Pulse Loading Research Articles

AN INTELLIGENT ENERGY MANAGEMENT SYSTEM FOR SHIP HYBRID POWER SYSTEM BASED ON RENEWABLE ENERGY RESOURCES

A hybrid ship power system with fuel cell and storage system batteries/supercapacitors can be developed by adding renewable energy sources. Adding PV to the hybrid system enhances the system's reliability and dependability. However, a high-level control strategy is needed to manage the generated power between the fuel cell and the photovoltaic array and determine the suitable time to charge or discharge the stored energy according to the load demand. The perfect solution is using an intelligent neural network technique to control the ship's hybrid power system because of the system's nonlinearity and the existence of pulsing and high-density load demand. This paper introduces an intelligent artificial neural network (ANN) technique that depends on previous experience. ANN is flexible and easy to modify, adding/removing power system components, and be scaled to any ship power system rating. Simulation results using MATLAB software prove that the robust, intelligent power management system can control and identify which energy source will be exploited according to the daylight. Moreover, calculate the amount of generating power depending on the shipload demand. In addition to that, it ensures the system dependability considering the other source as standby while the storage system is the power source in the transient period in case of switching between the two systems and maintaining the storage system in the high state of charge possible. Furthermore, this will reduce fuel consumption during the ship's cursing mission. يعتبر نظام القدره الکهربيه المکون من خلايا هيدروجينيه ونظام تخزين للطاقه مناکثر الانظمه استخداما فى جميع المجالات. يهدفهذا البحث الى تحسين أداء هذا النظام عن طريقه إضافه مجموعه خلايا شمسيه لزيادة اعتماديه النظام وتوفير الوقودالمستخدم وايضا الى تقليل التلوث البيئى . وجود اکثر من مصدر للطاقه الغير متجانس يتطلب وجود نظام اداره قوى لتحديد المصدر المناسب لتغذيه الاحمال وافضل الاوقات لشحن او تفريغ البطاريات. يقدم البحث نظام اداره الطاقه الذکى باستخدام تقنيه الشبکات العصبونيه والذى يتميز بالمرونه والقدره على التکيف اعتمادا على الخبرات السابقه للمستخدم وامکانيه اضافه او حذف اى مصدر او تعديل المدخلات . تم استخدام المخاکاة باستخدام الماتلاب لضمان واختبار النظام تبعا للخبرات السابقه.

Research of ANSYS Autodyn capabilities in evaluating the landmine blast resistance of specialized armored vehicles

The object of research is the processes of pulse explosive loading in an explicit formulation for simulation of complex nonlinear dynamics of solids, gases, and their interactions. One of the most problematic areas of modern studies of nonlinear dynamic loads of materials using a numerical analysis is that such studies usually do not take into account the characteristic transition of the stationary deformation zone of the loaded material to the unsteady one and the front pressure and shockwave velocity variation by time. The work is aimed at developing a mathematical model of a pulsed load of materials by a shockwave, developing a mathematical apparatus for calculating the parameters of a shockwave, creating analytical dependences of the interaction of a shockwave with a loaded surface. A study of dynamic explosive loading using software based on an explicit method for solving the equations of continuum mechanics is proposed. In this work, the stress-state equation at a point of the material under pulsed load conditions was further developed, methods for determining the principal stresses and the invariant of the stress tensor, taking into account the pulsed nature of the load, were established. The character of the behavior of the shockwave formed as a result of the detonation of the explosive has been established. Analytical dependences of the interaction of a shockwave with a loaded surface are compiled. A mathematical apparatus has been developed for calculating such parameters of the shockwave as the detonation front pressure and its change in time and the velocity of the shockwave at the moment when it reaches the surface. Mathematical dependences have been developed and proposed, which, in contrast to the existing ones, make it possible to determine the current values of stresses and strains passing through the points of the actual stress curve, as well as the intensity of stresses and strains under pulse loading of metals. On the basis of theoretical and experimental studies of the parameters of body material deformation under the action of explosive loading, the mechanisms of destruction of the KrAZ «Shrek» and KrAZ «Fiona» (Ukraine) specialized armored vehicles body were clarified to establish the compliance of the declared landmine resistance of vehicles with the STANAG 4569 standardization agreement.

