Wednesday, November 18, 2009

PAST MECHANICAL BOARD EXAM QUESTION: Machine Design Set-1 (solutions and answers)






The following are the solutions and answers to MODIFIED PAST MECHANICAL BOARD EXAM QUESTION: Machine Design Set-1 posted on this blog last Saturday, November 14, 2009.




Again, I want to stress out that most of the questions here are modified from its original form for the purpose of improving the question.

Past Mechanical Engineering Board Exam Question Number 1
A 4 inches diameter short shaft carrying 2 pulleys close to the bearings transmits how much horsepower if the shaft makes 120 rpm.

A.200HP               B. 199 HP

C.198 HP              D. 202 HP

P = (D3N )/38 -- for mula for short shafts from PSME code

P = (4)3(120)/38

P= 202 HP

Past Mechanical Engineering Board Exam Question Number 2
An instrument that measures the hardness of the work piece in terms of elasticity.

a. Durometer

b. Scleroscope

c. Mohs's Scale

d. Brinell Tester

Source: Machinery’s Handbook



Past Mechanical Engineering Board Exam Question Number 3
A cylindrical tank with 15 in inside diameter contains oxygen gas at 3000 psi. Calculate the required wall thickness in (mm) under stress of 25,000 psi.

A.11.44mm                    B. 22.86mm

C.15.36mm                    D. 15.86mm

S = PD/2t -- thin walled vessel formula

25000=3000(15)/2t

t=0.9 in x 25.4 = 22.86 mm

Past Mechanical Engineering Board Exam Question Number 4
The minimum clearance allowed for meshing spur gears with a circular pitch of 0.1571 and diametral pitch of 20. The spur gear has 25 teeth.

A. 0.003578                       B. 0.007855

C. 0.007558                       D. 0.007585

Clearance = 0.1571/Pd

= 0.1571/ 20

= 0.007855

Past Mechanical Engineering Board Exam Question Number 5
SAE steel that responds to heat treatment:

A.SAE 1060              B.SAE 1030

C.SAE 1117              D.SAE 1020

The principle is: the more carbon content, the more responsive to heat treatment the steel would be.

Past Mechanical Engineering Board Exam Question Number 6
The differential of the shear equation is which one of the following:

A. load of the beam                         B. slope of the elastic curve

C. bending moment of the beam       D. tensile strength of the beam



Past Mechanical Engineering Board Exam Question Number 7
To reduce cost in the manufacturing of large worm gears the materials to utilize:

A. alloyed aluminum rim with cast iron spider

B. bronze rim with cast steel spider

C. cast iron rim with bronze spider

D. all of these


Past Mechanical Engineering Board Exam Question Number 8
8. The _____ test is used for determining the hardness of metallic materials consists in applying a known load to the surface of the material to be tested through a hardened steel ball of known diameter.

a. Shore

b. Vicker

c. Brinell

d. Rockwell

Source: Machinery's Handbook

Past Mechanical Engineering Board Exam Question Number 9
It is hardening treatment whereby a cast metal is being heated to a very temperature then suddenly subjected to rapid cooling to improve hardness is called:

A. normalizing                        B. quenching

C. tempering                          D. annealing

Source: Design of Machine Elements by V. M Faires

Past Mechanical Engineering Board Exam Question Number 10
Determine the estimated weight of an A-36 steel plate of size 3/16 x 5 x 15.

A. 515 lbs                              B. 625 lbs

C. 485 lbs                              D. 575 lbs

Density of steel = 0.284 Ib/in3

Weight = (3/16) (5x 12) (15 x 12) (0.284) = 575 lbs

Past Mechanical Engineering Board Exam Question Number 11
Split pulley or pulley made of separate section bolted together at the rim, the maximum speed should be limited to about _____% of the maximum speed of solid pulley,

A. 45 to 50%                   B. 65 to 70%

C. 55 to 60%                   D. 80 to 90%

Past Mechanical Engineering Board Exam Question Number 12
Killed steel is very much associated with:

A. manganese                  B. phosphorous

C. sulphur                        D. silicon

Sulfur is the most commonly used deoxidizer for steels.

Past Mechanical Engineering Board Exam Question Number 13
It is a measure of the ease with which a crack progresses through a material from an existing notch, crack, or sharp corner.

A. Creep Rate

B. Brittleness

C. Notch sensitivity

D. Moh's Scale

Source: Machinery's Handbook

Past Mechanical Engineering Board Exam Question Number 14
Calculate the estimated weight of a steel plate size 1/4 x 5 x 8.

A. 480 kg                  C. 100 kg

B. 186 kg                 D. 409 kg

Weight = (1/4) (5x 12) (8 x 12) (0.284) = 575 lbs/2.2 = 186 kg

Past Mechanical Engineering Board Exam Question Number 15
A type of welding whereby a wire or powder from the nozzle of a spray gun is fuse gas flame, arc or plasma jet and the molten particles are projected in form of a spray by means of compressed air or gas.

A. electro-slug building                    B. plasma-arc welding

C. electro-beam welding                 D. metal spray welding

Source: PSME Code

Past Mechanical Engineering Board Exam Question Number 16
Heating of metal above the critical temperature and then cooling slowly usually furnace to reduce the hardness and improve the machinability is called:

A. normalizing                                 B. tempering

C. annealing                                    D. quenching

Source: Design of Machine Elements by V. M. Faires

Past Mechanical Engineering Board Exam Question Number 17
Accident prevention is:

A. an association of employers, organization and individuals

B. a job of a safety engineer

C. the foreman's responsibility just as much as production

D. the responsibility of top management

Accident prevention is everybody’s responsibility.

Past Mechanical Engineering Board Exam Question Number 18
Major component of bronze casting:

A. copper                              B. zinc

C. manganese                        D. lead

Past Mechanical Engineering Board Exam Question Number 19
Commonly utilized/cheapest shaft material available in the market with carbon cont 0.28 to 0.34% C.

A. SAE 4140                        B. SAE 1030

C. SAE 1117                        D. SAE 4130


Past Mechanical Engineering Board Exam Question Number 20
20. Continuing changes in dimensions of a stressed material over time is called ____.

A. Aging

B. Embrittlement

C. Creep

D. Deformation

Source: Machinery’s Handbook

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6 comments:

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  4. The answer for killed steel is wrong. The deoxidizing agent is Silicone

    ReplyDelete
  5. regarding question 8, how could you believe in that formula stated in such "PSME Code" if it has no discussion how did they come up with that short cut? It's unbelievable to determine the shaft HP without any changes on the momentum of the shaft. it should start somehow or change the question to"determine the maximum hp transmitted by the 4 inch shaft carrying 2 pulleys each with 8" radius accelerating from 20 rpm to 120 rpm at 20 seconds? these data should be given to calculate the total torque, the flywheel/pulley mass moment of inertia, and finally the shaft power.

    wag basta basta maniniwala sa sabi sabi ni psme code, ni review center at ni prof.

    ReplyDelete