How is hardness defined in material science?

Hardness in material science is defined as a measure of a material's resistance to localized deformation, which encompasses permanent indentation or scratching. This property is crucial for applications where materials are subject to wear and tear, ensuring they maintain structural integrity and performance under mechanical stress. Testing methods, such as the Rockwell, Vickers, or Brinell hardness tests, quantify this resistance by applying a specific force to a standardized indenter and observing the size or depth of the resulting impression. Materials with higher hardness values are typically more durable and able to withstand greater loads without yielding or becoming permanently deformed, making hardness a key factor in material selection for engineering and manufacturing processes.