3D Numerical Analysis of Cracked Ti-TiB FGM Plate with a Semicircular Notch Subjected to Different Modes Load Conditions

This study has been made to determine the performance of the (Ti-TiB) FGM plate to reduce the J-integral calculated for the crack tip emanating from the semicircular notch root in mode I and mixed mode, when the crack is propagated from the notch root. In this paper, 3D finite element method is applied to analyze the behavior of a crack emanating from semicircular notch root growing from the metal (Ti) and is oriented perpendicularly in direction of ceramic (TiB). The J-integral has been found for several combinations laws of FGM plates with respect to the variable combination of the crack length, the plate thickness, the notch radius, Young modulus of FGM plate constituents and the crack orientation. These parameters must be optimized in order to improve the best performances

Two-dimensional fracture analysis of FGM under mechanical loading

This paper extends the concept to isotropic functionally graded materials and addresses fracture problems under mechanical loading. The mode-I and mixed mode stress intensity factors (SIFs) are determinate by combination between the finite element method and the displacement extrapolation technique (DET). The variation continue of the elastics properties is incorporated at the centroid of each finite element, using the Ansys Parametric Design Language (APDL). In this work, two examples are analysed to check for the robustness of the present approach, the FGM disk with a central inclined crack subjected to concentrated couple forces and the three-point bending specimen with crack parallel to material gradation. The numerical results obtained by present technique are discussed by comparison with other published results

Stress Intensity Formulas for Three-dimensional Cracks in the Vicinity of an Interface

In this study, stress intensity formulas are considered in terms of the square root of area parameter to evaluate arbitrary shaped defects or cracks in the vicinity of an interface. Here “area” is the projected area of the defect or crack. Stress intensity factors for an elliptical crack parallel to a bimaterial interface are considered with varying the distance, aspect ratio of the crack, and combinations of material\u27s elastic constants. Also, stress intensity factors of an interface crack and a crack in a functionally graded material are investigated. Then, it is found that the maximum stress intensity factors normalized by the square root of area are always insensitive to the crack aspect ratio. They are given in a form of formulas useful for engineering applications

FRACTURE PARAMETERS EVALUATION FOR THE CRACKED NONHOMOGENEOUS ENAMEL BASED ON THE FINITE ELEMENT METHOD AND VIRTUAL CRACK CLOSURE TECHNIQUE

To accurately solve the fracture parameters of enamel, we have established computational nonhomogeneous enamel models and constructed the fracture element of enamel dumb nodes, based on the enamel mineral concentration, nonhomogeneous mechanical properties, and virtual crack closure technique. Through the commercial finite element software ABAQUS and the fracture element of the enamel dumb nodes, we have established the user subroutines UMAT and UEL, which enabled solving of the energy release rates of the nonhomogeneous enamel structure with cracks. The stress intensity factors of central cracks, three-point bend and compact stretched enamels, and double-edge notched stretched enamels are determined. By comparing them with analytical solutions, we have proved that the fracture element of the enamel dumb nodes is highly accurate, simple, and convenient. In addition, the cracks can be other elements rather than singular or special elements; they show versatility and other advantages. The stress intensity factor of the dental enamel can be solved more realistically. Thus, a new numerical method for prevention and treatment of dental diseases is provided

Application of laser aided manufacturing process for functionally graded thermal barrier coatings

Laser Aided Manufacturing Process (LAMP) is a rapid prototyping process used to build three dimensional functional metal and ceramic parts. The process developed in the LAMP laboratory at University of Missouri-Rolla uses a 5-axis fadal CNC machine and a 2.5 KW Nd:YAG (TEM00) Rofin Sinar laser. The laser power and metal/ceramic powder are the input along with auxiliary systems such as shielding gas delivery, RT data acquisition, coolant system. The hybrid process makes use of metal deposition and machining to obtain parts meeting design tolerances. LAMP is used to improve upon the process of Thermal Barrier Coating (TBC) deposition and enhance the material properties of TBC. LAMP is proposed to give better bond strength as a metallurgical bond is formed between the coating and the substrate. Improved life and operating temperatures of the coatings can result in increased efficiency of operation of the turbines and engines and result in better cost efficiency. Functional grading of the 8% Yittria stabilized Zirconia and NiCoCrAlY TBC is evaluated for thermo mechanical properties such as surface roughness, porosity to evaluate the deposition quality. The LAMP is optimized by using Taguchi method of Design of Experiments to obtain the improved TBC. The variation of the influence of various control factors with the changing composition of NiCoCrAlY and Zirconia is studied and influential control factors are identified. The variation of energy density as a function of surface roughness and material composition is plotted. The coating is characterized by residual stress, microhardness and micro structure analysis --Abstract, page iii

Fracture initiation in bi-material joints subject to combined tension and shear loading

The author acknowledges David Reid and Mark Gourlay for assistance with the experiments.Peer reviewedPostprin