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Fundamentals of Linear Elastic Fracture Mechanics
Published in Cameron Coates, Valmiki Sooklal, Modern Applied Fracture Mechanics, 2022
Cameron Coates, Valmiki Sooklal
Since KIc is constant beyond a certain thickness, it is conservatively chosen as the maximum value that the stress intensity factor can be prior to a crack becoming unstable under Mode I loading. It is a measure of the material’s resistance to brittle failure. Ductile materials therefore generally have a higher fracture toughness than brittle materials. Table 2.4 provides fracture toughness values of selected materials. ASTM standards E1820-18, ASTM E399, E1290, and E1921 provide standard test methods to measure the fracture toughness for a variety of materials. These will be discussed in detail in Chapter 6.
Modeling, Simulation, and Analysis of Electric Motors
Published in Wei Tong, Mechanical Design and Manufacturing of Electric Motors, 2022
Fatigue in materials is the process of initiation and growth cracks under alternative tensile loading conditions. Fracture occurs when the effects of total stress and flaw size exceed a critical value commonly referred to as the fracture toughness. The fracture toughness depends upon a number of factors, such as microstructure and composition of the material, service temperature, loading rate, plate thickness, and fabrication processes [14.43]. However, an accurate determination of the fracture toughness is complicated.
Failure and Design
Published in Zainul Huda, Metallurgy for Physicists and Engineers, 2020
Plain Strain Fracture Toughness, KIC.Fracture toughness is a measure of a material’s resistance to brittle fracture when there exists a crack. For thick specimens with the thickness much greater than the crack size, the fracture toughness is equal to Kc; which can be computed by using Equation 10.15. However, for thin specimens, the value of Kc will strongly depend on the thickness of the specimen. As the specimen-thickness increases, Kc decreases to a constant value; this constant is called the plane strain fracture toughness, KIC (pronounced as kay-one-see). For example, the Kc of a 207-MPa yield-strength steel (thin specimen) decreases from Kc=230 MPa√m to a constant value around 93MPa√m as the thickness of the specimen increases; this constant value of Kc is reported as the plane strain fracture toughness, KIC of the steel. In general, it is the KIC that is reported as the fracture toughness property of the material since the value of KIC does not depend on the thickness of the component. The fracture toughness value ranges for some engineering materials are presented in Table 10.2.
Investigation the effect of short term aging on thermodynamic parameters and thermal cracking of asphalt mixtures modified with nanomaterials
Published in Road Materials and Pavement Design, 2021
Gholam Hossein Hamedi, Hasan Ghahremani, Dawud Saedi
The results of the fracture toughness parameter of the SCB test are presented in Figures 14–16. Fracture toughness indicates the amount of resistance to rupture or rapid failure of the material in the presence of a crack. Based on Figure 14, the aged asphalt mixtures performed better than the unaged asphalt mixtures in both base and nanomaterials modified states at the low temperature of the test. Also, the application of both NCC and NHL improved the fracture toughness of all samples in both control and aged states. From among the asphalt mixtures made with both types of asphalt binder, PG 58–22 in both aged and unaged states had a higher fracture toughness than PG 64-16, indicating the superior performance of mixtures manufactured with PG 58–22 against thermal cracking.
Determination of Vickers indentation fracture toughness of boronised alloyed ductile iron
Published in Transactions of the IMF, 2019
Fracture toughness is a crucial parameter for any brittle material. Many experimental methods have been developed to determine the fracture toughness of brittle materials, and the Vickers indentation method is the simplest and cheapest technique among them. The Vickers indenter is applied to a brittle surface under a load high enough to cause cracks in the corners of the indentation, and the lengths of the Vickers indent diagonals and the cracks are measured.6 This method can be applied to measure fracture toughness of ceramic materials in both bulk and coating/film forms. Moreover, residual stresses on the surfaces of ceramics or their coatings/films can also be estimated by the indentation fracture method, and the measurement accuracy depends on the reliability of the established indentation toughness equations.7
Surface damage characteristics of AlN ceramics induced by ultra-precision grinding
Published in Materials and Manufacturing Processes, 2022
Honggang Li, Renke Kang, Shang Gao, Xianglong Zhu
Fracture toughness represents the ability of brittle solids to resist crack propagation. We conducted the fracture toughness test on a microscopic hardness meter using the Vickers indenter. The indentation morphologies under the load at 0.5kgf and 1.0kgf were observed by SEM, as shown in Fig. 9(a) and (b), where the brittle cracks extend from Vickers indentation vertices. The previous studies have established a model for calculating the fracture toughness of indentation,[24] as presented in Equation (3), where E is elastic modulus, H is hardness, P is the load of indentation, c is the length of brittle crack.