bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Heat Treatment on Corrosion and Fracture Behavior of SPV50Q High Strength Steel Weldment in H2S-Containing Environment
Authors: Tang Jianqun , Gong Jian-Ming , Geng Luyang , Yong Jiang
Published: July 2009

SPV50Q high strength steel is often used to fabricate liquefied petroleum gas (LPG) spherical tanks with larger capacity, and tanks are expected to free post weld heat treatment (PWHT) for avoiding the possible reduction in strength. Sulfide stress corrosion cracking (SSCC), however, has been found in weldment, especially the heat-affected zone (HAZ), in LPG environment contaminated by wet H2S. The failure analysis showed that the existence of welding residual stress in weldment is one of the major factors in the occurrence of cracking. Post welding heat treatment (PWHT) is a feasible method of reducing welding residual stress. Therefore, in order to investigate the effect of heat treatment on mechanical properties, corrosion and fracture behavior of SPV50Q steel weldment, the difference in mechanical properties of the weldment with and without heat treatment at 590°C for 160 min after welding was measured using tensile test and impact test. The corrosion behaviors of base metal (BM), weld metal (WM) and HAZ metal in the weldment were investigated by potentiodynamic polarization in H2S-containing solution. In the same solution, the susceptibility to environmental cracking was evaluated by slow strain rate testing (SSRT). The feature of fracture and the morphologies of cracks were observed by scanning electrode microscope (SEM) and optical microscope (OP). The results indicate that the execution of heat treatment does not greatly change the properties of SPV50Q steel weldment, which can provide technology support for the remanufacturing of the LPG tanks having suffered from SSCC by repair welding following local or integral heat treatment.
Shaking Table Tests on Innovative Anti-Seismic Systems Developed in the Framework of the LESSLOSS European Integrated Project
Authors: Forni Massimo , Poggianti Alessandro , Ranieri Nicola , De Canio Gerardo
Published: July 2009

The Integrated Project LESSLOSS (Risk Mitigation for Earthquakes and Landslides), partially funded by the European Commission within the 6th Framework Programme, started on September 2004 and was concluded in August 2007. Activities were carried out by 46 European partners, with a total budget of 9.4 ME. The Project was divided into 11 Sub-Projects. This paper describes the activities performed in the framework of Sub-Project 6 (Development and Manufacturing of Energy Dissipation Devices and Seismic Isolators), which was coordinated by ENEA and whose partnership included two manufacturers of antiseismic devices (ALGA, Milan, Italy and MAURER SHO¨NE, Munich, Germany) and two consulting and construction companies (STAP, Lisbon, Portugal and VINCI, Paris-Rueil, France). Aim of Sub-Project 6 was the development and validation of two innovative antiseismic devices (a low stiffness isolator and an electroinductive damper), the improvement of the performances of a slider with curved surface and the evaluation of benefits and limits of isolation systems based on steel hysteretic dissipaters coupled with flat sliders. The Low Stiffness Isolator (LSI) was developed by ALGA; it is a natural rubber seismic isolator particularly addressed to light structures like family houses. The Electroinductive Damper (DECS), developed by ALGA, is an energy dissipater based on the interaction of a diamagnetic material, like aluminium, with an electric field generated by permanent magnets. The Sliding Isolation Pendulum (SIP) developed by MAURER is an improved curved surface slider, capable of withstanding high weights for long periods without creep effects and high velocity deformations without damages due to friction. Finally, several types of Steel Hysteretic (SH) elements of different geometries and materials have been analyzed and tested in order of evaluating the benefits and the limits of such devices, with particular regard to the re-centering capabilities. All the abovementioned devices have been tested on the ENEA shaking table of the Casaccia labs (near Rome), with a suitable mock-up capable of providing a 300 kN force on the devices in the acceleration and frequency ranges of interest, using several natural and artificial acceleration time histories purposely developed by ENEA. The paper describes the main features of the devices, the numerical activity aimed at the optimization of their behavior and the results of the four shaking table campaigns carried out on each device.
Certification of the NAC-LWT Cask for Shipment of Sodium Debris Bed Experiments
Authors: Liu Yung , Shah Vikram , Fabian Ralph , Shuler James
Published: July 2009

The Department of Energy Headquarters Certifying Official has issued a Certificate of Compliance for the shipment of sodium debris bed experiments (DBE) in the NAC International’s Legal Weight Truck (NAC-LWT) casks. The shipment is part of a major de-inventory project at Sandia National Laboratories. The sodium debris bed experiments consist of crucibles containing UO2 immersed in sodium. The uranium is 93% enriched U235. Potential sodium-water reaction and criticality safety under hypothetical accident conditions of transport are the two major technical issues for the design and certification of the NAC-LWT casks for the DBE shipment. The certification review took ≈ 13 months, including one round of questions and responses and source-verification QA audits of the fabrication and welding of the DBE transport canisters at two locations.
Unique Method for Generating Design Earthquake Time History Seeds
Authors: Spears R. E.
Published: July 2009

