Dissertations / Theses on the topic 'Strain analysis technique'

The work presented in the thesis is dedicated to the development and validation of a new technique to assess plastic strain based on thermoelastic stress analysis (TSA). Welding induced plasticity (WIP) and welding residual stresses can negatively affect the structural integrity of welded structures as they can exacerbate creep and stress corrosion cracking and limit the structure’s resistance to failure. Moreover, WIP has been shown to negatively affect weld integrity, since the associated accumulation of defects (dislocations) in the material will accelerate the nucleation of macro-scale defects that lead to component failure. There has been considerable amount of work published on determining the magnitude and distribution of the residual stresses both experimentally and by using numerical techniques. WIP can be predicted using finite element analysis (FEA), however, there is currently no standardised experimental method to characterise plastic strain and hence, model predictions are not readily validated with confidence. Recently, two techniques, based on electron backscatter diffraction and indentation respectively, were developed to assess WIP. However, both techniques are destructive and would not be applicable on in-situ components. TSA is a non-contact stress analysis method which is quick to apply and fully portable. TSA is based on the measurement of a small temperature change that occurs as a result of a change in the stress. The small temperature change is measured using an infrared detector. A method for plastic strain assessment (PSA) using TSA has been proposed based on the change in the thermoelastic response due to the plastic strain a material has experienced during a process, e.g. deformation or welding. TSA has the potential to be the first nondestructive, non-contact plastic strain assessment technique, termed as TSA-PSA. The aim of the PhD is to investigate the potential of using the TSA-PSA approach for assessing WIP in austenitic (AISI 316L) and ferritic (SA508 Gr.3 Cl.1) steels. The influence of welding induced microstructural changes on the thermoelastic response is investigated to establish any changes in the thermoelastic response relating to plastic straining only. The study focuses on two typical nuclear grade steels; ferritic SA508 Gr.3 Cl.1 and austenitic stainless steel AISI 316L. The effect of plastic strain on the thermoelastic response of both steels is investigated through the design and assessment of a calibration specimen used to determine the thermoelastic constant variation with plastic strain alongside with microstructural changes. It was found that the plastic strain has a stronger influence on the thermoelastic constant in SA508 than in AISI 316L. For uniform microstructures the influence of plastic strain on the thermoelastic response can be defined and, a larger influence of plastic strain on thermoelastic response was reported for coarse grains of austenite in AISI 316L and coarse grains of ferrite in SA508. The second part of the work concerns development finite element (FE) models of weld mock-ups to demonstrate application of TSA-PSA. The modelling enabled the plastic strain experienced during welding to be predicted and adjustments made to the design prior to the mock-up manufacture. Once satisfied that the mock-ups were suitable for TSA, they were manufactured at TWI Ltd. TSA experimental work was conducted on each mock-up and the outcome was compared with the outputs from the calibrated FE models. The capability of TSA to identify plastic strain in welded components is assessed through the use of the weld mock-ups. The thesis makes a novel contribution to the development of TSA as a portable non-destructive, non-contact technique to assess WIP in components with the investigation of the influence of microstructural changes similar to that found in welds on the technique, as well as the design, manufacture and plastic strain predictions in weldments dedicated to the technique. The results indicate a stronger influence of the plastic strain on the thermoelastic constant in coarse-grained microstructure in both grades of steel.

The optimum cutting of various parts of a shoe, prior to shoe manufacture requires knowledge of the topographical variation of what are termed “lines of tightness”. Currently the cutting operation for shoe parts is guided by a general assumption about the pattern of the lines of tightness. There is a need to have available a system which can determine, in a non-destructive way, the lines of tightness in an indvidual piece of leather. Initially an image analysis system was developed to investigate the uni-axial deformation behaviour of leather. This technique provided more information about the stress-strain behaviour of a leather sample along the gauge length than a conventional mechanical test and it was possible to accurately measure the strain distribution along the gauge length. A system was developed which could determine the relative displacement of marked spots along the gauge length of the sample using images captured during a uni-axial, bi-axial or multi-axial tensile test. The separation of the marked spots along the direction of applied stroke allowed the determination of longitudinal strain while contraction across the width was also measured in some cases, which was useful in calculating the Poisson’s ratio of leather for which a great variation was observed between different locations (Butt, Belly, Neck etc). Various approaches were investigated to determine the lines of tightness. Firstly, the local Poisson’s ratio was observed since a higher value of this parameter was associated with these lines of tightness. Secondly, biaxial stretching of leather by a series of actuators for each axis indicated the lines of tightness along the actuator with lower strain values. Thirdly, the strain was measured when the leather was stretched along number of known axes. This latter technique appeared to be the best approach and mathematical modeling was investigated to provide further refinement. A mechatronics-based device by industrial application of the third approach was also proposed. The software was written using a graphical programming system (LabVJ EW)

