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1.
光干涉法实现CH4浓度的直读式测量   总被引:1,自引:0,他引:1  
讨论了如何利用现代电子技术把矿用光干涉CH4检测仪变成为直读式测量仪表的原理和设计方法,从而使老仪表焕发青春。  相似文献
2.
One of the main features of typical elastohydrodynamic lubricating (EHL) contacts is the unique horseshoe film shape, which can be readily observed by using interferometry and quite accurately modelled by the well-established EHL theory. However, an anomalous EHL film, characterized by a wedge shape together with a tiny dimple at the inlet region, is observed under pure sliding conditions with ultra slow speeds of 3–800 μm/s in an optical EHL test rig. The variations of the wedge and the inlet dimple with different sliding speeds and loads are investigated using a series of polybutene oils of high viscosities. It is found that the inclination of the wedge is dependent on sliding speeds, loads and oil viscosities. The dimple always occurs at the inlet. The appearance of an inlet dimple together with a wedge film shape is reported for the first time. The phenomenon can be attributed to a non-Newtonian characteristic of the lubricant: the limiting shear strength. Additionally, the influence of starvation on the film shape is also examined.  相似文献
3.
The ultra-thin film interferometric method of measuring the thickness of very thin films in lubricated contacts has been refined so as to be able to measure films down to 0.3nm with a standard deviation of 0.15nm. The main remaining source of measurement variation for films below 3nm thick is the surface roughness of the contacting solids. This modified technique has been applied to study the film-forming properties of three fluids, hexadecane, a dilute solution of surfactant in hexadecane, and cyclohexane. Purified hexadecane shows a very slightly enhanced oil-film thickness below 1nm. The long-chain surfactant forms a boundary film 2nm thick. Cyclohexane behaves as though it forms a surface layer about 1nm thick with viscosity three times the bulk fluid viscosity.  相似文献
4.
Dedicated optical instruments for ultrasonic welder inspection and control   总被引:1,自引:0,他引:1  
Two different optical instruments for real-time vibration measurements, inspection and control of ultrasonic welders were designed, realized and characterized: a self-mixing laser interferometer and an optical triangulator, both studied for achieving high bandwidth and very good resolution within a short dynamic range. The implemented instruments can solve the problem of measurement and control of ultrasonic welders that until now has no low-cost solutions available on the market. The performance of the two developed instruments was compared in order to assess which is the most appropriate for this specific application. Finally, results of the real-time characterization of an ultrasonic welder are given and discussed.  相似文献
5.
In this paper, a flexible optical interferometer incorporated with both fast Fourier transform (FFT) and phase-shifting method is developed for three-dimensional (3D) testing of micro-components. Using light interference, microscopic optics, piezoelectric transducer (PZT) nanoscanning and a CCD camera, the proposed system can detect deformation and surface contour in the order of nanometers. An application of the proposed technique is demonstrated using two micro-components: a micro-beam in an accelerometer and a micromirror. The resulting interference fringes that are related to the deformation and surface contour are analyzed using FFT method or three-step phase-shifting method depending on the test surface features. Experimental results show the feasibility of the proposed method for 3D deformation and surface contour measurement of micro-components.  相似文献
6.
In this paper, the transient lubrication phenomena induced by isolated circular micro-cavities passing through an EHL point contact are analysed. A 52 100 steel ball was micro-machined using a femtosecond pulse laser, and is tested with an EHL tribometer. The experiments are simulated numerically with a 2D-multigrid solver. Under rolling–sliding conditions, the film thickness distribution is modified, and two opposite effects are observed. Deep micro-cavities induce an oil film decrease. On the contrary, a shallow micro-cavity locally generates a large increase in the film thickness. When the ball surface is the slowest, the propagation velocity of the local oil film reinforcement increases.  相似文献
7.
Soap lumps entering a grease-lubricated elastohydrodynamic lubrication (EHL) contact were traced as they passed through the contact by using optical interferometry in a standard Ball & Disc apparatus and a high-speed video camera with light enhancer. One specific soap lump could be traced when it was passing through the contact and sharp images of the passing lump could be captured. This paper presents a combined experimental and numerical approach to determine what is happening when such lumps pass through the contact. From the fringe pattern, obtained by optical interferometry, a film thickness map is created by using image processing. This is done for every time step (1 ms) as the lump is passing through the contact. These maps serve as input to a numerical computation of the pressure by assuming elastic deformation theory. Consequently, no assumptions about the rheological behaviour of the grease have to be made. Two greases were studied, based on the same synthetic poly-α-olefin but thickened with Li-12-OH and Li-complex respectively. It is seen that the soap thickened lumps can cause deep elastic indentations accompanied by large pressure fluctuations. The pressure level will in some cases be more than doubled due to lumps entering the contact region. The effects on noise level and operational life are also discussed.  相似文献
8.
Ultrathin film interferometry has been used to measure the boundary film-forming behaviour of long chain, carboxylic acid oiliness additives. It has been shown that in dry conditions, these acids form very thin films of around 2–3 nm thickness. However when water is present, some acids form significantly thicker films, around 10 nm in thickness. The behaviour of these films is very similar to that previously seen with metal carboxylate additive films, including thick film collapse at high rolling speeds followed by film reformation at slow speeds. It is suggested thick films formed by long chain carboxylic acid additives result from reaction of the acids at the rolling solid surfaces in the presence of water to form deposits of insoluble iron carboxylate.  相似文献
9.
An interferometric technique is applied to a temporal analysis of the far-field radiation from a near-field optical fibre probe. A balanced homodyne scheme combined with lock-in detection at dual harmonics allows one to evaluate the temporal form of weak signal pulses, even in the presence of some environmental vibrations that disturb the optical interference. The transmission properties of a small aperture are formulated theoretically. It is shown that the sub-wavelength aperture should not distort the femtosecond optical pulses temporally, which is consistent with the experimental observation.  相似文献
10.
Roland Larsson  Jan Lundberg 《Wear》1995,190(2):184-189
An experimental study of lubricated impacts between a steel ball and a flat glass surface has been performed. The experimental set-up consists of a Ø70 mm ball mounted on a pendulum which impacts onto a lubricated glass disc. The contact region is studied by means of optical interferometry using a monochromatic light source, a microscope and a high-speed video recording equipment.

The lubricants are of PAO type and the viscosity ranges from 27 to 2600 mm2 s−1 at the test temperature. The impact velocity is varied between 0.08 and 0.29 m s−1.

A dimple occurs at the centre of the contact where the lubricant is trapped. The influence of viscosity and impact velocity on the dimple's depth and diameter is studied.  相似文献

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