33 research outputs found
A microstructure-sensitive electro-chemo-mechanical phase-field model of pitting and stress corrosion cracking
An electro-chemo-mechanical phase-field formulation is developed to simulate pitting and stress corrosion in polycrystalline materials. The formulation incorporates dependencies of mechanical properties and corrosion potential on crystallographic orientation. The model considers the formation and charging dynamics of an electric double layer through a new general boundary condition for the solution potential. The potential of the model is demonstrated by simulating corrosion in polycrystalline materials with various grain morphology distributions. The results show that incorporating the underlying microstructure yields more extensive defects, faster defect kinetics, and irregular pit and crack shapes relative to a microstructurally-insensitive homogeneous material scenario
Calibration of rock cutting numerical model based on monitoring data
Prediction of the deformation increment and the final displacement of the rock cutting is a challenging task. Many ambiguities linked with unpredictable nature or rock mass make it difficult to apply the adequate contingency measures. Implementation of common approach, which includes modelling of discontinuity effects with estimated reduction of rock mass strength and modulus of elasticity, usually does not yield satisfactory results. Therefore, a calibration of FEM based numerical model was made by conducting parametric analysis which feeds upon data obtained from extensive on-site monitoring system. A step forward was made in description of numerical parameters of karst discontinuities through consideration of monitoring results, as well as excavation procedures, position, inclination and length of discontinuities and PDC (project design change)
Elastic critical load of longitudinally unstiffened I-girders subjected to patch loading
The paper considers the elastic critical load of longitudinally unstiffened I-girders subjected to a localized load of variable length in the plane of the web. In the current regulations, the contribution of the patch load length and the flange thickness is not considered for calculating the elastic critical load. The influence of the boundary conditions on the vertical edges of the loaded panel on the value of the buckling coefficient is presented. An improved expression for the calculation of the buckling coefficients of longitudinally unstiffened I-girders is proposed
Hur samhÀllskunskapslÀrare verksamma inom vuxenutbildning tÀnker kring sitt Àmne
SamhĂ€llskunskapsĂ€mnet Ă€r ett skolĂ€mne det forskas förhĂ„llandevis lite om och kring, detsamma gĂ€ller vuxenutbildning. Kombinerar man dessa tvĂ„ Ă€r forskningen nĂ€st intill obefintlig. Genom denna uppsats hoppas jag kunna bidra med förstĂ„else och perspektiv vad gĂ€ller undervisning i samhĂ€llskunskap inom vuxenutbildning. Arbetets syfte Ă€r att undersöka hur samhĂ€llskunskapslĂ€rare verksamma inom vuxenutbildning â med utgĂ„ngspunkt i Basil Bernsteins (2000) teori om kunskap - tĂ€nker kring och upplever Ă€mnets syfte och mĂ„l. Vidare Ă€mnar undersökningen lyfta deras tankar och erfarenheter nĂ€r det kommer till utveckling av kunskaper och förmĂ„gor inom Ă€mnet. En kvalitativ intervjustudie har genomförts och resultatet visar att de undersökta lĂ€rarnas syn Ă€r koncentrerad kring medborgarfostran och att de har en klar bild över hur de pĂ„ bĂ€sta sĂ€tt ska nĂ„ detta syfte och mĂ„l. DessvĂ€rre överstiger vuxenutbildningens utmaningar dess möjligheter vilket försvĂ„rar benĂ€genheten att nĂ„ mĂ„luppfyllelse
(O)likvÀrdig utbildning och (o)likvÀrdiga möjligheter
Denna kunskapsöversikt försöker bringa klarhet i effekterna av lÀroplansreformen 2011, för samhÀllskunskapsÀmnet pÄ de yrkesförberedande gymnasieprogrammen. Resultatet visar att Àmnet sedan 2011 har fÄtt en allt mer marginaliserad roll pÄ yrkesskolorna runt om i landet. Resultatet visar ocksÄ att de yrkesförberedande gymnasieprogrammen - pÄ grund av lÀroplansreformens skrivelser - premierar en annan typ av kunskapsdiskurs Àn vad man gör pÄ de högskoleförberedande programmen. Min slutsats Àr att eleverna pÄ yrkesskolorna inte ges likvÀrdig utbildning och att deras framtida möjligheter sÄledes begrÀnsas
