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1
Liu, S. Charles, and S. Jack Hu. "Sheet Metal Joint Configurations and Their Variation Characteristics." Journal of Manufacturing Science and Engineering 120, no. 2 (May 1, 1998): 461–67. http://dx.doi.org/10.1115/1.2830147.
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In sheet metal assembly, joints are designed to facilitate welding the parts. The three basic joints used in sheet metal assemblies are lap (slip) joints, butt joints, and butt-lap (corner) joints. Each joint configuration has its own variation characteristics. However, the currently available variation analysis methods, such as worst case analysis, root sum squares, etc., are not applicable to deformable sheet metal because they are based on rigid bodies. This paper analyzes the variation characteristics of simple assemblies constructed from the three basic joints, using Mechanistic Variation Simulation. Mechanistic Variation Simulation combines engineering structural models with statistical analysis in predicting deformable sheet metal assembly variation. Furthermore, the variation characteristics of the boxes constructed from the three basic joints are also evaluated. The developed models and analysis provide an improved understanding of sheet metal product design and process design.
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Chang, C. W., and A. A. Shabana. "Spatial Dynamics of Deformable Multibody Systems With Variable Kinematic Structure: Part 1—Dynamic Model." Journal of Mechanical Design 112, no. 2 (June 1, 1990): 153–59. http://dx.doi.org/10.1115/1.2912587.
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In this paper a method for the spatial kinematic and dynamic analysis of deformable multibody systems that are subject to topology changes is presented. A pieced interval analysis scheme that accounts for the change in the spatial system topology due to the changes in the connectivity between bodies is developed. Deformable bodies in the system are discretized using the finite element method and accordingly a finite set of deformation modes is employed to characterize the system vibration. Even though there are infinitely many arrangements for deformable body axes, computational difficulties may be encountered due to the use of a limited number of deformation modes. Therefore, the deformable body references have to be carefully selected, and accordingly as the system topology changes, new bases for the configuration space have to be identified. In order to guarantee a smooth transition from one configuration space to another, a set of spatial interface conditions or compatibility conditions that are formulated using a set of nonlinear algebraic equations are developed and solved in this paper. The solution of these equations uniquely define the spatial configuration of the deformable multibody system after the change in the system kinematic structure.
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Leal, Pedro BC, Marcelo A. Savi, and Darren J. Hartl. "Aero-structural optimization of shape memory alloy-based wing morphing via a class/shape transformation approach." Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 232, no. 15 (July 12, 2017): 2745–59. http://dx.doi.org/10.1177/0954410017716193.
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Because of the continuous variability of the ambient environment, all aircraft would benefit from an in situ optimized wing. This paper proposes a method for preliminary design of feasible morphing wing configurations that provide benefits under disparate flight conditions but are also each structurally attainable via localized active shape change operations. The controlled reconfiguration is accomplished in a novel manner through the use of shape memory alloy embedded skin components. To address this coupled optimization problem, multiple sub-optimizations are required. In this work, the optimized cruise and landing airfoil configurations are determined in addition to the shape memory alloy actuator configuration required to morph between the two. Thus, three chained optimization problems are addressed via a common genetic algorithm. Each analysis-driven optimization considers the effects of both the deformable structure and the aerodynamic loading experienced by the wing. Aerodynamic considerations are addressed via a two-dimensional panel method and each airfoil shape is generated by the so-called class/shape transformation methodology. It is shown that structurally and aerodynamically feasible morphing of a modern high-performance sailplane wing produces a 22% decrease in weight and significantly increases stall angle of attack and lift at the same landing velocity when compared to a baseline design that employs traditional control surfaces.
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Liu, S. C., S. J. Hu, and T. C. Woo. "Tolerance Analysis for Sheet Metal Assemblies." Journal of Mechanical Design 118, no. 1 (March 1, 1996): 62–67. http://dx.doi.org/10.1115/1.2826857.
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Traditional tolerance analyses such as the worst case methods and the statistical methods are applicable to rigid body assemblies. However, for flexible sheet metal assemblies, the traditional methods are not adequate: the components can deform, changing the dimensions during assembly. This paper evaluates the effects of deformation on component tolerances using linear mechanics. Two basic configurations, assembly in series and assembly in parallel, are investigated using analytical methods. Assembly sequences and multiple joints beyond the basic configurations are further examined using numerical methods (with finite element analysis). These findings constitute a new methodology for the tolerancing of deformable parts.
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Furman, B. J. "A New, Thermally Controlled, Non-Contact Rotor Balancing Method." Journal of Mechanical Design 116, no. 3 (September 1, 1994): 823–32. http://dx.doi.org/10.1115/1.2919456.
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Available alternative rotor balancing techniques applied to rotors manufactured in high volumes often have productivity limitations. A new method has been devised that allows a rotor to be balanced as it rotates, without physical contact. The method accomplishes balance correction by means of deformable torsion elements that permanently relocate discrete masses through local heating under the action of centrifugal forces. The method exploits the elevated temperature, time-dependent deformation behavior of metallic materials under stress to produce controlled incremental deformation through radiative pulse heating. The important aspects of the new method: the physical configuration of the deformable elements, the non-contact, local heating method, and the method of producing controlled incremental deformation of the mass relocation element have been modeled analytically and demonstrated experimentally.
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Manga, Michael, and H. A. Stone. "Buoyancy-driven interactions between two deformable viscous drops." Journal of Fluid Mechanics 256 (November 1993): 647–83. http://dx.doi.org/10.1017/s0022112093002915.
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Time-dependent interactions between two buoyancy-driven deformable drops are studied in the low Reynolds number flow limit for sufficiently large Bond numbers that the drops become significantly deformed. The first part of this paper considers the interaction and deformation of drops in axisymmetric configurations. Boundary integral calculations are presented for Bond numbers ℬ = Δρga2/σ in the range 0.25 ≤ ℬ < ∞ and viscosity ratios λ in the range 0.2 ≤ λ ≤ 20. Specifically, the case of a large drop following a smaller drop is considered, which typically leads to the smaller drop coating the larger drop for ℬ [Gt ] 1. Three distinct drainage modes of the thin film of fluid between the drops characterize axisymmetric two-drop interactions: (i) rapid drainage for which the thinnest region of the film is on the axis of symmetry, (ii) uniform drainage for which the film has a nearly constant thickness, and (iii) dimple formation. The initial mode of film drainage is always rapid drainage. As the separation distance decreases, film flow may change to uniform drainage and eventually to dimpled drainage. Moderate Bond numbers, typically ℬ = O(10) for λ = O(1), enhance dimple formation compared to either much larger or smaller Bond numbers. The numerical calculations also illustrate the extent to which lubrication theory and analytical solutions in bipolar coordinates (which assume spherical drop shapes) are applicable to deformable drops.The second part of this investigation considers the 'stability’ of axisymmetric drop configurations. Laboratory experiments and two-dimensional boundary integral simulations are used to study the interactions between two horizontally offset drops. For sufficiently deformable drops, alignment occurs so that the small drop may still coat the large drop, whereas for large enough drop viscosities or high enough interfacial tension, the small drop will be swept around the larger drop. If the large drop is sufficiently deformable, the small drop may then be ‘sucked’ into the larger drop as it is being swept around the larger drop. In order to explain the alignment process, the shape and translation velocities of widely separated, nearly spherical drops are calculated using the method of reflections and a perturbation analysis for the deformed shapes. The perturbation analysis demonstrates explicitly that drops will tend to be aligned for ℬ > O(d/a) where d is the separation distance between the drops.
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Ramirez-Alpizar, Ixchel G., Kensuke Harada, and Eiichi Yoshida. "A simple assembly planner for the insertion of ring-shaped deformable objects." Assembly Automation 38, no. 2 (April 3, 2018): 182–94. http://dx.doi.org/10.1108/aa-12-2016-181.
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Purpose The aim of this work is to develop a simple planner that is able to automatically plan the motion for a dual-arm manipulator that assembles a ring-shaped elastic object into a cylinder. Moreover, it is desirable to keep the amount of deformation as small as possible, because stretching the object can permanently change its size thus failing to perfectly fit in the cylindrical part and generating undesired gaps between the object and the cylinder. Design/methodology/approach The assembly task is divided in two parts: assembly task planning and assembly step planning. The first one computes key configurations of the robot’s end-effectors, and it is based on a simple heuristic method, whereas the latter computes the robot’s motion between key configurations using an optimization-based planner that includes a potential-energy-based cost function for minimizing the object’s deformation. Findings The optimization-based planner is shown to be effective for minimizing the deformation of the ring-shaped object. A simple heuristic approach is demonstrated to be valid for inserting deformable objects into a cylinder. Experimental results show that the object can be kept without deformation for the first part of the assembly task, thus reducing the time it is being stretched. Originality value A simple assembly planner for inserting ring-shaped deformable objects was developed and validated through several experiments. The proposed planner is able to insert ring-shaped objects without using any sensor (visual and/or force) feedback. The only feedback used is the position of the robot’s end-effectors, which is usually available for any robot.
