bluuebunny/crossref_metadata_2025 huggingface dataset:
Turbulence Intensity Evaluation in a Radial-Tangential Plane Within a Cyclone Separator Using PIV
Authors: Gutierrez Torres C. del C. , Jimenez-Bernal J. A. , Garcia-Sanchez J. A. , Aguilar Morales H.
Published: July 2010

Experimental results for turbulence intensity measurements within a cyclone separator are presented in this work. Experimental data was obtained in a tangential-radial plane located 5 mm from the top wall of the cyclone separator. PIV technique was used to obtain experimental data at three different flow conditions (Re = 3.66×104, Re = 9.15×104, and Re = 1.46×105). Reynolds number calculations was carried out using flow inlet velocity and cyclone diameter as characteristic length. Although the flow inside a cyclone separator is a swirling flow, velocity fields obtained using the PIV technique are reported in an orthogonal coordinate system. Therefore, turbulence intensity measurements presented are for u and v velocity components. Maximum values for turbulence intensities increase as Reynolds number increases; however, this increase is not a proportional one.
Microscale Heat Transfer Measurements of the Lateral Merger During Subcooled Pool Boiling of Pentane
Authors: Delgoshaei Payam , Kim Jungho
Published: July 2010

Measurements of space and time resolved heat transfer during lateral bubble merger during subcooled pool boiling of pentane in earth gravity environments were obtained using a microscale heater array. Data from individual heater elements in the array were synchronized with bottom and side view images from two high-speed cameras. The heat transfer due to the lateral merger was found to be closely related to the contact line movement on the heater.
A Curious Result: A Combined Heat-Pump and Rankine Cycle Which Supplies Work and Cold Air to the Ambient
Authors: Pothier Stephen G. , Chichka David
Published: July 2010

The Kelvin-Plank statement of the Second Law of Thermodynamics states that work cannot be taken from a constant temperature reservoir without putting energy in first. This means a device cannot be built that produces work from ambient air temperature without a constant supply of work or heat into the device. However, this paper presents the analysis of a particular coupling of two cycles that appears to do just that. The machine combines two thermodynamically matched cycles: a heat-pump cycle and a Rankine cycle. Each cycle runs the other, with the net result being shaft work available to the ambient and an exhaust product of cold air. The only input to the machine is 12°C air from the ambient atmosphere. The heat-pump uses ammonia as the working fluid, absorbing heat from ambient atmosphere and supplying heat to the Rankine engine boiler. The Rankine cycle expansion engine uses propane as the working fluid, and supplies shaft work to power the heat-pump compressor. Using standard, well-known analysis, the net result is a machine that, once started, supplies work and cold air to the ambient with no further work input. Under ideal analysis, the heat-pump operates with a coefficient of performance of 6.85 and the Rankine cycle operates with an efficiency of 21%. Multiplying these gives a combined cycle efficiency of 1.44. The heat-pump superheater operates at an average temperature of −44°C, with a mass flow rate of 1.00 kg/s. It absorbs 106 kW of heat from ambient temperature air and supplies that heat to the Rankine cycle boiler. The Rankine cycle expansion engine has a mass flow rate of 2.51 kg/s, and produces 364 kW of work. Of this, 254 kW is supplied to the heat-pump compressor, 4 kW to the Rankine cycle feed-pump, and the remaining 106 kW of work to the ambient. This equals the heat extracted from the ambient; there is no unexplained creation of energy. All analysis was performed from standard engineering text books, and all thermodynamic data was taken from common industry charts. The cycles are common and well known, and the temperatures, pressures, and expansion ratios well within believable values. The analysis has been peer reviewed and no errors found. Yet when these two cycles with these two working fluids are combined, the result is net work to the environment and cold air, with no work or heat input. The authors do not believe the second law is flawed. We expect an error will be discovered, either in our analysis or in the thermodynamic tables of the two fluids that we used. We present the analysis and result in the hopes of having the error pointed out.
Characterization of Vapor Escape Restriction in Biporous Wicks With Monolayers for Thermal Ground Plane Optimization
Authors: Reilly Sean W. , Catton Ivan
Published: July 2010

