Local Deflection Research Articles

Mass, energy, and momentum capture from stellar winds by magnetized and unmagnetized planets: implications for atmospheric erosion and habitability

The extent to which a magnetosphere protects its planetary atmosphere from stellar wind ablation depends upon how well it prevents energy and momentum exchange with the atmosphere and how well it traps otherwise escaping plasma. We focus on the former, and provide a formalism for estimating approximate upper limits on mass, energy, and momentum capture, and use them to constrain loss rates. Our approach quantifies a competition between the local deflection of incoming plasma by a planetary magnetic field and the increase in area for solar wind mass capture provided by this magnetosphere when the wind and planetary fields incur magnetic reconnection. Solar wind capture can be larger for a magnetized planet versus an unmagnetized planet with small ionosphere, even if the rate of energy transfer is less. We find this to be the case throughout Earth's history since the lunar forming impact-- the likely start of the geodynamo. Focusing of incoming charged particles near the magnetic poles can increase the local energy flux for a strong enough planetary field and weak enough wind, and we find that this may be the case for Earth's future. The future protective role of Earth's magnetic field would then depend on its ability to trap outgoing plasma. This competition between increased collection area and reduced inflow speed from a magnetosphere is likely essential in determining the net protective role of planetary fields and its importance in sustaining habitability, and can help explain the current ion loss rates from Mars, Venus and Earth.

Implementation of Timoshenko element local deflection for vertical track modelling

ABSTRACTA vertical track model suitable for the study of the dynamic response and the interaction between wheel and rail in the time domain is developed by using Timoshenko beam elements, and its performance is optimised by accounting for the local deflection of these type of elements. Implementation of the local system enables one to obtain an accurate description of the contact force in a more computationally efficient way than other numerical methods, and it leads to an almost total elimination of the discontinuities caused by the local displacement underestimation and the shear incompatibilities introduced by the conventional formulation with Timoshenko beam elements. The work presented here describes both static and dynamic approaches of the local system directly obtained through the resolution of the beam governing equations. The dynamic approach guarantees the shear rotation continuity and describes accurately the track frequency content. The method is tested for parametric excitation, in which it ensures the smoothness of the response. Secondly, it is tested for short-pitch corrugated rails, where overestimation of the contact force is avoided with a reduced model size when compared with conventional Timoshenko element formulation. The results are validated by comparison with those from previous studies.

Strength investigation of a small size floating dock unit by 3D-FEM models in head design waves

This study is focused on floating docks strength analysis by 3D finite element models, full extended over the dock length. The equilibrium position of the dock in the design equivalent quasi-static waves environment is obtained by own code, based on a non-linear iterative procedure. For the surrounding water and ballast tank water loads we have developed user procedures and functions implemented in the finite element programs. Also the still water conditions are analysed. The numerical study is developed for a small size floating dock, designed for multiple shipyards operation, with 60 m length and two constructive versions, having continuous and non-continuous side ballast tanks. As main operation cases of the small size floating dock are considered: light without docking ship, full ballast at maximum upper deck limit, three docking ship tests, with ship mass uniform, sagging and hogging type distributions, according to the shipbuilding classification societies rules. As assessment criteria, the 3D model yielding stress limit for global and local strength, buckling factor and maximum vertical deflection are considered. Also the freeboard criterion is considered. The results of the study are delivering the operation limits, in terms of design wave height, in order to ensure the strength safety rules requirements.

Shape estimation of a bent and twisted cylinder using strain from a sensor array in triple helices

This study proposes the use of strain sensors in a triple-helix configuration to measure the bending and twist deformation in a cylinder. Arranging the strain sensors on the cylinder in a triple-helix structure allows us to measure the twist and bending deformation simultaneously. The method consists of two steps: first to determine the local deformation factors from the surface strains, and second to reconstruct the overall deflected shape of the cylinder from the local deformation factors. We derived an exact analytical formula for the surface strain on a bent and twisted cylinder according to the deformation variables based on our original superhelix model, in which we regard the deformed cylinder segment as a helical coil and the sensors bound upon it as segments of superhelices. The local deflection rates are iteratively computed by the Newton–Raphson method using the surface strain formula. We incorporate the local deflection rates into the helical extension method, which is an exact solution to the Frenet–Serret formulas, to reconstruct the overall deflected shape of the cylinder. From the simulations, the proposed method was shown to determine the overall deformation state of a cylindrical body with remarkable precision. The position errors decreased rapidly with shorter spatial intervals of strain sensing and lower rates of the helical periodicity of the sensor arrays, showing a strong trend of convergence. Moreover, the pin-pointedness of the strain sensing was found to be one of the most crucial factors when attempting to ensure high accuracy of the shape estimation results. This study demonstrates a potential for general applicability to various fields, especially for the shape sensing of multicore optical fibers.

