bluuebunny/crossref_metadata_2025 huggingface dataset:
α‐Amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolepropionic Acid Receptors Participate in the Analgesic but Not Hypnotic Effects of Emulsified Halogenated Anaesthetics
Authors: Hang Lihua , Shao Donghua , Yang Yinghong , Sun Wenjin , Dai Tijun , Zeng Yinming
Published: June 2008

Abstract:  The present study was designed to investigate the role of α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolepropionic acid (AMPA) receptors in hypnosis and analgesia induced by emulsified inhalation anaesthetics. After having established the mice model of hypnosis and analgesia by intraperitoneally injecting appropriate doses of emulsified enflurane, isoflurane or sevoflurane, we intracerebroventricularly or intrathecally injected different doses of AMPA and then observed the effects on the sleep time using hypnosis test and the tail‐withdrawal latency using the tail‐withdrawal test. In hypnosis test, AMPA (50, 75 and 100 ng, intracerebroventricularly) had no distinctive effects on the sleep time of the mice treated with emulsified inhalation anaesthetics (P > 0.05). In tail‐withdrawal test, AMPA (0.25, 0.5 and 1.0 ng, intrathecally) significantly and dose‐dependently decreased the tail‐withdrawal latency (P < 0.05 or P < 0.01) in the mice treated with emulsified anaesthetics. These results suggest that AMPA receptors may participate in the analgesic but not in the hypnotic effects induced by emulsified enflurane, isoflurane or sevoflurane.
Introduction of exogenous substance into protoplasts of perennial ryegrass by electroporation
Authors: Unno Hiroki , Yamamoto Shinrô
Published: June 2008

Involvement of a substance in the tolerance of plants will be clarified by increasing the substance in the plants and detecting the effect on the tolerance. Some substances, however, are difficult to be increased in intact plants. Accordingly, the introduction of an exogenous substance into protoplasts of grass was investigated by means of electroporation using fructan as the exogenous substance. Protoplasts were freshly prepared from young leaves of perennial ryegrass by treating with 2% cellulase. Fifty percent of the protoplasts were alive after electroporation at 500 V/cm at 18 µF. Fructan concentration in the protoplasts was increased by electroporation as described above in the presence of exogenous fructan and the increase in the fructan was promoted with an increase in concentration of the exogenous fructan. The results obtained suggest that concentrations of substances in grass protoplasts are able to be increased by electroporation.
Transgenic expression of a viral EPS‐depolymerase is potentially useful to induce fire blight resistance in apple
Authors: Flachowsky H. , Richter K. , Kim W.‐S. , Geider K , Hanke M.‐V
Published: June 2008

Fire blight caused by Erwinia amylovora is the most destructive bacterial disease of pear and apple. The goal of this research was to improve fire blight resistance of apple by transformation with a gene encoding for an extracellular polysaccharide (EPS)‐depolymerase from the E. amylovora phage phi‐Ea1h. The EPS‐depolymerase gene (dpo) driven by the constitutive promoter CaMV35S was transferred into apple scion cv. ‘Pinova’ through Agrobacterium tumefaciens‐mediated leaf disk transformation using a binary vector and strains EHA105 or LBA4404. The integration of the dpo gene and the marker gene nptII was confirmed by polymerase chain reaction (PCR) and by Southern hybridisation. From 4560 leaves inoculated in 23 different transformation experiments, 33 independent shoots, regenerated from a single transformation event, were identified as transgenic. Nine of the shoots were randomly selected and vegetatively propagated to establish transgenic clones. The transgenic clones were diploid as was the non‐transgenic genotype ‘Pinova’ analysed by flow cytometry. Both transgenes (dpo and nptII) were transcriptionally active determined by reverse transcription (RT)‐PCR and quantitative RT‐PCR. EPS‐depolymerase was expressed in all transgenic clones showing substantial differences in its activity for different clones concerning EPS degradation. Resistance to E. amylovora was evaluated by infection of in vitro leaves as well as by artificial shoot inoculation of ex vitro plants in the greenhouse. No correlation was obtained for the transgenic lines between the level of dpo gene expression and both the level of depolymerase activity and the disease resistance in vitro, whereas, depolymerase activity did correlate positively with resistance to fire blight in vitro. Seven clones had less disease than the non‐transformed genotype when measured in greenhouse, but no statistically significant differences were found, except for line T373. One line showed the highest depolymerase activity and the least susceptibility to fire blight in vitro as well as in greenhouse (T187).
Purification and characterization of α‐glucosidase in Apis cerana indica
Authors: Chanchao Chanpen , Pilalam Suwisa , Sangvanich Polkit
Published: June 2008

