Assurance Of Structural Integrity Research Articles

Structure Design and Strength Analysis of the Glass Reinforcement Plastic (GRP) Malay Traditional “Perahu Bedar”

The Perahu Bedar, a traditional fishing boat in the Terengganu region of Malaysia, has been historically crafted from Cengal wood. In response to challenges posed by wood scarcity and limitations in skilled craftsmen, this study pioneers the exploration of Glass Reinforced Plastic (GRP) as a novel alternative material for constructing the traditional Perahu Bedar, measuring 4.32 meters in length. Through a rigorous analysis, the research delves into the structural design intricacies and strength attributes of the GRP Perahu Bedar, marking a significant departure from conventional wood-based construction methods. The study conducts a comprehensive analysis of the structure design and strength characteristics of the GRP Perahu Bedar. The weight, buoyancy force, and load distribution along the boat are analyzed. The data shows varying weight and buoyancy forces along the stations, with positive load values indicating upward forces contributing to buoyancy and negative load values representing downward forces. This analysis provides insights into the boat’s stability and distribution of forces. The sheer force and bending moment along the Perahu Bedar are evaluated. The sheer force values gradually increase or decrease along the boat, while the bending moment is highest at the midsection and decreases towards the ends. These results indicate the distribution of forces and stress on the boat’s structure, aiding in understanding its integrity and stability. The Factor of Safety (FoS) analysis demonstrates a FoS value of 2.2368, indicating a safety margin greater than 1. This suggests that the GRP Perahu Bedar design meets safety requirements and can withstand applied 
 
 stresses without exceeding yield strength. The FoS value provides assurance of structural integrity and safety during normal operating conditions. In summary, this study underscores the groundbreaking potential of Glass Reinforced Plastic (GRP) as a viable alternative to traditional wooden Perahu Bedar due to very high cost of Cengal Wood (wood that been used to build Peahu Bedar). By meticulously analyzing critical factors such as weight, buoyancy, load, shear force, bending moment, and Factor of Safety (FoS), the research offers invaluable insights into the structural integrity and safety aspects of GRP Perahu Bedar. These revelations not only herald a new era of sustainable and cost-effective boatbuilding practices but also serve as a crucial step towards safeguarding and perpetuating the rich maritime heritage of the region.

Aircraft Structural Design and Life-Cycle Assessment through Digital Twins

Numerical modeling tools are essential in aircraft structural design, yet they face challenges in accurately reflecting real-world behavior due to factors like material properties scatter and manufacturing-induced deviations. This article addresses the potential impact of digital twins on overcoming these limitations and enhancing model reliability through advanced updating techniques based on machine learning. Digital twins, which are virtual replicas of physical systems, offer a promising solution by integrating sensor data, operational inputs, and historical records. Machine learning techniques enable the calibration and validation of models, combining experimental inputs with simulations through continuous updating processes that refine digital twins, improving their accuracy in predicting structural behavior and performance throughout an aircraft’s life cycle. These refined models enable real-time monitoring and precise damage assessment, supporting decision making in diverse contexts. By integrating sensor data and updating techniques, digital twins contribute to improved design and maintenance operations by providing valuable insights into structural health, safety, and reliability. Ultimately, this approach leads to more efficient and safer aviation operations, demonstrating the potential of digital twins to revolutionize aircraft structural analysis and design. This article explores various advancements and methodologies applicable to structural assessment, leveraging machine learning tools. These include the utilization of physics-informed neural networks, which enable the handling of diverse uncertainties. Such approaches empower a more informed and adaptive strategy, contributing to the assurance of structural integrity and safety in aircraft structures throughout their operational life.

Continuous baseline update using recurrence quantification analysis for damage detection with guided ultrasonic waves

For the safe operation of vehicles and full utilization of lightweight materials, assurance of structural integrity is a prerequisite at all times. Structural health monitoring with permanently installed transducers offers a great advantage for primary load-bearing structures of all means of transportation and other safety-relevant components such as hydrogen tanks: allowing damage detection during operation. One means to detect internal defects is the method of guided ultrasonic waves (GUWs), which can be generated and recorded by piezoelectric transducers. GUWs propagate along the elongated dimension of a structure, and a transducer network can completely cover and monitor structures. Defects can alter the signal along affected paths and allow for their detection. However, a challenge and obstacle for the application of such a testing technique in the service of means of transportation is the large influence of temperatures. These influences are difficult to distinguish from the effect of defects. One approach to overcome this difficulty is the “continuous baseline update”. Recurrence quantification analysis is tested and compared to established features as a new approach to “continuous baseline update” in this paper. Publicly available GUW data (http://www.openguidedwaves.de/) recorded under varying temperature conditions have been used to show how the methods perform. They reliably separate temperature and damage effects, while the recurrence quantification analysis yields the best results.

