material parameters

Top PDF material parameters:

Simultaneous determination of Bingham material parameters using a ball probe concrete rheometer

Simultaneous determination of Bingham material parameters using a ball probe concrete rheometer

difference to the expected linear-affine curve progression in Couette rheometers with small gap. It is plausible, however, because with increasing shear rate the shear stress in the sample exceeds the yield stress at more and more locations. This effect can also be expected in the Couette arrangement of cylinders as soon as the assumption of the small gap is no longer valid [3]. By fitting eq. (4) using the material parameters on measurement curves, it is now possible to characterize the Bingham flow behavior. The method has already been successfully applied to fiber reinforced concrete of different consistencies [4, 5]. In particular, Schleiting [4] was able to validate the prediction of the yield stress using reference methods.
Mehr anzeigen

2 Mehr lesen

A simulation-based approach to evaluate objective material parameters from concrete rheometer measurements

A simulation-based approach to evaluate objective material parameters from concrete rheometer measurements

The method can also be used for other sample body geometries (cylinders, mortar paddles) or other rheome- ter types with flow conditions that are not described an- alytically or only approximatively (vane or similar), but also in situ experiments by evaluating the torque in the mixer are conceivable, so that a subsequent measurement would not be necessary. The assumed material model can be adapted to the expected material behavior and is not limited to Bingham plastic. By selecting a more complex material model (e.g. Herschel-Bulkley), one should how- ever consider that the highest shear rates occurring in this investigation were in the maximum order of 10 s −1 , de- pending on the material parameters. If the material shows effects like shear thinning at higher shear rates, these can only be measured in a concrete rheometer of the type dis- cussed here, if correspondingly higher shear rates predom- inate. This could be achieved by smaller gaps (unfavorable since the continuum hypothesis could be violated) or by higher rotational velocities.
Mehr anzeigen

11 Mehr lesen

Identification of Material Parameters from Temperature Measurements in Radio Frequency Ablation

Identification of Material Parameters from Temperature Measurements in Radio Frequency Ablation

For a realistic prediction of the outcome of an RFA we need a mathematical model that describes the physical effects as good as possible. Due to the lacking knowledge of the exact material parameters and the patient individual differences we addressed in this work to the patient individual identification of the material parameters during the RFA. To simulate the result of the RFA the temperature distribution during the treatment is modeled by a system of two coupled PDEs, the bio-heat transport equation and the potential equation. Both equations are significantly influenced by the material parameters. Therefore a parameter identification problem was formulated by fitting the temperature to a given temperature distribution. This states a minimization problem with tracking type functional. Since different parameters were considered which influ- ence the whole system in distinct ways the identification was split into two main parts. For the identification of the thermal conductivity the minimization problem was defined as the minimization of the difference between the calculated and the given temperature distribution. For the identification of the electrical conductivity a modified approach was needed. The electrical conductivity influences the temperature distribution only via the heat source, i.e. the right hand side of the heat equation. Due to the only local impact of the heat source on the temperature distribution the identification of a spatially varying electrical conductivity is nearly impossible. Therefore, a second minimization problem was considered where at first the heat source was identified from the temperature dis- tribution. Afterwards this identified heat source was used for the identification of the electrical conductivity. For both approaches the optimality systems were formulated and in a general form investigated concerning the existence of solutions.
Mehr anzeigen

157 Mehr lesen

Thermodynamically compatible modeling, determination of material parameters, and numerical analysis of nonlinear rheological materials

Thermodynamically compatible modeling, determination of material parameters, and numerical analysis of nonlinear rheological materials

In this section we have discussed a possible relation between the (viscoelastic) strain rate and the plastic strain rate in the spatial frame. This property can only be utilized in the spatial frame. The discussed relations are valid under the assumption of an isothermal process, although any viscous flow produces internal energy and entropy, thus, temperature increases. The isothermal simplification may be acceptable for some engineering approaches, however, from a theoretical point of view we need to observe the flow properties in a “non-isothermal fashion.” We will investigate ther- modynamic processes expressed in a Eulerian frame in the following sections. In a Eulerian frame we assume that the viscous flow causes an unrecoverable motion, which is identified as plastic strain in a spatial frame, therefore, we implicitly apply Eq. (V.3). Moreover, we have investigated the influence of the material parameters in a sigmoid model. Since the model includes the Newtonian fluids by observing k = 0 we may propose Eq. (V.7) as an appropriate model for viscous fluids. Therefore, we will analyze some processes augmented by the sigmoid model as the constitu- tive equation for the dissipative part of the Cauchy stress tensor in the following sections.
Mehr anzeigen

