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In this first paper of a three-paper sequence, we developed a standard work using the Lagrangian approach in LS-DYNA. The results were compared against experimental results. First, a simple one-dimensional beam centered impact problem was solved analytically to validate the results produced by LS-DYNA. For this case, the results were within 2.5% er...
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... Lagrangian method uses material coordinates (also known as Lagrangian coordinates) as the reference; these coordinates are generally denoted as X. The nodes of the Lagrangian mesh are associated to particles in the material under examination; therefore, each node of the mesh follows an individual particle in motion, this can be observed in Figure 1. This formulation is used mostly to describe solid materials. ...
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... contact type contains logic that allows the contact surface to be updated as the external elements are deleted. The deformation for this simulation and the force plot generated by LS-DYNA are shown in Figure 10. The maximum value of force obtained from the simulation was 0.114 MN (25628 lbf). ...
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... deformation was not as smooth as it was when using the *CONTACT ERODING NODES TO SURFACE. It can be seen in Figure 10 that at the final deformation, a considerable amount of the bird model actually penetrates the target. The main reason is that this contact type is suitable for metal stamping and not for rigid structures. ...
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... deformation of this simulation presented instability error. This error was similar to that observed in the simulation performed using *CONTACT FORMING NODES TO SURFACE, as shown in Figure 11. The force plot from this simulation was 0.0404 MN, resulting in a maximum force value same as in the previous simulation. ...
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... area was only an approximation to compute the maximum peak pressure. It was calculated measuring the diameter of the impact area as shown in Figure 13. The diameter was 41.18 mm therefore the approximated area was 1331.8 mm 2 . ...
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... using *MAT ELASTIC FLUID the approximate pressure was 9.15% higher to that value obtained by Barber et al. [6]. In addition, if we compare the force plots of the Lagrangian simulations using material elastic fluid, as shown in Figure 14, we observe that the highest value corresponds to the eroding contact type. The contact forming and nodes to surface have an error of 33.5% when compared with the experimental value of 40 from Barber et al. [6]. ...
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... variations in density and overall solid dimensions of the bird should not produce huge Moffat et al. [8] found that the maximum deflection in the leading edge was 1.05 in when a bird impacts the simulated tapered plate at 30°. The impact angle of the bird was 30° and was measured between the axis of the cylinder and the plane of the tapered plate as showed in Figure 15. Figure 16 shows the deformation of the tapered plate during the impact when the bird is modeled using *MAT ELASTIC FLUID. ...
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... impact angle of the bird was 30° and was measured between the axis of the cylinder and the plane of the tapered plate as showed in Figure 15. Figure 16 shows the deformation of the tapered plate during the impact when the bird is modeled using *MAT ELASTIC FLUID. As observed some elements are eliminated during calculations due to negative volumetric strains failure. ...
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... observed some elements are eliminated during calculations due to negative volumetric strains failure. Figure 18 shows the top view of the tapered plate leading edge deflection. ...
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... maximum deflection was found to be 1.19 in as seen in Figure 18. This deflection was measured using the tool of the LS-PREPOST to measure the change in coordinates using as point of reference the position of the corner of the plate which is constrained in translation and rotation in the x, y and z directions. ...
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... deflection was measured using the tool of the LS-PREPOST to measure the change in coordinates using as point of reference the position of the corner of the plate which is constrained in translation and rotation in the x, y and z directions. Also, Figure 18 shows the resultant force in the contact interface and the maximum value was 0.056 MN. Table 4 summarizes the results. ...
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... bird and plate properties were the same as the used in the 30° impact. Figure 19 shows the geometrical model for this case. Once again, results with *MAT NULL do not model the actual bird deformation as shown in Figure 20. ...
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In a bird strike, the bird undergoes large deformation like flows; while most part of the structure is in small deformation, the region near the impact point may experience large deformations, even fail. This paper develops a coupled shell-material point method (CSMPM) for bird strike simulation, in which the bird is modeled by the material point m...
Citations
... During the bird strike test, projectile at high velocity, behaves as a fluid and the impact force is diffused in a wide area of the target. According to the literature, several different modelling techniques can be used to simulate such phenomena: the Lagrangian [33], the Eulerian or their combination [34], named Arbitrary Lagrangian Eulerian (ALE), or the Smoothed Particle Hydrodynamics (SPH) [35]. The SPH technique is based on the Lagrangian method, but it is more affordable to simulate phenomena with large distortions. ...
