402 research outputs found
Space/time global/local noninvasive coupling strategy: Application to viscoplastic structures
The purpose of this paper is to extend the non-invasive global/local
iterative coupling technique [15] to the case of large structures undergoing
nonlinear time-dependent evolutions at all scales. It appears that, due to the
use of legacy codes, the use of different time grids at the global and local
levels is mandatory in order to reach a satisfying level of precision. In this
paper two strategies are proposed and compared for elastoviscoplastic models.
The questions of the precision and performance of those schemes with respect to
a monolithic approach is addressed. The methods are first exposed on a 2D
example and then applied on a 3D part of industrial complexity
Projection-based measurement and identification
A recently developed Projection-based Digital Image Correlation (P-DVC)
method is here extended to 4D (space and time) displacement field measurement
and mechanical identification based on a single radiograph per loading step
instead of volumes as in standard DVC methods. Two levels of data reductions
are exploited, namely, reduction of the data acquisition (and time) by a factor
of 1000 and reduction of the solution space by exploiting model reduction
techniques. The analysis of a complete tensile elastoplastic test composed of
127 loading steps performed in 6 minutes is presented. The 4D displacement
field as well as the elastoplastic constitutive law are identified. Keywords:
Image-based identification, Model reduction, Fast 4D identification, In-situ
tomography measurements. INTRODUCTION Identification and validation of
increasingly complex mechanical models is a major concern in experimental solid
mechanics. The recent developments of computed tomography coupled with in-situ
tests provide extremely rich and non-destructive analyses [1]. In the latter
cases, the sample was imaged inside a tomograph, either with interrupted
mechanical load or with a continuously evolving loading and on-the-fly
acquisitions (as ultra-fast X-ray synchrotron tomography, namely, 20 Hz full
scan acquisition for the study of crack propagation [2]). Visualization of fast
transformations, crack openings, or unsteady behavior become accessible.
Combined with full-field measurements, in-situ tests offer a quantitative basis
for identifying a broad range of mechanical behavior.Comment: SEM 2019, Jun 2019, Reno, United State
Sparse bayesian polynomial chaos approximations of elasto-plastic material models
In this paper we studied the uncertainty quantification in a functional approximation form of elastoplastic models parameterised by material uncertainties. The problem of estimating the polynomial chaos coefficients is recast in a linear regression form by taking into consideration the possible sparsity of the solution. Departing from the classical optimisation point of view, we take a slightly different path by solving the problem in a Bayesian manner with the help of new spectral based sparse Kalman filter algorithms
An error indicator-based adaptive reduced order model for nonlinear structural mechanics -- application to high-pressure turbine blades
The industrial application motivating this work is the fatigue computation of
aircraft engines' high-pressure turbine blades. The material model involves
nonlinear elastoviscoplastic behavior laws, for which the parameters depend on
the temperature. For this application, the temperature loading is not
accurately known and can reach values relatively close to the creep
temperature: important nonlinear effects occur and the solution strongly
depends on the used thermal loading. We consider a nonlinear reduced order
model able to compute, in the exploitation phase, the behavior of the blade for
a new temperature field loading. The sensitivity of the solution to the
temperature makes {the classical unenriched proper orthogonal decomposition
method} fail. In this work, we propose a new error indicator, quantifying the
error made by the reduced order model in computational complexity independent
of the size of the high-fidelity reference model. In our framework, when the
{error indicator} becomes larger than a given tolerance, the reduced order
model is updated using one time step solution of the high-fidelity reference
model. The approach is illustrated on a series of academic test cases and
applied on a setting of industrial complexity involving 5 million degrees of
freedom, where the whole procedure is computed in parallel with distributed
memory
Robust and parallel scalable iterative solutions for large-scale finite cell analyses
The finite cell method is a highly flexible discretization technique for
numerical analysis on domains with complex geometries. By using a non-boundary
conforming computational domain that can be easily meshed, automatized
computations on a wide range of geometrical models can be performed.
Application of the finite cell method, and other immersed methods, to large
real-life and industrial problems is often limited due to the conditioning
problems associated with these methods. These conditioning problems have caused
researchers to resort to direct solution methods, which signifi- cantly limit
the maximum size of solvable systems. Iterative solvers are better suited for
large-scale computations than their direct counterparts due to their lower
memory requirements and suitability for parallel computing. These benefits can,
however, only be exploited when systems are properly conditioned. In this
contribution we present an Additive-Schwarz type preconditioner that enables
efficient and parallel scalable iterative solutions of large-scale multi-level
hp-refined finite cell analyses.Comment: 32 pages, 17 figure
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