Probabilistic Approaches

Transcription

1 Probabilistic Approaches Boeing Commercial Airplane 17 September 2015 FAA/Bombardier/TCCA/EASA/Industry Composite Transport Damage Tolerance and Maintenance Workshop BOEING is a trademark of Boeing Management Company. Copyright 2013 Boeing. All rights reserved.

2 Probabilistic Approaches Agenda Moving Toward a Metals Equivalent B-basis Probabilistics used for Structural Temperatures Probabilistics Proposed for Moisture Content Probability of Detection, Energy Levels and Inspection Intervals Can we Determine Limit and Ultimate Load Probabilities Tire Impact Using Probabilities to Delay Full Inspection Probabilistics and other Impact Threats 2

3 Probabilistic Approaches Temperature and Moisture, First Studies Towards a Probabilistic Approach 3

4 Probabilistic Approaches 4

5 Probabilistic Approaches - Temperature Temperature and Moisture, First Studies Towards a Probabilistic Approach 5

6 Probabilistic Approaches - Temperature P(Ambient Temperature <= t) 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% Airport Ambient Temperature Probability 503 Airports, Hourly, 12 mos 503 Airports, Hourly, Summer Top 10 Airports, Hourly, Summer 98.72% 97.63% Temperature - t (F) Airport Temperatures and Wind Speeds Considered P(Wind Speed = v) Wind Speed Probability for Top 10 Airports (Hourly, Summer) Wind Speed - v (Knots) 6

7 Probabilistic Approaches - Temperature Radiation Convection Aerodynamic Cooling f T (t) 120F x Airport Temperature Airport Wind Speed Heat Transfer Analysis 160F x Structural Temp. at Critical Condition Absorptivity Emissivity Environment Survey Summer hourly records at major airports around the world Heat Transfer Analysis P(Temperature <= z) Probability integration or Monte Carlo simulations Upper Wing Skin Temperature Structural Temperature - z (F) P(Wind Speed <= y) Pooled Wind Speed from Top 10 Hottest Airports Wind Speed - y (Knots) Pooled Temperature from Top 10 Hottest Airports Probability Density Temperatrure - x (F) 7

8 Probabilistic Approaches - Moisture Temperature and Moisture, First Studies Towards a Probabilistic Approach 8

9 Probabilistic Approaches - Moisture Total Moisture Content over 20-year Service Life: RELATIVE MOISTURE CONTENT PERCENTAGE PLY PLY 60PLY 80PLY PLY 120PLY Time [Years] 9

10 Probabilistic Approaches - Impacts Probability of Detection, Energy Levels and Inspection Intervals Intervals Probability of Detection Linked to Inspection Interval is Similar to Metallic Approach Energy Level Based on Threat and Location is Derived. Manufacturing Flaws may also be Accounted for 10

11 Probabilistic Approaches - Loads Can we Determine Limit and Ultimate Load Probabilities Loads may be the difficult part as the probabilities have not been calculated for all load cases at limit load levels How the various structural details react to the loads is different depending on whether it s a flap or a vertical stabilizer for example Has to be handled like exceedance curves for fatigue evaluation but taken to limit load 11

12 Probabilistic Approaches - Loads Exceedance of max load per flight L max 1.E+00 Exceedance & CDF of Max Load per Flight E( L Let max E( L > s) = 1 P( L max max 10 > s) = s) at at L L max max = DLL P(L max s) can be approximated by a Lognormal distribution f L max 1 (ln( s) µ ) ( s) = exp 2 sσ 2π 2σ μ = DLL σ s = DLL = 1.5 DLL (pdf) ln( s) µ P( Lmax s) = f L ( s) ds = Φ (CDF) max σ 0 where Φ( ) = CDF for standard normal distribution 2 1.E Exceedance of Max Load per Flight 1.E-01 1.E-02 1.E-03 1.E-04 1.E-05 1.E-06 1.E-07 1.E-08 L max (DLL) Type I Extreme Log-normal 12

13 Probabilistic Approaches Impact Event Risk of Tire Event 13

14 Probabilistics and Other Impact Threats Barely Visible Impact Damage (Category 1): Tool Boxes, Drill Motors, Maintenance or Service Equipment, Manufacturing Environment Ground Hail: Removable Primary Structure and Non-removable Primary Structure Wheel and Tire Threats: Tire Burst, Wheel Well Over-pressure, Thrown Tread, Rim Release, Loose Tread, Flailing Tread, Brake Temps In-flight Hail: All Primary Structure with Exposed Frontal Area Lightning Strike Bird Impact Accidental Impacts ~ Detectable Damage (Category 2/3): VID (Visible Impact Damage) Accidental Impacts Discrete Source Damage (Category 4): Deterministically Defined, Thru-Penetration, Obvious Damage. Accidental Damage: Large Scale Breaching of a Pressurized Fuselage Compartment Areas Subject to Threats from Rotating Machinery Accidental Damage: Large Scale Breaching of a Pressurized Fuselage Compartment Decompression Venting 14