Light Wing Research Articles

Post-Neutron Mass Yield Distribution in the Thermal Neutron Induced Fission of 232U

In the thermal neutron–induced fission of 232U, cumulative and independent yields of various fission products within the mass ranges of 72 to 107 and 123 to 158 have been measured using an off-line gamma-ray spectrometric technique. The fission yields were determined relative to the yield of a monitor product 92Sr. Charge distribution correction was applied on the cumulative yields to obtain the post-neutron mass yield distribution. Mass yield distribution parameters such as full-width at tenth-maximum of light and heavy mass wings, average light mass number <AL> and heavy mass number <AH>, and average number of emitted neutrons <ν> were obtained. Data from the present and earlier work on the 232U(nth,f) reaction were compared with similar data of the 235U(nth,f) reaction. It was found that the mass chain yield distribution in the 232U(nth,f) reaction is asymmetric with two major humps as in the case of the 235U(nth,f) reaction. Besides this, in the 232U(nth,f) reaction, the mass yield distribution shows a small third hump for the symmetric fission products. It was also found that the standard II asymmetric mode of fission is favorable in the 232U(nth,f) reaction whereas the standard I asymmetric mode of fission is favorable in the 235U(nth,f) reaction.

Flutter prediction on combined EPS and carbon sandwich structure for light aircraft wing

Flutter prediction is an important step before conducting a flight test. In this study, we performed flutter prediction of a half-wing structure without control surfaces. The half-wing structure is made to resemble the scaled-down wing of a Boeing 737 NG at a scale of 1:39.34. The airfoil profile used is the wing profile of the Boeing 737 NG obtained from airfoiltools. The structure is constructed using a combination of carbon sandwich andEPS. The advantages of choosing this material are its low-cost and easymanufacture. We used the p-k method in the FEMAP software for flutter prediction. From the prediction results, the calculated flutter speed is ∼14.5 m/s. The flutter mode shape is a combination of lateral bending and twist. Dimensional analysis was also carried out to predict the maximum speed on the scaled model and predicted at 27.88 m/s. Based on calculated flutter speed, the maximum operating speed of a constructed structure should be far less than the flutter speed. Thus, the structure's maximum speed is below the predicted value. Based on carried out flutter prediction, the wing structure, constructed using a combination of carbon sandwich and EPS, can fly safely at a maximum cruise speed of 10 m/s.

Post-Neutron Mass Yield Distribution in the Epi-Cadmium Neutron-Induced Fission of 237Np

Mass yield distribution in the epi-cadmium neutron-induced fission of 237Np has been carried out by measuring the cumulative yields of fission products within the mass ranges of 78 to 117 and 123 to 157. A radiochemical and off-line gamma-ray spectrometric technique was used for the measurement. From the cumulative yields of the fission products, mass chain yields were obtained by applying the charge distribution correction. Mass yield distribution parameters such as the full-width at tenth-maximum of light and heavy mass wings, the peak-to-valley (P/V) ratio, and the average light mass <AL> and heavy mass (<AH>) as well as the average number of neutrons <ν> were obtained. The mass yield data in the epi-cadmium neutron-induced fission of 237Np were compared with the similar data in thermal and 14.5- to 14.7-MeV neutrons to examine the role of excitation energy in nuclear structure effect and P/V ratio.

Post-neutron mass yield distribution in the thermal neutron induced fission of 238Pu

The cumulative and independent yields of various fission products within the mass range of 83–155 have been measured in the thermal neutron induced fission of 238Pu by using an off-line γ-ray spectrometric technique. From the cumulative yields, post-neutron mass chain yields were obtained by using the charge distribution correction. From the mass yields data, the full width at tenth maximum (FWTM) of light and heavy mass wing, the average light mass (<AL > ) and heavy mass (<AH > ) as well as the average number of neutrons (<ν > ) emitted were obtained. The mass yield data in the 238Pu(nth, f) reaction was compared with the similar data of 241Pu(nth, f) reaction to examine the nuclear structure effect.

