eva‎luation of plastic zone around notches by using Digital Image Correlation (DIC)

8/30/2023 12:00:00 AM

The plastic zone around notches and cracks plays an essential role in crack growth and fatigue life of industrial parts. Therefore, the study of the plastic zone is an important issue. In this thesis, by using Digital Image Correlation Method(DIC), the plastic zone around sharp V-shaped notches under plane stress conditions, with different opening angles and under Mode I loading has been obtained. The method that has been used to estimate the size of the plastic zone by using the digital mapping method is based on the non-linear behavior of the material in the plastic zone. In this method, the non-linear behavior of the displacement fields obtained by the digital image correlation method is investigated and the beginning and end of the non-linear behavior observed in the displacements is considered as the plastic zone. For a notches that is in the horizontal axis, at a certain distance from the notch tip (interval X along the horizontal axis), the displacements obtained in the direction of the Y axis (related to the same X mentioned) are checked and if Observing sudden changes in the amount of displacements, the beginning and the end of this behavior is considered as the limit of the plastic region at the distance X from the notch tip. In the same way, for different distances (different X) from the notch tip, this method will be repeated and the range of the plastic zone around the notches will be obtained. To verify the accuracy of the method presented in this thesis, the results obtained from DIC method for calculating the plastic zone around the notches with the results obtained from the simulation with the finite element software and also the results obtained from the Irwin's first and second estimations were compared by considering the higher order terms of stresses. At loads close to the fracture load, the plastic zone obtained by the proposed method is consistent with the results obtained from the finite element method, and when load decreases, the agreement of the presented method is closer to Irwin's first estimation with one stress term. and it is different from the finite element method. In this thesis, the samples used have a sharp V-shaped notch. There is a good match between the proposed method based on DIC and Finite element results, but Irwin's first and second estimation did not have a proper assessment of the plastic zone around the notches in most cases.. It should be noted that in this research, two different materials, Aluminum 6061-T6 and Steel 4340, and two types of test were used. including four-point bending test and compressive tensile shear test.

ناحيه پلاستيك اطراف شيار , رهم نگاري ديجيتال , روش غيرخطي , تخمين اروين , ناحيه پلاستيك , شيار Vشك نوك تيز

Plastic zone around notches , Digital Image Correlation (DIC) , Non-linear method , Plastic zone , Irwin’s estimations , Sharp V-notches

hamed kariminezhad

Dr. Majid Reza Ayatollahi