against the action of the stylus during the scratching process. The scratch groove produced on the rock surface is observed under a scanning electron microscope. The Cerchar wear mechanism can be explained as follows: mineral grains are detached from damaged surface by fracturing after plastic deformation on stressed surface. Transition from plastic deformation-induced to cracking-induced wear are related to the rock microstructure.
For the Cerchar test, various factors affecting the Cerchar abrasivity index have been studied, which can be divided into testing condition-based and geotechnical-based factors. The influence of some dominant testing condition-based factors including surface condition, testing distance and velocity on the test result is investigated by using the new designed testing device, in which the sliding distance and scratching velocity can be exactly controlled during the test. Results show that the surface condition can affect the result of Cerchar index, especially for hard and inhomogeneous rocks, while the testing distance and velocity have no obvious influence on the Cerchar index.
As far as it is known, in rock mechanics, anisotropic features of rocks can affect the experimental results significantly. In the original Cerchar specification, testing procedure for stratified or foliated rocks is not specially discussed. Due to this, the influence of rock anisotropy on the Cerchar abrasivity index is investigated based on two intact metamorphic rocks of slate and gneiss. However, no significant dependency is found.
Cerchar scratch test is simulated based on a quasi-homogeneous model made of sandstone with respect to its mineralogical-mechanical properties. The numerical simulation is conducted by using the discrete element method-based particle flow code of PFC3D. As a result, the simulated scratching force shows a good agreement with the experimental result. A gap between numerical and experimental studies can be attributed to the testing condition-based factors, such as rock mineralogy and microstructure, scratching velocity and depth of scratch, tool abrasion and temperature.
Based on the calibrated sandstone model, numerical simulations of rock cutting are conducted under different testing conditions. The influence of tool geometry like tip shape, tip angle and tip wear, and cutting parameters including cutting velocity, depth of cut and rake angle on the cutting force and crack pattern is studied
Seismic Imaging of the Alpine Fault at Whataroa, New Zealand
Get PDFThis thesis presents new insights into Alpine Fault structures at the drill site of the Deep Fault Drilling Project (DFDP)-2B at Whataroa in New Zealand. Despite the challenging conditions for seismic imaging within a glacial valley filled with sediments and steeply dipping valley flanks, several structures related to the valley itself as well as the tectonic fault system are imaged.
The Alpine Fault at the West Coast in New Zealand is a major plate boundary forming a significant geohazard as large earthquakes (magnitude 7-8) occur regularly and the next earthquake is expected relatively soon. A major effort has been made to study the fault characteristics through scientific drilling in the Deep Fault Drilling Project (DFDP) Alpine Fault with the deepest DFDP-2B borehole located in the Whataroa Valley.
A great variety of seismic data are newly acquired. First, the WhataDUSIE (Whataroa Detailed University Seismic Imaging Experiment) data set is a ~5 km long 2D profile acquired in 2011 prior to the drilling. As the 2D profile could not fully explain the 3D structures in the Whataroa Valley, an extended surface and borehole data set was acquired in 2016 after the drilling. This data set consists of shorter 2D lines (< 3 km), a dense 3D-array, and vertical seismic profiling (VSP) using the DFDP-2B borehole including the fibre-optic cable.
3D seismic data proved to be essential to understand the complex 3D structures of the glacial valley and the major fault. First-arrival travel time tomography and prestack depth migration (PSDM) are applied to obtain a P-wave velocity model and seismic images of the subsurface (<5 km). In this complex setting, the Fresnel volume migration (a focusing PSDM method) proved to best obtain structural information about the subsurface.
Analysing the results of the seismic data processing, two major outcomes are achieved: improved knowledge about the glacial structures of the Whataroa Valley and structural images of the Alpine Fault zone.
The Whataroa Valley is an overdeepened glacial valley with details of the basement topography visible in the seismic images. A deep trough is identified south of the DFDP-2B borehole with horizontal layering of the sediments. Valley flanks are identified in both the seismic images and the P-wave velocity model, particularly the western valley flank. Thus, Quaternary and glacial processes can be analysed with the help of the newly derived seismic images.
