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Deformation Rates (deformation + rate)

Distribution by Scientific Domains

Polymers and Materials Science	30%
Earth and Environmental Science	30%
Chemistry	30%

Selected Abstracts

Application of a Depth Sensing Indentation Hardness Test to Evaluate the Mechanical Properties of Food Materials

JOURNAL OF FOOD SCIENCE, Issue 5 2002
N. ÖZkan
ABSTRACT: A depth sensing indentation hardness test with an associated analysis is described as a convenient and simple technique for characterizing mechanical properties of food materials, such as hardness (H), elastic modulus (E), and an elasticity index (IE), which represents the ratio of elastic to total deformation. Storage modulus (G,) and loss tangent (tan§) of the selected model food material, a whey protein concentrate (WPC) gel, have also been determined using an oscillatory dynamic testing. Fractal dimension (D) and strain rate (or frequency) exponent (n) of the WPC gels were determined using both the indentation and dynamic test results. A good correlation between the results from the indentation and the dynamic tests was established. The effects of protein concentration, deformation rate, and chemical treatment on the mechanical properties of the WPC gels were clearly illustrated using the indentation test. [source]

INFLUENCE OF UNIAXIAL COMPRESSION RATE ON RHEOLOGICAL PARAMETERS AND SENSORY TEXTURE PREDICTION OF COOKED POTATOES

JOURNAL OF TEXTURE STUDIES, Issue 1 2000
ANETTE KISTRUP THYBO
ABSTRACT The effect of uniaxial compression rate (20,1000 mm/min) on the parameters: Stress (,ftrue), strain (,fHencky) and work to fracture (Wf), modulus of deformability (Ed), maximum slope before fracture (Emax) and work during 75% compression (Wtotal) was investigated for ten potato varieties. Multivariate data analysis was used to study the correlation between and within the sensory and nonsensory measurements by Principal Component Analysis (PCA) which showed ,ftrue, Emax, Wf, and Wtotal to explain the same type of information in the data, and ,fHencky versus Ed another type of information in the data. The deformation rate had a large effect on ,fHencky. Nine sensory texture attributes covering the mechanical, geometrical and moistness attributes were evaluated. Relationships between uniaxial compression data at various deformation rates and the sensory texture attributes were studied by Partial Least Squares Regression (PLSR). A minor effect of deformation rate on the correlation with the sensory texture properties was obtained. Mechanical properties were predicted to a higher extent than the geometrical attributes and moistness. The prediction of the mechanical, geometrical and moistness attributes increased largely by using uniaxial compression supplemented by chemical measures such as dry matter and pectin methylesterase, but here no relevant effect of deformation rate was obtained. [source]

On the effect of pressure on the shear and elongational viscosities of polymer melts

POLYMER ENGINEERING & SCIENCE, Issue 7 2004
Tomas Sedlacek
The effect of pressure and temperature on the shear and elongational deformation rate,dependent viscosities has been experimentally investigated for several polymers (HDPE, LDPE, LLDPE, PP, PC, PMMA, and PS) on a capillary rheometer with a back-pressure device. Pressure, ,, and temperature, ,, coefficients have been determined through simultaneous fitting of the shear and extensional viscosity data by the modified White-Metzner model. The dependence of , and , on temperature and pressure, respectively, was investigated and it has been found that simple relationships exist between pressure and temperature sensitivity coefficients for individual polymers. Polym. Eng. Sci. 44:1328,1337, 2004. © 2004 Society of Plastics Engineers. [source]

Recent tectonics in the Turkana Rift (North Kenya): an integrated approach from drainage network, satellite imagery and reflection seismic analyses

BASIN RESEARCH, Issue 2 2004
W. Vétel
The Turkana rifted zone in northern Kenya is a long-lived and polyphased rift system where the lack of well-marked rift morphology makes it difficult to identify the zone of active deformation. A high-density river network is exceptionally well developed over the study area and shows evidence of drainage anomalies that suggest recent fault-induced movements at various scales. Correlation of surface drainage anomalies with Landsat remote sensing and deep seismic reflection data permits to characterize the deep geometry of the inferred fault structures. Seismic stratigraphy further allows distinction between the inherited (Oligocene,Pliocene) and the newly formed (<3.7 Ma) origin of the recent deformation. Evidence for neotectonics are observed (1) along a large-scale transverse (EW) fault rooted at depth along a steep basement discontinuity (Turkwell), (2) along a rift-parallel (NS) fault zone probably emplaced during the Pliocene,Pleistocene and currently bounding the Napedet volcanic plateau to the west and (3) over a round-shaped uplifted zone caused by positive inversion tectonics (Kalabata). The major contribution of this work is the recognition of a broad (80 km wide) zone of recent/active extensional deformation in the Turkana Rift in contrast with the narrow (20 km wide) N10°E-trending axial trough forming the Suguta valley to the south, and the Chew Bahir faulted basin to the north. These along-strike variations in structural style are partly controlled by the occurrence of rejuvenated Oligocene,Miocene rift faults and long-lived transverse discontinuities in the Turkana Rift area. More generally, this study has implications for the use of river drainage network about recent/active extensional domains with subdued topography and slow deformation rate. [source]

