System for detecting incipient failure in ball bearings is described. Ultrasonic equipment detects bearing system resonance and provides warning signal through electronic circuitry. Detector can be used to evaluate performance of newly installed bearings. Schematic diagram is provided to show components

Broderick, J. J.

Burchill, R. F.

Clark, H. L.

English

NASA Technical Reports Server

August 1972
	 B72-10494 
NASA TECH BRIEF 
Marshall Space Flight 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. 
A System for Early Warning of Bearing Failure 
Bearings on the verge of failure generate ultrasonic 
frequencies of measurable amplitude before audible or 
mechanical signals can be detected. This fact suggests 
that ultrasonic detection equipment may provide the 
most useful way to monitor incipient bearing failure. 
The ultrasonic signal appears prior to a temperature rise 
or increase in driving torque. A series of ball bearing 
performance tests were run on several identical ball 
bearings under a variety of load, speed, temperature, 
and lubrication conditions. Bearing temperature, torque, 
vibration, noise, strain, cage speed, etc. were monitored 
to discover which measurements were most suitable as 
indicators of ball bearing condition. A total of sixty-six 
data points were taken during the thirty-three different 
tests. 
The tests were conducted on a hybrid boost bearing 
test vehicle. Tape records were made under steady-state 
conditions of a variety of speeds and loads. Sample 
sections were selected from the taped data for a narrow 
band spectral analysis with a real time analyzer. An 
artificial flaw was created across the inner race surface 
of one bearing using an acid etch technique to produce 
the "scratch". Tape records obtained before and after 
the etching established a characteristic frequency re-
sponse that identifies the presence of the flaw. These data 
were used to develop a prototype diagnostic system. 
The experimental determination of a bearing system 
resonance that is related to an induced bearing defect 
provides criteria which can be used for the detection 
and evaluation of bearing faults. The availability of two 
discrete indications permits the construction of a logic 
circuit which will give a fault indication only when both 
are present. The overall signal level produced at 28 kHz 
provides the first indicator of a bearing fault. The second
indicator is that modulation occurs at discrete fre-
quencies depending upon the bearing speed and upon 
which component incurs the initial damage. 
The electronic circuit for the bearing fault detector 
is shown in the illustration. Housing vibration from the 
bearing under test is converted to a charge signal by a 
securely attached high-frequency response accelero-
meter. The charge is detected by a charge amplifier, 
and a voltage proportional to the housing acceleration 
is produced. This voltage is amplified and presented to 
the input of a bearing fault detector. The bearing fault 
detector clearly indicates the presence of damage in the 
bearing. In this test the level of damage is so minor that 
other indicators such as torque, noise, temperature, and 
direct audio range frequency vibration would not have 
detected the presence of a fault. The bearing fault 
detector may be used to evaluate the performance of 
newly installed bearings to guarantee that ball and race 
damage has not occurred prior to or during assembly as 
well as to monitor the rate of deterioration of an 
operating system. 
Notes: 
1. This test equipment may be of interest to bearing 
manufacturers and users, particularly those working 
with devices, such as gyros, in which the bearing 
operation is critical. 
2. Requests for further information may be directed to: 
Technology Utilization Officer 
Marshall Space Flight Center 
Code A&TS-TU 
Huntsville, Alabama 35812 
Reference: B72-10494
(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=19720000493 2020-03-17T03:40:03+00:00Z
4	 I 
- 
	
Charge Amp	 &Accelerometer 
Fault	 Bearing
Input	 _
 
Bearing	 Test 
Detector	
----
8 kHz Output	
A Band H 
B
 ______Pass 
Adjust
Integrator	 DC Output 
	
Gain	
°
Filter	 (
Filtered 
Gain Detected  
Adjust	 Output 
I	 Band Pass Filter	 Detector	 -	 lntegror I	 DC Output B 
Frequency 
Control 
Envelope , Detected Output 
DC Output
Comparator
Fault 
Ref	 Logic And	 In 
DC Output A
	
Comparator 
	
.____	 Point	
_______Driver O	 dicator 
	
Adjustment	 Lamp 
Schematic Of Bearing Fault Detector 
Patent status: 
Inquiries about obtaining rights for the commercial 
use of this invention may be made to: 
Patent Counsel 
Marshall Space Flight Center 
Code A&TS-PAT 
Huntsville, Alabama 35812 
Source: J. J. Broderick, R. F. Burchill, and 
H. L. Clark of
Mechanical Technology Inc. 
under contract to
Marshall Space Flight Center
(MFS .2 1877) 
	
B72-10494	 Category 06


A system for early warning of bearing failure

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server