bluuebunny/crossref_metadata_2025_split huggingface dataset:
Berechnung der Dauerschwingfestigkeit unter Berücksichtigung der spannungsmechanischen und statistischen Stützziffer
Authors: Liu J. , Zenner H. 
Published: December 2004

AbstractWird eine plastische Wechselverformung im Kerbgrund auch in Höhe der Dauerfestigkeit angenommen, so kann mit Hilfe der Neuber‐Formel und des zyklischen Spannungs‐Dehnungs‐Diagramms eine makroskopische Stützwirkung berechnet werden. Wird weiterhin der statistische Größeneinfluß nach dem Fehlstellenmodell berücksichtigt, so kann die Kerbwirkung bei Bauteilen mit ausreichender Genauigkeit abgeschätzt werden. Der Nachweis für die Treffsicherheit des Modells wird anhand von Versuchsergebnissen an Probestäben aus Stahl geführt.
Erhöhung der Dauerfestigkeit geschmiedeter Pleuel durch Kugelstrahlen unter Vorspannung
Authors: Engelmohr F. , Fiedler B. 
Published: December 2004

AbstractDie Eigenspannungsausbildung an der Oberfläche der Serienpleuel hängt von der Gleichmäßigkeit der beim Reinigungsstrahlen induzierten Eigenspannungen und der weiteren Fertigungsfolge ab.Aufgrund der Fertigungsfolge können in den anrißgefährdeten Bereichen sowohl Zug‐ als auch Druckeigenspannungen vorliegen. Im Bereich der Dauerfestigkeit führt dies zu einer großen Streuung der ertragbaren Beanspruchung, die bei der Auslegung entsprechend berücksichtigt werden muß.Durch Kugelstrahlen unter Vorspannung können in Belastungsrichtung der Pleuel Druckeigenspannungen bis in Höhe der Streckgrenze des Werkstoffes an der Oberfläche eingebracht werden. Dies führt nicht nur zu einer Anhebung der mittleren Dauerfestigkeit, sondern auch zu einer Verlagerung des Rißausgangsortes unterhalb der Bauteiloberfläche. Die Lebensdauer der unter Vorspannung gestrahlten Pleuel wird demnach vom Anrißort im Inneren des Pleuelschaftes bestimmt. Die schwingfestigkeitsmindernde Wirkung von Oberflächenfehlern kann somit bei Fehlern bis zu einer Tiefe von 0,3 mm größtenteils kompensiert werden. Dies ist ausschlaggebend für die geringe Streuung der unter Vorspannung gestrahlten Pleuel.
Komplexe Bewertung von Indentereindrücken zur Charakterisierung von Konstruktionskeramik
Authors: Dietz M. , Tietz H.‐D. , Zappek T. 
Published: December 2004

AbstractDurch das Einbringen von Indentereindrücken in spröde Werkstoffe und deren Bewertung ergeben sich Informationen zur Werkstoffcharakterisierung. Neben der bruchmechanischen Bewertung der Indentereindrücke, d.h. der damit in Verbindung stehenden Anrisse, zur Ermittlung der Bruchzähigkeit, sind Aussagen bezüglich der Härte. Der kritischen Größe von Oberflächendefekten, der Rißausbreitungskenngrößen. Der Nutzbarkeitsdauer sowie vorhandener Eigenspannungen abzuleiten.
Evaluation of stresses on polymeric materials – Lattice strains, macro‐ and micro‐residual stresses of an compound polypropylen/Al‐powder
Authors: Behnken H. , Chauhan D. , Hauk V. 
Published: December 2004

