DESIGN OPTIMIZATION AND STRUCTURAL ANALYSIS OF MISSILE CONTAINER Keerthi Siva Krishna 1, K. Lalit Narayan 2 and K. Venkateswara Rao 3

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1 Research Paper DESIGN OPTIMIZATION AND STRUCTURAL ANALYSIS OF MISSILE CONTAINER Keerthi Siva Krishna 1, K. Lalit Narayan 2 and K. Venkateswara Rao 3 Address for Correspondence 1 PG Student, 2,3 Associate Professor, Department of Mechanical Engineering SIR C.R.R.College of Engineering, (Affiliated to Andhra University) Eluru , West Godavari Dist, A.P ABSTRACT Missile is an object capable of being projected, usually with the intent of striking some distant object. More particularly, a missile is usually a weapon that is self-propelled after leaving the launching device. In other words, missile is a rocketpropelled weapon designed to deliver an explosive warhead with great accuracy at high speed. Missiles are sturdy, well-constructed machines. But, because of their size, weight, and bulk, they are not that easy to handle nor are missiles indestructible. Most missile damage is, unfortunately, a result of carelessness and poor handling practices. To reduce the possibility of damage, missiles are shipped, stored and handled with special equipments. Approved containers, canisters, and handling equipments provide maximum missile safety with minimum handling by personnel. The missile container used previously was of lid type (suitcase) containers. This type of container has large contact area at the closing region. So it is very important that the manufacturer has to take extreme care in producing this container without any warpage at the closing region. Else there will be a leakage of gas from the gap developed due to warpage. Therefore the manufacturing becomes more complex and more expensive. In this paper we have designed a container which is used for transportation and storage of missile. The Missile container is made of composite shell structure stiffened with rectangular ribs on the interior surface. The opening to insert the missile is given at the rear end, which has very small contact area at the closing region. As a result manufacturing becomes easier. We have identified several causes of disturbances which damages the container such as internal pressure load, Stacking load, Braking load and lifting load. Efforts have been made to design and optimize the container for the above mentioned loads. Detailed finite element stress analysis is carried out to determine the static response of the designed composite missile container structure under mechanical loads. Ansys package has been employed to perform the structural analysis. 1.0 INTRODUCTION Missile is an object capable of being projected, usually with the intent of striking some distant object. More particularly, a missile is usually a weapon that is self-propelled after leaving the launching device. In other words, missile is a rocket-propelled weapon designed to deliver an explosive warhead with great accuracy at high speed. Missiles are sturdy, well-constructed machines. But, because of their size, weight, and bulk, they are not that easy to handle nor are missiles indestructible. Most missile damage is, unfortunately, a result of carelessness and poor handling practices. To reduce the possibility of damage, missiles are shipped, stowed and handled with special equipments. Approved containers, canisters, and handling equipments provide maximum missile safety with minimum handling by personnel. There are different and specialized types of containers, canisters, and handling equipments in the ordnance field. Many are designed for a single purpose or use and cannot be interchanged with comparable items. The containers, canisters, and handling equipments used to deliver missiles to a ship. 1.1 Missile Containers A container is used for shipping and storage. The containers are similar, differing mostly in size and weight. Missile containers are large, rectangular aluminum boxes used for the shipment and storage of missiles. Missile containers are identified by a mark number. Become familiar with these numbers. Different types of containers are: Mk 372 container Standard missiles Mk 632 container Harpoon missiles Mk 183 container ASROC missiles Mk 372 container The Mk 372 Mod 5 container is used to ship and stow medium range (MR) Standard missiles (fig. 1). The bottom section of the container has an inner support (base) assembly. It is shock-mounted to the outer base assembly. A missile is secured to the inner assembly with its lower forward and aft launching shoes. A center missile support (U-frame) is installed over the upper forward launching shoe. It provides a downward force on the shoe and helps secure the missile. A clamping lever (or humping fork) is located below the center missile support. It also aids in securing and prevents the missile from sliding forward. Figure 1: Mk 372 Mod 5 containers for Standard MR missiles MK 632 container The Harpoon missile provides the Navy and the Air Force with a common missile for air, ship, and submarine launches. The weapon system uses midcourse guidance with a radar seeker to attack surface ships. Its low-level, sea-skimming cruise trajectory, active radar guidance and warhead design assure high survivability and effectiveness. The Harpoon missile and its launch control equipment provide the war fighter capability to interdict ships at ranges well beyond those of other aircraft.

