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An intergranular strain concept for material models formulated as rate equations

An intergranular strain concept for material models formulated as rate equations

the simulated standard laboratory tests, both approaches show almost the same results and are an improvement compared with the original model behaviour. Both approaches also work for elastoplastic material models, which is demonstrated for the MCCM. The original intergranular strain concept is a well-established concept to improve small-strain behaviour in hypoplastic models, but it still also has its shortcomings. However, the possibility to apply the intergranular strain concept to more constitutive models will make it available for a wider range of constitutive modellers and may also help to develop improvements for the concept.
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Inverse Design Based on Nonlinear Thermoelastic Material Models

Inverse Design Based on Nonlinear Thermoelastic Material Models

In order to prepare such an inverse formulation, we make the simplification of neglecting shape changes before the part is ejected from the mould. Thus, we effectively split the simulation into two parts. The first part encompasses the packing and cooling stages of the injection moulding process. In this part the material occurs both as a viscoelastic fluid and as a solid body. The solidification of the material must also be properly represented. The temperature boundary conditions that drive the cooling of the material can be determined from an optimised cooling layout, as described in the previous section. The second part of the simulation models the shrinkage and warpage of the part after ejection as it cools down to the ambient temperature. In this simulation part, the body is assumed to be completely solidified. The material behaviour is described with nonlinear thermoelastic models. The connection between these two simulation parts is made by transferring temperature and stress fields from the first part and using these as initial conditions for the second part.
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Performance evaluation of cord material models applied to structural analysis of tires

Performance evaluation of cord material models applied to structural analysis of tires

When tire cord is tested for FEA, detailed stress-strain curves should be recorded, covering the whole range of strain that is expected in future analyses. A standard tensile testing machine and clamps should be sufficient for the task, as the part of the curve near breaking point is not taken into account. The use of an extensimeter in the middle part of the specimen should be a better option than direct measuring of clamp displacement. Stress- strain points should be recorded electronically and exported to a text file, for later use in material modeling procedures. As belt cords may be subjected to tension during the tire manufacturing process [30], it may be appropriate to impose a certain amount of preload in the beginning of the test, or to slightly adjust (shift) the stress and strain values of the test data obtained without preload. In order to enable the use of viscoelastic/viscoplastic cord models, the unloading curve should also be recorded. Depending on the cord type, tire type and parameters of the curing process, the effects of exposure to high temperature or moisture should be taken into account.
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Numerical modelling of the long-term evolution of EDZ. Development of material models, implementation in finite-element codes, and validation

Numerical modelling of the long-term evolution of EDZ. Development of material models, implementation in finite-element codes, and validation

3 Validation of the proposed damage model In order to verify the implemented material model and to demonstrate the appli- cability of the model to describing the dilatant volumetric strain of rock salt, a number of different triaxial laboratory tests were investigated numerically. The calculated strain rates were compared to experimental data. The influence of different material parameters on the numerical results was studied as well. Taking into account the preliminary relation given in equation (13), the permeability of the samples was com- puted.

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Advanced material models for the crystal plasticity finite element method : development of a general CPFEM framework

Advanced material models for the crystal plasticity finite element method : development of a general CPFEM framework

misorientation where the kinematics of the interface prevailed in terms of the change in the Schmid factor across the boundary. The texture predictions obtained by the use of the physics-based non-local constitutive model (figures 5.10g – i ) reveal much smaller orientation scatter and smaller reorientation rates when compared to the simulations obtained by the local phenomenological model (figures 5.10d – f ). The simulated textures are in excellent agreement with the experi- mental pole figures. We explain this smoothing effect on the texture evolution mainly in terms of the influence of the geometrically necessary dislocations, which act twofold: First, their accumulation in conjunction with the generation of orientation gradients in- troduces a direct mechanical resistance to the further deformation of the material points affected by such gradients in terms of an increase in the overall local dislocation density. The second aspect (coupled to the first one) is the resulting constitutive tendency of the non-local model to reduce the difference in lattice rotation between neighboring material points. This means that the implicit introduction of the geometrically necessary dislo- cations imposes a strong penalty or respectively drag force against lateral gradients in the reorientation rates. The {1 1 1} pole figures shown in figures 5.10c and i reveal that the projected orientation points cluster in the form of two groups, while in subfigure f
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Micromechanical material models for polymer composites through advanced numerical simulation techniques

