Strength of Materials

Question 1

Two primary types of stress

Answer 1

-Normal stress - area is normal to the force
-Shear stress - area is parallel to the force

Question 2

Definition of ultimate stress

Answer 2

Su - Stress that would cause failure

Question 3

Definition of yield stress

Answer 3

Sy - maximum stress without causing deformation (within elastic limit)

Question 4

Formula of allowable stress (or safe stress)

Answer 4

(Ultimate stress)/(Factor of Safety (FS)) or
(Ultimate stress)/(Design Factor)

Question 5

What is design stress

Answer 5

-stress used in the determining of the size of a member
-equal to allowable stress or less
- Sd = Su/FS or Sy/FS

Question 6

Definition of working stress

Answer 6

Stress actually occuring under operating conditions

Question 7

What is tensile stress?

Answer 7

-the force per unit area which is perpendicular to the surface that produces stretching of a material by the application of pulling forces.
-St = F/A

Question 8

What is compressive stress?

Answer 8

-the stress state when the material is compact.
-Sc = F/A

Question 9

What is shearing stress?

Answer 9

-type of stress when a force applied produces a sliding failure of a material along a plane that is parallel to the direction of the applied force
-Ss = F/A

Question 10

What is bearing stress?

Answer 10

-The surface pressure acting on a machine member as a result of applied load dividing bearing area.
-Sb = F/LD
-L = length, D = Diameter

Question 11

What is torsional stress?

Answer 11

-shear stress on a transverse cross section resulting when one end of a machine member is twisted in one direction (usually shafts)

Question 12

Ultimate tensile strength given Brinell Hardness number

Answer 12

Tensile strength = BHN × 515 psi

Question 13

Formula for strain, ε

Answer 13

ε = y/L
-y = elongation
-L = length

Question 14

Formula for Modulus of Elasticity (Young’s Modulus), E

Answer 14

E = stress/strain = (F/A)/(y/L)