Bird strike simulation on sandwich composite structure of aircraft radome

A methodology for the numerical simulation of bird strike on a novel leading edge (LE) structure of a horizontal tail plane is presented. The innovative LE design is based on the ‘tensor skin’ concept, comprising one or more folded composite sub-laminates that unfold during the bird impact, thus providing high-energy absorption characteristics. The simulation technique is based on a non-linear dynamic finite element analysis and is performed in three steps. The first step deals with the development of suitable material damage models capable of representing the high-strain rate behaviour of the composite systems used in the LE structure. The second step deals with the development of a finite element modelling procedure for simulating the complex failure modes and unfolding mechanisms of quasi-static penetration of simple ‘tensor skin’ strips, which are representative of the complete LE composite structure. The third step deals with the numerical simulation of bird strike experiments on two novel aircraft LE designs. The influence on the numerical results of the critical modelling issues such as the mesh density of the highly impacted areas, the substitute bird flexibility as well as the material damage and contact interfaces parameters are discussed in detail. The numerical results are in good qualitative and quantitative agreement with the results of the experimental tests.

In this paper, by using the ANSYS/LS-DYNA nonlinear dynamic finite element analysis method. The numerical simulations for the integrity pile, and get the rules and characteristics of stress wave about complete pile. Verify the feasibility of the method of ANSYS/LS-DYNA nonlinear dynamic finite element analysis in the pile integrity detection applications. The research results can provide guidance for the pile integrity detection of different types. Then this paper simulated pile necking. And we get the patterns and characteristics of stress wave reflection about the necking pile, which show the method of ANSYS/LS-DYNA nonlinear dynamic finite element analysis can detect the type and location of pile foundation defect accurately.

This work presents a novel iterative approach for mesh partitioning optimization to promote the efficiency of parallel nonlinear dynamic finite element analysis with the direct substructure method, which involves static condensation of substructures' internal degrees of freedom. The proposed approach includes four major phases – initial partitioning, substructure workload prediction, element weights tuning, and partitioning results adjustment. The final three phases are performed iteratively until the workloads among the substructures are balanced reasonably. A substructure workload predictor that considers the sparsity and ordering of the substructure matrix is used in the proposed approach. Several numerical experiments conducted herein reveal that the proposed iterative mesh partitioning optimization often results in a superior workload balance among substructures and reduces the total elapsed time of the corresponding parallel nonlinear dynamic finite element analysis.

Analysis of Structural Second Order Effects on a Floating Concrete Platform for FOWT's

This paper deals with the assessment of adobe structures using non-linear dynamic Finite Element (FE) analysis. Numerical simulation of adobe masonry follows a continuum approach and is based on brittle fracture concepts that are expressed through a damaged plasticity constitutive law. The selection of appropriate modelling parameters is hereby discussed. Spatial FE models representing a traditional single-storey dwelling, before and after the implementation of certain strengthening interventions which modify the roof diaphragm configuration, are developed. The FE models are subjected to time history analyses using a real time accelerogram from a past earthquake. Comparisons among the structures’ seismic responses are made in terms of the predicted damage distribution, displacement capacity and overall lateral resistance. Useful conclusions regarding the effect that different roof diaphragm configurations may pose on the dynamic behavior of adobe structures are derived. Finally, critical issues that future research should address in order to enable the efficient computational analysis of earthen structures are identified.

The low and medium speed bird-strike impact damage of sandwich composite structure of drone radome during takeoff and landing is examined by numerical simulations, using nonlinear dynamic finite element analysis software LS-DYNA. For different impact velocities, the aircraft radome’s dynamic responses are obtained and the damage in composite panel is clearly demonstrated. The relations of impact energy, maximum impact force and the damage state are analyzed. The simulation results can provide some references for the aircraft radome design.

