Pandur Dynamic Driving Simulator - Analysis of mine blasteffects

Armando J. Loureiro da Silvasilva.ajl@mail.exercito.pt

Academia Militar, Lisboa, PortugalInstituto Superior Tecnico, Lisboa, Portugal

October 2016

Abstract

The work developed in this thesis aims at contributing to the Pandur Dynamic Driving Simulator.This contribution results from the creation a simulation event with the goal of increasing the simulationsystem capabilities. In order to do that, events related to a mine blast under the vehicle were createdwith an equivalent mass of TNT regulated by STANAG 4569.

Those events were analysed based on the development of a detailed study on blast explosive chargeand the respective influence on the vehicle, when the detonation occurs under the hull. The explosiveburst analysis was developed from a review of previous works and a design of numerical simulationsusing the finite element method, thought the LS-DYNAr software.

The results were then implemented in the simulator according to the architecture developed by ETIfor this project.

This investigation allowed to conclude that the obtained results are coherent and enough. However,to make a more precise investigation it would be necessary to evaluate other modelling and simulationmethods for mine blasting analysis.

Keywords: Dynamic Driving Simulator,Infantry Combat Vehicle 8x8 Pandur II, Mine Blast, NumericalSimulation, LS-DYNA

1. IntroductionThe expenses on military’s training and forma-

tion have been high. New technology has broughtnew solutions to this problem, such as virtual re-ality and simulation systems. These computationalmeans present themselves as solutions because theyallow us to reduce purchasing and maintenance’scosts. The development of the Pandur II DynamicDriving Simulator (PDDS), figure 1, rouse the Por-tuguese Army’s interest on this kind of technology,which brought many benefits to National Defenceindustry. The PDDS, which is being developed byEmpordef – Tecnologias e Informacao S.A. (ETI),was designed as a set of subsystems that, when in-tegrated into a system of systems, will delivery thevehicle’s necessary emulating functions intended forthe simulator.

The work developed intends to contribute toproject PDDS, in a way that addresses the effectscaused by the antitank mine on the vehicle, accord-ing to STANAG 4569 [12]. The analysis is madeby the modulation physic phenomena and respec-

tive implementation in the simulation’s package andvirtual reality’s control on the simulator.

Figure 1: Pandur Dynamic Driving Simulator.

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Nowadays it is highly accepted that numericalsimulations provide results that are close to reality,while reducing the use of the real system and, at thesame time, avoiding extensive costs that would turnthe intended investigation much more expensive.The analysis was performed using the LS-DYNAr

as computational tool.

2. BackgroundThe technical designation of the vehicle is

Wheeled Armoured Personnel Vehicle 8x8 PandurII, and the PDDS simulator is based on ICV versionof the vehicle, figure 2.

Figure 2: VBR 8x8 Pandur II ICV.

2.1. Empiric model of the blast wave propagationKingery [8] and the US Department of the Army

[1] compiled large sets of data obtained from ex-perimental tests. With this compilation they wereable to develop polynomial equations of high order,through interpolation of experimental data, that al-lows to foresee the parameters of a free field spher-ical blast and an hemispherical blast on a surface.These equations were accepted as regretion toolsby the engineering community and used as modelsfor open air blasts (with no obstacles) or blasts incontact with surfaces. Thanks to this, it was de-veloped a new software named CONWEP [7] thatfulfils all numeric calculations of the effects causedby conventional weapons. The TM5-855-1 [1] statesthat the pressure created by the blast wave decayis approached by a triangular pulse. In the otherhand, Remennikov [11] and Lahir [9] state that theCONWEP method uses Friedland’s equation to usea more realistic concept to describe the phenom-ena. Equation (1) translates this concept, whichalso represented in figure 3.

p(t) = (pmax − patm)[1 − t − ta

td

]e

− a(t−ta)td (1)

Figure 3: Pressure variation due to the blast wave[9].

