Hydro4.0
the current probability considered for this type of failure event is 10e-7. The event in itself does not constitute a catastrophic event - the certification requirements require the manufacturer to demonstrate a 1 in 20 case. All in all it has to be shown that an event like this ending in a catastrophe is less than 10e-9.
FAR/CS Part 21, 33, and FAA AC33.3, AC33.7 have various criteria for design standards for turbine discs, in relation to burst requirements to be evaluated. I have no reference to hand that shows a statistical probability in respect of the disc, except under part 25 Subpart E, where it is possibly inferred in 25.905(d) (1) and (2). The earlier references relate the certification requirements to overspeed loads, and related creep/burst modes. (Failure of the disc at the inner bore would be interesting from a hoop stress analysis following a material or machining defect, rather than a radial shear overload, IMHO).
can you provide your reference for the stated disc rupture statistical value? PM is fine. I have been working on a helicopter STC and failure mode analysis using monte carlo simulation, but do not have any regulatory precedent to hand.
AC20.128A provides: "Fuel tank penetration leak paths should be determined and evaluated for hazards during flight and ground phases of operation. If fuel spills into the airstream away from the airplane no additional protection is needed. Additional protection should be considered if fuel could spill, drain or migrate into areas housing ignition sources, such as engine or APU inlets or wheel wells. Damage to adjacent systems, wiring etc., should be evaluated regarding the potential that an uncontained fragment will create both an ignition source and fuel source. Wheel brakes may be considered as an ignition source during takeoff and initial climb. Protection of the wheel wells may be provided by airflow discharging from gaps or openings, preventing entry of fuel, a ventilation rate precluding a combustible mixture or other provisions indicated in ~~ 23.863 and 25.863". Which is what the system did.
Similar analysis methodolgies:
Aerospace Industries Association Rotor Integrity Subcommittee, “The Development of Anomaly Distributions for Aircraft Engine Titanium Disk Alloys,” Proceedings of the 38th Structures, Structural Dynamics, and Ma- terials Conference, AIAA, Reston, VA, 1997, pp. 2543–2553.
“Advisory Circular—Damage Tolerance for High Energy Turbine En- gine Rotors,” Federal Aviation Administration, Rept. AC 33.14-1, U.S. Dept. of Transportation, Washington, DC, Jan. 2001.
Almroth, P. (2008). 638103 IN718: Creep model. Internal report 1CS75032. Siemens Industrial Turbomachinery AB, Finspång, Sweden.
Andersson, R. (2004). GTX100 version A: Heat transfer data and transient scaling factors for the turbine rotor at DPO conditions. Internal report T10C 76/03. Siemens Industrial Turbomachinery AB, Finspång, Sweden.
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Booker, M. K., Booker, B. L. P. (1980). Analysis of available creep and creep‐rupture data for commercial heat‐treated alloy 718. Report ORNL/TM‐7134. Oak Ridge National Laboratory, Oak Ridge, USA.
Bykov, V. (1998). Turbine rotor 2D cooling & MIT analysis. Internal report TR010. ABB Uniturbo, Moscow, Russia.
Dahlberg, T., Ekberg, A. (2003). Failure fracture fatigue an introduction. Lund: Studentlitteratur.
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Enright, M. P., Millwater, H. R., and Huyse, L. (2006). Adaptive Optimal Sampling Methodology for Reliability Prediction of Series Systems AIAA JOURNAL Vol. 44, No. 3, March 2006.
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Leverant, G. R., McClung, R. C., Millwater, H. R., and Enright, M. P, “A New Tool for Design and Certification of Aircraft Turbine Rotors,” Journal of Engineering for Gas Turbines and Power, Vol. 126, No. 1, 2003, pp. 155–159.
Lindgren, H. (2006). GTX100 version A: 2D axisymmetric LCF life assessment and contact load calculation of the turbine rotor. Internal report GRC 68/04. Siemens Industrial Turbomachinery AB, Finspång, Sweden.
Montgomery, D. C. (2005). Introduction to statistical quality control (Fifth Ed.). Hoboken, NJ: John Wiley & Sons Inc.
Myers, R. H. (1995). Response surface methodology: process and product optimization using designed experiments. New York, NY: John Wiley & Sons Inc.
Nikolaidis, E., Chiocel, D. M., Singhal, S. (2008). Engineering design reliability applications for aerospace, automotive and ship industries. Boca Raton: CRC Press.
Nilsson, F. (2008). Probabilistic methods in solid mechanics. Department of solid mechanics, Kungliga tekniska högskolan, Stockholm, Sweden.
Petukhovsky, M. (1998). Turbine clearances calculation. Internal report TR012. ABB Uniturbo, Moscow, Russia.