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Multifunctional β-titanium alloy Gum Metal, characterized by a relatively low elastic modulus, superelastic-like behavior and high strength, was subjected to cyclic tensile loadings. The characteristics of macroscopic scale energy storage and dissipation in the consecutive loading–unloading cycles were studied. Various kinds of energy components related to the alloy deformation process were determined experimentally and analyzed using thermodynamic relations. The values of the entire work needed to deform the alloy Wext, the work used for recoverable deformation Wrec consisting of the elastic deformation energy Wel, the superelastic-like energy Wpt, and the energy of thermoelastic effect Eth, were derived from the Gum Metal stress and temperature vs. strain curves. The irrecoverable mechanical energy Wir expended on plastic deformation, the dissipation energy Q, and finally the stored energy Es were estimated. The stored energy represents a change in the internal energy of the deformed material and is an essential measure of cold-worked state. The Es value turned out to be not large for the Gum Metal, which confirms the alloy low hardening property. The energy components determined for each of the 24 loading cycles enabled us to analyze various stages of the Gum Metal deformation process, including necking and damage.

Fire investigators are trained to apply the scientific method to determine the origin and cause of a fire. They look for patterns that indicate the sequence of involvement of available fuel loads, including considering whether a given fuel load contains enough energy to ignite other fuels. It is common knowledge that cylindrical 18650 lithium-ion (Li-ion) battery cells contain significant electrochemical energy and that they have the potential to fail and cause fires, so they are often considered a potential ignition source. The presence of a damaged 18650 cell at a fire scene poses a challenge to fire investigators because regardless of whether the cell is the cause or a victim of the fire, its stored energy can be released energetically, leaving a burn pattern and rapidly involving other fuel loads. It is therefore desirable to identify post-fire physical features on 18650 Li-ion cells that indicate whether they were the cause or a victim of a fire. This work shows that several features have been incorrectly identified in previous investigations. Expulsion of cell contents, crimp deformation, a flat negative terminal, localized damage in the electrode windings, and a hole in the metal casing have been cited as indications that the cell failed and caused a fire. To test these hypotheses, 18650 Li-ion cells at various states of charge (SOC) were burned in a controlled and repeatable manner. Temperatures were recorded and the experiments were documented with still-photography and video. The post-fire condition of each cell was then characterized with radiography (X-ray), computed tomography, and optical imaging. Each of the post-fire physical features in question occurred in non-defective cells that were victims of controlled fires, thereby demonstrating that these features are not valid indicators of fire causation.

The frictional dissipation and energy stored in two spherical grains are investigated analytically for the sliding or combined slip-sliding regimes for the experimentally-typical cases of testing. The analytical formulae are proposed for the explicit and approximate predictions of the work of driving force, kinetic, dissipated and stored energies. Controlling the energy balance, a mathematical insight is also attained into the evolution and redistribution of these quantities over the contact interfaces. It is demonstrated that the total frictional dissipation expended by the moving sphere can be analytically represented as a sum of frictional dissipation given at each contact interface. It also provides for the geometrical construction of the reference contact paths using the overlap approach for contact interaction of two spheres of the same material. The rate of dissipation is expressed in terms of the relative contact zone velocities of two spheres.

This paper presents the development of a low-power electronic system powered by a thermoelectric generator, based on Peltier cells, which takes advantage of daily temperature variations in the environment using a tank with 6 liters of water as a thermal accumulator. The generator works both day and night, since it uses a dc-dc boost converter with bipolar input. The system avoids using batteries because it charges a 0.1 F supercapacitor module between 2.40 and 3.15 V, so the useful energy in each charging cycle is 208 mJ. This energy is sufficient so that the system can measure the ambient temperature, represent it on a display and record it along with the date and time on a memory card when there is enough stored energy. The PSpice model and the simulation of the generator is also presented and experimental results of its operation are presented for two days. It is derived that in that period, with a maximum temperature difference of 10 °C, the system is able to charge the supercapacitor thirteen times per day, which means a daily useful energy of 2.7 J. Finally, results of the autonomous system performance for four days are presented.

