Nondestructive Evaluation of Delaminations in Fresco Plaster Using Transient Infrared Thermography

Abstract

A transient method of thermal nondestructive testing is applied to detect subsurface delaminations in fresco plaster as a part of restoration work that is being conducted in Italy. A two-dimensional cylindrical model is used to estimate temperature distribution in materials with defects of various sizes and depths. The possibility of testing plaster with thickness up to 30 mm is illustrated. The choice of heating technique, which is supposed to be really nondestructive to ancient frescoes and powerful enough to create reasonable temperatures signals, is considered. Test duration and optimum sampling interval are discussed also. The structural noise of plaster and the influence of surface painting are investigated.     

纺织复合材料预制体成型过程无损检测技术研究进展

纺织复合材料多为各向异性材料,其力学性能很大程度上取决于成型后预制体内纤维的取向。为确保预制体成型后纤维的取向符合产品设计的要求,目前已有多种无损检测技术为纺织复合材料预制体成型过程及质量的检测提供服务。本文结合纺织复合材料预制体织造技术的发展趋势及预制体成型过程对无损检测的需求,就目前广泛用于科研和产业化生产当中的多种无损检测技术(包括接触式测量技术、光学检测技术、热成像检测技术、涡流检测技术、射线检测技术)进行了综述,总结各方法所具有的技术特点、应用情况与存在问题。最后,讨论了纺织复合材料预制体成型过程无损检测技术的发展趋势和面临的挑战。      

Zerstöurungsfreie Prüfung dünner CFK-Laminate mit innenliegenden Fehlern

Nondestructive Testing of thin CFRP-laminates with Internal Flaws Carbon fiber reinforced plastics (CFRP) are more and more used for primary aircraft structures. Therefore, nondestructive testing is of increasing importance for quality control and maintenance. Test specimens with different flaws show the accuracy by which even very small flaws in CFRP laminates can be detected when using ultrasonic (US) and X-ray-techniques. The US-measurements (C-scans) were effected by a highly resolving US-flaw detector. Details of the system and of testing methods are described. The C-scans are compared with X-ray evaluations. Internal flaws which cannot be found in a normal X-ray image due to X-ray absorption were filled with a contrast agent (TBE); afterwards they appeared very clearly on the X-ray film. A comparison of nondestructive tests and between nondestructive and destructive tests showed a good agreement.     

An overview of nondestructive evaluation methods

ondestructive evaluation is described as nondestructive testing (NDT), nondestructive inspection (NDI), and nondestructive examination (NDE). The activities associated with the evaluation include testing, inspection, and examination and primarily involve looking at (or through) and/or measuring some characteristic of an object. Frequently there is a desire to determine some characteristic of the object or to determine whether the object contains irregularities, discontinuities, or flaws. These examinations, inspections, or tests are used to determine the physical soundness of a material without impairing its usefulness. Nondestructive evaluation is a powerful tool that can help assure safety, quality, and reliability; increase productivity; decrease liability; protect the environment; and save money. In this article, nondestructive evaluation is represented by the acronym NDE.     

钢丝绳断丝检测仪器评估中标样制作方法研究

标准试样制作是钢丝绳无损检测仪器性能评估中的关键环节，其优劣决定了评估的效率和有效性。通过分析断丝检测流程、揭示影响仪器断丝检测能力的因素后，提出断丝配置的等相对差法和等绝对差法，比较了两者的适用性，等绝对差法对高精度仪器有效，等相对差法对低精度仪器有效。最后提出了评估中优选钢丝绳试样的方法。     

Improved synthetic aperture focusing technique by Hilbert-Huang transform for imaging defects inside a concrete structure

A useful nondestructive testing tool for civil engineering should immediately reveal defects inside concrete structures at the construction sites. To date, there are few effective methods to image defects inside concrete structures. In this paper, a new nondestructive testing method using elastic waves for imaging possible defects inside concrete is developed. This method integrates the point-source/point receiver scheme with the synthetic aperture focusing technique (SAFT) to increase functioning depth and enhance received signals. To improve image quality, received signals are processed by Hilbert-Huang transform (HHT) to get time-frequency curves for the SAFT process. Compared with conventional SAFT method processing with time-amplitude signals, this new method is capable of providing a better image of defects not only in the numerical simulation but also in the experimental result. The image can reveal the number of defects and their locations and front-end profiles. The results shown in this paper indicate that this new elastic-wave-based method exhibits high capability in imaging the defects of in situ concrete structures.     

Ein umfassendes Gerätesystem für die zerstörungsfreie,elektromagnetische Werkstoffprüfung. — Einflüsse auf das Prüfverfahren sowie die Möglichkeiten der Störgrößen-Unterdrückung

Equipment for nondestructive electromagnetic Testing A system of eddy-curvent-appliances for non destructive testing is presented to the export; it is to adapt for different demands in buildingblock fashion. The mode of operation is discussed; the possibilities of defect-discrimination and suppression of interference are demonstrated.     

