Search Results

A Mega-bracket is a cast bracket which connects a chassis frame of a truck to the front bumpers and usually there are two of these for a truck. The mega-brackets help provide clearance for the engine radiator and hence it has a curved shape. It is usually designed to support the towing load when a fully loaded truck needs to be towed following a break-down. A general method of designing a mega-bracket, using shape optimization techniques, is described with a case study. A preliminary design was found to be unsatisfactory to support the tow loads. Finite Element (FE) Topology optimization techniques were used to give us directions as to where ribs should be provided to support the tow loads. FE Shape optimization techniques were then applied to size the ribs and also the rest of the structure using shape variables, which are possible design variations. Since the mega-bracket is irregular in shape, it is extremely difficult and time consuming to generate shape vectors.

A case study of the application of shape optimization techniques to reduce the weight of a steering knuckle of a heavy truck suspension has been presented. Design analysts, who work with finite element shape optimization, face a daunting task while handling such complicated parts - uneven shape, multiple load cases and element distortions during shape optimization, etc. A baseline analysis confirmed that the knuckle was overweight. A shape optimization analysis was undertaken to bring down its weight and at the same time keep the stresses within design limits. A numerical interpolation method has been used to generate shape vectors. The weight of the knuckle was brought down by 12.7% and the final design was verified using II order solid finite elements.

A case study of an application of shape optimization techniques in the design of an upper control arm of an automotive suspension system has been presented. An existing design of an upper control arm had high stresses and low fundamental frequency. The designer's inputs as to the various possible shape changes, constraints of movements etc. were built into the optimizer as shape variables and constraints. Shape optimization was then performed using approximate direct linearization method of MSC/NASTRAN software. A number of design directions were obtained. With a 24% weight penalty the first frequency was raised to 834 Hz. and brought closer to the target of 900Hz. and the stresses were also brought down by 30%.

A methodology of using topological optimization technique for bring down the weight of a structure has been discussed. Special variables are defined for each of the finite elements, which are related to the thickness, density and Young's Modulus of the material. A Topology optimization problem is set up to solve for these special variables. The major advantage in this method is that the user can give additional stress and displacement constraints. Optimization solvers, which can handle discrete variables, are required. At the end of the optimization the special variables are snapped on to pre-defined extreme values which determine which elements could be successfully eliminated to reduce weight of the structure.

A case study of the application of topography and shape optimization techniques to the design of a jounce bumper bracket of a pick-up truck has been presented. First a sizing (gage) optimization was undertaken to redesign the jounce bumper bracket. Since the weight was not satisfactory it was decided to try shape optimization. A better solution was obtained. Topography optimization, a relatively new technique of bead formation, was then applied and a still better solution was obtained. All these options were presented to the designer to enable him to make a decision based on manufacturing and other constraints. Although all the three solutions seems to give good results the topography optimized jounce bracket results in the least weight, with the penalty of an additional manufacturing operation.

A case study of the application of optimization techniques to the design of rear-axles-connecting-linkage of heavy trucks with only two rear axles has been presented. The rear axles are made to move in tandem by designing a linkage connecting the two at each of its ends. The linkage locations are determined by the inter-axle-drive shaft, which is a telescopic tube. The drive-shaft is mounted with U-Joints on the two rear axles and follows the bumps and rebounds of the roads with minimal rotation about the lateral axis. Optimization techniques were applied to a planar ADAMS Model to minimize the drive shaft rotation.

Automotive drive shafts, which transmit power from the transmission unit to the rear axle are in general straight round tubes. An attempt has been made to explore other possible cross-sectional shapes to improve NVH (Noise Vibration and Harshness) performance. The first natural frequency is a very good indicator of the NVH performance. First, finite element based topology optimization and later topography optimizations were tried out. A number of design solutions were obtained from the study and a comparison has been made. A round drive shaft with a bulge at the center has been proposed for stiffenening the drive shaft to improve the first natural frequency.

The application of shape optimization techniques to reduce the weight of a power-take-off (PTO) casting housing has been presented. Shape vectors required for optimization were generated by numerical interpolation method using Autodv software. Shape optimization is performed in MSC/NASTRAN using ‘Direct Linearization’ method. The weight of the casting housing has been reduced by 40%. In conclusion, shape optimization techniques can be used to reduce the weight of any casting, which is non-uniform in shape and size.

The application of optimization technique in the frequency domain, to move the frequencies outside certain range, is presented. An engine cradle under development had very high responses in 50 - 60 Hz. range. A modal analysis identified the cause as the mounting springs' natural frequencies. Optimization technique (direct linearization method) was applied to change the spring stiffnesses to move its natural frequencies outside the range of interest. Response plots at various salient locations on the engine cradle, before and after optimization, confirmed the analysis. The large response in the frequency domain was moved outside the 50 - 60 Hz. range.