Developing better heat pipes requires advancement of technology in all aspects of construction. In this paper I am investigating the effect of vapor pathways on the performance of biporous wicks in heat pipes. Biporous evaporator wicks, generated by sintering copper particles into semi-uniform clusters, were demonstrated to achieve high flux, heat transfer performance for use in heat pipes by Semenic (2007). The effective thermal conductivity of thick biporous wicks at high heat fluxes was found to be reduced because the region next to the wall dried out prematurely, allowing the wall interface temperature to rise well above the saturation temperature. One possible way to reduce the size of the wall-wick interface dry-out region is to sinter a thin layer of uniform size particles on the wall as suggested by Seminic. The boiling curve for this “double layer” wick diverges from a standard “single layer” biporous wick at the point of nucleation by reducing the wall temperature, and concurrently the overall temperature drop across the wick needed to drive a given heat flux. The temperature drop across the wick is reduced because the thin layer of particles between the biporous wick and the wall reduces the wall-wick interface resistance and also provides additional capillary channels underneath the biporous wick. Experimental data supports this hypothesis by showing a clear divergence between measured wall temperatures for the double layer wick from its single layer counterpart with an indication that smaller cluster sizes in the biporous wicks perform better at lowering the superheat required to obtain high fluxes. In this work, we are looking to compare the performance of these wicks to similarly sized blocks of copper in order to investigate the performance increase offered by the wicks. In order to investigate this phenomenon we ran experiments in a similar manner to previous experiments done by Reilly (2009), but a plate was inserted into the chamber above the wick to restrict the vapor flow. To determine the behavior in the copper we ran several simulations in COMSOL (a finite element software used for doing conduction analysis) of copper disks at different representative thicknesses. We ran experiments with the plate at several heights above the wick, going so far as to place the plate flush with the upper surface of the wick to force vapor back through the wick laterally. By comparing the results between these two sets of experiments we were able to deduce that even in the case where there was no open space above the wick for vapor to escape, we were still able to double the performance with respect to a system of solid copper.
A Finite Element Parametric Study of Femur Fracture Force in Out-of-Position Seating Positions Fracture Femoral Forces to Abbreviated Injury Scale Level 2+ and 3+
Authors: Silvestri Chiara , Ray Malcolm H.
Published: July 2010

This research aimed at investigating the relationship between the femur forces of an out-of-position vehicle occupant and the potential injury severity occurring to the lower extremities during a frontal car crash. A better understanding and prediction of injuries allows for deriving thresholds to theoretically define values at which injuries could potentially occur, with the purpose of guiding engineers in the design of safer vehicles. A validated Knee-Thigh-Hip (KTH) finite element model of a 50th percentile male was used with the code LSDYNA to explore injury mechanisms in frontal impacts. The KTH joints were positioned at different angles of thigh flexion, adduction and abduction. Values for the Abbreviated Injury Scale (AIS) level 2+ and 3+ were calculated using peak femur forces obtained with the FE simulations and regression equations for predicting KTH injuries developed by Kuppa [1]. The study shows that the probability of KTH bone fracture is higher when the thigh is initially abducted. The study also shows that the probability of KTH bone fracture is lower when the thigh is initially flexed, rather than in a neutral position. When considering combinations of adduction and flexion, results show that the probability of KTH bone fracture is not significantly affected by the angle of thigh flexion. On the other hand, results also show that the probability of KTH bone injury when the thigh is flexed and either adducted or abducted to a relative high angle is lower.
System Dynamics Experimentation at Home
Authors: Jouaneh Musa K. , Palm William J.
Published: July 2010

Most Mechanical Engineering curricula include courses in system dynamics, controls, mechatronics, and vibrations. At most schools, these courses do not have a laboratory component. Even at schools that have such a component, laboratory access is often limited, and thus there is a need to increase students’ laboratory experience. This paper addresses the development and initial testing of instructional material in the form of take-home software and hardware kits that can be used to perform laboratory experiments and measurements at home to illustrate system dynamics concepts. Rather than having students perform an experiment in the university laboratory, the students are given a compact, low cost software and hardware kit with which they can perform an experiment at home using only their PC. The kits are designed so that the experiments can be conducted on a provided experimental setup such as a DC motor/tachometer system or can be used to perform dynamic measurements on engineering systems that are available at home such as motor powered devices and heating/cooling systems. The take-home kit consists of three components. The first component is a hardware interface board that is built around a PIC18F4550 microcontroller which interfaces with the student’s PC and with the experiment hardware. The second component is a Windows based user interface program that is loaded on the student’s PC and is used to run the experiment and collect data. The third component is the actual experimental setup or the sensor system to perform the measurement. Fifty five kits have been fabricated to perform five different experiments. Two of these experiments were tested in two courses in the mechanical engineering department at the University of Rhode Island. The paper discusses the design of the kit components, the details of the experiments, as well the initial experiences gained from using this new approach for laboratory experimentation.
Effect of Radiation, Chemical Reaction and Double Dispersion on Heat and Mass Transfer in Non-Darcy Free Convective Flow
Authors: Kameswaran P. K. , Murti A. S. N.
Published: July 2010

The present paper deals with the effect of chemical reaction, radiation and double dispersion on non-Darcy free convective heat and mass transfer from semi-infinite impermeable vertical wall in a fluid saturated porous medium. The Forchheimer extension is considered in the flow equations, while the radiation chemical reaction power-law term is considered in energy and concentration equations. The governing equations are solved numerically by means of fourth order Runge-Kutta method coupled with the double shooting technique. By giving appropriate hypothetical values for f′(0), θ′(0) to match with the corresponding boundary conditions at f′(∞) θ(∞) respectively. The influence of radiation on double dispersion, solute dispersion, velocity, temperature and concentration profiles as well as heat transfer and mass transfer rates are discussed.
Finite Element Analysis of a Locked Bolt With an Initial Crack
Authors: Kabche Jean Paul , Pacheco Mauri´cio Rangel , Thesi Ivan , Largura Luiz Carlos
Published: July 2010