195 Mehr lesen

Efficient Determination of Material Parameters for Robust Process Simulation of Semi-Crystalline Thermoplastic Composites

Efficient Determination of Material Parameters for Robust Process Simulation of Semi-Crystalline Thermoplastic Composites

Predicting material behaviour during and after consolidation using process simulation will be a decisive factor in the breakthrough of fibre reinforced high-temperature thermoplastics for primary aerospace structures. Since the materials are constantly being optimized with respect to processing and component properties, a new method is being developed to adapt existing material models for process simulations in order to quickly react to such modifications. A DoE analysis is carried out to find the model parameters with a significant effect on the process simulation which are then experimentally determined for CF/LM PAEK and implemented in an existing material model. By comparing the process-induced spring-in of vacuum-consolidated V-angles with the values derived from simulation, the adapted material model as well as the new methodology for a simplified adaptation of existing material models to novel materials is validated.
Mehr anzeigen

4 Mehr lesen

Dynamic Material Parameters in Molecular Dynamics and Hydrodynamic Simulations on Ultrashort-Pulse Laser Ablation of Aluminum

Dynamic Material Parameters in Molecular Dynamics and Hydrodynamic Simulations on Ultrashort-Pulse Laser Ablation of Aluminum

12 Ablation depth da and laser-induced processes in dependence of the absorbed laser fluence ˚abs for molecular dynamics simulations with IMD in comparison with results from hydrodynamic[r]

18 Mehr lesen

Investigation of correlation between material properties, process parameters and residual stresses in roller levelling

Investigation of correlation between material properties, process parameters and residual stresses in roller levelling

Fig. 5. Residual stresses from FEM and experimental measurement for different intermesh sets of a) P 2 = 0.82 mm, P 4 = 0.50 mm, P 6 = 2.06 mm and b) P 2 = 0.82 mm, P 4 = 1.14 mm, P 6 = 1.86 mm. 5. Conclusion In order to investigate the dependencies between process parameters in roller levelling, material parameters and residual stresses, a numerical study of the roller levelling process has been conducted and validated with accompanying experiments. Therefore, a numerical model of a seven-roll levelling machine is set up which uses a closed-loop control to achieve the working point leading to a flat sheet in a single simulation run. The seven-roll leveller consists of three individual load triangles which are defined by the positions of rolls 2, 4 and 6. Roll 2 is set to a fixed position leading to a constant plastification of the outer sheet fiber, roll 4 acts on the residual stress distribution and roll 6 ensures the flatness of the metal strip. In the numerical model purely kinematic hardening of the strip material is assumed and described by three parameters, the initial yield strength σ y,0 and the kinematic hardening parameters C and γ. According to the results these parameters are ranked by their impact on both the force acting at roll 2 and the intermesh at roll 6 leading to a flat strip in the order σ y,0 , C and γ. Since the results are used to investigate the possibility to set up a process control for roller levelling acting on both residual stresses and flatness based on the force measured at roll 2, a closer look on this parameter is done. Regarding the force at roll 2 the results indicate a distinct relationship between the force and the material properties suggesting also the possibility to determine the material properties via an inverse approach. Finally, an evaluation of the residual stresses proofs the possibility to achieve different residual stress distribution across the sheet thickness using different intermesh sets all resulting in a flat sheet. Future work will focus on the improvement of the quantitative calculation of residual stresses in an FE model by taking into account residual stresses from previous production processes the material to be levelled has undergone. Furthermore, optimization criteria will be defined to aim on a distinct residual stress distribution. Acknowledgements
Mehr anzeigen

8 Mehr lesen

Investigation of correlation between material properties, process parameters and residual stresses in roller levelling

