Analisam-se a variação de parâmetros obtidos da curva tensão-deformação dos solos, interpretada como uma hipérbole, em função dos parâmetros de compactação obtidos da curva de compactação Proctor Normal. Esta análise é feita em três solos típicos. / The variation of the parameters obtained by the stress-strain curve of the soils, understood as a hyperbola is analysed in function of the compactation parameters obtained from the Proctor Compactation Curve. This analysis is made with three typical soils.

Fatigue failures of driveline and suspensions components for ground vehicles under multiaxial loading conditions are common, since most those components are subjected to complex multiaxial loadings in service. In addition to the multiaxial loadings, many of those components contain notches and geometrical irregularities where the fatigue failure often occurs due to stress concentrations. Therefore, the origins of the multiaxiality can be related to various combinations of external loadings and notch geometries. A computational fatigue analysis methodology has been proposed here for performing multiaxial fatigue life prediction for notched components using analytical and numerical methods. The proposed multiaxial fatigue analysis methodology consists of an elastic-plastic stress/strain model and a multiaxial fatigue damage parameter. The multiaxial stress-strain notch analysis method originally proposed by Buczynski and Glinka is adapted to develop the elastic-plastic stress/strain model to compute local stress-strain responses using linear elastic FE results of notched components. An original multiaxial fatigue damage parameter based on the maximum fatigue damage plane is proposed to predict the fatigue life for notched components under multiaxial loadings. Results of the proposed multiaxial fatigue analysis methodology are compared to sets of experimental data published in the literature to verify the prediction capability of the elastic-plastic stress/strain model and the multiaxial fatigue damage parameter. Based on the comparison between calculated results and experimental data, it is found that the multiaxial elastic-plastic stress/strain model correlates well with experimental strain data for SAE 1070 steel notched shafts subjected to several non-proportional load paths. The proposed multiaxial fatigue damage parameter, when applied to the uniaxial loading to account for the mean stress effect on fatigue life, is found to correlate very well with four sets of experimental uniaxial mean stress fatigue data. In the case of multiaxial loadings, the proposed multiaxial fatigue damage parameter provides very good correlation with experimental fatigue data of thin-walled tube specimens of 1045 steel and Inconel 718. In addition, the proposed fatigue damage parameter is found to correlate reasonably well with experimental fatigue data of SAE 1045 steel notched shafts subjected to proportional and non-proportional loadings. The proposed multiaxial fatigue analysis methodology enables rapid durability evaluation for notched components design. The effect of changes in material, geometry and loads on the fatigue life can then be assessed in a short time frame. The proposed multiaxial fatigue analysis methodology provides more efficient and appropriate analysis methods preferable to very expensive experimental durability tests and more complex and time consuming life prediction methods using non-linear FE stress-strain analysis.

Development of new scientific disciplines such as bioengineering and micro-nano engineering adopting nonconventional materials requests innovative methodologies that can accurately measure the mechanical properties of soft biological materials and characterize surface energy and adhesion properties of them, independent of measurement conditions. One of emerging methods to measure the deformation of materials under stress is digital image correlation (DIC) technique. As a noncontact strain measurement method, DIC has the advantages of prevention of experimental errors caused by the use of contact type sensors and of flexibility in its application to soft materials that are hard to be tested by conventional method. In the first part of the thesis, 2 dimensional and 3 dimensional DIC codes were developed and optimized, and then applied to two critical applications: 1) determining the stress-strain behaviour of polydimethylsiloxane (PDMS) sample, as a model soft material, using the optical images across large deformation region, and 2) detecting the stiffness variation within the gel mimicking the breast tumour using ultrasound images. The results of this study showed the capability of DIC as a strain sensor and suggested its potential as a diagnosing tool for the malignant lesion causing local stiffness variation. In the characterization of surface energy and adhesion properties of materials, two most common methods are contact angle measurement and JKR-type indentation test. In the second part of the thesis, the experimental set-up for these methods were developed and verified by using the PDMS in static (quasi equilibrium) state. From the dynamic tests, it showed its possible usage in studying adhesion hysteresis with respect to speed. The adhesion hysteresis was observed at high speed condition in both contact angle measurement and JKR-type indentation tests.

