In ultrasonic machining process, the material removal rate will be higher for material with lower toughness.

Ultrasonic machining process:
Ultrasonic machining is a non-traditional machining process used to remove materials from workpieces by using high-frequency vibrations of a tool. It is commonly used for machining hard and brittle materials such as ceramics, glass, and composites.

Material removal rate:
Material removal rate (MRR) is a measure of the amount of material that can be removed from a workpiece in a given period of time. It is an important parameter in machining processes as it directly affects the efficiency and productivity of the process.

Toughness and material removal rate:
Toughness is a measure of a material's ability to absorb energy before fracture. Materials with higher toughness are more resistant to cracking and fracturing. In ultrasonic machining, the material removal mechanism involves the repeated impact of abrasive particles on the workpiece surface. The higher the toughness of the material, the more resistant it is to these impacts, resulting in a lower material removal rate.

Explanation:
When the workpiece material has higher toughness, it can withstand the repeated impacts of the abrasive particles during ultrasonic machining. The tough material absorbs the energy of the impacts and does not fracture easily. As a result, the material removal rate is lower because the abrasive particles are not able to effectively remove the material from the workpiece surface.

On the other hand, when the workpiece material has lower toughness, it is more prone to cracking and fracturing under the impact of the abrasive particles. The low toughness material cannot absorb the energy of the impacts and fractures easily. This allows the abrasive particles to effectively remove the material from the workpiece surface, resulting in a higher material removal rate.

Therefore, in the ultrasonic machining process, the material removal rate will be higher for materials with lower toughness.