AbstractNachdem in einer früheren Arbeit der Zusammenhang der Spannungen von α‐PP und Al‐Pulver in einer spritzgegossenen Platte aus PP + 10 Gew.% Al in Abhängigkeit von der Lastspannung untersucht wurde, werden Gitterdehnung, Makro(ES I)‐ und Mikro(ES II)‐Eigenspannungen an gleichem polymeren Material mit Röntgenstrahlen bestimmt. Die Ergebnisse, insbesondere die Ausbildung von Zug‐ oder Druck‐Mikro‐ES im Al‐Pulver werden mit Rechnungen und Abschätzungen verglichen.
Einfluß des Reinheitsgrades, der Kaltverformung und des Schweißens auf das Zeitstandverhalten von X20 CrMoV 12 1‐Rohrstahl bei 550 °C
Authors: Schubert J. , Jakobeit W. , Schneider K. 
Published: December 2004

AbstractIm Wasser‐Dampf‐Kreislauf des THTR wurde erstmals im Kraftwerksbau ein P‐ und S‐armer, hoch angelassener martensitischer 12% CrMoV‐Stahl mit verbesserter Kerbschlagzähigkeit für FD‐, Zwischenüberhitzer‐ sowie Kleinleitungen eingesetzt. Dabei kommen artgleiche Rohrschweißverbindungen und auf der Dampferzeugerseite die Mischverbindung mit dem austenitischen Stahl X5 NiCrAlTi 3120 vor. Beim Biegen der Kleinleitungen trat Kaltverformung auf.Im Rahmen der vom BMFT geförderten Werkstoffprogramme wurden vorlaufende und betriebsbegleitende Zeitstandversuche an mehreren Schmelzen bis derzeit rund 60 000 h bei 550 °C durchgeführt, die zu folgenden Ergebnissen führten:
Die Zeitstandfestigkeit und 1 %‐Zeitdehngrenze der zäheren Variante liegt in der unteren Streubandhälfte der Stahlsorte.
Bei betriebsnaher Zeitstandbeanspruchung muß damit gerechnet werden, daß der 3. Kriechbereich des Grundwerkstoffs und des artgleichen Schweißgutes nach rund 60% der Standzeit bis Bruch bzw. nach einer bleibenden Dehnung von etwa 1% beginnt.
Für verschiedene Spannungsbereiche können annähernd konstante, schmelzenunabhängige Kriechspannungsexponenten angegeben werden.
Eine langsame Belastungsgeschwindigkeit beeinträchtigt den stat. E‐Modul.
Zeitstandfestigkeit und ‐bruchverformung werden durch Kaltverformung beeinträchtigt.
Bei Beanspruchung quer zur Schweißnaht müssen bei der Auslegung gegen die Zeitstandfestigkeit Schweißminderungsfaktoren berücksichtigt werden. Die feinkörnige WEZ ist der zeitstandfestigkeitsmaßig schwächste Bereich.
Mit den gewonnenen Ergebnissen kann die Auslegung künftiger HTR‐Anlagen, konventioneller Kraftwerke und Chemieanlagen weiter optimiert werden.
Inhomogeneity of flow, force parameters and pass geometry in rotary Cone‐Roll Tube Piercing
Authors: Al‐Dahwi A. K. A. , Blazynski T. Z. 
Published: December 2004

AbstractThe relationship between redundant macroshearing and force parameters, related to a rational pass design, in a rotary 2‐cone roll seamless tube piercing process was investigated. Wax and lead billets were pierced in a range of working conditions involving decelerated, uniform and accelerated rates of flow, different plug advances, and four values of feed angles. The likely optimal piercing conditions are indicated.
Das totaldehnungskontrollierte Wechselverformungsverhalten unlegierter Stähle im normalisierten Zustand bei Raumtemperatur
Authors: Pan Y. , Eifler D. , Macherauch E. 
Published: December 2004

