Development of Carbon Nanotube-Reinforced Nickel-Based Nanocomposites Using Laser Powder Bed Fusion

Modern aerospace applications demand the development of high-performance components with advanced materials. The development of nanomaterial-reinforced metal matrix composites is a practical approach to improve properties. Laser powder bed fusion (LPBF) is one of the popular additive manufacturing approaches to fabricating metal parts with complex geometric structures. This research investigates multiwalled carbon nanotube (CNT)-reinforced nickel-based alloy (Haynes 230) nanocomposite for property improvement. Three volumetric concentrations (0%, 2.5%, and 5%) of CNTs in the metal matrix are investigated with different printing parameters. Different characterizations are conducted on the test specimens. Results show that LPBF-printed Haynes 230 with 2.5 vol% CNTs has higher relative density (99.36%) and less porosity compared to those printed with 5 vol% CNTs. Mechanical test results show that LPBF-printed Haynes 230 with 2.5 vol% CNTs has the highest hardness, modulus of elasticity, yield strength, and ultimate strength than those printed with as-received Haynes 230 powder (with 0 vol% CNTs), Haynes 230 with 5 vol% CNTs, and commercial Haynes 230 plates. The strengthening behavior of the CNTs in the metal matrix composites is discussed in this paper. The potential of CNT-reinforced nickel-based nanocomposites for applications requiring materials with outstanding mechanical properties, such as aerospace and defense, is demonstrated.     

Optimal topology for additive manufacture: A method for enabling additive manufacture of support-free optimal structures

Topology optimisation enables profound insight into the optimal material distribution for a given structural objective, applied loading and boundary conditions. The topologically optimal geometry is often geometrically complex and incompatible with traditional manufacturing methods. Additive manufacture can accommodate significantly more complex geometries than traditional manufacture; however, it is necessary that specific design rules be satisfied to ensure manufacturability. Based on identified design for additive manufacture rules, a novel method is proposed that modifies the theoretically optimal topology as required to ensure manufacturability without requiring additional support material. By assessing the manufacturing time and component mass associated with feasible orientations of the proposed geometry, an optimal orientation can be identified. A case study is presented to demonstrate the usefulness of the proposed method.     

车用CFRP油底壳的结构与制造工艺并行优化设计

为实现碳纤维增强复合材料（carbon fiber reinforced polymer,CFRP）油底壳的替代与制造,结合复合材料铺层可制造性分析软件FiberSim与铺层结构优化模块Optistruct,对CFRP油底壳开展了结构与制造工艺并行优化设计。参照CFRP壳体类零件的成型过程,采用FiberSim软件制定了满足制造工艺要求的CFRP油底壳铺覆方案。并在此基础上,分别以CFRP油底壳刚度最大、质量最小为优化目标,以振动模态、制造工艺要求为约束,采用Optistruct模块对CFRP油底壳的铺层结构进行优化设计。经仿真分析验证,制造工艺调整后的CFRP油底壳满足各项替代要求,且CFRP油底壳的质量较原金属油底壳减小了56.7%。所提出的结构与制造工艺并行优化设计方法可较好地兼顾结构特征、复合材料设计及制造工艺要求,为复合材料产品的优化设计提供了参考。     

Particle swarm-based structural optimization of laminated composite hydrokinetic turbine blades

Composite blade manufacturing for hydrokinetic turbine application is quite complex and requires extensive optimization studies in terms of material selection, number of layers, stacking sequence, ply thickness and orientation. To avoid a repetitive trial-and-error method process, hydrokinetic turbine blade structural optimization using particle swarm optimization was proposed to perform detailed composite lay-up optimization. Layer numbers, ply thickness and ply orientations were optimized using standard particle swarm optimization to minimize the weight of the composite blade while satisfying failure evaluation. To address the discrete combinatorial optimization problem of blade stacking sequence, a novel permutation discrete particle swarm optimization model was also developed to maximize the out-of-plane load-carrying capability of the composite blade. A composite blade design with significant material saving and satisfactory performance was presented. The proposed methodology offers an alternative and efficient design solution to composite structural optimization which involves complex loading and multiple discrete and combinatorial design parameters.     

