Book Review

The effect of humid ageing on the bond strength of steel-steel cyanoacrylate bonds has been investigated. Such systems rapidly lose most of their bondstrength while under similar conditions polycarbonate-polycarbonate bonds remain virtually unaffected. This loss of strength can be attributed to the formation of an oxide layer at the substrate - adhesive interface and the simultaneous surface hydrolysis of the polymer. It nas also been shown that the adhesive itself is relatively impermeable to water and that the most likely method of ingress into the bond would be via a “wicking” mechanism along the substrate/polymer interface.     

Ultrasonic Guided Waves Scattering Effects From Defects in Adhesively Bonded Lap Joints Using Pitch and Catch and Pulse-Echo Techniques

In this article a method to evaluate defect dimensions in adhesively bonded lap joints based on the measurement of scattering effects of ultrasonic guided waves is presented. A simplified theoretical model is proposed which was initially tested in plates with through holes. The experimental results obtained using both pitch-and-catch and pulse-echo techniques for 500 kHz and 1 MHz frequencies confirm the validity of this model. To evaluate the lap joint defects, a set of samples with artificial defects were manufactured and the form and dimensions were confirmed using C-scan ultrasonic images. With the same methodology used in through-hole analysis, scattering effects of defects were measured. The results obtained with the pitch-and-catch technique with 1 MHz transducers allow us to say that an estimate of defect dimensions could be done by using the proposed model with reasonable accuracy and according with the predictions.     

超声导波检测管道缺陷的实验研究

介绍了超声导波在管道缺陷检测中的应用,并介绍了超声导波的检测原理。利用超声导波对管道缺陷进行检测,通过实验对缺陷回波和转换模态信号进行分析,即可达到对缺陷准确定位的目的。     

导波在石化企业高温管道腐蚀检测中的应用

超声导波检测应用的范围与导波激发的原理有关,根据高温管道的特点,选择采用磁致伸缩效应作为高温管道超声导波检测的激发原理。介绍了采用新型基于磁致伸缩效应的导波仪MsS 3030以高温管道的导波检测为例进行的现场检测,同时利用现场测厚验证导波检测的可靠性。结果证明,基于磁致伸缩效应的导波检测可以实现高温管道的在线检测,能有效发现腐蚀等面积缺陷,具有广泛的应用前景。     

The Non-destructive Testing of Adhesively Bonded Structure: A Review

The types of defect encountered in adhesive joints and the non-destructive testing techniques available to detect them are reviewed. Three types of defect: complete voids or dis-bonds, poor cohesive strength of the adhesive layer and poor adhesion between the adhesive layer and adherend are commonly present. It is shown that a variety of techniques is available for dis-bond and void detection, ultrasonics and sonic vibration being the most commonly used. The detection of poor cohesive and adhesive properties, however, is much more difficult than void and dis-bond detection and is the subject of current research. At present there is only one commercially available instrument which claims to predict cohesive strength. There is no reliable non-destructive test to detect poor adhesion.     

An Examination of Interfacial Failure in Adhesively Bonded Aluminum

It is commonly accepted that the strength of an adhesive bond can be affected by varying the substrate material, substrate surface treatment prior to bonding and the adhesive used in bonding. Although high initial bond strengths can be evaluated and developed relatively easily this area is not usually of major concern to the implementation of bonding technology. Of greater importance for structural bonding applications is the retention of this bond strength with time and the ability of the bonded interface to withstand the presence of defects. The precise nature of the interactions which govern these aspects of behaviour are not currently fully understood.     

超声导波技术在压力管道缺陷检测中应用的局限性

超声导波检测技术是一种新型的长距离、快速检测手段。对影响超声导波检测结果的诸多因素进行了分析。在管线运行的状态下,利用MsS导波技术可以进行长距离管壁腐蚀等缺陷的检测。但该技术无法定量给出缺陷的形状、大小和性质,且具有诸多局限性,因而该技术的应用宜结合其他无损检测方法进行复验确认。     

Effect of Nanoclay Incorporation on the Impact Properties of Adhesively Bonded Composite Structures