Composite panels design based on post-buckling state with combined loading

Buckling is possible for thin composite skins of light aircraft wing high-lift devices loaded above limit level. Aim of this work is to create a method for orthotropic panels minimal thickness definition with possible post-buckling behavior considering residual strength support. Hinge supported composite panels loaded in compression and shear jointly are considered. Method based on analytic solution of non-linear problem and design method by post-buckling state is suggested in the paper. In order to explain peculiarities of above-mentioned method examples of panels design loaded with tangential force supporting strength and stability are shown in this work. It is demonstrated that for panels minimal thickness calculation by strength, stability, and post-buckling behavior conditions corresponding linear, second- and third-degree equations in unknown thicknesses are derived. In order to develop design method by post-buckling state with combined loading analytic solution of non-linear problem using Bubnov-Galerkin method is shown in the paper. Chai criterion including all components of acting forces and stress critical values for residual strength has been used for composite package based on the conditions of combined loading. Variants of developed applied methods of design based on post-buckling state with only tangential force acting and with combined loading by compression and shear flows are shown in this work.

Post-Neutron Mass Yield Distribution in the Spontaneous Fission of 252Cf

Cumulative and independent yields of various fission products within mass ranges of 86 to 119 and 127 to 162 were measured in the spontaneous fission of 252Cf by using an off-line gamma-ray spectrometric technique. From the cumulative yields of the fission products, their mass chain yields were obtained by using the charge distribution correction. Mass yield distribution parameters such as full-width at tenth-maximum of light and heavy mass wings, average light mass <AL> and heavy mass <AH>, and total average neutron multiplicity <ν>expt were obtained. Fission yield data in the 252Cf(SF) reaction were compared with similar data in neutron-induced fission and spontaneous fission of other actinides to examine the role of excitation energy and nuclear structure effect. The role of standard I and standard II asymmetric modes of fission is also discussed.

From Armenia to Poland ‘with love’s light wings’

On 30 July 2019, Yerevan State Chamber Theatre’s unconventional version of Romeo and Juliet was performed at the annual Gdańsk Shakespeare Theatre Festival in Poland, after successfully premiering in Yerevan, Armenia, in 2017. Following the overwhelming success of the production with local and international audiences and critics, invitations from other European festivals followed. When the current devastating restrictions imposed on theatres worldwide by the Covid-19 pandemic are finally lifted, the journey of the world’s best-known love story retold by this innovative theatre troupe will resume.

Post-neutron mass yield distribution in the epi-cadmium neutron induced fission of $${}^{{\mathbf {240}}}$$Pu

In the epi-cadmium neutron induced fission of $${}^{\text {240}}$$ Pu, cumulative yields of fission products within the mass range of 83–117 and 123–157 as well as independent yields of few fission products have been measured by using an off-line $$\gamma $$ -ray spectrometric technique. The post-neutron mass yields were obtained from the cumulative yields after applying the charge distribution correction. From the mass yields data, the mass distribution parameters like full width at tenth maximum (FWTM) of light and heavy mass wing, the peak-to-valley (P/V) ratio, the average light mass ( $$ $$ ) and heavy mass ( $$ $$ ) as well as the average neutrons number ( $$ $$ ) were obtained. Since, the even–odd effect in between the $${}^{\text {240}}$$ Pu(n, f) and $${}^{\text {241}}\hbox {Pu}(\hbox {n}_{\text {th}}$$ , f) reactions are comparable, the mass yield data in between the two fissioning systems were compared to examine the role of small difference in excitation energy on nuclear structure effect. The role of standard I and standard II asymmetric modes of fission was also examined.

Optimization and analysis of composite sandwich box beam for solar drones

Solar drones have garnered considerably research attention in recent years due to their continuous cruising capability, and the feasibility of design schemes is sensitive to the weight of structure. Sandwich box beam composed of carbon fiber and polymethacrylimide (PMI) foam is conducive to realize the lightweight of structure. In this study, a two-stage optimization design methodology for sandwich box beam is proposed. This methodology is primarily based on a low-order analytical method for evaluating stress/deflection and the linear buckling analysis method combined with experimental correction factor for predicting the buckling eigenvalues. Subsequently, a case study was conducted using an 18-m wingspan solar drone, where the results of mechanical test verified the optimization results. For validating the use of sandwich box beam in solar drones of other scales, additional analysis was conducted based on three aspects: (A) effects of stiffness and stability constraints on the design of sandwich box beam; (B) crucial role of the weight of foam inter layer and application scope of sandwich box beam; (C) best method to improve the buckling eigenvalue of sandwich box beam. Overall, the methodology and general rules presented in this paper can support the design of light wing beam for solar drones.

Inflected wings in flight: Uniform flow of stresses makes strong and light wings for stable flight

Flying animals morph and flex their wings during their flight. Their wings morph with the turbulent flow created around them. The wings of modern airplanes do not have this ability. In this study we show that the ability to flex the wings leads to greater stability (higher flutter speed), and that this is due to the more uniform distribution of stresses in the flexing wing. This way the flexing wing becomes the lightest per unit of flapping force, or the strongest per unit of weight.