Design and Optimization of Composite Automotive Hatchback Using Integrated Material-Structure-Process-Performance Method

The application of polymer composites as a substitution of metal is an effective approach to reduce vehicle weight. However, the final performance of composite structures is determined not only by the material types, structural designs and manufacturing process, but also by their mutual restrict. Hence, an integrated “material-structure-process-performance” method is proposed for the conceptual and detail design of composite components. The material selection is based on the principle of composite mechanics such as rule of mixture for laminate. The design of component geometry, dimension and stacking sequence is determined by parametric modeling and size optimization. The selection of process parameters are based on multi-physical field simulation. The stiffness and modal constraint conditions were obtained from the numerical analysis of metal benchmark under typical load conditions. The optimal design was found by multi-discipline optimization. Finally, the proposed method was validated by an application case of automotive hatchback using carbon fiber reinforced polymer. Compared with the metal benchmark, the weight of composite one reduces 38.8%, simultaneously, its torsion and bending stiffness increases 3.75% and 33.23%, respectively, and the first frequency also increases 44.78%.     

Ti-1023合金的研究现状

Ti-1023合金是一种为适应损伤容限性设计原则而生产的高结构效益、高可靠性和低制造成本的锻造钛合金。本文主要介绍了Ti-1023合金组织性能、工艺性能及应用现状。     

高温锻钢闸阀的温度场计算和热固耦合分析

针对高温锻钢闸阀的设计要求，基于美国机械工程师协会（American Society of Mechanical Engineers，ASME）标准规范和有限元分析方法，研究闸阀的虚拟性能评估技术。为了保证闸阀在高温条件下安全可靠运行，提出一种应用有限元软件Ansys计算高温锻钢闸阀温度场和应力场的方法。首先对高温锻钢闸阀的温度场和总应力场进行定量计算及分析，然后完成应力评定并对结构性能进行分析和评价。结果表明：该闸阀的阀盖圆筒高度足够，散热板设计面积合理，承压边界部件能够满足强度要求，具有良好的工程实用价值。     

Phase change microvalve for integrated devices

An active microvalve that uses a meltable piston in place of a conventional solid material to obstruct fluid flow in a microfluidic channel has been developed. This phase change valve is simple to operate and requires no additional fabrication steps. The valve is inherently latched, reusable, and leak-proof (to at least 250 psi) and can be electronically addressed using resistive heaters. The valve has been characterized for a range of operational parameters that will serve as a design guide. For the designs tested, piston displacements of 5 mm or more in 1 s have been achieved. Valves 1.4 mm in length in a 50 microm x 200 microm channel have been integrated on a biochemical reaction device, and successful DNA amplification using PCR has been achieved. The phase change valve can be easily implemented in an array format that can be used to realize complex microfluidic circuits.     

DN200液氧截止阀的设计与研究

从材料、密封形式的选用以及绝热形式的设计等几个方面介绍了DN200液氧截止阀的结构设计过程.并在二维结构设计的基础上,对DN200液氧截止阀进行了三维实体造型的研究,模拟了动态操作,为后续的加工装配奠定了坚实的基础.     

Optimization of plastic injection molding process parameters for manufacturing a brake booster valve body

The plastic injection molding (PIM) process parameters have been investigated for manufacturing a brake booster valve body. The optimal PIM process parameters is determined with the application of computer-aided engineering integrating with the Taguchi method to improve the compressive property of the valve body. The parameters considered for optimization are the following: number of gates, gate size, molding temperature, resin temperature, switch over by volume filled, switch over by injection pressure, and curing time. An orthogonal array of L₁₈ is created for the statistical design of experiments based on the Taguchi method. Then, Mold-Flow analyses are performed by using the designed process parameters based on the L₁₈ orthogonal array. The signal-to-noise (S/N) ratio and the analysis of variance (ANOVA) are used to find the optimal PIM process parameters and to figure out the impact of the viscosity of resin, curing percentage, and compressive strength on a brake booster valve body. When compared with the average compression strength out of the 18 design experiments, the compression strength of the valve body produced using the optimal PIM process parameters showed a nearly 12% improvement.     

激光熔覆与等离子喷焊WF218合金的组织和性能比较

气门密封面激光熔覆的工艺和性能研究较多,但激光熔覆的合金组织和性能与现在气门密封面生产应用的等离子喷焊合金的对比数据较少.为了推动激光熔覆技术在气门密封面生产中的应用,对目前应用的气门WF218合金进行了激光熔覆层与等离子喷焊层的对比研究.通过对同炉气体雾化生产的WF218合金粉末分别进行激光熔覆和等离子喷焊,对两者合金层研究结果显示,激光熔覆合金层更致密、组织更细小、成分更均匀、耐蚀性和耐磨性更好.根据研究数据,激光熔覆技术应用于气门密封面生产将进一步提高质量.     

