Creep analysis of polycrystalline sodium chloride in high temperature environment, and stress creep of sodium chloride-potassium chloride sample

Burke, P.

Sherby, O. D.

English

NASA Technical Reports Server

PROGRESS REPORT 
ON 
NASA RESEARCH GRANT SC-NGR-05-020-084 
MECHANICAL BEHAVIOR OF POLYCRYSTALLINE 
NON-METALLICS AT ELEVATED TEMPERATURE 
for the period 
October 1, 1966 through March 3 0 ,  1967 
submi t t ed to 
Office of Grants and Research Contracts 
Attention: Code SC 
National Aeronautics and Space Administration 
Washington, D. C. 20546 
submitted by 
Department of Materials Science 
Stanford University 
Stanford, California 
Professor Oleg D. Sherby, Principal Investigator 
Mr. Peter Burke , Research Assistant 
I 
https://ntrs.nasa.gov/search.jsp?R=19670017130 2020-03-12T11:20:31+00:00Z
MECHANICAL BEHAVIOR OF POLYCRYSTALLINE NON-METALLICS 
AT ELEVATED TEMPERATURE 
(SC-NGR-05-020-084) 
I .  Creep of P o l y c r y s t a l l i n e  Sodium Chloride ( P e t e r  Burke) 
Experimental r e s u l t s  t o  date  i n d i c a t e  t h a t  c r e e p  of p o l y c r y s t a l l i n e  
sodium c h l o r i d e  i s  s i m i l a r  i n  many ways t o  c reep  of pure me ta l s .  This  i s  
a new and important observat ion.  Typical  c r eep  curves f o r  sodium c h l o r i d e  
a r e  shown i n  F igu re  1. The curves show both primary and secondary o r  
s t eady  s t a t e  r eg ions  of behavior. 
E a r l i e r  t e s t s  by o t h e r  authors'') showed only s t eady  s t a t e  c reep  
i n  p o l y c r y s t a l l i n e  sodium c h l o r i d e  a t  a temperature near the  me l t ing  
p o i n t .  The c reep  ra te  was d i r e c t l y  p ropor t iona l  t o  t h e  c reep  s t r e s s .  
This  t ype  of c r e e p  behav io r ,  i n  which l i t t l e  primary c reep  occurs  and i n  
which t h e  c reep  r a t e  i s  l i n e a r l y  dependent upon c reep  stress,  i s  t h e  SO- 
c a l l e d  v i scous ,  d i f f u s i o n a l  or Nabarro-Herring type of c reep .  Our t e s t s  
i n d i c a t e ,  however, t h a t  i n  p o l y c r y s t a l l i n e  sodium c h l o r i d e ,  primary c reep  
d e f i n i t e l y  occur s ,  t h e  creep r a t e  i s  p r o p o r t i o n a l  t o  s t r e s s  t o  t h e  f i f t h  
power, subgra ins  form dur ing  creep(2)  and t h e  c reep  r a t e  i s  a p p a r e n t l y  
independent of g r a i n  s i z e  (165 t o  2000 microns) .  
i s t i c s  of t h e  d i s l o c a t i o n  g l i d e  and climb mode of deformation t h a t  has  been 
found t o  be t h e  predominant mode of c reep  deformation f o r  most pu re  poly- 
c r y s t a l l i n e  me ta l s .  
These a r e  a l l  c h a r a c t e r -  
The e f f e c t s  of temperature and stress on s t e a d y  s t a t e  c reep  of sodium 
c h l o r i d e  a r e  shown i n  F igu res  2 and 3 .  Data f o r  two ranges of g r a i n  s i z e  
a r e  included;  c o a r s e  (900-2000 microns) and f i n e  (165-375 microns) .  The 
- 1- 
* empi r i ca l  equa t ion  d e s c r i b i n g  t h e s e  curves i s  t h e  same a s  t h a t  f o r  many 
me ta l s  and i s  given by 
4.5 d = k ( o / E )  exp (-Q/RT) 
S 
where 
= s t eady  s t a t e  c reep  r a t e  
i s  
k = a m a t e r i a l  cons t an t  r e l a t e d  t o  s t a c k i n g  f a u l t  energy 
o = stress 
E = Young's modulus of e l a s t i c i t y  
Q = a c t i v a t i o n  energy f o r  c reep  
R = g a s ' c o n s t a n t  
T = a b s o l u t e  temperature 
The a c t i v a t i o n  energy, Q ,  i s  a measure of t h e  temperature  dependence 
of a process .  