Hur samhÀllskunskapslÀrare verksamma inom vuxenutbildning tÀnker kring sitt Àmne
SamhĂ€llskunskapsĂ€mnet Ă€r ett skolĂ€mne det forskas förhĂ„llandevis lite om och kring, detsamma gĂ€ller vuxenutbildning. Kombinerar man dessa tvĂ„ Ă€r forskningen nĂ€st intill obefintlig. Genom denna uppsats hoppas jag kunna bidra med förstĂ„else och perspektiv vad gĂ€ller undervisning i samhĂ€llskunskap inom vuxenutbildning. Arbetets syfte Ă€r att undersöka hur samhĂ€llskunskapslĂ€rare verksamma inom vuxenutbildning â med utgĂ„ngspunkt i Basil Bernsteins (2000) teori om kunskap - tĂ€nker kring och upplever Ă€mnets syfte och mĂ„l. Vidare Ă€mnar undersökningen lyfta deras tankar och erfarenheter nĂ€r det kommer till utveckling av kunskaper och förmĂ„gor inom Ă€mnet. En kvalitativ intervjustudie har genomförts och resultatet visar att de undersökta lĂ€rarnas syn Ă€r koncentrerad kring medborgarfostran och att de har en klar bild över hur de pĂ„ bĂ€sta sĂ€tt ska nĂ„ detta syfte och mĂ„l. DessvĂ€rre överstiger vuxenutbildningens utmaningar dess möjligheter vilket försvĂ„rar benĂ€genheten att nĂ„ mĂ„luppfyllelse
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Micromechanical modeling of joining and manufacturing processes
Diffusion bonding and advanced additive manufacturing produce parts applicable in a wide range of industries, extending from electronics and nuclear applications to the manufacturing of various engineering and aerospace components. Characteristics and homogenization of diffusion-bonded joints rely on many parameters of the process. 3D printing depends on particle sintering as one of the key process steps. However, the micromechanics of diffusion bonding and additive manufacturing is not well understood. The joining method produces residual stresses and defects in the joint so that the joint typically represents a weak link in applications. Sintering often results in parts that deviate from the intended shape, which is a major obstacle to realizing the potential of 3D printing technology. We address the mechanics and physical mechanisms, including the underlying driving forces, responsible for joint homogenization in diffusion bonding of ceramics and shape distortion in sintering. We consider diffusion bonding of ceramics with a metallic interlayer. The key process for joint homogenization is the diffusion of carbon from the carbide phase into the metallic interlayer, which when the critical carbon concentration is reached, initiates the phase transformation of the metallic interlayer to carbide structure. We show that the driving force for carbon diffusion is the interfacial energy dependence on the carbon concentration jump across the metal-ceramic interface.3D printing of nanoparticles is used to study shape distortion in nonhomogeneous sintering. Freestanding microstructures such as pillars and walls are considered. Experiments show that sintering-induced distortion produces no porosity gradients in distorted parts, revealing that a mass transport mechanism must exist. Two physical mechanisms for mass transport in nonhomogeneous are identified. A macroscopic continuum theory that accounts for mass transfer and applicable to both mechanisms is formulated. The model predicts transient and permanent deformation during nonhomogeneous sintering and exhibits numerical consistency with the experimental data.In addition to diffusion bonding and nonhomogeneous sintering, we develop the computational framework for diffusional creep of single grain crystals using the lattice continuum formulation. The model is tested and applied on various grain sizes, applied stresses, governing processes, and compared with the classical theory for diffusional creep