Browse Prior Art Database

Piezoelectric Hammer with On-Line Loadcell

IP.com Disclosure Number: IPCOM000104101D
Original Publication Date: 1993-Mar-01
Included in the Prior Art Database: 2005-Mar-18
Document File: 4 page(s) / 139K

Publishing Venue

IBM

Related People

Lee, CK: AUTHOR [+2]

Abstract

Disclosed is a piezoelectric (PZT) hammer with an on-line loadcell system which can be used as a driving mechanism to perform dynamic material testing, such as impact, dynamic micro-scratch and micro-wear tests. The results obtained from these tests can used to evaluate mechanical durability and reliability issues of thin film devices. Furthermore, the device disclosed below has ample applications in dynamic issues, such as structural modal test, self-alignment structure, acoustic and printer technologies.

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Piezoelectric Hammer with On-Line Loadcell

      Disclosed is a piezoelectric (PZT) hammer with an on-line
loadcell system which can be used as a driving mechanism to perform
dynamic material testing, such as impact, dynamic micro-scratch and
micro-wear tests.  The results obtained from these tests can used to
evaluate mechanical durability and reliability issues of thin film
devices.  Furthermore, the device disclosed below has ample
applications in dynamic issues, such as structural modal test,
self-alignment structure, acoustic and printer technologies.

      Quasi-static type mechanical tests [*]  usually face a
limitation when it comes to extrapolating measurement data to predict
mechanical behavior in a highly dynamic environment.  The technology
of recording thin film disks testing is one such example.  Although
the micromechanical testing technology developed in the past offers
several techniques in quantifying mechanical properties and provides
certain basic understanding on the issues of the mechanical behavior
of coating/substrate systems, there is still no good correlation
between the basic properties, e.g. microhardness, Young's modulus or
adhesion strength, and functional properties, e.g. wear rate or
mechanical durability.  To reduce the gap(s) between these
measurements, fundamental understanding based on the experimental
results obtained from the so-called intermediate tests, namely the
tests taking the dynamic situations into consideration but are not as
complicated as the real environment, are indispensable.  Therefore,
advancing from well-established microindentation and microscratch
techniques toward the impact, dynamic scratch or even micro-wear
tests is a natural direction to take.

1.   Piezoelectric Hammer

      The underlying principle of a piezoelectric hammer is to apply
voltage pulses to a mechanically restrained piezoelectric stack to
generate mechanical impulses on a designated blocking body.  Whenever
a significant amount of electric energy is dumped into a
piezoelectric stack in a short period of time (e.g., &app.20
&mu.sec), and abrupt expansion of the piezoelectric stack is produced
because of the quick build-up of elastic strains.  However, if there
is a mechanical structure arranged in such a way to block this
mechanical expansion, the piezoelectric stack then strikes on these
blocking bodies with a formidable force and, in turn, generates
mostly immense elastic shock waves to dissipate the electric energy.
The elastic waves generated are then focused and propagate through
the wave guide and finally burst an impact at the point in contact
with the flying head.  A schematic drawing which illustrates the
piezoelectric hammer working principle is shown in Fig. 1(a).

      Fig. 1(b) shows the detailed structural design of the
piezoelectric hammer.  The main PZT/PMN stack (3 in Fig. 1(b)) was
constructed by mating three 0.71 mils long PZT/PMN
(lead-zirconate-titanate/lead- magnes...