Power quality metrics for DC grids with pulsed power loads

<span lang="EN-GB">DC grids can effectively feed pulsed power loads (PPLs), integrating local energy storage to minimize the impact on other connected loads and implementing buffered sub-grids to isolate susceptible loads even more. The identification of regulatory limits for PPL integration and DC grid response and the assessment of PPL impact necessitate suitable Power Quality (PQ) metrics. Existing indexes and limits (e.g. ripple and distortion, voltage fluctuation) are compared to other metrics, derived from control methods and knowledge of the peculiar characteristics of PPL and interaction with DC grids in some examples. The objective is a unified approach for PQ metrics suitable for a wide range of DC grids and in particular to the behavior of PPLs.</span>

OSCILLATIONS OF A PULSE LOADED OSCILLATOR WITH A SQUARE RESISTANCE IN THE COMPOSITION OF THE DISSIPATIVE FORCE

The unsteady oscillations of a dissipative oscillator caused by an instantaneous impulse of the force are described. The case is considered when the dissipative force consists of quadratic viscous resistance and dry friction, and the theoretical results are generalized to the case of the sum of three forces. The third is the force of positional friction. Formulas for calculating the ranges of oscillations have been constructed In this case, the Lambert function of negative and positive arguments is used. It is a tabulated special function. Its value can also be calculated using its known approximations in elementary functions. It is shown that, due to the action of the dissipative force, the process of post-pulse oscillations consists of a finite number of cycles and is limited in time. This is due to the presence of dry friction among the resistance components. Examples of calculations that illustrate the possibilities of the stated theory are given. In order to check the reliability of the derived calculation formulas, numerical computer integration of the differential equation of motion was also carried out. The convergence of the numerical results obtained by two different methods is shown. Thus, it has been confirmed that with the help of analytical solutions it is possible to find the extreme displacements of the oscillator without numerically solving its nonlinear differential equation of motion. Using Lambert function and the first integral of the equation of motion made it possible to derive precise calculation formulas for determining the range of oscillations caused by the pulsed load of the oscillator. The derived formulas are suitable for calculating the value of the instantaneous impulse applied to the oscillator, which refers to the inverse problems of mechanics. Thus, by measuring the maximum displacement of the oscillator, it is possible to identify the initial velocity or instantaneous impulse applied to the oscillator. The performed numerical computer integration of the output differential equation confirmed the adequacy of the obtained analytical solutions, which concern not only direct, but also inverse problems of dynamics.

A Few Points of the Engineering Logic Discussed in ITER EDA on Evaluation of Halo- and AVDE-Induced Loads in Tokamaks

All tokamaks are designed to withstand a certain number of energetic electromagnetic (EM) transients caused by uncontrolled terminations of plasma pulses, including symmetric and asymmetric plasma vertical displacement events: VDEs and AVDEs. These events generate significant pulsed EM loads in all conductive components and coils. Axially symmetric transient EM loads induced by VDEs without Halo current have been calculated well since the 1980s; however, Halo-related EM load components and lateral loads associated with AVDEs still cause discussions. The author worked on fast plasma and EM transients in tokamaks quite a while ago then deviated to other areas but has been keeping track of the topic since. He is aware of discussions of the modelling of Halo currents and of significant scatter present in current estimates for AVDE-induced lateral loads and contends that some points of engineering logic formulated earlier on this topic may help reduce these uncertainties. This article summarises a few points of the engineering understanding developed in informal discussions within the ITER EDA team with the purpose to preserve these points for all tokamak developments.

