Please help Correct answer will be rated 5 star Explain the

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Explain the difference between safe life and damage tolerance strategies for managing fatigue life?

Solution

SAFE LIFE

A structure is designed in such a way that it remains free from defect for its whole life. Factor of safety is applied to the predicted mean life, to be ready against unexpected events. The factor of safety can assume different values, This method entrusts structural safety and reliability to an \'a priori\' replacement of the components, without any check on their further use.It involves very high costing with no evidence of greater safety, as the structure has never been really checked

. DAMAGE-TOLERANCE

It tolerates the presence of a defect also produced by manufacturing, and ontains the damage that this can involve in the safety of the structure until a planned maintenance operation can find and repair it.

This is based upon the scheduled maintenance operations, which are planned in such a way as to avoid catastrophic failures, but without an excessive frequency which could involve only higher costs and not higher safety.

The problem has three parts:

first involves the choice of inspecting methods: given a defect dimension

The second problem include the first inspection taking into consideration the fact that during nucleation and short-crack phase, cracks are not visible, so an inspection in the phase would only involve unnecessary costs,

The third part is inspection intervals , some cracks may be undetected during an inspection, so it is necessary to make sure that they will not grow to the critical length before the successive inspection, in which they can be easily detected and repaired.