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Ady, Bridget E., and Richard C. Whittaker. "Examining the influence of tectonic inheritance on the evolution of the North Atlantic using a palinspastic deformable plate reconstruction." Geological Society, London, Special Publications 470, no. 1 (March 19, 2018): 245–64. http://dx.doi.org/10.1144/sp470.9.
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AbstractTo accurately reconstruct plate configurations, there is a need for a quantitative method to calculate the amount and timing of crustal extension independent of any one model for the formation of rifted margins. This paper evaluates the suitability of the various plate modelling methods for structural inheritance studies and proposes a classification scheme for the methods that are currently in use. A palinspastic deformable margin plate kinematic model is most suitable for tectonic inheritance studies, particularly at hyperextended margins. This type of plate model provides a valuable analytical tool that can be used to show the temporal and spatial relationship between pre-existing orogenic structures, evolving rift axes and global plate reorganization events. We use a palinspastic deformable margin plate model for the southern North Atlantic and Labrador Sea to quantitatively restore up to 350 km of Mesozoic–Cenozoic extension. This provides us with a pre-rift restoration of the Proterozoic and Paleozoic terranes and structural lineaments on the conjugate margins that helps us to analyse their relationship to evolving rift axes and global plate reorganization events through time. Interpretation of these modelling results has led to a clearer understanding of the relationship between inherited structural features and their control on rifting and the break-up history.
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LI, WEIXIN, HAIJIE DONG, ZHENSHENG YUAN, and ZHENMAO CHEN. "NUMERICAL ANALYSIS OF ELECTROMAGNETO-MECHANICAL COUPLING USING LAGRANGIAN APPROACH AND ADAPTIVE TIME STEPPING METHOD." International Journal of Applied Mechanics 06, no. 05 (October 2014): 1450051. http://dx.doi.org/10.1142/s1758825114500513.
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Electromagneto-mechanical coupling effect associated with vibration induced eddy currents plays an important role in the evaluation and design of many magnetic devices, such as a tokamak. In this paper, a updated Lagrangian formulation for eddy current analysis of deformable bodies was presented through transformation from reference configuration to current configuration. A coupled analysis method based on Lagrangian meshes and Ar method was developed. A corresponding code was developed and verified by simulating Team Problem 16. The numerical method was further updated by introducing an adaptive time stepping procedure to improve its simulation efficiency.
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Min, Ling Kun, Zhi Zheng Wu, and Mei Liu. "Silver Liquid-Like Film Prepared by Self-Assembly for Magnetic Fluid Deformable Mirrors." Advanced Materials Research 1120-1121 (July 2015): 337–42. http://dx.doi.org/10.4028/www.scientific.net/amr.1120-1121.337.
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In this paper, a variety of methods to prepare nanometer thin films, such as LB film method, self-assembly method, vapor deposition method and oil-water two-phase interface deposition method, are first introduced and compared. Then the self-assembly method is used to prepare the silver liquid-like film for the magnetic fluid deformable mirror. The basic principle of configuration of the silver thin films is discussed and a large area of ordered and close-packed multilayer structures of encapsulated silver nanoparticles is fabricated. The results showed that the film has good reflectivity and stability.
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Kulikov, R. G., T. G. Kulikova, and Nikolai A. Trufanov. "Numerical Method for Solving the Problem of Thermomechanics of Polymeric Environment in Conditions of Phase Transition." Solid State Phenomena 243 (October 2015): 139–45. http://dx.doi.org/10.4028/www.scientific.net/ssp.243.139.
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A methodology and a numerical algorithm of solving boundary problems of mechanics of deformable crystallizing elastic polymer media have been developed. A class of problems describing processes taking place in polymer products during their manufacturing is considered. Due to the significance of shrinking deformations the problem is considered within finite deformations theory. Constitutive relations are built on base of Peng-Landel potential. A ‘weak’ variation problem statement based on Galerkin approach is used. The offered algorithm is based on linearization methodology when small deformations are applied to finite ones. Deformation process is considered as a sequence of transitions through intermediate configurations. This approach makes possible to bring the received solution to the sequence of linearized boundary problems for which effective numerical algorithms have been designed. Numerical procedure is based on the technology of finite element method. Increments of displacements on the considered time step are taken to be nodal unknowns. The offered algorithm is applied to solution of the problem concerning the polyethylene pipe deformation during its manufacturing. Main advantages of the proposed algorithm have been defined.
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Stanisławski, Jarosław. "Effectiveness of the Compound Helicopter Configuration in Rotorcraft Performance Increase." Transactions on Aerospace Research 2020, no. 4 (December 1, 2020): 81–106. http://dx.doi.org/10.2478/tar-2020-0023.
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Abstract The article presents the results of calculations applied to compare flight envelopes of varying helicopter configurations. Performance of conventional helicopter with the main and tail rotors, in the case of compound helicopter, can be improved by applying wings and pusher propellers which generate an additional lift and horizontal thrust. The simplified model of a helicopter structure, consisting of a stiff fuselage and the main rotor treated as a stiff disk, is applied for evaluation of the rotorcraft performance and the required range of control system deflections. The more detailed model of deformable main rotor blades, applying the Galerkin method, is used to calculate rotor loads and blade deformations in defined flight states. The calculations of simulated flight states are performed considering data of a hypothetical medium class helicopter with the take-off mass of 6,000kg. In the case of both of the helicopter configurations, the articulated main rotor hub is taken under consideration. According to the Galerkin method, the elastic blade model allows to compute blade deformations as a combination of the blade bending and torsional eigen modes. Introduction of additional wing and pusher propellers allows to increase the range of operational speed over 300 km/h. Results of the simulation are presented as time-runs of rotor loads and blade deformations and in a form of disk distribution plots of rotor parameters. The simulation method can be useful in defining requirements for a high speed rotorcraft.
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Zaidi, Lazher, Juan Antonio Corrales Ramon, Laurent Sabourin, Belhassen Chedli Bouzgarrou, and Youcef Mezouar. "Grasp Planning Pipeline for Robust Manipulation of 3D Deformable Objects with Industrial Robotic Hand + Arm Systems." Applied Sciences 10, no. 23 (December 6, 2020): 8736. http://dx.doi.org/10.3390/app10238736.
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In the grasping and manipulation of 3D deformable objects by robotic hands, the physical contact constraints between the fingers and the object have to be considered in order to validate the robustness of the task. Nevertheless, previous works rarely establish contact interaction models based on these constraints that enable the precise control of forces and deformations during the grasping process. This paper considers all steps of the grasping process of deformable objects in order to implement a complete grasp planning pipeline by computing the initial contact points (pregrasp strategy), and later, the contact forces and local deformations of the contact regions while the fingers close over the grasped object (grasp strategy). The deformable object behavior is modeled using a nonlinear isotropic mass-spring system, which is able to produce potential deformation. By combining both models (the contact interaction and the object deformation) in a simulation process, a new grasp planning method is proposed in order to guarantee the stability of the 3D grasped deformable object. Experimental grasping experiments of several 3D deformable objects with a Barrett hand (3-fingered) and a 6-DOF industrial robotic arm are executed. Not only will the final stable grasp configuration of the hand + object system be obtained, but an arm + hand approaching strategy (pregrasp) will also be computed.
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Du, Hongwang, Wei Xiong, Haitao Wang, and Zuwen Wang. "Physical deformation configuration of a spatial clamped cable based on Kirchhoff rods." Assembly Automation 38, no. 1 (February 5, 2018): 26–33. http://dx.doi.org/10.1108/aa-08-2016-098.
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Purpose In this study, a modeling method for a clamped deformable cable simulation based on Kirchhoff theory is proposed. This methodology can be used to describe the physical deformation configuration of any constrained flexible cable in a computer-aided design/manufacturing system. The modeling method, solution algorithm, simulation and experimental results are presented to prove the feasibility of the proposed methodology. The paper aims to discuss these issues. Design/methodology/approach First, Kirchhoff equations for deformable cables are proposed based on the nonlinear mechanics of thin elastic rods, and the general solution of the equations described by the Euler angles is given in the arc coordinate system. The parametric form solution of the Kirchhoff equations, which is easy to use, is then obtained in a cylindrical coordinate form based on Saint Venant’s theory. Finally, mathematical expressions that reflect the clamped cable configuration are given, and the deformable process is simulated based on an open source geometry kernel and is then tested by a 3D laser scanning technology. Findings The method presented in this paper can be adapted to any boundary condition for constrained cables as long as the external force and torque are known. The experimental results indicate that both the model and algorithm are efficient and accurate. Research limitations/implications A more comprehensive study must be executed for the physical simulation of more complicated constrained cables, such as the helical spring and asymmetric constraint. The influence of the material properties of the cable on the calculation efficiency must be considered in future analysis. Originality/value The semi-analytical algorithm of the cable simulation in cylindrical coordinates is a novel topic and is more accurate and efficient than the common numerical solution.