Dynamic Buckling of Fiber Metal Laminate Column

The aerospace industry puts forward many requirements for designers in the selection of appropriate materials. They should primarily be characterized by high strength and at the same time low weight. Also, they should not be sensitive to changing weather conditions, be resistant to corrosion and fire, and have high impact strength. The solution appeared in the second half of the twentieth century when the concept of combining a fiber composite with commonly used aluminium was created. The first hybrid structures - FML (Fiber Metal Laminates) consisting of alternately arranged, adhesive layers of aluminium and composite, formed at the University of Delft. Laminates based on glass fiber reinforced composites (GLARE) have found application in aviation constructions, among others Airbus A380 aircraft. As in aerospace industry strength to weight ratio is a crucial factor during the design process, thin-walled structures are commonly used. Nowadays GLARE are used e.g. as elements of stiffening the fuselage. Stringers are usually implemented to the fuselage as the channel, zed and omega section thin-walled profiles. In the most of thin–walled structures, the ultimate loading is limited not only by their strength but also by the stability. Buckling could occur both under static and pulse load. Although aircrafts are in the most cases subjected to high dynamic loads, today the design and certification procedures are mainly based on conservative static loading which leads to additional weight and, potentially, to a structurally unsafe aircraft. Thus, it seems to be necessary to pay more attention to the problem of dynamic buckling phenomenon.

Mechanical behaviour of bonded joints including viscoelasticity for the adhesive under triangular pulse loading and harmonic loading

The constitutive law of the interface is a prime issue when evaluating the strength of adhesively bonded joints. The polymer-based adhesives exhibit loading rate sensitivity and damping properties owing to their viscous nature, especially at high temperatures or under water. This paper aims to establish a shear-lag model to elucidate the mechanical behaviour of adhesively bonded joints under triangular pulse loading and harmonic loading. The extended shear-lag model is focused on improving the previous shear-lag models by including viscoelastic behaviour using the Kelvin model for the adhesive. Analytical expressions of the slip and interfacial shear stress distribution have been respectively presented for pull-push joint and pull-pull joint under triangular pulse loading. Compared with finite element simulation, the predictive model shows an excellent agreement with the FEA results. The damping properties including the storage modulus, loss modulus and loss factor for these two bonded joints subjected to harmonic loading are theoretically derived. Finally, results obtained from the predictive model are presented to illustrate how the bond length, loading rate and loading frequency affect the behaviour of such bonded joints.

Load Frequency Control of a Multi-Microgrid System Incorporating Electric Vehicles

Owing to high cost of conventional energy storage systems, battery of electric vehicles (EVs) is now being considered as their partial replacement to facilitate the demand side response. EVs can act as controllable bidirectional sources to restrain the frequency deviations in power system via vehicle-to-grid control. Consequently, this article proposes a load frequency control (LFC) scheme of a multi-microgrid (MMG) system incorporating EVs. A tilt integral derivative (TID) controller is enforced as the LFC controller in the proposed MMG system. To optimize the gains of the TID controller, a recently developed atom search optimization algorithm is implemented as a novel initiative. Diverse loading patterns that include random, sinusoidal, and pulse load disturbance patterns are considered in the MMG to establish the competence of the proposed control scheme. Simulation results reveal that the proposed LFC scheme enhances the dynamic responses of the MMG system in terms of attenuated oscillations, improved transient specifications and minimized objective function in the frequency and tie-line power deviations, and thus, satisfies the LFC requirements. The results are compared with some standard algorithms. Lastly, sensitivity of the proposed controller is validated subject to ±30% variation in various MMG parameters.

Determining the Rayleigh damping parameters of flexible pavements for finite element modeling

The dynamic analysis has been successfully used to predict the pavement response based on the finite element modeling, during which the stiffness and mass matrices have been established well, whereas the method to determine the damping matrix based on Rayleigh damping is still under development. This article presents a novel method to determine the two parameters of the Rayleigh damping for dynamic modeling in pavement engineering. Based on the idealized shear beam model, a more reasonable method to calculate natural frequencies of different layers is proposed, by which the global damping matrix of the road pavement can be assembled. The least squares method is simplified and used to calculate the frequency-independent damping. The best-fit Rayleigh damping is obtained by only determining the natural frequencies of the two modal. Finite element model and in-situ field test subjected by the same falling weight deflectometer pulse loads are performed to validate the accuracy of this method. Good agreements are noted between simulation and field in-situ results demonstrating that this method can provide a more accurate approach for future finite element modeling and back-calculation.

The Influence of Background Ultrasonic Field on the Strength of Adhesive Zones under Dynamic Impact Loads.