The Alpine Fault is directly imaged with the seismic data, which is the first time in this region at shallow depths (<5 km). Several shorter fault segments between depths of 0.2 km and 2.2 km dipping 40-56° to the southeast are directly imaged. Further identified reflectors and faults are interpreted to represent Alpine Fault structures in the form of a damage zone and induced faults adding further complexity to the fault zone.
In conclusion, the 3D seismic results presented in this thesis provide new insights into the Whataroa subsurface. Hence, the new results form a good basis for a deeper understanding of the Alpine Fault structures and underlying processes which is important for potential future drilling but also for the estimation of the geohazard in the region
Transformation and approximation of rational Krylov spaces with an application to 2.5-dimensional direct current resistivity modeling
Get PDFDie vorliegende Arbeit befasst sich mit der Fragestellung, inwiefern sich gegebene Verfahren zur Approximation von rationalen Krylow-Räumen zur Berechnung von Matrixfunktionen eignen. Als Modellproblem wird dazu eine 2.5D-Formulierung eines Problems aus der Gleichstrom-Geoelektrik mit finiten Elementen formuliert und dann mittels Matrixfunktionen auf rationalen Krylow-Unterräumen gelöst.
Ein weiterer Teil beschäftigt sich mit dem Vergleich zweier Verfahren zur Transformation bestehender rationaler Krylow-Räume. Bei beiden Varianten werden die zugrunde liegenden Pole getauscht ohne dass ein explizites Invertieren von Matrizen notwendig ist. In dieser Arbeit werden die über mehrere Publikationen verteilten Grundlagen einheitlich zusammengetragen und fehlende Zusammenhänge ergänzt. Beide Verfahren eignen sich prinzipiell um rationale Krylow-Räume zu approximieren. Dies wird anhand mehrerer Beispiele gezeigt. Anhand des Modellproblems werden Beschränkungen der Methoden verdeutlicht
Entwicklung einer Warmwalztechnologie für Warmband einer Mg-2Zn-1Al-0,3Ca-Legierung mit hoher Umformbarkeit
Get PDFIm Rahmen der vorliegenden Arbeit wurde eine Warmwalztechnologie für gießgewalztes Vorband der calciumhaltigen Magnesiumlegierung Mg-2Zn-1Al-0,3Ca (ZAX210) entwickelt. Ausgangspunkt war die Untersuchung des Verformungs- und Rekristallisationsverhaltens in Abhängigkeit der Umformtemperatur, Umformgeschwindigkeit und des Umformgrades. Dabei wurde die zwillingsinduzierte dynamische Rekristallisation als dominierender Rekristallisationsmechanismus vor allem bei erhöhten Umformgeschwindigkeiten identifiziert. Basierend auf den daraus gewonnenen Erkenntnissen konnte ein Prozessfenster für das Warmwalzen abgeleitet werden, welches die Erzeugung eines 2 mm dicken Fertigbandes mit abgeschwächter Textur, guten mechanischen Eigenschaften und einer verbesserten Umformbarkeit, insbesondere im Vergleich zu den Standardknetlegierungen AZ31 und ZE10, erlaubte. Die Warmwalzparameter sind unter Berücksichtigung gleicher Randbedingungen auf einen industriellen Warmwalzprozess übertragbar
Geological and mineralogical investigation of hydrothermal fluid discharge features at the sea bottom of Panarea, Italy
Get PDFThe thesis presents research on recent hydrothermal discharge features in a shallow marine hydrothermal system. It aims to clarify their occurrence, genesis, and preservation potential. A facies model is developed, being based on the processes involved in the formation and the prevailing lithofacies. It describes six major groups: channels, fractures, tubes, cones, bowls, and lineaments. Each of these groups subdivides into numerous facies types according to the cements or mineral precipitates prevailing. To clarify the rather complex formation processes of hydrothermal discharge features, genetic models for each facies are proposed. An integrated evolutionary model is developed considering the temporal evolution of the major types of hydrothermal discharge features in the Panarea system and their preservation potential. Confirming presumptions of former, preliminary data, the first documentation of secure paleo-evidences of such hydrothermal discharge features is presented.:1. Introduction ....11
1.1. Preamble .....11
1.2. Research questions, objectives, and hypotheses ......................................... 12
2. State of research - seafloor hydrothermal systems ................................ 15
2.1. Hydrothermal deposits in general ................................................................. 15
2.2. Deep-sea environments ............................................................................... 16
2.3. Shallow-water systems and their preservation potential ............................... 17
3. Panarea Island - the area of investigation ................................................ 20
3.1. The hydrothermal system of Panarea Island ................................................ 20
3.2. Fluid discharge features in Panarea ............................................................. 30
3.3. Study sites .................................................................................................... 34
4. Materials and methods ............................................................................... 40
4.1. Underwater research .................................................................................... 40
4.2. Field methods ............................................................................................... 41
4.3. Laboratory methods ..................................................................................... 44