2.2. Previews WorksIt is possible to find, in the scientific community

several developed works in this area, this is, aroundthe mine blasting modulation under military vehi-cles’ hulls resorting to LS-DYNAr as computationtool. Namely, Brill et al. [5], presents a maximumpressure of 0.1446 [GPa] in the vehicle’s hull, rela-tively to the vehicle’s dynamic. We can observe amaximum 0.065 [m] and 2.55 × 103 [m/s2] of dis-placement and acceleration respectively. Althoughthe vehicle in analysis (APC M113) presents a dif-ferent geometric configuration and different mo-ments of inertia from vehicle in analysis (APC Pan-dur II), both vehicles has a mass around the samemagnitude: APC M113, at 12500 [Kg], Pandur IIapproximately 18000 [Kg]. Some other publishedworks were considered, either the obtained resultsor the associated concepts of the blast phenomena.As for the additional literature, for a more profoundanalysis, it can be consulted [10, 2, 3, 4, 13].

3. Implementation3.1. Pandur Dynamic Driving Simulator

The PDDS has a compartment that simulates thedriver’s seat through a replica, fixed on a dynamicplatform that reproduces the motion and sensationto the driver. The simulation system software ismade by several packages, and to each one of themis assigned one specific function. The contributionof this work is given to the package Vehicle. Thispackage contains lamped model of the Pandur IIand its systems with the purpose to create a realisticsimulation of the vehicle, being responsible of pro-cessing all specific functions of the vehicle’s features,its user and its dynamics. The blast wave createdby the anti-tank mine produces a very high pressurevariation in a small space of time. This phenomenainduces forces and moments applied to the vehi-cle’s Center og Gravity (CG). The described occur-rence and the simulated system’s structure makesthe phenomena’s implementation analysis to be the

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calculation of the resultant forces and the momentsin the body of the vehicle in each degree of freedom(DOF) (Fx, Fy, Fy, Mx, My, Mz). After this, an-other package, named Vehicle Dynamic, calculatesthe vehicle’s dynamic response: linear and angularaccelerations, for each DOF.

Figure 4: Referential axis used by the simulationsystem.

3.2. Test descriptionThe model of the events that is intend to be anal-

ysed is shown in figure 5. As it is illustrated, it isintended to obtain results for the detonation to amass of 6 [Kg] of TNT, located after the left wheelin the first axis, this means, under the driver’s seat.The choice of the loading charge mass is due tothe STANAG 4569 [12], wich states that the blastdoesn’t cause damage in the vehicles personnel.

Figure 5: Position of the mine relative to the vehi-cle.

3.3. Model in LS-DYNAr

Vehicle’s body Due to a detailed geometric dataof the vehicle and resorting to draw computation’stool SLODWORKr, it was possible design a CADmodel of the vehicle. After that, the vehicle’s bodyis discretized in LS-Prepost, figure 3.3. However,there is a need of looking for a compromise betweena realistic approach and minimizing the spent timein computation processing. In this way, the designpresents only on level of detail necessary and enoughto keep the hull’s real measuring and configuration.

Vehicle suspension One used technique to cre-ate parts (*PART) of spring and damper effect isthe creation of discrete elements using the keyword*ELEMENT DISCRETE, figure 7. To do so, it isdefined discrete sections (*SECTION DISCRETE)between two nodes. The elasticity coefficients to thespring k and the damper c is defined as material,and the keywords are *MAT SPRING ELASTICand *MAT DAMPER VISCOUS respectively.

To avoid any compilation errors it is necessary todefine the mass that create the suspension. Thisway there shouldn’t exist any nodes without masswhen discrete elements are used. Therefore, it isdefined 1 [kg] of mass to the node that is part ofboth vehicle’s suspension and vehicle’s chassis (aconsiderably small mass to the vehicle’s mass). Tothe node that stays free and in contact with theground, it is defined a mass of 200 [kg] in order torecreated the corresponding weight of the vehicle’swheels, 150 [Kg] [6] in addition to its aggregatedelements, as the suspension mass itself.

Simulation of the blast load The CONWEPmethod, chosen for the generation of a blast wavecreated by the mine blast, it is implemented by the*LOAD BLAST ENHANCED card. This keywordallows the data related to the load blast to be en-tered: equivalent mass of TNT, charge location andactivation of calculations associated with both sys-tem units, which is intended to be consistent, andalso the equations that LS-DYNAr processes dur-ing these compilation.