Experience in the formation of power elements of an aircraft wing using topological optimization approaches

The process of designing aircraft structures, in most cases, involves finding solutions that will minimize weight, while maintaining the characteristics of strength and rigidity. To increase the mass efficiency of the aircraft glider, it is proposed to carry out topological optimization of structural and power elements at the initial stages of design with the help of modern software packages.&#x0D; Modern wings of traditional forms are close to exhausting their aerodynamic and weight characteristics, so all over the world there is an intensive search for new technical solutions. This indicates the relevance of developing new methods that use high-precision mathematical modeling in the early stages of design.&#x0D; Despite the significant number of publications on the topic of mass optimization, including aircraft structures, there are no quantitative indicators of the magnitude of the possible minimization of mass by topological optimization methods for the main structural and power elements of the aircraft wing.&#x0D; The article describes the results of the analysis of the effectiveness of the use of topological optimization methods to minimize the mass of the main structural and power elements of the aircraft wing. For a typical, typesetting structural and power scheme of a light aircraft wing, the values of possible minimization of the glider mass were determined.&#x0D; The use of topological optimization at the design stage of the power elements of the aircraft glider makes it possible to significantly reduce the mass of the main structural and power elements and allows to significantly reduce the takeoff mass of the aircraft. This approach using the results of optimization can be used to determine rational power schemes and predict the mass of the wings, taking into account the peculiarities of their geometric shapes and boundary conditions.

Structural optimization of a light aircraft composite wing

This paper presents the results of structural optimization of a two-spar composite wing for a light aircraft. Different lay-up structures of power components such as spars, ribs and skin panels was considered. The problem of optimization was solved using Pareto optimization method with two criteria: minimal wing weight and minimal wing deflection under aerodynamic load. The angle of ply orientation and power components thicknesses were considered as the optimization parameters. It was shown that the use of the optimized wing from carbon composite could reduce up to 60% of the wing weight comparing with aluminium one. The stress-strain and buckling analysis of the wing and its power components were carried out in FEMAP software package.

Design aspects of light aircraft wing spar—Differential and integral approach

Design aspects of light aircraft wing spar—Differential and integral approach

Aeroelastic optimization of composite wings including fatigue loading requirements

An analytical model to predict the fatigue life of a composite laminate is formulated. The model calculates stresses in each ply using classical lamination theory, degrades the residual strength using the linear wear-out law and predicts failure based on Tsai Wu failure theory. The cycles to failure are predicted using the updated cycle-by-cycle probability of failure. The predictions are validated for both a constant amplitude and a variable amplitude loading on a Glass/Epoxy laminate. Additionally the analytical model is extended to work with laminates described using lamination parameters instead of ply angles and stacking sequence. The analytical fatigue model is then integrated in the TU Delft aeroelastic and structural optimization tool PROTEUS. A thickness and stiffness optimization of the NASA Common Research Model (CRM) wing has been carried out. Results show that fatigue, strength and stiffness are the design drivers in the aeroelastic optimization of a composite wing. Furthermore, by including the analytical fatigue model instead of using a traditional knockdown factor to account for fatigue, a lighter wing is obtained.

Hot wings: thermal impacts of wing coloration on surface temperature during bird flight.

Recent studies on bird flight propose that hotter wing surfaces reduce skin friction drag, thereby improving flight efficiency (lift-to-drag ratio). Darker wings may in turn heat up faster under solar radiation than lighter wings. We used three methods to test the impact of colour on wing surface temperature. First, we modelled surface temperature based on reflectance measurements. Second, we used thermal imaging on live ospreys (Pandion haliaetus) to examine surface temperature changes with increasing solar irradiance. Third, we experimentally heated differently coloured wings in a wind tunnel and measured wing surface temperature at realistic flight speeds. Even under simulated flight conditions, darker wings consistently became hotter than pale wings. In white wings with black tips, the temperature differential produced convective currents towards the darker wing tips that could lead to an increase in lift. Additionally, a temperature differential between wing-spanning warm muscles and colder flight feathers could delay the flow separation above the wing, increasing flight efficiency. Together, these results suggest that wing coloration and muscle temperature both play important roles in modulating wing surface temperature and therefore potentially flight efficiency.

Capacity for heat absorption by the wings of the butterfly Tirumala limniace (Cramer).

