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Data-driven methods and model reduction techniques

A physics-informed GAN framework based on model-free data-driven computational mechanics

Our research introduces a novel approach to mechanical simulations by embedding physical laws directly into generative adversarial networks (GANs). This framework integrates physics into the GAN architecture, where the generator produces predictions, and the discriminator evaluates these predictions against data, providing continuous feedback for improvement. Specifically, the generator is guided by physical constraints, while the discriminator utilizes the closest strain–stress data to assess the authenticity of the generator’s output. This combined approach connects machine learning methods with computational mechanics simulations, establishing a new formalism that uses data-driven mechanics and deep learning to simulate and predict mechanical behaviors.

References:

  • Ciftci, K., & Hackl, K. (2024). A physics-informed GAN framework based on model-free data-driven computational mechanics. Computer Methods in Applied Mechanics and Engineering, 424, 116907.

Using a reduced set of Fourier modes in terms of an FFT-based microstructure simulation

Given a heterogeneous material, the mechanical behavior of its microstructure can be investigated by an algorithm that uses the Fourier representation of the Lippmann-Schwinger equation. By incorporating a model order reduction technique based on calculations with a reduced set of Fourier modes, the computational cost of this algorithm can be reduced. It has been shown that the accuracy of this model order reduction technique strongly depends on the choice of Fourier modes by considering a geometrically adapted rather than a fixed sampling pattern to define the reduced set of Fourier modes. Since it is difficult to define a geometrically adapted sampling pattern for complex microstructures, a strain-based sampling pattern was additionally introduced. While this strain-based sampling pattern has the advantage of its adaptability, it also leads to even more accurate simulation results.

In cooperation with:

  • Bob Svendsen (RWTH Aachen University / Max-Planck Institut für Eisenforschung, Düsseldorf)
  • Stefanie Reese (RWTH Aachen University / University of Siegen)

References:   

  • Gierden, C., Waimann, J., Svendsen, B., & Reese, S. (2021). FFT-based simulation using a reduced set of frequencies adapted to the underlying microstructure. Computer methods in materials science, 21.
  • Gierden, C., Waimann, J., Svendsen, B., & Reese, S. (2021). A geometrically adapted reduced set of frequencies for a FFT-based microstructure simulation. Computer Methods in Applied Mechanics and Engineering, 386, 114131.
  • Kochmann, J., Manjunatha, K., Gierden, C., Wulfinghoff, S., Svendsen, B., & Reese, S. (2019). A simple and flexible model order reduction method for FFT-based homogenization problems using a sparse sampling technique. Computer Methods in Applied Mechanics and Engineering, 347, 622-638.

Model-free Data-driven Computational Methods

Our research focuses on data-driven computational mechanics, which replaces traditional phenomenological models with datasets in the strain-stress space. This method formulates mechanical problems as optimization tasks, where the closest points in the strain-stress dataset are used to satisfy equilibrium and compatibility conditions. By removing the need for explicit constitutive equations, material behavior can be described directly from the data.

We have extended this approach to include inelastic material behavior by incorporating tangent space representations, enabling the accurate modeling of path-dependent effects such as plasticity. To address the complexity of inelastic problems, we employ data reduction techniques, including the transformation of datasets into Haigh-Westergaard coordinates. This transformation reduces the dimensionality of the data while preserving essential information about material responses. Additionally, we divide the dataset into subsets representing different material behaviors, with transition rules mapping between these subsets. This structured approach enhances the ability to model behaviors such as elasto-plasticity with isotropic hardening.

References:

  • Prume, E., Gierden, C., Ortiz, M., & Reese, S. (2025). Direct data-driven algorithms for multiscale mechanics. Computer Methods in Applied Mechanics and Engineering, 433, 117525.
  • Ciftci, K., & Hackl, K. (2023). Model-free data-driven inelasticity in Haigh–Westergaard space - A study how to obtain data points from measurements. Computer Methods in Applied Mechanics and Engineering, 416, 116352.
  • Ciftci, K., & Hackl, K. (2022). Model-free data-driven simulation of inelastic materials using structured data sets, tangent space information and transition rules. Computational Mechanics, 70(2), 425-435.