Extensive introduction of nondestructive inspection — an important method of increasing production quality

Conclusion The use of a programmed method and a systems approach to the treatment of the problem of increased product quality reveals that it is necessary to introduce extensively systems for ensuring the detection of defects which are based upon the solutions of a broad range of scientific-technical and organization problems. Among the problems there are, undoubtedly, standardization, unification, and the metrological security of the defect-detection facilities which are being created in the interests of all branches of the national economy and of science.Translated from Izmeritel'naya Tekhnika, No. 6, pp. 21–31, June, 1971.     

预应力T梁束孔管道压浆质量的无损检测试验研究

采用探地雷达技术、超声波透射法等多项技术方法对T梁的压浆质量进行试验性检测研究.首先采用超声波透射法在未压浆的钢束管道位置和正常混凝土位置（即避开波纹管位置）进行测试,然后将这两种类型的测试数据结果作为学习样本提供给神经网络进行学习;再将已压浆预应力T梁上的实测结果作为网络测试数据进行计算,根据神经网络的计算结果可预测钢束管道内的压浆质量,判断管道中是否有空隙存在.根据检测结果和开窗验证的情况来看,超声波透射法检测和神经网络的预测结果是准确可靠的,探地雷达技术不适合于T梁束孔管道的压浆质量检测.     

Microwave near-field nondestructive detection and characterization of disbonds in concrete structures using fuzzy logic techniques

This paper presents a near-field microwave nondestructive testing technique for disbond/crack detection and evaluation in a concrete structure backed by an infinite half space of any material. A model describing the interaction of waves radiated out from an open-ended rectangular waveguide, in the near-field, with any layered medium will be utilized. The theoretical model calculates the effective reflection coefficient of the structure, at the aperture of the waveguide, as a function of the frequency of operation, the thickness and dielectric properties of the layers of the structures, including the standoff distance. The frequency of operation and standoff distance (the measurement parameters) can be optimized to achieve maximum sensitivity to the presence of the disbond. The presence of a disbond in a structure is viewed as an additional layer and will change the properties of the effective reflection coefficient (phase and magnitude). This change will depend on the thickness and location of the disbond. This fact will be used to investigate the potential of utilizing multiple frequency measurements to obtain disbond location and thickness information. A fuzzy logic model relating the phase of reflection coefficient, frequency of operation, and standoff distance to the disbond thickness and depth was generated and utilized.     

Electromagnetic method and procedures of nondestructive inspection of the corrosion protection of underground pipelines

A triune mathematical model of an electromagnetic field is proposed, and procedures of fast noncontact inspection of underground pipelines are proposed. Methods and devices are developed for the determination of the distribution of cathodic protection current and the transition resistances of protective coatings in different sections of underground pipelines. The technology of integral, differential, and local inspections of main pipelines is described.     

Treatment of false calls in evaluating nondestructive inspection proficiency

A test designed to evaluate nondestructive flaw detection proficiency by ultrasonic and eddy current methods has been conducted. Test data for each participant are reduced to contingency table format, and analysis of these tables via traditional measures of association is used to rank individual performances. The presence of false calls in an inspection record introduces a random inflation in flaw detection results. Measures are required which compensate for that fact. Proficiency rankings based on two such measures, Somers'd coefficient and the mean square contingency coefficient, show reasonable consistency with intuition-based rankings by experienced observers. Finally, a weighted generalization of Somers'sd is suggested, although optimal selection of weights remains an open problem.     

混凝土试件的制作、养护、质量检查

介绍了混凝土试件的制作养护和质量检查步骤,为保证施工单位制作合格的混凝土试件,确保混凝土的工程质量符合设计要求,提供借鉴。     

Analytical model for tilted coils in eddy-current nondestructive inspection

The electromagnetic field and impedance of a cylindrical eddy-current probe coil are calculated analytically for arbitrary coil orientation above a conductive half-space. The remarkably simple closed-form expressions are provided as a function of coil tilt angle. The effect of tilt on the impedance change produced by a long crack is also investigated by combining the analytical model with an existing thin-skin theory for surface crack inspections. Results for both cracked and uncracked conductors are expected to be useful for evaluation of movement-generated noise in eddy-current inspections.     

Recommendations for estimation of quality of concrete in finished structures

The object of the present recommendations is to guide the engineer in the selection and the use of the procedures which he should adopt when he is required to estimate the quality of concrete in finished structures. Moreover, these recommendations are intended to provide a general background of the problems involved in this connection. It should be emphasized that the following recommendations are to be regarded as a guide only. They are not meant to be a “standard” or a “code of practice”. In this form, they may be expected to be of great value to engineers who are little familiar with this subject, and who might appreciate assistance in making their own judgements. The recommendations are accompanied with comments, which are set in italics.     

