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Topology optimization for minimum weight with compliance and simpli ed nominal stress constraints for fatigue resistance
Get PDFpeer reviewedThis work investigates a simpli ed approach to cope with the optimization of preliminary design of structures under local fatigue constraints along with a global enforcement on the overall compliance. The problem aims at the minimization of the weight of linear elastic structures
under given loads and boundary conditions. The expected sti ness of the optimal structure is provided by the global constraint, whereas a set of local stress-based constraints ask for a structure to be fatigue resistant. A modi ed Goodman fatigue strength comparison is implemented through the same formalism to address pressure-dépendent failure in materials as in Drucker-Prager strength criterion. As a simplification, the Sines approach is used to de ne the equivalent mean and alternating stresses to address the fatigue resistance for an infinite life time. Sines computation is based on the equivalent mean and alternate stress depending on the invariants of the stress tensor and itsdeviatoric part, respectively. The so-called singularity phenomenon is overcome by the implementation of a suitable qp-relaxation of the equivalent stress measures. Numerical examples are presented to illustrate the features of the achieved optimal layouts and of the proposed algorithm
Stress constrained topology optimization for additive manufacturing: Specific character and solution aspects
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Microstructural design using stress-based topology optimization
Get PDFNew additive manufacturing techniques break the limitations encountered for years when producing components descending from topology optimization. Classical design procedures focus on macro-structural optimization to sustain given loads but today innovative manufacturing processes allow considering structures exhibiting tailored microstructures, i.e. the well known microstructural design. The practical applications
of structures including material design is mainly motivated by the greater performances that can be achieved compared to classical solutions.
Microstructural design has been shown a great interest as attested by recent works[1, 2]. However, stress-based topology optimization has not yet been extensively exploited when addressing microstructural design using numerical homogenization though stress constraints is an important feature and have gained in interest in the field of topology optimization as pointed out by [3].This contribution investigates the problem of material design enforcing stress constraints within periodic microstructures by considering a representative volume element (RVE) subject to prescribed strain fields.
The SIMP approach is adopted as material interpolation law while the optimization problems are solved using a sequential convex programming approach. In particular the well known method of moving asymptotes (MMA) is considered. Numerical homogenization is used to assess the effective elastic properties of the microstructures. The Von Mises stress criterion is used to impose the constraints on the stress level.
This work discusses the formulation of a well-posed design problem as well as some numerical issues encountered. The developed solution procedure is first validated by comparison against analytical results, e.g. the single inclusion of Vigdergauz microstructure. Finally the optimized layouts are fabricated using a multimaterial inkjet polymer printing (Connex by Stratasys) to test the actual performances of optimized designs
Topology optimization for microstructural design under stress constraints
Get PDFThis work aims at introducing stress responses within a topology optimization framework applied to the design of periodic microstructures. The emergence of novel additive manufacturing techniques fosters research towards new approaches to tailor materials properties. This paper derives a formulation to prevent the occurrence of high stress concentrations, often present in optimized microstructures. Applying macroscopic test strain fields to the material, microstructural layouts, reducing the stress level while exhibiting the best overall stiffness properties, are sought for. Equivalent stiffness properties of the designed material are predicted by numerical homogenization and considering a metallic base material for the microstructure, it is assumed that the classical Von Mises stress criterion remains valid to predict the material elastic allowable stress at the microscale. Stress constraints with arbitrary bounds are considered, assuming that a sizing optimization step could be applied to match the actual stress limits under realistic service loads. Density–based topology optimization, relying on the SIMP model, is used and the qp–approach is exploited to overcome the singularity phenomenon arising from the introduction of stress constraints with vanishing material. Optimization problems are solved using mathematical programming schemes, in particular MMA, so that a sensitivity analysis of stress responses at the microstructural level is required and performed considering the adjoint approach. Finally, the developed method is first validated with classical academic benchmarks and then illustrated with an original application: tailoring metamaterials for a museum anti–seismic stand
Design of homogenized microstructure using stress-based topology optimization
No full textThis paper aims at designing microstructures using stress-based topology optimization. Most of the developments so far
have been made for compliance design in various field of applications as reflected in the literature. The emergence of the new additive
manufacturing techniques allows to consider porous material, such as lattice structures for instance, which ca be used for the design of
structural components subject to various solicitations. Those components must account for the stress level to prevent failure everywhere
in the microstructure and by extension the whole structure itself. This work proposes to design such microstructure using topology
optimization with limitation on the stress level within the microstructure before printing the result. The homogenization technique is
used to determine the equivalent material properties. The issues and perspectives are also discussed
Stress-based topology optimization with fatigue failure constraints
No full textThis paper shows how the design of a structure can evolve when considering a stressbased
topology optimization along with fatigue failure constraints. More precisely,
fatigue failure is added in a stress-based topology optimization Matlab code by following
the approach of the design of machine elements, i.e. based on S-N curves or
fatigue criteria. The fatigue is introduced through weel-known criteria for high-cycle
fatigue such as the Sines and Crossland criteria. The paper presents how these criteria
can be formulated for a topology optimization problem. Numerical results for
both criteria are successively compared and discussed. The character of fatigue failure
in the optimization procedure is illustrated as well as some issues that have to be
improved in future work.Contributions to topology optimization of structural components made by additive manufacturing - PhD thesi
Topology optimization of mechanical and aerospace components subject to fatigue stress constraints
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Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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