bluuebunny/crossref_metadata_2025 huggingface dataset:
Service Water Life Cycle Management
Authors: Houston Eric J. , Rahn Arlene S. , Licina George J.
Published: July 2009

Nuclear plant service water systems are a critical part of the facility’s infrastructure. System integrity and performance are vital for plant reliability and essential to achieving a plant life of 40 years and beyond. Corrosion, fouling (macrofouling, microfouling and sedimentation) and other effects that are detrimental to the reliability of the service water system led to the issue of NRC Generic Letter 89-13 “Service Water System Problems Affecting Safety-Related Equipment.” This generic letter continues to be a fundamental guideline for safety related service water systems at all U.S. nuclear plants. The low temperature and pressure service water piping systems are primarily degraded by corrosion. Because of the complexity and random nature of corrosion processes, it is nearly impossible to develop a mathematically deterministic model that accurately predicts pipe wall loss. However, if statistical distributions are used to describe the various corrosion processes, mathematical algorithms that incorporate all of the distributions, iterated a statistically significant number of times, can be used to forecast the most probable number of leaks. This paper predicts the condition of service water piping at Kewaunee Nuclear Power Plant using the described model and includes the expected number of through-wall leaks as a function of operating time.
Cyclic Deformation and Fatigue Behaviors of Stainless Steel 304L Including Mean Stress and Pre-Straining Effects
Authors: Le Roux Jean-Christophe , Taheri Said , Sermage Jean-Philippe , Colin Julie , Fatemi Ali
Published: July 2009

This paper discusses cyclic deformation and fatigue behavior of three grades of stainless steel 304L. Effects of pre-straining and mean stress were investigated and it was observed that these parameters influence both deformation and fatigue behaviors. At HCF, significant secondary hardening was observed for two of the materials, leading to a significant change in fatigue behavior at long lives. For two of the materials, pre-strained tests were also conducted. Hardening was observed as a consequence of pre-straining and affected further deformation and fatigue behaviors significantly. Mean stress effects on fatigue lives were as expected, as compressive mean stress lengthened life and tensile mean stress shortened life. The Smith-Watson-Topper (SWT) parameter was used to correlate the experimental data from all test conditions for the three materials and was found to correlate the experimental data reasonably well.
Technical Basis for Proposed Code Case of Using a Master Curve in Lieu of the Code KIc Curve in ASME Boiler and Pressure Vessel Code
Authors: Yoon Kenneth K. , Merkle John G.
Published: July 2009

The Master Curve method for determination of fracture toughness in the transition range in ASTM standard E1921 [1] brought an opportunity for the ASME Code to adopt a much better fracture toughness curve based on directly measured fracture toughness data. This also enables obtaining statistically based fracture toughness data. The industry, through PVRC Task Group (subsequently Section XI Task Group on Master Curve Fracture Toughness), took a two-phase approach to implement the adoption of the Master Curve method in the ASME Code. First, Phase I was completed with the issuance of ASME Code Cases N-629/N-631 [9, 10], published in 1999 which allowed the existing Code KIc curve to be used by means of an alternate indexing reference temperature RTT0. This provided an important new approach to allow material specific, measured fracture toughness curves for ferritic steels in the code applications. However, this only rectified part of the shortcomings of the present Code KIc curve. In Phase II, it is intended to develop a direct means to utilize a tolerance bound of the Master Curve itself in place of the ASME KIc curve. This paper summarizes a proposal for such a procedure whereby a Master Curve fracture toughness tolerance bound is made usable in the ASME flaw evaluation processes, i.e. in Appendix A and Appendix G to Section XI of the ASME Boiler and Pressure Vessel Code. A draft code case is presented in Appendix in this paper.
Experimental and Numerical Validation of Fitness-for-Service Assessment for Cylindrical and Spherical Pressure Vessel With Local Metal Loss
Authors: Kaida Takuyo
Published: July 2009

Fitness-For-Service (FFS) assessment procedure can be also used to determine a reduced Maximum Allowable Working Pressure (MAWP) for cylindrical and spherical pressure vessel with local metal loss. A reduced MAWP is calculated from the Remaining Strength Factor (RSF). RSF is defined as ratio between plastic collapse load of the damaged component and that of the undamaged component. RSF needs to be calculated accurately in order to continue the damaged component in service safely. In this paper, RSFs of the damaged components with variously-shaped local metal loss were investigated. Especially, effects of circumferential width of local metal loss for cylindrical pressure vessel are investigated by both hydrostatic burst test and finite element analysis (FEA). The configurations of the local metal loss are rectangle. The longitudinal length and minimum thickness are fixed. FEA using the criterion proposed by Miyazaki et al. is effective to estimate fracture ductility under the multi-axial stress condition accurately, and effects of circumferential width is evaluated. In addition, RSF for spherical pressure vessel with relatively large diameter/thickness ratio was calculated by finite element analysis. Both results were compared to the calculation results using the equation in API 579-1/ASME FFS-1. The FFS assessment procedure is validated as conservative assessment experimentally and numerically.
Experimental Evaluation of the Bending Load Effect on the Failure Pressure of Wall-Thinned Elbows
Authors: Kim Jin-Weon , Na Yeon-Soo , Lee Sung-Ho , Park Chi-Yong
Published: July 2009

