Crack in grinding wheel is developed due to

Grinding is a machining process that involves friction between the grinding wheel and the workpiece, which generates a significant amount of heat at the point of contact.

This high temperature causes localized thermal expansion of the grinding wheel material near the contact area, while the rest of the wheel remains relatively cool.

The uneven expansion creates thermal stresses within the wheel structure.

If these thermal stresses exceed the wheel’s tensile strength, cracks begin to develop, leading to possible wheel failure.

Grinding hard materials (Option B) increases the heat generation, but the root cause of cracking remains the excessive temperature rise.

Low wheel speed (Option C) generally reduces heat generation, so it is not a cause.

While high wheel speed (Option D) can contribute to heat and stress, the primary and most direct cause of cracking is the high temperature developed at the contact point.

Hence, the correct answer is High temperature developed at the contact of the wheel face and work.