creep. A knee i n  t h e  curve occurs a t  -530 C. F igu re  5 shows t h e  temper-  
a t u r e  dependence of d i f f u s i o n  of sodium and c h l o r i n e  i o n s  i n  sodium 
c h l o r i d e .  The s l o p e s  of t h e  curves i n  F igu res  4 and 5 g i v e  t h e  a c t i v a t i o n  
ene rg ie s  f o r  t h e  processes  of c r e e p ,  sodium d i f f u s i o n  and c h l o r i n e  d i f -  
f u s i o n  i n  sodium c h l o r i d e .  Figure 6 shows t h e  a c t i v a t i o n  e n e r g i e s  f o r  
F igu re  4 shows t h e  temperature dependence of s t eady  s t a t e  
0 
t h e s e  processes  a s  a f u n c t i o n  of temperature.  
0 The a c t i v a t i o n  energy f o r  c reep  above 530 C i s  s u b s t a n t i a l l y  t h e  same 
a s  t h a t  observed f o r  c h l o r i n e  i o n  d i f f u s i o n  i n  p o l y c r y s t a l l i n e  sodium 
~ h l o r i d e ' ~ ) .  
i n  creep i s  c h l o r i n e  ion  d i f f u s i o n ,  a t  l e a s t  above 530 C. . 
This  l e a d s  t o  the conc lus ion  t h a t  t h e  r a t e  c o n t r o l l i n g  s t e p  
0 
0 Below 530 C t h e r e  a r e  no d a t a  f o r  d i f f u s i o n  i n  p o l y c r y s t a l s ,  bu t  t h e  
a c t i v a t i o n  energy f o r  c reep  agrees f a i r l y  w e l l  w i th  t h a t  f o r  c h l o r i n e  i o n  
d i f f u s i o n  i n  crushed s i n g l e  c r y s t a l s  of h igh  d i s l o c a t i o n  d e n s i t y .  The 
- 2- 
. 0 presence  of d i s l o c a t i o n s  below 530 C enhances t h e  c h l o r i n e  i o n  d i f f u s i o n  
r a t e  and lowers t h e  a c t i v a t i o n  energy.  The d i s l o c a t i o n s  e i t h e r  a c t  a t  
d i f f u s i o n  s h o r t  c i r c u i t s  o r  else l e a d  t o  t h e  c r e a t i o n  of su rp lus  c h l o r i n e  
vacancies .  
0 
The a c t i v a t i o n  energy f o r  c reep  below 530 C a l s o  ag rees  f a i r l y  w e l l  
w i t h  t h a t  observed f o r  sodium d i f f u s i o n  i n  p o l y c r y s t a l s  a t  temperatures  
above 530OC. 
d i f f u s i o n  i s  c reep  r a t e  c o n t r o l l i n g  below 530 C. 
This  c o r r e l a t i o n  could  l ead  one t o  conclude t h a t  sodium i o n  
It seems u n l i k e l y ,  how- 0 
e v e r ,  t h a t  t h e  c reep  r a t e  c o n t r o l l i n g  p rocess  would change from c h l o r i n e  
i o n  d i f f u s i o n  t o  sodium i o n  d i f f u s i o n  a t  53OoC, because t h e  d i f f u s i o n  
0 c o e f f i c i e n t  observed f o r  sodium d i f f u s i o n  a t  530 C a r e  a t  l e a s t  t e n  
t i m e s  g r e a t e r  t han  those  observed f o r  c h l o r i n e  d i f f u s i o n .  Furthermore,  
t h e  a c t i v a t i o n  ene rg ie s  observed f o r  sodium d i f f u s i o n  i n  s i n g l e  c r y s t a l s  
below 53OoC a r e  much lower than those  observed f o r  c reep  below 530 C. 
The most l i k e l y  conclus ion  i s  t h a t  t h e  r a t e  c o n t r o l l i n g  s t e p  i n  c reep  of 
0 
p o l y c r y s t a l l i n e  sodium ch lo r ide  i s  c h l o r i n e  i o n  d i f f u s i o n  a t  a l l  temper- 
a t u r e s  and t h a t  t h e  a c t i v a t i o n  energy f o r  c h l o r i n e  d i f f u s i o n  and hence 
c reep  i s  reduced by t h e  presence of d i s l o c a t i o n s  and/or  g r a i n  boundaries  
a t  temperatures  below 530OC. 