A method has been developed which takes a single seed earthquake time history and produces multiple similar seed earthquake time histories. These new time histories possess important frequency and cumulative energy attributes of the original while having a correlation less than 30% (per the ASCE/SEI 43-05 Section 2.4 [1]). They are produced by taking the fast Fourier transform of the original seed. The averaged amplitudes are then pared with random phase angles and the inverse fast Fourier transform is taken to produce a new time history. The average amplitude through time is then adjusted to encourage a similar cumulative energy curve. Next, the displacement is modified to approximate the original curve using Fourier techniques. Finally, the correlation is checked to ensure it is less than 30%. This process does not guarantee that the correlation will be less than 30% for all of a given set of new curves. It does provide a simple tool where a few additional iterations of the process should produce a set of seed earthquake time histories meeting the correlation criteria.
Evaluation of Historical Longitudinal Seam Weld Failures in Grades 11, 12, and 22 Materials
Authors: Cohn Marvin J. , Paterson Steve R.
Published: July 2009

Since the catastrophic HEP seam weld failures of Mohave (1985) and Monroe (1986), electric power utilities have become more interested in developing and implementing examination and fitness-for-service evaluations of their HEP systems. At least 30 failures or substantial cracks in Grade 11 (1-1/4Cr – 1/2Mo), Grade 12 (1Cr – 1/2Mo) and Grade 22 (2-1/4 Cr – 1Mo) pipe longitudinal seam welds or clamshell welds have occurred from 1979 through 2000. This paper provides a statistical analysis of well-characterized Grade 11, Grade 12, and Grade 22 longitudinal seam weld failures or substantial cracks developed by long term creep rupture damage. Considering several applicable hoop stress parameters, linear regression analyses were performed to minimize scatter about a log stress versus Larson Miller Parameter (LMP) curve fit. Each of six applicable hoop stress equations was evaluated to determine the best fit stress space for the longitudinal seam weld failure data. These service experience industry data include pipe thicknesses ranging from 0.5 to 4.5 inches and failure times ranging from 71,000 to 278,000 hours.
Application of Nondestructive Instrumented Indentation Technique in Small-Scale Testing of Pressure Vessel and Piping Systems
Authors: Lee Kyung-Woo , Kim Kug-Hwan , Kim Kwang-Ho , Choi Young-Hwan , Chung Hae-Dong , Kwon Dongil
Published: July 2009

Most small-scale testing techniques are essentially scaled-down versions of conventional testing techniques: they use specimens of similar geometry applied in a similar manner to estimate properties equivalent to those obtained for larger specimens. However, using these techniques for safety assessment of structures and piping systems requires general agreement about the techniques and validation of their results. In addition, these techniques all require destructive testing. In this study we adopt a new nondestructive method to measure the mechanical properties using the instrumented indentation technique. This technique can be applied directly in small-scale and localized sections because of its high spatial resolution. It also has the significant advantage of simplicity of specimen preparation and experimental procedure. During instrumented indentation testing, the load and penetration depth of an indenter tip driven into the sample are monitored, and material properties such as strength, fracture toughness and residual stress are evaluated from this information: the tensile properties by defining a representative stress and strain underneath a spherical indenter; the residual stress values near weldments by using the stress-insensitive contact hardness model.
Predicting the Influence of Residual Stresses on Brittle Fracture Using Local Approach
Authors: Mirzaee-Sisan Ali , Hadidi-Moud Saeid , Smith David
Published: July 2009

This paper explores the application of the local approach to brittle fracture to predict the influence of residual stresses in a relatively thick pipe. Three different surface flaw sizes were assumed on the outside surface of the pipe and failure predictions were made using the local approach. Then the results of local approach prediction were compared with the well-known fracture assessment procedure, BS7910 which uses a failure assessment diagram (FAD). It has found that the local approach has an advantage of taking into account the details of stress re-distribution of residual stress around the crack tip compared to the conventional assessment procedure.
Computational Investigation of Different Turbulent Models When Predicting Airflow in an Enclosure
Authors: Wang Xi , Naji Hassan , Mezrhab Ahmed
Published: July 2009

In the present study, a numerical investigation is carried out for an isothermal case, a hot case and a cold case with FLUENT code. Three turbulence models are considered: the k-ε realisable model, the RNG k-ε model and the RSM linear model. The obtained results are compared to experiments and show generally a good agreement for the mean velocities and temperatures, but less satisfactory for the turbulent stress. The performance of the RSM model is remarkable. Even if none of the models is able to give the exact experimental pattern on the map of turbulence, the RSM model seems able to predict such configuration.
An Approach for Assessing Structural Uplifting Using Blast Motions
Authors: Nie Jinsuo , Xu Jim , Hofmayer Charles H. , Ali Syed A.
Published: July 2009