Nonlinear dynamic finite element analysis of vehicle impacts into road restraint systems

Parallel nonlinear dynamic finite element analysis of three-dimensional shell structures

Progressive collapse of a building can be triggered by damage to certain critical load-carrying elements immediately following a blast. The initial damage can be followed by a chain of events which progressively destabilize the building. The modelling of progressive collapse is very complex and must take into account the nature and extent of damage inflicted to the individual elements, the behaviour resulted from the damage and the structural interaction between the elements. Importantly, the chain of events to be modelled is dynamic in nature. This paper critically compares some analysis methods available for progressive collapse design from the very simple linear elastic static analysis to the most rigorous and time consuming nonlinear dynamic analysis which takes into accounts both the primary and secondary effects of the blast loading. Inelastic non-linear dynamic finite element analyses and computational fluid dynamics have been employed in the evaluation which revealed certain deficiencies with the simplified methods including the non-linear dynamic analysis method which does not take into account the direct impact of the blast loading.

This paper presents a mathematical model for the nonlinear dynamic analysis of aerial electric transmission lines subjected to conductor breakage. The model uses existing finite elements and validated numerical techniques available in most commercial programs capable of handling nonlinear dynamic analysis. ADINA is used in this study. In comparison with other models, the novel approach presented here focusses on the discretization of the conductors as well as the supporting structures, specially near the breakage point. Dynamic interactions between all the structural components are therefore considered and comparisons with simpler models emphasize the importance of these interactions, the effects of geometric nonlinearities present in the conductors and in the supporting structures, and the contribution of higher modes.The mathematical model is validated with 7 of 56 tests conducted on reduced-scale physical models, reported in work done for the American Electric Power Research Institute.The results of the present study are very encouraging for designers interested in validating their design criteria for longitudinal dynamic loads by use of existing nonlinear dynamic finite element analysis packages. Key words: Nonlinear dynamic analysis, electric transmission lines, conductor breakage simulation.

A new nonlinear finite element formulation is developed for the nonlinear dynamics of shell structures. Using a vectorial approach, the kinematics that can be used to describe very large displacements and large rotations are derived. Green strain measures and second Piola Kirchhoff stress measures are used in the determination of the total potential. A displacement-based eight-noded cylindrical shell element with a total of 36 degrees of freedom is developed. Several numerical examples are dynamically analyzed to observe the characteristics of large displacements and large rotations. A convergence study was carried out to establish the numerical accuracy of the model. The most efficient and accurate model was used. HE nonlinear vibration analysis of shells has been the focus of research for the past few years. Thin shells subjected to dynamic loads could encounter deflections of the order of the thick- ness of the shell. Dynamic response of thin shells also could lead to the phenomena of dynamic snapping or dynamic buckling. Be- cause these kinds of responses cannot be determined accurately using small displacement and small rotation theories, large defor- mation and large rotation theories are required. The complex nature of these theories requires solving numerous simultaneous, nonlin- ear, differential equations. Even with simplifying assumptions, these equations remain complex and extensive. As background, a few relevant past efforts are reviewed. Earlier work regarding the nonlinear vibrations for isotropic shell structures can be attributed to Carr, 1 Yeh,2 Clough and Wilson,3 Belytschko and Marchertas,4 and Belytschko and Tsay.5 These researchers used flat plate elements. Saigal and Yang6 developed a curved shell element for isotropic shells. For composite shell structures, Simitses7 provided an elegant analytical solution of thin laminated shells subjected to sudden loads. He ignored through-the-thickness shear effects and used Donnell-type kinematic relations. Raouf and Palazotto8'9 developed a perturbation procedure to derive a set of asymptotically consistent nonlinear equations of motion for an arbi- trary laminated composite cylindrical shell in cylindrical bending. They also neglected transverse shear effects. Simo and Tarnow10 de- veloped an energy and momentum conservating algorithm for shell analysis to analyze shells undergoing large rigid-body motions. Palazotto and Dennis11 presented the simplified large rotation (SLR) theory to analyze shells experiencing moderately large ro- tations. The SLR theory determines the equilibrium path of or- thotropic shells using a total Lagrangian approach and includes a parabolic transverse shear stress distribution. This approach cap- tures the appropriate kinematics through displacement polynomi- als. Green strain displacement relations are used, and all of the final displacement functions are carried into the expression for the total potential without making any attempt at separating the rigid- body movement. Using this approach, the features classically pre- sented for, including through-the-thickness shear (for example), can be exploited.12 Smith and Palazotto13 discussed eight higher-order shear theories to the nonlinear finite element analysis of compos- ite shells. They also used the Green-Lagrange strains and second Piola Kirchhoff stresses. These theories were successful for large displacements and moderately large rotations. A reason for the fail- ure of these theories in the modeling of large rotation can be at- tributed to the approximations used in the kinematics. Gummadi and Palazotto14 modified the kinematics incorporated in the SLR theory and successfully carried out the solutions to problems ex- hibiting the characteristics of very large displacements and rota- tions. In their work, a vectorial approach was followed to derive the appropriate kinematics that can capture the characteristics of large displacements and large rotations. Using appropriate assumptions, the kinematics for the SLR theory can be obtained as a special case. The large rotation kinematics was introduced through the use of sine and cosine functions. A 36-degree-of-freedom composite shell element was developed based on this theory. Based on the SLR theory, Tsai and Palazotto15 formulated a nonlinear dynamic finite element analysis procedure for composite cylindrical shells. In their work, a linear mass matrix was incorpo- rated along with the nonlinear stiffness matrix that was originally developed in SLR theory. This theory again has the same drawbacks as the SLR theory in terms of realizing the large displacements and large rotations. In the present paper, a theory that can capture the large displacement and large rotations is discussed. The present work is an extension of the authors' earlier work on large rotation theory for static analysis. A new mass matrix is generated using Hamilton equations. The mass matrix thus generated is a nonlin- ear mass matrix. A fi-M method15 is used to solve the nonlinear algebraic equations resulting from the finite element technique. Se- lected numerical examples are solved to determine the validity of the developed theory.

