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Fracture Mechanics
Published in Cameron Coates, Valmiki Sooklal, Modern Applied Fracture Mechanics, 2022
Cameron Coates, Valmiki Sooklal
A dislocation is a 1D defect within a crystalline structure. One such defect, referred to as an edge dislocation, occurs if a plane of atoms within the structure is discontinuous and the edge of the plane, called the dislocation line, lies within the crystal. Atomic distortions occur in the vicinity of the dislocation line. In another case, when a segment of the crystalline structure is subjected to shear loading, the segment may displace, breaking atomic bonds and forming new ones. The planes of atoms will then trace a spiral or helical path around the dislocation line; this is called a screw dislocation. “Plasticity” or “plastic deformation” refers to the phenomenon in which a solid material undergoes permanent deformation. Dislocations are the primary drivers of plastic deformation, and both types of dislocations result from shear loading.
Nanomaterials and Its Application as Biomedical Materials
Published in Savaş Kaya, Sasikumar Yesudass, Srinivasan Arthanari, Sivakumar Bose, Goncagül Serdaroğlu, Materials Development and Processing for Biomedical Applications, 2022
G.S. Mary Fabiola, P. Dhivya, M. Anto Simon Joseph
Mechanical properties of metals are often associated with mechanical characteristics of metal which include strength, toughness, hardness, brittleness, plasticity, elasticity, rigidity, malleability, and ductility. The traditional inorganic metals are brittle, hard, and rigid but lack plasticity and elasticity. Alternatively, organic materials are flexible but are not rigid, brittle, and strong. These disadvantages are overcome by the nanomaterials which possess high surface area, volume, and quantum effects when compared to micro- and macroscopic materials. The influence of the selection of nanomaterials, the process of fabrication, grain size, and structure of the grain boundary has a noteworthy effect on the mechanical properties of nanomaterials. In comparison with the bulk, nanomaterials refine the grain size and form inter/intragranular structure, improving the grain boundary and thereby enhancing the mechanical properties of nanostructured materials. The flexural strength of nano-Al2O3 ceramics is comparatively stronger when compared with micro-scale monolithic alumina ceramics (Teng et al. 2007).
Finite element simulation of consolidation at large strain
Published in J.-L. Auriault, C. Geindreau, P. Royer, J.-F. Bloch, C. Boutin, J. Lewandowska, Poromechanics II, 2020
D. Bernaud, V. Deudé, L. Dormieux, S. Maghous
The assumption of plastic incompressibility of the solid that yield equation (4) allows one to relate the effects of the elasticity-plasticity coupling to the plastic Jacobian F of the plastic deformation, i.e., C˜=C˜(Jp).
Additively manufactured aluminium nested composite hybrid rocket fuel grains with breathable blades
Published in Virtual and Physical Prototyping, 2023
Dandan Qu, Xin Lin, Kun Zhang, Zhiyong Li, Zezhong Wang, Guoliang Liu, Yang Meng, Gengxing Luo, Ruoyan Wang, Xilong Yu
Better mechanical properties of the Al nested composite fuel grain were observed in our previous work (Lin et al. 2022), which we hypothesise was due to the outer Al shell. Table 2 shows that the mechanical properties of the three types of Al blade are different. To determine the respective effects of the outer Al shell and inner Al blades, the mechnical behaviour of the composite grain was investigated in a finite element analysis using the ABAQUS/Standard analysis module. The simulation focused on compression tests in investigating the stress field and possible locations of damage by replicating the operating conditions of the experimental part. The material constitutive model considers elasticity and plasticity and comprises solid elements of paraffin-based fuel and Al substrate. The contact surfaces of the fuel and substrate are bound by ‘tie’ in the interaction module. On the basis of actual measurements and results of true compression tests, the density, elastic modulus, and yield stress are set for the fuel and substrate. The neutral axis algorithm is used to divide the hexahedron mesh with a minimum mesh size of 125 µm × 250 µm and 357,061 nodes (i.e. C3D8R cells). The centre point on the upper surface of the model is selected as the reference point. The displacement of the reference point is controlled to realise the compression action. The displacement control speed is 1 mm/min. Fixed boundary conditions are set on the lower surface of the model.
Development of TiCN-Co-Cr3C2-Si3N4-based cermets with improved hardness and toughness for cutting tool applications
Published in Powder Metallurgy, 2023
Balasivanandha Prabu Shanmugavel, Sri Harini Senthil Kumar, Chellammal Nandhini Aruna, Madhi Varshini Ramesh
The cracks that emanated from the edges of the indentation zones were measured and the toughness of the SN00, SN05 and SN10 are estimated to be 6.79 ± 0.61 MPa√m, 7.23 ± 0.45 MPa√m and 9.35 ± 3.10 MPa√m respectively using the Shetty’s Equation. Figure 3(a–c) shows the SEM images of the indentation zones for the SN00, SN05 and SN10 cermets respectively. The solid solution formed due to the reaction between TiCN and other ceramics formed in the rim structure, increased the fracture toughness. This process leads to an increase in the strength of the material, due to the introduction of a small amount of dissimilar atoms into the lattice of the material. This creates strain in the lattice, which serves as an obstacle for the movement of dislocation; the defects in the crystal structure are responsible for the deformation and plasticity in the metal. The material becomes tougher when it is more difficult for the crack to propagate. The fracture toughness was maximum for SN10 due to the presence of more secondary phases (in the rim structure) which acted as a medium for crack energy dissipation.
Combined effect of nanoparticle and grain refinement on yield stress of nanocomposite
Published in Philosophical Magazine, 2020
As discussed by Wu et al. [74] and Quek et al. [75], dislocations can also be emitted from GBs and their TJs as a result of stress buildup from GB sliding. Since sliding along one GB causes the development of a stress singularity at the TJs that cannot be fully relaxed by GB sliding along the other two GBs meeting at the TJs. GB sliding and dislocation emission from the TJs are synergistic GB mechanisms for stress relaxation of plastic deformation that are distinct from crystal plasticity [8]. However, in the present study, our goal is to consider the initial start of plastic deformation occurrence through grain and GB deformation near the misfit second-phase nanoparticle in this case, and predict the significant effects of the characteristics of nanoparticle, GBs and their TJs, meaning that other plastic deformations are not considered here.