Jikai Liu

A survey of manufacturing oriented topology optimization methods

Presents a survey of manufacturing oriented topology optimization methods.Investigates the length scale control and geometric feature based design for machining oriented topology optimization.Investigates the part ejection and rib thickness control for injection molding/casting oriented topology optimization.Proposes the future research direction for additive manufacturing oriented topology optimization. Topology optimization is developing rapidly in all kinds of directions; and increasingly more extensions are oriented towards manufacturability of the optimized designs. Therefore, this survey of manufacturing oriented topology optimization methods is intended to provide useful insight classification and expert comments for the community.First, the traditional manufacturing methods of machining and injection molding/casting are reviewed, because the majority of engineering parts are manufactured through these methods and complex design requirements are associated. Next, the challenges and opportunities related to the emerging additive manufacturing (AM) are highlighted. SIMP (Solid Isotropic Material with Penalization) and level set are the concerned topology optimization methods because the majority of manufacturing oriented extensions have been made based on these two methods.

A novel CACD/CAD/CAE integrated design framework for fiber-reinforced plastic parts

Presents a CACD/CAD/CAE integrated design framework for fiber-reinforced plastic parts.Develops the heterogeneous feature model for fiber-reinforced object modeling.Develops the level-set structure and material optimization for conceptual design.Applies the response surface method to optimize the injection molding process conditions.Improves the design optimality and shortens the design process. This work presents a novel CACD/CAD/CAE integrated framework for design, modeling, and optimization of fiber-reinforced plastic parts, which can greatly enhance the current design practice by realizing partial automation and multi-stage optimization. To support this framework, a new heterogeneous feature model (HFM) has been developed to model the fiber-reinforced objects and to be transferred between engineering modules. To be specific, the CACD (computer-aided conceptual design) module employs the level-set structure and material optimization to produce the initial design with thickness control, and also the initial HFM; the CAD (computer-aided design) module allows manual editing on the HFM to reflect various design intents; then, the injection molding CAE (computer-aided engineering) simulates the manufacturing process, and the response surface method (RSM) is applied to optimize the process parameters of gate location, injection flow rate, mold temperature and melt temperature, to approach the manufactured fiber orientation distribution close to the optimized result produced by the CACD module; besides, the structural analysis CAE module generates the mechanical performance result to support the CACD module, as well as to validate the final design. By applying this framework, the final structural design including the fiber orientation distribution, will perform better in mechanical properties, and consume less matrix and fiber materials; besides, the design maturity can be approached in shorter time. To prove the effectiveness, a plastic gripper design will be comprehensively studied.

Product design-optimization integration via associative optimization feature modeling

This paper addresses an important problem of integrating structural optimization into a traditional CAx system and therefore, realizes an integrated product design-optimization system. Specifically, structural optimization has been embedded as an independent module of most commercial CAx systems. It mainly communicates with CAD but can only have the STL-based CAD geometry as input. The knowledge-level information transfer is not supported which causes the optimization intent not fully captured. The consequence could be quite negative that the optimization process generates unsatisfactory or even useless design solutions and tedious manual efforts are required to modify or even redesign the immature solutions, which reduces the overall design efficiency and quality. To fix this issue, this paper proposes an integrated product design-optimization system by enabling the complete information transfer between CAD and structural optimization modules. Interfacing rules have been defined to enable the complete information transfer and the associative optimization feature concept is proposed to manage the transferred information for the structural optimization module. Furthermore, knowledge based reasoning is performed to capture the full optimization intent in order to create a fit-for-purpose optimization model, including both the optimization problem formulation and the solution strategy. For technical merits, this integrated product design-optimization system robustly ensures the timely and high-quality product design delivery which is superior to the existing commercial systems. Effectiveness of this proposed system has been proven through a few case studies.

Deposition path planning-integrated structural topology optimization for 3D additive manufacturing subject to self-support constraint

Abstract This paper presents a novel level set-based topology optimization implementation, which addresses two main problems of design-for-additive manufacturing (AM): the material anisotropy and the self-support manufacturability constraint. AM material anisotropy is widely recognized and taking it into account while performing structural topology optimization could more realistically evaluate the structural performance. Therefore, both build direction and in-plane raster directions are considered by the topology optimization algorithm, especially for the latter, which is calculated through deposition path planning. The self-support manufacturability constraint is addressed through a novel multi-level set modeling. The related optimization problem formulation and solution process are demonstrated in detail. It is proved by several numerical examples that the manufacturability constraints are always strictly satisfied. Marginally, the recently popular structural skeleton-based deposition paths are also employed to assist the structural topology optimization, and its characteristics are discussed.

