Stress Analysis of Smart Beam Energy Harvesters

In this paper, we study fully coupled electromagnetic-elastic behaviors present in the structures of smart beams using variational asymptotic beam sections and geometrically exact fully intrinsic beam equations combined in a consistent theory. We present results for smart beams under various oscillatory loads in both the axial and transverse directions and calculate the corresponding deformations. Recovery equations are employed to construct the full 3D stress and strain components in order to complete a full stress / strain analysis. Smart materials change mechanical energy to electrical energy; therefore, changing the structural dynamic behavior of the structure and its stiffness matrix.

Refinement and Scaling Effects on Peridynamic Numerical Solutions

One of the most common methods to implement peridynamics numerically is based on the discretization of the whole body by means of a structured and regular grid of nodes and a constant horizon size. That leads to an inefficient use of computational resources as well as to the impossibility to explore the multi-scale capabilities of peridynamics within a unique framework. Adaptive grid refinement and scaling seem to be a promising strategy to reduce those limitations, allowing to increase the resolution of the analysis and to reach the interested length-scale only in the desired regions. The application of such an approach in the peridynamic solutions requires certainly to be investigated, in particular, this is done by the comparison of numerical peridynamic solutions with the analytical solutions of classic linear elasticity theory.

Dynamic Characterization and Modeling of Carbon Composite Ballistic Behavior

Design of the new generation of aircraft is driven by the vastly increased cost of fuel and the resultant imperative for greater fuel efficiency. Carbon fiber composites have been used in aircraft structures to lower weight due to their superior stiffness and strength-to-weight properties. However, carbon composite material behavior under dynamic ballistic and blast loading conditions is relatively unknown. For aviation safety consideration, a computational constitutive model has been used to characterize the progressive failure behavior of carbon laminated composite plates subjected to ballistic impact conditions. Using a meso-mechanics approach, a laminated composite is represented by a collection of selected numbers of representative unidirectional layers with proper layup configurations. The damage progression in a unidirectional layer is assumed to be governed by the strain-rate dependent layer progressive failure model using the continuum damage mechanics approach. The composite failure model has been successfully implemented within LS-DYNA as a user-defined material subroutine. In this paper, the ballistic limit velocity (V50) was established for a series of laminates by ballistic impact testing. Correlation of the predicted and measured V50 values has been conducted to validate the accuracy of the ballistic modeling approach for the selected carbon composite material. The availability of this modeling tool will greatly facilitate the development of carbon composite structures with enhanced ballistic and blast survivability.

Effect of Axial Sweep and Tip Extension on Performance of an Axial Fan

Performance enhancement in terms of stall margin increment, increased pressure rise coefficient and increased efficiency is of great need for low speed axial fans. Stacking line modifications in terms of sweep, skew, dihedral or combination of these, as well as blade tip geometry modifications are assumed to be one of the ways to achieve finite performance improvement. Non radial stacking of blade profiles modifies secondary flows, tip vortex effects, hub passage vortex and thus affects aerodynamic performance parameters such as stall margin, efficiency, pressure rise, blade loading. In literature many studies have confined to comparison of few cases which led to conflicting results as modification of stacking line may have different effects in different cases. In the present work, comparison of performance of axial fan rotor with three different blade configurations BSL (baseline), SWP (swept blade) and EXTN (swept blade with extended tip) are considered. The BSL configuration is designed on basis of non-free vortex design. The SWP configuration is obtained by shifting radial stacking line of the BSL in axial flow direction by 10° (Forward sweep). The EXTN configuration is obtained by extending tip profile on pressure surface as well as suction surface by 3% locally. Experiments have been conducted on these three configurations to study effects of these modifications on aerodynamic performance. The flow field has been surveyed using Kiel probe, Three hole pressure probe at many flow rates starting from fully open to fully closed. Unsteady flow analysis at exit of rotors of all configurations is carried out using fast response pressure probe. Experimental results show slight performance improvement in terms of increased stall margin, efficiency, as well as total pressure rise for SWP rotor as well as EXTN rotor compared to BSL rotor at low flow coefficients.

Method of Fundamental Solutions in Micromechanics of Random Structure Linear Elastic Composites

One considers a linear elastic composite material (CM, [1]), which consists of a homogeneous matrix containing the random set of heterogeneities. An operator form of the general integral equation (GIE, [2–6]) connecting the stress and strain fields in the point being considered and the surrounding points are obtained for the random fields of inclusions in the infinite media. The new GIE is presented in a general form of perturbations introduced by the heterogeneities and defined at the inclusion interface by the unknown fields of both the displacement and traction. The method of obtaining of the GIE is based on a centering procedure of subtraction from both sides of a new initial integral equation their statistical averages obtained without any auxiliary assumptions such as the effective field hypothesis (EFH), which is implicitly exploited in the known centering methods. One proves the absolute convergence of the proposed GIEs, and some particular cases, asymptotic representations, and simplifications of proposed GIEs are presented for the particular constitutive equations of linear thermoelasticity. In particular, we use a meshfree method [7] based on fundamental solutions basis functions for a transmission problem in linear elasticity. Numerical results were obtained for 2D CMs reinforced by noncanonical inclusions.

