Determining the effect of triangular interwindow openings in a bus body on its structure, strength, and passive safety

The object of this study is a spatial model of the body frame for the Ukrautobusprom 4289 city bus, which is subject to structural optimization of the sidewalls in order to strengthen them because of the increase in equipped weight. The reason for loading is the need to install batteries on the roof, which is the only possible location, given the low-entry layout. Electrification of city buses is associated with the inevitable regulated reduction of CO2 emissions by 30 % by 2030 (Euro 7) and complete decarbonization by 2050. Making up 30–40 % of the total cost of the bus, the body requires preservation when re-equipping diesel city buses for electric traction. Electrification automatically imposes UNECE R100 requirements for the absorption of 5.5 and 6g accelerations by the battery pack together with the body. To solve the problem, a transition from classic rectangular to triangular inter-window openings of the sidewalls has been proposed. An analytical methodology for simulating full-scale tests is proposed, close to real physical tests. Owing to the higher rigidity of triangular structures, a reduction in maximum stresses by 2.85 and 16.75 % was achieved under the static torsion and bending modes while the structure was maintained within the yield strength of steel σy=252 MPa. Maximum deformations decreased by 28.71 % in bending and by 50.77 % in torsion. Stresses under R100 conditions decreased by 18.52 and 16.07 % under the 6.6g and 5g modes, respectively. Deformations in the latter case decreased by 46.09 % and amounted to 10.83 mm only. Owing to the proposed approach, it was possible to achieve unification of the body for any type of drive: diesel, hybrid, or electric. Given sufficient technological feasibility of bus body production, this solution could be used in practice