A characteristic of a material that reflects its strength and plasticity. Hardness is most often determined by pressing a ball or a prism into the specimen under test, or by scratching it. In the Vickers method a diamond pyramid of standard dimensions is pressed point-first into a body with a ground surface, and the hardness is determined as the ratio of a certain standard indenting force to 1 mm2 of the area of the impression. Brinell hardness is the ratio of the force pressing in a standard steel ball to the area of the impression. Rockwell hardness is the ratio of the indenting force to the depth to which the ball or prism penetrates.
A method of measuring hardness by means of ultrasonic vibrations is coming into use; it is based on measuring the response of an oscillating system (the change in its natural frequency) to the hardness of the material under test.
A method of measuring hardness by means of ultrasonic vibrations is coming into use; it is based on measuring the response of an oscillating system (the change in its natural frequency) to the hardness of the material under test.