Apis cerana indica foragers were used for the isolation of a full‐length α‐glucosidase cDNA, and for purification of the active nascent protein by low salt extraction of bee homogenates, ammonium sulphate precipitation and diethylaminoethyl‐cellulose and Superdex 200 chromatographies. The molecular mass of the purified protein was estimated by polyacrylamide gel electrophoresis resolution, and the pH, temperature, incubation, and substrate optima for enzymic activity were determined. Conformation of the purified enzyme as α‐glucosidase was performed by BLAST software homology comparisons between matrix assisted laser desorption ionization time of flight mass spectroscopy analysed partial tryptic peptide digests of the purified protein with the predicted amino acid sequences deduced from the α‐glucosidase cDNA sequence.
Students With Chronic Diseases: Nature of School Physician Support
Authors: Taras Howard , Brennan Jesse J.
Published: June 2008

Background:  To educate children with chronic diseases in the least restrictive environment, schools must prevent, recognize, and react appropriately to symptom exacerbations. Schools are often pushed to their limits of knowledge, resources, and comfort level. This study determined the health conditions of students for whom districts seek school physician consultation and the nature of school physician consultants’ involvement.

Methods:  A retrospective record review was performed on 250 of the most recent records of school‐elicited referrals from an academic center that provides physician consultation to school districts. Referrals were sent from 8 school districts in southern California (July 1996 to October 2006). Data collected were nature of student’s special health need, the school physician consultant’s intervention required to satisfy schools’ needs, student grade level, enrollment in special education, and health‐related excessive absenteeism.

Results:  No single chronic condition, symptom, or special health care need predominated. Six types of school physician consultant activities were used to overcome hurdles schools faced when accommodating students with special health care needs. The 3 most common were direct communication with students’ own physicians (70% of students), recommending an appropriate level of school health services when this was a matter of controversy (42%), and formulating portions of students’ individualized school health plans (38%).

Conclusions:  A portion of students with special health care needs benefited from district referral to a school physician consultant. Whether some of these referrals can be avoided if school personnel and students’ own physicians are supported and trained to communicate more effectively with one another needs to be explored.
Taxonomic review of the genus Gonioctena Chevrolat (Coleoptera: Chrysomelidae: Chrysomelinae) in the Korean Peninsula
Authors: CHO Hee Wook , LEE Jong Eun
Published: June 2008

A taxonomic review of the genus Gonioctena in the Korean Peninsula is presented. Ten species belonging to three subgenera are recognized. Gonioctena jacobsoni (Ogloblin et Medvedev) and Gonioctnea kamiyai Kimoto are recorded for the first time in Korea. A key, illustrations of diagnostic characters, and the coloration patterns of Korean Gonioctena are provided.
First record of the family Aulacidae in Korea (Hymenoptera: Evanioidea)
Authors: LEE Jong‐Wook , TURRISI Giuseppe Fabrizio
Published: June 2008

The family Aulacidae with one species, Pristaulacus intermedius Uchida, 1932, is recorded for the first time in Korea. A detailed description, illustrations of morphological features, and a brief discussion are provided.
Insect biogeography in the south‐western Sea of Korea with comments on the insect fauna of Kwanmae Island
Authors: LEE Sung‐Jin , YEO Jin‐Dong , SHIN Hyunchur
Published: June 2008

The insect species richness of each island in the south‐western Sea of Korea was considered on the background of the equilibrium theory. The species number of insects on Kwanmae Island in the present study (140 species) was much higher compared with a previous survey. Based on a literature survey of island biota surveys published in the 1980s, of 47 islands, the lowest species number (12 species) was on Kwanmae Island, and the most diverse insect fauna (254 species) was on Baekryong Island. The mean species number of surveyed islands was approximately 54 (53.96 with a standard deviation of 46.95). The median species number was 38 with a skew of +2.56. Insects, including the orders Odonanta, Orthoptera, Hemiptera, Lepidoptera, Coleoptera, Hymenoptera and Diptera, occurred on 32 of the 47 surveyed islands, and had an occurrence rate of more than 0.68. This indicates that these insects are distributed widely on the islands in the south‐western Sea of Korea. The species number showed a significant linear relationship with both area of an island and its distance from the mainland (P < 0.05), with an extremely low determinant coefficient (r2 = 0.13 for area vs species number and r2 = 0.28 for distance vs species number). Other factors tested in the study failed to show a significant relationship with species number. A multiple‐regression model established using area and distance as independent variables showed significant relationship with species number, with a relatively higher determinant coefficient (r2 = 0.70, P < 0.05). We present possible explanations to explain the difference between estimated and observed species number in Kwanmae Island.
Endangered species and nature conservation: science issues and challenges
Authors: SZARO Robert C.
Published: June 2008

The issues and challenges facing us in ensuring the survival of as many species and ecosystems as possible call for a renewed research focus to address how to improve management strategies and policy making now and into the future. The key issues to be addressed by activities of the International Union of Forest Research Organization's (IUFRO) Task Force on Endangered Species and Nature Conservation include such issues as: (i) preventing species from being listed by maintaining species populations at sufficient levels that they do not require listing; (ii) recovering threatened and endangered species; (iii) developing management practices and strategies; (iv) balancing actions affecting suites of threatened or endangered species; (v) developing conservation strategies for species without definitive taxonomic treatments; (vi) dealing with global change; (vii) dealing with invasive species; and (viii) restoring critical habitats.
Stresses in Thick Pressure Vessel Heads
Authors: Singh A. V. , Kumar V.
Published: June 2008