The dissipated energy ( $E_{\text{diss}}$ ) related to the resonant charging–discharging of a transistor output capacitance becomes a dominant loss factor for power converters operating in the MHz range. A recent letter has introduced a small-signal measurement method to quantify $E_{\text{diss}}$ with a frequency-dependent small-signal resistance, $R_{\text{s}}$ , and an effective small-signal output capacitance, $C_{\text{oss}}^{\text{eff}}$ . This letter provides further insights on the effect of $R_{\text{s}}$ and $C_{\text{oss}}$ upon the device losses in a broader sense. In particular, the $C_{\text{oss}}$ loss tangent, tan ( $\delta$ ), is introduced as a normalized $E_{\text{diss}}$ to combine the roles of $R_{\text{s}}$ and $C_{\text{oss}}$ together with the operating frequency into a single loss parameter. By evaluating commercial device families, it is demonstrated that tan ( $\delta$ ) is constant for a given family, independent of device on -state resistance, $R_{\text{DS(on)}}$ . It is shown that a minimum $E_{\text{diss}}$ is achieved by having the lowest tan ( $\delta$ ) for a given stored energy ( $E_{\text{oss}}$ ) in $C_{\text{oss}}$ . With accompanying guidelines, this letter identifies tan ( $\delta$ ) as a powerful figure of merit to classify field-effect transistors (FETs) for soft-switching applications, regardless of $R_{\text{DS(on)}}$ variations in devices within a family. The proposed concept provides a comprehensive method to characterize and benchmark field-effect transistors for efficient operation in high and very-high-frequency (VHF) applications.

The crystal plasticity finite element (CPFE) method is used in conjunction with a critical local stored energy criterion to predict crack nucleation life for Coarse Grain (CG) nickel superalloy RR1000. Artificial representative microstructures are generated using Dream3D, and through simulation of multiple microstructural instantiations, a distribution of simulated fatigue response is generated. Fatigue of CG RR1000 is studied at 300°C and 700°C and at two R ratios of R = 0.1 and R = −1 giving a range of conditions to test the stored energy method. At higher temperature failure frequently occurs from inclusions, these are represented in the model by adding an inclusion with cohesive zones between inclusion and matrix. The results at 300°C are very good with the one parameter model (the critical stored energy) able to predict the mean, slope and distribution of fatigue data. At 700°C, the results are also good; however, fatigue life at high strain amplitude is overpredicted.

The authors discuss a mathematical model of rock mass with regard to accumulation and release of stored energy. Self-balancing stresses are described using internal variables introduced. The type of a closed system of equations is examined. An algorithm is proposed for the numerical modeling of softening jumps within a quasi-static problem. The problem on deformation of rock mass around a tunnel is solved using the finite element method. Under certain conditions, self-balancing stresses can be unbalanced, which causes disastrous dynamic phenomena associated with confining pressure.

We present GPS velocities in Kashmir valley and adjoining regions from continuous Global Positioning System (cGPS) network during 2008 to 2019. Results indicate total arc normal shortening rates of ~ 14 mm/year across this transect of Himalaya that is comparable to the rates of ~ 10 to 20 mm/year reported else-where in the 2500 km Himalaya Arc. For the first time in Himalayas, arc-parallel extension rate of ~ 7 mm/year was recorded in the Kashmir valley, pointing to oblique deformation. Inverse modeling of the contemporary deformation rates in Kashmir valley indicate oblique slip of ~ 16 mm/year along the decollement with locking depth of ~ 15 km and width of ~ 145 km. This result is consistent with the recorded micro-seismicity and low velocity layer at a depth of 12 to 16 km beneath the Kashmir valley obtained from collocated broadband seismic network. Geodetic strain rates are consistent with the dislocation model and micro-seismic activity, with high strain accumulation (~ 7e−08 maximum compression) to the north of Kashmir valley and south of Zanskar ranges. Assuming the stored energy was fully released during 1555 earthquake, high geodetic strain rate since then and observed micro-seismicity point to probable future large earthquakes of Mw ~ 7.7 in Kashmir seismic gap.

