This work lays great emphasis on studying the technique of the laser cutting the closed curve shape inside glass with laser induced thermal-crack propagation. The conventional LITP cutting is unable to complete a closed curve. The reason and the crack propagation behavior are studied by the extended finite element method (XFEM) analysis and experiments. In order to achieve the closed curve shape inside glass, the stress-release crack is proposed for the first time. The stressrelease crack-tip with 90° and 1.5mm is the suitable arrange. This paper indicates the experiment of the LITP cutting the closed outer curve shape with the stress-release crack. Optical microscope photographs of the crack surface are obtained to examine the cutting quality. This work provides a method to cut the closed curve shape inside glass with LITP successfully
Viscoelastic dampers are one of popular vibration mitigation devices applied to tall buildings to reduce seismic and wind-induced vibiration. In this paper，a new kind of viscoelastic-wall damper, which could be installed at the shearwall location of high-rising buildings, is proposed to enhance the energy disspation ability. The seismic resistance behaviors of one tall building installed with the viscoelastic-wall dampers are investigated by numerical analysis. The mechanical property testing of the viscoelastic-wall damper is carried to investigate its performance parameter under various exciting frequency and strain amplitude. According to the testing results, a mathematical model of viscoelastic - wall damper is modeled based on Kelvin model. On the basis of a 36-floor frame-shear wall structure and using the finite element software ABAQUS, two finite element models of the high-rising building with and without viscoelastic-wall dampers are set up. Elasto-plastic time-history analysis is used to compare the seismic performance of the two structures subjected to the frequently and rarely earthquakes. It is proved that the seismic response of the structure is mitigated effectively when it is equipped with viscoelastic-wall dampers.
Applying Maxwell stress tensor and 3D FDTD methods, physical properties of nanoparticle trapping by evanescent wave
near the NSOM probe, including trapping size, trapping position and role of other forces versus optical trapping force,
are revealed. From the distribution of trapping force acted on a nanoparticle along three axis directions, it is found that
the nanoparticle tends to be trapped to the aperture edge and center surface of the probe tip. In experiments 120 nm
polystyrene particles are trapped in a multi-circular shape and two circles of polystyrene particles are arranged to
different positions on the substrate. The results indicate that the NSOM probe is able to trap nanoparticles with lower laser intensity than that required by conventional optical manipulator.
Impulse systems do not undergo the multipath destructive interference that manifests itself as Rayleigh fading prevalent
in continuous wave systems, but rather show up as delayed replicants of the direct impulse. In this paper, the path loss
characteristics for impulse signals propagation over a plane earth are proposed. The condition for direct pulse and its
replicant overlapping with each other is investigated. The polarization of the transmission signals, which was always
neglected by previous approaches, is taken into account here. Moreover, a new time domain reflection coefficient, which
is simple and accurate in comparing with conventional results, is adopted in developing the reflected pulsed field. The
simulation result shows that the path loss can be characterized as 3 zones with different path loss exponent as distance
between transmitter and receiver (T-R) increasing.
A new approximate time domain reflection coefficient, the relationship between the reflection and refraction on slab
surfaces, and expression for propagation loss term within the slab in time domain are deduced in this paper. By using
time domain convolution of the three terms, a simplified analytic solution for UWB impulse signal transmitting through
a finitely conducting slab is proposed. This solution takes into account the frequency range from 3.1 to 10.6 GHz and is
suitable for most common building construction materials within indoor environment. The simulations of incident
monocycle transmitting through slabs of different materials and thickness are presented by applying the simplified time
domain analytic solution to illustrate the characteristics of transmission and give some results in simplification of
transmission field analysis in indoor channel modeling.
Laser forming is a technique of using the energy from a laser beam to modify and adjust the curvature of sheet metals or
hard materials. 2-dimensional laser forming can reasonably accurately control bend angles with various materials. To
advance this process further for realistic forming applications in a manufacturing industry, it is necessary to consider
larger scale controlled 3-dimensional laser forming. However, this is a different situation for 3-dimensional laser
forming. The work presented in this paper uses the spider scanning path to form the thin square sheet to spherical dome
by laser forming. The explicit dynamic analysis on 3-dimentional laser forming is shown in the article. On the base of
temperature gradient mechanism of 2-dimensional laser forming, depending on the geometry and the thermo-physical
properties of stainless steel lCrl8Ni9Ti, develop the mechanism of laser forming of thin square sheet to the spherical
dome. This paper discusses the interaction between moving laser beam and sheet, the temperature field on the sheet, and
the step transition of stress and deformation in laser forming. In order to give the verification on the results of simulation,
the correlative experiment has progressed with Lumonics JK7O2H Nd:YAG laser. The results of experiments are in
accord with the simulation.