The finite element method is used to study stresses in two types of spherical pressure vessel heads having very wide range of applications in industries. The first problem involves a nozzle to sphere intersection reinforced by a pad and subjected to radial thrust load. The second problem deals with a pressurized thick hemispherical drumhead with a circular manhole. These structures are modeled using eight-node axisymmetric solid of revolution finite elements. Numerical values of circumferential and meridional stresses from the present analysis show excellent agreement with experimental data from the literature.
Restraint Effect of Fluid in the Annular Region Formed by Coaxial
Circular Cylinders
Authors: Ito T. , Fujita K.
Published: June 2008

Many studies have been made with regard to added mass and added damping of the fluid in the case of simple circular cylinders by Chen, Fritz, Mulcahy, etc.; but those effects for the noncircular cylinders are hardly available. In this study, added mass and added damping of the fluid for the coaxial circular cylinders with projection are investigated by both the experiment utilizing one-degree of freedom cylindrical models and the analysis by comparing those for the simple circular cylinders. Also, the method to evaluate the damping ratio of the beam which has the fluid restraint was derived.
The Influence of Residual Stress on Fatigue Cracking
Authors: Okamoto A. , Nakamura H.
Published: June 2008

The influence of residual stress on fatigue crack growth was experimentally and analytically investigated for surface cracks. Fatigue tests were performed on straight pipes of low-carbon steel with a circumferential inner surface crack in laboratory air environment. Some of the test pipes had been subjected to special heat treatments so as to have compressive or tensile residual stresses along inner surface. The results show that the compressive residual stress remarkably suppresses the surface crack growth, while the tensile residual stress does not accelerate the crack growth very much. The crack growth analyses were conducted by the application of power relationship between ΔK and da/dN. The stress intensity factors due to the nonlinear stress field were calculated by the weight function method. The analyses resulted in a confirmation of the behavior of the crack growth observed in the experiments.
Theoretical Investigation of Internal Wall Cooling of a Pressure
Vessel Engulfed in Fire
Authors: Birk A. M.
Published: June 2008

When a pressure vessel is exposed to an engulfing fire, the vessel can fail due to a combination of high internal pressure and material degradation due to high wall temperatures. In fire-engulfed vessels containing pressurized liquids in equilibrium with their vapors, high wall temperatures will occur in the upper regions of the vessel where the wall is in contact with vapor. Several methods exist for thermal protection of vessels, including thermal insulation and external water spray cooling. Recent tests have shown internal spray cooling to be potentially effective as thermal protection. The present paper presents a theoretical evaluation of a new concept in thermal protection which involves cooling the upper regions of vessel during fire engulfment by directing 2-phase fluid along the upper regions of the vessel wall during pressure relief. Based on observations of the internal cooling device from small-scale tests, a model was formulated and integrated with an existing vessel-in-fire computer model. This model was then used to study the effectiveness of internal spray cooling on an example system consisting of a rail tank-car carrying propane. Simulation results indicate that internal wall cooling could be effective at reducing the risk of thermal ruptures of vessels. The simulation results for internally cooled vessels are compared with previously validated simulations of an uninsulated tank-car filled with propane exposed to engulfing fires.
Reliability of Thermally Loaded Cylinders
Authors: Zibdeh H. S.
Published: June 2008

Cylinders often contain fluids at various temperatures. Temperature gradients develop across the cylinder which in turn produce thermal stresses. Using a perturbation technique, expressions for means and standard deviations of thermal stresses in cylinders are presented in this paper. These expressions include the probabilistic effects of changes due to inner and outer radii, modulus of elasticity, Poisson’s ratio, coefficient of thermal expansion, and temperature. It is found out that the cylinder is more sensitive to the geometrical changes than the mechanical and thermal changes. It is also noticed that the effect of variation in the inner radius is more than the outer radius at the inner half of the cylinder. On the other hand, the effect of variation in the outer radius is more than the inner radius at the outer half of the cylinder. Probabilities of failure are calculated for normal and log-normal distributions.
Water Hammer Response of Flexible Piping by Component Synthesis
Authors: Hatfield F. J. , Wiggert D. C.
Published: June 2008

Water hammer pressure in piping is modified by the consequent motion of the piping. In general, accurate estimates of dynamic pressure and pipe displacement must account for this interaction. One approach is to formulate and solve the coupled equations of motion for the liquid and pipe structure. Implementation for practical pipe systems would require a computer code comparable in scope to a structural finite element program combined with a hydrodynamics program. This paper presents an alternative approach that utilizes any available finite element program to compute natural frequencies and mode shapes of the piping, and then uses those modes to modify a hydrodynamic analysis and to predict motion of the piping. An example analysis demonstrates application of the method to assess the consequence of removing a brace intended to restrain pipe motion caused by water hammer. Results are compared to those given by analyses that neglect the effect of pipe motion on pressure.
A Proposed K1 Solution for Long Surface Cracks in Complex Geometries
Authors: Chaaban A. , Chaarani A.
Published: June 2008