Design and failure modes of automotive suspension springs

This paper is a discussion about automotive suspension coil springs, their fundamental stress distribution, materials characteristic, manufacturing and common failures. An in depth discussion on the parameters influencing the quality of coil springs is also presented.

Following the trend of the auto industry to continuously achieve weight reduction, coil springs are not exempt. A consequence of the weight reduction effort is the need to employ spring materials with significantly larger stresses compared to similar designs decades ago. Utilizing a higher strength of steel possesses both advantages and disadvantages. The advantages include the freedom to design coil springs at higher levels of stress and more complex stresses. Disadvantages of employing materials with higher levels of stress come from the stresses themselves. A coil’s failure to perform its function properly can be more catastrophic than if the coil springs are used in lower stress. As the stress level is increased, material and manufacturing quality becomes more critical. Material cleanliness that was not a major issue decades ago now becomes significant. Decarburization that was not a major issue in the past now becomes essential.

To assure that a coil spring serves its design, failure analysis of broken coil springs is valuable both for the short and long term agenda of car manufacturer and parts suppliers. This paper discusses several case studies of suspension spring failures. The failures presented range from the very basic including insufficient load carrying capacity, raw material defects such as excessive inclusion levels, and manufacturing defects such as delayed quench cracking, to failures due to complex stress usage and chemically induced failure. FEA of stress distributions around typical failure initiation sites are also presented.     

涡旋真空泵的设计与操作

本文总结了涡旋真空泵的工作原理、设计原则与经验、制造要点和使用注意事项；介绍了涡旋真空泵的设计与加工方法；讨论了涡旋盘的加工、密封的设计与选择、间隙的确定以及泵体的动平衡等问题并阐明这些问题是影响泵性能指标的几个重要因素；同时指出了涡旋真空泵使用的几个注意事项。     

增材制造压电陶瓷的现状与展望

压电陶瓷作为一类重要的功能陶瓷材料, 具备高强度、高硬度、耐腐蚀等优点, 可实现机械能和电能间的相互转换, 常被用于制备传感器、驱动器、电容器等压电器件, 在海洋探测、生物医疗、电子通讯等高端装备中发挥着重要作用。针对高端技术领域对压电功能器件智能化、集成化、轻量化的发展需求, 压电陶瓷的外形和结构越来越复杂。注浆、注射、模压、切割等传统的压电陶瓷制造工艺, 大多需借助模具或刀具完成, 很难甚至无法制造具有中空、悬垂等复杂结构的压电陶瓷, 制约了压电功能器件的进一步发展。增材制造技术基于逐层累加原理可实现任意复杂结构快速定制, 具有成型效率高、无需模具等优点, 可满足个性化、整体化、复杂化制造需求, 近年来受到国内外压电陶瓷领域研究人员的广泛关注。本文从粉体、浆料、块材三种原材料形态角度, 综述了当前增材制造压电陶瓷的主要工艺种类及发展现状, 综合对比了各种工艺成型特点; 介绍了增材制造压电陶瓷在不同领域的应用进展; 最后, 总结和展望了增材制造压电陶瓷所面临的挑战和未来可能的发展趋势。     

Integration and application of feature recognition and mould manufacturing planning navigating process

Plastic injection mould manufacturing is diverse and complex. Traditional mould manufacturing planning often relied on experience and techniques. Therefore, in order not to affect the operation or even cause some loss of the enterprises, geometry information of computer-aided design (CAD) should be converted into manufacturing information of computer-aided process planning (CAPP) and CAM for automatic feature recognition to shorten the lead time. This study is the secondary development in a CAD environment creating a network plastic injection mould manufacturing navigating system and CAD/CAPP for integration and application. As part design is feature-based, each processing step can be regarded as a feature. By applying the hybrid recognition technology of the graph-based approach, the rule-based approach and hint-based approach in the analysis of part feature appearances, it can automatically categorise all the manufacturing features of the part and convert them into corresponding processes. The CAPP developed in this study can convert the part manufacturing features into corresponding processes and plan the part process sequence according to the process priority constraint relations. As proved by the case studies, the use of CAPP in this study can reduce planning time by 87%. It can provide users with a reference regarding process sequence, and speed up the part planning progress. Coupled with the mould manufacturing navigating process, it can achieve automatic design and manufacturing.     

