Some crack problems in engineering structures

The failure of engineering structure by cracking is always undesirable. It involves human lives that are put in jeopardy, economic losses and the interference with the availability of products and services. Therefore, an understanding of fracture mechanics is crucial for engineers in designing engineering structure especially those under high tensile stress. The main concept being discussed in this Final Year Report is Stress Intensity Factor, KI, a parameter used for predicting crack growth. The report particularly deals with cracks found in structures with notch. There are 2 different types of crack case being investigated here, namely the Edge Crack case and the Central Crack case. For each of the case, the KI for different crack length are being computed using Finite Element Analysis by ANSYS for 3 different types of engineering structure: a plain sheet structure, a structure containing circular notch and a structure containing an elliptical notch. To date, there are many experiments or analysis done on the behaviour of KI of structure with notch for different crack length over notch radius, a/r. In this report, KI for structure containing circular and elliptical notch is being compare with the KI value of structure without notch. The comparison parameter KI/KI0(where KI0 is the stress intensity factor for structure without notch) is then being plotted on graph for different a/r. All the analysis will be based on the assumptions of Linear Elastic Fracture Mechanics and plane strain problem. The modeling will also be limited to homogeneous, isotropic (near the crack region) material and infinite width sheet structure.Bachelor of Engineering (Mechanical Engineering