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Difficulty: MediumThermal Expansion and Contraction

Match each mechanical design feature or procedure with its underlying thermal expansion principle or purpose.

  • Heating a solid metal pulley before sliding it onto a cold shaftRelies on thermal contraction to create a permanent interference fit once cooled
  • Designing a long steel pipeline with U-shaped expansion loopsAccommodates linear thermal expansion to prevent structural buckling
  • Riveting two distinct metal strips together to form a coilExploits unequal rates of thermal expansion to generate mechanical movement
  • Incorporating an accumulator or overflow tank in a closed hydraulic circuitPrevents dangerous pressure buildup by allowing for volumetric thermal expansion

Answer

The heated pulley matches with interference fit upon cooling; the pipeline loops match with preventing structural buckling; the riveted metal strips match with unequal expansion for movement; and the hydraulic accumulator matches with volumetric expansion of fluids.
Each distinct mechanical design feature intentionally harnesses or mitigates the physical size changes that occur when solid materials and fluids undergo temperature variations.

Step-by-Step Solution

1
Analyze the thermal behavior of a heated metal pulley placed on a cold shaft.
The heated pulley has an temporarily enlarged bore; upon cooling, thermal contraction reduces the bore size.
This physical reduction in size locks the pulley onto the shaft securely without fasteners.
2
Evaluate the mechanical purpose of U-shaped loops in long metal pipelines.
The loops provide a flexible section that can compress or stretch slightly.
Metal expands linearly when heated; without flexibility, the expansion would cause the pipe to warp or break under massive internal stress.
3
Determine the effect of heating two dissimilar metals riveted together (a bimetallic strip).
The metal with the higher coefficient of expansion grows more, forcing the entire bonded assembly to curl or bend.
This predictable bending motion is intentionally utilized to flip switches or move dials in temperature-sensing devices.
4
Assess why a closed fluid system requires an accumulator or overflow tank.
The tank provides an empty or gas-filled space for hydraulic fluid to enter as the system warms up.
Fluids expand when heated but are virtually incompressible; without extra volume, the expanding fluid would rupture the rigid lines.

Key Concept

Thermal Expansion and Contraction
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Topics

Thermal Expansion and Contraction

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