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Teixeira, Marcílio Baltazar, Christianne de Lyra Nogueira, and Waldyr Lopes de Oliveira Filho. "Numerical simulation of hillside mine waste dump construction." Rem: Revista Escola de Minas 65, no. 4 (December 2012): 553–59. http://dx.doi.org/10.1590/s0370-44672012000400018.
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In activities involving disposal of mine waste in a dump, it is necessary to carry out a preliminary study of the mechanical behavior of both dump and the foundation materials. Due to the complexity of this problem, numerical techniques are essential for providing an approximate answer to the problem. Thus, the finite element method (FEM) was used to evaluate the stress-strain-strength behavior of a hillside waste dump built on a deformable foundation by the ascending method; the results of which are herein presented. The dump material is considered to be Morh-Coulomb nonlinear elastic perfectly plastic while the foundation material is considered to be linear elastic. The numerical simulation of mine waste dump construction is carried out by the "gravity turn on" technique and the dynamic mesh procedure. Different geometric configurations are analyzed and it is concluded that some requirements established by law should be reviewed and refined.
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Hernandez, Monica, Ubaldo Ramon-Julvez, and Daniel Sierra-Tome. "Partial Differential Equation-Constrained Diffeomorphic Registration from Sum of Squared Differences to Normalized Cross-Correlation, Normalized Gradient Fields, and Mutual Information: A Unifying Framework." Sensors 22, no. 10 (May 13, 2022): 3735. http://dx.doi.org/10.3390/s22103735.
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This work proposes a unifying framework for extending PDE-constrained Large Deformation Diffeomorphic Metric Mapping (PDE-LDDMM) with the sum of squared differences (SSD) to PDE-LDDMM with different image similarity metrics. We focused on the two best-performing variants of PDE-LDDMM with the spatial and band-limited parameterizations of diffeomorphisms. We derived the equations for gradient-descent and Gauss–Newton–Krylov (GNK) optimization with Normalized Cross-Correlation (NCC), its local version (lNCC), Normalized Gradient Fields (NGFs), and Mutual Information (MI). PDE-LDDMM with GNK was successfully implemented for NCC and lNCC, substantially improving the registration results of SSD. For these metrics, GNK optimization outperformed gradient-descent. However, for NGFs, GNK optimization was not able to overpass the performance of gradient-descent. For MI, GNK optimization involved the product of huge dense matrices, requesting an unaffordable memory load. The extensive evaluation reported the band-limited version of PDE-LDDMM based on the deformation state equation with NCC and lNCC image similarities among the best performing PDE-LDDMM methods. In comparison with benchmark deep learning-based methods, our proposal reached or surpassed the accuracy of the best-performing models. In NIREP16, several configurations of PDE-LDDMM outperformed ANTS-lNCC, the best benchmark method. Although NGFs and MI usually underperformed the other metrics in our evaluation, these metrics showed potentially competitive results in a multimodal deformable experiment. We believe that our proposed image similarity extension over PDE-LDDMM will promote the use of physically meaningful diffeomorphisms in a wide variety of clinical applications depending on deformable image registration.
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Bergel, Guy L., and Panayiotis Papadopoulos. "A finite element method for modeling surface growth and resorption of deformable solids." Computational Mechanics 68, no. 4 (July 5, 2021): 759–74. http://dx.doi.org/10.1007/s00466-021-02044-y.
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AbstractThis work explores a continuum-mechanical model for a body simultaneously undergoing finite deformation and surface growth/resorption. This is accomplished by defining the kinematics as well as the set of material points that constitute the domain of a physical body at a given time in terms of an evolving reference configuration. The implications of spatial and temporal discretization are discussed, and an extension of the Arbitrary Lagrangian–Eulerian finite element method is proposed to enforce the resulting balance laws on the grown/resorbed body in two spatial dimensions. Representative numerical examples are presented to highlight the predictive capabilities of the model and the numerical properties of the proposed solution method.
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Steffan, Kay-Eric, Michel Fett, Daniel Kurth, and Eckhard Kirchner. "IDENTIFICATION OF OPTIMIZATION AREAS OF A TRANSTIBIAL PROSTHESIS THROUGH THE POTENTIALS OF ADDITIVE MANUFACTURING PROCESSES." Proceedings of the Design Society 1 (July 27, 2021): 1807–16. http://dx.doi.org/10.1017/pds.2021.442.
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AbstractAdditive manufacturing enables new possibilities for the design of end products. These are rooted in the potentials of the manufacturing technology, such as flexible, tool-free production. These potentials can be used for the economic and flexible production of customized products. To support the use of the potentials, a development method was created which identifies optimization areas within a product. Therefore, the complexity is reduced by using of product functions. Characteristic functions and structural configurations are used to identify optimization areas. This contribution describes the application of the new development method to an existing mechanical transtibial prosthesis. In doing so optimization areas are identified which may make use of the potentials provided by additive manufacturing. One area is the interface between the prosthesis and the ground. By analyzing walking environments and the gait cycle the need for walking assistance on deformable surfaces was identified. Significant improvements were achieved through a functional integrated, additive manufactured foot sleeve.
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De Rosis, Alessandro. "Analysis of blood flow in deformable vessels via a lattice Boltzmann approach." International Journal of Modern Physics C 25, no. 04 (March 6, 2014): 1350107. http://dx.doi.org/10.1142/s0129183113501076.
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In this paper, the lattice Boltzmann (LB) method is used in order to simulate non-Newtonian blood flows in deformable vessels. Casson's rheological model is adopted and a local correction to the relaxation time is implemented in order to modify the viscosity. The hyperelastic, hardening and anisotropic behavior of a flexible arterial wall is discussed and a closed-form solution is used to predict the deformed configuration of the vessel. A partitioned staggered-explicit strategy to couple the LB method and such analytical prediction is proposed.
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Naghibzadeh, S. Kiana, Noel Walkington, and Kaushik Dayal. "Accretion and ablation in deformable solids with an Eulerian description: examples using the method of characteristics." Mathematics and Mechanics of Solids 27, no. 6 (November 18, 2021): 989–1010. http://dx.doi.org/10.1177/10812865211054573.
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Accretion and ablation, i.e., the addition and removal of mass at the surface, are important in a wide range of physical processes, including solidification, growth of biological tissues, environmental processes, and additive manufacturing. The description of accretion requires the addition of new continuum particles to the body, and is therefore challenging for standard continuum formulations for solids that require a reference configuration. Recent work has proposed an Eulerian approach to this problem, enabling side-stepping of the issue of constructing the reference configuration. However, this raises the complementary challenge of determining the stress response of the solid, which typically requires the deformation gradient that is not immediately available in the Eulerian formulation. To resolve this, the approach introduced the elastic deformation as an additional kinematic descriptor of the added material, and its evolution has been shown to be governed by a transport equation. In this work, the method of characteristics is applied to solve concrete simplified problems motivated by biomechanics and manufacturing. Specifically, (1) for a problem with both ablation and accretion in a fixed domain and (2) for a problem with a time-varying domain, the closed-form solution is obtained in the Eulerian framework using the method of characteristics without explicit construction of the reference configuration.
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Guo, Fei, Shoukun Wang, Binkai Yue, and Junzheng Wang. "A Deformable Configuration Planning Framework for a Parallel Wheel-Legged Robot Equipped with Lidar." Sensors 20, no. 19 (October 1, 2020): 5614. http://dx.doi.org/10.3390/s20195614.
