Piezo Vibrations
andPiezo Shakers
Generating- High Forces- High Acceleration Rates- High Frequencies
within the audio
and ultrasonic range

Keywords• Acceleration testing• Acoustics• Dynamic sound generation• Fretting test
• Fatigue testing• Flaw detection• Microstructure testing• Modal thrusters• Non destructive testing (NDT)• Structure borne acoustics• Structure borne noise• Vibration research• Vibration control

Piezo-shakers versus electro-magnetic shakers?
Piezo-shakers are covering a different application spectrum than electro-magnetic shakers.
Per actuator volume, magnetic systems provide larger motion amplitudes and limited forces.
Piezo actuators are high stiffness devices with high specific forces and limited displacement(solid state actuators: electro-elastic deformation of a solid).
Small sized piezo-electric structures like piezo-mini-shakers show much higher energy densities
than magnetic actuators.
The small mass-load of piezo -elements together with high forces results in potentially very highacceleration rates and cycle frequencies.

Fig. 1: Schematic of the stroke/force characteristics of piezo shakers versus electro-magnetic shakers
per unit volume. Piezo shakers provide higher specific force levels.
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Highlights of piezo-shakers• High stiffness• High mechanical forces / pressures• High frequency generation capability• Very Compact designs• Miniature dimensions feasible
Structure borne acoustics amplitudes are ranging in the sub-micro-meter scale, which can be createdeven by small-sized piezo-actuators.
Due their potentially small dimensions, piezo-shakers can be easily integrated into mechanical structurese.g. to generate elastic deformation even in the low-frequency audio range for structure borne soundanalysis.
Nevertheless you can also get big sized piezo-shakers, which handle tens of kiloNewtons.

Piezo-shakers are used for• Material characterisation with respect to frequency/velocity/acceleration• Modal analysis• Investigation on structure borne noise/sound of machine parts• Fatigue testing of mechanical components• Fretting arrangements• Flaw detection in composite materials

Piezostack-based shakers most promising features
Frequency ranges:

From audio range up to > 100 kHz(depending on shaker size and amplitude)frequencies are tuneable over a wide range

Amplitudes:µm to sub-millimeter range(depending on frequency)

Modulating forces:

Up to tens of Kilo Newtons (blocking limit)(depending on shaker’s dimensions, shaking
configuration and frequency)

Acceleration rates:>> 1000 g (depending on actuator design and electronic driver)For shock excitation up to 10.000 g => check
Piezomechanik’s Impactors / Accelerators PIA

Very compact designs:

Millimeter dimensions feasible

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Working principle of a Piezo Shaker (PiSha)
A piezo-shaker PiSha uses basically stacks or rings of PZT-piezo-ceramics converting an electricalsignal into a mechanical motion by activation of piezo-electric PZT-ceramics as it is widely used for otherpurposes (e.g. positioning by piezomechanical actuators)(see brochure “Piezomechanics: An Introduction”)
To handle the shaker-specific high forces / accelerations and high electrical and mechanical power levels
in a reliable way, special designs of the shaker structure and driving electronics are a “must”.

Examples of shaker configurations
Geo-Shakerfor harmonic and pulsed soil excitation:
Type of actuator:
Coupling to ground:
Force generation:
Driving electronics:

bulk stack
via base plate
reaction typeswitching amplifier RCV1000/7 with energy recuperation

Seismic/inertial mass:
Max. amplitude:
Max. modulation force:
1st resonance:
Operating voltage:

up to 200 kilograms
up to 80 µm
approx. +/- 15 kiloNewtons
approx. 220 Hz
up to 1000 Volts

Fig. 2: Geo-shaker for low frequency excitation of soil orbuildings (PC case for comparison of size)

Fig: 3: Schematic of geo-shaker’soperation principle4Micro shaker: washer typeFor local mechanical excitation
Mounting: clamped or reaction type
1. resonance:
Max. Amplitude:
Max. modulating forces:
Operating voltage:
Driving electronics amplifier:up to 100 kHz (at reduced amplitudes)
up to 5 Micrometers
up to 1000 Newtons (clamped; depending on type)
up to 150 Volts
LE 150/100 EBW

Fig. 4: Set of various types of micro shakers, thimble for comparison of size

Using common ultrasound generators as piezo-shakers?
Ultrasound generators are piezo-based mechanical resonators, running with high efficiency on a fixed
single frequency.
Common shaking applications require a frequency tuning over a wide range at reasonable power levels ina non-resonant operating mode.
Broadband shakers and driving electronics require other design principles than resonating single
frequency systems.

