In-service Operation Research Articles

Investigation of multiple-stresses on mechanical and thermal properties of 9000 h Aged RTV-SiR composites for high-voltage insulation

Due to many advantages, polymer composite insulators have been extensively used for high-voltage (HV) transmission lines and substation insulations. The in-service operation, various environmental and electrical stresses degrade their mechanical and thermal characteristics. In this study, nine thousand-hour (9000 h) multi-stress (HV, heat, acid rain, salt fog, ultraviolet (UV) radiation, and humidity) accelerated lab-weathering evaluation of alumina-trihydrate (ATH) and silicon dioxide (SiO2) filled silicone rubber (SiR) composites were utilized. Moreover, to quantify the influence of multiple stresses over 9000 h lab-aging, the tensile strength, elongation at break, hardness, and thermal properties were evaluated and compared with the characterization results of neat (un-aged) composites. Winter and summer-aging cycles were designed in accordance with the actual service environment of Islamabad (Pakistan). Mechanical results of SiR blends showed a decrease in the tensile strength and the elongation at break (EAB), whereas the hardness increased over 9000 h lab-aging. The maximum deviation of ∼57.1% in tensile strength was found for hybrid samples (micro-ATH+ nano-Silica blend: SMNC), whereas the minimum change of ∼25.73% was exhibited by micro-silica-filled SiR specimen SMC3. Compared to neat blends, the maximum variation in EAB was ∼61% for a neat sample (SiR), whereas minimum change was noticed for SMC2 (of ∼31%) over 9000 h lab-aging. Additionally, after 9000 h lab-aging, the maximum (of ∼79.6%) and minimum (of ∼24.4%) variation in hardness was found for hybrid and SiR samples, respectively. Moreover, thermogravimetric (TGA) analysis showed that relative to neat samples, the thermal stability of aged specimens was decreased over weathering. Among aged specimens, only ATH filled samples (SMC1, SMC2) exhibited superior performance for a given temperature range (from 0°C to 900°C) by leaving a higher residual weight of ∼68.6% for SMC2. Hence to simulate and quantify the influence of environmental stresses over insulant performance, accelerated lab weathering can be adopted as an efficient tool.

Impact of dislocations and dislocation substructures on molten salt corrosion of alloys under plasticity-imparting conditions

Molten-salt-based energy-generation and energy-storage systems are expected to function under plasticity-imparting in-service operating conditions. It is thus of utmost importance to understand the effect of these operating conditions on the corrosion performance of molten-salt-facing structural alloys. Here, we investigate the impact of high-temperature creep on the molten salt corrosion of a NiMoCr alloy in FLiNaK molten salt. We show that high-temperature creep leads to an increased susceptibility of the alloy to molten salt corrosion via the development of a dislocation substructure, which promotes mass diffusion of alloying elements towards the salt–alloy interface (exposed surface). In addition, the corrosion-affected near-surface layer undergoes recrystallization leading to a significant increase in the amount of grain boundaries, which further promotes ongoing diffusion processes. This then causes increased molten salt corrosion attack resulting in an accelerated mass loss during the alloy’s exposure to the molten salt. The present results thus unambiguously highlight the importance of the state of the microstructure as well as the evolution of the microstructure under in-service operating conditions on the alloy’s molten salt corrosion performance.

Hinge joint damage identification method of soft yoke mooring system based on multibody dynamic modeling and structural monitoring data

Soft yoke mooring system (SYMs) is a single-point mooring system used in shallow water oil and gas development. In general, SYMs consists of mooring framework support, mooring legs, yoke, and single-point turret and it forms a multibody dynamic system with 13 hinge joint structures such as universal joints and thrust bearings. The hinge joint is one of the key components of SYMs; therefore, it is necessary to accurately evaluate the operating behavior of the hinge joints. In this study, real-time damage identification is conducted based on the multibody dynamic features of the SYMs. First, a long-term monitoring strategy for the prototype application is developed based on the multibody governing equations of the SYMs. The motion behaviors and stress state of the hinge joints and bodies are calculated using prototype monitoring data. A hinge joint damage identification based on the virtual moment is proposed by considering the changes in the friction coefficient in the damage state. The virtual moment method is used to transform the damage identification problem of the SYMs into a problem of seeking the optimal solution to the dynamics identification function. Genetic algorithm (GA) is implemented to seek the optimal solution of the friction coefficient of each hinge joint. A large-scale model testing system of the SYMs is established to perform the damage identification of the bottom hinge joints of the SYMs. The results show that the proposed method can effectively identify the damage degree and position of the hinge joints of the SYMs and provide a real-time warning system for the in-service operation of the SYMs.