A probabilistic method for structural integrity assurance based on damage detection structural health monitoring data

The value of using permanently installed monitoring systems for managing the life of an engineering asset is determined by the confidence in its damage detection capabilities. A framework is proposed that integrates detection data from permanently installed monitoring systems with probabilistic structural integrity assessments. Probability of detection (POD) curves are used in combination with particle filtering methods to recursively update a distribution of postulated defect size given a series of negative results (i.e. no defects detected). The negative monitoring results continuously filter out possible cases of severe damage, which in turn updates the estimated probability of failure. An implementation of the particle filtering method that takes into account the effect of systematic uncertainty in the detection capabilities of a monitoring system is also proposed, addressing the problem of whether negative measurements are simply a consequence of defects occurring outside the sensors field of view. A simulated example of fatigue crack growth is used to demonstrate the proposed framework. The results demonstrate that permanently installed sensors with low susceptibility to systematic effects may be used to maintain confidence in fitness-for-service while relying on fewer inspections. The framework provides a method for using permanently installed sensors to achieve continuous assessments of fitness-for-service for improved integrity management.

Estimation of Damage Thickness in Fiber-Reinforced Composites using Pulsed Thermography

Nondestructive testing (NDT), including active thermography, has become an inevitable part of composite process and product verification, post manufacturing. However, there is no reliable NDT technique available to ensure the interlaminar bond integrity during composite laminate integration, bonding or repair where the presence of thin air gaps in the interface of dissimilar polymer composite materials would be detrimental to structural integrity. This paper introduces a novel approach attempting to quantify the damage thickness of composites (the thickness of air gaps inside composites) through a single-side inspection of pulsed thermography. The potential of this method is demonstrated by testing on three specimens with different types of defect, where the Pearson correlation coefficients of the thickness estimation for block defects and flat-bottom holes are 0.75 and 0.85, respectively. This approach will considerably enhance the degradation assessment performance of active thermography by extending damage measurement from currently two dimensions to three dimensions, and become an enabling technology on quality assurance of structural integrity.

Effect of cross section on B2 stress index for Nuclear Pipe Bends subjected to Closing Bending

Nuclear piping components have been designed against plastic loads using the guidelines provided by section III, NB-3652 of Boiler & Pressure vessel code, ASME. For safe operation in the power plants, the structural integrity assurance of pipe bends is essential. The B2 stress index is used in the design equation for evaluating the primary stresses due to moment loading in the piping components. The code based B2 stress index is expressed in bend characteristic only. In real practice, consideration of bend angle, bend radius, nominal pipe thickness, and material properties of the pipe bends are needed. This paper presents a detailed investigation of the combined effects of variable wall thinning and ovality on B2 stress indices for pipe bends under closing moment using three dimensional finite element nonlinear analyses. Twice elastic slopemethodology (TES) was employed to get the collapsing moment from load deflection curve drawn for each model. From finite element analysis, it is observed that, the wall thinning produces a negligible effect on the B2 stress index, whereas the ovality produces significant effect.

Ultrasonic phased array examination of circumferential weld joint in reactor pressure vessel of BWR

The weld joints in the reactor pressure vessel (RPV) of Boiling Water Reactors (BWR) are required to be examined periodically for assurance of structural integrity. Ultrasonic phased array examination technique has been developed in authors’ laboratory for inspection of the top flange to shell circumferential weld joint in RPV of BWRs, which are in operation in India since the late 1960s. The development involved detailed simulation studies for computation of focal laws followed by validation on mock-up. The paper brings out the limitations of the conventional ultrasonic technique and how this can be overcome by the phased array approach for the weld joint under consideration. The phased array technique was successfully employed for field examination of this weld joint in RPV during the re-fuelling outage.

Prioritization of failure risk in subsea flexible pipes via data envelopment analysis

Risk-based inspection is nowadays the predominant approach to structural integrity assurance in complex engineering systems, such as those designed for and operated in deepwater environments. One of the major tasks in risk-based planning is risk ranking of the components comprising an engineering system. In this paper, a mathematical model based on data envelopment analysis is developed for this purpose, whereby two types of weights are employed: subjective judgmental weights which are provided as input, and objective which constitute the output of the model. The use of the mathematical model is illustrated in a real world system of subsea flexible pipes, which operational in the south Atlantic Shelf off the Southeast Coast of Brazil.