Micromechanical material models for polymer composites through advanced numerical simulation techniques

In addition, another study on the influence of the number of particles which has been carried out can also be considered a study versus the size of the particles. The volume fraction is fixed and all particles have same size, thus as number of particles increases the size of particles decreases proportionally. The results showed that as number of inclusions increases, more stable homogenized material properties are obtained or minimal statistical dispersion (<<< 1%). This is plausible, because as the number of inclusions in the RVE tends to infinity the heterogeneous microstructure tends to homogeneity and the effect of the inclusions randomness in the microstructure tends to zero. As the results show, a minimum of 40 spherical inclusions is a good number to avoid undesired statistical errors. Previously, some research was done on the influence of the size of the RVE on output results; for example, (Zeman,2003) [68] reported that the transverse elastic behavior of continuously reinforced composites can be satisfactorily described by unit cells containing arrangements of 10 to 20 fibers. For the case of elastic statistically isotropic composites with matrix and sphere-like particles, (Drugan and Willis,1996)[69] estimated that for approximating the overall moduli with errors of less than 5% or less than 1%, respectively, a non-periodic RVE with edge sizes of approximately two or five inclusion diameters are sufficient for any volume fraction; see also (Drugan,2000) [70]. Those researchers used the ratio between the cube edge length “L” and the same size spheres’ diameter “D” and came up with a range of 2 to 5. In our case the range of 10 to 60 same size particles is equivalent to range of “L/D” between 3.3 and 6.0, but the less than 1% relative deviation was found near and above the “L/D = 5.2” which is equivalent to approximately 40 same size spherical particles inside a unit volume cubic RVE.
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Consistent Higher Order Accurate Time Discretization Methods for Inelastic Material Models

Consistent Higher Order Accurate Time Discretization Methods for Inelastic Material Models

Local time discretization error of the h- and the residual method for the displacement, the viscoplastic strain, and the stress field for distinct time integration methods within multifiel[r]

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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]

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Index of /Material/Pruefungen

Index of /Material/Pruefungen

Das Prüfungszimmer wird jeweils im Stundenplan eingetragen.. Klasse 1.[r]

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Index of /Material/Pruefungen

Index of /Material/Pruefungen

Das Prüfungszimmer wird jeweils im Stundenplan eingetragen.. Klasse 1.[r]

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Index of /Material/MA

Index of /Material/MA

Die Kriterien für die Beurteilung des Konzeptes werden schriftlich abgegeben (siehe Anhang).. Termin für die Abgabe des Konzeptes: siehe Terminliste.[r]

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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]

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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]

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Sluggish raw material markets

Sluggish raw material markets

Ibgether with the increased production of other rubber products the growth in motor vehicle production and tyre manufacturing in 1986, however, probably only led to [r]

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Sheep models for evaluation of novel patch and prosthesis material in vascular surgery: tips and tricks to avoid possible pitfalls

Sheep models for evaluation of novel patch and prosthesis material in vascular surgery: tips and tricks to avoid possible pitfalls

Background In vascular surgery, synthetic prosthesis material is glob- ally used for patch-angioplasties, interpositions, bypasses and straight shunts. Such prosthesis material is required either when suitable autologous veins are not available or in order to save time during critical operations. Addition- ally, the current standard procedure requires prosthesis straight or loop shunts, if there is not enough time for the maturation of a native shunt. An ideal vascular prosthe- sis would display the following characteristics: long-term patency, biocompatibility, durability, low porosity, lack of stich hole bleeding, ease of handling, kink resistance, and resistance towards infection; ideally all at a reasonable cost. In 1957, DeBakey introduced the first polyethylene terephthalate (PET; e.g. Dacron) prosthesis in aortic sur- gery [ 1 ]. In 1976, the first successful clinical implantation of polytetrafluoroethylene (PTFE) grafts was reported [ 2 ]. Currently, Dacron and PTFE are the most widely used prosthesis materials. Compared to veins, however, they have a higher risk of anastomotic neointimal hyper- plasia, thrombosis, and infection. In spite of significant efforts by industrial and academic research groups over the past 60  years, an ideal synthetic vascular graft has not been developed. Hence, the development of an opti- mal vascular prosthesis is a challenging issue in vascular surgery research [ 3 ]. Evaluation of new vascular prosthe- sis material in preclinical animal studies is required to assess biocompatibility, thrombogenicity, endothelializa- tion as well as the capacity of the prosthesis to maintain a physiologic function in the circulatory system. It is also a prerequisite for registration of a medical device, as demanded by the Food and Drug Administration (FDA) and European Medical Devices Directive (MDD).
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Perception of Material Kinematics