The influence of background ultrasonic field on the ultimate dynamic strength of adhesive joints is studied using fracture mechanics analysis. Winkler foundation-type models are applied to describe the cohesion zone, and the incubation time fracture criterion is used. The challenging task is to study whether relatively weak ultrasound is able to decrease the threshold values of the external impact load depending on a joint model, such as an “elastic membrane” or “beam” approximation, and various boundary conditions at the ends. The specific task was to investigate the case of short pulse loading through application of time-dependent fracture criterion instead of the conventional principle of critical stress. Three different load cases, namely, step constant force, dynamic pulse, and their combination with ultrasonic vibrations, were also studied. The analytical solution to the problem demonstrates that background vibrations at certain frequencies can significantly decrease threshold values of fracture impact load. Specific calculations indicate that even a weak background sonic field is enough to cause a significant reduction in the threshold amplitude of a dynamic short pulse load. Additionally, non-monotonic dependency of threshold amplitude on pulse duration for weak background field was observed, which demonstrates the existence of optimal regimes of impact energy input. Moreover, this phenomenon does not depend on the way in which the beam edges mount, whether they are clamped or hinged, and it could be applied for micro-electro-mechanical switch design processes as an additional tool to control operational regimes.

Heat conduction in microstructured solids under localised pulse loading

Heat conduction in microstructured solids under localised pulse loading

Investigation of impulse load attenuation in closed-cell foam in the framework of couple stress elasticity

The article analyzes the processes of attenuation of impulse loads in foam materials with closed-cell. In the framework of the couple stress elasticity, the analysis of the distribution of dynamic radial stresses in foam media with tunnel cavities of constant cross-section under the action of an impulse load of different duration applied to the cavity boundary in the radial direction is performed. An analytical-numerical approach is used for calculating of the dynamic stresses, which is based on the application of the Fourier transform over time and the modified boundary integral equation method. Numerical calculations of the dynamic stresses were performed using the method of mechanical quadrature and collocation method. The modified algorithm for discrete inverse Fourier transform was used for the calculation of the originals of the dynamic radial stresses. Based on the analysis of numerical calculations, the influence of the impulse duration on the attenuation rate of the pulse load in foam media is established.

Fatigue analysis of the Spallation Neutron Source 2 MW target design

Upgrades to the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory are under way with two major projects. The first project is the Proton Power Upgrade (PPU), which will double the power capacity of the SNS accelerator system to enable the operation of a future second neutron source target station—the second project. PPU also will increase power to the SNS first target station – which currently operates at 1.4 MW with 1.0 GeV protons – to 2 MW with 1.3 GeV protons. Final design of the PPU 2 MW target module is finished, including all necessary design and analysis calculations. The fatigue evaluation described herein is an assessment of the fitness of the PPU 2 MW target mercury vessel to resist failure from cyclic loading from the pulsed 60 Hz proton beam and thermal changes from disrupted operation. In addition to the reliability predictions, the method, detail, and depth of this fatigue evaluation are superior to those of past target design assessments. The thermal fatigue life is predicted to exceed 3125 thermal cycles per 1250 h of operation for all load cases. The design also meets the (relative) fatigue design goal for combined thermal and pulse loading of greater than 0.5 times the minimum fatigue life calculated for a jet-flow target design operating at 1.4 MW—the most robust design to date in terms of resistance to fatigue failure. From the onset of the PPU, it has been known that pulse loading requires effective application of helium gas injection into the target mercury to reduce beam pressure loading. For the PPU 2 MW target, none of the pulse load cases requires a maximum strain reduction from gas injection of more than 50% (for base material) to meet the fatigue design goal. This level of reduction is achievable from gas injection, according to historical strain measurements from 1.4 MW target operation. Overall, the PPU 2 MW target design is predicted to have superior resistance to fatigue failure compared with past target designs.

