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Deformation Behaviour (deformation + behaviour)
Selected AbstractsMonotonic and Cyclic Deformation Behaviour of the SiC Particle-Reinforced Aluminium Matrix Composite AMC225xe,ADVANCED ENGINEERING MATERIALS, Issue 4 2010Marek Smaga The monotonic and cyclic deformation behaviour of the aluminium matrix composite AMC225xe , i.e., the aerospace grade aluminium alloy AA 2124 reinforced with 25,vol.-% ultrafine SiC particles , is characterised in detail on the basis of mechanical stress,strain hysteresis curves as well as temperature and electrical resistance measurements. A pronounced difference in plastic strain response is observed between tension and compression under monotonic and cyclic loading. In fully reversed stress-controlled constant amplitude tests, negative plastic mean strains developed. The cyclic deformation behaviour of AMC225xe is characterised by pronounced initial cyclic hardening. The endurance limit is reliably estimated in continuous load increase tests. In particular, electrical resistance data are used as input parameters for fatigue life calculations analogous to the Basquin equation. Microstructural details are investigated by light and scanning electron microscopy. [source] The Effect of Grain Size on the Deformation Behaviour of Magnesium Alloys Investigated by the Acoustic Emission Technique,ADVANCED ENGINEERING MATERIALS, Issue 5 2006J. Bohlen Extruded round bars from magnesium alloys ZM21, ZK30, ZE10 and ZEK100 with various grain sizes were tested in tension and compression. The effect of grain size on the deformation behaviour of the alloys was investigated through the Hall-Petch relation. In-situ acoustic emission measurements were conducted during testing to evaluate the mechanisms of plastic deformation. The results are discussed with respect to twinning as one important deformation mechanism in magnesium alloys. [source] Monotonic and Cyclic Deformation Behaviour of the SiC Particle-Reinforced Aluminium Matrix Composite AMC225xe,ADVANCED ENGINEERING MATERIALS, Issue 4 2010Marek Smaga The monotonic and cyclic deformation behaviour of the aluminium matrix composite AMC225xe , i.e., the aerospace grade aluminium alloy AA 2124 reinforced with 25,vol.-% ultrafine SiC particles , is characterised in detail on the basis of mechanical stress,strain hysteresis curves as well as temperature and electrical resistance measurements. A pronounced difference in plastic strain response is observed between tension and compression under monotonic and cyclic loading. In fully reversed stress-controlled constant amplitude tests, negative plastic mean strains developed. The cyclic deformation behaviour of AMC225xe is characterised by pronounced initial cyclic hardening. The endurance limit is reliably estimated in continuous load increase tests. In particular, electrical resistance data are used as input parameters for fatigue life calculations analogous to the Basquin equation. Microstructural details are investigated by light and scanning electron microscopy. [source] "PHYBAL" a Short-Time Procedure for a Reliable Fatigue Life CalculationADVANCED ENGINEERING MATERIALS, Issue 4 2010Peter Starke Abstract The reliable calculation of the fatigue life of high-strength steels and components requires the systematic investigation of the cyclic deformation behaviour and the comprehensive evaluation of proceeding fatigue damage. Besides mechanical stress-strain hysteresis measurements, temperature and electrical resistance measurements were used for the detailed characterisation of the fatigue behaviour of the steel SAE 4140 in one quenched and tempered, one normalised, one bainitic and one martensitic condition. To guarantee optimal operation conditions the new fatigue life calculation method "PHYBAL" on the basis of generalised Morrow and Basquin equations was developed. It is a short-time procedure which requires the data of only three fatigue tests for a rapid and nevertheless precise determination of S-N (Woehler) curves. Consequently, "PHYBAL" provides the opportunity to reduce significantly experimental time and costs compared to conventional test methods. [source] Formability of Accumulative Roll Bonded Aluminum AA1050 and AA6016 Investigated Using Bulge Tests,ADVANCED ENGINEERING MATERIALS, Issue 12 2008I. Topic The paper reports one of the very first attempts to investigate the formability of ultrafine-grained aluminum sheets produced by a severe plastic deformation process known as accumulative roll bonding. During hydraulic bulge testing the samples