Ramadan A. Esmaeel

Improvement of a Vibration-Based Damage Detection Approach for Health Monitoring of Bolted Flange Joints in Pipelines

Early detection of bolt loosening is a major concern in the oil and gas industry. In this study, a vibration-based health monitoring strategy has been developed for detecting the loosening of bolts in a pipeline’s bolted flange joint. Both numerical and experimental studies are conducted to verify the integrity of our implementation as well as of an enhancement developed along with it. Several damage scenarios are simulated by the loosening of the bolts through varying the applied torque on each bolt. An electric impact hammer is used to vibrate (excite) the system in a consistent manner. The induced vibration signals are collected via piezoceramic sensors bonded onto the pipe and flange. These signals are transferred remotely by a wireless data acquisition module and then processed with a code developed in-house in the MATLAB environment. After normalization and filtering of the signals, the empirical mode decomposition is applied to establish an effective energy-based damage index. The assessment of the damage indices thus obtained for the various scenarios verifies the integrity of the proposed methodology for identifying the damage and its progression in bolted joints as well as the major enhancements applied onto the methodology.

Computational simulation and experimental verification of a new vibration-based structural health monitoring approach using piezoelectric sensors

Detection of damage in vital and high-cost infrastructures has been one of the major concerns of operators of such structures in the past two decades. The growing demands in oil and gas have forced extraction of such vital fuels in deep waters. Bolted joints are widely used in pipes transporting oil and gas in deep waters. However, they do develop in-service problems, such as loosened bolts, which if remained undetected, could cause significant environmental damage and economical loss, especially in the case of pipes used in deep-water oil extraction. In this study, the energy damage index (EDI) calculated based on a novel vibration-based damage detection methodology using the empirical mode decomposition (EMD) is used to establish the existence of damage due to loosened bolts in common industrial bolted joints. A complete finite element (FE) model is established to simulate the whole process using the implicit dynamic solver of the commercial software ABAQUS©. Also, a comprehensive experimental program was designed and carried out to verify the FE results. Results show that the EDI based on the EMD method is a powerful tool for not only detecting the damage, but also the progression of the damage in bolted joints.

Stress Analysis of Tubular Adhesive Joints with Delaminated Adherend

The use of adhesive joints is becoming increasingly important in aerospace, automotive and other industries where the use of traditional fasteners is discouraged. When using composite adherends, the use of adhesively bonded joints is preferable rather than the traditional bolts and other types of fasteners, because they do not require holes, thereby removing the problems of stress concentrations around the holes. However, when using an adhesively bonded joint, there will be concentrations of the distributions of shear and peel stresses within the adhesive layer which should be controlled effectively. Therefore, the investigation of such stress variation has attracted many researchers. The aforementioned stress distributions become more complicated if the composite adherend contains a pre-existing delamination. Delamination is one of the most common failure modes in laminated composite materials; it can occur due to sudden impact by an external object, during the manufacturing process (e.g., during the filament winding process), or as a result of excessive stresses due to an applied load. It is clear that the existence of a delamination in any composite structure causes a reduction in its stiffness and in some critical situations, it may cause complete failure. This paper investigates the effect of delamination on the structural response of an adhesively bonded tubular joint with composite and aluminum adherends. The finite element method, using the commercial package ABAQUS, is used to conduct a parametric investigation. The effects of the delaminations spatial location, length, width, and the applied loading are studied. Results provide interesting insight (not necessarily intuitive) into the effect of an interlayer delamination on the stress distribution within the adhesive.

Application of a robust vibration-based non-destructive method for detection of fatigue cracks in structures

This paper presents the application of a novel vibration-based technique for detecting fatigue cracks in structures. The method utilizes the empirical mode decomposition method (EMD) to establish an effective energy-based damage index. To investigate the feasibility of the method, fatigue cracks of different sizes were introduced in an aluminum beam subjected to a cyclic load under a three-point bending configuration. The vibration signals corresponding to the healthy and the damaged states of the beam were acquired via piezoceramic sensors. The signals were then processed by the proposed methodology to obtain the damage indices. In addition, for the sake of comparison, the frequency and damping analysis were performed on the test specimen. The results of this study concluded with two major observations. Firstly, the method was highly successful in not only predicting the presence of the fatigue crack, but also in quantifying its progression. Secondly, the proposed energy-based damage index was proved to be superior to the frequency-based methods in terms of sensitivity to the damage detection and quantification. As a result, this technique could be regarded as an efficient non-destructive tool, since it is simple, cost-effective and does not rely on analytical modeling of structures. In addition, the capability of the finite element method (FEM) in mimicking the experiments, and hence for consideration as an effective tool for conducting future parametric studies, was also investigated.

