bluuebunny/crossref_metadata_2025_split huggingface dataset:
Determination of Minimum Vessel Wall Thickness Under Design Condition Loadings
Authors: Ratcliffe Simon E. 
Published: August 2013

During the concept design phase of a series of pressure vessels for nuclear application, an approach was developed to provide minimum vessel sizing under dynamic loading conditions. Calculations had been undertaken to determine an initial tentative vessel wall thickness using ASME III Subsection NB, however only a limited assessment of mechanical loading was undertaken.
This paper outlines a static analysis approach for extending the structural analysis of a pressure vessel shell to include design condition loadings. These include dynamic loading, support reactions and external piping reactions which can have a significant influence on the required minimum wall thickness.
This paper is limited to outlining generic rules and assumptions that can be applied to the preliminary concept design of pressure vessels. The method was originally captured to aid knowledge sharing within the design team. It does not prescribe an exact methodology but rather an interpretation and application of the design code. The aim is to provide a better defined vessel geometry upon which to base the detailed finite element stress analyses for both design and service conditions. The perceived benefit of this approach is that there will be a lower likelihood of major design changes being during the detail phase.
Modelling the Graphite Fracture Mechanisms
Authors: Jacquemoud C. , Marie S. , Nédélec M. 
Published: August 2013

In order to define a design criterion for graphite components, it is important to identify the physical phenomena responsible for the graphite fracture, to include them in a more effective modelling.
In a first step, a large panel of experiments have been realised in order to build up an important database; results of tensile tests, 3 and 4 point bending tests on smooth and notched specimens have been analysed and have demonstrated an important geometry related effects on the behavior up to fracture.
Then, first simulations with an elastic or an elastoplastic bilinear constitutive law have not made it possible to simulate the experimental fracture stress variations with the specimen geometry, the fracture mechanisms of the graphite being at the microstructural scale. That is the reason why a specific F.E. model of the graphite structure has been developed in which every graphite grain has been meshed independently, the crack initiation along the basal plane of the particles as well as the crack propagation and coalescence have been modelled too. This specific model has been used to test two different approaches for fracture initiation: a critical stress criterion and two criteria of fracture mechanic type. They are all based on crystallographic considerations as a global critical stress criterion gave unsatisfactory results. The criteria of fracture mechanic type being extremely unstable and unable to represent the graphite global behaviour up to the final collapse, the critical stress criterion has been preferred to predict the results of the large range of available experiments, on both smooth and notched specimens. In so doing, the experimental observations have been correctly simulated: the geometry related effects on the experimental fracture stress dispersion, the specimen volume effects on the macroscopic fracture stress and the crack propagation at a constant stress intensity factor. In addition, the parameters of the criterion have been related to experimental observations: the local crack initiation stress of 8MPa corresponds to the non-linearity apparition on the global behavior observed experimentally and the the maximal critical stress defined for the particle of 30MPa is equivalent to the fracture stress of notched specimens.
This innovative combination of crack modelling and a local crystallographic critical stress criterion made it possible to understand that cleavage initiation and propagation in the graphite microstructure was driven by a mean critical stress criterion.
Buckling of Truncated Cones With Localized Imperfections
Authors: Błachut J. 
Published: August 2013

The paper shows that both the inward and outward bulge-type axisymmetric shape imperfections can significantly lower the buckling strength of steel conical shells. The FE results are provided for: (i) axial compression, (ii) external pressure, and (iii) combined action of both loads. Sensitivity of buckling loads to outward bulges has not been generally known or expected. It is shown that the sensitivity of buckling load depends not only on the shape, amplitude but also on the position of the imperfection along the slant.
Geometry of recently tested cones was also used in order to assess the influence of measured shape deviations on the buckling strength. The amplitudes of imperfections in these machined models were small (up to 5 % of wall thickness). As a result their influence on the buckling strength was found to be negligible.
Prediction of Time to Significant Cracking and Actual Behavior of an Impulsively Loaded Detonation Chamber for Chemical Weapons Destruction
Authors: Asahina Joseph K. , Akasaka Koichi , Nickell Robert E. , Hamada Toshio 
Published: August 2013

For repeated operation of a detonation chamber, evaluation of its fatigue damage and estimation of time to crack initiation are of considerable importance from the aspect of safe operation.
This paper proposes the use of a sufficiently conservative operation control fatigue evaluation curve, based upon the ASME Code fatigue design curve and the best fit laboratory air curve upon which the design curve is derived, in order to define operational points for actions to inspect for possible fatigue damage and initiate repairs, as needed. The paper also recommends appropriate actions to verify that any needed repairs maintain structural integrity during subsequent operations.
Modeling of the Effect of Plasticity on the Response of Pipe Systems to Internal Explosions
Authors: Smeulers Jan P. M. , Pape Gersom , Ligterink Norbert E. 
Published: August 2013