Bolted connections are largely employed in various types of engineering structures to transfer loads from one member to another. In particular, the off-shore industry has made extensive use of these connections, predominantly at the sub-sea level. In spite of their advantages, bolted joints are critical regions and may become sources of structural weakness due to large stress concentrations. Under severe operating conditions, micro-cracks can develop in the bolt, creating regions of elevated stress which may significantly reduce the integrity of the connection and ultimately lead to failure. This paper presents the three-dimensional finite element analysis of a steel locked bolt assembly aimed to assess the effect of micro-cracks on the structural integrity of the assembly using the commercial finite element package ANSYS. Non-linear contact between the bolt and nut threads is considered, where frictional sliding between components is allowed. A bi-linear isotropic hardening model is used to account for non-linear material behavior. The assembly is loaded by applying a pre-load of fifty percent of the yield stress of the material, according to the API-6A Norm. Two geometric models are investigated: a healthy locked bolt assembly with no initial cracks; and a damaged model, where a circular crack is introduced at the root of the bolt threads. The effect of the crack size is studied by modeling the crack with three different radius sizes. The J-Integral fracture mechanics methodology was used to study the stress concentrations in the damaged model.
IPMC Force Scanner
Authors: Martinez Manuel N. , Schmitt Brian R. , Lumia Ronald
Published: July 2010

This paper describes the design and development of device capable of measuring the force output of ionic polymer-metal composites (IPMC) actuators in two dimensions. Results from an experiment on a rectangular IPMC (17 mm × 7 mm × .07 mm) are used to show that blocked force output across the actuator varies by greater than 85% for a 3V input (Fig. 1). This decrease in blocked force output is shown to be exponential and occurring along the length. Deviations in single digit mN force output for the actuator are shown to generally be less than 10%.
The Effect of Pulsed Active Steering on the Dynamic Roll Response of a Passenger Vehicle
Authors: Abdel-Rahman Akram , Khajepour Amir , McPhee John
Published: July 2010

Using a pulsed signal instead of a constant signal as the output of an active steering system arises new areas to study. This paper focuses on the effect of changing the characteristics of the pulse signal of an active steering system on the roll response of a passenger car. The characteristics of a pulse consist of its frequency, its amplitude, and its pattern. A vehicle model was built in DynaFlexPro to be used in a MATLAB/Simulink environment to study the roll response for various simulation runs. There were three sets of simulations carried out, each set consists of fixing two characteristics and changing the third. The results obtained were compared through the rollover coefficient, R, of the model throughout the simulations.
Experiment and 2D Numerical Simulation of Cooking Process of Chicken Breast
Authors: Giorges Aklilu T. G. , Stewart John , Pierson John A.
Published: July 2010

In this work, we presented the experimental and numerical work of the cooking process of chicken breast muscles. The experimental cooking process was done in a convection oven where the chicken breast was placed on top of the plate. The experimental thermal history of the cooking and cooling process was measured using thermal probes at six locations. The measured temperature is used to evaluate the numerical model and define the heat transfer coefficient. Indeed, the result illustrates that the surface irregularity and the shape have a significant effect on the local temperature profile. In addition, the two-dimensional model illustrates the significance of the product variation in thickness. Although the computational simulation can generate detailed local data, there is no new method developed to quantify and evaluate the efficiency of cooking. Therefore, quantitiave estimation of the degree of cooking process (over- or undercooking) is attempted. Based on the cooking requirement (critical temperature), cooking process, and product shape, the two-dimensional analysis allows quantification of the shape factors that can lead to over and/or undercooking. Furthermore, knowing the cooking profile effect and the product shape and variations, the cooking process may be adjusted and optimized. In addition, the result of the numerical work shows that it is possible to realistically simulate the cooking process of a complicated shape like a chicken breast.
Numerical Study of Nozzle Design on Cadmium Quenching Process in Thermochemical Splitting of Water
Authors: Nie Jianhu , Chen Yitung , Wong Bunsen , Brown Lloyd C.
Published: July 2010

Three-dimensional liquid-gas flow with condensation during cadmium quenching process for hydrogen production was numerically simulated in order to effectively guide the design of solar decomposer and vapor quencher. The mixture model was selected for modeling the multiphase flow, and the two-equation RNG k-ε model was used to model the turbulent flow and heat transfer. Numerical results including velocity, temperature, pressure, and mole fraction distributions were obtained for different nozzle designs. Numerical results showed that flow is relatively low in the decomposer and close to the bottom and the top inlets. The maximum velocity develops in the region near the entrance of the quenching nozzle as the nozzle angle is small. As the nozzle angle is large, the maximum velocity appears in the exit tube. Temperature, pressure and cadmium vapor distributions are also directly affected by the nozzle angle.
Fatigue Life Prediction of Al-Li Alloy Butt-Welded Joints in Aerospace Structures
Authors: Wahab Muhammad A. , Raghuram Vinay
Published: July 2010