Sensing for aerospace combustor health monitoring

Purpose This paper proposes new methods of fault detection for fuel systems in order to improve system availability. Novel fault systems are required for environmentally friendly lean burn combustion, but can carry high risk failure modes particularly through their control valves. The purpose of the developed technology is the rapid detection of these failure modes, such as valve sticking or impending sticking, and therefore to reduce this risk. However, sensing valve state is challenging due to hot environmental temperatures, which results in a low reliability for conventional position sensing. Design/methodology/approach Starting with the business needs elicited from stakeholders, a quality functional deployment process is performed to derive sensing system requirements. The process acknowledges the difference between test-bed and in-service aerospace needs through weightings on requirements and maps these customer requirements to systems performance metrics. The design of the system must therefore optimise the sensor suite, on- and off-board signal processing and acquisition strategy. Findings Against this systems engineering process, two sensing strategies are outlined which illustrate the span of solutions, from conventional gas path sensing with advanced signal processing to novel non-invasive sensing concepts. While conventional sensing may be feasible within a test cell, the constraints of aerospace in-service operation may necessitate more novel alternatives. Acoustic emission (detecting very high frequency surface vibration waves) sensing technology is evaluated to provide a non-invasive, remote and high temperature tolerant solution. Through this comparison, the considerations for the end-to-end system design are highlighted to be critical to sensor deployment success in-service. Practical implications The paper provides insight into different means of addressing the important problem of monitoring faults in combustor systems in gas turbines. By casting of the complex design problem within a systems engineering framework, the outline of a toolset for solution evaluation is provided. Originality/value The paper provides three areas of significant contributions: a diversity of methods to diagnosing fuel system malfunctions by measuring changes fuel flow distributions, through novel means, and the combustor exit temperature profiles (cause and effect); the use of analytical methods to support the selection (types and quantities) and placement of sensors to ensure adequate state awareness while minimising their impact on the engine system cost and weight; and an end-to-end data processing approach to provide optimised information for the engine maintainers allowing informed decision-making.

Bearing Health Monitoring Based on the Orthogonal Empirical Mode Decomposition

Bearing is a crucial component of industrial equipment, since any fault occurring in this system usually affects the functionality of the whole machine. To manage this problem, some currently available technologies enable the remote prognosis and diagnosis of bearings, before that faults compromise the system function and safety, respectively. A system for the in-service monitoring of bearing, to detect any inner fault or damage of components and material, allows preventing undesired machine stops. Moreover, it even helps in performing an out-monitoring action, aimed at revealing any anomalous behaviour of the system hosting bearings, through their dynamic response. The in-monitoring can be based on the vibration signal measurement and exploited to detect the presence of defects in material. In this paper, the orthogonal empirical mode decomposition is analysed and tested to investigate how it could be effectively exploited in a lean in-service monitoring operation and remote diagnosis. The proposed approach is validated on a test rig, where an elementary power transmission line was set up. The activity highlights some main properties and practical issues of the technological implementation, as well as the precision of the Orthogonal Empirical Mode Decomposition, as a compact approach for an effective detection of bearing faults in operation.

서비스 운행 중인 도시철도차량 피로수명 평가기법 연구

도시철도 차량과 같은 장수명 구조물은 서비스 기간 중 부식 및 반복되는 피로하중에 의해 점차 차체의 강성이 저하되는 노화 현상이 발생 된다. 강성저하로 인한 하중진폭의 증가는 차량의 피로손상을 가속화시켜 안전운행을 저해할 수 있기 때문에 노화를 고려하여 잔존 서비스 기간 중 충분한 안전성을 입증할 필요가 있으며, 이를 위해 피로수명 평가가 수행되고 있다. 피로하중을 받는 일반 구조물의 잔존수명평가는 Miner의 선형누적손상이론을 기반으로 하며, BS 7608, AWS D1-1 등의 규격에서는 이를 위한 용접부의 S-N 선도를 제시하고 있다. 최근에는 철도전용 규격으로 prEN 17149 규격이 준비되고 있다. 그러나 이러한 절차는 초기 설계시 전체 피로수명을 평가하기 위한 것으로 사용 중 잔존수명을 평가하기 위한 절차는 제시되어 있지 않다. 본 연구에서는 사용 중 철도차량 차체의 잔존수명을 평가하기 위한 연구의 일환으로 부식에 의한 차체강성 저하와 BS 7608, AWS D1-1 및 prEN 17149 규격의 S-N 선도특성을 비교하였으며, 현재의 하중이력을 바탕으로 제작초기의 상태를 고려하여 총 수명을 예측할 수 있는 방안을 제시하였다.

