THE EXPERIMENTAL IDENTIFICATION OF TORSIONAL ANGLE ON A LOAD-CARRYING TRUCK FRAME DURING STATIC AND DYNAMIC TESTS

The underframe of a truck is one of the most loaded parts of a vehicle. It is a spatial unit and it must be strong enough to withstand random loading within many years of maintenance. The most severe form of deformation is in torsion. So, frame side members are often made from elements with channel sections, rigid for bending and flexible for torsion. Authors have conducted the research of 6x6 high mobility wheeled vehicle assigned to 20-feet container. Their load-carrying structure is made from two separate underframes: longitudinal and auxiliary connected with bolted joints. The goal of the research was to check if the torsional angle of deformation of the underframe during static and dynamic tests is within an acceptable range. The static test was carried out for the main underframe first to assess the characteristic of torsional stiffness without the auxiliary frame. After connecting both frames together the measure was conducted again. In the experiment the diagonal wheels were lifted up and the resulting displacement of the ends of the frame side members was recorded. Simultaneously the strain at chosen points of the underframe was measured with a system of turned half bridge strain gauges. After calibrating the measuring system a second part of experiment was conducted within proving ground tests when the vehicle was fully loaded. The collected strain data at chosen points allowed for calculating the resultant displacement of the ends of the frame side members in function of sort of road and to indicate the influence of auxiliary frame on increasing the torsional stiffness of the underframe.