Perception of Material Kinematics

Studies of the visual perception of ‘stuffishness’ thus far have primarily looked at the material properties of objects at rest. But the world is not static-- objects fall to the ground, popsicles melt, we deform fruits and vegetables with our hands to tell if they are ripe and ready to eat. Based on our interactions with (and observations of) objects in the world, we develop expectations regarding the expected outcome of an object in motion, based largely in part on its material qualities. We interact with objects and deform them with hands and tools, giving us an impression of material composition that is much stronger (and more reliable) than that of a static image alone. We expect dropped plates to shatter, popped bike tires to deflate, and gooey grilled cheese to hang between two slices of bread when pulled apart. Perceiving the shape and motion of an object, the deformations that arise from the collision of an object with a solid surface, and recalling the predictions that are associated with certain shapes and materials allows an individual to navigate the physical world, avoid danger, and remain alive.
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Akusto-optische Signalverarbeitung mit dem Material Rutil

Akusto-optische Signalverarbeitung mit dem Material Rutil

Da für eine Allan-Plot Messung eines jeden Spektrometers verschiedene Rauschquellen benutzt wurden, kann man dies als Indiz dafür ansehen, daÿ die Stabilität durch die Rauschquellen limi[r]

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Material and Discursive Militarisation in Democracies

Material and Discursive Militarisation in Democracies

A third material indicator of militarisation is the amount of societal resources al- located to the armed forces. To evaluate this, we draw on the Global Militariza- tion Index (GMI) from the Bonn International Center for Conversion (BICC), which includes military expenditures, the size of the armed forces, and their arsenal of heavy weapons (Mutschler 2019). Figure 3 shows the trends in the average GMI for democracies and dictatorships from 1991 to 2018. After the end of the Cold War, democracies were, on average, considerably more militarised than authoritarian regimes. However, the data show that while autocracies, on average, increased spending on their militaries throughout the first decade of this century and thereby returned to 1990s levels of militarisation, democracies, on average, demilitarised almost continuously after a brief increase in the early 1990s. In 2018, the last year for which GMI data is available at the time of writing, the average degree of milita- risation was considerably lower in democracies than in autocracies.
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Material- und Energieflussbasierte Kosten- und Klimaanalyse-MEKKA

Material- und Energieflussbasierte Kosten- und Klimaanalyse-MEKKA

Methodenbezogene Fragen, die keinesfalls trivial sind, kommen bereits in der physischen Ma- terialflussanalyse auf. Beispielsweise können alle Input- und Outputflüsse von Energie und Material innerhalb des Unternehmens gesammelt werden, die wahre Herausforderung besteht jedoch darin, sie einander zuzuordnen. Unternehmen produzieren normalerweise eine Reihe von Produkten und Nebenprodukten. Der Material- und Energieeinsatz sowie die zurückblei- benden Materialien, Abfälle und Emissionen (mit anderen Worten die Outputseite) müssen diesen Produkten ebenfalls zugewiesen werden. In manchen Fällen mag der eigentliche Zweck eines Unternehmens auf der Inputseite liegen. Beispielsweise verdient eine Müllver- brennungsanlage ihr Geld mit der Annahme von Abfallmaterialien. Dieser Abfalleintrag bildet nun den Bezugspunkt für alle Ausgaben des Unternehmens. So werden die Flüsse nicht länger nach Input und Output sortiert, sondern stattdessen nach Aufwand (Materialien, Energie, Ab- fälle, Emissionen) und Ertrag (Produkte) im allgemeineren oder physischen Sinne.
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