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1
Johnson, Gregory. "Residual stress measurements using the contour method." Thesis, University of Manchester, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.489521.
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The aim of this dissertation is to explore and evaluate the contour method, a recently developed destructive technique for measuring residual stresses. It is a valuable addition to the suite of tools available to the researcher.
2
Whitley, Dixon T. "Practical Application of Residual Stress Measurements on Maritime Vessels." Thesis, Monterey, California. Naval Postgraduate School, 2012. http://hdl.handle.net/10945/7430.
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This thesis examines the practical application of portable X-ray diffraction to measure residual stresses on board active maritime platforms. These measurements will provide better understanding of structural failures in aluminum hulls and superstructures. The feasibility of this process was analyzed by comparing data from welded aluminum test samples using portable X-ray diffractometers from three different sources. The effects on residual stress from ultrasonic impact treatments were measured using laboratory X-ray diffraction. A comprehensive list of technical requirements for the purchase and deployment of a portable X-ray diffractometer was written. A case study for measurement of residual stresses on board a USN cruiser was developed.
3
Melamed, Samuel. "Compact ESPI device for isotropic measurements of residual stress." Thesis, University of British Columbia, 2015. http://hdl.handle.net/2429/54699.
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Residual stresses are self-equilibrating stresses that exist within bodies without any external loads acting on them. Monitoring residual stresses is vital to engineer safe and reliable structures. A reliable means of measuring residual stress is by drilling a small hole in the body and observing the resulting redistribution of the stress using an electronic speckle pattern interferometer (ESPI). Current ESPI systems are not suitable to measure stress on large or immovable structures because they depend on highly coherent laser sources that are bulky, delicate and not suitable for rugged field conditions. Additionally, ESPI is limited to a single direction of measurement. If the measurement axis is misaligned with the principal stress direction accuracy is reduced. This presents a practical challenge when measuring unknown residual stress states in the field. A compact ESPI device providing an isotropic residual stress measurement is presented here. The compactness of the device is possible by a novel optical arrangement that uses a diffraction grating and a miniature laser diode. This optical arrangement can be geometrically tuned to provide high quality measurements even with low coherence laser diodes. Furthermore, the device is constructed with two orthogonal measurement axes to reduce the influence of instrument alignment on measurement accuracy and to improve the overall precision by doubling the quantity of data. Experimentation with a calibrated bend specimen showed that the device has an accuracy ranging 9-12MPa and precision of 13MPa. This integration of ESPI and hole drilling modules into a compact, stand-alone unit is a significant milestone for in-field residual stress measurements.Applied Science, Faculty of
Mechanical Engineering, Department of
Graduate
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Cavusoglu, Mehmet Cagdas. "Improvements in electronic speckle pattern interferometry for residual stress measurements." Thesis, University of British Columbia, 2007. http://hdl.handle.net/2429/31579.
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Electronic Speckle Pattern Interferometry (ESPI) is an optical technique used for measuring surface displacements in the order of a wavelength of light by comparing interference patterns taken before and after surface deformation. Residual stress measurement is one of the applications where ESPI is useful. The technique is attractive because it provides very detailed information on deformation field and low per-measurement cost. However, ESPI data possess high noise content due to its high sensitivity to disturbances. In this research, factors that affect the quality of ESPI data were studied. The most important ones were found to be the specimen surface quality, illumination level and speckle size. The image quality was greatly improved by surface preparation. Good and faulty data were separated by evaluating their modulation level and identifying the saturated pixels. Mathematical methods were proposed to improve the data quality by either replacing the faulty data with good data or smoothing the data by filtering. Two common-path arrangements with single and double mirrors, which provide in-plane sensitive measurements, were designed to eliminate the separate and delicate optical paths. They improved the stability of ESPI measurements and greatly reduced the pixel drift that was a problem in the existing arrangement. The double mirror arrangement provided the measurement of full stress field. The single mirror method was confirmed by stress measurement, whereas the double mirror method could not be validated due to low data quality. Recommendations were made for an enhanced future design of this method.Applied Science, Faculty of
Mechanical Engineering, Department of
Graduate
5
Chipanga, Tendai. "Determination of the accuracy of non-destructive residual stress measurements methods." Thesis, [S.l. : s.n.], 2009. http://dk.cput.ac.za/cgi/viewcontent.cgi?article=1100&context=td_cput.
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Garza, Rodriguez Carlos. "Deep-hole drilling measurements of residual and assembly stress in composite materials." Thesis, University of Bristol, 2016. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.720824.
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Haggett, Michelle E. "Systematic review of UIT parameters on residual stresses of sensitized AA5456 and field based residual stress measurements for predicting and mitigating stress corrosion cracking." Thesis, Monterey, California: Naval Postgraduate School, 2014. http://hdl.handle.net/10945/41385.
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Approved for public release; distribution is unlimited.This thesis focuses on the use of x-ray diffraction to measure residual stresses around welds in aluminum ship structures both in the laboratory and in the field. Tensile residual stresses are often generated during welding and, in sensitized aluminum structures, can cause extensive stress corrosion cracking. Peening techniques, such as ultrasonic impact treatment (UIT), can mitigate and even reverse these tensile residual stresses. This research uses x-ray diffraction to measure residual stresses around welds in AA5456 before and after UIT. In particular, we examined the importance of UIT parameters such as peening amplitude and pin size. We found that all combinations of UIT parameters removed the tensile residual stresses and resulted in compressive stress several hundred microns below the weld surface. The exact level of compressive residual stress was sensitive to the pin size used with a smaller, but measurable, dependence upon the displacement amplitude. In an effort to extend these measurement techniques to the field, we successfully performed the first x-ray residual stress measurements on a U.S. naval combatant.
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Wagner, James Michael. "A hybrid finite element analysis of shot peen contour forming using residual stress measurements." Thesis, Wichita State University, 2013. http://hdl.handle.net/10057/7049.
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In order to develop surfaces that have the proper curvature for aerospace structures, it is
sometimes necessary to use shot peen forming, also known as contour forming, to create the
desired shape in a piece of metal. Since the preferred metal in aerospace continues to be
aluminum and its alloys, this study will concentrate on the effects of shot peening on aluminum.
Typically, shot intensity is measured using standard Almen strips made from cold rolled
SAE 1070 spring steel. Since the effects of the shot on aluminum is the chief concern of this
study, aluminum strips of the same size and thickness will be used to determine the intensity of
the shot on aluminum parts. These strips will be exposed for different amounts of time to
different intensities, measured using the steel Almen strips, and then the intensity (or arc height)
will be measured on the aluminum strips. The residual stresses in these strips will then be
measured using the hole drill method (ASTM E837).
The stresses from the residual stress test will then be used to develop a finite element
model that simulates the aluminum strips and the deformation in them. The model will then be
calibrated with the empirical data. From there, it will be the goal of this study to be able to
predict the deformation of aluminum parts when exposed to certain shot peen intensities. This
will enable more efficient contour forming processes with less rework. Furthermore, the trial
and error of a manual process can be avoided with the use of robotics. Robotics/Automation can
also help in creating more consistent results.Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Mechanical Engineering.
9
TANAKA, Keisuke, and Yoshiaki AKINIWA. "Diffraction Measurements of Residual Macrostress and Microstress Using X-Rays, Synchrotron and Neutrons." The Japan Society of Mechanical Engineers, 2004. http://hdl.handle.net/2237/9178.
