Effect Of Deflection Research Articles

Heat Transfer Characteristics of Submerged and Free Surface Air-assistant Water Jet Impingement

Heat transfer and fluid flow characteristics of air-assistant submerged and free surface water impinging jets are experimentally investigated. Results showed that the Nusselt number and pressure decrease exponentially in both free surface and submerged jets for all volumetric qualities in jet deflection region. In transition region, the Nusselt number and pressure of the submerged jet and free surface jet decrease since the jet deflection effect was disappeared. In buoyance effect region, the Nusselt number and pressure increase in the free surface jet since the potential energy increases, while the Nusselt number and pressure decrease in the submerged jet since the bubbles are not impinged the plate due to the buoyancy effect.

Showerhead film cooling injection orientation design on the turbine vane leading edge considering representative lean burn combustor outflow

The heat transfer performance of showerhead film cooling on the vane leading edge was numerically investigated considering representative lean burn combustor swirling outflow. Three cases with different inflow conditions (uniform inflow, positive swirling inflow, and negative swirling inflow) and three cases with different film injection angles (45°, 90°, and 135°) were studied. As the first study to explore the showerhead film design principle under swirling inflow, a newly designed asymmetrical counter-inclined (45° and 135°) film cooling was also proposed. To examine the design principles, the cooling effectiveness, heat transfer augmentation, and heat flux reduction of the newly designed asymmetrical case were evaluated compared with the traditional symmetrical case. The results show that the swirling inflow introduces obvious radial pressure gradient on the vane. The radial pressure gradient is the key influence factor to deflect the coolant migration, decrease the cooling effect, and degrade the homogeneity. The film with opposite orientation to the radial pressure gradient can weaken the deflect effect. The radial pressure gradient direction differs in different regions, making it impossible for the film with congruent injection orientation to simultaneously resist the pressure gradient on the entire vane. For the new design, the boundary line of the counter-inclined holes is consistent with the twisted stagnation line to guarantee that the injection orientation of all the film holes is opposite to the radial pressure gradient. As expected, the new design can effectively weaken the deflection effect and show uniform film distribution. The higher coolant mass ratio provides more obvious enhancement effect. At coolant mass ratio 3.71% and 4.56%, the overall area-averaged heat flux reduction (Δ q) is increased by 0.311 and 0.576, and the overall area-averaged relative standard deviation is reduced by 12.17 and 11.66 compared with the traditional design. The results have confirmed the adaptability of the film design principle under swirling inflow.

Fatigue crack deflection and branching behavior of low carbon steel under mechanically large grain condition

In situ SEM observation of fatigue crack growth behavior of low carbon steel under mechanically large grain condition, and EBSD analysis were carried out to investigate mechanisms of crack deflection and branching and effects of crystal orientation on them. It is found that the crack propagates along the activated slip bands in the present material and the crack deflection can be formed when a new activated slip band is created in a different direction from the growing crack. The crack branching can be formed by the following process: (1) the slip band along the crack cannot be activated further due to the restraint by such as grain boundary or strain hardening, (2) the crack cannot propagate further in the same direction, and (3) the secondary slip plane is activated to form a new slip band behind the crack tip. Not the stress intensity factors Kdef for deflected crack and ΔKeff for crack closure but rather the ΔKeff,tip is the intrinsic fracture mechanics parameter for controlling fatigue crack growth behavior of the material with crack deflection and branching.

Adapted Fringe Projection Sequences for Changing Illumination Conditions on the Example of Measuring a Wrought-Hot Object Influenced by Forced Cooling

Optical 3D geometry reconstruction, or more specific, fringe projection profilometry, is a state-of-the-art technique for the measurement of the shape of objects in confined spaces or under rough environmental conditions, e.g., while inspecting a wrought-hot specimen after a forging operation. While the contact-less method enables the measurement of such an object, the results are influenced by the light deflection effect occurring due to the inhomogeneous refractive index field induced by the hot air around the measurand. However, the developed active compensation methods to fight this issue exhibits a major drawback, namely an additional cooling of the object and a subsequent transient illumination component. In this paper, we investigate the cooling and its effect on temporal phase reconstruction algorithms and take a theoretical approach to its compensation. The simulated compensation measures are transferred to a fringe projection profilometry setup and are evaluated using established and newly developed methods. The results show a significant improvement when measuring specimens under a transient illumination and are easily transferable to any kind of multi-frequency phase-shift measurement.Dataset License: CC-BY

