Agricultural/Bioengineering Strength of Materials 5

Question 1

A sprinkler pipe made of PVC has an inner diameter of 50 mm, wall thickness of 4 mm, and internal water pressure of 0.8 MPa. What is the hoop stress?

Accepted Answer

5 MPa

Answer

Hoop stress = pr/t = 0.8 × 0.025 / 0.004 = 5 MPa (r = inner radius = 25 mm).

Question 2

Which of the following best describes 'creep' in a polymer biofilm carrier used in a wastewater treatment bioreactor?

Accepted Answer

Time-dependent plastic deformation under sustained stress below yield strength

Answer

Creep is the slow, continuous deformation of a material under constant stress over time, especially significant in polymers at elevated temperatures.

Question 3

In a combined loading scenario, a tractor PTO shaft simultaneously carries a torque of 800 N·m and a bending moment of 400 N·m. The von Mises equivalent stress is used to assess failure against:

Accepted Answer

Tensile yield strength of the shaft material

Answer

The von Mises criterion predicts yielding when the equivalent stress equals the uniaxial tensile yield strength of the material.

Question 4

A rectangular cross-section timber beam (b=150 mm, d=300 mm) is loaded in bending. The maximum shear stress in the beam occurs:

Accepted Answer

At the neutral axis

Answer

For a rectangular cross-section, the shear stress distribution is parabolic and reaches its maximum at the neutral axis.

Question 5

A steel wire rope used to lift bales in a hay storage system has a rated breaking strength of 50 kN. If a safety factor of 5 is required, what is the maximum allowable working load?

Accepted Answer

10 kN

Answer

Allowable load = Breaking strength / Safety factor = 50 kN / 5 = 10 kN.

Agricultural/Bioengineering Practice Test

Agricultural/Bioengineering Practice Test

Agricultural/Bioengineering Strength of Materials 5