Proposal of an Estimation Method of Welding Residual Stresses in Welded Pipes for Risk-Analysis-Based Assurance of Structural Integrity (2nd Report: Application of the L-Curve and the Artificial Noise Methods)

To assure structural integrity for operating welded plants, it is required to evaluate welding residual stresses without crippling the functions of the parts. As a nondestructive method, the bead flush method has been proposed. By applying this method, all the 6 stress components that satisfy the self-equilibrium condition in whole structure can be computed, since solutions are calculated by the FEM analysis from eigen-strains that are estimated from released strains during removal of reinforcement of the weld. In the previous report, a new approach to apply this method to welded pipes with relatively low height of reinforcement was proposed. In there, released raw strain data were pre-treated in consideration of a prior knowledge before conducting the inverse analysis. In this study, to improve statistical estimation accuracy, the L-curve method and the artificial noise method are introduced as well as “the truncated singular value decomposition method”. By using these methods, it is shown stable solutions of multiple residual stress distributions can be obtained from a single measurement of released elastic strains.

Proposal of an Estimation Method of Welding Residual Stresses in Welded Pipes for Risk-Analysis-Based Assurance of Structural Integrity (1st Report: Improvement of Accuracy by Pre-Treatment of Strain Data)

In welded structures, it is indispensable to evaluate welding residual stresses for assurance of structural integrity. Today, several nondestructive evaluation methods of residual stresses have been proposed, however measured results can not be applied to the FEM (Finite Element Method) analysis. For the FEM applications, all the 6 components of stresses in the whole structure must be estimated and those solutions should satisfy the self-equilibrium condition. From this view point, authors have proposed the bead flush method. In this method, welding residual stresses are calculated nondestructively by a simple elastic FEM analysis from eigen-strains which are estimated by the inverse analysis from released strains during removal of reinforcement of the weld. By now, the effectiveness of this method has been proved for welded plates and pipes with relatively high bead height. As decreasing bead height down to below one mm level, however, it is difficult to satisfy both high accuracy and stability because of higher effect of measurement error. In this study, to obtain multiple residual stress distribution from a single measurement, released raw strain data were pre-treated in consideration of a prior knowledge before conducting the inverse analysis.

PS53 リスク解析援用型構造健全性保証のための溶接配管の残留応力推定手法の概念提案 : 第3報(フェロー賞対象ポスターセッション)

PS53 リスク解析援用型構造健全性保証のための溶接配管の残留応力推定手法の概念提案 : 第3報(フェロー賞対象ポスターセッション)

PS10 リスク解析援用型構造健全性保証のための溶接配管の残留応力推定手法の概念提案(第2報)(ポスターセッション)

PS10 リスク解析援用型構造健全性保証のための溶接配管の残留応力推定手法の概念提案(第2報)(ポスターセッション)

ANALYSIS AND DESIGN OF CRYOGENIC BALL VALVE

Natural gas is being hailed as alternative energy sources for a petroleum, because it is almost no emissions of pollutants in the environment. Use of equipment for liquefied natural gas, along with increased demand for natural gas is also growing. Cryogenic ball valve is used to control the liquified natural gas which temperature is -196 , supplied pressure �� is 168kg/cm 2 . To acquire the safety along with durability of cryogenic ball valve, we should consider the structural mechanics such as stress, deformation and dynamic vibration characteristics and identify those important aspects in the stage of preliminary design engineering. For the cryogenic ball valve, the assurance of structural integrity and operability are essential to meet not only normal, abnormal loading conditions but also functionality during a seismic event. In this study, analytical approach and results using finite element analysis and computational method are herein presented to evaluate the aspects of structural integrity along with operability of cryogenic ball valve. Moreover, we have done the optimal design through special processing and heat treatment and so on. Finally, we designed the high pressure cryogenic ball valve that accomplishes zero leakage.

PS01 リスク解析援用型構造健全性保証のための溶接配管の残留応力推定手法の概念提案(ポスターセッション)

PS01 リスク解析援用型構造健全性保証のための溶接配管の残留応力推定手法の概念提案(ポスターセッション)

2501 リスク解析援用型構造健全性保証のための溶接配管の残留応力推定手法の概念提案(S29-1 原子力発電(1),21世紀地球環境革命の機械工学:人・マイクロナノ・エネルギー・環境)

It is indispensable to evaluate welding residual stresses for assurance of structural integrity in welded structures. Since residual stresses have to be estimated nondestructively for operating plants, the bead flush method, which is based on the eigen-strain evaluation, has been proposed. In this method, welding residual stresses are calculated by an elastic analysis from eigen-strains that can be estimated by the inverse analysis from measured elastic strain changes when the reinforcement of the weld is removed. Although the accuracy of this method have been proved in welded plates and pipes with relatively high bead height, it is difficult to estimate reasonalby accurate residual stresses because absolute values of experimental errors usually become higher as the bead height decreases down to the actual level. Further problem is lack of statistical point of view for the risk assessment. In this study, to solve these difficulties, stabilizing methods are applied to the inverse analysis to restrict the space of solution and the released raw strain data are pretreated according to the foresight information.

