Exam. 2A 
Machine Elements Design 

Student Name: 
Student No. 
1) Define the following (3 only +): 

a Spring rate:
b
Allowable shear stress:
c Wahl factor:
d Spring buckling:
1) B Write the types of spring functions:

Spring function 
Type of spring 
1 


2 


3 


1) C If k_{1 }= 800 N/mm, k_{2} = 200
N/mm, k_{3} = 500 N/mm
+ i Which one of the three
springs will need more force to get the same
deflection as the rest of the springs?
ii Find the equivalent spring rate for the figure shown:
iii What is the deflection of the springs in the figure under a load of 1300 N
2 A helical compression spring is made of steel of 2000 MPa, with mean spring diameter (D) of 10 mm, and wire diameter (d) of 1mm. If the required safety factor (SF) is 5. Find:
i The maximum force the spring can carry, corresponding to
the allowable stress of the wire.
ii Find the spring rate, if the spring
ends are squared and there are 12 total turns,
G = 81,400 MPa.
iii Check the shear stress using the nomogram, using D, d, p, C
+ vi What are the outside diameter and the closed length.
3 A 36 mm diameter shaft is subjected to a tangential load
of 60,000 N around its circumference. If the required safety factor is 2, and
the shaft material is EN32A. Find
i Overall dimensions of the key (b x h x L).
+ ii – The torque the shaft is carrying.

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