热挤压AZ91D镁合金线材的组织与性能研究

对铸态AZ91D合金进行400~460℃不同温度下的正挤压,制备出直径为3~4 mm的线材。利用光学显微镜分析线材的组织,测试其拉伸力学性能和热膨胀系数。结果表明,在不同挤压温度下均可制备出AZ91D镁合金线材,挤压温度越低,线材晶粒越细小。线材具有优异的力学性能,经400℃热挤压成形的线材抗拉强度和伸长率高达285.6 MPa和5.3%,明显高于同牌号铸态合金的性能。线材的平均线膨胀系数为(21.3~27.4)×10-6K-1。较低挤压温度下制备的线材具有较高的力学性能与较小的线膨胀系数。     

塑料线缆挤管式模具的设计及选配

影响塑料线缆产品质量的因素很多,其中最重要的因素之一是挤出模具。介绍了塑料线缆挤出模具的主要形式,着重阐述了挤管式模具的设计参数选择,并以低烟无卤材料挤出护套的特殊实例,详细剖析了挤管式模具的参数选择。     

发射药挤压破碎动力学分析

发射药床在运动过程中的挤压破碎机理是发射安全性研究中的核心问题,采用数值仿真的方法识别发射药粒的破碎机理.用有限元软件分别对药粒在静载及冲击载荷作用下的力学行为进行了数值仿真,仿真结果表明,在不同的承载模式下发射药颗粒在运动过程中挤压有体积破碎与接触破碎两种基本模式.对药粒在不同承载方式下的破碎规律进行了数值仿真,并对破碎块度的分布进行了分析,分别建立了不同承载方式下破碎块度与载荷幅度间的关系式,为火炮发射安全性研究奠定了基础.     

Automatic Transformation of Membrane‐Type Electronic Devices into Complex 3D Structures via Extrusion Shear Printing and Thermal Relaxation of Acrylonitrile–Butadiene–Styrene Frameworks

This work demonstrates a means of automatic transformation from planar electronic devices to desirable 3D forms. The method uses a spatially designed thermoplastic framework created via extrusion shear printing of acrylonitrile–butadiene–styrene (ABS) on a stress‐free ABS film, which can be laminated to a membrane‐type electronic device layer. Thermal annealing above the glass transition temperature allows stress relaxation in the printed polymer chains, resulting in an overall shape transformation of the framework. In addition, the significant reduction in the Young's modulus and the ability of the polymer chains to reflow in the rubbery state release the stress concentration in the electronic device layer, which can be positioned outside the neutral mechanical plane. Electrical analyses and mechanical simulations of a membrane‐type Au electrode and indium gallium zinc oxide transistor arrays before and after transformation confirm the versatility of this method for developing 3D electronic devices based on planar forms.     

铝合金齿轮泵泵体半固态挤压成形的数值模拟研究

采用半固态挤压方法生产零部件,可以消除铸造方法产生的气孔或疏松。通过线性回归的方法建立半固态A356铝合金在570～580℃高固相率温度范围内,不同应变和应变速率下的刚粘塑性本构关系。采用商业有限元模拟软件Deform-3D对A356铝合金材料半固态挤压成形齿轮泵泵体的成形过程进行数值模拟,得到成形过程的流动速度场、有效应力应变场、压力-行程曲线等,并对其进行简要的分析,得出成形过程中的金属流动情况。     

前缸盖的间接挤压铸造技术研究

以SD510汽车空调压缩机前缸盖为研究对象,采用优化成分的6061、6082变形铝合金进行合金净化技术、细化技术、间接挤压铸造技术及热处理技术试验研究,并结合Procast铸造软件对间接挤压铸造的成形过程进行计算机数值模拟。结果表明:优化后的6061合金可用于间接挤压铸造;在一定压力范围内,提高间接挤压压力可相应地提高铸件的综合力学性能及内部组织的致密度;计算机数值模拟技术可有效指导间接挤压铸造工艺参数的选择。     

深孔黄铜火帽壳体的冷挤压成形研究

研究了某型号武器弹药黄铜火帽壳体的冷挤压成形加工工艺,并成功地用于大批量的工业生产中。该黄铜火帽壳体 外形为多台阶型,内孔为细长深盲孔(其高径比H／D=3．6)的复杂形状,因此需要采用多道次冷挤压工序来完成。在成形过 程中,通过变形程度的合理分配,选择合适的润滑剂和坯料软化退火工艺规范,获得了尺寸精度、表面质量均满足设计要 求的最终零件形状。由于材料的加工硬化作用以及可保持金属流线连续,因此冷挤压火帽壳体的强度和韧性均比切削加 工件有所提高,避免了机械加工壳体在使用过程中的胀大和开裂等缺陷。     

A Hybrid Decoupled Power Flow Method for Balanced Power Distribution Systems

This paper proposes a hybrid decoupled power flow method for balanced power distribution systems with distributed generation sources.The method formulates the power flow equations in active power and reactive power decoupled form with polar coordinates.Second-order terms are included in the active power mismatch iteration,and constant Jacobian and Hessian matrices are used.A hybrid direct and indirect solution technique is used to achieve efficiency and robustness of the algorithm.Active power correction is solved by means of a sparse lower triangular and upper triangular(LU) decomposition algorithm with partial pivoting,and the reactive power correction is solved by means of restarted generalized minimal residual algorithm with an incomplete LU pre-conditioner.Typical distribution generation models and distribution load models are included.The impact of zero-impedance branches is explicitly modeled through reconfiguring of the adjacent branches with impedances.Numerical examples on a sample distribution system with widespread photovoltaic installations are given to demonstrate the effectiveness of the proposed method.     

3D Printing and Nanotechnology: A Multiscale Alliance in Personalized Medicine

3D printing and nanotechnology have been two important tools in the development of therapeutic approaches for personalized medicine. More recently, their alliance has been improved in an effort to build innovative, versatile, multifunctional, and/or smart medical and pharmaceutical products. Therefore, an extensive review about scientific studies that ally 3D printing and nanomaterials in the development of new approaches for pharmaceutical and medical applications for the treatment and prevention of diseases is presented here. The articles are classified into five categories according to their main application: Cell growth and tissue engineering, antimicrobial, drug delivery, stimulus-response, and theranostics. Semisolid extrusion, inorganic nanoparticles, and cell growth and tissue engineering are the most reported 3D printing technique, type of nanomaterial, and application, respectively. The increase in papers dedicated to these areas is also notable, especially in the 2019 and 2020, when semisolid extrusion became the most used technique, overcoming fused deposition modelling. In fact, this review highlights that the possibility of an alliance between 3D printing and nanotechnology for the production of multiscale materials is undoubtedly a great opportunity for knowledge and innovation in the pharmaceutical and medical area.     

大尺寸物理发泡绝缘挤出生产线的设计

为满足当今需求量激增的大尺寸射频同轴电缆、漏泄电缆的生产需要,摆脱大尺寸物理发泡绝缘挤出生产线依赖进口的局面,成功开发了大尺寸物理发泡绝缘挤出生产线,填补了国产设备在该领域的空白。针对大尺寸物理发泡绝缘电缆绝缘生产设备的关键配置及电缆生产中部分重要工艺参数的控制展开了详细分析。