Problems on Mechanical properties

1. Problems on Mechanical properties 1-a specimen of copper having a rectangular cross section 15.2 mm x 19.1mm(0.60 in x 0.75 in)ispulled in tension with44,500 N (10,000Ibf) force,producing only elastic deformation. Calculate the resulting strain. • 2-For a brass alloy, the stress at which plastic deformation begins is 345 MPa (50,000 psi), and the modulus of elasticity is 103 GPa (15.0 x106 psi). • (a) What is the maximum load that may be applied to a specimen with a cross-sectional area of 130mm2 (0.2 in2) without plastic deformation? • (b) If the original specimen length is 76 mm (3 in.), what is the maximum length to which it may be stretched without causing plastic deformation?

2. Review Some Definitions • Crystalline: • A crystalline material is one in which the atoms are situated in a repeating or periodic a • array over large atomic distances. • Crystal structure: • Some of the properties of crystalline solids depend on the crystal structure of the material, the manner in which atoms, ions, or molecules are spatially arranged. • Lattice: lattice is used in the context of crystal structures; in this sense ‘‘lattice’’ means a three-dimensional array of points coinciding with atom positions (or sphere centers). • UNIT CELLS: The atomic order in crystalline solids indicates that small groups of atoms form a repetitive pattern. • The coordination number: • For metals, each atom has the same number of nearest-neighbor or touching atoms, which is the coordination number.

3. The atomic packing factor (APF) Answer the following questions: • Define stress –strain relation. • State Hooke’s law. • Modules of elasticity. Tensile strength ,percent elongation ,Ductility

4. Hardness and the different tests methods for measuring it. • Brittle fracture ductile fracture. • Fatigue. • Elastic deformation and plastic deformation

5. DENSITYCOMPUTATIONS—METALS

6. Crystallographic Points and Directions