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It is necessary to detect danger as soon as possible to avoid rollover of a vehicle in sudden events. Using rollover index in real time can be used for this purpose. The traditional rollover indices currently applying in the vehicles can only detect the untripped rollover due to severe lateral acceleration in vehicles. These indices cannot detect the tripped rollover resulted from vertical external forces in a long direction. There are recently many quantitative studies about the tripped rollover and an index was also introduced to this kind of rollover. In this research, we examined the dynamics of a SUV to improve this index and also presented a new index to detect the both types of rollovers. The precision and accuracy of the new index was evaluated by simulation in industrial software of Carsim. The numerical results of the new developed model were compared with the test results of an automobile at one-eighth scale in equal conditions and inputs. The results are indicative of the better performance of the new model presented in this research. KeywordsVehicle dynamics, Tripped rollover, Untripped rollover, Rollover index, Suspension system Rollover Index for the Diagnosis of Tripped and Untripped Rollovers

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In this article, a strain energy density function of the Saint Venant—Kirchhoff type is expressed in terms of a Lagrangian deformation measure. Applying the governing postulates to the form of the strain energy density, the mathematical expression of this measure is determined. It is observed that this measure, which is consistent with the strain energy postulates, is a strain type with the characteristic function more rational than that of the Seth—Hill strain measures for hyperelastic materials modelling. In addition, the material parameters are calculated using a novel procedure that is based on the correlation between the values of the strain energy density (rather than the stresses) cast from the test data and the theory. In order to evaluate the performance of the proposed model of the strain energy density, some test data of pure homogeneous deformations are used. It is shown that there is a good agreement between the test data and predictions of the model for incompressible and compressible isotropic materials.