During normal operating conditions, piping systems in nuclear power plants are subject to internal pressure and to bending loads induced by deadweight, thermal expansion, and internal pressure, and understanding the effect of bending load on the failure of wall-thinned elbows is important to evaluate the failure pressure reliably. This study includes a series of burst tests using real-scale 4-inch schedule 80 elbow specimens with local wall-thinning under combined internal pressure and in-plane bending load applied by displacement control. The results are compared with those tested under simple internal pressure only. In the tests, various circumferential thinning angles (θ/π = 0.125, 0.25, 0.5, 1.0) and thinning locations (intrados, extrados, and full circumference) were considered. Each specimen was initially subjected to an in-plane bending load, closing mode for extrados wall-thinned elbows and opening mode for intrados wall-thinned elbows, and then internal pressure was applied up to point of final failure. The results showed that the effect of in-plane bending on the failure pressure and failure mode was minor under all wall-thinning conditions. In addition, the dependence of failure pressure on the circumferential thinning angle and thinning locations was identical to that observed under simple internal pressure.
Numerical Simulations of a Building-Acoustic Volume Interaction System Excited by Multiple Human Footfall Impacts
Authors: Xing Jing Tang , Xiong Ye Ping
Published: July 2009

A mixed finite element method is used to simulate a building structure-acoustic volume interaction system subject to multiple human footfall impacts. The pressure in the acoustic volume and the displacement of the structure are chosen as the fundamental variables to describe air-structure interaction dynamics. The governing equations and the corresponding variational formulation for generalised air-structure interaction systems are presented. From the variational formulation, the finite element and substructure-subdomain equations are derived. The available experimental results of footfall impact load histories are described and discussed. Based on an experimental result, an approximate footfall load time function is proposed to model the footfall loads in two successive human foot-steps. This approximate footfall load is applied at each structure point at which a left or right foot contacts at the corresponding time instant. Therefore, this footfall load is a moving load with a speed equalling the human walking speed. Following a generalised description of the developed numerical approach and footfall loads, an example is given. In this example, three cases involving two people walking along two perpendicular directions on the top floor of the structure are simulated, respectively. The dynamic responses of the displacement of the structure and the acoustic pressure in the acoustic volume are obtained. The calculated results are compared and discussed to illustrate the developed method and to reveal the mechanism of low-frequency vibration produced by human footfall impacts. The advantages of the proposed method are summarised to provide some guidelines to house designs.
An Overview of Creep-Fatigue Damage Evaluation Methods and an Alternative Approach
Authors: Asayama Tai , Jetter Robert
Published: July 2009

Renewed interest in elevated temperature nuclear reactors has occasioned a reassessment of creep-fatigue damage evaluation methods. Points to be improved in the current methods employed in Subsection NH of the ASME B&PV Code and other design codes are discussed as well as an alternate approach which avoids some of these problems. Most current creep-fatigue damage evaluation methods separately evaluate cyclic fatigue damage and creep damage and assess the combined damage through interaction diagrams. Typically test data are evaluated through a Miner’s Rule summation of fatigue damage and either a time fraction summation of creep damage or a ductility exhaustion approach in order to establish the appropriate interaction curve. In these approaches, cycles to failure can be counted directly but creep damage is a calculated parameter, subject the limitations of the evaluation technique. There can be considerable scatter in the results. The process is reversed for design and the methodology chosen to assess creep damage will have a major impact on the viability of the design process. This was found to be particularly true for advanced alloys such as Mod9Cr-1Mo-V, aka Grade 91. An alternate approach to determination of cyclic life has been proposed which avoids parsing the damage into creep and fatigue components. This approach, called the Simplified Model Test (SMT), employs a test specimen with elastic follow-up sized to represent the stress and strain redistribution encountered in more complex structures. The correlation parameter between test and design is the elastically calculated strain and the dependent test variable is the observed cycles to failure. The SMT approach has two major advantages. First, because the correlation parameter is elastically calculated strain, it is not necessary to calculate the inelastic stress-strain history for a design evaluation; either directly through inelastic analysis or indirectly through manipulation of elastic analyses. Second, because the test specimen itself incorporates the hardening, softening and aging effects of the structure it represents, it is not necessary do rely on theoretical modeling of these effects in an artificial separate accounting of creep and fatigue damage.
The Energy Approach of EPFM Applied to the Prediction of Crack Arrest
Authors: Wadier Yves , Meziere Yves , Bonnamy Marc
Published: July 2009

