Tuesday, March 9, 2010

Board Exam Refresher: Machine Design (calculation)

Here are some refresher questions you may try in preparation for the upcoming board exam.

Machine Design: Strength of Materials

Select the best answer.

1. A steel rod 40 mm in diameter 800 mm long cannot extend longer than 41.5 mm. Find the maximum allowable load it can carry in Newtons. E for steel is 200 GPa.
A. 471240
B. 600000
C. 188495
D. 712440

2. A simply supported beam 3m long has a load of 3KN 1 m from the left support. Calculate the maximum moment.

A. 2.25 kN-m
B. 2.0 kN-m
C. 4.5 kN-m
D. 6.0 kN-m

3. Calculate the maximum deflection of a 12 m beam with fixed ends if the load applied on it is 3KN located at its center. (I=4,200,000 E=200 GPa).

A. 128.6 mm
B. 32.14 mm
C. 0.17 mm
D. 0.27 mm

4. A 40mm short shaft has is rotating at 300RPM. Calculate the power capacity.
For short shaft: (PME Code)
A. 30.83 kW
B. 23 kW
C. 16.34 kW
D. 10.93 kW

5. Calculate the wall thickness required for a 1m spherical thin walled vessel carrying 30Mpa of fluid pressure. The maximum allowable stress is 150Mpa.
A. 100mm
B. 200 mm
C. 150 mm
D. 50 mm

6. A 33 mm long single leaf spring is carrying a load of 50 grams 3 mm from its tip. If the material used in making the spring is a 0.3 mm sheet metal, calculate the required width if the allowable stress is not to exceed 250 Mpa.

A. 4.12 mm
B. 0.71 mm
C. 3.92 mm
D. 1.18 mm

7. A compression spring has the following data:
Wire diameter: 0.5 mm
Solid height: 5mm
OD: 4 mm
Load 50 grams
Calculate the Wahl’s factor.
A. 1.213
B. 1.184
C. 1.145
D. 1.162

8. A spring has a Wahl’s factor of 1.212, a free length of 8 mm, and an index of 7 calculate the curvature factor.

A. 1.125
B. 1.051
C. 0.962
D. 1.131

9. A 20 mm diameter, 700 cm long rod elongates 2 mm at a load of 15KN. Calculate the modulus of elasticity of the material used.

A. 167 Gpa
B. 668 GPa
C. 743 GPa
D. 334 GPa

10. Calculate the force required to punch a 10 mm diameter hole into a 2 mm thick sheet metal with the these properties: Sy=155 Mpa Su=300 Mpa

A. 11.31 kN
B. 9.74 kN
C. 18.85 kN
D. 14.14 kN

Answers will be provided next week.

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