Stereological Evaluation of Precipitates within Ferrite Grains in Heat-Treated 1.25Cr0.5Mo Steel Previously Exposed to Service

The objective of this work was to study the effect of the heat treatment and further operation aging on the stereological parameters (size, quantity and volume fraction) of precipitates within ferrite grains of a creep-resistant 1.25Cr0.5Mo steel after long-term operation. The heat treatment was similar to the treatment that is carried out in industrial steam pipelines after welding (post weld heat treatment - PWHT) during installation and/or repairing. The operation aging corresponds to a subsequent long in-service operation after repairing. To determine the stereological parameters, SEM digital images were taken from samples of this material after conditions of in-service-aged (after long-term operation), in-service-aged and heat-treated (simulating repairing) and in-service-aged, heat-treated and in-laboratory aged (simulating subsequent long-term operation after repairing). The results indicate that the changes in the stereological parameters of the precipitates within ferrite grains after PWHT is associated with the coarsening process of the within-ferrite-grain precipitates as well as stabilizing the microstructure, since the material aging after PWHT of an in-serviced aged material would not change the stereological parameters.

Nonlinear ultrasonic inspection of smart carbon fibre reinforced plastic composites with embedded piezoelectric lead zirconate titanate transducers for space applications

Carbon fibre reinforced plastic composites used in spacecraft structures are susceptible to delamination, debonds and fibre cracking that may arise during manufacturing, assembly or in-service operations (e.g. caused by debris impacts in near-Earth orbital spaceflights). Therefore, in situ and real-time health monitoring is necessary to avoid time-consuming and unsafe visual inspections performed either on-ground or during extra vehicular activities. In this article, a recently created ‘smart’ carbon fibre reinforced plastic composite structure with embedded piezoelectric lead zirconate titanate transducers was used to detect multiple areas of artificial delamination and real impact damage of different size using nonlinear ultrasound. The electrical insulation of embedded piezoelectric lead zirconate titanate transducers was achieved by interlacing a dry layer of woven glass fibre fabric between the sensor and the carbon fibre reinforced plastic plies before curing. Damage detection was successfully demonstrated using both second harmonic generation and nonlinear modulation (sidebands) of the measured ultrasonic spectrum. The material nonlinear response at the second harmonic and sidebands frequencies was also measured with a laser Doppler vibrometer to validate the nonlinear ultrasonic tests and provide damage localisation. Experimental results revealed that the proposed configuration of embedded piezoelectric lead zirconate titanate transducers can be utilised for on-board ultrasonic inspection of spacecraft composite parts.

Collision derailments on bridges containing ballastless slab tracks

Train derailment on bridges is an infrequent event, yet when it occurs, it's usually catastrophic. These incidents can toss-out part of the derailed train from the bridge deck and collapse whole or a part of the bridge. Understanding the derailment mechanisms of trains on bridges and identifying the dynamic characteristics of bridges subjected to the impact of the derailed train is fundamental to minimising severities of these incidents. This paper presents the formulation of a train-track-bridge interaction model for predicting the response of bridges under in-service operation and post-derailment behaviour. The model is used to illustrate the collision induced derailment mechanisms of a passenger train travelling on a box girder bridge; the effect of impact due to the derailed train to the dynamic response of the bridge is also narrated. The nonlinear behaviour of the train-track-bridge system under derailment impacts is detailed through the sensitivity of the wheel/rail contact and the suspension components of the train as well as the parameters of the slab-track. It is shown that the risk of the derailed vehicles being tossed out of the slab-track bridge is high although the bridge deformation and bending moment are low.

