Meaning
Directional coefficients of dimensional change relative to temperature provide the metrics for predicting the fit of precision components. A thermal expansion tensor allows engineers to calculate how a part will warp when heated. It is especially important for anisotropic materials where expansion is not uniform.
The resulting calculations determine if a production batch will meet tolerance requirements at operational temperatures.
Dimensional Change
Size variations occur as the atomic bonds vibrate more vigorously with increasing heat. The thermal expansion tensor describes the magnitude of this effect along each principal axis. If the expansion is not properly modeled, the assembly may seize or leak.
Lattice Variation
Atomic spacing increases as energy is added to the system. Within the thermal expansion tensor, the individual values represent the strain per degree of temperature rise. A demonstrated rate of expansion in a prototype must be verified across the entire production run to ensure consistency.
Thermal Fatigue
Repeated heating cycles cause internal stresses that lead to microcracking. When a material possesses a large thermal expansion tensor, the risk of failure increases during rapid temperature ramps. Calling a design ready for production without cycling tests often leads to high field failure rates.
Stability is measured against the theoretical maximum of the material.