showed a tendency to higher achievable burst pressures and/or von Mises equivalent strains with increasing number of accumulative roll bonding cycles, indicating promising deformation behaviour and good formability. [source] The Effect of Grain Size on the Deformation Behaviour of Magnesium Alloys Investigated by the Acoustic Emission Technique,ADVANCED ENGINEERING MATERIALS, Issue 5 2006J. Bohlen Extruded round bars from magnesium alloys ZM21, ZK30, ZE10 and ZEK100 with various grain sizes were tested in tension and compression. The effect of grain size on the deformation behaviour of the alloys was investigated through the Hall-Petch relation. In-situ acoustic emission measurements were conducted during testing to evaluate the mechanisms of plastic deformation. The results are discussed with respect to twinning as one important deformation mechanism in magnesium alloys. [source] Modelling ductile fracture behaviour from deformation parameters in HSLA steelsFATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 10 2004S. SIVAPRASAD ABSTRACT In this work, an attempt is made to model the ductile fracture behaviour of two Cu-strengthened high strength low alloy (HSLA) steels through the understanding of their deformation behaviour. The variations in deformation behaviour are imparted by prior deformation of steels to various predetermined strains. The variations in parameters such as yield strength and true uniform elongation with prior deformation is studied and was found to be analogous to that of initiation fracture toughness determined by independent method. A unique method is used to measure the crack tip deformation characterized by stretch zone depth that also depicted a similar trend. Fracture toughness values derived from the stretch zone depth measurements were found to vary in the same fashion as the experimental values. A semiempirical relationship for obtaining ductile fracture toughness from basic deformation parameters is derived and model is demonstrated to estimate initiation ductile fracture toughness accurately. [source] Ankerung im Untertagebau , Entwicklungen in Theorie und PraxisGEOMECHANICS AND TUNNELLING, Issue 5 2008Stefan Kainrath-Reumayer Dipl.-Ing. Die systematische Ankerung des Gebirges stellt ein wesentliches Verfahren zur Stabilisierung unterirdischer Hohlraumbauten dar. Die geschichtliche Entwicklung verschiedener Ankersysteme wird kurz vorgestellt und Unterteilungsmöglichkeiten werden aufgezeigt. Unterschiedliche Ansätze der Systemankerungen in analytischen und numerischen Berechnungen werden mit der diskreten Modellierung des Gesamtssystems in numerischen Berechnungen mit FLAC3D verglichen. Der Einfluss von Systemankerungen auf das Systemverhalten ist von einer Reihe von Randbedingungen abhängig, der Erfolg der Anwendung oftmals von den verwendeten Ankersystemen. Extreme Spannungszustände im Gebirge stellen hohe Anforderungen an die Methodik der Gebirgsankerung in Untertagebauwerken, die mit den herkömmlichen Ankerungssystemen nur eher unzufriedenstellend zu bewältigen sind. In Abhängigkeit von den Eigenschaften des Gebirges ist unter solch hohen, die Festigkeit des intakten Gebirges meist bereits überschreitenden Spannungszuständen mit großen Verschiebungen, Stabilitätsproblemen sowie Bergschlagphänomenen zu rechnen. Um diesen Anforderungen bestmöglich gerecht zu werden, wird ein neuartiger, energieabsorbierender Ankertyp "Roofex" vorgestellt, der sowohl unter langsam kriechenden, statischen, wie auch abrupten, dynamischen Beanspruchungen einen kontrollierbaren und konstanten Widerstand entlang eines definierten Gleitwegs aufweist. Rock bolting in subsurface constructions , developments in theory and praxis The systematic bolting of rock is a key support element in NATM tunnelling. A short review on the historical development and methods of classification is presented. Different methods of implementation in analytical and numerical calculations are compared to the discrete modelling of the system via FLAC 3D. The influence of the systematic rock bolting to the system behaviour is dependent on many boundary conditions, the success often depends on the used rock bolting techniques. High rock mass stress conditions in underground excavations are serious challenges for rock bolting systems, where conventional bolting systems can only cope with in an rather unsatisfactory way. Depending on the rock mass conditions, high stresses, which mostly exceed already the intact rock mass strength, will lead to serious stability problems, high deformation rates and rockburst phenomena. To provide the