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The wheel-legged hybrid robot (WLHR) is capable of adapting height and wheelbase configuration to traverse obstacles or rolling in confined space. Compared with legged and wheeled machines, it can be applied for more challenging mobile robotic exercises using the enhanced environment adapting performance. To make full use of the deformability and traversability of WHLR with parallel Stewart mechanism, this paper presents an optimization-driven planning framework for WHLR with parallel Stewart mechanism by abstracting the robot as a deformable bounding box. It will improve the obstacle negotiation ability of the high degree-of-freedoms robot, resulting in a shorter path through adjusting wheelbase of support polygon or trunk height instead of using a fixed configuration for wheeled robots. In the planning framework, we firstly proposed a pre-calculated signed distance field (SDF) mapping method based on point cloud data collected from a lidar sensor and a KD -tree-based point cloud fusion approach. Then, a covariant gradient optimization method is presented, which generates smooth, deformable-configuration, as well as collision-free trajectories in confined narrow spaces. Finally, with the user-defined driving velocity and position as motion inputs, obstacle-avoidancing actions including expanding or shrinking foothold polygon and lifting trunk were effectively testified in realistic conditions, demonstrating the practicability of our methodology. We analyzed the success rate of proposed framework in four different terrain scenarios through deforming configuration rather than bypassing obstacles.
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Matvienko, Oleg, Olga Daneyko, and Tatyana Kovalevskaya. "Mathematical modeling of plastic deformation of a tube from dispersion-hardened aluminum alloy." MATEC Web of Conferences 243 (2018): 00008. http://dx.doi.org/10.1051/matecconf/201824300008.
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The influence of the internal and external pressure subjected to the tube from dispersion-hardened aluminium alloy was investigated. The approach which combines methods of crystal plasticity and mechanics of deformable solid was used to explore the limits of elastic and plastic resistance. The mathematical model of plastic deformation includes balance equations for deformation defects with regard to the generation and annihilation of shear dislocations, vacancy and interstitial prismatic dislocation loops, and dislocations in dipole configurations of vacancy and interstitial types and also equilibrium equation, geometrical and physical relations between the deformations, displacements and stresses. It has been established that as the temperature increases, the limits of the elastic and plastic resistance decrease. Results of investigation demonstrate that the hardening the alloy by nanoparticles significantly improves the strength characteristics of the material.
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Hirwani, C. K., T. R. Mahapatra, S. K. Panda, S. S. Sahoo, V. K. Singh, and B. K. Patle. "Nonlinear Free Vibration Analysis of Laminated Carbon/Epoxy Curved Panels." Defence Science Journal 67, no. 2 (March 14, 2017): 207. http://dx.doi.org/10.14429/dsj.67.10072.
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Nonlinear frequency responses of the laminated carbon/epoxy composite curved shell panels have been investigated numerically and validated with in-house experimentation. The nonlinear responses have been computed numerically via customised computer code developed in MATLAB environment with the help of current mathematical model in conjunction with the direct iterative method. The mathematical model of the layered composite structure derived using various shear deformable kinematic models (two higher-order theories) in association with Green-Lagrange nonlinear strains. The current model includes all the nonlinear higher-order strain terms in the formulation to achieve generality. Further, the modal test has been conducted experimentally to evaluate the desired frequency values and are extracted via the transformed signals using fast Fourier transform technique. In addition, the results are computed using the simulation model developed in commercial finite element package (ANSYS) via batch input technique. Finally, numerical examples are solved for different geometrical configurations and discussed the effects of other design parameters (thickness ratio, curvature ratio and constraint condition) on the fundamental linear and nonlinear frequency responses in details.
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Christensen, A. P., and A. A. Shabana. "Exact Modeling of the Spatial Rigid Body Inertia Using the Finite Element Method." Journal of Vibration and Acoustics 120, no. 3 (July 1, 1998): 650–57. http://dx.doi.org/10.1115/1.2893879.
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In the classical finite element literature beams and plates are not considered as isoparametric elements since infinitesimal rotations are used as nodal coordinates. As a consequence, exact modeling of an arbitrary rigid body displacement cannot be obtained, and rigid body motion does not lead to zero strain. In order to circumvent this problem in flexible multibody simulations, an intermediate element coordinate system, which has an origin rigidly attached to the origin of the deformable body coordinate system and has axes which are parallel to the axes of the element coordinate system in the undeformed configuration was introduced. Using this intermediate element coordinate system and the fact that conventional beam and plate shape functions can describe an arbitrary rigid body translation, an exact modeling of the rigid body inertia can be obtained. The large rigid body translation and rotational displacements can be described using a set of reference coordinates that define the location of the origin and the orientation of the deformable body coordinate system. On the other hand, as demonstrated in this investigation, the incremental finite element formulations do not lead to exact modeling of the spatial rigid body mass moments and products of inertia when the structures move as rigid bodies, and such formulations do not lead to the correct rigid body equations of motion. The correct equations of motion, however, can be obtained if the coordinates are defined in terms of global slopes. Using this new definition of the element coordinates, an absolute nodal coordinate formulation that leads to a constant mass matrix for the element can be developed. Using this formulation, in which no infinitesimal or finite rotations are used as nodal coordinates, beam and plate elements can be treated as isoparametric elements.
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Ilyukhin, A. A., and D. V. Timoshenko. "Conformation Control of DNA Molecules by Means Geometric and Physical Parameters." Mekhatronika, Avtomatizatsiya, Upravlenie 20, no. 9 (September 5, 2019): 550–59. http://dx.doi.org/10.17587/mau.20.550-559.
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A conceptual approach to the problem of managing spatial configurations of DNA molecules is considered. The work is problematic in nature and is a synthesis of the authors’ research in the field of modeling the behavior and structure of DNA by the methods of the mechanics of a deformable solid. The subject of research in this paper is the question of the applicability of methods of control theory to a living object by the example of a DNA molecule. The paper considers both issues of controllability on examples of the influence of the parameters of a molecule on its configuration, and questions of observability and identification of parameters of a molecule, based on the visible configuration in the natural environment. A brief review of the authors’ results in terms of adaptation to the objects of research of existing and development of new mathematical models of deformable elastic objects with regard to their internal structure is given. The proposed approach is based on the concept of transition using known methods of molecular dynamics from a multi-element discrete medium to a continuum containing momentary stresses. To this end, in previous works, the authors obtained the dependence of the components of the strain tensors, force and moment stresses on various types of interatomic interaction potentials (LennardJones potential, Born-Meyer potential, etc.). The need to choose as the base model of a continuum containing momentary stresses is dictated by the peculiarities of the main object of study - nucleic acid molecules and biopolymers - which have several degrees of freedom of rotational motions. Also, as an example, we consider the case for which the reduction from the three-dimensional problem of the asymmetric theory of elasticity to a one-dimensional one was carried out by splitting the three-dimensional problem into a set of two-dimensional and one-dimensional problems. The kinematic parameters that are necessary to attract in order to obtain a closed system of equations of the one-dimensional moment theory of rods with the system of Kirchhoff’s differential equations are indicated. The remaining geometrical values are found from the relations defining them. The proposed approach is consistent with current trends in the field of molecular modeling in biophysics and physico-chemical biology, and it seems promising in solving the problems of controlling genetic and biochemical processes involving DNA.
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Kiss, Balázs, and András Szekrényes. "Fracture and mode mixity analysis of shear deformable composite beams." Archive of Applied Mechanics 89, no. 12 (September 17, 2019): 2485–506. http://dx.doi.org/10.1007/s00419-019-01591-4.
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Abstract To analyse delaminated composite beams with high accuracy under mixed-mode I/II fracture conditions first-, second-, third- and Reddy’s third-order shear deformable theories are discussed in this paper. The developed models are based on the concept of two equivalent single layers and the system of exact kinematic conditions. To deduce the equilibrium equations of the linearly elastic system, the principle of virtual work is utilised. As an example, a built-in configuration with different delamination position and external loads are investigated. The mechanical fields at the delamination tip are provided and compared to finite element results. To carry out the fracture mechanical investigation, the J-integral with zero-area path is introduced. Moreover, by taking the advantage of the J-integral, a partitioning method is proposed to determine the ratio of mode-I and mode-II in-plane fracture modes. Finally, in terms of the mode mixity, the results of the presented evaluation techniques are compared to numerical solutions and previously published models in the literature.
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WANG, DONGDONG, and YUE SUN. "A GALERKIN MESHFREE METHOD WITH STABILIZED CONFORMING NODAL INTEGRATION FOR GEOMETRICALLY NONLINEAR ANALYSIS OF SHEAR DEFORMABLE PLATES." International Journal of Computational Methods 08, no. 04 (November 20, 2011): 685–703. http://dx.doi.org/10.1142/s0219876211002769.