Friction-Stir-Welding (FSW) has been adopted as a major process for welding Aluminum aerospace structures. AA-2195 is one of the new generations Aluminum alloy (Al-Li) that has been used on the new super lightweight external tank of the space shuttle. The Lockheed Martin Space Systems (LMSS), Michaud Operations in New Orleans is continuously pursuing FSW technologies in its efforts to advance fabrication of the external tanks of the space shuttle. The future launch vehicles which will have to be reusable, mandates the structure to have good fatigue properties, which prompts an investigation into the fatigue behavior of the friction-stir-welded aerospace structures. The butt-joint specimens of Al-2195 are fatigue tested according to ASTM-E647. The effect of Stress ratios, Corrosion-Preventive-Compound (CPC), and periodic Overloading on fatigue life is investigated. Scanning Electron Microscopy (SEM) is used to examine the failure surfaces and examine the different modes of crack propagation i.e. tensile, shear, and brittle modes. It is found that fatigue life increases with the increase in stress ratio, the fatigue life increases from 30–38% with the use of CPC, the fatigue life increases 8–12 times with periodic overloading; crack closure phenomenon dominates the fatigue facture. Numerical Analysis using FEA has also been used to model fatigue life prediction scheme for these structures, the interface element technique with critical bonding strength criterion for formation of the new surfaces has been used to model crack propagation. The fatigue life predictions made using this method are within the acceptable ranges of 10–20% of the experimental fatigue life. This method overcomes the limitation of the traditional node-release scheme and closely follows the physics of crack propagation.
Development of Analytical Skills Through Cooperative Learning
Authors: Ghosh Amitabha
Published: July 2010

Learning analytical skills in the context of formulating and solving a well-posed fluid flow problem requires special considerations which are often missed by students or under-emphasized by faculty during instructional delivery of materials. This paper presents the results of a pilot study in the class Transport Phenomena to determine if cooperative learning and working in groups would assist better understanding of these topics. Cooperative learning was found to have many benefits related to comprehension and positive interdependence. But benefits derived from this approach are limited unless such methods are reinforced in several places in the curriculum. Comparative performance data is presented with and without this approach. Issues related to Bloom’s taxonomy and cognitive apprenticeship were investigated and discussed in context of the class Transport Phenomena.
Sliding Mode Controller and Filter Applied to a Pneumatic McKibben Muscle Actuator
Authors: Jouppila V. , Gadsden S. A. , Habibi S. R. , Bone G. M. , Ellman A.
Published: July 2010

In this paper, a robust and stable control strategy is applied to a Festo fluidic muscle actuator, with the objective of trajectory following control. A complete model of this system is not available which leads to unmodeled dynamics and uncertainties. Furthermore, full-state feedback is required for this type of control. However, in practice not all of the states are measurable or available due to cost or availability of instruments, thus a full-state observer is required. The Smooth Variable Structure Filter (SVSF) is a recently introduced robust predictor-corrector method used for state and parameter estimation, and has a form that is able to provide full-state information. In this regard, a new strategy that combines Sliding Mode Control (SMC) with the SVSF is used to control this system. The estimated states from the SVSF are used by the sliding mode controller to obtain a discontinuous control signal. This signal drives the plant to follow a desired state trajectory required by the pneumatic McKibben muscle actuator. Simulation results were generated based on a realistic desired trajectory. The results of the SMC-SVSF control strategy are compared with a tuned PID controller. The described control strategy is able to overcome the nonlinearities present in the system, has a fast response time, and is robust to modeling uncertainties and measurement noise.
Characterizing Wind Speed and Air Density for Wind Energy Estimation
Authors: Qu Xiuli , Shi Jing
Published: July 2010

Wind energy is the fastest growing renewable energy source in the past decade. To estimate the wind energy potential for a specific site, the long-term wind data need to be analyzed and accurately modeled. Wind speed and air density are the two key parameters for wind energy potential calculation, and their characteristics determine the long-term wind energy estimation. In this paper, we analyze the wind speed and air density data obtained from two observation sites in North Dakota and Colorado, and the variations of wind speed and air density in long term are demonstrated. We obtain univariate statistical distributions for the two parameters respectively. Excellent fitting performance can be achieved for wind speed for both sites using conventional univariate probability distribution functions, but fitting air density distribution for the North Dakota site appears to be less accurate. Furthermore, we adopt Farlie-Gumbel-Morgenstern approach to construct joint bivariate distributions to describe wind speed and air density simultaneously. Overall, satisfactory goodness-of-fit values are achieved with the joint distribution models, but the fitting performance is slightly worse compared with the univariate distributions. Further research is needed to improve air density distribution model and the joint bivariate distribution model for wind speed and air density.
Increasing the Efficiency of a Gas Turbine Power Plant by Waste Heat Recovery
Authors: Shukla P. , Izadi M. , Marzocca P. , Aidun D. K.
Published: July 2010