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Tamura, Mariana Tiemi. "An assessment of the drilling process employed by the hole-drilling method for residual stress measurements." reponame:Repositório Institucional da UFSC, 2016. https://repositorio.ufsc.br/xmlui/handle/123456789/167751.
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Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Engenharia Mecânica, Florianópolis, 2016.Made available in DSpace on 2016-09-20T04:16:54Z (GMT). No. of bitstreams: 1 339489.pdf: 89627893 bytes, checksum: 27264112985d98d934df23ec5f7ae7d2 (MD5) Previous issue date: 2016
Abstract: Predictive maintenance is important to prevent catastrophic accidents inoil and gas distribution networks, since failures in pipelines and other mechanical components may lead to serious economic and environmental consequences. A possible approach to perform predictive maintenance isto monitor periodically loads that act on these structures. This task can becarried out through the Hole-Drilling Method to measure residual stresses,a consolidated semi-destructive technique for both in-field and in-lab applications. Standardised by ASTM E837 - 13a, this method is based on ablind hole drilling that relieves local stresses; the stress relief that occurs after material removal induces a microstructure reorganization, settling the material in a new equilibrium state after producing strains on the hole surrounding surface. These strains are related to the stresses that caused them according to Hooke's law in linearly elastic isotropic materials. The measurement result provided by this technique is intrinsically sensitive to the drilling process and produced hole characteristics, since machining induced residual stresses can mislead the true stress value. Besides, the hole geometry may differ significantly from the model recommended by the standard, provoking further errors in stress calculation. This work aims to investigate a cutting tool and cutting parameters combination that presents the best performance for residual stress measurements through the Hole-Drilling Method from two perspectives: machining and Electronic Speckle Pattern Interferometry application to measure strains. Two square end mills (two and four flutes) with TiAlN coating were used to drill the following workpiece materials: aluminium alloy AA 6061, carbon steel AISI 1020 and stainless steel AISI 304L. Chip and burr formation are investigated in preliminary analysis concerning the optical technique application since the seelements can cause loss of correlation and produce unreliable data. Rotational speed and feed rates effects on machining induced residual stresses are analysed through analysis of variance. Chip analysis is performed to assess qualitatively plastic deformation suffered during the process. This information are complemented with microhardness measurements to verify microstructural changes caused by the drilling process. Four-flute end mill presented lower machining induced residual stress absolute values. Particularly, the cutting tool and cutting parameters combination yielded satisfactory results when drilling AA 6061 and AISI 1020. However, AISI304L presented highly compressive machining induced residual stresses for almost all conditions. The most influential cutting parameter on machining induced residual stress introduction was the feed rate in the majority of the tested conditions.
A manutenção preditiva tem um papel importante na prevenção de acidentes catastróficos em redes de distribuição de petróleo e gás, uma vez que falhas em dutos e componentes mecânicos integrantes destas malhas podem trazer graves consequências econômicas e ambientais. Um dos procedimentos usados para tal fim é o monitoramento periódico dos esforços que atuam sobre estas estruturas; isto pode ser feito através do Método do Furo Cego para medição de tensões residuais, uma técnica semi-destrutiva consolidada tanto em aplicações em campo quanto em laboratórios. Este método, normatizado pela ASTM E837 - 13a, consiste na produção de um furo cego, o qual alivia tensões localizadas; o alívio proporcionado pela remoção de material provoca a reorganização da estrutura, a qual se acomoda em uma nova condição de equilíbrio, que se expressa em deslocamentos na superfície vizinha ao furo. Os deslocamentos estão associados às tensões que as provocaram através de lei de Hooke em materiais isotrópicos linearmente elásticos. O resultado de medição desta técnica é intrinsicamente susceptível à qualidade do processo de furação e do furo produzido, pois tensões induzidas pela usinagem podem mascarar o valor de tensão que sede seja conhecer, além de produzir características geométricas que diferem significativamente do modelo padronizado pela norma e podem provocar erros no cálculo das tensões. Este trabalho visa estudar uma combinação de parâmetros de corte e ferramenta que apresente o melhor desempenho para medição de tensões residuais através do Método do Furo Cego tanto do ponto de vista da usinagem quanto da aplicação da Interferometria speckle na medição dos deslocamentos. Duas fresas de topo reto (dois e quatro gumes) com revestimento de TiAlN foram utilizadas na furação de corpos de prova dos seguintes materiais: liga de alumínio AA 6061, aço carbono AISI 1020 e aço inoxidável AISI 304L. Formação de cavaco e rebarba são avaliados em análise preliminar quanto à utilização da técnica óptica para medição de deslocamentos, uma vez que podem provocar perda de correlação e inutilizar pontos de medição. Os efeitos da rotação e da velocidade de avanço na tensão residual induzida pela usinagem são analisados através de análise de variância. Análise do cavaco é usada para avaliar qualitativamente a deformação plástica sofrida durante o processo; estas informações são complementadas com medições de microdureza para verificar alterações na microestrutura causadas pela furação. Fresas de quatro gumes apresentaram menores valores absolutos de tensão residual induzidas pela usinagem. Em particular, a combinação de ferramenta e parâmetros de corte mostrou-se satisfatória no caso do AA 6061 e AISI 1020, no entanto para o AISI 304L foram encontrados valores de tensão residual induzidas pela usinagem de caráter bastante compressivo em quase todas as condições. Observou-se que o parâmetro de corte de maior influência na introdução de tensões residuais pela usinagem foi a velocidade de avanço na maioria das condições testadas.
11
Pettersson, Natalie. "Investigation of material removal techniques for residual stress profile determination on induction hardened steel." Thesis, Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-62618.
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The residual stress profile is a major factor on the fatigue life of components that are subjected to cyclic loading. In order to measure these stresses x-ray diffraction (XRD) is commonly used. The penetration depth of x-rays is limited for this method and thus, it must be combined with material removal to determine in-depth stress profiles.At SKF Manufacturing Development Center (SKF MDC), where the work for this thesis was carried out, the current layer removal method is restricted to a depth of 0.5 mm. Consequently, an additional method of material removal is necessary to obtain information at greater depths. The purpose of this thesis was to investigate possible material removal techniques that can be implemented with XRD measurements. Two different material removal techniques were studied; electrochemical etching and milling in combination with electrochemical etching. The electrochemical etching equipment was developed at SKF MDC prior to this thesis but needed further testing and validation. The residual stress profiles of induction hardened cylinders were studied using the two different removal techniques combined with XRD measurements and the results were compared with stresses measured by Electronic Speckle Pattern Interferometry (ESPI) with hole drilling. In addition, the results were compared with simulations performed at SKF MDC India. It was concluded that both the material removal methods could be successfully combined with XRD measurements. However, for practical reasons the methods should be refined before being implemented on a regular basis. Unfortunately, poor correlation between XRD and ESPI measurements were obtained due to reasons not fully understood.
12
Lestari, Saskia. "Residual Stress Measurements of Unblasted and Sandblasted Mild Steel Specimens Using X-Ray Diffraction, Strain-Gage Hole Drilling, and Electronic Speckle Pattern Interferometry (ESPI) Hole Drilling Methods." ScholarWorks@UNO, 2004. http://scholarworks.uno.edu/td/90.