At present, the conventional methodology used to assess the structural integrity of RPV does not take into account any possible extension of the initial crack. Nevertheless, in order to improve the methods and obtain a second level of assessment, it could be useful to analyse the possibilities of crack arrest after crack initiation. It is the reason why we have applied the energy approach of elastic-plastic fracture mechanics to the analysis of a cracked disk submitted to a thermal shock inducing very fast crack propagation and crack arrest. This energy approach, originally based on the definition of an energy release rate Gp, for a crack modeled by a notch, has been applied successfully to the analysis of shallow crack and warm pre-stress effects. It gives a good prediction of crack initiation but it cannot predict the distance of crack propagation, at the same time. Nevertheless, if we consider that the critical time of initiation is known, it is then possible to reconsider a sharp tipped crack model and, using energy balance considerations, to predict the distance of crack propagation. In this approach the dynamic effects are not taken into account, the analysis being purely static, which seems to imply a conservative estimation of crack arrest. This simplified static model is presented in the paper including the case of a variable toughness material, which is verified in the study where the material is strongly depending on the temperature. The numerical analysis was performed at EDF-R&D with the Code-Aster, the finite element code of EDF. The mesh was very refined all along the crack propagation area. A non linear thermal finite element analysis was performed in order to determine the thermal field during the crack propagation. Then, the static analysis was performed assuming that the temperature at initiation remains constant during the crack propagation period which is very short. Concerning the values of temperature measured by thermocouples we have found a good agreement between experimental and predicted results. At the time of initiation, t = 7 sec, the KJ value is equal to 36 MPa.m1/2, in agreement with the value predicted by the French Code RCCM. The critical value Gpc of the Gp parameter have been identified at different temperatures. For that it was necessary to interpret different tests on CT specimens submitted to uniform temperature. Assuming that the critical time of initiation is known it was then possible to compute the Gp parameter as a function of the distance of propagation Δl, which can be compared to the Gpc function in order to obtain the distance of crack arrest. The predicted results obtained are in good agreement with the experimental results and less conservative than the results obtained using the RCCM code.
Effect of Tube Spacing on the Vortex Shedding Characteristics of Laminar Flow Past an Inline Tube Array
Authors: Liang C. , Luo X. , Papadakis G.
Published: July 2009

The effect of tube spacing on the vortex shedding characteristics and fluctuating forces in an inline tube array is examined. The array consists of 6 cylinders in tandem, the examined Reynolds number is 100 and the flow is laminar. The numerical methodology and the code employed to solve the equations in an unstructured grid are validated against available results from the literature for the flow past two cylinders in tandem. Computations are then performed for the 6 row inline bank for 8 pitch-to-diameter ratios s ranging from 2.1 to 4. The instantaneous flow patterns are visualised for different spacings and the lift and drag coefficients for all cylinders are recorded and analysed. At the smallest spacing examined (s = 2.1) there are five stagnant and symmetric recirculation zones and weak vortex shedding activity occurs behind the last cylinder only. As s increases, the symmetry of the recirculation zones breaks leading to vortex shedding. This process progressively moves upstream, so that for s = 4 there is clear shedding for every row. The shedding frequency behind each cylinder is the same and increases with tube spacing. A spacing region between 3d and 3.6d is identified, within which rms drag and lift coefficients attain maximum values. This behaviour is explained with the aid of instantaneous flow patterns.
Development of New Material Testing Apparatus in 230 MPa Hydrogen and Evaluation of Hydrogen Gas Embrittlement of Metals
Authors: Fukuyama Seiji , Imade Masaaki , Iijima Takashi , Yokogawa Kiyoshi
Published: July 2009

A new materials testing apparatus using an external loading system in 230 MPa hydrogen at room temperature was developed. The apparatus consisted of a pressure vessel with a loading device for the slow strain rate technique (SSRT). The elimination of the axial load due to high pressure acting on the pull rod was achieved by the pressure balance method. The apparatus was designed to measure the actual load on the specimen with an external load cell irrespective of the axial load caused by high pressure and friction at the sliding seals. The hydrogen gas embrittlement (HGE) of austenitic stainless steels, SUS304, SUS316, SUS316LN, SUS316L and SUS310S of the Japanese Industrial Standard (JIS), and an iron-based superalloy, SUH660 JIS, and a nickel-based superalloy, Hastelloy C22, was evaluated by conducting SSRT tests in 210 MPa hydrogen using the apparatus at room temperature. The following was observed: SUS304, moderate HGE in stage II; SUS316, moderate HGE in stage III; SUS316LN, light HGE in stage III; SUS316L, light HGE in FS; SUS310S, undetectable HGE; SUH660, light HGE in stage III; and Hastelloy C22, heavy HGE in stage II. The HGE of the materials was also discussed.
A Global Limit Load Solution for Plates With Embedded Elliptical Cracks Under Combined Tension and Bending
Authors: Li Rongsheng , Fang Zhiming , Liang Lihua , Gao Zengliang , Lei Yuebao
Published: July 2009

