Why do old springs lose bounce?
Show answer & explanation
Answer: Repeated stress causes fatigue
Metal becomes brittle over time — Wrong. Metal doesn't become brittle from use (unless extreme heat). Springs lose bounce from plastic deformation—repeated stress exceeds elastic limit.
Repeated stress causes fatigue ✓ — Correct! Metal fatigue! Springs work through elastic deformation—compress/extend, return to original shape. Elastic limit: maximum stress before permanent deformation. Repeated cycles gradually exceed limit—microscopic plastic deformation accumulates. Spring permanently deformed—loses 'springiness'. Same principle: bending paperclip back/forth breaks it—metal fatigue. Quality springs (better alloys, heat treatment) resist fatigue longer. Mattress springs weaken over years!
Springs naturally unwind — Wrong. Coil springs don't 'unwind'. They lose bounce from metal fatigue—repeated stress causes permanent deformation reducing elasticity.