The major part of solid-state transformations modeling has concentrated on transformations taking place from a homogeneous matrix. Nonetheless, there are situations in which one finds an inhomogeneous matrix. An example is the recrystallization of metals subjected to an inhomogeneous deformation. If the recrystallization takes place in the regions where the stored energy of cold work is high, one has both a higher number of nuclei and faster growth velocity than in the region where the stored energy is low. In this work, we conduct computer simulations of transformations of a matrix possessing inhomogeneous nucleation and growth. We compare the computer simulations with an analytical solution that considers at the same time both the variation of the number of nuclei and the velocity. These results are compared with results obtained when only inhomogeneous nucleation is considered, whereas the velocity is kept constant throughout the matrix. For the number of nuclei and velocity gradients used here the main simulation results were: a) the inhomogeneous velocity does have a substantial effect on the transformation kinetics and microstructural evolution, b) the inhomogeneous distribution of nuclei has a more significant impact on the microstructure than an inhomogeneous distribution of velocity

This current research work was aimed to develop an innovative panel by combining the nail-laminated timber (NLT) and cross-laminated timber (CLT) into a single product named nail-cross-laminated ti...

In this research, amplified spontaneous emission (ASE) is studied along a rod amplifier length where intensities travel in two opposite longitudinal axis directions. The effect of ASE intensity on amplifier stored energy was discussed. An expression was obtained for stored energy in an amplifier in which a nonuniform gain distribution shaped due to ASE saturation effect. Time evolution of population inversion in a pulsed amplifier at the presence of ASE effect was also obtained, using the new relation of stored energy. Numerical calculations were used to verify accuracy and validity of the obtained relations. The numerical calculations included solving rate equation of population inversion of amplifier and simultaneous solving of two intensity equations for two beams traveling in opposite directions along the amplifier length.

Na0.3Sr0.4Bi0.3TiO3 with various concentrations in La modified ceramic specimens were fabricated using a traditional die-press process. All the obtained NBT-ST-xLa ceramics exhibited a typical perovskite structure with a single phase, and the grain sizes were found to be uniform and fine. The electric breakdown strength of the sample after La doping increased significantly. In particular, the ceramic electric breakdown strength of x = 0.02 component reached 190 kV/cm, the stored energy density reached 1.67 J/cm3, and the efficiency was stable and greater than 80%. In addition, the ceramic with x = 0.02 La also exhibited an excellent temperature, frequency stability, and good fatigue resistance. More specific and detailed analysis were conducted in this study.

Globus-M2—a new 1-Tesla spherical tokamak—was recently launched. The main features and research directions of this machine in scope of fusion–fission reactor development are described. Main results of the first experimental campaign with toroidal magnetic field up to 0.73 T and plasma current up to 0.33 MA are discussed. Significant improvement of the discharge parameters as compared to Globus-M was achieved. Plasma total stored energy higher than 7 kJ was obtained. Energy confinement time increase was consistent with predictions by spherical tokamak scalings. Toroidal Alfven eigenmode-induced losses decrease with increase of plasma current and toroidal magnetic field. For the first time, LHCD with the toroidal wave slowing-down was successfully used at a spherical tokamak.

A defibrillator pulse generator designed by E. E. Gorokhov-Miroshnikov for generation of biphasic defibrillation pulses with stepwise regulation of shape and optimum fixed duration (~10 ms) in the range of load impedance 25-175 Ω is presented. The generator, built using relatively low-cost electronic components, provides a high stored energy utilization coefficient. The main characteristics of the biphasic pulse generated by the prototype of generator are given. The design features of the generator are described.

