Explicit Dynamic Analysis of Bird Strike Simulations and Design Optimization of Composite Aircraft Structures

Transcription

1 Explicit Dynamic Analysis of Bird Strike Simulations and Design Optimization of Composite Aircraft Structures Manoj Susarla Jr Design Engineer Octants Engineering Innovations Dr no ,Ayyevari street, Gunupudi Bhimavaram India Chetan Deshmukh Founder Director Octants Engineering Innovations 1 st Floor, Chetan Chandana Building, Teachers Colony, Hastinapuram, Hyderabad , India chetan@octantsengineering.com Muthu Ganesan Rathinasamy Co-Founder Director Octants Engineering Innovations 1 st Floor Chetan Chandana building, Teachers Colony, Hastinapuram Hyderabad , India muthu@octantsengineering.com Abbreviations: FEA-Finite Element Analysis Keywords: Explicit Dynamic Analysis, RADIOSS, Optimization, Bird strike. Abstract The objective of this study is Composite materials are increasingly being used for aeronautic primary structures such as wing components or fuselage panels. The reliability of the bird model is validated by comparing the numerical result with experimental results of a real bird of similar mass impacting normally at an impact velocity of 80 m/s, 116 m/s, 170 m/s on to a flat rigid panel. Results are compared in terms of pressure profile, the modelling of the structure and the bird SPH model is done using CAD package. The focus of the current study is on the numerical modelling and simulation of high velocity impact loads from soft body projectiles on composite structures with ALTAIR HYPERWORKS/explicit. At first, the impact on flat composite plates is studied in experiment and simulation, which allows for the validation of the modelling methods. Some of these plates have been preloaded in tension or compression in order to investigate the influence on the mechanical behavior. The numerical results obtained from the various formulation shows close conformity implying their appropriateness as alternative in the simulation of bird strike, and the design optimization of the composite aircraft structure is carried out in SOLID THINKING INSPIRE workbench. Introduction Bird strike event has been one of the most dangerous risks to the safety of aircrafts. Although most bird strike event involves relatively small birds, which doesn t cause the catastrophic consequences, the possibility of severe damage generated by impacts with larger birds cannot be neglected. In order to ensure tolerance to bird strike damage, aircraft structures have to fulfil the airworthiness specifications prescribed by FAA or JAA. Since the leading edge structure is very likely to be impacted by birds, it is very essential to research the failure mechanism of bird strikes by using numerical simulations [1-3] which could reduce, or even replace, time consuming and costly gas gun experiments on design of components of a new aircraft.in order to deal with the numerical prediction of structural behaviour and damage caused by bird strikes in an airplane leading edge structure using finite element method, interactions of several complex numerical problems including contacts [4, 5], various damage initiation and accumulation models [6-10], finite element failure and removal of failed elements, different bird modelling strategies [5-10], etc., are involved. 1

2 Process Methodology CASE (1):- To perform explicit analysis various methods are followed they are 1. Design of the bird SPH model using CAD package software 2. Converting the respective file in to IGES, parasolid format. 3. Importing the model in to hypermesh Applying the following material performing the static structural analysis. To simulate ductile failure of metallic leading edge structure under bird strike, the progressive dynamic failure model is involved. Johnson-Cook (J-C) model which includes constitutive relation and fracture criterion is most widely used in numerical analysis of structure under dynamic loading or impact [6, 7]. However, J-C model has some shortcomings: (1) the constitutive relation is only based on the stress strain curve of round bar test, without considering the effects of different stress states on plasticity evolution; (2) as for the fracture criterion, only the effect of tri axiality which represents the hydrostatic stress is concerned in damage accumulation and crack initiation,ignoring the effect of Lode angle and the coupling effect of pressure and Lode angle which are reported to be the paramount factors for damage accumulation in the recent research of ductile fracture model under quasi-static loading [8-10]. To overcome the shortcomings, a novel fracture model [9, 10] taking the effects of both stress states and strain rate on fracture under dynamic loading into consideration is applied in the present bird strike simulations. Moreover, different bird modelling techniques have apparent effects on the results of simulations, which is essential to accurately predict the damage caused by bird strikes. There are three commonly used approaches to simulate the bird in impact: the Lagrangian approach, the Arbitrary Lagrangian Eulerian (ALE) approach [8-10] and the Smooth Particle Hydrodynamics (SPH) method. Each has different advantages over others under certain circumstances. Among them the recently developed SPH approach is gaining more and more interests in bird modelling since it could better simulate the hydrodynamic property of a bird during impact. The SPH approach is a mesh free method in which the bird is discretized by a set of discrete, mutually interacting particles. Since this approach is grid-less, it is well suited for impact problems where large distortions may occur during simulations. This method has been used to simulate the bird strike on a variety of components of aircraft structures. In this paper followed the SPH bird modelling approach, nonlinear bird strike simulations have been performed using explicit dynamic finite element program LS-DYNA, with the novel dynamic fracture model considering the effects of both stress states and strain rate on fracture incorporated into the user s subroutine to simulate the failure of leading edge structure due to bird strike. 2