Visose pramonės šakose, ypatingai energetikoje, plačiai taikomos plonasienės metalinės konstrukcijos. Tokių konstrukcijų pavyzdžiu yra antžeminiai vertikalūs ci-lindriniai rezervuarai. Kadangi šių statinių konstrukcijų gamybos ir montavimo darbus sudėtinga atlikti be lokalių ar bendrų nukrypimų nuo idealios cilindrinės formos, tikslus jų įvertinimas labai svarbus tokiems potencialiai pavojingiems statiniams. Šio darbo tyrimų pagrindinis tikslas yra: talpyklos sienelės su įduba įtemptojo deformuotojo būvio identifikavimas baigtinių elementų metodu ir eksperimentiniu metodu. / In all branches of industry, especially in power-engineering, thin wall steel structures are extensively used. Land vertical cylindrical tanks are examples of such structures. The manufacture and assembling of these structures are usually accompanied by deviations from an ideal cylindrical form. Therefore, the exact evaluation of real local imperfections and common deviations from the analytical model of the tank is very important for such potentially dangerous structures. The main objective of the presented investigations is to identify stress/strain state of the wall tank with local imperfections from the ideal cylindrical surface, taking into account the membrane theory of the shells by using the natural experiment and finite element’s method.

In all branches of industry, especially in power-engineering, thin wall steel structures are extensively used. Land vertical cylindrical tanks are examples of such structures. The manufacture and assembling of these structures are usually accompanied by deviations from an ideal cylindrical form. Therefore, the exact evaluation of real local imperfections and common deviations from the analytical model of the tank is very important for such potentially dangerous structures. The main objective of the presented investigations is to identify stress/strain state of the wall tank with local imperfections from the ideal cylindrical surface, taking into account the membrane theory of the shells by using the natural experiment and finite element’s method. / Visose pramonės šakose, ypatingai energetikoje, plačiai taikomos plonasienės metalinės konstrukcijos. Tokių konstrukcijų pavyzdžiu yra antžeminiai vertikalūs ci-lindriniai rezervuarai. Kadangi šių statinių konstrukcijų gamybos ir montavimo darbus sudėtinga atlikti be lokalių ar bendrų nukrypimų nuo idealios cilindrinės formos, tikslus jų įvertinimas labai svarbus tokiems potencialiai pavojingiems statiniams. Šio darbo tyrimų pagrindinis tikslas yra: talpyklos sienelės su įduba įtemptojo deformuotojo būvio identifikavimas baigtinių elementų metodu ir eksperimentiniu metodu.

Darbe pasiūlyta tempiamojo betono įtempių - deformacijų priklausomybė trumpalaikio ir ilgalaikio apkrovimo atveju. Pasiūlyta priklausomybė gauta, taikant EC2 momentų–kreivių priklausomybių apskaičiavimo metodiką. Atlikta lenkiamųjų gelžbetoninių elementų įtempių ir deformacijų priklausomybių analizė. Apžvelgti tokių elementų deformacijų skaičiavimo metodai ir matematiniai modeliai, apžvelgti paskelbti literatūros šaltiniai, susijusę su lenkiamųjų gelžbetoninių elementų deformacijomis. Skaitinio eksperimento pagalba sudaryta lenkiamųjų gelžbetoninių elementų duomenų imtis, išnagrinėta trumpalaike ir ilgalaike apkrova veikiami lenkiamieji gelžbetoniniai elementai, deformacijos ir jas lemiantys faktoriai, atlikta jų analizė. Taikant VGTU tiltų ir specialiųjų statinių katedroje pasiūlytą sluoksnių metodą iš skaitinių eksperimentų gautų momentų-kreivių diagramų gautos supleišėjusio tempiamojo betono įtempių-deformacijų priklausomybės. Parinkti pagrindiniai teorinės diagramos parametrai, priklausomai nuo betono klasės, armavimo procento bei valkšnumo koeficiento. Gautoji priklausomybė pritaikyta gelžbetoninių sijų kreivių apskaičiavimui sluoksnių metodu. Gautieji rezultatai palyginti su empirinėmis EC2 normų prikalsumybėmis gautais rezultatais. Palyginamoji gautų skaičiavimo rezultatų analizė parodė gerą abiem metodais gautų rezultatų atitikimą. Gautoji priklausomybė gali būti pritaikyta netiesiniuose skaičiavimuose, taikant baigtinių elementų metodą. / The paper suggests tension concrete stress-strain dependence of the short-term and long-term case-load of the EC2 method. Bending reinforced concrete elements of stress and strain dependence are analyzed. Presented overview of such elements deformation calculation methods and mathematical models, highlight the relevance literature review, relating to bending reinforced concrete elements. Collected bending reinforced concrete elements (numerical experiments) data, examined short-term and long term effects of load to bended reinforced concrete elements, deformations and the determining factors, performed their analysis. For the purposed of VGTU bridges and special structures department’s constitutive model from the numerical experiments obtained moment-curvature relationships derived the charts of cracked pulling concrete stress-strain dependence. Choose the basic theoretical parameters of the relationships, depending on the class of concrete, reinforcement rates, and creep coefficient. The calculation results are compared with the experimental beam data. Performed calculation results of the analysis showed quite accurate results with the derived dependencies.

