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Browsing Materials Research Group by Author "Aliabadi, M.H."
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Item Metadata only Detection of delamination damage in a composite laminate beam utilising the principle of strain compatibility(Trans Tech Publications, 2010) Wildy, S.; Cazzolato, B.; Kotooussov, A.; Aliabadi, M.H.; Abela, S.; Baragetti, S.; Guagliano, M.; Lee, H.S.This paper presents an experimental investigation of a new method for damage detection based on the most fundamental concept in continuum mechanics: strain compatibility. Compliance with this principle implies a deformed material is free from discontinuities, which are indicative of many types of structural damage. Therefore the principle of strain compatibility, in its ability to identify discontinuities, is very promising as a new foundation for future research into non-destructive evaluation and structural health monitoring technologies. The proposed method has many advantages compared to existing damage detection techniques, such as its invariance to material properties, type and intensity of loading, and the geometry of the structure. In this paper, a proposed formulation of the strain compatibility equation for beam structures, which is invariant to loading intensity, is presented. An experimental investigation of the proposed algorithm was conducted on a delaminated cantilever beam, utilising a PSV-3D scanning laser vibrometer. The experiment demonstrated that the strain compatibility technique can accurately locate delamination damage in composite beam structures.Item Metadata only Do notched thick plates have strength in shear?(Trans Tech Publications, 2010) Harding, S.; Kotooussov, A.; Aliabadi, M.H.; Abela, S.; Baragetti, S.; Guagliano, M.; Lee, H.S.This paper summarizes recent theoretical studies on the three-dimensional singular stress state at sharp notches in infinite (or large) plates of finite thickness subjected to in-plane loading. In general, such loading produces a number of singular states: in-plane singularities (normally described as KI and KII fracture modes and known as Williams’ solution), singular states associated with corners and the out-of-plane singularity (KO mode), which is generated due to the Poisson’s effect. The latter mode has an interesting behavior and its intensity increases as a power function with the increase of the plate thickness when the notch is stresses in shear mode. From finite fracture mechanics considerations it is clear that at some certain thickness the out-of-plane singular mode will dominate over the fracture zone and with the further increase of the plate thickness will affect the strength of the notched plate, virtually reducing it to zero.Item Metadata only Effect of plate thickness and load history on fatigue crack growth(Trans Tech Publications, 2010) Codrington, J.; Kotooussov, A.; Wildy, S.; Ho, S.; Aliabadi, M.H.; Abela, S.; Baragetti, S.; Guagliano, M.; Lee, H.S.A new theoretical approach is presented for investigating fatigue crack growth in plates of finite thickness. The developed approach utilizes a modified strip-yield analysis and the concept of plasticity-induced crack closure. A number of typical fatigue crack growth phenomena are investigated including the thickness effect on constant amplitude fatigue crack growth, retardation due to a tensile overload cycle, and short crack growth from sharp notches. Theoretical predictions are compared with experimental data and are found to be in very good correlation.Item Metadata only Investigation of thermo-mechanical properties of slurry based thermal barrier coatings under repeated thermal shock(Trans Tech Publications, 2010) Nguyen, P.; Kotooussov, A.; Ho, S.; Wildy, S.; Aliabadi, M.H.; Abela, S.; Baragetti, S.; Guagliano, M.; Lee, H.S.Thermal Barrier Coatings have existed for over 40 years, and with in the last 15 years their use in industrial applications has dramatically increased. Thermal Barrier Coatings (TBCs) are currently used in gas turbines, diesel engines, throughout aerospace and nuclear power industries. The purpose of TBC is to reduce temperature and thermal stresses, and, as a result, increase the reliability and life of load-bearing components subjected to high temperature or temperature flux. However, TBCs often fail under thermal cyclic loading with reliability still being the major issue impeding their wide-spread applications. The focus of this work is on experimental investigations of zirconia/nickel graded TBC system, subject to thermal shock loading. The graded TBC systems were fabricated utilising a recently developed slurry spray manufacturing technique. This is a robust technique, and is able to cover large and curved surfaces at low cost, and provides many advantages in comparison with its alternatives. This paper describes the developed technique and presents selected results of thermo-mechanical and fracture testing of the TBCs including graded coatings fabricated using this new technique.Item Metadata only On buckling of long interface cracks(Trans Tech Publications, 2010) Kotooussov, A.; Harding, S.; Aliabadi, M.H.; Abela, S.; Baragetti, S.; Guagliano, M.; Lee, H.S.The paper deals with the buckling instability of long interface cracks subjected to shear and tensile (compressive) loading parallel to the interface. A simplified mathematical model is developed within the Kirchhoff’s plate bending theory; and a general semi-analytical solution is obtained based on the classical strategy for solving for the Euler buckling load. Asymptotic solutions are derived for extreme cases of the applied shear to tensile (compressive) load ratios. The obtained results correlate well with previous numerical studies and can be used to analyze many traditional problems in composite as well as many others, for example, the problem of triggering snow avalanches.