Power generation companies are under a great deal of Government and other pressure to achieve and maintain their plants to a high efficiency standard with minimum release of CO2 into the atmosphere. Achieving and maintaining the required high level of operational integrity of large complex generating plants is a demanding task. One key requirement is to have data on the functional integrity of all major components of a power station plant This is to provide for removal from the plant of time expired components. This is particularly important for components that can only be replaced by shutting down the plant and having to do this very often is a problem. This dissertation relates to the life monitqfing of steam pipes and other components that are .subject to· demanding high temperatures and stresses. Life monitoring· of these components requires instrumentation that can withstand for long periods these very hostile conditions on and about the steam pipes. Creep monitoring is one key requirement and sensors need to be able to detect very small growth movements of the material and have the ability not to be affected by the hostile environment in which they are located. Ideally, for creep monitoring in steam pipe material, required is a precise point-to-point measurement in two or more directions together with strain mapping of the region in and about the point-ta-point sensors. E.ONUK is supporting this research to improve their life-monitoring systems and in so doing have regard for the trend to use even high temperature steam pipes in the next generation of power stations. To illustrate the above in this thesis, the development of a Strain Monitoring System is presented: the Auto Reference Creep Management And Control System (ARCMAC). This is a strain sensor system which is developed at Imperial College in collaboration with E.ON. UK. From design studies and operational experience of pipe degradation rates and failures, useful information is available as to parts of the pipe system that need to be monitored to obtain reliable data on the remaining life of the pipes. Also known is that a good and feasible monitoring method to reveal the onset of failure processes is the measurement of the increases in micra-strain generated in the outer skin of the pipe material. For these measurements, the ARCMAC system has been developed. The ARCMAC measurement system utilizes precision optics to capture successive images of a 'target' strain gauge and digital image processing is used to obtain estimates of creep s~in accumulated over the plant-operating period. The Digital Image Correlation (DIC) technique is also presented as an alternative measurement technique. In this technique a series of digital images of a surface is uSed under various levels of load, upon which a paint pattern has been applied. The first such pattern to be used in the UK on a power station was applied in Ratcliffe power station as part of this study. The DIC technique will be used in conjunction with ARCMAC gauges to evaluate any unusual strain distribution surrounding the gauge area in an effort to create a unified Strain Monitoring System combining both techniques. Full field case studies are examined and presented showing encouraging initial results.

This research seeks to evaluate the local stress and strain distributions formed in adhesively bonded composite joints under quasi static and high strain rate loading. A literature review of current analytical, numerical and experimental studies of adhesively bonded joints is presented and identifies the lack of knowledge in the behaviour of composite bonded joints in the through-thickness direction. Detailed analysis of the stress and strain in the joint, and their impact on the development of damage prior to and during failure have been obtained using Digital Image Correlation (DIC). An experimental methodology is established to perform DIC at the mesoscopic scale using high magnification optics, enabling accurate, high spatial resolution analysis of the strains around the geometric discontinuity between adherends. It is demonstrated that the small through-thickness strains are critical in the development of damage in the joint around the discontinuity between adherends. Errors in the DIC technique are assessed using a robust morphological methodology to evaluate the quality of different speckle patterns based upon the properties of the speckles in the pattern. The strain data is manipulated to evaluate the principal stresses in the joint, which govern failure in the brittle epoxy matrix of the composite, providing a concise evaluation of the transfer of load between the adherends and damage initiation within the joint. The DIC results and methodology are validated against independent infra-red measurements using Thermoelastic Stress Analysis (TSA). Limitations in the TSA analysis approach are identified around joint discontinuity due to the varying principal stress direction. A new TSA analysis methodology is presented to overcome this. The results of the experimental analysis are used to validate a representative 2D finite element model modelling approach for adhesively bonded joints, showing good agreement to the experimental data. Finally the full-field DIC methodology is applied to analyse the response of a single lap joint during high strain rate loading, providing unprecedented full-field measurement of the strain fields up to failure.