Development of new scientific disciplines such as bioengineering and micro-nano engineering adopting nonconventional materials requests innovative methodologies that can accurately measure the mechanical properties of soft biological materials and characterize surface energy and adhesion properties of them, independent of measurement conditions. One of emerging methods to measure the deformation of materials under stress is digital image correlation (DIC) technique. As a noncontact strain measurement method, DIC has the advantages of prevention of experimental errors caused by the use of contact type sensors and of flexibility in its application to soft materials that are hard to be tested by conventional method. In the first part of the thesis, 2 dimensional and 3 dimensional DIC codes were developed and optimized, and then applied to two critical applications: 1) determining the stress-strain behaviour of polydimethylsiloxane (PDMS) sample, as a model soft material, using the optical images across large deformation region, and 2) detecting the stiffness variation within the gel mimicking the breast tumour using ultrasound images. The results of this study showed the capability of DIC as a strain sensor and suggested its potential as a diagnosing tool for the malignant lesion causing local stiffness variation. In the characterization of surface energy and adhesion properties of materials, two most common methods are contact angle measurement and JKR-type indentation test. In the second part of the thesis, the experimental set-up for these methods were developed and verified by using the PDMS in static (quasi equilibrium) state. From the dynamic tests, it showed its possible usage in studying adhesion hysteresis with respect to speed. The adhesion hysteresis was observed at high speed condition in both contact angle measurement and JKR-type indentation tests.

Fatigue failures of driveline and suspensions components for ground vehicles under multiaxial loading conditions are common, since most those components are subjected to complex multiaxial loadings in service. In addition to the multiaxial loadings, many of those components contain notches and geometrical irregularities where the fatigue failure often occurs due to stress concentrations. Therefore, the origins of the multiaxiality can be related to various combinations of external loadings and notch geometries. A computational fatigue analysis methodology has been proposed here for performing multiaxial fatigue life prediction for notched components using analytical and numerical methods. The proposed multiaxial fatigue analysis methodology consists of an elastic-plastic stress/strain model and a multiaxial fatigue damage parameter. The multiaxial stress-strain notch analysis method originally proposed by Buczynski and Glinka is adapted to develop the elastic-plastic stress/strain model to compute local stress-strain responses using linear elastic FE results of notched components. An original multiaxial fatigue damage parameter based on the maximum fatigue damage plane is proposed to predict the fatigue life for notched components under multiaxial loadings. Results of the proposed multiaxial fatigue analysis methodology are compared to sets of experimental data published in the literature to verify the prediction capability of the elastic-plastic stress/strain model and the multiaxial fatigue damage parameter. Based on the comparison between calculated results and experimental data, it is found that the multiaxial elastic-plastic stress/strain model correlates well with experimental strain data for SAE 1070 steel notched shafts subjected to several non-proportional load paths. The proposed multiaxial fatigue damage parameter, when applied to the uniaxial loading to account for the mean stress effect on fatigue life, is found to correlate very well with four sets of experimental uniaxial mean stress fatigue data. In the case of multiaxial loadings, the proposed multiaxial fatigue damage parameter provides very good correlation with experimental fatigue data of thin-walled tube specimens of 1045 steel and Inconel 718. In addition, the proposed fatigue damage parameter is found to correlate reasonably well with experimental fatigue data of SAE 1045 steel notched shafts subjected to proportional and non-proportional loadings. The proposed multiaxial fatigue analysis methodology enables rapid durability evaluation for notched components design. The effect of changes in material, geometry and loads on the fatigue life can then be assessed in a short time frame. The proposed multiaxial fatigue analysis methodology provides more efficient and appropriate analysis methods preferable to very expensive experimental durability tests and more complex and time consuming life prediction methods using non-linear FE stress-strain analysis.

