I did an experimental study of the common shape memory alloy nitinol about =
eight years ago. It yielded a paper titled "Study of friction at the mesos=
cale using nitinol shape memory alloy". The paper is online at
http://arxiv.org/html/physics/0308077
There you will see that I postulated that the remarkable properties of th=
ese alloys is also the result of mesoanelastic complexity. The nature of t=
he metastabilities is different, however, for nitinol than for ordinary met=
al alloys. The 'locking' is possible in shape memory systems because of a =
phase transition. The large difference between the martensite (low tempera=
ture) and austenite (high temperature) states is dramatic in terms of their=
internal friction. After correcting for the air influence (viscous) dampi=
ng contribution, by doing free decays in vacuum-I found that the quality fa=
ctor in the austenite phase was greater than that of the martensite phase b=
y a whopping seven-fold.
At the end of this paper I have described, in my opinion, "how nitino=
l remembers a shape". It is closely related to the arguments I have been p=
resenting on this list-serve. Just as nitinol reverts to a previous shape =
as the result of a slight temperature rise (from below to above the transit=
ion temperature), I believe that springs will also (all by themselves) reve=
rt to a slightly different, previously held shape configuration, following =
a change in temperature or load.
There is another experiment for which the observations support this cl=
aim. It was one performed under my oversight by cadets at the U.S. Milita=
ry Academy (West Point) while I was a Visiting Professor there. In their e=
xperiment, Messrs Coy and Molnar drove a gravitationally restored pendulum =
using an argon-ion laser. The drive mechanism was one involving lithium fl=
uoride crystals into which color centers had been introduced by fast neutro=
n irradiation. In my PhD research, fast neutrons were used to pin dislocat=
ions in copper single crystals to harden them. In the lithium fluoride, th=
e neutrons caused crystalline vacancies (knock-out of atoms from their cust=
omary site), responsible for their beautiful color as compared to their tr=
ansparency before irradiation. Not only did the irradiation cause their in=
ternal friction to change, it also made for a multitude of metastabilities =
that influenced the pendulum's behavior. It is worthy of note that lithium=
fluoride is used in radiation dosimetry devices. One can place the crysta=
l, after it has been irradiated, in an oven, along with a photomultiplier t=
ube. As the temperature is ramped upward, one counts the number of light f=
lashes that occur (when a vacancy gets refilled, because of elimination of =
the low level metastabilities). Testament to the small (low level energy =
changes) required for these flashes to occur-is that thermal energy is give=
n by the product of Boltzmann's constant and the temperature. And the con=
stant k is very small at 1.38 x 10^(-23) J/K.
A summary of the cadets' work is provided on my webpage at http://phys=
ics.mercer.edu/petepag/pend.htm#optical
I want also to point out that my experiences with 'strange' solids go way b=
ack to about 1969. As a young faculty member at the University of Mississi=
ppi I was involved with acoustic nonlinearity in strontium titanate. These=
crystals undergo a 2nd order phase transition (no latent heat type) at abo=
ut 103 K. There is a dramatic
difference in the manner with which they influence ultrasonic pulse echoes,=
as the temperature is lowered through this transition temperature. A pape=
r associated with this work is one I wrote with colleague Roy Arnold in 197=
1, titled "Ultrasonic third harmonic generation in Strontium Titanate Singl=
e Crystals", J. Appl. Phys. 42, (3) 1971.
Then there is the remarkable, more recent (2002) discovery by my diss=
ertation director, Mack Breazeale (deceased 2009), involving acoustic 'memo=
ry', as demonstrated with lithium niobate. http://www.nature.com/news/2002=
/020923/full/news020916-19.html
This work was performed at the National Center for Physical Acoustics (also=
in Oxford, MS), and his colleague Igor Ostrovskii has written about their =
discovery in a JASA article last year, titled "Research on acoustical memor=
y discovered in the laboratory of Mack Breazeale", J. Acoust. Soc. 127 (3)=
, p. 1843 (2010) .
I see this in support of my postulate that a phonon maser should be poss=
ible, on the basis of stimulation of excited defect states in crystals. In=
other words a device that uses internal friction. It has been said of fri=
ction that it is "the smartest force in nature-it always robs you'. If a p=
honon maser can be built by this means, it will be a case in which 'nature'=
has stopped robbing us with friction.
