Abstract
This article presents a novel methodology for the inspection scheduling of gas turbine welded structures, based on reliability calculations and overhaul findings. The model was based on a probabilistic crack propagation analysis for welds in a plate and considered the uncertainty in material properties, defect inspection capabilities, weld geometry, and loads. It developed a specific stress intensity factor and an improved first-order reliability method. The proposed routine alleviated the computational cost of stochastic crack propagation analysis, with accuracy. It is useful to achieve an effective design for manufacturing, to develop structural health monitoring applications, and to adapt inspection schedules to airplane fleet experience.
Highlights
Damage tolerance analysis methods have been used since the early 1970s to design and determine inspection intervals for aircrafts
We present a new probabilistic fatigue analysis methodology for gas turbine welded structures, which is similar to those reported in the literature,[3,5,7,8] but with several substantial differences
The inspection update is based on reliability evaluation with a constant final crack size, as explained in section ‘‘Defect rate forecasting.’’ As shown in Figure 13, the first-order reliability method (FORM) predicts a good correlation with the 10,000 MonteCarlo simulation (MCS) crack propagation analysis data and is considered the exact solution for the numerical example in parts sections ‘‘Loop 3 part 1 and 2: Inspection-finding forecasting’’ and ‘‘Loop[3] part 3: Inspection plan’’
Summary
Damage tolerance analysis methods have been used since the early 1970s to design and determine inspection intervals for aircrafts. We present a new probabilistic fatigue analysis methodology for gas turbine welded structures, which is similar to those reported in the literature,[3,5,7,8] but with several substantial differences It uses an improved first-order reliability method (FORM) which includes fracture variability to evaluate the component reliability as was done by Madsen et al.,[9] Kale and Haftka,[5] and Feng et al.,[10,11] and to estimate the crack size distribution after inspection. In this sense, the new methodology is more efficient. KIc Welding geometry y and acceptance tw criteria e mm mm mm21 – (mm/cycle)/(MPan m2n/2) MPa m1/2 – mm – a rad
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