Using standard piezo-actuators as shakers?
Standard piezo stack actuators are mostly designed for positioning tasks with limited dynamics/
accelerations and powers (both peak and average). To certain extend, they can be used to generatemechanical vibrations with limited amplitudes/power levels.
Piezo-shaking with high powers requires the adoption of the piezo-mechanical converter to the potentiallyvery high cycle rates, high dynamical force loading, high self-resonance levels, self-heating and highelectrical current ratings.
Piezomechanik is offering both: normal piezo-actuators and piezo-shakers.
You can be sure to get the optimum solution for your problem.
► Contact PIEZOMECHANIK
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Mounting examples for piezo-shakers
The mechanical excitation efficiency by piezo-shakers depends strongly on the coupling quality of theshaker to the excited structure. Poor coupling by improper means results in low excitation levels of yourtest piece and reduced frequency range.
The PiSha-shakers can be used in various mounting configurations like stud-mount reaction typeelements or by clamping with external supports or others.

Conventional shaker excitation:
The shaker body is mounted fix on a solid base/table-top (infinite large mass).
The moving part of the shaker is the front pin, where the test object is mounted onto.

Fig. 5: Schematic of a shaker tester, rigid mounting

The achievable maximum acceleration b depends on shaker’s frequency and amplitude accordingb = a (2π f)²

f: shaker’s frequency; a: shaker’s amplitude

The achieved peak force F is defined by the accelerated mass m of the test-body and the applied
acceleration b according
F=mb

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Reaction type arrangement
The shaker is mounted via the front pin to the test object (e. g. by a stud or bolt), so themain part of shaker body moves freely relative to the test-object.
Due to shaker’s mass, the shaker vibration generates inertial or acceleration forces, which are transferredto the test structure (fig. 6)
To enhance the force generation, the PiSha device can bear a distinct seismic mass SM in its bottom
section. For big masses SM, high modulating forces can be achieved even at low frequency levels.
The achieved force levels are the higher, the larger the stiffness of the test structure is.

Fig 6: Schematic of structure borne noise/acoustics generation and detection set up using inertial forces(reaction type)

Clamped operation of a piezo-Shaker PiSha
The piezo-shaker is simply pressed onto the test structure (fig.7) by a clamping mechanism.
When the shaker is electrically activated, a force and/or displacement modulation of the test-body(example: bell) occurs.
The theoretically achievable maximum force limit is achieved under blocking conditions of the shaker (nodisplacement due to an infinitely large stiffness of clamping and test-piece).
Clamped shaker arrangements are used for structural borne noise analysis.
Very tiny piezo-shaking elements can be used for easy integration to the test body.
Structural resonances with high quality factors are easy to detect even with very low excitation levels.

Fig. 7: Schematic of structure borne acoustics/noise generation and detection, clamped arrangement

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Special mounting solutions
The above shown examples cover a wide range of applications.
Nevertheless in special cases, new mounting strategies are necessary.
One example is to avoid mechanical damages/modifications of the test structure for mounting the shaker(e.g. inserting of tapped holes for a stud mount shaker into sensitive parts).
PIEZOMECHANIK offers a wide support of defect-free mounting techniques
based on magnetism, vacuum or other techniques.

Piezomechanik’s offer:
Contact PIEZOMECHANIK for analysing your shaker application
to provide the best-matched piezo solution.

Berg-am-Laim-Str. 64 · D-81673 Munich · Phone ++ 49/89/4315583 · Fax ++ 49/89/4316412
e-mail: info@piezomechanik.com · http://www.piezomechanik.com

Stand: Mai 2006

PIEZOMECHANIK’s shaker and actuator program covers a wide rangeof mechanical parameters with regard to power, oscillating amplitudes,
blocking forces together with well-adapted mechanical designs
for matching individual test-arrangements.