Lecture 6

Question 1

Definition: Tension

Answer 1

Stress applied to elongate a material.

Question 2

Definition: Compression

Answer 2

Stress applied to shorten a material

Question 3

Definition: Shear

Answer 3

Stress that causes sliding between material layers.

Question 4

Definition: Torsion

Answer 4

Twisting stress applied to a material

Question 5

Definition: Stress-Strain Graph

Answer 5

Graphical representation of material deformation

Question 6

Definition: Stress

Answer 6

Force per unit area, measured in pressure units.

Question 7

Definition: Strain

Answer 7

Deformation relative to original length, dimensionless.

Question 8

Definition: Elastic Theory

Answer 8

Describes reversible deformation under stress. caused by the stretching of the bonds between atoms

Question 9

Definition: Brittle Fracture

Answer 9

Sudden failure without significant plastic deformation

Question 10

Definition: Plastic Deformation

Answer 10

Permanent deformation after stress exceeds yield strength. Cause by atom bonds breaking at dislocations

Question 11

Definition: Youngs Modulus

Answer 11

Measure of a material stiffness, ratio of stress to strain

Question 12

Definition: Ultimate Strength

Answer 12

Maximum stress a material can withstand before failure

Question 12

Definition: Yield Strength

Answer 12

Stress at which material begins to deform plastically

Question 13

Definition: Ductility

Answer 13

Ability of a material to deform without breaking

Question 14

Definition: Isotropic

Answer 14

Material properties are the same in all directions

Question 15

Definition: Anisotropic

Answer 15

Material properties vary with direction

Question 16

Definition: Fatigue Testing

Answer 16

Evaluates material durability under cyclic loading

Question 17

Definition: Shear Stress

Answer 17

Stress that acts parallel to the surface

Question 18

Definition: Hydrogel

Answer 18

Water absorbent polymer with flexible properties

Question 19

Definition: Creep

Answer 19

Slow, permanent deformation under constant load

Question 20

Definition: stress-relaxation

Answer 20

decrease in stress under constant strain over time

Question 21

Definition: Axial Stretch Ration

Answer 21

ratio of length in tensile testing

Question 22

Force is ____ to cross-sectional area

Answer 22

proportional

Question 23

Displacement is ___ to
sample length

Answer 23

relative

Question 24

How do you tell where the elastic region is on a stress-strain curve?

Answer 24

It is the linear portion

Question 25

How do you tell where the plastic region is on a stress-strain curve?

Answer 25

It is the part that is not the elastic region

Question 26

What happens if the material only goes through the elastic part of a stress-strain curve?

Answer 26

It will go back to its original shape

Question 27

How does the plastic region affect the shape of the material?

Answer 27

It permanently deforms it

Question 28

How do you find the Youngs Modulus on a stress-strain curve?

Answer 28

The slope of the elastic region

Question 29

What does the value of the youngs modulus mean?

Answer 29

The higher the value, the stiffer a material is and the less elastic deformation there will be

Question 30

Order metals, ceramics, and polymers based on their youngs modulus (lowest to highest).

Answer 30

Polymers

Question 31

How is youngs modulus and bonds related?

Answer 31

proportionally

Question 32

Why is youngs modulus important?

Answer 32

For engineers, it is important to keep elastic deformation minimum and helps in the material selection process