The purpose of this study was to determine the stored energy of dual-phase (DP) steels after hot rolling, coiling, and cold reduction using electron backscattered diffraction analysis. Three methods for stored energy evaluation were examined and compared: the sub-grain boundary, image quality, and kernel average misorientation methods. The results demonstrated that the sub-grain method, in which stored energy was calculated as a function of sub-grain boundary misorientations and total sub-grain boundary length, can provide more accurate stored energy values, since cold work was responsible for forming numerous dislocation structures such as shear bands, cells, and cell walls. As expected, the steels with the combination of a low coiling temperature of 580 °C and 60 pct cold reduction had the highest stored energy values. This information is important in defining how pre-anneal processing conditions might control the response of DP steels to the various transformations occurring during continuous galvanizing line simulations.

Gradient polyconvex materials are nonsimple materials where we do not assume smoothness of the elastic strain but instead regularity of minors of the strain is required. This allows for a larger class of admissible deformations than in the case of second-grade materials. We describe a possible implementation of gradient polyconvex elastic energies in nonlinear finite strain elastostatics. Besides, a new geometric interpretation of gradient-polyconvexity is given and it is compared with standard second-grade materials. Finally, we demonstrate application of the proposed approach using two different models, namely, a Saint Venant-Kirchhoff material and a double-well stored energy density.

Актуальность исследования. Один из лидеров по производству алюминиевых порошков в России ООО "СУАЛ ПМ" перешел от выпуска грубодисперсных порошков к производству микронных порошков, имеющих более высокую реакционную способность. Микропорошки алюминия применяются во многих отраслях промышленности: порошковой металлургии, самораспространяющемся высокотемпературном синтезе новых материалов, водородной энергетике, пиротехнике и ракетных топливах. Повышение реакционной способности порошков алюминия в различных процессах приводит к понижению энергозатрат и экономии ресурсов. Цель: получение и объяснение экспериментальных данных по изменению параметров активности микропорошков алюминия после их облучения в зависимости от дозы γ-облучения. Объекты: микропорошки алюминия АСД-6, АСД-6М. Методы: дифференциальный термический анализ, рентгенофазовый анализ, методика облучения микропорошков алюминия [gamma]-излучением, методика расчета параметров активности порошков алюминия. Результаты. Получены количественные показатели реакционной способности микропорошков алюминия АСД-6 и АСД-6М до и после облучения [gamma]-излучением изотопа Со{60} с энергией 1,17 и 1,33 МэВ, т. е. энергией существенно ниже порога фотоядерных реакций. Дозы облучения образцов порошков составляли 1, 2, 4, 8 и 10 Мрад. После [gamma]-облучения температура начала окисления микропорошков снизилась максимально на 90 и 85 °С; максимальная скорость окисления возросла на 83 и 36 %; степень окисленности (при нагревании до 1250 °С) повысилась на 5,1 %, и минимально понизилась на 1,3 % для микропорошков АСД-6 и АСД-6М, соответственно. Удельный тепловой эффект окисления после [gamma]-облучения всеми дозами был больше, чем для необлученных порошков. Максимальные значения удельного теплового эффекта для АСД-6 на 199,5 кДж/моль, а для АСД-6М - на 134,8 кДж/моль больше тепловых эффектов, чем для необлученных порошков, что существенно превышает стандартную теплоту плавления алюминия (10,8 кДж/моль). Следовательно, такое состояние системы "алюминий - оксид алюминия" характеризуется запасенной энергией в 9 раз больше стандартной теплоты плавления алюминия, что с позиции классической термодинамики невозможно. В то же время известно, что запасание энергии в нанопорошках происходит за счет формирования двойного электрического слоя в частицах алюминия. The relevance of the research. One of the leaders in production of aluminum powders in Russia OOO "SUAL-PM" has passed from production of coarse powders to production of micron powders with higher reactivity. Aluminium micropowders are used in many branches of industry: powder metallurgy, self-propagating high-temperature synthesis of new materials, hydrogen energy, pyrotechnics and rocket fuels. Increase of aluminium powders reactivity in various processes leads to reduction in energy consumption and resource saving. The main aim of the research was to obtain and explain experimental data on changes in activity parameters of aluminium micropowders after radiation exposure, depending on the [gamma]-radiation dose. Objects: micron-scaled aluminium powders ASD-6, ASD-6М. Methods: differential thermal analysis, X-ray diffraction analysis, method of aluminium micropowders exposure with [gamma]-radiation, method of calculation of the activity parameters of aluminium powders. Results. Quantitative indicators of the reactivity of aluminium micropowders ASD-6 and ASD-6M before and after exposure with [gamma]-radiation were obtained. The radiation source was the Co{60} isotope with the energy of 1,17 and 1,33 MeV, i. e. the energy substantially below the threshold of photonuclear reactions. The doses to the powder samples exposure were 1, 2, 4, 8, and 10 Mrad. After [gamma]-radiation exposure the micropowders oxidation start temperature has maximally decreased on 90 and 85 °C; maximal oxidation rate increased by 83 and 36 %; the degree of oxidation (at heating up to 1250 °C) increased by 5,1 %, and minimally decreased by 1,3 % for the ASD-6 and the ASD-6M micropowders, accordingly. The specific thermal effect of oxidation after [gamma]-radiation exposure with all doses was greater than for non-exposed powders; the maximum values of the specific thermal effect was on 199,5 kJ/mol for ASD-6, and 134,8 kJ/mol for ASD6M higher than thermal effects for non-exposed powders, which significantly exceeds the standard heat of aluminium melting (10,8 kJ/mol). Consequently, such a state of the «aluminium - aluminium oxide» system is characterized by the stored energy, 9 times higher than the standard heat of aluminium melting, which is impossible according to thermodynamics. At the same time, it is known that energy is stored in nanopowders due to the formation of a double electric layer in aluminium particles.