Referential axis To a numeric analysis, the fig-ure fig:coordenadas, illustrates the axis system usedand the references to the wheels.

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(a) Complete vehicle

(b) vehicle’s hull

(c) Vehicle’s 3D CAD model designed inSOLDWORKSr

YY

XX

ZZ

LS-DYNA keyword deck by LS-PrePost

(d) Discretized model, LS-DYNAr

Figure 6: Vehicle’s 3D CAD Model and discretizedplan in 4 steps.

Figure 7: Discrete elements of the suspension.

Figure 8: Vehicle body, axis and distnces betweenwheels and CG.

4. Results

Is shown in figure 9 the propagation of the blastwave around the vehicle’s hull. It can be seen theradial propagation of the pressure caused by theblast wave, starting at the point where the load islocated. The charge was placed at a distance of 500[mm] from the vehicle’s hull, given that the distancebetween the hull and the ground is approximately448 [mm]. it is considered, this way, that the mineis at around a 52 [mm] depth under the ground.

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YY

ZZ

XX

min=0, at elem# 1

Contours of Pressure, P=P(Pi,Pr,Theta)

max=218.514, at elem# 2705

8.741e+01 _

1.093e+02 _

Time = 2.0001

LS-DYNA keyword deck by LS-PrePost

0.000e+00 _

2.185e+01 _

4.370e+01 _

6.555e+01 _

1.311e+02 _

1.530e+02 _

1.748e+02 _

1.967e+02 _

2.185e+02 _

Fringe Levels

Figure 9: Load pressure caused in the vehicle’s hullat the starting instant

The pressure distribution along the vehicle’s hullis represented in the figure 10, in which the curvescorresponds to the elements that presents the high-est pressure in each moment established in 0.1, 0.5,0.7, 2.1 and 3.8 [ms] respectively. The analysis ofthis diagram allows to observe a peak of pressure of219 [MPa] in the closest element to the load.

Figure 10: Pressure distribution along the vehicle’shull due to mine blast.

Relatively to the vehicle’s mass’ centre displace-ment and acceleration, It can be seen in figure 11and its respective variations over time.

A maximum displacement 58 [mm] and a maxi-mum acceleration of 1.98× 103 [m/s2] can be ob-served, figure 11.

4.1. Simulator - Vehicle dynamicIn figure 12, its illustrated the vertical linear ac-

celerations for both implementations, this is, for theoriginal data and for when the resultant of forcesapplied in the CG are multiply by a 1.5. factor.

(a) Displacement

(b) Acceleration

Figure 11: Vertical displacement and accelerationthe vehicle in rest.

Tempo (ms)0 0.5 1 1.5 2 2.5 3 3.5 4

Ace

lera

ção

linea

r (m

/s2)

-3500

-3000

-2500

-2000

-1500

-1000

-500

0

500

Factor 1.0Factor 1.5

Figure 12: Linear vertical acceleration for imple-mented models.

Note that the axis system of the PDDS, figure4, is not the same used by the numerical simula-tions, figure 8. About the vertical axis zz, it canbe observed a maximum 2275 [m/s2] accelerationin negative direction of the zz, which means, in theopposite direction of the ground.

The vehicle should have a visually better be-haviour if the results of the applied forces in theCG were multiplied by a 1.5 factor. It can be, infact, verified a maximum 3412 [m/s2] acceleration.It is a close factor to the one proposed by Bill et al.[5] for the CONWEP method.

To the angular accelerations verified by the sim-ulator’s dynamic are shown in figure 13.

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Tempo (ms)0 0.5 1 1.5 2 2.5 3 3.5 4

Ace

lera

ção

angu

lar

(rad

/s2)

-14000

-12000

-10000

-8000

-6000

-4000

-2000

0

2000

Fator 1.0 em θFator 1.0 em φFator 1.5 em θFator 1.5 em φ

Figure 13: Angular Acceleration for the imple-mented models.

4.2. DiscussionIn this work it is intended to achieve the final

goal, implement the numerical results in the PDDS.Table 1 allows to validate the vehicle’s model’sphysical properties, namely, the mass and the ve-hicle’s CG main moments of inertia.

