Vol 32 No 1 | CONTENTS |
April 2004 |
A Novel Approach for Integrated Fault Diagnosis Based on Wavelet Packet transform
S. Zhang, J. Mathew, L. Ma and Y. Sun
Determining Individual Member Stiffness of Bridge Structures Using a Simple Dynamic Procedure
J. Li, B. Samall and K. Crews
Crack Detection in Welded Mechanical Structures Using Coupled Vibrations
D. Liu, H. Gurgenci and M. Veldt
Dynamic Modelling and Applications for Passenger Car Powertrains
A.R. Crowther and N. Zhang
Identification of Transient Axial Vibration on Double-Suction Pumps During Partial Flow Operation
M.R. Hodklewlcz and Jo Pan
How to Build a 100 Watt Loudspeaker
N. Fletcher
Book Reviews
New Members
FASTS
Future Meetings
News
New Products
Code of Ethics
Diary
Acoustics Australia Information
Australian Acoustical Society Information
Advertisers Index
Vol. 32, No. 1 pp 5 - 8 (2004)
ABSTRACT: Integrated machine fault diagnosis is usually conducted by considering
different types of signals so as to improve the accuracy of diagnosis. This
paper presents a novel approach for integrated machine fault diagnosis based
on the vibration signals alone. Wavelet packet transform is adopted to analyze
the vibration signals, followed by the selection of best bases. We consider
each best basis as a local site, then extract features from it and make a
local decision using probabilistic neural networks. The local decisions from
each best basis are fused to be a global conclusion using a weighted average
method. The whole diagnosis process is implemented under a uniform framework.
An experimental case shows that this approach improves the accuracy of diagnosis.
Vol. 32, No. 1 pp 9 - 12 (2004)
ABSTRACT: A reliable determination of the structural condition of timber bridges
presently requires costly load testing. A new dynamic based testing method
was developed by authors to reduce the cost and shorten the testing time.
The method has been successfully used to undertake field-testing of more than
40 timber bridges across NSW: The dynamic testing procedure involves the attachment
of accelerometers underneath the bridge girders. The bridge girders are then
excited .by a modal hammer. The method requires tests with and without extra
mass, so that the overall flexural stiffness of the bridge can be obtained.
However, in order to accurately estimate the load carrying capacity of the
bridge, it is necessary to obtain the stiffness values of individual members
from test results without complicating the current testing procedure. In this
paper, the authors review the dynamic testing procedure and propose a method
to determine individual member stiffness for a bridge structure based on the
field dynamic testing data. The outcomes of this work not only enable more
accurate prediction of the load carrying capacity of the bridge but will also
identify defective members of the bridge structure.
Vol. 32, No. 1 pp 13 - 18 (2004)
ABSTRACT: Detection of a fatigue crack in a welded frame structure is studied in this paper using coupled response measurements. Similarity to real engineering structures is maintained in the fabrication of the test frame with hollow section chords and branch members. The fatigue crack was created by a special reciprocating mechanism that generates cyclic stress on a beam member of the structure. The methodology of coupled response measurements is first demonstrated on a single hollow section beam by analytical simulation and experimental validation. The issues of using this approach for fatigue crack detection in real structures are then examined. Finally, the experimental results of the frame under different scenarios are presented. The existence of the crack is clearly observable from the FRF plots. It is suggested that this approach offers the potential to detect cracks in welded frame structures and is a useful tool for routine maintenance work and health assessment
Vol. 32, No. 1 pp 19 - 24 (2004)
ABSTRACT: Torsional finite elements for direct, geared, branched and grounded connections are presented. For a simple three-degrees-of-freedom powertrain model the finite elements are defined and the global system assembly is detailed. The appropriateness of the finite element method for powertrain systems is illustrated via examples for modelling manual, automatic and continuously variable transmissions. The use of custom elements is discussed for an element for toroid-roller contact and for a two-stage planetary gear set. A test rig is presented and model verification is discussed.
Vol. 32, No. 1 pp 25 - 32 (2004)
ABSTRACT: The impeller in double-suction pumps is hydraulically balanced in
the axial direction due to symmetry in the flow entering the two opposing
suction eyes. While an assumption of axial balance is valid at design flow,
process plant experience has shown that partial flow operation can result
in dynamic axial displacement of the impeller causing mechanical seal and
bearing failures. This paper investigates the effects of flow reduction on
the axial vibration response of three sets of double-suction pumps and identifies
transient axial vibration at partial flow using Short Time Fourier and Discrete
Wavelet Transform techniques.