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The objectives of this research are to measure residual stress in both unblasted and sandblasted mild steel specimens by using three different techniques: X-ray diffraction (XRD), strain-gage hole drilling (SGHD), and electronic speckle pattern interferometry (ESPI) hole drilling, and to validate the new ESPI hole drilling method by comparing its measurement results to those produced by the SGHD method. Both the XRD and SGHD methods were selected because they are accurate and well-verified approaches for residual stress measurements. The ESPI hole drilling technique is a new technology developed based on the SGHD technique, without the use of strain gage. This technique is incorporated into a new product referred to as the PRISM system, manufactured by Hytec, Incorporated, in Los Alamos, New Mexico. Each method samples a different volume of material at different depths into the surface. XRD method is especially different compared to the other two methods, since XRD only measures stresses at a depth very close to the surface (virtually zero depth). For this reason, no direct comparisons can be made between XRD and SGHD, as well as between XRD and ESPI hole drilling. Therefore, direct comparisons can only be made between SGHD and ESPI hole drilling methods.
13
Anderoglu, Osman. "Residual stress measurement using X-ray diffraction." Texas A&M University, 2004. http://hdl.handle.net/1969.1/1507.
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This paper briefly describes the theory and methods of x-ray residual stress
measurements.
Residual stresses can be defined as the stresses which remain in a material in the
absence of any external forces. There are many stress determination methods. Some of
those methods are destructive and some are nondestructive. X-ray residual stress
measurement is considered as a nondestructive method.
X-ray diffraction together with the other diffraction techniques of residual stress
measurement uses the distance between crystallographic planes as a strain gage. The
deformations cause changes in the spacing of the lattice planes from their stress free
value to a new value that corresponds to the magnitude of the residual stress. Because of
Poissons ratio effect, if a tensile stress is applied, the lattice spacing will increase for
planes perpendicular to the stress direction, and decrease for planes parallel to the stress
direction. This new spacing will be the same in any similarly oriented planes, with
respect to the applied stress. Therefore the method can only be applied to crystalline,
polycrystalline and semi-crystalline materials.
The diffraction angle, 2θ, is measured experimentally and then the lattice spacing
is calculated from the diffraction angle, and the known x-ray wavelength using Bragg's
Law. Once the d-spacing values are known, they can be plotted versus 2 sin ψ, ( ψ is the
tilt angle). In this paper, stress measurement of the samples that exhibit a linear behavior
as in the case of a homogenous isotropic sample in a biaxial stress state is included. The
plot of d vs. 2 sin ψ is a straight line which slope is proportional to stress. On the other
hand, the second set of samples showed oscillatory d vs. 2 sin ψ behavior. The oscillatory
behavior indicates the presence of inhomogeneous stress distribution. In this case the xray
elastic constants must be used instead of E and ν values. These constants can be
obtained from the literature for a given material and reflection combination. It is also
possible to obtain these values experimentally. Calculation of the residual stresses for
these samples is beyond the scope of this paper and will not be discussed here.
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Ghidini, Davide. "Accurate Portable Residual Stress ESPI Measurement Device." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020.
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An Electronic Speckle Pattern Interferometer residual stress measurement device based on the hole-drilling technique was designed and built: by carefully design both the mechanical and the optical systems, it has been possible to achieve very nice measurement results, with a compact and cheap device, which promise great on-field capabilities but also large room for further improvement.
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Hodgson, David Zhuang. "Residual stress measurement across different length scales." Thesis, University of Bristol, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.544354.
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Godin, Michael A. (Michael Alan). "Mobile neutron sources for residual stress measurement." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/28105.
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Jo, Jinmyun. "Residual stress measurement in railroad car wheels." Diss., Virginia Polytechnic Institute and State University, 1989. http://hdl.handle.net/10919/54206.
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A new failure criterion for discriminating good and bad (overheated) railroad car wheels is proposed. This criterion can replace the conventional “four inch" discoloration rule. The procedure for the new discrimination criterion is based on the fluctuations of the azimuthal residual stress in the tread of the wheel. This criterion is based on a maximum likelihood statistical analysis of data obtained from six different wheels as deterrmined by x-ray diffraction. Of these locations, the analysis showed the tread, and perhaps a critical point on the top of the flange, to be the most sensitive to residual stress. The variance analysis showed that fluctuations in stress at the most sensitive location in the tread appeared to be related to the service history. The residual stresses showed an oscillatory pattern in the hoop direction around the wheels.
Extension of the measurement technology to the use of magnetoelastic stress measurement is proposed. To evaluate the inaccuracy in stress data possible from a large sample with curved surface, corrections for a deliberate tilt of the plane of the x-ray diffractometer from the normal to the sample surface have been developed. Analysis of different misalignments are discussed. To validate our x-ray residual stress data, residual stresses were also measured by hole drilling. Excellent agreement between two techniques was found. Finally, stress variation with depth below surface was determined by the hole drilling technique.Ph. D.
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An, Yuntao. "Residual stress measurement using cross-slitting and ESPI." Thesis, University of British Columbia, 2008. http://hdl.handle.net/2429/5028.
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Residual stresses are “locked-in” within a material, and exist without any external loads.
Such stresses are developed during most common manufacturing processes, for example
welding, cold working and grinding. These “hidden” stresses can be quite large, and can
have profound effects on engineering properties, notably fatigue life and dimensional
stability. To obtain reliable and accurate residual stress measurements for uniform and
non-uniform stress states, a novel and practical method using crossing-slitting and ESPI
is presented here. Cross-slitting releases all three in-plane stress components and leaves
nearby deformation areas intact. The ESPI (Electronic Speckle Pattern Interferometry)
technique gives an attractive tool for practical use, because measurements provide a large
quantity of useful data, require little initial setup and can be completed rapidly and at low
per-measurement cost. A new ESPI setup consisting of shutter and double-mirror device
is designed to achieve dual-axis measurements to balance the measurement sensitivities
of all in-plane stress components. To evaluate data quality, a pixel quality control and
correction procedure is also applied. This helps to locate bad data pixels and provides
opportunities to correct them. The measurement results show that this procedure plays an
important role for the success of residual stress evaluation. Based on the observed
displacement data and finite element calculated calibration data, an inverse computation
method is developed to recover the residual stresses in a material for both uniform and
non-uniform cases. By combining cross-slitting and ESPI, more reliable results for the
three in-plane residual stress components can be obtained.
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Bourke, Mark A. M. "Residual stress measurement in engineering components by neutron diffraction." Thesis, Imperial College London, 1990. http://hdl.handle.net/10044/1/47782.
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Abraham, Colin. "Hole-drilling residual stress measurement in an intermediate thickness specimen." Thesis, University of British Columbia, 2011. http://hdl.handle.net/2429/37744.
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The hole-drilling method for measuring residual stresses is generally applied to two extreme cases. In the “thick” case, the specimen depth is very large compared with the hole depth. The far boundary is then sufficiently distant that its effect can be neglected. In the “thin” case, the specimen has the form of a thin plate through which the hole penetrates fully. The thin plate creates plane-stress conditions and it is usually assumed that the associated residual stresses are uniform through the plate thickness. This research focuses on the intermediate case where the specimen has a thickness modestly greater than the hole depth. The far boundary is then near enough to give significant influence, and the through-thickness residual stresses are non-uniform. The finite specimen thickness and non-uniform residual stresses create significant bending deformations of the specimen during hole-drilling that are not present in either extreme case. This bending effect creates out-of-plane deformations that can provide an opportunity for a novel measurement approach. The “intermediate” case is investigated using an analytical model and by finite element analysis. Experimental measurements are made using Electronic Speckle Pattern Interferometry (ESPI), and a comparison is made of the theoretical and experimental results.
