Thermal Expansion Coefficient Converter

About Thermal Expansion Coefficients

Thermal expansion coefficients describe how the dimensions of a material change with temperature. These coefficients are essential parameters in engineering, materials science, and construction, where accounting for dimensional changes due to temperature variations is critical.

Types of Thermal Expansion Coefficients

There are several types of thermal expansion coefficients:

• Linear thermal expansion coefficient (α): Describes the change in length per unit length per degree of temperature change
• Area thermal expansion coefficient (β): Describes the change in area per unit area per degree (approximately β = 2α)
• Volumetric thermal expansion coefficient (γ): Describes the change in volume per unit volume per degree (approximately γ = 3α for isotropic materials)

This converter focuses on linear thermal expansion coefficients, which are the most commonly used.

Common Thermal Expansion Coefficient Conversions

• 1 per Kelvin (K⁻¹) = 1 per Celsius degree (°C⁻¹)
• 1 per Fahrenheit degree (°F⁻¹) = 1.8 per Kelvin (K⁻¹)
• 1 per Kelvin (K⁻¹) = 100 percent per Kelvin (%/K)
• 1 per Kelvin (K⁻¹) = 1,000,000 parts per million per Kelvin (ppm/K)
• 1 percent per Kelvin (%/K) = 0.01 per Kelvin (K⁻¹)
• 1 part per million per Kelvin (ppm/K) = 10⁻⁶ per Kelvin (K⁻¹)

Understanding Temperature Scales in Thermal Expansion

When working with thermal expansion coefficients, it's important to understand how different temperature scales affect the values:

• Kelvin and Celsius scales have the same size of degree, so the expansion coefficient values are identical (e.g., 20 × 10⁻⁶ K⁻¹ = 20 × 10⁻⁶ °C⁻¹)
• Fahrenheit degrees are smaller than Celsius/Kelvin degrees (a Fahrenheit degree is 5/9 of a Celsius degree), so the coefficient values differ by a factor of 9/5 (e.g., 20 × 10⁻⁶ K⁻¹ = 11.1 × 10⁻⁶ °F⁻¹)

Typical Thermal Expansion Coefficient Values

Different materials have widely varying thermal expansion coefficients:

Material	Linear Thermal Expansion (α) at 20°C
Aluminum	23 × 10⁻⁶ K⁻¹ (23 ppm/K)
Copper	17 × 10⁻⁶ K⁻¹ (17 ppm/K)
Steel (mild)	12 × 10⁻⁶ K⁻¹ (12 ppm/K)
Glass (borosilicate)	3.3 × 10⁻⁶ K⁻¹ (3.3 ppm/K)
Concrete	12 × 10⁻⁶ K⁻¹ (12 ppm/K)
Quartz (fused silica)	0.55 × 10⁻⁶ K⁻¹ (0.55 ppm/K)
Invar (36% Ni steel alloy)	1.2 × 10⁻⁶ K⁻¹ (1.2 ppm/K)
Diamond	1.0 × 10⁻⁶ K⁻¹ (1.0 ppm/K)

Applications and Considerations

Thermal expansion coefficients are crucial in numerous applications:

• Structural engineering: Designing expansion joints in bridges, buildings, and infrastructure
• Mechanical engineering: Ensuring proper fits and clearances in machine components at different operating temperatures
• Electronics: Managing thermal stresses in integrated circuits and electronic packages
• Materials science: Developing low-expansion materials for precision instruments and applications
• Aerospace: Accounting for thermal cycling in aircraft and spacecraft components
• Pipeline design: Calculating expansion loops and supports for pipelines carrying high-temperature fluids
• Glass manufacturing: Creating glass-to-metal seals with compatible expansion characteristics

Calculating Linear Thermal Expansion

The change in length due to thermal expansion can be calculated using:

ΔL = α × L₀ × ΔT

Where:

• ΔL is the change in length
• α is the linear thermal expansion coefficient
• L₀ is the original length
• ΔT is the change in temperature

Anisotropic Materials

Some materials exhibit anisotropic thermal expansion, meaning the expansion coefficient varies with direction. In these cases, multiple coefficients may be specified for different crystallographic directions.

Temperature Dependence

Thermal expansion coefficients are not always constant; they can vary with temperature. The values typically provided are for a specified reference temperature (often 20°C). For precision applications, the temperature dependence of the coefficient should be considered.

Our thermal expansion coefficient converter provides accurate conversions between all these units, making it easy to translate between different measurement systems for engineering calculations, materials selection, and research applications.