mining and tunnelling industry with a rock reinforcement fixture that is better suited to mining with high stress conditions, Atlas Copco GDE designed a new, energy absorbing rock bolt "Roofex" that can accommodate both very large displacements (static yielding) and high energy release (dynamic rupture) in the rock mass by offering an accurate pre-set deformation behaviour. [source] Application of SAR interferometry to a large thrust deformation: the 1999 Mw= 7.6 Chichi earthquake in central TaiwanGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 1 2004C. P. Chang SUMMARY Application of the interferometric method to four ERS2-SAR images acquired before and after the 1999 Chichi earthquake has allowed determination of the coseismic surface displacement in the footwall area of the Chelungpu fault. The interferometric results revealed a relative shortening in the round trip distance between the radar antenna and the ground of the footwall side of Chelungpu fault, during the earthquake. This shortening progressively increased from the west to the east and reaches the maximum amount of approximately 26 cm near the central segment of the Chelungpu fault. Our interferometric results have been precisely examined using a dense GPS network in the investigated area. We mapped the GPS coseismic measurements into the radar line of sight and implemented a forward simulation of SAR interferogram from this synthesized result to control our unwrapping performance. In this study, these two observations are compared with a 3-D dislocation model of the fault. Finally, a deformation analysis based on our interferometric result has indicated that a segment with irregular deformation behaviour can be distinguished in the footwall area of the Chelungpu fault. This segment may result from either the influence of inherited basement faults or the presence of a structural terrace that provide local opportunities for superficial deformation. [source] The influence of the construction process on the deformation behaviour of diaphragm walls in soft clayey groundINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 7 2006R. Schäfer Abstract Conventional numerical predictions of deep excavations normally neglect the construction process of the retaining structure and choose the earth pressure at rest as initial condition at the beginning of the simulation. The presented results of simulation and measurements during the construction process of the Taipei National Enterprise Center show, that such an assumption leads to an underestimation of the horizontal wall deflection, the surface ground settlements as well as the loading of the struts in case of normally to slightly over-consolidated clayey soil deposits. The stepwise installation process of the individual diaphragm wall panels results in a substantial modification of the lateral effective stresses in the adjacent ground. Especially the pouring process of the panel and the fresh concrete pressure causes a partial mobilization of the passive earth pressure and a distinct stress level increase in the upper half of the wall. As a consequence of the increased stresses prior to the pit excavation, up to 15% greater ground and wall movements are predicted. Moreover, the increased stress level due to the installation process of the diaphragm wall leads to substantial higher strut loadings during the excavation of the pit. Copyright © 2006 John Wiley & Sons, Ltd. [source] Experimental Investigation of Eclogite Rheology and Its Fabrics at High Temperature and PressureJOURNAL OF METAMORPHIC GEOLOGY, Issue 2 2007J. ZHANG Abstract Eclogite plays an important role in mantle convection and geodynamics in subduction zones. An improved understanding of processes in the deeper levels of subduction zones and collision belts requires information on eclogite rheology. However, the deformation processes and associated fabrics in eclogite are not well understood. Incompatible views of deformation mechanism have been proposed for both garnet and omphacite. We present here deformation behaviour of eclogite at temperatures of 1027,1427 °C, confining pressures of 2.5,3.5 GPa, and strain rates of 1 × 10,5 s,1 to 5 × 10,4 s,1. We obtained a power-law creep for the high temperature and pressure deformation of a ,dry' eclogite (50 vol.