Non-destructive Testing Inspection Research Articles

Robotic Technology Enables Automated Nondestructive Weld Inspection in Subsea Zone

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 215588, “Automated Nondestructive Weld Inspection in Splash/Subsea Zone,” by Karsten Husby, Magnus Bjerkeng, and Jens T. Thieleman, SINTEF, et al. The paper has not been peer reviewed. _ Jacket structures all over the world are now reaching the limit of their estimated service life, but new discoveries and improved production methods require lifetime extension of the assets. The complete paper presents an automated underwater robot and a nondestructive testing (NDT) eddy-current probe for alternating-current field-measurement analysis of jacket main welds. This robot makes integrity testing, which often is required for lifetime extensions, possible. Introduction Jacket lifetime calculations are based on long service intervals. Some welded braces in the splash zone often are considered unserviceable because of the hostile environment. Thus, divers or remotely operated vehicles cannot be used under normal weather conditions and wave heights. Structural integrity is ensured with long service intervals, often long enough for the lifetime of the jacket. However, multiple jacket platforms are approaching their certified lifespan limit. The question, then, is whether they should be decommissioned, reused, or have their lifespan extended. New discoveries and improved production methods make extended operation desirable for certain fields. For other platforms, repurposing for offshore wind, aquaculture, or geothermal energy may be a cost-effective alternative. Regardless, before any action can be taken, the integrity of the jackets must be tested. There is, therefore, a growing need for subsea condition monitoring of aging offshore jacket steel platforms. To speed up operations and to handle complicated health, safety, and environment (HSE) issues in the splash zone, robots can be used. A robot for NDT inspection in the hostile splash zone is pictured in Fig. 1. The robot clamps itself to the circular braces and is equipped with 3D vision camera, kinematics algorithms, and an NDT probe. Integrity Testing Under Rough Conditions Testing for integrity of critical infrastructure often is performed by different NDT methods. In this study, eddy-current testing was chosen as the preferred method because it is fast and can penetrate layers of marine growth on the surface. The normal procedure is to use lightweight hand-held equipment. The splash zone, however, is often inaccessible under modern HSE standards. In this project, an automated NDT robot helped conduct efficient NDT testing for longer periods in challenging conditions. This robot offloads the NDT operator and makes testing more efficient.

FalconScan: A hybrid UAV-crawler system for NDT inspection of elevated pipes in industrial plants

Periodic non-destructive testing (NDT) of pipes and tanks is vital in industrial plants, such as Oil & Gas facilities, to proactively detect defects and corrosion before leaks and forced shutdowns occur. This paper presents a hybrid system, consisting of a UAV and a crawler, which enables detailed contact-based inspection of elevated pipes, in pursuit of eliminating the need for dangerous scaffolding and manual inspection to improve safety and reduce cost. Similar to avian animals, the UAV autonomously perches on the pipe to conserve energy. A small inspection crawling robot is carried by the UAV, and is subsequently released onto the pipe’s surface to inspect its health. The crawler uses magnetic wheels for agile mobility and houses an ultrasonic testing (UT) sensor to thoroughly scan the pipe and detect wall thinning, which is a precursor for leaks. Finally, the crawler re-docks with the UAV, which in turn detaches from the pipe to fly back home or inspect another pipe. The multi-robot system is designed for and tested on pipe diameters as small as 8 in.

Non-destructive evaluation and Structural Health Monitoring of impact induced damage in composite structures using ultrasonic approaches and shearography

Composite structures are massively used thanks to the high strength-to-weight ratio, making them ideal for lightweight and durable structures in aviation. However, Impact may arise at any time during lifetime on composite aerostructures and ensuring their structural integrity via fast inspection is essential to meet airworthiness criteria. Multimodal NDT (Non-Destructive Testing) inspection and characterization of composite structures is a critical process to verify the quality of the composite material and identify any defects. In this context, the paper shows a comparison of several techniques as nondestructive methods: shearography, laser ultrasonics and phased array ultrasonics. In particular, using shearography and laser ultrasonics as non-contact approaches can increase the inspection speed and reliability compared to the state of the art phased array ultrasonics, which is the standard approach used in the aerospace field. For this reason, a sample of interest to the aerospace industry is subject to different low velocity impacts which are characterized by different energies leading to barely visible damage. The results show the capabilities of both approaches in identifying small emerging defects along with the advantage and drawbacks of both methodologies through a critical review of performance thereof evaluating the parameters of their use. In addition, the same approaches are adopted on a stiffener composite plates and compared with continuous health monitoring approaches. In this regard, NDT approaches are demonstrated useful to enhance the SHM warnings.