5. Results ........................................................................................................ 47
5.1. Prevailing lithologies ..................................................................................... 47
5.1.1. Hardrocks ..................................................................................................... 47
5.1.2. Sedimentary rocks ........................................................................................ 51
5.1.3. Sediments .................................................................................................... 54
5.1.4. Cements ....................................................................................................... 58
5.2. Underwater investigation sites and findings ................................................. 66
HYDROTHERMAL FLUID DISCHARGE FEATURES IN PANAREA, ITALY PAGE 10 | 174
5.2.1. Area 26 ......................................................................................................... 66
5.2.2. Basiluzzo ...................................................................................................... 75
5.2.3. Black Point ................................................................................................... 77
5.2.4. Bottaro North ................................................................................................ 79
5.2.5. Bottaro West ................................................................................................. 81
5.2.6. Cave ............................................................................................................. 84
5.2.7. Fumarolic Field ............................................................................................. 87
5.2.8. Hot Lake ....................................................................................................... 89
5.2.9. La Calcara .................................................................................................... 92
5.2.10. Point 21 ........................................................................................................ 98
5.2.11. Subaerial locations ..................................................................................... 100
5.3. Summarizing tables .................................................................................... 104
6. Interpretation ............................................................................................ 106
6.1. Discharge features and secondary processes ............................................ 106
6.1.1. Complex genesis and development of discharge features and their
occurrence throughout the system ............................................................. 119
6.1.1.1. Cones, bowls, and lineament structures ..................................................... 119
6.1.1.2. Tubes ......................................................................................................... 128
6.2. Preservation potential and paleo-record ..................................................... 138
7. Conclusion and Discussion .................................................................... 141
7.1. General context of the formation of hydrothermal discharge features in
Panarea ...................................................................................................... 141
7.2. Evolution of hydrothermal discharge features in Panarea .......................... 142
7.3. Comprehensive summary ........................................................................... 14
Mechanical characterisation of Nb3Sn Rutherford cable stacks
Get PDFNb3Sn Rutherford cables are used in CERN’s superconducting 11 T dipole and MQXF quadrupole magnets, which are proposed for the instantaneous luminosity (rate of particle collisions) upgrade of the Large Hadron Collider (LHC) by a factor of five to a High Luminosity-Large Hadron Collider (HL-LHC). Nb3Sn-based conductors are the key technology for the envisioned Future Circular Collider (FCC) with an operating magnetic dipole field of 16 T. The baseline superconductor of the LHC dipole magnets is Nb–Ti, whereas an operation above 10 T is not possible due to the current carrying performance limitations of this superconductor at higher magnetic fields. Therefore, a superconducting material such as Nb3Sn has to be used with proven performance capabilities of 10 T and above. The conductor choice towards Nb3Sn-based cables affects the magnet manufacturing process, as it requires a heat treatment up to 650°C, an epoxy resin impregnation and introduces mechanical diffculties as the superconducting filaments are brittle and strain sensitive. A mechanical over loading of the filaments lead to irreversible conductor damage. The designs of 11 and 16 T magnets are supposed to push the conductor towards its mechanical and electrical performance limitations. The magnetic field induced forces on the current carrying conductor are balanced by mechanical pre-loading of the magnet. Thereby the highest controlled mechanical pre-load for the 11 T dipole magnet is set at ambient temperature. The mechanical stress limits of Nb3Sn-based cables have been investigated at cryogenic temperatures. The material strength and stiffness of the cable insulation system, formed by glass-fibre-reinforced resin, is increased at low temperatures. The ultimate stress values, determined at cryogenic temperature, are therefore not