A global limit load solution is obtained in this paper for an embedded elliptical crack in a plate under combined tension and bending, based on the net-section collapse principle. The limit load solution is compared with three-dimension finite (3-D) element analysis limit load solution and the global limit load solution of a plate with an embedded rectangular crack. The limit load solution developed in this paper is conservative and close to the elastic-perfectly-plastic FE solutions. It is suitable for the estimation of the limit load. By comparison, it can be observed that the limit load of an embedded elliptical crack is larger than that of a rectangular crack. The difference between limit loads of these two cracks is negligible as the ratio of the depth to length of the crack is close to zero, however, the difference gets distinct as the ratio increases. The rectangular solutions are accurate enough as the ratio is less than 0.5 in engineering applications, and the elliptical solutions are more appropriate to the calculated limit load when the ratio is larger than 0.5.
Nonlinear Seismic Correlation Analysis of the JNES/NUPEC Large-Scale Piping System Tests
Authors: Nie Jinsuo , DeGrassi Giuliano , Hofmayer Charles H. , Ali Syed A.
Published: July 2009

The Japan Nuclear Energy Safety Organization/Nuclear Power Engineering Corporation (JNES/NUPEC) large-scale piping test program has provided valuable new test data on high level seismic elasto-plastic behavior and failure modes for typical nuclear power plant piping systems. The component and piping system tests demonstrated the strain ratcheting behavior that is expected to occur when a pressurized pipe is subjected to cyclic seismic loading. Under a collaboration agreement between the U.S. and Japan on seismic issues, the U.S. Nuclear Regulatory Commission (NRC)/ Brookhaven National Laboratory (BNL) performed a correlation analysis of the large-scale piping system tests using detailed state-of-the-art nonlinear finite element models. Techniques are introduced to develop material models that can closely match the test data. The shaking table motions are examined. The analytical results are assessed in terms of the overall system responses and the strain ratcheting behavior at an elbow. The paper concludes with the insights about the accuracy of the analytical methods for use in performance assessments of highly nonlinear piping systems under large seismic motions.
Development of Repair Welding Guidelines on Pressure Equipment
Authors: Yamamoto Eiichi , Hara Yasuhiro , Okazaki Tukasa , Tahara Takayasu , Minami Fumiyoshi
Published: July 2009

Responding to the needs of petroleum and chemical industries, the Japan Welding Engineering Society has been working to establish guidelines to repair welding of pressure equipment in petroleum and chemical industries. This paper describes the current status of the activity for developing the guidelines.
Effects of Material Moduli on Compressible Fluid-Solid Systems Using Implicit Immersed Continuum Methods
Authors: Wang X. Sheldon
Published: July 2009

Using a compressible fluid-solid test system, we would like to illustrate the need for implicit immersed continuum method. The implicit mixed finite element formulation for both solid and fluid domains solves the volume conservation problem associated with immersed methods. The immediate extension of the implicit compressible immersed continuum method is to handle continuum-continuum coupling in soft material designs.
Vibration of Timoshenko Beam Structures Resting on a Two-Parameter Elastic Foundation Solved by DQEM Using Chebyshev DQ Model
Authors: Chen Chang-New
Published: July 2009

The development of DQEM solution of vibration of Timo-shenko beam structures resting on a two-parameter elastic foundation was carried out. The DQEM uses Chebyshev DQ model to discretize the governing differential eigenvalue equation defined on each element, the transition conditions defined on the inter-element boundary of two adjacent elements and the boundary conditions of the beam. Numerical results solved by the developed numerical algorithms are presented. The convergence of the developed DQEM analysis models is efficient.
Fracture Mode Prediction Method for Pipe With Wall-Thinning by Using the History Data of Strain Ratio
Authors: Herman Irwan , Meshii Toshiyuki
Published: July 2009

In this study, based on the burst test results of pipes with wall-thinning, we have investigated the effect of flaw length δz and pipe size (mean radius Rm) on the burst pressure by using finite element analysis (FEA). Then, the history data of strain ratio εz/εθ along the load increment was used for the fracture mode prediction. Moreover, effect of the wall thickness at the flaw portion t1 on the fracture mode was investigated. Finally, fracture mode prediction method for pipes with wall-thinning was proposed.
Comparison of Strain Range Measures and Environmental Fatigue Calculation Methodologies for the Stepped Pipe Tests
Authors: Gurdal Robert , Xu Steven X.
Published: July 2009

Various strain measure formulas exist at this time for the calculation of the strain amplitude required for fatigue calculations, and various methodologies have been suggested in the years 2005 through 2008 to take into account — in general — the environmental effects on fatigue (EAF = Environmentally-Assisted Fatigue). The purpose of this technical paper is to compare these strain measure formulas and these EAF methodologies for the case of the thermal fatigue tests of a stainless steel stepped pipe for which results have been published in the Proceedings of the 2004 PVP Conference [1]. Thermal transient finite element analyses and cyclic elasto-plastic finite element analyses were performed to obtain the thermal gradients through the pipe thickness and the resulting strain ranges. These strain ranges are based on the various strain measure definitions presented at the 2001/2005 PVP Conferences (see Ref. [2] and [3]). These various strain measure definitions were compared. Using one of the stepped pipe inside surface locations and using one of the strain range values (out of the various strain measure definitions), the allowable number of design cycles has been calculated, based on the currently mandated methodologies for the environmental effects on fatigue (EAF). These methodologies are the EAF methodologies to be applied in the United States for future fatigue calculations, either for license renewal of the currently operating nuclear power plants or for the design of new plants. The fatigue results are compared and discussed for their implication in component design.
An Analytical Solution of Hydraulically Expanded Tube-to-Tubesheet Joints With Linear Strain Hardening Material Behaviour
Authors: Laghzale Nor Eddine , Bouzid Abdel-Hakim
Published: July 2009

