Alternative flexible correction forming of a blade: multipoint correction with surface measurement and deformation simulation

Distortion during the forging or machining processes of a blade causes problems in subsequent manufacturing. This paper proposes an alternative multipoint correction method integrated with blade measurement, determination of correcting parameters, and adjustment of the correcting die. An iterative algorithm for determining the correcting parameters is proposed. Measuring equipment combining a laser displacement sensor with multipoint flexible support is manufactured to measure the blade shape. Multipoint correcting equipment with an adaptive lower die and rapid adjustment is manufactured, and software is developed for data analysis and equipment control. The correction experiment for a rough-machined steam-turbine blade indicates that the correcting parameters can be determined after one modification based on numerical simulation, and that a rough blade that meets the allowance for finish machining can be obtained using the determined correction parameters.

Fast Measurement of Dielectric Conductivity for Space Application by Surface Potential Decay Method

Surface potential decay of polymers for electrical insulation can help to determine the dark conductivity for spacecraft charging analysis. Due to the existence of radiation-induced conductivity, it decays fast in the first few hours after irradiation and exponentially slowly for the remaining time. The measurement of dark conductivity with this method usually takes the slow part and needs a couple of days. Integrating the Fowler formula into the deep dielectric charging equations, we obtain a new expression for the fast decay part. The experimental data of different materials, dose rates and temperatures are fitted by the new expression. Both the dark conductivity and the radiation-induced conductivity are derived and compared with other methods. The result shows a good estimation of dark conductivity and radiation-induced conductivity in high-resistivity polymers, which enables a fast measurement of dielectric conductivity within about 600 rain after irradiation.

New Approach for Measured Surface Localization Based on Umbilical Points

Measured surface localization （MSL） is one of the key essentials for the assessment of form error in pre- cision manufacturing. Currently, the researches on MSL have focused on the corresponding relation search between two surfaces, the performance improvement of localization algorithms and the uncertainty analysis of localization. However, low efficiency, limitation of localization algo- rithms and mismatch of multiple similarities of feature points with no prior are the common disadvantages for MSL. In order to match feature points quickly and fulfill MSL efficiently, this paper presents a new localization approach for measured surfaces by extracting the generic umbilics and estimating their single complex variables, describing the match methods of ambiguous relation at umbilics, presenting the initial localization process of one pair matched points, refining MSL on the basis of obtained closet points for some measured points by the improvement directed projection method. In addition, the proposed algorithm is simulated in two different types of surfaces,two different localization types and multiple similar sur- faces, also tested with the part of B-spline surface machined and bottle mould with no knowledge, finally the initial and accurate rigid body transformation matrix, localization errors between two surfaces and execution time are got. The experimental results show that the pro- posed method is feasible, more accurate in localization and high in efficiency. The proposed research can not only improve the accuracy and performance of form error assessment, but also provide an effective guideline for the integration of different types of measured surfaces.

Development of Squirming Robot for the Inspection of Internal Surface

In many cases, the internal surface of the mechanical elements is required to detect and measure. For this task, a special mobile device should be utilized. A squirming robot is presented for the purpose, which is working on the controlled deformation of a pneumatic columnar elastic shell. This elastic shell is made of caoutchouc. It is strengthened by the internal spiral metal wire, which also restricts its deformation in radial direction, so it can only deform in axis direction. The squirming robot also involves four osculums and a vision system. It can go forward and back and turn around easily by controlling the four osculums and the moving velocity can be controlled through the pressure of compressed air. The moving step can be flexibly adjusted. In this paper, the working principle and mechanical characteristics of the columnar elastic shell are analyzed and discussed in detail. The relationship between the elongation X and the pressure of compressed air P, the bending angular degree θ and the pressure of compressed air P are first established by using the theory of elasticity mechanics. And also we simulate its nonlinear dynamic system in certain diving force F and elastic coefficient E of elastic shell. The results indicate this squirming robot is simple in structure, low cost in manufacture and being apt to be miniaturized. It can be used in detecting the internal surface of mechanical elements or inside certain complicate pipe, when this equipment is manufactured in special, and that this process is able to be fulfilled.

