Finite Element Analysis Of Blast Loaded Armoured Vehicle

Finite Element Analysis Of Blast Loaded Armoured Vehicle

* N. Madan Mohan Reddy, ** G.Venkat Rao Assistant Professor, Professor Department Of Mechanical Engineering

CVSR College of Engineering, Hyderabad, Andhrapradesh, INDIA

Abstract

Armoured vehicles are used to carry both soldiers and machinery in the war environment. These are affected from the Blast loads severely in view of the environment of fighting or peace- k eeping. In the present work on the Analysis of An Armoured Vehicle for Blast loading the effect of blast loading on the vehicle. Both explosions on the underside and on one side of the vehicle are considered in the analysis. Finite Element Analysis has been carried out to perform the analysis for which purpose ANSYS code has been used.

The load is created by a medium sized crack er

.The displacement has been measured by a video – based technique. Blast loading on vehicles tak es place in few milliseconds, in the experimentation video based methodology used to capture the blast effect on armoured vehicle by the 2.5 mega pixel camera.

By using CATIA V5 and ANSYS 11.0 analysis has been carried out for underside blast loading of the model. The measurement technique has been applied to a 1:16 size scaled model vehicle of HMM WV M1025. The same model is tested experimentally.

Finally deflections of bottom plate of armoured vehicle as obtained by Experimental & FEA results are compared and conclusions drawn.

1. Introduction

   Blast loading may result from the detonation of high exp losives, chemical a mmun itions. The type of e xtraordinary dynamic load it has to be described by two parameters; peak overpressure and duration.

   Exp losions create high-pressure, high-temperature that can create permanent deformation of vehicles or structures around it and rupture or tearing of meta l takes place and generate flying frag ments which can effect the surrounding Environment.

   Fig.1. Generat ion of blast wave fro m rapid combustion

   Expansion of co mbustion products due to conversion of chemical to therma l energy in combustion and creation of gaseous products in High e xp losives. Expansion ratio for gaseous

   Exp losions depend on thermodynamics and e xpansion rate depends on chemical kinetics and flu id mechanics with Fla me speeds & Detonation velocity.

2. Scope of Wo rk

   Blast loading occurs due to accidents from detonation of chemica l plants, gas cylinder e xplosions, attacks by anti-social ele ments and other reasons. Therefore, concerted efforts have been underway during the past three to four decades to design structures and vehicles so as to resist large impact loads such as those due to blast.

   The difficulty of carrying out experimental tests on blast loaded structures like bea ms, plates, cylindrica l shells, armoured vehic les etc is that the blast takes place in about a few mic roseconds (1E-7 to 1E-6 seconds). The resultant peak effects have to be recorded in such short durations. Strain gauge techniques, optical sensors, high speed photography are a few techniques available for measuring displace ments and stresses in order to assess the structural integrity.

   In the Present Project, finite ele ment analysis and videography-based experimental methods are used on model of HMM WV M 1025 model tests are carried out on armoured vehicle . The fin ite ele ment formu lations, the boundary conditions and loading are d iscussed in detail for the transient analysis of short-term event due to impact. A few test cases are carried out in order to establish the

   methodology for analyses. The displacements and stresses in the vehicle during the loading event are presented in detail. The displace ments are compared as obtained from the FE analysis and the tests. The advantages and limitations of the techniques are highlighted.

3. Experimentation

   A special test rig has been designed and fabricated for carrying out experimental work in this project Expe rimental details are:

   Expe rimental Test rig is experimental equipment designed to measure practically the blast effects on loads on GI (Ga lvanized Iron) Sheets and MS (Mild Steel) Plate. Test rig is having the different accessories for the attachment of Dial gauges to measure the deflections of sheet, plates during the blast pressure. It is used to apply a small charge of e xplosives like festival cracke rs.

   The Experimental Test Rig is designed with proper dimensions it looks like U Shaped and having a C-channel in both side of rigs. Experimental Test Rig is a Equipment to find the deflections Under Blast Loading It is Dra fted first and given required dimensions and then it is designed in Catia v 5 and after designing Test rig is Fabricated as per the design. Material of test rig is Mild steel and having total weight 24 kg together with c la mps and nut bolts, and Fabricated with Gas Welding and Black coated.

   Fig2.Expe rimentalTestRigFabricated

   Co mputer Aided Design Model of a HMM WV M1025 (High Mobility Multipurpose Wheeled Vehic le Model 1025) as given in be low figure. Surface Modeling is done in CATIA V5 Design Software. Solid modeling of Veh icle which will takes more time and gives lacks of nodes while meshing in analysis because of having the number of solid parts in the vehicle assembly. Surface modeling will take less time and gives precision results and it is easy to understand the behavior of vehicle under blast load. Vehic le is having overall

   length 4.8m and a width base of 3.4m and other dimensions are given in below d imensioned figure.