The mechanism of failure of tube-to-tubesheet joints is related to the level of stresses produced in the tube expansion and transition zones during the expansion process. Maintaining a lower bound limit of the initial residual contact pressure over the lifetime of the expanded joint is a key solution to a leak free joint. An accurate model that estimates these stresses can be a useful tool to the design engineer to select the proper material geometry combination in conjunction with the required expansion pressure. Most existing design calculations are based on an elastic perfectly plastic behavior of the expansion joint materials. The proposed model is based on a strain hardening with a bilinear material behavior of the tube and the tubesheet. The interaction of these two components is simulated during the whole process of the application of the expansion pressure. The effects of the gap and the material strain hardening will be emphasized. The model results are validated and confronted against the more accurate numerical FEA models. Additional comparisons have been made to existing methods.
The Ultimate Strength of Cylindrical Liquid Storage Tanks Under Earthquakes: Seismic Capacity Test of Tanks Used in PWR Plants — Part 2, Static Post-Buckling Strength Tests
Authors: Iijima Toru , Suzuki Kenichi , Okafuji Takashi , Morita Hideyuki , Fujimoto Ryo
Published: July 2009

Since 2002, Japan Nuclear Energy Safety Organization (JNES) has been carrying out seismic capacity tests for several types of equipment which significantly contribute to core damage frequency. The primary purpose of this study is to acquire the seismic capacity data of thin walled cylindrical liquid storage tanks in nuclear power plants and to establish an evaluation procedure of the ultimate strength. As for the refueling water storage tank and the condensate storage tank which are used in PWR plants, elephant-foot bulge (EFB) is the typical buckling behavior of those tanks and the primary failure mode to be focused on. In the previous study, by conducting the dynamic and static buckling tests with aluminum alloy, it was confirmed that static buckling test represents dynamic buckling and post-buckling behavior in terms of energy absorption capacity. In this study, static buckling tests with actual material were performed in order to evaluate the ultimate strength of real tanks. Although the buckling mode did not differ among materials, tests with actual materials (steel, stainless steel) resulted higher seismic capacity compared to the aluminum alloy, and inner water leakage occurred from the cracks initiated at the secondary buckling on the EFB section.
Quantitative Detection of Low Energy Impact Damage in a Sandwich Composite UAV Wing
Authors: Aktas Engin , Seaver Mark , Nichols Jonathan M. , Trickey Stephen T.
Published: July 2009

This work describes damage detection efforts applied to a foam core composite wing following a series of low energy impacts in adjacent locations. The wing is a sandwich composite, composed of 4 layers of woven carbon fiber fabric surrounding a short aluminum core in the center (where it’s connected to the fuselage) and a foam core for the outer portions of the wing. The wing measures 1320 mm. × 152.4 mm. × 13.4 mm and has an airfoil cross-section. Thirteen impacts (6 – 8 J deposited energy) were applied at adjacent locations approximately 1/3 of the way out from the center. Following one or two impacts, the wing was tested using static tip deflection and dynamic vibrational excitation. Static and dynamic strains were measured using 8 fiber Bragg grating (FBG) sensors. Dynamic acceleration was also monitored using 3 conventional accelerometers. Dynamic excitation included the output of a Lorenz oscillator (0 – ∼150 Hz), simulated gust loading (0 – 150 Hz), and Gaussian white noise (0 – 1500 Hz). The analysis is a quantitative assessment of response nonlinearity based on the assumption that the undamaged wing behaves linearly and that the damage introduces nonlinearity into the vibrational response.
The Use of Non-Viral Nucleic Acids Carriers for the Modulation of Leukocytes
Authors: Meng Wilson S. , Kovacs Jeffrey R. , Gawalt Ellen S.
Published: July 2009

Induction of drug-free permanent organ accommodation is the ultimate goal of transplant therapy. Current pharmacological agents, however, are non-specific in their actions and generally do not confer immunological tolerance. Inhibitors of T cell receptor signaling (tacrolimus and cyclosporine A) represent the mainstay in transplant management. These agents exert their therapeutic effects by dampening the activities of all T cells. Chronic exposure to these agents increases the risk of developing opportunistic infections and malignancies. Given that more than 20,000 Americans undergo organ transplantations each year, there is an urgent need to develop specific therapies to mitigate graft rejection and create conditions conducive for long-term transplant accommodation.
Nonlinear and Time-Varying Dynamics of High-Dimensional Models of a Translating Beam With a Stationary Load Subsystem
Authors: Xu G. Y. , Zhu W. D.
Published: July 2009