Determination of Surface Roughness in Wire and Arc Additive Manufacturing Based on Laser Vision Sensing

Wire and arc additive manufacturing(WAAM) shows a great promise for fabricating fully dense metal parts by means of melting materials in layers using a welding heat source. However, due to a large layer height produced in WAAM, an unsatisfactory surface roughness of parts processed by this technology has been a key issue. A methodology based on laser vision sensing is proposed to quantitatively calculate the surface roughness of parts deposited by WAAM.Calibrations for a camera and a laser plane of the optical system are presented. The reconstruction precision of the laser vision system is verified by a standard workpiece. Additionally, this determination approach is utilized to calculate the surface roughness of a multi-layer single-pass thin-walled part. The results indicate that the optical measurement approach based on the laser vision sensing is a simple and effective way to characterize the surface roughness of parts deposited by WAAM. The maximum absolute error is less than 0.15 mm. The proposed research provides the foundation for surface roughness optimization with different process parameters.

CAD-DIRECTED INSPECTION PLANNING FOR FREEFORM SURFACE USING CONTACT PROBES

A methodology for CAD-directed measurement of freeform surface using a coordinate measuring machine equipped with a touch-trigger probe is presented, mainly including adaptive sampling of measurement points and registration of freeform surface. The proposed sampling method follows four steps： Freeform surface is fitted by bi-cubic B-spline; Curvedness measure of the surface is computed; Given a number of sampling points, an iterative algorithm is constructed for selecting a set of measurement points by employing the curvedness information; The measurement points is regularized for tradeoff between maximizing the measurement accuracy and minimizing the sampling time and cost. The aforesaid algorithm is demonstrated in term of a marine propeller blade. An offset surface registration method is presented to improve alignment accuracy of freeform objects, and Monte Carlo simulation is conducted to verify the effectiveness of the method.

Polypyrrole Chitosan Cobalt Ferrite Nanoparticles Composite Layer for Measuring the Low Concentration of Fluorene Using Surface Plasmon Resonance

Fluorene is a polycyclic aromatic hydrocarbon, which is a hazardous toxic chemical in the environment. The measurement of low concentrations of fluorene is a subject of intense interest in chemistry and in the environment. Polypyrrole chitosan cobalt ferrite nanoparticles are prepared using the electrochemical method. The prepared layers are characterized using field emission scanning electron microscopy, Fourier transform infrared spectroscopy, and energy dispersive spectroscopy. The layers are used to detect fluorene using the surface plasmon resonance technique at room temperature. The composite layer is evaluated after detection of fluorene using atomic force microscopy. The fluorene is bound on the layer, and the shift of the resonance angle is about 0.0052°, corresponding to the limitation of 0.01 ppm.

Design of TE_(01δ) Test Probe for Measuring the Microwave Surface Resistance of HTS Thin Film

A new TEo1δ test probe with proper transmission factor is fabricated for the measurement of surface resistance of high temperature superconductor （HTS） thin film. Coupling holes instead of coupling loops are used in the probe for its easier machining and relatively low loss. Two 6 mm × 3 mm × 8 mm dielectric waveguides, one side of them is coated by silver, are used for coupling. The measurement result of S21 agrees well with the simulation because the size of the probe can be rigidly controlled by machine. The microwave surface resistance of four YBCO/MgO films are measured at 77 K and 12 GHz and scaled to 10 GHz according to thef2 rule. The average surface resistance of four HTS thin fdms is 0.38 mΩ, the standard deviation and relative standard deviation of one single HTS thin film are 0.009 mΩ and 2.4%, respectively.