The finite element method is used to derive a general stress intensity factor expression for straight-fronted and circumferential surface cracks subjected to an arbitrary stress field. The superposition technique is used: the stress field normal to the crack face is resolved into uniform tension and linear bending stress distributions. The K1 expression is given in terms of magnification factors that are function of these two types of stress field, the geometry considered and the opening of the crack at the free surface under loading. The results obtained using this method are in good agreement with other numerical and experimental K1 solutions of cracks under simple or complex conditions.
NDE Engineering in the Materials Life Cycle
Authors: Pangborn R. N. , Bakis C. E. , Holt A. E.
Published: June 2008

The emergence of nondestructive evaluation as a factor to be considered in the entire life cycle of materials, from design, through fabrication of components and structures, to in-service monitoring, is reviewed. Current directions in research and development and in practical application are discussed within the context of NDE as an engineering function. Particular emphasis is directed towards reliability, requirements for in-process and health monitoring, and implementation for the inspection and analysis of composite materials, that offer a particularly challenging domain in which to demonstrate the performance of NDE techniques and procedures.
The Generalized Local Stress Strain (GLOSS) Analysis—Theory and Applications
Authors: Seshadri R.
Published: June 2008

GLOSS analysis is a simple and systematic method for carrying out inelastic evaluations of mechanical components and structures on the basis of two linear elastic finite element analyses. The underlying theory relates redistribution of inelastic stresses at a given location under consideration to the uniaxial stress relaxation process. GLOSS analysis is emerging as a useful technique for determining multiaxial stress relaxation, follow-up, creep damage, inelastic strain concentrations and low-cycle fatigue estimates, limit analysis and issues pertaining to stress-classification.
Control of Pipeline Dynamics With Disk Spring Restraints (Design Paper)
Authors: Goodling E. C.
Published: June 2008

Dynamic transients such as steam hammer or water hammer in power plant or process piping can generate high destructive reactions if rigid restraints or snubbers are used in an attempt to exert total control of pipe response. However, where some movement can be tolerated, adequate control can be maintained with much lower resulting loads in the restraining structures and components. The disk spring restraint has been demonstrated to be a practical device for controlling piping movements caused by typical dynamic upset conditions in steam and boiler feedwater piping and in drain lines carrying mixed phase (water and vapor) flow. This paper discusses the simplified mathematics used in estimating loads to design disk spring restraints for such applications.
Fatigue Life Prediction of an Autofrettaged Thick-Walled Pressure Vessel With an External Groove
Authors: Koh S. K. , Stephens R. I.
Published: June 2008

An autofrettaged thick-walled pressure vessel with an external groove subjected to a pulsating internal pressure can have fatigue failures at the external groove root due to the combination of tensile autofrettage residual stress, operating stress, and stress concentration. To predict the fatigue life of the autofrettaged thick-walled pressure vessel with an external groove, the local strain approach was applied. The residual stress distribution due to autofrettage and the operating stress distribution due to internal pressure were determined using finite element analysis which resulted in theoretical stress concentration factors. To account for the mean stress effects on the fatigue life prediction of the pressure vessel, low-cycle fatigue behavior with several strain ratios was obtained using smooth axial specimens taken from the ASTM A723 thick-walled steel pressure vessel. Fatigue life predictions were made by incorporating the local strains determined from the linear rule and Neuber’s rule and the Morrow and SWT mean stress parameters determined from low-cycle fatigue tests. The predicted fatigue lives were within factors of 2 to 4, compared to simulated experimental fatigue lives based upon fatigue cracks of 2.5 mm in length. These procedures appear to be realistic for evaluating fatigue lives for this complex pressure vessel.
Postbuckling Behavior of Unanchored Steel Tanks Under Lateral Loads
Authors: Peek R. , El-Bkaily M.
Published: June 2008

A simplified approach is described for determining the extent of plastic buckling of the tank wall near the base (elephant’s foot bulging) for ground-supported unanchored liquid storage tanks subjected to seismic overturning moments. The method is applied to a 100-ft diameter and 40-ft high tank with a roof. Results show that the ultimate seismic overturning moment that can be withstood by the tank is 31 percent higher than the overturning moment at which elephant’s foot bulging begins. The reason for this is redistribution of vertical compressive stresses in the tank wall: initially these vertical compressive stresses are concentrated over a small contact length. However, as the elephant’s foot bulge develops, the size of the contact length increases, resulting in a more favorable distribution of stresses.
Parametric Resonance of Liquid Storage Axisymmetric Shell Under Horizontal Excitation
Authors: Takayanagi M.
Published: June 2008