Investigation of correlation between material properties, process parameters and residual stresses in roller levelling

Ȗ ܺ ஼ ఊ ൫ െ ൫െߛ߳ ௣௟௔௦௧ ൯൯ Ȗ of roll bearings to minimize friction and the distance between the centres of the bearings is 63 mm which correlates to the distance between the leveller rolls. In total five bending cycles with an amplitude of 2 mm resulting in a plastic longitudinal strain of approx. 1 % in the outer sheet fiber and a tool velocity of 0.5 mm/s are conducted. According to the testing parameters, an FE model is used for the invers determination of the material parameters. The model is called from an optimization-loop set up in the Matlab environment using an interior-point algorithm.
Mehr anzeigen

8 Mehr lesen

Regionale Material- und Energieflußrechnungen

Regionale Material- und Energieflußrechnungen

Seit Mitte der 90-er Jahre gibt es auch bei den Statistischen Landesämtern Ansätze, diese Konzeption und die Ergebnisse des Bundes auf Länderebene zu regionalisieren. Für die Durchführung von Material- und Energieflussrechnungen sind zwei aufeinander aufbauende Schritte erforderlich: Gewinnung, Bereitstellung und Aufbereitung des Datenmaterials sowie die eigentliche Flussrechnung. Momentan haben die Arbeiten im Land Brandenburg ihren Schwerpunkt in der Datenbereitstellung und –aufbereitung. An einigen Stellen erscheint eine Modifikation zum Bundesprogramm auf Grund der unterschiedlichen Datenlage notwendig. Berechnungen sind einerseits erfolgt zu den Ausgaben des Staates und des Produzierenden Gewerbes für den Umweltschutz und zu dem Anlagevermögen für den Umweltschutz im Produzierenden Gewerbe, andererseits zu den Energieflüssen.
Mehr anzeigen

11 Mehr lesen

Asian material culture

Asian material culture

the former sense of colour, as literally applied to Miao ‘Long Skirt’ costume, solicits observers’ attention during visits to Shang Langde (Upper Langde) village 1 , an increasingly popular tourist destination which lies 32 kilometres east of Kaili city, nestled in the mountains and outlying rural surrounds. The latter refers to a socio-political context for which the euphemistic metaphor of the ethnic mosaic (Harrell 1995; Moser 1985) stands – an assemblage of 55 officially recognised shaoshu minzu (Chinese ethnic groups or ‘nationalities’), including nine million so-named Miao, alongside the majority Han. As state journalism, television talent quests and recent telecasts of the torch relay and opening ceremony rehearsals for the 2008 Olympic Games might have viewers know, the harmonious co-existence of minzu is aptly mirrored in the myriad of brightly coloured folk costumes staged by their multi-ethnic wearers, often hand in hand, for each show. At Langde, song and dance performance in traditional Miao dress appeals to local political consciousness as an index to these pervasive spectacles of collective national colour. But what of the foreign visitor whose cultural background is markedly dissimilar? In taking the place of the Western textiles enthusiast on cultural tour that departs from Kaili city, colour, specifically the material pigmentation of Miao traditional costume, is still, I believe, far from mere surface ornamentation and a highly agentive force. Map of the People’s Republic of China
Mehr anzeigen

234 Mehr lesen

Enhancing Material Nature

Enhancing Material Nature

us the tools … to play with the ultimate toy box of nature – atoms and molecules. Everything is made from it … The possibilities to create new things appear limitless” (NSTC 1999, p. 2). Gerd Binnig also received the Nobel Prize (for the development of the scanning tunnelling microscope) and expresses himself even more explicitly: “At this time we humans are witnesses and shapers of a second genesis, a fundamentally new evolution of material structures that we are as of yet not even able to name properly” (Binnig 2004). Binnig develops this idea more extensively in his book Aus dem Nichts: “We have to become familiar with the idea that there is nothing inferior about dead matter. All the wonders of the world are contained, for example, in a stone, as all the laws of nature (and thus all the possibilities that can emerge from them) are reflected in it” (Binnig 1992).
Mehr anzeigen

18 Mehr lesen

Determination of Johnson-Cook material model parameters for AISI 1045 from orthogonal cutting tests using the Downhill-Simplex algorithm