% garnet, 40% omphacite and 10% quartz) with A = 103.3 ± 1.0, n = 3.5 ± 0.4, ,E =403 ± 30 KJ mol,1 and ,V = 27.2 cm3 mol,1. The two principal minerals of eclogite have greatly different strengths. Progressive increase of garnet results in a smooth increase in strength. Analysis by electron back-scattered diffraction shows that: (1) garnet displays pole figures with near random distributions of misorientation angle under both dry and wet conditions; (2) omphacite shows pronounced lattice preferred orientations (LPOs), suggesting a dominant dislocation creep mechanism. Further investigation into the water effects on eclogite show: (3) water content does not influence the style of omphacite fabric but increases slightly the fabric strength; (4) grain boundary processes dominate the deformation of garnet under high water fugacity or high shear-strain conditions, yielding a random LPO similar to that of non-deforming garnet, despite the strong shape preferred orientation (SPO) observed. {110} [001] slip may dominate the deformation of rutile. Quartz displays complicated and inconsistent LPOs in eclogite. These results are remarkably similar to observations from deformed eclogites in nature. [source] Strain-Controlled Tensile Deformation Behavior and Relaxation Properties of Isotactic Poly(1-butene) and Its Ethylene CopolymersMACROMOLECULAR SYMPOSIA, Issue 1 2004Mahmoud Al-Hussein Abstract The tensile deformation behaviour of poly(1-butene) and two of its ethylene copoloymers was studied at room temperature. This was done by investigating true stress-strain curves at constant strain rates, elastic recovery and stress relaxation properties and in-situ WAXS patterns during the deformation process. As for a series of semicrystalline polymers in previous studies, a strain-controlled deformation behaviour was found. The differential compliance, the recovery properties and the stress relaxation curves changed simultaneously at well-defined points. The strains at which these points occurred along the true stress-strain remained constant for the different samples despite their different percentage crystallinities. The well-defined way in which the different samples respond to external stresses complies with the granular substructure of the crystalline lamellae in a semicrystalline polymer. [source] Superplasticity and high temperature deformation behaviour in nano grain Tungsten compactsMATERIALWISSENSCHAFT UND WERKSTOFFTECHNIK, Issue 4-5 2008K. Ameyama Abstract Nano grain tungsten is fabricated by Mechanical Milling (MM) process, and its grain growth behavior and high temperature deformability is investigated. As a result, a nano grain structure, whose grain size is approximately 20 nm or less, is obtained after MM for 360ks. Those nano grains demonstrate an irregular grain boundary structure, i.e., "non-equilibrium grain boundary", and they change to a smooth grain boundary structure by annealing at 1023 K for 3.6 ks. Compacts with nano grain structure indicate superior sintering property even at 1273 K (0.35 Tm). Rhenium addition prevents grain growth during sintering and thus the compacts indicate a further improvement in deformability. The compact is composed of equiaxed grain, whose grain size is 420 nm, and has low dislocation density even after the large deformation. The strain rate sensitivity, i.e., m-value, of 0.41 is obtained in the W-Re compact at 1473 K. Those results strongly imply that the nano grain W-Re compacts show superplasticity at less than half of the melting temperature, i.e., 1473 K (0.42 of the solidus temperature). [source] Veränderungen der mechanischen Eigenschaften von Magnesium-Druckgusslegierungen nach langzeitiger thermischer BeanspruchungMATERIALWISSENSCHAFT UND WERKSTOFFTECHNIK, Issue 2 2004D. Regener Pressure die cast magnesium alloys; long-term annealing; microstructure; mechanical properties Abstract Die thermische Belastbarkeit von Magnesium-Druckgusslegierungen ist noch nicht ausreichend untersucht. Um die Auswirkung einer thermischen Belastung auf die Gefügestabilität und damit auf das Festigkeits- und Verformungsverhalten einschätzen zu können, werden die Legierungen AZ91, AM50 und AE42 bei 150,°C und 200,°C einer 1000 h-Langzeitglühung unterworfen. Nach der Glühung werden Zugversuche, in situ-Zugversuche und Mikrohärtemessungen bei Raumtemperatur durchgeführt und die Ergebnisse anhand der mikrostrukturellen Veränderungen diskutiert. Changes of the Mechanical Properties of Pressure Die Cast Magnesium Alloys Subjected to Long-Term Thermal Exposure The thermal resistance of pressure die cast magnesium alloys is yet not investigated sufficiently. In order to assess the effect of a thermal exposure on the microstructural stability and on the strength and deformation behaviour, the alloys AZ91, AM50 and AE42 are subjected to a long-term annealing for 1000 h at 150,°C and 200,°C. After