Application of a simple and cost-effective method for detection of bolt self-loosening in single lap joints

One of the major advantages of bolted joints (BJs) over welded, riveted and adhesively bonded joints is the disassembling option. This option facilitates the manufacturing and transportation of large-scale structures that are commonly formed as assemblage of various large structural components. However, this option is not always problem free, in that, during the life cycle of such structures, the bolts used to fasten the joints may become loosened. Although several techniques have been developed to mitigate bolt self-loosening (BSL), nonetheless, development of a methodology for detecting BSL has consumed considerable attention in recent years. As a result, several researchers have been seeking simple and reliable methods for detecting bolt-loosening in BJs, without compromising their stability. In this study, piezoelectric sensors are used to collect the vibration signals of a laboratory-scale single lap joint, joining two steel plates with three bolts. The acquired signals are then processed using the empirical mode decomposition method and the energies of the respective signals are calculated. A recently developed effective method is then employed to establish the so-called energy damage index, evaluated based on the energy stored in certain modes of the collected signal, in both the damaged and healthy states of the system. This method is found to be quite effective in detecting bolt loosening and the progression of self-loosening.

Assessment of the Environmental Effects on the Performance of FRP Repaired Steel Pipes Subjected to Internal Pressure

The use of composite materials for repair and rehabilitation of corroded steel pipes has been increasingly growing in the oil and gas industry. However, there exists a noticeable gap in the literature on the long term performance of composite repaired pipes, especially those subjected to large internal pressure magnitudes. This work is an attempt toward filing the gap by gaining a better understanding of the effects of environmental conditions on the long term performance of composite repaired pipes subjected to large internal pressures. Finite element method (FEM) is used to simulate typical composite warp-repaired gouged steel pipes, conditioned in various environments and subsequently subjected to internal pressure. The influence of the resulting degradation in composite’s mechanical properties on the performance of the system was evaluated. To validate the results, an experimental program was designed and carried out. Repaired specimens were conditioned in an environmental chamber under certain thermal and moisture conditions; then, the specimens were tested to failure subject to internal pressure. Good correlation was obtained after fine tuning of FEM model’s material data through the use of the experimentally obtained data.

Experimental investigation of the effect of aging on perforated composite tubes under axial compressive loading

The use of fiber-reinforced polymer (FRP) composite materials in various applications such as aerospace, automotive, sport equipment, and oil and gas industries has been growing in a steady rate in recent years. The potential use of perforated FRP tubes (pipes) in oil and gas industry-related applications can become significantly greater, provided that the influence of the harsh environmental conditions specific to the industry could be tolerated by the materials used to form such tubes, with minimal degradation to system’s mechanical and physical properties. Unfortunately, there is not adequate database and information in the literature in regards to the long-term response of perforated FRP tubes. The purpose of this study is therefore to investigate whether FRP could be confidently used in structural applications that are primarily subjected to compressive loading and exposed to harsh environments, without significant deterioration of their physical and mechanical properties. For that, three sets of perforated glass fiber-reinforced plastic (GFRP) pipes were fabricated and subjected to accelerated aging conditions in an acid. Subsequently, the pipes were tested to failure under an axially applied compressive load. Results showed a considerable decrease in the load carrying capacity and axial stiffness of perforated pipes having certain D/t ratios, as a result of the aging.

Application of a Remote Health Monitoring System for Pipeline Bolted Joints

Early detection of bolt loosening is a major concern in the oil and gas industry. In this study, a vibration-based health monitoring strategy has been developed for detecting loosened bolts in pipeline. Both numerical and experimental studies are conducted to verify the integrity of the proposed method. Several damage scenarios for a bolted joint connecting two steel pipes (ASTM A53/A53M–07) are considered by simulating the loosening of the bolts through varying the applied torque on each bolt. An electric impact hammer is used to excite the pipe’s vibration in a consistent manner. The induced vibration signal is collected remotely via piezoceramic sensors bonded onto the pipe as well as the flange. The gathered vibration signals are transferred remotely to an in-house developed MATLAB code by a wireless data acquisition (DAQ) module. The data is processed with the embedded signal processing code, which incorporates normalization, filtering of data and the empirical mode decomposition (EMD) to establish an effective energy-based damage index. The assessment of the damage indices obtained for the damage scenarios verifies the integrity of the proposed methodology in identifying the damage and its progression in bolted joints.Copyright