3D Remote Assistance for NDT Inspections

In this work, we present a system architecture that is especially designed for remote ultrasound testing inspections (UT). The system itself is realized using a real-time session service and a web service based on a REST API (REST: Representational State Transfer; API: application programming interface). This web service is used to store data persistently, e.g., sample geometries, raw nondestructive testing (NDT) data and derived inspection results in a shared dataspace. In the current development state, the results consist of textures mapped onto the sample geometry. This approach allows us to display the UT results directly on the real sample using mixed reality technologies. We also implemented a feature to assist the inspector remotely by making use of the availability of this digital representation. Hence, it is necessary to share additional data like the current UT-signal, temporary position marks, user and device positions, etc. between the different participants. A real-time distribution of this highly dynamic data is required to create an effective assistance environment. Therefore, a separate session service is used. The inspection data generated in this temporary session can also be transferred to the afore mentioned dataspace to be saved persistently. The system features mixed reality visualization for the inspector and optionally a virtual reality or a 3D Desktop environment for one or more remote assistants.

Efficient Autonomous Path Planning for Ultrasonic Non-Destructive Testing: A Graph Theory and K-Dimensional Tree Optimisation Approach

Within the domain of robotic non-destructive testing (NDT) of complex structures, the existing methods typically utilise an offline robot-path-planning strategy. Commonly, for robotic inspection, this will involve full coverage of the component. An NDT probe oriented normal to the component surface is deployed in a raster scan pattern. Here, digital models are used, with the user decomposing complex structures into manageable scan path segments, while carefully avoiding obstacles and other geometric features. This is a manual process that requires a highly skilled robotic operator, often taking several hours or days to refine. This introduces several challenges to NDT, including the need for an accurate model of the component (which, for NDT inspection, is often not available), the requirement of skilled personnel, and careful consideration of both the NDT inspection method and the geometric structure of the component. This paper addresses the specific challenge of scanning complex surfaces by using an automated approach. An algorithm is presented, which is able to learn an efficient scan path by taking into account the dimensional constraints of the footprint of an ultrasonic phased-array probe (a common inspection method for NDT) and the surface geometry. The proposed solution harnesses a digital model of the component, which is decomposed into a series of connected nodes representing the NDT inspection points within the NDT process—this step utilises graph theory. The connections to other nodes are determined using nearest neighbour with KD-Tree optimisation to improve the efficiency of node traversal. This enables a trade-off between simplicity and efficiency. Next, movement restrictions are introduced to allow the robot to navigate the surface of a component in a three-dimensional space, defining obstacles as prohibited areas, explicitly. Our solution entails a two-stage planning process, as follows: a modified three-dimensional flood fill is combined with Dijkstra’s shortest path algorithm. The process is repeated iteratively until the entire surface is covered. The efficiency of this proposed approach is evaluated through simulations. The technique presented in this paper provides an improved and automated method for NDT robotic inspection, reducing the requirement of skilled robotic path-planning personnel while ensuring full component coverage.

Synchronism system for generating ultrasonic images of complex geometry pieces using industrial robots

This paper presents a synchronism system that has been designed to facilitate the generation of ultrasonic images of pieces with complex geometry through the use of industrial robots. Modern robotic manipulators and, more specifically, industrial robotic arms integrated with server computers, sensors and actuators have revolutionized the way automated non-destructive testing is performed. Currently there are commercial industrial robots that have the precision, speed and repetitiveness in their movements that make them suitable for use in numerous non-destructive testing inspections whose designs are carried out by small and medium sized specialized companies. Automatic ultrasonic inspection of complex parts remains one of the most difficult challenges according to the specific and increasingly exigent demands of the markets. The closed configuration of these complex robotic arms makes it difficult to maintain adequate synchronism between the movement of the robot and the acquisition of the data, making it difficult to generate ultrasonic images consistent with the geometry of the part. This is a serious problem in the inspection of aerospace components where high quality is necessary to assess the condition of the inspected component. In this paper, we present an autonomous independent external system that provides control signals to synchronize the ultrasound system with the robot trajectories without needing to access its position in real time. A methodology to obtain the timing pattern for a given part inspected with a given robotic system will also be presented here.

