Chapter 3 - Book Review & Quiz Questions
Which one of the following materials has the highest modulus of elasticity: (a) aluminum, (b) diamond, (c) steel, (d) titanium, or (e) tungsten
(b) diamond
Which one of the following types of stress-strain relationship best describes the behavior of most metals at room temperature: (a) elastic and perfectly plastic, (b) elastic and strain hardening, (c) perfectly elastic, or (d) none of the above
(b) elastic and strain hardening
Viscosity can be defined as the ease with which a fluid flows: (a) true or (b) false
(b) false
The plastic region of the stress-strain curve for a metal is characterized by a proportional relationship between stress and strain: (a) true or (b) false
(b) false its actually characterized by a power function or flow curve
The shear strength of a metal is usually (a) greater than or (b) less than its tensile strength?
(b) less than its tensile strength
If stress values were measured during a tensile test, which of the following would have the higher value: (a) engineering stress or (b) true stress
(b) true stress
State Hooke's law.
stress = E*strain
Which one of the following materials has the highest hardness: (a) alumina ceramic, (b) gray cast iron, (c) hardened tool steel, (d) high carbon steel, or (e) polystyrene
(a) alumina ceramic
Which of the following are the three basic types of static stresses to which a material can be subjected (three correct answers): (a) compression, (b) hardness, (c) reduction in area, (d) shear, (e) tensile, (f) true stress, and (g) yield
(a) compression (d) shear (e) tensile
Which one of the following types of stress-strain relationship best describes the behavior of metals at temperatures above their respective recrystallization points: (a) elastic and perfectly plastic, (b) elastic and strain hardening, (c) perfectly elastic, or (d) none of the above
(a) elastic and perfectly plastic
If strain measurements were made during a tensile test, which of the following would have the higher value: (a) engineering strain, or (b) true strain
(a) engineering strain
Most hardness tests involve pressing a hard object into the surface of a test specimen and measuring the indentation (or its effect) that results: (a) true or (b) false
(a) true
Which one of the following types of stress-strain relationship best describes the behavior of brittle materials such as ceramics and thermosetting plastics: (a) elastic and perfectly plastic, (b) elastic and strain hardening, (c) perfectly elastic, or (d) none of the above
(c) perfectly elastic
Which one of the following is the correct definition of ultimate tensile strength, as derived from the results of a tensile test on a metal specimen: (a) the stress encountered when the stress-strain curve transforms from elastic to plastic behavior, (b) the maximum load divided by the final area of the specimen, (c) the maximum load divided by the original area of the specimen, or (d) the stress observed when the specimen finally fails
(c) the maximum load divided by the original area of the specimen
What is viscoelasticity, as a material property?
A property mainly found in polymers where the strain of the material is a function of stress and temperature over time.
What is work hardening?
Aka strain hardening, where strength in metals are increased through repeated plastic deformation from processes such as cold working.
What is the complicating factor that occurs in a compression test?
Barreling of the test specimen due to friction at the contacts with the machine's platens.
Why cannot a direct conversion be made between the ductility measures of elongation and reduction in area using the assumption of constant volume?
Because necking occurs to the specimen during the tensile test.
How is the shear modulus of elasticity G related to the tensile modulus of elasticity E, on average?
G = 0.4*E on average
How does the change in cross-sectional area of a test specimen in a compression test differ from its counterpart in a tensile test specimen?
In compression test, cross-sectional area increases, while in tensile test the cross-sectional area decreases due to necking.
What is the dilemma between design and manufacturing in terms of mechanical properties?
In design, strength of the material is very important. However, in manufacturing, a material is easier to fabricate when the material is not strong and more ductile.
What is the defining characteristic of a Newtonian fluid?
Newtonian fluid is where there is a constant viscosity at a given temperature.
What is hardness, and how is it generally tested?
Resistance to indentation of a material, which is generally tested by pressing a hard object into the material and then measuring size of the indentation
How is shear strength S related to tensile strength TS, on average?
S = 0.7*(TS) on average
Why are different hardness tests and scales required?
Since different materials have widely varied hardnesses
Define the recrystallization temperature for a metal.
Temperature at which a metal recrystallizes or forms new grains
Define yield strength of a material.
The point of stress where a material begins to plastically deform.
Define viscosity of a fluid.
The resistance to flow of fluid materials, greater viscosity is found in thicker fluids.
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?
Three point bending test, which measures the transverse rupture strength.
In what case does the strength coefficient have the same value as the yield strength?
When the material is perfectly elastic and does not strain harden.
What is the difference between engineering stress and true stress in a tensile test?
engineering stress divides load by the original area true stress divides load by the instantaneous area.
Define tensile strength of a material.
maximum stress experienced by material during a tensile test, or maximum load divided by original area during tensile test.
What are the three types of static stresses to which materials are subjected?
tensile compressive shear