A procedure for analyzing parametric resonance of liquid storage axisymmetric shells is proposed that is an extension of the procedure presented at PVP-89 for parametric resonance of empty axisymmetric shells with lumped weights. Free vibration modes of axisymmetric shells containing liquid are calculated considering the effect of initial stress due to static liquid pressure by using a conical shell finite element. The calculated free vibration modes are used to expand the free vibration modes of the axisymmetric shell with lumped weights and internal liquid. A type of Mathieu equation is derived considering the effects of the translational motion of the attached weight in the radial direction or the effects of the beam-type motion of the shell without lumped weight. The harmonic balance method is used to obtain the parametric resonance regions. Principal resonance of a circular cylindrical shell with an attached weight and combination resonance of a liquid storage circular cylindrical shell without attached weights are analyzed. Analytical results show good agreement with experimental results.
Failure Probability Analysis for a Cylinder Subjected to General Loading Conditions
Authors: Zibdeh H. S.
Published: June 2008

This paper studies stresses and failure probabilities for a cylinder subjected to different combinations of inner pressure, outer pressure, axial load, torque, and thermal loading. Probabilistic analyses are used to predict the effects of variations of the geometric, mechanical, and load variables on the normal and log-normal probabilities of failure. The results show that these variables have different effects on the failure of the cylinder. Therefore, the probabilistic approach is important to predict the exact state of failure. Otherwise, the deterministic approach may yield erroneous decisions concerning the performance of the cylinder.
Narrow Belt Stiffening for Reducing the Stress Concentrations in Joints Existing on Vessels, Pipings and Other Related Structures (Design Paper)
Authors: Suviolahti M.
Published: June 2008

It is shown, in the light of three very different case studies, that a narrow belt stiffening when suitably attached at the geometric discontinuity of a joint existing on a vessel, tank or pipe intersection, is able to produce a remarkable reduction in the stress concentration. This is reason to believe that the narrow belt stiffening, when dimensioned correctly and attached properly, may be used extensively to reduce stress gradients in joints existing on vessels, tanks, pipings and related structures. Understandably, a narrow belt stiffening should be used with great caution for junctions that do not operate at ambient temperature, being unsuitable for applications involving substantial thermal stresses.
Weight Loss Correlation for Sheet Gasket Materials
Authors: Marchand L. , Derenne M. , Bazergui A.
Published: June 2008

Elevated temperature aged tests were performed on two fiber-reinforced sheet gasket materials with acrylonitrile-butadiene rubber (NBR) binder; a compressed asbestos and a compressed aramid. Weight loss, relaxation and cross-fiber tensile strength measurements were taken. An aging parameter (Ap) based on weight loss correlation is proposed which successfully groups data for different test times and temperatures. Ap is shown to have good potential as an accurate predictive parameter for determining long-term operating temperature on the basis of short-term tests. The use of the thermogravimetric approach is also discussed.
Seismic Response of Unanchored Fluid-Filled Tanks Using Finite Elements
Authors: Yi Wei , Natsiavas S.
Published: June 2008

A finite element model is presented for the seismic response of liquid-filled tanks. This type of analysis is complicated for unanchored tanks, because the bases of these tanks separate from their foundations during strong ground motion. This changes the dynamic behavior of these structures considerably and may result in severe loading. The analysis starts by geometrically discretizing the shell structure using cylindrical finite elements. Then, application of Hamilton’s principle in the structural domain yields the equations of motion for the coupled fluid/structure system. The foregoing analytical procedure employs the closed-form solution for the hydrodynamic response problem, resulting in a compact system of equations of motion. Primary attention is paid to the formulation of the nonlinear base uplift problem. Effects due to shell and ground flexibility are also included.
An Adaptive Growth Method for Shape Refinement: Methodology and Applications to Pressure Vessels and Piping
Authors: Azegami H. , Okitsu A. , Ogihara T. , Takami A.
Published: June 2008

A simple shape refinement technique for improving strength has been developed. The technique is to deform shapes with growth bulk strain which springs up in proportion with deflection of a strength measure to a basic value in all parts of a body. The scheme for the shape refinement consists of the iteration of the two steps with finite element method: 1) analysis step of a strength measure distribution, and 2) growth deformation step with the growth bulk strain. Numerical experiments on static and dynamic test problems and practical problems of pressure vessel and piping system indicate the effectiveness of this technique for improving strength.
Stress Analysis of Pressure Vessel With Wound-Flat Steel Ribbons
Authors: Huang P. S. , Zhu G.
Published: June 2008

Pressure vessels with wound-flat steel ribbons, also called ribbon-wound vessels, have excellent engineering and economic advantages and are widely used in the People’s Republic of China. A brief description of the structure and characteristics, and a comparison between the ribbon-wound technique with other methods are given. In this paper, a new mechanical model for the ribbons, in which the axial displacement and change of spiral angle are taken into account, is put forward. Then the universal formulas for the ribbon are obtained and a precise stress analysis of the vessel is presented. The spring effect of the ribbon layers has a great strengthening effect on the axial strength of the vessel and enables the vessel to support axial load. A formula for the spring effect is suggested. A comparison between theory and test is made, and the results are excellent.
Approximate Crack Opening Displacement Solutions for Long Circumferential Cracks in Pipes Subjected to Bending and Tension
Authors: Yoo S. H. , Pan J.
Published: June 2008

