Geometric Large Deformation Research Articles

Multi-Objective Shape Optimization Design for Liquefied Natural Gas Cryogenic Helical Corrugated Steel Pipe

Recently, the flexible cryogenic hose has been preferred as an alternative to exploit offshore liquefied natural gas (LNG), in which helical corrugated steel pipe is the crucial component with C-shaped corrugation. Parametric finite element models of the LNG cryogenic helical corrugated pipe are established using a three-dimensional shell element in this paper. Considering the nonlinearity of cryogenic material and large geometric structural deformation, mechanical behaviors are simulated under axial tension, bending, and internal pressure loads. In addition, design parameters are determined to optimize the shape of flexible cryogenic hose structures through sectional dimension analysis, and sensitivity analysis is performed with changing geometric parameters. A multi-objective optimization to minimize stiffness and stress is formulated under operation conditions. Full factorial experiment and radial basis function (RBF) neural network are applied to establish the approximated model for structure analysis. The set of Pareto optimal solutions and value range of parameters are obtained through nondominated sorting genetic algorithm II (NSGA-II) under manufacturing and stiffness constraints, thereby providing a feasible optimal approach for the structural design of LNG cryogenic corrugated hose.

Super-Elastic Behavior Analysis of Shape Memory Alloy Vascular Stent

NiTi shape memory alloy (SMA) vascular stent, with good bio-compatibility and super-elastic properties, has become an important medical device in clinical treatment of cardiovascular or cerebrovascular diseases. The free expansion of stent in vessel involves the mechanical behavior of geometric large deformation related to the structure of super-elastic. In this paper, the nonlinear mechanical model for the substructure of NiTi shape memory alloy vascular stent is established, and the displacement deformation equation is derived. The geometric non-linearity of the structure is proved. Furthermore, the geometric nonlinear mechanical model is verified by numerical method. The mechanical analysis model of NiTi shape memory alloy vascular stent is widely used in the field of tracheal stent and so on.

Experimental investigations and variability considerations on 3D interlock textile composites used in low velocity soft impact loading

This study investigates the performance of three-dimensional (3-D) woven interlock composite plates subjected to impact loading. Low velocity (lower than 10m·s−1) impacts with highly deformable rubber impactor are addressed. Response variability is investigated by conducting several impact tests in the same conditions. The effect of mass and velocity on damage tolerance is studied by varying the impact conditions. Force–time, displacement–time and force–displacement curves are first analyzed in such various impact conditions. Secondly, damage mechanisms are highlighted through microscopic observations. The large geometrical deformation of the rubber impactor during impact leads to a loading less localized than for a hard impactor which induces a wide spread damage distribution. Comments on the relations between damage states and mass–velocity conditions are proposed.

Nonlinear Response of Cantilever Beams Due to Large Geometric Deformations: Experimental Validation

Many structural elements, such as gas turbine fans, wind turbine blades, springboards among others are designed as slender elements. Since their dynamic behaviour can be modeled as cantilever beams, it is important to understand their nonlinear behaviour due to large deformations. In this way, this work presents the experimental validation of a simplified model of a cantilever beam. The model is formulated considering large geometric deformations and assuming a Galerkin approach. The model is validated experimentally, and it is found that there is a characteristic frequency related to the nonlinear terms. The data is analysed using time-frequency maps produced with the continuous wavelet transform.

Nonlinear vibration of fluid-conveying single-walled carbon nanotubes under harmonic excitation

In this paper, the nonlinear vibration of a single-walled carbon nanotube conveying fluid is investigated utilizing a multidimensional Lindstedt–Poincaré method. Considering the geometric large deformation of the single-walled carbon nanotube and external harmonic excitation force, based on nonlocal elastic theory and Euler–Bernoulli beam theory, the nonlinear vibration equation of a fluid-conveying single-walled carbon nanotube is established. Analyzing the equation through the multidimensional Lindstedt–Poincaré method, and from the solvability condition of the nonlinear vibration equation, the cubic algebraic equation which indicates the amplitude–frequency relation is obtained. Based on the root discriminant of the cubic equation, the first order primary response of the pinned–pinned carbon nanotube is discussed. The relations among internal resonance, the amplitude and frequency of the external excitation force are analyzed in detail. When the external excite force frequency is around the first mode natural frequency, the first mode primary resonance occurs. If simultaneously the first two modes natural frequency ratio is around 3, internal resonance occurs and the internal resonance region depends on the amplitude of external excitation force.