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A Galerkin meshfree approach formulated within the framework of stabilized conforming nodal integration (SCNI) is presented for geometrically nonlinear analysis of large deflection shear deformable plates. This method is based upon a Lagrangian curvature smoothing in which the smoothed curvature is constructed within a nodal representative domain on the initial configuration. It is shown that the Lagrangian smoothed nodal gradients of the meshfree shape function is capable of exactly representing arbitrary constant curvature fields in the discrete sense of nodal integration. The consistent linearization is performed on the weak form of large deflection plate in the context of the total Lagrangian description. Subsequently, the discrete incremental equations are obtained by the method of SCNI in which to relieve the locking as well as ensure the stability of the present scheme, the bending contribution is evaluated using the smoothed nodal gradients, while the membrane and shear contributions are computed with the direct nodal gradients. The effectiveness of the present method is thoroughly demonstrated through several numerical examples.
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Sadovsky, Alexander V., Pierre F. Baldi, and Frederic Y. M. Wan. "A Theoretical Study of the In Vivo Mechanical Properties of Angiosperm Roots: Constitutive Theories and Methods of Parameter Estimation." Journal of Engineering Materials and Technology 129, no. 3 (March 20, 2007): 483–87. http://dx.doi.org/10.1115/1.2744435.
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To investigate the constitutive relation of a plant tissue regarded as a deformable continuum, stress and strain must be determined experimentally for the same configurations. Such experiments are hindered by the inherent theoretical complexity of continuum mechanics, and by the technical difficulties of effecting external stress loads or body forces on the tissue without invasion, especially on a small scale. An understanding of appropriate mechanical problems and their solutions can help the experimentalist overcome these difficulties to a certain extent. Based on recent work on fiber-reinforced material, we formulate a constitutive theory for the root of different angiosperm species and suggest a set of loading conditions to determine the parameter values in a specific tissue sample. The loading conditions are formulated with a view toward experimental realization in vivo or with minimal invasion. For each loading condition, we formulate the corresponding mechanical problem and show how to obtain the values of the elastic parameters from known solutions. This framework can be used to analyze the interplay between mechanical and metabolic behavior in plants and to study the elastodynamics of plant tissues.
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Hadwin, Paul J., Mohsen Motie-Shirazi, Byron D. Erath, and Sean D. Peterson. "Bayesian Inference of Vocal Fold Material Properties from Glottal Area Waveforms Using a 2D Finite Element Model." Applied Sciences 9, no. 13 (July 6, 2019): 2735. http://dx.doi.org/10.3390/app9132735.
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Bayesian estimation has been previously demonstrated as a viable method for developing subject-specific vocal fold models from observations of the glottal area waveform. These prior efforts, however, have been restricted to lumped-element fitting models and synthetic observation data. The indirect relationship between the lumped-element parameters and physical tissue properties renders extracting the latter from the former difficult. Herein we propose a finite element fitting model, which treats the vocal folds as a viscoelastic deformable body comprised of three layers. Using the glottal area waveforms generated by self-oscillating silicone vocal folds we directly estimate the elastic moduli, density, and other material properties of the silicone folds using a Bayesian importance sampling approach. Estimated material properties agree with the “ground truth” experimental values to within 3 % for most parameters. By considering cases with varying subglottal pressure and medial compression we demonstrate that the finite element model coupled with Bayesian estimation is sufficiently sensitive to distinguish between experimental configurations. Additional information not available experimentally, namely, contact pressures, are extracted from the developed finite element models. The contact pressures are found to increase with medial compression and subglottal pressure, in agreement with expectation.
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Atkinson, Jeffrey D., D. Louis Collins, Gilles Bertrand, Terry M. Peters, G. Bruce Pike, and Abbas F. Sadikot. "Optimal location of thalamotomy lesions for tremor associated with Parkinson disease: a probabilistic analysis based on postoperative magnetic resonance imaging and an integrated digital atlas." Journal of Neurosurgery 96, no. 5 (May 2002): 854–66. http://dx.doi.org/10.3171/jns.2002.96.5.0854.
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Object. Renewed interest in stereotactic neurosurgery for movement disorders has led to numerous reports of clinical outcomes associated with different treatment strategies. Nevertheless, there is a paucity of autopsy and imaging data that can be used to describe the optimal size and location of lesions or the location of implantable stimulators. In this study the authors correlated the clinical efficacy of stereotactic thalamotomy for tremor with precise anatomical localization by using postoperative magnetic resonance (MR) imaging and an integrated deformable digital atlas of subcortical structures. Methods. Thirty-one lesions were created by stereotactic thalamotomy in 25 patients with tremor-dominant Parkinson disease. Lesion volume and configuration were evaluated by reviewing early postoperative MR images and were correlated with excellent, good, or fair tremor outcome categories. To allow valid comparisons of configurations of lesions with respect to cytoarchitectonic thalamic boundaries, the MR image obtained in each patient was nonlinearly deformed into a standardized MR imaging space, which included an integrated atlas of the basal ganglia and thalamus. The volume and precise location of lesions associated with different clinical outcomes were compared using nonparametric statistical methods. Probabilistic maps of lesions in each tremor outcome category were generated and compared. Statistically significant differences in lesion location between excellent and good, and excellent and fair outcome categories were demonstrated. On average, lesions associated with excellent outcomes involved thalamic areas located more posteriorly than sites affected by lesions in the other two outcome groups. Subtraction analysis revealed that lesions correlated with excellent outcomes necessarily involved the interface of the nucleus ventralis intermedius (Vim; also known as the ventral lateral posterior nucleus [VLp]) and the nucleus ventrocaudalis (Vc; also known as the ventral posterior [VP] nucleus). Differences in lesion volume among outcome groups did not achieve statistical significance. Conclusions. Anatomical evaluation of lesions within a standardized MR image—atlas integrated reference space is a useful method for determining optimal lesion localization. The results of an analysis of probabilistic maps indicates that optimal relief of tremor is associated with lesions involving the Vim (VLp) and the anterior Vc (VP).
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Fanel Dorel, Scheaua, Goanta Adrian Mihai, and Dragan Nicusor. "Review of Specific Performance Parameters of Vertical Wind Turbine Rotors Based on the SAVONIUS Type." Energies 14, no. 7 (April 1, 2021): 1962. http://dx.doi.org/10.3390/en14071962.
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Increasing energy demand and environmental regulations around the world provide an adequate framework for developing methods of obtaining energy from renewable sources. Wind force is a resource with a high potential through which green energy can be obtained with no negative impact on the environment. Different turbine typologies have been developed, which can convert the wind force into mechanical and electrical energy through turbine rotational motion. Starting from the classic vertical-axis SAVONIUS rotor model, other models have been designed, which, according to the numerical studies and experimental test results, show higher performance parameters in operation. Such models present specific rotor blade geometries to achieve better operational results in terms of shaft torque and generated power. There are multiple research results from numerical analysis on virtual models or experimental tests that use rotor models in different constructive configurations aiming to improve operation performance. These research activities are related to the rotor blade number, the aspect and overlap ratio values, the blade profile geometry modification, the use of end plates connected to the rotor blades, curtain mounting solutions for directing the air flow on the active blade alone, and rotor constructive variants with deformable blades during operation. Some of the results obtained from the mentioned research activities are shown in this review for special rotor configurations whose performance results in terms of torque or power values are compared to the classical SAVONIUS model.
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MOHRI, TETSUO. "SHORT RANGE ORDERING AND LOCAL DISPLACEMENT OF ALLOYS STUDIED BY CVM." International Journal of Computational Materials Science and Engineering 01, no. 02 (June 2012): 1250018. http://dx.doi.org/10.1142/s2047684112500182.
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Cluster Variation Method (CVM) is a powerful statistical mechanics means to investigate phase equilibria of an alloy. The advantageous feature of the CVM stems from the fact that wide range of atomic correlations which play an important role at the phase transition is efficiently incorporated into the free energy formula. Hence, configurational fluctuation can be systematically studied through the calculations of correlation functions in the real space and short range order diffuse intensity spectrum in the k-space. However, one of the deficiencies of the conventional CVM is the fact that local lattice distortion (local atomic displacement) is not correctly dealt with. In order to improve such shortcomings, Continuous Displacement Cluster Variation Method (CDCVM) has been developed. In the CDCVM, local lattice distortion is mapped onto the configurational freedom of a multi-component alloy on a rigid (uniformly deformable) lattice. With CDCVM, the applicability of CVM is enlarged and the calculations of diffuse intensity spectrum originating from local lattice distortion can be performed.
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Zhuang, Yongchen, Yamin Zheng, Shibing Lin, Deen Wang, Yifan Zhang, and Lei Huang. "Surface Shape Distortion Online Measurement Method for Compact Laser Cavities Based on Phase Measuring Deflectometry." Photonics 9, no. 3 (March 3, 2022): 151. http://dx.doi.org/10.3390/photonics9030151.
