ANALYSIS OF THE GENERAL STRESS-STRAIN STATE AT THE JOINT AREA OF THE BULKHEAD RIB AND WING SKIN

Abstract

Ensuring the assigned fatigue life of the structural elements of the wing is achieved by choosing structural materials, the level of design stresses, structural and technological methods for improving the fatigue resistance characteristics, both regular and irregular zones of the structure. The value and character of local stresses in structural elements significantly affect fatigue life. Therefore, knowledge of the character of stresses (especially in irregular zones) makes it possible to increase the fatigue life of the structure. The article analyzed one of the irregular zones on the wing – joint of the rib and the lower skin. The SIEMENS NX CAD system was used to build the calculation model. For further analysis, the model was imported into the ANSYS CAE system. All geometric characteristics of structural elements were specified (thickness and cross-sectional area, which were obtained from the sizing analysis), and appropriate materials were assigned (which were chosen for each elements from design considerations to increase weight efficiency and fatigue life). When high – lift devices is used, the general stress-strain state of the wing changes. In addition to the torque moment due to the mismatch between the center of pressure and the center of rigidity of the wing section, when the high-lift devices are retracted, an additional force acts and changes the values and influence of the torque moment at specific wing section. For design cases, such as cruising, takeoff and landing, aerodynamic characteristics were obtained (depending on the position of slats and flaps, flight speed and altitude, mass characteristics), which were subsequently used to obtain the stress-strain state of the analyzed section of wing. The analyzed section of wing was chosen with the presence of a slat and flap zone. In the course of the analysis, the stresses in the skin were compared in each case near the rib-skin joint. This area has a complex stress state due to the action of tensile forces and shear flow (between the skin and the rib). For further study of fatigue life in this area, depending on the level of loading, maximum stresses and shear stresses were analyzed.