Gradient Stiffness Leaf Spring Design

The suspension leaf spring is one of the most widespreadly used mechanical elements in modern vehicles. The gradual rigidity leaf spring is a suspension machine with the rigidity changing according to the load on it. The rigidity of a leaf spring has much to do with the vehicle ' s kilter and with good kilter the passengers and the driver of the vehicle will feel easy and the goods are safe. So with an advanced suspension machine on a automobile, you will get improved productivity on transportation, get more life-span and more reliability on the parts of the vehicles and consume less fuel. The rigidity curve of the gradual rigidity leaf is close to the ideal curve and the gradual rigidity leaf id widespreadly used.In order to improve the method of gradual rigidity leaf spring design, a series of research works in the relevant areas including geometric design, testing of stress of gradual rigidity leaf spring, management of geometric data of leaf spring and parametric drawing of leaf spring have been taken in this dissertation.Based on the restrictive principle of linear model, the typical currently used models are thoroughly analyzed, with their fatal errors being indicated, and the new model used to determine spring rate leaf stress and clamped spring camber, clamp stress are developed. Compared with the old ones, the new model has more accuracy, fitting for means of optimization. The optimization models of gradual rigidity leaf spring are established as following: dimension parameters as design variables, weight and life-span as the objective function, performances, geometrical and stress conditions as the constraints. An example is calculated by this means and the result is discussed to verity that this method is reliable.In order to know whether the design is under the command of rigidity and strength, the stiff and stress of a gradual rigidity leaf spring are tested. In the test, gradual loading is used. By analyzing the test result, the inter-leaf contact and the gradual rigidity are determined and someuseful conclusions are obtained.We have developed special software in Windows environment to manage geometric data of leaf spring. We can accomplish all the tasks easily, including browsing data, appending data, deleing data and modifying data. Moreover, the software has the characters: speedy operation, good agility and good integrity. With the virtues of great agility and good integrality, the software functions very well and applies widely. With this software, geometric data of leaf spring in the drawing can be stored as data record and the drawing may be obtained instantaneous by means of parametric drawing.We have made an application program with AutoLISP in the AutoCAD environment and with this program we can finish a drawing of leaf spring, which takes only several minutes. So with it the designers may get rid of the unimportant things and after trial it is improved.Those two parts have friendly interfaces and work well. We have use them and found they are easy to run. If we work with them, efficiency may be achieved.In this paper, the design method of gradual rigidity leaf spring has been studied and the precision of the design outcome on gradual rigidity has been improved. A test on special gradual rigidity leaf spring has been done and the test result prove the outcome of the calculation. The optimization on gradual rigidity leaf spring has also been studied. There is only study on optimization of other types of leaf spring before. The special software about parametric drawing and management on geometric data of leaf spring has bring us efficiency.