Pipe systems that are used in the process industry may occasionally be subjected to internal deflagration and detonation waves. In those cases the design of the pipe system should be explosion resistant or even explosion proof. The usual design rule for the analysis of the mechanical response is based on the hoop stress calculated with an equivalent static pressure load, which depends on the magnitude of the detonation pressure. However, it has been found that the response of a pipe to a traveling detonation wave shows a number of effects that lead to much higher stresses. See [1] and [2]. One of these effects is mode coupling, i.e., the excitation of circumferential bending modes, coupled to the initial hoop stress or breathing mode, which may lead to an increase of the local maximum stress by a factor 2.6.
Mode coupling has been investigated theoretically for rings and it has been demonstrated also experimentally, among others by Li c.s. [5]. Using finite element modeling we have investigated under what conditions mode coupling can occur in pipes in which a detonation wave propagates. It appears that a condition for mode coupling in a 3D configuration is that the detonation velocity is larger than the first critical velocity Vc0. For a pipe section of limited length mode coupling will be enhanced by the flanges at both boundaries which reflect flexural waves that propagate in axial direction.
Furthermore, the effect of limited plasticity has been investigated. The results show that mode coupling is being reduced by plasticity. The conclusion is that with plasticity the detonation load can be larger without bursting of the pipe. However, mode coupling will still occur in spite of plastic deformation.
In the paper the modeling of 2D mode coupling is presented and compared with the theoretical analysis. Moreover, the extension of the model to a pipe with a finite length and an “infinite pipe” is discussed and the effect of plasticity is analyzed. The analysis incorporates the influence of the material strain rate sensitivity and it considers the response for regular structural pipe steel as well as high strength steel.
Quantification of Creep Cavity Evolution Using a Novel Replica Image Processing Technique
Authors: Yang Haoliang , Davies Catrin M. , Dear John P. 
Published: August 2013

In industry, the surface replication technique is employed as a practical method for the lifetime assessment of high temperature components. However, the method is limited as it is a time consuming processes, is susceptible to subjective interpretations and is only sensitive to surface damage, whereas creep damage often initiates sub-surface. A replica of a component’s surface is made by applying a softened plastic foil to it. This foil moulds itself to the alloy’s surface when pressed. After its removal from the alloy, the plastic replica provides an exact copy of the etched surface’s microstructure, which can then be examined.
A new image processing technique has been developed that provides a reliable and repeatable, quantified measure of creep cavitation using images obtained from replica films. A series of interrupted tests have been performed at the same load on 2.25CrMo (P22) ferritic steel at 650 °C. Post testing, samples were prepared and replication performed. A quantitative 2D map of the cavities across the specimens’ surface has been obtained using a novel image processing technique. The results are related to the specimens’ strain measurements using a displacement gauge and a novel potential drop technique. This new image processing technique may provide a valuable tool for industry.
Characterizing Austenitic Materials and Nickel Alloys With Electro-Magnetic Imaging
Authors: Kuljis Zoran , Lisowyj Bob 
Published: August 2013

Stress Corrosion Cracking (SCC) consists of two stages, an incubation stage followed by a crack propagation stage. The crack propagation stage can be tracked fairly accurately by using Arrhenius energy values. However, the incubation stage can take a long time (20 years is not uncommon), and is far less predictable with no indication of its development. SCC is also localized making it difficult to detect, and is often only found when cracking has gone through-wall and produced a leak. Welds are known to be areas where SCC originates. Any manufacturing repairs to weld locations produce augmented levels of residual stress in the weld area and increase the probability of SCC.
Manufacturing effects also alter the electro-magnetic property of a material, and by monitoring the changes in electro-magnetic property it is possible to characterize material conditions that contribute to the SCC process. Evaluation of these manufacturing effects on several Reactor Vessel nozzles with Dissimilar Metal Butt Welds (DMBWs) has found electro-magnetic property changes, which can characterize, define and produce images of localized repairs, and also show where lack of adequate stress relieving heat treatments exists.
This electro-magnetic property methodology can predict the development of SCC in the incubation process, and can directly confirm where any initial fabrication repairs were performed, or when lack of proper stress relieving exists. A full material characterization history enabling prediction of the future susceptibility to SCC has been achieved. This complete, material characterization history of Alloy 600 components and stainless steel components was the goal of this research. Eddy Current Testing (ECT) was chosen as the NDE technique of choice, because it is sensitive to surface changes and can detect electro-magnetic property changes. Using an imaging process, which detects electro-magnetic property changes, has successfully characterized the complete history of the investigated materials.
Residual Stress Distributions and Guidelines for Crack Inspection in Pipe Bends
Authors: Yetisir Metin , Walker Zane 
Published: August 2013