Double active thermographic inspection of additive manufacturing composites: numerical modelling and validation

This study investigates the Non-Destructive Testing (NDT) inspection of 3D-printed fibre-reinforced polymers, comparing the conventional Active Transient Thermography (ATT) technique with a novel variant known as Double Active Transient Thermography (DATT). Finite element models for the simulation of both inspection techniques are validated by evaluating two statistical measures to correlate the numerical results with the experimental responses. The thermal contrast obtained with DATT was approximately twice the one obtained with ATT, for all tested samples. Numerical models allowed an insight evaluation of the heat dissipation along the thickness of the specimens, specifically around the fibres and the defects. These validated numerical models evidenced a relevant tool to predict the results of thermal contrast and to optimize the inspection parameters.

A BIM-Based Approach for Pavement Monitoring Integrating Data from Non-Destructive Testing Methods (NDTs)

Monitoring of critical civil engineering infrastructures has become a priority for public owners and administrative authorities. Several laws and regulations have been issued on this topic, emphasizing the crucial role of Building Information Modeling (BIM)- based procedures for the design and management of civil infrastructures. This study aims at examining the potential of an interoperable and upgradeable BIM model supplemented by ground-based non-destructive survey data, such as Mobile Laser Scanner (MLS) and Ground-Penetrating Radar (GPR), for the analysis of the potential distresses identified in a transport infrastructure’s pavement. The main goal of the work is to implement an infrastructure management process that aims to reduce the limits associated with the separate observation of these assessments and to provide a more efficient way to store data regarding the status of a linear transport infrastructure, to the advantage of an integrated analysis. As on-site surveys are carried out, preliminary analyses on the condition of the inspected infrastructure are performed by relying on the information provided by Non-Destructive Testing (NDTs) inspections. Subsequently, a digital informative model capable of storing the data obtained by the surveys is generated, integrating both the MLS and GPR information to accurately represent the status of the infrastructure’s pavement in a three-dimensional environment. Data obtained from these instruments were used as the input for the digitalization process, making use of parametric digital elements capable of adapting their configuration to the information provided by the NDT surveys. As more analysis on the surveys’ results is carried out, potential distresses in the deep layers of the pavement are identified, and the information related to these elements is then integrated into the BIM model previously created. The process hereby described allows for an analysis of the three-dimensional configuration of the pavement, along with potential distresses and their location into the road’s superstructure. This digitalization process has shown promising viability for data management aimed at supporting asset managers in various management phases.

Non-Destructive Testing Inspection for Metal Components Produced Using Wire and Arc Additive Manufacturing

The wire and arc additive manufacturing (WAAM) process enables the creation and repair of complex structures based on the successive deposition of fed metal in the form of a wire that is fused with an electric arc and then solidifies. The high number of depositions required to create or repair parts increases the likelihood of defect formation. If these are reliably detected during manufacturing, timely correction is possible. However, high temperatures and surface irregularity make inspection difficult. Furthermore, depending on the size, morphology, and location of the defect, the part can be rejected. Recent studies have shown that non-destructive testing (NDT) based on different physical phenomena for the timely, reliable, and customized detection of defects can significantly reduce the rejection rate and allow in-line repair, which consequently reduces waste and rework. This paper presents the latest developments in NDT for WAAM and its limitations and potential.

Automatic Detection and Imaging of Rivet Hole Defects for Aircraft Structures With Optimized Sensor Array Using Eddy Current Method and Image Analysis

Fatigue cracking in riveted lap joints on aircraft could cause severe safety consequences in flight. The prior inspection for the integrity of the second layer of aircraft structure with rivet removed is necessary due to the priority of safety. Methods such as radiographic and ultrasonic testing are widely applied but require relatively expensive equipment, mechanical scanning or professional operators. Eddy current method can be adopted for non-destructive testing (NDT) inspection, which is safe and low-cost. In this paper, a hand-held eddy current (EC) sensor array was optimised based on sensitivity map analysis. The EC sensor array was used with a multi-channel EM instrument, which was capable of inspecting defects around the fastener locations covered by the head of rivets. A simulated sample of riveted joint with defects was examined with the eddy current sensing system and the collected data was processed by Hough Circle Transformation (HCT) and texture analysis. The analysis results could detect and locate fatigue cracks on the sample. The presented eddy current sensing system in this paper achieved an automatic, real-time, portable, convenient and accurate inspection method for defects in riveted joints.

