Analysis of High Cycle Fatigue In Welded Joints Of Profiles With Thin Walls Used In Bus Structures Subjected To Combined Loads Through Comparative Analysis 2019-36-0074

Projects of bus body structures must be developed taking into consideration the dynamic loads that this type of vehicle is subjected to. Experimental and numerical methods can be used to evaluate fatigue life in order to determine the durability of these vehicles. Bus structures are basically constructed using welded thin walled profiles that are often oversized due to the lack of knowledge of several product characteristics such as the conditions of the pavements, deficiency of characterization of welded joints and the quality of the materials used. Allied to this the Brazilian road system counts on several types of roads, presenting roads in good conditions of conservation until roads in precarious conditions with extremely high severity. In addition, vehicle safety standards have been intensifying their requirements. With that in mind, bus body manufacturers are investing in research to produce more durable, efficient and safe buses, expanding the search through engineering tools to develop better and more competitive products. The aim of this work was to analyze high cycle fatigue life of welded joints of thin-walled profiles used in bus structures subject to dynamic loads, comparing the use of three different raw materials to understand the impacts of the replacement of the materials already used in these structures for materials with better mechanical properties. This work began with the study to understand the real application of coaches. To perform this task was elaborated an experimental procedure that encompasses the main routes used by these vehicles, and through the acquisition of experimental data it was possible to evaluate the real loads that this kind of structures are submitted to. With the results obtained through the sensors it was possible to understand the loads that the roads produce in the structure of the vehicle and from these data a laboratory test was elaborated to represent the real application of the vehicle. The data acquired were inserted into the virtual model and through them it was possible to find the forces and loads that were applied to the welded joint that was chosen as object of study to perform the experimental fatigue test. Proof bodies were elaborated to represent the real application of the vehicle, those were produced using three different raw materials, two of them commonly used in bus bodies structures and a third steel, dual-phase, commercially called DP 980. The materials were submitted to several experiments and based on the results of the tests it is possible to conclude that DP 980 present a better performance than the others. This material has presented a fatigue life more than two times higher than the others for the same conditions. It was also possible to assure that, using DP 980 steel, it is possible to develop safer structures for buses, because this material has higher mechanical properties and greater capacity to absorb energy when compared to the others.