Materials Final Exam Notecards - 1 The yield strength is the maximum value of stress on an engineering stress-strain curve FALSE 2 When temperature

Materials Final Exam Notecards - 1 The yield strength...

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1) The yield strength is the maximum value of stress on an engineering stress-strain curve. 2) When temperature is sufficiently high compared to the melting point, atoms diffuse away from their initial position in a random-walk manner. 3) The Young’s modulus of a material is the slop of the stress strain curve in the elastic deformation region, and is specific to each material. 4) Plastic deformation in a metal is accomplished by means of point defects moving within preferred slip systems. 5) For a ductile material, all deformation up to the ultimate tensile stress is uniform throughout the sample, however, at maximum stress, a small constriction (necking) begins to form. 6) A ductile failure has extensive plastic deformation in the vicinity of the advancing crack. Crack opening proceeds relatively slowly and any further extension requires increased levels of applied stress. 7) Cold-working increases the yield strength and tensile strength and decreases the ductility of a material. 8) A brittle material can become ductile as temperature decreases. 9) Materials are not as strong as predicted by theory because flaws act as stress concentrators and lead to failure at stresses lower than theoretical values. 10) Cracks propagate if the stress at their tip exceeds a critical value. The largest and the most highly stressed crack will grow first. 1) In materials, dislocations are created by the application of shear stress. 2) Point-defects are also created by the application of shear stress. 3) Materials with strong chemical bonds tend to have high melting points. 4) X-rays are ionizing radiations because their photon energy is larger than the binding energy of electrons in an atom. 5) The fact that X-ray can ionize matter is used in the standard X-ray diffraction technique. 6) The atomic linear density (LD) is defined as the number of atoms per unit length whose centers lie on the directionvector for a specific crystallographic direction. 7) When repeated over and over, the stacking sequence ABABAB… yields a FCC structure. 8) In an FCC structure, [100] is a close-packed direction. 9) In general, the physical properties of single-crystals and glasses are isotropic (i.e. do not depend on the directionof measurement).

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