Finite element analysis of viscoelastic laminates embedded with shape-memory-alloy wires under low-velocity impact considering large deflection

This paper presents an experimentally validated finite element analysis of the low-velocity impact on viscoelastic laminates embedded with shape memory alloy (SMA) with consideration of large deflection effects. Substantial impact outputs, including contact force and deflection distribution, are then derived and a fully implicit numerical solution is utilized. The finite element model contains the following innovative items to develop more sophisticated results: (1) A user-defined (UMAT) is prepared in ABAQUS to simulate the viscoelasticity of composite laminate and superelasticity of SMA wires simultaneously. (2) The generalized Maxwell model consisting of 3 Mx elements is utilized for the viscoelastic feature of the composite laminate. (3) A modified phenomenological constitutive law, which is capable of modeling superelasticity and one-way shape memory effect, is used for SMA wires. (4) Large deflection effects on dynamical response are investigated for both conventional and SMA-reinforced composites. Many researchers have not regarded viscoelasticity in their calculation (especially polymeric composites), although the results show that the viscoelastic feature of laminates has a pronounced effect on the dynamical response of composite laminates embedded with SMA wires. It is also shown that large deflection effects have a significant influence on the results of SMA-reinforced composites. This model achieved good conformance with experimental results.

Estimation of Aircraft-Dependent Bumpiness Severity in Turbulent Flight

Atmospheric turbulence threatens flight safety of civil aviation aircraft by inducing aircraft bumpiness. A severity estimation method of aircraft bumpiness in turbulent flight is explored according to in-situ Eddy Dissipation Rate (EDR) indicator. With the turbulence intensity derived from EDR value, a time series of longitudinal and vertical turbulence was generated according to von Karman turbulence model. In order to obtain the vertical acceleration response of aircraft, the continuous change of aerodynamic force on the assembly of wing and horizontal tail was computed by Unsteady Vortex Lattice Method (UVLM). The computing accuracy was improved by using semi-circle division and assigning the vortex rings on the mean camber surface. Furthermore, the adverse effects of control surface deflections on bumpiness severity estimation can be effectively removed by separating turbulence-induced and aircraft maneuvers-induced aerodynamic force change. After that, the variance of vertical acceleration, as the severity indicator of aircraft bumpiness, was obtained by Welch spectrum estimation. With the refined grid level, the pitching moment change due to control surface deflections can be solved accurately by UVLM. The instantaneous acceleration change obtained by UVLM approximates recorded acceleration data with better accuracy than linear transfer function model. A further test with a set of flight data on the same airway shows that compared with in-situ EDR indicator, the proposed method gives an aircraft-dependent estimation of bumpiness severity, which can not only be used to estimate in-situ bumpiness but also be applied to forecast the bumpiness severity of other different aircrafts.

Comparison of a standardized four-point bending test to an implant system test of an osteosynthetic system under static and dynamic load condition.

Current test standards of osteosynthetic implants examine the bone plate and screw separately leading to unrealistic load scenarios and unknown performance of the system as a whole, which prevents the identification of characteristic failures in clinical use. A standardized static and dynamic four-point bending test (ASTM F382) was performed on a bone plate. Based on that standard, an advanced implant system test (IST) was designed and performed to test a mechanical construct consisting of a bone plate, screws and an artificial bone substitute out of Polyoxymethylene (POM). The test object was an osteosynthetic system to treat fractured ulna bones. Both results of the conventional and advanced test method were analyzed and compared to one another. The static results show a similar yield point (YP) relative to the bending moment with just 9% difference. Dynamic results show a bi-phasic behavior of the displacement vs. cycle data for the IST. The secondary phase can be defined as a constantly increasing plastic deflection or ratcheting effect quantified by its slope inmm per onemillion cycles, leading to a 10 times higher slope for the IST than the conventional test. The IST has a high impact on the test results and the resultant interpretation of the mechanical behavior of the osteosynthetic system. A constantly increasing plastic deflection might lead to fatigue failures and to a loss of the mechanical durability. The development of new standardizations referring to the whole system within reasonable boundary conditions of individual biomechanical applications is crucial for high quality mechanical analysis.