Numerical Computations of MHD Flow on Hypersonic and Re-Entry Vehicles

In hypersonic flight of reentry vehicles the radio blackout is a typical problem, in particular because it arises during a critical mission operation point. To mitigate this radio blackout the magnetic window concept is proposed. In this work a numerical model is presented to accurately simulate the effect of a magnetic field interacting with ionized plasma surrounding the vehicle. The numerical model is based on the MHD flow equations. Initially, the code is validated for pure hypersonic gas dynamics. Diverse high resolution spatial discretisation schemes, within a Finite Volume framework, are analyzed for robustness. Afterwards, the numerical code is further validated for MHD flows using the well-known Hartmann case. A very good comparison between numerical and analytical results is verified. This allows a proper validation of the method in terms of Lorentz force, in particular under low-magnetic Reynolds number conditions. A very tough test-case is finally computed, being typical of a reentry capsule geometry. The accuracy of the model is then verified for different applied magnetic fields.

Wind Tunnel Test of a Blended Wing Aircraft in Ground Effect With Active Flow Control

This paper describes the test methodology and results for a wind tunnel experiment featuring a blended wing aircraft in ground effect with built-in circulation control. A 82.55cm wingspan blended wing model was tested in a subsonic wind tunnel at velocities ranging from 18m/s – 49m/s and corresponding Reynolds numbers ranging from 130k – 350k. Pitch angle was held constant at 0 degrees and the height above the wind tunnel floor was modified to determine lift and drag modification due to ground effect. At a normalized height (y/bw) of 0.06, ground effect increased lift production by 24% and reduced drag by 22% when compared to a normalized height of 0.5. The addition of the circulation control significantly increased the lift production of the model at a cost of increased drag. At a normalized height of 0.031, the lift production increased by 200% at a blowing coefficient of 0.01, but the drag also increased by 72%, ultimately increasing L/D by 178%. Experimental results also suggest that ground effect and circulation control have a synergistic effect when used simultaneously. The effects of Reynolds number and circulation control slot height are also investigated.

Optimization on High Adhesive Ability of Lunar Rover Wheel Based on Discrete Element Method

The acquirement of lunar soil samples is the foundation to analyze and know about the composition of lunar soil and the lunar geologic structure. Because of the restrictions of the sampling method, the size of driller, the drilling pressure and the driller’s output power, the traditional digging method and vertical drilling method can only acquire the samples from lunar surface to 3 meters deep. In order to acquire the deeper samples based on the existing technique methods, a new exploration concept in which a driller fixed on the rover takes a horizontal drilling and sampling at the cross section of a crater after cleaning the surface chaotic soil was proposed in this paper. When drilling horizontally, the maximum drilling pressure is limited by the low adhesive ability between wheels and soil. For the purpose of making sure enough drilling pressure, study was carried out in this paper to improve the wheel’s adhesive ability by modifying the wheel’s surface. A wheel with a new kind of micro convex structures was proved to be more adhesive and stable during horizontal drilling by comparing with the existing wheel structures, such as wheel with thorns or discontinuous rims. The structural parameters of the convex structures may have significant influences on the adhesive ability. In order to study the effects of the convex structure’s parameters on wheel’s adhesive ability, the motion process of wheels on sandy road was simulated by using a DEM software EDEM. According to the simulation results, when the structural parameters of the convex structures are: flat-end shape, length/diameter = 5 and distribution density = 81/mm2, the wheel’s adhesive ability is much better than the wheel with other parameters based on a criterion which is the ratio of the tangential force to the normal force in the tangential motion process. Besides, the friction coefficient of wheels with convex structures is about 5 times as much as the friction coefficient of normal wheels, which proves that it is a useful method to improve wheel’s adhesive ability by modifying wheel’s surface with the convex structures.

A Component-Wise Approach to Analyse a Composite Launcher Structure Subjected to Loading Factor

The space structures are realized by combining skin and reinforced components, such as longitudinal reinforcements called stringers and transversal reinforcements called ribs. These reinforced structures allow two main design requirements to be satisfied, the former is the light weight and the latter is a high strength. Solid models (3D) are widely used in the Finite Element Method (FEM) to analyse space structures because they have a high accuracy, in contrast they also have a high number of degrees of freedoms (DOFs) and huge computational costs. For these reasons the one-dimensional models (1D) are gaining success as alternative to 3D models. Classical models, such as Euler-Bernoulli or Timoshenko beam theories, allow the computational cost to be reduced but they are limited by their assumptions. Different refined models have been proposed to overcome these limitations and to extend the use of 1D models to the analysis of complex geometries or advanced materials. In this work very complex space structures are analyzed using 1D model based on the Carrera Unified Formulation (CUF). The free-vibration analysis of isotropic and composite structures are shown. The effects of the loading factor on the natural frequencies of an outline of launcher similar to the Arian V have been investigated. The results highlight the capability of the present refined one-dimensional model to reduce the computational costs without reducing the accuracy of the analysis.

The Efficient Multi-Objective Optimization of Finite Element Analysis Model Using ModelCenter

The multi-objective optimization for a nested flying vehicle (NFV) of space science experiments is carried out aiming at the launch weight, frequency response and vacuum effect. The parametric model and finite element analysis are adopted to implement the structural analysis. The NFV is optimized to enhance the performance in the space environment where the lunch weight and structural strength are key constraints to concern about. The CAX software, analysis models and algorithms are integrated based on ModelCenter framework which makes modeling, analyzing and optimization more convenient and efficient. The optimizer of ModelCenter is chosen to optimize the structural performance of NFV, including the total mass, maximum deformation caused by vacuum environment and frequency response. As to validate the results, both weighting method with gradient optimization algorithm and Genetic Algorithm (GA) for multi-objective optimization are used. The optimization results of NFV verify the approaches proposed in this paper can improve the performance of NFV and apply to the finite element analysis model.