1Titanium Rotors in Military Aero Engines- Designed to Weight and Life

Aero engines for military aircraft traditionally have to fulfil the requirement of high thrust to weight ratio, what means that additionally to the high thrust also low weight is required. As the parts also have to withstand significant temperatures, materials with low specific weight but high strength even under elevated temperatures are necessary. The answer is twofold: Titanium alloys for parts under moderate temperature (e.g. compressors) and Nickel alloys for the high temperature region (e.g. turbines). A further requirement is a component life which allows for a 30 to 40 year engine life. Both requirements together call for the best and latest alloys and for highly sophisticated design and manufacturing procedures. Cost drivers in the development and production phase are demanding material properties and material quality as well as manufacturing efforts. Production cost can be influenced in the development phase if the criteria of minimum number of parts and design to manufacturing are observed. Cost of ownership is driven by maintenance efforts and spare part cost. One of the requirements is to reduce or bundle maintenance activities. Another aspect could be a trade off between new parts ' cost and parts life. Cost reduction can be achieved by optimum exploitation of the parts ' life potential. The means are improvement of the lifing concepts which should allow for safe extension of life in the crack propagation regime beyond the classical crack initiation life as well as improved accuracy of the life prediction procedures. Accurate records of life consumption under real operation obtained by individual life usage monitoring contribute to cost reduction, too