Root cause investigations of feeder pipe cracks detected in one CANDU™ nuclear power plant indicated that the residual stress had a significant role in these failures. As a result, numerous residual stress measurements of pipe bends were obtained and models for predicting the residual stress distributions associated with various bending processes were developed.
This paper provides a comprehensive review of pipe bend residual stress data and provides guidelines for identifying the most susceptible locations for targeted crack inspections. Residual stress data, generated since 1997 as part of the CANDU feeder cracking investigation, was compiled and presented for the quick dissemination of information. This information is summarized in quick lookup tables where likely crack locations are identified for pipe bends manufactured using various fabrication techniques.
New Manufacturing Cycle to Improve the Life of Packing Cups for Hyper-Compressors
Authors: Maggi Carmelo , Tognarelli Leonardo , Capanni Alessio , Wojnar Jan 
Published: August 2013

Hyper-compressors are subjected to very high operating pressure, maximum and fluctuating, strongly impacting design and life of all cylinder components. Components subjected to fatigue (both high cycle fatigue and low cycle fatigue) can experience a failure in a very short time that may cause large production losses.
Packing cups proved to be one of the most critical cylinder components and the fatigue behavior of the packing cups subjected to alternating loads, due to the suction and discharge conditions, is their key design factor.
A thorough study has been performed in order to increase the safety factors in all critical regions of the packing cups analyzing a new manufacturing cycle that allows optimizing the compressive pre-stresses on the lube oil parts due to the autofrettage procedure. The approach included a dedicated sensitivity FEM analysis of the autofrettage pressure to determine the correct residual stresses at the lube oil parts in order to keep them under compressive stress in operating conditions and Fracture Mechanics Calculations based on BSI7910 aimed at achieving a design able to survive with a threshold defect larger than the minimum detectable defect.
Bolted Joint Fracture Analysis Study Using Modern Methods
Authors: Griffin David , Reed Gary , Mills Andrew , Brayshaw Russell 
Published: August 2013

This paper describes the outcome of a fracture study to ascertain the benefits of using modern three dimensional finite element techniques. The defects considered are postulated to be present at the root of a threaded fastener. The defects are explicitly modelled using three dimensional finite element analysis to extract the relevant fracture parameters.
A large number of thumbnail defects of varying size and aspect ratio have been incorporated into the root of the first engaged thread of studs typically used in pressure vessels. Stress intensity factors at the defect surface and depth locations have been extracted for a number of thermal transient events using a domain integration technique within the general finite element code ANSYS.
The above stress intensity factors were then used to generate fracture calculations using an R6 based procedure [1] for:
• Toughness-based fracture margins for each defect modelled;
• Critical defect size;
• Comparisons with a fully extended defect.
Optical Strain Monitoring Techniques
Authors: Narayanan Aditya , Morris Andy , Davies Catrin M. , Dear John P. 
Published: August 2013

The Auto-Reference Creep Management and Control (ARCMAC) system is being developed as a technique to evaluate the remaining life of power plant components. The system consists of a pair of Inconel plates with a configuration of silicon nitride (SiN) spheres on them, and a camera system used to take images of the gauge during the component’s deformation. The purpose of the system is to measure the creep strain accumulated by a component at regular intervals, tracking the relative motion of the spheres in order to measure a point-to-point value of strain. The system is currently used to capture images of gauges already installed on power plants in the UK as part of scheduled maintenance during plant outages.
It is also possible to use the ARCMAC system to capture speckle paint pattern data used in digital image correlation (DIC) in order to visualise the strain field across the heat affected zones (HAZ) in welds and around other strain concentration features. A newer version of the system: the Digital Single Lens Reflex (DSLR) ARCMAC is being developed specifically to capture this kind of data in order to complement the point-to-point strain measurements obtained.
This article presents results of experiments performed at room temperature with the purpose of establishing the basic accuracy of the conventional ARCMAC and the DSLR ARCMAC in order to compare their performance. It also intends to evaluate the performance of the latter when used for digital image correlation. The results showcase the accuracy of the technique at high strains using the DSLR camera, showing its usefulness as a tool to measure creep strain.
Analysis of Ductile Crack Growth in Pipe Test in STYLE Project
Authors: Yin Shengjun , Williams Paul T. , Klasky Hilda B. , Bass B. Richard 
Published: August 2013