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Goudar, Devkuma Murugesh. "Quantifying uncertainty in residual stress measurement using hole drilling techniques." Thesis, University of Bristol, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.549436.
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Traore, Yeli. "Controlling plasticity in the contour method of residual stress measurement." Thesis, Open University, 2013. http://oro.open.ac.uk/54680/.
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The contour method has emerged as a promising technique for residual stress measurement in relatively large, thick and complex engineering components. The method involves making a cut in the sample of interest, measuring the subsequent relaxed deformation profile of the cut surface and using this profile to back-calculate the original out-of-plane residual stress field by finite element modelling. The method is based on the theory of elasticity in that the stress relaxation during test specimen cutting is assumed to be entirely elastic. However, when measuring residual stresses of magnitude approaching the material yield strength, plasticity can occur which introduces errors in the measured stress profile. The main aim of this thesis was to develop methods of mitigating and estimating plasticity induced errors in contour method residual stress measurements. Based on the principles of fracture mechanics, an analogy was made between the stress relaxation process and a cracked plate to investigate the origin of plasticity in the contour method. It was demonstrated that that the cut tip stress intensity factor (KT) and the corresponding plastic zone parameters are the most important parameters for characterising plasticity-induced errors in the contour method. Extensive finite element analyses were carried out to understand and control the errors associated with plasticity with a view of improving the accuracy and reliability of the method. The outcomes of this research provide a valuable insight into how accumulation of plasticity for different restraining conditions affects the performance of the contour method. A novel cutting strategy that aims at mitigating plasticity-induced error by controlling the severity of the cut tip stress concentration (i.e. stress intensity factor) during the cutting process has been developed. Furthermore, procedures (correlations) are developed to estimate the plasticity-induced errors in the results of the contour method. Finally guidelines are proposed and applied to a case study for mitigating the errors associated with plasticity in a contour method residual stress measurement.
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Li, Fang. "Study of stress measurement using polariscope." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/34762.
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The goal of this research was to investigate an experimental infrared transmission technique to extract the full stress components of the in-plane residual stresses in thin multi crystalline silicon wafer, and try to meet the need of photovoltaic industry to in situ measure residual stress for large cast wafers.
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Dutta, Monojit. "Residual stress measurement in engineering materials and structures using neutron diffraction." Thesis, Open University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.301945.
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Kingston, Edward James. "Advances in the deep-hole drilling technique for residual stress measurement." Thesis, University of Bristol, 2004. http://hdl.handle.net/1983/af2b2d1f-d751-4497-98bf-45685f156d5f.
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Most engineering components contain defects (e. g. cavities and cracks) which are usually generated during the manufacture process. During the service life of the component it is possible that the defects could grow leading to ultimate failure of the component. For safety critical engineering components, such as those used in nuclear power plant systems, rail track systems and aerospace systems, ultimate failure is not permitted. To eliminate failure, the structural integrity of the component is assessed using knowledge of both the applied and residual stress distributions present. The applied stress distributions are calculated, whereas the residual stress distributions are measured using methods like the deep-hole drilling technique. The deep-hole drilling residual stress measurement technique was investigated to increase its accuracy and reliability in measuring the residual stress distributions present within components. It is a semi-invasive technique that involves drilling a small hole through the component and then the accurate diameter measurement thereof. A cylinder of material containing the hole is then extracted from the component causing the hole to deform due to the relaxation of the residual stresses present. The hole diameter is then re-measured and the change is used to determine the pre-existent residual stress distribution. The applicability of the technique was extended through modifications made to the machining processes, to include both thicker and thinner components. The accuracy of the measurements recorded and analysis thereof were improved. A portable machine was made to carry out "on-site" deep-hole drilling residual stress measurements on large components. Calibration experiments were carried out on components containing various known stress distributions to test the accuracy and modifications of the technique, and its applicability to different materials. Finally, an extensive set of residual stress measurements were undertaken on different components varying in geometry and material composition to test the accuracy and reliability of the technique in comparison with alternative measurement methods.
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George, Daniel Bernard François. "Determination of residual stresses in large section stainless steel welds." Thesis, University of Bristol, 2000. http://hdl.handle.net/1983/6286d2db-484e-4705-99c6-a291ea6d52f3.
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Knowles, Craig Russell. "Residual stress measurement and structural integrity evaluation of SLM Ti-6Al-4V." Master's thesis, University of Cape Town, 2012. http://hdl.handle.net/11427/13845.
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Includes bibliographical references.The constant drive toward cleaner, more powerful and more efficient jet turbines in the aerospace industry has narrowed the gap between the aircraft performance envelope requirements and the material limits. The most advanced turbine engines are incredibly complex in design and the weight-saving requirements have placed significant pressure on material capabilities and the manufacturing systems. The next generation of manufacturing methodologies are being developed in the Additive Manufacturing (AM) arena from which Selective Laser Melting (SLM) has emerged as a promising candidate for producing highly complex components. Selective Laser Melting is a laser-based AM technique which builds 3-dimensionsal parts from CAD models in a layerwise fashion...
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Proudian, Joanne. "Simulating Residual Stress in Machining; from Post Process Measurement to Pre-Process Predictions." Thesis, KTH, Industriell produktion, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-103003.
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Metal cutting is a widely used manufacturing technique in the industry and has been the focus of many research and studies in both academic and industrial fields. Prediction of induced residual stresses in a machined component is essential in a component’s fatigue life and surface integrity approximation. Furthermore, it plays a significant role in optimizing cutting process conditions as well as cutting tool geometries. Research has found that using experimental techniques in measuring residual stresses in a machined component is both time consuming and expensive as a method. In the attempt of eliminating the post process measuring drawbacks, the finite element modeling and simulation has proven its efficiency, as a tool, in predicting mechanical and thermal variables, hence, providing a pre-process prediction of variables which may prevent future component failures. This thesis uses the finite element method to study, model and simulate orthogonal metal cutting using the commercial software DEFORM. Orthogonal cutting simulations of 20NiCrMo5 steel are performed and simulation results are validated against experimental data. The influence of the feed rate, cutting speed and rake angle variations on the induced residual stress are investigated and analyzed. Simulation results offer an insight into cutting parameters and tool geometry influence on the induced residual stresses. Based on the simulation results, cutting speed and rake angle showed a trend when varying the parameters on the induced residual stress; however more investigation is needed in determining a trend for the feed rate influence.
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Altenkirch, Jens. "Stress engineering of friction stir welding : measurement and control of welding residual stresses." Thesis, University of Manchester, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.505389.
