Analysis of unsymmetrical cracks emanating from a circular hole placed centrally in a thin plate using FEM
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Date
2021-02
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G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand)
Abstract
Almost all of the structural failures occur due to cracks propagation. Holes, cavities, inclusion are perfect site for crack nucleation and growth ultimately leading to fracture. However, holes are sometimes inevitable in structures to provide some functionality. In the present study an investigation has been made to ascertain the parameter that would play a role in failure of structures if cracks emanate from these holes. A plane stress condition is assumed. Finite element method is used. Different like and alike cracks emanating from a hole have been studied. The effect of various parameters like crack inclination angle, crack length ratio, hole diameter and biaxiality factor have been studied. The presence of a secondary crack has two type of effect viz. intensification and shielding. The increase in the crack inclination angle of secondary crack changed the mode of loading from mode I to mode II. The value of mode I SIF for crack tip A increases significantly as the hole diameter increases from 1 to 3mm. The decrease in mode II SIF is seen to be phenomenal as diameter (d) of hole increases to 2mm. After 2mm diameter, mode II SIF further increases significantly producing intensification effect. At d=3mm, mode I is 0.60 times mode II. The hole diameter has greater impact as both stress intensity factor continuously increases. It can be concluded that hole diameter is going to play a critical role in determining structural integrity. The value of mode I decreases significantly of crack tip A as the crack length ratio is increased from 0.5 to 1.5. Whereas mode II stress intensity factor decreases to a2/a1=1. When both the crack tips A and B are further apart from each other stress intensity factor decreases. The value of mode I and mode II stress intensity factor decreases significantly as the crack length ratio (a2/a1) is increased from 0.5 to 1.5. Since these kind of scenarios are almost certain to happen in structures, the findage
may help in ascertaining the life before failure and the mechanism associated is to take the necessary steps before any unfortunate incident happen.