The Oak Ridge National Laboratory (ORNL) is conducting structural analyses, both deterministic and probabilistic, to simulate a large scale mock-up experiment planned within the European Network for Structural Integrity for Lifetime Management – non-RPV Components (STYLE).
The paper summarizes current ORNL analyses of STYLE’s Mock-Up3 experiment to simulate/evaluate ductile crack growth in a cladded ferritic pipe. Deterministic analyses of the large-scale bending test of a ferritic surge pipe, with an internal circumferential crack, are being simulated with a number of local micromechanical approaches, such as Gurson-Tvergaard-Needleman (GTN) model. Both FEACrack [1] and ABAQUS [2] general purpose finite element programs are being used to predict the failure load and the failure mode, i.e. ductile tearing or net-section collapse, as part of the pre-test phase of the project.
Companion probabilistic analyses of the experiment are utilizing the ORNL developed open-source Structural Integrity Assessment Modular - Probabilistic Fracture Mechanics (SIAM-PFM) framework. SIAM-PFM contains engineering assessment methodologies such as the tearing instability (J-T analysis) module developed for inner surface cracks under bending load. The driving force J-integral estimations are based on the SC.ENG1 or SC.ENG2 models. The J-A2 methodology is used to transfer (constraint-adjust) J-R curve material data from standard test specimens to the Mock-Up3 experiment configuration. The probabilistic results of the Mock-Up3 experiment obtained from SIAM-PFM will be compared to those generated using the deterministic finite element modeling approach. The objective of the probabilistic analysis is to provide uncertainty bounds that will assist in assessing the more detailed 3D finite-element solutions and to also assess the level of confidence that can be placed in the best-estimate finite-element solutions.
Correlation of Piping System Detonation Test Data and System Analyses
Authors: Ligon Thomas C. , Gross David J. , Minichiello John C. 
Published: August 2013

This paper describes hydrogen and nitrous oxide detonation experiments that were performed using an approximately 200-ft long 2-inch schedule 40 piping system. The objective of these experiments was to develop an understanding of the loads and forces imposed by internal detonation on piping combinations representative of a typical industrial piping system. The apparatus contained numerous straight pipe lengths with 90° and 45° bends, 90° elbows, and a tee along with rigid foundation supports that were connected to the pipe using typical u-bolt fasteners.
As a detonation wave propagates through a gas-filled piping system, the pipe begins to respond globally once a detonation encounters a change in flow direction, such as a bend, causing a pressure imbalance due to both the internal detonation pressure and change in momentum of the reaction products. The resultant force imparts both axial forces and moments on the pipe exciting both extensional and bending modes.
The test data was used to validate two finite element (FE) models developed using the ANSYS finite-element program: a hybrid model that made use of both shell and beam elements, to determine the interaction between shell and beam modes, and an all beam element model. An additional beam element model was developed using the Bechtel National Inc. software ME101 that was also found to be in agreement with the measured and ANSYS calculated frequencies and support loads. In addition to the detonation testing, the finite-element models were validated against experimental modal analysis data of the piping system that identified the primary modal frequencies and vectors. These data were compared to the modes extracted from finite-element models of the piping system.
Unique Fracture Behaviour of Multi-Perforated Media
Authors: Billon F. , Taborda F. , Lesage J-O. 
Published: August 2013

Concerning the risk of fast fracture, multi-perforated tubesheets have a unique behavior. For the fracture analysis, it is assumed that a small ligament is fully cracked from the skin and that failure leads into the two holes on either side of this ligament in a square pitch. This approach is referred to as a “Broken Ligament Approach”, which can be analyzed using four main steps:
(a) Calculation of the elementary stresses in all the tubesheet using a global 3D Finite Element model,
(b) Conversion of the elementary stresses in membrane stresses and bending stresses along the thickness of the tubesheet at the location of the assumed broken ligament,
(c) Creation of a Representative Local Volume (RLV) containing the broken ligament to which boundary loads are applied to obtain the stresses defined in the global model,
(d) Calculation of the Stress Intensity Factor (SIF) along the crack front of the broken ligament with different depth of the crack.
The result is that the SIF passes through a maximum value as the depth of the broken ligament increases through the thickness of the tubesheet. It is thus possible to find an absolute maximum value of the SIF (called SIFam) over the tubesheet for its most severe loadings. Under these conditions, if the toughness of the tubesheet material is greater than SIFam, there is no risk of a fast fracture of the tubesheet. The existence of SIFam is a strong characteristic of the fracture behavior of multi-perforated media.