Study on Leaf Spring Torsion with Elastic Large Deformation

The aim of this study is to show the relationship of elastic large deformation between torque and torsional angle for a bar with rectangular cross section. The formula about torque and torsional angle is modified by numerical analysis and experimental verification. High order item of torsional angle is added to the traditional formula, based on different boundary condition, which was set to zero before in the textbook. Using improved formula higher accuracy loading will be gotten when a leaf spring is twisted to elastic large deformation. Two types of leaf springs are used with depth of 6.8mm and 7.7mm with the same width of 100mm. The leaf springs are analyzed by finite element software of ANSYS with unit of SOLID 45. They are also tested by mechanical torsional loading device, with linear loading from 0 to 830N.m or 0 to 560N.m respectively. Both theoretical analysis and experimental results show that, there are some nonlinear characteristics when leaf springs with elastic large deformation. With comparison to linear fitting and cubic curve fitting, the linear fitting has larger error than cubic curve fitting. The cubic curve fitting can improve accuracy about 2 orders. In order to improve precision of leaf spring loading, the high-order curve should be used.