Investigation of dynamic buckling of fiber metal laminate thin-walled columns under axial compression

This paper presents an investigation of the dynamic buckling phenomenon in thin-walled Fiber Metal Laminate short columns subjected to axial compressive loading. The numerical analysis is performed with the FEM ANSYS software for three profiles differentiate in the laminate stacking sequence. Two groups of criteria were implemented to assess the structure resistance to dynamic pulse loading: the dynamic buckling criteria and strength failure criteria. Parametric analysis was performed to determine the effect of initial geometric imperfection, laminate stacking sequence, and the pulse load's shape on the dynamic stability. The value of the amplitude of initial geometric imperfection and the shape of pulse load influence the value of critical Dynamic Load Factor strongly. Aluminium yielding was observed as the primary failure source developed in the FML structure subjected to the pulse loading.

The impact of parasitic inductance on the dV/dt ruggedness of 4H-SiC Schottky diodes

In this study, the dV/dt ruggedness of commercial 4H-SiC Schottky diodes C3D02060A (Wolfspeed) with DC blocking voltage of 600 V and continuous forward current of 2 A was investigated. The quasi-static reverse current-voltage characteristics of the diodes were measured in the recoverable avalanche breakdown regime up to currents of about 7 A. The mature avalanche breakdown voltage was measured to be 1180 V which is almost twice the rated blocking voltage of 600 V. The dV/dt tests were performed with the use of a pulse current generator capable of generating short (3 ns), high-current (up to 80 A), high-voltage (up to 4 kV at 50-ohm load) pulses. The dV/dt limit was found to be 1260 V/ns, in combination with the value of diode terminal voltage of 750 V. Based on TCAD simulations, the impact of unavoidable lead inductance of TO-220A package on the dV/dt limit is pointed out. It is shown that a high voltage is induced on semiconductor structure being higher than the voltage on diode external terminals. As a result, diode failure occurs, although the diode terminal voltage is significantly lower than the mature avalanche breakdown voltage of semiconductor structure.

Combined feedback–feedforward control of Ćuk CCM converter for achieving fast transient response

The Ćuk converters operating in continuous conduction mode (CCM) can be preferred in applications such as microprocessor power delivery and pulsed load because these circuits have advantages of being able to step up/down, a small number of power components, and low input/output current ripples. However, they show poor transient performance due to right-half-plane-zeros (RHPZs) in the closed-loop transfer function of the Ćuk CCM converter. To enhance the transient response, a combined feedback–feedforward control for the Ćuk CCM converter is proposed. The proposed control scheme comprises a feedback control signal based on a Lyapunov function and a duty-ratio feedforward control signal. A Lyapunov-function-based controller (LBC) achieves fast dynamic response even under large-signal variations from the operating point. The duty ratio feedforward controller (DFFC) is developed to predict the effect of the disturbances and compensate it, while alleviating the burden of LBC. The proposed control logic makes the closed-loop system of the Ćuk CCM converter globally exponentially stable and thus provides a fast transient response even under large-signal variations. To construct the proposed controller, the authors make use of the large-signal averaged model of the Ćuk CCM converter, and consider the parasitic elements. To verify the proposed control scheme, numerical simulations and experimental tests are conducted.

2-D Analysis of Generalized Thermoelastic Porous Medium under the Effect of Laser Pulse and Microtemperature

The paper presents the analytical solutions for a generalized thermoelastic medium consisting of microtemperatures and voids subjected to a laser pulse loading the medium thermally. The 0.02 ps pulse duration of the non-Gaussian laser beam is apt for heating a homogenous isotropic elastic half-space. A method called the normal mode analysis is employed to evaluate numerically the effects of various variables such as the micro-temperature vector, variation in the fraction field of the volume, first heat flux moment tensor, temperature distribution on the stresses and displacement components of the medium. In addition, the graphical illustration of the physical response of the medium has been presented in the presence and absence of void parameters, as well as in the presence of laser pulse with two different acting periods.