AbstractDas Wechselverformnungsverhalten unlegierter normalisierter Stähle mit Kohlenstoffgehalten 0,1 ≤ C ≤ 1.05 (in Masse‐%) ist in totaldehnungskontrollierten mitteldehnungsfreien Versuchen durch ausgeprägte zyklische Entfestigungs‐ und schwache Verfestigungsvorgänge gekennzeichnet. Die zyklischen Spannungs‐Dehnungskurven werden mit wachsendem Kohlenstoffgehalt zu größeren Spannungsamplituden verschoben. Die mittelspannungsfrei ermittelten zyklischen Spannungs‐Dehnungskurven unlegierter Stähle sind unabhängig von der Versuchsführung. Die Übergangslastspielzahl, bei der in der Dehnungswöhlerlinie εa,e = εa,p wird, verschiebt sich mit wachsendem Kohlenstoffgehalt zu kleineren Werten.
Neue Werkstoffe und Verbundbauweise für Hochleistungsmaschinen der Verfahrenstechnik
Authors: Dietz P. , Rübbelke L. 
Published: December 2004

AbstractHerkömmliche Abweiseradsichter lassen bei besonderer Beachtung kerbarmer und kraftßuagerechter Gestaltung Umfangsgeschwindigkeiten von 140 m/s zu. Es wird aufgezeigt, daß durch die Verknüpfung von verschiedenen Werkstoffen mit ihren unterschiedlichen Eigenschaften Rotoren entwickelt werden können, die den Einsatz bis zur verfahrenstechnischen Grenze des Klassierprozesses, der Schallgeschwindigkeit, erlauben. Die Benutzung eines Faserverbundringes im Außenbereich führt zu einem sogenannten Selbsthilfeeffekt, der die entstehenden Spannungen mindert. Relativ einfach aufgebaute vielschichtige Laminate wie die Lamellen und die Haltestabe lassen sich nach Kriterien hinsichtlich ihrer Hauptbelastungen optimieren. Fur die Faserverbundteile und den Rotorgrundkörper muß eine Verschleißschutzbeschichtung vorgesehen werden.
The effects of RE on Toughness of 30CrMnSi wear‐resistant cast steel
Authors: Jingpei Xie , Quande Chen , Yanpei Shong 
Published: December 2004

AbstractThe effects of RE (La and Ce) on toughness of 30CrMnSi wear‐resistance cast steel have been investigated by means of analysing microstructures and mearsering the properties of the steel with and without RE. The results show that RE can refine the as‐cast microstructures, hinder or eliminate needle and network ferrite, increase the dislocation density and the quantity of dislocated martensite, and improve the shape and distribution of inclusions. Therefore the mechanical properties of the steel can be greatly enhanced, especially the toughness of the steel.
Epidemiologic studies of adverse effects of anti‐retroviral drugs: how well is statistical power reported
Authors: Halpern Scott D. , Barton Todd D. , Gross Robert , Hennessy Sean , Berlin Jesse A. , Strom Brian L. 
Published: December 2004

AbstractPurposeTo determine whether there is a difference in average statistical power between pharmacoepidemiologic studies of anti‐retroviral adverse drug effects (ADEs) sponsored by for‐profit versus non‐profit organizations.MethodsWe studied all published pharmacoepidemiologic studies of ADEs associated with the 15 anti‐retroviral drugs approved through the end of 1999. A priori, the primary outcome was the power of each study to detect a clinically important difference in the risk for an adverse effect among patients exposed to the study drug(s). We could not evaluate this outcome because of the infrequent reporting of power calculations. We instead report the distribution of studies across a 5‐tiered measure of adequacy of reporting of statistical power, as well as the sponsorship of these studies.ResultsOf 48 studies meeting our inclusion criteria, only 1 (2%) reported either a completed, a priori power calculation or sufficient details for readers to calculate the power to detect a pre‐defined, clinically important effect. Thirty‐five studies (73%) reported the minimum information required for sophisticated readers to determine the power to detect an event rate of interest to them; 6 additional studies (13%) reported confidence intervals around at least one summary effect measure and 6 (13%) provided no indication of power or uncertainty. Of the 41 studies for which sponsorship was determined, only 3 (7%) were sponsored by for‐profit organizations.ConclusionsThe poor reporting of statistical power in this sample suggests a need for guidelines to improve the reporting of pharmacoepidemiologic studies of ADEs. Future research is needed to determine whether the observed paucity of industry‐sponsored observational studies of anti‐retroviral ADEs extends to other clinical areas, and if so, to identify the causes of this phenomenon. Copyright © 2004 John Wiley & Sons, Ltd.
Gel sensitivity of polybutadiene‐based rubber subjected to thermal abuse
Authors: James D. E. 
Published: December 2004