This research presents a step forward in the area of structural health monitoring by developing the scientific basis for a method to detect and locate damage in asymmetric building structures accurately and efficiently. The method is based on the changes in the vibration characteristics of asymmetric buildings such as natural frequencies and associated mode shapes. The thesis first investigated the difference in vibration behavior between symmetric and asymmetric buildings and compared the capability of different damage detection methods that uses the vibration characteristics. Then a modified method (MMSE) and an improved method (MCA-DI) were proposed based on the comparative study and verified through experimental testing of a laboratory scale asymmetric setback structure model.

Several genera of bacteria residing in the sea surface microlayer and in the near-surface layer of the ocean have been found to be involved in the production and decay of surfactants. Under low wind speed conditions, surfactants can suppress short gravity capillary waves at the sea surface and form natural sea slicks. These features can be observed with both airborne and satellite-based synthetic aperture radar (SAR). Using a new microlayer sampling method, a series of experiments have been conducted in the Straits of Florida and the Gulf of Mexico in 2013 to establish a connection between the presence of surfactant-associated bacteria in the upper layer of the ocean and sea slicks. In a number of cases, sampling coincided with TerraSAR-X and RADARSAT-2 satellite overpasses to obtain SAR images of each study site. Samples collected from slick and non slick conditions have been analyzed using real time PCR techniques to determine Bacillus relative abundance in each area sampled. Previous work has shown that the sea surface microlayer plays a role in air-sea gas exchange, sea surface temperature, climate-active aerosol production, biochemical cycling, as well as the dampening of ocean capillary waves. Determining the effect of surfactant-associated bacteria on the state of the sea surface may help provide a more complete global picture of biophysical processes at the air-sea interface and uptake of greenhouse gases by the ocean.