New rolling technique, i.e. asymmetric rolling combined with cross rolling is adopted to produce Ta sputtering targets in this study. Electron backscatter diffraction (EBSD) analysis suggests that (111) and (100) deformed grains distribute alternately along normal direction in cross rolling (CR) and asymmetric cross rolling (ACR) samples. Misorientation angle distribution indicates that severe orientation-dependent grain fragmentation exists in the CR sample, which is also confirmed by kernel average misorientation and grain reference orientation deviation-hyper. Grain average misorientation (GAM) and distribution of geometrically necessary dislocations (GNDs) suggest that the effect of increasing shear strain introduced by asymmetric rolling on deformation microstructure is mainly reflected in the (100) grains, which is further verified by orientation-dependent microhardness values. The computation of Schmid factor indicates that slip within (100) grains in the ACR sample is easier, and the system with higher Schmid factor can alone accommodate the majority of plastic strain. Transmission electron microscopy (TEM) reveals that dense dislocation walls (DDWs) are formed within the (100) deformed grains in the ACR sample, while only sparse dislocation lines can be observed in the CR sample. X-ray line profile analysis (XLPA) displays that ACR can significantly increase the stored energy of the (100) deformed grains and thus weaken the orientation-dependent stored energy distribution. The enhanced recrystallization ability of the (100) grains in the ACR sample facilitates homogenization of the annealing microstructure. (Less)

Challenges of microgrids (MGs) energy management have gained more relevance with the presence of uncertainties in power generation and local loads. These problems significantly increase when related to network of smart MGs (NSMG). To address these challenges, this study presents a stochastic constrained control problem for the optimal management of a cooperative NSMG with interconnections allowing power exchanges. In this model, each MG can exchange power locally among each other as well as with the main electric grid. The proposed control approach is based on a linear-quadratic Gaussian problem definition for the optimal control of power flows under quadratic constraints limiting the variability of the power exchange as well as of the stored energy in each MG. The developed framework is applied to a cooperative network of four smart MGs to test and validate its effectiveness and performance. The network is connected to the main electric grid allowing power exchanges. The results demonstrate that the role of energy storage systems is undoubtedly becoming more and more relevant in the context of reacting to the stochastic behaviour of the balance between produced and consumed powers in MGs.

