Most infrastructures in the world are made with reinforced concrete (RC), and one of the ‎crucial concerns in North America is corrosion of steel reinforcement in RC structures. ‎Corrosion can lead to severe degradation which can affect the serviceability and ultimate limit ‎state, and cause failure. One solution for overcoming this phenomenon is the use of corrosion-‎resistant fibre-reinforced polymer (FRP) reinforcement. In addition to corrosion resistance, ‎FRPs also present other advantages such as high strength and light weight compared to steel ‎reinforcing bars. Their mechanical properties differ from those of steel; therefore, the flexural ‎and shear behaviour of FRP-RC members requires investigation. In general, predictions from flexural design equations are close to results from experimental ‎data. However, shear strength predictions based on different modelling approaches can vary ‎greatly. Thus, in the last century, one of the main controversies in the field of structural ‎engineering attracting continuous attention is the shear behaviour of RC members. In previous ‎studies, factors such as concrete strength, reinforcement ratio, beam depth, beam width, size ‎effect, aggregate size, fracture energy and shear slenderness have been investigated in an effort ‎to solve the riddle of shear in beams. Recently, a new rational theory named "Shear Crack ‎Propagation Theory" (SCPT) was introduced that combines crack kinematics with constitutive ‎material behaviour to predict shear behaviour over the entire loading process, rather than only ‎focusing on the point of failure. To date, the SCPT has only been used to predict the shear behaviour of RC beams containing ‎steel reinforcement. The present study is the first to apply the SCPT to RC beams with non-‎metallic reinforcement. The numerical analysis using SCPT on RC members was validated ‎against published test data and examines the role of important parameters such as ‎reinforcement modulus of elasticity, reinforcement ratio, bond condition, and dowel resistance.‎

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IF Steel to be used in this thesis which only have 50ppm carbon is approach Iron. It to be part of BCC. Because BCC material have much slip system when increase the cycle will induce to create multiple slip system. The dislocation structure often to become cell. We observation the same result of SEM and TEM in low cycle fatigue. The cell size is small in high plastic strain amplitude. The cell size is big in low strain amplitude. The difference of dislocation structures in front of crack tip which obtained under propagation rates o f 10-4, 10-5, 10-6 and 10-7 mm/cycle is the volume percentage occupied by the dislocation structures viz. misorientation cell, cell, wall, PSBs.

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Understanding failure mechanics of mechanical equipment is one of the most important aspects of structural and aerospace engineering. Crack growth being one of the major forms of failure in structural components has been studied for several decades to achieve greater reliability and guarantee higher safety standards. Conventional approaches using the finite element framework provides accurate solutions, yet they require extremely complicated numerical approaches or highly fine mesh densities which is computationally expensive and yet suffers from several numerical instabilities such as element entanglement or overly soften element behavior. The eXtended Finite Element Method (XFEM) is a relatively recent concept developed for modeling geometric discontinuities and singularities by introducing the addition of new terms to the classical shape functions in order to allow the finite element formulation to remain the same. XFEM does not require the necessity of computationally expensive numerical schemes such as active remeshing and allows for easier crack representation. In this work, verifies the validity of this new concept for quasi-static crack growth in tension with Abaqus' XFEM is employed. In the course of the work, the effect of various parameters that are involved in the modelling of the crack are parametrically analyzed. The load-displacement data and crack growth were used as the comparison criterion. It was found that XFEM is unable to accurately represent crack growth in the models in the elastic region without direct manipulation of the material properties. The crack growth in the plastic region is found to be affected by certain parameters allowing us to tailor the model to a small degree. This thesis attempts to provide a greater understanding into the parametric dependencies of XFEM crack growth. / Master of Science / Crack propagation is one of the major causes of failure in equipment in structural and aerospace engineering. The study of fracture and crack growth has been taking place for decades in an effort to increase quality of design and to ensure higher standards of safety. In the past, an accurate representation of crack growth within a specimen using conventional numerical analysis was computationally expensive. The eXtended Finite Element Method (XFEM) is a concept introduced that would reduce computational effort yet improving the fidelity of the analysis while allowing for easier representation of crack growth. This thesis, verifies the validity of XFEM in simulating crack growth in a specimen undergoing tension using a commercially available code, Abaqus. The various parameters involved in the modeling of this crack and their effects are studied. The study had shown that the inaccuracy of XFEM in its ability to model crack growth, however, it gives us some understanding into certain parameters that would allow us to tailor the model to better represent experimental data.