共查询到20条相似文献,搜索用时 15 毫秒
1.
2.
Refraction contrast X-ray imaging using synchrotron source with ultra-bright light and highly directional beam is a unique method to diagnose non-destructively cracks or voids formed in materials, providing us in principle completely different information from conventional methods such as absorption contrast X-ray imaging. The authors have applied this imaging technique in SPring-8 to materials fracture study. We have also introduced home-made, in-situ observation facility system of crack formation and propagation in materials and the originally-designed 3D X-ray imaging systems to the experimental Hutch C of BL24XU (Hyogo BL) of SPring-8. Using these 3D X-ray imaging technique, in-situ observations of initiation and propagation of corrosion fatigue crack of Al-10%Mg alloy were conducted. The absorption contrast X-ray images were also obtained for comparison. It is concluded that the X-ray imaging method using ultra-bright synchrotron radiation is very useful for fracture research of materials and 3D X-ray contrast images are much more distinct than the conventional X-ray images to obtain information of the crack initiation and propagation behavior in the alloy. 相似文献
3.
The design of a prototype binocular stereoscopic X-ray imaging system for a security screening application is presented. This is based on an innovative technique [Evans JPO, Robinson M, Godber SX. A new stereoscopic imaging technique using a single X-ray source: theoretical analysis. NDT&E International 1996;29(1):27–35] utilising a single X-ray source and a pair of linear X-ray detector arrays. The image data is collected whilst the object under inspection is linearly translated past the X-ray detectors. The machine constructed enables approximately one cubic metre of object space to be imaged in five seconds. The resultant images may also be used for the extraction of three-dimensional coordinate information. 相似文献
4.
A computer package for the simulation of the X-ray imaging process in nondestructive evaluation (NDE) is presented. The components of the radiographic inspection system are considered independently, i.e. the characteristics of the source, the geometry and the material properties of objects and defects, as well as the imaging process itself. The model is based on a ray tracer technique describing the attenuation of the radiation. The scattering effect is included in terms of built-up factors. A CAD-interface provides the opportunity to arrange independent CAD objects, e.g. the component geometry or defect shapes, defining a testing scheme. Complicated defect shapes are created by a preprocessor, the built-up factors can be received from experiments or from a separate model using an efficient solution of the scattering problem based on the theory of Markovian processes with random structure. 相似文献
5.
Infrared thermography (thermal imaging) is an important and powerful technique for consideration when investigating any structural situation where a ready source of surface heating (or cooling) is available, or where the item under investigation itself supplies such conditions. The methods used are totally non-destructive and non-invasive, and can be highly cost-effective. This paper explores a wide range of applications; particularly relating to structural investigation situations. Some guidance is given on optimum timing, conditions and viewing locations for the various situations described as well as limitations of the technique. 相似文献
6.
上海光源是第三代同步辐射光源,其X射线成像具有高空间分辨、快时间分辨、高衬度分辨的特点,可对材料样品实现原位、无损、高分辨、三维和动态成像,利用同步辐射光源的高度相干性可以实现相位衬度成像,从而可以实现聚合物等低Z材料的高衬度X射线成像,而传统的X射线吸收衬度成像在对轻元素材料成像上获得的衬度极低。为更好地支持用户,基于上海光源X射线成像线站,建立和发展了定量相衬成像、动态CT成像、基于多种衬度机制的CT成像、快速CT重构等成像方法。本文简要介绍了上海光源X射线成像方法学发展及其在材料科学上的应用研究进展。 相似文献
7.
Focused ultrasonic monolithic transducers are often used for internal imaging of pipelines. The transducers yield a high lateral resolution as long as the distance between the pipe wall and the transducer corresponds to the transducer focal length. If the distance to the wall changes, for example due to increasing pipe diameter or de-centering of the inspection robot, the lateral resolution is decreased. We propose using synthetic aperture focusing with the virtual source method to extend the effective range of the focused transducer. It is assumed that the measurements are performed over a cylindrical surface, and we employ the Cylindrical Phase Shift Migration algorithm to perform the synthetic aperture focusing. The imaging algorithm is applied to scans of both pointlike scatterers and a corroded pipe surface, and the results demonstrate that a high lateral resolution can be obtained even when the pipe wall is several focal lengths away from the transducer. 相似文献
8.
9.
射线数字成像检测技术 总被引:5,自引:4,他引:5
介绍多种射线数字成像(DR)系统的组成及成像机理,分析其性能指标、优缺点及应用领域。光子放大的DR系统(如图像增强器DR系统)实时性好,但适应的射线能量低,检测灵敏度相对较低;其它系统的检测灵敏度较高但成像时间较长。DR系统成像方式的主要区别在于射线探测器,除射线转换方式外,影响系统检测灵敏度的主要因素是散射噪声和量子噪声;可采用加准直器和光量子积分降噪的方法提高检测灵敏度。 相似文献
10.
11.
The quantitave measurement of the positions and diameters of steel reinforcements in buildings is based on the concept of non-linear backprojection (NLBP). Advantages are 3D-image reconstructions from a small number of views, fast numeric algorithms and the consideration of the statistical, spectral and other characteristics of the object. For the radiographic inspection a 60Co source was used and both X-ray films and imaging plates for detection. The imaging plates were combined with special filter screens for contrast optimization. The digitized images from the plates have a high dynamic range and can be read into a computer without a photographic developing process. A numerical preprocessing procedure was developed as space filtering in different directions followed by a combination of the image angle components. A generalized Hough or Radon transformation and a statistical evaluation of the resulting image was employed. The special advantage of this method is the reconstruction of direction-selective structures. 相似文献
12.