When a nuclear power plant (NPP) structure is subjected to beyond-design-basis seismic motions, a localized nonlinear effect on the soil-structure system is attributed to separations between the structure and the surrounding soils such as basemat uplift. Experiments involving field tests for real seismic events are usually difficult because of the low probability for large earthquakes at any particular site. To this end, the magnitudes of blast-induced ground motions at a coal mine have been found to be predicatable and can reach very large values. An approach has been developed to investigate whether the strong ground motions recorded at this coal mine can be used to evaluate the basemat uplift effect. This approach involves the use of a scaled ground motion to establish the relationship between the basemat uplift and the peak ground acceleration (PGA). This paper summarizes the field measurements for the ground motions at a coal mine by the Japan Nuclear Safety Organization (JNES) and a method using large scale finite element analyses for basemat uplift assessment performed by Brookhaven National Laboratory for the US Nuclear Regulatory Commission.
A Comparison of FAC Programs in Japan and the United States
Authors: Crockett Harold M. , Hiranuma Naoki , Honjin Masao , Horowitz Jeffrey S.
Published: July 2009

Dealing with the consequences of flow accelerated corrosion (FAC) has become an important problem for nuclear utilities worldwide. Recent fatal accidents at the Mihama Unit 3 nuclear station in Japan and at the fossil-fired Iatan Power Plant in the US unit have highlighted the importance of this issue. This paper will examine and compare the programmatic approaches taken by the Japanese nuclear power industry and the approach taken in the United States. In both countries, formal FAC programs were initiated, to a large degree, in response to the failure of a condensate elbow at the Surry Unit 2 station in 1986. In spite of this common beginning, different paths were taken. In Japan, JSME established three voluntary consensus standards after the Mihama accident. One standard provides generic requirements and two separate standards for BWRs and PWRs. The two specific standards require a comprehensive inspection program followed by re-inspections at fixed intervals. The areas inspected were defined by the general operating conditions and the system design specifications. After the Surry accident, the United States nuclear utilities developed a consensus based on inspecting a sample of locations, and performing follow-on work based on the results of these inspections. The inspection locations were determined by analysis, operating experience, and engineering judgment. This approach was documented in NSAC-202L.
A New Empirical Life Prediction Equation for Stress-Controlled Fatigue-Creep Interaction
Authors: Jiang Huifeng , Chen Xuedong , Fan Zhichao , Dong Jie
Published: July 2009

A new empirical life prediction method is developed. The equivalent radius of cavities at grain boundary is adopted as the damage parameter. Similar with Nam’s model, in this paper, it is also assumed that cavities only nucleate during fatigue cycles and further grow with the development of creep. Then the number of cavities nucleated in a cycle is proportional to the fatigue effect, i.e. the amplitude of loading stress. As the creep process is composed of the static creep and the cyclic creep during the fatigue-creep interaction, then the equivalent stress causing cavity growth should be proportional to the maximum hold stress (static creep) and the mean stress (cyclic creep). Therefore, this model is applicable to stress control mode and includes the effects of fatigue, static creep and cyclic creep during the fatigue-creep interaction. By employing this method, the fatigue-creep lives are assessed for 1.25Cr0.5Mo steel at 520°C and 540°C. The predicted lives are compared with the tested ones and a good agreement is found between them. Moreover, it is found that the coefficient of the mean stress is 3-order larger than that of the stress amplitude, which means the effect of static creep is much punier than that of cyclic creep. Considering the detailed test parameters, the short hold duration for peak load may be responsible for this.
Experimental Investigation of Hydrogen Effect on Mechanical Properties of 304L Stainless Steel
Authors: Jiang Yong , Gong Jianming , Tang Jianqun , Geng Luyang
Published: July 2009

Hydrogenation reactor is one of the key equipments in the production process of purified terephthalic acid (PTA). The safe and reliable operation of hydrogenation reactor decides the safety of PTA installation. Service experience has shown that some longitudinal cracks occurred on the internal wall of the 304L stainless steel (SS) hydrogen nozzle. In this paper, a series of electrochemical hydrogen charging tests were carried out for 304L stainless steel at the ambient temperature. The comparison on mechanical properties was investigated before and after hydrogen charging in order to investigate the effect of mechanical properties of 304L SS. Fractography was analyzed by using scanning electron microscope (SEM). The results showed that the mechanical strength of 304L SS was not basically lost after hydrogen charging, but the ductility reduced in a certain extent. The fractography also showed the hydrogen embrittlement effect on the fracture.
Study of Composite Joint Strength With Carbon Nanotube Reinforcement
Authors: Faulkner Susan D. , Kwon Y. W.
Published: July 2009

Strengthening of composite joints is a topic of recent research. The benefits of using locally applied carbon nanotubes to reinforce a carbon fiber composite joint were studied. The effect of carbon nanotubes on enhancing the fracture toughness and joint interface strength was investigated by performing Mode I and Mode II fracture with and without carbon nanotubes applied locally at the joint interface. During the study, the image correlation technique was used to examine the fracture mechanisms altered by the introduction of carbon nanotubes. The experimental study showed that carbon nanotubes increased the fracture toughness of the composite interface significantly, especially for the Mode II fracture, with altering the fracture mechanism.
Elastic-Plastic Fracture Mechanics Method for Poor Penetration Crack in Welded Piping Branch Junction
Authors: Bai Yong-Qiang , Wang Tong , Lv Lianghai , Sun Liang , Shuai Jian
Published: July 2009