Experimental and analytical investigation of PBO FRCM-concrete bond behavior using direct and indirect shear test set-ups

Externally bonded reinforcement (EBR) represents an effective solution to strengthen existing reinforced concrete (RC) members. EBR comprising fiber-reinforced cementitious matrix (FRCM) has been increasingly adopted due to some advantages with respect to the more diffused fiber-reinforced polymer (FRP). Externally bonded FRCM often reported debonding failure at the matrix-fiber interface. In the literature, the matrix-fiber bond behavior was studied using mostly single- and double-lap direct shear (DS) tests. An alternative is represented by modified beam (MB) test set-ups. In this paper, a MB test set-up is adopted to study the effect of flexural deflection on the bond behavior of a polyparaphenylene benzobisoxazole (PBO) FRCM composite bonded to a concrete substrate. Two different MB test layouts are investigated and the results obtained are analyzed and compared with those of corresponding DS tests with the same PBO FRCM. Then, an analytical model able to describe the results of both DS and MB tests accounting for the presence of stresses normal to the matrix-fiber interface is proposed. The experimental results and analysis presented in this paper help to clarify the influence of the test set-up on the bond behavior of FRCM composites, which represents a key parameter for the design of FRCM EBR.

Experimental characterization of nonlinear static and dynamic behaviors of circular capacitive microplates with initial deflection

In this paper, the effects of initial deflection on the static and dynamic behaviors of circular capacitive transducers are experimentally investigated. The obtained results are in good agreement with numerical simulations. It is shown that the initial deflection has a major impact on the static response of the resonator by shifting the pull-in voltage, and on its dynamic response by increasing the resonance frequency and modifying the bifurcation topology from softening to hardening behavior. Moreover, the dynamic behavior of the microplate may display nonlinear periodic and quasiperiodic responses due to geometric and electrostatic nonlinearities.

A Fluid–Solid–Heat Coupling Analysis for Water-Lubricated Rubber Stern Bearing Considering the Deflection of Propeller Shaft

The novelty of the present study is that it investigates the effect of propeller shaft deflection, caused by the propeller self-weight and interfacial mixed forces, on the fluid–solid–heat (FSH) coupling performance of water lubricated rubber stern bearing (WLRSB). In the FSH coupling model, the generalized average Reynolds equation and the Kogut–Etsion asperity contact model are used to determine the hydrodynamic and the elastic–plastic contact behaviors of WLRSB. In the thermal analysis, the journal, water film, and rubber bushing are considered as an integrated system (JWR system) using the Euler method. To prove the correctness of the developed model, the predicted results are verified by comparisons with the experimental results given in the literature. In addition, to assess the effect of the force-driven deflection during FSH simulation, comparisons of the FSH predictions between the aligned journal case and the deflected journal case are carried out. The results indicate that, especially under a heavy load condition, the deflection of the stern shaft should be incorporated into the lubrication gap between the journal–rubber interface during the analysis of FSH performance of the JWR system.

Effect of angle deflection on deformation characteristic and mechanical property of electromagnetic riveted joint

During automatic electromagnetic riveting, the positioning deviation between punch and rivet is easy to occur. This leads to the asymmetric deformation of rivet tail and affects the performance of riveted joint. In this paper, the riveted specimens under various angle deflections (0°, 2°, 4°, 6°) were prepared to investigate the effect of angle deflection on deformation characteristic and mechanical property of electromagnetic riveted joint. The microstructure observation, interference analysis, hardness measurement, and shear and pull-out test were performed to evaluate the performance of riveted joints. Results showed that the angle deflection had significant effects on the deformation characteristics and mechanical properties of riveted joints. Compared to the riveted joint with 0° angle deflection, the rivet shaft of riveted joints with 2°, 4°, and 6° angle deflection would tilt. The tilt of the rivet shaft caused relative displacement between riveted sheets and generated a clearance between the rivet shaft and riveted sheets, affecting the interference of riveted joints. The mechanical property of riveted joint decreased with the increase of angle deflection. For shear tests, the failure modes were all rivet failure, and the rupture positions were all in the middle portion of the rivet shaft. For the pull-out test, there were three failure modes. In addition, the reliability of automatic electromagnetic riveted joint could be preliminarily judged by this work, which provided scientific guidance for the engineering application of automatic electromagnetic riveting technology.

