Caribbean Maritime Institute
Assignment #1
Dynamic Noise and Vibration
Group: Beng Yr 3, F/T
April 21, 2021
Duration: 3 Hours
Instructions:
i.
Do all questions.
ii.
Show steps for deriving answers.
iii.
All answers should be written in black or blue ink pen except for diagrams, which
should be in pencil if not typed.
iv.
Use APA format through script.
v.
No more than four (4) persons in a group. Only names on script will be awarded
marks.
vi.
This project is due 3 hours after being posted. Note time and date to avoid late
submission.
vii.
Late submission will attract 10 % reduction in marks within the first 24 hours.
Then, ‘5% mark will be lost for each day up to 10 days that the assignment (project)
is outstanding. Any assignment received after the first ten days but up to the three
weeks after the stated deadline will see 50% points deducted. After three weeks (15
days) any assignment received will attract a mark of zero.’
1. It is required to design a helical compression spring subjected to a maximum force of
1250 N. The deflection of the spring corresponding to the maximum force should be
approximately 30 mm. The spring index can be taken as 6. The spring is made of
patented and cold-drawn steel wire. The ultimate tensile strength and modulus of
rigidity of the spring material are 1090 and 81 370 N/mm2, respectively. The
permissible shear stress for the spring wire should be taken as 50% of the ultimate
tensile strength. Design the spring and calculate
i.
ii.
iii.
iv.
v.
vi.
Wire diameter
Mean coil diameter
Number of active coils
Total number of coils
Free length of the spring
Pitch of the coil
[20 Marks]
2. Calculate the natural frequencies and modes shapes for the system below.
[20 Marks]
3. Calculate the frequency and periodic time for the oscillation produced by a mass –
spring system given that the mass is 0.5 kg and the spring stiffness is 3 N/mm.
[10 Marks]
The End!