   Fig.3 Dimensions of Veh icle

   Fig.4 Perspective Vie w of vehicle

   3.1 Specifications of Model Vehicle:

   Model of HMM WV M1025 Armoured vehicle has been manufactured as per the original model by 1:16 scale rat io. Specifications are given below

   Material : GI Sheet. Thickness: 0.21 mm. Wheel Radius: 37.5mm

   Dimensions: As per given in Figure Thickness of Shaft for Wheels: 2 mm. Process: spot welding.

   After load scaling to actual vehicle 1:600

   Seats at 1:600 Ratio: 110grm each one (440g rm for 4 seats)

   Total Weight of Vehic le : 1.26 Kg.

   Fig.5 Scaled model vehicle

   Fig.8 Blast Pressure 100N

   400mm

   6mm

   Fig.9 Displace ment of Bottom p late 6.049mm

   Festival Cracke r Test Rig Fig.6 Deformation by Explosive blast

4. FEA on Bottom Plate of Model Ar moure dVehicle

   Analysis is done on model vehicle by using Ansys Software

   Fig.7 Meshing of Bottom plate 1mm thic k

   Fig.10 Blast Pressure on Bottom Plate

   Fig.11 De format ion Vs Time: 6.059mm in UZ Direction of 7.8 ms

5. RESULTS & DISCUSSION

   The fallowing table-3 co mpares the results obtained fro m the FEA (Fin ite Ele ment Analysis) and model vehicle of HMM W V M1025 e xperimentation.

   Expe riment Numbe r	Expe rimental Armoure d Vehicle De flection (mm)	FEA Armoure d Vehicle De flection (mm)	Re sults Ratio (%)
   1	6.0	6.049	99.2

   Table-1 Co mparison of Experimental & FEA Results of Model Armoured Vehic le.

6. CONCLUS ION

   A detailed analysis has been carried out on armoured vehicle model of HMM W V M1025 using finite ele ment method and a novel e xperimental technique. The majo r conclusions are as follows.

   FEA FOR ACTUAL VEHICL E:

   THE MA X DEFLECTIONS=30.963mm in 60

   milliseconds by 1000N Blast pressre.

   VON MISSES STRESS is SMIN= -39364 N/ mm2, SMAX=7600 N/ mm2

   ELASTIC STRAIN=3.8 in 60 milliseconds.

   FEA FOR MODEL VEHICL E:

   THE MAX DEFLECTIONS=6.049mm in

   8milliseconds by 100N Blast Pressure.

   VON MISSES STRESS is SMIN= -160.67 N/ mm2, SMAX=159.762 N/ mm2

   ELASTIC STRAIN=0.007181 in 8 milliseconds. EXPERIMENT FOR MODEL VEHICL E: THE MAX DEFLECTIONS=6.0mm

   The values in the model as obtained by FEM and Expe riment are well a llied.

   The methodology described in the paper, with some refine ments can improve the b last resisting strength in the armoured vehicle and also

   increase the safety of soldiers. In future, more scaled models can be tested for different loads of blast which vary due to distance and strength of e xplosive. Better material modelling as available in progra ms like LS Dyna can be used.

7. References

1. Grujicic, M ., W C Bell, G Arakere & I Haque Finite element analysis of the effect of up -armouring on the off-road breaking and sharp -turn performance of high-mobility multi-purpose wheeled vehicle .

2. Alon Brill, Boaz Cohen & Paul A. Du Bois Simulation of a M ine Blast Effect on the Occupants of an APC .

3. Kentaro ohashi, Harald Kleine, & Kazuyoshi Takayama Characteristics of Blast Waves generated by milligram charges. .

4. Kadid.A, Lahbari.N & Fourar Blast loaded Stiffened Plates .

5. Stephen D.Boyd Acceleration of a plate subjected to explosive blast loading.

6. Ngo.T, .M endis, .Gupta.A & Rmsay.J Blast Loading & Blast Effect on Structures .

7. Kevin Williams, Scott M cLennan, Robert Durocher & Benoit St-Jean & Jocelyn Tremblay Validation of a Loading M odel for Simulating Blast M ine Effects on Armoured Vehicles .

8. A.D.Gupta Evaluation of fully assembled armoured vehicle hull-turret model using computational and experimental modal analysis .

9. M ichael J.M ullin & Brendan J. O Toole Simulation of Energy Absorbing M aterials in Blast Loaded Structures .

10. M akris.A, Nerenberg, and DionneJ.P Reduction of Blast Induced Head Acceleration in the Field of Anti- Personnel M ine Clearance .

11. Kevin Williams & Francois Fillian-Gourdeau Numerical Simulation of Light Armoured Vehicle Occupant Vulnerability to Anti-Vehicle M ine Blast .