AbstractThe thermal instability of polybutadiene‐based rubber used to improve the impact strength of vinyl‐type polymers often presents processing problems. Rubber manufacturers have attempted to alleviate this situation by incorporating various types of stabilizers. However, this is not always successful. One of the consequences of using a rubber that is not sufficiently stable in the production of modified vinyl‐type polymers is the formation of insoluble gel particles during processing. In an attempt to prevent this from occurring, a test was developed that can differentiate between rubbers of acceptable and non‐acceptable thermal stability. In principle, the test consists of exposing the rubber in question to a controlled thermal abuse of such intensity and duration as to approximate the thermal abuse to which the rubber will be subjected in a normal processing sequence. (The extent of abuse will vary for different processes and must be empirically established for each system.) Following this controlled exposure, the rubber is tested for gel‐particle content by filtration of a specific solution, much the same way that the rubber manufacturer tests for initial gel‐particle content. Sufficient data have been compiled to statistically describe the validity of the test.
Polybutylene properties of a packaging material
Authors: Lindergren C. R. 
Published: December 2004

AbstractThe unusual physical properties of polybutylene are ascribed to details of morphology and a unique crystalline transformation. Inherent properties important for industrial film uses include toughness, low creep, relatively high temperature resistance, stress crack resistance and flexibilty. Four types of packaging applications are described for a new polybutylene resin based on butene‐1 monomer. These include industrial film, easy opening tear packages, shrink film, and rotationally molded tanks.A polybutylene shrink film is described having a combination of optical and shrink properties similar to vinyl shrink film, but with mechanical properties typical of polyolefin shrink films.Rotationally molded parts exhibit an unusual degree of toughness, stress crack resistance, and low crystallization stresses in thick parts.
Time‐dependent properties of versamid cured epoxies
Authors: Moehlenpah A. E. , Dibenedetto A. T. , Ishai O. 
Published: December 2004

AbstractVersamid cured‐epoxy specimens were loaded in tension, compression, and flexure at different strain rates and temperatures to determine the yield stress and strain, and tangent, secant, and relaxation moduli. A torsion pendulum was used to measure the dynamic properties as a function of temperature and frequency. The time‐temperature superposition principle was used to reduce this data to master curves. It was concluded that the time‐temperature shift factors for secant moduli up to the yield point, for stress relaxation and for dynamic moduli were identical and were independent of the mode of loading. It was also shown that the presence of fillers or reinforcing agents likewise had no effect on the shift factors.
Polymer solubility parameters determined from measurements in a single solvent
Authors: Song W. R. , Brownawell D. W. 
Published: December 2004

AbstractThe solubility parameter of polyisobutylene has been determined from intrinsic viscosity measurements in a single solvent as a function of temperature. The change in solubility parameter of the solvent as a function of temperature was calculated form the equation \documentclass{article}\pagestyle{empty}\begin{document}$ \frac{{d{\rm}ln \delta s}}{{d{\rm}ln Vs}} = - \frac{{n + 1}}{2} $\end{document} where Vs, the molal volume, changes with temperature. The vlaue for the solubility parameter thus obtained compares well with values reported in the literature for intrinsic viscosity measurements in a series of solvents. Similar measurements were made with an ethylenepropylene copolymer. The solubility parameter of 87 mole % C2 ethylene‐propylene copolymer was determined to be 8.1‐8.6 in either toluene or methylcyclohexane.
Processability of high‐density polyethylene bottles with special reference to melt flow properties
Authors: Hirata S. , Kishimoto A. 
Published: December 2004