无损检测固体表面、次表面不均匀性和缺陷的激光光热偏转技术

本文介绍非接触无损检测固体物质表面、次表面不均匀性和缺陷的激光光热偏转技术,设计并建立了测量装置。文中列出了对光学薄膜弱吸收率的测量,对碳素纤维材料、光学薄膜表面激光损伤和对金属材料次表面模拟缺陷的成像检测等一些应用的结果。     

铁磁材料硬度电磁检测模型

针对铁磁材料硬度无损检测问题，借助近代电磁理论，推导出含有复宗量贝塞耳函数的差动探头散射阻抗解析模型。将阻抗解析与铁磁材料硬度检测试验相结合，建立了用于钢轨硬度无损检测的电磁场数学模型，检测系统不确定度在1HRC范围内。     

Ultrasonic arrays for monitoring cracks in an industrial plant at high temperatures

A piezoelectric linear array structure has been designed to operate at temperatures up to 400 degrees C for nondestructive testing of steel components of a hot industrial plant. It is intended that these arrays be fixed permanently to the test subject so that known defects can be monitored by comparing measurements taken over a period of time without needing to shut down the plant. The arrays are used in pairs: the transmitter is a phased array producing a variable angle steered beam, and a second array is used for receiving. The defect can be identified from a series of scans collected from individual elements of the second array. A simple monolithic array structure was used, based on a single crystal of lithium niobate and operating in the frequency range 3 to 5 MHz. Prototype devices have 64 elements on a 0.5 mm pitch. Simulated defects in steel blocks have been scanned at high temperatures to illustrate the arrays' capability for nondestructive testing. The results suggest an accuracy better than 1 mm in finding the location of crack tips.     

利用近饱和磁化产生的巴克豪森效应测量铁磁件二轴应力

讨论了一种检测铁磁材料的内部应力的无损检测新技术。利用该技术,以近饱和磁化产生的巴克豪森效应与应力的关系,测量了铁磁构件的二轴应力和焊接构件的残余应力。检测结果与传统的Ｘ射线检测法的结果相一致。该检测技术在工程检测中有广泛的适用性。     

提高混凝土无损测强曲线拟合精度的措施研究

研究了提高混凝土无损检测测强曲线拟合精度的方法.提出,在最小二乘法的基础上,选用合适的函数形式,采用分段拟合,以相对误差最小为目标,消除异常值的影响或采用人工神经网络等方法,提高测强曲线拟合的精度.     

Models of the methods and instruments for the nondestructive testing of the hardness of articles

Models of the methods of nondestructive testing of the physical-mechanical properties of the materials of articles, for which integrated methods have limited application, are considered. The parameters of the amplitude-frequency characteristics obtained in instruments for the nondestructive testing of the hardness of articles are established on the basis of an analysis of the system of vibration-contact methods. __________ Translated from Izmeritel'naya Tekhnika, No. 1, pp. 27–30, January, 2006.     

On the application of moment methods to electromagneticnondestructive evaluation

The application of moment methods (MMs) to eddy-current testing problems for nondestructive evaluation (NDE) is considered. A general formulation for the MM that can be used to analyze NDE problems is derived, and calculated results and experimental data obtained from eddy-current testing of an artificially made sample are presented. Good agreement between the calculated results and the experimental data confirms the validity of the method and shows that the MM can be used as an alternative to the finite-element method (FEM) and the boundary-element method (BEM) in NDE     

材料的红外无损检测技术及其进展

目的　介绍材料的红外无损检测以及红外无损检测技术这一领域的最新进展 .方法　综述了材料的红外无损检测技术的理论基础和影响其测试精度的因素 ,以及国内外的进展 .结果与结论　红外无损检测技术可检测到其它检测技术所无法检测的区域 ,与其它检测技术有互补的作用 .作者综述了这种技术在近年来比较活跃的几个方面     

Current aspects of nondestructive materials testing

Conclusion Major tasks are formulated in mathematical physics as arising in nondestructive testing. Contemporary numerical and numerical-analytical methods are required. The position of mathematical simulation is defined in relation to the physical phenomena occurring in a general nondestructive test scheme.Karpenko Physicomechanics Institute, Ukrainian Academy of Sciences, L'vov. Translated from Fiziko-Khimicheskaya Mekhanika Materialov, No. 1, pp. 97–105, January–February, 1993.     

Infrared scanning thermography for a quantitative detection of cavities in a plane slab and a rectangular prism

An approach for treating nondestructive testing as the solution of inverse problems in mathematical physics has been used for the detection of cavities. The approach is developed based on the use of an additional boundary condition of scanned temperature on the surface to solve for the cavity geometry. For the present study, the condition at the cavity side is taken to be that of a specified temperature, and the experiment is carried out to meet this condition. Two specimens are tested in this paper, a plane slab and a rectangular prism. In both bodies the cavity is rectangular in shape. For the testing of the plane slab, the method is able to detect the cavity wall with high accuracy, whereas the cavity depth error is larger (6%). The detection of the cavity position in the rectangular prism has an error ranging from –9.7 to 7.7%. Errors in the experiment are attributed to the uncertainties in the measurements of temperature and the Biot number. The former is read off from the analog data output of the infrared scanner. The latter is not measured separately, but is computed from the scanned data and thus becomes a portion of the total nondestructive testing output. A final note is also made in this paper to relate how the presented method can be used in actual practice.     

无损检测技术在装备中的应用

无损检测技术对构成系统的部件进行检测，确保装备可靠性，避免损失，提高部队战斗力，节约经费。本文介绍了无损检测技术在装备硷测中的作用，以及现代无损检测技术的发展，介绍了红外热成像法、超声检测法、涡流法和磁检测法在无损检测中的应用，并阐明了各种方法的优劣及适用领域。