Coupled Topology Optimization Research Articles

A gradient-evolutionary coupled topology optimization for sheet reinforcement based on the mechanics of Voronoi pattern on dragonfly wings

The intricate network of veins on dragonfly wings has captured the attention of many researchers due to its fascinating configuration and excellent mechanical properties. In this paper, based on the observation of the layout of the vein domains on the hind wing of dragonfly, the types of domains were characterized from the aspects of area and shape. The numerical analysis revealed that different shaped domains enhance either stiffness or vibration stability of the wing. According to this feature, a multi-objective gradient optimization algorithm based on stiffness, mass transport efficiency and first order frequency was proposed. Associated by the size constraints, the optimal layout of the venation was obtained and subsequently used to generate the Voronoi patterns, whose positions and shapes could be further optimized by an evolutionary algorithm to match the mechanical analysis results. The effectiveness of this multi-cellular configuration was verified by testing the bending and vibration stability of the additive manufactured model. The aerodynamic simulation analysis of this flapping wing structure was also investigated. This study has important implications for understanding the evolutionary mechanisms of venation on biological wings and designing reinforcement for sheets.

Topology optimization of regenerative cooling channel in non-uniform thermal environment of hypersonic engine

Regenerative cooling technology is widely used in the active thermal protection system of hypersonic airbreathing engine. However, the overall efficiency of active cooling with limited total coolant quantity needs to be improved due to flow non-uniformity, hydrocarbon fuel pyrolysis and other factors. This paper presents a fluid–structure coupled topology optimization design of the regenerative cooling channel to improve heat transfer efficiency. To further verify the advantages of topology-optimized cooling channels under real operating conditions, detailed three-dimensional numerical simulations were conducted to investigate the supercritical flow and heat transfer processes of hydrocarbon fuel in the topology-optimized channels. Results reveal that compared to the traditional straight cooling channel, the topology-optimized channel has improved the heat transfer efficiency and flow distribution significantly. Many micro-channels perpendicular to the mainstream direction which can be termed as “capillary-like” zone in the optimized channel distribute the inlet fuel to the adiabatic walls, thus significantly improving the overall heat transfer. Remarkable cooling capacity robustness of the topology-optimized cooling channels has been found under different non-uniform heat flux conditions. Comparing to the straight channels, the averaged temperature of the heated wall in the optimized channels can be decreased up to 5.8% and the pressure drop can be decreased up to 20.6%. The uniformity of the fuel temperature distribution is about 2 times better than that of the straight channel. However, although overall heat transfer efficiency is high, complex flow and heat transfer phenomenon occurs in the topology-optimized cooling channel, such as the reverse flow phenomenon induced by adverse pressure gradient near the entrance and the stagnated flow in the “capillary-like” zone near the exit, which impair the local heat transfer and cause the existence of high temperature regions.

Coupled topology optimization of structure and connections for bolted mechanical systems

This work introduces a new coupled topology optimization approach for a structural assembly. Considering several parts connected by bolts, the shape and topology of potentially each part, as well as the position and number of bolts are simultaneously optimized. The main ingredients of our optimization approach are the level-set method for structural optimization, a new notion of topological derivative of an idealized model of bolt in order to decide where it is advantageous to add a new bolt, coupled with a parametric gradient-based algorithm for its position optimization. Both idealized bolt and its topological derivative handle prestressed state complexity. Several 3d numerical test cases are performed to demonstrate the efficiency of the proposed strategy for mass minimization, considering Von Mises and fatigue constraints for the bolts and compliance constraint for the structure. In particular, a simplified but industrially representative example of an accessories bracket for car engines demonstrates significant benefits. Optimizing both the structure and its connections reduces the mass by 24% compared to classical “structure-only” optimization.

Topology optimization of connections in mechanical systems

One of the issues for the automotive industry is weight reduction. For this purpose, topology optimization is used for mechanical parts and usually involves a single part. Its connections to other parts are assumed to be fixed. This paper deals with a coupled topology optimization of both the structure of a part and its connections (location and number) to other parts. The present work focuses on two models of connections, namely rigid support and spring that prepares work for bolt connection. Rigid supports are modeled by Dirichlet boundary conditions while bolt-like connections are idealized and simplified as a non-local interaction to be representative enough at a low computational cost. On the other hand, the structure is modeled by the linearized elasticity system and its topology is represented by a level set function. A coupled optimization of the structure and the location of rigid supports is performed to minimize the volume of an engine accessories bracket under a compliance constraint. This coupled topology optimization (shape and connections) provides more satisfactory performance of a part than the one given by classical shape optimization alone. The approach presented in this work is therefore one step closer to the optimization of assembled mechanical systems. Thereafter, the concept of topological derivative is adapted to create an idealized bolt. The main idea is to add a small idealized bolt at the best location and to test the optimality of the solution with this new connection. The topological derivative is tested with a 3d academic test case for a problem of compliance minimization.

Design and analysis of the thermal-stress coupled topology optimization of the battery rack in an AUV

To reduce the mass of underwater vehicles and the temperature gradient of battery racks, the methods of element birth and death is used to study topology optimization. First, with an objective function based on the minimum configuration flexibility, the optimization results can be obtained by varying the proportion of optimization. Second, the structural minimum temperature gradient is considered as the objective function to achieve a further topology optimization by varying the proportion of optimization. Finally, under the condition of a given topology optimization ratio, the thermal-stress coupled topology optimization is applied by changing the proportion of the thermal load to the stress load. The corresponding battery frame structures are obtained, and the correctness of the mathematical model is verified.

Topology optimization of members of flexible multibody systems under dominant inertia loading

The topology optimization of members of flexible multibody systems is considered for energy-efficient lightweight design, where the gradient calculation has an essential role. In topology optimization of flexible multibody systems, where the function evaluations are very time consuming, the gradient information is necessary to accelerate the optimization process. Different approaches have been introduced and tested for the gradient calculation in the fully coupled topology optimization of flexible multibody systems. However, the computation and implementation costs of these methods are high, which limits the optimization size and the possible number of design variables. In this work, we present a modified gradient calculation based on the equivalent static load (ESL) method, which combines the time efficiency of gradient calculation of the ESL method with the higher accuracy of gradient calculation in the fully coupled methods. This modified approach, which takes into account the linear dependencies of inertial loads on acceleration, is tested on the application example of a flexible slider-crank mechanism, and the results are compared with the weakly coupled ESL method and a fully coupled optimization where gradients are calculated using the adjoint variable method.