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Friction stir welding (FSW) is a maturing welding technique using a rotating tool for simultaneous heating and stir deforming th~ material interface to form a solid bond. Significant tensile residual stresses (RS) and component distortion may be produced even with optimized FSW parameters. Recent stress engineering techniques such as global mechanical or roller tensioning may reduce tensile RS and distortion. This dissertation reports on the first systematic investigation into the efficiency of insitu global mechanical tensioning (IS GMT) as well as roller tensioning applied in-situ (ISRT) and post welding (PWRT) for mitigation of tensile RS and plate distortion in high strength aluminium alloy plates joined by FSW. The techniques were evaluated by measuring the distribution of RS across the weld-line by means of neutron and synchrotron X-ray diffraction as well as' the levels of plate distortion. In each case the weld microstructure and hardness distribution were characterised. The data were rationalised against the ISGMT load and roller tensioning down force respectively. The results have shown that ISGMT and PWRT significantly mitigate longitudinal tensile RS and component distortion. ISGMT was found to decrease the tensile RS by an amount approximately equal to that of the load applied. Consequently, a stress free weld is produced with an ISGMT load equal to the magnitude of the weld-line RS in the as-welded condition~ PWRT decreases the tensile RS as the rolling down force increases and significant compression may be introduced once a certain magnitude is exceeded. ISRT, at least for the range tested, was found to be less effective. The component distortion reduced along with RSÇ'ú mitigation. No effects on the microstructure or hardness distribution due to mechanical stress engineering were observed. Furthermore, it was demonstrated that in order to make accurate stress measurements by diffraction, the effect of precipitation on the stress free lattice spacing must be taken into account for age hardening alloys. In order to complete this study an automated robotic sample manipulation system was developed. Finally, the degree of stress relaxation occurring on cutting down large welds was evaluated by progressively shortening test welds and determining the RS for each length. The amount of stress relaxation for each weld follows the same behaviour and appears to depend on the width of the tensile weld zone only.
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SOARES, ANA CRISTINA COSME. "EVALUATION OF PLASTIC EFFECTS IN RESIDUAL STRESS MEASUREMENT BY THE HOLE DRILLING TECHNIQUE." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2003. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=4411@1.
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COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIORUma das técnicas mais aplicadas para medir tensões residuais em componentes mecânicos é a técnica do furo cego. Esta técnica é de fácil aplicação industrial e é normalizada pela ASTM E 837. Entretanto, devido à concentração de tensões gerada pelo furo, há restrições quanto à aplicação deste método quando as tensões residuais presentes excedem 0.3 da tensão de escoamento do material, Sy. Há na literatura trabalhos que avaliam, por elementos finitos, os erros gerados ao se aplicar diretamente estes coeficientes em componentes com altos níveis de tensões residuais. Em alguns casos, o erro pode chegar a 140%, para tensões da ordem de 0.9 de Sy. Porém, para retrocalcular as tensões residuais estes trabalhos também usam hipóteses válidas apenas no regime elástico, de forma que os resultados por eles apresentados podem ter imprecisões. Neste trabalho propõem-se novas metodologias numéricas para avaliar a validade da norma ASTM E 837 em regime plástico, através de uma modelagem mais realística do alívio de tensão gerado pela usinagem do furo, evitando o uso de hipóteses linear-elásticas. Estas metodologias são: Estado Equivalente, na qual uma tensão equivalente àquela agindo no componente é aplicada na borda do furo; metodologia Morte de Elementos na qual os elementos presentes na região em que o furo será usinado são eliminados numericamente em vários passos, de forma a simular o processo de usinagem; e a metodologia Tensão Substituta, na qual o material presente na região do furo é substituído pela tensão que nele age, a qual é retirada gradativamente. Foram modeladas em elementos finitos placas com furos passantes e cegos, submetidas a carregamentos uniaxiais e biaxiais, desde 0.3 Sy até 0.9 Sy. Além disso, foram utilizados nas simulações materiais tendo limite elástico e de escoamento coincidentes e não coincidentes. Os erros encontrados entre as tensões retrocalculadas e as tensões aplicadas, para todas as situações são menores que encontrados por outros pesquisadores, obtendo-se no pior caso 70 por cento. Finalmente, conclui-se que as metodologias Tensão Substituta e Morte de Elementos são as que simulam de forma mais próxima da realidade o processo de usinagem de um furo em um placa submetida à altas tensões.
One of the most popular techniques applied to measure residual stresses is the hole-drilling technique. The technique is easy to be applied at industry, and is normalized ASTM E 837. However, due to the stress concentration caused by the machined hole, the technique can not be used if the residual stresses are higher than one third of the material yield strength, Sy. There are several researches articles that evaluate the errors aroused from the use of linear-elastic coefficients in case where plastic strains are present. In general, those articles apply the finite element to simulate the process of drilling the hole and stress relief. In certain case it is showed that the error can reach 140% of the applied stress. However,those articles use linear-elastics hypothesis and therefore their predictions can also include mistakes. The present work proposes new numerical methodologies to evaluate the usefulness of the hole- drilling technique, as it is described by the ASTM E 387, in the plastic range. The aim is to model the stress relief caused by the hole`s drilling process in a more realistic way, in order to avoid the use of linear-elastics hypothesis. The proposed methodologies are: Equivalent State, in which is applied in the hole a stress equivalent to that one acting externally on the component; Element Death, in which the drilling process is simulated by eliminating numerically in several steps the material which vanishes during the drilling process, and the Replacement Stress; in which the material in the hole is replaced by the stress that is acting at its walls. Those mentioned methodologies were implemented using a commercial finite element program which simulated plates with through the thickness and blind holes. Those plates have been loaded with three different loadings which varied from 0.3 to 0.9 Sy. Two materials with different stress-strain curves have been used. One of them had the elastic limit equal to the yield limit and the other one has those two limits different. In the worst case the errors found were 70 percent, which is smaller than those found by others researchers. It was concluded that, the Replacement Stress and the Elements Death methodologies are those that best simulate the process of drilling a hole in a plate which is under high stresses.
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Araujo, de Oliveira Jeferson. "Characterisation of a novel metal matrix composite & improved residual stress measurement method." Thesis, Open University, 2016. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.699821.
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The demand for materials with high strength- and stiffness-to-weight ratios has been driving the development of new metal matrix composites for the past few decades. Among the various possibilities, the 2124 aluminium alloy reinforced with silicon carbide particles is a good alternative in applications where quasi-isotropic properties are required. Although faster quench cooling rates generally result in improved mechanical properties in these composites, residual stress levels also become higher. High residual stress levels, although beneficial in some circumstances, may lead to distortions or even premature failure of the structure. This thesis presents the following original contributions to knowledge: (1) the characterisation of the mechanical properties of two novel composites reinforced with different volume fractions of sub-micrornetre-sized SiC particulates after a quench in either cold water or a 25%vol. polymer-glycol solution followed by annealing, where simultaneous improvement in tensile strength, ductility, hardness, fracture toughness and fatigue crack growth have been observed with the use of cold water as a quenchant; (2) the validation and first application of the contour method to measure residual stresses in such particulate reinforced composites, which showed that although better mechanical performance is obtained with the use of cold water as a quenchant, the residual stress levels introduced by this quench are also higher, which was undesired; (3) the first attempt to apply the fracture contour method to a pair of surfaces containing a fatigue crack and a new method to extend the fracture contour method to measure 2-D maps of shear-residual residual stresses in addition to the normal component, which was the first experimental proof of the entire theory of the contour method and possibly of Bueckner's superposition principle in 3-D.
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Pogue, Vanessa Ann. "Measurement and analysis of wire sawing induced residual stress in photovoltaic silicon wafers." Thesis, Georgia Institute of Technology, 2016. http://hdl.handle.net/1853/55071.