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Conventional phase measuring deflectometry (PMD) takes up a large measurement space and is not suitable for compact online measurement, as the liquid crystal display (LCD) has to be placed in parallel with the mirror under test. In this paper, a compact online phase measuring deflectometry (COPMD) with the LCD screen set perpendicular to the mirror under test is presented for surface shape distortion real-time measurement. The configuration of the COPMD in an enclosed laser cavity is proposed, and the principle of the method is theoretically derived by using the vector-form reflection law. Based on the analysis model, the fringe modulation regulation of the LCD is revealed, and the measurement errors caused by misalignments of the components are illustrated. The validity and flexibility of the COPMD method are verified in the experiment by using a single-actuator deformable mirror as the mirror under test and the PMD method as the comparison. The proposed COPMD method remarkably expands the application range of the conventional PMD method, as it could make efficient use of compact space and is applicable for real-time measurement in enclosed laser facilities and assembled laser systems.
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Soldatos, K. P. "Buckling of Shear Deformable Antisymmetric Angle-Ply Laminated Cylindrical Panels Under Axial Compression (Design Paper)." Journal of Pressure Vessel Technology 114, no. 3 (August 1, 1992): 353–57. http://dx.doi.org/10.1115/1.2929051.
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This paper deals with the buckling problem of antisymmetric angle-ply laminated circular cylindrical panels subjected to a uniform axial compression. Since a flat plate configuration occurs as a particular case of the cylindrical panel geometry (zero shallow angle parameter), the corresponding flat plate problem is studied as a particular case of the problem considered. The theoretical analysis is based on a nonlinear theory developed in a previous paper (Soldatos, 1992), which accounts for parabolically distributed transverse shear strains through the shell thickness. The linearized differential equations, governing the buckling behavior of a simply supported panel, are solved on the basis of Galerkin’s method. Comparisons of corresponding numerical results, based on both the refined shell theory employed and a classical Love-type shell theory, show the influence of transverse shear deformation on the buckling loads of such laminated composite panels.
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Su, S. Z., M. Z. Li, C. G. Liu, C. Q. Ji, R. Setchi, J. Larkiola, I. Panteleev, I. Stead, and R. Lopez. "Flexible Tooling System Using Reconfigurable Multi-Point Thermoforming Technology for Manufacturing Freeform Panels." Key Engineering Materials 504-506 (February 2012): 839–44. http://dx.doi.org/10.4028/www.scientific.net/kem.504-506.839.
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In this paper, authors present a highly flexible tooling system based on reconfigurable multi-point thermoforming (MPTF) methodology, which has been developed within an EU-granted FP7 project. The MPTF technology employs an actuated-punch matrix to dynamically configure a controllable tool working surface through digitally adjusting relative displacement of each punch in the matrix. Novel MPTF methods have been proposed through re-changing configurations of actuated-punch tooling system according to rapid thermoforming principles and relevant cladding applications. The tooling system includes an industrial-scale prototype of an MPTF tooling integrated with functional CAD/CAE/CAT software interfaces. The numerical simulation with an explicit FEM predicts the unexpected deformation defects of dimples and wrinkles regarding to discrete contact boundaries between punches and the sheet blank. Innovative techniques of variable blank-holder and deformable cushion have been implemented to suppress wrinkling and eliminate dimpling effectively. The tooling system has been successfully applied to manufacture complex double-curved panels, which are described as application examples. Compared with conventional fixed moulds, the flexible tooling offers robust, rapid and re-changeable means to make mould-less manufacturing large freeform panels.
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Morandini, Chiara, Daniele Malomo, and Andrea Penna. "Equivalent frame discretisation for URM façades with irregular opening layouts." Bulletin of Earthquake Engineering 20, no. 5 (January 22, 2022): 2589–618. http://dx.doi.org/10.1007/s10518-022-01315-0.
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AbstractResearchers and practitioners widely employ simplified Equivalent Frame Models (EFM) for reproducing the in-plane governed response of unreinforced brick masonry (URM) structures, as they typically represent an acceptable compromise between numerical accuracy and computational cost. However, when considering URM structural systems with irregular opening distribution, the definition of the effective height and length of deformable components (i.e. pier and spandrel elements) still represents an open challenge. In this work, the influence of irregular distribution of openings on the predicted lateral response of full-scale URM façades was investigated. To this end, several geometrical combinations characterised by various degrees of irregularity were considered and idealised according to commonly employed EF discretisation approaches. Then, after a preliminary calibration process against experimental tests on both individual piers and a full-scale building façade, EFM results were compared with micro-modelling predictions, carried out within the framework of the Applied Element Method and used as a benchmark. Although in specific irregular configurations using some discretisation approaches, macro and micro-models converge to similar results, non-negligible differences in terms of initial lateral stiffness, base-shear and damage distribution were observed with other EF schemes or opening layouts, thus indicating that a careful selection of appropriate criteria is indeed needed when performing in-plane analyses of URM systems with irregular opening distributions. Finally, building on inferred simulated data, potential solutions are given to overcome typical EF discretisation issues and better approximate micro-modelling outcomes.
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Manière, Charles, Elisa Torresani, and Eugene Olevsky. "Simultaneous Spark Plasma Sintering of Multiple Complex Shapes." Materials 12, no. 4 (February 13, 2019): 557. http://dx.doi.org/10.3390/ma12040557.
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This work addresses the two great challenges of the spark plasma sintering (SPS) process: The sintering of complex shapes and the simultaneous production of multiple parts. A new controllable interface method is employed to concurrently consolidate two nickel gear shapes by SPS. A graphite deformable sub-mold is specifically designed for the mutual densification of both complex parts in a unique 40 mm powder deformation space. An energy efficient SPS configuration is developed to allow the sintering of a large-scale powder assembly under electric current lower than 900 A. The stability of the developed process is studied by electro-thermal-mechanical (ETM) simulation. The ETM simulation reveals that homogeneous densification conditions can be attained by inserting an alumina powder at the sample/punches interfaces, enabling the energy efficient heating and the thermal confinement of the nickel powder. Finally, the feasibility of the fabrication of the two near net shape gears with a very homogeneous microstructure is demonstrated.
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Chiariello, Antonio, Salvatore Orlando, Pasquale Vitale, Mauro Linari, Raffaele Longobardi, and Luigi Di Palma. "Development of a Morphing Landing Gear Composite Door for High Speed Compound Rotorcraft." Aerospace 7, no. 7 (June 30, 2020): 88. http://dx.doi.org/10.3390/aerospace7070088.
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In the framework of fast rotorcraft, smoothness and flushness of external aerodynamic surfaces present challenges for high-speed conditions, where aerodynamics is the driver of helicopter performance. For AIRBUS-RACER helicopter the main landing gear trap doors are parts of the lower wing skins (in retracted configuration) affecting helicopter performance by minimizing the drag. Flushness requirements must not be in contrast with the functionally of the Landing gear system that must open and close the doors during the landing gear retraction-extension phases at moderately low velocity. To manage these goals, a novel design logic has been identified to support the trap doors development phase. The identified way to proceed needs of relevant numerical method and tool as well. This method is aimed at identifying the main landing gear composite compartment doors in pre-shaped configuration to match the smoothness and door-stopper engagements over each aerodynamic conditions. The authors propose a detailed non-linear Finite Element method, based on MSC Nastran (MSC Software, Newport Beach, US) SOL-400 solver in which the structure is modelled with deformable contact bodies in a multiple load step sequence, open door condition and pre-shaped, deformed under actuator pre-load, under flight load conditions. The method includes the entire pre-stressed field due to the preload and the actual door stiffness, considering the achieved large displacement to verify the most representative strain field during loads application. The paper defines a robust methodology to predict the deformation and ensure the most appropriate door “pre-bow” and pre-load, in order to achieve the desiderated structural shape that matches aerodynamic requirements. The main result is the identification of a pre-shaped doors configuration for the Airbus RACER Fast Rotorcraft.
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Zhao, Hang, Houfei Fang, Matthew J. Santer, Lan Lan, Yangqing Hou, Ke Wu, and Hengkun Jiang. "The Selection and Optimization of the Reconfigurable Shaped Reflector Structure Material." MATEC Web of Conferences 175 (2018): 01024. http://dx.doi.org/10.1051/matecconf/201817501024.
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The method of applying deformable 2-D lattice materials in design of the main structure of a reconfigurable shaped reflector is proposed in this paper. Hex-chiral NPR (Negative Poisson's Ratio) lattice, re-entrant NPR lattice and star ZPR (Zero Poisson's Ratio) lattice are investigated in forming the main structure of a reflector, according to the mechanical properties requirement. Finite element models of reflectors built by these three types of lattice materials are developed. An example of a reflector with reconfigurable shape, which is transformed from a standard paraboloid, is given. The curvature change of the deformed shape is calculated. Then, the region with the largest curvature changing rate is found and the configuration of such area is regenerated. Finally, the surface accuracy of the region with the largest curvature changing rate is evaluated for reflectors built by the three compared lattice materials. The simulation results show that the highest surface accuracy is obtained when applying the hex-chiral lattice to the design of the reconfigurable shaped reflector.