Logical reconfiguration of reconfigurable manufacturing systems with stream of variations modelling: a stochastic two-stage programming and shortest path model

Designing flexible manufacturing systems in general, and flexible material handling system in particular, is a complex problem, typically approached through several stages. Here the focus is on the conceptual design stage during which valid approximation-based methods are needed. The segmented flow topology (SFT) AGV systems were developed to facilitate control of complex automated material handling systems. This paper introduces a decomposition method, directly derived from timed Petri nets (TPN) theories, to calculate the expected utilization of AGVs (as servers of SFT systems) and to derive simple operational decision rules leading to maximum system productivity at steady state, for a given deterministic routeing of discrete material through the manufacturing system.     

下开阀式塑料灌装阀

目的研发一种适合灌装腐蚀性溶液的灌装阀。方法打破金属灌装阀的传统设计理念,塑料灌装阀以高分子塑料为主体结构,利用塑料阀杆柔韧、抗拉的特点,当阀杆被向上拉起时,灌装阀关闭,同时阀杆下端的阀芯和导向阀体形成线性密封;当阀杆被推动下移时,灌装阀打开。另外灌装阀设置了弹簧,用于保障气路故障时灌装阀仍处于关闭状态,避免泄漏。结果塑料灌装阀不但能够抵抗强酸、强碱等液体的腐蚀,而且具有结构合理、安全可靠、成本低等优点。结论塑料灌装阀成功地解决了化工领域腐蚀性溶液灌装的难题。     

An efficient fatigue and creep‐fatigue life prediction method by using the hysteresis energy density rate concept

Fatigue damage, time‐dependent creep damage and their interaction are considered as the main failure mechanisms for many high temperature structural components. A generalized methodology for predicting both the high temperature low cycle fatigue (HTLCF) and creep‐fatigue lives by using the hysteresis energy density rate (HEDR) and fatigue damage stress concepts was proposed. Experimental data for HTLCF and creep‐fatigue in Alloy 617, Haynes 230 and P92 steel were respectively collected to validate the method. A better prediction capacity and most of the data points that fall within a 1.5 scatter band were obtained compared with the traditional energy‐based method, time fraction rule and ductility exhaustion model. Moreover, a creep‐fatigue damage diagram was also constructed by using the proposed approach.     

Optimum design of structures by accounting for the manufacturing process

A mathematical statement of the problem of optimum design of structures by accounting for the manufacturing process, called a problem of bioptimum design, is examined. It is shown that solution of this problem reduces to successive solution of the problem of optimum design and optimization of the manufacturing process. To this end, a special minimizing sequence has been constructed. A problem of bioptimum design of hydraulic cylinders is discussed as an example. Four manufacturing process alternatives, including the following finishing operations, are presented: machining, autofretting with internal pressure; shaping on a mandrel; drawing with thinning. As the solution of the problem showed, drawing is the most effective process from the viewpoint of strength of hydraulic cylinders. It provides for a favorable residual stress field and best strengthening of the cylinder material.Translated from Problemy Prochnosti, No. 5, pp. 64–68, May, 1991.     

Robust design of composites manufacturing processes with process simulation and optimisation methods

Due to the increasing variations in raw materials and manufacturing processes, composite manufacturing processes have more part-to-part variations compared with the metal manufacturing processes. To improve part quality consistency, tooling design optimisation is an imperative step for addressing the stochastic behaviour of composite manufacturing processes. This paper presents an optimisation approach for the typical composite manufacturing technique of resin transfer moulding (RTM), which minimises the sensitivity of the mould design to uncertain material properties by choosing appropriate locations of injection gates and vents. This paper proposes a stochastic simulation based approach for the RTM processes. Normal distribution and Weibull distribution were utilised as the statistical models for representing the permeability values for the main region and race-tracking, respectively. Based on the statistical properties of the permeability, a graph-based two-phase heuristic (GTPH) was adopted to minimise the flow dispersion value (a quantitative measure for part quality consistency) such that the process design is not sensitive to the material and process parameter variations.