Nonlinear vibration and dynamic stability analyses of distributed structural systems have often been conducted for their low-dimensional spatially-discretized models, and the results obtained from the low-dimensional models may not accurately represent the behavior of the distributed systems. In this work the incremental harmonic balance method is used for the first time to handle a variety of problems for high-dimensional models of distributed structural systems, including determination of linear and nonlinear frequency responses, optimization of system parameters, determination of simple parametric instability region boundaries, analysis of parametrically-excited nonlinear systems, and determination of linear and nonlinear frequency responses under combined parametric and forcing excitations. The methodology is demonstrated on a translating tensioned beam with a stationary load subsystem and some related systems. With sufficient numbers of included trial functions and harmonic terms, convergent and accurate results are obtained in all the cases. The effect of nonlinearities due to the vibration-dependent friction force between the translating beam and the stationary load subsystem, which results from non-proportionarity of the load parameters, decreases as the number of included trial functions increases. A low-dimensional spatially-discretized model of the nonlinear distributed system can yield quantitatively and qualitatively inaccurate predictions. The methodology can be applied to other nonlinear and/or time-varying distributed structural systems.
Robust Autonomous Damage Detection and Assessment in Polymeric Composite Structures
Authors: Kesavan Ajay , John Sabu , Li Henry , Herszberg Israel
Published: July 2009

This paper introduces the some of the experimental and analytical work behind the autonomous damage detection technique. The research study conducted here resulted in the development of a Structural Health Monitoring (SHM) system for a 2-D polymeric composite T-joint, used in maritime structures. Two methods of damage detection are discussed — A statistics-based outlier technique and one using Artificial Neural Networks (ANNs). The SHM using ANNs system was found to be capable of not only detecting the presence of multiple delaminations in a composite structure, but also capable of determining the location and extent of all the delaminations present in the T-joint structure, regardless of the load (angle and magnitude) acting on the structure. The system developed relies on the examination of the strain distribution of the structure under operational loading. Finally, on testing the SHM system developed with strain signatures of composite T-joint structures, subjected to variable loading, embedded with all possible damage configurations (including multiple damage scenarios), an overall damage (location & extent) prediction accuracy of 94.1% was achieved. These results are presented and discussed in detail in this paper.
Lamb Wave Based Damage Identification in Structures With Complex Geometry
Authors: Lu Xi , Li Fucai , Meng Guang , Ye Lin , Lu Ye
Published: July 2009

Structural health monitoring (SHM) plays a significant role in terms of fatigue life and damage accumulation prognostics. SHM for structures with complex geometry are much more practical in engineering applications. In this paper, complex aluminium alloy structures with “U” shape section were evaluated in terms of both finite element method (FEM)- and experiment-based Lamb wave analysis for the purpose of damage detection and identification. In the FEM-based analysis, three-dimensional finite element model was established to simulate the propagation behavior of Lamb wave in the structures. On the other hand, in the experiments, piezoelectric (PZT) wafers, functioning as both actuator and sensor, were used to generate Lamb waves propagating in the structures and collect the Lamb wave signals from the complex structures. Quantitative relationship between crack location and the reflection coefficient was constructed by taking advantage of continuous wavelet transform (CWT) and Hilbert transform (HT), which are based on the collected Lamb wave signals. Furthermore, the differences between simulated and experimental results in respect of crack severity evaluation and the reasons were discussed.
Optimal Placement of Sensors and Actuators for Modal Measurement/Control of CFRP Laminated Plates
Authors: Kameyama Masaki , Fukunaga Hisao
Published: July 2009

In this paper, based on the optimal placement of sensors and actuators, the vibration control by using a system of modal sensor and modal actuator with a small number of sensors and actuators is realized for a plate structure. The modal sensor consisting of accelerometers as well as the modal actuator of lead zirconate titanate (PZT) is built up for a CFRP cantilevered plate. The structural vibration control is realized by the independent modal space control based on the linear quadratic regulator (LQR) control theory. Sensors and actuators are optimally placed so that the best accuracy of measurement of modal velocity and the maximum control effect can be acquired. From the numerical and experimental results, it is demonstrated that the optimal placement of sensors and actuators is very important to stabilize a control system when the number of sensors/actuators is limited, and the vibration of plate can be suppressed by the state feedback control for each mode using the modal sensor and actuator optimally designed.
Optimal Sensor Placement for Active Sensing
Authors: Flynn Eric , Todd Michael
Published: July 2009

