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GATE 2020 ME (ME1) – Question 19

Machine Design · Shafts and springs · 1 mark · Multiple choice

A helical gear with 20° pressure angle and 30° helix angle is mounted at the midspan of a shaft supported between two end bearings. Identify the nature of stresses induced in the shaft.

  1. Normal stress due to bending only
  2. Normal stresses due to bending in one plane and axial loading; shear stress due to torsion
  3. Normal stresses due to bending in two planes and axial loading; shear stress due to torsion
  4. Normal stresses due to bending in two planes; shear stress due to torsion

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Correct answer: (A) Normal stress due to bending only; (C) Normal stresses due to bending in two planes and axial loading; shear stress due to torsion

Explanation

The tangential and radial gear forces bend the shaft in perpendicular planes. The helix produces axial thrust, while the tangential force also transmits torque. Consequently there are normal stresses from two-plane bending and axial loading, plus torsional shear. **Answer: C.** The source key accepts A or C. C describes the usual gear force components; the printed setup does not fully specify the torque transfer and bearing thrust arrangement. Preserve the multiple accepted answers in scored use.