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This paper presents the results of fatigue performance
tests performed up to 10 million cycles on a load-measuring pot bearing with
built-in load cell to verify its field applicability and proposes an empirical
temperature correction formula. In Part I of this work, various measurement
performances of the load-measuring pot bearing were evaluated through static
and dynamic loading tests. Bridge bearings are subjected to the effect of
fatigue caused by the repeated application of moving loads and exposed to harsh
site conditions including cold and hot weathers differently to laboratory conditions.
Accordingly, the durability of the load-measuring pot bearing with built-in
load cell shall be secured and the environmental effects like temperature shall
be minimized for its application on field. This study conducted fatigue tests
up to 10 million cycles on a load-measuring pot bearing with the capacity of 1000
kN to examine eventual degradation of the measurement accuracy with respect to
the number of fatigue loading cycles. In addition, the experimental temperature
correction procedure is proposed to obtain the temperature correction formula
enabling to correct the effect of temperature on the load measurement.
This paper presents the underlying principle and the
results of various performance evaluations for a load-measuring pot bearing
with built-in load cell. The pot bearing composed of a pot made of steel in
which an elastomer disk is inserted is a bearing supporting larger loads than
the elastomeric bearing and accommodating rotational movement. Owing to a
Poisson’s ratio close to 0.5, elastomer withstands hydrostatic pressure when
confined in a rigid body. Accounting for this principle, the vertical load
applied on the pot bearing can be obtained by converting the pressure acting on
the elastomer. Therefore, a load-measuring pot bearing is developed in this
study by embedding a load cell exhibiting remarkable durability in
the base plate of the bearing. The details for the insertion of the load cell
in the base plate of the pot were improved through finite element analysis to
secure sufficient measurement accuracy. The evaluation of the static
performance of the pot bearing applying these improved details verified that
the bearing exhibited sufficient accuracy for the intended measurement purpose.
The dynamic performance evaluation results indicated that accurate measurement of
the dynamic load was also achieved without time lag.
Nitinol is used in various
industries, especially for biomaterials. Generally, the surface integrity of
sub-micron level and non-surface flaw is required in nitinol for biomaterial.
However, surface flaws, such as scratches, pits, and residual stress, can occur
on the polished surface, and it is difficult to remove these surface flaws. The
corrosion is accelerated continuously and causes bad influence in the body.
Therefore, in this study, conventional polishing and MR polishing were used to minimize
the corrosion and residual stress when the nitinol is used as biomaterial.
X-ray diffraction and Tafel extrapolation were used to investigate the residual
stress and the corrosion, and the strain hardening was investigated by
nanoindentation. Surface integrities were also evaluated by SEM image and
surface roughness results. As a result, the increased residual stress in conventional
polishing was decreased by MR polishing. The result of corrosion test was
improved from ?301 mV to ?280 mV. The residual stress was improved from ?38.18 MPa
to ?31.17 MPa. Finally, it is certified that MR polishing can be used to
minimize surface flaws and to improve the corrosion properties.