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The manufacturing process of a photovoltaic Si wafer comprises of first a high temperature heating process to produce a Si ingot from polycrystalline Silicon, which is then cut into bricks and subsequently sawn into wafers using a wire saw. These processes create residual stresses both from the thermal gradient induced by solidification and from either the rolling-indenting or scratching-indenting processes caused by the type of wire saw used. The objective of this research is to study silicon wafer residual stress as a result of the typical industry manufacturing processes and by doing so, better understand the mechanical properties that lead to increased fracture. This thesis aims to quantify the amount of residual stress generated by the solidification/thermal gradient produced during the casting of Si ingots separately from the residual stress generated by the wire sawing process. Samples from industry are used to compare the effects of the manufacturing processes on residual stress in multi-crystalline silicon (mc-Si) wafers including the effects of fixed abrasive diamond wire sawing (DWS) vs. loose abrasive (LAWS) slurry wire sawing used in the wafering process.
Near-infrared birefringence polariscopy and polarized micro-Raman spectroscopy are used to study wafer residual stresses within grains and at grain boundaries in mc-Si as a function of etch-depth. While near-infrared birefringence polariscopy allows for the measurement of full-field maximum shear stress, micro-Raman spectroscopy provides decomposition of the stress tensor into both principal and shear in-plane stress components. Consequently, regions of high tensile stress, which are detrimental to the mechanical integrity of the wafer, can be easily identified.
In addition to the mechanical characterization, the residual stress produced by the thermal gradient/solidification process for multi-crystalline Si wafers was also correlated to electrical performance of mc-Si wafers using photoluminescence.
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Pratihar, Sumit. "Residual stress measurement on different length scales using neutron and synchrotron X-ray diffraction." Thesis, Open University, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.439239.
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Myers, Donald G. "Method for measurement of residual stress and coefficient of thermal expansion of laminated composites." [Gainesville, Fla.] : University of Florida, 2004. http://purl.fcla.edu/fcla/etd/UFE0003180.
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Gang, Zheng. "Development of the deep hole drilling method for residual stress measurement in metallic welds." Thesis, University of Bristol, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.618551.
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Residual stresses can be defined as the self-equilibrating internal stresses that remain in a body in the absence of external forces or thermal gradients. They can arise from kinds of manufacturing processes and thermal treatments, where welding is a common process that generates residual stresses. Residual stresses are known to affect the fatigue, creep and brittle fracture properties of engineering components as well as their structural stability, wear and corrosion behaviour. Techniques that can accurately measure and predict residual stresses are therefore very important. The purpose of this project is to develop and improve the measurement of residual stress using deep hole drilling and neutron diffraction techniques. This is done using experimental methods and finite element analysis methods. Based on these developments, a series of measurements were undertaken to obtain through thickness distributions of residual stress in a variety of welded components. The deep hole drilling residual stress measurement technique is a semi-destructive, mechanical strain relief technique, which the strain components are measured during stress relief from the removal of a small amount of material. Neutron diffraction, a non-destructive technique, is based on Bragg's law and the components of strains are obtained from measurement of lattice spacing of polycrystalline material. The standard deep hole drilling, a newly developed incremental deep hole drilling techniques and the neutron diffraction technique were applied to a variety of metal welds to characterise the through thickness residual stresses generated by different welding methods, validate and develop the application range of these techniques. The finite element method was adopted for a ring weld specimen to simulate the welding process to obtain the residual stress field and to simulate the deep hole drilling techniques. An over-core deep hole drilling mcthod, a development from previous deep hole drilling techniques, was examined in this study. The extraction step in the over-core deep hole drilling technique allowed a hybrid procedure to combine the deep hole drilling and neutron diffraction techniques and increased the accuracy and reliability of residual stress measurements.
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Anantharaman, Satish. "RESIDUAL STRESS MEASUREMENT IN PLASTIC WELDED JOINS AND ITS APPLICATION TO THE DESIGN AND MANUFACTURE OF HYBRID ELECTRIC VEHICLE BATTERIES." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1250695031.
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England, Roger D. "Measurement Of Residual Stresses in Diesel Components using X-ray, Synchrotron, and Neutron Diffraction." University of Cincinnati / OhioLINK, 2000. http://rave.ohiolink.edu/etdc/view?acc_num=ucin966625751.
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田中, 啓介, Keisuke TANAKA, 賢一 水野, Kenichi MIZUNO, 修太郎 町屋, Shutaro MACHIYA, 義明 秋庭, and Yoshiaki AKINIWA. "シリコン単結晶の重回帰分析を用いたX線応力測定." 日本機械学会, 2006. http://hdl.handle.net/2237/9153.
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田中, 啓介, Keisuke TANAKA, 義明 秋庭, Yoshiaki AKINIWA, 裕介 森下, and Yusuke MORISHITA. "ショットピーニングしたセラミックスの表面下の残留応力分布." 日本機械学会, 2005. http://hdl.handle.net/2237/9134.
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Allard, Christopher E. "Development of a non-destructive optical method to measure residual stress in thin rectangular samples employing digital image processing." Thesis, Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/20645.
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Velicheti, Dheeraj. "Nondestructive Residual Stress Assessment of Shot-Peened IN718 Using Hall Coefficient Spectroscopy." University of Cincinnati / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ucin161374262949063.
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Solis, Dominic (Dominic R. ). "COMSOL finite-element analysis : residual stress measurement of representative 304L/308L weld in spent fuel storage containers." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/97965.
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Thesis: S.B., Massachusetts Institute of Technology, Department of Nuclear Science and Engineering, 2014.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 30-31).
The ultimate storage destination for spent nuclear fuel in the United States is currently undecided. Spent fuel will be stored indefinitely in dry cask storage systems typically located on-site at the reactor or at a dedicated independent spent fuel storage installation (ISFSI). Since these canisters were not originally designed or qualified for indefinite storage, there is a need to quantify the length of time they will be viable for storing spent fuel. Stress corrosion cracking (SCC) is a concern in these canisters if they are exposed to an aqueous, chloride-containing film. Canisters are fabricated using a concrete overpacking, along with austenitic stainless steel on the inside which is welded together. One factor that would significantly impact SCC behavior inside these canister welds, if the proper conditions developed such that SCC occurred, is the tensile residual stress profile. As the highest residual stresses are present in the welds and their heat-affected zones (HAZ), it would be useful to investigate their influence by predicting the residual stress profile in the container. These data will support further research into the life expectancy of these canisters and the possible ways in which they might fail due to SCC. Residual stress data for nuclear waste canisters are scarce. Without experimental measurements, initial insight must be attained through computational analysis using finite-element analysis (FEA) packages such as COMSOL. Using a representative 304L/308L weld plate as a model in COMSOL, predicted residual stress shows some agreement with expected trends: high tensile stresses in the weld/ HAZ regions and compressive stresses in the surrounding material. Hardness tests show trends similar to the hardening profiles that were created after the weld simulation. Additionally, the thermal model may offer insight in predicting the HAZ profiles in the weld. While the 2D model is simplified and would benefit from further refinement and validation, preliminary results suggest that FEA could be used for residual stress measurement predictions.
by Dominic Solis.
S.B.
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Chenelle, Brendan F. "Friction Stir Welding in Wrought and Cast Aluminum Alloys: Microstructure, Residual Stress, Fatigue Crack Growth Mechanisms, and Novel Applications." Digital WPI, 2011. https://digitalcommons.wpi.edu/etd-theses/1215.