Randall
I did an experim=
ental study of the common shape memory alloy nitinol about eight years ago.=
It yielded a paper titled “Study of friction at the mesoscale =
using nitinol shape memory alloy”. The paper is online at<=
/o:p>
http://arxiv.org/html/physics/0308077
There you will see that I postulated that the remarkable prop=
erties of these alloys is also the result of mesoanelastic complexity. =
; The nature of the metastabilities is different, however, for nitinol than=
for ordinary metal alloys. The ‘locking’ is possible in =
shape memory systems because of a phase transition. The large differe=
nce between the martensite (low temperature) and austenite (high temperatur=
e) states is dramatic in terms of their internal friction. After corr=
ecting for the air influence (viscous) damping contribution, by doing free =
decays in vacuum—I found that the quality factor in the austenite pha=
se was greater than that of the martensite phase by a whopping seven-fold. =
At =
the end of this paper I have described, in my opinion, “how nitinol r=
emembers a shape”. It is closely related to the arguments I hav=
e been presenting on this list-serve. Just as nitinol reverts to a pr=
evious shape as the result of a slight temperature rise (from below to abov=
e the transition temperature), I believe that springs will also (all by the=
mselves) revert to a slightly different, previously held shape configuratio=
n, following a change in temperature or load.
There is another experiment for =
which the observations support this claim. It was one performed=
under my oversight by cadets at the U.S. Military Academy (West Point) whi=
le I was a Visiting Professor there. In their experiment, Messrs Coy =
and Molnar drove a gravitationally restored pendulum using an argon-ion las=
er. The drive mechanism was one involving lithium fluoride crystals i=
nto which color centers had been introduced by fast neutron irradiation.&nb=
sp; In my PhD research, fast neutrons were used to pin dislocations in copp=
er single crystals to harden them. In the lithium fluoride, the neutr=
ons caused crystalline vacancies (knock-out of atoms from their customary s=
ite), responsible for their beautiful color as compared to their tran=
sparency before irradiation. Not only did the irradiation cause their=
internal friction to change, it also made for a multitude of metastabiliti=
es that influenced the pendulum’s behavior. It is worthy of not=
e that lithium fluoride is used in radiation dosimetry devices. One c=
an place the crystal, after it has been irradiated, in an oven, along with =
a photomultiplier tube. As the temperature is ramped upward, one coun=
ts the number of light flashes that occur (when a vacancy gets refilled, be=
cause of elimination of the low level metastabilities). Testame=
nt to the small (low level energy changes) required for these flashes to oc=
cur—is that thermal energy is given by the product of Boltzmann=
’s constant and the temperature. And the constant k is very sma=
ll at 1.38 x 10^(-23) J/K.
A summary of the cadets’ work is =
provided on my webpage at http://physics.mercer.edu/petepag/pend.htm#optical
I want also to point out that my experiences w=
ith ‘strange’ solids go way back to about 1969. As a youn=
g faculty member at the University of Mississippi I was involved with acous=
tic nonlinearity in strontium titanate. These crystals undergo a 2nd order phase transition (no latent heat type) at about 103 K.&nbs=
p; There is a dramatic
difference in the=
manner with which they influence ultrasonic pulse echoes, as the temperatu=
re is lowered through this transition temperature. A paper associated=
with this work is one I wrote with colleague Roy Arnold in 1971, titled &#=
8220;Ultrasonic third harmonic generation in Strontium Titanate Single Crys=
tals”, J. Appl. Phys. 42, (3) 1971.
Then there is the remarkable, more recent =
(2002) discovery by my dissertation director, Mack Breazeale (deceased 2009=
), involving acoustic ‘memory’, as demonstrated with lithium ni=
obate. http://www.nature.com/news/2002/020923/full/news020916-19.html=
This work was performed at the Nati=
onal Center for Physical Acoustics (also in Oxford, MS), and his colleague =
Igor Ostrovskii has written about their discovery in a JASA article last ye=
ar, titled “Research on acoustical memory discovered in the laborator=
y of Mack Breazeale”, J. Acoust. Soc. 127 (3), p. 1843 (2010) .=
I see this in suppor=
t of my postulate that a phonon maser should be possible, on the basis of s=
timulation of excited defect states in crystals. In other words a dev=
ice that uses internal friction. It has been said of friction that it=
is “the smartest force in nature—it always robs you’.&nb=
sp; If a phonon maser can be built by this means, it will be a case in whic=
h ‘nature’ has stopped robbing us with friction.
Randall
<=
/o:p>
=