Estimation of Lorentz force detuning and its compensation on 650 MHz βg = 0.92 single cell SCRF cavity

Superconducting technologies are widely used in modern radiofrequency (RF) cavities for particle accelerators in various fields of applications. The Superconducting radiofrequency (SCRF) cavities are highly sensitive to small perturbation on cavity dimensions. The operation of the superconducting cavity becomes challenging due to narrow resonance bandwidth on account of a very high-quality factor. The main perturbing source is Lorentz Force acting on the cavity wall, which detunes the cavity from resonance. Finite element (FE) analysis has an important role in Lorentz force detuning (LFD) estimation, which requires coupled-field FE analysis between the structural and RF domains of the cavity. The LFD effect can be mitigated up to a certain extent by using a proper fast tuning methodology. This paper represents the methodology for structural-high frequency electromagnetic coupled field simulation for LFD calculation of 650MHz, βg = 0.92 single-cell SCRF cavity. First, the static LFD is calculated for various voltage gradients of SCRF cavity structure and then dynamic behavior of cavity due to LFD pressure pulse is studied at different pulse widths (PW) and pulse repetition rates (PRR). A comparison of transient FE analysis of the single-cell cavity with one end fixed and another end free and cantilever beam for similar loading is done for benchmarking. To counter the detuning effect, the SCRF cavity employs a piezo tuning device. The dynamic behavior of piezo pulse response on the cavity is also studied. An experimental test of the piezo tuner system has been performed at room temperature to validate the FE coupled simulation. Further, dynamic analysis has been carried for the combined effect of LFD pressure and piezo load pulse to compensate for the LFD effect. Optimizing the piezo load for compensating the frequency shift is also discussed and based on optimum load, LFD has been mitigated for different acceleration gradients.

Methodological aspects of testing brittle materials using the split Hopkinson bar technique

AbstractThis paper presents the features of a method for determining the dynamic properties of brittle materials using the split Hopkinson bar technique on mortar as an example. Experiments were conducted both with and without a loading pulse shaper, a deformable copper disc (pad) placed on the impacted end of the input bar. Experimental data from the experiments without the pad were processed with and without dispersion correction based on a direct solution of the Pochhammer–Chree frequency equation of pulses in the measuring bars. There were compared both the deformation graphs and mechanical characteristics of the tested material for three variants of the split Hopkinson pressure bar experiments: with and without a loading pulse shaper, and with the dispersion correction procedure for pulses in the measuring bars. The phenomena observed during these experimental schemes and the processing of obtained data are described and discussed; further, the effect of the nature of the load increase is revealed.

Performance of liquid-lithium-filled 3D-printed tungsten divertor targets under deuterium loading with ELM-like pulses in Magnum-PSI

A fusion reactor divertor must withstand heat flux densities <10 MW m−2. Additionally, it may have to withstand millisecond pulses on the order of 0.5 to 30 MJ m−2 due to (mitigated) edge-localized modes (ELM) occurring with 30 to 60 Hz. We investigate if these requirements can be met by capillary porous system (CPS) liquid lithium divertors (LLD). 3D-printed tungsten CPS targets were exposed in the linear plasma device Magnum-PSI, to deuterium plasma discharges lasting 15 s, generating 1.5 to 16 MW m−2, and T e ∼ 1.5 eV. Additionally, ELM-like pulses were superimposed on top of the steady state for 3 s with a frequency of 2 and 100 Hz, power flux densities of 0.3 to 1 GW m−2, and T e up to ∼14 eV. All Li targets survived without damage. The surface temperature (T s) was locked at ∼850 °C, which was attributed to power dissipation via vapor shielding. Meanwhile, unfilled reference targets melted during the severest pulsed loading. A blue grayish layer of presumably LiD formed when T s < 500 °C, but disappeared when the locking temperature was reached. This implies that LiD formation can be avoided, but that it may require a surface temperature at which Li evaporation excessively contaminates the core plasma in a tokamak. During pulsed loading the plasma facing surface remained wetted in all conditions. Bolometry indicated that, only during pulses, there was a large increase in radiative power dissipation compared to targets without Li. A high speed camera with a Li-I filter showed that strong Li evaporation continued up to 5 ms after a pulse. Overall, the liquid-lithium-filled 3D-printed tungsten targets were found to be highly robust, and 3D-printing can be considered as a promising manufacturing technique for LLDs. Further research is needed particularly on the formation of LiD and the associated tritium retention, as well as the impact of enhanced evaporation during and after ELMs on the core plasma.