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Friction Stir Welding (FSW) is a new solid-state welding process that shows great promise for use in the aerospace and transportation industries. One of the primary benefits of this process is that mechanical properties of the base material are not as severely degraded as they are with conventional fusion welding. However, fatigue crack initiation and growth properties of the resulting weld nugget are not fully understood at this time. The primary goal of this project is to characterize the fatigue crack growth properties of friction stir welds in 6061-T6 aluminum as relates to the microstructural evolution of the weld. This was accomplished by producing friction stir welds and testing fatigue crack growth response in different crack orientations with respect to the weld. In addition, residual stress measurements were conducted for all cases, using both the crack compliance and contour methods. The results from the methods were compared in order to evaluate the accuracy of each method. Being an immature technology, the potential for discovery of new applications for the FSW process exist. With this in mind, novel applications of the FSW process, including the addition of particles during welding were explored. The first step was the investigation of property changes that occur when secondary cast phases are refined using the FSW process. The FSW process successfully refined all secondary phases in A380 and A356, producing an increase in hardness. Next, methods for the creation of particle metal matrix composites using FSW will be investigated. Nano-scale alumina particles were successfully added to the matrix and homogenously distributed. Using multiple weld passes through the composite was found to increase the uniformity of particle distribution. However, the alumina particle composite failed to provide any statistically significant hardness increase over the base material. The FSW process was also evaluated for weldability of traditionally difficult alloy systems. FSW was found to show very good weldability for dissimilar cast and wrought alloys, as well as for high-pressure die castings. Lastly, the feasibility of friction stir welding/processing in repairing crack defects in complex structural members in combination with cold-spray technology was determined. Friction Stir processing was used on a cold spray 6061-T6 block, resulting in significant increases in hardness over the base material, as well as a reduction in porosity. In addition, FSP was shown to eliminate crack-type defects in cold spray materials, a finding that has important applications in part repair. The deliverables of this work include an understanding of the fatigue crack growth response of FSW/FSP 6061-T6, as well as a feasibility study exploring novel uses for the FSW/FSP process. In addition, the deliverables include CNC code, fixtures, procedures, and analytical code for the creation and analysis of FSW/FSP joints. This will be important for the continuation of FSW/FSP work at WPI.
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SUZUKI, Kenji, Keisuke TANAKA, and Yoshiaki AKINIWA. "Estimation of Spalling Stress in Thermal Barrier Coatings Using Hard Synchrotron X-Rays." The Japan Society of Mechanical Engineers, 2004. http://hdl.handle.net/2237/9176.
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Kulkarni, Kanchan Avinash. "Experimental Characterization and Finite Element Simulation of Laser Shock Peening Induced Surface Residual Stresses using Nanoindentation." University of Cincinnati / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1352489043.
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Li, Chun. "Measurement and understanding the residual stress distribution as a function of depth in atmosphere plasma sprayed thermal barrier coatings." Thesis, University of Manchester, 2018. https://www.research.manchester.ac.uk/portal/en/theses/measurement-and-understanding-the-residual-stress-distribution-as-a-function-of-depth-in-atmosphere-plasma-sprayed-thermal-barrier-coatings(e4dd38cc-2800-4719-bfe5-cccd0d6ff8c8).html.
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Residual stresses are generally considered to be the driving forces for the failure of APS TBCs. In this thesis, the residual stress distribution as a function of depth in APS TBC has been measured by synchrotron XRD and explained by image based modelling based on the microstructure detailed studied by SEM and CT. The residual stress/ strain distribution as a function of depth was measured by synchrotron XRD in transmission and reflection geometry. The residual stress/ strain values were analysed using full pattern Rietveld refinement, the sin square psi method and XRD2 method. For the reflection geometry, a new method was developed to deconvolute the residual stress value in each depth from the measured averaged values. Two types of residual stress/strain distribution were observed. The first kind of residual stress was found to be compressive and followed a non-linear trend, which increased from the surface to the interface, decreased slightly and increased again to the interface. This trend showed a jump feature near the interface. The second kind of residual stress distribution possessed two jump features: one near the interface similar to the first kind and another jump feature near the sample surface. The residual stress in both beta and gama phase in the bond coat were also investigated which showed a tensile stress state. The stress trend predicted by our analytical model followed a linear relationship. Comparing this with the first kind of residual stress distribution, two main differences were shown. Firstly the jump feature near the interface and secondly the much larger overall stress gradient. The 3D and 2D microstructure of the sample with the first kind of residual stress distribution was observed by X-ray CT and SEM. The effect of pores, inter-splat cracks and the rumpling interface on the residual stress distribution was investigated by image based modelling. It was proved that the pores and the inter-splat cracks had no large influence on the stress distribution and the jump feature near the interface was a result of the rumpling interface. The much larger stress gradient observed in the measured residual stress distribution was an indication of the stress relaxation in the coating which was proved by a specially designed mechanical test. To explain the jump feature near the sample surface in the second kind of stress distribution. 3D microstructures of the measured samples were observed using X-ray CT. The effect of vertical and the side cracks on the stress distribution were investigated by image based modelling. It was found that the vertical crack had no large influence on the residual stress distribution and the jump feature in the stress trend near the surface could be attributed to the side crack. The effect of other kinds of cracks that were not directly observed in our samples, such as middle or through side cracks, were also investigated. These results were used to develop a semi-destructive method to determine the existence and distribution of cracks in APS TBC.
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鈴木, 賢治, Kenji SUZUKI, 修太郎 町屋, Shutaro MACHIYA, 啓介 田中, Keisuke TANAKA, 喜久 坂井田, and Yoshihisa SAKAIDA. "熱遮へいコーティング膜の変形特性のＸ線的研究." 日本機械学会, 2001. http://hdl.handle.net/2237/9163.
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鈴木, 賢治, Kenji SUZUKI, 修太郎 町屋, Shutaro MACHIYA, 啓介 田中, Keisuke TANAKA, 喜久 坂井田, and Yoshihisa SAKAIDA. "熱遮へいジルコニアコーティングのX線的弾性定数と残留応力分布." 日本機械学会, 2001. http://hdl.handle.net/2237/9167.
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Andersson, Henrik. "Yt- och strukturpåverkan vid finfräsning av härdat verktygsstål." Thesis, Örebro universitet, Institutionen för naturvetenskap och teknik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:oru:diva-51787.