conservative. The ultimate stress limitation of the insulated conductor is assumed to be lower at ambient temperature. The cable limitations at ambient temperature need to be known for the ongoing magnet manufacturing process and also for future design approaches. Furthermore, the compressive stress–strain behaviour of a coil conductor block at ambient temperature is the key material characteristic, in order to recalculate the stress level in the coil during the assembly process. Existing approaches using an indirect strain measurement method provide uncertainties in the low-strain regime, which is the essential strain range for a material compound consisting of major fractions composed of heat-annealed copper and epoxy resin. Compressive stress–strain data of an impregnated conductor block are required, based on a direct strain measurement system, as available data have been collected on samples based on a different strand type and insulation system. The elaborated direct strain measurements can be correlated to strain gauge data, measured directly on a coil. The stress distribution in a Nb3Sn Rutherford cable need to be understood and validated to understand strain-induced degradation effects in the insulated conductor. This knowledge can also help to optimise the stress distribution envisioned magnet designs. The stress–strain state in the copper and Nb3Sn phase of a loaded conductor block has to be determined experimentally. This dissertation describes a test protocol and first elaborated results on the investigated stress limitations of a Nb3Sn Rutherford cable under homogeneous load applied in transversal direction. The compressive stress–strain behaviour of impregnated Nb3Sn Rutherford cable stacks was investigated experimentally. This includes a detailed report on the sample manufacturing process, measurements performed and validation of results through a comparison with the elaborated data of cable stacks extracted from a coil. The presented results from neutron diffraction measurements of loaded cable stacks allow the determination of the stress–strain level of the copper and Nb3Sn phase in the impregnated conductor. The relevant measured results have been recalculated with numerical calculations based on the Finite Element Method (FEM).:1. Introduction 1
1.1. The LHC and the HL-LHC project
1.2. The FCC study
1.3. Superconducting materials for accelerator magnets
1.4. Multi-filamentary wires and Rutherford cables
1.5. Coil manufacturing process
1.6. Magnet coil assembly
1.7. Objectives of this thesis
2. Theory: fundamental principles 17
2.1. Analytical calculation: sector coil dipole
2.2. Mechanical behaviour of composite materials
2.3. Failure criteria and strength hypotheses for materials
2.4. Compressive tests
2.5. Fundamental principles of Neutron scattering
2.5.1. Test apparatus and measurement method
2.5.2. Lattice plane and Miller indices
2.5.3. Bragg diffraction and interference
2.5.4. Diffraction-based strain calculation
2.5.5. Diffraction-based stress calculation
2.6. Fundamental principles of FEM
3. Homogeneous transversal compression of Nb3Sn Rutherford cables
3.1. Superconducting cable test stations
3.2. The FRESCA test facility and specific sample holder
3.3. The sample description
3.4. Experimental procedure
3.5. Review of existing contact pressure measurement system
3.6. Compressive test station
3.7. Validation of the pressure-sensitive films
3.8. Press punch
3.9. Improvement of the contact stress distribution
3.9.1. First test: cable pressed between the bare tools
3.9.2. Second test: tool shimmed with a soft Sn96Ag4
3.9.3. Third test: tool shimmed with a soft Sn60Pb40
3.9.4. Fourth test: tool shimmed with a soft indium
3.9.5. Fifth test: tool shimmed with a polyimide film
3.10. Test results
3.11. Conclusion
4. Material characterisation by a compression test
4.1. Test set-ups for compressive tests and validation
4.2. Sample preparation
4.3. Compressive stress–strain measurement
4.4. Ten-stack sample stiffness estimation-based composite theories
4.5. Dye penetration test on loaded and unloaded samples
4.6. Conclusion
5. Neutron diffraction measurements 80
5.1. Test set-up for neutron diffraction measurement
5.2. The samples
5.3. Experiment: lattice stress–strain measurements
5.4. Conclusion
6. Simulation and modelling of Nb3Sn cables
6.1. The models
6.2. The 2D simulation results
6.3. The 3D simulation results
6.4. Conclusion
7. Comprehensive summary
7.1. Summary
7.2. Critical review
7.3. Next steps
Appendix 113
A. Calculation of the magnetic field components in a sector coil without iron
B. Approaches for the determination of diffraction elastic constants
C. Manufacturing drawings
D. FEM calculation results of the 2D model
E. FEM calculation results of the 3D model
F. Source Codes
Bibliograph
The Gemological Collection of Abraham Gottlob Werner
Get PDFThe gemological collection of Abraham Gottlob Werner contains 1374 sample numbers for 25 different minerals with 38 gemological varieties, including 15 newly added numbers of samples, which were not recorded in the original catalog of 1823. In total, 168 samples were recorded as lost by the later researchers, 4 samples were taken for the chain for the rector of the university, samples of 2 different numbers in the catalog were exchanged for cut stones, and 3 times’ volume requisitions happened. A total of 256 sample numbers show discrepancies and therefore are not in accordance with the original record in the catalog.