High Temperature Oxidation of Zircaloy-4 Under Conditions Simulating a Loss of Cooling Accident in Spent Fuel Pools Examined with Raman Imaging and 18O Tracer Techniques

Since the Fukushima accident, an increased attention is continuously paid to the vulnerability of the Spent Fuel Pools (SFPs). In SFPs, for different reasons, degradation of the fuel rods induced by oxidation in air-steam mixtures after dewatering is a major safety concern: (i) the cladding material is the only barrier left against fission product dissemination, (ii) the heat released by the oxidation reactions can overcome the residual decay heat of the fuel and may become the main driving force to the accident escalation, (iii) hydrogen production is a strong concern because of the presence of steam, (iv) presence of air in the atmosphere is known to be an aggravating factor because of the “catalytic” role of nitrogen on the oxidation mechanism. In this study, high temperature oxidation tests in oxygen, air and air - steam atmospheres were performed with Zircaloy-4 cladding tubes and plates specimens. Because spent fuels are concerned, the presence of the corrosion oxide scale formed in reactor during in-service operation was also considered. The tests described in this study were restricted to the 700 – 950°C range, and mostly performed at 850°C. Raman imaging was used to examine the specimens after the oxidation tests, either directly at the oxide surface, or on metallographic preparations for cross-section examinations. We first used new opportunities given by Raman imaging to analyze, at least qualitatively, the structural and mechanical phenomena involved in this particular corrosion phenomena. Indeed, this method can provide information on the nature of phases that are present in the scale and on the stress level with sub-micron spatial resolution. The different methods used to extract this information that is present in the Raman data will be described and discussed. Moreover, isotopic substitution was also considered. Actually, Raman spectroscopy has also the ability to quantitatively extract the 18O distribution in a zirconia oxide scale after a two stage experiment with a fair accuracy. Raman imaging gave clear evidence for different characteristic distributions of 18O in the scales. Some of them have been correlated with the development of cracks and porosity in the oxide which allows the corroding medium to penetrate locally in the scales. Nitrogen appears to have no or limited influence on the oxygen diffusion, but is observed to reach the metal/oxide interface much faster than oxygen. Thus, we also emphasize the potential of this method to investigate the 18O distribution in such complex corrosion scales.

Partial Discharge in Nanofluid Insulation Material with Conductive and Semiconductive Nanoparticles.

This study provides a thorough investigation of partial discharge (PD) activities in nanofluid insulation material consisting of different types of nanoparticles, which are conductive and semiconductive when subjected to high voltage stress is presented. Nanofluids have become a topic of interest because they can be an alternative to liquid insulation in electrical apparatus due to their promising dielectric strength and cooling ability. However, during in-service operation, PDs can occur between conductors in the insulation system. Therefore, this study presents the behavior of PDs within nanofluid dielectric materials consisting of conductive and semiconductive nanoparticles. The results show that there is an improvement in the PD resistance and a reduction in the tan delta of nanofluids at power frequency after the incorporation of conductive or semiconductive nanoparticles in the nanofluid oil. However, the most suitable concentration of conductive and semiconductive nanoparticles in the base fluid was found to be, respectively, 0.01 g/L and 1.0 g/L at PD inception and PD steady-state conditions. The clustering of nanoparticles in a nanofluid suspension due to PD activities is also discussed in this study.

Research on management strategy of coordination behavior of task conflicts in in-service thermal power unit operation based on big data modeling

With the development of the internet and information technology, the in-service thermal power unit is facing more challenges, and the innovation of the operation and management mode of the in-service thermal power unit is urgent and necessary. From the perspective of work conflict, this paper constructs a multi-objective genetic algorithm, which introduces big data modelling technology into the management innovation of in-service thermal power units. The algorithm solves the relationship between various operating entities in active thermal power units through functions. In order to get the optimal solution for vehicle distribution. Firstly, the contingency theory is introduced into the innovative design scheme of the in-service thermal pow?er unit information system to optimize the management decision-making distribution path in the big data environment, design the multi-objective genetic algorithm steps, construct the non-dominated set, and combine the target cross-variation operations. The genetic sub-categories are jointly derived, and then the relationship between the parties in the management and decision-making innovation management activities of the in-service thermal power units is solved. The experimental results show that the shortest running time of the algorithm during the experimental operation is 0.56 seconds, and the longest running time is 2.48 seconds. The average running time in the whole process is less than 1 second, which meets the actual demand. The genetic algorithm can help the in-service thermal power unit. Reasonable arrangements for managing the delivery route of the decision-making fleet. The research in this paper has implications for the management innovation of in-service thermal power units in the information environment, and further expands the application field of big data modelling, which has practical significance.