Since  c reep  i n  sodium c h l o r i d e  i s  c o n t r o l l e d  by c h l o r i n e  i o n  d i f f u s -  
s i o n ,  t h e  emperical  equa t ion  f o r  c reep  may now be  w r i t t e n  a s  
= k '  D ( o / E > ~ ' ~  or  d s  = k '  ( o / E )  4.5 - 
D 
where 
D = Do exp (-Q/RT) 
= d i f f u s i o n  c o e f f i c i e n t  o f  c h l o r i n e  i o n s  i n  sodium c h l o r i d e .  
- 3- 
T h i s  equa t ion  has  been ex tens ive ly  used t o  d e s c r i b e  m e t a l l i c  behavior ;  
h e r e  D i s  the s e l f - d i f f u s i o n  c o e f f i c i e n t  f o r  t h e  metal .  
Figure 7 shows a p l o t  of i / D  ve r sus  o / E  f o r  sodium c h l o r i d e  and f o r  
aluminum . (3)* The c l o s e  c o r r e l a t i o n  e x h i b i t e d  s t r eng thens  our impression 
t h a t  high temperature deformation of sodium c h l o r i d e  i s  s i m i l a r  t o  t h a t  
o f  pure me ta l s .  It i s  of i n t e r e s t  t o  no te  t h a t  t h e  breakdown of t h e  
power law f o r  creep of p o l y c r y s t a l l i n e  sodium c h l o r i d e ,  t h a t  i s ,  t h e  up- 
sweep of t h e  curve i n  Figure 7 a t  h igh  creep r a t e s ,  occurs  a t  about 
i / D  =: 10 cm . This value i s  i n  agreement wi th  t h e  va lues  found f o r  pure 
metals'''), i n c l u d i n g  W ,  Cu, A l ,  N i  and C Y - T ~ .  
9 - 2  
The obse rva t ion  t h a t  creep r a t e s  i n  sodium c h l o r i d e  a r e  p r o p o r t i o n a l  
t o  t h e  d i f f u s i o n  c o e f f i c i e n t  of a c h l o r i n e  i n d i c a t e s  t h a t  t h e  s lowest  
d i f f u s i n g  s p e c i e s  c o n t r o l s  creep. F igu re  5 shows t h a t  c h l o r i n e  always 
d i f f u s e s  more slowly than  sodium. Deformation during c reep  occurs  by 
t h e  g l i d e  and climb of d i s l o c a t i o n s .  F igu re  8 shows a ske tch  of t h e  
Weertman model f o r  g l i d e  and climb. Sketches of d i s l o c a t i o n s  i n  me ta l s  
and compounds a r e  shown i n  Figure 9.  For climb t o  occur ,  atoms must d i f -  
f u s e  away from t h e  d i s l o c a t i o n s .  I n  sodium c h l o r i d e  both sodium and 
c h l o r i n e  i o n s  must d i f f u s e  away from d i s l o c a t i o n s  s imultaneously i n  o r d e r  
t o  ma in ta in  charge n e u t r a l i t y .  F igu re  10 shows t h e  climb p rocess  occur r ing  
i n  a metal  and i n  sodium ch lo r ide .  The slow moving c h l o r i n e  i o n s  c o n t r o l  
* The D va lues  used f o r  sodium c h l o r i d e  a r e  i n d i g a t e d  by squa res  i n  
F igu re  5.  D values  f o r  temperatures above 530 C were taken t o  be 
equal  t o  those  measured f o r  c h l o r i n e  d i f f u s i o n  i n  1000 micron g r a i n  
s i z e  sodium c h l o r i d e ( 4 ) .  D va lues  f o r  temperatures  below 53Ooc 
were obtained by drawing a l i n e  on t h e  d i f f u s i o n  graph of s l o p e  
equal  t o  t h e  a c t i v a t i o n  energy expe r imen ta l ly  observed f o r  c reep  
(1 e 34eV = 30 e 7 Kcal /mol). 
-4 -  
t t h e  r a t e  a t  which climb can occur and hence t h e  r a t e  a t  which deformation 
occur s .  
