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1. Circle Tor F (True or False) for the following statements (1 mark each = 18 marks) Example: F 1+1=2 IT F 2 T F 3 T F F ST F OT F F T F F F F Porosity decreases the thermal conductivity of ceramic materials. For a circular crack (hole) in the material, the maximum stress at the tip of the crack is 1/3rd of the applied (nominal) stress. Substitutional atoms replace the solvent atoms in a unit cell. Plastic deformation involves the breaking and reforming of atomic bonds. Ductility is equivalent to the plastic strain to failure. The yield stress is the stress at which the elastic deformation stops and plastic deformation starts Poisson's ratio is the ratio of longitudinal to parallel strain. Thermal stresses may be introduced into a structure by rapid heating or cooling. Hardness is a fundamental material property. When the radius of the crack tip is same, a shorter crack prevents crack propagation compared to a long crack. Each atom in BCC is connected to 8 closest neighboring atoms. BCC contains a close-packed plane. A high ductile-to-brittie transition temperature is desirable in low temperature applications. Binding energy is indirectly proportional to the melting point. The same material can fracture in a ductile and brittle mode. For cooling, the surface stresses will be compressive. Secondary bonding only occurs in polymers. The number of vacancies decreases with increasing temperature. (10 T F TF 2T F 1 F 14 TF 15 T F (16 T F 17) T F 18 T F