This paper provides two types of engineering J estimation equations for welded piping branch junctions with poor penetration crack under internal pressure. The first type is the so-called GE/EPRI type J estimation equation based on Ramberg-Osgood (R-O) materials. Based on detailed 3-D FE results using deformation plasticity, plastic influence functions for fully plastic J components are tabulated for practical ranges of the inner radius of brace to the inner radius of chord ratio, the thickness of brace to the thickness of chord, the thickness of chord to the inner radius of chord ratio, the crack depth to the thickness of chord ratio, the strain hardening index for the R-O material, and the location along the poor penetration crack front. Based on tabulated plastic influence functions, the GE/EPRI-type J estimation equation along the crack front is proposed. For more general application, the effective remote stress method based on GE/EPRI-type solutions is provided. This method provides a simpler equation for J, which could be used for any stress-strain relationship material, including Ramborg-Osgood (R-O) material and non-R-O materials under monotonic increasing loading. The proposed effective remote stress based J estimation equation is compared with elastic-plastic 3-D FE results using actual stress–strain data for a Type 304 strainless steel. Good agreement between the FE results and the proposed reference stress based J estimation provides confidence in the use of the proposed method for elastic-plastic fracture mechanics of pressurized welded piping branch junction.
Stress Mitigation Design of Tubesheets With Consideration of Thermal Stress Inducement Mechanism
Authors: Ando Masanori , Takasho Hideki , Kawasaki Nobuchika , Kasahara Naoto
Published: July 2009

Adoption of double-wall-straight tube steam generators made of Mod.9Cr-1Mo steel is planned for next generation fast breeder reactors in Japan. One of the major concerns relevant to the SG is structural integrity of tubesheets. In the reactor transient operation, thermal stress is induced by the temperature distribution in tubesheet and the magnitude of it depends on configurations of tubesheet. Stress generation mechanism of tubesheets was revealed through Finite Element analysis. Semi-spherical tubesheet models were investigated for the first survey of the thermal stress mechanism. As calculated results, semi-spherical tubesheet model gave the extensive peak stress around the outermost hole. Recognized thermal stress mechanism of semi-spherical tubesheet is as follows. (1) Dominant thermal stress is hoop stress caused by temperature difference between the perforated region and surrounding region. (2) Thermal stress is insensitive to size of specific portion, although is dominated by interaction mechanism between perforated and surrounded regions. (3) Stress concentration around hole’s edge generates peak stress. (4) Amplitude of peak stress depends on the tubesheet penetration angle and stress concentration becomes high near the outermost hole. Based on the above stress generation mechanism, authors proposed a stress mitigated tubesheet. It is center flatted spherical tubesheet (FST) as improved configuration. Calculated peak stress of FST was smaller than that of semi-spherical tubesheet. Further investigation revealed the detailed stress generation mechanism of FST during thermal transient. There were two different comparable thermal peak stress mechanisms in FST. Both location and magnitude of maximum peak stress depend on sodium temperature histories at thermal transient. One depends on the range (ΔT) of sodium temperature change. This type of peak stress was radial stress caused by the structural discontinuity, and it was located at the outermost hole. The other depends on the rate (dT/dt) of sodium temperature change. This type of peak stress was hoop stress caused by interaction between perforated region and surrounding region, and it was located at the one inner layer hole from outermost layer holes.
Design of Floating Type Bolted Flange Connections With GRP Flanges
Authors: Roos Eberhard , Kockelmann Hans , Kurz Hariolf
Published: July 2009

Essential results of a research project “design of floating type bolted flange connections with glass-fibre reinforced plastic flanges for the chemical industry” are summarized in the following: • Various gaskets on the basis of rubber (EPDM) and PTFE were investigated in view of the boundary conditions in bolted flange connections with glass-fibre reinforced plastic (specified in the following as GRP) flanges in compliance with DIN EN 13555. The rubber gasket, the rubber-steel gasket with PTFE envelope and the PTFE based gasket with diffusion barrier meet the leakage rate criterion of TA Luft under the conditions of bolted flange connections with GRP flanges. • The mechanical behaviour of bolted flange connections diameter 50, DN50, with GRP flanges was investigated and is taken under consideration in a new calculation procedure. This draft procedure in the context with experimental pre-tests (already demanded in DIN 16966) is now available to design bolted flange connections with GRP flanges. Thus, the high materials reduction factors defined in AD-Merkblatt N1 can be ignored.
A Statistical Framework for Analysing Weld Residual Stresses for Structural Integrity Assessment
Authors: Nadri Brahim , Bouchard Peter J. , Truman Christopher E. , Smith David J.
Published: July 2009