In the collection, 6.8% of the numbers are rock sample with embedded crystals, 20.7% of the numbers are in the form of crystal, 30.6% of the numbers are fragments, 11.6% of the numbers are grains, and the remaining 711 samples are cut. Except for Esa. No. 644a containing four cushion cut samples, all faceted cuts were recorded in the original catalog of 1823. However, the brilliant, oval, step, emerald, scissor, and radiant cut forms were invented after the gemological collection of Werner, which means 189 samples do probably not belong to the original collection. They could be from another collection due to the requisitions, or the later researchers of the collection added or exchanged the samples with new ones.
The mineral names of the catalog from 1823 refer to Werner's mineral system, some of the mineral's names are not used anymore. With the development of mineralogy and gemology, the special names of the gemstones as varieties of minerals are gradually standardized. 51 samples are wrong identifications and 8 pieces of glass have been recognized.
The zircon samples of the collection provide a research resource for the study of metamictization. Both color and density of zircon could be an indicator of the metamictization degree. The metamictization has a significant influence on the gemological properties of zircon. The green tone and low density cannot be considered as an identifying characteristic of metamict zircon, although they are still a sign of metamictization.
Comparing six mineralogical or geological collections at Werner’s time, the catalogs of five collections used his nomenclature of samples and only the catalog of the mineralogical collection of Adolf Traugott von Gersdorf is geographical. To his time the outstanding gemological collection of Abraham Gottlob Werner represented the broadest quantity of gemological varieties.
A modern gemological database of the collection has been founded, the meta-data provides an important base for further research and development.:Acknowledgements I
Abstract III
Table of Contexts IV
List of figures VI
List of tables VII
1. Introduction 1
1.1 Abraham Gottlob Werner 1
1.2 The mineral system of Werner 1
1.3 The gemological collection of Werner 3
2. Methods 6
2.1 Specific gravity (SG) measurements 6
2.1.1 Hydrostatic weighing 6
2.1.2 He-pycnometer 6
2.2 Color 6
2.2.1 Munsell color system 7
2.2.2 The CIE L*C*h color system 8
2.3 The optical measurements 9
2.3.1 Polariscope 9
2.3.2 Refractometer 10
2.3.3 Dichroscope 11
2.4 Ultraviolet (UV) fluorescence test 12
2.5 Raman spectroscopy 12
3. New model for the inventory of the gemological collection of Werner 13
4. Discussion 16
4.1 Cut cutting in the course of time 16
4.2 Classification of gemstones 24
4.2.1 Individual names of gemstones 25
4.2.2 Different identifications with the catalog of 1823 29
4.2.3 Imitation of gemstones 31
4.3 Raman spectrum study of zircons 32
4.4 Comparison of the outstanding Werner Collection with other collections in the second half of 18th century 39
4.4.1 The natural history collection of Linck family (1638-1807) 39
4.4.2 The Minerals cabinet of Eugen Pabst von Ohain (1718-1784) 40
4.4.3 The natural history collection of the University of Rostock 40
4.4.4 The mineralogical collection of Adolf Traugott von Gersdorf (1744-1807) 41
4.4.5 The mineralogical, geological and paleontological collection of Johann Wolfgang von Goethe (1749-1832) 42
4.4.6 Summary of the additional collections to Werner's time 43
5. Summary 44
Reference 46
Appendix A 59
Appendix B 63
Appendix C 6
A single-cell view on the intra- and inter-population metabolic heterogeneity and ecophysiology of microorganisms at different ecological scales
