Exam. 2-C Machine Elements Design Student Name: Student No.

 1) A- Define the following:

a- Spring stiffness (rat):

b- Area second moment of inertia:

c- Double shear:

d- Helical spring active coil number:

B- Write the type of car suspension springs:

 Type of spring Type of car 1 2 3 C- If k1 = 900 N/mm, k2 = 300 N/mm

i- Which one of the two springs is the softer spring?

ii- Find the equivalent spring rate in case:

a- the two springs are in parallel

b- the two springs are in seires

iii- What is the deflection of the springs in parallel under a load of  1000 N

2) A) Find the shear stress of the coil spring due to

i- Torsion only

ii-                 Torsion + direct shear

iii-               Torsion + direct shear + wire curvature

Where:

P = 6000 N

D = 150 mm

d =  15 mm

n = 17

Type of ends (Squared and ground)

B) Find the spring deflection in that case (G = 91,400 N/mm2)

C) Check the nomogram for case B and C

3) A force of 50,000 N is applied to the clevis pin with a required safety factor of 3. If the pin diameter is 18 mm, determine a suitable material for the pin. 