This paper presents a signal processing technique of chatter detection for boring bar based on the Hilbert–Huang
Transform (HHT). HHT is suitable for the analysis of non-stationary and non-linear signals. The flow of HHT for
processing chatter signal and the principle are introduced. Two kinds of signals from strain gauge and FBG sensor are
compared by HHT. The signals are decomposed into several intrinsic mode functions (IMFs) using empirical mode
decomposition (EMD). The Hilbert transform is then applied on each IMF to obtain the instantaneous frequencies with
time and their amplitudes. Finally, the marginal and the Hilbert spectrums of strain signals were produced using selected
IMFs. The results show that the HHT-based strain signal analysis can also be considered as a simple and reliable method
for chatter vibration detection.
According to the experimental force of optical fiber in an earth dam model, an analysis model of fiber embeded in an
earth dam is set up using ansys 9.0 software. Stress analysis of optical fiber in dams becomes easy after the boundary
conditions is simplified. The deformation of optical fiber under different pressure loads are calculated. The relationship
between the stress and the weight applied to the optical fiber is obtained while the settlement occurred in the dam model,
even badly collaps happened. The relationship between the depth of the optical fiber away the top of the dam model and
the sensitivity of optical fiber to applied loads is described.
Aim at the force of optical sensing cable for a distributed optical fiber sensing monitoring system applied in embankment
dams, a loading apparatus is designed. The apparatus is to simulate work condition when the optical sensing cable is in
use. Some grooves with different angles at the bottom of loading board of the apparatus are set to perform variety of
forces applied to the optical sensing cable under the loading board. The groove angles represent different direction of the
force in the embankment dams. The commercial finite element analysis software Ansys9.0 is applied to analyze the
deformation of the optical cable in loading experiments. The results of analysis are helpful to guide the experiment in the
next step.
A method for seepage and settlement monitoring in earth embankment dams using fully distributed sensing along optical
fibres is proposed. A model is developed for simulating and monitoring seepage and settlement systems. This model
relates the strains and the temperature changes to the fiber Brillouin gain spectrum in the embankment dam embedding
the optical fiber sensors. The model consists of two parts. Submodel 1 addresses the simulation of seepage inside the
embankment dam. Submodel 2 relates the measurement of the fiber Brillouin gain spectrum to the changes in
temperature and strain inside the embankment dam. Both the changes in temperature and strain during the process are
used to reveal serious seepages and settlements occurring inside the embankment dam. The continuously decreasing
temperature curve shows an abrupt dramatic increasing rate, which shows that the change is not caused by the
temperature of the seepage water but the strain. In this paper, as an example, a model filled with the soil from Yellow
River is built and bare optical fibers are embedded under different soil layers near the seepage path. The simulated
seepage flows under various flow rates are monitored using the optical fibers and measured by a DiTeSt -STA202
distributed temperature and strain analyzer. A partial settlement within the embankment dam model is observed.
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