Experimental Studies Into the Durability of the Elements of Vehicle Frames Under Complex State of Loads

So far, permissible stress in the form of Wöhler's curves have been determined on very simple samples and under single load, e.g. at bilateral bending, torsion, tension etc. Hence, their uselessness is rather obvious when thin-walled structures consisting of rods subject to a complex state of loads.

This paper presents the results of studies into the durability of thin-walled elements of frames for different values of the quotient of torsional loads-to-loads bending the frame. Studies were performed on a special stand which allowed to widely change both torsional and bending loads and their relation - such in the same way as it happens when vehicle travels along the road. The results are given in the Wöhler's diagrams form and in analytical way as well. It has been demonstrated that permissible fatigue stresses for the tested elements of frame differ considerably from those published in Standards and Regulations