Damage-Tolerant Design
Definition
A structural-design philosophy that assumes cracks will form and specifies inspection intervals short enough to detect and repair cracks before they reach critical size.
- Type
- Structural engineering design philosophy
- Assumption
- Cracks will inevitably form in service
- Mechanism
- Scheduled inspection before cracks reach critical size
- Contrast
- Alternative to safe-life design assumptions
Common questions
How does damage-tolerant design change what a forensic failure investigator looks for after a structural fracture?+
Because the design assumes cracks exist and grow predictably, the investigator's key question becomes whether the required inspection schedule was actually followed and whether the inspection method was capable of detecting a crack at the size it needed to be caught, rather than whether any cracking occurred at all.
What distinguishes damage-tolerant design from a component that is simply defective?+
A damage-tolerant component developing a crack within its design life is expected behavior, not a defect; failure investigation instead centers on whether crack growth outpaced the inspection interval, whether an inspection was missed, or whether the crack detection method used was inadequate for the crack size present.
Related terms
- Beach Marks
- Macroscopic curved bands on a fatigue fracture surface, visible without magnification, produced by changes in crack growth rate during service (load changes,...
- Ductile Dimples
- Microscopic cup-shaped depressions visible on a ductile overload fracture surface under SEM, formed by nucleation, growth, and coalescence of microvoids at second-phase...
- Fatigue Striations
- Microscopic parallel marks on a fatigue fracture surface, formed during individual loading cycles in Stage II crack growth. Visible by SEM at...
- Fractography
- The systematic examination and interpretation of fracture surfaces to determine the mechanism, origin, and propagation direction of fracture; uses optical and scanning...
- MCAS
- Maneuvering Characteristics Augmentation System; the Boeing 737 MAX software feature that repeatedly commanded nose-down stabiliser trim based on a single AoA sensor...
- Progressive Collapse
- A failure mode in which local structural failure triggers a sequence of failures in adjacent members, resulting in collapse disproportionate to the...
- River Patterns
- Fan-shaped or river-delta-like markings on brittle-cleavage fracture surfaces that indicate crack propagation direction; rivers diverge from the origin and converge toward the...
- S-N Curve
- A plot of cyclic stress amplitude (S) against the number of cycles to failure (N), used to characterise a material's fatigue life;...
- Safe-Life Design
- A structural-design philosophy where a component is retired from service before its predicted fatigue life is consumed; does not require crack detection...
- Stress-Concentration Factor (Kt)
- A dimensionless multiplier representing the ratio of the actual maximum stress at a notch, hole, or corner to the nominal stress in...
- Stress-Corrosion Cracking (SCC)
- A failure mode combining sustained tensile stress with a specific corrosive environment, producing branching, often intergranular cracks that grow at stress intensities...