During manufacturing or service conditions, adhesively bonded composites are often subjected to impact. This impact may result in a reduction in strength and structural integrity of engineering components that are composed of adhesively bonded composite structures. The investigation of the degradation of strength of structural joints is, therefore, of paramount importance for their successful performance. Impact resistance of bondline in adhesively joined composites can be altered by the addition of nanoclay in the adhesive during fabrication of adhesive joints. In this study, impact test was carried out on graphite–epoxy composite panels bonded with nanoclay adhesive at different impact energies using drop-weight impact test equipment. Adhesive joints were fabricated by adding nanoclay in volume fractions of 1, 2 and 5% in the adhesive bondline. For comparison, plain adhesive joints were fabricated without nanoclay incorporation in the bondline. Impact testing was performed on these joints at 5, 10 and 20 J, to study the effect of inclusion of nanoclay in the epoxy adhesive. In order to determine the flexural load bearing capacity and stiffness reduction after impact, a three-point bending test was conducted on unimpacted and impacted specimens. The results showed that there was an improvement in impact capacity, however there was a reduction in flexural strength due to nanoclay incorporation.     

The Static Failure of Adhesively Bonded Metal Laminate Structures: A Cohesive Zone Approach

Adhesively bonded metal laminates are used in aerospace applications to achieve low cost, light weight structures in the aerospace industry. Advanced structural adhesives are used to bond metal laminae to manufacture laminates, and to bond stringers to metal laminate skins. Understanding the failure behaviour of such bonded structures is important in order to provide optimal aircraft designs. In this paper, the static failure behaviour of adhesively bonded metal laminate joints is presented. A cohesive zone model was developed to predict their static failure behaviour. A traction–separation response was used for the adhesive material. Three joint configurations were considered: a doubler in bending, a doubler in tension and a laminated single lap. The backface strains and static failure loads obtained from experimental tests were used to validate the results from finite element modelling. The models were found to be in good agreement with experiments.     

Influence of Thermal Spikes on the Ageing of Adhesively Bonded Structures - A Dielectric Study

Dielectric measurements are reported on epoxy bonded aluminium joints exposed to moisture at 75°C. The observed changes in the dielectric spectrum that occur with time of exposure are correlated with the variation in the mechanical strength. Certain joints were subjected to periodic cooling to -20°C to simulate the shock of aircraft flight. The effects of dehydration were examined for joints that had been exposed to moisture for a prolonged period of time. The data indicate that the initial hydration process lowers the glass transition temperature and the stress released creates micro-voids. Further ageing leads to hydroxide formation in the interfacial layer. Freezing of water during the thermal spike experiments induces cracking in the adhesive, and leads to greater water uptake. Plasticisation of the resin appears to be to a large extent reversible and dehydration allows some recovery of the bond strength. The shock cooling of the joints has only a relatively small effect on the ageing of the joints but does, however, produce differences in the dielectric data. This study illustrates the power of the dielectric technique for the assessment of ageing in adhesively bonded structures.     

长距离超声导波检测应用研究

介绍超声导波理论和传统超声做对比,分析其优缺点。针对不同的管线进行导波检测,从导波的角度出发,探讨超声导波检测技术在石油丁业的前景。     

导波检测技术在“抚-鲅”线上的应用

用导波技术对管道缺陷检测进入工业现场应用阶段。介绍了超声导波技术的发展历史及基本理论。表述了导波检测技术"抚-鲅"线缺陷检测中的具体应用过程,检测缺陷结论经现场观测验证准确。表明管道缺陷导波检测技术在"抚-鲅"线上的应用成功。并指出随着超声导波技术的发展,其在管道缺陷检测工程中将得到广泛的应用。     

压力管道超声导波检测技术的实验研究

介绍了超声导波检测技术在压力管道缺陷检测和安全评价方面的优势,采用纵向和扭转组合波对模拟管道进行实验研究,对比分析检测结果与实际的误差,验证Teletest系统对管道管段特征和缺陷的分辨性能和检测灵敏度。     