Effect of pectoral fin kinematics on manta ray propulsion

Recent advancement of bio-inspired underwater vehicles has led to a growing interest in understanding the fluid mechanics of fish locomotion, which involves complex interaction between the deforming structure and its surrounding fluid. Unlike most natural swimmers that undulate their body and caudal fin, manta rays employ an oscillatory mode by flapping their large, flattened pectoral fins to swim forward. Such a lift-based mode can achieve a substantially high propulsive efficiency, which is beneficial to long-distance swimming. In this study, numerical simulations are carried out on a realistic manta ray model to investigate the effect of pectoral fin kinematics on the propulsive performance and flow structure. A traveling wave model, which relates a local deflection angle to radial and azimuthal wavelengths, is applied to generate the motion of the pectoral fins. Hydrodynamic forces and propulsive efficiency are reported for systematically varying kinematic parameters such as wave amplitude and wavelengths. Key flow features, including a leading edge vortex (LEV) that forms close to the tip of each pectoral fin, and a wake consisting of interconnected vortex rings, are identified. In addition, how different fin motions alter the LEV behavior and hence affect the thrust and efficiency is illustrated.

Enhancing fatigue strength of high-strength ultrafine-scale Cu/Ni laminated composites

Fatigue strength of the Cu/Ni laminated composites with different thickness ratios of the Ni layer to the Cu layer was investigated. The result reveals that the Cu/Ni laminated composite with the thickness ratio of the Ni layer to the Cu layer of 9.0:1 not only has an ultrahigh strength (1361.80MPa), but also is of a relatively high fatigue ratio approaching to 0.30 compared with ultrafine-grained and nanocrystalline Ni. The introduction of the ultrathin Cu layers into the ultrafine-scale Ni leads to alternate variation of local delamination and crack deflection crossing the layers in the Cu/Ni laminated composites subjected to fatigue loading, maximizing the cracking resistances in spatial directions.

Deflection detection and curve fitting in three-roll continuous straightening process for LSAW pipes

Aiming at the low efficiency of three-point mold bending straightening, a new method of three-roll continuous straightening is proposed in this paper, which is full in consideration of the geometric features and bending characteristics of LSAW pipes. Using the characteristics of the roll straightening device, a straightness detection method for large pipes is proposed just by adding a laser displacement sensor, and the calculation model for overall deflection based on local deflection is established. Based on the detected deflection data, a piecewise fitting algorithm with constraints by introducing the Kuhn-Tucker condition is proposed for straightness calculation, and a simple polynomial fitting method with fourth order is determined for the calculation of curvature and straightening moment. Further, using the semi-automatic experimental prototype for small pipes, the deflection detection experiments show that the overall deflection error is less than 3.5% compared with that of CMM, the piecewise fitting results show that the ideal order of the mid-segment is 10-th, and the three-roll continuous straightening experiments show that the novel method can correct the straightness to less than 0.2%, meeting the standard requirements.

Analogies for simply supported nonlocal Kirchhoff plates of polygonal planform

In the present paper, we consider nonlocal linear elastic Kirchhoff plates, where we restrict to thin, isotropic, and homogeneous plates under the action of static transverse forces, utilizing the differential equation form of the Eringen nonlocal continuum theory. For the case of simply supported plates of polygonal planform, we derive analogies between the solutions of the nonlocal Kirchhoff theory and its local counterpart. First, we extend the Marcus decomposition method for local Kirchhoff plates, where we show that, analogous to the local case considered by Marcus, the moment sum and the nonlocal deflection are both governed by Poisson boundary value problems, which correspond to auxiliary (local) membrane problems. In the present context, it eventually follows that there is a nonvanishing term responsible for a correction of the deflection due to the nonlocal effect, while the moments and shear forces of the local and the nonlocal plate coincide. The nonlocal correction of the deflection turns out to be governed by a membrane-type boundary value problem again. From this fact, it follows immediately that the correction for the deflection due to the nonlocal effect can be derived alternatively from both the local deflection and the local moment sum, which represents a substantial simplification of the nonlocal computations. For the sake of demonstration, we consider examples with closed form solutions. We first consider (as limiting case) infinite plates under the action of single forces, where the singular behavior of Green’s function of the nonlocal Kirchhoff theory can be clarified. Then we discuss the bending of nonlocal plate strips for comparison sake, as well as equilateral triangular plates. To our best knowledge, no results for bending of nonlocal triangular plates have been presented in the literature so far. The present paper has been strongly influenced by a former contribution on analogies between simply supported polygonal Kirchhoff plates rigid in shear and shear-deformable plate solutions. This paper was co-authored together with our teacher, the late Professor Franz Ziegler, to whom we dedicate the present paper. In light of this latter contribution, and extending an idea promoted by Professor Franz Ziegler and his co-workers in the framework of various other fields, we finally show in the Appendix that the deflections of simply supported nonlocal Kirchhoff plates can be considered as deflections of a local “background” Kirchhoff plate under the action of additional fictitious eigenstrain loadings, such as thermal moments.

