首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   20篇
  完全免费   4篇
  一般工业技术   19篇
  机械仪表   4篇
  自动化技术   1篇
  2016年   3篇
  2015年   1篇
  2012年   5篇
  2011年   5篇
  2010年   5篇
  2009年   2篇
  2008年   2篇
  2007年   1篇
排序方式: 共有24条查询结果,搜索用时 125 毫秒
1.
3D digital image correlation methods for full-field vibration measurement   总被引:2,自引:0,他引:2  
In the area of modal test/analysis/correlation, significant effort has been expended over the past twenty years in order to make reduced models and to expand test data for correlation and eventual updating of the finite element models. This has been restricted by vibration measurements which are traditionally limited to the location of relatively few applied sensors. Advances in computers and digital imaging technology have allowed 3D digital image correlation (DIC) methods to measure the shape and deformation of a vibrating structure. This technique allows for full-field measurement of structural response, thus providing a wealth of simultaneous test data. This paper presents some preliminary results for the test/analysis/correlation of data measured using the DIC approach along with traditional accelerometers and a scanning laser vibrometer for comparison to a finite element model. The results indicate that all three approaches correlated well with the finite element model and provide validation for the DIC approach for full-field vibration measurement. Some of the advantages and limitations of the technique are presented and discussed.  相似文献
2.
Today, accelerometers and laser Doppler vibrometers are widely accepted as valid measurement tools for structural dynamic measurements. However, limitations of these transducers prevent the accurate measurement of some phenomena. For example, accelerometers typically measure motion at a limited number of discrete points and can mass load a structure. Scanning laser vibrometers have a very wide frequency range and can measure many points without mass-loading, but are sensitive to large displacements and can have lengthy acquisition times due to sequential measurements. Image-based stereo-photogrammetry techniques provide additional measurement capabilities that compliment the current array of measurement systems by providing an alternative that favors high-displacement and low-frequency vibrations typically difficult to measure with accelerometers and laser vibrometers. Within this paper, digital image correlation, three-dimensional (3D) point-tracking, 3D laser vibrometry, and accelerometer measurements are all used to measure the dynamics of a structure to compare each of the techniques. Each approach has its benefits and drawbacks, so comparative measurements are made using these approaches to show some of the strengths and weaknesses of each technique. Additionally, the displacements determined using 3D point-tracking are used to calculate frequency response functions, from which mode shapes are extracted. The image-based frequency response functions (FRFs) are compared to those obtained by collocated accelerometers. Extracted mode shapes are then compared to those of a previously validated finite element model (FEM) of the test structure and are shown to have excellent agreement between the FEM and the conventional measurement approaches when compared using the Modal Assurance Criterion (MAC) and Pseudo-Orthogonality Check (POC).  相似文献
3.
The reliance of the aerospace industry on finite element models during the design of new products requires the best possible models for the prediction of the dynamic behaviour and so it is usually necessary to validate an original model using some additional reference data as the basis—usually data measured on a test structure. Finite element model updating can lead to the required accuracy, and while attempts are under way to minimise the required experimental testing involved in the process, measurements still are an integral part of the procedure. To improve the validation process, a major aim of current experimental research is to provide a more complete set of data from a single experiment in a shorter amount of time, so as to increase the overall efficiency of the updating routine. To this end, a new continuously scanning laser Doppler vibrometery measurement technique is presented for application to cylindrical structures. It allows the measurement of the dynamic behaviour of a cylindrical structure with a previously unachievable spatial resolution in a much shorter time than conventional measurement methods. The introduced method is evaluated through a detailed simulation in order to investigate its robustness and to ensure data quality, and the results from a proof-of-concept test rig are presented.  相似文献
4.
In this work, the digital image correlation (DIC) technique was used as full-field measurement to analyze the shear properties of the 3D orthogonal woven C/C composites. Both the in-plane and the through-the-thickness specimens were tested and the macroscopic average strain was obtained. The composites were composed of lots of periodic units and the macroscopic average strain was dependent on these meso-structures. There were three regions within one unit, which showed different mesoscopic strain. The relationship between the shear test region and the macroscopic average strain was systematically studied. Finally, the accuracy of conventional strain-gauge rosette measurement was also discussed.  相似文献
5.