Thermal and mechanical processes during welding introduce complex three-dimensional distributions of residual stress. Management of residual stresses represents a major challenge for engineers in order to achieve safe and reliable operation of existing engineering plants. Consideration of how such stresses vary through the wall within welded components is critical in structural integrity assessments. Development of more accurate and realistic weld residual stress profiles through statistical analysis of high quality measured data is highly desirable. This can not be achieved without adequate interpretation of measured weld residual stress data through the development of an appropriate framework. This paper proposes a framework for analysing measured data at four levels of complexity depending on its spatial distribution. The framework provides clear guidance on how to perform appropriate statistical analyses of residual stress data and proposes how to deal with some practical issues that may arise from various stress measurements; for example the gauge size, spatial distribution, measurement uncertainties and data analysis assumptions. Parts of the proposed framework are then applied to measured stress data in a simple welded laboratory test specimen.
Loosening Resistance Evaluation of Double-Nut Tightening Method, Spring Washers, and Conical Spring Washers: Finite Element Study
Authors: Yokoyama Takashi , Izumi Satoshi , Sakai Shinsuke
Published: July 2009

The mechanisms of loosening resistance components are investigated within the framework of the three-dimensional finite element method (FEM). Here, the results of the double-nut tightening method (DN), spring washers (SW), and conical spring washers (CSW) are shown. This paper focuses on the comparison among the components above based on the results that have been published separately. For details on each analysis, readers are referred to [10–12]. We have found that DN shows significant loosening resistance if the locking is properly realized in the tightening process. However, if the locking is not performed properly, its ability to resist loosening completely disappears. SW shows negative loosening resistance because the sticking area on the contact surfaces is limited to two corner edges of the SW and the rotational force around these edges thus drastically leads to loosening. In regard to CSW, in the case of high axial force, it shows no apparent effect on preventing loosening. On the other hand, in the case of low axial force, it shows two opposite effects. The negative effect is an increase in the loosening rotation angle, while the positive one is the prevention of a decrease in axial force. When complete bearing-surface slip occurs, a CSW can prevent loosening because the positive effect becomes larger than the negative one. However, when only small bearing-surface slip occurs, a CSW cannot prevent loosening because the negative effect cancels the positive one.
Measurement of Internal Strains in Graphite Using the Deep Hole Drilling Technique
Authors: Nakhodchi Soheil , Flewitt Peter E. J. , Truman Chris , Smith David J.
Published: July 2009

Currently, measurement of internal strains deep inside graphite is extremely difficult. As a consequence there is a need to assess the ability of a deep-hole drilling (DHD) method to measure internal strains in reactor core graphite and explore the potential for in-situ measurement. DHD technique is a semi-destructive method for measurement of the through thickness residual stresses. The technique previously has been applied successfully to metallic and composite materials. In this paper, the method for stress measurement in graphite is examined particularly when a significant volume fraction of porosity is present. Two types of graphite were used, PGA and PG25 filter graphite. In PGA graphite the Young’s modulus of elasticity was orientation dependent. As a consequence samples were cut from blocks in two directions. PG25 filter graphite is a surrogate for service exposed material. Known loads were applied to graphite beam samples and the DHD method was used to measure the stress/strain profile through the material. The results were compared with the strain data obtained from strain gauges bonded to the samples. Overall, there was an excellent agreement between the DHD measured stress/strain and applied stress. It is shown that deep-hole drilling technique can measure linear stress distributions in graphite.
Inelastic Seismic Test of the Small Bore Piping and Support System: Part 3 — Simulation Analysis for the Piping Seismic Test
Authors: Shirai Eiji , Eto Kazutoshi , Umemoto Akira , Yoshii Toshiaki , Kondo Masami , Tai Koichi
Published: July 2009

Seismic safety is one of the major key issues of nuclear power plant safety in Japan. It is demonstrated that nuclear piping possesses large safety margins through the small bore piping and support system test, consisted of three dimensional piping, supports, U-bolts, and concrete anchorages, using the E-defense vibration table of National Research Institute for Earth Science and Disaster Prevention, Hyogo Earthquake Engineering Research Center at Miki city, by the extremely higher seismic excitation level [1, 2]. A simulation analysis for the piping system is described with a focus on the inelastic behavior of the support to the whole piping system response, and the subsequent interaction when both piping and support shows inelastic behavior. The analysis for the inelastic response of the piping seismic test was conducted using the FEM program ABAQUS. It requires a large amount of time to carry out a strain behavior analysis of the localized piping element and also calculate the dynamic inelastic response of the whole piping system, simultaneously. Therefore the following two steps analysis method is proposed. (Step 1) Seismic response analysis of the piping system. (Step 2) Evaluation for local strain of elbows. The simplified piping system model is adopted to solve the non-linear dynamic response both of the supports and elbows of the piping system in (Step 1). On the other hand, the piping system model with partially detailed elbow shell elements is applied to evaluate local strain behavior of the elbow in (Step 2).
Seismic Mitigation Assessment of Building Using Multiple Direction Optimized-Friction Pendulum System
Authors: Tsai C. S. , Chen Wen-Shin , Lin Yung-Chang , Lin Chi-Lu
Published: July 2009