2 Figure 2 : Mk 632 Mod 0 containers for Harpoon missiles MK 183 Container The Mk 183 container is used to handle ASROC missiles. Figure 1.3 shows an external view of the container. Note the prominent extensions on the top cover. They accommodate the fins of the missile. This container may be handled by sling, forklift truck, and also by hand lift trucks. Figure 4: 3D view of the container 3.0 STRUCTURAL ANALYSIS OF A MISSILE CONTAINER Static analysis deals with the conditions of equilibrium of the bodies acted upon by forces. A static analysis can be either linear or nonlinear. All types of nonlinearity are allowed such as large deformations, plasticity, creep and stress. Static analysis result of structural displacements, stresses and strains in structures for components caused by loads will give a clear idea about whether the structure or components will withstand for the applied maximum loads. If the stress values obtained in this analysis crosses the allowable values it will result in the failure of the structure in the static condition itself. To avoid such a failure, this analysis has been carried out. 3.1 Structural Analysis of Missile Container with 4mm Thickness Case 1 Internal Pressure of MPa (Existing) Figure 3: Mk 183 containers for ASROC missiles. 2.0 DESIGN CONSTRAINTS AND MODELLING 2.1 Construction of Missile Container Missile container is constructed by using fiber reinforced composite, i.e., E-glass epoxy, because of its unique properties like high strength, low density and easy to manufacturing etc. The container of the missile is made of composite shell structure stiffened with rectangular ribs on the interior surface. The missile is placed on the bulk head which supports the weight of the missile. The arrestors are made of mild steel used to locate the missile in the container. Nitrogen gas is filled in the container to maintain low temperature for the sensors of the missile. Fill port, vent port and pressure gauges are used for filling nitrogen gas. Lifting hooks are made of forged alloy steel are provided to facilitate lifting of the missile container. Fiber arrangement plays major role in carrying the loads. Fiber arrangement (layer orientation) is to optimize resistance to loads: ±45 degree plies give buckling stability and carry shear 0 degree plies give column stability and carry tension or compression ±90 degree plies carry transverse load Layer orientation = -90, -45, 0, 45, 90 Table 1: Different thickness of container Figure 5: Von mises stress plot The maximum VonMises Stress observed is 37Mpa Internal Pressure of MPa (Modified) Figure.6: Von mises stress plot The maximum stress singularity is 97.4 MPa. Case 2 Stacking Load of 1320 Kg (Existing) Figure.7 : Von mises stress plot The maximum VonMises Stress observed is 46Mpa Stacking Load of 1320 Kg (Modified) Figure.8: Von mises stress plot

3 Case 3 Braking Load of N (Existing) The maximum VonMises Stress observed is 27Mpa Stacking Load of 1320 Kg (Modified) Figure.9: Von mises stress The maximum VonMises Stress observed is 71Mpa Braking Load of N (Modified) Figure.16: Von mises stress Case 3 Braking Load of N (Existing) Figure.10: Von mises stress Case 4 Lifting Load of 1320 kg (Existing Figure.17: Von mises stress The maximum VonMises Stress observed is 38Mpa Braking Load of N (Modified) Figure.11: Von mises stress The maximum VonMises Stress observed is 36Mpa Lifting Load of 1320 kg (Modified) Figure.18: Von mises stress Lifting Load of 1320 kg (Existing) Figure.12: Von mises stress 3.2 Structural Analysis of Missile Container With 6mm Thickness Case 1 Internal Pressure of MPa (Existing) Figure.19: Von mises stress The maximum VonMises Stress observed is 21MPa Lifting Load of 1320 kg (Modified) Figure.13: Von mises stress plot The maximum VonMises Stress observed is 23Mpa Internal Pressure of MPa ( Modified) Figure.14: Von mises stress plots CASE 2 Stacking Load of 1320 Kg (Existing) Figure.20: Von mises stress 4.0 RESULTS AND DISCUSSIONS Composite container was studied for 4 different cases for existing and modified model with 4mm and 6mm thickness: Case 1 Internal pressure of 0.689Mpa Case 2 Stacking analysis Case 3 Braking analysis with 0.5g acceleration Case 4 Lifting analysis The strength of EGlass/Epoxy in different directions is tabulated below. The results obtained for various analyses with 4mm thickness for existing and modified models are tabulated below The above table shows the results of the missile container with 4mm thickness Figure.15: Von mises stress plot