AbstractA phenomenological treatment has been developed for correlations between melt flow properties of high‐density polyethylenes and the processability of bottles. Defining two parameters for the flow properties, it was found experimentally that linear relationships hold satisfactorily between these flow parameters for the raw materials and those of corresponding extrudates. Several kinds of defects in high‐density polyethylene bottles can be represented in terms of the flow parameters. These parameters may provide useful measures in predicting good appearance of bottles blow‐molded with high‐density polyethylene.
Fine structures and fracture processes in plastic‐rubber two‐phase polymer systems III. Temperature dependence of Charpy impact strength
Authors: Matsuo M. , Ueda A. , Kondo Y. 
Published: December 2004

AbstractNotched Charpy impact strengths of a series of plasticrubber two‐phase polymer systems were measured over a wide range of temperatures. Blends of polyvinylchloride and rubbers with varying chemical structures, and several ABS polymers were investigated.In all systems, Charpy impact strength began to increase near the Tg of the rubber component followed by a logarithmic increase with increasing temperature. The trend is expressed by the following empirical relation:

where I is Charpy impact strength, A and B are constants, and T is the absolute temperature. This equation is applicable between the Tg's of the plastic and the rubber components. The increasing tendency of impact strength, i.e. the B value of the above equation, is depressed mainly by the decrease of the compatibility and/or the interfacial adhesive force between the two phases. Toughening mechanism and the ways of increasing toughness are discussed based on the craze formation mechanism.
A modified melting model for plastifying extruders
Authors: Hinrichs D. R. , Lilleleht L. U. 
Published: December 2004

AbstractThe extursion melting model of Tadmor et al. (1967) has been modified to include the effects of screw channel curvature and melt leakage through the screw flight‐barrel clearance. An alternate coordinate system was used in modifying the model to simplify the addition of curvature corrections. Also proposed is an improved method of computing solid bed velocity. A substantial number of typographical errors and truncations appeared in the original data published by Tadmor et al., and verification of their computations with corrected data was successful in all cases. Channel curvature corrections and the improved method of computing solid bed velocity increased the predicted rate of solid bed width decrease by approximately 14% during the initial stages of melting. Addition of leakage flow to the model tended to offset this effect completely or in part. Leakage flow effects always predominated during the later stages of melting, however. These effects may interact differently for other extruder sizes or screw designs; therefore, the modified melting model should be a more accurate model for use in the design of extruder screws and in studies of extruder performance.
Inflation and compression of rubber tubes between parallel plates
Authors: Charrier J. M. , Gent A. N. 
Published: December 2004

AbstractWhen a thin‐walled rubber tube containing an incompressible fluid is compressed between two parallel plates the internal pressure rise depends on the restraints in the contact regions. When there is no friction in the contact zone the pressure rise is lower than when slip is prevented, so that the tube, regarded as a spring, has a compression stiffness which depends on the frictional conditions. The same considerations apply to the inflation of a tube between fixed parallel plates. In this case unstable inflation sets in at a critical pressure when the interfaces are frictionless; the tube develops a pronounced bulge when this pressure is approached. Simple theoretical relations are derived for the internal pressure and compressive force for both these deformations, and for both boundary conditions, assuming that the rubber is Neo‐Hookean in elastic behavior. Experimental measurements on tubes of different dimensions are shown to be in reasonably good quantitative agreement with these theoretical predictions in all cases.
Strength properties of discontinuous fiber composites
Authors: Chen P. E. 
Published: December 2004

AbstractThe longitudinal strengths of unidirectional discontinuous fiber composites have been calculated based on the concept of perturbation effect and the distortional energy criterion, utilizing the finite‐element method. The theoretical results thus obtained are compared with the experimental data as well as the results of shear lag analysis for tungsten‐copper, boron‐aluminum, glass‐epoxy and boron‐epoxy composites. Based on the Jackson‐Cratchley equations, modified for discontinuous fibers, a formula is also proposed for calculating the strengths of randomly oriented discontinuous fiber composites. The results calculated from this formula are compared with the experimental data for aluminum oxide‐aluminum‐silicon and glass‐epoxy composites.
Measurements on the biaxial extension viscosity of bulk polymers: The inflation of a thin polymer sheet
Authors: Denson C. D. , Gallo R. J. 
Published: December 2004