the annealing, tensile tests, in situ tensile tests and microhardness measurements are carried out and the results are discussed on the basis of the microstructural changes. [source] Pulsed-Plasma Polymeric Allylamine Thin FilmsPLASMA PROCESSES AND POLYMERS, Issue 8 2009Zhilu Yang Abstract High surface functional groups concentration, excellent dynamical stability and mechanical properties are ideal for biomedical plasma polymers. Herein, we report a simple and effective approach to fabricating such an ideal plasma polymeric allylamine film on 316L stainless steel (SS) by pulsed plasma polymerization. The experimental results show that the concentration of the primary amine groups (NH2/C) of the plasma polymeric allylamine film was 2.4,±,0.4%. The plasma polymeric allylamine film possesses not only high surface NH2 concentration, but also high cross-linking degree and close-knit network structure that could well resist hydrolysis, and dissolution in the aqueous solution. Furthermore, the plasma polymeric allylamine film was used as a stent coating that shows a good resistance to the deformation behaviour of compression and expansion of the stent. [source] Zum Kontaktverhalten zwischen suspensionsgestützten Ortbetonwänden und dem anstehenden BodenBAUTECHNIK, Issue 11 2007Anna Arwanitaki Dipl.-Ing. Eingangsparameter für analytische und numerische Berechnungen eines Baugrubenverbaus ist der Wandreibungswinkel. Dieser beschreibt die Fähigkeit, wieviel Schubspannungen aus dem Boden an der Grenzfläche Boden,Verbauwand von der Verbauwand bei einer vorgegebenen Normalspannung aufgenommen werden können. Die national gültigen Normen und Empfehlungen geben für Berechnungen im GZ1 einen Wandreibungswinkel von |,| , ,/2 vor. Für den Nachweis der Gebrauchstauglichkeit GZ2 hat sich die Methode der Finiten Elemente etabliert. Mit zunehmender Verfeinerung der Berechnungen stellt sich somit die Frage, ob der Ansatz von |,| , ,/2 noch zutreffend ist. Bei der Herstellung von Schlitzwänden sowie von unverrohrten Bohrpfahlwänden erfolgt der Bodenaushub im Schutze einer Stützflüssigkeit aus Wasser und Bentonit. Nach Erreichen der Schlitzendtiefe wird im Kontraktorbetonverfahren die Stützsuspension von unten nach oben verdrängt. Dabei können Reste der Suspension oder des entstehenden Filterkuchens in der Kontaktfläche Boden,Verbauwand verbleiben und den Wandreibungswinkel beeinflussen. In-situ-Proben des Filterkuchens einer Schlitzwandbaugrube zeigten, dass die Filterkuchenfestsubstanz ein Gemisch aus Bentonit und dem anstehenden Boden ist. Durch die Aushubarbeiten vermischt sich der anstehende Boden mit der Suspension, wobei die feinen Kornfraktionen durch die Fließgrenze der Suspension in Schwebe gehalten werden. Der durch den Filtrationsprozess an der Erdwandung entstehende Filterkuchen kann daher nicht mehr als Schmierschicht aus Bentonit bezeichnet werden, sondern besitzt eine beachtliche Scherfestigkeit. Dieser Beitrag stellt Ergebnisse von Baustellen- und Laboruntersuchungen zur Beschaffenheit des Filterkuchens und zur Ermittlung des Kontaktverhaltens des Boden-Schlitzwand-Systems vor. Skin friction of cast-in-place walls. Analytical and numerical calculations of retaining structures require the wall friction angle as an input parameter. It is specified as the maximal shear strength of the concrete-soil interface due to normal effective load. For the design of diaphragm walls the national engineering standards recommend an angle of wall skin friction of |,| , ,/2. In the framework of present design numerical calculations are performed to determine the deformation behaviour of structures, so that the contact formulation becomes fundamental. Bentonite suspensions are used to support the sides of excavation for diaphragm walls and uncased cast-in-place piles. When concrete is cast by tremie methods the filter cake remains adhering on side walls and becomes part of the concrete-soil interface and influences the characteristics of wall skin friction. In-situ specimens of the filter cake were taken from a diaphragm wall and examinations reveal that the filter cake consists of bentonite and fine soil particles. Due to the excavation process fine particles from the soil are suspended into the supporting fluid due to the liquid limit of the bentonite slurry. Thus, the suspension, in a process of filtration into the surrounding soil, forms a filter cake with a certain shear strength caused by the fine soil particles. This paper presents the results of field and laboratory tests for the investigation of the effective contact behaviour between cast-in-place walls and the surrounding soil. [source] Erfahrungen mit dem Spannungs-Verformungsverhalten von mit Geogittern bewehrten StützkonstruktionenBAUTECHNIK, Issue 11 2007Florian Bussert Dr.