11. Creep of p o l y c r y s t a l l i n e  NaC1-KC1 s o l i d  s o l u t i o n s  (Roger Cannon) 
During t h e  l a s t  s i x  months equipment has  been p e r f e c t e d  f o r  producing 
samples of sodium c h l o r i d e  i n  s o l i d  s o l u t i o n  with potassium c h l o r i d e  and 
most of t h e  samples have been f a b r i c a t e d .  
The procedure f o r  producing samples i s  f i r s t  t o  c a s t  a b i l l e t  from 
a mixture  of t h e  powders. 
This  b i l l e t  i s  t hen  extruded i n t o  a rod form. The rod i s  c u t  up t o  sample 
l e n g t h  and t h e  ends a r e  polished. 
This procedure ensu res  good mixing i n  t h e  sample. 
Several  problems were encountered i n  c a s t i n g  b i l l e t s .  The c a s t i n g s  
clung t o  t h e  s i d e s  of t h e  carbon d i e  which made them d i f f i c u l t  t o  remove 
and caused them t o  break up. By p o l i s h i n g  t h e  s i d e s  of t h e  d i e  and making 
a screw out  t ype  bottom, most of t h e  problems were solved.  
Since t h e  carbon d i e  must f i t  i n  a h o r i z o n t a l  t ube  fu rnace  i t  could 
n o t  b e  very t a l l .  Compacting t h e  powders b e f o r e  c a s t i n g  made i t  p o s s i b l e  
t o  c a s t  a l a r g e r  b i l l e t .  
Extrusion of s o l i d  s o l u t i o n  sodium chlor ide-potasium c h l o r i d e  i s  very 
d i f f i c u l t ,  While making t h e  second e x t r u s i o n  t h e  d i e  became so badly 
scored t h a t  t h e  o u t e r  c y l i n d e r  cracked wh i l e  t r y i n g  t o  remove t h e  s h a f t s .  
A new s t r o n g e r  d i e  has  now been made which works w e l l .  It was a l s o  
necessary t o  make up a new l a r g e r  fu rnace  which would f i t  around t h e  ex- 
t r u s i o n  d i e .  
While wa i t ing  f o r  t h e  d i e  t o  be machined an a t t empt  was made t o  pro- 
duce f i n e  g ra ined  samples of potassium c h l o r i d e .  
f i n e  g r a i n  s i z e ,  a t e n t h  of a p e r  c e n t  of 0 .1  micron aluminum oxide was 
- 5- 
I n  o rde r  t o  ma in ta in  a 
added. The one c reep  tes t  completed showed a creep r a t e  w i t h i n  a f a c t o r  
of two of t h a t  f o r  sodium c h l o r i d e  a t  t h e  same temperature and stress. 
The g r a i n  s i z e  d id  no t  remain sma l l ,  however, bu t  grew t c  apprcximately 
200 microns during t h e  t e s t .  A p o s s i b l e  exp lana t ion  f o r  such seve re  g r a i n  
growth i s  t h a t  t h e  aluminum oxide s e t t l e d  t o  t h e  bottom of t h e  c a s t i n g  and 
was not  p re sen t  t o  a g r e a t  ex ten t  i n  t h i s  p a r t i c u l a r  sample. Some o t h e r  
method of f a b r i c a t i o n  w i l l  be necessary t o  r e t a i n  t h e  aluminum oxide i n  
t h e  sample. 
R e s u l t s  on t h e  c o n s t a n t  s t r e s s  c reep  tes ts  run thus  f a r  on samples 
of f i f t y  pe r  cen t  sodium c h l o r i d e - f i f t y  p e r  cen t  potassium c h l o r i d e  show 
no s t eady  s t a t e  c reep .  A t y p i c a l  c r eep  curve f o r  t h e  s o l i d  s o l u t i o n  a l l o y  
t e s t e d  i s  shown i n  Figure 9.  The creep r a t e  i n c r e a s e s  wi th  t i m e  a s  i s  
t h e  case  wi th  t e r t i a r y  c reep .  The upsweep, however, may no t  be a creep 
phenomenon. Samples were h igh ly  cracked a f t e r  t he  creep tes ts .  The 
i n c r e a s e  i n  c reep  r a t e  may have been due t o  t h e  formation and propagat ion 
of c racks .  
