Machining fixture layout design using ant colony algorithm based continuous optimization method

In any machining fixture, the workpiece elastic deformation caused during machining influences the dimensional and form errors of the workpiece. Placing each locator and clamp in an optimal place can minimize the elastic deformation of the workpiece, which in turn minimizes the dimensional and form errors of the workpiece. Design of fixture configuration (layout) is a procedure to establish the workpiece–fixture contact through optimal positioning of clamping and locating elements. In this paper, an ant colony algorithm (ACA) based discrete and continuous optimization methods are applied for optimizing the machining fixture layout so that the workpiece elastic deformation is minimized. The finite element method (FEM) is used for determining the dynamic response of the workpiece caused due to machining and clamping forces. The dynamic response of the workpiece is simulated for all ACA runs. This paper proves that the ACA-based continuous fixture layout optimization method exhibits the better results than that of ACA-based discrete fixture layout optimization method.     

Topology optimization based on the harmony search method

A new topology optimization scheme based on a Harmony search (HS) as a metaheuristic method was proposed and applied to static stiffness topology optimization problems. To apply the HS to topology optimization, the variables in HS were transformed to those in topology optimization. Compliance was used as an objective function, and harmony memory was defined as the set of the optimized topology. Also, a parametric study for Harmony memory considering rate (HMCR), Pitch adjusting rate (PAR), and Bandwidth (BW) was performed to find the appropriate range for topology optimization. Various techniques were employed such as a filtering scheme, simple average scheme and harmony rate. To provide a robust optimized topology, the concept of the harmony rate update rule was also implemented. Numerical examples are provided to verify the effectiveness of the HS by comparing the optimal layouts of the HS with those of Bidirectional evolutionary structural optimization (BESO) and Artificial bee colony algorithm (ABCA). The following conclusions could be made: (1) The proposed topology scheme is very effective for static stiffness topology optimization problems in terms of stability, robustness and convergence rate. (2) The suggested method provides a symmetric optimized topology despite the fact that the HS is a stochastic method like the ABCA. (3) The proposed scheme is applicable and practical in manufacturing since it produces a solid-void design of the optimized topology. (4) The suggested method appears to be very effective for large scale problems like topology optimization.

     

基于动态需求的复杂系统敏捷化布局优化策略

为解决市场动态需求下复杂制造系统的布局规划组合问题,基于分解策略,提出了一种将模糊理论与系统仿真相结合的设施布局两阶段解决方法.基于动态需求,利用模糊理论,实现了复杂制造系统的敏捷化成组布局,以在布局整体策略上追求费用最小化;利用计算机仿真技术,可视化地实现了单元间及单元内设施布局的有效构建及系统性能的进一步完善,通过实例验证了所提方法的有效性.     

多工况下塔带机工作平台拓扑优化设计

为了避免单工况优化设计的局限性,对塔带机工作平台进行了多工况拓扑优化设计,得到其优化的结构构型,使工作平台在各种工况下既具有足够的刚度,又适当的减少了材料用量.以工作平台的整体结构柔度最小为优化目标,利用带权重的折衷规划法协调多个目标函数,构建多工况拓扑优化数学模型,利用HyperWorks/Optistruct求解优化模型,得到工作平台的拓扑型式.根据拓扑型式重构几何模型,对其进行静力分析,并与原结构模型静力分析的结果进行比较,对比的结果证明了文中优化设计的有效性.     

基于模块间约束的机床布局优化方法

机床的占地面积是生产线布局的一个重要约束,为获得占地面积最小的机床布局方案,提出了基于模块间约束的机床布局优化方法。首先将待优化机床三维模型主要模块映射为二维矩形布局图元,并在此基础上构建了机床二维布局数学模型,然后根据不干涉算法设计了相邻算法,用来更精确地表达机床模块间的不干涉和相邻位置约束,最后应用改进的遗传算法通过Matlab计算得到机床布局优化后的方案。通过案例研究,得到较好的机床布局优化结果,验证了该优化方法的有效性。     

Multi-objective optimization in single-row layout design using a genetic algorithm

This paper presents the development of a genetic algorithm for determining a common linear machine sequence for multi-products with different operation sequences and facilities with a limited number of duplicate machine types available for a job. This work aims to minimize the total flow distance traveled by products, reduce the number of machines arranged in the final linear sequence, and decrease the total investment cost of the machines used in the final sequence. We assume that product flow runs only in the forward direction, either via in-sequence or bypass movement. We demonstrate the effectiveness of the proposed algorithm by solving a typical layout design problem taken from literature, and several randomly generated problems. Results indicate that the proposed algorithm serves as a practical decision support tool for resolving layout problems in manufacturing facilities.     

