33
Contemporary Machining Processes
Cong and Pai (2013) emphasize the following advantages of this burrless and distortionless process:
• The process does not produce a heat-affected zone and residual stresses on
machined parts and may also increase the high cycle fatigue strength of a
machined part.
• Complex three-dimensional contours can be machined as quickly as simple
ones.
• Dimensional accuracy of 5 μm and surface roughness of 0.1–0.0125 mm
can be achieved.
• The equipment is safe and easy to operate.
USM is a mechanical material removal process. High-frequency electrical energy is
converted into mechanical vibrations with a resonant frequency, usually via a piezoceramic or magnetostrictive transducer. An excited vibration is subsequently transmitted through a horn in order to focus energy and to amplify the vibration amplitude
before it is delivered to the tool. The tool, appropriately shaped and located directly
above the workpiece, starts vibrating along its longitudinal axis. A slurry comprising
hard abrasive particles in water or oil is constantly supplied into the machining area.
The vibrating tool causes abrasive particles dipped in the slurry to be hammered on
the stationary workpiece performing material removal. Parameters of this process
are usually as follows (Sawant, 2020):
• Amplitude of vibrations: 15 to 50 μm
• Frequency of vibrations is 19 to 25 kHz, or according to Koryagin et al.
(2000), even up to 44 kHz
• Abrasive material is usually Al 2 O 3 , SiC, diamond or, according to Koryagin
et al. (2000), boron carbide
Material removal mechanism in USM is mainly attributed to brittle fracture, initiation and propagation of cracks, and chipping of brittle material. During the USM
process, a sequence of single-point indentations occurs. The crack formation as part
of the single-point indentation process can be summarized in the following steps
(Cong and Pei, 2013):
1. A single sharp indenter produces a plastic deformation zone.
2. At a certain threshold, a median crack suddenly develops.
3. With the increase of load, the median crack grows.
4. During unloading, the median crack begins to close and lateral cracks form.
5. After unloading, the lateral cracks propagate toward the workpiece surface
and may consequently lead to chipping.
USM can be applied to the machining of workpieces harder than 40–60 HRC
that cannot be machined with traditional methods. The process tolerance
Contemporary Machining Processes
Cong and Pai (2013) emphasize the following advantages of this burrless and distortionless process:
• The process does not produce a heat-affected zone and residual stresses on
machined parts and may also increase the high cycle fatigue strength of a
machined part.
• Complex three-dimensional contours can be machined as quickly as simple
ones.
• Dimensional accuracy of 5 μm and surface roughness of 0.1–0.0125 mm
can be achieved.
• The equipment is safe and easy to operate.
USM is a mechanical material removal process. High-frequency electrical energy is
converted into mechanical vibrations with a resonant frequency, usually via a piezoceramic or magnetostrictive transducer. An excited vibration is subsequently transmitted through a horn in order to focus energy and to amplify the vibration amplitude
before it is delivered to the tool. The tool, appropriately shaped and located directly
above the workpiece, starts vibrating along its longitudinal axis. A slurry comprising
hard abrasive particles in water or oil is constantly supplied into the machining area.
The vibrating tool causes abrasive particles dipped in the slurry to be hammered on
the stationary workpiece performing material removal. Parameters of this process
are usually as follows (Sawant, 2020):
• Amplitude of vibrations: 15 to 50 μm
• Frequency of vibrations is 19 to 25 kHz, or according to Koryagin et al.
(2000), even up to 44 kHz
• Abrasive material is usually Al 2 O 3 , SiC, diamond or, according to Koryagin
et al. (2000), boron carbide
Material removal mechanism in USM is mainly attributed to brittle fracture, initiation and propagation of cracks, and chipping of brittle material. During the USM
process, a sequence of single-point indentations occurs. The crack formation as part
of the single-point indentation process can be summarized in the following steps
(Cong and Pei, 2013):
1. A single sharp indenter produces a plastic deformation zone.
2. At a certain threshold, a median crack suddenly develops.
3. With the increase of load, the median crack grows.
4. During unloading, the median crack begins to close and lateral cracks form.
5. After unloading, the lateral cracks propagate toward the workpiece surface
and may consequently lead to chipping.
USM can be applied to the machining of workpieces harder than 40–60 HRC
that cannot be machined with traditional methods. The process tolerance