The paper is devoted to an optimal (i.e. noise-robust) determination of stress intensity factors and crack tip locations based on a displacement field measured over an arbitrarily shaped domain. As the minimization of the noise sensitivity is included within the proposed extraction technique, this is especially dedicated to corrupted displacement fields, e.g. as measured by an optical technique. The main idea is to construct for mode I and II fields an extracting function so that its L2 scalar product with the actual displacement field yields the sought parameter. The extracting function is also constrained to be orthogonal to a set of admissible elastic fields. Two applications are considered to illustrate the technique. The first example deals with a fatigue crack in steel for which small scale yielding occurs. A second example with a low signal/noise ratio illustrates the capability of the approach to analyze a crack in silicon carbide with sub-pixel openings.  相似文献
6.
This paper presents a neural network modelling method for damage behaviour of composite materials in conjunction with full-field strain measurements. The proposed method utilises the overall structural response of a laminate composite specimen to develop the constitutive model of a single ply unidirectional laminate. Based on an energy principle, a performance function for training the neural networks is derived in terms of the applied external work and the induced strain energy. This allows the proposed method to develop the neural networks without the presence of stress information that is not necessarily obtainable in experiments with non-uniform deformation. The use of neural networks also enables the proposed method to model the damage behaviour without the constraints on the parameter space, such that a more representative model is developed for the actual material behaviour. An example of tailoring the proposed method to model the in-plane shear damage behaviour of a carbon fibre reinforced plastic (CFRP) laminate is demonstrated as well as its numerical validation. The practical application of the proposed method to multi-axial damage-related nonlinear behaviour of composite is presented using the experimental data obtained from a tensile test with an open-hole specimen.  相似文献
7.
This study presents a full-field surface plasmon resonance (SPR) sensor induced by attenuated total reflection (ATR)-couple for liquid refractive index measurement. The system adopts a common-path heterodyne interferometer to measure the phase difference between P- and S-wave after passing through the SPR sensor. In order to realize the full-field measurement, it adopts a three-frame integrating-bucket method. The experimental results show great consistency profile between single point and full-field liquid refractive index measurement from 1.330 to 1.340 RIU. It shows that the best sensitivity and resolution of a single pixel in charge couple device (CCD) for liquid refractive measurement are 3.3 × 104 (deg/RIU) and 3.53 × 10−6 (RIU), respectively. As compared with traditional single-point method, the proposed method with a regular CCD has no degradation. Therefore, the system has many applications in chemistry and biology.  相似文献
8.
The increasing use of structural adhesive in industry leads to the need of a detailed failure criterion. In this paper, a structural adhesive especially designed for automotive crashworthiness applications named BETAMATE 1496V™ is studied. The authors propose a new failure criterion based on an equivalent failure strain which evolves with the triaxiality stress ratio and the strain rate. This criterion is identified by means of new measurement techniques on a large range of strain rates and for different loadings like tensile, shear and compressive.  相似文献
9.
Using Electronic Speckle Pattern Interferometry (ESPI), full-field displacement measurement was performed on the edge of a cracked cross-ply graphite/epoxy laminate subjected to a tensile loading. The displacement jumps corresponding to cracks are clearly visible and can be used to determine the crack opening displacement (COD) values along the cracks. The main objective of this study is to determine if the application of successive loads of increasing magnitude may have modified the existing cracks and thereby changed the COD dependence on the applied stress. Moreover, we have tested the applicability of the assumed linear elastic COD behavior in the presence of very high stress concentration at the crack tips. The profile of the opening along the crack was also studied.  相似文献
10.
The purpose of the paper is to provide a comprehensive experimental and numerical analysis of one of the encountered and critical state modes in sheet metal forming processes. The study is carried out with the help of the full-field measurement techniques. In order to confer some generality to the proposed work, several materials and different specimen shapes are considered that exhibit more or less homogeneous strain field. The proposed experimental study of the plane strain test is completed by a preliminary identification of the material parameters for non-linear behaviour at finite strains, using heterogeneous strain field.  相似文献
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号