Dr.Ing. Dustin Roman Jantos
30823 Garbsen

Research projects
 Topology and Material Optimization with fiber reinforced materials, tension and compression affine materials (steel/concrete)
 Numerical efficient gradientenhanced regularization techniques for FEM and meshfree methods
 Additive Manufacturing

The neighbored element method for damage processesDamage processes are modeled by a softening behavior in a stress/strain diagram. This reveals that the stiffness loses its ellipticity and the energy is thus not coercive. The underlying partial differental equation wouldn't have a unique solution and the numerical implementation of such an illposed problem yields results that are strongly dependent on the chosen spatial discretization. Consequently, regularization strategies have to be employed that render the problem wellposed. A prominent method for regularization is a gradient enhancement of the free energy. This, however, results in field equations that have to be solved in parallel to the EulerLagrange equation for the displacement field. Therefore the number of degrees of freedom (unknowns) would increase and the system solution using a finite element approach would be cumbersome and numerically demanding. A gradientenhanced material model for brittle damage using Hamilton’s principle for nonconservative continua was developed. The model is based on an improved algorithm, combining the finite element with strategies from meshless methods, for a fast update of the damage field function. This numerical treatment is referred to as neighbored element method (NME). The model proves to be numerically stable and fast, with simulation times close to purely elastic problems. In addition, the model provides meshindependent results.Led by: P. Junker, D. R. JantosYear: 2018

Thermodynamic topology optimizationFor the optimization of the topology, the local material density is defined as design variable within a given design space. The design space describes the geometrical bounds of the structure and to which the (mechanical) boundary value problem is applied. In each point of the design space, the density indicates whether material should be applied in that region or not. For mathematical relaxation, the density variable is continuous allowing intermediate densities during the optimization process, i.e. porous material. Intermediate densities are penalized so that the final topology contains approximately only full and void material (SIMPapproach). The underlying mathematical problem is illposed and according regularization techniques have to be applied. A gradientenhanced regularization is added for the density field and the evolution equation is formulated in its strong form. With the backward Euler scheme and an internal loop for numerical stability, no additional equation systems besides the FEM have to be solved within the optimization process. The second spacial derivatives in the strong form are computed via the neighbored element method. Herein, only the minimum number of neighboring points are used to calculate the required second spatial derivatives to reduce the calculation effort even further. The formulation is independent of the spacial discretization of the design variable: only data on the close neighborhood between points is required. Therefore, the method is suitable for meshbased as well as for meshfree methods. The minimum member size, i.e. the minimum cross section width of a structure feature, can be directly controlled by a usergiven parameter. Furthermore, the regularization technique can also be applied to regularization in other material models, as for example damage, wherein the width of the damaged zone can be controlled directly.Led by: D. R. Jantos, P. JunkerYear: 2021

PlasticityPlastic deformation or plastic zones can weaken the structure drastically or are also planned into the design of structure. Usual approaches for optimization with plastic material require the calculation of a full plasticity analysis with multiple load steps until convergence for each design optimization step, which results in a large number of mechanical analysis steps and therefore large calculation efforts. In the novel approach, a dissipationfree plasticity model is developed, whose evolution is pathindependent, so that only one mechanical analysis step is required for each optimization step. In combination with the operator split, the calculation effort for the optimization with plastic material is negligible higher than for an optimization with pure elastic material.Led by: P. Junker, D. R. JantosTeam:Year: 2021

Anisotropic materialsHigh performance materials, as for example carbon fiber reinforced polymers but also structures produced with additive manufacturing inhere anisotropic material properties, which can be influenced during the production process, i.e. the applied direction of fibers or print path within 3D printing. Since the material orientation has a major influence on the structure performance, the local material orientation should also be considered as design variable for the optimization process. With the thermodynamic optimization approach, evolution equations for the optimal material direction described by Euler angles can be found and are combined with a simultaneous topology optimization, which results in significantly different varying optimal typologies in comparison to a topology optimization with isotropic material. For some production processes, as for example reinforcement with long fibers, or simply for a smoother fiber path design, the maximum fiber curvature can be constrained via a filtering technique with the filter radius R given by the user.Led by: D. R. Jantos, P. JunkerYear: 2021

Tension and compression affine materialsConcrete is economical but rather weak under tension load, whereas steel may bear tension and compression very well, but is much less economical. Therefore, an simplified approach for economical steelconcrete structures is to apply concrete only in regions predominant to compression loading and steel under tension loading. By introducing an energetic penalization, this approach can be implemented into an topology optimization with two elastic materials, in which one material is affine to compression (e.g. concrete) and one is affine to tension (e.g. steel). Due to different elastic properties of the both materials, i.e. Young's modulus an Poisson's ratio, the resulting optimization depends strongly on the load direction.Led by: D. R. Jantos, P. JunkerYear: 2021

