Two views on how materials break — the S–N curve that predicts cyclic life, and the Paris-law growth of a single crack from sub-critical flaw to final rupture.
The S–N (Wöhler) curve plots stress amplitude σa against cycles to failure Nf. Slide σa to read off life. Ferrous alloys show a true endurance limit — below it, life is effectively infinite. Aluminum and most non-ferrous alloys do not.
High-cycle fatigue: stress is below yield, life dominated by crack initiation. Reduce σa below σe for unlimited life.
The entirety of this work — including, without limitation, its text, illustrations, diagrams, interactive visualizations, animations, source code, layout, and design — is the intellectual property of Teerapong Poltue and is protected under the copyright laws of the Kingdom of Thailand and applicable international copyright treaties.
No part of this material may be reproduced, copied, distributed, transmitted, displayed, published, adapted, reverse-engineered, or used to create derivative works, in whole or in part, by any means or in any form, without the prior express written permission of the copyright holder.