Nonlinear characteristics in fracture strength test of ultrathin silicon die

The precise evaluation of fracture strength of ultrathin (<50 μm thick) silicon chips/ribbons plays a critical role in design of deformability and lifetime of flexible/stretchable electronics. In its three-point bending test, however, the classical linear theory used to convert the experimental fracture load into fracture strength value fails to match the emerged geometrically nonlinear characteristics for such an ultrathin silicon die. Here, we consider the geometric large deformation and present its nonlinear solution to more reliably evaluate the fracture stress of ultrathin specimen by virtue of the obtained experimental fracture load. A quite good agreement on experiments shows that the nonlinear analytical predictions allow a more comprehensive understanding for the effects of the silicon samples’ thickness on the transformation from linear relation to nonlinearity. The comparisons indicate that the fracture strength values are lower from linear evaluations, and to this the corresponding correction factor is defined to enhance the estimate precision.

Nonlinear seismic analysis of reinforced concrete frames using the force analogy method

SUMMARYA method of nonlinear seismic analysis for RC framed structures considering full‐range factors, including stiffness and strength degradation, geometric nonlinearity, and structural member failure, is established based on the fundamental concept of the force analogy method. The strong material nonlinearity, large geometric deformation, and internal forces redistribution due to the member failure can be depicted by the proposed local plastic mechanisms, the rotation hinges at the member ends and the slide hinges assigned to the columns, of which the measurement relationships are moment versus plastic rotation and shear force versus shear plastic deformation, respectively. They are capable of evaluating the exact response of RC structures. Because only unchanging initial stiffness matrices are used through the whole computation process, the state‐space formulation was used for solving the equations of motion. The advantages of the force analogy method, such as high efficiency and stability, are still retained. The exactness of the proposed local plastic mechanisms is verified against a group of tests data, and the application of the proposed procedure is performed to an RC framed structure to simulate the full‐range nonlinear response by increasing the excitation step by step until failure of partial structural members appear. Copyright © 2014 John Wiley &amp; Sons, Ltd.

Nonlinear static analysis of a dual-track multi-span continuous cable car system

This paper presents a nonlinear static analysis of a dual-track, multi-span continuous cable system for cable cars and ski lifts. The end supports are assumed to be frictionless bull wheels and the intermediate supports are assumed to be frictionless pulley supports. As geometrical and contact nonlinearities are involved, a nonlinear finite element solver ABAQUS is adopted for the static analysis of the cable system. The interfaces between cables and frictionless supports are modelled by frictionless interaction in normal direction and “hard contact” that allows for separation after contact in the tangential direction. Load cases due to different arrangements of cable cars are considered in the nonlinear analysis of the cable system. The proposed method for analysis used herein should be useful for solving various engineering problems involving cables undergoing large geometrical deformation and contact nonlinearity.

A Nonlinear Numerical Simulation Method of Bionic-Robot-Fish Quick Start

Fishtail skeleton, muscles and nerves controlling body swinging were simulated using alloy sheet, giant magnetostrictive material (GMM) posted on this sheet and outside magnetic field in this study. Thus, the quick start of part natural fishes was simulated. The non-linear model related to large geometric deformation and non-linear damping was established after analysis and research. A recurrence formula is obtained using eigensolution, nonlinear dynamic equation and small parameter expansion method, and a numerical method for solving nonlinear problem is formed. The numerical analysis reveals the swimming mechanism of bionic robot fish, and the best start mode of this fish was designed. It also reveals the effect of material, geometric parameters, environmental factors, etc. on the starting of robot fish. The results show that there is an optimum frequency in the starting process of bionic robot fish. The optimum mode is a rapid transition from low order mode to high order mode, thus achieving the quick start of robot fish. These provide a theoretical basis and data support for designing the quick start of bionic robot fish. DOI : http://dx.doi.org/10.11591/telkomnika.v12i3.4430 Full Text: PDF

