Materials¶
Fatigue and corrosion¶
Rules found in this domain: P28, P29.
Illustrative, not evidence.
Scenario. A bracket on a coastal crane is made of steel fastened to aluminium plates. It sees small load cycles every day for decades, in salt air. The largest single lift is well inside its strength.
- P28: The designers do not stop at the largest single lift. They design for the damage that builds up over the whole life, with a fatigue test that represents real use and measures crack growth.
- P29: Steel and aluminium touch in a wet environment, so the designers verify compatibility in the real environment. They find a galvanic corrosion risk and separate the metals: insulating washers and sleeves keep the steel bolts off the aluminium, and a sealant keeps salt water out of the joint.
Forensic engineering¶
Rules found in this domain: P83.
Illustrative, not evidence.
Scenario. A steel hook fails at a work site. A crew wants to straighten the bent parts and put the equipment back to work the same day.
- P83: The investigators document and preserve the as-found state before any repair, with photos and the fracture surface kept clean. They record who handled the parts, forming a chain of custody. The incident record lists the evidence captured before the first repair.
Welding¶
Rules found in this domain: P61.
Illustrative, not evidence.
Scenario. A fabricator welds pressure vessel seams. Even radiography afterwards cannot fully show a weld's internal quality, and it cannot show the toughness of the weld metal at all.
- P61: The fabricator proves the welding procedure by a test before using it on the vessel. Each welder is qualified, and a test record exists for the procedure and a qualification record for each welder.
Ceramics and brittle materials¶
Rules found in this domain: P34.
Illustrative, not evidence.
Scenario. A maker of ceramic tiles tests a small sample and finds no failures under load. The product then ships by the million, and some tiles crack.
- P34: As the number of parts grows, rare failures become frequent. The maker estimates a failure rate per tile and multiplies it by the planned volume, then designs and tests for that scale, not for the small sample.
Metallurgical¶
Rules found in this domain: P14.
Illustrative, not evidence.
Scenario. A forge buys steel bars from several mills for a safety-critical part. An audit asks where one failed part's steel came from.
- P14: The forge traces each bar to its origin, melt batch and mill certificate. For any finished part it can show origin, build and certificate.
Electronic materials¶
Rules found in this domain: P28.
Illustrative, not evidence.
Scenario. A maker of solder joints on circuit boards heats and cools the board each day in service. The joints pass a single strength test when new.
- P28: The maker designs for damage that builds up over the whole life, not for one load. A thermal cycling soak test runs for a period that represents real use, and the growth of cracks in the joints is measured.
Polymers¶
Rules found in this domain: P28.
Illustrative, not evidence.
Scenario. A plastic housing holds a clip under steady load. Over years in sunlight and heat, the plastic slowly creeps and becomes brittle.
- P28: The designers account for creep and ageing over the design life, not only for the largest single load. An endurance test at raised temperature and UV exposure represents real use, and the growth of deformation is measured.
Nanotechnology¶
Rules found in this domain: P15.
Illustrative, not evidence.
Scenario. A company wants to use a new nanoparticle in a sunscreen. Early tests hint that it might harm aquatic life, but the data is incomplete. Harm to a river would be hard to undo. The company filters the particles out of its factory wastewater. It also holds back a water-resistant beach product, whose use washes the particles straight into open water, until more tests are done.
- P15: The possible harm is serious and irreversible, and the evidence is incomplete. The company takes proportionate protective measures on both paths to the water without waiting for full proof, and a record states the measures taken.