Eddy current nondestructive testing by a perturbation method

This paper presents an analytical solution for the change in impedance due to a flaw of rectangular cross-section in the case when the conductivity of the flaw is sufficiently close to the conductivity of the surrounding medium. The solution, which is found by the small perturbation method, is used to compute the impedance change as a function of the parameters of the flaw. An eddy current nondestructive method based on this consideration can detect the presence of such flaws and, in some cases, determine their size.     

GPR inspection of concrete bridges

Ground-penetrating-radar (GPR) has become an important method for the non-destructive testing of concrete bridges. Although there are standards and guidelines available today, the quality of results does not only depend on the object inspected but also on the qualification and experience of the team carrying out the radar survey. This situation is unsatisfactory for engineers that have to decide whether a radar survey is suitable to solve their problem.EMPA has been active in the field of non-destructive testing of concrete structures for more than ten years. During this time, procedures for efficient data acquisition, processing interpretation and reporting have been developed. In addition, a large number of concrete structures has been inspected for research and services.In a research project completed in 2005, radar inspections using the EMPA approach were carried out on bridges designated for demolition. Results were laid open before the bridges were taken down. After the demolition radar results were verified with the help of the bridge parts. Thus, the accuracy and reliability of radar surveys was quantified under realistic circumstances.     

钢筋混凝土框架结构弹塑性数值子结构分析方法

大型复杂土木工程结构在地震作用下失效破坏可能由部分关键构件严重损伤破坏导致,而大部分构件仍处于弹性或小变形状态。该类结构的地震损伤和破坏全过程分析涉及超大规模系统强非线性动力分析,目前尚缺乏能很好兼顾效率和精度的计算理论,基于此,该文提出一种新型高效且实用的弹塑性数值子结构理论和计算方法,将大型复杂结构系统的大规模非线性计算问题转化为整体结构适度规模的线弹性分析和数量与规模均较小的局部隔离子结构非线性分析,其中,线弹性整体结构刚度矩阵的集成及LU三角分解仅需进行一次,大大提高计算效率;少数屈服构件的子结构非线性分析采用精细化有限元模型或不同类型单元模型,精确模拟构件局部损伤破坏机理,有效提高结构整体的计算精度。最后通过对一榀平面钢筋混凝土框架结构进行地震动力弹塑性数值子结构方法分析,验证其高效性与精确性。     

二维自由振动的有限元线法自适应分析新进展

该文建立圆弧形曲梁裂纹的截面损伤缺陷比拟方案,实现裂纹大小(深度)、位置、数目的模拟。引入变截面Euler-Bernoulli梁的h型有限元网格自适应分析方法,求解含裂纹损伤圆弧曲梁弹性屈曲问题,得到优化的网格和满足预设误差限的高精度屈曲荷载和屈曲模态解答。数值算例表明该算法中网格非均匀加密可适应裂纹损伤引起的屈曲模态变化,应用于各类曲梁夹角和裂纹损伤分布工况下的弹性屈曲研究,定量分析了裂纹损伤程度对圆弧曲梁的屈曲荷载和屈曲模态的影响,检验了该文算法的精确性和可靠性。     

Acoustic resonance-multiplicative method in thickness measurement of extensive concrete building structures

Problems of acoustic monitoring of extensive concrete building structures are considered. The disadvantages of existing methods of measuring the thickness of concrete articles are demonstrated. A new resonance-multiplicative method is proposed that increases measurement accuracy and reliability. Results are provided for a test model of a thickness meter. __________ Translated from Izmeritel’naya Tekhnika, No. 5, pp. 15–18, May, 2008.     

Non-periodic inspection by Bayesian method I

This paper introduces a Bayesian analysis methodology to determine appropriate non-periodic inspection intervals of fatigue-sensitive structures, so that their reliability remains above a prespecified minimum level throughout their service life. Fatigue damage is considered to initiate in a structural element when cracks develop, whether or not they are detected. The fatigue process then continues by crack propagation, resulting in strength degradation. If a fatigue crack is detected during an inspection, the cracked component is assumed to be repaired or replaced with a new one, resulting in the renewal of its residual strength and fatigue characteristics and increasing thus the overall reliability of the structure. The Bayesian approach introduced in this paper is unique and novel in that it allows one to utilize judiciously the results of earlier inspections for the purpose of determining the time of the next inspection and estimating the values of several parameters involved in the problem that can be treated as uncertain. Numerical simulations verify the above-mentioned capabilities of the Bayesian method.     

The combined benefits of CPF and RHA in improving the durability of concrete structures

The work presented is a laboratory study of controlled permeability formwork (CPF) applied to concrete where cement was partially replaced (10%, 15% and 20%) with Portuguese rice husk ash (RHA). Portuguese rice husk is a by-product which may be incinerated industrially. Various tests were carried out to evaluate the durability of concrete made with RHA at 10%, 15% and 20% replacement of cement by weight and cast with both the usual formwork and CPF. Tests carried out so far, reported in this paper, concern strength, absorption by capillarity and chloride ion penetration. Results lead to the conclusion that CPF enhances concrete performance even further when using partial cement replacement by RHA.