4 From the results shown in the above table for existing model with 4mm thickness it is observed that the maximum linearized stress of 37Mpa, 46Mpa, 71Mpa and 36Mpa is observed for Internal Pressure, Stacking, Bracking and lifting loads respectively for the existing model with 4mm thickness. From these results it can be concluded that the stresses are more than the fibre strength in transverse direction and shear. From the above results it can be concluded that that existing missile container with 4 mm thickness is not safe under the given operating conditions. From the results shown in the above table for Modified model with 4mm thickness it is observed that the maximum linearised stress of 27.8Mpa, 68Mpa, 87Mpa and 27Mpa is observed for Internal Pressure, Stacking, Bracking and lifting analysis respectively for the modified model with 4mm thickness. From these results it can be concluded that the stresses are more than the fibre strength in transverse direction and shear for stacking and bracking loads. From the above results it can be concluded that that modified missile container with 4 mm thickness is not safe under the given stacking and bracking operating conditions. The results obtained for various analyses with 6mm thickness for existing and modified models are tabulated below The above table shows the results of the missile container with 6mm thickness From the results shown in the above table for existing model with 6mm thickness it is observed that the maximum linearised stress of 23Mpa, 27Mpa, 38Mpa and 21Mpa is observed for Internal Pressure, Stacking, Bracking and lifting loads respectively for the existing model with 6mm thickness. From these results it can be concluded that the stresses are less than the fibre strength for all operating loads. From the above results it can be concluded that that existing missile container with 6 mm thickness is safe under the given operating conditions for all operating loads. But to reduce the manufacturing complexity a modified model with 6mm thickness is designed and analyzed. From the results shown in the above table for Modified model it is observed that the maximum linearised stress of 21Mpa, 30Mpa, 31Mpa and 20Mpa is observed for Internal Pressure, Stacking, Bracking and lifting analysis respectively for the modified model with 6mm thickness. From these results it can be concluded that the stresses are less than the fibre strength in for all operating loads. This stress can be still be reduced by rubber mountings at the stress locations. From the above results it can be concluded that that modified missile container with 6 mm thickness is safe under the given internal pressure, stacking, bracking and lifting operating conditions. From the above table, we can conclude that braking analysis is the worst case and the container is in failure state in the transverse direction with 4 mm thickness. So, the design is not safe for 4mm thickness. By increasing the thickness from 4mm to 6mm, the stress has been decreased so it is recommended that design is safe. By this we can conclude that 6mm thickness is better than 4mm thickness. 5.0 CONCLUSION The Missile container is made of composite shell structure stiffened with rectangular ribs on the interior surface. To reduce the possibility of damage, missiles are shipped, stored and handled with approved missile containers. Approved containers, provide maximum missile safety with minimum handling by personnel. This makes the design and manufacturing of missile container a critical importance. It is also identified that the missile container is subjected to internal pressure load, Stacking load, Braking load and lifting load. In this paper we have designed and optimized the topology of the existing container which was of the lid type (suitcase) containers. This container has large contact area at the closing region due to which there was a huge manufacturing complexity. Detailed finite element stress analysis was also done to determine the static response of the existed and modified composite missile container for the loads mentioned above. Finite element analysis was done on the missile container for 4 different cases for existing and modified model: Case 1 Internal pressure of 0.689Mpa Case 2 Stacking analysis Case 3 Braking analysis with 0.5g acceleration Case 4 Lifting analysis The analysis results for the above loading conditions are documented and tabulated. From the results it is observed that VonMises stress is exceeding the yield strength of the material in the transverse direction with 4mm thickness in braking analysis which is the worst case.so, it is concluded that the design is not safe for 4mm thickness. Then the thickness of the container is increased from 4mm to 6mm and a detailed finite element analysis has been done for all above load cases. From the results it is observed that VonMises stress is less than the yield strength of the material in all the 4 load cases. Therefore it is concluded that the modified model with 6mm thickness is safe for all above operation loads. REFERENCES 1. Dorothy S. Ng (1999). Structural Analysis of Storage Container, U.S. department of energy. 2. Serena, Joseph M (1996). An On-Site Demilitarization Container for Unexploded Ordnance, Proc InstnMech Engrs Part C, No Bob Matthews (1998). Applied Stress Analysis, Marcel Dekker, Inc London. 4. Charles P. Haber (1976). Dynamic and Structural Analysis of Reusable Shipping & Storage Container for Encapsulated Harpoon Missile, Defense Technical Information Center, Europe. 5. Cardinal, J. W., Dobosz, S. A., Pomerening, D. J (1987). Nondestructive Analysis of MK 607 Harpoon Missile container, Southwest research institute, Federico A. Tavarez, Lawrence C. Bank, and Michael E. Plesha (2003). ACI structural journal, Analysis of Fiber-Reinforced Polymer Composite, Vol. 36, No. 8, Panos Y. Papalambros (1990). Journal of Mechanisms, Journal on Mechanical Design, Vol. 40, No Stephen W. Tsai (1996), Structural Behavior of Composite Materials, NASA, U.S. 9. M.J Hinton, P.D Soden (1998). Predicting failure in composite laminates, A. Puck, H. Schürmann (1998). Failure Analysis of FRP Laminates,

5 11. Hwai-Chung Wu, Bin Mu, Kraig Warnemuende (2003). Failure Analysis of FRP Sandwich Bus Panels by Finite Element Method, Swanson, R. S. (1997). Introduction to design and analysis with advanced composite materials. Prentice hall, Inc 13. Tuttle, M. E. (2004). Structural analysis of polymeric composite materials. Marcel Dekker Inc. 14. Berthelot J. M. (1999). Composite materials: Mechanical behaviour and structural analysis. Springer Verlag, New York. 15. J.L. Curiel Sosa (1997). Advances in Composites Materials - Ecodesign and Analysis, Marcel Dekker, Inc London. 16. Ever J. Barbero (1988). An Inelastic Damage Model for Fiber Reinforced Laminates, International Fiber Science and Technology,