Tool material used in ultrasonic machining (USM) In ultrasonic machining, which tool material is commonly employed because the tool must be tough and ductile enough to withstand high-frequency vibration and transmit abrasive action effectively?

Introduction / Context:
Ultrasonic machining (USM) removes material by micro-chipping under abrasive slurry while a tool vibrates at ultrasonic frequency. The tool material must transmit vibrations, resist fatigue, and shape easily to the negative of the cavity to be produced.

Given Data / Assumptions:

• Abrasive slurry: typically silicon carbide, boron carbide, or aluminum oxide in water.
• Frequency: roughly 20–40 kHz with small amplitudes.
• Work materials: hard/brittle (glass, ceramics, carbides).

Concept / Approach:
Ductile, relatively soft metals like brass and copper are preferred tool materials in USM. They damp undesirable stresses, are easy to machine into intricate shapes, and survive the cavitation-like impacts of abrasive grains. Extremely hard tool materials (e.g., carbide) are unnecessary and can be brittle under cyclic loading; diamond is used as abrasive, not as bulk tool in USM.

Step-by-Step Solution:

Verification / Alternative check:
USM process descriptions consistently list soft ductile metals (brass, copper) and sometimes mild steel or Monel as tool materials, paired with hard abrasives like boron carbide.

Why Other Options Are Wrong:
Tungsten carbide and diamond: unnecessarily hard and brittle as bulk tools in USM; diamond is the abrasive in other contexts.Stainless steel/HSS: usable in some cases, but brass or copper are standard due to superior formability and damping.

Common Pitfalls:
Assuming the tool must be harder than the work as in cutting; in USM, the abrasive does the cutting while the tool shapes and delivers energy.

Final Answer:

Brass or copper