Refined model of incremental emplacement based on structural evidence from the granodioritic Newry igneous complex, Northern Ireland

Although many intrusions are now known to have been incrementally emplaced, the mechanisms through which this takes place are generally poorly understood. The Newry igneous complex was incrementally emplaced within the Southern Uplands-Down-Longford terrane of Northern Ireland during late Caledonian sinistral transtension. This study uses a variety of new and existing data and techniques to provide a fuller and firmer understanding of incremental emplacement than has previously been available, addressing both deep-crustal processes and those operating within the emplacement site. Host-rock orientations suggest that some of the accommodation space for the Newry igneous complex was generated due to pull-apart tectonics operating within the Southern Uplands-Down-Longford terrane. Local host-rock deflections, concentric igneous foliations, and concentric linear anisotropy of magnetic susceptibility (AMS) fabrics show that inflation due to magma overpressure also generated significant space. Strong AMS fabrics close to the boundaries of some magma pulses in turn suggest that inflation was accomplished by injection of individual magma pulses and was thus incremental. The dome-like orientations of mineral foliations within plutons and the truncation of steep local host-rock tracts by the Newry igneous complex imply that the complex consists of four laccolithic bodies. On a larger scale, it is suggested that the deep-seated Argyll and Newry lineaments represent faults that allowed magma generated at depth to ascend to the crustal level of the Southern Uplands-Down-Longford tract boundaries. It is also inferred that sinistral movement along the Argyll and Newry lineaments may have produced the releasing bend within the Southern Uplands-Down-Longford terrane. Higher in the crust, reduced confining pressure resulted in tectonic opening along this releasing bend. This local stress field induced horizontal magma flow and emplacement of the Newry igneous complex as laccolithic bodies. This study suggests that simplistic emplacement models should largely be abandoned in favor of holistic models incorporating the multiple interdependent processes operating during magma ascent and emplacement.

Indentation failure of foam cored sandwich structures subjected to elevated temperatures

This research explores the detrimental effect of elevated temperatures on local indentation failure of polymer foam cored sandwich structures with laminated glass fibre reinforced epoxy face sheets. A simple analytical model to predict the critical indentation failure load at elevated temperatures is presented and validated against experimental observations. For this purpose, a sandwich beam loaded in three-point bending with an induced through-thickness elevated temperature profile was studied experimentally and by means of analytical and finite element models. In the experiment, the through-thickness temperature gradient was induced with an infrared lamp pointing on the top face sheet, while the local displacement and strain fields near the applied point load were recorded by digital image correlation. The analytical model proposed, which accounts for temperature degraded/reduced foam core properties, superimposes the local response, approximated by the classical Winkler foundation model, and the global response obtained by sandwich beam theory. The comparative study has shown that the critical load causing core crushing failure reduces significantly with elevated temperatures by as much as 50% at an elevated temperature of 90℃. It is shown that the simple analytical model can predict the local deflections and core stresses of foam cored composite sandwich structures subjected to simultaneous localized mechanical loading and elevated temperatures. Thus, the analytical model can be used as a preliminary design tool to determine the critical core crushing load at elevated temperatures.

