Adhesive disbond detection of automotive components using first mode ultrasonic resonance

Adhesive bond inspection methods used in the aerospace industry are not suitable in the automotive industry, primarily owing to wide variations in adhesive thickness, and a requirement for couplant-free testing. This paper describes a robust technique for the detection of disbonds, based on the fundamental through-thickness resonance (mode 1) frequency of a joint. During testing, the mode 1 resonance is excited in the joint and the received signal is windowed, leaving the ringing of the first mode. If this resonance frequency falls into the range predicted for bonded joints based on the possible limits of adhesive thickness, then the bond integrity is confirmed; mode 1 resonance above the predicted frequency range indicates the joint is disbonded. Further investigation has shown that narrow beads of adhesive and tapered adhesive layers, which commonly occur in practice, do not affect the reliability of this technique. The development of a novel dry-contact dabber probe is also described, which comprises a low-loss rubber delay line with a highly attenuative rubber bonded to the side walls to eliminate side wall reflections. Results from prepared samples and automotive structures are then presented.     

超声相控阵声束控制特性分析

超声相控阵技术通过对超声阵列换能器中各阵元进行相位控制,获得灵活可控的合成波束,从而实现对整个检测对象的扫描。它具有可进行动态聚焦、可成像检测、可检测复杂形状物体等一些优点,近年来正成为国际无损检测领域的研究热点,并已经在医学和工业领域得到应用。在研究超声相控阵技术原理的基础上,建立了数字声束模型来分析线阵换能器参数对声束控制的影响,并用计算机软件进行仿真分析声束的偏转聚焦。通过这种方法,可以很清楚的了解超声相控阵声束控制特性。     

Analysis of plastic bending of adhesive-bonded sheet metals taking account of viscoplasticity of adhesive

The present authors proposed a new technique of plastic bending of adhesive-bonded sheet metals. In this process, large transverse shear deformation occurs in the adhesive layer, which in some cases would induce the geometrical imperfection (so-called ‘gull-wing bend’) and the delamination. Since the strength of the adhesive is highly rate-sensitive, the amount of shear deformation of the adhesive layer and, as a result, ‘gull-wing bend’, are strongly influenced by the forming speed. In the present work, the effect of forming speed on the deformation characteristics of adhesively bonded aluminium sheets was investigated by performing V-bending experiments with various punch speeds at room temperature. In order to discuss the effect quantitatively, the numerical simulations for the bending were also conducted using a rate-dependent constitutive model of plasticity for the adhesive. Consequently, it was found that the large shear deformation and ‘gull-wing bend’ are suppressed by high-speed forming since the deformation resistance becomes higher at high strain rate.     

Nano-multilayer Ti-Zr-N coating by a central configured multi-arc coating process

In this work, a novel arc ion plating (AIP) system, consisting of a centrally configured multi-arc source array (CCMA), is developed. This system is aimed to satisfy the present industrial demands for the large-scale production of multicomponent, multilayered, and superlattice coatings. The central array is made up of three flat, independently powered, arc sources. These form a triangular pillar.The newly developed CCMA AIP system is used to deposit TiN/ZrN coatings, in order to evaluate its performance. The surface hardness of the specimens is measured by micro Vickers indentation. A scratch test is used to determine the adhesive strength of the coatings. Scanning electron microscopy (SEM) is used to observe the cross-sectional morphology and to measure the film thickness. An energy dispersive spectrometer (EDS) is used to characterize film composition. The crystal structures of the coatings are characterized by an X-ray diffractometer and transmission electron microscope (TEM).The deposited coatings range from a micro- to nano-layered (TiN/ZrN) structure as the rotation speed of the substrate table was increased. Each layer exhibits a (111) preferred orientation. At rotating speeds in excess of 10 rpm, a nano-multilayered Ti(Zr)N structure is formed, again with each layer having (111) preferred orientation. At the highest rotation speeds the greatest surface hardness and film adhesion strength are attained. This is attributed to the maximized stress accommodation of the nano-multilayer structure, through the different shear elastic modulus of each layer. This research demonstrates that this novel CCMA AIP system is highly flexible in coating material design and capable of mass production.     

