Dilatometer application in measurement and materials testing: identify the physical quantity a dilatometer is designed to measure when a specimen experiences temperature changes during a controlled program.

Introduction / Context:
Dilatometry quantifies dimensional change in a specimen as temperature varies. It is widely used to determine linear thermal expansion coefficients, softening points, transformation temperatures (e.g., glass transition), and sintering behavior of ceramics and metals.

Given Data / Assumptions:

• Specimen is heated/cooled under a defined temperature program.
• Instrument measures length change with high resolution.
• Environmental effects (atmosphere, load) are controlled.

Concept / Approach:
A dilatometer records ΔL (change in length) as a function of temperature T and time t. From ΔL/L0 versus T, the linear thermal expansion coefficient α is computed as α = (1/L0) * dL/dT. The instrument is not intended to directly measure stress or general strain fields; instead it measures thermal expansion or contraction along a specimen axis. While “strain” could describe ΔL/L0 abstractly, the conventional wording for a dilatometer’s purpose emphasizes thermal expansion/contraction due to temperature changes.

Step-by-Step Solution:

Verification / Alternative check:
Instrument datasheets specify outputs as length change versus temperature, confirming the intended measurand.

Why Other Options Are Wrong:

Common Pitfalls:
Equating thermal strain with mechanical strain under load; dilatometry is usually performed under minimal or controlled load.

Final Answer:
Contraction/expansion due to changes in temperature