In the repertoire of an experimental condensed matter physicist, the ability to tune continuously through features in the electronic structure and to selectively break point-group symmetries are both valuable techniques. The experimental technique at the heart of this dissertation, uniaxial stress, can do both such things. The thesis will start with a thorough discussion of our new technique, which was continually developed over the course of this work, presenting both its unique capabilities and also some guidance on the best working practices, before moving on to describe results obtained on two different strongly correlated electron materials. The first, Sr2RuO4, is an unconventional superconductor, whose order parameter has long been speculated to be odd-parity. Of interest to us is the close proximity of one of its three Fermi surfaces to a Van Hove singularity (VHs). Our results strongly suggest that we have been able to traverse the VHs, inducing a topological Lifshitz transition. T[sub]c is enhanced by a factor ~2.3 and measurements of H[sub](c2) open the possibility that optimally strained Sr2RuO4 has an even-parity, rather than odd-parity, order parameter. Measurements of the normal state properties show that quasiparticle scattering is increased across all the bands and in all directions, and effects of quantum criticality are observed around the suspected Lifshitz transition. Sr3Ru2O7 has a metamagnetic quantum critical endpoint, which in highly pure samples is masked by a novel phase. Weak in-plane magnetic fields are well-known to induce strong resistive anisotropy in the novel phase, leading to speculation that a spontaneous, electronically driven lowering of symmetry occurs. Using magnetic susceptibility and resistivity measurements we can show that in-plane anisotropic strain also reveals the strong susceptibility to electronic anisotropy. However, the phase diagram that these pressure measurements reveal is consistent only with large but finite susceptibility, and not with spontaneous symmetry reduction.

Doctor of Philosophy / Department of Civil Engineering / Asadollah Esmaeily / Over the past 30 years, FRP composites (carbon, glass, or aramid fibers) have arisen as a method of retrofitting existing reinforced concrete structures to bring them up to current code standards of confinement and ductility. The development of stress-strain models for FRP confined concrete began with the adaptation of steel confinement models then progressed to models specifically developed based on test results from FRP confined specimens. State of the art stress-strain models for FRP confined concrete models may now be validated against a wide variety of published experimental results. Recent publications show researchers branching out and looking at other aspects of FRP confined concrete behavior, including the impact of sustained service loads on long term and ultimate behavior. An experimental program which examines the effects of sustained service loading on the ultimate axial performance of FRP confined concrete is presented. The program's purpose is to determine whether or not a material model developed without the presence of a sustained load accurately predicts the ultimate stress-strain response of FRP confined concrete previously subjected to a sustained service load. Equipment and procedures were developed to model the critical events in a building life cycle: construction, sustained service loading, minor critical events, rehabilitation, and ultimate performance. Varying the order of these events produces a simulated life cycle allowing analysis of the impact of strain history on ultimate performance. The results of the experimental program indicate that the presence of a sustained service load changes the expected failure mode from FRP rupture to FRP de-lamination and the stress-strain response of a specimen is approximately 10% below published models when sustained service loads are included in the life cycle. A comprehensive modeling process is proposed for modeling significant events in a structure's life cycle. Impacts on earthquake engineering and reliability studies are addressed and future research suggested. This research shows that life cycle modeling can improve the design and rehabilitation of structures so that they meet safety requirements in future seismic events.