�޷�ֹܵij���������⼼�����豸

 无缝钢管的超声相控阵检测是近年兴起的一项无损检测技术。本文介绍了一种无缝钢管超声相控阵检测设备的技术原理、方法,构成和应用特点等。     

Development of micro co-axial diamond wheel-tool array using a hybrid process of electrochemical co-deposition and RWEDM technique

This study presents a novel hybrid technique for fabricating a multi-edged co-axial micro diamond wheel-tool array. The technique combines an electrochemical process with a RWEDM (Rotary Wire Electrical Discharge Machining) technique to precisely electroform a diamond wheel-blank and then produce a co-axial wheel-tool array. A duplex tank design, containing a mini-tank made of porous aluminium-dioxide material is developed for the electrochemical co-deposition of a nickel-based diamond matrix onto a cylindrical aluminium alloy substrate. Optimal conditions for the co-deposition are examined and tested in the production of the wheel-blank. A small RWEDM mechanism that uses permanent magnet tension braking to maintain wire tension and reduce wire vibration is also proposed. The RWEDM process is used for slicing, truing and dressing the grinding edges of the blank. Experimental findings and machining examples show that the proposed novel hybrid process can successfully fabricate a co-axial diamond wheel-tool with a grinding-edge array that has extremely thin high integrity cutting edges.     

Fabrication of biomimetic wet adhesive pads with surface microstructures by combining electroforming with soft lithography

Biomimetic adhesive pads, which include seta adhesive pads and wet adhesive pads, are compel-ling to be applied for a climbing robot. A novel approach for fabricating biomimetic wet adhesive pads with surface microstructures by combining electroforming process with soft lithography is proposed in this paper. According to the principle of wet adhesive of insects?? pads, the mechanism of wet adhesion is analyzed. Polydimethylsiloxane wet adhesive pads with surface microstructures with the width of 100 ??m and height of 25 ??m have been obtained experimentally. A series of testing experiments have been carried out to prove that microstructures on the surface of pads fabricated by the proposed technique can effectively improve the wet adhesive ability.     

Trockenchemische Vorbehandlung von Titan und Kunststoffen für das Kleben

Dry chemical pretreatment of titanium and polymers for adhesive bonding Titan alloys have to be pretreated to increase the adhesive bonding strength. Because of environmental reasons dry chemical pretreatment methods are preferred compared to wet chemical techniques. One successful method is a silicatisation referring to the ®Saco-technique. Layers generated by this method on titanium or polymer substrates lead to highly water-resistant adhesive bondings. Also adhesive joints of Ti with polymer show high bond strength when polymer and Ti are ®Saco treated. With a suitable optimization of the technological parameters it is possible to adhesively bond polymers also with anaerobic acrylic esters.     

射频等离子体改性PTFE表面液滴撞击接触起电对润湿性的影响∗

液滴撞击固体表面是自然界的常见现象，研究超疏水表面的液滴撞击对其润湿性的影响，对于超疏水性材料的潜在应用具有重要的科学意义。采用 3、10、20 min 氧等离子体处理（OPT）和 1 min 八氟环丁烷等离子体聚合沉积（PPD）的等离子体方法改性聚四氟乙烯（PTFE）表面，获得具有不同尺寸和间距的微 / 纳米锥的超疏水 PTFE 表面，研究射频等离子体改性 PTFE 表面的液滴静态接触角、滚动角及液滴撞击动力学行为，分析在不同个数液滴撞击后 PTFE 表面的润湿性和液滴撞击行为变化，确定 PTFE 表面液滴撞击起电效应的影响机制。结果表明：通过 1~9 个液滴撞击后，PTFE 表面的静态接触角随撞击液滴数量增加而减小，导致静态接触角低于 150°；液滴滚动角随撞击液滴数量增加而增大，造成液滴滚动角高于 10°。 撞击液滴的接触时间随撞击液滴数量增加而增大，回弹系数随撞击液滴数量增加而减小。随撞击液滴数量增加，回弹液滴的正电荷和 PTFE 表面的负电压增大，PTFE 表面的负电荷对液滴产生强吸引作用，导致低粘附超疏水性被破坏。3 min OPT 和 1 min PPD 改性 PTFE 表面的纳米锥间距小，密度大，表面负电荷量增加明显，造成 PTFE 表面的疏水性降低的程度最显著。 研究结果可为改善超疏水稳定性的表面织构设计提供理论依据。     

一种新型钢铁防锈(高分子)发黑剂的研制

采用有机高分子化合物及其他添加物,研制出了使用工艺简单、节水、节电、无污染的钢铁防锈发黑剂.论述了钢铁防锈(高分子)发黑剂的热聚合-沉积发黑方法与原理,并对膜层性能进行了检验.发黑膜层与基体结合力强、耐蚀性高、致密性好且色泽光亮,是一种理想的钢铁防锈发黑剂.     