The objective of this paper is to evaluate methods to increase the efficiency of a gas turbine power plant. Advanced intercooled gas turbine power plants are quite efficient, efficiency reaching about 47%. The efficiency could be further increased by recovering wasted heat. The system under consideration includes an intercooled gas turbine. The heat is being wasted in the intercooler and a temperature drop happens at the exhaust. For the current system it will be shown that combining the gas cycle with steam cycle and removing the intercooler will increase the efficiency of the combined cycle power plant up to 60%. In combined cycles the efficiency depends greatly on the exhaust temperature of the gas turbine and the higher gas temperature leads to the higher efficiency of the steam cycle. The analysis shows that the latest gas turbines with the intercooler can be employed more efficiently in a combined cycle power application if the intercooler is removed from the system.
Influence of Cutting Parameters and Tool Wear on Martensitic Stainless Steel Surface Integrity After a Face Milling Process
Authors: Mun˜oz de Escalona Patricia , Maropoulos Paul G.
Published: July 2010

Surface finish is one of the most relevant aspects of machining operations, since it is one of the principle methods to assess quality. Also, surface finish influences mechanical properties such as fatigue behavior, wear, corrosion, etc. The feed, the cutting speed, the cutting tool material, the workpiece material and the cutting tool wear are some of the most important factors that affects the surface roughness of the machined surface. Due to the importance of the martensitic 416 stainless steel in the petroleum industry, especially in valve parts and pump shafts, this material was selected to study the influence of the feed per tooth and cutting speed on tool wear and surface integrity. Also the influence of tool wear on surface roughness is analyzed. Results showed that high values of roughness are obtained when using low cutting speed and feed per tooth and by using these conditions tool wear decreases prolonging tool life.
About Relation Between Irradiation Hardening of Ferritic Steels and Ductile Fracture Toughness Decrease
Authors: Novak Jiri
Published: July 2010

We showed recently that temperature dependence of the ductile fracture toughness can be predicted on the base of two assumptions: 1) assumption of constant characteristic length, 2) assumption of proportionality between J-R curve slope and deformation work in unit volume, evaluated from zero to critical strain for initiation of deformation bands determined in plane strain geometry for material modeled by deformation theory of plasticity. Temperature dependence of ductile fracture toughness results simply from temperature dependence of the stress-strain curve. Irradiation hardening changes stress-strain behavior in a qualitatively different way: It is observed that irradiation hardening to certain yield stress level changes the stress-strain curve of the material in the same way as prestraining of the unirradiated material to the same flow stress level does. Equivalence of irradiation and prestraining concerns all key properties of deformation theory; namely the secant modulus should be taken from the stress-strain curve of unirradiated material. With exception of this specific feature, the task of finding relative fracture toughness decrease by irradiation is the same as prediction of relative decrease of fracture toughness by temperature change. In the frame of the corresponding theory, relative decrease of ductile fracture toughness expressed by J-R curve slope can be obtained from the stress-strain curve of unirradiated material and irradiation hardening level. Quantitative results are presented for the weld metals 72W and 73W, studied in the Fifth Irradiation Series in the Heavy-Section Steel Irradiation Program, and compared with experimental data.
In-Service Refinery and Pipeline Cracking Initiated by Hydrostatically Induced Strain
Authors: Messer Barry , Beaulieu Keith , Wright Andrew , Hatch Kevin
Published: July 2010

A new phenomenon of in-service cracking has been observed in carbon steel pipelines, refinery piping and refinery equipment that is initiated by sources such as hydrostatic testing and is identified as Strain Accrual Hydrogen Cracking. Although hydrostatic testing is beneficial to blunting crack tips and reducing crack propagation, high hydrostatic test pressures approaching yield cause localized threshold strains in weldments and base materials that consequently increases the susceptibility to nascent hydrogen embrittlement at strain boundaries. This paper discusses strain accrual hydrogen cracking mechanisms, beneficial and detrimental effects of high hydrostatic test pressures, increased Code allowable stresses, micro alloying additions and strain based design, case histories, and suggests mitigation practices.
Fracture Estimation Method for Pipe With Multiple Circumferential Surface Flaws
Authors: Li Yinsheng , Hasegawa Kunio , Onizawa Kunio , Shimomoto Masayoshi
Published: July 2010