The water-jet guided laser processing is a new compound micro-machining process in which the laser beam passes
through the water-jet by full reflection onto the workpiece. In this paper, a new key component:the coupling unit was
designed and which would form a long, slim, high-pressure and stable water-jet. The couple unit made the fluid field in
the chamber symmetry; the coupling quality of the laser beam and the water-jet could be easily detected by CCD camera.
For its excellent surface quality, the nozzle with a
&fgr; 0.18mm hole got better machining effect than other nozzles.
Aiming at finding optimum machining parameters, experiments were carried out. The results showed the attenuation of
laser energy bore relation to water-jet stability. The energy intensity distributed over the water-jet cross section nearly
homogeneous and the laser energy nearly did not decrease in long working distance. When water-jet pressure was high,
efficient cooling of the workpiece prevented burrs, cracks and heat affected zone from forming. During cutting Si wafer
process, nearly no cracking was found; Adjusting reasonable laser parameters grooving 65Mn, the machining accuracy
would combine with the speed.
Experiments on femtosecond laser micromachining of grooves in spring steel (65Mn) were performed with Ti:Sapphire
laser pulses of 5Ofs duration. The relationships between the dimensions of the grooves and the cutting parameters were
analyzed. A logarithmic dependence of the groove depth on laser fluence was observed with two regimes characterized
by different ablation rates and different thresholds. The groove depth was found to be inversely proportional to cutting
speed and proportional to the number of passes. A depth limit was found with decreasing cutting speed or increasing
number of passes. Cutting speed and the numbers of passes have little effect on the width of grooves. The
morphological of period surface structures and unevenness depth was observed using scanning electron microscope.
The result in the paper provides instructive guide for future research on three-dimension microstructures.
In this paper, the vision sensor is made up of four laser devices (LD) and four cameras. Standard difference value contrast method of calibration is put forward. The whole system’s parameter calibration is consisted by four sub-system’s calibration independently. Special target probe moves in standard grid mode in the measured two-dimensional plane. Gray-level centroid method is used to acquire four groups standard grid node. From the difference of standard grid node the segment linear calibration equations are obtained. The whole measured section is divided as grid block by every adjacent group standard mean coordinate values Z and Y. In the grid block all the measured coordinate values are calibrated by segment linear equations along Z and Y axis direction. The whole system is calibrated only by getting data once. The system calibration result shows the system measurement errors is less than 0.2 mm within 100 mm depth measurement.
Laser forming of sheet is a forming technology of sheet without a die that the sheet is deformed by internal thermal stress induced by partially irradiation of a laser beam. In this paper, the bending behavior of common stainless steel 1Cr18Ni9Ti sheet is studied after being irradiated by straight line with a Nd:YAG pulse laser beam. The aim of the investigation is to find out the relationship of the bending angles with the pulse parameters of the laser. The experimental results show that higher width of pulse is advantageous to increase the bending angles if the total outer power and the rate of the pulse are constant. The bending angle increases as the rate of the pulse increase and begins to decrease at a certain processing parameters. And the bending angle firstly increases with the pulse energy increasing and begins to decrease at a certain processing parameters, as there is a certain pulse energy parameter resulting in a maximum bending angle for a certain material and processing parameters. The pulse energy is the most important factor influences the bending angles of pulse laser forming in the pulse parameters. By qualitative analysis of experimental result, the conclusion obtained may provide basis for theoretical investigation and possible industrial application of laser bending process in the future.
In this paper, the experiments of cutting titanium alloy sheet with Nd:YAG pulsed laser were carried out and the effects of the type of shielding gases, gas pressure and laser parameters on kerf width, surface quality and metamorphic layer thickness were studied. The results showed that compressed air is suitable for laser cutting of titanium alloy, the Argon gas does better, while Oxygen gas has undesirable effects; the metamorphic layer is thicker with compressed air as assisted gas in comparison to that with Argon gas; the kerf width increases as the power density, pulse frequency and pulse width increase; higher cutting speed can be applied and the cutting quality is improved when the pulse frequency is increased.
High temperature alloy is a complex alloy with excellent high temperature strength, thermal stability and fatigue property, which can work in 600~1000C oxidizing condition. However, it has poor machinability. This article present experimental research of laser assisted cutting of GH4169 high temperature alloy. Comparative experimental research between conventional cutting and laser assisted cutting is done to detect the cutting force variation curve with cutting depth and cutting speed. The experiment results show that cutting forces in laser assisted cutting are evidently reduced by approximately 50%, and tool wear is reduced leading to longer tool life.
In this paper we present a multi-point magnetic inclinometer which is of great value to oil well drilling. When directionfixed
drilling is finished, the spatial position of the well must be measured and compared with the design. By using a
compass type sensor, the apparatus detects the principal parameters indicating the spatial position of the well axis,
inclination and azimuth angles. The angles shown by the angle-measuring system are recorded through photography method.
Based on the direction-fixed properties of both the compass and the weight force, design of the sensing part is
introduced. The electronic control of the photographic and film feeding system is also described based on the predetermined