Determination of Johnson-Cook material model parameters for AISI 1045 from orthogonal cutting tests using the Downhill-Simplex algorithm

of the integral process results when comparing the two heat treatments. These results motivated for the development of a methodology capable to determine material model parameters robust and inversely from the machining process, which can be used with lower computational effort. To simulate the machining process, a Coupled-Eulerian-Lagrangian (CEL) model of the orthogonal cutting process has been set up. The material model parameters have been inversely determined using the Downhill-Simplex-Algorithm, which has been modified for this case. By using the Downhill-Simplex- Algorithm, it was possible to determine material model parameters within 17 iterations and achieving an average deviation between the experiment and the simulations below 10 %. Thereby, different process observables such as temperature, forces, and chip form have been used for the evaluation. Through this method, it is possible to determine material model parameters, which enable a good match between experiments and simulations with a low computational effort.
Mehr anzeigen

12 Mehr lesen

A Statistical Evaluation of the Influence of Different Material and Process Parameters on the Heat Transfer Coefficient in Gravity Die Casting

A Statistical Evaluation of the Influence of Different Material and Process Parameters on the Heat Transfer Coefficient in Gravity Die Casting

The behavior of the mold and core wall interfaces at 460 °C differs significantly from the behavior at higher temperatures, as previously described. The impact factors for the interface temperature 460 °C for the two contact cases are shown in Figure 6. The significant change in contact condition at or above this temperature, experienced in different ways by the two contact zones, leads to the replacement of thermal conductivity of the wall material (k m , k c ) with parameters dependent on the contact conditions as the most impactful factors influencing the HTC. For the mold wall, the newly important parameter is the thermal conductivity of air (k air ), followed by the nearly unchanged impact of the distance of the cooling channels to the interface (cc) and increasing impact of the gap width (wg). This can be attributed to the formation of a gap between casting and mold wall, replacing the previously active mechanisms for heat flow with the one dominated by the air-filled gap. In contrast to this, the significant impactful parameters at the core-side interface are more widespread, but with a smaller overall impact for the dominating influence, which is the age of the coating (ac). The second highest influence at the core interface is the heat capacity for air (cp air ). This is probably due to the formation of a gap at the outer mold wall severely limiting the heat flow in that direction, dependent on the air’s heat capacity. The impact of gap width (wg) and heat capacity of the mold material (cp m ) can be considered to affect the heat flows in a similar way. The impact of the age of the coating, on the other hand, is directly connected to the contact condition at the core interface and becomes the most dominating influence. The increasing pressure induced by a shrinking casting leads to a higher influence on the overall heat flow at the interface as influencing parameters such as surface roughness come into account [14]. Since the analysis of variance is based on linear models, a possible attenuation of the effect with more worn coatings cannot be found with this analysis.
Mehr anzeigen

12 Mehr lesen

Material and Methods 

Material and Methods 

Anti­ nociceptive activity was expressed as the reduction of the number of abdominal contractions between control animals and mice pretreated with morusin and standard dru[r]

5 Mehr lesen

Lamination Parameters for Sandwich and Hybrid Material Composites

Lamination Parameters for Sandwich and Hybrid Material Composites

Beyond 20 plies the sandwich fails by crimping. For loads of 2000 kN, the curves could suggest the designer should probably select a core material with a higher shear stiffness. This isn’t always simple since core materials with higher shear stiffness are often more expensive and more difficult to manufacture. Additionally, the core shear stiffness of the panel maybe need to be knocked down to allow for impact damage tolerance. Choices such as aluminum cores will also mean the sandwich will become susceptible to factors such as rust. If no other core material is available sandwich structures should be avoided at this load level. This is because with a very shallow load carrying slope, a small increase in load requirements can require a very large increase in facesheet thickness (up to 3 times) or sudden catastrophic failure. The study demonstrated here assumes a maximum core thickness of 50mm. With both crimping and buckling improving as the core thickness is increased, it can be expected that having a larger core limit would result in the sandwich design being able to carry higher loads, limited then by OHC. This is also seen in Figure 9 , showing the optimal core thickness with respect to the maximum allowed core thickness, for different facesheet thickness.
Mehr anzeigen

