Apparatus permits application of significantly greater number of cycles or equivalent number of cycles in shorter time than conventional fatigue test machines. Environment eliminates problems associated with high temperature oxidation and with sensitivity of refractory alloy behavior to atmospheric contamination

Honeycutt, C. R.

Martin, T. F.

English

NASA Technical Reports Server

October 1971
	 Brief B71-10405 
NASA TECH BRIEF 
Lewis Research Center
	 4V 
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 Off i ce, NASA, Code KT, Washington, D. f. 20546. 
Combined High Vacuum/High Frequency Fatigue Tester 
Elevated temperature creep and high frequency 
fatigue test capabilities have been combined with an 
ultra-hieh vacuum environment in a sin g le ap-
paratus to provide a unique device for testing 
refractory alloys. The high frequency fatigue test 
capability permits the applicatioii of it significantly 
greater number of cycles or, alternatively, an 
equivalent number of cyles in a much shorter time 
than with conventional fatigue test devices. The 
Ultra-hi g h vacuum	 test environment eliminates
problems associated with high temperature oxida-
tion and with the sensitivity of refractory alloy 
behavior to atmospheric contamination. 
The unit permits the application of a constant 
stress to a test specimen in addition to the varying 
fatigue stress. This capability allows interactions 
between creep and high temperature fatigue to be 
conveniently studied. In addition, the significantly 
decreased test time provided by the high frequency 
fatigue testing reduces the effort required for 
fatigue design characterization in structural ma-
terials. 
The technique consists of introducing a standing 
longitudinal displacement wave into a load train 
which is mechanically tuned to resonate at the 
desired test frequency (see Fig. I). In order that the 
load train can be incorporated into a vacuum 
chamber (see Fig. 2), the system is designed so that 
the vacuum seal occurs at a displacement node 
(a zero-displacement point) on the load train, 
thereby permitting a rigid, metal-to-metal, ultra-high 
vacuum seal. The load train is suspended vertically 
in the furnace and test chamber and is designed so 
that the center of the test specimen is also a dis-
placement node. Static loads, when used, are 
normally applied externally from the bottom 
through a metal bellows seal and, again, are 
coupled to the load train at a displacement node. 
The resonant load train is driven from the top, 
using a piezoelectric transducer driven by an 
amplifier and high frequency oscillator. Stepped 
horns are used in the load train to mechanically 
amplify the strain. 
Optical strain measurements are made through 
windows in the furnace and vacuum chamber. 
continucd o ei'kai) 
• Oscillator H_AmpI if ierH Trfoiner1 
Titanium 
Half-Wave Stub 
Titanium 
Stepped I 1 PZT Transducer 
Horn	 *.. (Piezoelectric) 
\itanium Flange 
Weld for Mounting in 
Vacuum Chambers 
Test Specimen—_. Stepped Horn 
(Velocity Transformer) 
Columbium Static 
Load Coupling 
Load  
Capacitive 
Pickup 
OscilloscJ 
Figure 1. Ultrasonic Drive Train
This document was prepared under the sponsorship of the National 
Aeronautics and Space Administration. Neither the United States 
Government nor any person acting on behalf of the United States
Government assumes any liability resulting from the use of the 
information contained in this document, or warrants that such use 
will be free from privately owned.rights. 
https://ntrs.nasa.gov/search.jsp?R=19710000402 2020-03-17T02:30:02+00:00Z
Feed Throughs
	 Top Support and Dynamic 
Load Assembly
Front Head Access 
Port';
4" Dia. 
Sightport 
Spool Piece 
I---
L L: 1 L.	 -- -J 1P
Coldwall Furnace 
(Inside) 
7t
Feed Through 
utter Control 
CoIdwall Furnace 
(Inside) 
4_4 Dia. 
Sightport 
Vacuum Gage 
Front Head
Extension 
Chamber 
Static Load 
Bellows 
Rougiing Valve 
and Flange 
Port for Vibration 
Monitor 
Ion Pump 
Cells
Mass Analyzer 
Flight Tube
Side View	 Front View
Figure 2. Vacuum Fatigue System 
These windows also permit optical temperature	 2. Technical questions may be directed to 
measurements	 to	 be	 niade	 as	 supplements	 to	 the Technology Utilization Officer 
potentiometric	 methods used	 for primary	 tempera- Lewis Research Center 
ture measurement and control. 21000 Brookpark Road 
Tests	 were	 conducted	 at	 temperatures	 up	 to Cleveland, Ohio 44135 
2600°	 F.	 The	 theoretical	 temperature	 limit	 of the Reference: B71-10405 
apparatus	 approaches	 4000°	 F, depending on	 the Patent status: 
material	 being	 tested	 and	 the	 ability	 of. the	 load No patent action is contemplated by NASA. 
train to handle the load at that temperature.
Source: C. R. Honeycutt and T. F. Martin of Notes: TRW Inc. 
1. The	 following	 documentation	 may	 be	 obtained
under contract to 
from: Lewis Research Center
 National Technical Information Service (LEW-1 1210) 
Springfield, Virginia 22151 
Single document price $6.00 
(or microfiche $0.95) 
Reference: 
NASA CR-72241 (N67-2736), Elevated 
Temperature Fatigue of TZC Molybde-
num Alloy Under High	 Frequency and 
High Vacuum Conditions
Brief 71-10405	 Category 06	 0 


Combined high vacuum/high frequency fatigue tester

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