Jagadeep Thota

Optimization of a Vehicle Space Frame Under Ballistic Impact Loading

Shock from impact loading may risk the lives of the occupants of a military vehicle and damage the sensitive electronic components within it. A finite element model (FEM) for a space-frame based military vehicle is presented in this paper. An approach is developed to optimize the design of the joints within the space frame structure to reduce the mass of the vehicle while maintaining its structural integrity. The process starts by creating a parametric FEM of the vehicle. The optimization variables are the lengths of joint branches. The effect of joint location within the space frame is also explored. The problem is subject to geometry and stress constraints. Results show that a mass reduction can be achieved without adversely affecting integrity of the vehicle.Copyright

Finite Element Modeling of a Lightweight Composite Blast Containment Vessel

This paper presents various approaches for finite element modeling of a cylindrical lightweight composite vessel for blast containment purposes. The vessel has a steel liner that is internally reinforced with throttle and gusset steel plates and wrapped with a basalt fiber/epoxy composite. The vessel design is fairly complex, including many geometric details and several components with different material models. The objective of this work is to determine an accurate and efficient procedure for modeling this type of vessels. This model can be used within an iterative optimization process. Different modeling approaches using various combinations of element types, material models, and geometric details are explored. Results of these models are compared to available experimental data. Accuracy and computational time between all these models are also compared. A suitable modeling method is recommended based on these findings.

Simulation of Shock Response in a Lab-Scale Space Frame Structure Using Finite Element Analysis

Space frames are usually used to enhance the structural strength of a vehicle while reducing its overall weight. Impact loading is a critical factor when assessing the functionality of these frames. In order to properly design the space frame structure, it is important to predict the shocks moving through the members of the space frame. While performance of space frame structures under static loads in well-understood, research on space frame structures subjected to impact loading is minimal. In this research, a lab-scale space frame structure, comprising of hollow square members that are connected together through bolted joints which allow for quick assembly/disassembly of a particular section, is manufactured. Non-destructive impact tests are carried out on this space frame structure and the resulting acceleration signals at various locations are recorded. A finite element (FE) model of the lab-scale structure is created and simulated for the experimental impact loads. Acceleration signals from the FE model are compared with the experimental data. The natural frequencies of the structure are also compared with the results of the FE model. The results show a good match between the model and the experimental setup.Copyright

Structural Response Optimization of a Light-Weight Composite Blast Containment Vessel

This paper proposes an optimization technique for increasing the structural integrity of a light-weight composite blast containment vessel. The vessel is cylindrical with two hemispherical ends. It has a steel liner that is internally reinforced with throttles and gusset plates and wrapped with a basalt-plastic composite. A computationally-efficient finite element model of the blast containment vessel was proposed and verified in an earlier work. The parameters of the vessel are incorporated within an iterative optimization procedure to decrease the peak strains within the vessel, which are caused by internal blast loading due to an explosive charge placed at the center of the vessel. The results of the proposed procedure are validated for different initial guesses of the design variables.

COMPUTATIONAL PREDICTION OF LOW IMPACT SHOCK PROPAGATION IN A LAB-SCALE SPACE BOLTED FRAME STRUCTURE

Bolted space frames are usually used to allow easy assembly and disassembly, as well as replacing defective components. Although the performance of bolted space frame structures under static loads is well understood, research on the shock propagation through these frames is limited. The focus of this study is to understand shock propagation through space frames, which is a critical factor when assessing the functionality of these frames. In this research, a lab-scale space frame structure, comprising hollow square members that are connected together through bolted joints is constructed. Non-destructive impact testing is carried out on this structure and the resulting acceleration signals at various locations are recorded. The objective of this work is to develop a finite element (FE) modeling approach that can reasonably replicate experimental results.

