DAMAGE TOLERANCE EVALUATION OF AN AIRCRAFT SKIN STRUCTURE BY MVCCI TECHNIQUE (2D ANALYSIS) USING MSC – NASTRAN / PATRAN

K.S.Vishwanath Vashisht

Abstract: An Aircraft is a light weight airbreathing semi-monococque complex aerostructure comprising of longerons, bulkheads, stiffeners, stringers, lugs, bolts and joints, ribs and other special forms of structures. In its service, it has to sustain aerodynamic, structural, propulsive, fatigue and impact loads. Even though the load carrying agents are the stiffening materials, the loads are firstly faced by the aircraft skin in the form of shear loads and later on transferred to the stiffening structures inside. In the present study, A small portion of the aircraft skin is considered and is analyzed by Damage Tolerance technique, ie, by assuming a minute flaw to be present at the time of manufacturing itself or by other processing efforts. While in operation, due to the crack initiation, the accumulated crack propagates to critical sizes leading to catastrophic failure. The main objective of this paper is to determine the normalized stress intensity factor in the opening mode KI for a finite width plate in uniform tension with a central crack. The report will start with a brief review of fracture proceeding further with the concept of Stress Intensity Factor in opening mode, i.e., KI, and common design strategies (Assumptions) to assure the structural integrity of components and of the role that stress intensity factor plays through different modes of failures. And it also covers an overview of energy approach and stress intensity approach to a problem. Using MSC NASTRAN/PATRAN, Stress Intensity Factor in opening mode, KI is found by MVCCI technique and is validated with the theoretical results obtained by Feddersen empirical modeling.

Keywords: Crack Propagation, Damage Tolerance, Energy Release Rate, Fracture Toughness, MVCCI, Stress Intensity Factor

DOI: https://doi.org/10.15623/ijret.2016.0505096