Glass fiber-reinforced polymers (GFRPs) have received increasing attention in recent years due to their overall performance of light weight, low cost and corrosion resistance, and they are increasingly used as reinforcement in concrete structures. However, GFRP material has low elastic modulus and linear elastic properties compared with steel bars, which introduces different bonding characteristics between bars and concrete. Therefore, a reliable monitoring method is urgently needed to detect the bond slip in GFRP-reinforced concrete structures. In this paper, a piezoceramic-based active sensing approach is proposed and developed to find the debonding between a GFRP bar and the concrete structure. In the proposed method, we utilize PZT (lead zirconate titanate) as two transducers. One acts as an actuator which is buried in the concrete structure, and the other acts as a sensor which is attached to the GFRP bar by taking advantage of machinability of the GRRP material. Both transducers are strategically placed to face each other across from the interface between the GFRP bar and the concrete. The actuator provokes a stress wave that travels through the interface. Meanwhile, the PZT patch that is attached to the GFRP bar is used to detect the propagating stress wave. The bonding condition determines how difficult it is for the stress wave traveling through the interface. The occurrence of a bond slip leads to cracks between the bar and the concrete, which dramatically reduces the energy carried by the stress wave through the interface. In this research, two specimens equipped with the PZT transducers are fabricated, and pull-out tests are conducted. To analyze the active sensing data, we use wavelet packet analysis to compute the energy transferred to the sensing PZT patch throughout the process of debonding. Experimental results illustrate that the proposed method can accurately capture the bond slip between the GFRP bar and the concrete.

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Real-Time Monitoring of Bond Slip between GFRP Bar and Concrete Structure Using Piezoceramic Transducer-Enabled Active Sensing.

This issue was proposed and organized as a means to present recent developments in the field of non-destructive testing of materials in civil engineering. For this reason, the articles highlighted in this editorial relate to different aspects of non-destructive testing of different materials in civil engineering, from building materials to building structures. The current trend in the development of non-destructive testing of materials in civil engineering is mainly concerned with the detection of flaws and defects in concrete elements and structures, and acoustic methods predominate in this field. As in medicine, the trend is towards designing test equipment that allows one to obtain a picture of the inside of the tested element and materials. Interesting results with significance for building practices were obtained.

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Non-Destructive Testing of Materials in Civil Engineering.

Interfacial imperfection detection for steel-concrete composite structures using NDT techniques: A state-of-the-art review

Abstract The paper describes experimental and numerical results of quasi-static splitting tensile tests on concrete specimens at meso-scale level. The experiments were carried out on cylindrical specimens with the diameter of 0.15 m. The loading strip was made of plywood or steel. Fracture in concrete was detected at the aggregate level by means of three non-destructive methods: 3D X-ray micro-computed tomography, 2D scanning electron microscope and manual 2D digital microscope. The discrete element method was used to directly simulate experiments at the meso-scale. Concrete was modelled as a random heterogeneous 4-phase material composed of aggregate particles, cement matrix, interfacial transitional zones and macro-voids based on micro-tomographic images. Two-dimensional calculations with real concrete microstructure were carried out. The effect of the different loading/supporting strip type on the stress-strain curve and fracture process was studied. This effect proved to be significant. A satisfactory agreement between numerical and experimental results was achieved. The evolution of contact normal forces, coordination number, broken contacts, grain rotations and crack displacements was also investigated. In addition, each energy component was calculated and analyzed at a different stress-displacement stage.

Experimental and numerical investigations of concrete behaviour at meso-level during quasi-static splitting tension

Structural adhesive joints have numerous applications in many fields of industry. The gradual deterioration of adhesive material over time causes a possibility of unexpected failure and the need for non-destructive testing of existing joints. The Lamb wave propagation method is one of the most promising techniques for the damage identification of such connections. The aim of this study was experimental and numerical research on the effects of the wave frequency on damage identification in a single-lap adhesive joint of steel plates. The ultrasonic waves were excited at one point of an analyzed specimen and then measured in a certain area of the joint. The recorded wave velocity signals were processed by the way of a root mean square (RMS) calculation, giving the actual position and geometry of defects. In addition to the visual assessment of damage maps, a statistical analysis was conducted. The influence of an excitation frequency value on the obtained visualizations was considered experimentally and numerically in the wide range for a single defect. Supplementary finite element method (FEM) calculations were performed for three additional damage variants. The results revealed some limitations of the proposed method. The main conclusion was that the effectiveness of measurements strongly depends on the chosen wave frequency value.

Wave Frequency Effects on Damage Imaging in Adhesive Joints Using Lamb Waves and RMS

Adhesive bonding has become increasingly important in many industries. Non-destructive inspection of adhesive joints is essential for the condition assessment and maintenance of a structure containing such joints. The aim of this paper was the experimental investigation of the damage identification of a single lap adhesive joint of metal plate-like structures. Nine joints with different defects in the form of partial debonding were considered. The inspection was based on ultrasonic guided wave propagation. The Lamb waves were excited at one point of the analyzed specimen by means of a piezoelectric actuator, while the guided wave field was measured with the use of a laser vibrometer. For damage imaging, the recorded out-of-plane vibrations were processed by means of the weighted root mean square (WRMS). The influence of different WRMS parameters (i.e., the time window and weighting factor), as well as excitation frequencies, were analyzed using statistical analysis. The results showed that two-dimensional representations of WRMS values allowed for the identification of the presence of actual defects in the adhesive film and determined their geometry.

/pdf/damage-imaging-in-lamb-wave-based-inspection-of-adhesive-3son154btc.pdf

Damage Imaging in Lamb Wave-Based Inspection of Adhesive Joints

Characterization of fracture process in polyolefin fibre-reinforced concrete using ultrasonic waves and digital image correlation

Monitoring the curing process of epoxy adhesive using ultrasound and Lamb wave dispersion curves

https://mostwiedzy.pl/pl/publication/download/1/interpolation-methods-in-gpr-tomographic-imaging-of-linear-and-volume-anomalies-for-cultural-heritag_44276.pdf

Erwin Wojtczak

Papers

Damage Imaging in Lamb Wave-Based Inspection of Adhesive Joints

Wave Frequency Effects on Damage Imaging in Adhesive Joints Using Lamb Waves and RMS

Characterization of fracture process in polyolefin fibre-reinforced concrete using ultrasonic waves and digital image correlation

Monitoring the curing process of epoxy adhesive using ultrasound and Lamb wave dispersion curves

Interpolation methods in GPR tomographic imaging of linear and volume anomalies for cultural heritage diagnostics