Table 1: Mass and the vehicle’s CG principal mo-ments of inertia

Mass(ton)

AttitudeMoments of Inertia(ton.mm2 × 107)

Roll 1.38Numerical

Model18.034 Pitch 7.42

Yaw 8.41Roll 1.04

Real 18.000 Pitch 3.5Yaw 3.78

To make a discussion about the obtained results,the table 2 presents the peaks of pressure, acceler-ation and vertical displacement obtained for eachnumerical model. The table’s line corresponding tothe simulator allows a results’ discussion about theway the implementation is made. This last modelhas the purpose to validate the implemented nu-merical model.

Table 2: Comparation between results to each fase.Modelo

Pressao(MPa)

Aceleracao(m/s2)

Deslocamento(mm)

Numerical Analysis 219 1980 58Simulator 1.0 - 2275 -

1.5 - 3412 -APC M113 Brill et al. [5] 144.6 2550 65

After analysing table 2, it can be seen in a generalway that, for each parameter evaluated, they found

themselves in the same order of magnitude, in eachparameter evaluated, the variation that is seen ineach approach or method are

Relatively to the final goal, it can be seen thatwhen it comes to vertical acceleration, the val-ues obtained by the simulation system (packagevehicle dynamic), are consistent and close to theones predicted by the numeric simulations. Namelythe acceleration obtained for the detailed geometrymodel, 1980 [m/s2], and the acceleration obtainedby the PDDS, 2275 [m/s2].

The data collected in the bibliographic revision,help validate the numeric models. In the vehicleVBL M113 model’s case presented by Brill et al [5],it can be seen a diference of 570 [mm/s2] of verticalacceleration and a diference between pressures of74,4 [Mpa], related to the geometry detailed model.As it was expected, the Pandur II shows a minoracceleration, due to the fact that the VBL M113’smass is lower.

5. ConclusionsThis work presents a methodology of a numeri-

cal analysis based on bibliography and previous in-vestigation. The objective was to develop virtualsimulations of mine blasting under the hull of VBRPandur II close to reality. After analysing the ob-tained results, it was possible to verify that thisdata is consistent and properly validated comparedto previous works.

In view of an application of the intended resultsfor the reality simulation in the PDDS, we can verifyits utility and positive implementation.

The numerical analysis was made in a progressiveway, increasing the detail level of each model. Ineach step of the project we can verify:

• The blast phenomena occurs in a short periodof time;

• The amount of pressure caused on an obstacleis considerably influenced by the distance thatthe obstacle is from the blasting mind

This work turns out to be a propose of method-ology in the mine blast under the Pandur II’s in-vestigation, as well. This contribution also needsimprovement in numeric simulations. This means:

• It would be necessary to test more methods(ALE and coupled methods) in order to verifyif the results would be better, more precise orstrict;

• Not just use the LS-DYNA R© in the discretiza-tion step, but also resort to other programmes,in order to look for the potential and advan-tages that each software presents. This way,it possible to use each advantage to bridge the

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gaps and disadvantages of the others. The LS-DYNAr presents a considerable potential tobe part of the process and calculations, thekeywords basis is intuitive and efficient in theapplication of specific models. Is less userfriendly in geometric creation and respectivemesh, making it necessary another software tobridge this gap.

• Making experimental tests would help to vali-date the developed work, in order to make an-other kind of analysis, for example to verifyif a vehicle fulfils, in reality, what’s stated bySTANAG 4569.

After introducing the numeric model in thePDDS, it was concluded that, due to the fact thatthe sample time was too high and because the blastwas also quick, it would be necessary to low thespeed of the simulator itself, however due to factslike the level of hardware or even the platform werenot implemented in a detailed form. However, tothe implemented model in the virtual simulation inPDDS, was verified a use and a positive implemen-tation.

AcknowledgementsPart of the documentation used in this work

were provided by EMPORDEF - Tecnologias de In-forma cao S.A. under a Non Disclosure Agreement.ETI also provided access to the PDDS for the ex-perimental part of this work.

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