Force required to pull free a small circular plate imbedded in gel liquid is determined. Procedure for measuring the structure of a gel is given

Cabeal, J. A.

Globus, R. H.

English

NASA Technical Reports Server

August 1972
	
B72-10416 
NASA TECH BRIEF 
Ames Research Center	 4r
NASA Tech Briefs announce now technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a subscription basis from the National Technical Information 
Service, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Electromagnetic Rheometer 
The problem: 
To measure the degree of structure of propellant 
gel systems.
Outlet 
Operate	
]J'-	
,, Limit Stop 
Solenoid
+ 
If
Stop 
Return 
Solenoid II	 Soft Iron Rod and Plate 
(see detail)
Rod 
Holes 
Inlet	 Plate Detail 
The solution: 
Determine the force required to pull free a small 
circular plate that has been imbedded in the gel 
liquid. For remote operation and for simplicity, the 
plate is pulled by an electromagnet. 
How it's done: 
The rheometer consists of a glass tube inside of 
which is a soft iron rod and perforated plate. The 
rheometer is mounted within two solenoids as mdi-
cated in the diagram; the magnets are used to pull 
the soft iron rod and plate through gels. Voltmeters 
attached to the input lines to the magnets are used 
to give an indication of the force exerted on the soft 
iron rod and plate. The entire apparatus can be 
heated or cooled as required; the upper limit stop 
can be used as an electrical contact to indicate when 
the iron rod has reached the limit of its upper travel. 
The procedure for measuring the structure of a gel 
is as follows: The tube is filled with a gel and the 
return solenoid is energized to pull the inner rod 
down to the stop; then the solenoid current is inter-
rupted. The upper solenoid is then energized in small 
step-wise increments until the magnetic field is just 
strong enough to start the soft iron rod moving 
through the gel. The voltage applied to th solenoid 
is recorded. 
The structure index is computed as follows: 
Structure Index = (G —N) (98.07) W/AE 
where C = volts required to move the rod and plate 
in the gel, 
N = volts required to move the rod and plate 
in neat liquid, 
E = volts required to move the rod and plate 
in empty rheometer, 
W = weight of the rod and plate in grams, 
A = area of the rheometer plate, in m2, 
and the structure index is in newtons per square 
meter. 
The following table shows correlation of the struc-
ture index obtained by a prototype electromagnetic 
rheometer and the sphere method; the data were 
obtained on a series of water gels.
(continued overleaf) 
This document was prepared under the sponsorship of the National
	 Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration. Neither the United States
	 information contained in this document, or warrants that such use 
Government nor any person acting on behalf of the United States
	 will be free from privately owned rights. 
https://ntrs.nasa.gov/search.jsp?R=19720000415 2020-03-17T03:38:54+00:00Z
a 
Structure Index, N/rn2 
Sphere Electromagnetic 
Sample Method Rheorneter 
A 110 95 
B 150 155 
C 175 190 
D 190 205 
E 250 255 
Although the values obtained with the electro-
magnetic rheometer are not absolute, they can be 
used as a relative indicator of gel structure.
Notes: 
1. NASA Tech Brief B72-10026 describes a similar 
rising-plate rheometer suitable for gel structure
determinations. 
2. No additional documentation is available. Specific 
questions, however, may be directed to: 
Technology Utilization Officer 
Ames Research Center 
Moffett Field, California 94085 
Reference: B72-10416 
Patent status: 
No patent action is contemplated by NASA. 
Source: Robert H. Globus and 
Jackie A. Cabeal of 
Aerojet Liquid Rocket Company 
under contract to 
Ames Research Center 
(ARC-10525) 
B72-10416	 Category 04 


Electromagnetic rheometer

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