Chemical state and atomic scale environment of nickel in the corrosion layer of irradiated Zircaloy-2 at a burn-up around 45 MWd/kg

Zircaloy-2 is used as fuel cladding in commercial boiling water reactors (BWR). A limiting factor for fuel longevity is the waterside corrosion of the cladding during in-service reactor operation and associated hydrogen pickup to the alloy. It is well known that the alloying elements (such as Cr, Fe, Ni etc.) including intermetallic precipitates (also termed as SPP) distribution influences both the oxidation process and hydrogen uptake evolution in this material. This paper reports an experimental investigation on the atomic scale microstructure of nickel-containing intermetallic particles with an emphasis on the oxidation and nickel-dissolution of SPP, and a combined experimental and computational study of solute nickel located in the corroded zirconium oxide microstructure. An irradiated cladding sample, taken from a BWR fuel rod, was prepared for the analysis using electron probe microanalysis (EPMA) and synchrotron-based micro-beam X-ray techniques (μXRF, μXRD and μXAS). The results show that the Ni-bearing SPP in the oxide layer are neither fully dissolved nor entirely oxidized at the given burn-up of the sample investigated. Conversely, all solute nickel present in the corroded layer is mostly oxidized and has an apparent homogeneous Ni2+ distribution. By analyzing the μXAS spectra measured at the Ni absorption edge, we have obtained quantitative structural information about both irradiated SPP and the Ni coordination environment in the corrosion layer. There exists strong structural disorder in intermetallic Ni-bearing SPP as also evidenced by μXRD study. The basic structure away from SPP in the oxide area is composed of oxidized nickel atoms adjacent to oxygen vacancies. Finally, first-principles density functional theory (DFT) calculations have been used to discern the nickel speciation in zirconium oxide microstructure that is complementary to the multitude of experimental information. From this joint theoretical and experimental approach, significant insights into the structural specificity of Ni2+ ions in monoclinic ZrO2, electronic factors governing the electron transport processes in the corrosion layer, and the apparent influence of nickel on the hydrogen ingress behavior in Zircaloy-2 are obtained.

Estudo de filas e análise qualitativa do desempenho de um restaurante universitário

Verificar o desempenho de operações em serviço pode auxiliar na indicação de oportunidades de melhoria dessas operações. Neste contexto, o presente artigo tem o objetivo de verificar em uma escala de 0% a 100% o nível de serviço de uma operação de produção (restaurante universitário) segundo cinco objetivos de desempenho: qualidade do serviço, qualidade do produto, flexibilidade do produto, custo do produto e desempenho do sistema de filas. Para alcançar o objetivo proposto, estruturou-se um procedimento composto por quatro etapas. Essas etapas envolvem (1) a definição do local de aplicação e suas características, (2) a coleta de dados quantitativos em campo e definição das características operacionais da fila, (3) a definição e a coleta de dados qualitativos em campo e tabulação desses dados, além da (4) análise dos dados qualitativos e características operacionais da fila. De um modo geral, a qualidade do serviço, a qualidade do produto e a flexibilidade do produto se destacaram com baixo nível de insatisfação. No caso do desempenho do sistema de filas, há oportunidade de melhoria, pois o tempo real médio de espera é superior ao tempo que os respondentes acham adequado para esperar na fila. Outro ponto de melhoria é o custo do produto, com redução ideal deste valor em 33%, segundo os respondentes.

Real-Time Evaluation of the Dynamic Loading Capability of Indoor Distribution Transformers

With the integration of the renewable energy-based distributed small power plants, whose generated energies are uncertain, in addition to the increasing usage of the charging stations for electric vehicles, the determination of the dynamic loading of distribution transformers appears to be crucial. Therefore, the issues of the model-based online monitoring of distribution transformers may achieve acceptance, if a cost–benefit compromise is reached. In this paper, a new thermal model is proposed to calculate the top-oil temperature of indoor distribution transformers using calculated tank temperature which accounts for convection, radiation, conduction, and ventilation heat transfer phenomena. The model is validated using measurements during the in-service operation of two indoor distribution transformers. Moreover, a method for calculating the loading capability of indoor distribution transformers without sacrificing the transformer's life is presented which can be easily adjusted for other distribution transformers. Furthermore, the results of the hardware implementing the proposed model and method for a model-based online assessment of the loading capability during the in-service operation of an indoor distribution transformer are presented.