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I detta examensarbete har undersökningar kring finfrästa ytor i härdat verktygsstål utförts i samarbete med verktygsstålsproducenten Uddeholms AB i Hagfors. Vid spånskärande bearbetning påverkas materialet ibland negativt. En försöksserie om totalt 90 finfrästa ytor i härdade varmarbetsstålen Uddeholm Orvar Supreme och Uddeholm Dievar har frästs, mätts och utvärderats för att ta reda på hur fräsprocessen inverkar på materialets egenskaper. Det visar sig att materialet påverkas olika mycket beroende på hur fräsningen utförs och med vilken typ av fräsverktyg som används. I detta arbete har endast ändradiefräsar av solid hårdmetall använts. Analysen av ytorna har gjorts med en rad mätmetoder så som optisk ytjämnhetsmätning, hårdhetsmätning med Vickersmetoden, restspänningsmätning med röntgendiffraktion och okulär inspektion av stålets mikrostruktur i ljusmikroskop. Mätningarna utfördes för att se hur materialet påverkas mekaniskt av bearbetningen. I de mest ogynnsamma försöksfallen är den mekaniska påverkan från fräsbearbetningen av stålets ytor så stor att bearbetningen riskerar försämra tillverkade komponenters livslängd sett ur utmattningssynpunkt. Målet med arbetet är att identifiera det mest gynnsamma sätt fräsningen kan utföras på för att kunna minimera påverkan på materialets egenskaper. Detta ger möjligheten för Uddeholms AB att ge faktabaserade råd till sina kunder om vilket körsätt som ger minsta påverkan av verktygsstålet vid bearbetning. Kunderna kan nyttja då materialet till dess fulla kapacitet.In this thesis, investigations on hardened finish milled surfaces was done in collaboration with the tool steel manufacturer Uddeholms AB in Hagfors, Sweden. The steel material is affected by machining operations, sometimes in a negative destructive manner. An experimental test series containing a total of 90 surfaces in hot work steels Uddeholm Orvar Supreme and Uddeholm Dievar were milled, measured and evaluated to clarify the milling operations effect on the steels mechanical properties. It was found that the material is affected differently according to how the milling was preformed and with which type of milling tool. In this thesis, only solid carbide end-radius milling tools were used. The surface analysis were conducted with a range of measuring techniques including optical surface roughness measurements, hardness measurements in Vickers scale, residual stress measurements with X-ray diffraction (XRD) and microstructural analysis with optical light microscope. These measurements were conducted in order to determine the milling operations mechanical affects and grade of alteration of the tool steels surfaces. In the least favorable cases, the effect from machining are so profound, that degradation of produced components can be expected in terms of fatigue wear resistance. The goal of the thesis is to identify the most favorable process parameters, in order to minimize degradation of the tooling material in customer user cases, together with the opportunity to give fact based advice to Uddeholms AB customers on the most favorable process parameters in finish milling with radius-mills of hardened hot work tool steels. In this way the customer can utilize the tooling material at its full potential.
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Sorsa, A. (Aki). "Prediction of material properties based on non-destructive Barkhausen noise measurement." Doctoral thesis, Oulun yliopisto, 2013. http://urn.fi/urn:isbn:9789526200682.
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Abstract Barkhausen noise measurement is an intriguing non-destructive testing method suitable for ferromagnetic materials. It is based on the stochastic movements of magnetic domain walls when the tested sample is placed in an external varying magnetic field. Barkhausen noise is typically utilised so that some features are calculated from the signal and then compared with the studied material properties. Typical features are, for example, the root-mean-square value (RMS), peak height, width and position. Better utilisation of the method, however, requires quantitative predictions of material properties. The aim of this thesis is to study and select a suitable methodology for the quantitative prediction of material properties based on Barkhausen noise measurement. The prediction considered is divided into four steps: feature generation, feature selection, model identification and model validation. In feature generation, a large set of features is calculated with different mathematical procedures. This feature set is explored in the feature selection step to find the most significant features in terms of predictions. A model with the selected features is identified and some independent data are usually used for model validation. This thesis presents the developed procedures required in feature generation and the results of the studies using different feature selection strategies and modelling techniques. The studied feature selection methods are forward selection, simulated annealing and genetic algorithms. In addition, two-step algorithms are investigated where a pre-selection step is used before the actual selection. The modelling techniques used are multivariable linear regression, partial least squares regression, principal component regression and artificial neural networks. The studies also consider the use and effect of different objective functions. The results of the studies show that the proposed modelling scheme can be used for the prediction task. The models identified mainly include reasonable terms and the prediction accuracy is fairly good considering the challenge. However, the application of Barkhausen noise measurement is very case-dependent and thus conflicts may occur. Furthermore, the changes in unmeasured material properties may lead to the unexpected behaviour of some features. The results show that linear models are adequate for capturing the major interactions between material properties and Barkhausen noise but indicate that the use of neural networks would lead to better model performance. The results also show that genetic algorithms give better selection results but at the expense of the computational costTiivistelmä Barkhausen-kohina-mittaus on ferromagneettisille materiaaleille soveltuva materiaalia rikkomaton testausmenetelmä. Mittaus perustuu magneettisten alueiden välisten rajapintojen stokastisiin liikkeisiin, kun testattava kappale asetetaan vaihtuvaan magneettikenttään. Tyypillisesti Barkhausen-kohina-mittaussignaalista lasketaan piirteitä, joita sitten verrataan tutkittaviin materiaaliominaisuuksiin. Usein käytettyjä piirteitä ovat signaalin keskineliön neliöjuuri (RMS-arvo) sekä piikin korkeus, leveys ja paikka. Menetelmää voidaan soveltaa paremmin, jos tutkittavia materiaaliominaisuuksia voidaan ennustaa kvantitatiivisesti. Tämän tutkimuksen tavoitteena on tutkia ja valita menetelmiä, jotka soveltuvat materiaaliominaisuuksien kvantitatiiviseen ennustamiseen Barkhausen-kohina-mittauksen perusteella. Ennustusmallit luodaan neljässä vaiheessa: piirteiden laskenta, piirteiden valinta, mallin identifiointi ja mallin validointi. Piirteiden laskennassa yhdistellään erilaisia matemaattisia laskutoimituksia, joista tuloksena saadaan suuri joukko erilaisia piirteitä. Tästä joukosta valitaan ennustukseen soveltuvimmat piirteiden valinta -vaiheessa. Tämän jälkeen ennustusmalli identifioidaan ja viimeisessä vaiheessa sen toimivuus todennetaan riippumattomalla testausaineistolla. Väitöskirjassa esitetään piirteiden laskentaan kehitettyjä algoritmeja sekä mallinnustuloksia käytettäessä erilaisia piirteiden valintamenetelmiä ja mallinnustekniikoita. Tutkitut valintamenetelmät ovat eteenpäin valinta, taaksepäin eliminointi, simuloitu jäähtyminen ja geneettiset algoritmit. Väitöskirjassa esitellään myös kaksivaiheisia valintamenettelyjä, joissa ennen varsinaista piirteiden valintaa suoritetaan esivalinta. Käytetyt mallinnustekniikat ovat monimuuttujaregressio, osittainen pienimmän neliösumman regressio, pääkomponenttiregressio ja neuroverkot. Tarkasteluissa huomioidaan myös erilaisten kustannusfunktioiden vaikutukset. Esitetyt tulokset osoittavat, että käytetyt menetelmät soveltuvat materiaaliominaisuuksien kvantitatiiviseen ennustamiseen. Identifioidut mallit sisältävät pääasiassa perusteltavia termejä ja mallinnustarkkuus on tyydyttävä. Barkhausen-kohina-mittaus on kuitenkin erittäin tapauskohtainen ja täten ristiriitoja kirjallisuuden kanssa voidaan joskus havaita. Näihin ristiriitoihin vaikuttavat myös ei-mitattavat muutokset materiaaliominaisuuksissa. Esitetyt tulokset osoittavat, että lineaariset mallit kykenevät ennustamaan suurimmat vuorovaikutukset materiaaliominaisuuksien ja Barkhausen-kohinan välillä. Tulokset kuitenkin viittaavat siihen, että neuroverkoilla päästäisiin vielä parempiin mallinnustuloksiin. Tulokset osoittavat myös, että geneettiset algoritmit toimivat piirteiden valinnassa paremmin kuin muut tutkitut menetelmät