Quasi-3D Aerodynamic Analysis Method for Blended-Wing-Body UAV Configurations

The current study presents a low-fidelity, quasi-3D aerodynamic analysis method for Blended-Wing-Body (BWB) Unmanned Aerial Vehicle (UAV) configurations. A tactical BWB UAV experimental prototype is used as a reference platform. The method utilizes 2D panel method analyses and theoretical aerodynamic calculations to rapidly compute lift and pitching moment coefficients. The philosophy and the underlying theoretical and semi-empirical equations of the proposed method are extensively described. Corrections related to control surfaces deflection and ground effect are also suggested, so that the BWB pitching stability and trimming calculations can be supported. The method is validated against low-fidelity 3D aerodynamic analysis methods and high-fidelity, Computational Fluid Dynamics (CFD) results for various BWB configurations. The validation procedures show that the proposed method is considerably more accurate than existing low-fidelity ones, can provide predictions for both lift and pitching moment coefficients and requires far less computational resources and time when compared to CFD modeling. Hence, it can serve as a valuable aerodynamics and stability analysis tool for BWB UAV configurations.

Power loss by blade deflection in flexible rotor wind turbines

Effects of deflection onto the performance of small wind turbines with flexible rotor-blades have been studied and analysed. The goal of the study has been the evaluation of the wind turbine output power loss due to angular deflection because of bending effects caused by gravity. Wind turbine blades have been deformed under constant load at the tip of the blade for periods up to 40 days. Deformation process has been accelerated using a very heavy load and the corresponding angular deflection has been obtained. Wind turbine performance has been characterized through the P-V curve for different wind speed operation conditions. Tests have been run for different deformation states to compare the evolution of the power loss with angular deflection. Results from experimental tests have shown there is a constant power loss with deformation increase. Power reduction for angular deflection of 2.3o is between 35% and 45% for blade tip wind speed from 27.6 m/s to 42 m/s. Power coefficient, C p , has also been analyzed and determined for the angular deflection of 2.3o and 4.3o; the reduction of the power coefficient value has been computed through a power loss factor, f P , that shows a reduction in the range of 25% to 50% for the 2.3o angular deflection, and between 45% and 55% for the angular deflection of 4.3o.

Characteristics assessment on riveted, bonded and hybrid joints using GFRP composites

A major type of material used now-a-days in restructuring the existing structures are composite materials because of its excellent mechanical properties. Many sub structures arranged in a proper manner constitute a well defined structure which also forms a load transmission unit. This unit is meant to be as joints which are the weak zone in a properly defined structure. There could be various failures that would occur in case of joints. The main reason behind these failures are more amount of deflection, stress concentrations or a combined effect of both stress and deflections. Many applications uses mechanical fasteners or adhesives to join various different types of materials together. It could be used in order to increase the strength and rigidity of the joint in glass fiber epoxy composites. In this paper, a suitable configuration has be chosen which could be used in various different applications by understanding the complete potential of composites analysing the stress and strain distribution over the materials.

Damage Identification of Multi-span Bridge Structure Based on the Recognition of Influence Line

The stress and deflection effects of the line changes before and after the bridge damage are used as indicators to evaluate the bridge damage and the initial damage site. Then a method of combining information is proposed to improve the accuracy of the damage site. Three-span continuous reinforced concrete was used in the analysis. According to the test, the effectiveness of damage identification based on the damage change of the influence line and the feasibility of the damage location method based on multi-sensory information fusion are confirmed.

Research on control effectiveness of fluidic thrust vectoring.

In view of the control effects of fluidic thrust vector technology for low-speed aircraft at high altitude/low density and low altitude/high density are studied. The S-A model of FLUENT software is used to simulate the flow field inside and outside the nozzle with variable control surface parameters, and the relationship between the area of control surface and the deflection effect of main flow at different altitudes is obtained. It is found that the fluidic thrust vectoring nozzle can effectively control the internal flow in the ground state and the high altitude/low density state. and the mainstream deflection angle can be continuously adjusted. The maximum deflection angle of the flow in the ground state is 21.86°, and the maximum deviation angle of the 20 km high altitude/low density state is 18.80°. The deflecting of the inner flow of the nozzle is beneficial to provide more lateral force and lateral torque for the aircraft. The high altitude/low density state is taken as an example. When the internal flow deflects 18.80°, the lateral force is 0.32 times the main thrust. For aircraft with high altitude and low density, sufficient lateral and lateral torque can make the flying aircraft more flexible, which can make up the shortcomings of the conventional rudder failure and even replace the conventional rudder surface.

