Design of Leaf Spring

The main functions of automobile suspension systems are to isolate the structure and the occupants from shocks and vibrations generated by the road surface. The suspension systems basically consist of all the elements that provide the connection between the tyres and the vehicle body. A spring is an elastic object used to store mechanical energy. It is an elastic body that can be twisted, pulled, or stretched by some force. It can return to their original shape when the force is released. It is a flexible element used to exert a force or a torque and, at the same time, to store energy. The force can be a linear push or pull, or it can be radial, acting similarly to a rubber band around a roll of drawings. The torque can be used to cause a rotation. The main objective of this research paper is to through some light on the fatigue stress analysis of springs used in automobiles. Theoretical, Numerical and Experimental methods are used for the analysis of springs but Finite Element Method is the best for its analysis and calculating the fatigue stress, life cycle and shear stress springs.

This paper presents a nonlinear finite element model for the leaf spring that can be used in multibody applications and vehicle dynamic simulations. The floating frame of reference formulation is used in this investigation to model leaf spring nonlinear dynamics. This formulation accounts for the coupling between different modes of deformation as well as the nonlinear coupling between the rigid body motion and the elastic deformation. By employing component mode synthesis techniques, a reduced order model is obtained for the leaf spring while maintaining a good degree of accuracy. The inertia shape integrals can be calculated once in advance using a preprocessor and then stored to be used to automatically generate the nonlinear equations of motion of the leaf spring. The use of a preprocessor to evaluate the inertia shape integrals before the dynamic simulation leads to considerable saving in CPU time and allows the utilization of existing finite element computer codes to obtain the data required for the flexible body simulation. This reduced order model is implemented in a general multibody algorithm in order to examine the effectiveness and robustness of the proposed techniques. As an application, the wind-up deformation of the front suspension system of a typical sport utility vehicle under severe braking condition is investigated.

Nowadays weight optimization is increasingly becoming an important tool for manufacturing and mechanical design. A formulation and solution technique using Particle Swarm Optimization (PSO) and Simulated Annealing (SA) for design optimization of Composite Leaf Springs is presented in this work. Leaf Springs are long and narrow plates attached to the frame of a trailer that rest above or below the trailer's axle. This paper aims at minimizing the weight of leaf spring subjected to certain constraints. The dimensions of an existing conventional leaf spring of a light commercial vehicle are used to design mono composite (E-Glass epoxy) leaf spring which is of great interest to the transportation industry. The constant cross-section design is used due to its capability for mass production and to accommodate continuous reinforcement of fibres. The design constraints are bending stresses and deflection. Compared to the steel spring, the composite spring has stresses and deflection that are much lower, and the spring weight is nearly 85.02% lower using Particle Swarm Optimization and 78.87% lower using Simulated Annealing. From the results, it is observed that the composite leaf spring is lighter and more economical than the conventional steel spring with similar design specifications and two techniques are compared which shows that Particle Swarm Optimization has outperformed Simulated Annealing.

Recently, genetic algorithms (GA) and particle swarm optimization (PSO) technique have attracted considerable attention among various modern heuristic optimization techniques. Since the two approaches are supposed to find a solution to a given objective function but employ different strategies and computational effort, it is appropriate to compare their performance. This paper presents the application and performance comparison of PSO and GA optimization techniques, for Thyristor Controlled Series Compensator (TCSC)-based controller design. The design objective is to enhance the power system stability. The design problem of the FACTS-based controller is formulated as an optimization problem and both the PSO and GA optimization techniques are employed to search for optimal controller parameters. The performance of both optimization techniques in terms of computational time and convergence rate is compared. Further, the optimized controllers are tested on a weakly connected power system subjected to different disturbances, and their performance is compared with the conventional power system stabilizer (CPSS). The eigenvalue analysis and non-linear simulation results are presented and compared to show the effectiveness of both the techniques in designing a TCSC-based controller, to enhance power system stability.

Genetic algorithms (GA) and particle swarm optimization (PSO) are the most famous optimization techniques among various modern heuristic optimization techniques. These two approaches identify the solution to a given objective function, but they employ different strategies and computational effort; therefore, a comparison of their performance is needed. This paper presents the application and performance comparison of the PSO and GA optimization techniques for a static synchronous series compensator-based controller design. The design objective is to enhance power system stability. The design problem of the FACTS-based controller is formulated as an optimization problem, and both PSO and GA optimization techniques are employed to search for the optimal controller parameters.

Conventional leaf spring made up of conventional materials like plain carbon steel are heavy and add weight to vehicle which reduces mileage. This necessitates new material which is light in weight and could provide adequate strength to leaf spring along with higher strain energy absorption to absorb shocks. The current research is intended to study the structural and vibrational characteristics of leaf spring made of P100/6061 Al, P100/AZ 91C Mg and structural steel materials. The investigation is carried out using ANSYS FEA software. The FEA results have shown that P100/AZ/ 91C generated lower stresses as compared to P100/6061 Al and structural steel material. The modal analysis of leaf spring aided to determine mass participation factor and mode shapes corresponding to each frequency.