Design and optimization of machining fixture layout using ANN and DOE

In machining fixtures, minimizing workpiece deformation due to clamping and cutting forces is essential to maintain the machining accuracy. This can be achieved by selecting the optimal location of fixturing elements such as locators and clamps. Many researches in the past decades described more efficient algorithms for fixture layout optimization. In this paper, artificial neural networks (ANN)-based algorithm with design of experiments (DOE) is proposed to design an optimum fixture layout in order to reduce the maximum elastic deformation of the workpiece caused by the clamping and machining forces acting on the workpiece while machining. Finite element method (FEM) is used to find out the maximum deformation of the workpiece for various fixture layouts. ANN is used as an optimization tool to find the optimal location of the locators and clamps. To train the ANN, sufficient sets of input and output are fed to the ANN system. The input includes the position of the locators and clamps. The output includes the maximum deformation of the workpiece for the corresponding fixture layout under the machining condition. In the testing phase, the ANN results are compared with the FEM results. After the testing process, the trained ANN is used to predict the maximum deformation for the possible fixture layouts. DOE is introduced as another optimization tool to find the solution region for all design variables to minimum deformation of the work piece. The maximum deformations of all possible fixture layouts within the solution region are predicted by ANN. Finally, the layout which shows the minimum deformation is selected as optimal fixture layout.     

Creep life prediction for udimet 720 material using the initial strain method (ISM)

Despite of considerable research results of uniaxial tension creep available for superalloys, few studies have been made on high temperature creep using the Initial Strain Method (ISM). In this paper, the real-time prediction of high temperature creep strength and creep life for the nickel-based superalloy Udimet 720 (high-temperature and high-pressure gas turbine engine materials) was performed on round-bar type specimens under pure static load at the temperatures of 538°C, 649°C, and 704°C. The predictive equation derived from the ISM in creep tests showed better reliability than those from LMP(Larson-Miller Parameter) and LMPISM (Larson Miller Parameter-Initial Strain Method) specially for long time creep prediction (10³-10⁵h)     

碰撞载荷工况下某城市客车车架拓扑优化设计

在满足车辆行驶安全的前提下,实现结构的轻量化设计是必不可少的.以某城市混合动力电动客车车架结构为研究对象,对其进行多载荷工况下有限元分析,并考虑正面碰撞载荷工况条件.建立车架的多目标拓扑优化数学模型,采用权重比法确定各子目标函数的权重,最后按照各工况的最佳权重比对车架进行拓扑优化设计,并对新车架结构进行有限元校核.结果表明:优化后的车架减重5.02％,满足轻量化要求,同时新结构达到碰撞安全标准,所提设计方法有效.     

New mass optimization technique to achieve low mass BIW designs using optimal material layout methodology on the frontal vehicle crash

Journal of Mechanical Science and Technology - BIW is the car body made of sheet metals welded together. Numerous researches were performed across the world to optimize and save mass on the car...     

复合地层下盾构刀盘滚刀刀具的布置与优化

盾构滚刀刀具直接与岩土接触并进行切削。在复合地层下,滚刀布置的优劣和刀具的寿命与盾构掘进性能的好坏有着直接的联系,影响着盾构的施工效率。以滚刀的布置规律为基础,结合工程实例,分析了某复合地层下影响盾构滚刀刀具布置的关键因素和盾构刀盘刀具的轨迹曲线,并对刀盘的力学性能进行了校核,最后利用遗传算法对滚刀刀具的布置进行了优化,实现了刀盘滚刀刀具布置的最优化。研究结果为复合地层下盾构刀盘刀具的合理布置提供了理论依据,同时也保证了盾构施工的安全性,对提高刀具的使用寿命具有重要的科学意义与工程价值。     

SSLP法在飞机结构件生产线平面布置优化中的应用

在对工业工程系统化设施布置规划方法的特点、要素、研究步骤等技术进行分析的基础上,介绍了如何利用SSLP方法对某飞机结构件产品生产线进行平面布置优化,运用经典简化的系统化布置设计方法(SSLP)得到设施间的相互关系、作业单位之间的物流关系或非物流关系等,最终求得了该生产厂的平面布置优化方案。随后对优化的平面布置方案进行评估。通过现场运用,结果证实改进效果明显。     

Topology optimization for lightweight cellular material and structure simultaneously by combining SIMP with BESO

This paper presents a hybrid algorithm for topology optimization of lightweight cellular materials and structures simultaneously by combining solid isotropic material with penalization (SIMP) and bi-directional evolutionary structural optimization (BESO). Microstructure of the lightweight cellular material is assumed unique in the structure to make the proposed method feasible. A new sensitivity analysis formula with respect to the discrete variable is derived by a principal submatrix stiffness matrix, by which the material can be effectively removed from or added to cellular. Moreover, the validity of the proposed method is then demonstrated through two numerical examples (a simple supported beam and a cantilever beam), which can be easily applied in a variety of practical situations.

