Automated Data Acquisition and Reduction System (ADAR) evaluates damping coefficient and relative rigidity by storing four successive peaks of waveform and time period between two successive peaks. Damping coefficient and relative rigidity are then calculated and plotted against temperature or time in real time

Carl, G. L.

Dalal, S. K.

Inge, A. T.

Johnston, N. J.

English

NASA Technical Reports Server

May 1975	 B75-10073 
NASA TECH BRIEF 
Langley Research Center 
NASA Tech Briefs announce new 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. 
Automated Data Acquisition and Reduction System for Torsional Braid Analyzer 
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Torsional braid analysis (TBA) has become a well-
developed and widely accepted technique for gener-
ating the dynamic thermomechanical spectra of 
polymeric materials over a wide temperature range. It 
is possible to measure the capacity of a polymeric 
material to store and dissipate mechanical energy of 
deformation using the technique. Such data enable 
the polymer chemist and engineer to establish 
relationships between chemical structure, submolecu-
lar motions, and processing and curing conditions. 
The TBA method records the decaying torsional 
oscillations of a specimen, but it differs from a 
torsional pendulum apparatus in that it permits the 
investigation of materials that cannot support their 
own weight. The method is, therefore, suitable for 
studies of such chemical processes as resin curing and 
environmental degradation, and it allows the in-situ 
study of the effect of prehistory on thermomechanical 
behavior. It is particularly useful for investigating new
polymer systems, since only a very small amount of 
polymer is required (<0.01 gram) and the principal 
criterion for making the test specimen is the simple 
solubility of the polymer in a removable solvent. 
A specimen is prepared by the impregnation of a 
multifilament braid substrate with a solution of the 
material to be tested, followed by thermal removal of 
the solvent. The impregnated braid is enclosed in a 
chamber that can be cooled or heated in an inert 
environment (see Figure 1). The braid is set into free 
torsional oscillation by an initial torsional displace-
ment. The subsequent displacement-time curve (a 
damped sinusoidal waveform), automatically record-
ed, provides data that, together with numerical and 
geometrical factors, are used to obtain the material 
parameters which are related directly to the storage 
and loss of energy of mechanical deformation. 
The amount of data produced and handled during 
an experiment is enormous. A waveform is produced 
every few seconds, and each has to be individually 
analyzed during the data workup. An automated 
system, described below and shown in Figure 2, was 
developed to operate the TBA experiment automati-
cally, i.e., to analyze each waveform and to provide 
low-scatter, high-resolution data in real time. The 
Automated Data Acquisition and Reduction System 
(ADAR) evaluates the damping coefficient and 
relative rigidity by storing four successive peaks of the 
waveform and the time period between two successive 
peaks. The damping coefficient and relative rigidity 
are then calculated and plotted against temperature 
or time in real time. 
At the start of a sequence, a cam attached to a dc 
motor moves a spring-restrained lever which pulses 
the specimen. A wedge in the cam provides a positive 
starting and stopping point for the lever, thus 
ensuring that the initial amplitude of the specimen, 
when it is activated, is the same each time. The 
oscillations begin, and a calculator searches for the 
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Figure 1. Torsional Braid Analysis (TBA) Apparatus
(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 Slates 	 will be free from privately owned rights. 
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Figure 2. Automated Data Acquisition and Reduction System (ADAR) for 
Torsional Braid Analysis (TBA) 
peaks in the damped sinusoid at a rate of 192 times 
per second, which is sufficiently fast to ensure 
accurate peak resolution. 
When the calculator finds the first peak, it stores 
the data, initiates a counter, and starts counting the 
incoming pulses. The calculator then searches for the 
second peak (of the opposite polarity from the first 
peak), stores the second peak, and searches for the 
third peak (of the same polarity as the first peak). The 
calculator stores the third peak, accepts the counter 
data, and stores it at the time period of the damped 
sinusoid. A sequence control unit then resets the 
counter unit to its original state, as it does for each 
cycle. The calculator searches for and stores the 
fourth peak (of the opposite polarity from the first and 
third peaks). 
The calculator acquires and stores the temperature 
information and proceeds to calculate the damping 
coefficient and the rigidity of the waveform. These are 
plotted versus temperature on a plotter and an output 
writer. The calculator then continues to search for 
peaks, always subtracting two adjacent peaks, until a 
preset minimum is reached, at which time the 
specimen is repulsed and the entire sequence is 
repeated. 
Based on over 200 runs, this new TBA system has 
proved to be durable, with no observed degradation in 
performance. It has required less repair and less 
manpower for operation than conventional systems 
and has tripled the number of analyses per man-hour. 
It has minimized human error in the handling and 
calculation of data. Also, with real-time operation, a 
B75-10073
spectrum can be monitored as an experiment 
proceeds; hence, conditions and operational pro-
cedures can be altered or corrected, as required, 
during the experiment. 
Note: 
Requests for further information may be directed 
to:
Technology Utilization Officer 
Langley Research Center 
Mail Stop 139-A 
Hampton, Virginia 23665 
Reference: B75-10073 
Patent status: 
Inquiries concerning rights for the commercial use 
of this invention should be addressed to: 
Patent Counsel 
Langley Research Center 
Mail Stop 313 
Hampton, Virginia 23665 
Source: G. L. Carl, A. T. Inge, and
N. J. Johnston
Langley Research Center and
S. K. Dalal of
Wyle Laboratories, Inc.
under contract to
Langley Research Center 
(LAR- 11578) 
Categories: 04 (Materials) 
02 (Electronics Systems)
S 


Automated data acquisition and reduction system for torsional braid analyzer

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