We present a novel approach for optimal actuator and sensor placement for active sensing-based structural health monitoring (SHM). Of particular interest is the optimization of actuator-sensor arrays making use of Lamb wave propagation for detecting damage in thin plate-like structures. Using a detection theory framework, we establish the optimum configuration as the minimization of the expected percentage of the structure to show type I or type II error during the damage detection process. The detector incorporates a statistical model of the active sensing process which implements both pulse-echo and pitch-catch actuation schemes and takes into account line of site and non-uniform damage probabilities. The optimization space was searched using a genetic algorithm with a time varying mutation rate. We provide four example actuator/sensor placement scenarios and the optimal solutions as generated by the algorithm.
Damage Detection Based on Adaptive Estimation of Amplitude and Phase
Authors: Azizi Yousof , McNamara David M. , Ziarani Alireza K. , Jha Ratneshwar
Published: July 2009

This paper presents a novel structural health monitoring method that shows promise in identifying damage location within a structure while providing some means of indicating the severity of the damage. The proposed method is based on an adaptive sinusoid-tracking algorithm (STA), which is capable of tracking sinusoid parameters, namely amplitude, phase, and frequency. The proposed method makes use of the estimated amplitude and phase parameters obtained by processing strain recordings at individual sensors located along an excited structure to identify damage locations and severity. Damage indices have been developed that compare the tracked amplitude/phase from a baseline (or healthy) case to the tracked amplitude/phase from the structure under test at specific locations. The proposed methodology is applied to both simulated and experimental plates in a number of damage scenarios. The results of both simulated and experimental data indicate that the proposed method is promising in the detection of the damage, its location and its severity.
Magnetically Actuable Scaffolds for Tissue Regeneration
Authors: Mack Julia J. , Corrin Abigail A. , dos Santos e Lucato Sergio L. , Cox Brian N. , Andrew Jennifer S. , Clarke David R. , Lam Mandy , Dunn James C. Y. , Wu Benjamin W.
Published: July 2009

Presented here are methods to fabricate magnetically modified biocompatible polymer scaffolds, which can be actuated by remotely applied magnetic fields. The magnitude of the actuation is shown to be biologically useful by simple tests in known magnetic fields and magnetic field gradients. Methods of processing the functionalized polymers into three-dimensional scaffolds have been demonstrated, suggesting wide applicability in tissue engineering.
Torque Loss and Crack Monitoring Near Fasteners for Isotropic and Composite Helicopter Tail Boom Structural Models
Authors: Choi Young-Tai , Purekar Ashish S. , Wereley Norman M.
Published: July 2009

Structural Health Monitoring (SHM) techniques based on high frequency wave propagation (Acousto-Ultrasonics) are of interest due to their sensitivity to incipient damage in structures. Techniques that use small, low profile transducers allow for in-situ sensing and actuation and are particularly useful for integration on aerospace structures. Additionally, signal processing and interpretation of the data becomes important in the diagnosis process. Commonly, the development of an integrated hardware and software system based on Acousto-Ultrasonics is performed on simple structures such as flat metallic panels. In this study, the curved metallic and composite panels are examined as they provide complexity in both geometry and material used to represent helicopter tail boom structures. Damage at the edges of the curved panel is investigated as these locations typically experience damage related to fatigue. Piezoelectric transducers are mounted to the structures and used to excitation and sensing of the wave modes. The data was acquired and damage indices are used to quantify the effect of two types of damage: bolt torque loss, crack propagation between two bolts.
Bio Inspired Living Skins for Fouling Mitigation
Authors: Ganguli Rahul , Mehrotra Vivek
Published: July 2009

A biomimetic method to mitigate marine biofouling using a pilot-whale inspired sacrificial skin concept has been developed. We developed a method to form conformal, protective skins in-situ underwater using a circulatory system. In addition, the materials chemistry was tuned such that the skin dissolves after a tunable stable period, removing any foulants that may have collected on it. A very large reduction in biofouling was demonstrated for surfaces protected by the sacrificial skin compared to identical unprotected surfaces, when high fouling pressure was generated using bacteria in artificial seawater. Skin formation, stability, and dissolution have been studied by forming skins on 6 inch square flat substrates, and curved surfaces. Several different materials and material combinations were tested for their skin-forming ability. Rheology studies were conducted to determine the changes in viscosity of the materials upon exposure to seawater. The materials microstructure and composition was probed before and after seawater exposure. These experiments helped explain the mechanisms by which skin formation and dissolution occurs. Biofouling experiments consisted of culturing and growing the bacteria Pseudoalteromonas carrageenovera, a strain known to cause biofouling in marine environments. Efforts focused on determining experimental conditions necessary to achieve high levels of biofouling growth in the shortest amount of time. Marine-like environments were created in the range of a few hundred milliliters of artificial seawater and scaled to several liters, large enough to contain a 6 inch × 6 inch substrate.
Forced-Controlled Nanomanipulation Utilizing Nano-Robotic Manipulator and Nanomechanical Cantilever
Authors: Saeidpourazar Reza , Jalili Nader
Published: July 2009

