In-Situ Observation of Lüders Band Formation in Hot-Rolled Steel via Digital Image Correlation

Although the Luders yield phenomenon has been investigated for more than 150 years, some understanding of Luders band formation lack substantial support from experimental evidence. In-situ observation of Luders band formation in hot-rolled steel experimentally clarified the following facts: (i) When stress reaches the true upper yield stress, the Luders band begins to nucleate. True upper yield stress is greater than nominal upper yield stress. (ii) Gross stress concentration promotes the Luders band formation, and the size of the gross stress concentration region determines the initial width of the Luders band. (iii) The Luders band nucleates far ahead of the gross yield point.