User talk:Kandregula prasad

VARIOUS TRENDS IN DESIGN OF MODERN AIRCRAFT STRUCTURE KANDREGULA PRASAD, M.TECH (IIT-KANPUR) - Modern Aircrafts must undergo severe conditions such as differences in atmospheric pressure and temperature, or heavy structural load applied upon vehicle components. The current generations of civil transport aircraft were designed for at least 20 to 25 years and up to 90,000 flights. Consequently, they are usually products of complex synthesis of various technologies and sciences, including developing new design methods, preparing advanced materials, Special NDI application and formulating novel production processes. Future aircraft types are designed for the same goals, but structure with higher fatigue life (endurance), higher damage tolerance capability and higher corrosion resistance are required to minimize the maintenance costs and to comply with the requirements of the operator and the enhanced airworthiness regulations. During the design of aircraft structures several aspects have to be considered to reach sufficient static strength as well as sufficient fatigue and damage tolerance behavior. The result of iterative calculations is an optimized design regarding weight, costs and aircraft performance Fig: Design principle 'damage tolerant - multiple load path - inspectable for less than one complete load path failure' An evaluation of the strength, detailed design, and fabrication must show that a catastrophic failure due to fatigue, corrosion, or accidental damage, will be avoided throughout the operational life of the airplane. The ultimate purpose of the damage tolerance evaluation is the development of a recommended structural inspection program considering probable damage locations, crack initiation mechanisms, crack growth time histories and crack detectability. The damage tolerance design principle comprises two categories which are 'single load path' and 'multiple load path' structure. Single load path is where the applied loads are eventually distributed through a single member within an assembly, the failure of which would result in the loss of the structural integrity of the component involved. Multiple load path is identified with redundant structures in which (with the failure of individual elements) the applied loads would be safely distributed to other load carrying members. Innovative materials research and engineering is essential to achieve the high-strength, heat-resistant, lightweight structures required in advanced subsonic and supersonic aircraft. General and specific research opportunities were determined for the civil aircraft industry using the HSCT (high-speed civil transport) as a basis for analysis. The effects of material selection is to consider the use of Materials and stress levels that, after initiation of cracks, provide a controlled slow rate of crack propagation combined with high residual strength.