Free Principles and Practice of Engineering Examination — Mechanical: Machine Design and Materials Practice Questions

Sample Practice Questions

Try these 10 sample questions from the Principles and Practice of Engineering Examination — Mechanical: Machine Design and Materials practice bank. Each includes the answer and explanation. Continue with the interactive practice above to review the full question set.

1. 1A dimensionless layout is printed at its original size with a scale of 1/2 inch = 1 foot. A machine skid measures 2.5 inches on the drawing. What actual length does that represent?

   1. A. 1.25 ft
   2. B. 2.5 ft
   3. C. 5.0 ft
   4. D. 60.0 ft

   Answer: C

   Explanation: The handbook states, "1/2 inch (on the drawing) equals 1 foot (on the actual component or system)." Thus 2.5/0.5 = 5.0 ft. Multiplying by the scale, ignoring it, or reporting inches as feet gives the other values.

   Reference: DOE Fundamentals Handbook: Engineering Symbology, Prints, and Drawings, Volume 1 — PR-01, Drawing Scale, p. 4

2. 2A prismatic tie rod carries a centered axial tensile load of 24 kN through a 200 mm² cross section. Away from the load introduction, what is its nominal normal stress?

   1. A. 60 MPa
   2. B. 120 MPa
   3. C. 240 MPa
   4. D. 480 MPa

   Answer: B

   Explanation: The handbook defines stress as "the load per unit area". Hence σ = 24,000/200 = 120 MPa. Halving the load, halving the area, or quartering the area gives the other choices.

   Reference: DOE Fundamentals Handbook: Material Science, Volume 1 — MS-02, Stress, p. 2, Equation 2-1

3. 3An ideal equal-leg fillet weld has a flat face joining perpendicular plates. Each leg is 6 mm. What is the theoretical throat thickness, excluding penetration?

   1. A. 3.00 mm
   2. B. 4.24 mm
   3. C. 6.00 mm
   4. D. 8.49 mm

   Answer: B

   Explanation: FAA describes the fillet throat as a plane at "45 degrees" and uses a 0.707 factor. The shortest root-to-face distance is 6 sin 45° = 4.24 mm. Half the leg, the full leg, or the hypotenuse gives the distractors.

   Reference: FAA Acceptable Methods, Techniques, and Practices—Aircraft Inspection and Repair — Chapter 4, Section 5, paragraph 4-82, p. 4-56

4. 4An engineer needs cylindrical gears for parallel shafts with straight teeth parallel to the shaft axes. Which gear type has this geometry?

   1. A. Spur gear
   2. B. Helical gear
   3. C. Bevel gear
   4. D. Worm gear

   Answer: A

   Explanation: The handbook states, "Spur gears are cylindrical in form and operate on parallel axes with the teeth straight and parallel to the axes." The other gear types have different tooth inclination or shaft relationships.

   Reference: Handbook of Reliability Prediction Procedures for Mechanical Equipment — Section 8.2, Gear Designs, p. 8-2

5. 5A thin-walled, closed-end cylindrical vessel has internal gauge pressure 2 MPa, internal radius 100 mm, and wall thickness 5 mm. Ignoring end effects and using unit joint efficiency, what are the hoop and longitudinal membrane stresses, respectively?

   1. A. 20 MPa and 40 MPa
   2. B. 40 MPa and 40 MPa
   3. C. 20 MPa and 20 MPa
   4. D. 40 MPa and 20 MPa

   Answer: D

   Explanation: The handbook derives thin-wall stress from "the equilibrium of a half cylinder" and longitudinal equilibrium. Equations 15-3 and 15-5 give σh = Pr/t = 40 MPa and σl = Pr/(2t) = 20 MPa. The alternatives swap the directions or use one formula for both.

   Reference: Handbook of Reliability Prediction Procedures for Mechanical Equipment — Section 15.4, Thin Wall Cylinders, pp. 15-7–15-8, Equations 15-3 and 15-5

6. 6An engineer specifies a process that fabricates a complex part directly from a digital design by successively depositing thin material layers. Which manufacturing approach is specified?

   1. A. Subtractive manufacturing
   2. B. Closed-die forging
   3. C. Investment casting
   4. D. Additive manufacturing

   Answer: D

   Explanation: NIST states, "Additive manufacturing (AM) uses digital designs to fabricate three-dimensional products that are built up layer by layer." Removing stock, deforming a solid blank, and filling a mold describe the alternative approaches.

   Reference: NIST: What is Additive Manufacturing? — Summary

7. 7An engineer compares two copies of a gearbox drawing that carry the same drawing number. One has a later revision entry. Which information in that entry identifies what changed?

   1. A. The summary of the revision
   2. B. The scale of the projection
   3. C. The vendor identification
   4. D. The drawing grid designation

   Answer: A

   Explanation: The handbook says the revision entry provides "the revision number, a title or summary of the revision, and the date of the revision." Its summary identifies the change; scale, vendor, and grid have different drawing functions.

   Reference: DOE Fundamentals Handbook: Engineering Symbology, Prints, and Drawings, Volume 1 — PR-01, Revision Block, p. 6

8. 8A uniform 1,000 mm tension rod has area 100 mm² and Young's modulus 200,000 N/mm². Its centered axial load is 20,000 N, within the proportional range. What is its elastic elongation?

   1. A. 0.10 mm
   2. B. 0.50 mm
   3. C. 2.00 mm
   4. D. 1.00 mm

   Answer: D

   Explanation: The handbook describes Young’s modulus as "the ratio of stress to strain". With σ = P/A and ε = δ/L, δ = PL/(AE) = 1.00 mm. The distractors reflect a factor-of-ten conversion error, using twice the area, or using half the modulus.

   Reference: DOE Fundamentals Handbook: Material Science, Volume 1 — MS-02, Strain, p. 7; Young's Modulus, p. 12, Equations 2-2, 2-6–2-7

9. 9A welded connection's weld-metal section can sustain 25 kN, but its adjacent heat-affected parent-metal section can sustain only 15 kN under the same applied load path. With other modes adequate, what load limits the connection?

   1. A. 40 kN
   2. B. 25 kN
   3. C. 10 kN
   4. D. 15 kN

   Answer: D

   Explanation: NASA states, "the strength of both the weld metal and the adjacent parent metal must" be considered. The serial load path is limited by the 15 kN parent-metal capacity. Adding, selecting only weld strength, or subtracting capacities gives the distractors.

   Reference: NASA Astronautic Structures Manual, Volume I — Fusion Welding, printed p. 46

10. 10A designer replaces a spur gear pair with a single-helical gear pair on parallel shafts. Which additional shaft-force component is a characteristic bearing-design concern for the helical pair?

    1. A. Centrifugal force
    2. B. Axial thrust force
    3. C. Tangential driving force
    4. D. Radial separating force

    Answer: B

    Explanation: The handbook identifies the helical gear disadvantage: "a thrust load is introduced along the gear shaft". Spur gears also transmit tangential and radial mesh forces; the characteristic added component is axial thrust.

    Reference: Handbook of Reliability Prediction Procedures for Mechanical Equipment — Gears and Splines, printed p. 8-5, helical-gear design discussion