-Ing. Seit mehreren Jahrzehnten hat sich der Bau geokunststoffbewehrter Erdkörper erfolgreich bewährt. Die Errichtung der Stützkonstruktionen auf stark wechselndem oder gering tragfähigem Untergrund, bei hohen Verkehrslasten oder großen Konstruktionshöhen hat sich vielfach als äußerst ökonomische und ökologische Alternative zu klassischen Bauweisen bewiesen. Um Erfahrungen mit einer neuen Bauweise zu sammeln, wird häufig die sogenannte Beobachtungsmethode angewandt, d.h., das Spannungs-Verformungs-Verhalten wird sowohl während der Erstellung als auch in der ersten Nutzungsphase des Bauwerks messtechnisch ermittelt. Aus diesen Messergebnissen wird deutlich, dass auch bei hoher Beanspruchung der Konstruktionen die Gesamtverformungen kleiner sind als erwartet. Vor allem die gemessenen Dehnungen der Geogitter sind kleiner als die berechneten Werte. Das derzeit verwendete Konzept zur Abschätzung der Dehnungen scheint damit weit entfernt vom tatsächlichen Verhalten derartiger Konstruktionen. Die Erfahrungen von ausgeführten Baumaßnahmen werden vorgestellt und die Ergebnisse diskutiert. Experiences with the tension deformation behaviour of retaining structures reinforced with geosynthetics. Since several decades the application of geosynthetic-reinforced earth bodies successfully worked. The establishment of the retaining structures on strongly changing or small load-carrying underground, with high live loads or large construction heights proved itself often as extremely economic and ecological alternative to classical building methods. In order to gain experiences with a new building method, frequently the so-called observation method is used, which means the stress-deformation behaviour becomes both while the construction and the first utilization phase of the building is determined by measuring techniques. From these results of measurement it becomes clear that also when high loaded the total deformations of the constructions are smaller than expected. From all the measured results the deformations of the geosynthetics are smaller than the analyzed values. The concept for the estimation of the deformations, used at present, seems far thereby from the actual behaviour of such constructions. The experiences of completed structures are presented and the results are discussed. [source] Neue Erkenntnisse zum Verformungsverhalten des Frankfurter TonsBAUTECHNIK, Issue 3 2007Rudolf Dürrwang Dipl.-Ing. Anhand des Bauvorhabens "Opernturm" von Tishman Speyer auf dem ehemaligen Gelände der Zürichversicherung "Zürichhaus" an der Alten Oper im Zentrum von Frankfurt am Main wird dargestellt, daß der Effekt der Entlastung/Wiederbelastung ausschließlich zeitabhängig ist. Dies wurde möglich, da erstmals in Frankfurt nach dem Abbruch der alten Zürichhäuser sechs Jahre vergingen, bis mit dem Neubau begonnen wurde. In diesem Zeitraum wurden die Hebungen der alten Gründung (Bestandskeller) und der Nachbarn (u.a. U-Bahn) als Teil des Beweissicherungsverfahrens beobachtet. Weiterhin werden die Ergebnisse von Cross-hole-Messungen zur Bestimmung der dynamischen Baugrundsteifigkeit des Frankfurter Baugrunds dargestellt und diskutiert. New knowledge about the deformation behaviour of Frankfurt clay und unloading conditions. Tishman and Speyer planed the construction of a new building complex "Opernturm" in the down town of Frankfurt, Germany. The construction of the new High-Rise building required the demolishing of the old two high rise buildings of the Zurich insurance company. After demolishing the old high rise buildings, a time delay of about 6years has occurred. The deformations of the rest basement of the old buildings as well as the deformation of Neighbouring construction such as the underground tunnel were observed with time as a part of validating the serviceability requirements of the neighbouring constructions. The results of these measurements regarding the time effect on the behaviour of Frankfurt overconsolidated clay under unloading conditions will be presented. Furthermore, the results of cross hole tests that were carried out as a part of the design of the suggested piled raft foundation of the new high rise building to investigate the dynamic behaviour of Frankfurt subsoil will be demonstrated and discussed. [source] Numerische Modellierungen mit einem zyklisch-viskoplastischen Stoffansatz für granulare BödenBAUTECHNIK, Issue 1 2005vormals Universität Kassel Tim Stöcker Dr.