Get PDFMetabolic heterogeneity (MH) occurs when isogenic microbial populations display cell-to-cell differences in metabolic traits, albeit exposed to homogeneous conditions. Despite the increasing focus on MH, its triggering factors remain largely unknown. In the present thesis, I used stable isotope probing and chemical imaging with nanoscale Secondary Ion Mass Spectrometry (nanoSIMS) to study MH at single-cell level, in model organisms, synthetic and natural communities, to understand i) how abiotic factors, biotic interactions and antibiotics exposure influence MH and ii) its potential ecological role. Moreover, I optimized sample preparation for chemical and high-resolution imaging and suggested two different indices as ‘unit measure’ of MH. As results, I have shown for the first time that MH is displayed by microorganisms under favorable growth conditions, although none of the tested abiotic factors prevailed as the main trigger of MH. I brought insights on how biotic interactions play a role in the functional heterogeneity using bacteria pseudo-fungi co-cultures. I found that antibiotics reduce Carbon and Nitrogen assimilation rates of targeted phylogenetic groups in river-water communities, while increasing their MH, pointing to its ecological importance in natural environments. To conclude, I provided novel insights on the phenomenon of MH and its dynamics at different ecological scales.:Abbreviation list
Summary
Introduction
Knowledge gaps
Results and discussion
- Optimization of sample preparation
- Validation of quantitation methods
- Abiotic factors shaping metabolic heterogeneity in bacterial populations
- Influence of biotic factors in shaping heterogeneity
- Metabolic Heterogeneity and ecophysiology of natural microbial populations
influenced by emerging contaminants
Conclusions
Outlook
Bibliography
Appendix
Acknowledgments
Curriculum Vitae
List of publication
Verbesserte Dehnungsmessung im Betonbau durch verteilte faseroptische Sensorik
Get PDFDie verteilte faseroptische Sensorik (VFOS) auf Basis von Rayleighstreuung stellt ein besonderes und vielversprechendes Verfahren zur Dehnungsmessung im Betonbau und im Structural Health Monitoring (SHM) dar. Neben einer hohen Ortsauflösung und Messempfindlichkeit kann sie geringste Dehnungsänderungen an jedem Punkt der Messfaser erfassen. Für einen zuverlässigen Einsatz fehlen aktuell Material- und Handlungsempfehlungen; in der Literatur finden sich widersprüchliche Aussagen zu den Dehnungsübertragungsverlusten zwischen Substrat und Messfaser. Diesbezüglich beschäftigt sich die vorliegende Arbeit mit der Validierung des Messverfahrens für Szenarien im Betonbau. Neben der Applikation auf Stahl- und Betonoberflächen wurde die Integration in der Matrix untersucht. Im Zuge dessen sollten die Dehnungsübertragungsverluste verschiedener Fasercoatings bzw. Fasercoating-Klebstoff-Kombinationen überprüft werden. Darüber hinaus wurde ein Auswerteverfahren mithilfe der Programmiersprache Python entwickelt, das eine automatisierte Datenaufbereitung und Substituierung der Messabweichungen der enormen Datenmengen ermöglicht.
Im Zuge der Validierung auf der Stahloberfläche wurden die Dehnungswerte der verschiedenen Coating-Klebstoff-Kombinationen an Präzisionsflachstählen im 4-Punkt-Biegeversuch mit einer photogrammetrischen Dehnungsmessung verglichen. Im Rahmen der Validierung auf der Betonoberfläche kamen Betondruckzylinder zum Einsatz, an denen zusätzlich zu den Coating-Klebstoff-Kombinationen der Einfluss einer Grundierung untersucht wurde. Induktive Wegaufnehmer dienten im Verlauf der Druckversuche als Vergleichsmesstechnik. Die Validierung verschiedener Coatingmaterialien in der Matrix fand anhand von Schwindversuchen an Betonprismen statt; als Vergleichsmessmethode dienten digitale Messuhren. Zur Bewertung der aus den Validierungsversuchen abgeleiteten Material- und Handlungsempfehlungen wurden Bauteilversuche an Betonbalken durchgeführt.