Finite element analysis of buried continuous pipeline subjected to fault motion

Pipeline generally extends over long distances traversing through wide variety of different soils, geological conditions and regions with different seismicity. Most analytical models developed in the past for pipeline fault crossing are of limited usage as models developed were useful only for strike slip fault. Incorporating the large geometric changes in analytical study is a tricky task; however pipeline subjected to the fault motion itself is a phenomenon of large geometric changes, especially when pipeline subjected to compression in addition to material deformation, it also undergoes local buckling with bending. With computational advancement in numerical modelling, pipes under compression can also be studied. In this paper, a 3D FE-based numerical model is suggested to carry out pipeline performance of buried pipeline subjected to fault motion including material non-linearity and large geometric deformations. A 3D FE programme is developed using MATLAB. Displacement controlled arc-length technique is implemented to solve the non-linear behaviour.

Elasto-Plastic Dynamic Responses Analysis of Double-Layer Spherical Lattice Shells under Multiple Earthquake Excitations

Based on the large geometric deformation and nonlinear of material theories, the seismic responses of a double-layer spherical lattice shells structure were studied. The results show that under multi-dimensional earthquake, the maximum displacement and axial stress, as well as plastic ratio of the structure will be obviously increased than those corresponding to the responses under single-dimensional earthquake. When long-period seismic wave was taken as the input wave, the responses of the structure were the maximum.

Numerical Simulation Analysis on Shear Bearing Capacity Experiments of Cold-Formed Steel Self-Drilling Screws Connection

Cold-formed steel self-drilling screws connection are imitated to carry out numerical simulation analysis, in which geometric large deformation, materials nonlinear and contact problem are taken into account. From the comparison of computer analysis with experimental results, it comes out that the finite element numerical simulation method is accurate and feasible.

FEM Analysis on Seismic Behavior of Hybrid Coupled Wall System with Steel Boundary Elements

A nonlinear 3D solid model of hybrid coupled wall system with steel boundary elements has been founded by using FEM software ABAQUS to study its hysteretic behavior under cyclic loading, which considering the geometric large deformation and materials nonlinearity. To verify the efficiency of the model, two specimens with various coupling ratios of 30% and 45% are analyzed, and the results of analysis are compared with test ones. As the bearing capacities of both agree well in different loading stages, so the FEM model has enough accuracy and could be used to study the seismic behavior of hybrid coupled wall system with steel boundary elements. In addition, the results show that this new system dissipates energy by shear deformation of steel beams along and plastic hinge deformation at the bottom of wall, so it has better seismic performance.

Double Non-Linear Mechanical Characteristics of Transmission Tower Structure Based on Model Amendment

Transmission tower, being of evident nonlinear characteristic, is a complex space structure. Linear theory is generally adopted in the process of designing, which results in a waste of resource and disaster. Starting from the problems exiting in the process of transmission tower designing, the space beam element is adopted in the thesis, which reduces material nonlinearity through the rod end of the plastic method, and the geometric large deformation problem is involved by considering the amendment of the element stiffness matrix. Arc-length method of iterative computation is adopted as the solution method. On the premise of clarifying the process of dual non-linear solution, this thesis combines specific project example through self-organizing the finite element programming to calculate displacement - load curve, and the results show that the transmission tower structural system possesses obvious nonlinear characteristics. The research lays a foundation for improving the accuracy of space truss structure and developing the large specific finite element software.

CFD-based optimization of hovering rotors using radial basis functions for shape parameterization and mesh deformation

Aerodynamic shape optimization of a helicopter rotor in hover is presented, using compressible CFD as the aerodynamic model. An efficient domain element shape parameterization method is used as the surface control and deformation method, and is linked to a radial basis function global interpolation, to provide direct transfer of domain element movements into deformations of the design surface and the CFD volume mesh, and so both the geometry control and volume mesh deformation problems are solved simultaneously. This method is independent of mesh type (structured or unstructured) or size, and optimization independence from the flow solver is achieved by obtaining sensitivity information for an advanced parallel gradient-based algorithm by finite-difference, resulting in a flexible method of ‘wrap-around’ optimization. This paper presents results of the method applied to hovering rotors using local and global design parameters, allowing a large geometric design space. Results are presented for two transonic tip Mach numbers, with minimum torque as the objective, and strict constraints applied on thrust, internal volume and root moments. This is believed to be the first free form design optimization of a rotor blade using compressible CFD as the aerodynamic model, and large geometric deformations are demonstrated, resulting in significant torque reductions, with off-design performance also improved.