Ankerung im Untertagebau , Entwicklungen in Theorie und Praxis

GEOMECHANICS AND TUNNELLING, Issue 5 2008
Stefan 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]

Crustal versus asthenospheric relaxation and post-seismic deformation for shallow normal faulting earthquakes:the Umbria,Marche (central Italy) case

GEOPHYSICAL JOURNAL INTERNATIONAL, Issue 3 2000
R. Riva
Summary Following a normal mode approach for a stratified viscoelastic earth, we investigate the effects induced by shallow normal faulting earthquakes, on surface post-seismic vertical displacement and velocity at the surface, when stress relaxation occurs in the crust or in the asthenosphere. The modelled earthquake is a moderate one characteristic of some slowly deforming plate boundaries in the central Mediterranean region. We focus on the Umbria,Marche (central Italy) region where deep seismic reflection studies (CROP03) and the 1997 earthquake sequence clearly show a seismogenic layer decoupled from the lower crust by a sizeable transition zone. Accordingly, the crust is subdivided into three layers: an elastic upper crust, a transition zone and a low-viscosity lower crust. The fault is embedded in the upper crust. The layered viscoelastic structure of the crust and mantle imposes a pattern and scale on the modelled coseismic and post-seismic deformation with a major contribution from the transition crustal zone and low-viscosity lower crust, stress relaxation in the mantle being negligible. We show that significant vertical deformation rates of the order of 1 mm yr, 1 could be expected for a shallow and moderate event such as the recent Umbria,Marche earthquake for viscosity values of 1019 and 1018 Pa s in the crustal transition zone and lower crust, respectively. [source]

INFLUENCE OF UNIAXIAL COMPRESSION RATE ON RHEOLOGICAL PARAMETERS AND SENSORY TEXTURE PREDICTION OF COOKED POTATOES

Superplastic Behavior of Fine-Grained ,-Silicon Nitride Material under Compression

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 4 2000
Guo-Dong Zhan
The deformation behavior of a hot-pressed, fine-grained ,-Si3N4 ceramic was investigated in the temperature range 1450°,1650°C, under compression, and the results for strain rate and temperature dependence of the flow stress are presented here. The present results show that the material is capable of high rates of deformation (,10,4,10,3 s,1) within a wide range of deformation temperatures and under a pressure of 5,100 MPa; no strain hardening occurs in the material, even at slow deformation rates, because of its stable microstructure; Newtonian flow occurs, with a stress exponent of approximately unity; and the material has activation energy values for flow in the range 344,410 kJ·mol,1. Grain-boundary sliding and grain rotation, accommodated by viscous flow, might be the mechanisms of superplasticity for the present material. [source]

The effect of recycling on LDPE foamability: Elongational rheology

POLYMER ENGINEERING & SCIENCE, Issue 1 2008
Eddy Twite Kabamba
The purpose of this work was to investigate changes in the elongational rheology of low density polyethylene (LDPE) when recycled. Both foamed and unfoamed LDPE were submitted up to 10 generations in a closed loop using constant extrusion conditions and azodicarbonamide as a chemical blowing agent. For both foamed and unfoamed polymers, decreasing elongational properties in terms of strain hardening was observed, indicating progressive loss of foamability with the number of time the polymer is recycled. It was also found that the elongational properties of the foamed polymer decreased more rapidly than its unfoamed counterpart. It is believed that higher mechanical degradation of polymer may be the result of higher deformation rates (biaxial) associated with foaming and the accumulation of blowing agent residues limiting polymer chain mobility and entanglement. POLYM. ENG. SCI., 48:11,18, 2008. © 2007 Society of Plastics Engineers [source]

Seismic reflection imaging of active offshore faults in the Gulf of Corinth: their seismotectonic significance

BASIN RESEARCH, Issue 4 2002
A. Stefatos
ABSTRACT High resolution seismic reflection surveys over one of the most active and rapidly extending regions in the world, the Gulf of Corinth, have revealed that the gulf is a complex asymmetric graben whose geometry varies significantly along its length. A detailed map of the offshore faults in the gulf shows that a major fault system of nine distinct faults limits the basin to the south. The northern Gulf appears to be undergoing regional subsidence and is affected by an antithetic major fault system consisting of eight faults. All these major faults have been active during the Quaternary. Uplifted coastlines along their footwalls, growth fault patterns and thickening of sediment strata toward the fault planes indicate that some of these offshore faults on both sides of the graben are active up to present. Our data ground-truth recent models and provides actual observations of the distribution of variable deformation rates in the Gulf of Corinth. Furthermore they suggest that the offshore faults should be taken into consideration in explaining the high extension rates and the uplift scenarios of the northern Peloponnesos coast. The observed coastal uplift appears to be the result of the cumulative effect of deformation accommodated by more than one fault and therefore, average uplift rates deduced from raised fossil shorelines, should be treated with caution when used to infer individual fault slip rates. Seismic reflection profiling is a vital tool in assessing seismic hazard and basin-formation in areas of active extension. [source]