scholarly journals Prediction of Crack Initiation Based on Energy Storage Rate during Low-Cycle Fatigue of Austenitic Stainless Steel

Materials ◽  
2021 ◽  
Vol 14 (19) ◽  
pp. 5526
Author(s):  
Wojciech Grodzki ◽  
Wiera Oliferuk ◽  
Michał Doroszko ◽  
Jarosław Szusta ◽  
Leszek Urbański

The low-cycle deformation of 304L austenitic stainless steel was examined in terms of energy conversion. Specimens were subjected to cyclic loading at the frequency of 2 Hz. The loading process was carried out in a hybrid strain–stress manner. In each cycle, the increase in elongation of the gauge part of the specimen was constant. During experimental procedures, infrared and visible-range images of strain and temperature fields were recorded simultaneously using infrared thermography (IR) and digital image correlation (DIC) systems. On the basis of the obtained test results, the energy storage rate, defined as the ratio of the stored energy increment to the plastic work increment, was calculated and expressed in reference to selected sections of the specimen. It was shown that, before the specimen fracture in a specific area, the energy storage rate is equal to zero (the material loses the ability to store energy), and the energy stored during the deformation process is released and dissipated as heat. Negative and close-to-zero values of the energy storage rate can be used as a plastic instability criterion on the macroscale. Thus, the loss of energy storage ability by a deformed material can be treated as an indicator of fatigue crack initiation.

2015 ◽  
Vol 75 ◽  
pp. 57-68 ◽  
Author(s):  
Bai-Mao Lei ◽  
Van-Xuan Tran ◽  
Saïd Taheri ◽  
Jean-Christophe le Roux ◽  
François Curtit ◽  
...  

2014 ◽  
Vol 620 ◽  
pp. 438-442 ◽  
Author(s):  
Takahiro Matsueda

Aspect ratio is a key factor to calculate stress intensity factor (SIF) K using fracture mechanics. Cracks are approximated to be semi-circle or semi-ellipse in simple calculation, however, their empirical shapes are changed by stress concentration. In this study, in order to calculate K simply and precisely, a new method to predict fatigue crack initiation stress, σw1 of austenitic stainless steel with modified aspect ratio is discussed. The new method succeeded to predict σw1 within 20% error from empirical values using average austenite grain sizes.


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