-Ing. In der Geotechnik, insbesondere aber im Verkehrswegebau, gewinnt die Frage der Boden-Bauwerk-Interaktion bei nichtruhenden Lasteinwirkungen zunehmend an Bedeutung. Dabei stehen neben sicherheitsrelevanten Aspekten besonders Fragen zur Gebrauchstauglichkeit sowie wirtschaftliche Aspekte im Vordergrund. Ziel einer anwendungsorientierten Forschung muß daher die Entwicklung eines praxisorientierten Verfahrens zur ingenieurmäßigen Modellierung der Langzeitverformungen bzw. des Langzeitverhaltens des Baugrundes unter nichtruhender Belastung sein. Die dargestellten Arbeiten beschäftigen sich daher mit der Implementierung, Validierung und Anwendung eines neuen, im folgenden als "zyklisch-viskoplastisch" bezeichneten Stoffansatzes für granulare Böden unter nichtruhender Lasteinwirkung. Die wesentlichen Grundlagen dieses Ansatzes sind dabei im Heft 4, 2004, dieser Zeitschrift beschrieben, [1]. Das erreichte Ziel war, den Stoffansatz für numerische Berechnungsmodelle ingenieurmäßig aufzubereiten, zu implementieren, sowie das Berechnungsmodell zu verifizieren und auf reale Problemstellungen anzuwenden. Numerical modelling with a cyclic viscoplastic constitutive approach for granular soils. In modern Geotechnics, especially in track engineering, research for soil-structure interaction under cyclic loading has been gaining importance over the past decades. Next to states of system/structure failure, the long-term (deformation) behaviour is of major interest, as it has a major impact on e.g. maintenance costs in track engineering. Hence, the objective of this work is to be seen in the necessity of investigations on the long-term deformation behaviour of granular soils and ballast under cyclic loading. In the present paper the validation and implementation of a cyclic viscoplastic constitutive approach for granular under cyclic dynamic loading, [1], into a numerical model is carried out. The investigation and set up of a theoretical and physical complete model has not been intended. The objective rather is the development of an engineering type model, appropriate for practical tasks. Some modelling examples are given to illustrate modelling capacities. [source] Das Druckgurtmodell für StahlbetonbauteileBETON- UND STAHLBETONBAU, Issue 8 2009Der nachfolgende Beitrag erscheint aus Anlass des 60. Berechnungs- und Bemessungsverfahren; Versuche Abstract In den vergangenen Jahren wurden verschiedene auf die Bemessung von Stahl- und Spannbetonbauteilen ausgerichtete theoretische Modelle entwickelt. Heute stehen das Zuggurtmodell, das Modell der gerissenen (Steg-)Scheibe und das Druckgurtmodell zur Verfügung, auf deren Grundlage Verformungsverhalten und Tragwiderstände umfassend beurteilt werden können. Auf das Druckgurtmodell wird im vorliegenden Beitrag detailliert eingegangen. Es berücksichtigt die Festigkeits- und Duktilitätssteigerung durch eine Umschnürungsbewehrung sowie die bruchmechanisch begründete Entfestigung des Betons und die damit einhergehende Verformungslokalisierung. Auf der Grundlage neuerer Versuchsergebnisse können für die komplexen Interdependenzen zwischen diesen Effekten plausible Beziehungen angegeben werden. Die mithilfe des Druckgurtmodells gewonnenen Erkenntnisse sind für die Baupraxis von Bedeutung: Das Verhalten von auf Druck beanspruchten Bauteilen (z. B. Druckplatten von Brückenquerschnitten, Stützen) lässt sich zuverlässig erfassen; darüber hinaus ergeben sich wichtige Hinweise für die konstruktive Durchbildung. Compression Chord Model for Structural Concrete In recent years, several theoretical models have been developed with the scope on the design of reinforced and prestressed concrete structures. Today, the tension chord model, the cracked membrane model and the compression chord model are available, with which the deformation behaviour as well as ultimate loads can be determined. In the present contribution the compression chord model is discussed in detail. The model takes the increase of strength and ductility due to a confining reinforcement into account and considers the softening as well as the localisation of deformations accompanying the fracture of concrete. On the basis of new test results plausible relations for the complex interdependencies between these effects are found. The results of the compression chord model are relevant for practical applications: The behaviour of compressed members (e.g. in bridge girders or columns) can be assessed reliably; moreover, hints for the detailing of reinforcement can be deduced. [source] | ||||||||||||||||||||||||||||