The use of a distributed optical fiber sensor based on optical frequency-domain reflectometry (OFDR) is proposed for drilling monitoring of carbon fiber reinforced polymer (CFRP) plates. The OFDR sensor response provides information of the drilling-induced temperature and strain over the CFRP plate within a 2D area closely located to the drilled hole. The different stages of the drilling process can be easily identified over time. In addition, a time-frequency analysis based on short-time Fourier transform allows the monitoring of the dynamic strain spectral content generated over the CFRP plate during drilling. Besides the spectral components resulting from the spindle rotation speed of the drill, this analysis allows for the detection of eventual microcracks and delamination of the CFRP plate, as experimentally verified.
A novel real-time monitoring system based on Fiber Bragg Grating (FBG) sensor has been developed to detect chatter in boring process. In the system, a boring bar with large length-to-diameter ratio (FSTUP3225R/L-16S) was the test subject. The FBG sensor was installed on the surface of the boring bar with the length of 225mm. A classical strain gauge was employed to measure the vibratory strain and compare the results with the ones from FBG sensor. The measurements were carried out using various cutting parameters to obtain the desired chatter phenomenon. The analysis of the experimental data was verified the chatter happened during the deep hole boring. Comparison between the experimental results from two kinds of sensors demonstrated that the measurement technique could be used to detect the dynamic strain, as well as the permitting one to research the method to identify boring chatter on-line be using optical fiber sensor system.
We propose a practical tool for exploring the dynamic relation between road profiles and vehicle motion in the time domain. It is symmetric in the sense that the direct (vehicle response to a given road profile) and the inverse (ideal road profile for a given response) problems are both solved by means of digital filtering. The dynamics of each vehicle is described by linear time-invariant differential equations found from a frequency domain vibration analysis. These are then synthesized in a time-domain digital 'vehicle filter'. The approach is here applied to ideal road hump construction for single axle vehicle models. The responses at various speeds to the derived optimal hump as well as some existing profiles are compared. These results are condensed into simple guidelines for optimal road hump design.
Dynamic response of lightweight structures is affected by the mass of a transducer. The additional mass of the transducer
is defined as a mass loading for the system, which is comparable to the weight of the structures, such as composites and
thin cantilever beam/bar. In this paper, we measure the bending and torsion mode frequencies with and without mass
loading to the lightweight structures by using lightweight optical fiber sensor (OFS) and conventional accelerometer.
The frequency difference is verified by the finite element method using ANSYS software. The OFS, benefited to its
lightweight, has shown the advantage of measuring vibration frequency accurately without affecting the dynamic
response of the structure.