RR
R. Ranjan
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1
Additive manufacturing (AM) has revolutionized part manufacturing, offering unprecedented design freedom and the ability to fabricate intricate structures. Computational design methods like topology optimization (TO) effectively capitalize on AM's design freedom. However, manufacturability constraints must be considered to ensure reliable manufacturing. A significant constraint is local overheating, prevalent in metal additive manufacturing, leading to defects, part distortion, and diminished mechanical properties. While overhangs are commonly associated with overheating, they are not the only geometric features prone to overheating. This thesis addresses the overheating issue in topology optimization by a novel geometric approach. Specifically, we propose to estimate the local conductivity around each element by evaluating the material distribution in its vicinity. This is then used to generate a pseudo temperature field (i.e., hotspot map) to assess overheating risks. Formulated as a constraint in topology optimization, our approach creates optimized structural layouts free of local overheating during additive manufacturing. Additionally, the approach is implemented in space-time topology optimization, limiting overheating risks by simultaneous optimization of structural layout and fabrication sequence. Compared with existing overheating prevention methods, the geometry-based constraint demonstrates significant computational advantages. Transient thermal AM simulations were conducted on the final designs obtained using the physics-based method from the literature and the novel geometry-based overheating prevention method. The numerical results have shown that the proposed geometric approach is efficient and effective in controlling local overheating in topology optimization for metal additive manufacturing.
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Additive manufacturing (AM) has revolutionized part manufacturing, offering unprecedented design freedom and the ability to fabricate intricate structures. Computational design methods like topology optimization (TO) effectively capitalize on AM's design freedom. However, manufacturability constraints must be considered to ensure reliable manufacturing. A significant constraint is local overheating, prevalent in metal additive manufacturing, leading to defects, part distortion, and diminished mechanical properties. While overhangs are commonly associated with overheating, they are not the only geometric features prone to overheating. This thesis addresses the overheating issue in topology optimization by a novel geometric approach. Specifically, we propose to estimate the local conductivity around each element by evaluating the material distribution in its vicinity. This is then used to generate a pseudo temperature field (i.e., hotspot map) to assess overheating risks. Formulated as a constraint in topology optimization, our approach creates optimized structural layouts free of local overheating during additive manufacturing. Additionally, the approach is implemented in space-time topology optimization, limiting overheating risks by simultaneous optimization of structural layout and fabrication sequence. Compared with existing overheating prevention methods, the geometry-based constraint demonstrates significant computational advantages. Transient thermal AM simulations were conducted on the final designs obtained using the physics-based method from the literature and the novel geometry-based overheating prevention method. The numerical results have shown that the proposed geometric approach is efficient and effective in controlling local overheating in topology optimization for metal additive manufacturing.
Topology optimization of compliant mechanisms
With focus on overheating prevention during Additive Manufacturing
A compliant mechanism (CM) is a special kind of mechanism which has seen an increase in use in various high-tech applications. A CM is a structure designed with the intention to deform: motion is achieved by deformation of flexible members of its body. CMs are designed by topology optimization (TO) algorithms, which use boundary conditions as an input and give a design as an output. Additive manufacturing (AM) is used to fabricate the designed CMs, as geometric complexity is much less of a problem compared to conventional methods. One issue with AM is that local overheating during printing can cause defects in the design, specifically for metal designs, as the temperature is very high during printing. In this thesis, a CM is designed using TO and fabricated using AM. The design is then printed and analysed for overheating defects to determine if any defects due to overheating are present. Also, a computationally inexpensive AM model is integrated into the TO for CM, which can detect zones prone to local overheating. Next to that, the robust optimization method is used to obtain a design which needs much less post-processing. The obtained designs are compared to existing TO methods and it is found that the added constraint can reduce overheating by a large amount while maintaining a relatively high CM performance.
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A compliant mechanism (CM) is a special kind of mechanism which has seen an increase in use in various high-tech applications. A CM is a structure designed with the intention to deform: motion is achieved by deformation of flexible members of its body. CMs are designed by topology optimization (TO) algorithms, which use boundary conditions as an input and give a design as an output. Additive manufacturing (AM) is used to fabricate the designed CMs, as geometric complexity is much less of a problem compared to conventional methods. One issue with AM is that local overheating during printing can cause defects in the design, specifically for metal designs, as the temperature is very high during printing. In this thesis, a CM is designed using TO and fabricated using AM. The design is then printed and analysed for overheating defects to determine if any defects due to overheating are present. Also, a computationally inexpensive AM model is integrated into the TO for CM, which can detect zones prone to local overheating. Next to that, the robust optimization method is used to obtain a design which needs much less post-processing. The obtained designs are compared to existing TO methods and it is found that the added constraint can reduce overheating by a large amount while maintaining a relatively high CM performance.