Die Auswertung der Validierungsversuche zeigte, dass vor allem mit einem Ormocer-Coating gute Ergebnisse hinsichtlich der Dehnungsübertragung erzielt werden konnten. Im Falle einer Applikation empfiehlt sich die Verwendung eines Cyanacrylatklebstoffs -- besonders der M-Bond 200 überzeugte durch geringe Dehnungsverluste. Betonoberflächen sollten vorher geschliffen und mit Epoxidharz grundiert werden. Im Falle einer Integration in die Betonmatrix zeigten auch die Ormocer-Fasern minimale Unterschiede zur Vergleichsmessung. Die Ergebnisse der Bauteilversuche verifizieren die Handlungs- und Materialempfehlungen: Die Dehnungswerte der Fasern decken sich mit denen der analytischen Bemessung der Betonbalken. Lediglich an den Lasteinleitungsstellen konnten Oszillationen des Dehnungsverlaufs durch Gefügestörungen festgestellt werden.
Forschungsbedarf besteht v.a. hinsichtlich der Validierung weiterer Komponenten (Klebstoff, Coating, Grundierungsmittel) und deren Langzeitstabilität, insbesondere bei chemischen und dynamischen Beanspruchungen. Im Rahmen dieser Arbeit konnte ein Überblick über verschiedene Materialien geschaffen werden, jedoch ist das Repertoire an verfügbaren Komponenten immens, gerade bei den Klebstoffen. Bei der Validierung auf der Betonoberfläche und in der Matrix kam eine Feinkornbetonmischung zum Einsatz. Diesbezüglich sollten in weiteren Forschungen unterschiedliche Matrices und Korngrößen Untersuchungsgegenstand sein.Distributed fiber optic sensor (DFOS) technology based on Rayleigh scattering is a unique and promising method for strain measurement in concrete structures as well as structural health monitoring (SHM). It can detect the smallest strain changes at any point in the measuring fiber with a high spatial resolution and sensitivity. Currently, there exist no material and handling recommendations for a reliable application, and the literature contains contradictory statements on strain transfer losses between substrate and fiber. The present study deals with the validation of this measuring method for scenarios in concrete structures. Besides applications on steel and concrete surfaces, the integration in a concrete matrix was investigated. The validation yields results for strain transfer losses for different fiber coatings or fiber coating/adhesive combinations. Furthermore, the development of an evaluation method using the computer language Python provides automated data preparation and measurement error substitution of the enormous data volumes.
For the validation on steel surfaces, the strain values of different coating-adhesive combinations on precision flat steels were compared in a 4-point bending test with a photogrammetric strain measurement. For the validation on concrete surfaces, concrete pressure cylinders were used to investigate the influence of a primer and different coating-adhesive combinations. Inductive displacement transducers served as a comparative measuring technique during the compression tests. Shrinkage tests allowed the validation of different coating materials in a matrix on concrete prisms. Digital dial gauges were used as a comparative measuring method. For evaluation purposes, the material and handling recommendations derived from the validation were tested on concrete beams.
The results of the validation tests indicate good results regarding strain transfer with an Ormocer coating. For application as tested , the use of a cyanoacrylate adhesive is recommended -- especially M-Bond 200 was convincing due to its low strain losses. Concrete surfaces should be sanded and primed with epoxy resin. If integrated into a concrete matrix, the Ormocer fibers also showed minor differences from the comparative measurement. The results of the evaluation tests verify the handling and material recommendations: the strain values of the fibers correspond to the values obtained in concrete-beam analysis. Oscillations of the strain profile due to microstructural disturbances could only be detected at the load application points.
Further research regarding the validation of additional components (adhesives, coating, primer) and their long-term stability, especially chemical and dynamic loads, is necessary. This study provides an overview of different coating and adhesives. However, the repertoire of available components is immense - especially for adhesives. During the validation on concrete surfaces and in matrix, a fine-grained concrete mixture was used. In this respect, different matrices and grain sizes should be the subject of further research
3. Freiberger Kolloquium Elektrische Antriebstechnik: Kolloquium im Rahmen des 72. BHT - Freiberger Universitätsforum 2021
Get PDFDieser Konferenzband stellt alle schriftlich eingereichten Beiträge zum 3. Freiberger Kolloquium Elektrische Antriebstechnik zusammen. Thematische Schwerpunkte waren 2021: Modellierung und Simulation von elektrischen Maschinen und Antrieben, Auslegung und Fertigung neuer Motorenkonzepte, Thermische Untersuchungen an elektrischen Maschinen, Regelung elektrischer Maschinen, Ladetechnologien für Elektrofahrzeuge, Theoretische Elektrodynamik von Traktionsantriebe