Optimization and additve manufacturingThe results from the topology optimization are usually very difficult or even impossible to manufacture with conventional methods. However by use of additive manufacturing, as for example 3D printing, the production becomes not only feasible but most optimized structures can be directly produced without modification. However, the material characteristics and also bounds of the additive manufacturing processes, as for example material anisotropy, print directions, overhangs, thermomechanical properties should be considered as constraints for the optimization. Those effects strongly depend on the chosen additive manufacturing process and are considered in future projects.Led by: D. R. Jantos, P. JunkerYear: 2021

Publications
PEERREVIEWED ARTICLES
Topology optimization with anisotropic materials, including a filter to smooth fiber pathways. / Jantos, Dustin Roman; Hackl, Klaus; Junker, Philipp.
In: Structural and Multidisciplinary Optimization, Vol. 61, No. 5, 05.2020, p. 21352154.Research output: Contribution to journal › Article › Research › peer review
Tension/compression anisotropy enhanced topology design. / Gaganelis, Georgios; Jantos, Dustin Roman; Mark, Peter; Junker, Philipp.
In: Structural and Multidisciplinary Optimization, Vol. 59, No. 6, 2019, p. 22272255.Research output: Contribution to journal › Article › Research › peer review
An accurate and fast regularization approach to thermodynamic topology optimization. / Jantos, D.R.; Hackl, K.; Junker, P.
In: International Journal for Numerical Methods in Engineering, Vol. 117, No. 9, 02.03.2019, p. 9911017.Research output: Contribution to journal › Article › Research › peer review
Comparison of thermodynamic topology optimization with SIMP. / Jantos, Dustin Roman; Riedel, Christopher; Hackl, Klaus; Junker, Philipp.
In: Continuum Mechanics and Thermodynamics, Vol. 31, No. 2, 27.08.2019, p. 521548.Research output: Contribution to journal › Article › Research › peer review
Innovative Ansätze zur Topologie und Materialoptimierung basierend auf thermodynamischen Prinzipien. / Jantos, Dustin Roman.
2019.Research output: Thesis › Doctoral thesis
Structural and material optimization based on thermodynamic principles. / Jantos, Dustin Roman; Hackl, Klaus; Junker, Philipp.
In: Proceedings in applied mathematics and mechanics, 2019.Research output: Contribution to journal › Article › Research › peer review
A fast and robust numerical treatment of a gradientenhanced model for brittle damage. / Junker, Philipp; Schwarz, Stephan; Jantos, Dustin Roman; Hackl, Klaus.
In: International Journal for Multiscale Computational Engineering, Vol. 17, No. 2, 2019, p. 151180.Research output: Contribution to journal › Article › Research › peer review
On an accurate and fast regularization approach to thermodynamic based topology optimization. / Jantos, Dustin Roman; Hackl, Klaus; Junker, Philipp.
In: Proceedings in applied mathematics and mechanics, 2018.Research output: Contribution to journal › Article › Research › peer review
Optimized growth and reorientation of anisotropic material based on evolution equations. / Jantos, D.R.; Junker, P.; Hackl, K.
In: Computational mechanics, Vol. 62, No. 1, 2018, p. 4766.Research output: Contribution to journal › Article › Research › peer review
Topology and material orientation optimization based on evolution equations. / Jantos, Dustin Roman; Junker, Philipp; Hackl, Klaus.
In: PAMM  Proceedings in Applied Mathematics and Mechanics, 2017.Research output: Contribution to journal › Article › Research
A variational growth approach to topology optimization. / Junker, P.; Jantos, D.R.; Hackl, K.
Proceedings of the 14th International Conference on Computational Plasticity  Fundamentals and Applications, COMPLAS 2017. 2017.Research output: Chapter in book/report/conference proceeding › Conference contribution › Research
An evolutionary topology optimization approach with variationally controlled growth. / Jantos, D.R.; Junker, P.; Hackl, K.
In: Computer Methods in Applied Mechanics and Engineering, 2016.Research output: Contribution to journal › Article › Research › peer review
An evolution equation based approach to topology optimization. / Jantos, Dustin Roman; Junker, Philipp; Hackl, Klaus.
In: PAMM  Proceedings in Applied Mathematics and Mechanics, 2016.Research output: Contribution to journal › Article › Research
Analyse und Weiterentwicklung eines variationellen Wachstumsmodells zur Topologieoptimierung. / Jantos, Dustin Roman.
2015.Research output: Thesis › Doctoral thesis

CV
20102015 Bachelor and Master of Science (mechanical engineering) at RuhrUniversität Bochum (Degree with Distinction) 20152019 PhD (mechanical engineering) at RuhrUniversität Bochum (Degree with Distinction).
Dissertation (in german): Innovative Ansätze zur Topologie und Materialoptimierung basierend auf thermodynamischen Prinzipien20192021 PostDoc at Chair of Mechanics  Material Theory of Prof. Hackl at RuhrUniversität Bochum Seit 2021 Senior Engineer at IKM 
Awards and Memberships
20112014 Scholarship for outstanding academic achievements and special commitment of the RuhrUniversität Bochum 20182021 Member of GAMMJuniors 2020 Eickhoff Award of the Eickhoff Maschinenfabrik u. Eisengießerei GmbH for excellent scientific achievements in the doctoral process