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Mayorkinos 1 - Coggle Diagram
Mayorkinos 1
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Maintenance Strategies
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Risk-based or predictive
Data, model or both driven
Higher uncertainty and variability, particularly for stochastic loading
Normal accident theory
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System is susceptible to normal accidents if it is complex, tightly coupled and has catastophic potential
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Fault tolerant design
Design considerations:
-Estimated flaws
-Tolerance limit set
-Initial flaw size is assumed
-Time or cycles for crack growth defined
-Inspection requirements defined
Fail safe and safe life
Safe life: no crack initiation, or cracks do not grow to critical dimension to cause failure during operational lifetime
Fail safe: Cracks are not allowed to grow to point of causing failure. Partial failure should not compromise overall safety
Equations
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Paris-Erdogan Law
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a is crack length (mm), n is number of load cycles, C and m are material constants, deltaK is stress intensity factor range (MPa \(\sqrt{m}\) )
Structural integrity
Applied loads can be:
- Static
- Cyclic
- Stochastic (random)
- Impact
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Failure patterns
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A. Bathtub, B. Wear out, C. Fatigue, D. Initial break-in, E. Random, F. Infant mortality
Stress, strain etc
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Fatigue limit
Lab testing shows steels have a safe stress at which failure will not occur, regardless of cycles
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