Amongst the most critical in-service loads to be considered during the design phase to ensure the flight safety the bird strike event plays a key-role. Under this scenario, regulations pay particular attention on the wing leading edge component. In this paper, starting by a verified Finite Element (FE) modelling technique, herein discussed, a numerical tendency analysis on the leading edge of a new concept of Tiltrotor has been carried out to support its design and to have indications on the best thickness to strength ratio which is able to satisfy the crashworthiness requirements. Given the bird impact scenarios (impact locations and impact angles), different thicknesses of the metallic component have been investigated, to assess the potential weight saving hence preserving the safety of flight. The results show consistency between the investigated thicknesses and impact scenarios, giving indications for the subsequent phase of the wing design.
... Over the years, various research studies have been dedicated to this problem. Experiments can be found, for example, in References [3,4], while a multitude of numerical simulations have been presented in the years to extend/support complex experimental protocols (see References [5][6][7][8][9][10] and others). A common aspect of several aircraft-related studies was the evidence of severe vulnerability for mechanical aircraft components, but also for glass elements. ...
... Nowadays, commercial software packages offer various options for modeling the effect of bird collisions on structural components. Maximum effects can be, for example, predicted based on FE numerical approaches according to unpractical Lagrangian description of bird bodies, but such a method is often inaccurate for bird-strike applications and unpractical due to distortion phenomena [8,40]. The herein adopted SPH approach has the intrinsic meshless feature. ...
Differing from present structural design procedures, most of the existing glass windows and even historic components in traditional/old buildings are not specifically designed to resist possible accidental loads. Rather thin monolithic ordinary annealed glass panels can be found in vertical non-structural envelopes, where they are often arranged to cover large surfaces. As such, an accidental glass fracture could originate even from rather common and moderate impact events and result in severe risk for people, due to propagation of dangerous shards from these vulnerable and fragile building components. To assess potential risks and support possible mitigation strategies, the present study is focused on the bird-strike analysis of existing/historic linearly restrained non-structural glass windows, based on a parametric Smoothed-Particle Hydrodynamics (SPH)–Finite Element (FE) model. Starting from a 1 m–wide and 1.5 m–high configuration, the attention is first given to various influencing parameters, such as impactor features (mass, 0.35–1.81 kg; impact speed, 0–40 m/s; and, thus, impact energy) and the target window (glass thickness, 4–6 mm; impact point; and, thus, glass stiffness). Local and global effects due to parametric localized bird-strikes are discussed based on non-linear dynamic numerical analyses and in terms of expected deflections, tensile stress peaks, and damage extension/severity (i.e., D1 to D3 damage levels). Scale effects are also examined for a case-study historic envelope (≈7 m in total size, 5 mm in thickness), and one of its 2.58 m × 3.3 m large glass components. Furthermore, a simplified empirical approach based on analytical formulations and normalized charts is proposed for a preliminary vulnerability assessment of historic monolithic glass envelopes, including parameters to account for impactor features and glass panel size/thickness, based on vibration-frequency considerations.
... At the same time, however, careful attention must be paid for description and characterization of model components, as well as impactor features [2,3,29]. Actually, maximum effects can be predicted based on efficient analytical models [30], or numerical approaches according to (unpractical) Lagrangian description of birds [31], or to the meshless Smooth Particle Hydrodynamic (SPH) approach [32][33][34] or even to the mesh-dependent, fixed boundary Coupled Eulerian-Lagrangian (CEL) approach [35,36]. A promisingly efficient alternative approach to the classical CEL method is represented by the movable Eulerian domain option available in ABAQUS/Explicit [37], in which the Eulerian volume is not fixed in space but can move and allow a strong reduction in the mesh refinement. ...
Bird-strike analysis is of particular relevance for aircraft engineering applications, where major wing or fuselage components may suffer for possible collision during flying stage and result in serious structural damage. To this aim, the Federal Aviation Regulations requires dedicated bird-strike resistance assessment tests and certifications. In building applications, glass is also largely used for vertical and horizontal load-bearing components. In such a kind of structural design context, major attention is given to wind pressure, seismic loads, impact due to crowd and human body (i.e., to prevent falling out), or even explosions, and rather null consideration is posed for bird-strike analysis, due to their expected limited impact forces and effects on glass. This paper investigates such a topic giving evidence of the dynamic response of an existing glass facade built in 60 s as a part of a museum in Italy. The vulnerability analysis is carried out with computationally efficient Finite Element (FE) numerical models of consolidated use for bird-strike, based also on preliminary mechanical characterization from in-field geometrical inspection and Operational Modal Analysis (OMA) experiments. Local and global dynamic effects due to localized bird-strike on the examined glass facade are discussed based on parametric numerical analysis from Coupled Eulerian Lagrangian (CEL) method.