Qualification of superpolished substrates for laser-gyro by surface integrated scatter measurement

Integrated scatterometer for qualification of superpolished substrates for laser-gyro by surface scatter loss measurement is constructed. Different from the qualification of substrate by surface roughness, the scatterometer measures the forward surface scatter loss to check whether the mirror made of the substrate will be suitable for the required laser-gyro lock-in specification. The scatterometer utilizes convex lens instead of integrating sphere to collect scatter light. Special sample support and baffle are designed to block unwanted light. The result of stability test is given, which is about 0.4% over 10 h.

Vibration shape testing of space sheet structure

The space sheet for a solar array structure is large in dimension, and flexible to induce complex distortion. It is difficult to measure the distortion. A large-scale flexible test prototype system is built for sheet structure vibration monitoring based on the vibration information of the solar array in space. The system provides an intelligent test method for flexible space structure with embedded sensors and non-visualization reinstruction. Multiple fiber Bragg grating （FBG） sensors are packaged and embedded into the structure with spatial division multiplexing （SDM） and wavelength division multiplexing （WDM）. The sensor interrogator distinguishes wavelength shifts that can be turned into curvature of the curve. The structure shape is reconstructed based on the curvature information and the arc-length, and then displayed. The experiment shows that the system has a high FBG sensitivity. The reconstruction algorithm is fast with high precision. The system has great potential for use in health monitoring of the space sheet structure.

A Semi-Automatic Thickness Inspection Technique for Marine Propellers

This paper describes the design and development of a Semi-Automatic Precision Caliper System to measure the thickness of an outboard marine engine propeller blade. Several commonly used methods for measuring the thickness of a propeller blade are reviewed in this paper. These include the P rops Scan, 3D Vision System and Black Dog. However, the operating practices and availability of different facilities in industry necessitate a more cost-effect ive approach. An alternative method using a Semi-Automatic Precision Caliper S ystem is therefore proposed. Details of the design criteria, principles of oper ation as well as the testing and verification of the system are presented. The paper concludes that the Semi-Automatic Precision Caliper System is a low cost and effective method for measuring the thickness of a propeller.

Higher Harmonics Generation in Tapping Mode Atomic Force Microscope

The contribution of higher harmonics to the movement of a micro rectangular cantilever in tapping mode AFM is investigated. The dependence between the phase lag of the higher harmonic components and tip-sample separation are found to be an order of magnitude higher than the base one, reflecting an increasing sensitivity to local variations of surface properties compared to the normal phase signal The strong correlation between the higher harmonic amplitude and average sample deformation implies that the higher harmonic amplitude can be taken to monitor the tapping force or as feedback variable to fulfill a constant repulsive force mode.

Screener3D:a gaseous time projection chamber for ultra-low radioactive material screening

In experiments searching for rare signals,background events from the detector itself are some of the major factors limiting search sensitivity.Screening for ultra-low radioactive detector materials is becoming ever more essential.We propose to develop a gaseous time projection chamber(TPC)with a Micromegas readout for radio screening.The TPC records three-dimensional trajectories of charged particles emitted from a flat sample placed in the active volume of the detector.The detector can distinguish the origin of an event and identify the particle types with information from trajectories,which significantly increases the screening sensitivity.For a particles from the sample surface,we observe that our proposed detector can reach a sensitivity higher than 100 l Bq m-2 within two days.

Absolute surface form measurement of flat optics based on oblique incidence method

In this Letter, a test method based on oblique incidence is practically implemented in the interferometric measurement process. Three sets of wavefront data are achieved through cavity interference measurement with a Fizeau interferometer and one oblique incidence measurement. An iterative algorithm is applied to retrieve the absolute surface shape of the test flat. By adding two sets of measurements, the absolute surface error of the interferometer＇s reference flat can be obtained. The new method can not only calibrate the reference flat error of interferometer, but also provide the absolute measurement method for high precision optical components applied in high power laser systems.