Methodology for the Generation of High-Quality Ultrasonic Images of Complex Geometry Pieces Using Industrial Robots

Industrial robotic arms integrated with server computers, sensors and actuators have revolutionized the way automated non-destructive testing is performed in the aeronautical sector. Currently, there are commercial, industrial robots that have the precision, speed and repetitiveness in their movements that make them suitable for use in numerous non-destructive testing inspections. Automatic ultrasonic inspection of complex geometry parts remains one of the most difficult challenges in the market. The closed configuration, i.e., restricted access to internal motion parameters, of these robotic arms makes it difficult for an adequate synchronism between the movement of the robot and the acquisition of the data. This is a serious problem in the inspection of aerospace components, where high-quality images are necessary to assess the condition of the inspected component. In this paper, we applied a methodology recently patented for the generation of high-quality ultrasonic images of complex geometry pieces using industrial robots. The methodology is based on the calculation of a synchronism map after a calibration experiment and to introduce this corrected map in an autonomous, independent external system developed by the authors to obtain precise ultrasonic images. Therefore, it has been shown that it is possible to establish the synchronization of any industrial robot with any ultrasonic imaging generation system to generate high-quality ultrasonic images.

Machine learning-based defect characterization in anisotropic materials with IR-thermography synthetic data

Infrared (IR) thermography (IRT) is a non-destructive testing inspection technique widely used in numerous applications for void and defect detection in various materials such as fiber-reinforced composites. The IRT implementation requires solving the inverse heat transfer problem, i.e., calculating the defect attributes (e.g., shape, size, location) from a measured temporal and spatial surface temperature variation. This inverse problem, unlike its equivalent forward problem, is ill-posed and the uniqueness of the solution is not proven. To tackle this challenge, the k-nearest neighbors (k-NN) machine learning (ML) algorithm is employed to provide a model for predicting a penny-shaped defect size, thickness, and location in composite laminates. The study is based on simulations and synthetic data produced by ABAQUS finite element analysis (FEA) of the heat transfer model in defective composites to train the ML algorithm. The surface temperature vs. time and vs. distance diagrams are extracted from the FEA. The data diagrams are then used to extract the training features of the ML by considering the physics of the problem. This ML is trained by 502 FEA run data sets where firstly 10 features, and then 4 features, are selected from the mentioned FEA diagrams to predict the defect traits.

Terahertz non-destructive testing of power generator bars with a dielectric waveguide antenna

AbstractTerahertz technologies for non-destructive testing (NDT) are continuing to find their way into the industrial sector in the context of very specific inspection tasks. Part of this development is the capability to adapt terahertz systems in such a way that they can meet the sometimes harsh challenges and requirements of real-world industrial scenarios. One such scenario is the inspection of components with limited available measurement space. In particular, we show here the terahertz NDT inspection of the mica insulation of generator bars of turbogenerators at power plants, where an early on-site detection of defects and cracks in the insulation can be crucial, but where only few centimeters of space between adjacent bars are available. To address this problem, we have developed a measurement system combining a 100 GHz all-electronic terahertz transceiver with a low-loss dielectric waveguide antenna with 90 degree tip. We achieve sub-wavelength image resolution by scanning the waveguide antenna's tip over the surface of the generator bars in a near-field measurement setup. Employing a frequency-modulated continuous wave technique, we obtain depth-resolved, volumetric terahertz images of the objects under test. We discuss here the implementation and performance of the implemented measurement system for terahertz NDT inspection. keywords: terahertz, non-destructive testing, dielectric waveguides, frequency-modulated continuous wave, millimeter waves, power generators

What Is Probability of Detection?