AbstractAn experimental study of the inflation of a thin polymer sheet has been conducted to determine whether this technique can be used to measure the biaxial extensional viscosity of bulk polymers. Viscosities were determined at various extensional strain rates using two undiluted polyisobutylene samples having different molecular weights. Advantages, limitations, and errors associated with the method are discussed.
Characterization of polyvinyl chloride part II. The unperturbed end to end distance values obtained from a new GPC method and viscometry
Authors: Chan Richard K. S. 
Published: December 2004

AbstractA new gel permeation chromatography (GPC) method is proposed for determining the unperturbed end‐to‐end distance, \documentclass{article}\pagestyle{empty}\begin{document}$ \left({\frac{{r_0 ^2 }}{M}} \right)^{0.5} $\end{document}, of polymers of known molecular weights, Mn and Mw. This method requires the value of \documentclass{article}\pagestyle{empty}\begin{document}$ \left({\frac{{r_0 ^2 }}{M}} \right)^{0.5} _{{\rm ps}} $\end{document} of polystyrene which was determined through viscometry to be 0.735 \documentclass{article}\pagestyle{empty}\begin{document}$ \left({\frac{{{\rm {\AA}}^2-{\rm mole}}}{{gm}}} \right)^{0.5} $\end{document} Polyvinyl chloride (PVC) was chosen to illustrate the method and \documentclass{article}\pagestyle{empty}\begin{document}$ \left({\frac{{r_0 ^2}}{M}} \right)^{0.5} _{pvc} $\end{document} was found to be 0.99 from GPC data which is in agreement with the result obtained from viscometry, \documentclass{article}\pagestyle{empty}\begin{document}$ \left({\frac{{r_0 ^2}}{M}} \right)^{0.5} _{pvc} $\end{document} = 1.01. All \documentclass{article}\pagestyle{empty}\begin{document}$ \left({\frac{{r_0 ^2 }}{M}} \right)^{0.5} $\end{document} values were determined at 30°C. The advantage to this method lies in its speed and economy of materials.
The mechanical performance of cross‐plied composites
Authors: Lavengood R. E. , Ishai O. 
Published: December 2004

AbstractThe mechanical performance of fiber glass epoxy, cross‐plied laminates having either ductile or brittle matrices, was evaluated in tension. The laminates with ductile matrices have higher initial strength, slower crack propagation in the transverse layers and higher ultimate stress and strain. In both the ductile and brittle systems, the laminae have higher strength, stiffness and toughness than equivalent unidirectional composites. This improved performance results from the interaction between the perpendicular layers which gives them additional stiffness due to shear and transverse coupling effects and also increases the resistance of each individual layer to crack propagation and plastic flow.
Analysis of volatile combustion products and a study of their toxicological effects
Authors: Seader J. D. , Einhorn I. N. , Drake W. O. , Mihlfeith C. M. 
Published: December 2004

AbstractAn experimental program was conducted to study the thermochemical, flammability and toxicological characteristics of uncoated and coated polyisocyanurate foams. The coatings used were fluorinated copolymer and an intumescent material. Flammability testing methods included the XP‐2 chamber smoke test, ASTM D‐1692, infrared photography, Bureau of Mines penetration test, and a JP‐4 fuel combustion chamber. The results of these tests are presented in a companion paper. Combustion and pyrolysis gases were analyzed by gas chromatography and mass spectrometry. The LD‐50 and LD‐100 tests were performed on Sprague‐Dawley rats housed in an environmental chamber. The isocyanurate foam, flourinated‐copolymer‐coated foam, and the intumescent‐coated foam were found to have excellent flammability and insulation characteristics, although smoke development was substantial. The LD‐50 values for Sprague‐Dawley rats, based on a two‐week survival, were approximately 2.0 gm/ft3 for all three materials. Examination indicated an absence of any significant cause of death except carbon monoxide poisoning.