Local Oceanic Vertical Deflection Determination with Gravity Data Along a Profile

ABSTRACTDeflections of the vertical (DOVs) over oceans cannot be directly measured, which restricts their applications. A local covariance function of anomalous potential is put forward in this paper in conjunction with the least-squares collocation (LSC) method to compute the oceanic DOVs utilization of oceanic gravity data along a profile. The covariance functions of gravity field quantities have been derived directly as functions of x, y and z without the need to introduce coordinate transformations corresponding to along- or cross-profile components. In the proposed methodology, gravity data along a profile were used to calculate the residual gravity anomaly using the remove-compute-restore technique. The residual gravity anomaly was used to calculate the parameters of the proposed covariance function of the local anomalous gravity field, which was used in the LSC to compute the residual DOVs along the profile. The residual DOVs added model DOVs to recover the DOVs along the profile. The results of a simulation experiment prove that the proposed methodology is feasible and effective.

Initiation and propagation of fatigue cracks in cold-drawn pearlitic steel wires

In this paper the important role of manufacturing by progressive cold drawing on initiation and propagation of fatigue cracks in cold-drawn pearlitic steel wires is addressed by analyzing the initiation (from surface defects) and propagation of fatigue cracks in two pearlitic steels with very different cold drawing degree or cumulative plastic strain (and the subsequent very distinct microstructural arrangement): a hot rolled pearlitic steel bar and a commercial high-strength cold-drawn prestressing steel wire to be used asa component of prestressed concrete in structural engineering. Experimental results show that the initiation of fatigue cracks in pearlitic steels takes place at the location of small surface defects, many of them in the form of localized damage in the area of material surface (in the case of hot rolled bar) or voids created by tearing during drawing due to the existence of particles near the wire surface (in the case of the cold drawn wire). In both materials, fatigue cracks are mostly transcollonial and tend to fracture pearlite (ferrite/cementite) lamellae, so that different micro-mechanisms of fatigue damage appear in the material such as non-uniform crack opening displacement, micro-discontinuities, branchings, bifurcations and frequent local deflections, all creating a sort of microstructural roughness in the fatigue crack path that is different in the hot rolled bar and in the cold drawn wire, thereby determining their distinct fatigue performance.

Space\u2013time analysis of gravitropism in etiolated Arabidopsis hypocotyls using bioluminescence imaging of the IAA19 promoter fusion with a destabilized luciferase reporter

Imaging analysis was carried out during the gravitropic response of etiolated Arabidopsis hypocotyls, using an IAA19 promoter fusion of destabilized luciferase as a probe. From the bright-field images we obtained the local deflection angle to the vertical, A, local curvature, C, and the partial derivative of C with respect to time, partial C/partial t. These were determined every 19.9 µm along the curvilinear length of the hypocotyl, at ~10 min intervals over a period of ~6 h after turning hypocotyls through 90° to the horizontal. Similarly from the luminescence images we measured the luminescence intensity of the convex and concave flanks of the hypocotyl as well as along the median of the hypocotyl, to determine differential expression of auxin-inducible IAA19. Comparison of these parameters as a function of time and curvilinear length shows that the gravitropic response is composed of three successive elements: the first and second curving responses and a decurving response (autostraightening). The maximum of the first curving response occurs when A is 76° along the entire length of the hypocotyl, suggesting that A is the sole determinant in this response; in contrast, the decurving response is a function of both A and C, as predicted by the newly-proposed graviproprioception model (Bastien et al., Proc Natl Acad Sci USA 110:755–760, 2013). Further, differential expression of IAA19, with higher expression in the convex flank, is observed at A = 44°, and follows the Sachs’ sine law. This also suggests that IAA19 is not involved in the first curving response. In summary, the gravitropic response of Arabidopsis hypocotyls consists of multiple elements that are each determined by separate principles.

О влиянии локальных прогибов на устойчивость и закритическое поведение композитных цилиндрических оболочек при внешнем давлении

О влиянии локальных прогибов на устойчивость и закритическое поведение композитных цилиндрических оболочек при внешнем давлении

Impact of Concrete Pavement Structural Response on Rolling Resistance and Vehicle Fuel Economy

Reduction in vehicle fuel consumption is one of the main benefits considered in technical and economic evaluations of road improvements. The study described in this paper investigated the increase in vehicle energy consumption caused by the structural response of a concrete pavement to a moving load. First, the day and night falling weight deflectometer deflection time histories were measured for three concrete sections; their mechanical characteristics were then backcalculated. Second, a finite element model (DYNASLAB) was used to determine the pavement structural response under moving load for all three sections under different wheel loading conditions (passenger car, SUV, and articulated truck), vehicle speeds, and temperatures. As the rolling wheels move forward, the local deflection basin caused by the delayed deformation of the subgrade and the rotation of the slab form a positive slope. The energy dissipated was calculated as the energy required for a rolling wheel to move uphill. Finally, the calorific values of gasoline and diesel were used to convert energy into fuel consumption excess. The maximum deflection-induced energy consumption is about 0.08% of the total consumption for articulated trucks, which is small compared with 1.9% for asphalt pavements at high temperatures and low speeds, as reported by other studies.

