Engineering Design and Analysis
What to master
Design is a structured process: define requirements, generate concepts, evaluate alternatives, detail the design, verify, and document. Know the design cycle, functional requirements vs constraints, design reviews, verification vs validation (verification: built right; validation: right thing built), failure modes and effects analysis (FMEA), design for safety (inherent safety over add-on protection), and lifecycle considerations.
Traps
- Confusing verification and validation: verification checks conformance to spec; validation checks fitness for purpose.
- Skipping the requirements baseline: changes without traceability cause scope creep.
- Treating FMEA as a checklist: severity, occurrence, and detection combine into a risk priority number (RPN); high-RPN items need action.
- Ignoring interfaces: most failures occur at system boundaries.
- Optimising one parameter at the expense of others: cost, safety, maintainability trade-offs.
Worked example
An FMEA entry has severity 8, occurrence 4, detection 3. RPN = 8 × 4 × 3 = 96. If the team's action threshold is 100, this item is below threshold but close - document rationale and monitor. Reducing detection to 2 (better inspection) gives RPN = 64, a meaningful improvement without design change.
Rule of thumb
Prefer inherent safety (eliminate the hazard) over engineering controls, then administrative controls, then PPE. This hierarchy recurs throughout design and safety questions.