Minimum void length scale control in level set topology optimization subject to machining radii

This paper presents a minimum void length scale control method for structural topology optimization. Void length scale control has been actively investigated for decades, which intends to ensure the topology design manufacturable given the machining tool access. However, only a single lower bound has been applied in existing methods, which does not fit the multi-stage rough-to-finish machining. To fix this issue, the proposed minimum void length scale control method employs double lower bounds which corresponds to the rough and finish machining operations, respectively. This method has been implemented under the level set framework. For technical details, the rough machining lower bound is satisfied by developing a signed distance-related constraint, which ensures enough space for the rough machining tool movement and thus, guarantees the machining efficiency. The finish machining lower bound is addressed through the curvature flow control, which ensures the small features manufacturable and also a good finish dimension and surface. Through a few numerical case studies, it is proven that the minimum void length scale can be effectively controlled without sacrificing much of the structural performance.

Computer-aided design–computer-aided engineering associative feature-based heterogeneous object modeling

Conventionally, heterogeneous object modeling methods paid limited attention to the concurrent modeling of geometry design and material composition distribution. Procedural method was normally employed to generate the geometry first and then determine the heterogeneous material distribution, which ignores the mutual influence. Additionally, limited capability has been established about irregular material composition distribution modeling with strong local discontinuities. This article overcomes these limitations by developing the computer-aided design–computer-aided engineering associative feature-based heterogeneous object modeling method. Level set functions are applied to model the geometry within computer-aided design module, which enables complex geometry modeling. Finite element mesh is applied to store the local material compositions within computer-aided engineering module, which allows any local discontinuities. Then, the associative feature concept builds the correspondence relationship between these modules. Additionally, the level set geometry and material optimization method are developed to concurrently generate the geometry and material information which fills the contents of the computer-aided design–computer-aided engineering associative feature model. Micro-geometry is investigated as well, instead of only the local material composition. A few cases are studied to prove the effectiveness of this new heterogeneous object modeling method.

Sustainable Design-Oriented Level Set Topology Optimization

This paper presents a novel sustainable design-oriented level set topology optimization method. It addresses the sustainability issue in product family design, which means an end-of-life (EoL) product can be remanufactured through subtractive machining into another lower-level model within the product family. In this way, the EoL product is recycled in an environmental-friendly and energy-saving manner. Technically, a sustainability constraint is proposed that the different product models employ the containment relationship, which is a necessary condition for the subtractive remanufacturing. A novel level set-based product family representation is proposed to realize the containment relationship, and the related topology optimization problem is formulated and solved. In addition, spatial arrangement of the input design domains is explored to prevent highly stressed material regions from reusing. Feature-based level set concept for sustainability is then used. The novelty of the proposed method is that, for the first time, the product lifecycle issue of sustainability is addressed by a topology optimization method. The effectiveness of the proposed method is proved through a few numerical examples. [DOI: 10.1115/1.4035052]

Multi-material plastic part design via the level set shape and topology optimization method

This work presents a new multi-material level set topology optimization method which is developed especially for designing plastic parts. Instead of representing the structure using multiple level set functions, this new method employs only one level set function to describe the material/void interface. The injection moulding filling simulation is used to determine the material/material interfaces. Because plastic parts are targeted, domain-specific knowledge is carefully investigated to improve the optimization algorithm. Both homogeneous and heterogeneous fibre-reinforced plastics are considered as potential material phases. For the latter, one extra design freedom, fibre orientation distribution, is introduced. Instead of generating incremental interior voids, which complicates the mould design and part ejection, shape-fixed interior voids could be predefined inside the design domain for functional or assembly purposes. This is represented by an additional level set function. A few numerical examples are studied to demonstrate the effectiveness of the proposed method.

Truss-like structure design with local geometry control

This paper presents a local geometry control method when designing truss-like structures. Two kinds of local geometry measures are proposed: the local grid area and the local grid incircle radius. Both measures work effectively in constraining the local geometry and the selection is problem-dependent. To prove the effectiveness of the local geometry control, two shape optimization examples are studied by optimizing the nodal design freedoms. For topology optimization, the ground structure problem plus nodal design freedoms are employed and the simultaneous optimization approach is adopted to solve the optimization problem. It is highlighted that the local geometry constraints are dynamically applied to varying objects because of the grid merging caused by truss element elimination. The dynamic constraints would cause local fluctuation during the optimization process but would not impact the overall convergence.

Design History Retrieval Based Structural Topology Optimization

This paper presents a novel topology optimization (TO) method which relies on design history retrieval and surrogate modeling. With this method, a new design case starts by retrieving the design history to find similar cases in both design domain geometry and boundary condition (BC), for which an innovative BC similarity evaluation has been developed. For the best-match history case, feature based topological design was available in database and is predictably similar to that of the new design case. Therefore, it can be used as the feature model input of the new design case, and the TO problem is simplified into a sizing optimization problem to find the optimal feature parameter set. Surrogate model based method has been employed to solve the sizing optimization problem. Overall, this new TO method characterizes as: first, the efficiency is much higher than the conventional TO methods; second, it obtains feature-based topological design without post-treatment effort.