O Vírus da Imunodeficiência Humana (HIV) é o agente etiológico da Síndrome da Imunodeficiência Adquirida (AIDS). A AIDS é uma doença de distribuição mundial, e estima-se que existam atualmente pelo menos 36,9 milhões de pessoas infectadas com o vírus. Durante o seu ciclo replicativo, o HIV promove diversas alterações na fisiologia da célula hospedeira a fim de promover sua sobrevivência e potencializar a replicação. A rápida progressão da infecção pelo HIV-1 em humanos e em modelos animais está intimamente ligada à função da proteína acessória Nef. Dentre as diversas ações de Nef está a regulação negativa de proteínas importantes na resposta imunológica, como o receptor CD4. Sabe-se que esta ação resulta da indução da degradação de CD4 em lisossomos, mas os mecanismos moleculares envolvidos ainda são totalmente elucidados. Nef forma um complexo tripartite com a cauda citosólica de CD4 e a proteína adaptadora 2 (AP-2), em vesículas revestidas por clatrina nascentes, induzindo a internalização e degradação lisossomal de CD4. Pesquisas anteriores demonstraram que o direcionamento de CD4 aos lisossomos por Nef envolve a entrada do receptor na via dos corpos multivesiculares (MVBs), por um mecanismo atípico, pois, embora não necessite da ubiquitinação de carga, depende da ação de proteínas que compõem os ESCRTs (Endosomal Sorting Complexes Required for Transport) e da ação de Alix, uma proteína acessória da maquinaria ESCRT. Já foi reportado que Nef interage com subunidades dos complexos AP-1, AP-2, AP-3 e Nef não parece interagir com subunidades de AP-4 e AP-5. Entretanto, o papel da interação de Nef com AP-1 e AP-3 na regulação negativa de CD4 ainda não está totalmente elucidado. Ademais, AP-1, AP-2 e AP-3 são potencialmente heterogêneos devido à existência de isoformas múltiplas das subunidades codificadas por diferentes genes. Todavia, existem poucos estudos para demonstrar se as diferentes combinações de isoformas dos APs são formadas e se possuem propriedades funcionais distintas. O presente trabalho procurou identificar e caracterizar fatores celulares envolvidos na regulação do tráfego intracelular de proteínas no processo de regulação negativa de CD4 induzido por Nef. Mais especificamente, este estudo buscou caracterizar a participação do complexo AP-1 na modulação negativa de CD4 por Nef de HIV-1, através do estudo funcional das duas isoformas de ?-adaptina, subunidades de AP-1. Utilizando a técnica de Pull-down demonstramos que Nef é capaz de interagir com ?2. Além disso, nossos dados de Imunoblot indicaram que a proteína ?2-adaptina, e não ?1-adaptina, é necessária no processo de degradação lisossomal de CD4 por Nef e que esta participação é conservada para degradação de CD4 por Nef de diferentes cepas virais. Ademais, por citometria de fluxo, o silenciamento de ?2, e não de ?1, compromete a diminuição dos níveis de CD4 por Nef da membrana plasmática. A análise por imunofluorêsncia indireta também revelou que a diminuição dos níveis de ?2 impede a redistribuição de CD4 por Nef para regiões perinucleares, acarretando no acúmulo de CD4, retirados por Nef da membrana plasmática, em endossomos primários. A depleção de ?1A, outra subunidade de AP-1, acarretou na diminuição dos níveis celulares de ?2 e ?1, bem como, no comprometimento da eficiente degradação de CD4 por Nef. Além disso, foi possível observar que, ao perturbar a maquinaria ESCRT via super-expressão de HRS (uma subunidade do complexo ESCRT-0), ocorreu um acumulo de ?2 em endossomos dilatados contendo HRS-GFP, nos quais também detectou-se CD4 que foi internalizado por Nef. Em conjunto, os resultados indicam que ?2-adaptina é uma importante molécula para o direcionamento de CD4 por Nef para a via ESCRT/MVB, mostrando ser uma proteína relevante no sistema endo-lisossomal. Ademais, os resultados indicaram que as isoformas ?-adaptinas não só possuem funções distintas, mas também parecem compor complexos AP-1 com diferentes funções celulares, já que apenas a variante AP-1 contendo ?2, mas não ?1, participa da regulação negativa de CD4 por Nef. Estes estudos contribuem para o melhor entendimento dos mecanismos moleculares envolvidos na atividade de Nef, que poderão também ajudar na melhor compreensão da patogênese do HIV e da síndrome relacionada. Em adição, este trabalho contribui para o entendimento de processos fundamentais da regulação do tráfego de proteínas transmembrana no sistema endo-lisossomal.
The Human Immunodeficiency Virus (HIV) is the etiologic agent of Acquired Immunodeficiency Syndrome (AIDS). AIDS is a disease which has a global distribution, and it is estimated that there are currently at least 36.9 million people infected with the virus. During the replication cycle, HIV promotes several changes in the physiology of the host cell to promote their survival and enhance replication. The fast progression of HIV-1 in humans and animal models is closely linked to the function of an accessory protein Nef. Among several actions of Nef, one is the most important is the down-regulation of proteins from the immune response, such as the CD4 receptor. It is known that this action causes CD4 degradation in lysosome, but the molecular mechanisms are still incompletely understood. Nef forms a tripartite complex with the cytosolic tail of the CD4 and adapter protein 2 (AP-2) in clathrin-coated vesicles, inducing CD4 internalization and lysosome degradation. Previous research has demonstrated that CD4 target to lysosomes by Nef involves targeting of this receptor to multivesicular bodies (MVBs) pathway by an atypical mechanism because, although not need charging ubiquitination, depends on the proteins from ESCRTs (Endosomal Sorting Complexes Required for Transport) machinery and the action of Alix, an accessory protein ESCRT machinery. It has been reported that Nef interacts with subunits of AP- 1, AP-2, AP-3 complexes and Nef does not appear to interact with AP-4 and AP-5 subunits. However, the role of Nef interaction with AP-1 or AP-3 in CD4 down-regulation is poorly understood. Furthermore, AP-1, AP-2 and AP-3 are potentially heterogeneous due to the existence of multiple subunits isoforms encoded by different genes. However, there are few studies to demonstrate if the different combinations of APs isoforms are form and if they have distinct functional properties. This study aim to identify and characterize cellular factors involved on CD4 down-modulation induced by Nef from HIV-1. More specifically, this study aimed to characterize the involvement of AP-1 complex in the down-regulation of CD4 by Nef HIV-1 through the functional study of the two isoforms of ?-adaptins, AP-1 subunits. By pull-down technique, we showed that Nef is able to interact with ?2. In addition, our data from immunoblots indicated that ?2- adaptin, not ?1-adaptin, is required in Nef-mediated targeting of CD4 to lysosomes and the ?2 participation in this process is conserved by Nef from different viral strains. Furthermore, by flow cytometry assay, ?2 depletion, but not ?1 depletion, compromises the reduction of surface CD4 levels induced by Nef. Immunofluorescence microscopy analysis also revealed that ?2 depletion impairs the redistribution of CD4 by Nef to juxtanuclear region, resulting in CD4 accumulation in primary endosomes. Knockdown of ?1A, another subunit of AP-1, resulted in decreased cellular levels of ?1 and ?2 and, compromising the efficient CD4 degradation by Nef. Moreover, upon artificially stabilizing ESCRT-I in early endosomes, via overexpression of HRS, internalized CD4 accumulates in enlarged HRS-GFP positive endosomes, where co-localize with ?2. Together, the results indicate that ?2-adaptin is a molecule that is essential for CD4 targeting by Nef to ESCRT/MVB pathway, being an important protein in the endo-lysosomal system. Furthermore, the results indicate that ?-adaptins isoforms not only have different functions, but also seem to compose AP-1 complex with distinct cell functions, and only the AP-1 variant comprising ?2, but not ?1, acts in the CD4 down-regulation induced by Nef. These studies contribute to a better understanding on the molecular mechanisms involved in Nef activities, which may also help to improve the understanding of the HIV pathogenesis and the related syndrome. In addition, this work contributes with the understanding of primordial process regulation on intracellular trafficking of transmembrane proteins.