COMPACT PHASE GRATING INTERFERENCE SENSOR FOR MICRO-DISPLACEMENT

On the basis of existing techniques, a compact micro-displacement sensor of phase grating interference （PGI） is described, which adopts cylindrical hologram diffraction grating as the calibration standard. The optical principle of the sensor is explained, and the relation between the grating motion displacement and the phase shift of interference stripes is deduced. The improvement of the integral structure and the method of photoelectric signal processing are described in detail. With the software system based on the virtual instrument development platform Labwindows/CVI and other hardwares such as the precision displacement worktable, the surfaces of typical parts are measured and the characterization results are given. The sensor has wide measuring range and high resolution, its sensitivity and resolution being independent of the wavelength of the incident light. The vertical measuring range is 0-6 mm, and the vertical resolution is 0.005μm. The experimental results show that the sensor can be used to measure and characterize the surface topography parameters of the plane and curved surface.

Research on Patch Near-field Acoustic Holography Based on HELS Algorithm

A Patch NAH method based on HELS( helmholtz equation least-squares) algorithm is proposed for the measurement requirement of underwater large structures. This method chooses HELS algorithm to approximate the sound field completely,and calculates the sound field data outside the measurement region to enlarge the measurement aperture. It can reconstruct the sound field by the measurement data and the extrapolation data,through the reconstruction result it can be researched for the minimum measurement surface and the range of the extrapolation data in application. The paper analyzes the effect from the different measurement surfaces and different extrapolation ranges to the extrapolation data by simulations,and compares these reconstructed results with the conventional algorithm results. The simulation results indicate that the method can simplify the holographic measuring system,save the cost of the project and improve the accuracy of the sound field reconstruction,which can be effectively used for measuring and analyzing the underwater large structures.

Competition between Radiative Power and Dissipation Power in the Refrigeration Process in Oxide Multifilms

The maximum refrigeration power dependence on the doping density in the p-BaTiO3/BaTiO3/SrTiO3/BaTiO3/ n-BaTiO3 system and in the p-AlGaAs/AlGaAs/GaAs/AlGaAs/n-AlGaAs system is obtained respectively based on the opto-thermionic refrigeration model. The results show that the maximum refrigeration power in the p-BaTiO3/BaTiO3/SrTiO3/BaTiO3/n-BaTiO3 system increases dramatically with the increase of doping density from 1.0×1018 cm-3 to 5.0×1019 cm-3 while that in the p-AlGaAs/AlGaAs/GaAs/AlGaAs/n-AlGaAs system is nearly a constant. It is found that the different Auger coefficients and the competition between radiative power and dissipation power lead to the different behavior of the maximum refrigeration power dependence on the doping density of the two systems.

Comparative Study on Polarization of DNA and CdSe Quantum Dots

The polarizabilities of DNA in transverse direction and CdSe semiconductor quantum dots （QDs） deposited on mica surface are compared by means of electrostatic force microscopy （EFM）. We observe clear EFM-phase shift over CdSe QDs, while no obvious signal on DNA is detected, suggesting that DNA molecules is an electrical insulator.

Influence of Oxygen Pressure on Structural and Sensing Properties of β-Ga2O3 Nanomaterial by Thermal Evaporation

We prepare the gallium oxide （β-Ga2O3） nanomaterials from gallium and oxygen by thermal evaporation in the argon atmosphere and research their oxygen sensing under UV illumination with different oxygen pressures. X-ray diffraction reveals that the synthesized product is monoclinic gallium oxide, it is further confirmed by electron diffraction of transmission electron microscope, and its morphology through the observation using scanning electron microscope reveals thatβ-Ga2O3 nanobelts with a breadth less than lOOnm and length of severai micrometers are synthesized under low oxygen pressure, while the nano/microbelts are synthesized under high oxygen pressure. Room-temperature oxygen sensing is tested under at 254 nm illumination and it is found that the current decreases quickly first and then slowly with oxygen pressure from low to high.

Measurement of rectangular surface mobility of an infinite plate

A measuring method of surface mobility for an infinite plate subject to a uniform conphase velocity excitation is investigated. In the measurement, a finite plate is employed to simulate an infinite plate and a rigid cone is used to make a uniform conphase velocity excitation. A method to deduct the affect of additional mass is derived. The results of the measurement agree with that calculated theoretically.