When a flaw is detected in a stainless steel piping system of a nuclear power plant during in-service inspection, the fracture estimation method provided in the codes such as the ASME Code Section XI or the JSME S NA-1-2004 can be applied to evaluate the integrity of the pipe. However, in these current codes, the fracture estimation method is only provided for the pipe containing a single flaw, although independent multiple flaws such as stress corrosion cracks have actually been detected in the same circumference of stainless steel piping systems. In this paper, a fracture estimation method is proposed by formula for multiple independent circumferential flaws with any number and arbitrary distribution in the same circumference of the pipe. Using the proposed method, the numerical solutions are compared with the experimental results to verify its validity, and several numerical examples are provided to show its effectiveness.
Prediction of Failure Bending Moment for a Pipe With an Arbitrary-Shaped Circumferential Flaw
Authors: Li Yinsheng , Hasegawa Kunio , Shibuya Akira
Published: July 2010

When a flaw is detected in a stainless steel piping system, failure bending moment can be predicted by limit load criterion in accordance with Appendix E-8 in the JSME S NA-1-2004 and Appendix C in the ASME Code Section XI. However, in these current codes, the limit load criterion is only calculated for the case of a pipe containing a single flaw with constant depth, although the actual flaw depth is variable along the circumferential direction. Particularly, geometrical shapes of stress corrosion cracks are generally complex. The objective of this paper is to propose a method for predicting the load-carrying capacity by formula for a pipe containing a circumferential surface flaw with any arbitrary shape. The failure bending moment is obtained by dividing the surface flaw into several sub-flaw segments. Using this method, good agreement is observed between the numerical solution and the reported experimental result. Several numerical examples are also given to show the validity of this method. Finally, it can be found that the number of the sub-flaw segments is sufficient to be three for the semi-elliptical surface flaw.
The Ultimate Strength of Cylindrical Liquid Storage Tanks Under Earthquakes: Seismic Capacity Test of Tanks Used in BWR Plants
Authors: Iijima Toru , Suzuki Kenichi , Higuchi Tomokazu , Sato Yuji
Published: July 2010

Since 2002, Japan Nuclear Energy Safety Organization (JNES) has been carrying out seismic capacity tests. The condensate storage tank (CST) which is used in a BWR plant is one of the most important equipment from the viewpoint of seismic Probabilistic Safety Assessment (PSA). Many CST have the shape characteristics of a large diameter and relatively low height. And typical damage mode is expected to be elephant-foot bulge (EFB) or shear buckling. In this study, JNES performed shaking table tests using scaled models of the tank to clarify failure mode and ultimate strength, or acceleration level which caused failure of the tank. The excitation level was increased until the tank reached the failure mode, or ultimate state. In the excitation tests, EFB and shear buckling were observed, and the tank resulted in the ultimate state in which internal water leaked from cracks caused by shear buckling on the sidewall. The seismic capacity and dynamic response reduction effect were evaluated from test results, and the method to estimate seismic capacity of the thin walled cylindrical tank like CST using FEM analysis and the dynamic response reduction factor was proposed.
Evaluation of Alignment Rules Using Stainless Steel Pipes With Non-Aligned Flaws
Authors: Hasegawa Kunio , Miyazaki Katsumasa , Saito Koichi , Bezensek Bostjan
Published: July 2010

Multiple flaws such as stress corrosion cracks are frequently detected in the same welded lines in pipes. If multiple discrete flaws are in close proximity to one another, alignment rules are used to determine whether the flaws should be treated as non-aligned or as coplanar. Alignment rules are provided in fitness-for-service codes, such as ASME, JSME, API 579, BS 7910, etc. However, the criteria of the alignment rules are different among these codes. This paper briefly introduces these flaw alignment rules, and four-point bending tests performed on stainless steel pipes with two non-aligned flaws. The experimental plastic collapse stresses are determined from the collapse loads and compared with collapse stresses calculated from the limit load criteria. The limit loads are obtained for single non-aligned or aligned coplanar flaws in accordance with the alignment rules. On this basis, the conservatism of the alignment rules in the above codes is assessed.
Interaction Effect Analysis of Two Surface Cracks Using S-Version FEM
Authors: Kikuchi Masanori , Wada Yoshitaka , Suyama Hitomi , Li Yulong
Published: July 2010

Fatigue crack growth under mixed mode loading conditions is simulated using S-version FEM. By using S-FEM technique, only local mesh should be re-meshed for new crack configuration, and it becomes easy to simulate crack growth. By combining with auto-meshing technique, local mesh easily re-meshed and curved crack path is modeled easily. Fully automatic crack growth simulation system in 3-dimensional problem is developed. Using this system, a basic slant surface crack problem is solved, and it is shown that surface crack grows under pure mode I condition, which is similar to 2-dimensional problem. It is also shown that this system is available for complicated structures, for example, surface crack at inner surface of pipe. Finally, interaction effect of two surface cracks is evaluated.
Structural Integrity Assessment of RPV With Brittle Fracture Criterion: Issues and Advanced Approaches
Authors: Karzov George , Margolin Boris , Shvetsova Victoria , Kostylev Victor
Published: July 2010