碩士
國立成功大學
材料科學及工程學系碩博士班
98
It’s the first time in Taiwan using EBSD (electron back-scattering diffraction) techniques to analyze two dimensional distributions of residual strain and dislocation density. This thesis has two parts: firstly, using DIC (digital image correlation) and EBSD to measure two dimensional distribution of residual strain; secondarily, combining critical stress analysis and EBSD technique to calculate two dimensional distribution of dislocation density. Single aluminum, single copper and alumni nitride thin film on single silicon substance were chosen as experimental materials and performed using indentation testing. The maximum of residual tensile strain in the vicinity of the indentation tip is 0.02 for AlN/Si. The maximum value of residual strain and total dislocation density for 10g-indented single Al are 0.012 and m-2, respectively. In the case of single Cu using 5g nano-indentation, the maximum residual and total dislocation density are 0.041 and m-2, respectively. The maximum residual and total dislocation density are 0.087 and m-2 for single Cu loaded by 10g nano-indentation, respectively.

Thesis (M.S.)--University of Wisconsin--Madison, 2007
Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 260-268).

碩士
國立嘉義大學
生物科技研究所
93
Aflatoxins(AF) are toxic and carcinogenic secondary metabolites produced by Aspergillus section Flavi, Aspergillus flavus and A. parasiticus. Particularly aflatoxin B1 is the most potent known hepatocarcinogenic compound. The regular meeting in stores up on the improper grain to accumulate, but causes the humanity or the domestic animal which eats by mistake has in the health the concealed worry. TLC (Thin- Layer Chromatography) analysis was used to detect aflatoxin production of 2 strains of A. flavus, CCRC 30231, CCRC 30290 and 5 strains of A. parasiticus, CCRC 30117, CCRC 30150, CCRC 30160, CCRC 30164 and CCRC 30172. The strains were grown in YES (aflatoxin-inducive) and YEP (non- aflatoxin-inducive) broth. It is indeed that all seven strains were able to produce aflatoxin in YES broth, but differed in aflatoxin types and contents. Furthermore we determined the culture medium content, as well as incubation time, influenced regulatory mechanism of aflatoxin biosynthetic pathway. Fifty genes related to aflatoxin biosynthesis were studied, included thirty-one genes which are involved in aflatoxin B1 biosynthesis: fas1, fas2, pks, pksA, nor1, norA, norB, nor, avnA, adhA, adh1, adh2, avfA, estA1, estA2, vbs, verB, verA, ver1, omtB, omtA, omt1, omt12, ordA, ordB, ord1, ord2, aflR1, aflR2, aflT and aflJ；seven genes which are involved in carbohydrate metabolism: moxY, nadA, hxtA, glcA, sugR, amy1 and hxt1；three genes which are involved in nitrogen metabolism: niiA, niaD and areA；eight other genes which function was still unknown in aflatoxin biosynyhesis: cypX, cypA, cyp51A, cyp51B, lipA, alk1, hypA, amdS12 and one housekeeping gene： tub. 99 RT-PCR products of A. flavus CCRC 30290 and A. parasiticus CCRC 30172（A. flavus lacks of aflR2 gene）on the membran with 9 negative controls. 7 aflatoxigenic strains and 4 non-aflatoxigenic strains (A. flavus CCRC 30166, A. parasiticus CCRC 30227, A. sojae CCRC 30103 and A. oryzae CCRC 30120) were cultivated in YES broth for 48h and 72h, respectively. Total RNA were extracted and purified and biotin-labeled-cDNA probes were prepared by reverse transcription. The hybridization results showed that housekeeping gene (tub) and adh1 expressed in all strains incubated in YEP broth. There were 6 genes: ordA, ordB, ord1, ord2, cyp51A and cyp51B expressed only in aflatoxigenic strains and unexpressed in non-aflatoxigenic strains cultivated in YES broth. Consequently, whether aflatoxigenic isolates or potential Aspergillus species, which being able produced AF, could be decided from the presence of transcripts remains further studies.