In this study, a ceramic with a 0.7Bi0.5K0.5TiO3-0.3SrTiO3 composition was designed to enhance its energy storage performance via rolling technology. Temperature had a great influence on microstructural refinement and energy storage density. A high recoverable energy storage density of 2.31 J/cm3 and efficiency of 77.7% were obtained under an optimal sintering temperature of 1175 °C. Specifically, a pulsed circuit indicated that stored energy was quickly released at a sub-microsecond scale of 0.26 μs. This study showed that Bi0.5K0.5TiO3-based ceramics, as new lead-free bismuth-based perovskite-type solid-solutions are promising candidates in pulsed-power applications.

The results of the experimental studies on the effect of hydrostatic pressure, charge voltage, stored discharge energy, and wire diameter on the amplitude of a pressure wave upon an electric wire explosion in water are presented. It is shown that the amplitude of the pressure wave generated in a liquid increases with an increase in the stored energy and charge voltage, and at an optimum diameter of the wire, the maximum amplitude of the pressure wave is ensured. When hydrostatic pressure is elevated, an amplitude decrease of the generated pressure wave was observed for a thin initiating wire (0.14 mm diameter), and no effect was observed for a thick wire (0.5 mm diameter or larger). In addition, the need to ensure a good hard contact between the electrodes of the electrode system and the metal wire during the electrical explosion of the wire in a liquid was shown, in default of which there is a loss of the efficiency of the mechanical action occurs owing to a decrease in the amplitude of the pressure wave.

Control over the inelastic deformation of polycrystals aimed at achieving desired performance characteristics of finished products is impossible without analyzing the structural evolution of the material at different scale levels. A major task in this respect is to develop physically sound mathematical models for describing the internal structure evolution as it determines the material properties. An effective tool for addressing this task is a multilevel approach to describing the thermomechanical processing of crystalline materials, in which carriers and physical mechanisms of processes are considered explicitly. Thermomechanical processing allows a good control over the defect and grain/subgrain structure of the material to achieve desired macrocharacteristics. This paper explores the subgrain/grain structure evolution during static recrystallization that occurs through strain-induced boundary migration. Modeling is carried out in two stages. The first stage models the plastic deformation of a crystalline material at room temperature. The second stage considers holding at an elevated temperature resulting in recrystallization. Both stages are modeled within a unified multilevel approach. The problem of modeling static recrystallization is formulated, and an algorithm for its numerical implementation is described. The modeling results are obtained for a bicrystal in which each grain is represented by a group of lower-scale elements (subgrains). Recrystallization causes profound changes in the subgrain structure geometry, the average size of subgrains, and their shape change. Recrystallized subgrains are more elongated compared to the original ones. During recrystallization more defective grains are replaced with less defective grains, and as a result the energy stored in the material decreases. The developed model qualitatively describes the release of stored energy. Numerical experiments revealed a critical plastic strain value below which recrystallization does not occur.

Controlling the texture of tantalum sheets is of critical importance to fabricate good sputtering targets. In the present study two tantalum sheets were produced by clock rolling to 70% thickness reduction in 1 or 2 cycles. The results show that the stored energy and grain subdivision within the {111} grains {//normal direction (ND)} after 1 cycle are significantly higher than those after 2 cycles, leading to fast recrystallization kinetics and strong {111} recrystallized texture upon annealing. Simulations with Taylor model indicate that shear strain occurred on more slip systems in the 2-cycle sample, which could explain the formation of cell blocks in {111} grains. Keywords: Clock rolling cycle, Texture, Stored energy, Taylor model, Recrystallization kinetics