A simple parabolic formula that describes the opening profile of a sufficiently long circumferential crack in a pipe subjected to bending and tension was found after a proper normalization of the second-order asymptotic expansion of the solutions of Sanders and Alabi [5-9]. Here the crack is sufficiently long in the sense that approximately the crack angle is larger than a small parameter which has the same order of magnitude as the ratio of the wall thickness to the pipe radius, and the pipe is sufficiently long enough not to consider the end effects. These linear elastic solutions can be superposed for combined bending and tension loading. The smile parabolic formula is shown to be a good approximation of the crack opening profile and can be used to evaluate the leak rate for crack length up to one-half of the circumference.
Two and Three-Dimensional Simulations of Moving Pressure Fronts in Gun Tubes
Authors: Rabern D. A. , Lewis M. W.
Published: June 2008

Options were added to the PRONTO2D and PRONTO3D structural dynamics finite element codes to include the effect of a traveling pressure front that follows a projectile while transiting pressurizing axisymmetric and nonstraight gun tubes. Pressure varied in magnitude and location with time and projectile displacement to predict the dynamic structural response of the projectile and gun tube. Two and three-dimensional simulations were performed to study the effect of this pressure front and its influence on projectile gun tube interaction and lateral movement of the projectile in the gun tube caused by variation of the gun centerline during projectile launch and recoil. Discussions of theory, implementation, and results from simulations are presented.
The Optimal Design for an Internal Stiffener Plate in a Penstock Bifurcation
Authors: Zhou Y. , Bryant R. H.
Published: June 2008

This paper presents the optimum design of an internal stiffener plate in a penstock bifurcation. It is assumed that the monetary cost of the structure is dependent on the amount of material used. Hence, the weight (volume) of the plate is minimized subject to an allowable stress constraint. This is accomplished by determining the shape of the moving, free boundary of the plate, while the loaded boundary remains fixed. The mathematics of the problem is based on the variational principles of elasticity, the material derivative concept of continuum mechanics, and a gradient projection method of analysis. A sensitivity analysis is performed to examine the influence of the moving boundary of the plate on the stress constraint. At the optimum design the moving boundary reaches the predefined allowable stress. The finite element analysis package ANSYS is used for the stress calculations.
Static Analysis of Buttress Threads Using the Finite Element Method
Authors: Chaaban A. , Jutras M.
Published: June 2008

The finite element method has been used to investigate the stress field in threaded end closures of thick-walled high pressure vessels. A set of elastic analyses of vessels with 5, 8, 11, 15, 20 and 25 standard Buttress threads was used to propose a method for predicting the load distribution along the length of the thread. Root stress index factors in the region of the first three active threads are also included. The results of the present work contribute to the development of the new division of the ASME Pressure Vessel Code which is related to thick-walled high pressure vessels.
A New Correlation Between MC Precipitate Size, Aging Time and Temperature for an Advanced Austenitic Steel
Authors: Todd J. A. , Ren J. C.
Published: June 2008

The MC precipitate size distributions have been measured for times of 1, 10, 100, 300 and 1000 hr at 700 and 900° C in a 16Ni-14Cr advanced austenitic steel. A new correlation between the mean precipitate size, aging time and temperature has been developed. The new correlation is compatible with a solute exhaustion mechanism, which may explain why (i) the MC precipitates formed on matrix dislocations resist coarsening for up to 3000 hr at 900°C; and (ii) the degree of cold work (i.e., the dislocation density), which determines the number of MC nucleation sites, controls the limiting precipitate size.
Comments on the Problem of Crack Extension From a Defect in a Weld
Authors: Smith E.
Published: June 2008

The paper discusses the problem of crack extension in a weld in an engineering structure, and how this relates to crack extension in a small specimen of weld material. For the case where the parent material is softer than the weld material, it is argued that the J integral crack growth resistance curve for the small specimen can be above that for the structure, for which the curve depends on the flow properties of both the weld and parent materials, and also the crack size and weld thickness. The onset of crack extension can be conservatively predicted using the weld material’s toughness properties and the parent material’s flow properties, but nonconservative results may arise if the same approach is used to make instability predictions. The focus of attention is the case where the weld crack is parallel to the plane of the weld, a situation for which the J integral is path-independent with regard to any contour surrounding a crack tip.
Sensitivity Analysis in Shape Optimization Design for Pressure Vessel
Authors: Younsheng L. , Ji L.
Published: June 2008