Development of a multi-nozzle drop-on-demand system for multi-material dispensing

Besides its application in media printing, drop-on-demand (DoD) printing is becoming an attractive alternative to traditional micro-fabrication to build 3D structures with wide applications. In DoD printing, each type of nozzle (ejector) has its uniqueness and limitation in the dispensing material properties, driving parameters, and the ejected droplet dimension. This paper presents a multi-nozzle DoD printing machine to satisfy the increasing demand for multi-material dispensing in industry. On the hardware aspect, a microcontroller-based synchronizer is designed to synchronize the printing process from multi-nozzles with respect to a movable positioning stage. This real-time control contributes to accurate micro-droplet deposition. On the software aspect, a three-layer framework is proposed, including user interface, system manager, and hardware interface layer. This proposed structure greatly improves the system flexibility with which the user can dynamically configure the desired dispensers for 3D structure printing. Integrating these techniques into the printing system, the developed DoD system can achieve a flexible and friendly user interface, while dispensing a wide range of functional materials using various types of dispensing nozzles.     

Bonding strength in structural adhesive bonded joint

Adhesive bonding has emerged as a unique and highly developed joining process with applicability to a wide variety of engineering materials. Because the stresses of adhesive bonded joints are distributed much more uniformly than mechanical fasteners and many welds, they can be used to improve fatigue resistance and to join thin or fragile parts. This study is to investigate whether welding structure can be replaced by adhesive bonding as structural joints. The bonding strength was evaluated with the manufacturing factors of overlap length, overlap width, added pressure and surface treatment. These data provide bonding structure with design criterion and contribute to raising productivity and reducing in cost.     

Longitudinal mode magnetostrictive patch transducer array employing a multi-splitting meander coil for pipe inspection

Recently, a magnetostrictive patch transducer (MPT) by means of the highly magnetostrictive (such as nickel or iron–cobalt alloy) patch attached on the specimen has been applied in nondestructive ultrasonic testing in waveguides. In the study, we proposed a new MPTs array employing a multi-splitting meander coil (MSMC) for generating and receiving longitudinal guided waves in pipes. In the suggested configuration, the directions of the static magnetic field produced by the permanent magnets and the dynamic magnetic field produced by the MSMC are in the axial direction of the pipe. Two finite element models were established to simulate the distribution of the static and dynamic magnetic fields in the patch, respectively. The proposed MSMC was made of flexible printed circuit (FPC), so it could be easily installed on pipe surface. The performance of the proposed MPTs array was experimentally studied. Firstly, it was experimentally verified that the axisymmetric longitudinal guided wave mode, L(0,2), could be effectively generated and received in pipes with the developed MSMC-MPTs array. Secondly, the frequency response characteristics of the developed MSMC-MPTs array were related to D (the distance between adjacent belts of the MSMC). Thirdly, we demonstrated the ability of the developed MSMC-MPTs array for the identification and location of a crack defect in pipes. Finally, we compared the performances of the MSMC-MPTs array and conventional meander coil-MPTs and proved that the signals of the longitudinal guided wave mode could be enhanced by using the developed MSMC-MPTs array.     

A magnetic sensor array for spot welding quality monitor

Spot welding is affected by many factors and is difficult to monitor the nugget information with single sensor. In this paper, a new monitor system based on sensors array technique was developed for spot welding quality detection. The key part in the system is cross magnetic sensor array. It is composed of six magnetic sensors. An improved algorithm was proposed to extract the signal eigenvalue, which was based on principle component analysis. The results show that in the case of the 60 mm experiment, cross magnetic sensor array works well. And when the eigenvalues range of the cross magnetic sensor array is 0.090 1-0.098 2, the spots quality is good. The analysis of the eigenvalues of the cross magnetic sensor array allows us to determine whether the spot quality is good or bad.     

Development of a mobile fused deposition modeling system with enhanced manufacturing flexibility

