Title

Low-Deflection Loss And Hysteresis Measurements On A Spacecraft Test Joint

Report Number

WL-TR-91-3078 Volume III, p. IBC-1 thru IBC-19

Creator

Austin, Eric M.

Flora, Timothy L.

Goodding, James C.

Corporate Author

CSA Engineering, Inc.

Lockheed Missiles and Space Company, Inc.

Date

1991

Date Issued

1991-08

Extent

19

Identifier

ADA241313

Format

1 online resouce

Abstract

Passive damping has been demonstrated to be an effective and efficient means
for limiting the effects of on-board excitations on the dynamics of space vehicles.
High-precision applications require these treatments to both be effective at very low
excitation levels and not affect the dimensional stability of the structure under quasistatic
and thermal-mechanical loads. This work documents a study of two important
issues facing structures damped with viscoelastic materials: hysteresis and loss at low
deflection levels.
The test article is an I-beam-like structure designed to simulate an experimental
method of fabricating graphite-epoxy /honeycomb structures without using any
mechanical fasteners. After identifying the most critical vibrational modes from a
separate system-level analysis, a damping treatment was designed for the test joint
using standard finite element techniques. A modal test using very low random excitation
levels was performed on the resulting damped structure. Statistical methods
were used to determine that the maximum displacement level of the free-free structure
was of the order of nano-meters. Subsequently, hysteresis tests were performed on the
same damped beam. Laser interferometry was used to measure displacements of the
joint after undergoing cyclic static loads of varying magnitudes. Percent hysteresis
was measured while the joint was loaded in three-point bending. Hysteresis behavior
during displacements as small as 150 nano-meters was recorded.

Description

Passive damping has been demonstrated to be an effective and efficient means
for limiting the effects of on-board excitations on the dynamics of space vehicles.
High-precision applications require these treatments to both be effective at very low
excitation levels and not affect the dimensional stability of the structure under quasistatic
and thermal-mechanical loads. This work documents a study of two important
issues facing structures damped with viscoelastic materials: hysteresis and loss at low
deflection levels.
The test article is an I-beam-like structure designed to simulate an experimental
method of fabricating graphite-epoxy /honeycomb structures without using any
mechanical fasteners. After identifying the most critical vibrational modes from a
separate system-level analysis, a damping treatment was designed for the test joint
using standard finite element techniques. A modal test using very low random excitation
levels was performed on the resulting damped structure. Statistical methods
were used to determine that the maximum displacement level of the free-free structure
was of the order of nano-meters. Subsequently, hysteresis tests were performed on the
same damped beam. Laser interferometry was used to measure displacements of the
joint after undergoing cyclic static loads of varying magnitudes. Percent hysteresis
was measured while the joint was loaded in three-point bending. Hysteresis behavior
during displacements as small as 150 nano-meters was recorded.

Distribution Classification

1

Distribution Conflict

No

DTIC Record Exists

No

Illinois Tech Related

No

Photo Quality

Not Needed

Report Availability

Full text available

Type

article

Is Part Of

Proceedings of Damping '91: 13-15 February 1991 San Diego, California (GCA-1 through JCB-17)