... A. A liquid column as the bird model. Material model MAT_NULL was examined for a comparison with a widely used model in form of a liquid column [11], [18]. The material model is combined with the Gruneisen equation of state. ...
... High-frequency vibrations generated by the strike superimpose on the strain curve in the area of the initial strike. 18 3. The average density of the plucked bird, as measured by water displacement, is 950 kg/m 3 , which is close to the published experimental results. This density is reliable for computations of a bird strike. ...
This article presents an experimental and computational study of bird collision with a flexible plate at different impact speeds. Tests were carried out with the aid of a pneumatic gun. The bird mass in the study was about 300 g, and the speed range was 49-75 m/s. The actual mechanical properties of the plate were determined with tensile tests of flat specimen-witness. A video recording and strain gauging were performed during the strike. Some frames of high speed video recording for the highest bird’s velocity c = 75 m/s are presented in the article to demonstrate the process of bird rupturing. Different models of the bird material were examined to compare computational and measured strains.
... Among the extensive literature research, different works focusing on the bird impact behavior on the windshield [6,7], wing flap [8] and leading edge [9-11]; these results made it possible to implement different material configurations, such as composite incorporated with shape memory alloy material [12,13] or laminated material [14,15], by evaluating the behavior of the dynamic impact even at full scale [16], and in an attempt to improve components crashworthiness with respect to mass saving [17]. Moreover, several investigations were carried out by varying the characteristics of the volatile mass by using different projectile formulations, as smooth particle hydrodynamic (SPH) [18,19] and Lagrangian [20][21][22]. ...
This paper aims to investigate the crashworthiness capability of a commercial aircraft metallic sandwich leading edge, subjected to bird strike events. A sensitivity analysis is presented, aimed to assess the influence of the skin parameters (inner and outer faces and core thicknesses) on the leading-edge crashworthiness and to determine, among the configurations able to withstand a bird strike event, the best compromise in terms of weight and structural performances. In order to easily manage the design parameters and the output data, the ModeFrontier code was used in conjunction with the FE code Abaqus/Explicit. A dedicated python routine was developed to define a fully parametric simplified leading-edge model. To fulfill the aerodynamic requirements, the external surfaces were considered fixed during the sensitivity analysis, and, thus, only the internal leading edge’s components were modified to study their influence on the structural response. The total mass of the model, the maximum deformation and the energy dissipated due to material failure and the plastic deformations were monitored and used to compare and assess the behavior of each configuration.
... Although all formulations discussed require high computational power, SPH models are, relatively seen, computationally less expensive [21]. Goyal et al. [22][23][24] developed three different finite element models based on ALE, LM and SPH to compare the capabilities of the model, simulating bird strike. Liu et al. [25][26][27][28] established a series of finite element model, coupled with SPH, in addition to experimental work to design a tail leading edge subjected to bird strike. ...
The bird strike incident is a hazard that affects the structural integrity of the aircraft. Bird strikes cause a surge on the wing profile affecting the aerodynamic performances and flight safety of the aircraft. Flight authorities enforce the manufacturers to perform numerous tests before the aircraft are available in the aviation market. Numerical studies and bird strike simulations have become an essential part of aircraft components design to avoid frequent costly tests. The bird strike incidents have been widely studied by numerous researchers as numerically, although only a few considered the effect of bird strike deformation on flow and aerodynamic conditions of an aircraft component. Therefore, this paper aims to present a Computational Fluid Dynamics (CFD) analysis for the aerodynamic behavior of a damaged wing due to a bird strike. To obtain a deformed wing profile for the CFD analysis, the bird strike analysis is performed using Smoothed Particle Hydrodynamics (SPH) for the bird model. Then the deformed airfoil geometry is imported to the CFD solver to obtain the lift, drag, and moment coefficients. The drag coefficient of the deformed wing profile increases due to the pressure distribution disruption of the deformed airfoil. The lift coefficient is also affected by the bird strike but varies with changing angles of attack (AoA, α). Similarly, the deformed wing profile delivers an impaired coefficient of the moment for smaller angles of attack, reaching a negative value.