A key input to calculation of the structural integrity of the RPV by the brittle fracture criterion is known to be the fracture toughness of a material. When calculating resistance of RPV to brittle fracture it was taken earlier that fracture toughness, KJC, depends only on temperature, and does not depend on thickness of specimens if this thickness is sufficiently large so that the plane strain condition is satisfied. To date it has become clear by many researches that KJC depends on a crack front length. This follows from the statistical nature of brittle fracture in steels. It means that for adequate assessment of RPV structural integrity, the dependence of KJC on the postulated flaw size has to be taken into account. Moreover, it has been shown that the KJC values for specimens with shallow cracks are larger than for specimens with deep cracks, and the KJC values obtained from small-size fracture toughness specimens (for example, pre-cracked Charpy specimens) are larger than the values for CT specimens with thickness of 25 mm, and KJC values may be affected load biaxiality. These findings are explained by the loss of constraint. Thus, for adequate assessment of RPV structural integrity by the brittle fracture criterion, the scale factor has to be taken into account, with two causes being responsible: the physical cause connected with the statistical nature of brittle fracture and the mechanical one related to the difference in constraint for specimens of various geometries. This analysis is important for assessment of RPV structural integrity because i) for most cases the postulated flaws in RPV, due to their size and location, may be considered as shallow cracks; ii) the KJC values for irradiated RPV steels are usually obtained from small-size surveillance specimens that are as a rule, pre-cracked Charpy specimens; iii) for a postulated flaw in RPV, a load acts both perpendicular and along a crack front. i.e. loading is biaxial. For adequate assessment of RPV structural integrity by the brittle fracture criterion it is also necessary to take into account that distribution of the stress intensity factor along a crack front in RPV is heterogeneous, and loading is non-monotonic and non-isothermal. In the present report, advanced approaches are considered for assessment of RPV structural integrity that allow solving the above problems. The considered approaches have been included in Russian Standards for assessment of RPV structural integrity.
Structural Integrity Assessment of WWER Internals on Stress Corrosion Cracking Criterion
Authors: Fedorova Valentina , Margolin Boris
Published: July 2010

Stress-damage dose curve (SDDC) is introduced on the basis of the analysis of experimental data on susceptibility to intergranular stress corrosion cracking (IGSCC) of irradiated stainless steels (SS). Approaches to determination of the SDDC parameters are considered. Based on SDDC calculative procedure for estimation of reactor vessel internals (RVI) lifetime by criterion of initiation crack due to IGSCC is proposed.
Analysis of Crack Growth Conditions in WWER Internals Undergone High Neutron Irradiation
Authors: Margolin B. Z. , Fomenko V. N. , Sorokin A. A.
Published: July 2010

Conditions of stable and unstable crack growth by the mechanism of ductile fracture under quasi-static loading are analyzed. Simulation of crack growth by the finite element method (FEM) based on the strain fracture criterion was carried out. The effect of ratio of an elementary crack extension size to a plastic zone size on the kind of JR-curves is investigated. Based on these investigations conditions are determined under which unstable crack growth is possible for small scale and large scale yielding. The criterion is formulated for the absence of unstable crack growth in highly irradiated austenitic materials including the situation when the Feγ→Feα transition happens.
Stress Re-Distribution Induced by Creep Relaxation Around a Notch Loaded in Tension: Measurement and Modeling
Authors: Leitch Brian W. , Christodoulou Nicolas , Rogge Ronald
Published: July 2010

The majority of the pressure-retaining components in the core of a CANDU power generation system are manufactured from zirconium. The horizontal fuel channel components and the fuel bundles that contain the natural uranium fuel are manufactured using various grades of zirconium. The fuel channel consists of two concentric tubes; an internally pressurized tube (Zr-2.5%Nb) that contains the fuel bundles (Zr-4) and the re-circulating heavy-water primary coolant, enclosed by a larger diameter calandria tube (Zircaloy) that separates the pressure tube from the heavy-water moderator. Re-fuelling and other fuel management operations can create surface defects in the tubes and fuel bundle sheathing. Stress analyses of these small notches may indicate that, under certain conditions, cracks can be formed at the root of these notches. These flaws are locations of stress concentration in the internally pressurized tube and can initiate a failure mechanism known as Delayed Hydride Cracking. The anisotropic material properties of these zirconium components adds an additional level of complexity in an analysis. However, the occurrences of these life-limiting events appear to be minimized mainly due to beneficial contributors such as stress relaxation around the scratches. One of the most likely reasons for this relaxation is thermal creep. Previously [1], the measurement and modeling of thermal creep relaxation under constant displacement was examined using 2-D finite element (FE) models. This paper extends both the measurement and modeling of the relaxing stress/strain field to the more demanding boundary condition of constant applied load. Neutron diffraction is used to determine the changing strain field around a single notched, axially orientated specimen loaded in tension. This specimen orientation and loading configuration is modeled in three dimensions using a hybrid explicit FE program [2] that contains materials subroutines that describe high stress creep specially developed to simulate the highly anisotropic creep response of pressure tube materials. Despite the difficulty of obtaining precise delineation of the moving strain field, a good agreement between the measurements and the 3-D FE creep results is achieved. Using the creep subroutines, the FE models are used to examine the creep response of a single notched, transversely orientated specimen loaded in tension in the hoop direction.
Presentation of RCC-MR Code 2007 for High Temperature Reactor and ITER Projects: Improvement of the Leak-Before-Break Procedure and Related Defect Assessment Tools
Authors: Marie S. , Kayser Y. , Drubay B. , Ne´de´lec M. , Delaval C. , Deschanels H. , Sperandio M.
Published: July 2010