The Finite Element Analysis of Effect Factor about the Shear Behavior of Cold-Formed Steel Composite Wall

This paper adopts the finite element method to study the shear resistance of the first floor cold-formed steel composite walls in six stories residential structures, plastic shell element is used, materials nonlinearity and geometric large deformation are considered. The screws connecting sheathing and frame are modeled through coupling methods. Analyzing the influence of factors such as stud spacing，Brace and rigid bracing's establishment，component wall thickness to the shear behavior of cold-formed steel composite wall， these dates can provide certain theory for the actual project.

Rubber Impact on 3D Textile Composites

A low velocity impact study of aircraft tire rubber on 3D textile-reinforced composite plates was performed experimentally and numerically. In contrast to regular unidirectional composite laminates, no delaminations occur in such a 3D textile composite. Yarn decohesions, matrix cracks and yarn ruptures have been identified as the major damage mechanisms under impact load. An increase in the number of 3D warp yarns is proposed to improve the impact damage resistance. The characteristic of a rubber impact is the high amount of elastic energy stored in the impactor during impact, which was more than 90% of the initial kinetic energy. This large geometrical deformation of the rubber during impact leads to a less localised loading of the target structure and poses great challenges for the numerical modelling. A hyperelastic Mooney-Rivlin constitutive law was used in Abaqus/Explicit based on a step-by-step validation with static rubber compression tests and low velocity impact tests on aluminium plates. Simulation models of the textile weave were developed on the meso- and macro-scale. The final correlation between impact simulation results on 3D textile-reinforced composite plates and impact test data was promising, highlighting the potential of such numerical simulation tools.

Adhesion of an Elastic Convex Shell onto a Rigid Plate

An elastic spherical shell is compressed between two parallel rigid plates and undergoes large geometrical deformation. The convex surface conforms and adheres to the plates. The shell profile and contact stresses under large deformation are obtained numerically using a finite difference method. A thermodynamic energy balance following the classical Johnson-Kendall-Roberts (JKR) model is established to construct the adhesion mechanics, such that the sum of potential energy of the external load, elastic energy stored in the elastic shell, and surface energy to create new surface is minimized. Interrelationship between applied load, approach distance, contact radius, and deformed profile, as well as the “pull-off” phenomenon, are derived. A comparison is made between this model and existing models for a solid sphere in the literature.

Analysis of cavitation problem of heated elastic composite ball

The cavitation problem of a composite ball under a uniform temperature is investigated, and the ball is composed of two elastic solid materials. The nonlinear mathematical model of the problem is established with the finite logarithmic strain measure for a large geometric deformation and by the Hooke law for elastic materials. The analytic solutions in a parametric form are derived for the thermal dilatation of the composite ball with a large elastic deformation. Solution curves are given to describe the variations of the critical temperature in the cavitation with the geometric and material parameters. The bifurcation curve is also given to reveal the cavity growth after void nucleation. The numerical results for a computational example indicate that the radius of the cavity will rapidly grow above the critical temperature, and the loop stress will become infinite when void nucleation. This means that the materials near the cavity will produce a plastic deformation leading to local failure and fracture if the material of the internal ball is elastoplastic. In addition, the cavitation of the composite ball appears at a low temperature if the elastic property of the material of the internal ball is nearly uncompressible.

Seismic Performance of Concrete-Filled Square Tubular Column and Reduced Steel Beam Joints

According to anti-seismic design principle of strong column and weak beam, and of strong joint and weak member, reduced beam section (RSB) is often used to shift away plastic hinge from end of beam to the weaken region of the beam. The non-linear finite element models are established for concrete-filled steel square tubular column and reduced steel beam with holes in flange or in flange and web, considering geometric large deformation and material nonlinear. Comparison is made on load-displacement curves, the stress distribution of reduced beams, the ultimate load-carrying capacity, the ductility, and the energy-dissipating ability between analysis results of different RBS joints and experimental results. It shows that the stiffness and ultimate load-carrying capacity of new RBS joints are close to traditional RBS joint, the plastic hinge in the new joints with reduced beam section can be moved to the reduced region, and the new joints display good ductility, energy-dissipating ability and seismic behavior.