3 Figure 1: Geometry (a) and the SPH model (b) of a bird Young s 10.0 GPa modulus Poisson s ratio density 950 Kg.m -3 Yield stress 1 MPa Figure 2: CAD model of bird strike on a panel Table 1: material properties of bird In calibration, the SPH bird impacts on the target plate are performed. The size of target plate is 600mm 400mm 5mm which is meshed in shell elements with discrete size 8mm.Different impact velocities of bird and discretization of SPH particle are selected. The mass of bird is 3.6kg, and the initial velocities, i.e. 80m/s, 116m/s and 170m/s. Furthermore, in order to verify the different mesh size of shell element of structure on the numerical results, discrete sizes with 3mm, 6mm,8mm, 10mm and 15mm of pate are selected. In impact simulations, the mass of bird is still3.6kg with a velocity of 170m/s and the discretization size of SPH particle in bird modelling is selected as the cm3. The weight of bird is also set to be 3.6kg, the initial speed is 125m/s and the initial kinetic energy is J. The angle between the speed and the cord line is

4 In the case 1 the bird model i.e. SPH is designed and the bird strike on the composite panel is calculated with respect to the three velocities i.e. 80,116,170 respectively.the explicit analysis is done in hypermesh RADIOSS workbench in order to calculate the equivalent stress The following pictures below describe the equivalent stress and graph related to time vs pressure with respect to three velocities Figure 3: bird strike on a panel at v=80m/s Figure 4: bird strike on a panel at v=116m/s Figure 5: bird strike on a panel at v=170m/s 4

5 Graph 1:-: time vs pressure (Von-Mises stress v=80m/s) Graph 2:-: time vs pressure (Von-Mises stress v=116m/s) 5

6 Graph 3:-: time vs pressure (Von-Mises stress v=170m/s) CASE (2):- To perform optimization in SOLIDTHINKING INSPIRE workbench the model is imported to inspire and given the parameters i.e. fixed support, force, calculate the displacement, factor of safety, vonmises stress, tension and compression. And assign the design space in order to optimize the composite structure and finally calculate the mass before optimization after optimization 6

7 Figure 6: Displacement Figure 7: Factor of Safety Figure 8: Tension and compression Figure 9: Von-mises stress 7

8 Figure 10: Optimization process Figure 11: After Optimization Results & Discussions CASE (1):- From the figure we can see the maximum strength at v=80m/s is e11 Pa Similarly at v=116m/s the maximum strength is e11 Pa At v=170m/s the maximum strength is e11 Pa CASE (2):- From the figure the optimization is done for the composite structure to calculate the Displacement: e-007m Factor of safety: e+018 Tension and compression: e+005 Pa Von-mises stress: e+005 Pa Mass of composite structure before optimization: gms Mass of composite structure after optimization: gms 8

9 Benefits Summary The Explicit analysis that is carried out for the given parameters had given a good result to know behavior of the material and safety factor. ALTAIR hyperworks is having complete software for analysis which can easily understand and user friendly software for both educational and industries. The Explicit analysis is much benefited for all users who are using ALTAIR products. The design optimization is easier to understand and we can do the topology optimization in the Solid thinking INSPIRE.. Challenges As this project is having more number of iterations it is difficult to calculate for each iteration and to give constraints but as the no of iterations increases in particular model it is a tough challenge to perform explicit analysis and optimization. Future Plans As the results obtained from the experiment in future we are going to do analysis for the high standard wing configuration and to do optimization of composite structures in aircraft using ALTAIR products. Conclusions A bird strike event on the slat of an aircraft wing structure is successfully simulated with Hyperworks/Explicit. With its strong damage and failure modelling capabilities, fastener functionality and general contact algorithm, Hyperworks/Explicit is an ideal tool for such highly dynamic, nonlinear applications. While the present application focuses on metallic materials, Hyperworks/Explicit also allows for the simulation of composite aerospace structures. And the optimization is done in INSPIRE workbench.. REFERENCES [1] Richard A. Dolbeer, John Weller, Michael J. Begier, Wildlife strikes to civil aircraft in the united states Federal Aviation administration national wildlife strike database serial report number 19, September [2] Allan, John R. and Orosz, Alex P., The Costs of Bird strikes to Commercial Aviation (2001) Bird Strike Committee- USA/Canada, Third Joint Annual Meeting, Calgary, AB. Paper 2, Page 2. [3] Richard A. Dolbeer, John Weller, Michael J. Begier, Wildlife strikes to civil aircraft in the united states Federal Aviation administration national wild life strike database serial report number 19, September 2013, page 42. [4] Richard A. Dolbeer, John Weller, Michael J. Begier, Wildlife strikes to civil aircraft in the united states Federal Aviation administration national wildlife strike database serial report number 19, September 2013, page 40 [5] B Langrand, A-S Bayart, Y Chauveau and E Deletombe, Assessment of multi-physics FE methods for bird strike modelling- Application to a metallic riveted airframe, International Journal of Crashworthiness, 2002, 7: 4, [6] B. Langrand, E. Deletombe, Riveted joint modelling for numerical analysis of airframe crashworthiness, Finite Elements in Analysis and Design 38 (2001) [7] Guida M, Marulo F, Meo M, et al. Analysis of bird impact on a composite tail plane leading edge. Applied Composite Materials, Vol. 15, No. 4-6, pp , [8] Smojver I, Ivančević D. Numerical simulation of bird strike damage prediction in airplane flap structure. Composite structures, Vol. 92, No. 9, pp , [9] Wang F S, Yue Z F. Numerical simulation of damage and failure in aircraft windshield structure against bird strike. Materials & Design, Vol. 31, No. 2 pp , [10] Hanssen A G, Girard Y, Olovsson L, et al. A numerical model for bird strike of aluminium foam based sandwich panels. International Journal of Impact Engineering, Vol. 32, No. 7, pp ,