Abstract
Some low-carbon steels, magnesium-aluminum alloys, and nickel-based alloys exhibit plastic flow instability at their respective yield points in the form of a drop and plateau of stress in the stress-strain curve. This phenomenon is often referred to as the Lüder phenomenon in the yield point elongation region of the stress-strain curve. The Lüder phenomenon is characterized by the formation of regions, or bands, of high strain intensity at certain locations on the material. This behavior has been shown to be affected by several parameters such as material composition, grain size, temperature, strain rate, and microstructure to name a few. This capstone project studies the effects of interrupted tensile loading on 1 mm specimens of AISI 1524 hot-rolled steel alloy using a universal testing machine in conjunction with digital image correlation. The interruption of loading consists of unloading test specimens at 25%, 50%, and 75% of the plateau region independently until the stress is almost zero, then followed by reloading it at the same rate until failure. All other conditions and variables such as strain rate, temperature, and test setup were kept identical between all tests performed. Two tests were conducted for each unloading case as well as two additional control tests where loading was not interrupted: for a total of eight tests. The results show that interrupted loading up to 50% of the yield point elongation region increased the Lüder’s plateau by an average of 9.5% whereas interrupted loading past 50% decreased the Lüder’s plateau by an average of 8%. Excluding specimens which experienced anomalies in the formation of Lüder bands, all other specimens formed two primary Lüder bands, one at each shoulder of the specimen. Lüder bands form just before the onset of yielding and the material does not go into strain hardening until all strain bands merge such that the strain intensity is uniform across the whole specimen. Interrupted loading did not affect the development of Lüder bands in an observable manner.
Publication Date
12-2023
Document Type
Master's Project
Student Type
Graduate
Degree Name
Mechanical Engineering (ME)
Advisor
Wael A. Samad
Recommended Citation
Almatroushi, Mohamed Rashid, "The Effect of Tensile Reloading on the Lüder Phenomena in AISI 1524 Steel Alloy" (2023). Thesis. Rochester Institute of Technology. Accessed from
https://repository.rit.edu/theses/12202
Campus
RIT Dubai