-6- 
REFERENCES 
1. W.  D. Kingery and E. D.  Montrone, J. Appl .  Phys. 36, 2412 (1965). 
2. Progres s  Report on NASA Research Grant SC-NGR-05-020-084, "Mechanical 
Behavior of P o l y c r y s t a l l i n e  Non-Metallics a t  Elevated Temperature," 
f o r  t h e  per iod October 1, 1965 through March 31, 1966. 
3. C. R. B a r r e t t ,  A. J. Ardel l  and 0. D. Sherby, Trans.  AIME 230, 200 
(1964). 
4. J. F. Laurent and J. Benard, J. Phys. Chem. S o l i d s ,  1, 218 (1958). 
5. J. F. Aschner, Thes i s ,  Un ive r s i ty  of I l l i n o i s  (1954); c i t e d  i n  
A. B. L i d i a r d ,  Hdb. de r  Physik, 20, 333 (1957). 
6.  D. Mapother, N. Crooks and R. Maurer, J. Chem. Phys., 18, 1231 (1950). 
7 .  J.  Cabane, J. Chim. Physique, 59, 1123 (1962). 
8. N. Laurance, Phys. Rev., 120, 57 (1960). 
9. L. W.  Barr ,  J. A. Morrison and P. A.  Schroeder,  J. Appl .  Phys., 3 L  
624 (1965). 
10. L. W.  Ba r r ,  I. M. Hoodless, J. A. Morrison and R. Rudham, Trans.  
Faraday SOC., 56, 637 (1360) 
11. 0. D. Sherby and P e t e r  M. Burke, 'Wechanical Behavior of S o l i d s  a t  
Elevated Temperature," t o  b e  publ ished.  
- 7- 
. 
630 psi 
is = 2.3~10-5sec-1 
44Opsi 
&s 2.6xIO%ec-I 
- e 
1 -  
A 
c " -" 
" I 
u 
315 psi 
& s  = 6.8~IO-~sec-l 
4: .' .I I YI .." .08 f E .06 Q m W 
3 
E .04 
.o 2 
.oo 
c 
1 I I 1 I 
'T=448'C 
50 100 150 200 250 300 350 
TIME (minutes) 
Figure  1. Typical  c r eep  curves  f o r  p o l y c r y s t a l l i n e  sodium c h l o r i d e ,  showing 
primary and s teady  s t a t e  c reep .  
-1.0 
-2.0 
h - 
I 
V 
Q, 
v) -3.0 
Y 
W 
l- a 
-4.0 
n 
w 
W 
LL 
W 
I- 
* -5.0 
s g -6.0 
a 
W 
-7.0 !5 
9 
c3 
- 8.0 
-9.0 
+ 603 
A 742 
/ -  I 
I 
I 
I 
I 
I 
40 IO0 200 400 1000 2000 
STRESS (PSI) 
Figure  2.  E f f e c t  of stress and temperature  on s t eady  s t a t e  c reep  r a t e  of 
sodium c h l o r i d e .  
. 
- - 
I 
-3.0 
In - 
W 
I- s -4.0 
a 
W 
W 
p: 
0 -5.0 
G 6 
L 
s 
& -6.0 
Q 
W 
-7.0 
-8.0 
4 . O   
-2.0 c 
- 
- 
- 
- 
- 
- 
I 
- 
Q= 2.46 eV 
= 56.6 KCALIMOL - 
r = CONSTANT - 
- 
- 
- CONSTANT 0- 
E 
_ -  
- 
Q = 1.34 eV 
30.7 KCAL/MOL - 
$" COARSE GRAIN SIZES n,O,o,+,A 
I FINE GRAIN SIZES =,*,e 
-9.0' ' I I I 
-5.0 -4.5 -4.0 -3.5 
Lo G (STRESS/YOUNG'S MODULUS) 
Figure  3 .  E f f e c t  of s t r e s s  and temperature on s t eady  s t a t e  c reep  r a t e  of 
sodium c h l o r i d e ,  co r rec t ed  f o r  temperature  v a r i a t i o n  of Young's 
Modulus of E l a s t i c i t y .  
