共查询到20条相似文献,搜索用时 46 毫秒
1.
2.
3.
4.
5.
6.
7.
金属材料超声表面强化技术的研究与应用进展 总被引:12,自引:1,他引:12
简要回顾几种传统的表面机械强化技术及其特点。对近年来得到迅速发展和应用的金属材料超声表面强化技术进行介绍和评述。这包括超声冲击处理技术、超声喷丸强化技术和超声深滚强化与滚光技术。介绍以上几种技术在国内外的研发和应用的历史和现状,对比几种技术在不同应用中的特点与限制,并与传统的表面机械强化技术进行比较。展望金属材料超声表面强化技术的发展与应用前景。在总结归纳的基础上,从强化机理、强化工艺、工程应用和技术规范等方面提出金属材料超声表面强化技术的研究和应用发展建议。为相关技术领域的研究机构、研究人员和工程应用单位提供有关金属材料超声表面强化的较为全面的信息。 相似文献
8.
9.
10.
本文通过对冷冲模工作条件及失效形式的分析 ,提出了采用硬质合金堆焊技术和电火花表面强化技术 ,对冷冲模表面进行强化 ,从而延长冷冲模的使用寿命。 相似文献
11.
The properties of thin layers of materials can be different from those in the bulk form. The response of a coating to any given load and its ability to remain bonded to the substrate will depend on its elastic modulus and Poisson's ratio. In this study a measurement method based on ultrasonic bulk wave reflection was evaluated. As a model system, a thin layer of polyethylene was pressed between two solid steel bodies. The reflection spectra of longitudinal and shear ultrasonic waves were recorded from the coating. The frequencies at which the layer resonates were measured and from this the wave speeds deduced. The Poisson's ratio can be determined from these two wave speeds and if the layer thickness is known the modulus is also available. The tests yielded reasonable values for both. This approach is only suitable if the layer can be made to resonate by the available ultrasonic frequencies; typically this will be the case for thicker coatings (tens of microns). Further, good coupling between the layer material and the steel bodies is necessary so that the interfaces do not themselves act to reflect ultrasound. This is better achieved with a smooth soft coating. 相似文献
12.
Yao-Chen Tsai Chung-Yi Huang Kuan-Yuan Lin Jiing-Yih Lai Wen-Der Ueng 《The International Journal of Advanced Manufacturing Technology》2009,42(1-2):152-167
The computer-aided design model reconstruction process is generally very complex, as it requires substantial efforts in planning and editing data points, curves, and surfaces. A novel method is developed in this study for automatic surface reconstruction from a huge number of triangular meshes. The proposed method is mainly composed of the following five steps: mesh simplification, quadrilateral mesh generation, curve net construction, connectivity data preparation, and multiple surfaces fitting with G1 continuity across the boundaries. The first three steps build the boundary curves of the surfaces. The fourth step prepares the data needed for surface fitting, which includes segmented points, continuity conditions on the boundaries, and topological relationship of the data. In the final step, all regions of points are fitted into appropriate surfaces, with the accuracy and smoothness of the surfaces controlled and G1 continuity between the surfaces. A detailed discussion for each of the above algorithms is provided. Successful examples are also presented to demonstrate the feasibility of the proposed method. 相似文献
13.
14.
An ultrasonic self-calibrating technique for the characterization of a ceramic which was fabricated by change pressing time
during the HIP process has been applied by using the ratio of the reflection and transmission coefficients of normal incidence
longitudinal waves. The ratio is self-compensated, in that it is independent of the characteristics for transmission and reception
of ultrasound by the transducer and the condition of the couplant. The insensitive direction in parameter space is defined
as the direction in which the variation of the ratio to changes of two parameters vanishes. For inverse problem the distribution
of minima in an error surface is investigated. 相似文献
15.
Kyung Cho Kim Hiroaki Fukuhara Hisashi Yamawaki 《Journal of Mechanical Science and Technology》2002,16(12):1627-1632
In this paper, a simplified ultrasonic CT system, which uses the information in three directions, that is, 90°, +45° and —45°
about the inspection plane, is applied to the high strength steel, and the frequency analysis method for enhancing the C scan
or CT image is developed. This frequency analysis method is based on the frequency response property of the material. By comparing
the magnitudes in the frequency domain, the special frequency which shows a significant difference between the welded joint
and base material was found and used to obtain a C scan or CT image. Experimental results for several kinds of specimens,
having a welded joint by electron beam welding, a weld joint by arc welding, on a fatigue crack, showed that the obtained
C scan or CT image has better resolution than the results of previous experiments using the maximum value of the received
waveform. 相似文献
16.