Let $\Omega\in\mathbb{R}^n$, $n=2,3$, be the region occupied by a hyperelastic body in its reference configuration. Let $E(\cdot)$ be the stored energy functional, and let $x_0$ be a flaw point in $\Omega$ (i.e., a point of possible discontinuity for admissible deformations of the body). For $V>0$ fixed, let $u_V$ be a minimizer of $E(\cdot)$ among the set of discontinuous deformations $u$ constrained to form a hole of prescribed volume $V$ at $x_0$ and satisfying the homogeneous boundary data $u(x)=Ax$ for $x\in\partial \Omega$. In this paper we describe a regularization scheme for the computation of both $u_V$ and $E(u_V)$ and study its convergence properties. In particular, we show that as the regularization parameter goes to zero, (a subsequence) of the regularized constrained minimizers converge weakly in $W^{1,p}(\Omega\setminus{{\mathcal{B}}_{\delta}(x_0)})$ to a minimizer $u_{V}$ for any $\delta>0$. We obtain various sensitivity results for the dependence of the energies and Lagrange multipliers of the regularized constrained minimizers on the boundary data $A$ and on the volume parameter $V$. We show that both the regularized constrained minimizers and $u_V$ satisfy suitable weak versions of the corresponding Euler--Lagrange equations. In addition we describe the main features of a numerical scheme for approximating $u_V$ and $E(u_V)$ and give numerical examples for the case of a stored energy function of an elastic fluid and in the case of the incompressible limit.

In dc-dc LLC resonant converters, the Litz-wired high-frequency gapped-transformer (LHFGT) plays an important role, as it provides the necessary isolation, the required voltage-conversion, and the desired magnetizing inductance (Lm) for efficient converter operation. Since the LHFGT makes a significant contribution to the overall converter weight and size, so the converter designers must rely on complicated and advanced optimization techniques, with a large number of iterations, for its design. This dependence is due to the shortcomings in the conventional analytical modeling techniques for optimal size-selection of the core and winding in the LHFGT. Hence, this manuscript proposes an optimal area-product (Aprod) model (OAPM)-based non-iterative LHFGT design methodology that maximizes the efficiency and power density, minimizes the losses and volume, integrates the Lm, and maintains the temperature-rise within limits. The method takes into consideration the LLC circuit parameters, the Litz-wire strand-radius (rs), the core material and geometrical parameters, the excitation-waveform shape, the stored energy due to coreairgap, and the peak flux-density (Bpk) inside the core. The accuracy improvement is attained through the proposal of accurate Aprod-based core-geometry features estimation (ACGFE) models and by keeping in view the interdependency between the transformer-design parameters (TDPs). The optimized design is obtained in a single iteration, based on the proposed OAPM, the proposed optimal rs selection model, and the proposed optimal TDPs' models. The proposed design routine is validated through the analytical and experimental results of a prototype LHFGT for a 200W-110kHz-400VDC/12VDC LLC resonant converter.

The article provides an analytical overview of ways to contact the capacitor welding. Using rigid modes effects on the bonding region in most cases causes the formation of a contact during the crystallization in the liquid phase, which is highly undesirable when connecting non-ferrous metals and their alloys. Forming permanent joints in the liquid phase facilitate processes atomic hetero diffusion or reactive diffusion, which intensifies the nucleation of intermetallic phases. The use of high-voltage capacitor welding with an induction-dynamic drive allows minimizing the processes of nucleation of intermetallic phases due to the use of super-hard modes of action on the connection zone when converting the stored energy in capacitor banks to synchronous thermodynamic effects. The proposed methods of high-voltage capacitor welding for joining dissimilar alloys and powder compositions are considered, the physical nature of the process and the kinetics of the impact are described. The results of the energy-spectral analysis of compounds in a heterogeneous combination of AlMg2.5, Cu01, Br63, and HfC alloys showed the absence of atomic hetero diffusion or reactive diffusion and the formation of compounds during high-voltage capacitor welding in super-hard modes in the solid phase.