In order to prevent a building near a fault from earthquake damage, in this study an advanced base isolation system called the multiple direction optimized-friction pendulum system (Multiple DO-FPS or MDO-FPS) is proposed and examined to address its mechanical behavior through the finite element formulation and evaluate its efficiency in seismic mitigation through a series of shaking table tests. On the basis of the finite element formulation, it is revealed that the natural period, the capacity of the bearing displacement and damping effect for the Multiple Direction Optimized-Friction Pendulum System (Multiple DO-FPS) change continually during earthquakes. Therefore, the MDO-FPS isolator can avoid possibility of resonance of enriched frequencies from ground motions and provide an efficient capacity of the bearing displacement and damping during the earthquakes. Simultaneously, the shaking table test results also illustrate that the Multiple DO-FPS isolator possesses an outstanding seismic mitigation capabilities.
Crack Opening Area Solutions for Through-Wall Cracks in a Complex Geometry
Authors: Charles R. , Sharples J. K. , Budden P. J.
Published: July 2009

This paper presents the results of a finite element study that has been undertaken to evaluate crack opening areas (COA) for through-wall flaws located in the region where an attachment is “welded” to a plate geometry. This represents the first stage of a study to evaluate crack opening area solutions for flaws situated in complex geometries such as pipe elbows, nozzles and other attachments. The work has been performed by way of 3D finite element methods. In addition to COA evaluations, stress intensity factors have been determined in the study. The crack opening areas and stress intensity factors evaluated for this complex geometry have been compared with those for the same flaw sizes located in a simple plate geometry. This has led to an initial understanding of how conservative or otherwise the use of plate solutions is for representing the more complex geometry cases.
Influence of Weld Mismatch on the Structural Integrity of Pipes for Reeling
Authors: Castelluccio Gustavo M. , Cravero Sebastian , Ernst Hugo A.
Published: July 2009

Structural integrity analysis of tough materials based on Elastic-Plastic Fracture Mechanics (EPFM) has been successfully employed in the assessment of components. EPFM has originally been developed for homogeneous materials and its applicability to inhomogeneous materials has some peculiarities. In particular, Fitness for Service design of welded pipes requires to know the weld fracture toughness and to estimate accurately the J-integral applied on the actual structural member. In this work, finite element analyses of simulated welds have been carried out in order to qualify and quantify the lack of accuracy of experimental methodologies for measuring fracture toughness of welds and the influence of welds on the applied J-integral in a pipe under bending. Different weld widths and cracks positions are characterized for single edge notch specimens in tension (SE(T)) and pipes. It has been found that inhomogeneity affects elastic-plastic fracture parameters for cracks centered in welds of certain widths. Moreover, the applied J-integral on pipes with circumferential cracks depends significantly on the weld width and crack position.
Small Punch Creep Properties of Heat Affected Zones of Reduced Activation Ferritic Steel
Authors: Kato Taichiro , Komazaki Shin-Ichi , Kohno Yutaka , Tanigawa Hiroyasu
Published: July 2009

The small punch (SP) creep test was carried out at the temperatures of 823∼923 K by using a further miniaturized specimen, namely, TEM disk-type specimen (φ 3.0×t0.25 mm). The tests were applied to the fine grain heat affected zone (FGHAZ), tempered HAZ (THAZ) and base metal (BM), respectively, which were removed from the joint of the reduced activation ferritic steel welded by an electron beam welding, in order to investigate the creep properties of such local regimes. The results obtained from the SP creep test were correlated with those of uniaxial creep tests using the base metal (BM) and welded joint (WJ). Experimental results revealed that there were no large differences between the SP creep rupture strengths of the FGHAZ and THAZ and that of the BM at the relatively high load levels. This result was in good agreement with the fact that the uniaxial creep strength of the WJ was almost coincident with that of the BM at the relatively high stress levels. In addition, the ratio of load (P) to stress (σ), which gave same rupture time, was calculated by using the creep rupture data of the BMs. As a result, the ratio was determined to be 0.43, resulting in the following equation; P = 0.43 σ.
Assessing Brittle Fracture in Pressurized Equipment Using a FAD
Authors: Thornton David R.
Published: July 2009

While the probability of brittle fracture in pressurized equipment has typically been rare, the consequences are usually unacceptable from a risk standpoint. This article first briefly reviews the method used to prevent brittle fracture in new equipment used by most codes. The article then presents the approaches of increasing complexity to preventing brittle fracture in existing equipment with an emphasis on the fracture mechanics approach and the use of a Failure Assessment Diagram (FAD). Two examples are discussed, one of determining the maximum acceptable flaw size for a given operating scenario and the other of determining an acceptable operating envelope for a given flaw size.
Analytical Evaluation of Weld Residual Stress Distribution for BWR Pipings
Authors: Ando M. , Nakata K. , Sumiya R. , Itow M. , Tanaka N.
Published: July 2009

