Stress analysis for truck chassis with riveted joints

The fact that most of the transportation is carried out on highways in our country, increases the importance of truck-type vehicles. Heavy loads and unstable road conditions may cause some structural problems on these vehicles after a certain service life. Typical problems are some time dependent failures caused by the increase in stress in some critical locations. Therefore, it is important to investigate the stress and strain values of chassis connections, which might lead to the solution of problems by design development. In this study stress analyses of a truck chassis with riveted joints has been investigated. Nowadays, computer programs using finite elements are utilized for static and dynamic analysis of complex structures. In the method, a mathematical model of the structure is described. The model which has the static and dynamic properties of a real structure, is divided into finite elements of known elastic properties, and written in matrix form. Developing computer technology and software are the tools for the solution of the problem. ANSYS. A general purpose finite element program has been used in this study. First of all, stress analysis of a general model of the chassis has been made. Results of this stage were rough due to the great dimensions of the model. Submodeling technique was utilized for more accurate results. The results of the first solution were used as the boundary conditions for the detailed models of the connections. In the first stage of this study, stress distributions of two different chassis models, one of which has a fixed spring hanger(model 1). While other has movable (model 2), have been analyzed under three different road conditions.II Under the normal road conditions (road case 1), the stress values of the two different type of chassis have been found to be similar. But in the chassis model which has a fixed spring hanger(model 1), maximum principal stresses across the flange of the beam increases sharply. In the case of one rear wheel is free(road case2), which may occur the wheel drops into a hollow, the absolute stress values of the chassis with movable spring hanger(model 2) are found to be smaller than the other types values. In the case of a front wheel is free (road case3) stress values of the two types of connections increase. In the second stage of the study, the chassis with movable spring hanger (model2) which has lower stress values has been considered. And the effects of some modifications in connection plate have been investigated for the two road cases. Results can be summarized as follows: Stress distribution of connection plates with various thickness as 6mm, 8mm, and 10mm has been analyzed. Maximum principal stresses decrease with increasing plate thickness. The connection plate width has been changed (1=390, 430 and 470mm). Increasing plate width slightly decreases stress values under normal road conditions (road easel), while it increases stress values in the case of a fee front wheel (road case3). The increase in connection plate width decreases the flexibility of the connection which leads to an increase in stress and formation of tree axial stresses. The main profile thickness of the chassis increased from 8mm to 1 3 mm, while the connection plate thickness decreased from 6 mm to 5 mm. Maximum principal stress decreases with increasing moment of inertia. But chassis weight increase %8. It has been observed that any change of rivet distribution, rivet diameter and shape of connection plate also effects the maximum principal stress distribution. Choosing a convenient rivet placement and optimizing connection width and thickness seem to be practical solutions for decreasing the stress values when a modification in the main profile of the chassis is not possible.