0 
-I 
- - k -2 
P -3  
In - 
U 
(L 
Q 
W 
w -4 a 
0 
W 2 -5  
v) 
> a 5 -6 
I- 
v) 
W 3 -7 
-8 
-9 
'1
1 
742 603 513 449 365 O C  
.9 1.0 1 . 1  1.2 1.3 1.4 1.5 1.6 1.7 
I I I I I I I 
I 
T 
Pi uilre L L -  Temnerati ire  denendenre nf  s t e n d v  s tate  creen rate- 
. -8 
-9 
-10 
- I  I 
h 
v 
Q, 
v) 
\ 
(u 
E 
0 -12 
n 
Y 
0 
0 - 
-13 
-14 
-15 
-16 
I I I 1 I I 
800 700 600 500 400 mu 
SODIUM I O N  DIFFUSION 
.I 
IVa 
IVb 
I V C  
IVd 
Va 
Vb 
vc 
Vd 
VIa 
VIb 
VIIa 
VIIb 
V I I C  
VIId 
V I I I a  
V I I I b  
Gra in  S i z e  Doping Refer -  
Microns ppm ence 
4 I 500-1000, SC - 
I I b  SC 40 
T I C  SC 14 
I I a  SC 5 Cd 5 J: I I d  sc 30 
CHLORINE I O N  DIFFUSION 
Gra in  S ize ,  Doping, 
Microns ppm 
50 
110 
1000 
sc 
80 Ca, H 2 0  
80 Ca, NO H 2 0  
500 NO Ca OR H 2 0  7 
sc NO Ca OR H 2 0  7 
sc <1 Ca 8 
sc 100-1000 Ca 8 
sc 350 Ca 9 
sc 350 Ca 9 
sc 700 Ca 9 
sc 9 
sc 10 
sc c rushed ,  un- 
annea led  10 
I I I I 1 I -17 
'E( OK- '  ) 
T 
Figure 5. Diffusion coefficients of sodium and chlorine in sodium chloride 
versus reciprocal absolute temperature. 
3 
I I I I I I - 
CHLORINE ION DIFFUSION 
IN POLYCRYSTALLIN E 
SODIUM CHLORIDE 
CREEP OF POLYCRYSTALLINE 
SODIUM CHLORIDE 
CHLORINE DIFFUSION IN CRUSHED 
SINGLE CRYSTALS OF SODIUM CHLORID 
i L 
i 
I 
LSODIUM ION DIFFUSION 
IN POLYCRYSTALLINE 
SODIUM CHLORIDE IN SINGLE CRYSTALS OF 
SODIUM CHLORIDE 
742 603 513 449 365 “C 
I I I I I 
9 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 
1ooo ( O K - ’ )  
T 
70 
60 
50 2 
5 
-I 
U 
40 
>- 
W 
X 
30 
z 
0 
20 !gj 
- 
I- o a 
10 
Figure 6. Experimentally determined activation energies for sodium diffusion, 
chlorine diffusion and creep in sodium chloride as a function of 
temperature. 
12 
I I  
!O 
9 
8 - 
Y 
- 7  5 
.$IO 
6 
c3 
0 
-J 
5 
4 
3 
2 
I 
I I I I 
I I I I 
-5.0 -4.5 - 4.0 -3.5 
LOG 
Figure 7. Plot of g s / D  versus o/E, showing similarity between sodium 
chloride and aluminum. 
4 
Figure 8. Sketch showing Weertman model for dislocation glide and climb 
controlled creep. Dislocation climb occurs in the direction 
of the arrows. 
EXTRA HALF PLANES 
OF ATOMS 
METAL SODIUM CHLORIDE 
Figure 9. Sketch of edge dislocations in metals and in sodium chloride. 
EXTRA HALF PLANES / OF ATOMS \ 
h SODIUM ION 
CHLORINE ION METAL VACANCY 
METAL ATOM 
METAL SODIUM CHLORIDE 
Figure 10. Sketch illustrating climb of edge dislocations in metals and in 
sodium chloride. 
0.3C 
- 0.20 c 
.. 
0.10 
0 
0 
I I I I I I 
Stress = 700psi 
1000 2000 3000 4000 5000 6000 -7000 
Time, (sec.) 
Figure  11. Creep s t r a i n  versus  time of p o l y c r y s t a l l i n e  NaC1-KC1 s o l i d  
s o l u t i o n .  Temperature i s  51OoC. 


Mechanical behavior of polycrystalline non-metallics at elevated temperature Progress report, 1 Oct. 1966 - 30 Mar. 1967

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server