Chapter 6

Question 1

elastic means ____________

Answer 1

reversible

Question 2

plastic means__________

Answer 2

permanent

Question 3

stress has units _________ or _______

Answer 3

stress has units N/m^2 or lb/in^2

Question 4

strain is always ___________

Answer 4

dimensionless

Question 5

units for
E:
v:

Answer 5

E=GPA or psi

v: dimensionless

Question 6

slope of stress strain plot (________________________) depends on bond strength of metal

Answer 6

which is proportional to the elastic modulus

Question 7

material, geometric, and loading parameters all contribute to ___________

Answer 7

deflection

Question 8

large ________ minimize elastic deformation

Answer 8

elastic moduli

Question 9

yield strength=?

Answer 9

stress at which noticeable deformation has occured

Question 10

metals:
polymers:

Answer 10

metals- occurs when noticeable necking starts

polymers: occurs when polymer backbone chains are aligned and about to break

Question 11

what is toughness?

Answer 11

energy to break a unit volume of material

approximate by the area under the stress-strain curve

Question 12

what is hardness?

Answer 12

resistance to permanently indenting the surface
large hardness means:
-resistance to plastic deformation or cracking in compression
-better wear properties

Question 13

rockwell:

Answer 13

no major sample damage

Question 14

elastic modulus is material property

critical properties depend largy on sample flaws (defects etc) large sample to sample variabilit

Answer 14

?

Question 15

design or safety factors:

Answer 15

design uncertainties mean we do not push the limit

Question 16

stress and strain:

Answer 16

these are size independent measures of load and displacement, respectively

Question 17

elastic behavior:

Answer 17

the reversible behavior often shows a linear relation between stress and strain to minimize deformation, select a material with a large elastic modulus (E or G)

Question 18

plastic behavior:

Answer 18

the permanent deformation behavior occurs when the tensile (or compressive) uniaxial stress reaches shear stress y

Question 19

toughness

Answer 19

the energy needed to break a unit volume of a material

Question 20

ductility

Answer 20

the plastic strain at failure