What type of cracking is caused by stresses from normal expansion and contraction in a burner front?

Radial cracking is the correct answer because this type of cracking occurs in a circular pattern and is typically caused by thermal stresses resulting from the expansion and contraction of materials as temperatures fluctuate in a burner front. In a burner front, the high heat from combustion causes the metal to expand, and when the burner cools, the metal contracts. This repeated cycle can lead to cracks emanating from the center of the burner towards the edges, hence the term "radial."

Longitudinal cracking generally runs parallel to the axis of a component, which is not typical for the stresses encountered in a burner front. Transverse cracking, on the other hand, runs perpendicular to the axis and does not correlate with the specific stress patterns related to thermal expansion and contraction in circular areas such as burner fronts. The term "inferior cracking" is not a standard term used within this context and does not specifically describe a known type of crack related to thermal stress in burner operations.