... During the bird strike test, the projectile behaves as a fluid, hence the bird can be modelled by using a highly deformable projectile adopting the Lagrangian, Eulerian or a combination of two continuum descriptions, to represent the deformation, as reported in Ref. [2,3]. A wise choice could be the combination between a meshless method as SPH technique, adopted to describe the projectile, and the finite element method to characterize the structure deformation, as reported in Ref. [4]. ...
The work aims to investigate the capability of a vertical tail leading edge to withstand bird strike and to provide general considerations on the improvement of such capability with respect to the mass saving and to the required structural performances by considering different material systems. The assessment of the numerical models was ensured by a double check, and therefore considering the two test cases, aimed to calibrate and validate the numerical models against experimental data, coming from literature: 1) bird strike on metallic flat square plate; 2) bird strike on wing leading-edge with the skin made in metallic sandwich structure (both the honeycomb core and the outer and inner face was in aluminum). Finally, the crashworthy design of several leading-edge configurations, modifying the material and thickness of the skins and the central core of the leading edge, without changing its external geometrical shape, was investigated by adopting the numerical procedures used for the validation test cases. Actually, unidirectional fiber-reinforced composite material systems were considered for the outer and inner face of the skins, while different materials were adopted for the core. A comparison among the developed configurations, in terms of requirement fulfillment, global deformation parameters and weight, was performed.
... The SPH method which is meshless and relatively new, was first developed by introducing variable nodal connectivity for hypervelocity impact simulations such as orbital debris impacting problems that result in large deformations and displacements [4]. Both SPH and Lagrangian method can be used with marginal error, less than 7%, for bird strike events [5]. However, Main drawback of SPH method is that the connectivity between particles has to be calculated repeatedly which increases computational time for analysis [6]. ...
... Again, researchers have used different velocities to analyze the bird impacts [17]. In our case, we have chosen the speed as 198 m/s which is recommended by [5] for bird strike event. In order to create oblique impacts, reference axes with 10 0 , 20 0 and 30 0 were created from the global axes of the model, Fig. 3(b). ...
In this current research paper, oblique impacts of bird strike on aircraft wing made of Composite Material and Aluminum Alloy are investigated. FE code Ansys Autodyn is adopted to perform bird strike events using Smoothed-Particle Hydrodynamics (SPH) Method. Orthotropic failure model is used to investigate the post-strike failure of composite wings. Based on the damaged models, it is found that, aluminum wing performs better than composite wing in terms of bird impacts.
... Different bird modeling techniques appeared in recent years having apparent effects on the results of simulations and experimental validation [11,12,13,14], which is essential to predict the damage caused by bird impact. ...
Bird strike is a major threat to both fixed and rotary wing aircraft, damaging the nose section, wings, or propulsion elements. It involves a complex material failure under dynamic, loads. The purpose of this work is to perform numerical predictions in the case of a horizontal tail plane, considering a number of span wise impact locations. Three types of water birds are considered, using a Lagrangian model, shaped as a rounded cylinder. A bilinear isotropic material with failure criterion is considered, in order to overcome the numerical problems typically related to the large displacements of Lagrangian models. Simulations help to locate the most damaged zones and are helpful for improving the structure design by changing the position and size of the structural members. The results are going to be correlated with accident records in order to better understand safety requirements.
... Smojver and Ivancevic 9 performed bird strike damage analysis of real aeronautical structures using ABAQUS/Explicit and the coupled Eulerian Lagrangian (CEL) approach. Goyal et al. [10][11][12] performed a bird striking on a flat plate based on the Lagrangian, smooth particles hydrodynamic (SPH), and arbitrary Lagrange Eulerian (ALE) approach respectively in LS-DYNA. Classical test data available in the literature and numerical models were used for basis of comparison. ...
In order to examine the potential of using the coupled smooth particles hydrodynamic (SPH) and finite element (FE) method to predict the dynamic responses of aircraft structures in bird strike events, experimental bird-strike tests on the sidewall structure of an aircraft nose are carried out and numerically simulated. The bird is modeled with SPH and described by the Murnaghan equation of state, while the structure is modeled with finite elements. A coupled SPH-FE method is developed to simulate the bird strike experiments and a numerical model is established using a commercial software PAM-CRASH. The bird model shows no signs of instability and correctly modeled the break-up of the bird into particles. Finally the dynamic response such as strains in the skin is simulated and compared with experimental results, and the simulated deformation and fracture process of the sidewall structure is compared with images recorded by a high speed camera. Good agreement between the simulation resuls and experimental data indicates that the coupled SPH-FE method can provide a very powerful tool in predicting the dynamic responses of aircraft structures in events of bird strike.