Probability of detection (POD) evaluation is a widely accepted practice for quantifying the reliability of a nondestructive testing (NDT) technique. Inspections are often conceptualized and developed in laboratory environments, where factors affecting the inspection are highly controlled. However, when implemented in practice, NDT inspections suffer from many sources of variability, including changes from nominal geometry of the test piece, sensor variability, differences between operators, environmental effects on the sensor response including thermal and electromagnetic interference, and a myriad of other factors that are not present in the lab. Thus, to transition the NDT from the lab to production environments, engineers must have a quantified understanding of uncertainties. This is especially true for NDT systems that are implemented for safety-critical structures, where the life of the component may be managed with NDT. A fundamental question that must be answered in this context is: What is the largest discontinuity that could be missed when this NDT technique is implemented?

Air-Coupled Ultrasound Sealing Integrity Inspection Using Leaky Lamb Waves in a Simplified Model of a Lithium-Ion Pouch Battery: Feasibility Study.

Inspecting the sealing integrity of lead tabs is an important means of ensuring the reliability and safety of pouch-type lithium-ion (Li-ion) batteries with a thin multi-layered aluminum (Al) laminated film. This paper presents a new air-coupled ultrasonic non-destructive testing (NDT) inspection method based on leaky Lamb wave transmission; and reception for evaluating the sealing integrity between the lead tab and the Al pouch film. The proposed method uses the critical incidence angle between the air and the layer with the fastest Lamb wave velocity to maximize the signal-to-noise ratio in the through-transmission mode. To determine the critical incidence angle, phantom experiments with two test pieces (i.e., an Al tab and an Al tab sealed with an Al pouch film) are conducted. In addition, 2D scans are performed at various incidence angles for an inhouse pouch-type Li-ion battery with a 1-mm-wide foreign material inserted as a defect. At the critical incidence angle (i.e., 22°), the proposed air-coupled ultrasonic NDT method in through-transmission mode successfully identifies the shape and location of the defect through c-scan image reconstruction. These preliminary results indicate that the proposed air-coupled ultrasonic NDT method with leaky Lamb waves can be used to inspect the sealing integrity of Li-ion pouch batteries in dry test conditions.

The interface design of storage and examination system for BWR spent nuclear fuel dry storage demonstration project in Taiwan

Due to the lack of Boiling Water Reactor (BWR) fuel examination data after dry storage, Taiwan Power Company and Institute of Nuclear Energy Research jointly launched the “Taiwan Nuclear Fuel Storage Demonstration Project” to collect fuel characteristics data under simulated dry storage. To meet the project requirements, BWR fuel rods in different fuel designs will be selected and then store in simulated storage containers in different environments for 10 years. The interface considerations and design results of the auxiliary equipment for spent nuclear fuel storage, transfer, and non-destructive testing in the simulation stage of spent fuel dry storage were summarized. In addition, the possibility of operating at high heating power and avoiding deformation of the components due to thermal extension of the storage containers after heating was included in the design consideration. A simplification concept was introduced, with frequent NDT (Non-destructive Testing) inspections that will be performed through the spent fuel transfer process. The test results showed that the interface design can meet the requirements of long-term experiment, maintenance and radiation protection requirements, and is ready for further demonstration.

First insights into the human-related risks of tunnel inspection

Whereas human factors in the non-destructive testing (NDT) of metallic components are a poorly investigated topic (in comparison to other industrial fields such as aviation), human factors in the inspection of concrete components are even less known. Studies have shown that there is always some variability between individuals in their inspection results and that human factors affect the reliability of NDT inspections. And even though those human factors (the effects of and interaction between technology, organisation, environment, and individual characteristics) do not necessarily lead to negative inspection outcomes, their understanding is a vital step towards preventing possible structure-breaking failures and thereby ensuring the safety of industry, environment and infrastructure. To identify the possible human-related risks in the tunnel inspection, a systematic approach to risk management has been adopted. This involves identification of risks, their characterisation, and suggestions for risk treatment. In line with this approach, the inspections will be observed followed by interviews with inspectors to collect initial information about the inspections in the field and possible performance shaping factors. Furthermore, a human-oriented Failure Modes and Effects Analysis (FMEA) will be used to identify possible human-related risks throughout data collection and evaluation and to evaluate them with respect to their possible causes, consequences, the probability of their occurrence and with respect to existing and possible preventive measures. The results aim to increase our overall understanding of human factors related to NDT, provide first insights and understanding of human factors in tunnel inspection and suggest measures to prevent human error in that application.