Approximate equations for the meshing stiffness and the load sharing ratio of spur gears including hertzian effects

In this paper, the meshing stiffness of spur gear pairs, considering both global tooth deflections and local contact deflections, is evaluated at any point of the path of contact and approximated by an analytical, simple function. With this function, the load sharing ratio is calculated and compared with previous results obtained from the hypothesis of minimum elastic potential energy (MEPE model), considering the tooth deflections, but neglecting the hertzian deflections. Critical bending and contact stresses from both models are also compared both for standard and high contact ratio spur gears.

Stability and Postcritical Behavior of Cylindrical Composite Shells with Local Imperfections Under External Pressure

An approach to solving the problem of the nonlinear deformation of orthotropic cylindrical shells is proposed. On the surface of the shell, there is a local deflection bounded by segments of the coordinate lines. The Timoshenko–Mindlin shell theory, the Byskov–Hatchinson asymptotic method, and the continuous continuation method for solving nonlinear algebraic equations are used. To determine the critical loads and deformation paths, it is necessary to estimate the number of interacting modes sufficient to achieve satisfactory accuracy. Examples of analyzing composite shells with an initial local deflection of positive or negative amplitude are given

Non-linear bending analysis of multi-layer orthotropic annular/circular graphene sheets embedded in elastic matrix in thermal environment based on non-local elasticity theory

In this paper, the large deflection of multi-layer orthotropic annular/circular graphene sheets is investigated based on the non-local elasticity theory. The plate is considered to be in thermal environment. The equilibrium equations are derived in terms of generalized displacements and rotations considering the FSDT non-local elasticity theory and the van der Waals interaction between the layers. In order to solve the governing equations, the differential quadrature method (DQM) which is an accurate numerical method and a new semi-analytical polynomial method (SAPM) are applied. By applying DQM or SAPM, the ODE's would be converted to non-linear algebraic equations. In continue, the Newton–Raphson iterative scheme is applied to solve the obtained non-linear algebraic equations. The results of DQM and SAPM are compared. Although, the SAPM's formulation is considerably simpler than DQM, however, the results of two methods are so close to each other. The results are validated with the other available researches. The effect of small scale parameter, temperature effects on non-local results, the value of van der Waals interaction between the layers for bi-layer and triple layers graphene sheet, different values of elastic foundation matrix and load for various small scale parameters, the comparison between local and non-local deflections and linear to non-linear analysis are investigated.

Effect of flexion on the propulsive performance of a flexible flapping wing

A numerical study was carried out to investigate the effect of chordwise flexion on the propulsive performance of a two-dimensional flexible flapping wing. The wing undergoes a prescribed sinusoidal heaving motion with a local deflection. A deformable overset grid dynamic mesh method was employed to implement the motion of the grid instantaneously. The effect of flexural pattern, flexural amplitude and flapping frequency in terms of Strouhal number are evaluated. Unsteady flow around the wing is computed using an in-house developed Unsteady Reynolds-Averaged Navier-Stokes (URANS) solver. The results show that the different flexural patterns will create different flow fields, and thus the thrust generation will be significantly varied. The thrust and propulsive efficiency do not increase monotonically with the flexure amplitude while a peak value is revealed. It is found that the wake vortices after the flapping motion assembly behave as a reverse von-Karman vortex street, which can principally create thrust. The thrust is found to increase with increasing Strouhal number. Propulsive efficiency is beneficial from the chordwise flexibility and peaks within the range of 0.2 < St < 0.4, which is evidenced by natural flyers.

On the Relationship Between Journal Misalignment and Web Deflection in Crankshafts

To characterize the severity of misaligned journal bearings, two independent parameters are needed: degree of misalignment and misalignment angle. These parameters are routinely used to predict the behavior of steadily loaded bearing. However, in the case of dynamically loaded bearings, the associated measurement of these parameters becomes much more complex. It is shown that the local crankshaft deflection can be obtained from the rigid body motion of the main journal with computed deflection angles. A model is developed which provides a relationship between the web deflection and crankshaft deflection. It enables one to conveniently characterize the severity of misalignment by measuring web deflection.