13 Mehr lesen

Material science examination on pineapple fruit puree and raw material

Material science examination on pineapple fruit puree and raw material

Mechanism of solubility, D-mannose differs from D-glucose only in the stereochemistry at C-2. Therefore, it can fine that D-mannan is an insoluble fibrous material similar to its D-glucose analogue, cellulose. This behavior is attributed to the formation of stable crystalline regions in the solid in which the linear chains lie in close proximity. The inclusion of side chains spoils this crystallinity and thereby promotes the penetration of water and enhances solubility. Thus, commercial gums showing high substitution ratio, such as guar, tend to hydrate fully in cold water, while gums with limited substitution, such as locust bean gum, hydrate completely only in hot water. Commercial gums exhibiting high substitution ratio (i.e. guar gum) are better hydrated in cold water than gums with limited substitution (i.e. LBG), because the presence of side chain interferes with the formation of stable crystalline regions and promotes water penetration, thereby enhance solubility. This behavior is reflected in the viscosity of the hot- and cold-prepared solution. Galactomannans don’t hydrate instantaneously in water. At 25 o C, guar gum may require up to 120 min hydrate fully and yield its maximum potential viscosity. This time can be shortened by using a high-shear mixer, a fine powder or by increasing the temperature. However, at temperatures above 80 o C, thermal degration become significant and the maximum potential viscosity will not achieve. The rate and degree of hydration may be dramatically reduced by the presence of other solutes. When using galactomannans in formulated food, it is good practice, therefore, to hydrate these first in any free water present in recipe before adding the remaining ingredients.
Mehr anzeigen

160 Mehr lesen

Perception of Material Kinematics

Perception of Material Kinematics

Banks, 2002, Knill 2007), where the sensory cues may be in conflict with one another and/or the prior belief. While we do not aim to model our results formally, we still believe that this analogy is useful in interpreting our findings. We will first focus on the rating differences that we found in the Expected and Surprising conditions. Here, objects that physically deformed, i.e. Wrinkled, splashed, etc, in the same way were not rated the same way. In fact, in many cases, ratings were ‘pulled’ towards the expected material property, not the signaled one. For example, a wrinkling spoon or teacup was rated harder than any of the wrinkling cloths. Here, prior knowledge about spoons and teacups being hard seems to have led to increased ratings of hardness compared to their soft curtain counterparts, despite all of these objects wrinkling. This outcome would be best explained by a so-called down- weighing of the cues (Knill, 2007) to hardness, which suggests that the visual system entertains multiple priors (strong and weaker ones) about the state of the world, and that, depending on the sensory input, it adjusts the weights of these priors. This implies that in a cue-conflict situation, the unlikely interpretation of the input does not simply get vetoed down (Landy et al. 1995), but that instead it would factor into the final percept – just as we observed it in our results.
Mehr anzeigen

152 Mehr lesen

Saturn Material Ringe - WIS

Saturn Material Ringe - WIS

Wenn du ganz nah herangehen könntest, dann würdest du aber sehen, dass sie in Wirklichkeit aus unheimlich vielen kleinen Gesteins- und Eisbrocken bestehen, die wie ganz kleine Monde u[r]

1 Mehr lesen

Titan: Vom exklusiven Material zum Massenwerkstoff?

Titan: Vom exklusiven Material zum Massenwerkstoff?

Es muss jedoch auch berücksichtigt werden, dass die Reduktion der Kosten ganz wesentlich durch eine Verringerung des Energieeinsatzes zur Metallgewinnung erzielt wird.. Zum anderen wird [r]

2 Mehr lesen

Anwendungsbeispiele der Material- und Gasfeuchtemessung in der Planetenforschung

Anwendungsbeispiele der Material- und Gasfeuchtemessung in der Planetenforschung

• Ist das kapazitive Messverfahren zur Messung der relativen Feuchte im Grobvakuum und bei Temperaturen bis -70°C geeignet. • Sind kommerzielle kapazitive Polymersensoren geeignet[r]

40 Mehr lesen

Show all 1480 documents...