This paper presents forced-controlled nanomanipulation utilizing nano-robotic manipulator and nanomechanical cantilever. A three degree of freedom (3 DOF) nanomanipulator with revolute revolute prismatic (RRP) actuator structure, named here MM3A®, can be utilized for a variety of nanomanipulation tasks. Previous publications of the authors present the mathematical modeling and robust control of manipulator’s tip using fused visual servoing and force sensor feedbacks. Due to lack of position and velocity feedbacks in MM3A® nanomanipulator, a fused vision/force feedback robust controller has been recently designed by the authors. Previous publications of the authors present the optimal utilization of the visual servoing and force sensor feedbacks for use in the nanomanipulation tasks. More specifically, the visual servoing and force feedback structures are investigated through extensive simulations in order to reveal issues in practical implementation. In modeling the force sensing module of the designed fused feedback controller, previous publications of the authors present a closed-form distributed-parameters based modeling framework for piezoresistive Nanomechanical Cantilever (NMC)-based force sensors used in a variety of cantilever-based nanomanipulation actions. Current modeling practices call for a simple lumped-parameters framework rather than modeling the piezoresistive NMC itself. Due to the widespread applications of such NMCs in nanoscale force sensing or non-contact atomic force microscopy with nano-Newton to pico-Newton force measurement requirements, precise modeling of the piezoresistive microcantilevers is essential. Instead of the previously used lumped-parameters modeling, a distributed-parameters modeling framework is proposed and developed in previous publications of the authors to arrive at the most complete model of the piezoresistive NMC including tip-mass, tip-force and base movement considerations. Here, experimental results are presented to demonstrate the accuracy of the proposed distributed-parameters model when compared with the previously reported lumped-parameters modeling approach. It is shown that by utilizing the distributed-parameters model rather than lumped-parameters approach and by predicting the exact motion of each point on the NMC, the precision of the piezoresistive NMC’s model is significantly enhanced. Such novel modeling framework could pave the pathway towards nanomechanical cantilever-based manipulation and positioning as detailed in the second part.
On-Line Life Prediction of a Structural Hotspot
Authors: Mohanty Subhasish , Chattopadhyay Aditi , Peralta Pedro
Published: July 2009

Current aerospace practice follows an engineering model based on damage-tolerant reliability whereby structural components are regularly inspected and replaced. Under this practice, engineering designs are generally based on a physics-based fracture mechanics approach, in which the life of structural component is estimated using an assumed initial damaged condition. However, in a real time environment, keeping track of the damage condition of a complex structural component manually is quite difficult and requires automatic damage state estimation. The real-time damage state information can be regularly fed to a prognosis model to update the residual useful life estimation in event of a new prevailing situation. The present paper discusses the use of an adaptive hybrid prognosis model, which estimates the residual useful life of a structural hotspot using information on the damage condition obtained in real time. The hybrid prognosis model has two modules: an off-line prognosis module that forecasts the future damage state, and an on-line state estimation module, which regularly predicts the current damage state and feeds into the off-line module in real time. Both the off-line and on-line modules are probabilistic models and use the concept of Bayesian inference based on input-output mapping through a Gaussian process.
Effects of nitrogen doping of ZnO during or after deposition
Authors: Yen Tingfang , DiNezza Michael , Haungs Alan , Kim Sung Jin , Anderson Wayne A. , Cartwright Alexander N.
Published: July 2009

Effects of nitrogen doping of ZnO (ZnO:N) during deposition and after postdeposition annealing have been studied by optical techniques, electronic properties, and the application to metal-semiconductor-metal photodetectors (MSM-PDs). Films of ZnO, nitrogen doped during rf sputtering, show larger grain size, narrower full width at half maximum, band gap emission shift in photoluminescence, and higher conductivity. Postannealing has been studied using tube furnace and rapid thermal annealing in nitrogen. These annealing methods not only reconstruct the lattice structure but also activate the nitrogen in the film to improve the conductivity of the film. The MSM-PDs having high photo to dark current ratio of 104 and responsive (R) of 1.79 A/W have been fabricated with those films.
Sub-10-nm nanolithography with a scanning helium beam
Authors: Sidorkin Vadim , van Veldhoven Emile , van der Drift Emile , Alkemade Paul , Salemink Huub , Maas Diederik
Published: July 2009

Scanning helium ion beam lithography is presented as a promising pattern definition technique for dense sub-10-nm structures. The powerful performance in terms of high resolution, high sensitivity, and a low proximity effect is demonstrated in a hydrogen silsesquioxane resist.
THE IMPACT OF PARAMETERS FOR ELASTIC WAVES IN A PHONONIC CRYSTAL LAYER COATED ON HALF-INFINITE UNIFORM SUBSTRATE
Authors: LI WU , FAN TIAN YOU
Published: July 2009

In this paper, we make a great effort to find out the impact of parameters for elastic wave propagation in a plate with a phononic crystal layer coated on half-infinite uniform substrate by the method of plane wave expansion, and the characteristic or the position of the band structure. In calculation, a phononic crystal consisting of circular steel cylinders that form a square lattice in a silicon matrix is considered as the layer and the substrate is formed by silicon. Our results show that there exist distinct band gaps when the substrate is correspondingly soft and infinite. The stop band of the system is demonstrated. Parameters that influence the formation of band gaps are stated. We also give a qualitative explanation of the results.