Inelastic behavior of large diameter extended pile shafts subjected to earthquake shaking and liquefaction-induced lateral spreading is investigated. A series of Nonlinear Dynamic Finite Element Analyses (NDA) are performed covering a range of soil, pile, and ground motion conditions. Results showed that combined effects of lateral spreading and inertia produce larger demands that cannot always be enveloped by designing the pile for each load case separately. The NDA results were used to develop an Equivalent Static Analysis (ESA) method.

The seismic design of extended pile shafts for the combined effects of dynamic shaking and liquefaction-induced lateral spreading is investigated using nonlinear dynamic finite element analyses (NDA). Results of NDA parameter studies are used to illustrate how inertia and lateral spreading loads combine during shaking. The NDA results are used to evaluate equivalent static analysis (ESA) methods. Implications for design practice are discussed.

Explicit nonlinear dynamic finite element analysis on homogeneous/heterogeneous parallel computing environment

Nuclear power plant components are designed to withstand reversed dynamic loading like earthquake loading. Such reversed dynamic loads may induce plastic deformation in nuclear power plant components like pipe elbows. Plastic deformation in nuclear power plant components is limited by equation (9) of ASME Boiler &Pressure Vessel Code, Section III, NB-3652. ASME B&PV Code was revised in the year 2000 to accommodate plastic ratcheting as a mode of failure instead of plastic collapse under reversed dynamic load. The modified Code contains B2′ index, which is given as 2/3 rd of B2 index for butt-welded elbows. In the earlier work [1] B2′ indices were determined for several elbows using quasi-static nonlinear finite element analysis. In the present work an attempt is made to determine the ratio B2/B2′ for elbows using plastic nonlinear dynamic finite element analysis. Elbows of different sizes were considered in the present study. For each elbow linear static, linear dynamic, plastic nonlinear static and plastic nonlinear transient dynamic analyses are carried out to determine B2′ index in terms of B2 index. Elastic-perfectly plastic material model is used for the elbows. Collapse loads are obtained under static and dynamic conditions. Load vs. deflection curves are obtained for elbows under linear static and nonlinear quasi-static analyses. Deflection vs. time-curves are obtained from linear dynamic and plastic nonlinear dynamic analyses. The ratio B2/B2′ is computed for elbows of different sizes. The computed stress indices are compared with the Code values.