SCC (stress corrosion cracking) of low-carbon stainless steel piping has been found in Japanese BWR plants since 2002. According to JSME Fitness-for-Service Code, flaw evaluations are required to verify the life-time of piping if SCC is detected. In order to evaluate the SCC propagation behavior, it is necessary to obtain the residual stress distribution through the thickness of piping. In this study, the mock-up PLR (Primary Loop Recirculation system) piping weld joints made of L-grade Type 316 stainless steel with 300 mm and 600 mm diameter were fabricated and residual stress analyses were performed in order to obtain stress distributions. Material properties (specific heat, thermal conductivity, Young’s modulus, stress-strain curve, etc.) were obtained and temperature history during welding and weld residual stress were measured using these mock-ups. Material properties were used in the heat transfer and stress analyses. Measured temperature history and residual stress were compared with the results of heat transfer and stress analyses, respectively. Residual stress analysis of the pipe weld joint is commonly performed using axisymmetric element. In some cases of the combination of pipe diameter and thickness, residual stress obtained by the conventional method might differ from the experimental result owing to the difference of heating and constraint conditions between the axisymmetric model and the actual condition. In order to obtain more precise results, heat transfer and stress analyses were performed, taking into account the adjustment of the boundary condition in the weld passes of the last layer and the constraint condition using a spring element, respectively. On the outer and inner surfaces, almost the same residual stress distributions were obtained for the FEM analysis and the measurement. The residual stress distributions for PLR piping with different diameters, thicknesses, welding processes and groove angles were obtained by FEM analysis. Based on the results of the analyses, the influences of these parameters on residual stress were evaluated.
Low Cycle Fatigue Behavior of Elbow Pipe With Local Wall Thinning
Authors: Takahashi Koji , Tsunoi Satoshi , Hara Takumi , Watanabe Sota , Mikami Akira , Takada Hajime , Ando Kotoji , Shiratori Masaki
Published: July 2009

Low cycle fatigue tests were conducted using 100A elbow specimens with local wall thinning. Local wall thinning of 50% of the nominal pipe wall thickness was machined on the inside of elbow in order to simulate erosion/corrosion metal loss. The local wall thinning areas are located at three different areas, called extrados, crown and intrados. The elbow specimens were subjected to cyclic in-plane bending under displacement control without internal pressure. When the local wall thinning was located at intrados, fatigue life was the shortest. In addition, three-dimensional elastic-plastic analyses were also carried out using the finite element method. As a result, the crack penetration area and the crack growth direction were successfully predicted by the analyses. The fatigue lives estimated by the analyses were close to those obtained by the experiments.
Study on Reducing Relative Displacement of Isolation Device With Friction Surface of Inclination
Authors: Shintani Masanori , Tanaka Hiroki
Published: July 2009

This paper deals with an isolation device by using friction force. An isolation device decreases response acceleration and external force. Therefore, earthquake damage is reduced. However, an isolation device has a demerit for large relative displacement. The purpose of this research is to decrease the relative displacement by using the friction force. Then, an analytical model in consideration of the friction force is proposed, and a simulation is analyzed with well-known earthquake waves. Consequently, it is thought that optimal friction force exists, and this force decreases both the response acceleration and the relative displacement. This is considered to change with the properties of earthquake waves. Then, it analyzed using the regular random wave. The result, the proportional relation was seen between relative displacement and the optimal coefficient of friction. Then, by changing a friction coefficient according to relative displacement, it is thought that both response acceleration and relative displacement can be reduced. However, it is difficult to change a friction coefficient. So, in this research, reduction of response acceleration and relative displacement is aimed by changing the angle of a friction surface and friction force. Furthermore, an angle is changed in the middle of a slope. It is thought that it becomes possible to reduce response acceleration and relative displacement further. An experimental device is made under the same conditions as the proposed analytical model. The experimental results are compared with the analytical results.
Dynamic Strength Evaluation of Straight Pipe Using Energy Balance Method
Authors: Minagawa Keisuke , Fujita Satoshi , Kitamura Seiji , Okamura Shigeki
Published: July 2009

This paper describes a relationship between fatigue failure and the input energy from results of forced vibration experiment using straight pipe. In Japan, mechanical structures installed in nuclear power plants such as piping and equipment are usually designed statically in the elastic region. Although these mechanical structures have a sufficient seismic safety margin, understanding the ultimate strength is very important in order to improve the seismic safety reliability in an unexpected severe earthquake such as the Great Kobe Earthquake (1995) and the Niigataken Chuetsu-oki Earthquake (2007) in Japan. A rational design method is also being required in accordance with a revision of seismic standard in Japan. In this study, the ultimate strength of a mechanical structure is investigated from a viewpoint of the energy balance equation that is one of valid methods for the structural calculation. A main feature of the energy balance equation is that explains accumulated information of motion. Therefore the energy balance is adequate for an investigation into the influence of cumulative load. Authors have already confirmed a relationship between fatigue failure and the input energy from results of experiments using simple single degree of freedom models in a previous study. In this paper, straight pipe models are adopted instead of simple single degree of freedom models, and the relationship between fatigue failure and the input energy is investigated. The straight pipe model is made of stainless steel, and has natural frequency of approximately 21 Hertz. The investigation is implemented by forced vibration experiments that lead the experimental model to fatigue failure. In the experiment, colored random waves whose predominant frequencies are similar to natural frequency of the experimental model are input. The experimental model vibrates in the elasto-plastic region due to the colored random wave input, and cracks finally. As a result of the experiment, it is confirmed that the input energy for failure increase with an increase of time for failure. In other words, much input energy for failure is needed in case of small input level. This tendency is same as the result of the previous study using simple single degree of freedom model. Therefore it is expected that any actual piping satisfy this tendency, and time for failure can be expected by using energy balance.
Elastic-Plastic Analysis of an Elbow With Axial Part-Through Internal Crack at Crown Under In-Plane Bending
Authors: Prabhakaran K. M. , Bhate S. R. , Bhasin V. , Ghosh A. K.
Published: July 2009