Predicting microstructure and (micro-)texture evolution during thermo-mechanical processing requires the combined simulation of plastic deformation and recrystallization. Here, a simulation approach based on the coupling of a full-field dislocation density based crystal plasticity model and a cellular automaton model is presented. A regridding/remeshing procedure is used to transfer data between the deformed mesh of the large-strain crystal plasticity model and the regular grid of the cellular automaton. Moreover, a physics based nucleation criterion has been developed based on dislocation density difference and changes in orientation due to deformation. The developed framework is used to study meta-dynamic recrystallization during double-hit compression tests and multi-stand rolling in high-resolution representative volume elements. These simulations reveal a good agreement with experimental results in terms of texture evolution, mechanical behaviour and growth kinetics, while enabling insights regarding the effect of nucleation on kinetics and crystallographic texture evolution.

The objective of this thesis is to develop a methodology to determine fast the fatigue properties of materials, from the evolution of the stored energy with respect to the stress amplitude and number of cycles applied. This evolution is estimated during fatigue tests conducted at high frequency and for very high number of cycles. The understanding of the link between the evolution of stored energy and the activation of fatigue damage mechanisms would help to improve the credibility of the methodology.The stored energy is estimated by establishing an energy balance from the difference between the mechanical work that is brought to the specimen and the energy that is dissipated as heat. The mechanical work is estimated from in situ time resolved X-ray diffraction measurements and the dissipated energy from thermographic measurements. To study the very high fatigue lives, fatigue tests are conducted by using an ultrasonic fatigue machine working at 20 kHz.The results show, on the first hand, that the stored energy decreases with the number of cycles, down to reach a stabilized regime. On the other hand, the stored energy increases with the stress amplitude. In the case of copper, the evolution of the stored energy with respect to the stress amplitude is also correlated to the appearance of slip bands, which are precursors of the appearance of fatigue damage.Keywords : Very high cycle fatigue, Ultrasonic fatigue machine, Energetic balance, Mechanical work, In situ time-resolved X-ray diffraction, Dissipated energy, Infrared thermography, Copper single crystal, C70 pearlitic steel., L'objectif de cette thèse est de développer une méthode de détermination rapide des propriétés des matériaux en fatigue, à partir de l’évolution de l’énergie stockée en fonction de l’amplitude de contrainte et du nombre de cycles appliqués. Cette évolution est estimée pendant des essais de fatigue menés à haute fréquence et pour des très grands nombres de cycles. La compréhension du lien entre l’évolution de l’énergie stockée et l’activation des mécanismes d’endommagement en fatigue permettrait de renforcer la crédibilité de la méthode.L’énergie stockée est estimée en réalisant un bilan d'énergie, qui correspond à la différence entre le travail mécanique apporté au matériau et l'énergie qu’il dissipe sous forme de chaleur. Le travail mécanique est estimé par diffraction des rayons X in situ résolue en temps et l'énergie dissipée par thermographie. Pour étudier le domaine des très grands nombres de cycles, un machine de fatigue ultrasonique fonctionnant à 20 kHz est utilisée.Les résultats des mesures montrent d'une part que l'énergie stockée décroit avec le nombre de cycles, jusqu’à atteindre un régime stabilisé et d'autre part qu'elle augmente avec l’amplitude de contrainte. Dans le cas du cuivre, l’évolution de l’énergie stockée en fonction de l’amplitude de contrainte semble également être corrélée à l’apparition de bandes de glissements, précurseurs de la formation d'endommagement en fatigue.Fatigue à très grand nombre de cycles, Machine de fatigue ultrasonique, Bilan d'énergie, travail mécanique, Diffraction des rayons X in situ résolue en temps, Energie dissipée, Thermographie infrarouge, Cuivre monocristallin, Acier C70 perlitique.