Mobile Wall-Climbing Robot for NDT inspection of vertical concrete structures

Concrete structures, such as bridges or viaducts, play an important role in global road infrastructure. These types of structures are relatively expensive to build and they are susceptible to outer external influences, which in time deteriorate and lead to the reduction of their structural resistance. To reduce this effect, regular inspection is needed, which is often done manually by using specialized equipment to reach certain parts of bridges and viaducts. This process is both expensive and dangerous for the inspectors to conduct. Within the research project ASAP (Autonomous System for Assessment and Prediction of Infrastructure Integrity) in order to overcome these challenges, we have developed a prototype of a wall-climbing robot (WCR) for nondestructive testing (NDT). In this paper, different iterations of the developed WCR prototypes are presented. In four consecutive prototype designs, we have evaluated and upgraded the adhesion and locomotion system. Finally, a fifth prototype that carries the NDT equipment is presented. The final version of the WCR is equipped with robust and flexible adhesion that enables the robot to adhere to different types of surfaces. We have also addressed the challenges of integrating NDT equipment into the robot. To successfully conduct an inspection, besides the WCR, a safety system, control, and power systems are needed, which are further presented and discussed.

3D ultrasonic imaging of surface-breaking cracks using a linear array

Ultrasonic linear arrays have great potential to generate high-quality three-dimensional (3D) images by scanning the array. However, the generated images suffer from low resolution in the elevation plane, limiting the image quality for a reliable 3D Non-Destructive Testing (NDT) inspection. Although several ultrasonic imaging methods have been implemented to inspect different types of defects, there has been limited research to characterise surface-breaking cracks (SBCs) in 3D quantitatively. To improve the characterisation of surface-breaking cracks (SBCs), a 3D hybrid imaging method is proposed by combining the Half Skip Total Focusing Method (HSTFM) and the Synthetic Aperture Focusing Technique (SAFT) using a linear array. This paper proposed the implementation of an array with a reduced element length for full matrix capture (FMC) data acquisition. In conjunction with the hybrid imaging method, a reduced element array enables the utilisation of the information from a broad ultrasonic beam in the elevation direction to achieve improved image resolution. The imaging capability is assessed via a point spread function (PSF) as well as numerical simulations. From the PSF measurements, the image resolution is shown to improve with the smaller element length of the array, which is attributable to the combination of wide beamwidth and hybrid imaging method. Thereafter, experimental validation was performed with arrays of different elevation lengths, where an excellent match with the numerical results was observed. Furthermore, the crack sizing was performed using a 6-dB-drop rule, which assisted in accurately predicting the shape and size of the SBCs and is shown to measure the depth of SBCs with greater confidence. It is shown that a reduced array elevation with the hybrid imaging method and sizing method yields improved image resolution contrary to conventional linear arrays. This approach can offer a significant improvement in manifesting complete comprehension of the spatial defect relationship, enabling NDT engineers to analyse the inspection results quantitatively in 3D for progressive reliability.

Application of bird-strike verified analysis for the design of fast helicopter composite cowling

PurposeThe purpose of this paper is to describe the approach for the design of cowlings for a new fast helicopter from the perspective of airworthiness requirements regarding high-speed impact resistance.Design/methodology/approachValidated numerical simulation was applied to flat and simple curved test panels. High-speed camera measurement and non-destructive testing (NDT) results were used for verification of the numerical models. The final design was optimized and verified by validated numerical simulation.FindingsThe comparison between numerical simulation based on static material properties with experimental results of high-speed load shows no significant influence of strain rate effect in composite material.Research limitations/implicationsOwing to the sensitivity of the composite material on technology production, the results are limited by the material used and the production technology.Practical implicationsThe application of flat and simple curved test panels for the verification and calibration of numerical models allows the optimized final design of the cowling and reduces the risk of structural non-compliance during verification tests.Originality/valueNumerical models were verified for simulation of the real composite structure based on high-speed camera results and NDT inspection after impact. The proposed numerical model was simplified for application in a complex design and reduced calculation time.