Mok, Kam Ming.
Thesis (M.Phil.)--Chinese University of Hong Kong, 2010.
Includes bibliographical references (leaves 36-44).
Abstracts in English and Chinese.
Abstract --- p.ii
Chinese abstract --- p.iii
Acknowledgement --- p.iv
Table of contents --- p.V
List of figures --- p.vii
List of tables --- p.viii
Chapter Chapter 1: --- Introduction --- p.1
Chapter Chapter 2: --- Review of literature --- p.3
Chapter 2.1 --- Why prevent ankle ligamentous sprain? --- p.3
Chapter 2.2 --- A sequence of injury prevention --- p.4
Chapter 2.3 --- Biomechanical approaches in defining injury mechanism --- p.5
Chapter 2.4 --- Injury mechanism of ankle ligamentous sprain in sports --- p.6
Chapter 2.5 --- Model-Based Image-Matching motion analysis --- p.7
Chapter Chapter 3: --- Development of an ankle joint Model-Based Image-Matching motion analysis technique --- p.9
Chapter 3.1 --- Introduction --- p.9
Chapter 3.2 --- Materials and method --- p.10
Chapter 3.2.1 --- Cadaver test --- p.10
Chapter 3.2.2 --- Model-Based Image-Matching motion analysis --- p.12
Chapter 3.2.3 --- Statistical analysis --- p.14
Chapter 3.3 --- Results --- p.15
Chapter 3.3.1 --- Validity --- p.15
Chapter 3.3.2 --- Intra-rater reliability --- p.16
Chapter 3.3.3 --- Inter-rater reliability --- p.17
Chapter 3.4 --- Discussion --- p.17
Chapter 3.5 --- Conclusion --- p.21
Chapter Chapter 4: --- Biomechanical motion analysis on ankle ligamentous sprain injury cases --- p.22
Chapter 4.1 --- Introduction --- p.22
Chapter 4.2 --- Materials and method --- p.24
Chapter 4.2.1 --- Case screening --- p.24
Chapter 4.2.2 --- Model-Based Image-Matching motion analysis --- p.24
Chapter 4.3 --- Results --- p.28
Chapter 4.3.1 --- High Jump Injury --- p.28
Chapter 4.3.2 --- Field hockey Injury --- p.28
Chapter 4.3.3 --- Tennis Injury --- p.29
Chapter 4.4 --- Discussion --- p.30
Chapter 4.5 --- Conclusion --- p.34
Chapter Chapter 5: --- Summary and future development --- p.35
References --- p.36
List of publications --- p.42
List of presentations at international and local conference --- p.43
List of Awards --- p.44

Different methods for the determination of cantilever properties in non-contact atomic force microscopy (NC-AFM) are under investigation. A key aspect is the determination of the cantilever stiffness being essential for a quantitative NC-AFM data analysis including the extraction of the tip-surface interaction force and potential. Furthermore, a systematic analysis of the displacement noise in the cantilever oscillation detection is performed with a special focus on the thermally excited cantilever oscillation. The propagation from displacement noise to frequency shift noise is studied under consideration of the frequency response of the PLL demodulator. The effective Q-factor of cantilevers depends on the internal damping of the cantilever as well as external influences like the ambient pressure and the quality of the cantilever fixation. While the Q-factor has a strong dependence on the ambient pressure between vacuum and ambient pressure yielding a decrease by several orders of magnitude, the pressure dependence of the resonance frequency is smaller than 1% for the same pressure range. On the other hand, the resonance frequency highly depends on the mass of the tip at the end of the cantilever making its reliable prediction from known cantilever dimensions difficult. The cantilever stiffness is determined with a high-precision static measurement method and compared to dimensional and dynamic methods. Dimensional methods suffer from the uncertainty of the measured cantilever dimensions and require a precise knowledge its material properties. A dynamic method utilising the measurement of the thermally excited cantilever displacement noise to obtain cantilever properties allows to characterise unknown cantilevers but requires an elaborative measurement equipment for spectral displacement noise analysis. Having the noise propagation in the NC-AFM system fully characterised, a proposed method allows for spring constant determination from the frequency shift noise at the output of the PLL demodulator with equipment already being available in most NC-AFM setups.