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Pal, Suman, and Debabrata Das. "A tangent stiffness–based approach to study free vibration of shear-deformable functionally graded material rotating beam through a geometrically non-linear analysis." Journal of Strain Analysis for Engineering Design 52, no. 5 (July 2017): 310–32. http://dx.doi.org/10.1177/0309324717714186.
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An improved mathematical model to study the free vibration behavior of rotating functionally graded material beam is presented, considering non-linearity up to second order for the normal and transverse shear strains. The study is carried out considering thermal loading due to uniform temperature rise and using temperature-dependent material properties. Power law variation is assumed for through-thickness symmetric functional gradation of ceramic–metal functionally graded beam. The effects of shear deformation and rotary inertia are considered in the frame-work of Timoshenko beam theory. First, the rotating beam configuration under time-invariant centrifugal loading and thermal loading is obtained through a geometrically non-linear analysis, employing minimum total potential energy principle. Then, the free vibration analysis of the deformed beam is performed using the tangent stiffness of the deformed beam configuration, and employing Hamilton’s principle. The Coriolis effect is considered in the free vibration problem, and the governing equations are transformed to the state-space to obtain the eigenvalue problem. The solution of the governing equations is obtained following Ritz method. The validation is performed with the available results, and also with finite element software ANSYS. The analysis is carried out for clamped-free beam and for clamped–clamped beam with immovably clamped ends. The results for the first two modes of chord-wise and flap-wise vibration in non-dimensional speed-frequency plane are presented for different functionally graded material compositions, material profile parameters, root offset parameters and operating temperatures.
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Payandeh, Shahram, John Dill, and Zhu Liang Cai. "On interacting with physics-based models of graphical objects." Robotica 22, no. 2 (March 2004): 223–30. http://dx.doi.org/10.1017/s0263574703005617.
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Enhancing graphical objects whose behaviors are governed by the laws of physics is an important requirement in modeling virtual physical environments. In such environments, the user can interact with graphical objects and is able to either feel the simulated reaction forces through a physical computer interface such as a force feedback mouse or through such interactions, objects behave in a natural way. One of the key requirements for such interaction is determination of the type of contact between the user controlled object and the objects representing the environment. This paper presents an approach for reconstructing the contact configuration between two objects. This is accomplished through usage of the time history of the motion of the approaching objects for inverse trajectory mapping of polygonal representation. In the case of deformable objects and through usage of mass-spring-damper system this paper also presents a special global filter that can map the local deformation of an object to the adjacent vertices of polygonal mesh. In addition to offering a fast computational framework, the proposed method also offers more realistic representation of the deformation. The results of this paper are shown through detailed examples and comparison analysis using different computational platforms.
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Cai, Yingfeng, Ze Liu, Hai Wang, Xiaobo Chen, and Long Chen. "Vehicle Detection by Fusing Part Model Learning and Semantic Scene Information for Complex Urban Surveillance." Sensors 18, no. 10 (October 17, 2018): 3505. http://dx.doi.org/10.3390/s18103505.
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Visual-based vehicle detection has been studied extensively, however there are great challenges in certain settings. To solve this problem, this paper proposes a probabilistic framework combining a scene model with a pattern recognition method for vehicle detection by a stationary camera. A semisupervised viewpoint inference method is proposed in which five viewpoints are defined. For a specific monitoring scene, the vehicle motion pattern corresponding to road structures is obtained by using trajectory clustering through an offline procedure. Then, the possible vehicle location and the probability distribution around the viewpoint in a fixed location are calculated. For each viewpoint, the vehicle model described by a deformable part model (DPM) and a conditional random field (CRF) is learned. Scores of root and parts and their spatial configuration generated by the DPM are used to learn the CRF model. The occlusion states of vehicles are defined based on the visibility of their parts and considered as latent variables in the CRF. In the online procedure, the output of the CRF, which is considered as an adjusted vehicle detection result compared with the DPM, is combined with the probability of the apparent viewpoint in a location to give the final vehicle detection result. Quantitative experiments under a variety of traffic conditions have been contrasted to test our method. The experimental results illustrate that our method performs well and is able to deal with various vehicle viewpoints and shapes effectively. In particular, our approach performs well in complex traffic conditions with vehicle occlusion.
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Loginov, Yuri, Nickolay Zagirov, and Evgeniy Ivanov. "Evaluation of the level of hardening of aluminum alloy chips intended for subsequent pressure treatment." Metal Working and Material Science 23, no. 1 (March 15, 2021): 45–55. http://dx.doi.org/10.17212/1994-6309-2021-23.1-45-55.
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Introduction. It is noted that the chip is an undesirable type of metal scrap, because it has a developed surface, which creates conditions for more intense interaction with the surrounding atmosphere. This creates conditions for oxidation and gas saturation, especially at elevated temperatures typical of remelting processes. Therefore, the process of chip utilizing is considered, bypassing the remelting stage. The aim of the work is to establish the level of work hardening of chips during the processing of aluminum alloys and to predict its effect on the subsequent processing process. Research methods: to assess the deformed state, the finite element method was applied, implemented in the RAPID-2D software package. The sequence of actions included the creation of the initial shape of the deformation region and the configuration of the tool. The mutual displacement of the tool and the deformable material is specified using the corresponding boundary conditions. The deformable medium is a viscous-plastic material with power-law hardening, the physical and mechanical properties correspond to an aluminum-magnesium alloy. Results and discussion: the solution obtained shows that the degree of shear deformation in the chips can reach a value of more than 2. In this case, a higher level of deformation is localized on the side of the convex part of the chip. The comparison of the solution with those obtained earlier by other authors is carried out and its similarity is shown. In the considered solution, the difference in the degree of work-hardening of the chips along its thickness is 36 %. A variant of the sequence of processing the workpiece first by cold deformation, and then by cutting is considered. The field of application of the results of the work is the development of methods for the processing of technogenic formations. Conclusions. During the cutting process, the plastic deformation of the chips reaches significant values. In this paper, the difference in the degree of shear deformation in the chip thickness is established, depending on the proximity of the cut layer to the surface of the cutting tool. It is proposed to take this difference into account at the subsequent stages of chip processing. The presence of the marked inhomogeneity of mechanical properties leads to consequences in the form of an inhomogeneous distribution of the temperature of the beginning of recrystallization during subsequent operations of heat treatment or hot deformation treatment. The principle of additivity of the degree of deformation obtained by the metal at the stage of plastic shaping of the workpiece and the shaping of the chip itself is introduced.
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Azizi, Arash, Charles C. Tremblay, Kévin Gagné, and Sylvain Martel. "Using the fringe field of a clinical MRI scanner enables robotic navigation of tethered instruments in deeper vascular regions." Science Robotics 4, no. 36 (November 27, 2019): eaax7342. http://dx.doi.org/10.1126/scirobotics.aax7342.
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Navigating tethered instruments through the vasculatures to reach deeper physiological locations presently inaccessible would extend the applicability of many medical interventions, including but not limited to local diagnostics, imaging, and therapies. Navigation through narrower vessels requires minimizing the diameter of the instrument, resulting in a decrease of its stiffness until steerability becomes unpractical, while pushing the instrument at the insertion site to counteract the friction forces from the vessel walls caused by the bending of the instrument. To reach beyond the limit of using a pushing force alone, we report a method relying on a complementary directional pulling force at the tip created by gradients resulting from the magnetic fringe field emanating outside a clinical magnetic resonance imaging (MRI) scanner. The pulling force resulting from gradients exceeding 2 tesla per meter in a space that supports human-scale interventions allows the use of smaller magnets, such as the deformable spring as described here, at the tip of the instrument. Directional forces are achieved by robotically positioning the patient at predetermined successive locations inside the fringe field, a method that we refer to as fringe field navigation (FFN). We show through in vitro and in vivo experiments that x-ray–guided FFN could navigate microguidewires through complex vasculatures well beyond the limit of manual procedures and existing magnetic platforms. Our approach facilitated miniaturization of the instrument by replacing the torque from a relatively weak magnetic field with a configuration designed to exploit the superconducting magnet-based directional forces available in clinical MRI rooms.
