Lightweight Design And Research On Skeleton Structure For Commercial Vehicle Cab

With the problems about energy crisis and global warming, lightweight of Automobile has been a hot topic. The lightweight of Automobile can not only reduce fuel consumption but also allow to fit more equipments to improve the car's performance. In order to reduce Automobile weight, we can consider from three aspects: materials, processes and structure. This paper mainly studies to use the framework to substitute the original cab's skeleton structure. According to the requirement of strength, stiffness, and vibration characteristics, it implements the lightweight design on commercial vehicle cab.The traditional cab that meets the strength, stiffness and vibration requirements is made from welded sheet metal, but its skeleton structure has a great mass, which restricts the lightweight design of cab. The method of using framework instead of original cab's skeleton structure can not only make cab stronger, higher, and more secure, also effectively reduce the quality of the cab.First of all, the hard points of original cab are determined on the basis of its finite element model. According to the coordinate of hard points, the finite element model of the framework is built in HyperMesh. In the solver OptiStruct, the cross-section parameters of each beam in the framework is firstly optimized through size optimization to get a framework that has more or less the same properties as original cab; secondly, through topology optimization the best position of stiffening beams are found, then according to topology optimization result, measures of improvements are proposed and the improved framework is built; thirdly, we must once again use size optimization to optimize the cross-section parameters of each beam in the improved framework, in order to get a lighter framework under the conditions of the same structural performance with the original cab; finally, the shape of the lighter framework is optimized through shape optimization to increase the first natural frequency. At this point, the optimum framework is obtained, and its total mass is 157kg Secondly, the 3D model of the optimum framework is established in Catia and imported into HyperMesh. The optimum framework's finite element model is built based on shell element, then the skin, simplified steering mechanism and seat finite element model are added to the optimum framework's finite element model to establish a finite element model of the framework cab. Furthermore the finite element model of the suspension brackets and vehicle frame are built, the framework cab, suspension brackets and vehicle frame then assembled together through the rigid element. According to the front impact, roof strength and rear wall strength of virtual test analysis in LS-DYNA, you will found that the framework cab satisfies specified requirements of the ECE R29 regulations.At last, the total mass of framework cab is 235kg, it is a great achievement compared the total mass 330kg of original cab.