The fourth edition of the RCC-MR code was issued in French and English versions in October 2007 by AFCEN (Association Franc¸aise pour les re`gles de Conception et de Construction des Mate´riels des Chaudie`res Electro-nucle´aires). In the frame of this new edition, important changes have been made in the appendix A16 for the Leak-Before-Break (LBB) procedure and the related tools (defect assessment procedures and fracture mechanics parameter compendia). This paper presents the evolution of the appendix A16 from the 2002 edition of the RCC-MR code: - Defect size determination at penetration and after penetration in the LBB procedure has been modified. - Compendia for KI and reference stress have been improved and extended for cracked plates, pipes and elbows. - Combined mechanical and thermal loading interaction in the Fracture Mechanics parameters (J and C*) calculation has been revised. - A new procedure for the analysis of creep crack growth under cyclic thermal loading is proposed.
Evaluation of Fire Protection Piping in a DOE Performance Category 3 Structure
Authors: Buchanan Larry P.
Published: July 2010

National Fire Protection Association (NFPA) Standard 13 [1] establishes rules and criteria to provide a reasonable degree of protection for life-safety and property loss concerns resulting from fire. These rules and criteria are typically established for commercial type facilities governed by the Uniform Building Code (UBC) [2] or a comparable code. In concert with this stated purpose, NFPA 13 includes provisions for protection against damage when subject to earthquakes. The effectiveness of these rules and criteria may be challenged, however, when the safety function is extended beyond life-safety and property loss to Natural Phenomena Hazards (NPH) evaluation where nuclear safety is also an important issue. This paper presents a criteria and methodology for the evaluation of fire protection piping involving grooved couplings in a Department of Energy, Performance Category 3, multi-story structure. The footprint of the structure is approximately 540 feet by 250 feet or 135,000 square feet. Grooved type couplings are used extensively in the fire protection industry and represent a non-integral type connection between adjacent piping segments, as opposed to welded connections. Due to the nonintegral type connection and the allowable axial and lateral spans permitted by the National Fire Protection Association (NFPA) Standard 13, these type couplings are sometimes considered to be “weak links” when subjected to earthquake loadings. The paper also presents a sample walk-down screening checklist focusing on criteria compliance as well as additional potential weak links that could result in additional seismic demands on the grooved couplings and the fire protection piping system.
Weld Residual Stress Predictions in Reactor Vessel Head Penetrations: FE Simulation
Authors: Teughels Anne , Suanno Rodolfo L. M. , Malekian Christian , Ferrari Lucio D. B.
Published: July 2010

The penetrations in the early Pressurized Water Reactors Vessels are characterized by Alloy 600 tubes, welded by Alloy 182/82. The Alloy 600 tubes have been shown to be susceptible to PWSCC (Primary Water Stress Corrosion Cracking) which may lead to crack forming. The cracking mechanism is driven mainly by the welding residual stress and, in a second place, by the operational stress in the weld region. It is therefore of big interest to quantify the weld residual stress field correctly. In this paper the weld residual stress field is calculated by finite elements, using a common approach well known in nuclear domain. It includes a transient thermal analysis simulating the heating during the multipass welding, followed by a transient thermo-mechanical analysis for the determination of the stresses involved with it. The welding consists of a sequence of weld beads, each of which is deposited in its entirety, at once, instead of gradually. Central as well as eccentric sidehill nozzles on the vessel head are analyzed in the paper. For the former a 2-dimensional axisymmetrical finite element model is used, whereas for the latter a 3-dimensional model is set up. Different positions on the vessel head are compared and the influence of the sidehill effect is illustrated. In the framework of a common project for Angra 1, Tractebel Engineering (Belgium) and Eletronuclear (Nuclear Utility, Brazil) had the opportunity to compare their analysis method, which they applied to the Belgian and the Brazilian nuclear reactors, respectively. The global approach in both cases is very similar but is applied to different configurations, specific for each NPP. In the article the results of both cases are compared.