Therefore this dynamical system describes how
the effective model changes as the scale changes. The basic idea is to use microscale
simulations on patches (which are local spatial-temporal domains) to mimic
the macroscale behavior of a system through interpolation in
space and extrapolation in time. Macroscale models require constitutive relations which are almost always obtained empirically, by guessing.
- Finally the experimental and simulation results will be presented, along with comparisons of measured versus modeled distortion, and a discussion of validation methods.
- The observation from in situ or on scale 1 loops such as Hermes (CEA) or Kopra (AREVA NP) measurements give important feedback on wear facieses, kinetics and mechanisms.
- Traditional multi-grid method is a way of efficiently solving a large
system of algebraic equations, which may arise from the discretization
of some partial differential equations. - The renormalization group method has found applications in a variety
of problems ranging from quantum field theory, to statistical physics,
dynamical systems, polymer physics, etc. - A fine-scale moving source mechanical response analysis of the small volume is performed.
- Efficiency is vital as up to 30 fused images are produced each second which precludes the use of some algorithms that work well on still images, most importantly many of the multi-scale approaches.
Multiscale ideas have also been used extensively in contexts where no
multi-physics models are involved. Another
important ingredient is how one terminates the quantum mechanical
region, in particular, the covalent bonds. Many ideas have been
proposed, among which we mention the linked atom methods, hybrid
orbitals, and the pseudo-bond approach.
Nanoindentation/scratching at finite temperatures: Insights from atomistic-based modeling
The validation of thermo-mechanical models can be achieved using either in-situ or post-process methods. In-situ measurement techniques, such as using thermocouples or displacement sensors to monitor the development of thermal histories and distortion during manufacturing, allows insights into the physical phenomena during additive manufacturing [17,18]. The Netfabb Simulation FE solver has been validated previously using a variety of both in-situ and post-process methods for the modeling of direct energy deposition (DED) and LPBF components [14,19–23]. In the heterogeneous multiscale method (E and Engquist, 2003), one starts
with a preconceived form of the macroscale model with possible missing
components, and then estimate the needed data from the microscale
model. Quasicontinuum method (Tadmor, Ortiz and Phillips, 1996; Knap and Ortiz, 2001)
is a finite element type of method for analyzing the mechanical
behavior of crystalline solids based on atomistic models.
Concurrent coupling allows
one to evaluate these forces at the locations where they are needed. At LANL, LLNL, and ORNL, the multiscale modeling efforts were driven from the materials science and physics communities with a bottom-up approach. Each had different programs that tried to unify computational efforts, materials science information, and applied mechanics algorithms with different levels of success.
Numerical modelling for predicting failure in textile composites
While extremely powerful, the technology has several challenges, including often damaging the object being imaged. This limits the types of objects and materials that can be imaged using STEM, often excluding delicate systems like biological tissue and other soft materials, such as polymers used in fuel cells and batteries. One way around this drawback is to image the samples at cryogenic temperatures, making the structures more resilient to the electron beam. Chi earned her PhD in materials science and engineering from the University of California, Davis. Miaofang Chi has joined the faculty of the Department of Mechanical Engineering and Materials Science in Duke University’s Pratt School of Engineering.
Three-dimensional scans produce surface maps of finished products which can be compared to the source CAD geometry which was attempted to be built. These scans can be used to investigate part distortion, and can be compared with thermo-mechanical simulation results to validate their predictive capabilities. For these reasons GEGRC has produced scans for the two geometries simulated in the present study using Netfabb Simulation. Roughly speaking, one might regard HMM as an example of the top-down
approach and the equation-free as an example of the bottom-up
approach. In HMM, the starting point is the macroscale model, the
microscale model is used to supplement the missing data in the
macroscale model.
3 Methodology
However, even with a carefully designed geometry and support structures, unwanted plastic deformation often occurs. To further mitigate this, build orientation may be altered, support structures may be added or thickened, or the build component geometry itself may need to be redesigned. This may be very costly as complex builds can easily cost thousands or tens-of-thousands of dollars [8]. Using a validated thermo-mechanical model however may reduce the need for costly experimental iterations. Classically this is a way of
solving the system of algebraic equations that arise from discretizing
differential equations by simultaneously using different levels of
grids. In this way, one can more efficiently eliminate the errors on
different scales using different grids.
Another factor is that experiments have conclusively shown the connection between microscale physics and macroscale deformation. Finally, the concept of linking disparate length and time scales has become feasible recently due to the ongoing explosion in computational power. Averaging methods were developed originally for the analysis of
ordinary differential equations with multiple time scales. The main
idea is to obtain effective equations for the slow variables over long
time scales by averaging over the fast oscillations of the fast
variables (Arnold, 1983).
Title:Introduction to the method of multiple scales
Thermocouples are also effectively applied to the validation of a Tungsten Inert Gas (TIG) welding [25], DED models [26,27]. Infrared video techniques are an alternate technique to capture thermal histories, which is utilized in the validation of multipass welding [28], DED builds [29–31], and LPBF [32] modeling efforts. In-situ measurements can yield deeper understanding of the relationship between process parameters and geometry with thermal behavior and the resulting development of residual stresses and plastic deformation.
Despite the fact that there is no physical basis behind these procedures, built-in refinements of the geometry based on extensive experimental measurements provide good results when compared to micro-computed tomography (μ-CT) scans of a textile unit cell. WiseTex software is based on a mechanical approach using the principle of minimum mechanical energy (Lomov et al., 2000). Using the data about a weaving pattern and mechanical behaviour of dry yarns, WiseTex software can accurately predict yarn paths.
Macro-micro formulations for polymer fluids
Making the right guess often requires and represents far-reaching physical insight, as we see from the work of Newton and Landau, for example. It also means that for complex systems, the guessing game can be quite hard and less productive, as we have learned from our experience with modeling complex fluids. A part-scale layer by layer mechanical analysis is performed, using modeling information from both the part-scale thermal analysis and the fine-scale mechanical analysis, to determine the distortion of https://wizardsdev.com/en/news/multiscale-analysis/ the part during production. Here the macroscale variable \(U\) may enter the system via some constraints,
\(d\) is the data needed in order to set up the microscale model. For
example, if the microscale model is the NVT ensemble of molecular
dynamics, \(d\) might be the temperature. The idea is to decompose the whole
computational domain into several overlapping or non-overlapping
subdomains and to obtain the numerical solution over the whole domain
by iterating over the solutions on these subdomains.
However, experimental determination of mechanical behaviour of dry yarns requires additional studies and can be a challenging problem. In the context of motion estimation, such a multi-resolution or multi-scale representation is very appealing. Due to the smoothing and spatial subsampling, coarse resolution levels allow efficient and robust estimation of large-scale motions. Conversely, fine local motions can accurately be estimated at finer resolution levels. An additional advantage of multi-resolution motion estimation techniques is the potentially significant reduction in computational complexity.