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Development of Four Three-Dimensional Strain Transducers with Application to
Analysis of Cement Mantle in a Femoral Model of a Total Hip Replacement
Prostheses
Ciara O’Driscoll, Prof. Edward Little, Dr. Walter Stanley
Department of Mechanical, Aeronautical and Biomedical Engineering, University of Limerick
ciara.odriscoll@ul.ie
Abstract
The strain tensor, principal strains and precision of the
estimates of these values are derived for a range of
different patterns of three-dimensional (3D) strain
rosettes. These values are based on the Monte-Carlo
technique applied to experimental work which was
carried out on transducers tested in the same
laboratory. The estimates of precision are determined
theoretically and compared with results based on
experimental findings. A new design of a miniature trirectangular
tetrahedral rosette was manufactured and
tested. Results suggest that this transducer does not
perform as well as the rectangular patterns.
1. Introduction
The life-span of cemented implants is a cause for
concern, and to better understand this, testing of the
cement mantle must be undertaken experimentally [1].
Experimental models can use either surface strain
gauges or embedded 3D strain transducers. Threedimensional
strain gauge rosettes are made up by an
array of at least 6 single strain gauges. This can be a
combination of single and/or stacked rosettes.
Measurement uncertainty and reliability of rosettes are
critically affected by the shape of the array of straingauge
grids [2].
2. Research Methods
To predict which is the best transducer of those
assessed it was necessary to embed four different 3D
rosettes into the same epoxy prismatic bar (Figure 1)
and test them under identical conditions in the same
laboratory.
Figure 1: A closer view of the prismatic bar with embedded 3D
transducers.
Several studies have previously been conducted to
predict the response of various designs of 3D embedded
strain rosettes and the most precise embedment
technique. Researchers [3] developed the nine-gauge
3D rosette as shown in Figure 2. This configuration
consisted of a plane rectangular rosette lying in each of
the three orthogonal planes. Investigators [4] further
developed this rosette design by rotating the rosettes on
each plane through 45° to avoid duplication of strain
68
measurements. Further more [5] developed a ninegauge
rosette based on a double-tetrahedron (60°angle).
A further development of the double-tetrahedron
(90°angle) was created by [4].
Figure 2: Four different configurations of 3D transducer used
An experimental evaluation of the transducer
designs was conducted by embedding all four patterns
within a single CT1200 prismatic bar of length 370mm
and 70mm square cross-section and simultaneously
measuring the strain values recorded by each when the
bar was subjected to a compressive load. By rotating
the bar about its vertical axis and repeating the
measurements in each position at 90°, 180°, 270° and
360°, it is then possible to fit sine waves to the data at
maximum load. The angle of embedment of the
transducer is offset from the principal axis so as to yield
new results from that of the previous studies. These
results are then compared with theoretical results and
based on these findings, the most accurate 3D strain
transducer for application in the cement mantle is
proposed.
3. References
[1] Colgan, D., et al., “Three-dimensional embedded strain
gauge analysis of the effect of collared versus collarless
prostheses on cement mantle stresses in a femoral model of a
total hip replacement”, Journal of Strain Analysis for
Engineering Design, 1996. 31(5): p. 329-339.
[2] Rossetto S., Bray A. and Levi R. “Three-dimensional
strain rosettes; pattern selection and performance evaluation”,
Experimental mechanics 15, 1975, 375-381.
[3] Bazergui, A. and Meyer, M., “Embedded strain gages for
the measurement of strains in rolling contact”, Experimental
Mechanics, 1968. 8(10): p. 433-441.
[4] Barbato G. and Little E.G. “Performance analysis of the
three-dimensional strain rosettes using computer simulation”,
Technical note: Instituto di Metrologia, Turin, Italy, 1984.
[5] Brandt A.M. “Nine-gauges device for strain measurements
inside concrete”, Strain, 1973, 122-124.