针对钨资源储量、分布现状 ,就世界钨资源开发利用及钨制品供需情况 ,运用数据对比分析 ,预测未来钨制品市场走势 ,探讨合理开发、利用钨资源 ,以及有效控制钨资源的战略意义。 相似文献
13.
为了得到板状复合材料X射线数字成像最佳的检测图像质量,采用CIVA仿真模拟软件计算不同检测电压和检测电流对板状复合材料构件内部间隙X射线数字成像检测结果的影响,得到优化的射线源工艺参数,即焦点尺寸0.8 mm、检测电压100 kV、检测电流9 mA。将该射线源工艺参数应用于含有预制0.5 mm间隙尺寸的试样X射线数字成像检测试验中,间隙尺寸的测量误差仅为2%,表明采用CIVA仿真模拟软件可以指导检测工艺参数的确定,保证检测结果的可靠性。 相似文献
14.
15.
Two different techniques for ultrasonic imaging of concrete are presented, namely a weighted sum technique and a statistical technique. The techniques utilize both the scattered elastic compressional and the mode converted shear wave fields. Since the conventional imaging techniques utilize either the compressional or the shear wave mode to generate the subsurface image, information contained in the scattered ultrasonic field is partially utilized. The proposed techniques intend to use more information contained in the scattered field leading to an improvement in the final image. Synthetic full matrix data is generated using the finite difference in time domain scheme for simulation of elastic wave propagation in concrete with embedded rebars and aggregates. The proposed imaging techniques are then used to generate the subsurface image of the medium. Experiments were also performed to generate full matrix data on two concrete slabs with different geometry, sizes and distribution of rebars. The applicability of the proposed imaging techniques is demonstrated on the experimentally acquired data. The images when compared to the ones generated by the conventional single mode approach, show improvement in resolution and distinction between the embedded features, e.g. closely spaced rebars. It is also observed that the weighted sum technique performs slightly better in comparison to the statistical technique with respect to suppression of background noise. 相似文献
16.
复合材料序列热图无损检测 总被引:2,自引:0,他引:2
应用序列脉冲激光热加载的红外热成象技术对复合材料进行无损检测,扫描式测量给出复合材料表面时间序列热图象,实验与理论计算结果表明,序列热图象无损检测复合材料非常有效。 相似文献
17.
Richard L. Sandberg Zhifeng Huang Rui Xu Jose A. Rodriguez Jianwei Miao 《JOM Journal of the Minerals, Metals and Materials Society》2013,65(9):1208-1220
For many years, x-ray microscopy has been attractive for materials studies with its ability to image thick samples and provide nanometer-scale resolution. However, the ability to manufacture high-resolution x-ray optics has been a hurdle to achieving the full potential of diffraction limited x-ray imaging. Recently, the advent of bright and coherent x-ray sources at synchrotrons and x-ray free electron lasers has enabled a lensless imaging technique called coherent diffractive imaging (CDI). Since it was first demonstrated in 1999, CDI has been rapidly developing into a materials imaging technique with resolutions approaching a few nanometers. This review provides an overview of the development of CDI and several applications to nanometer-scale imaging in two and three dimensions of biological and condensed mater materials. Also, we review the development of tabletop, coherent, soft x-ray sources that provide a complimentary and potentially more accessible source for nanometer-scale coherent imaging of materials. 相似文献
18.
介绍了微波成像技术的特点和优势,同时对微波成像的现存算法进行了总结概述,着重介绍了几种具有代表性的重构算法,如ω-k算法、局部形状函数算法、波恩近似算法、对比源算法、粒子群优化算法和非精确牛顿算法。文章通过对几种电磁逆散射算法进行比较,给出不同算法各自的原理、特点及使用范围,并对电磁逆散射算法的发展趋势做了展望。 相似文献
19.
Images of defects in a plate-like structure can be obtained from amplitude distributions measured using the scanning laser source technique. This paper discusses high-speed non-contact imaging for defects in a plate. Fundamental experiments conducted using a contact piezoelectric transducer as a receiving device revealed the effect of the generated wave shape and measurement speed on the defect images. Generating tone-burst waves consisting of multiple frequency components and averaging the images obtained in multiple frequency bands (frequency image averaging, FIA) gave clearer defect images in which noisy effects due to low signal-to-noise ratio and spurious images due to multiple reflections in high-speed imaging were reduced. Moreover, FIA was shown to be effective for high-speed non-contact imaging using a laser Doppler vibrometer. 相似文献
20.
An image intensifier based computed tomography scanner and a tube source of X-rays are used for nondestructive evaluation, imaging of small objects for archaeological studies and conservation of works of art and micro analysis of soft materials. It consists of a charge coupled device (CCD) camera and an acquisition board. The CCD camera and the acquisition board allow image processing, filtration and restoration. The object is irradiated by an X-ray tube with a conical collimator and rotated on 180°. Projections are obtained at various angles as cross sectional image slices. A reconstruction program written in pascal is able to give the reconstruction matrix of the linear attenuation coefficients, simulates the matrix and related tomography. The flux emitted by the tube is filtered using the appropriate filters at the chosen optimum energy and reasonable monochromacy is achieved for all the images. Although X-ray imaging is a potential tool for strongly attenuating materials, the images of weakly attenuating materials provide new information to know about their structure and also the foreign body for the image reconstruction at an optimum value. The image of the plastic material which contains the internal defect is studied thoroughly at the optimum value in order to image the small objects for nondestructive testing, archaeological studies and conservation of works of art. The images are analysed using the profile data showing the internal defect of the object to obtain information at the optimum value. At the optimum value and with the aid of the tomographic image, the size and location of the defect could be ascertained. 相似文献