     

Topology and thickness optimization of an indenter under stress and stiffness constraints

Journal of Mechanical Science and Technology - Indenter is one of the core components of a waste compression station. In this paper, a new layout free from the existing structure for indenter with...     

Topology optimization of compressor bracket

Topology optimization is very useful engineering technique especially at the concept design stage. It is common habit to design depending on the designer’s experience at the early stage of product development. Structural analysis methodology of compressor bracket was verified on the static and dynamic loading condition with 2 bracket samples for the topology optimization base model. Topology optimization is able to produce reliable and satisfactory results with the verified structural model. Base bracket model for the topology optimization was modeled considering the interference with the adjacent vehicle parts. Objective function was to minimize combined compliance and the constraint was the first natural frequency over 250 Hz. Multiple load cases such as normal mode calculation and gravity load conditions with 3-axis direction were also applied for the optimization, expecting an even stress distribution and vibration durability performance. Commercial structural optimization code such as optistruct of Altair Engineering was used for the structural topology optimization. Optimization was converged after 14 iterations with the satisfaction of natural frequency constraint. New bracket shape was produced with the CATIA based on the topology optimization result. The new bracket from topology optimization result was compared with the traditional concept model and topology optimization base model under 4 load cases. 14 % 1’st natural frequency of new bracket with only 4 % mass increment increased compared to the concept model. 31 % mass decreased compared to the base model without the increment of stress under gravity load cases. It was analyzed thata new bracket would not fail during a vibration durability test, and these results were verified with a fabricated real sample under the durability condition.     

Design of loop layout in flexible manufacturing system using non-traditional optimization technique

Layout arrangement is important to achieve high productivity in flexible manufacturing system (FMS). This paper discusses the design of loop layout in FMS. The objective of the loop layout problem is the determination of the ordering of machines around a loop, to minimize the total number of loop traversals for a family of parts. This paper details the design, development and testing of particle swarm optimization (PSO) technique to solve the loop layout problem. The proposed method is validated with bench mark problems. The clearance between the machines is also considered in the design of loop layout. This aspect aids in selecting the best layout.     

Recent developments on machining fixture layout design, analysis, and optimization using finite element method and evolutionary techniques

A review of the recent development of the machining fixture configuration/layout is presented in this paper. The literature review is mainly focused on the recently developed optimal fixture configuration under the dynamic conditions of the workpiece. In this review paper, the fixture design, fixture analysis, fixture synthesis, fixture layout design, optimization of fixture layout design, various optimization algorithms, and case studies of two- and three-dimensional workpiece geometries under dynamic conditions have been emphasized specially. The further scopes of the research are finally summarized.     

A lightweight design approach for an EMU carbody using a material selection method and size optimization

This study proposes a weight reduction design approach for urban transit carbody using a material selection method and size optimization. First, the material selection method, which uses specific stiffness and strength indices to predict the weight reduction rate, is set up when the materials of the under-frame and roof structure are substituted. The CFRP was chosen as the best weight reduction material in terms of the material selection method but was not appropriate for application to an urban transit carbody as a thin panel because of out-of-plane deformation. Therefore, we applied CFRP-AL honeycomb sandwich composites to the under-frame and roof structures, and the size optimization method was subsequently applied to derive a lightweight composite hybrid carbody design. Finally, the proposed approach was applied to an urban transit carbody, i.e., a Korean electrical multiple units carbody made of aluminum extrusion profiles. The weight of the optimized composite hybrid carbody design was 29.0% lighter than that of the original K-EMU. The resulting composite hybrid carbody design satisfied the design guidelines of the Performance test standard for K-EMU according to the corresponding FE simulations.

     

Topology optimization of transient problem with maximum dynamic response constraint using SOAR scheme

Frontiers of Mechanical Engineering - This paper proposes a novel method for the continuum topology optimization of transient vibration problem with maximum dynamic response constraint. An...