Effect of Ultrasonic Waves on the Saccharification Processes of Lignocellulose

The pretreatment and saccharification process of lignocellulose were subjected to ultrasonic waves to enhance the saccharification rate. The morphology, structure and crystal performance of the original and treated lignocellulose samples were characterized by SEM and FTIR. Moreover, the effect of different pretreatment methods on the structure of the raw materials and the influence of ultrasonic waves on the saccharification rate, were studied. SEM photographs show that the surface conformation of the granulated raw material is not changed, because the energy of the ultrasonic vibration is too low to cause changes to its structure. A FTIR spectrum shows that the ultrasonically assisted alkali pretreatment effectively destroys the intermolecular hydrogen bonding of lignocellulose and decreases its crystallinity. The catalytic efficiency of cellulase was increased by 70 % under ultrasonic treatment. Therefore, the ultrasonically assisted alkali pretreatment can improves the degradation rate of lignin and the saccharification rate of zymohydrolysis. The mechanism of the effect of ultrasonic waves on the enzymatic catalysis process is also discussed in detail.     

我国超声波处理污泥技术的研究进展

针对我国污水处理厂日趋增多,污泥产量大,处理费用高,污泥处置存在很多问题,阐述了污泥减量化的重要性.超声波处理污泥技术具有污泥减量效果好而且无污染的特点,同时对提高污泥活性,促进污泥消化、脱水以及用于处理污泥的联合效应中也有很好的效果,同时提出了超声波技术处理污泥存在的问题.     

Ultrasonic Evaluation of Adhesive Bonding

The capabilities of existing ultrasonic nondestructive evaluation (NDE) methods for the strength-related properties of bonds in structural components is reviewed. The severe limitations of conventional NDE methods in yielding quantitative results are indicated. Some recent results of a joint theoretical and experimental program of research using leaky Lamb waves (LLW) in laboratory specimens are presented. The LLW technique is shown to have several advantages over conventional techniques. Potential applications of the technique to determine non-destructively the quality of bonds in a variety of models are discussed.     

Ultrasonic Evaluation of Adhesive Bonding

The capabilities of existing ultrasonic nondestructive evaluation (NDE) methods for the strength-related properties of bonds in structural components is reviewed. The severe limitations of conventional NDE methods in yielding quantitative results are indicated. Some recent results of a joint theoretical and experimental program of research using leaky Lamb waves (LLW) in laboratory specimens are presented. The LLW technique is shown to have several advantages over conventional techniques. Potential applications of the technique to determine non-destructively the quality of bonds in a variety of models are discussed.     

超声导波检测技术在管道检验检测中的应用

介绍了应用于管道腐蚀检测的超声导波检测技术,并以检测案例来说明该技术在现场的应用情况.     

Detection of Disbonds in Multi-layer Structures by Laser-Based Ultrasonic Technique

Adhesively bonded multi-layer structures are frequently used, mostly in the aerospace industry, for their structural efficiency. Nondestructive evaluation of bond integrity in these types of structures, both after manufacturing and for periodic inspection during service, is extremely important.

A laser-based ultrasonic technique has been evaluated for non-contact detection of disbonds in aluminum multi-layer structures. Two configurations have been used to detect disbonded areas: pitch-catch with unidirectional guided wave scan and through-transmission with bidirectional scan. Guided wave scanning was done with a laser line source and air-coupled transducer sensing at 500 kHz, 1 MHz, and 2 MHz. Signals showed attenuation of the main frequency component and frequency shift on disbonded areas, whereas, a regular and standard waveform is seen outside disbonds. In through-transmission the longitudinal wave at normal incidence was monitored with a 1 MHz probe. One sample showed, besides the introduced inserts, other disbonded areas. After the ultrasonic measurements the sample was cut to visually check adhesive and interfaces.

The guided wave pitch-catch scan allowed fast inspection and quick indication of disbonded zones, while the through-transmission C-Scan provided better definition of defects but was slower and required access from both sides of the test part.     

磁致伸缩导波技术在工业管道腐蚀检测中的应用

介绍了磁致伸缩导波检测管道腐蚀缺陷的原理,并采用MsSR3030R导波检测系统对钢质常温压缩空气管道和高温水蒸汽管道(工作温度198℃)进行了现场在线检测。结果表明,该技术可以发现管道发生的腐蚀缺陷,并较为准确地确定其长度方向上的位置,但不能确定缺陷的性质,需要通过其他检测手段进行确认。同时,该技术现场检测的有效长度受到焊缝、支架、弯管等因素的影响较大。