Which property, when increased, tends to improve thermal shock resistance?

• A. Low thermal conductivity
• B. Low fracture strengths
• C. The material has low toughness
• D. High fracture strengths

Answer: (D)

Thermal shock resistance is about resisting crack initiation when a material undergoes a rapid temperature change. The key is the balance between the thermal stresses generated by the temperature gradient and the material’s ability to withstand those stresses without fracturing. The stronger the material, the higher the stress needed to cause a crack. So increasing fracture strength raises the threshold for crack initiation under a thermal pulse, making the material more resistant to thermal shock. The other options don’t provide as direct an improvement: higher thermal conductivity tends to spread heat faster and can increase gradients, while toughness helps if a crack has already started but doesn’t raise the stress required to start cracking; lower values of those properties are not what you want to improve thermal shock resistance.