344 中性子照射などにより延性が著しく低下する場合の構造健全性確保の概念(OS10-3 照射劣化,溶接部評価,OS10 エネルギー機器の経年変化に関する健全性評価手法の開発とその適用(2))

A new, systematic concept of structural integrity assurance is proposed for application to components with reducing or reduced ductility materials. The current structural codes are all based on the assumption of no significant changes in mechanical property in service and high ductility. Intense neutron irradiation at moderate temperatures in nuclear reactors and fusion machines, for example, induces hardening, e.g., a significant change in yield strength, and then reduction in ductility. Therefore, failure modes to be prevented are discussed, first, for components with such materials. Second, a new concept of limiting strength is proposed. Then, a systematic concept of ductile fracture prevention is proposed, by reasonably applying loading type-depending limiting strengths.

Stochastic service load simulation for engineering structures

Most engineering structures are subjected to varying service loads. These variations are as a result of working loads and structural response, which may lead to dynamic amplification effects. Irrespective of the design philosophy implemented at the design stage of an engineering structure, both global and local service loads are very important and will often have to be assessed and reassessed for structural integrity assurance and maintenance planning. Therefore, general load forecasting and stochastic load simulation are very important. This methodology has been successfully developed at University College London and applied to the analysis of offshore structures. However, the problem of variable loading is not limited to the offshore applications as it is relevant to other core engineering industry sectors. This paper recognizes the significance of this and presents a generalized approach to stochastic load simulation. The methodology is illustrated with an example model based on the Jack–up platform and gives details of a simulated Jack–up offshore load history (JOSH) developed for use in the fatigue testing of structural members used in the construction of Jack–up structures.

Elements of structural integrity assurance

My association with Professor Dr Jaap Schijve's work goes back over 20 years. After having studied his numerous and excellent publications on spectrum effects on fatigue, it was a thrill to meet in conjunction with the International Committee on Aeronautical Fatigue (ICAF). I have been fortunate to continue to learn from his expertise in fatigue and fracture, and the impact of Professor Jaap Schijve's work on Boeing test and analysis procedures has been significant. The opportunity also to be invited to his home during my visits to The Netherlands has added a personal friendship which truly will endure. My efforts over the last 20 years at Boeing have been focused on technology standards development

Structural integrity assurance of high-strength steel gas cylinders using fracture mechanics

This paper describes fracture mechanics criteria employed in the development of fracture-safe, 155–175 ksi strength level steel cylinders. A new steel composition was developed to obtain the toughness required to satisfy leak-before-break and plastic fracture mode criteria. Cylinders were fabricated from the new steel, and tests were conducted to characterize their flaw tolerance capability. Leak-before-break and plastic fracture mode performance was verified. Flawed cylinder tests were also conducted on conventional 3AA 4130X steel cylinders (105–125 ksi strength level) to characterize their flaw tolerance capability. The flaw tolerance capability of the high-strength cylinders was found to be equal to that of the conventional low strength steel cylinders at respective service stresses.

Japanese developments in the ultrasonic examination of pressure vessels

In Japan, nuclear power plant has grown to such an extent that it now provides a fundamental part of total power generation. In consequence, the assurance of structural integrity is increasingly important. The activities of three representative organizations, the Nuclear Power Engineering Test Center (NUPEC), the Japan Pressure Vessel Research Council (JPVRC) and the Japan Power Engineering and Inspection Corporation (JAPEIC) are briefly overviewed in this paper. NUPEC is carrying out the proving test program of in-service inspection. Manual ultrasonic inspection testing was completed in early 1984; factors affecting defect detection and sizing were examined and some of these test results are introduced here. Mechanized automatic inspection testing with devices now in use in recent operating plants is underway. JPVRC is participating in the international round robin test, PISC-II, and in the test between US-PVRC to investigate the reliability of ultrasonic examination, and some test results are introduced. JAPEIC recently expanded its activities into research and development in the area of structural integrity, robotics, mechanized inspection and non-destructive inspection. Some topical items for these programs are overviewed.