In this paper, sensitivity analysis for a finite element model during shape optimization design for a pressure vessel is discussed. The derivation is emphatically carried out for the derivatives of stiffness matrix and various load ranks with respect to design variables. Because the information resulting from the finite element analysis is fully utilized in this method, the programs are greatly simplified so that it becomes possible to carry out the shape optimization with comparatively more versatility. The conclusion is illustrated by an example.
Vibration Response Characteristics of Tandem Two Circular Cylinders Subjected to a Two-Phase Cross Flow—Effects of Pitch-to-Diameter Ratio
Authors: Hara F. , Iijima T. , Nojima T.
Published: June 2008

This paper deals experimentally with the comparison of air bubble effects on the vibration of two circular cylinders installed in tandem at pitch-to-diameter ratios of 1.5 and 3.0. Experiments were done for both the pitch-to-diameter ratios changing the void fraction from 0 to about 20 percent for the reduced velocity ranging from 0.5 to 8; vibrational accelerations were measured in both the lift and drag directions for each cylinder and the results were compared with for each other between the pitch-to-diameter ratios of 1.5 and 3. The comparison revealed that 1) the vibration of the tandem two-cylinder system having a pitch-to-diameter ratio of 1.5 or 3 was excited by air bubbles in the flow for small reduced velocity, but the effect of pitch-to-diameter ratio was found in the response characteristics of the upstream cylinder’s vibration in the lift direction; 2) a small amount of air bubbles equivalent to about 4 percent of the void fraction suppressed the strong, out-of-phase vibration in the downstream cylinder of a large P/D of 3 when the reduced velocity was about 7, but the cylinder arrangement with a small pitch-to-diameter ratio of 1.5 showed a weaker vibration reduction due to adding air bubbles in the flow at high flow velocity; and 3) the vibration suppression was likely due to the entrainment of air bubbles in the wake region behind the upstream cylinder.
Coupling of Rotor-Gear-Casing Vibrations During Extreme Operating Events
Authors: Choy F. K. , Padovan J. , Ruan Y. F.
Published: June 2008

During extreme operating environments (i.e., seismic events, base motion-induced vibrations, etc.), the coupled vibrations developed between the rotors, bearings, gears and enclosing structure of gear-driven rotating equipment can be quite substantial. Generally, such large vibrational amplitudes may lead to failures in both the rotor-gearing system and/or the casing structure. This paper simulates the dynamic behavior of rotor-bearing-gear system resulting from motion of the enclosed structure. The modal synthesis approach is used in this study to synthesize the dynamics of the rotor systems with the vibrations of their casing structure in modal coordinates. Modal characteristics of the rotor-bearing-gear systems are evaluated using the matrix transfer technique, while the modal parameters for the casing structure are developed through a finite element model using NASTRAN. The modal accelerations calculated are integrated through a numerical algorithm to generate modal transient vibration analysis. Vibration results are examined in both time and frequency domains to develop representations for the coupled dynamics generated during extreme operating conditions. Typical three-rotor bull gear-driven power plant equipment (compressors, pumps, etc.) is used as an example to demonstrate the procedure developed.
Simple Bounds on Limit Loads by Elastic Finite Element Analysis
Authors: Mackenzie D. , Nadarajah C. , Shi J. , Boyle J. T.
Published: June 2008

A method for bounding limit loads by an iterative elastic continuum finite element analysis procedure, referred to as the elastic compensation method, is proposed. A number of sample problems are considered, based on both exact solutions and finite element analysis, and it is concluded that the method may be used to obtain limit-load bounds for pressure vessel design by analysis applications with useful accuracy.
Acoustic and Ultrasonic Signals as Diagnostic Tools for Check Valves
Authors: Au-Yang M. K.
Published: June 2008

A typical nuclear plant has between 60 and 115 safety-related check valves ranging from 2 to 30 in. The majority of these valves control water flow. Recent studies done by the Institute of Nuclear Power Operations (INPO), Electric Power Research Institute (EPRI) and the US Nuclear Regulatory Commission (NRC) found that many of these safety-related valves were not functioning properly. Typical problems found in these valves included disk flutter, backstop tapping, flow leakage, disk pin and hinge pin wear, or even missing disks. These findings led to INPO’s Significant Operating Experience Report (SOER, 1986), and finally, NRC generic letter 89-04, which requires that all safety-related check valves in a nuclear plant be regularly monitored. In response to this need, the industry has developed various diagnostic equipment to monitor and test check valves, using technologies ranging from acoustics and ultrasonics to magnetic—even radiography has been considered. Of these, systems that depend on a combination of acoustic and ultrasonic techniques (Au-Yang et al., 1991) are among the most promising for two reasons: these two technologies supplement each other, making diagnosis of the check valves much more certain than any single technology, and this approach can be made nonintrusive. The nonintrusive feature allows the check valves to be monitored and diagnosed without being disassembled or removed from the piping system. This paper shows that by carefully studying the acoustic and ultrasonic signatures acquired from a check valve, either individually or in combination, an individual with the proper training and experience in acoustic and ultrasonic signature analyses can deduce the structural integrity of the check valve with good confidence. Most of the conclusions are derived from controlled experiments in the laboratory where the diagnosis can be verified. Other conclusions were based on test data obtained in the field.
Prestress Analysis of Flat Steel Ribbon-Wound Vessel
Authors: Huang P. S. , Zhu G. B. , Barron R.
Published: June 2008

