MODELLING AND ANALYSIS OF LEAF SPRING IN HEAVY TRUCK PROJECT REPORT
LEAF SPRING.doc (Size: 1.98 MB / Downloads: 138)
In order to conserve natural resources and economize energy, weight reduction has been the main focus of automobile manufacturers in the present scenario. Weight reduction can be achieved primarily by the introduction of better material, design optimization and better manufacturing processes. The suspension leaf spring is one of the potential items for weight reduction in automobiles as it accounts for 10% - 20% of the unsprung weight. This achieves the vehicle with more fuel efficiency and improved riding qualities. The introduction of composite materials was made it possible to reduce the weight of leaf spring without any reduction on load carrying capacity and stiffness. Since, the composite materials have more elastic strain energy storage capacity and high strength to weight ratio as compared with those of steel, multi-leaf steel springs are being replaced by mono-leaf composite springs. The composite material offer opportunities for substantial weight saving but not always be cost-effective over their steel counterparts.
NEED FOR ANALYSIS
Recently, automotive industry requires higher level of design and calculation almost in every part in both fabrication and testing which can make it possible to improve and develop products. Leaf spring, one of automotive parts, was mainly design based on trial-and-error techniques and simplified equations using a 3-link The method developed, especially nonlinear analysis, makes it possible to accurately design leaf springs. A research using nonlinear analysis to solve leaf spring problem was discussed by Liu, however, only single leaf spring model was considered. The purpose of design development for the suspension springs are not only to reduce weight and vibration for a soft ride, improve durability when subjected to cyclic loading, or improve quality of spring material and processing, but also to reduce time and manufacturing cost in the design process to gain the highest economic benefit. Computer technology in terms of CAD/CAE (Computer-Aided Design and Engineering) has been applied to solve engineering problems for several decades. Finite element method is an effective part of CAD/CAE applied in design and analysis to solve complicated problems. Leaf spring simulation using commercial code such as ANSYS, MSC/NASTRAN and MDI/ADAMS by employed beam elements to model leaf spring showed accurate behavior prediction. Currently, the design of multi-leaf springs and the prediction of behaviors are more efficient using finite element methods as presented in Ref.
Materials constitute nearly 60%-70% of the vehicle cost and contribute to the quality and the performance of the vehicle. Even a small amount in weight reduction of the vehicle, may have a wider economic impact. Composite materials are proved as suitable substitutes for steel in connection with weight reduction of the vehicle. Hence, the composite material have been selected for leaf spring design.
The commonly used fibers are carbon, glass, keviar, etc.. Among these, the glass fiber has been selected based on the cost factor and strength. The types of glass fibers are C-glass,S-glass and E-glass. The C-glass fiber is designed to give improved surface finish.S-glass fiber is design to give very high modular, which is used particularly in aeronautic industries. The E-glass fiber is a high quality glass, which is used as standard reinforcement fiber for all the present systems well complying with mechanical property requirements. Thus, E-glass fiber was found appropriate for this application.
In a FRP leaf spring, the inter laminar shear strengths is controlled by the matrix system used. since these are reinforcement fibers in the thickness direction , fiber do not influence inter laminar shear strength. Therefore, the matrix system should have good inter laminar shear strength characteristics compatibility to the selected reinforcement fiber. Many thermo set resins such as polyester, vinyl ester, azpoxy resin are being used for fiber reinforcement plastics(FRP) fabrication . Among these resin systems, epoxies show better inter laminar shear strength and good mechanical properties. Hence, epoxide is found to be the best resins that would suit this application. different grades of epoxy resins and hardener combinations are classifieds , based on the mechanical properties.
Among these grades , the grade of epoxy resin selected is Dobeckot 520 F and the grade of hardener used for this application is 758. Dobeckot 520 F is a solvent less epoxy resin.
Which in combination with hardener 758 cures into hard resin . Hardener 758 is a low viscosity polyamine. Dobeckot 520 F , hardener 758 combination is characterized by
Good mechanical and electrical properties.
Faster curing at room temperature. Good chemical resistance properties