Development of a flexible and mobile fused deposition modeling (FDM) system from an existing FDM system to enable deposition of material on virtually any surface without being confined to a build chamber is described. Flexibility of the system was demonstrated by depositing ABS on different surfaces, and simple pull tests were performed to determine bonding strength between the deposited materials. To develop the flexible FDM system, a Stratasys FDM 3000 machine was used and modified by reversing the z stage and attaching the x-y table controlling the FDM head to the bottom of the z stage. In this new configuration, the z stage transports the x-y table vertically, and the x-y table controls the x-y motion of the FDM dispensing head, which is exposed at the bottom of the machine. The mean of the absolute value of the difference between 49 part dimensions (based on 20 part features) measured on a modified Grimm test part (n = 5) was ∼0.44 mm for parts fabricated using the developed flexible FDM system, while a mean of ∼0.11 mm was measured using parts produced by the commercial system (n = 5). The dimensional accuracy of the flexible system was comparable but expectedly larger than the commercial system, due to the configuration of the flexible FDM system with the x-y table attached at the bottom of the z stage. There are many possible design improvements particularly focused on reducing deflections in the mechanical components that can be explored and implemented to improve the overall dimensional accuracy of the flexible system, but these investigations are left for future research. Instead, manufacturing flexibility of this new configuration was demonstrated by successfully building a cylinder on flat and 3D cupped surfaces, including building a horizontally oriented cylinder on a wall by orienting the FDM system in the horizontal position. Pull tests were performed and showed that bonding strength for the cylinders built on flat surfaces compared favorably to a glued part (3.06 ± 1.38 MPa for the specimens manufactured with the flexible FDM system compared with 2.00 ± 1.06 MPa for the glued specimens). Additional flexibility was demonstrated by printing directly on a complex curved surface, thus illustrating the possibilities for using AM (a traditional 2D layer-stacking processing technique) in conformal printing applications. It is concluded that this new machine can provide enormous flexibility in freeform manufacturing with applications in part repair, 3D conformal adhesive dispensing, and a number of applications where the removal of the size constraints imposed by the build chamber enables one to deposit new arbitrary features directly on existing parts.     

Nondestructive characterization of defects using a novel hybrid ultrasonic array sensor

The concept of a novel hybrid array transducer is introduced in this article. Based on the principles of dynamic beam steering and ultrasonic shadowing, a transducer consisting of an assembly of a linear phased array and a static array is developed. Using a dynamic pitch-catch configuration, the transducer is capable of determining the location, size and orientation of a planar defect without scanning or relocating the transducer. A theoretical shadow analysis carried out in this work allows for developing a scheme to characterize a single defect. To demonstrate the feasibility of the technique, a rail specimen with real defect has been assessed. This scheme proves to be a viable approach for characterizing transverse defects (TD) with good accuracy.     

Design philosophy of a bonded gear box

A new technique for manufacturing gear boxes is presented. The technique is based on the use of adhesive bonding as a replacement for the traditional methods of casting and welding. The philosophy of the design is to make use of the advantages of adhesives particularly for bonding different materials. This is because the novel technology of adhesive bonding allows dissimilar materials to be joined. The applicability of flexible manufacturing systems for the manufacture of the bonded gear box is also considered.     

超声相控阵技术应用于风电球墨铸铁件检测的研究

介绍了超声相控阵技术的工作原理及其相较于传统超声波检测技术的特点及优势,对现行的超声相控阵检测与球墨铸铁件的检测标准进行了归纳。通过在标准试块与铸件实物上的一系列试验,探索了超声相控阵技术应用于风电球墨铸铁件质量检测的方法,并编制了相应的探伤工艺规程。     

Measurement of the ultrasonic nonlinearity of kissing bonds in adhesive joints

This paper presents a study of the detectability of kissing bonds in adhesive joints using an ultrasonic inspection technique to measure nonlinearity. Kissing bonds are defined as adhesive bonding defects in which the adhesive and the substrate are not fully bonded together but are in some way connected, for example, through contact between disbonded surfaces or through coupling via a very thin layer of contaminant. The result is a region that exhibits reduced normal or shear stiffness and is difficult to detect using conventional non-destructive testing techniques. It is hypothesised that when an ultrasonic wave of large magnitude propagates through the kissing bond area, the system will behave nonlinearly. This hypothesis is the starting point for this paper, and it is tested by measuring the degree of nonlinearity exhibited by perfectly and imperfectly bonded specimens. Perfectly disbonded adhesive joints are tested over a range of compressive loads from an initial zero-load ‘open’ condition to a final highly loaded ‘closed’ condition and the degree of nonlinear behaviour measured. It is shown that adhesive joints exhibit significant nonlinearity under light compressive loads and that the level of nonlinearity decreases rapidly with compressive load. Good agreement is also observed between experimental results and a nonlinear spring model of the adhesive joint, based on its quasi-static interfacial stiffness.     

基于AD9273的超声相控阵检测系统设计

提出了一种基于AD9273的高集成度超声相控阵检测系统设计方案。在传统超声相控阵检测系统的基础上,利用新型高集成度芯片AD9273和HV748完成32通道高压发射电路和接收采集电路设计;采用FPGA子系统结合ARM平台的方式构成系统数字信号处理的核心;采用数字正交包络检波技术完成接收波束成形。系统满足探伤的实时、高速的要求。系统在小型化和数字化方面有显著提高,可为便携式超声相控阵检测系统设计奠定基础。