The flat steel ribbon-wound vessel is a relatively new type of wound pressure vessel. This type of vessel consists of a thin-walled inner core and helically wound flat steel ribbons. The outstanding safety in service of this type of vessel is due, in part, to the large circumferential and axial prestresses introduced during the ribbon-winding process. This paper presents a model for determination of prestresses in such a vessel. The model considers the fabrication procedures producing the prestress in the vessel. Experimental results from tests using full-scale vessels are presented. Agreement between the theoretical model and the experimental results is excellent.
Postbuckling Analysis of Plates Under Combined Loads by a Mixed Finite Element and Boundary Element Method
Authors: Ye J. Q.
Published: June 2008

The postbuckling behavior of thin plates under combined loads is studied in this paper by using a mixed boundary element and finite element method. The transverse and the in-plane deformation of the plates are analyzed by the boundary element method and the finite element method, respectively. Spline functions were used as the interpolation functions and shape functions in the solution of both methods. A quadratic rectangular spline element is adopted in the finite element procedure. Numerical results are given for typical problems to show the effectiveness of the proposed approach. The possibilities to extend the method developed in this paper to more complicated postbuckling problems are discussed in the concluding section.
A Finite Element Analysis of Flange Connections
Authors: Zahavi E.
Published: June 2008

The present work pertains to nonlinear analysis of forces and deformation in pressurized flange connections, taking into consideration changes of geometry and friction. This allows greater accuracy in computing bolt forces and in predicting the leakage point.
Local Flexibility of Cylindrical Shells and Pipes at the Support
Authors: Ong L. S.
Published: June 2008

This article presents a parametric study for the determination of the flexibility and stiffness of a cylindrical shell at its support location. The parametric equation incorporates the geometric variables of both cylindrical shell and support; namely, the shell radius, thickness, and length, and the support width and embracing angle. A mathematical model has been devised to provide the theoretical data of flexibilities for establishing the parametric equation. The model is based on a contact stress formulation and uses a cylindrical shell theory. The validity and accuracy of the proposed parametric equation has been checked against available experimental results obtained from literature. There is close agreement between the two. The present study and results should be useful to designers who wish to determine the induced support force (or displacement) due to applied displacement (or force) at the support.
Determination of Dynamic Fracture-Initiation Toughness Using a Novel Impact Bend Test Procedure
Authors: Yokoyama T.
Published: June 2008

A novel impact bend test procedure is described/or determining the dynamic fracture-initiation toughness, KId, at a loading rate (stress intensity factor rate), K˙I, of the order of 106MPam/s. A special arrangement of the split Hopkins on pressure bar is adopted to measure accurately dynamic loads applied to a fatigue-precracked bend specimen. The dynamic stress intensity factor history for the bend specimen is evaluated by means of a dynamic finite element technique. The onset of crack initiation is detected using a strain gage attached on the side of the specimen near a crack tip. The value of KId is determined from the critical dynamic stress intensity factor at crack initiation. A series of dynamic fracture tests is carried out on a 7075-T6 aluminum alloy, a Ti-6246 alloy and an AISI 4340 steel. The KId values obtained for the three structural materials are compared with the corresponding values obtained under quasi-static loading conditions.
Probability of Fracture for HFIR Pressure Vessel Caused by Random Crack Size or by Random Toughness
Authors: Chang S.-J.
Published: June 2008

The probability of fracture (or the fracture fragility) for a range of internal pressure-pulses for the HFIR pressure vessel is obtained. The fracture is assumed to be caused by randomly distributed cracks and by fracture toughness of variable magnitudes. The probability curve is applied to estimate the vessel fracture strength against the pressure-pulses of hypothetical accident. Both the crack population and the fracture toughness are assumed to be random variables of given distribution functions. Possible hoop stress is based on the numerical solution of the vessel response after a point pressure-pulse is applied at the center of the reactor vessel. The fluid-structure interaction and radiation embrittlement are both considered in the analysis. Only elastic fracture mechanics is used. The probability of vessel fracture for a single crack caused by either a variable crack depth or a variable toughness is first derived. Then the probability of fracture with multiple number of cracks is obtained. The probability of fracture is further extended to include different levels of confidence and variability.
A Study on Buried Pipeline Response to Fault Movement
Authors: Chiou Y.-J. , Chi S.-Y. , Chang H.-Y.
Published: June 2008

This study investigates the buried pipeline response to strike slip fault movement. The large deflection pipe crossing the fault zone is modeled as an elastica, while the remaining portion of small deflection pipe is modeled as a semi-infinite beam on elastic foundation. The finite difference method is applied for the numerical solution and the results agree qualitatively with the earlier works.