Butterflies can directly absorb heat from the sun via their wings to facilitate autonomous flight. However, how is the heat absorbed by the butterfly from sunlight stored and transmitted in the wing? The answer to this scientific question remains unclear. The butterfly Tirumala limniace (Cramer) is a typical heat absorption insect, and its wing surface color is only composed of light and dark colors. Thus, in this study, we measured a number of wing traits relevant for heat absorption including the thoracic temperature at different light intensities and wing opening angles, the thoracic temperature of butterflies with only one right fore wing or one right hind wing; In addition, the spectral reflectance of the wing surfaces, the thoracic temperature of butterflies with the scales removed or present in light or dark areas, and the real-time changes in heat absorption by the wing surfaces with temperature were also measured. We found that high intensity light (600–60,000 lx) allowed the butterflies to absorb more heat and 60−90° was the optimal angle for heat absorption. The heat absorption capacity was stronger in the fore wings than the hind wings. Dark areas on the wing surfaces were heat absorption areas. The dark areas in the lower region of the fore wing surface and the inside region of the hind wing surface were heat storage areas. Heat was transferred from the heat storage areas to the wing base through the veins near the heat storage areas of the fore and hind wings.

Fatigue crack paths in light aircraft wing spars

Different cracks paths in three different wing spar designs are analysed (differential, integral and optimized integral) to explore how those cracks paths affect fatigue life estimation. First, numerical analysis was carried out and verified, using the experimental data for differential wing spar, followed by numerical analysis of both optimized integral wing spars. The optimized integral spar was obtained by analysing three different cross-sections regarding fatigue life. Crack propagation simulation and fatigue life estimation were carried out by the extended finite element method, using Morfeo/Crack for Abaqus. Results provided better understanding and prediction of multiple cracks propagation in 3D structures.

Structural sizing for the weight estimation of a very light aircraft wing

The design process is no longer a trial-and-error procedure due to the introduction of computer-aided tools and optimization techniques. The product development process is therefore accelerated, allowing to produce more in a relatively lesser time. Moreover, the best possible design, with regard to the performance, can hence be obtained. When applied to the design of an aircraft wing, the optimization objective is usually to minimize the structural weight under failure-based constraints. This paper presents an optimization strategy that allows the determination of the wing surface structural thicknesses corresponding to the minimal weight while keeping the structure safe in terms of strength and buckling. This strategy is applied for the wing sizing process of a new two-seater very light aircraft, currently under development. The design process goes through geometric modeling, aerodynamic calculations using vortex lattice method, and finite element modeling. Structural optimization is performed within MATLAB, and is based on the automatic execution of the finite element solver MSC.NASTRAN.

Research of elastic-deformed state Hard and light wings of great loading

Due to the growth of economic requirements for modern aircraft, the parameter of the aerodynamic range Kmax • M, where Kmax is the maximum aerodynamic quality of the airplane, has become especially relevant, M is the flight speed relative to the speed of sound. The increase in the aerodynamic range at the expense of M for modern aircraft of the transport category is problematic because the flight speed reaches M = 0,7 ÷ 0,9, and the increase due to Kmax became possible due to an increase in the lengthening of the wing λ or a decrease in its swept angle χ.Under load, the wing deforms and the nature of the load distribution changes along the width of the wing. Such a phenomenon of static aeroelasticity (SA) leads to a decrease or increase in the existing bending and twisting moments of the wing, especially in the case of swept wings (λ ≥ 8). Therefore, the reliability of the determination of external loads, taking into account the influence of static aeroelasticity, is important. Load is the input parameters for calculation of strength, analysis of elastic-deformed state (EDS) of the design and forecasting its weight efficiency.Taking into account the effects of static aeroelasticity reduces the external load in some sections by wings up to 14%. The comparison of relative moment’s shows that the value of the bending moment coincides with the bending moment obtained from the experimental data.The method of aerodynamic influence coefficients (AIC) has a significant advantage over other methods, which is that a once-defined matrix of aerodynamic influence coefficients can be used in different load scenarios. This reduces the time spent on the calculations and eliminates the need for repeated experiments.

Design and Optimization of Wing Structure for a Fixed-Wing Unmanned Aerial Vehicle (UAV)

The wing, one of the most important parts of aircraft, always requires sophis-ticated design to increase lift, reduce drag and weight. For modern fixed-wing UAV, extending cruising time is always a requirement for the overall design. Designing a most light wing that can match the requirements of work condi-tions is desired. In this work, according to the work conditions, we compare several types of wing and chose beam-type wing. Then we made the detailed design and optimization to reduce the weight of wing. At last, we draw the 3D model for potential realistic production.