DAMAGE TOLERANCE EVALUATION OF WING IN PRESENCE OF LARGE LANDING GEAR CUTOUT THROUGH STRESS ANALYSIS USING FEM

Aircraft is symbol of a high performance mechanical structure, which has the ability to fly with a very high structural safety record. Aircraft experiences variable loading in se rvice. Rarely an aircraft will fail due to a static overload during its service life. For the continued airworthiness of an aircraft duri ng its entire economic service life, fatigue and da mage tolerance design, analysis, testing and service experience correlatio n play a pivotal role. The present study includes t he stress analysis and damage tolerance evaluation of the wing through a stiffene d panel of the bottom skin with a landing gear cuto ut. Wing bottom skin experiences tensile stress field during flight. Cut outs required for fuel access and landing gear open ing and retraction in the bottom skin will introduce stress concentration. Fa tigue cracks will initiate from high tensile stress locations. An integral stiffened panel consisting a landing gear cutout is considere d for the analysis. Stress analysis will identify tmaximum tensile stress location in the panel. In a metallic structure fatigue manifests itself in the form of a crack which p ropagates. If the crack in a critical location goes unnoticed it could lead to a catastrophic failure of the airframe. A critical c ondition will occur when the stress intensity factor (SIF) at the crack tip becomes equal to fracture toughness of the material. SI F calculations will be carried out for a crack with incremental crack lengths usin g MVCCI method. Analytical evaluation of the crack arrest capability of the stiffening members ahead of the crack tip will be c arried out.