Piping elbows under bending moment are vulnerable to cracking at crown. The structural integrity assessment requires evaluation of J-integral. The J-integral values for elbows with axial part-through internal crack at crown under in-plane bending moment are limited in open literature. This paper presents the J-integral results of a thick and thin, 90-degree, long radius elbow subjected to in-plane opening bending moment based on number of finite element analyses covering different crack configurations. The non-linear elastic-plastic finite element analyses were performed using WARP3D software. Both geometrical and material nonlinearity were considered in the study. The geometry considered were for Rm/t = 5, and 12 with ratio of crack depth to wall thickness, a/t = 0.15, 0.25, 0.5 and 0.75 and ratio of crack length to crack depth, 2c/a = 6, 8, 10 and 12.
Application of Bolted Flange Joint Assembly Guidelines HPIS Z103 TR to ePTFE Sheet Gasket
Authors: Tsuji Hirokazu , Terui Yuuki
Published: July 2009

Bolt tightening guidelines HPIS Z 103 TR for flange joint assemblies have been developed to provide a simple and effective procedure to tighten flange joint bolts. This assembly procedure is applicable to compressed fiber sheet gaskets and spiral wound gaskets, but is not applicable to expanded PTFE (ePTFE) sheet gaskets for the reason that the ePTFE material has lower modulus of elasticity and higher creep/relaxation rate. In this study, expansion of the application scope of HPIS Z103 TR to ePTFE sheet gaskets is investigated. Tightening tests are conducted using flange joint specimens of JPI 4 inch and 6 inch, and all bolt forces and flange gaps are measured at each tightening step to check for uneven tightening. Uniformity of the bolt forces and flange gaps are comparable to those obtained by other types of gaskets or by tightening procedure ASME PCC-1. The influences of gasket relaxation and elastic interaction on the bolt forces are also demonstrated. As a result, flange joint assembly guidelines HPIS Z 103 TR can be considered applicable to the high-density ePTFE sheet gasket, although a post-tightening step of 1 or 2 passes is necessary to compensate for the bolt force reduction induced by gasket relaxation.
Research and Development of Vibration Control Device by Using Displacement Amplification Mechanism
Authors: Watakabe Tomoyoshi , Fujita Satoshi , Omi Toshio , Kurabayashi Hiroshi , Ogata Keiji
Published: July 2009

Many types of dampers have been developed as seismic technique for architectural buildings, and some of these devices have been applied in Japan. In recent years, these dampers begin to be applied to the low-rise structures having the natural frequency in higher range. However, the deflection of low-rise structures is small, and the performance of damper isn’t obtained against small amplitude vibrations. In this study, the new type of damper which has the displacement amplification mechanism has been developed to solve the above problem. To amplify the displacement by applying the principle of leverage, the damper can achieve good performance even if the deformation transmitted to damper is small. This paper reports on the results obtained from loading test of the proposed damper and the vibration control performance of the proposed damper which was investigated by seismic response analysis.
Master Curve Approach for Some Japanese Reactor Pressure Vessel Steels
Authors: Tomimatsu Minoru , Hirano Takashi , Asada Seiji , Saeki Ryoichi , Miura Naoki , Yamashita Norimichi , Yonehara Akira , Saito Itaru
Published: July 2009

The Master Curve Approach for assessing fracture toughness of reactor pressure vessel (RPV) steels has been accepted throughout the world. The Master Curve Approach using fracture toughness data obtained from RPV steels in Japan has been investigated in order to incorporate this approach into the Japanese Electric Association (JEA) Code 4206, “Method of Verification Tests of the Fracture Toughness for Nuclear Power Plant Components”. This paper presents the applicability of the Master Curve Approach for Japanese RPV steels.
Management of Header End Cap Cracking in an HRSG Fabricated From P91 and Other Steels
Authors: Paterson Iain R. , Brett Colin R.
Published: July 2009

This paper describes the development of an assessment method to manage the integrity of numerous header end caps in an HRSG, some of which possess cracks. Following replacement of a P91 header, a subsequent inspection uncovered the presence of cracking in the end cap welds. There was evidence throughout of poor manufacturing quality and concerns over the end cap design, which analysis showed to be highly stressed. From a detailed assessment employing the methodology of the R5 procedure used in the UK, a life assessment provided a ranking list of end cap designs from which a targeted inspection strategy was devised. An NDE inspection procedure, using Phased Array and TOFD methods, was developed to inspect a sample of end caps. Further cracking across the header population was detected in both P91 other materials. Crack depths were compared to model predictions and an inspection strategy developed, taking account of both fatigue cracking as well as the perceived threat posed by Type IV cracking. Various recommendations are presented including the need for further materials data to support the process to enable the station to extend periods between re-inspections.