Embedded Files
Weight reduction has always been desirable to enhance the vehicle performance, by giving the vehicle greater power to weight ratio. In 2-wheeler industry, there are continuous attempts to optimize the design for weight reduction or to come up with a new design to reduce the weight.
The figure some of the examples of optimization for weight reduction and material reduction.
This project was mainly to look into the area of weight reduction and optimization of wheels. Wheels, being an important component in 2 wheeler, transfers the motion generated by power train to the vehicle and also affects the handling of the vehicle. The earliest light-alloy wheels were made of magnesium alloys. Although they lost favour for common vehicles, they remained popular through the 1960s, although in very limited numbers. In the mid to late 1960s, aluminium-casting refinement allowed the manufacture of wheels that were safe. Until this time, most aluminium wheels suffered from low ductility, usually ranging from 2-3% elongation. This meant these earlier aluminium-alloy wheels were quite brittle. Because light-alloy wheels at the time that were often made of magnesium (often referred to as "mags"), these early wheel failures were later attributed to magnesium's low ductility, when in many instances these wheels were poorly cast aluminium alloy wheels. Once these aluminium casting improvements were more widely adopted, the aluminium wheel took the place of magnesium as low cost, high-performance wheels for Motorsports. Lighter wheels can improve handling by reducing unsprung mass, allowing suspension to follow the terrain more closely and thus improve grip, however not all alloy wheels are lighter than their steel equivalents. Reduction in overall vehicle mass can also help to reduce fuel consumption. Better heat conduction can help dissipate heat from the brakes, which improves braking performance in more demanding driving conditions and reduces the chance of reduced brake performance or even failure due to overheating.The rider comfort with respect to road vibrations can directly be correlated to wheel stiffness.
The FEA of wheel, which includes static stress analysis, fatigue analysis, stiffness analysis,etc is done extensively throughout the industry. The various preprocessor, solvers and post processors are incorporated, mainly being, Hypermesh, simlab, ABAQUS, ANSYS, etc.
Introduction on Mag alloys: Magnesium alloys are mixtures of magnesium with other metals (called an alloy), often aluminium, zinc, manganese, silicon, copper, rare earths and zirconium. Magnesium is the lightest structural metal and its alloys have a hexagonal lattice structure, which affects the fundamental properties of these alloys. The strength-to-weight ratio of the precipitation-hardened magnesium alloys is comparable with that of the strong alloys of aluminium or with the alloy steels. Magnesium alloys, however, have a lower density, stand greater column loading per unit weight and have a higher specific modulus. They are also used when great strength is not necessary, but where a thick, light form is desired, or when higher stiffness is needed. Magnesium's particular merits are similar to those of aluminium alloys: low specific gravity with satisfactory strength. Magnesium provides advantages over aluminium, in being of even lower density (approx. 1800 kg/m³) than aluminium (about 2800 kg/m³). Mechanical properties of magnesium alloys, however, are below those of the strongest of the aluminium alloys.A particular attraction of magnesium alloys lies in their extraordinarily good machining properties. The idea behind the choice of magnesium alloy for design of alloy wheel came from the above specified advantages. This helped in reducing the weight by 10% of the original weight of the component and helped in enhancing few properties like rider comfort,etc.
Optimization: The various load cases were formulated as per test standards and road conditions. The cyclic loads were taken into account for fatigue analysis. Then, the optimization of this particular component was carried out both using the manual iterations and using OptiStruct(optimization tool provided by Altair software) , enforcing the stress and stiffness constraints, design and manufacturing constraints, to reduce the weight of the component. The final design obtained was then tested as per standards and also checked for rider comfort. The new design came out to be better than existing designs. Then another procedure was established for design of magnesium wheels. The optimized design was different from the existing aluminium wheel designs. After the positive testing and rider comfort results, the design came out to be 10% less than the original aluminium alloy wheel. But the material itself has few shortcomings, like low melting point, corrosion, etc.
The optimized results of a similar problem is shown in the above figure. reference : http://www.hindawi.com/journals/smr/2013/831017/
Google Sites
Report abuse