Data-Driven Analysis of Ultrasonic Inspection Data of Pressure Tubes

Pressure tubes are critical components of CANDU reactors and other pressurized heavy water–type reactors because they contain the nuclear fuel and the coolant. Manufacturing flaws as well as defects developed during in-service operation can lead to coolant leakage and can potentially damage the reactor. The current inspection process of these flaws is based on manually analyzing ultrasonic data received from multiple probes during planned, statutory outages. Recent advances in ultrasonic inspection tools enable the provision of high-resolution data of significantly large volumes. This highlights the need for an efficient autonomous signal analysis process. Typically, automation of ultrasonic inspection data analysis is approached by knowledge-based or supervised data-driven methods. This work proposes an unsupervised data-driven framework that requires no explicit rules or individually labeled signals. The framework follows a two-stage clustering procedure that utilizes the Density-Based Spatial Clustering of Applications with Noise density-based clustering algorithm and aims to provide decision support for the assessment of potential defects in a robust and consistent way. Nevertheless, verified defect dimensions are essential in order to assess the results and train the framework for unseen defects. Initial results of the implementation are presented and discussed, with the method showing promise as a means of assessing ultrasonic inspection data.

Dynamic Loading in High-Speed Ball Bearings

The numerical dynamic model of a ball-bearing with angular contact and oil lubricant, which allows to study movement of the bearing parts, having six degrees of freedom, is developed. The general parameters, characterizing loading of bearing retainer, are analyzed. The influence of general structural parameters of several ball-bearings on in-service operation conditions of their retainers is analyzed.

Fatigue behaviour of additively manufactured polylactide (PLA)

Additive manufacturing (AM) is a group of fabrication techniques through which materials are joined, usually layer upon layer, to make objects from three-dimensional virtual models. Owing to its unique features, this disruptive technology is set to transform the way designers across all engineering disciplines engage with manufacturing. Since this fabrication process affect the way materials behave under static, dynamic and time-variable loading, it is evident that the mechanical performance during in-service operation of AM materials must be studied in depth in order to effectively de-risk their usage in situations of engineering interest. Not only by running appropriate experiments, but also by re-analyzing a number of data sets taken from the literature, the present paper investigates the influence of raster orientation as well as of non-zero mean stresses on the fatigue behavior of AM polylactide (PLA). PLA is biodegradable polymer that can be 3D printed easily and at a relatively low cost. As far as objects are manufacture flat on the build plate, the results being obtained suggest that: (i) the effect of the raster direction can be neglected with little loss of accuracy; (ii) the presence of non-zero mean stresses can be modelled effectively by simply using the maximum stress in the cycle.

In-service operating conditions affecting on weld HAZ hardness for API5L Gr.B pipe steel maintenance.

This study aims to investigate the influences of in-service welding conditions on maximum HAZ hardness, namely heat input, pipe wall thickness, and medium flow rate. The research consists of two parts; computationally thermal analysis and actual welding experiments. In conclusion, it suggested that increasing heat input resulted in decreasing maximum HAZ hardness, as well as, the range of run pipe thickness in the experiment was insignificantly influenced on HAZ hardness. Additionally, the higher flow rate induced more HAZ hardness with a certain flow rate level. HAZ hardness between the sleeve plate and the run pipe was insignificantly different. Nevertheless, it indicated that HAZ hardness prediction via computational analysis was more conservative than experiments.

Elastic-plastic fracture analyses for misaligned clad pipeline containing a canoe shape surface crack subjected to large plastic deformation

Offshore pipelines are subjected to large plastic deformation during the reeling stage or in-service operation. These pipelines are joined together by a welding process, and defects and weld misalignment are frequently introduced into the pipelines, posing tremendous challenges to the integrity of these pipelines. In this study, the fracture responses of misaligned clad pipeline containing a canoe shape surface crack located in weld centre line (WCL) and fusion line (FL) were investigated using 3-D elastic-plastic finite element (FE) analyses. The influences of crack depth ratio, crack length to perimeter diameter ratio and centerline offset ratio on the crack tip opening displacement (CTOD) were analyzed in detail. The relationship between the CTOD and the global strain (εg) was built up, and a linear relationship was observed for εg ranging from 0.6% to 2%. The fracture assessment equation of British Standard (BS) 7910 predicted an over-conservative result in comparison with that obtained by FE analyses. Therefore, a new strain-based failure assessment curve was developed to assess the fracture behaviour of misaligned clad pipeline subjected to large plastic deformation.