Pareto Optimization of GMDH-Type Neural Networks for Modelling and Prediction of Hoop Strain in Explosive Forming Process

In this paper, Evolutionary Algorithms (EAs) are deployed for multi-objective Pareto optimal design of Group Method of Data Handling (GMDH)-type neural networks that have been used for modelling of the effect of dynamic yield stress, thickness, charge mass, centre deflection and distance from centre on the hoop strain in explosive forming process using some input-output experimental data. In this way, EAs with a new encoding scheme is firstly presented to evolutionary design of the generalized GMDH-type neural networks in which the connectivity configurations in such networks are not limited to adjacent layers. Multi-objective EAs (non–dominated sorting genetic algorithm, NSGA-II) with a new diversity preserving mechanism are secondly used for Pareto optimization of such GMDH-type neural networks. The important conflicting objectives of GMDH-type neural networks that are considered in this work are, namely, Training Error (TE), Prediction Error (PE) and number of neurons (N) of such neural network. Different pairs of these objective functions are selected for 2-objective optimization processes. Therefore, optimal Pareto fronts of such models are obtained in each case which exhibit the trade-offs between the corresponding pair of conflicting objectives and, thus, provide different non-dominated optimal choices of GMDH-type neural networks models for the explosive forming process. Moreover, all the three objectives are also considered in a 3-objective optimization process which consequently lead to some more non-dominated choices of GMDH-type models representing the trade-offs among the training error, prediction error, and number of neurons (complexity of network), simultaneously. The overlay graphs of these Pareto fronts also reveal that the 3-objective results include those of the 2-objective results and, thus, provide more optimal choices for the multi-objective design of GMDH-type neural networks in terms of minimum training error, minimum prediction error and minimum complexity.

Trade destruction and deflection effects of US‐China trade frictions on China’s tariff‐targeted products

AbstractThis paper probes into the impacts of US‐China trade rows on China's exports of products covered under the applicable tariff lines. We scrutinise the monthly trade data of China with the US and third‐party markets from January 2017 to June 2019, employing the DID model. It is found firstly that the US levy of tariffs on $50 billion and $200 billion worth of Chinese products have produced a significant and adverse trade destruction effect on China's exports to the US. Meanwhile, the tariffs levied on these products have played a significant and positive role in deflecting China's export to third‐party markets. Second the US additional tariffs on $50 billion of China's products have produced greater trade destruction and deflection effects on China's export of tariff‐targeted products to the US, whereas only the US additional tariffs on $200 billion of China's products have caused a net trade destruction effect. Third, it is confirmed that the trade destruction effects of US additional tariffs on Chinese products exported to the US are mainly concentrated on high tech‐intensive manufactures and primary goods, while the trade deflection effect of China's export to third‐party markets is concentrated on differentiated products. The findings render crucial policy implications.

A micromechanical model of fiber bridging including effects of large deflections of the bridging fibers

A micromechanical model of cross-over fiber bridging is developed for the prediction of macroscopic mixed-mode bridging laws (traction-separation laws). The model is based on non-linear beam theory and takes into account debonding between fiber and matrix as well as buckling of fibers in compression. Further, it is shown how failure of the bridging fibers can be taken into account through a Weibull distributed failure strain. Predictions made by the proposed model are compared with predictions made by detailed 3D finite element models, and a very good agreement was observed. It is shown that models based on linear beam theory are only valid for small transverse deflections of the bridging ligament and greatly underestimate the force transferred by ligaments subjected to moderately large deflections. The novel model, on the other hand, is applicable in the entire range where the bridging problem transitions from a beam bending problem to a bar-like problem. Finally, an example of how the proposed model can be used for parameter/sensitivity studies is given. A conclusion from this study is that reducing the fracture toughness, Gc, of the interface between fibers and matrix may lead to increased energy dissipation through cross-over fiber bridging as more fibres remain intact longer.

Experimental new ultra-high-speed all-optical coherent streak-camera

We have experimentally studied for the first time a new operation principle of the all-optical coherent streak-camera (Rabi deflector). In the experiment, we observed an effect of significant dynamical angular deflection of a pulse of semiconductor laser during the resonant pumping of the D2 line (780.24 nm) of 87Rb vapor in the range of diffraction angles ϕ = ± 5.45°. We propose to use the Rabi deflector as an energy efficient shaper of classical and single-photon wave packets. We analyze a possibility of the Rabi deflector operation in quantum systems with feedback.