Shoupeng Song 《Russian Journal of Nondestructive Testing》2010,46(1):69-74
A new signal processing technique for separating the reflection of a flaw near a surface from the surface reflection itself
is proposed. The method is based on ultrasonic scattering energy function model of flaw close to the material surface. Flaw
sensitive component in the model, which corresponding to the low frequency signal, is remained by using a low pass digital
filter. In order to make the recognition procedure easier and enhance the recognition effect, a reference signal is introduced
to avoid the influence of the surface echo. Thus, the surface flaw is easily and clearly recognized. The good performance
of the approach is experimentally verified in laboratory on a steel sample with different man-made surface flaws. 相似文献
17.
A. Takeuchi 《Lubrication Science》2009,21(10):397-413
Evaluation of lubrication conditions for a real frictional surface, such as a steel bearing, becomes an important issue for safe operation of a machine. In this paper, an application of ultrasonic technique is attempted for a purpose of evaluating the lubrication conditions. Ultrasonic waves emitted towards a hydrodynamic lubrication interface are reflected multiple times in oil film, and an echo height of reflected waves from the boundary is dependent on film thickness. The results of this study indicated that the ultrasonic technique is able to measure film thickness of approximately 50 nm in the case of a standstill surface having extremely small surface roughness. Furthermore, a potential for estimating the oil film thickness between a piston ring and cylinder is also indicated. In addition, in the case of a ball bearing, quantitative measurement of a size of dent, which forms the origin of flaking, is important for an evaluation of lubrication conditions. This becomes possible with an observation of a change in the echo height reflected from a boundary surface between a housing and an outer ring of the ball bearing. In this study, quantitative measurement of an indentation having 0.32 mm width on a raceway surface of an inner ring was achieved. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
18.
The received signal in ultrasonic pulse-echo inspection can be modeled as a convolution between an impulse response and the reflection sequence, which is the impulse characteristic of the inspected object. Deconvolution aims at approximately inverting this process to improve the time resolution so that the overlap between echoes from closely spaced reflectors becomes small. This paper presents a modified minimum entropy blind deconvolution algorithm for deconvolving ultrasonic signals. Enhancement of the resolution is achieved by using the presented method. In addition, the presented approach will, in many cases, lead to a faster computation. A nonlinear function is the key point to the efficiency of the modified blind deconvolution algorithm, which is used to increase the sparsity of the iteration output and to decrease the influence of the added noise by replacing each iteration output by output of the nonlinear function. Simulations showed the efficiency of the modification as compared with minimum entropy deconvolution when deconvolving synthetic ultrasonic signals. Experimental results using real ultrasonic data evaluated further that the exact solution consistently yields good performance. The thickness of a thin steel sample can be calculated by the modified blind deconvolution filter with a reasonable accuracy. 相似文献
19.
Adaptive filters, with their efficiency and simplicity, have been used successfully in various ultrasonic NDT signal processing contexts. Of these, the adaptive deconvolution with the conventional least-mean-squares (LMS) adaptive filter has improved time resolution. However; the convergence speed of LMS is restricted by the eigenvalue spread of the input correlation matrix. This paper explores the potential of other adaptive algorithms, namely, normalized least-mean-squares (NLMS), recursive least squares (RLS) and QR-decomposition-based RLS (QR-RLS) to handle the deconvolution of ultrasonic NDT signals and compare their performances with that of the conventional LMS algorithm. Furthermore, the mean square error (MSE) behavior in the different adaptive filtering algorithms for ultrasonic NDT signals deconvolution is briefly introduced. Experiments results are explained by graphs and discussed based on the performance criteria. The proposed methods enhanced the resolution quality, offering more alternatives for this application according to specific case requirements. 相似文献
20.
In this paper a new approach to enhance the dynamic range of a fringe projection system for measuring 3D profile of objects with wide variation in their optical reflections is proposed. The high dynamic range fringe images are acquired by recursively controlling the intensity of the projection pattern at pixel level based on the feedback from the reflected images captured by the camera. A four step phase shifting algorithm combined with a quality guided algorithm is used to obtain the unwrapped phase map of the object from the acquired high dynamic range fringe images. Simulation and experimental results show that the proposed technique can accurately measure the 3D profile of objects with wide variation in their optical reflectivity. 相似文献