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Review questions - ch. 2, 3, 4
atomic structure, bonding, crystalline structures
Terms in this set (32)
The elements listed in the Periodic Table can be divided into three categories. What are these categories and give an example of each?
metals, nonmetals, and metalloids (transition group)
Which elements are noble elements
helium, neon, argon, krypton, xenon, and radon - exhibit great chemical stability and low reaction rates
What is the difference between primary and secondary bonding in the structure of materials?
primary - generally associated with formation of molecules (ionic, covalent, and metallic)
secondary - generally associated with attraction between molecules (dipole forces, London forces, and hydrogen bonding; dipole+london are van der Waals forces)
What is the difference between crystalline and noncrystalline structures in materials?
crystalline structure is one in which the atoms are located at regular and recurring positions in three dimensions
Among the common point defects in a crystal lattice structure, what is a vacancy?
the simplest defect, involving a missing atom within the lattice structure
What is an ion-pair vacancy?
aka Schottky defect, missing PAIR of ions of opposite charge in a compound that has an overall charge balance
What is an interstitialcy?
a lattice distortion produced by the presence of an EXTRA atom in the structure
Define the difference between elastic and plastic deformation in terms of the effect on the crystal lattice structure
elastic deformation is temporarily deformed - once load is removed, lattice will return to normal, while plastic deformation results in permanent deformation
Identify some materials that have a crystalline structure
metals (solid), some ceramics (not glass)
Identify some materials that possess a noncrystalline structure
liquids and gases, glass, plastics, rubber
CHAPTER 3: What are the three types of static stresses to which materials are subjected?
tensile, compressive, shear
State Hooke's law
Define tensile strength of a material
the engineering stress when applied load F reaches a maximum value
Define yield strength of a material
the point where the stress strain curve for the material intersects a line that is paraellel to the straight portion of the curve, but offset from it by a strain of 0.2% (marks the TRANSITION to the plastic region)
Why cannot a direct conversion be made between the ductility measures of elongation and reduction in area using the assumption of constant volume?
necking occurs, and thus has an associated nonunifrom effect on elongation and area reduction
What is work hardening
aka strain hardening - in metallic crystal structures, the grain boundaries will absorb all the deformation so that it will become stronger with increasing stress
Which stress always has the greater value, engineering stress or true stress
A stress-strain relationship that exhibits behavior that is elastic and perfectly plastic is characteristic of what types of materials?
metals when hot worked
A stress-strain relationship that exhibits behavior that is elastic and strain hardening is characteristic of what types of materials?
metals when cold worked
Under what circumstances does the strength coefficient have the same value as the yield strength?
What is the complicating factor that occurs in a compression test that might be considered analogous to necking in a tensile test?
cross section increases due to compression (barreling), and the load increases more rapidly, resulting in HIGHER value of calculated engineering stress
Tensile testing is not appropriate for hard brittle materials such as ceramics. What is the test commonly used to determine the strength properties of such materials?
By what failure mode do brittle materials such as ceramics fail in a bending test?
How is the shear modulus of elasticity G related to the tensile modulus of elasticity E, on average?
How is shear strength S related to tensile strength TS, on average?
What is hardness, and how is it generally tested?
resistance to permanent indentation. indication of how the material is resistant to scratching and wear
How does Brinell hardness test work?
used for metals and nonmetals of LOW TO MEDIUM hardness; hardened steel ball of 10 mm diameter is pressed into a surface of a specimen using a load of 500 1500 or 3000 kg (see equation 3.19 for relationship)
How does the Rockwell hardness test work?
cone shaped indenter or small diameter ball is pressed into a specimen using a minor load of 10 kg for seating - then 150kg major load (or more) is applied; penetration distance d is converted into a rockwell hardness reading by testing mahcine
How does the Knoop hardness test work?
uses a pyramid shaped DIAMOND indenter with applied loads (generally lighter than vickers test) to test MICROHARDNESS
Define viscosity of a fluid.
the resistance to flow that is characteristic of a fluid. measure of the internal friction that arises when velocity gradients are present in the fluid
What is the defining characteristic of a Newtonian fluid?
viscosity was a constant property of a given fluid at a given temperature; Newtonian fluid follows this concept
What is viscoelasticity, as a material property?
the peroperty of a material that determines the strain it experiences when subjected to combinations of stress and temperature over time
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