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Chekmarev, D. T., M. H. Abuziarov, and Cheng Wang. "ABOUT SMOOTH INTERPOLATION OF A TRIANGULATED SURFACE." Problems of strenght and plasticity 82, no. 2 (2020): 147–55. http://dx.doi.org/10.32326/1814-9146-2020-82-2-147-155.
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A method and algorithm for rebuilding a surface triangulation in three-dimensional space defined by an STL file is proposed. An initial surface in 3D space (STL file) is represented as a polyhedron composed of triangular faces. The method is based on the analytical representation of the surface as a piecewise polynomial function. This function is built on a polyhedral surface composed of triangles and satisfies the following requirements: 1) within one face, the function is an algebraic polynomial of the third degree; 2) the function is continuous on the entire surface and preserves the continuity of the first partial derivatives; 3) the surface determined by the function passes through the vertices of the initial triangulated surface. The restructuring of computational meshes is required in cases of distortion of the shape of cells when solving problems of mathematical physics using mesh methods (finite-difference, FEM, etc.). Cell distortion can be due to various reasons. These can be large distortions of moving Lagrangian meshes in the calculations in the current configuration, with instability of the hourglass type, with distortion of the faces of the interface between interacting gaseous, liquid and elastoplastic bodies. The rebuilding of the mesh reduces to solving the problem of constructing a smooth surface passing through the nodes of an existing triangulated surface or part of it. Later the nodes of the new mesh are placed on the constructed smooth surface with existing requirements for the size and shape of the cells. The construction of a smooth piecewise polynomial surface is based on the ideas of spline approximation and reduces to the building of a cubic polynomial on each triangular face, taking into account the smooth conjugation of polynomial pieces of the surface constructed on adjacent faces. The proposed method for rebuilding surface triangulation can be useful for calculating the motion of deformable bodies when solving problems of the dynamics of continuous media on immovable Euler grids.
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ESMAEELI, ASGHAR, and GRÉTAR TRYGGVASON. "Direct numerical simulations of bubbly flows. Part 1. Low Reynolds number arrays." Journal of Fluid Mechanics 377 (December 25, 1998): 313–45. http://dx.doi.org/10.1017/s0022112098003176.
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Direct numerical simulations of the motion of two- and three-dimensional buoyant bubbles in periodic domains are presented. The full Navier–Stokes equations are solved by a finite difference/front tracking method that allows a fully deformable interface between the bubbles and the ambient fluid and the inclusion of surface tension. The governing parameters are selected such that the average rise Reynolds number is O(1) and deformations of the bubbles are small. The rise velocity of a regular array of three-dimensional bubbles at different volume fractions agrees relatively well with the prediction of Sangani (1988) for Stokes flow. A regular array of two- and three-dimensional bubbles, however, is an unstable configuration and the breakup, and the subsequent bubble–bubble interactions take place by ‘drafting, kissing, and tumbling’. A comparison between a finite Reynolds number two-dimensional simulation with sixteen bubbles and a Stokes flow simulation shows that the finite Reynolds number array breaks up much faster. It is found that a freely evolving array of two-dimensional bubbles rises faster than a regular array and simulations with different numbers of two-dimensional bubbles (1–49) show that the rise velocity increases slowly with the size of the system. Computations of four and eight three-dimensional bubbles per period also show a slight increase in the average rise velocity compared to a regular array. The difference between two- and three-dimensional bubbles is discussed.
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Solona, Olena, Vladimir Kovbasa, and Igor Kupchuk. "THE CONTACT INTERACTION DYNAMICS OF THE WORKING TOOL OF THE MOLE PLOWSHARE WITH THE SOIL DURING FORMING PROSESS A CHANNEL FOR AN ANTI-FILTRATION SCREEN." Vibrations in engineering and technology, no. 2(97) (August 27, 2020): 81–89. http://dx.doi.org/10.37128/2306-8744-2020-2-9.
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Today's realities of agriculture are increasingly prompting the need for the introduction of technologies for subsoil irrigation, as a possible tool to obtain maximum efficiency indicators of agricultural activities of agricultural enterprises. At the same time, the large-scale introduction of intra-soil irrigation technologies at the enterprises of the agro-industrial complex is significantly complicated due to the poor practical and theoretical development of its methods, as well as the lack of extensive experimental verification of this method of irrigation. The development of many processes in the construction of irrigation and engineering structures requires substantiation of the geometric parameters and operating modes of the working bodies that are used to implement these processes. One of the working bodies that is used to form the cavity along which communication is stretched is a mole plow, which, depending on the expected working conditions, may have a different geometric configuration and size. The results of investigations of the interaction of the mole ploughshare with the soil in cavity formation for laying the anti-filtration screen are describe in this article. The authors propose to consider the soil in the form of an elastic-viscous model. By solving the contact problem of the interaction of a rigid body with a deformed medium, the stress components in the soil on the contact surface with the ploughshare are determined, and soil compaction is determined. The components of forces that appear on the surface of the ploughshare because of its interaction with the soil are determined depending on its geometric parameters and the mechanical properties of the soil. This solution is a general approach for the analytical solution of the class of problems of the contact interaction of a rigid body with a deformable medium possessing the properties of elasticity and viscosity.
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Muarat, Nurul Farhanah, Mohamed Hussein, Raja Ishak Raja Hamzah, Z. A. B. Ahmad, Maziah Mohamad, Mohd Zarhamdy Md Zain, and Norasikin Mat Isa. "Adjustable Acoustical Performance Based on Deformable Origamic Shapes: A Preliminary Experimental Investigation." Applied Mechanics and Materials 660 (October 2014): 526–30. http://dx.doi.org/10.4028/www.scientific.net/amm.660.526.
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This paper describes a preliminary investigation on the possible use of deformable origamic shapes as a technique to provide adjustable acoustical performance in multi-purpose hall. The term ‘deformable’ means that the origamic shape undergoes deformation which automatically resulted into the change of its geometrical configurations. The experimental investigation has been carried out on three types of origamic shapes with several geometrical configurations. The measurement tests were conducted in a reverberation room and in accordance to ISO 354:2003 Measurement of Sound Absorption Coefficients in a Reverberation Room. Findings from the preliminary investigation show good trends indicating that the origamic shapes have the capability of adjusting the sound absorption coefficients by varying their geometrical configurations. Following those results, future works with details investigation will be undertaken as to validate the preliminary results.
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Cheng, De, Yihong Gong, Jingjun Wang, and Nanning Zheng. "Balanced Mixture of Deformable Part Models With Automatic Part Configurations." IEEE Transactions on Circuits and Systems for Video Technology 27, no. 9 (September 2017): 1962–73. http://dx.doi.org/10.1109/tcsvt.2016.2564818.
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Ameduri, Salvatore, Ignazio Dimino, Antonio Concilio, Umberto Mercurio, and Lorenzo Pellone. "Specific Modeling Issues on an Adaptive Winglet Skeleton." Applied Sciences 11, no. 8 (April 15, 2021): 3565. http://dx.doi.org/10.3390/app11083565.
Full textAbstract:
Morphing aeronautical systems may be used for a number of aims, ranging from improving performance in specific flight conditions, to keeping the optimal efficiency over a certain parameters domain instead of confining it to a single point, extending the flight envelope, and so on. An almost trivial statement is that traditional skeleton architectures cannot be held as a structure modified from being rigid to deformable. That passage is not simple, as a structure that is able to be modified shall be designed and constructed to face those new requirements. What is not marginal, is that the new configurations can lead to some peculiar problems for both the morphing and the standard, supporting, elements. In their own nature, in fact, adaptive systems are designed to contain all the parts within the original geometry, without any “external adjoint”, such as nacelles or others. Stress and strain distribution may vary a lot with respect to usual structures and some particular modifications are required. Sometimes, it happens that the structural behavior does not match with the common experience and some specific adjustment shall be done to overcome the problem. What is reported in this paper is a study concerning the adaptation of the structural architecture, used to host a winglet morphing system, to make it accomplish the original requirements, i.e., allow the deformation values to be under the safety threshold. When facing that problem, an uncommon behavior of the finite element (FE) solver has been met: the safety factors appear to be tremendously dependent on the mesh size, so as to raise serious questions about the actual expected value, relevant for the most severe load conditions. On the other side, such singularities are more and more confined into single points (or single lines), as the mesh refines, so to evidence somehow the numerical effect behind those results. On the other side, standard engineering local methods to reduce the abovementioned strain peaks seem to work very well in re-distributing the stress and strain excesses to the whole system domain. The work does not intend to give an answer to the presented problem, being instead focused on describing its possible causes and its evident effects. Further work is necessary to detect the original source of such inconsistencies, and propose and test operative solutions. That will be the subject of the next steps of the ongoing research.