Material Characterization of Rubberized Aramid for Shock Mitigation

Modern military vehicles can reduce transmitted shocks to critical components within it through the use of composite armor and rubberized material at the space frame joints. Therefore, proper material models of these shock absorbing materials are imperative to accurately understand shock transmission. While quasi-static mechanical characteristics of candidate materials may be well understood, their behavior under dynamic conditions has not been studied as much. This research presents the mechanical characterization of rubberized aramid, which is used as a part of a composite armor. Since the rubberized aramid material may be subjected to large deformations due to the high impact loading, a strain-sensitive material model is proposed to describe this material computationally. Tensile tests on rubberized aramid are conducted under various strain rates. Additionally, dynamic mechanical analysis (DMA) vibration tests are conducted to determine the damping property of the rubberized aramid material. These measured characteristics can be incorporated in the material models that will be used in the computational analysis of the armored vehicle under shock loading.Copyright

Shock Optimization in a Military Vehicle With Internal Space Frame

Space frames are usually used to enhance structural strength of the vehicle while reducing its overall mass. These frames are comprised of beams that are joined together. Recently, space frames are being incorporated in military vehicles. Space frames in military vehicles are however subjected to different types of loading than what is encountered in civilian vehicles such as projectile impacts and land mine blasts. Due to the need to replace a damaged section of the space frame quickly, the proposed space frame is composed of hollow square cross-section bars and angle sections that are bolted together. The space frame is enclosed by uniform-thickness armor, except at the turret. The vehicle is subjected to high impact load to simulate a projectile hit. The objective of this work is to minimize shocks at various critical locations of the space frame while maintaining the overall structural integrity of the vehicle. The vehicle model is parameterized to achieve this objective. This problem is solved using the Successive Heuristic Quadratic Approximation (SHQA) technique, which combines successive quadratic approximation with an adaptive random search within varying search space. The entire optimization process is carried out within MATLAB environment.Copyright

Optimization of a Military Vehicle Space Frame Subject to High Impact Loading

Space frames are usually used to enhance structural strength of the vehicle while reducing its overall weight. These frames are comprised of beams connected together at joints. Recently, space frames are incorporated in military vehicles. However, space frames in this case are subjected to different types of loading than what is encountered in civilian vehicles such as, projectile and land mine attacks. In this paper, a finite element model for the upper half of the space frame of an armored vehicle is developed. The space frame is composed of hollow square cross-section bars and angle sections and is enclosed by uniform-thickness armor, except at the turret. The vehicle is subjected to high impact load that simulates an impact of a projectile. The model is parameterized to minimize the mass of the space frame and vehicle armor by varying the cross-sectional parameters of the beam members and joints, and the thickness of the armor plate, while maintaining the overall structural integrity of the space frame. This problem is solved using the Successive Heuristic Quadratic Approximation (SHQA). This algorithm combines successive quadratic approximation with an adaptive random search within varying search space. The entire optimization process is carried out within MATLAB environment. Results show significant reduction of the mass of the vehicle.Copyright

Optimization of a Light-Weight Composite Blast Containment Vessel Structural Response

This paper proposes an optimization technique for increasing the structural integrity of a light-weight composite blast containment vessel. The vessel is cylindrical with two hemispherical ends. It has a steel liner that is internally reinforced with throttles and gusset plates and wrapped with a basalt-plastic composite. A finite element model of the blast containment vessel was proposed and verified in an earlier work. The parameters of the vessel are incorporated within an iterative optimization procedure to decrease the peak strains within the vessel, which are caused by internal blast loading due to an explosive charge placed at the center of the vessel. The procedure is validated for different initial guesses of the design variables.Copyright

Modeling of a Light-Weight Composite Blast-Containment Vessel

This paper presents finite element modeling of a lightweight composite vessel for blast containment purposes. The vessel has a steel liner that is internally reinforced with throttles and gusset plates and wrapped with a basalt fiber/epoxy composite. The vessel design is fairly complex, including many geometric details, and several different materials. The objective of this work is to determine an efficient analysis procedure that can be used in an iterative optimization process. Analysis approaches using various combinations of element type, material models, and geometric detail are explored. Finite element results are compared to experimental data. Accuracy and efficiency are compared for all cases and a suitable analysis method is recommended.Copyright