Key Engineering Materials Vols. 381-382

Abstract: A method of straightness error compensation is presented, which is used in ultra-precision machining with nano-scale accuracy for a large mandrel manufacture. A set of measurement system in situ is developed, in which an ultra-smooth glass-ceramic flatness gauge and a non-contact micro displacement sensor with nano-scale resolution were used as a reference and sensor to get the straightness error of machine tool movement. The real straightness error can be obtained after subtracting the surface profile of the gauge from the original straightness error curve. Based on the real straightness error data, a new NC program was made for compensating the error from the axis movement of machine tool. As a result, after straightness error compensation, the straightness errors of two axes of ultra-precision machine tool are 68nm/400mm and 54nm/300mm respectively.

Abstract: We have been developing an intellectual manufacturing process applying IT (V-Cam system fabrication processes) based on Volume-CAD (VCAD) system which can express internal information of materials. This paper introduces the ultra-precision grinding, ray tracing (optical path) simulation software ‘V-Opt’ and the measurement of actual optical functions in the development of optical element taking gradient refractive index (GRIN) lens with functionally graded material properties as a model. In finish ground GRIN lens using SD#8000 wheel, the P-V (Peek to Value) of 27.07 nm, surface roughness (Ra) of 1.83 nm is obtained. ‘V-Opt’ developed for GRIN lens have two main functions; one is the visualizations of ray tracing and the other is the evaluation of spot diagram and focal length.

Abstract: The paper presents the results of measurements of surface topographies of chromium coatings after pneumatic ball peening. The studies were conducted on steel samples. Four pneumatic ball peening parameters were changed: ball diameter, shot peening pressure, distance between nozzle and workpiece and time of machining. The changes of 3D surface parameters were analysed. The correlation analysis was applied in order to obtain minimum number of parameters describing shot peened surface. Connection between fatigue strength and selected surface topography parameters was investigated.

Abstract: This article presents a calculation method for simple flat air bearing with central feed hole and pocket. A non-dimension relative expression between the load and air lift is obtained by applying some assumptions for the flow, Navier Stokes equations and the equation of equilibrium. The diameter of the feed hole and the central pocket are computed in order to work in optimal regime for the case the working lift is 20µm and the load is 20kG. The results of the theoretical calculation are match with the experimental results and used to manufacture air-bearing slide carrier at Hanoi University of Technology.

Abstract: A novel vibration system for dynamic balancing measurement is presented based on flexure hinges mechanism. A kinetics modeling for this novel vibration system is established, and its equivalent stiffness and natural frequencies are analyzed in depth. Finally the obtained simulation results by ANSYS FEM validate the correction of the theoretical analysis and provide advantageous conclusions for optimal design of vibration system.

Abstract: One hydraulic pressure generator has been developed with a unique rotating valve and the waveform of generated waves is approximately square-like shape under the low rotating speed. The generated wave has advantages for research in the dynamic characteristics of hydraulic components. The unique rotating valve consists of a rotor and stator which have a number of rectangle grooves precisely milled on the peripheries of the rotor and stator as fluid channels. The rotating rotor alternately switches the fluid channels to open and close state, therefore the waveform is close to square in principle. The pressure transient on the generated wave plays a major role and influences dynamic performances of generated wave. For analyzing the performances of the generator, one sensitivity pressure transducer mounted on the outlet of the generator to measure waveform in time domain. In addition, through Fourier series expansion the spectrum of generated waves clearly indicates the harmonic components of generated waves. Results show the waveform is close to square-like under the low rotating speed in time domain. In the frequency domain, the spectrum of the generated wave demonstrates the bandwidth is abundant. Thus, the generator could be one kind of function generator to performing the calibration of the hydraulic components.

Abstract: The system bases on the theory of rolling-wheel to measure large diameter, by applying double counters to record the round grating’s signal and using the method of three rolling-wheels paralleling data acquisition, redundancy measurement and error amendment and so on, realizes the measurement of large axis workpieces’ diameter with high precision in on-line and dynamic condition. The experiment shows that the system can achieve the on-line dynamic measurement precision in m D µ 5 at the range of the diameter m m D 5 ~ 1 = complexly combining hardware and soft under the relevant control methods.

Abstract: This paper presents a method for online measurement of the dimensions of thermal train wheel by one frame of photo-thermal image. A measurement system and its mathematics model is setup. The effect of the spectrum of laser source to restrain thermal background noise is analyzed, then, a special laser is selected. A weighting method of the gray value transform is added into the image process. The high temperature fields of a measured train-wheel are analyzed by use of limited element method. The experiment result shows that the measurement standard deviation of the thermal train-wheel rim is less than 0.55 mm.

Abstract: The purpose of this research is to estimate the dimensional stability derivatives in linear dynamic model of a fixed-wing model-scale unmanned aerial vehicle (UAV) by real flight data logged by an onboard flight computer. The paper described the experimental setup, operation procedure of raw flight data, process of nonlinear least squares estimation, and cause-effect examination of impulse responses. The simulation-based results of the estimated model indicated a very good accuracy with real flight data. The linear longitudinal and lateral models are very helpful for designing the stability-augmentation system or autopilot for the UAV.

Abstract: The optical-fiber alignment system is a critical role on micro/nano precision engineering. In this paper, the design and fabrication of a novel, six-axis compliant nano-stage which uses flexure hinge and negative Poisson’s Ratio is presented. Every single axis is a designed planar geometry, so it is easily fabricated via laser cutting processes that enable cost down to achieve batch products. The material of six-axis mechanism is aluminum. The micromechanism consists of six trapeziform displacement structures and two hexagonal plates which are on the top and bottom. The displacement structures includes of a signal layer flexure hinge toggle mechanism stage and asymmetrical multi-layer flexure hinge toggle mechanism stage. The computer simulation of the transferring behavior was performed with a commercial package, named SolidWorks ANSYS@. The model states of stress, strain and the displacement of ratio can be estimated. The experiment was carried out with Piezoelectric(PZT) actuators and LVDT which drives and measures the displacement. Comparison of the simulation and experimental result between the single-axis and six-axis stage are presented. The results shown that the displacement of ratio is 32 times as the single-axis structures. The system maximum displacement of vertical translation, horizontal translation, tilt angle and rotational angle is 50 µm, 50 µm, 0.5° and 0.5°. In experimental, the results not only demonstrate that this micromechanism of flexure hinge and negative Poisson’s Ratio increases the displacement of ratio and reduces the size of system, but can also be applied on the optical-fiber alignment system.